ALBERT

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Geometallurgy is an interdisciplinary field aimed at describing potential ore deposits in terms that mine planners and economists can use to design and run profitable mining operations. The major geologic contribution to the field is defining the spatial variability of potential and active mining resources so that planning and scheduling can accurately predict the economic performance and environmental impact of mining in time to respond efficiently to variations in ore type. This information is needed at the feasibility stage and throughout the mine life. We review the available literature on how geologists have contributed to these predictions in the past. There have been substantial advances in predicting comminution behavior. Prediction of recovery and environmental impacts are less advanced. This introductory paper provides a brief review of geometallurgy and a synopsis of the papers in the Special Issue, along with suggestions on future directions.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Phoenix mine and predecessor operations in north-central Nevada have produced an aggregate of 5.2 Moz of gold and 550 million pounds of copper from an Eocene-aged Au-Cu porphyry-related skarn. The complex skarn mineralogy intimately associated with ore-grade mineralization poses significant challenges to blasting, mining, comminution, and process operations. These challenges are rooted in highly variable silicate mineralogy, which manifests as fine-grained, submillimeter grain-size, generally green colored rocks that inhibit accurate identification in the field. Prior to this study, all mineralogical data utilized in Phoenix mine ore control were sourced from blast hole cuttings mapped by ore control geologists in the field—the standard practice at many modern mine sites. At Phoenix, a direct link between mineralogy and mill performance was recognized; however, mineralogical data captured in the field was not sufficient to optimize process operations.To address this, it was determined that analytical work was necessary to quantify fine-grained mineralogy of variable ore types. A visible-near and short-wave infrared (VNIR-SWIR) hyperspectral imaging system provided the ideal tool, as it allows near real-time mineralogical data acquisition and semiquantitative determination of mineral abundances. Multiple iterative studies were conducted to prove that hyperspectral imaging of Phoenix ore types provides results suitable for process optimization. This six-month study described here included hyperspectral imaging of 3,008 blast hole cuttings samples from three pits, and 877 crusher feed, rougher feed, and rougher tails samples. Hyperspectral feature extractions derived from mill samples were paired with associated mill performance data and used to build predictive Au-Cu recovery, grade, and throughput models using multiple linear regression, partial least squares, and deep learning techniques with R-correlation values to observed data of 0.56 to 0.71. Blast hole hyperspectral data were then applied to recovery, grade, and throughput models to calculate predicted recoveries and throughputs that were spatially kriged with excellent correlations to geologic features.The application of VNIR-SWIR hyperspectral imaging to blast hole cuttings is a powerful predictive and diagnostic geometallurgical tool in operations where silicate mineralogy has a strong impact on process operations.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Cadia East porphyry deposit, located approximately 20 km south of Orange, New South Wales, Australia, contains a significant resource of copper and gold. This resource is hosted within the Forest Reefs Volcanics and is spatially and temporally associated with the Cadia Intrusive Complex. To extract ore, the underground mine currently uses the block cave mining method. The Cadia East geotechnical model provides data inputs into a range of numerical and empirical analysis methods that make up the foundation for mine design. These data provide input into the construction of stress models, caveability models, ground support design, and fragmentation analysis. This geotechnical model encompasses two commonly used rock classification systems that quantify ground conditions: (1) rock mass rating (RMR) and (2) rock tunneling quality index (Q index). The RMR and Q index are calculated from estimates of rock quality designation (RQD), number of fracture sets, fracture roughness, fracture alteration, and fracture spacing. Geologists and geotechnical engineers collect information used to produce these estimates by manually logging sections of drill core, a time-consuming task that can result in inconsistent data.Modern automated core scanning technologies offer opportunities to rapidly collect data from larger samples of drill core. These automated core logging systems generate large volumes of spatially and spectrally consistent data, including a model of the drill core surface from a laser profiling system. Core surface models are used to extract detailed measurements of fracture location, orientation, and roughness from oriented drill core. These data are combined with other morphological and mineralogical outputs from automated hyperspectral core logging systems to estimate RMR and the Q index systematically over contiguous drill core intervals. The goal of this study was to develop a proof-of-concept methodology that extracts geotechnical index parameters from hyperspectral and laser topographic data collected from oriented drill core.Hyperspectral data from the Cadia East mine were used in this case study to assess the methods. The results show that both morphological and mineralogical parameters that contribute to the RMR and Q index can be extracted from the automated core logging data. This approach provides an opportunity to capture consistent geologic, mineralogical, and geotechnical data at a scale that is too time-consuming to achieve via manual data collection.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Geometallurgy aims to develop and deploy predictive spatial models based on tangible and quantitative resource characteristics that are used to optimize the efficiency of minerals beneficiation and extractive metallurgy operations. While most current applications of geometallurgy are focused on the major commodity to be recovered from a mineral deposit, this contribution delineates the opportunity to use a geometallurgical approach to provide an early assessment of the economic potential of by-product recovery from an ongoing mining operation.As a case study for this methodology, possible rare earth element (REE) recovery as a by-product of Nb production at the Chapadão mine in the Catalão I carbonatite complex is used. Catalão I is part of the Alto Paranaíba igneous province in the Goias Province of Brazil. Currently, niobium is produced in the complex as a by-product of the Chapadão phosphates mine. This production is performed in the Tailings plant, the focus of this study. REEs, albeit present in significant concentrations, are currently not recovered as by-products.Nine samples from different stages of the Nb beneficiation process in the Tailings plant were taken and characterized by mineral liberation analyzer, X-ray powder diffraction, and bulk-rock chemistry. The recovery of REEs in each of the tailing streams was quantified by mass balance. The quantitative mineralogical and microstructural data are used to identify the most suitable approach to recover REEs as a by-product—without placing limitations on niobium production. Monazite, the most common rare earth mineral identified in the feed, occurs as Ce-rich and La-rich varieties that can be easily distinguished by scanning electron microscopy (SEM)-based image analysis. Quartz, Fe-Ti oxides, and several phosphate minerals are the main gangue minerals. The highest rare earth oxide content concentrations (1.75 wt % total rare earth oxides) and the greatest potential for REE processing are reported for the final flotation tailings stream. To place tentative economic constraints on REE recovery from the tailings material, an analogy to the Browns Range deposit in Australia is drawn. Its technical flow sheet was used to estimate the cost for a hypothetical REE production at Chapadão. Parameters derived from SEM-based image analysis were used to model possible monazite recovery and concentrate grades. This exercise illustrates that a marketable REE concentrate could be obtained at Chapadão if the process recovers at least 53% of the particles with no less than 60% of monazite on their surface. Applying capital expenditure and operational expenditure values similar to those of Browns Range suggests that such an operation would be profitable at current REE prices.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The juxtaposition of a Triassic evaporite diapir with the organic matter-rich Fahdene Formation (Albian-Vra-conian) along major faults in the Slata ore district raises the question of the roles played by halokinesis, hydrocarbons, and tectonics in mineralization. The Slata mining district, located in the Tunisian salt diapiric zone, contains Ba-Pb-(± Zn) ore hosted in the Aptian carbonates. The mineralogical paragenetic sequence consists of barite (Ba-1)–galena ± sphalerite ± calcite (Ca-1)–barite (Ba-2) and finally, late calcites (Ca-2 and Ca-3). Fluid inclusions from early barite reveal that it was precipitated from a warm (134°–157°C), H〈sub〉2〈/sub〉O-NaCl-KCl-CaCl〈sub〉2〈/sub〉, moderately saline (13.3–24.6 wt % NaCl equiv) basinal brine. This fluid is thought to have resulted from the mixing of a deep-seated, hot, metal-bearing fluid with a cooler, dilute SO42−-rich fluid. Early calcite and cogenetic sulfides (galena and sphalerite) precipitated from fluids of similar salinities and temperatures as the barite-forming fluids, but with the additional involvement of hydrocarbons. Sulfur isotope data suggest that thermochemical sulfate reduction of Triassic gypsum was the main source of reduced sulfur for sulfides. Late barite precipitated as a result of the mixing between a Ba-rich, hot, ascending fluid with a cooler, dilute Triassic sulfate-rich fluid in the absence of hydrocarbons. The homogeneous Pb isotope compositions of galena along with the Sr isotope compositions of barite point to a Paleozoic reservoir as the main source of metals with a contribution from the Triassic-Cretaceous rocks. The emplacement of the ore occurred during the Eocene-Miocene Alpine compressional tectonic activity that triggered the circulation of Paleozoic-derived metal-bearing fluids.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Mineralogy is a fundamental characteristic of a given rock mass throughout the mining value chain. Understanding bulk mineralogy is critical when making predictions on processing performance. However, current methods for estimating complex bulk mineralogy are typically slow and expensive. Whole-rock geochemical data can be utilized to estimate bulk mineralogy using a combination of ternary diagrams and bivariate plots to classify alteration assemblages (alteration mapping), a qualitative approach, or through calculated mineralogy, a predictive quantitative approach. Both these techniques were tested using a data set of multielement geochemistry and mineralogy measured by semiquantitative X-ray diffraction data from the Productora Cu-Au-Mo deposit, Chile.Using geochemistry, samples from Productora were classified into populations based on their dominant alteration assemblage, including quartz-rich, Fe oxide, sodic, potassic, muscovite (sericite)- and clay-alteration, and least altered populations. Samples were also classified by their dominant sulfide mineralogy. Results indicate that alteration mapping through a range of graphical plots provides a rapid and simple appraisal of dominant mineral assemblage, which closely matches the measured mineralogy.In this study, calculated mineralogy using linear programming was also used to generate robust quantitative estimates for major mineral phases, including quartz and total feldspars as well as pyrite, iron oxides, chalcopyrite, and molybdenite, which matched the measured mineralogy data extremely well (R〈sup〉2〈/sup〉 values greater than 0.78, low to moderate root mean square error). The results demonstrate that calculated mineralogy can be applied in the mining environment to significantly increase bulk mineralogy data and quantitatively map mineralogical variability. This was useful even though several minerals were challenging to model due to compositional similarities and clays and carbonates could not be predicted accurately.〈/span〉

Beschreibung: Understanding how the Antarctic ice sheet will respond to global warming relies on knowledge of how it has behaved in the past. The use of numerical models, the only means to quantitatively predict the future, is hindered by limitations to topographic data both now and in the past, and in knowledge of how subsurface oceanic, glaciological and hydrological processes interact. Incorporating the variety and interplay of such processes, operating at multiple spatio-temporal scales, is critical to modeling the Antarctic’s system evolution and requires direct observations in challenging locations. As these processes do not observe disciplinary boundaries neither should our future research.

Beschreibung: Natural dissolved organic matter (DOM) comprises a broad range of dissolved organic molecules in aquatic systems and is among the most complex molecular mixtures known. Here we show, by comparing detailed structural fingerprints of individual molecular formulae in DOM from a set of four marine and one freshwater environments, that a major component of DOM is molecularly indistinguishable in these diverse samples. Molecular conformity was not only apparent by the co-occurrence of thousands of identical molecular formulae, but also by identical structural features of those isomers that collectively represent a molecular formula. The presence of a large pool of compounds with identical structural features in DOM is likely the result of a cascade of degradation processes or common synthetic pathways that ultimately lead to the formation of a universal background, regardless of origin and history of the organic material. This novel insight impacts our understanding of long-term turnover of DOM as the underlying mechanisms are possibly universal.

Beschreibung: Traditionally, the description of microorganisms starts with their isolation from an environmental sample. Many environmentally relevant anaerobic microorganisms grow very slowly, and often they rely on syntrophic interactions with other microorganisms. This impedes their isolation and characterization by classic microbiological techniques. We developed and applied an approach for the successive enrichment of syntrophic hydrocarbon-degrading microorganisms from environmental samples. We collected samples from microbial mat-covered hydrothermally heated hydrocarbon-rich sediments of the Guaymas Basin and mixed them with synthetic mineral medium to obtain sediment slurries. Supplementation with defined substrates (i.e., methane or butane), incubation at specific temperatures, and a regular maintenance procedure that included the measurement of metabolic products and stepwise dilutions enabled us to establish highly active, virtually sediment-free enrichment cultures of actively hydrocarbon-degrading communities in a 6-months to several-years' effort. Using methane as sole electron donor shifted the originally highly diverse microbial communities toward defined mixed cultures dominated by syntrophic consortia consisting of anaerobic methane-oxidizing archaea (ANME) and different sulfate-reducing bacteria. Cultivation with butane at 50 °C yielded consortia of archaea belonging to Candidatus Syntrophoarchaeum and Candidatus Desulfofervidus auxilii partner bacteria. This protocol also describes sampling for further molecular characterization of enrichment cultures by fluorescence in situ hybridization (FISH), and transcriptomics and metabolite analyses, which can provide insights into the functioning of hydrocarbon metabolism in archaea and resolve important mechanisms that enable electron transfer to their sulfate-reducing partner bacteria.

Beschreibung: The construction of high capacity data sharing networks to support increasing government and commercial data exchange has highlighted a key roadblock: the content of existing Internet-connected information remains siloed due to a multiplicity of local languages and data dictionaries. This lack of a digital lingua franca is obvious in the domain of human food as materials travel from their wild or farm origin, through processing and distribution chains, to consumers. Well defined, hierarchical vocabulary, connected with logical relationships—in other words, an ontology—is urgently needed to help tackle data harmonization problems that span the domains of food security, safety, quality, production, distribution, and consumer health and convenience. FoodOn (http://foodon.org) is a consortium-driven project to build a comprehensive and easily accessible global farm-to-fork ontology about food, that accurately and consistently describes foods commonly known in cultures from around the world. FoodOn addresses food product terminology gaps and supports food traceability. Focusing on human and domesticated animal food description, FoodOn contains animal and plant food sources, food categories and products, and other facets like preservation processes, contact surfaces, and packaging. Much of FoodOn’s vocabulary comes from transforming LanguaL, a mature and popular food indexing thesaurus, into a World Wide Web Consortium (W3C) OWL Web Ontology Language-formatted vocabulary that provides system interoperability, quality control, and software-driven intelligence. FoodOn compliments other technologies facilitating food traceability, which is becoming critical in this age of increasing globalization of food networks.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 1287, doi:10.1038/s41467-018-03468-6.

Beschreibung: Warm subtropical-origin Atlantic water flows northward across the Greenland-Scotland Ridge into the Nordic Seas, where it relinquishes heat to the atmosphere and gradually transforms into dense Atlantic-origin water. Returning southward along east Greenland, this water mass is situated beneath a layer of cold, fresh surface water and sea ice. Here we show, using measurements from autonomous ocean gliders, that the Atlantic-origin water was re-ventilated while transiting the western Iceland Sea during winter. This re-ventilation is a recent phenomenon made possible by the retreat of the ice edge toward Greenland. The fresh surface layer that characterises this region in summer is diverted onto the Greenland shelf by enhanced onshore Ekman transport induced by stronger northerly winds in fall and winter. Severe heat loss from the ocean offshore of the ice edge subsequently triggers convection, which further transforms the Atlantic-origin water. This re-ventilation is a counterintuitive occurrence in a warming climate, and highlights the difficulties inherent in predicting the behaviour of the complex coupled climate system.

Beschreibung: Support for this work was provided by the Norwegian Research Council under Grant agreement no. 231647 (L.H. and K.V.), the Bergen Research Foundation under Grant BFS2016REK01 (K.V.), and the Centre for Climate Dynamics at the Bjerknes Centre through the FRESHWATER project (K.V.). Additional funding was provided by the Swiss National Science Foundation grants P2EZP2162267 and P300P2174307 (L.P.), the National Science Foundation grant OCE-1558742 (M.A.S.), the Norway Fulbright Foundation (K.V.), the Canada Fulbright Foundation (G.W.K.M.), and the Natural Sciences and Engineering Research Council of Canada (G.W.K.M.).

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 4917, doi:10.1038/s41598-018-23167-y.

Beschreibung: Intertidal inhabitants are exposed to the 24-hour solar day, and the 12.4 hour rising and falling of the tides. One or both of these cycles govern intertidal organisms’ behaviour and physiology, yet little is known about the molecular clockworks of tidal rhythmicity. Here, we show that the limpet Cellana rota exhibits robust tidally rhythmic behaviour and gene expression. We assembled a de-novo transcriptome, identifying novel tidal, along with known circadian clock genes. Surprisingly, most of the putative circadian clock genes, lack a typical rhythmicity. We identified numerous tidally rhythmic genes and pathways commonly associated with the circadian clock. We show that not only is the behaviour of an intertidal organism in tune with the tides, but so too are many of its genes and pathways. These findings highlight the plasticity of biological timekeeping in nature, strengthening the growing notion that the role of ‘canonical’ circadian clock genes may be more fluid than previously thought, as exhibited in an organism which has evolved in an environment where tidal oscillations are the dominant driving force.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 8128, doi:10.1038/s41598-018-26484-4.

Beschreibung: The kakapo is a critically endangered, herbivorous parrot endemic to New Zealand. The kakapo hindgut hosts a dense microbial community of low taxonomic diversity, typically dominated by Escherichia fergusonii, and has proven to be a remarkably stable ecosystem, displaying little variation in core membership over years of study. To elucidate mechanisms underlying this robustness, we performed 16S rRNA gene-based co-occurrence network analysis to identify potential interactions between E. fergusonii and the wider bacterial community. Genomic and metagenomic sequencing were employed to facilitate interpretation of potential interactions observed in the network. E. fergusonii maintained very few correlations with other members of the microbiota, and isolates possessed genes for the generation of energy from a wide range of carbohydrate sources, including plant fibres such as cellulose. We surmise that this dominant microorganism is abundant not due to ecological interaction with other members of the microbiota, but its ability to metabolise a wide range of nutrients in the gut. This research represents the first concerted effort to understand the functional roles of the kakapo microbiota, and leverages metagenomic data to contextualise co-occurrence patterns. By combining these two techniques we provide a means for studying the diversity-stability hypothesis in the context of bacterial ecosystems.

Beschreibung: This work was supported by funding from the Department of Conservation (DOC) as well as a University of Auckland Faculty Research Development Fund grant (9841 3626187) to MWT, and a University of Auckland Doctoral Scholarship to DWW.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 7363, doi:10.1038/s41598-018-25565-8.

Beschreibung: Satellite-tracking of mature white sharks (Carcharodon carcharias) has revealed open-ocean movements spanning months and covering tens of thousands of kilometers. But how are the energetic demands of these active apex predators met as they leave coastal areas with relatively high prey abundance to swim across the open ocean through waters often characterized as biological deserts? Here we investigate mesoscale oceanographic variability encountered by two white sharks as they moved through the Gulf Stream region and Sargasso Sea in the North Atlantic Ocean. In the vicinity of the Gulf Stream, the two mature female white sharks exhibited extensive use of the interiors of clockwise-rotating anticyclonic eddies, characterized by positive (warm) temperature anomalies. One tagged white shark was also equipped with an archival tag that indicated this individual made frequent dives to nearly 1,000 m in anticyclones, where it was presumably foraging on mesopelagic prey. We propose that warm temperature anomalies in anticyclones make prey more accessible and energetically profitable to adult white sharks in the Gulf Stream region by reducing the physiological costs of thermoregulation in cold water. The results presented here provide valuable new insight into open ocean habitat use by mature, female white sharks that may be applicable to other large pelagic predators.

