ALBERT

Description: The stability of the West Antarctic Ice Sheet is threatened by the incursion of warm Circumpolar Deepwater which flows southwards via cross-shelf troughs towards the coast there melting ice shelves. However, the onset of this oceanic forcing on the development and evolution of the West Antarctic Ice Sheet remains poorly understood. Here, we use single- and multichannel seismic reflection profiles to investigate the architecture of a sediment body on the shelf of the Amundsen Sea Embayment. We estimate the formation age of this sediment body to be around the Eocene-Oligocene Transition and find that it possesses the geometry and depositional pattern of a plastered sediment drift. We suggest this indicates a southward inflow of deep water which probably supplied heat and, thus, prevented West Antarctic Ice Sheet advance beyond the coast at this time. We conclude that the West Antarctic Ice Sheet has likely experienced a strong oceanic influence on its dynamics since its initial formation.

Description: New inorganic and organic geochemical data from thucholite in the Upper Permian (Wuchiapingian) Kupferschiefer (T1) shale collected at the Polkowice-Sieroszowice Cu-Ag mine in Poland are presented. Thucholite, which forms spherical or granular clusters, appears scattered in the T1 dolomitic shale at the oxic-anoxic boundary occurring within the same shale member. The composition of thucholite concretions and the T1 shale differs by a higher content of U- and REE-enriched mineral phases within the thucholite concretions compared to the T1 shale, suggesting a different mineralising history. The differences also comprise higher Ntot, Ctot, Htot, Stot contents and higher C/N, C/S ratios in thucholite than in the T1 shale. The hydrocarbon composition of the thucholite and the surrounding T1 shale also varies. Both are dominated by polycyclic aromatic compounds and their phenyl derivatives. However, higher abundances of unsubstituted polycyclic aromatic hydrocarbons in the thucholite are indicative of its pyrogenic origin. Pyrolytic compounds such as benz[a]anthracene or benzo[a]pyrene are more typical of the thucholite than the T1 shale. Microscopic observations of the thucholite and its molecular composition suggest that it represents well-rounded small charcoal fragments. These charcoals were formed during low-temperature combustion, as confirmed by semifusinite reflectance values, indicating surface fire temperatures of about 400 °C, and the absence of the high-temperature pyrogenic polycyclic aromatic hydrocarbons. Charred detrital particles, likely the main source of insoluble organic matter in the thucholite, migrated to the sedimentary basin in the form of spherical carbonaceous particulates, which adsorbed uranium and REE in particular, which would further explain their different contents and sorption properties in the depositional environment. Finally, the difference in mineral content between thucholite and the T1 shale could also have been caused by microbes, which might have formed biofilms on mineral particles, and caused a change in the original mineral composition.

Description: Light pollution has increased globally, with 80% of the total population now living under light-polluted skies. In this Review, we elucidate the scope and importance of light pollution and discuss techniques to monitor it. In urban areas, light emissions from sources such as street lights lead to a zenith radiance 40 times larger than that of an unpolluted night sky. Non-urban areas account for over 50% of the total night-time light observed by satellites, with contributions from sources such as transportation networks and resource extraction. Artificial light can disturb the migratory and reproductive behaviours of animals even at the low illuminances from diffuse skyglow. Additionally, lighting (indoor and outdoor) accounts for 20% of global electricity consumption and 6% of CO2 emissions, leading to indirect environmental impacts and a financial cost. However, existing monitoring techniques can only perform a limited number of measurements throughout the night and lack spectral and spatial resolution. Therefore, satellites with improved spectral and spatial resolution are needed to enable time series analysis of light pollution trends throughout the night.

Description: Pyrite is a ubiquitous sulfide mineral found in diverse geological settings and holds great significance in the formation of Au deposits as well as the safe utilization of groundwater due to its remarkable ability to incorporate substantial amounts of As. However, despite its importance, there remains a dearth of fundamental data on the partitioning of As between pyrite and fluid, which is key for accurately modeling the As distribution in these environments. Here, we present new insights into the partitioning behavior of As between pyrite and fluid at conditions that mimic natural fluid systems. Pyrite was synthesized by replacement of natural siderite in hydrothermal experiments at 200 °C and pH 5 applying a wide range of fluid As concentrations, spanning from 0.001 to 100 µg/g. The As distribution and concentration in synthetic pyrite was analyzed by quantitative LA-ICP-MS mapping providing a high spatial resolution and sensitivity at 2–3 µm image pixel size at a detection limit of ∼1 µg/g at the single pixel scale. Pyrite-fluid partitioning coefficients (DAs(py/fluid)) between synthetic pyrite and experimental fluid agree with previously published data for high fluid As concentrations of 1 µg/g to 100 µg/g (DAs 〈 2000). However, at low As concentrations in the experimental fluid (〈1 µg/g), a steep increase in the DAs(py/fluid) values of up to ∼30,000 was detected, demonstrating even stronger As partitioning into pyrite. This is confirmed by the analyses of natural pyrite that precipitated from As-poor fluids (0.3–0.4 ng/g) within a deep anoxic aquifer in SE Sweden. The discovery holds significant implications for the mobility and scavenging of As, which in turn is important for understanding the formation and fingerprinting of mineral deposits as well as for the secure utilization of groundwater resources.

