ALBERT

Description: 〈p〉Publication date: Available online 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Kevin L. Shelton, B. Danielle Cavender, Laura E. Perry, James D. Schiffbauer, Martin S. Appold, Isac Burstein, David A. Fike〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Mississippi Valley-type (MVT) deposits of the Viburnum Trend are typically lead-dominant and occur in the upper portion of the Cambrian Bonneterre Dolomite. Unusual zinc- and copper-rich ores, with notable enrichments in Ni, Co, and Ag, have been discovered within the lower Bonneterre Dolomite, more than 30 m below the district’s main ore-bearing horizon. These ores appear to be localized along fault/fracture zones within the Lamotte Sandstone, which promoted extreme dissolution of the base of the overlying Bonneterre Dolomite and resulted in pronounced vertical zoning of early Ni-Co, Cu, Zn and Pb ores above the sandstone/dolomite contact.〈/p〉 〈p〉Stable isotope and fluid inclusion studies were undertaken to assess whether the deep ores resulted from a single fluid reservoir that evolved from Cu-Ni-Co-rich to Zn-rich to Pb-rich or are instead products of distinct fluids unrelated to the stratigraphically higher, main Pb-rich ores of the district. Sphalerite-hosted fluid inclusions from the lower orebody appear to be geochemically distinct from those that formed the upper orebodies. They record the highest K/Na and Mg/Na ratios in the southeast Missouri MVT district, suggesting dominance of siliceous lithologies (arkose and/or felsic igneous rocks) over limestones along their ore-fluid pathways. Paragenetic trends indicate that distinct fluid compositions are associated with specific generations of sphalerite, which likely reflects the presence of multiple fluids.〈/p〉 〈p〉The δ〈sup〉34〈/sup〉S values of ore minerals (early pyrite and chalcopyrite, -7 to +5‰; early sphalerite, +6 to +15‰; main sphalerite, +7 to +17‰ V-CDT) indicate deposition from fluids that utilized isotopically distinct sulfide reservoirs. Low- δ 〈sup〉34〈/sup〉S sulfur sources for early ores likely included sulfide in local brines within the Lamotte Sandstone and diagenetic sulfide minerals within the basal units of the Bonneterre Dolomite. A trend of increasing δ 〈sup〉34〈/sup〉S values of ore sulfides (from -5 toward +17‰) with vertical distance above the Lamotte Sandstone-Bonneterre Dolomite contact indicates that as the deep ore fluid system worked its way upward, it breached less permeable units in the lower Bonneterre Dolomite, allowing incorporation of high- δ 〈sup〉34〈/sup〉S sulfide from brines present higher in the stratigraphic section. A concomitant up-section pattern of decreasing δ 〈sup〉18〈/sup〉O values of dolomite cement and recrystallized remnant host rock (from -3 toward -9‰ V-PDB) is also consistent with a localized, deep mineralizing fluid system, which interacted progressively with the stratigraphically higher, regional-scale, Pb-rich fluid system.〈/p〉 〈p〉The episodic nature of metal sulfide deposition in the lower ore zone points to a system in which fluid mixing would have been highly variable, both temporally and spatially. Reaction path models require mixing of multiple, ore metal-specific and sulfide-bearing fluids in order to form the orebody. The sequence and concentrations of metal sulfides are inconsistent with ore formation from a single, evolving metal-bearing fluid.〈/p〉 〈p〉This study indicates that faults localized early metal- and sulfide-bearing fluids, facilitating mixing of fluids that resulted in the accumulation of high-grade ores near the Bonneterre Dolomite-Lamotte Sandstone contact. Recognition of fault/fracture patterns beneath more typical Pb-rich orebodies in the Viburnum Trend may be a viable exploration strategy for similar Zn-Cu-Co-Ni-rich deposits.