Beschreibung: This work was supported by the WHOI Ocean Life Institute and awards from NASA and NSF.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 2398, doi:10.1038/s41467-018-04809-1.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 10610, doi:10.1038/s41598-018-28871-3.

Beschreibung: Foraminifera in sediments exposed to gas-hydrate dissociation are not expected to have cellular adaptations that facilitate inhabitation of chemosynthesis-based ecosystems because, to date, there are no known endemic seep foraminifera. To establish if foraminifera inhabit sediments impacted by gas-hydrate dissociation, we examined the cellular ultrastructure of Melonis barleeanus (Williamson, 1858) from the Vestnesa gas hydrate province (Arctic Ocean, west of Svalbard at ~79 °N; ~1200-m depth; n = 4). From sediments with gas hydrate indicators, living M. barleeanus had unusual pore plugs composed of a thick, fibrous meshwork; mitochondria were concentrated at the cell periphery, under pore plugs. While there was no evidence of endosymbioses with prokaryotes, most M. barleeanus specimens were associated with what appear to be Type I methanotrophic bacteria. One foraminifer had a particularly large bolus of these microbes concentrated near its aperture. This is the first documented instance of bona fide living M. barleeanus in gas-hydrate sediments and first documentation of a foraminifer living in close association with putative methanotrophs. Our observations have implications to paleoclimate records utilizing this foundational foraminiferal species.

Beschreibung: JMB was funded by a WHOI Independent Study Award (Mellon Grant), with partial support from NSF grant OCE-1634469. GP and CAGE 15-2 cruise were supported by the Research Council of Norway through CAGE Center for Excellence in Arctic Gas Hydrate Environment and Climate project 223259 and NORCRUST (project number 255150).

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 2809, doi:10.1038/s41467-018-05253-x.

Beschreibung: Voltage-sensing (VSD) and cyclic nucleotide-binding domains (CNBD) gate ion channels for rapid electrical signaling. By contrast, solute carriers (SLCs) that passively redistribute substrates are gated by their substrates themselves. Here, we study the orphan sperm-specific solute carriers SLC9C1 that feature a unique tripartite structure: an exchanger domain, a VSD, and a CNBD. Voltage-clamp fluorimetry shows that SLC9C1 is a genuine Na+/H+ exchanger gated by voltage. The cellular messenger cAMP shifts the voltage range of activation. Mutations in the transport domain, the VSD, or the CNBD strongly affect Na+/H+ exchange, voltage gating, or cAMP sensitivity, respectively. Our results establish SLC9C1 as a phylogenetic chimaera that combines the ion-exchange mechanism of solute carriers with the gating mechanism of ion channels. Classic SLCs slowly readjust changes in the intra- and extracellular milieu, whereas voltage gating endows the Na+/H+ exchanger with the ability to produce a rapid pH response that enables downstream signaling events.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 14955, doi:10.1038/s41598-018-33021-w.

Beschreibung: Glomeruli are the functional units of olfactory information processing but little remains known about their individual unit function. This is due to their widespread activation by odor stimuli. We expressed channelrhodopsin-2 in a single olfactory sensory neuron type, and used laser stimulation and simultaneous in vivo calcium imaging to study the responses of a single glomerulus to optogenetic stimulation. Calcium signals in the neuropil of this glomerulus were representative of the sensory input and nearly identical if evoked by intensity-matched odor and laser stimuli. However, significantly fewer glomerular layer interneurons and olfactory bulb output neurons (mitral cells) responded to optogenetic versus odor stimuli, resulting in a small and spatially compact optogenetic glomerular unit response. Temporal features of laser stimuli were represented with high fidelity in the neuropil of the glomerulus and the mitral cells, but not in interneurons. Increases in laser stimulus intensity were encoded by larger signal amplitudes in all compartments of the glomerulus, and by the recruitment of additional interneurons and mitral cells. No spatial expansion of the glomerular unit response was observed in response to stronger input stimuli. Our data are among the first descriptions of input-output transformations in a selectively activated olfactory glomerulus.

Beschreibung: Funded by the World Class Institute/National Research Foundation of Korea (KRF: WCI 2009-003) and NIH: DC005259 and NS099691 grants.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 15517, doi:10.1038/s41598-018-33610-9.

Beschreibung: Subduction zones impose an important control on the geochemical cycling between the surficial and internal reservoirs of the Earth. Sulphur and carbon are transferred into Earth’s mantle by subduction of pelagic sediments and altered oceanic lithosphere. Release of oxidizing sulphate- and carbonate-bearing fluids modifies the redox state of the mantle and the chemical budget of subduction zones. Yet, the mechanisms of sulphur and carbon cycling within subduction zones are still unclear, in part because data are typically derived from arc volcanoes where fluid compositions are modified during transport through the mantle wedge. We determined the bulk rock elemental, and sulphur and carbon isotope compositions of exhumed ultramafic and metabasic rocks from Syros, Greece. Comparison of isotopic data with major and trace element compositions indicates seawater alteration and chemical exchange with sediment-derived fluids within the subduction zone channel. We show that small bodies of detached slab material are subject to metasomatic processes during exhumation, in contrast to large sequences of obducted ophiolitic sections that retain their seafloor alteration signatures. In particular, fluids circulating along the plate interface can cause sulphur mobilization during several stages of exhumation within high-pressure rocks. This takes place more pervasively in serpentinites compared to mafic rocks.

Beschreibung: This project was supported by NSF-EAR grant 1324566 to E.M.S. and B.C.G., and NSF EAR award 1250470 to M.J.C. We acknowledge support by the German Research Foundation and the Open Access Publication Fund of the Freie Universität Berlin.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 3077, doi:10.1038/s41467-018-05574-x.

Beschreibung: Paleoclimate reconstructions are only as good as their chronology. In particular, different chronological assumptions for marine sediment cores can lead to different reconstructions of ocean ventilation age and atmosphere−ocean carbon exchange history. Here we build the first high-resolution chronology that is free of the dating uncertainties common in marine sediment records, based on radiocarbon dating twigs found with computed tomography scans in two cores from the Eastern Equatorial Pacific (EEP). With this accurate chronology, we show that the ventilation ages of the EEP thermocline and intermediate waters were similar to today during the Last Glacial Maximum and deglaciation, in contradiction with previous studies. Our results suggest that the glacial respired carbon pool in the EEP was not significantly older than today, and that the deglacial strengthening of the equatorial Pacific carbon source was probably driven by low-latitude processes rather than an increased subsurface supply of upwelled carbon from high-latitude oceans.

Beschreibung: The lab work at NOSAMS was supported by Ocean Ventures Fund from WHOI and an NOSAMS graduate internship granted to N.Z

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 15219, doi:10.1038/s41598-018-33283-4.

Beschreibung: This Article corrects an error in Equation 1

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 15740, doi:10.1038/s41598-018-33640-3.

Beschreibung: Hurricanes passing over the ocean can mix the water column down to great depths and resuspend massive volumes of sediments on the continental shelves. Consequently, organic carbon and reduced inorganic compounds associated with these sediments can be resuspended from anaerobic portions of the seabed and re-exposed to dissolved oxygen (DO) in the water column. This process can drive DO consumption as sediments become oxidized. Previous studies have investigated the effect of hurricanes on DO in different coastal regions of the world, highlighting the alleviation of hypoxic conditions by extreme winds, which drive vertical mixing and re-aeration of the water column. However, the effect of hurricane-induced resuspended sediments on DO has been neglected. Here, using a diverse suite of datasets for the northern Gulf of Mexico, we find that in the few days after a hurricane passage, decomposition of resuspended shelf sediments consumes up to a fifth of the DO added to the bottom of the water column during vertical mixing. Despite uncertainty in this value, we highlight the potential significance of this mechanism for DO dynamics. Overall, sediment resuspension likely occurs over all continental shelves affected by tropical cyclones, potentially impacting global cycles of marine DO and carbon.

Beschreibung: Support for J. Moriarty was provided by the USGS Mendenhall Program.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 2864, doi:10.1038/s41467-018-05313-2.

Beschreibung: The mechanisms of transfer of crustal material from the subducting slab to the overlying mantle wedge are still debated. Mélange rocks, formed by mixing of sediments, oceanic crust, and ultramafics along the slab-mantle interface, are predicted to ascend as diapirs from the slab-top and transfer their compositional signatures to the source region of arc magmas. However, the compositions of melts that result from the interaction of mélanges with a peridotite wedge remain unknown. Here we present experimental evidence that melting of peridotite hybridized by mélanges produces melts that carry the major and trace element abundances observed in natural arc magmas. We propose that differences in nature and relative contributions of mélanges hybridizing the mantle produce a range of primary arc magmas, from tholeiitic to calc-alkaline. Thus, assimilation of mélanges into the wedge may play a key role in transferring subduction signatures from the slab to the source of arc magmas.

Beschreibung: This project was supported by the WHOI Ocean Exploration Institute (OEI) 27071178 to V.L.R.; Previous related projects were supported by NSF EAR-1348063 and WHOI OEI to H.R.M.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Cell Death and Disease 9 (2018): 663, doi:10.1038/s41419-018-0704-9.

Beschreibung: The poor regenerative capacity of descending neurons is one of the main causes of the lack of recovery after spinal cord injury (SCI). Thus, it is of crucial importance to find ways to promote axonal regeneration. In addition, the prevention of retrograde degeneration leading to the atrophy/death of descending neurons is an obvious prerequisite to activate axonal regeneration. Lampreys show an amazing regenerative capacity after SCI. Recent histological work in lampreys suggested that GABA, which is massively released after a SCI, could promote the survival of descending neurons. Here, we aimed to study if GABA, acting through GABAB receptors, promotes the survival and axonal regeneration of descending neurons of larval sea lampreys after a complete SCI. First, we used in situ hybridization to confirm that identifiable descending neurons of late-stage larvae express the gabab1 subunit of the GABAB receptor. We also observed an acute increase in the expression of this subunit in descending neurons after SCI, which further supported the possible role of GABA and GABAB receptors in promoting the survival and regeneration of these neurons. So, we performed gain and loss of function experiments to confirm this hypothesis. Treatments with GABA and baclofen (GABAB agonist) significantly reduced caspase activation in descending neurons 2 weeks after a complete SCI. Long-term treatments with GABOB (a GABA analogue) and baclofen significantly promoted axonal regeneration of descending neurons after SCI. These data indicate that GABAergic signalling through GABAB receptors promotes the survival and regeneration of descending neurons after SCI. Finally, we used morpholinos against the gabab1 subunit to knockdown the expression of the GABAB receptor in descending neurons. Long-term morpholino treatments caused a significant inhibition of axonal regeneration. This shows that endogenous GABA promotes axonal regeneration after a complete SCI in lampreys by activating GABAB receptors.

Beschreibung: Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund 2007–2013 (Grant number: BFU2014-56300-P) and Xunta de Galicia (Grant number: GPC2014/030). D.R.-S. was supported by a fellowship from EMBO (Ref.: 7010) to carry out a short-term stay at the laboratory of JRM. A.B.-I. was supported by a grant from the Xunta de Galicia (Grant number: 2016-PG008) and a grant from the crowdfunding platform Precipita (FECYT; Spanish Ministry of Economy and Competitiveness; grant number 2017-CP081).

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 2431, doi:10.1038/s41467-018-04421-3.

Beschreibung: Tectonic landforms reveal that the West Antarctic Ice Sheet (WAIS) lies atop a major volcanic rift system. However, identifying subglacial volcanism is challenging. Here we show geochemical evidence of a volcanic heat source upstream of the fast-melting Pine Island Ice Shelf, documented by seawater helium isotope ratios at the front of the Ice Shelf cavity. The localization of mantle helium to glacial meltwater reveals that volcanic heat induces melt beneath the grounded glacier and feeds the subglacial hydrological network crossing the grounding line. The observed transport of mantle helium out of the Ice Shelf cavity indicates that volcanic heat is supplied to the grounded glacier at a rate of ~ 2500 ± 1700 MW, which is ca. half as large as the active Grimsvötn volcano on Iceland. Our finding of a substantial volcanic heat source beneath a major WAIS glacier highlights the need to understand subglacial volcanism, its hydrologic interaction with the marine margins, and its potential role in the future stability of the WAIS.

Beschreibung: This research was supported by the NSF Antarctic program through Award #1341630.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 11997, doi:10.1038/s41598-018-30091-8.

Beschreibung: The abundance of organic carbon (OC) in vegetation and soils (~2,600 PgC) compared to carbon in the atmosphere (~830 PgC) highlights the importance of terrestrial OC in global carbon budgets. The residence time of OC in continental reservoirs, which sets the rates of carbon exchange between land and atmosphere, represents a key uncertainty in global carbon cycle dynamics. Retention of terrestrial OC can also distort bulk OC- and biomarker-based paleorecords, yet continental storage timescales remain poorly quantified. Using “bomb” radiocarbon (14C) from thermonuclear weapons testing as a tracer, we model leaf-wax fatty acid and bulk OC 14C signatures in a river-proximal marine sediment core from the Bay of Bengal in order to constrain OC storage timescales within the Ganges-Brahmaputra (G-B) watershed. Our model shows that 79–83% of the leaf-waxes in this core were stored in continental reservoirs for an average of 1,000–1,200 calendar years, while the remainder was stored for an average of 15 years. This age structure distorts high-resolution organic paleorecords across geologically rapid events, highlighting that compound-specific proxy approaches must consider storage timescales. Furthermore, these results show that future environmental change could destabilize large stores of old - yet reactive - OC currently stored in tropical basins.

Beschreibung: We acknowledge funding support from the Agouron Institute Postdoctoral Fellowship (K.L.F), the US National Science Foundation (Awards: OCE-1333387 and OCE-13333826), the Investment in Science Fund given primarily by WHOI Trustee and Corporation Members, and the Swiss National Science Foundation (Award: 200020_163162).

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 13478, doi:10.1038/s41598-018-31175-1.

Beschreibung: Agricultural intensification offers potential to grow more food while reducing the conversion of native ecosystems to croplands. However, intensification also risks environmental degradation through emissions of the greenhouse gas nitrous oxide (N2O) and nitrate leaching to ground and surface waters. Intensively-managed croplands and nitrogen (N) fertilizer use are expanding rapidly in tropical regions. We quantified fertilizer responses of maize yield, N2O emissions, and N leaching in an Amazon soybean-maize double-cropping system on deep, highly-weathered soils in Mato Grosso, Brazil. Application of N fertilizer above 80 kg N ha−1 yr−1 increased maize yield and N2O emissions only slightly. Unlike experiences in temperate regions, leached nitrate accumulated in deep soils with increased fertilizer and conversion to cropping at N fertilization rates 〉80 kg N ha−1, which exceeded maize demand. This raises new questions about the capacity of tropical agricultural soils to store nitrogen, which may determine when and how much nitrogen impacts surface waters.

Beschreibung: This project was supported by grants from NSF (DEB-1257944, DEB-1257391, DEB1457017, EF-1541770, EF-1655432, EF-1519342, IOS-1660034, IOS-1457662, and EAR-1739724) to M. Macedo, C. Neill, and M.T. Coe.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 10140, doi:10.1038/s41598-018-28455-1.

Beschreibung: Haynesina germanica, an ubiquitous benthic foraminifer in intertidal mudflats, has the remarkable ability to isolate, sequester, and use chloroplasts from microalgae. The photosynthetic functionality of these kleptoplasts has been demonstrated by measuring photosystem II quantum efficiency and O2 production rates, but the precise role of the kleptoplasts in foraminiferal metabolism is poorly understood. Thus, the mechanism and dynamics of C and N assimilation and translocation from the kleptoplasts to the foraminiferal host requires study. The objective of this study was to investigate, using correlated TEM and NanoSIMS imaging, the assimilation of inorganic C and N (here ammonium, NH4+) in individuals of a kleptoplastic benthic foraminiferal species. H. germanica specimens were incubated for 20 h in artificial seawater enriched with H13CO3− and 15NH4+ during a light/dark cycle. All specimens (n = 12) incorporated 13C into their endoplasm stored primarily in the form of lipid droplets. A control incubation in darkness resulted in no 13C-uptake, strongly suggesting that photosynthesis is the process dominating inorganic C assimilation. Ammonium assimilation was observed both with and without light, with diffuse 15N-enrichment throughout the cytoplasm and distinct 15N-hotspots in fibrillar vesicles, electron-opaque bodies, tubulin paracrystals, bacterial associates, and, rarely and at moderate levels, in kleptoplasts. The latter observation might indicate that the kleptoplasts are involved in N assimilation. However, the higher N assimilation observed in the foraminiferal endoplasm incubated without light suggests that another cytoplasmic pathway is dominant, at least in darkness. This study clearly shows the advantage provided by the kleptoplasts as an additional source of carbon and provides observations of ammonium uptake by the foraminiferal cell.

Beschreibung: This work was supported by the Swiss National Science Foundation (grant no. 200021_149333) and was part of the CNRS EC2CO-Lefe project ForChlo. It was also supported by the Region Pays de la Loire (Post-doc position of TJ, on FRESCO project) as well as the WHOI Robert W. Morse Chair for Excellence in Oceanography and The Investment in Science Fund at WHOI.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 13556, doi:10.1038/s41598-018-31710-0.

Beschreibung: In mammals, a complex array of oral sensors assess the taste, temperature and haptic properties of food. Although the representation of taste has been extensively studied in the gustatory cortex, it is unclear how the somatosensory cortex encodes information about the properties of oral stimuli. Moreover, it is poorly understood how different oral sensory modalities are integrated and how sensory responses are translated into oral motor actions. To investigate whether oral somatosensory cortex processes food-related sensations and movements, we performed in vivo whole-cell recordings and motor mapping experiments in rats. Neurons in oral somatosensory cortex showed robust post-synaptic and sparse action potential responses to air puffs. Membrane potential showed that cold water evoked larger responses than room temperature or hot water. Most neurons showed no clear tuning of responses to bitter, sweet and neutral gustatory stimuli. Finally, motor mapping experiments with histological verification revealed an initiation of movements related to food consumption behavior, such as jaw opening and tongue protrusions. We conclude that somatosensory cortex: (i) provides a representation of the temperature of oral stimuli, (ii) does not systematically encode taste information and (iii) influences orofacial movements related to food consummatory behavior.

Beschreibung: This work was supported by the Marine Biological Laboratory, Humboldt Universität zu Berlin and Neurocure.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 3500, doi:10.1038/s41467-018-05804-2.

Beschreibung: Subduction zone magmas are more oxidised on eruption than those at mid-ocean ridges. This is attributed either to oxidising components, derived from subducted lithosphere (slab) and added to the mantle wedge, or to oxidation processes occurring during magma ascent via differentiation. Here we provide direct evidence for contributions of oxidising slab agents to melts trapped in the sub-arc mantle. Measurements of sulfur (S) valence state in sub-arc mantle peridotites identify sulfate, both as crystalline anhydrite (CaSO4) and dissolved SO42− in spinel-hosted glass (formerly melt) inclusions. Copper-rich sulfide precipitates in the inclusions and increased Fe3+/∑Fe in spinel record a S6+–Fe2+ redox coupling during melt percolation through the sub-arc mantle. Sulfate-rich glass inclusions exhibit high U/Th, Pb/Ce, Sr/Nd and δ34S (+ 7 to + 11‰), indicating the involvement of dehydration products of serpentinised slab rocks in their parental melt sources. These observations provide a link between liberated slab components and oxidised arc magmas.