Description: Aragonite (CaCO3) is a stable calcium carbonate phase under high pressure conditions. However, its formation in (sub)surface environments, where calcite is the stable polymorph, is widespread. Regardless of its origin, aragonite is expected to undergo transformation into calcite under moderate pressures and temperatures. However, this transformation does not always take place, which results in the presence of abundant aragonitic relics in the geological record. Traditionally, this preservation has been explained by the presence of chemical inhibitors that prevent the conversion of aragonite to calcite. While it is widely accepted that magnesium (Mg) plays a key role in the polymorphic selection of CaCO3, the influence of other ions has also been suggested. This work evaluates the effect that different concentrations of sulfate (SO42−) in the fluid has on the progress of the aragonite-to-calcite transformation at 220 °C. Our results show that, upon reaction with deionized water or sulfate-poor solutions ([SO42−]aq 〈 0.1 mM), aragonite single crystals are extensively replaced by calcite aggregates (crystal size 〉 15 µm) through an interface coupled dissolution-precipitation reaction. The replacement starts at the aragonite crystal surfaces and advances inwards thanks to the development of an extensive network of fractures. Contrarily, when the solution bears higher concentrations of sulfate ([SO42−]aq 〉 0.1 mM), only a thin layer of smaller crystals of calcite (〈 10 µm) form on the aragonite substrates, without any further transformation taking place. We interpret that these smaller crystals exert too little crystallization pressure and fail to promote the development of a network of fractures. In the absence of this network, the aragonite-calcite transformation cannot take place. The transformation does not occur neither when the experiments are conducted with deionized water and fragments of gypsum or anhydrite together with the aragonite grains. The results of this study shed light on the influence of dissolved sulfate in the kinetics of the fluid-driven transformation of aragonite into calcite. These results are useful to understand the preservation of aragonite in a variety of current geological settings and provide valuable insights for better understanding the diagenesis of sedimentary carbonates.

Description: Important features of Sn mineralization are the heterogeneous geographic distribution and frequent regional separation from W mineralization in spite some similarities of Sn and W behavior during magmatic processes. Major Sn and W mineralization is often spatially associated with peraluminous granites, which are derived from partial melting of metasediments. Several concepts have been suggested to explain those features, such as a weathering-related Sn-enriched source, Sn redistribution between melts and restite during protolith melting, and extensive fractional crystallization. We demonstrate the importance of protolith composition for the formation of Sn (and W) granites by using a comprehensive bulk-rock composition dataset from Precambrian metasediments of the South China Sn-W province and employing a thermodynamic modeling approach. We used four compositional proxies for phase equilibria calculations, which are the metasediments of the Mengdong, Sibao, Pingbian, and Shuangqiaoshan Groups. It is well documented that those Precambrian metasediments are important protoliths of Sn granites in South China. We present quantitative evaluation of the control of protolith composition in the generation of Sn-enriched granitic melts using South China as example, but our conclusions may also be applicable to worldwide Sn–enriched granites. Our results indicate that the protolith major-element geochemistry controls the anatectic reactions and melt productivity at specific melting conditions, and consequently the partitioning behavior of Sn. Further, pre-enrichment of Sn is crucial to the fertility of granitic melt and may be a prerequisite, particularly for the formation of giant Sn deposits. We propose that the heterogeneous distribution of favorable source rocks is one of the important factors that control the spatial distribution of major Sn (and W) districts in South China and other regions worldwide.