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819308972-ga1.jpg" width="101" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 24 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Meng–Ting Chen, Jun–Hao Wei, Yan–Jun Li, Wen–Jie Shi, Nai–Zhong Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Low sulfidation (LS) epithermal gold deposits within the Southeastern China Fold Belt (SCFB) are generally associated with Early Cretaceous volcanism (91–110 Ma). The Shangshangang (SSG) gold deposit (3 t Au @ 2.7 g/t) is proposed to be a LS ore system hosted by Early Cretaceous volcanic-subvolcanic rocks in the Dongkeng Basin (DVB), northern SCFB. Early Cretaceous felsic volcanic-subvolcanic rocks within the DVB possess high-K calc-alkaline and metaluminous to weakly peraluminous signatures. They show rare trace element (REE) and trace element patterns resembling those of Early Cretaceous A-type granites and rhyolites in the SCFB with significantly Eu negative anomalies (Eu/Eu*=0.1–0.3). These volcanic-subvolcanic rocks are potentially formed by mixing of melts from crust and Early Cretaceous enriched mantle under an extensional tectonic setting. This is indicated by their negative ε〈sub〉Hf〈/sub〉(〈em〉t〈/em〉) values (–8.8 to –5.2), young two-stage Hf model ages (T〈sub〉DM2〈/sub〉=1.32–1.48 Ga), and variable Sr-Nd isotopic compositions.〈/p〉 〈p〉The epithermal event at SSG is represented by three mineralization stages characterized by four distinct quartz vein types. These are: (1) greyish green crustiform comb quartz veins (type A) and smoky grey fine-grained (〈0.5 mm) quartz veins (type B) in the early stage, (2) ivory medium- to coarse-grained (〉1 mm) quartz veins (type C) in the middle stage, and (3) late white calcite-rich quartz veins (type D). Quartz veins are typically accompanied by hydrothermal alteration with zoning (kaolinite-illite-chlorite zone, adularia-chlorite-quartz zone, and adularia-sericite-quartz zone). Gold mineralization is identified in the early stage and free gold exists as micrometer-sized inclusions of native gold within pyrite. Pb–Zn mineralization dominates the middle stage. Hydrothermal fluids within the ore system are of low salinity (〈7 wt.% NaCl) and gas-poor. The fluid temperatures decreases from 224−316 °C for Au mineralization to 190−261 °C for Pb-Zn mineralization. No indication for fluid boiling is found. The H–O isotopes indicate mixing of magmatic and meteoric fluids and a larger portion of meteoric water at a later stage. The 〈em〉δ〈/em〉〈sup〉34〈/sup〉S values of pyrite related to Au mineralization are 1.1−2.0‰ and of sphalerite and galena related to Pb-Zn mineralization range from −1.8 to 2.5‰. The Pb isotopic compositions of sulfides from the early and middle stages are relatively homogeneous and similar with those of subvolcanic rocks within the DVB. Deposit geology, microthermometric result, and isotopic data support a LS epithermal origin for the SSG gold deposit, and therefore suggest a co-existing relationship between low and intermediate sulfidation epithermal gold mineralization within the DVB.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819305505-ga1.jpg" width="102" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Xiao-Yu Zhao, Hong Zhong, Wei Mao, Zhong-Jie Bai, Kai Xue〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The Zijinshan Cu-Au deposit, located in Fujian Province, is the largest high-sulfidation epithermal (HSE) deposit in Southeastern China and is usually regarded as a major part of the porphyry Cu system in the Zijinshan ore field. Molybdenite samples collected from the Cu mineralization zone yield a first weighted mean Re-Os age of 111.31±0.70 Ma, which is explained as the time of dickite-alunite alteration. Combining the newly reported muscovite 〈sup〉40〈/sup〉Ar-〈sup〉39〈/sup〉Ar and zircon U-Pb ages (∼113 Ma), the mineralization of Zijinshan is likely to initiate before ca. 110 Ma. This result is obviously older than the Re-Os age of the adjacent Luoboling porphyry Cu-Mo deposit (∼105 Ma).