Beschreibung: We acknowledge financial support by the Australian Research Council (DE120100513 and DP120104240) and the ESRF for beam time (EC1061 and ES238).

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 9478, doi:10.1038/s41598-018-26948-7.

Beschreibung: Tidal wetlands produce long-term soil organic carbon (C) stocks. Thus for carbon accounting purposes, we need accurate and precise information on the magnitude and spatial distribution of those stocks. We assembled and analyzed an unprecedented soil core dataset, and tested three strategies for mapping carbon stocks: applying the average value from the synthesis to mapped tidal wetlands, applying models fit using empirical data and applied using soil, vegetation and salinity maps, and relying on independently generated soil carbon maps. Soil carbon stocks were far lower on average and varied less spatially and with depth than stocks calculated from available soils maps. Further, variation in carbon density was not well-predicted based on climate, salinity, vegetation, or soil classes. Instead, the assembled dataset showed that carbon density across the conterminous united states (CONUS) was normally distributed, with a predictable range of observations. We identified the simplest strategy, applying mean carbon density (27.0 kg C m−3), as the best performing strategy, and conservatively estimated that the top meter of CONUS tidal wetland soil contains 0.72 petagrams C. This strategy could provide standardization in CONUS tidal carbon accounting until such a time as modeling and mapping advancements can quantitatively improve accuracy and precision.

Beschreibung: Synthesis efforts were funded by NASA Carbon Monitoring System (CMS; NNH14AY67I), USGS LandCarbon and the Smithsonian Institution. J.R.H. was additionally supported by the NSF-funded Coastal Carbon Research Coordination Network while completing this manuscript (DEB-1655622). J.M.S. coring efforts were funded by NSF (EAR-1204079). B.P.H. coring efforts were funded by Earth Observatory (Publication Number 197).

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Communications Biology 1 (2018): 177, doi:10.1038/s42003-018-0183-7.

Beschreibung: The oceans are warming and coral reefs are bleaching with increased frequency and severity, fueling concerns for their survival through this century. Yet in the central equatorial Pacific, some of the world’s most productive reefs regularly experience extreme heat associated with El Niño. Here we use skeletal signatures preserved in long-lived corals on Jarvis Island to evaluate the coral community response to multiple successive heatwaves since 1960. By tracking skeletal stress band formation through the 2015-16 El Nino, which killed 95% of Jarvis corals, we validate their utility as proxies of bleaching severity and show that 2015-16 was not the first catastrophic bleaching event on Jarvis. Since 1960, eight severe (〉30% bleaching) and two moderate (〈30% bleaching) events occurred, each coinciding with El Niño. While the frequency and severity of bleaching on Jarvis did not increase over this time period, 2015–16 was unprecedented in magnitude. The trajectory of recovery of this historically resilient ecosystem will provide critical insights into the potential for coral reef resilience in a warming world.

Beschreibung: Funding for this study was provided by National Science Foundation awards OCE 1537338, OCE 1605365, and OCE 1031971 to A.L.C., and the Robertson Foundation to A.L.C., National Science Foundation Graduate Research Fellowships to T.M.D. and A.E.A., and a National Defense Science and Engineering Graduate Fellowship to H.E.R.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 17437, doi:10.1038/s41598-018-35309-3.

Beschreibung: During recent years, rapid seasonal growth of macroalgae covered extensive areas within the Yellow Sea, developing the world’s most spatially extensive “green tide”. The remarkably fast accumulation of macroalgal biomass is the joint result of high nitrogen supplies in Yellow Sea waters, plus ability of the macroalgae to optionally use C4 photosynthetic pathways that facilitate rapid growth. Stable isotopic evidence shows that the high nitrogen supply is derived from anthropogenic sources, conveyed from watersheds via river discharges, and by direct atmospheric deposition. Wastewater and manures supply about half the nitrogen used by the macroalgae, fertiliser and atmospheric deposition each furnish about a quarter of the nitrogen in macroalgae. The massive green tides affecting the Yellow Sea are likely to increase, with significant current and future environmental and human consequences. Addressing these changing trajectories will demand concerted investment in new basic and applied research as the basis for developing management policies.

Beschreibung: This work was supported by the State Key Project of Research and Development Plan (2016YFC1402106).

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 5179, doi:10.1038/s41467-018-07346-z.

Beschreibung: Sunlight is the dominant control on phytoplankton biosynthetic activity, and darkness deprives them of their primary external energy source. Changes in the biochemical composition of phytoplankton communities over diel light cycles and attendant consequences for carbon and energy flux in environments remain poorly elucidated. Here we use lipidomic data from the North Pacific subtropical gyre to show that biosynthesis of energy-rich triacylglycerols (TAGs) by eukaryotic nanophytoplankton during the day and their subsequent consumption at night drives a large and previously uncharacterized daily carbon cycle. Diel oscillations in TAG concentration comprise 23 ± 11% of primary production by eukaryotic nanophytoplankton representing a global flux of about 2.4 Pg C yr−1. Metatranscriptomic analyses of genes required for TAG biosynthesis indicate that haptophytes and dinoflagellates are active members in TAG production. Estimates suggest that these organisms could contain as much as 40% more calories at sunset than at sunrise due to TAG production.

Beschreibung: This work was supported by a grant from the Simons Foundation, and is a contribution of the Simons Collaboration on Ocean Processes and Ecology (SCOPE award # 329108, B.A.S.V.M.). K.W.B. was further supported by the Postdoctoral Scholarship Program at Woods Hole Oceanographic Institution & U.S. Geological Survey.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 4702, doi:10.1038/s41467-018-07076-2.

Beschreibung: The orbital-scale timing of South Asian monsoon (SAM) precipitation is poorly understood. Here we present new SST and seawater δ18O (δ18Osw) records from the Bay of Bengal, the core convective region of the South Asian monsoon, over the past 1 million years. Our records reveal that SAM precipitation peaked in the precession band ~9 kyrs after Northern Hemisphere summer insolation maxima, in phase with records of SAM winds in the Arabian Sea and eastern Indian Ocean. Precession-band variance, however, accounts for ~30% of the total variance of SAM precipitation while it was either absent or dominant in records of the East Asian monsoon (EAM). This and the observation that SAM precipitation was phase locked with obliquity minima and was sensitive to Southern Hemisphere warming provides clear evidence that SAM and EAM precipitation responded differently to orbital forcing and highlights the importance of internal processes forcing monsoon variability.

Beschreibung: This study was partly funded by the German Science Foundation, DFG, IODP Priority Program (grant HA 5751/3-1).

Beschreibung: Conduit geometry affects magma ascent dynamics and, consequently, the style and evolution of volcanic eruptions. However, despite geological evidences support the occurrence of conduit widening during most volcanic eruptions, the factors controlling conduit enlargement are still unclear, and the effects of syn-eruptive variations of conduit geometry have not been investigated in depth yet. Based on numerical modeling and the application of appropriate stability criteria, we found out a strong relationship between magma rheology and conduit stability, with significant effects on eruptive dynamics. Indeed, in order to be stable, conduits feeding dacitic/rhyolitic eruptions need larger diameters respect to their phonolitic/trachytic counterparts, resulting in the higher eruption rates commonly observed in dacitic/rhyolitic explosive events. Thus, in addition to magma source conditions and viscosity-dependent efficiency for outgassing, we suggest that typical eruption rates for different magma types are also controlled by conduit stability. Results are consistent with a compilation of volcanological data and selected case studies. As stability conditions are not uniform along the conduit, widening is expected to vary in depth, and three axisymmetric geometries with depth-dependent radii were investigated. They are able to produce major modifications in eruptive parameters, suggesting that eruptive dynamics is influenced by syn-eruptive changes in conduit geometry.

Beschreibung: Published

Beschreibung: 4125

Beschreibung: 5V. Processi eruttivi e post-eruttivi

Beschreibung: JCR Journal

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 4494, doi:10.1038/s41598-018-22758-z.

Beschreibung: Six velocity sections straddling Cape Hatteras show a deep counterflow rounding the Cape wedged beneath the poleward flowing Gulf Stream and the continental slope. This counterflow is likely the upper part of the equatorward-flowing Deep Western Boundary Current (DWBC). Hydrographic data suggest that the equatorward flow sampled by the shipboard 38 kHz ADCP comprises the Upper Labrador Sea Water (ULSW) layer and top of the Classical Labrador Sea Water (CLSW) layer. Continuous DWBC flow around the Cape implied by the closely-spaced velocity sections here is also corroborated by the trajectory of an Argo float. These findings contrast with previous studies based on floats and tracers in which the lightest DWBC constituents did not follow the boundary to cross under the Gulf Stream at Cape Hatteras but were diverted into the interior as the DWBC encountered the Gulf Stream in the crossover region. Additionally, our six quasi-synoptic velocity sections confirm that the Gulf Stream intensified markedly at that time as it approached the separation point and flowed into deeper waters. Downstream increases were observed not only in the poleward transport across the sections but also in the current’s maximum speed.

Beschreibung: This research was supported by NSF through OCE-1558521 and OCE-1332667 and by a grant from North Carolina to the Renewable Ocean Energy Program.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 660, doi:10.1038/s41467-018-02984-9.

Beschreibung: Efforts to estimate the physical and economic impacts of future climate change face substantial challenges. To enrich the currently popular approaches to impact analysis—which involve evaluation of a damage function or multi-model comparisons based on a limited number of standardized scenarios—we propose integrating a geospatially resolved physical representation of impacts into a coupled human-Earth system modeling framework. Large internationally coordinated exercises cannot easily respond to new policy targets and the implementation of standard scenarios across models, institutions and research communities can yield inconsistent estimates. Here, we argue for a shift toward the use of a self-consistent integrated modeling framework to assess climate impacts, and discuss ways the integrated assessment modeling community can move in this direction. We then demonstrate the capabilities of such a modeling framework by conducting a multi-sectoral assessment of climate impacts under a range of consistent and integrated economic and climate scenarios that are responsive to new policies and business expectations.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 3926, doi:10.1038/s41598-018-22313-w.

Beschreibung: Despite concerted international effort to track and interpret shifts in the abundance and distribution of Adélie penguins, large populations continue to be identified. Here we report on a major hotspot of Adélie penguin abundance identified in the Danger Islands off the northern tip of the Antarctic Peninsula (AP). We present the first complete census of Pygoscelis spp. penguins in the Danger Islands, estimated from a multi-modal survey consisting of direct ground counts and computer-automated counts of unmanned aerial vehicle (UAV) imagery. Our survey reveals that the Danger Islands host 751,527 pairs of Adélie penguins, more than the rest of AP region combined, and include the third and fourth largest Adélie penguin colonies in the world. Our results validate the use of Landsat medium-resolution satellite imagery for the detection of new or unknown penguin colonies and highlight the utility of combining satellite imagery with ground and UAV surveys. The Danger Islands appear to have avoided recent declines documented on the Western AP and, because they are large and likely to remain an important hotspot for avian abundance under projected climate change, deserve special consideration in the negotiation and design of Marine Protected Areas in the region.

Beschreibung: We gratefully acknowledge the financial support of the Dalio Foundation, Inc. through the Dalio Explore Fund, which provided all the financing for the Danger Island Expedition. We would like to thank additional support for analysis from the National Science Foundation (NSF PLR&GSS 1255058 - H.J.L. and P.M.; NSF PLR 1443585 – M.J.P.) and the National Aeronautical and Space Administration (NNX14AC32G; H.J.L. and M.S.). Geospatial support for the analysis of high resolution satellite imagery provided by the Polar Geospatial Center under NSF PLR awards 1043681 & 1559691.

Beschreibung: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 115, doi:10.1038/s41598-017-00091-1.

Beschreibung: Mutations in Fused in Sarcoma/Translocated in Liposarcoma (FUS) cause familial forms of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease characterized by progressive axonal degeneration mainly affecting motor neurons. Evidence from transgenic mouse models suggests mutant forms of FUS exert an unknown gain-of-toxic function in motor neurons, but mechanisms underlying this effect remain unknown. Towards this end, we studied the effect of wild type FUS (FUS WT) and three ALS-linked variants (G230C, R521G and R495X) on fast axonal transport (FAT), a cellular process critical for appropriate maintenance of axonal connectivity. All ALS-FUS variants impaired anterograde and retrograde FAT in squid axoplasm, whereas FUS WT had no effect. Misfolding of mutant FUS is implicated in this process, as the molecular chaperone Hsp110 mitigated these toxic effects. Interestingly, mutant FUS-induced impairment of FAT in squid axoplasm and of axonal outgrowth in mammalian primary motor neurons involved aberrant activation of the p38 MAPK pathway, as also reported for ALS-linked forms of Cu, Zn superoxide dismutase (SOD1). Accordingly, increased levels of active p38 MAPK were detected in post-mortem human ALS-FUS brain tissues. These data provide evidence for a novel gain-of-toxic function for ALS-linked FUS involving p38 MAPK activation.

Beschreibung: We are grateful for funding from NIH/NINDS (R01 NS078145, R01 NS090352, and R21 NS091860 to D.A.B., R01 NS066942A and R21 NS096642 to G.M., R01NS023868 and R01NS041170 to S.T.B.), the ALS Therapy Alliance/CVS Pharmacy (to D.A.B. and G.M.) and the ALS Association (to C.F. and J.M.).

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 1124, doi:10.1038/s41467-018-03134-x.

Beschreibung: The ocean’s role in global climate change largely depends on its heat transport. Therefore, understanding the oceanic meridional heat transport (MHT) variability is a fundamental issue. Prevailing observational and modeling evidence suggests that MHT variability is primarily determined by the large-scale ocean circulation. Here, using new in situ observations in the eastern subpolar North Atlantic Ocean and an eddy-resolving numerical model, we show that energetic mesoscale eddies with horizontal scales of about 10–100 km profoundly modulate MHT variability on time scales from intra-seasonal to interannual. Our results reveal that the velocity changes due to mesoscale processes produce substantial variability for the MHT regionally (within sub-basins) and the subpolar North Atlantic as a whole. The findings have important implications for understanding the mechanisms for poleward heat transport variability in the subpolar North Atlantic Ocean, a key region for heat and carbon sequestration, ice–ocean interaction, and biological productivity.

Beschreibung: J.Z. was financially supported by the Postdoctoral Scholar Program at WHOI, with funding provided by the Ocean and Climate Change Institute. This work was also supported by the US National Science Foundation (OCE-1258823 and OCE-1634886), as well as by China’s national key research and development projects (2016YFA0601803), the National Natural Science Foundation of China (41521091 and U1606402), the Qingdao National Laboratory for Marine Science and Technology (2015ASKJ01), and the Fundamental Research Funds for the Central Universities (201424001 and 201362048).

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 742, doi:10.1038/s41598-017-18757-1.

Beschreibung: In mammals, spinal cord injury (SCI) leads to dramatic losses in neurons and synaptic connections, and consequently function. Unlike mammals, lampreys are vertebrates that undergo spontaneous regeneration and achieve functional recovery after SCI. Therefore our goal was to determine the complete transcriptional responses that occur after SCI in lampreys and to identify deeply conserved pathways that promote regeneration. We performed RNA-Seq on lamprey spinal cord and brain throughout the course of functional recovery. We describe complex transcriptional responses in the injured spinal cord, and somewhat surprisingly, also in the brain. Transcriptional responses to SCI in lampreys included transcription factor networks that promote peripheral nerve regeneration in mammals such as Atf3 and Jun. Furthermore, a number of highly conserved axon guidance, extracellular matrix, and proliferation genes were also differentially expressed after SCI in lampreys. Strikingly, ~3% of differentially expressed transcripts belonged to the Wnt pathways. These included members of the Wnt and Frizzled gene families, and genes involved in downstream signaling. Pharmacological inhibition of Wnt signaling inhibited functional recovery, confirming a critical role for this pathway. These data indicate that molecular signals present in mammals are also involved in regeneration in lampreys, supporting translational relevance of the model.

Beschreibung: We gratefully acknowledge support from the National Institutes of Health (R03NS078519 to OB; R01GM104123 to JJS; R01NS078165 to JRM), The Feinstein Institute for Medical Research and The Marine Biological Laboratory, including the Charles Evans Foundation Research Award, the Albert and Ellen Grass Foundation Faculty Research Award, and The Eugene and Millicent Bell Fellowship Fund in Tissue Engineering.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 266, doi:10.1038/s41467-017-02571-4.

Beschreibung: Because microbial plankton in the ocean comprise diverse bacteria, algae, and protists that are subject to environmental forcing on multiple spatial and temporal scales, a fundamental open question is to what extent these organisms form ecologically cohesive communities. Here we show that although all taxa undergo large, near daily fluctuations in abundance, microbial plankton are organized into clearly defined communities whose turnover is rapid and sharp. We analyze a time series of 93 consecutive days of coastal plankton using a technique that allows inference of communities as modular units of interacting taxa by determining positive and negative correlations at different temporal frequencies. This approach shows both coordinated population expansions that demarcate community boundaries and high frequency of positive and negative associations among populations within communities. Our analysis thus highlights that the environmental variability of the coastal ocean is mirrored in sharp transitions of defined but ephemeral communities of organisms.

Beschreibung: This work was supported by grants from the U.S. National Science Foundation (OCE-1441943) to M.F.P. and the U.S. Department of Energy (DE-SC0008743) to M.F.P. and E.J.A. A.M.M.-P. was partially supported by the Ramon Areces foundation through a postdoctoral fellowship. D.J.M. was supported by the U.S. National Science Foundation (OCE-1314642) and National Institute of Environmental Health Sciences (1P01ES021923-01) through the Woods Hole Center for Oceans and Human Health.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 121, doi:10.1038/s41467-017-02504-1.

Beschreibung: Sediments in deep ocean trenches may contain crucial information on past earthquake history and constitute important sites of carbon burial. Here we present 14C data on bulk organic carbon (OC) and its thermal decomposition fractions produced by ramped pyrolysis/oxidation for a core retrieved from the 〉7.5 km-deep Japan Trench. High-resolution 14C measurements, coupled with distinctive thermogram characteristics of OC, reveal hemipelagic sedimentation interrupted by episodic deposition of pre-aged OC in the trench. Low δ13C values and diverse 14C ages of thermal fractions imply that the latter material originates from the adjacent margin, and the co-occurrence of pre-aged OC with intervals corresponding to known earthquake events implies tectonically triggered, gravity-flow-driven supply. We show that 14C ages of thermal fractions can yield valuable chronological constraints on sedimentary sequences. Our findings shed new light on links between tectonically driven sedimentological processes and marine carbon cycling, with implications for carbon dynamics in hadal environments.

Beschreibung: This study is supported by Doc.Mobility Fellowship (P1EZP2_159064) (R.B.) from the Swiss National Science Foundation (SNSF). This work is also supported by SNF “CAPS-LOCK” project 200021_140850 (T.I.E.), by SNSF grant (133481) (M.S.), and Austrian Science Foundation (P 29678-N28) (M.S.).