Description: The evolution of topography in forearc regions results from the complex interplay of crustal and mantle processes. The Southern Apennines represent a well‐studied forearc region that experienced several tectonic phases, initially marked by compressional deformation followed by extension and large‐scale uplift. We present a new structural, geomorphic and fluvial analysis of the Pollino Massif and surrounding intermontane basins (Mercure, Campotenese and Castrovillari) to unravel their evolution since the Pliocene. We constrain multiple tectonic transport directions, evolution of the drainage, and magnitude and timing of long‐ term incision following base level falls. Two sets of knickpoints suggest two phases of base level lowering and allow to estimate ∼500 m of long‐term uplift (late Pleistocene), as observed in the Sila Massif. On a smaller spatial scale, the evolution and formation of topographic relief, sedimentation, and opening of intermontane basins is strongly controlled by the recent increase in rock uplift rate and fault activity. At the regional scale, an along‐strike, long‐wavelength uplift pattern from north to south can be explained by progressive lateral slab tearing and inflow of asthenospheric mantle beneath Pollino and Sila, which in turn may have promoted extensional tectonics. The lower uplift of Le Serre Massif may be explained as result of weak plate coupling due to narrowing of the Calabrian slab. The onset of uplift in the Pollino Massif, ranging from 400 to 800 ka, is consistent with that one proposed in the southern Calabrian forearc, suggesting a possible synchronism of uplift, and lateral tearing of the Calabrian slab.

Description: We address the possible link between the age of subducting oceanic lithosphere and growth of elevated cordilleras versus extension-dominated arc regions. Singularity exists in South America: the lowest elevated Andean segments are found in Patagonia where the active Chile Ridge enters the trench. Subduction of active ridge triggers thermal doming, crustal extension and attenuation of former cordilleras. At the Antarctica–South America connection, three active ridge subductions induced the disruption of a former continuous cordillera during the opening of Drake Passage. Active ridge subduction induces lithosphere thermal erosion and related crustal extension in the upper plate. Evolution of regions worldwide experiencing ridge subduction confirms this hypothesis.

Description: Robust chronologies and time equivalent tephra markers are essential to better understand spatial palaeoenvironmental response to past abrupt climatic changes. Identification of well-dated and widely dispersed volcanic ash by tephra and cryptotephra (microscopic volcanic ash) provides time synchronous tie-points and strongly reduces chronological uncertainties. Here, we present the major, minor and trace element analyses of cryptotephra shards in the Dead Sea Deep Drilling sedimentary record (DSDDP 5017-1A) matching the Campanian Ignimbrite (CI). This geochemical identification expands the known dispersal range of the CI to the southeastern Mediterranean, over 2300 km from the volcanic source. Due to the CI eruption occurring near-synchronous with North Atlantic ice surge of Heinrich Event 4 (HE4), this tephra provides insights into regional responses to large-scale climatic change in the Mediterranean. In the Dead Sea, the CI layer is associated with wetter climatic conditions. This contrasts with the contemporaneous occurrence of the CI deposition and dry conditions in the central and eastern Mediterranean suggesting a possible climate time-transgressive expansion of HE4. Our finding underscores the temporal and spatial complexity of regional climate responses and emphasises the importance of tephra as a time marker for studying large-scale climatic changes verses regional variations.

Description: Since 2018, large parts of Europe have experienced below-average annual precipitation and above-average air temperatures. These phenomena were accompanied by falling water levels in lakes and groundwater, low flow conditions in rivers, damage to ecosystems and negative impacts in various economic sectors, leading to a public debate on the current and future availability of water resources. In Germany, this debate has been boosted by media reports on drastically decreasing terrestrial water storage (TWS) based on satellite gravimetry of GRACE and GRACE-FO, in which results based on data of the U.S. analysis center JPL (JPL Mascons data) indicate a TWS decrease of -2.4 Gt/year for Germany from 11/2002 to 10/2021. To provide a more robust scientific basis for the ongoing debatethis paper first introduces the concept of satellite gravimetry, including its potential and limitations. Besides the JPL Mascons data, we then analyze three other GRACE and GRACE-FO data products (COST-G, GFZ and ITSG Graz / University of Bonn), resulting in German-wide TWS trends of -0.7 to -1.3 Gt/year for this period. Due to the measurement and processing principles, satellite gravimetry also captures mass changes beyond the area of interest, so that Alpine glacier mass loss leads to spuriously more negative TWS trends for Germany, which were corrected in the present analysis. The spread of results based on different data products illustrates the uncertainty of GRACE data so that a comparative analysis of different data sets is recommended. The markedly different results of the JPL-Mascons data set may be due to its processing method that differs from the other data sets in several aspects. In view of extreme positive TWS anomalies in 2002 due to high rainfall and very negative anomalies in the drought years 2018 and 2019, the resulting trend values are strongly dependent on the selected time period. A longer TWS time series for Germany simulated with a hydrological model shows a good correspondence to the TWS observations and indicates that the trend values for the period of satellite gravimetry are not representative of the long-term dynamics. Extrapolating future water storage trends from them is thus not recommended.