〈/p〉 〈p〉Pyrite, chalcopyrite, bornite, digenite, and covellite collected from the deep potassic, middle phyllic and upper epithermal zones are used to conduct LA-ICP-MS trace element analysis. The spatial zonings of mineralization and alteration and the regular variations of trace elements in sulfides at vertical direction imply a potentially complete transition from porphyry to epithermal mineralization and the deep origin of ore-forming fluids. Mineralogical and trace element characteristics indicate that the chalcopyrite formed in both stages, whereas bornite is the product of epithermal mineralization, rather than a porphyry stage residue. The majority of digenite and covellite has hypogene genesis. Pyrite and digenite in the epithermal zone are major carriers of primary Au. Au in pyrite is Te-Bi related and exists as solid solutions or different-sized telluride and Bi-sulfosalt inclusions. Compared to As, Te and Bi played more important roles to scavenge Au and Ag and achieve the primary Au enrichment. Differently, Au in digenite is independently locked in digenite lattice. Bornite and digenite are good carriers of primary Ag, which mainly exists as solid solutions. The high sulfidation state stage is the major period for concentrations of primary Au and Ag. The upward increase of Au in primary sulfides of HSE Cu zone implies that the distribution pattern of upper Au enrichment and lower Cu enrichment is not only caused by supergene process, but is also controlled by hypogene trend.〈/p〉 〈p〉Based on the mineralization and alteration zonings, the spatial variation of trace elements and the presented Re-Os age, the ore-forming fluids of the Zijinshan Cu-Au deposit most likely originate from deep region, rather than from the adjacent Luoboling porphyry deposit. The Zijinshan and the Luoboling deposits should belong to two independent hydrothermal systems.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819310066-ga1.jpg" width="317" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Nicolas Gaillard, Anthony E. Williams-Jones, James R. Clark, Stefano Salvi, Stéphane Perrouty, Robert L. Linnen, Gema R. Olivo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The world-class, oxidized intrusion-related Canadian Malartic gold deposit, with reserves estimated at 5.56 Moz Au grading 1.10 g/t Au, and a total geological endowment of 16.3 Moz Au, is one of the largest gold deposits in the Archean Superior Province of Canada. The gold mineralization is hosted predominantly by Pontiac Group metasedimentary rocks, Piché Group metavolcanic rocks, and quartz monzodiorite to granodiorite porphyritic intrusions. The ore takes the form of a low-grade envelope of disseminated pyrite (0.35 to 1 g/t Au) grading inwards into higher grade (〉1 g/t Au) stockwork and breccia zones. Hydrothermal alteration in the metasedimentary rocks is zonally distributed around the fluid pathways. Proximal alteration is characterized by a microcline±albite-quartz replacement-type assemblage, with lesser phlogopite, calcite〈/p〉 〈p〉±Fe-dolomite, pyrite and rutile. The distal alteration assemblage comprises biotite, microcline±albite, phengite, quartz, calcite, pyrite and rutile.〈/p〉 〈p〉In this study, we assess the magnitude and distribution of fluid–rock interaction in the metasedimentary rocks of the Malartic district. The metaturbidites are separated into four lithotypes based on grain size to reduce the effects of primary depositional processes on mass change calculations. Despite the variability in protolith compositions, the metasedimentary rocks define a geochemically consistent, cogenetic sequence. The results of the mass transfer calculations indicate progressive gains in CO〈sub〉2〈/sub〉-S–K〈sub〉2〈/sub〉O and LOI, as well as Au–Te–W-Ag-(As-Be-Sb-Bi-Mo-Pb), from background, to distal and proximal alteration zones (relative to the least-altered samples). Molar element ratio analysis (alkali/aluminum) indicates an increase in alkali metasomatism (K and Na) adjacent to the main hydrothermal fluid pathways, which is manifested by the progressive stabilization of microcline and albite at the expense of oligoclase, biotite and white mica.〈/p〉 〈p〉Ore-associated pathfinder elements delineate broad enrichment patterns around the deposit, and are used to understand hydrothermal fluid circulation in the Malartic district. A statistical approach based on a comparison of the mass change results with the background composition provides robust constraints on the magnitude and extent of the lithogeochemical haloes. Generally, the alteration forms envelopes that extend along the S〈sub〉2〈/sub〉 fabric, with the largest lithogeochemical anomalies (〈em〉e.g.