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 8 (2018): 4547, doi:10.1038/s41598-018-22732-9.

Beschreibung: The assembly of membranous extensions such as microvilli and cilia in polarized cells is a tightly regulated, yet poorly understood, process. Peptidylglycine α-amidating monooxygenase (PAM), a membrane enzyme essential for the synthesis of amidated bioactive peptides, was recently identified in motile and non-motile (primary) cilia and has an essential role in ciliogenesis in Chlamydomonas, Schmidtea and mouse. In mammalian cells, changes in PAM levels alter secretion and organization of the actin cytoskeleton. Here we show that lack of Pam in zebrafish recapitulates the lethal edematous phenotype observed in Pam−/− mice and reveals additional defects. The pam−/− zebrafish embryos display an initial striking loss of microvilli and subsequently impaired ciliogenesis in the pronephros. In multiciliated mouse tracheal epithelial cells, vesicular PAM staining colocalizes with apical actin, below the microvilli. In PAM-deficient Chlamydomonas, the actin cytoskeleton is dramatically reorganized, and expression of an actin paralogue is upregulated. Biochemical assays reveal that the cytosolic PAM C-terminal domain interacts directly with filamentous actin but does not alter the rate of actin polymerization or disassembly. Our results point to a critical role for PAM in organizing the actin cytoskeleton during development, which could in turn impact both microvillus formation and ciliogenesis.

Beschreibung: This study was supported by grants DK032949 (to BAE and REM), DK044464 (to JDG) and GM051293 (to SMK) from the National Institutes of Health.

Beschreibung: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in The ISME Journal 12 (2018): 1-16, doi:10.1038/ismej.2017.187.

Beschreibung: The rock-hosted subseafloor crustal aquifer harbors a reservoir of microbial life that may influence global marine biogeochemical cycles. Here we utilized metagenomic libraries of crustal fluid samples from North Pond, located on the flanks of the Mid-Atlantic Ridge, a site with cold, oxic subseafloor fluid circulation within the upper basement to query microbial diversity. Twenty-one samples were collected during a 2-year period to examine potential microbial metabolism and community dynamics. We observed minor changes in the geochemical signatures over the 2 years, yet the microbial community present in the crustal fluids underwent large shifts in the dominant taxonomic groups. An analysis of 195 metagenome-assembled genomes (MAGs) were generated from the data set and revealed a connection between litho- and autotrophic processes, linking carbon fixation to the oxidation of sulfide, sulfur, thiosulfate, hydrogen, and ferrous iron in members of the Proteobacteria, specifically the Alpha-, Gamma- and Zetaproteobacteria, the Epsilonbacteraeota and the Planctomycetes. Despite oxic conditions, analysis of the MAGs indicated that members of the microbial community were poised to exploit hypoxic or anoxic conditions through the use of microaerobic cytochromes, such as cbb3- and bd-type cytochromes, and alternative electron acceptors, like nitrate and sulfate. Temporal and spatial trends from the MAGs revealed a high degree of functional redundancy that did not correlate with the shifting microbial community membership, suggesting functional stability in mediating subseafloor biogeochemical cycles. Collectively, the repeated sampling at multiple sites, together with the successful binning of hundreds of genomes, provides an unprecedented data set for investigation of microbial communities in the cold, oxic crustal aquifer.

Beschreibung: This work was supported by NSF OCE1062006 to JAH and NSF OCE1061827 to BTG. The Gordon and Betty Moore Foundation sponsored most of the observatory components at North Pond through grant GBMF1609. The Center for Dark Energy Biosphere Investigations (C-DEBI) (OCE-0939564), a National Science Foundation-funded Science and Technology Centers of Excellence also supported the participation of CGW, JAH and BJT.

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 209, doi:10.1038/s41467-017-02105-y.

Beschreibung: Correction to: Nature Communications 8:172 https://doi.org/10.1038/s41467-017-00197-0; Article published online: 2 August 2017

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 305, doi:10.1038/s41467-017-02701-y.

Beschreibung: Correction to: Nature Communications https://doi.org/10.1038/s41467-017-01229-5, Article published online 07 November 2017

Beschreibung: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in The ISME Journal 12 (2018): 237–252, doi:10.1038/ismej.2017.165.

Beschreibung: Temperate coastal marine environments are replete with complex biotic and abiotic interactions that are amplified during spring and summer phytoplankton blooms. During these events, heterotrophic bacterioplankton respond to successional releases of dissolved organic matter as algal cells are lysed. Annual seasonal shifts in the community composition of free-living bacterioplankton follow broadly predictable patterns, but whether similar communities respond each year to bloom disturbance events remains unknown owing to a lack of data sets, employing high-frequency sampling over multiple years. We capture the fine-scale microdiversity of these events with weekly sampling using a high-resolution method to discriminate 16S ribosomal RNA gene amplicons that are 〉99% identical. Furthermore, we used 2 complete years of data to facilitate identification of recurrent sub-networks of co-varying microbes. We demonstrate that despite inter-annual variation in phytoplankton blooms and despite the dynamism of a coastal–oceanic transition zone, patterns of microdiversity are recurrent during both bloom and non-bloom conditions. Sub-networks of co-occurring microbes identified reveal that correlation structures between community members appear quite stable in a seasonally driven response to oligotrophic and eutrophic conditions.

Beschreibung: PLB is supported by the European Research Council Advanced Investigator grant ABYSS 294757 to Antje Boetius. AF-G is supported by the European Union’s Horizon 2020 research and innovation program (Blue Growth: Unlocking the potential of Seas and Oceans) under grant agreement no. (634486) (project acronym INMARE). This study was funded by the Max Planck Society. Further support by the Department of Energy Joint Genome Institute (CSP COGITO) and DFG (FOR2406) is acknowledged by HT (TE 813/2-1) and RA (Am 73/9-1).