〈/em〉, Au, W, Te and Ag) reaching up to 10 kilometers in length, and 2 kilometers in width. The results of this study demonstrate that whole-rock lithogeochemistry can provide a valuable tool with which to define vectors toward gold mineralization in a regional exploration context.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136820300317-ga1.jpg" width="315" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Fudong Jia, Changqing Zhang, Huan Liu, Xuyang Meng, Zhigang Kong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Yangla copper deposit is a rare Triassic intrusion-related Cu skarn system in the central part of the Jinshajiang tectonic belt, central Sanjiang orogenic belt, southwest China. Major- and trace-element compositions of apatites from ores, fertile calc-alkaline intrusions and its mafic microgranular enclaves, and barren calc-alkaline intrusions from the Yangla skarn copper deposit were measured by electron probe microanalysis and laser ablation–inductively coupled plasma–mass spectrometry. Results indicate that apatites grown within ores, fertile intrusions and its enclaves show similar features, but are different from that grown within barren intrusions. Apatite from fertile intrusions has higher Ca and correspondingly lower total trace-element contents, which partition onto the Ca sites, relative to that from barren intrusions. Apatites from the barren intrusions have high F and low Cl contents, and correspondingly high F/Cl ratios, which may have resulted from the assimilation of sediment. Apatites from fertile intrusions show relatively high Cl and low F contents, which may reflect crystallization from magmas with high water contents. Redox-sensitive elements in apatite can be used as indicators of the oxidation state of magmas. Apatites from the barren intrusion have lower V and As contents, higher Mn, Fe, and U contents, and more pronounced negative Eu anomalies than those from fertile intrusion, indicating that the barren magma was more reduced, consistent with its lower whole-rock Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉/FeO and zircon Ce〈sup〉4+〈/sup〉/Ce〈sup〉3+〈/sup〉 ratios. These findings demonstrate that apatites are effective in distinguishing fertile from barren intrusions and can be used as a robust tool in mineral exploration.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819307425-ga1.jpg" width="293" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Yan-Jun Wang, Wei-Guang Zhu, Hui-Qing Huang, Zhong-Jie Bai, Hong Zhong, Jun-Hua Yao, Hong-Peng Fan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The Dahongshan Fe-Cu ore deposit, hosted in the Paleoproterozoic meta-volcanic and meta-sedimentary sequences, is a giant deposit in the Fe-Cu metallogenic province of southwestern China. Two ore types have been identified: (1) massive and disseminated Fe ores hosted dominantly in meta-volcanic rocks and (2) disseminated and banded Fe-Cu ores in meta-sedimentary rocks. Magnetite presents in all orebodies, and is dominant in the Fe ores. Chemistry of magnetite suggest that the fluids for iron mineralization in the Fe and Fe-Cu orebodies are likely chemically similar and cogenetic. Minor sulfides (e.g., molybdenite) occur at the end of iron mineralization stage, indicating the gradually decrease in oxygen fugacity for the mineralizing fluids with magnetite precipitation. Along with evolution, mineralizing fluids generate magnetite with depletions in Cr, Ni, Ga and V, but enrichments in Mn, Sn and Co, which are primarily reflective of the temperature decrease of fluids.〈/p〉 〈p〉We have discovered some magnetite grains that are extremely rich in V (∼10000 ppm), but low in Ti and Cr. Geochemical patterns suggest they were formed by fluids similar to those of ordinary ores. Available knowledge about the unique high-V magnetite indicates highly-reduced marine environments for its generation. Ore bulk REE patterns showing remarkable positive Eu anomalies and absence of obvious Ce anomalies suggest a BIF-like marine environment, consistent with the morphology of both Fe and Fe-Cu orebodies. Our results provide independent evidence for submarine environment in the formation of the giant Precambrian stratiform Fe(-Cu) ore deposit.