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Fluid inclusion studies give unique insights into physical conditions and composition of fluids involved in geologic processes. Most studies to date are performed on transparent minerals. Near-infrared (NIR) microscopy allows microthermometry to also be performed on minerals that are opaque to the visible light, such as pyrite, hematite, wolframite, enargite, and stibnite. The main drawback of this technique is the underestimation of the recorded phase-change temperatures with increasing light intensity—up to several hundred percent in the case of ice-melting temperatures. Although this issue has been known for a decade, it is poorly understood. We address this problem based on a systematic study of synthetic fluid inclusions in a variety of opaque minerals.For the first time, fluid inclusions have been cosynthesized with success in quartz and opaque minerals. Fracturing the host minerals by in situ quenching allowed for fluid-mineral equilibration prior to fluid inclusion formation. In this study, we assess the impact of mineral intrinsic parameters, mainly absorption and thermal conductivity, and experimental settings (light source operative power, diaphragm aperture, and the use of filters) on recorded phase-change temperatures. We show that these are underestimated due to local overheating of the sample caused by radiative heating from the light source. It affects all minerals, and the extent of the temperature shift of the observed phase changes depends on sample thickness, mineral characteristics, and the amount of light reaching the sample. Thus, any calibration of the temperature shift as a function of the amount of light is complicated and, in most cases, impracticable. However, we demonstrate, based on cogenerated inclusions in opaque minerals and quartz that yield similar values during NIR microthermometry, that for any mineral there is a range of light power and microscope settings for which no shift is noticeable within the thermal-stage accuracy. These are defined as “ideal measuring conditions,” ensuring reliability of acquired microthermometry data.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Karouni orogenic gold deposits are located in north-central Guyana 35 km to the west of the 5 Moz Omai gold deposit. They are hosted in a 2200 to 2100 Ma greenstone belt within the Paleo- to Neoproterozoic Guiana Shield. Karouni consists of two deposits, Smarts and Hicks, located 2 km apart along the NW-striking Smarts-Hicks shear zone. Both deposits are hosted within a sequence of greenschist facies mafic volcanic rocks and felsic intrusions. The hydrothermal alteration mineral assemblages vary according to lithology and are characterized by narrow selvages (〈1–4 m in width). A chlorite-talc-calcite assemblage dominates in high MgO basalt, whereas in high TiO〈sub〉2〈/sub〉 dolerite a progression toward the vein is seen from chlorite-calcite-rutile- to albite-dominated mineralogy. Karouni is anomalous among orogenic gold deposits for its dominant sodic alteration and distinct lack of potassic alteration. Gold is located within inclusions in coarse, disseminated pyrite associated with the proximal alteration zones and as coarse native gold within the quartz-carbonate veins. Minor gold is also located within Au-bearing telluride minerals. The high TiO〈sub〉2〈/sub〉 dolerites formed a favorable chemical trap due to their high magnetite content, suggesting sulfidation via redox reaction as a possible mechanism of gold deposition. Mass balance modeling of the hydrothermal alteration indicates a wall rock-dominated system with limited addition or subtraction of major elements with the exception of C, S, and Na. Modeling of the proximal alteration has also shown strong trace element enrichment of W-Bi-Ag-Te-Mo-Pb, all of which are correlative with gold. In situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) trace element geochemistry and secondary ion mass spectrometry (SIMS) S isotope analyses of pyrite from the gold-bearing hydrothermal system within the deposit indicate a geochemically and isotopically homogeneous system with only minor trace element variation due to differences in host rock, suggesting a single hydrothermal pulse correlative with the late stages of the Trans-Amazonian orogeny.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Fluid inclusions in clearly defined fluid inclusion assemblages (FIAs) from various geologic environments were examined to assess the uncertainty associated with determining the temperature of a fluid event based on fluid inclusion homogenization temperatures (T〈sub〉h〈/sub〉). A fluid event is defined as a physical or chemical process such as the healing of a microfracture or the formation of a growth zone in a crystal that occurs in the presence of a fluid phase and results in trapping of fluid inclusions to form an FIA. Examination of data from a large number of fluid events collected within a rigorous temporal and spatial (paragenetic) framework forms the basis for developing a complete fluid pressure-temperature-composition (PTX) history.The range in homogenization temperatures of fluid inclusions within well-constrained FIAs was determined, and the minimum (smallest) range in T〈sub〉h〈/sub〉, the median range in T〈sub〉h〈/sub〉, and the first quartile (Q1 at 25%) and third quartile (Q3 at 75%) of the median T〈sub〉h〈/sub〉 ranges were calculated for different fluid environments, including the following: 〈ul〉 〈li〉Low-permeability sedimentary environments: 49 out of 144 FIAs show a range in T〈sub〉h〈/sub〉 of ≤1°C; the median range = 2°C (from Q1 = 1°C to Q3 = 3.7°C).〈/li〉 〈li〉Mississippi Valley-type deposits: 11 out of 137 FIAs show a range in T〈sub〉h〈/sub〉 of ≤ 1°C; the median range = 4.1°C (from Q1 = 2.3°C to Q3 = 8.3°C).〈/li〉 〈li〉Epithermal deposits: 102 out of 923 FIAs show a range in T〈sub〉h〈/sub〉 of ≤1°C; the median range = 9°C (from Q1 = 3.8°C to Q3 = 19°C).〈/li〉 〈li〉Porphyry-type deposits: 24 out of 271 FIAs show a range in T〈sub〉h〈/sub〉 of ≤ 1°C; the median range = 15°C (from Q1 = 8°C to Q3 = 30°C).〈/li〉 〈li〉Orogenic Au deposits: 21 out of 231 FIAs show a range in T〈sub〉h〈/sub〉 of ≤1°C; the median range = 8.7°C (from Q1 = 4°C to Q3 = 20°C).〈/li〉 〈/ul〉While all environments show some FIAs in which all the fluid inclusions homogenize at essentially the same temperature (range = ≤1°C), we propose that the median range in T〈sub〉h〈/sub〉 reported here represents a reasonable and achievable constraint on the uncertainty associated with the temperature of a fluid event in the environments examined. In summary, the temperature of a fluid event, as represented by the range in T〈sub〉h〈/sub〉 of the fluid inclusions within an individual FIA, can be constrained to better than 15°C in all environments examined, and in Mississippi Valley-type and low-permeability (deep) sedimentary basin environments, the range in T〈sub〉h〈/sub〉 can be constrained to better than 2°C.The processes that produce variability in T〈sub〉h〈/sub〉 of fluid inclusions within an FIA are many and include natural variations in temperature, pressure, or fluid composition during trapping of the FIA, trapping of immiscible fluids, various forms of reequilibration in nature such as necking, stretching, and leakage, and modification of the inclusions during sample preparation and data collection. If the range in homogenization temperature for an individual FIA is found to be greater than the median range determined here for that environment, then assessment of the cause of the variability might provide useful information concerning the trapping and posttrapping history of the sample.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Better tools are needed to map the thermal structure of ore deposits. Here, carbonate clumped isotope thermometry is applied for the first time in epithermal, skarn, and carbonate-hosted deposits to identify the conditions involved in metal transport and deposition. Clumped isotope temperature calibrations were tested by measurement of carbonates from three geothermal fields in the Taupo volcanic zone, New Zealand, that record growth temperatures between 130° and 310°C. Results for modern Taupo volcanic zone calcites were paired with known fluid 〈span〉δ〈/span〉〈sup〉18〈/sup〉O values and these indicate precipitation in equilibrium with produced geothermal waters. Measurements carried out at the Waihi low sulfidation deposit in New Zealand, the Antamina polymetallic skarn in Peru, and the Mount Isa sediment hosted Pb-Zn and Cu deposit in Queensland, Australia, demonstrate that clumped isotope values are sensitive to temperature gradients defined using other methods. At Waihi, an andesite-hosted deposit, temperature controls the majority of variation in carbonate mineral 〈span〉δ〈/span〉〈sup〉18〈/sup〉O. At Mount Isa, ~300° to 400°C temperatures were recorded in a 1.5 Ga orebody, which are consistent with fluid inclusion values, highlighting the longevity of clumped isotope archives in dolomite minerals. Collectively, these results demonstrate the potential for clumped isotopes to delineate the heat footprint around deposits that contain carbonates, and to more effectively disentangle magmatic and meteoric fluid 〈span〉δ〈/span〉〈sup〉18〈/sup〉O signals.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Physical properties and compositions of ore-forming fluids in magmatic-hydrothermal systems have been mostly investigated by conventional fluid inclusion studies in transparent gangue minerals that are assumed to be co-genetic with the mineralization. However, ore-precipitating fluids can be directly studied by analyzing fluid inclusions in opaque ore minerals, such as wolframite, stibnite, pyrite, and enargite, by using near-infrared (NIR) petrography and microthermometry in combination with laser ablation-inductively coupled plasma-mass spectrometry analysis of individual inclusions. Although results of NIR fluid inclusion studies of ore minerals were first published in 1984, the technique is still not commonly used in fluid inclusion research due to a number of limitations related to the analytical equipment used, sample preparation, and NIR mineral transmittance.In this contribution, we present new data on the applicability of NIR fluid inclusion studies of ore minerals (pyrite, stibnite, enargite, and wolframite) from a series of magmatic-hydrothermal systems, according to their chemical composition and physical behavior during microthermometry. Our results reveal strong correlation between NIR transmittance and high trace element (Co, Ni, Cu, As) content in pyrite, enargite (Fe, Bi), and wolframite (Sc, V, Fe). Despite this, the restricted distribution of these elements in oscillatory and sector zoning has allowed observation of NIR mineral features and fluid inclusions. Energy absorption of opaque minerals, either as light energy during microscopy or as thermal conductive energy during fluid inclusion microthermometry, presents a second limitation for NIR fluid inclusion studies. Our results confirm the relevance of fluid inclusion studies in ore minerals by combining NIR microscopy and microthermometry. Despite some limitations due to trace element composition of the host mineral and its physical behavior at high temperature, a successful NIR fluid inclusion study can be performed on some ore minerals that are opaque in the visible light range, allowing the direct study of hydrothermal ore-forming fluids.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Grota Funda iron oxide copper-gold (IOCG) deposit is situated within a regional WNW-ESE–striking shear zone in the northwestern portion of the Carajás domain, an Archean (3.0–2.55 Ga) segment of the Carajás Province, Brazil. Metavolcano-sedimentary sequences of the Igarapé-Pojuca Group, comprising basalt, diabase, gabbro, dacite, and banded iron formations, are the main lithotypes recognized in the deposit area. In this sequence, mafic igneous rocks represent the main hosts to the copper (-gold) mineralization stages. The paragenetic evolution of the Grota Funda hydrothermal system encompasses an early high-temperature cal-cic-sodic alteration (albite-hastingsite-scapolite), followed by intense Fe metasomatism (magnetite-grunerite-almandine), potassic alteration with biotite, chlorite-quartz-tourmaline assemblage, and late carbonate-quartz veining. Copper (-gold) mineralization stages are spatially and temporally associated with iron-enriched (mineralization I), potassically altered (mineralization II), and chlorite-altered zones (mineralization III). Molybdenite from grunerite-magnetite veins yielded a Re-Os model age of 2530 ± 60 Ma, which is interpreted as the mineralization I age. The main sulfide ore (mineralization II) predominantly forms breccia bodies characterized by a chalcopyrite-magnetite-sphalerite-pyrrhotite assemblage. Chalcopyrite 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values (0.9 ± 0.9‰) point to a magmatic source for sulfur, probably leached from the host mafic rocks. Development of early and high-temperature (〉500°C) alteration assemblages is attributed to regional circulation of deep-seated hypersaline and metalliferous fluids. Mixing with moderate- to high-salinity (24–29 wt % NaCl + CaCl〈sub〉2〈/sub〉 equiv) and cooler fluids may have triggered ore precipitation in the main ore zone of mineralization II, due to a decrease in temperature and Cl〈sup〉–〈/sup〉 activity. Postore alteration assemblages resulted from considerable temperature and pH decreases.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Mount Carlton is a Paleozoic high-sulfidation epithermal deposit located in the northern segment of the Bowen Basin, northeast Queensland, Australia. The deposit is hosted in Early Permian volcanic and sedimentary rocks, and an open-pit mining operation includes the Au-rich V2 pit in the northeast and the Ag-rich A39 pit in the southwest. Mineralization at Mt. Carlton occurred during active rifting, partly contemporaneously with the deposition of volcanic sediments in localized half-graben and graben basins. Steep normal faults and fracture networks related to the rifting acted as fluid conduits and localized cores of silicic alteration. The silicic cores transition outward to zones of quartz-alunite alteration, which are, in turn, enveloped by a zone of quartz-dickite-kaolinite alteration. Epithermal mineralization at Mt. Carlton developed in three stages: Cu-Au-Ag mineralization dominated by enargite was overprinted by Zn-Pb-Au-Ag mineralization dominated by sphalerite, which, in turn, was overprinted by Cu-Au-Ag mineralization dominated by tennantite. Proximal Au-Cu mineralization in the V2 pit occurs in networks of steep faults associated with veins and hydrothermal breccias within a massive rhyodacite porphyry. Three distinct ore zones (Eastern, Western, and Link) are aligned, en echelon, along a broadly E trending corridor. The Western ore zone continues along ~600-m strike length to the southwest into the A39 pit, and it shows a metal zonation, from proximal to distal, of Au-Cu → Cu-Zn-Pb-Ag → Ag-Pb-(Cu) → Ag. Distal Ag mineralization in the A39 pit is concentrated in a volcanolacustrine sedimentary sequence that overlies the rhyodacite porphyry. It occurs in a stratabound position oriented parallel to primary sedimentary layering and locally exhibits synsedimentary ore textures. Such textures are interpreted to have formed as mineralizing fluids discharged into what most likely were lakes developed within localized rift basins, at the same time that the volcanolacustrine sediments were deposited. At depth, equivalent ore textures were produced within open spaces in the structural roots of the rift basins. 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar dating of hydrothermal alunite yielded an age range of 284 ± 7 to 277 ± 7 Ma, which links the formation of the Mt. Carlton deposit to the Early Permian back-arc rifting stage in the Bowen Basin. Prolonged extension provided rapid burial of the deposit beneath a postmineralization, volcanosedimentary cover, which was essential for the exceptional preservation of Mt. Carlton. The same extension caused displacement of the rock pile along a series of shallowly dipping detachment faults and segmentation and rotation of the ore zones across steeply dipping normal faults. This deformation would have displaced any underlying porphyry mineralization relative to the current location of Mt. Carlton.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Karouni orogenic gold deposit is located in north-central Guyana, 35 km to the west of the 5 Moz Omai gold mine. The deposit is hosted within 2.2 to 2.1 Ga volcano-sedimentary rocks of the Barama-Mazaruni Supergroup, part of the Paleo- to Neoproterozoic Guiana Shield. Karouni consists of two zones, Smarts and Hicks, located 2 km apart along the NW-striking Smarts-Hicks shear zone, a second-order splay of the regional-scale Makapa-Kuribrong shear zone. The Karouni camp is composed of a lower sequence of mafic volcanic rocks, overlain by a lower sequence of immature sandstone and conglomerate, and an upper sequence of sandstone and laminated carbonaceous siltstone, intruded by several generations of felsic plutons and dikes. Whole-rock geochemical analysis indicates their formation in oceanic island-arc environment, and mantle-like characteristics of the high MgO basalts may indicate the presence of deep-seated structures during the early history of the camp. Regional-scale deformation during the Trans-Amazonian orogeny led to tectonic inversion of the volcano-sedimentary basins, greenschist facies metamorphism, and the development of strike-slip shear zones. Late movement on these shear zones is interpreted to be responsible for hydrothermal fluid flow, alteration, and gold mineralization within the Karouni gold camp. The Smarts and Hicks orebodies are localized within dilatational bends formed at changes in strike of the Smarts-Hicks shear zone during late dextral transcurrent movement. Rheological contrast played a dominant role in the formation of the deposits with shear-hosted, NW-striking, and steeply dipping quartz-carbonate-chlorite ± tourmaline-pyrite-gold (V〈sub〉2a〈/sub〉) veins preferentially hosted in ductilely deformed, high MgO basalts, whereas mineralized N-S, quartz-carbonate-chlorite ± tourma-line-pyrite-gold (V〈sub〉2b〈/sub〉) veins are hosted within rheologically competent high TiO〈sub〉2〈/sub〉 dolerite sills and granodiorite dikes. The interaction of these structures with favorable lithology is key for localizing high-grade orebodies.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Tulaergen Ni-Cu-Co sulfide deposit is associated with a small differentiated mafic-ultramafic body (ca. 300 Ma) in the eastern Tianshan orogenic belt, northwestern China. The mafic-ultramafic complex comprises amphibole lherzolite, amphibole olivine websterite, amphibole websterite, and amphibole gabbro. Amphibole lherzolite is characterized by the occurrence of mafic enclaves (gabbro-granodiorite), some of which show coarse blebby to semimassive sulfide mineralization. No chilled or baked margins exist along the margins of mafic enclaves. In contrast, inward-pointing cusps/embayments of amphibole lherzolite around the margins of mafic enclaves are observed. Some mafic enclaves form accumulations (tens of cm) comprising discrete patches (several mm–5 cm). These features indicate that mafic enclaves formed as a molten state within the hosting magma. Mafic enclaves and ultramafic host rocks exhibit similar trace element signatures (e.g., similar incompatible trace element patterns and comparable Th/Nb values, avg. 0.51 relative to avg. 0.52) and overlapping initial Sr and Nd isotope ratios (〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr〈sub〉i〈/sub〉(t) = 0.7028–0.7036 relative to 0.7021–0.7047 and 〈sup〉143〈/sup〉Nd/〈sup〉144〈/sup〉Nd〈sub〉i〈/sub〉(t) = 0.5126 relative to 0.5125–0.5127). The uniform geochemical features among mafic enclaves and ultramafic host rocks rule out the possibility that the mafic enclaves were products of contamination of crustal xenomelts or insufficient mixing with a foreign intermediate magma. Mafic enclaves contain unique hydrous alteration assemblages; hence, they were originally enriched in aqueous fluids. The coexistence of aqueous mafic enclaves and hydrous Tulaergen silicate melt (primary amphibole and phlogopite) is consistent with the fluid immiscibility of magma, which could be induced by partial melting of metasomatized mantle occurring above the second critical endpoint at about 3.8 GPa and 1,000°C (~110 km).The mineralized mafic enclaves contain a pyrrhotite-pentlandite-chalcopyrite assemblage and platinum group element (PGE) patterns similar to those of the other sulfide ores in the Tulaergen Cu-Ni-Co sulfide deposit, indicating the same source of sulfide segregated from the Tulaergen primary magma. However, they are distinguished from the other sulfide ores by strong enrichment in Pt-Pd-Cu (Pd/Ir = 396 and 834 in mineralized mafic enclaves relative to avg. 80, and Ni/Cu = 0.2 and 1.0 in mineralized mafic enclaves relative to avg. 5.8). Lack of negative correlations between Ir and Pt-Pd tenors contradicts the effect of sulfide fractionation on the Pt-Pd-Cu enrichment in the residual sulfide liquid. Together with the aqueous nature of mafic enclaves and evidence of hydrothermal remobilization of sulfide in mineralized mafic enclaves, Pt-Pd-Cu enrichment in mineralized mafic enclaves is attributed to their high mobility in aqueous fluids relative to Ir-Ru-Rh-Ni.The Tulaergen mafic-ultramafic intrusive rocks were derived from a magma that originated from depleted mantle (〈span〉ε〈/span〉Nd(t) ~4.9–8.5), which was metasomatized by slab-derived fluids during the closure of the ancient Tianshan Ocean. Partial melting of the metasomatized mantle above approximately 110 km generated immiscible aqueous fluid and hydrous silicate melt, which eventually gave rise to mafic enclaves and the Tulaergen mafic-ultramafic complex, respectively. The general PGE depletion in sulfide deposits within the eastern Tianshan orogenic belt could be attributed to a low PGE budget in the depleted mantle source(s) and/or low degree(s) of partial melting.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Caboclo dos Mangueiros deposit, the most recent discovery of Ni-Cu sulfide mineralization in Brazil, has estimated resources of 200 million tonnes (Mt) with grades of 0.20 wt % Ni and 0.13 wt % Cu. The deposit is located in the northwestern margin of the São Francisco craton, close to the contact with the Rio Preto Neoproterozoic fold belt. Due to regional covers of Tertiary-Quaternary sediments and ferruginous lateritic crusts, geologic features of the deposit and its ultramafic plutonic host rocks were mainly described using drill hole logs and geophysical surveys. Mineralization is hosted within an elongated (~2 km long and ~500 m wide) ultramafic sill emplaced into sedimentary country rocks. The absence of well-defined layering, together with abrupt changes in textures, suggests a magmatic structure broadly similar to those described in channelized sills. Except for minor discrete sheared zones and a thin (〈4 m thick) fine-grained border zone, the ultramafic intrusion consists of massive cumulates with magmatic textures. Primary minerals are partially to extensively altered to hydrous minerals, as indicated by the pseudomorphic replacement of olivine by serpentine and magnetite and of clinopyroxene by tremolite-actinolite. Metamorphic assemblages described in the country rocks (i.e., albite + quartz + biotite + muscovite + epidote), cumulate pseudomorphs (i.e., tremolite-actinolite + serpentine + magnetite), and rocks from the border zone (i.e., actinolite + chlorite), are consistent with recrystallization under conditions of the greenschist facies of regional metamorphism. The dynamic magmatic system consists of dunite in the channelized facies and more fractionated wehrlite and clinopyroxenite toward the margins. Bulk-rock composition and the compositional range of Mg# of cumulus clinopyroxene from 0.78 to 0.94 support a moderate to primitive mafic composition for the parental magma. Sulfide Ni-Cu mineralization consists of disseminated sulfide blebs (1–5 vol %) with mineralogy and textures typical of those originated from immiscible sulfide liquids segregated from mafic-ultramafic magmas. Disseminated sulfides, homogeneously distributed in different cumulates, occur throughout the entire ultramafic intrusion. Positive correlations between S-Ni (0.81) and S-Cu (0.87) in the sulfide ore indicate that both metals are mainly contained in sulfides. The sulfide mineralization has moderate Ni (3.46 wt %) and Cu (2.93 wt %) tenors and Ni/Cu ratios close to 1. Positive correlations between S-Pd (0.90) and S-Pt (0.87) in the sulfide ore indicate that both metals are associated with sulfides. High Cu/Pd ratios and very low Pt and Pd tenors indicate a sulfide liquid composition depleted in platinum group elements (PGEs). Combined modeling of Cu, Pt, and Pd tenors suggests that metal contents of the parental magma resulted from previous sulfide segregation of the primitive magma, possibly during residence in lower staging chambers. The Caboclo dos Mangueiros deposit, the first significant Ni-Cu sulfide mineralization hosted in a dynamic magmatic system in the underexplored northern margin of the São Francisco craton, opens a new window for exploration for Ni-Cu-PGE sulfides in Brazil.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The formation of ore minerals in hydrothermal deposits is the result of a complex interplay between physical and chemical processes that are conditioned by the geologic environment in which they occur. In the last decades, research has increasingly indicated that many of these processes display different forms of scale invariance, i.e., they show fractal geometry. This suggests that behind the apparent disorder and irregularity of the geometry of mineral deposits at different scales, an underlying regular pattern is present. If properly understood, this regular geometrical pattern could be useful in a variety of theoretical and applied fields. A great portion of this scale invariance is given by the structural framework during mineralization because structures are a dominant factor controlling fluid flow. Here, we assess the geometry of iron oxide copper-gold (IOCG) mineralization in the world-renowned Carajás mineral province, focusing on one of the largest and most economically important orebodies, the Sossego deposit. The geometry of mineralization is evaluated at the microscale (ore minerals in thin sections), local scale (orebodies in mine maps), and regional scale (deposit distribution on regional maps). We show that the spatial distribution and shape of ore minerals at the microscale is largely nonrandom, presents fractal geometry, and displays defined trends in spatial distribution and anisotropy. Additionally, the geometric trends observed at the microscale mimic those of the local-scale geometry of orebodies, as well as the regional-scale distribution of mineralization. The main property controlling the observed scale invariance is permeability, which is intrinsically associated with structures at multiple scales. These results contribute to further understanding the fractal nature of processes controlling mineral deposit formation and revealing new multiscale approaches to investigate structural controls on ore deposition.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The ability of hydrothermal scheelite (CaWO〈sub〉4〈/sub〉) and calcite (CaCO〈sub〉3〈/sub〉) to bind Sr in their crystal lattices makes them useful minerals for tracing fluid-rock interaction in mineralizing systems. Strontium isotopes in scheelite, calcite, and epidote were measured in situ by laser ablation-multicollector-inductively coupled plasma-mass spectrometry to assess the extent of fluid-rock interaction for Early Cretaceous orogenic W-Au mineralization occurring in the Otago Schist in New Zealand. Scheelite Sr isotope populations, regardless of their geographical location or stage of mineralization, are mostly homogeneous and cluster between 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr = 0.7068 and 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr = 0.7087, with the lack of Rb indicating that these are the initial ratios of the mineralizing fluids. However, while scheelite 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr values in the Hyde-Macraes shear zone and the Barewood and Bendigo deposits overlap with the age-corrected 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr values of the host Rakaia terrane, scheelite 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr values in the Glenorchy and Waipori deposits are commonly more radiogenic than the age-corrected values of the host Caples terrane rocks. Because the Caples terrane was thrust over more radiogenic rocks before mineralization, the Caples terrane scheelite deposits are interpreted to result from fluids that were derived from deep crustal dehydration reactions within the underlying radiogenic and dominantly metaturbiditic (grayschist) Rakaia and Aspiring terranes, and/or that acquired their Sr isotope signatures from extensive fluid-rock reaction with Rakaia and Aspiring terrane grayschists during ascent. It is also evident that the scheelite 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr values in the Caples terrane become more similar to the host-rock values with increasing incorporation of wall rock at the deposit scale as well as with increasing distance above the Caples-Rakaia/Aspiring terrane boundaries. Late-stage calcite that has replaced scheelite takes on the scheelite Sr isotope composition, whereas tabular calcite grains in the same samples have less radiogenic compositions that are equivalent to the wall rock. Application of in situ 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr analysis therefore reveals that (1) there was extensive fluid-rock exchange of Sr during the formation of orogenic W-Au deposits, and (2) the Cretaceous W-Au mineralizing fluids in the Otago Schist were mobile over at least km-scale and probably greater vertical distances.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The world-class Irish Zn-Pb(-Ag) deposits occur within one of the world’s major metallogenic provinces. While it has been well documented that these orebodies are structurally controlled, exactly how fluids migrated from source to trap is still poorly understood. Using 3-D modeling techniques, the current study investigates metal distribution patterns at the Silvermines and Lisheen deposits to gain insights into fluid pathways and structural controls on mineralization. Distinct points along segmented normal faults are identified as the feeders to individual orebodies, allowing hot, hydrothermal, metal-bearing fluids to enter host rocks and form orebodies. These points are characterized by highly localized and elevated Ag, Cu, Co, Ni, and As concentrations as well as low Zn/Pb ratios, which increase away from the feeders. Metal distributions are initially controlled by major and minor normal faults and subsequently affected by later oblique-slip dextral and strike-slip faults. High-tonnage areas without typical feeder signals are interpreted to be structural trap sites, which are distal to fault-controlled feeder points. This study highlights both the importance of a well-connected plumbing system for metal-bearing fluids to reach their basinal traps and the control that an evolving structural framework has on spatial distribution of metals.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Northwest quartz-pyrite-gold veins are situated 500 m east of the Lepanto fault in Mankayan, Luzon, Philippines. Most vein mineralization is hosted by the Lepanto metavolcanic basement rocks at an elevation between 700 and 1,050 m. The earliest stage, stage 1, is characterized by sphalerite + chalcopyrite + pyrite ± magnetite veins cutting the host rocks that were altered to chlorite + illite + epidote. Precious metal deposition started in stage 2 as electrum, native gold, and gold-silver tellurides deposited with pyrite, quartz, and carbonate. Deposition of gold and silver tellurides continued in stage 3a with abundant pyrite and tennantite-tetrahedrite solid solution intergrown with chalcopyrite, bornite, and minor sphalerite. The stage 3a veins and host-rock alteration are characterized by abundant muscovite and quartz, while the stage 3b veins and alteration consist of quartz, pyrophyllite, alunite, and dickite. Enargite and luzonite are the dominant sulfide minerals in stage 4, which are either disseminated in silicified host rock or within wide quartz veins. Lesser amounts of quartz and abundant pyrite with inclusions of enargite and luzonite were precipitated in stage 5.Microthermometry on fluid inclusions in quartz of stages 2, 3a, and 4 indicates boiling of the hydrothermal fluids. Bulk gas analysis on fluid inclusions in quartz shows that the stage 2 and 4 fluids had components derived from basaltic and andesitic magma, respectively. Fluids that formed stage 4 quartz were more diluted by meteoric water than the fluids that formed the stage 2 veins. Radiometric 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar dating on alunite separated from the stage 3b advanced argillic alteration zone yielded 2.2 ± 0.1 Ma. Sulfur isotope compositions of the Northwest quartz-pyrite-gold deposit reveal a bulk 〈span〉δ〈/span〉〈sup〉34〈/sup〉S of approximately 5‰, similar to the calculated value for the adjacent Far Southeast porphyry deposit. Calculated oxygen and hydrogen isotope ratios of the fluids of the Northwest quartz-pyrite-gold deposit stage 3b dickites are similar to those that formed the illite alteration in the Far Southeast porphyry deposit but are higher in 〈span〉δ〈/span〉〈sup〉18〈/sup〉O when compared to the fluids that formed the kandites in the Lepanto enargite deposit. The northward cooling of mineralizing fluids previously reported in the Lepanto enargite deposit is not consistent with the mineralogic indications in the Northwest quartz-pyrite-gold deposit. These data indicate multiple mineralization events in the Mankayan district, which is one of the largest mineral districts in the western Pacific.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉This paper describes the structural setting of the Globe-Progress and Blackwater orogenic gold deposits, the only two +1-million ounce (Moz) deposits discovered to date within the Reefton goldfield of central New Zealand. Most of the Globe-Progress deposit is located along the Globe-Progress shear zone, a curviplanar, brittle-ductile, structure that juxtaposes tightly folded rocks in its footwall against largely unfolded rocks in its hanging wall. At its eastern end the Globe-Progress shear zone merges with the fold-parallel Oriental shear zone, with the Globe-Progress shear zone acting as a tear fault that transferred contractional deformation on the Oriental shear zone across the structural grain of the adjacent folded rocks, during or soon after the end of greenschist facies metamorphism. An early phase of mineralization at ca. 438 Ma (K-Ar, sericite) accompanied this contractional deformation, whereas a second phase of mineralization occurred during later brittle, oblique-normal, reactivation of the two shear zones at ca. 386 Ma (K-Ar, sericite). The resulting ore shoots plunge moderately towards the southwest, along intersections between (1) the two shear zones, (2) the Globe-Progress shear zone and minor normal faults in its hanging wall, and (3) the Globe-Progress shear zone and W-dipping bedding in its hanging wall.The kilometer-long Birthday reef in the Blackwater mine is located on a narrow, mineralized, brittle-ductile fault that can be traced for 3+ km through the adjacent Greenland Group sandstones and argillites. The reef occupies that part of the fault that is close to parallel with bedding on a relatively gently (~60°) W-dipping segment of the western limb of the Waiuta anticline. The reef pinches out where the dip of the host fault steepens and its strike swings from north-northeast toward north. This change in orientation occurs where the fault refracts onto the near vertical axial plane of the Waiuta anticline above/north of the reef, and follows an open flexure in the orientation of bedding on the western limb of the Waiuta anticline below/south of the reef. Both ends of the reef, and its more intensely mineralized internal ore shoots, plunge 35° toward the north-northeast, parallel to the intersection of the host fault and the axial planar cleavage associated with the adjacent Waiuta anticline.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Isocon and Pearce element ratio diagrams are two means of recovering the nature and extent of material transfer processes from rock compositions. Both use the concept of a conserved property to relate changes in concentrations to extensive compositional variations. We demonstrate the fundamental commonality of the two methods and show the sole differences to be a scaling factor and the choice of graphical projection (i.e., diagram axes). We propose a modification of the isocon diagram that improves visualization of element behavior and is especially effective for dilute components that normally plot near the origin. The procedure involves transforming the mass concentration data to Pearce element ratios and then subtracting a reference rock composition from all other compositions. The former step establishes a proportionality with material transfer, and the latter step translates the data set such that the reference composition corresponds to the origin. The translated rock compositions explicitly show the material differences between each sample and the reference composition; positive values represent gains and negative values losses. Presentation of the translated ratios in a spider diagram-like figure enables straightforward visualization of geochemical variability. The algorithm proposed herein is amenable to all geochemical problems involving material transfer processes where at least one element is conserved. We demonstrate the approach by application to synthetic and real data sets.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The southwest Guizhou Province, China, contains numerous sediment-hosted Au deposits with Au reserves greater than 700 tonnes. To date, the source of ore fluids that formed the Guizhou sediment-hosted Au deposits is controversial, hampering the formulation of genetic models. In this study, we selected the Shuiyindong and Jinfeng Au deposits, the largest strata-bound and fault-controlled deposits in Guizhou, respectively, for detailed research on pyrite chemistry and S isotope composition using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and laser ablation-multicollector-inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS), respectively.Petrography and pyrite chemistry studies distinguished five generations of pyrite. Among these, pre-ore pyrite 2 and ore pyrite are the most abundant types in the deposits. Pre-ore pyrite 2 is anhedral to euhedral and with ~2,639 ppm As and wider ranges of Cu, Sb, and Pb (〈~22–4,837 ppm, 〈~6 to 532 ppm, and 〈~4 to 1,344 ppm, respectively). Gold in pre-ore pyrite 2 is below the detection limit of LA-ICP-MS (~2 ppm). Pre-ore pyrite 2 is interpreted to have a sedimentary (syngenetic or diagenetic) origin. Ore pyrite commonly rims the four identified pre-ore pyrites or occurs as individual, anhedral to euhedral crystals. Ore pyrite is enriched in Au (~641 ppm), As (~9,147 ppm), Cu (~1,043 ppm), Sb (~188 ppm), Hg (~43 ppm), and Tl (~22 ppm) in both deposits. Ore pyrite formed mainly by sulfidation of Fe in Fe-bearing host rocks, mainly Fe dolomite, and As, Cu, Sb, Hg, and Tl, also in ore fluids, were incorporated into ore pyrite.In situ 〈span〉δ〈/span〉〈sup〉34〈/sup〉S isotope ratios for pre-ore pyrite 2 and ore pyrite were measured by LA-MC-ICP-MS. Pre-ore pyrite 2 from Shuiyindong and Jinfeng deposits resulted in 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values ranging from −0.8 to +3.4‰ and from 5.1 to 10.5‰, respectively. Analyses of ore pyrite from the Shuiyindong have 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values that vary from −3.3 to +2.5‰, with a median of 0.7‰; analyses of ore pyrite from the Jinfeng range from 8.9 to 11.2‰, with a median at 10.3‰. Available bulk and in situ 〈span〉δ〈/span〉〈sup〉34〈/sup〉S data in the literature for pre-ore pyrites 1 and 2 and ore-related sulfide minerals including ore pyrite, arsenopyrite, and late ore-stage stibnite, realgar, orpiment, and cinnabar from several Guizhou sediment-hosted Au deposits were compiled for comparison. Pre-ore-stage pyrites from Guizhou sediment-hosted Au deposits have a broad range of 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values, from −33.8 to + 17.9‰ (including in situ and available bulk 〈span〉δ〈/span〉〈sup〉34〈/sup〉S data). Ore-related sulfide minerals in all Guizhou sediment-hosted Au deposits, except Jinfeng, have very similar 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values, and most data plot between ~−5 and +5‰. In the Jinfeng deposit, the ore-related sulfide minerals exhibit 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values ranging from 1.9 to 18.1‰, with most data plotting between 6 and 12‰.The broad range of S isotope compositions for the sedimentary pyrites (pre-ore pyrites 1 and 2) indicate that S in these pre-ore pyrites was most likely generated by bacterial reduction from marine sulfate. The narrow range of 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values (~−5–+5‰) for ore-related sulfide minerals in all Guizhou sediment-hosted Au deposits, excepting the Jinfeng deposit, suggests that the deposits may have formed in response to a single widespread metallogenic event. As the S isotope fractionation between hydrothermal fluids and sulfide minerals in a sulfide-dominated system is small (〈2‰) at ~250°C, the initial ore fluids that formed the Guizhou sediment-hosted Au deposits would have had 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values similar to the ore-related sulfide minerals, between ~−5 and +5‰. At Jinfeng, initial ore fluids may have mixed with local fluids with heavier 〈span〉δ〈/span〉〈sup〉34〈/sup〉S, possibly basin brine (〈span〉δ〈/span〉〈sup〉34〈/sup〉S〈sub〉basin brine〈/sub〉 〉18‰), resulting in elevated 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values of ore-related sulfide minerals and especially late ore-stage sulfide minerals.Although few igneous rocks are exposed in the mining area around these deposits, there is evidence of magmatic activity ~20 km away. Furthermore, gravity and magnetic geophysical investigations indicate the presence of a pluton ~5 km below the surface of the Shuiyindong district. Based on in situ S isotope results and recent data indicating proximal intrusions, we interpret a deep magmatic S source for the ore fluids that formed the Guizhou sediment-hosted Au deposits. However, as the age for Au mineralization of Guizhou sediment-hosted Au deposits is still debated, the mineralization-magma connection remains hypothetical. Identifying an ore fluid source and time frame for Guizhou Au mineralization continues to be a critically important research goal for this district.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉WorldView 3 (WV3) standard 2A visible near-infrared (VNIR) and short-wave infrared (SWIR) data of Mountain Pass, California, were calibrated to reflectance and used to map rock types and minerals using true- and false-color composite images, band ratios, and logical operator algorithms. VNIR true-color composite (V5 = red, V3 = green, and V2 = blue) and band ratio imagery were useful for mapping Fe〈sup〉3+〈/sup〉-rich Proterozoic gneiss, the Aztec Sandstone, and carbonatite rocks in the Sulphide Queen rare earth element (REE) mine pit but were unable to map neodymium-rich rocks due to low spectral resolution at VNIR wavelengths and overlap of REE spectral absorption features with those of Fe〈sup〉3+〈/sup〉-bearing minerals.SWIR false-color composite images, band ratio grayscale images, band ratio false-color composite images, and logical operator-derived mineral maps were able to map muscovite-rich Proterozoic granitic gneiss and Jurassic hydrothermally altered granites using the Al-O-H spectral absorption feature, chlorite-epidote–rich Proterozoic schist and Jurassic skarn deposits using the ferrous iron and Fe, Mg-O-H spectral absorption features, and calcite-rich Paleozoic limestone and dolomite-rich Paleozoic dolostone using the CO32− spectral absorption feature. In addition, logical operator algorithms were able to discriminate Fe-bearing muscovite from muscovite in the polymetallic (gold and silver) Morning Star mine, which supports previous studies that suggest Fe-bearing muscovite is closely associated with mineralization.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Silver isotopes are a potential tracer for understanding the geochemical enrichment of gold, which is monoisotopic but occurs in metallic form with silver as a stable alloy component. This study applies high-precision measurements of silver isotope ratios to two of the oldest world-class hydrothermal gold vein deposits from the Archean (3.55–3.10 Ga) Barberton greenstone belt of the Kaapvaal craton in South Africa. Published structural-geologic and geochronological results show that the hydrothermal gold deposits formed late in the tectono-metamorphic history of the greenstone belt, well after major crustal deformation and regional metamorphism, probably postdating even postorogenic granitic intrusions. Gold is concentrated in extensional brittle-ductile structures, indicating a common extensional stress field during mineralization. Orebodies occur close to the stratigraphic contact between older (ultra-)mafic submarine lavas (the Onverwacht Group) and overlying carbonaceous siltstones and graywackes (the Fig Tree Group), marked by a variably tectonized former chert. Observations at New Consort (higher temperature, close to granitoid contact), Fairview, and Sheba (lower temperature in the interior of the greenstone belt) confirm the structurally late introduction of gold into veins and sulfide replacement orebodies.Chemical and isotopic analyses were performed on native gold from Barberton, on two other lode gold deposits and two carbon leader-type samples from the Witwatersrand, and on native silver from various epithermal silver deposits. All native gold samples contain significant (1–12 wt %) Ag but only trace levels of other metals such as Cu or Hg. Stepwise leaching experiments show that native gold is the main carrier of silver even in sulfide-rich ores. Different gold samples from Barberton yield 〈span〉ε〈/span〉〈sup〉109〈/sup〉Ag values (differences in 〈sup〉109〈/sup〉Ag/〈sup〉107〈/sup〉Ag relative to NIST SRM 978a in parts per 10,000) from −4.2 ± 0.4 to 3.6 ± 0.4, encompassing almost the entire range of reported terrestrial Ag isotope variations and all hydrothermal silver samples. Gold samples from New Consort have negative 〈span〉ε〈/span〉〈sup〉109〈/sup〉Ag values, whereas samples from Sheba have variably positive 〈span〉ε〈/span〉〈sup〉109〈/sup〉Ag values.Isotopically different metal sources of the structurally coeval deposits at Barberton are less likely than a process of isotopic fractionation during transport and ore deposition. The observed isotopic difference can be explained by reduction of dissolved Ag〈sup〉+〈/sup〉 complexes in the ore fluid to native Ag〈sup〉0〈/sup〉 in the gold alloy. Assuming that the oxidized Ag〈sup〉+〈/sup〉〈sub〉(aq)〈/sub〉 is enriched in the heavy isotope compared with the reduced metallic form, as in other heavy metal systems, the variation in 〈span〉ε〈/span〉〈sup〉109〈/sup〉Ag between the two deposits can be explained by fractional precipitation of precious metals from a fluid that enters the greenstone belt from an external source, in line with published geologic arguments. Following a Rayleigh distillation model, a first fraction of silver that precipitated close to the contact of the greenstones against surrounding granitoids is isotopically light, as observed at New Consort. Residual silver reaching the interior of the greenstone belt eventually precipitates with a high 〈span〉ε〈/span〉〈sup〉109〈/sup〉Ag, as seen at Sheba.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Rare earth element (REE) orebodies are typically associated with alkaline igneous rocks or develop as placer or laterite deposits. Here, we describe an economically important heavy (H)REE mineralization type that is entirely hydrothermal in origin with no demonstrable links to magmatism. The mineralization occurs as numerous xenotime-rich vein and breccia orebodies across a large area of northern Australia but particularly close to a regional unconformity between Archean metasedimentary rocks of the Browns Range Metamorphics and overlying Proterozoic sandstones of the Birrindudu Group. The deposits formed at 1.65 to 1.61 Ga along steeply dipping faults; there is no known local igneous activity at this time.Depletion of HREEs in the Browns Range Metamorphics, together with the similar nonradiogenic Nd isotope composition of the orebodies and the Browns Range Metamorphics, indicates that ore metals were leached directly from the Browns Range metasedimentary rocks. We propose an ore genesis model that involves fluid leaching HREEs from the Browns Range Metamorphics and subsequently mixing with P-bearing acidic fluid from the overlying sandstones in fault zones near the unconformity. The union of P and HREEs via fluid mixing in a low-Ca environment triggered extensive xenotime precipitation.This mineralization is unlike that of any other class of REE ore deposit but has a similar setting to unconformity-related U deposits of Australia and Canada, so we assign it the label “unconformity-related REE.” Further discoveries of this REE mineralization type are expected near regional unconformities within Proterozoic intracontinental sedimentary basins across the globe.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Sandaowanzi gold deposit in the Great Hinggan Range metallogenic belt, northeast China, is unusual because the mineralization takes the form of Au- and Ag-bearing tellurides. This mineralization, which constitutes a resource of 28 t Au, is hosted in 20 NW-trending, syntaxial, layered quartz veins and tension gashes within almost coeval trachyandesites and andesitic breccias that overlie the Sandaowanzi monzogranite. Alteration halos are developed around the quartz veins and tension gashes. They consist of an inner silicic-pyritic zone, two intermediate zones containing quartz-illite-sericite and quartz-adularia, and an outer zone containing a quartz-calcite-kaolinite-chlorite assemblage.Fluid inclusion microthermometric data reveal that the Sandaowanzi ores precipitated from moderate-temperature (200°–280°C), low-pressure (70–130 bar), and low- to moderate-salinity (mostly 〈6.0 wt % NaCl equiv) hydrothermal fluids. Temperature and pressure are interpreted to have decreased with the evolution of the system. The 〈δ〈sup〉34〈/sup〉S〈sub〉H〈sub〉2〈/sub〉S〈/sub〉 (–2.2 to –0.2‰) values indicate that the sulfur is of magmatic origin and suggest that it was leached by the ore fluid from the host volcanic rocks. A magmatic origin is also interpreted for the metals, based on Pb isotope data (〈sup〉206〈/sup〉Pb/〈sup〉204〈/sup〉Pb = 18.2366–18.3146, 〈sup〉207〈/sup〉Pb/〈sup〉204〈/sup〉Pb = 15.5404–15.5624, 〈sup〉208〈/sup〉Pb/〈sup〉204〈/sup〉Pb = 38.0901–38.2293). In contrast, the δ〈sup〉18〈/sup〉O〈sub〉H〈sub〉2〈/sub〉O〈/sub〉 (–13.6 to –7.6‰) and δD〈sub〉H〈sub〉2〈/sub〉O〈/sub〉 (–127 to –96‰) values indicate that the hydrothermal fluids were dominantly meteoric. Physicochemical modeling shows that sulfidation of the host rocks (decrease of 〈span〉α〈/span〉〈sub〉HS〈/sub〉〈sup〉–〈/sup〉〈sub〉(aq)〈/sub〉) and condensation of H〈sub〉2〈/sub〉Te-bearing vapors (increase of 〈span〉α〈/span〉〈sub〉HTe〈/sub〉〈sup〉–〈/sup〉〈sub〉(aq)〈/sub〉) were the dominant controls on precipitation of the Au and Ag telluride ores. This study emphasizes the importance of fluid-rock interaction (sulfidation) and the mixing of low-density H〈sub〉2〈/sub〉Te-bearing magmatic fluids with meteoric waters in producing large Au and Ag telluride deposits.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Xiarihamu Ni deposit is located in the East Kunlun orogenic belt in the northern part of the Qinghai-Tibet plateau. The regional tectonic setting, lithology, and mineralogy suggest that the Xiarihamu Ni deposit formed in a postcollisional setting. We use a slab break-off model to explain the simultaneous appearance of the Xiarihamu magmatic Ni sulfide deposit and the high-pressure eclogite exhumation in the East Kunlun orogenic belt. In situ 〈span〉δ〈/span〉5〈sup〉34〈/sup〉S〈sub〉V-CDT〈/sub〉 value of pyrite from the country rock (granitic gneiss) of the Xiarihamu complex is 11.2‰, whereas in situ 〈span〉δ〈/span〉5〈sup〉34〈/sup〉S〈sub〉V-CDT〈/sub〉 value of sulfides from the Xiarihamu I complex range from 2.4 to 7.7‰, with an average of 4.5‰. Crustal sulfur most likely accounts for approximately 40 to 60% of the total sulfur content in the Xiarihamu magma. Our modeling shows that the Xiarihamu parental magma may have achieved sulfide saturation and experienced approximately 0.005% sulfide segregation before complex emplacement. Based on previous studies and the platinum group element data in this study, we believe that the Xiarihamu magma was sulfide saturated when olivine began to crystallize. The zones with rapidly declining olivine Fo and clinopyroxene Mg〈sup〉#〈/sup〉 values correspond well with the locations of orebodies, implying that the crystallization of olivine or clinopyroxene played a role in the sulfide saturation. The whole-rock Ni content of the peridotite is inversely related to the Cr〈sup〉#〈/sup〉 and FeO contents in spinel, and the whole-rock Ni content of the websterite is negatively correlated with orthopyroxene Mg〈sup〉#〈/sup〉; thus, during the crystallization of spinel and orthopyroxene, more sulfide formed. Our calculation shows that the decrease in sulfur content at sulfide saturation (SCSS) during fractional crystallization depends mainly on a decrease in temperature, and the change in the melt composition is a secondary or minor factor. Although the contribution of fractional crystallization to total sulfur content may be only approximately 3.3 to 6.0%, an increasing concentration of sulfides were accumulated at the latest crystallization in the host rock because of the incompatibility of sulfur. Recognizing this phenomenon is important for ore exploration. We logged 11 drill cores meter by meter and prepared 110 thin sections from across these 11 drill cores. The lithofacies distribution and crosscutting phenomena have been clearly determined. Combined with systematic geochemical data on the cross section, this paper summarizes the mineral crystallization sequence in different locations of the Xiarihamu I mafic-ultramafic magma chamber and depicts a six-stage model for sulfide saturation during the consolidation process of the Xiarihamu complex.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Late Devonian Dajiangping pyrite deposit in South China is a giant sediment-hosted stratiform deposit and contains 〉200 Mt of pyrite ores with an average grade of 30 wt % S. The orebodies are hosted in carbonaceous siltstone and black shale and consist mainly of laminated pyrite ore. Small euhedral pyrite crystals (pyrite 1) and larger subhedral pyrite crystals (pyrite 2) are the main ore mineral and occur as laminated aggregates of subhedral to euhedral grains. Anhedral pyrite crystals (pyrite 3) associated with pyrrhotite are present in the host rocks and are interbedded with the ore layers. Mass-balance calculations reveal that the pyrite ores have Al-normalized Ca, Mg, Mn, Si, Na, K, and organic carbon contents similar to the host sedimentary rocks, precluding substantial carbonate dissolution and a stratiform replacement origin for the ores.Pyrite 1 and 2 crystals in the laminated ores have δ34S values ranging from −28.7‰ to 23.6‰, and mostly lower than −16‰. Such highly negative values indicate that the sulfur in these ores was sourced from bacterially reduced seawater sulfate in an open system. Pyrite 1 and 2 crystals within a single laminated ore sample have similar δ34S values. The mostly negative sulfur isotope composition implies that the pyrite crystallized above to just below the seawater-sediment interface by consuming aliquots of H2S supplied by bacterial sulfate reduction (BSR) in sulfate-dominated shallow muds. Pyrite 3 crystals have mostly positive δ34S values, ranging from −3.2 to 42.8‰ with a mean of 5.7‰. There are also large ranges of δ34S values within a single sample, for example, from 12.1 to 42.8‰ in sample YF0204. Such positive and highly heterogeneous δ34S values likely resulted from thermochemical sulfate reduction (TSR) and anaerobic oxidation of methane (AOM) coupled with sulfate reduction in a tightly closed system of deep sediments that experienced strong Rayleigh fractionation during diagenesis.We propose that the laminated pyrite ores of the Dajiangping deposit formed by sedimentary exhalation in an anoxic seawater column. Hydrothermal fluids leached Fe from the metamorphic basement underlying the stratiform orebodies, as indicated by the similar Pb isotope compositions of the laminated ores and metamorphic basement, and vented onto the sea floor. Mixing of Fe〈sup〉2+〈/sup〉 from the exhaled metalliferous fluids with H2S from the ambient anoxic seawater resulted in the precipitation of pyrite 1 and 2 crystals above and immediately below the sea floor, respectively, and the formation of laminated ores. This was followed by crystallization of a small proportion of pyrite 3 in the pores within the deep sediment pile.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Paleoproterozoic Monchegorsk Complex in northwest Russia represents one of the largest layered intrusions in Europe and hosts several examples of broadly stratiform platinum group element (PGE) mineralization at different stratigraphic levels of the intrusion that have been suggested to represent reef-style mineralization.The Sopcha reef occurs in the ultramafic lower portion of the complex and constitutes an up to 6-m-thick succession of layered, mineralized dunite, harzburgite, and olivine-orthopyroxenite, with peak grades of 3.4 ppm Pt + Pd and 1.1 wt % Ni. Another PGE occurrence is hosted by the leucogabbronoritic to anorthositic Vuruchuaivench intrusion, which represents part of the mafic upper portion of the Monchegorsk Complex. The disseminated sulfide mineralization reaches up to 7.3 ppm Pt + Pd and is concentrated in several lenticular bodies over a strike length of ~5 km, rather than in a laterally continuous reef as previously suggested. Moreover, our work identified a previously unreported minor enrichment in precious metals of up to 0.2 ppm Pt + Pd in leucogabbroic rocks of the Monchetundra intrusion, which represents the uppermost portion of the Monchegorsk Complex and belongs to the more than 60-km-long mafic Main Ridge.Detailed lithophile and chalcophile element data, coupled with mineral chemistry, indicate that the PGE mineralization at Sopcha and Vuruchuaivench does not represent classic reef-style mineralization, which is commonly narrow and marked by a sharp increase in Cu/Pd ratios, reflecting the in situ sulfide saturation within a large magma chamber. Instead, it is more likely that the Sopcha reef was emplaced as a crustally contaminated and sulfide-saturated, olivine-rich crystal mush that was sourced from a deeper chamber. The Sopcha mineralization is characterized by Pd/Pt 〉 5 and Pd/Ir 〉 55, similar to contact-style mineralization elsewhere in the complex, possibly suggesting a common origin of the sulfides. The mineralized Vuruchuaivench rocks have similar Pd/Pt but much higher Pd/Ir ratios of up to 600, whereas the unmineralized host rocks, below as well as above the mineralization, have Pd/Ir ratios 〈100 and Pd/Pt ratios 〈2. These data indicate that the PGE-rich sulfides did not segregate in situ from the same magma that crystallized the host gabbronorites and anorthosites at Vuruchuaivench. Considering R factor and sulfide fractionation modeling results, we suggest that the mineralized Vuruchuaivench rocks represent a sill-like intrusion of gabbroic crystal mushes, which have entrained fractionated sulfide liquid that is related to an earlier sulfide saturation event.In contrast, the mineralized leucogabbroic rocks from the Monchetundra intrusion are characterized by a sharp increase in Cu/Pd ratios, which is consistent with a classic PGE reef model, in which sulfide saturation was triggered in situ by extensive fractionation and possibly affected the entire magma chamber. Furthermore, the Pd/Ir and Pd/Pt ratios of the mineralized horizon are distinctly lower at 〈66 and 〈1 in comparison to all other types of mineralization in the Monchegorsk Complex. The potential of this mineralization style elsewhere in the Main Ridge remains to be evaluated.〈/span〉