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136818305845-ga1.jpg" width="276" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Feng Bai, Jiming Du, Jingjing Li, Bohan Jiang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new nephrite deposit with potential for economic exploitation was recently discovered in Dahua county, Hechi City, Guangxi Autonomous Region, China. Previous studies have focused primarily on white, black, and black-cyan nephrite from Dahua, whereas few studies have been carried out on green nephrite. In this study, the mineralogical, petrological, and geochemical characteristics of nephrite from this new deposit were systematically studied using polarized light microscopy, scanning electron microscopy, electron probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry, and the deposit genesis was discussed. The results show that Dahua green nephrite consists of interwoven microfibers, and the main mineral component is tremolite. The Mg〈sup〉2+〈/sup〉/(Mg〈sup〉2+〈/sup〉+Fe〈sup〉2+〈/sup〉) ratio ranges from 0.951 to 1.00, andthe subordinate minerals include diopside, chlorite, calcite, quartz, apatite, albite, titanite, and andradite.The contents of trace elements (Cr, Ni, and Co) are much lower than in metasomatized serpentinite-type nephrite. The rare earth element content is generally high (62.011–223.116ppm) with a positive Eu anomaly (1.009–2.343), positive and negative Ce anomalies (0.913–1.078), enrichment in light rare earth elements, and flatness in heavy rare earth elements. The distribution curves of the rare earth elements differ between the nephrite and the surrounding rock samples, indicating multiple sources and a multiperiod superposition of the ore-forming fluids. The Fe〈sup〉2+〈/sup〉/(Mg〈sup〉2+〈/sup〉+Fe〈sup〉2+〈/sup〉) ratio in Dahua green nephrite is lower than 0.06, indicating that the nephrite deposit is surrounded by carbonates. By taking c(Ca〈sup〉2+〈/sup〉), c(Mg〈sup〉2+〈/sup〉), and c(Fe〈sup〉2+〈/sup〉+Fe〈sup〉3+〈/sup〉) as endmembers for projection, amphibole can be concluded to have originated from contact metasomatism. Considering the findings of the geological survey, the Dahua green nephrite likely belongs to the magmatic hydrothermal metasomatic type, and its ore deposit is related to basic intrusive rocks such as diabase and hydrothermal fluid carried by magma. Contact metasomatism and hydrothermal metamorphism occurred with dolomitic limestone and other carbonate rocks under certain temperature and pressure conditions during the Variscan–Indosinian period. This systematic study of the newly discovered Dahua green nephrite deposit provides a theoretical basis for the prospecting of nephrite deposits in the study area.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819309643-ga1.jpg" width="269" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Ji-Long Han, Jing-Gui Sun, Yang Liu, Xiao-Tian Zhang, Yun-Peng He, Fan Yang, Xiao-Lei Chu, Lin-Lin Wang, Shu Wang, Xin-Wen Zhang, Chun-Tao Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Jiapigou mining district (JMD) in the northeastern part of the North China Block mainly contains quartz vein- and altered rock-type gold deposits that have been prospected and mined for over 200 years. Recently, a breccia-type gold deposit, known as Toudaoliuhe, was discovered in the JMD, that has attracted attention for prospecting and exploration. In this paper, we report the ore geology, gold-bearing sulfide (i.e., pyrite, galena, and sphalerite) Rb–Sr age, fluid inclusions (FIs), and H–O–S–Pb–Sr isotope data of the Toudaoliuhe gold deposit to determine its genesis and ore-forming mechanisms. Gold orebodies mainly occur in the breccia cements, as well as in several quartz veins controlled by NW-trending brittle faults. There were three hydrothermal stages: the early (quartz–pyrite), main (quartz–polymetallic sulfide), and late (quartz–carbonate) stages. Gold mineralization occurred in the main hydrothermal stage. Three types of FIs were identified: CO〈sub〉2〈/sub〉–H〈sub〉2〈/sub〉O–NaCl (C-type), H〈sub〉2〈/sub〉O–NaCl (W-type), and pure CO〈sub〉2〈/sub〉 (PC-type). The FIs in quartz from the early hydrothermal stage are predominantly of the C- and W-types (with traces of PC-type), and have homogenization