Beschreibung: 〈span〉〈strong〉Mineralogy of Uranium and Thorium〈/strong〉. Robert J. Lauf. Pp. 352. Schiffer Publishing, Ltd. 2016. Hardcover. ISBN 978-0-76-435113-6. US$59.99.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Porphyry Cu deposits form in the shallow crustal parts of arc magmatic systems, which root in the mantle wedge, evolve in lower crustal MASH (melting, assimilation, storage, homogenization) zones and lower to mid-crustal hot zones, and accumulate in mid- to upper crustal batholiths at depths of 5 to 10 km. A small proportion of the magma and most of the volatile load rises toward the surface due to buoyancy, and may erupt as volcanic or fumarolic emissions. Low levels of volcanism and fumarolic activity, as well as subsurface hydrothermal flow and alteration, are normal and semicontinuous features of active arc magmatic systems, which may operate for millions of years. Porphyry Cu deposits, on the other hand, form rarely (typically ≤1 per batholith) and rapidly (≤ 100,000 years) in the subsurface (2–5 km depth), where hydrous volatiles exsolved from the underlying batholith are channeled into structurally controlled cupola zones and cool before reaching the surface. The explosively brecciated character of early mineralization stages (breccia pipes and stockworks) suggests that the initiation of fluid flow may be essentially instantaneous and catastrophic, with the longer total duration of hydrothermal activity reflecting slower kinetically controlled fluid exsolution processes, or draining of deeper parts of the system. These fluids generate intense subsurface hydrothermal alteration, and may precipitate economic concentrations of Cu-sulfide minerals in potassic alteration zones as they cool between ~400° and 300°C.The suddenness and infrequency of these ore-forming hydrothermal events suggest that they are triggered by an external process acting on otherwise normally evolving magmatic systems. Sudden depressurization or agitation of a large, primed, volatile-saturated or supersaturated mid-upper crustal magma chamber could lead to rapid and voluminous volatile exsolution and fluid discharge. This sudden volatile flux could result in either a large explosive volcanic eruption if the surface is breached, or a large magmatic-hydrothermal system that could form a porphyry Cu deposit if fluid flow is restricted to the subsurface. Candidates for triggers of these destabilizing events are catastrophic mass wasting such as volcanic edifice collapse, or mega-earthquakes, the latter possibly causing the former. The frequency of such catastrophic events occurring in proximity to active arc batholiths may approximate the recurrence rate of formation of large porphyry Cu deposits.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Daxueshan deposit is the first magmatic Ni-Cu sulfide deposit that has been discovered in the eastern part of the Tethyan orogenic belt, which stretches from southwest China to Turkey. Although the size of the deposit is small, containing ~0.52 million tonnes of sulfide ore with grades of 0.67 wt % Ni and 0.46 wt % Cu, it provides a unique opportunity to learn more about nickel metallogeny in arcs. The host intrusion of this deposit is composed of gabbro, harzburgite, and lherzolite. Sulfide mineralization occurs as disseminated and massive sulfides (pyrrhotite, pentlandite, and chalcopyrite) in the basal zone of the ultramafic rocks. Sensitive high-resolution ion microprobe U-Pb dating of zircon crystals from the gabbro yields a crystallization age of 300.5 ± 1.6 Ma. The 〈span〉ε〈/span〉〈sub〉Hf〈/sub〉(t) values of these zircon crystals are from −2 to −11. The forsterite contents of olivine from sulfide-bearing (〉0.3 wt % S) and sulfide-barren (〈0.3 wt % S) ultramafic rocks are from 80 to 83 mol % and from 76 to 80 mol %, respectively. Coexisting pyroxenes are bronzite and augite. The Al/Ti ratios of augite from the Daxueshan intrusion and global arc cumulates are similar. Coeval arc basalts in the area are characterized by light rare earth element (REE) enrichments relative to heavy REEs, pronounced negative Nb-Ta anomalies, elevated initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios from 0.7065 to 0.7071, and slightly negative 〈span〉ε〈/span〉〈sub〉Nd〈/sub〉(t) values from −0.8 to −0.3. The Daxueshan mafic-ultramafic rocks have higher initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios from 0.7116 to 0.7139, lower 〈span〉ε〈/span〉〈sub〉N〈/sub〉d(t) values from −5.7 and −7.1, and higher degrees of light REE enrichments. These differences can be explained by higher degrees of crustal contamination (up to 20% more) for the mafic-ultramafic intrusive rocks than the coeval basalts. The 〈span〉δ〈/span〉〈sup〉34〈/sup〉S and 〈span〉γ〈/span〉〈sub〉Os〈/sub〉 values of sulfide separates from the deposit are from −2.6 to 1.2‰ and from 28 to 482, respectively. The former are similar to the typical mantle value (0 ± 2‰), whereas the latter are significantly different from the primitive mantle value, indicating contamination with organic matter-bearing (and hence Os-rich) sedimentary rocks. Olivine chemistry and Sr-Nd-Hf-Os isotope data indicate that fractional crystallization and crustal contamination played a role in triggering sulfide saturation in the Daxueshan magma, although their relative significance is unclear. Like most arc-type magmatic sulfide deposits worldwide, the platinum group element (PGE) tenors of the Daxueshan deposit are extremely low, indicating a severe PGE depletion of the parental magma due to previous sulfide segregation at depth, including the lower part of the arc crust, to form sulfide-bearing, Cu-PGE–rich cumulates. This finding supports the notion that the formation of sulfide-bearing cumulates in the lower part of the arc crust may be a critical step in continent building or the genesis of porphyry ore deposits because new magma or volatiles may cannibalize sulfides from the previous cumulates in the pathway.〈/span〉