temperatures of 299.8–340.0 °C and salinities of 6.5–14.8 wt. % NaCl equivalent (E). The FIs in the quartz and sphalerite forming the main hydrothermal stage are also predominantly of the C- and W-types (with trace PC type), and have homogenization temperatures of 169.1–298.7 °C and salinities of 5.7–16.5 wt. % E. The FIs in the quartz and calcite from the late hydrothermal stage were solely of the W-type, and have homogenization temperatures of 126.0–210.2 °C and salinities of 2.1–11.4 wt. % E. The ore-forming fluids are characterized by moderate temperature and low salinity, suggesting a CO〈sub〉2〈/sub〉–H〈sub〉2〈/sub〉O–NaCl system. The H–O–S–Pb–Sr isotopic results suggest that the ore-forming fluids were dominated by magmatic water, and that the ore-forming materials were mainly extracted from the Middle Jurassic magmatic reservoir (177–163 Ma), sourced mainly from the lower crust with trace mantle components. Fluid boiling was the dominant mechanism for gold and associated sulfide precipitation. The Rb–Sr isochron age of the gold-bearing sulfides at 177.7 ± 1.7 Ma indicates that gold mineralization occurred in the early Middle Jurassic. We therefore proposed that the Toudaoliuhe is a mesothermal gold deposit that formed in an extensional setting related to the subduction of the Paleo-Pacific Plate beneath the Eurasian continent.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphic abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136818310394-ga1.jpg" width="370" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Zhenwei Guo, Guoqiang Xue, Jianxin Liu, Xin Wu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Electromagnetic methods play an important role in mineral exploration and are widely used in the search for metallic resources such as copper, molybdenum, lead-zinc, bauxite, uranium, etc. In this paper, we focus on reviewing the application and development of electromagnetic methods, such as magnetotelluric (MT), audio magnetotelluric (AMT), controlled-source audio magnetotelluric (CSAMT), and transient electromagnetic (TEM), respectively. This paper also presents examples of electromagnetic methods applied to the exploration of metal deposits on land, airborne and in the marine environment. Furthermore, we discuss the future development of electromagnetic prospecting tools, the data processing, modeling and inversion, interpretation, and their application in complex geological environments. The future of successful mineral exploration using EM methods will be focused on concealed and deep target exploration, and possibly one day on resources on the seafloor.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): C.A. Spier, A. Kumar, A.P.L. Nunes〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Phosphorus is a major deleterious element in iron ore where it occurs as primary apatite in hypogene ore, and adsorbed into Mn-, Fe-hydroxides and forming secondary phosphates in supergene ore. Secondary phosphate minerals have been formed during a long history of weathering of itabirite and hypogene iron ore in the Quadrilátero Ferrífero (QF), ongoing since the end of the Cretaceous (∼70 Ma). The distribution and genesis of these secondary phosphates are poorly documented in the literature. The purpose of this study was to investigate the mineralogy, mineral chemistry and formation of rare secondary phosphate minerals found in P-bearing concretions hosted in the iron ore at the Serra do Curral, QF. Detailed mineralogical investigation revealed that three generations of secondary phosphates were formed by weathering of carbonate veins hosted within fracture zones of itabirite and iron ore. Turquoise, augelite and senegalite comprise the bulk of the secondary phosphates whereas remnants of Ca-, Ba-, Ce- and Sr-bearing minerals (crandallite, gorceixite, florencite and goyazite) are subordinated. Sulphate members of aluminium-phosphate-sulphate (APS) minerals are absent, likely due to low SO〈sub〉4〈/sub〉〈sup〉2-〈/sup〉 activities in the weathering solution. Apatite hosted within unweathered itabirite and carbonate veins was the source of P to the weathering solutions whereas Cu, Zn and Ba were released from sulphides