Beschreibung: 〈span〉〈strong〉Geology of Mineral Resources.〈/strong〉 Michel Jébrak and Éric Marcoux. Geological Association of Canada, 2015. Pp. 668. ISBN: 978-1-897-09573-7. Price Hardback, CAD$81.81; Members CAD$45.00. (https://www.gac.ca/publications.php)〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Copper Cliff porphyry copper prospect, located 48 km east-southeast from Missoula, Montana, presents two distinct phyllic alteration events: an early green-colored expression, locally texturally destructive and associated with specular hematite and hypogene copper mineralization, and a later white variety generally structurally controlled and associated with pyrite. Variations in the mineral chemistry of white micas were evaluated by short-wave infrared spectroscopy, electron microprobe analysis, and laser ablation-inductively coupled plasmamass spectrometry (LA-ICP-MS). The analytical results allow the identification of a systematic compositional variation of the white micas, possibly controlled by redox changes in the system. The early green phyllic expression consists of Fe-bearing white micas characterized by longer Al-OH absorption wavelength (2,206–2,210 nm) and formed by oxidized magmatic fluids, whereas the late white phyllic phase contains white micas enriched in V and Sc with shorter Al-OH absorption wavelengths (2,197–2,206 nm) formed under less oxidizing conditions. Based on LA-ICP-MS trace element analyses of white micas, Cu concentrations decrease exponentially with distance from the porphyry center, in contrast to Zn, which tends to increase. The application of the Cu/Zn ratio of white micas in a manner analogous to the chlorite proximitor equation of 〈a href="https://pubs.geoscienceworld.org/economicgeology#r62"〉Wilkinson et al. (2015)〈/a〉 allows the estimation to the center of the hydrothermal system within a radial distance of approximately 710 m in samples of the early green phyllic alteration phase and within approximately 1,300 m in samples of the late white phyllic alteration style. Therefore, the Cu/Zn ratio in white micas at Copper Cliff deposit may provide a useful tool for targeting the hydrothermal center.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Copper is vital to modern life and has an often-irreplaceable role in everyday infrastructure and technology. However, while the planet’s Cu endowment is finite, global Cu production continued to increase over the past century—a growth that has been matched by significant growth in estimated Cu mineral reserves and mineral resources. Here, we present a study of 2015 global Cu resources and reserves, updated from a previous paper (〈a href="https://pubs.geoscienceworld.org/economicgeology#r68"〉Mudd et al., 2013a〈/a〉) that outlined global Cu resources for 2010. The 2015 global Cu resource database consists of 2,301 deposits, of which 1,284 have code-based resources and 1,017 have noncode-based resources, with a further 403 of these projects having code-based reserves and a further four having noncode-based reserves. All mineral deposit types within the database have recorded an increase in Cu resources between 2010 and 2015 (except one), although grades are often similar or slightly lower (by ~5%) or are significantly lower, depending on the mineral deposit type considered. Porphyry deposits still dominate global Cu resources and reserves, containing ~75% of the contained Cu in our database. Equally unsurprisingly, Chile dominates global Cu resources and reserves, followed by the United States and Peru. The resources within the database contain some 3,034.7 million tonnes (Mt) of Cu, up from the 1,861.3 Mt reported in our 2010 study, plus we report 640.9 Mt of Cu contained in reserves (included in resources). This is a significant increase, even if all noncode-based resources were removed (i.e., 2,489.4 Mt Cu in code-based projects). There are three main reasons for this increase. First, this study is more comprehensive, with an increase in deposit numbers (730 vs. 2,301). Second, there have been new discoveries made (or rather resources outlined) between 2010 and 2015. Third, a significant proportion of resources within the 2010 study have grown in size (by a mean value of 13%), often coincident with significant amounts of production. This highlights the approaches taken by mining companies that do not delineate entire mineral deposits, especially if the systems are not completely understood, but instead drill out parts of mineralized systems, putting these into production and then often using the revenue to expand resources and reserves. This needs to be factored in when researchers are considering global metal resources, as using snapshots of resource data without considering they will most likely grow over time can often lead to erroneous conclusions. Finally, our study presents key long-term trends in Cu production as well as relationships between production, reserves, and resources. Overall, this study demonstrates that Cu resources continue to grow over time coincident with production, again suggesting that although discovery is important, the other factors that control the conversion of resources to reserves to production (e.g., mineralogic, environmental, political, logistical, and economical) are even more influential in terms of the future supply of Cu.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Porphyry copper deposits consist of low-grade stockwork and disseminated sulfide zones that contain characteristic vein generations formed during the evolution of the magmatic-hydrothermal systems. The present contribution proposes an interpretive framework for the formation of porphyry veins that is based on quartz solubility calculations in the H〈sub〉2〈/sub〉O-NaCl system at temperatures of 100° to 1,000°C and pressures of 1 to 2,000 bar. The model predicts that high-temperature (≳500°C) quartz in A veins of deep (≳4 km) porphyry deposits forms as a result of the cooling of ascending intermediate-density fluids at lithostatic conditions. In deposits of intermediate depths (~1.5–4 km), A vein quartz is mostly formed through cooling of ascending hydrothermal fluids under closed-system conditions or quasi-isobaric cooling under open-system conditions within the two-phase field of the H〈sub〉2〈/sub〉O-NaCl system. In shallow (≲1.5 km) porphyry deposits, rapid decompression can also result in quartz precipitation, forming so-called banded veins. The high-temperature quartz in A veins is associated with potassic alteration. During continued cooling of the magmatic-hydrothermal system, quartz is formed at intermediate temperatures (≳375°–500°C). This quartz overprints earlier A veins and forms B veins. The fluid inclusion inventory of this quartz generation suggests formation at fluctuating pressure conditions, marking the lithostatic to hydrostatic transition, and the change of wall-rock behavior from ductile to brittle conditions. The quartz is precipitated because of cooling and decompression of the magmatic-hydrothermal fluids under K-feldspar-stable conditions. Textural evidence from many porphyry veins suggests that hypogene sulfide minerals present in A and B veins postdate the quartz, as contacts between quartz and sulfide minerals commonly show dissolution textures. Hypogene sulfide minerals in C veins form at conditions of retrograde quartz solubility, explaining why these veins contain little to no quartz. The quartz solubility calculations suggest that C vein formation occurs at temperatures of ~375° to 450°C from low-salinity, single-phase fluids escaping from the lithostatic to the hydrostatic environment. At the upper end of this temperature range, C veins are biotite stable. However, these veins are associated with chlorite, chlorite-K-feldspar, or chlorite-sericite alteration in most deposits. Late quartz is formed during continued cooling of the hydrothermal fluids at ≲375°C within the single-phase field of the H〈sub〉2〈/sub〉O-NaCl system as quartz solubility under these conditions decreases with temperature. This process is responsible for the formation of quartz in D veins and later base metal-bearing E veins, which are associated with phyllic, advanced argillic, or argillic alteration.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Red Chris porphyry Cu-Au deposit is located in the Stikinia island-arc terrane in northwest British Columbia. It is hosted by the Red Stock, which has five phases of porphyry intrusions: P1, P2E, P2I, P2L, and P3. New U-Pb dating of zircon shows that these intrusions were emplaced over a ~10 m.y. period, with P1 intruded at 211.6 ± 1.3 Ma (MSWD = 0.85), P2I at 206.0 ± 1.2 Ma (MSWD = 1.5), P2L at 203.6 ± 1.8 Ma (MSWD = 1.5), and P3 at 201.7 ± 1.2 Ma (MSWD = 1.05). The ore-forming event at Red Chris was a short-lived event at 206.1 ± 0.5 Ma (MSWD = 0.96; weighted average age of three Re-Os molybdenite analyses), implying a duration of 〈1 m.y., as defined by the uncertainty range, coincident with the emplacement age of the P2 porphyries.Zircons from P1 to P3 porphyry rocks have consistently high Eu〈sub〉N〈/sub〉/Eu〈sub〉N〈/sub〉* ratios (mostly 〉 0.4), indicating that their associated magmas were moderately oxidized. The magmatic water contents estimated from plagioclase and amphibole compositions suggest H〈sub〉2〈/sub〉O contents of ~5 wt %. Taken together, the P1 to P3 porphyries are interpreted to be moderately oxidized and hydrous.The porphyry phases are differentiated by sulfur and chlorine contents. The SO〈sub〉3〈/sub〉 contents of igneous apatite microphenocrysts from the mineralization-related P2 porphyries are higher (P2E: 0.28 ± 0.10 wt %, 〈span〉n〈/span〉 = 19; P2I: 0.32 ± 0.17, 〈span〉n〈/span〉 = 15; P2L: 0.29 ± 0.18 wt %, 〈span〉n〈/span〉 = 100) than those from the premineralization P1 (0.11 ± 0.03 wt %, 〈span〉n〈/span〉 = 34) and postmineralization P3 porphyries (0.03 ± 0.01 wt %, 〈span〉n〈/span〉 = 13). The chlorine contents in apatite grains from the P2E, P2I, and P2L porphyries are 1.47 ± 0.22 (n = 19), 0.82 ± 0.10 (n = 15), and 1.47 ± 0.28 wt % (n = 100), also higher than those from P1 (0.51 ± 0.3 wt % Cl, 〈span〉n〈/span〉 = 34) and P3 (0.02 ± 0.02 wt % Cl, 〈span〉n〈/span〉 = 17). These results imply that the sulfur and chlorine contents of the P2 magmas were higher than in the P1 and P3 magmas, suggesting that elevated magmatic S-Cl contents in the P2 porphyries may have been important for ore formation. Although the process that caused the increase in sulfur and chlorine is not clear, reverse zoning seen in plagioclase phenocrysts from the P2 porphyry, and the occurrence of more mafic compositions in P2L, suggest that recharge of the deeper magma chamber by a relatively S-Cl-rich mafic magma may have triggered the ore-forming hydrothermal event.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉We present the first systematic characterization of the Fe isotope composition of magmatic pyrrhotite for the application of Fe isotopes to the origin and evolution of magmatic sulfide deposits. Iron isotopes provide constraints on redox, temperature, fluid exsolution, fractional crystallization, and intermineral diffusion at magmatic or subsolidus conditions. Paired with S isotopes, Fe isotopes have proven to be useful tracers of crustal contamination in bulk magmatic sulfide. Relative and specific Fe isotope values exist for major Fe-bearing igneous minerals; however, there is a paucity of well-constrained Fe isotope data for sulfides. Recent studies indicate that pyrrhotite will strongly influence the Fe isotope systematics of magmatic systems, yet there are few published 〈span〉δ〈/span〉〈sup〉56〈/sup〉Fe values (〈sup〉56〈/sup〉Fe/〈sup〉54〈/sup〉Fe in the sample relative to IRMM-14) of natural pyrrhotite. To provide this fundamental information, we report the first dataset for magmatic pyrrhotite from nine deposits of various origins and ages. The 〈span〉δ〈/span〉〈sup〉56〈/sup〉Fe value of pyrrhotite samples (〈span〉n〈/span〉 = 17) ranges from –0.55 ± 0.04‰ to +0.05 ± 0.03‰, and reflects the composition of the sulfide, variable degrees of assimilation, and crystallization history of each deposit. Only the impact-related Sudbury deposit shows especially light 〈span〉δ〈/span〉〈sup〉56〈/sup〉Fe values for pyrrhotite (–0.89 ± 0.04‰; (–0.62 ± 0.04‰; 〈span〉n〈/span〉 = 2). A modeling approach using these new data confirms the potentially strong influence of pyrrhotite on the Fe isotope systematics of a magmatic system. A global dataset of pure individual sulfide minerals will aid in more accurately tracing the processes at play in the formation and evolution of deposits containing magmatic sulfide.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Nanling region is the largest W-Sn metallogenic district on Earth and hosts several giant W-Sn deposits, all except one of which are spatially and genetically associated with highly evolved Mesozoic granitic stocks. Volumetrically, however, Caledonian granites (Paleozoic), mainly batholiths, approach their Mesozoic equivalents in importance and have been the target of recent exploration. This has resulted in the discovery of a number of economic W-Sn deposits in or near the Caledonian batholiths, including the giant Zhangjialong deposit, which is located on the southern margin of the Penggongmiao granite batholith. The unresolved question is whether this is evidence for an important Caledonian epoch of W-Sn mineralization. In this contribution, we report the results of high-precision secondary ion mass spectrometry (SIMS) zircon U-Pb, muscovite Ar-Ar, and molybdenite Re-Os age determinations that constrain the timing relationships among granitic magmatism, greisenization, and W mineralization related to the Zhangjialong deposit. The molybdenite Re-Os age of the W mineralization is 160.2 ± 2.2 Ma, which is similar to, albeit slightly older than, the muscovite Ar-Ar age of the greisen (153.5 ± 1.0 Ma). These ages, however, are considerably younger than the zircon SIMS U-Pb age of 441.3 ± 2.4 Ma for the spatially associated granite. These data demonstrate that the W mineralization and greisenization of the Zhangjialong W deposit is of Late Jurassic rather than Silurian age, which precludes a temporal and genetic link between the hydrothermal W mineralization and the regional Caledonian magmatism. Instead, the W mineralization is interpreted to be genetically related to a hidden Late Jurassic granitic pluton. A compilation of published whole-rock geochemical data indicates that the large granite batholiths are less differentiated and poorer in W and Sn than the W-Sn bearing granite stocks, irrespective of whether they are Paleozoic or Mesozoic in age. This suggests that the metallogenic potential of the large granitic batholiths is limited, and that W-Sn deposits hosted within granite batholiths are likely to be genetically related to highly evolved granitic stocks that in some cases have not been exposed.〈/span〉

Beschreibung: 〈span〉〈strong〉Geological Belts, Plate Boundaries, and Mineral Deposits in Myanmar〈/strong〉. A.H.G. Mitchell. Pp. 508. Elsevier, 2018. Hardcover. ISBN 978-0-12-803382-1. US$127.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉Vein and stratabound Zn-Pb sulfides are hosted within siliciclastic rocks and marine carbonates of Cretaceous age and within caprock carbonates at the margins of the Murguía and Orduña saline diapirs in the Basque-Cantabrian basin. Organic matter is ubiquitous, and textures indicate a genetic link to sulfide precipitation. Sulfides (pyrite, sphalerite, and galena) precipitated from brines with halogen ratios compatible with halite dissolution. Thermal indicators (fluid inclusion, organic matter, and sulfur isotope data), point to formation temperatures between 150° and 200°C.The 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values of sphalerite and galena (4.1–15.1‰) suggest a sulfur source related to the reduction of evaporite sulfate (thermochemical sulfate reduction) of Triassic age (15.3–17.4‰). The interaction of carbon-poor, metal- and sulfate-bearing hot brines with host rocks activated the cracking of organic matter, triggering sulfide precipitation at a rate controlled by the H〈sub〉2〈/sub〉S production.Textural relationships suggest that ore precipitation was related to dolomitization of host rocks (siliciclastic rocks, marine carbonates, and caprock). The 〈span〉δ〈/span〉〈sup〉13〈/sup〉C and d〈sup〉18〈/sup〉O of carbonates range from 3.5 to –20.5‰ and from 16.1 to 28.7‰, respectively, indicative of different carbon sources and host-rock types. Carbonates associated with sulfide mineralization depict 〈span〉δ〈/span〉〈sup〉13〈/sup〉C/〈span〉δ〈/span〉〈sup〉18〈/sup〉O assemblages and 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios (0.70801–0.71202) resulting from the interaction of a basinal brine with the different host rocks. Galena Pb isotope ratios—〈sup〉206〈/sup〉Pb/〈sup〉204〈/sup〉Pb from 18.643 to 18.696, 〈sup〉207〈/sup〉Pb/〈sup〉204〈/sup〉Pb from 15.650 to 15.676, and 〈sup〉208〈/sup〉Pb/〈sup〉204〈/sup〉Pb from 38.720 to 38.780—point to metal source rocks similar to other Mississippi Valley-type (MVT) deposits of the Basque-Cantabrian basin.Sulfide concentrations around the Murguía and Orduña diapirs are not concomitant with caprock formation but with dolomitization, as in MVT deposits. This is in contrast with the diapir-related deposits of the Gulf Coast and shares characteristics with the diapir-related mineralization in North Africa.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Triassic Pulang porphyry Cu-Au deposit, located in the South Yidun terrane, is the oldest and one of the largest porphyry deposits in the southeastern Tibetan Plateau. The mineralization occurs mostly in the potassic alteration zone of the Pulang intrusive complex. U-Pb-He triple dating, namely apatite (U-Th)/He, zircon U-Pb, and zircon (U-Th)/He dating, together with inverse thermal modeling, reveals that the Pulang complex was emplaced at a paleodepth of ~5.0 to 6.5 km at 215 ± 2 Ma. The deep-level emplacement of the complex, coupled with the episodic replenishment of the magma chamber, gave rise to the establishment of a prolonged magmatic-hydrothermal system at Pulang.Although a range of single-grain zircon and apatite (U-Th)/He ages were obtained on each sample, the weighted mean zircon and apatite (U-Th)/He ages vary systematically with elevation, defining a multistage cooling/denudation history at Pulang. Specifically, three phases of cooling were recognized from inverse thermal modeling, including rapid cooling (80°–120°C/m.y.) in the Late Triassic, moderate cooling (3°–5°C/m.y.) from the Late Triassic to Early Cretaceous, and a protracted slow cooling period (〈1°C/m.y.) from the Early Cretaceous to the present day. The first phase of cooling can be mainly attributed to magmatic cooling, whereas the later two phases of cooling were predominantly controlled by uplift and denudation processes. Moreover, the remarkable decrease in the cooling rate from the second to the third phase can be linked to a decreasing erosion rate during the third phase, supported by age-elevation relationships. Overall, our results indicate that the Pulang complex experienced two stages of exhumation at 33 to 45 m/m.y. and 5 to 17 m/m.y. Based on these data, we estimate that approximately 558- to 1,099-m thickness of materials have been removed from the Pulang complex during uplift and erosion, including a large volume of ore.The long time span (〉50 m.y.) of extremely slow cooling and erosion at Pulang could be related to the formation and preservation of a peneplain on the southeastern Tibetan Plateau since the Late Cretaceous. A relict peneplain thus signifies a favorable tectonic environment for the preservation of ancient porphyry systems worldwide.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Tamarack Intrusive Complex (1105 ± 1.2 Ma), in northeastern Minnesota, occurs within the Midcontinent rift system and hosts potentially economic Ni-Cu-(PGE) mineralization. The system represents “conduit-style” mineralization and with 1.3 wt % Ni, 0.7 wt % Cu, 0.3 ppm Pt, and 0.25 ppm Pd, is similar in many aspects to the Eagle deposit in Michigan. Sulfur, O, and Os isotopes have been used to evaluate the role of crustal contamination in promoting sulfide liquid saturation. All of the types of mineralization in the Tamarack Intrusive Complex are characterized by 〈span〉δ〈/span〉〈sup〉34〈/sup〉S values between –0.2 and 2.8‰, values that are not strongly anomalous relative to uncontaminated mantle values near 0‰. The values are very similar to those from the Eagle deposit, but contrast sharply with values of disseminated sulfides in intrusions of the Duluth Complex and Crystal Lake Gabbro, which may be as elevated as 17‰. Initial 〈sup〉187〈/sup〉Os/〈sup〉188〈/sup〉Os ratios in the Tamarack Intrusive Complex are between 4 and 44% higher than the same ratio of the undepleted primitive mantle at 1105 Ma and correspond to gamma Os values for all magmatic sulfide types from the Tamarack Intrusive Complex ranging from 10 to 92. These values are consistent with crustal contamination but for S, the isotopic ratios are remarkably lower than those from mineralization in the Duluth Complex, where initial 〈sup〉187〈/sup〉Os/〈sup〉188〈/sup〉Os ratios are more than 110% higher than that of primitive mantle and 〈span〉γ〈/span〉〈sub〉Os〈/sub〉 values may be in excess of 1,000. Olivine from an unmineralized but sparsely serpentinized portion of the Tamarack Intrusive Complex has O isotope compositions from 5.2 to 5.5‰, indicating a fraction of a percent crustal contamination of the parental magma.The striking contrast between Os-S isotope systematics in conduit-type deposits associated with the intrusions that formed during the Main stage in the history of the rift is a primary characteristic of these ore systems and as such is important to explain by a geologic model. High Re and Os contents are found in sulfide minerals and organic matter in the sedimentary country rocks. Selective contamination via partial melting and devolatilization involving these phases could have been responsible for S and Re-Os transfer from country rocks to the sulfides without affecting the silicate magma. Therefore, the contamination of the system may have been an order of magnitude greater than that recorded by the silicate portion of the system. Alternatively, the rather low degrees of crustal contamination indicated by the Re-Os and S systems in the Eagle intrusion and the Tamarack Intrusive Complex may also be related to isotopic exchange between contaminated and pristine magmas in the conduit system during the Early stage of the rift development. The high Ni grades of the complex are in part related to the dynamic conduit environment and contamination of picritic magmas promoting sulfide saturation before large quantities of Ni were sequestered by olivine.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The unconformity-related U deposits associated with the Proterozoic Athabasca Basin are among the largest and richest U deposits in the world. The conventional genetic model suggests that mineralization occurred under deep-burial (〉5 km), diagenetic-hydrothermal conditions at normal geothermal gradients (~35°C/km). Based on regional geochronostratigraphic and ore geochronological data, it is inferred that, at the time of primary U mineralization (≥ ca. 1540 Ma), the burial depths of the unconformity surface were likely 〈~3 km. The elevated fluid pressures (up to 1,500 bars) used to support the deep-burial model were probably overestimated due to misinterpretation of accidentally entrapped halite crystals as daughter minerals in fluid inclusions. The elevated fluid temperatures (180°–250°C) estimated from fluid inclusion and clay mineral geothermometry from both mineralized and barren areas, which were interpreted to have resulted from deep burial at normal geothermal gradients at the time of mineralization, may be alternatively explained by local or basin-scale elevation of geothermal gradients at the time of mineralization, followed by continued burial and/or temporarily increased thermal gradients after mineralization. The shallow-burial mineralization model can better explain the geologic characteristics of the unconformity-related U deposits, including development of pervasive clay alteration halos, breccia zones, and dissolution vugs locally filled with drusy quartz, as well as evidence of fluid boiling recorded by fluid inclusions. The modified model emphasizes the importance of combined basinal (development of brines) and deep-seated geodynamic factors for large-scale U mineralization. Recognition of these factors is important for U exploration in the Athabasca Basin and similar basins elsewhere.〈/span〉

Beschreibung: 〈span〉〈div〉Abstract〈/div〉The Daqiao gold deposit is hosted in organic-rich Triassic pumpellyite-actinolite facies metamorphosed turbidites in the West Qinling orogen, central China. Gold mineralization is characterized by high-grade hydraulic breccias (B and C ores) that overprint an earlier tectonic breccia (A ore). A complex paragenesis is defined by four sulfide stages: S1 diagenetic preore pyrite (py), S2 hydrothermal early ore disseminated pyrite and marcasite (mc), S3 main ore pyrite and marcasite aggregates, and S4 late ore coarse-grained marcasite with minor pyrite and stibnite. However, multiple generations of pyrite and marcasite may develop within one individual stage. Ore-related hydrothermal alteration is dominated by intensive silicification, sulfidation, sericitization, and generally distal minor carbonatization.Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) trace element analyses show that the stage S1 py1 from the shale interlayers within turbidites contains low gold contents (mean of 0.05 ppm) and other trace elements (Mn, Co, Ni, Cu, Mo, Bi, and Pb), indicating an anoxic to euxinic sedimentary environment. Stage S2 contributed only minimally to the gold endowment with relatively low gold in various sulfides including py2 (mean of 0.09 ppm), py3 (0.84 ppm) to py4 (0.70 ppm), along with mc1 (0.02 ppm) and mc2 (0.14 ppm). Most of the gold was deposited in stage S3, which formed rapidly crystallized, irregular (e.g., framboids, colloform and cyclic zonation) cement-hosted py5a (mean of 27.35 ppm), py5b (9.71 ppm), and mc3 (5.94 ppm) during repeated hydraulic fracturing. Other trace elements (e.g., Ag, As, Sb, Hg, Tl, and W) are also significantly enriched in the main ore-stage pyrite and marcasite. Little or no gold is detected in the S4 py6 and mc4.Sulfur isotopes determined from in situ LA-multicollector (MC)-ICP-MS analyses of hydrothermal pyrite and marcasite from the Daqiao deposit vary significantly from –31.3 to 22.0‰ (〈span〉δ〈/span〉〈sup〉34〈/sup〉S values) but fall mostly between –10 to 10‰ and provide important information on the source and evolution of sulfur and of the ore-forming fluids. The results show that S2 ore fluids (mean 〈span〉δ〈/span〉〈sup〉34〈/sup〉S〈sub〉sulfide〈/sub〉 = –0.8 to 5.2‰) were most likely derived from deep-seated Paleozoic carbonaceous sediments during regional metamorphism associated with orogenesis of the West Qinling orogen. Main ore S3 fluids (mean 〈span〉δ〈/span〉〈sup〉34〈/sup〉S〈sub〉sulfide〈/sub〉 = –9.7 to –6.0‰) are relatively depleted in 〈sup〉34〈/sup〉S relative to those of S2, presumably due to fluid oxidation associated with hydraulic fracturing caused by the overpressurized fluids.The textural, chemical, and isotopic data indicate two distinct gold-introducing episodes at Daqiao, forming sulfide disseminations during early ore S2 and cement-hosted sulfide aggregates during main ore S3. The S2 mineralization took place in a tectonic breccia beneath low-permeability shale seals that capped the flow of deep-seated metamorphic fluids, facilitating reaction with preexisting carbonaceous material and the host turbidites to form sulfide disseminations and pervasive silicification. Raman spectroscopy analysis suggests that carbonaceous material in the ores is poorly crystallized, with low maturity, giving estimated temperatures of 283° to 355°C that are much higher than those of the ore fluids (100°–240°C). This temperature difference indicates an in situ sedimentary origin modified by the regional pumpellyite-actinolite facies metamorphism for the carbonaceous material in the host rocks, rather than a hydrothermal origin. In S3, continuous flux of hydrothermal fluids caused fluid overpressure and consequent hydraulic fracturing of the competent silicified rocks. Subsequent rapid fluid pressure fluctuations led to phase separation and thus massive oxidation of ore fluids, which triggered fast precipitation of gold and other trace elements within the fine-grained irregular sulfides. Results presented here, in combination with geologic evidences, suggest that the Daqiao gold deposit can be best classified as the shallow-crustal epizonal orogenic type, genetically associated with orogenic deformation and regional metamorphism of the West Qinling orogen.〈/span〉

Beschreibung: Infections arising from multidrug-resistant pathogenic bacteria are spreading rapidly throughout the world and threaten to become untreatable. The origins of resistance are numerous and complex, but one underlying factor is the capacity of bacteria to rapidly export drugs through the intrinsic activity of efflux pumps. In this Review, we describe recent advances that have increased our understanding of the structures and molecular mechanisms of multidrug efflux pumps in bacteria. Clinical and laboratory data indicate that efflux pumps function not only in the drug extrusion process but also in virulence and the adaptive responses that contribute to antimicrobial resistance during infection. The emerging picture of the structure, function and regulation of efflux pumps suggests opportunities for countering their activities.

Beschreibung: Arctic permafrost caps vast amounts of old, geologic methane (CH4) in subsurface reservoirs. Thawing permafrost opens pathways for this CH4 to migrate to the surface. However, the occurrence of geologic emissions and their contribution to the CH4 budget in addition to recent, biogenic CH4 is uncertain. Here we present a high-resolution (100 m × 100 m) regional (10,000 km²) CH4 flux map of the Mackenzie Delta, Canada, based on airborne CH4 flux data from July 2012 and 2013. We identify strong, likely geologic emissions solely where the permafrost is discontinuous. These peaks are 13 times larger than typical biogenic emissions. Whereas microbial CH4 production largely depends on recent air and soil temperature, geologic CH4 was produced over millions of years and can be released year-round provided open pathways exist. Therefore, even though they only occur on about 1% of the area, geologic hotspots contribute 17% to the annual CH4 emission estimate of our study area. We suggest that this share may increase if ongoing permafrost thaw opens new pathways. We conclude that, due to permafrost thaw, hydrocarbon-rich areas, prevalent in the Arctic, may see increased emission of geologic CH4 in the future, in addition to enhanced microbial CH4 production.

Beschreibung: Sponges (Porifera) are abundant and diverse members of benthic filter feeding communities in most marine ecosystems, from the deep sea to tropical reefs. A characteristic feature is the associated dense and diverse prokaryotic community present within the sponge mesohyl. Previous molecular genetic studies revealed the importance of host identity for the community composition of the sponge-associated microbiota. However, little is known whether sponge host-specific prokaryotic community patterns observed at 97% 16S rRNA gene sequence similarity are consistent at high taxonomic ranks (from genus to phylum level). In the present study, we investigated the prokaryotic community structure and variation of 24 sponge specimens (seven taxa) and three seawater samples from Sweden. Results show that the resemblance of prokaryotic communities at different taxonomic ranks is consistent with patterns present at 97% operational taxonomic unit level.