hosted in carbonate veins and Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 from country rocks. The link between the secondary phosphates to hydrothermal breccias and carbonate veins highlights the significance of hydrothermal fluids as a source of P in iron ore deposits. Furthermore, it brings attention to the structural control imposed on P-bearing minerals in these deposits. Geochemical modelling shows that the secondary phosphates were formed in response to changes in pH of the weathering fluids, providing an additional example to the literature about the application of secondary phosphate minerals as valuable trackers of paleoenvironmental weathering conditions.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819307668-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 118〈/p〉 〈p〉Author(s): N.V. Berdnikov, V.G. Nevstruev, P.K. Kepezhinskas, A.G. Mochalov, O.V. Yakubovich〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report in this paper an unusual occurrence of platinum-group minerals in evolved explosive breccia associated with the Poperechny iron-manganese deposit (Lesser Khingan Range, Far East Russia). PGMs in andesite breccia are represented by Fe-Pt solid solutions (85%) and PGM (mostly Os-Ir-Ru) solid solutions, sulfides and sulfarsenides (15%). Textural and compositional variations in PGM assemblages suggest that Pt-Fe and Os-Ir-Ru solid solutions, as well as erlichmanite-laurite series sulfides were formed during high-temperature fractionation of mantle-derived mafic parental melt (similar to Alaskan-type complexes) and were entrained in the evolved andesitic melt during its emplacement in the crust. Pd-Pt plumbostannide and copper-gold solid solutions reflect late magmatic re-crystallization and metasomatism. Early Cretaceous (~125 Ma) age of ferroplatinum in the explosive breccia suggests that PGM-bearing ultramafic material could have been sampled during regional slab-window tectonics related to the Late Mesozoic subduction of Izanagi plate along southern margin of the North Asian continent.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Distribution of platinum-group minerals (PGMs) in explosive andesite breccia from the Poperechny iron-manganese deposit compared with orogenic chromitites, Alaskan-type ultramafic-mafic complexes and ophiolites. Predominance of Pt-Fe solid solutions among PGMs in Poperechny andesites suggests derivation from Alaskan-type ultramafic source by ascending andesite during its emplacement at mid- and upper crustal levels.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819308534-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Tao Ren, Hong Zhong, Xing-chun Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Langdu Cu skarn deposit is the highest grade Cu deposit (average 6.49 % Cu) in the Zhongdian polymetallic district in SW China. Skarns and ore bodies occur primarily in the contact zone of Upper Triassic Qugasi Formation (Fm.) and Late Triassic (ca. 217 Ma) intrusions. Disseminated, massive, stockwork, and vein-like sulfide ores occur in the skarn, quartz-calcite veins, porphyry and marble. Skarn minerals include pyroxene, garnet, actinolite, and epidote. Four types (six subtypes) of fluid inclusions (FIs) are identified in the sulfide-bearing quartz veins. Type-I liquid-rich two phase FIs have varying vapor/liquid ratios, and yielded homogenization temperatures of 110–338°C and salinities of 1.7–29.5 wt.% NaCl eqv. Type-II vapor-rich FIs contain CH〈sub〉4〈/sub〉-N〈sub〉2〈/sub〉 bubbles and homogenized to vapor at 262–425°C. Type-III FIs are single phase at room temperature (20°C). A vapor phase is present at below –120°C, and the FIs homogenized at –117 to –114°C. Type-IV daughter mineral-bearing FIs homogenized by halite disappearance at 295–392°C, and have salinities of 37.8–46.6 wt. % NaCl eqv. Such characteristics suggest that FIs were trapped by fluid immiscibility and phase separation. The δ〈sup〉34〈/sup〉S〈sub〉CDT〈/sub〉 values of chalcopyrite and pyrrhotite are of –5.3 to 0.7‰. On the δ〈sup〉34〈/sup〉S histogram, all Langdu data show a cluster of 〈sup〉32〈/sup〉S-rich (δ〈sup〉34〈/sup〉S〈sub〉CDT〈/sub〉= –5.3 to –4.6‰) and a cluster of 〈sup〉34〈/sup〉S-rich (δ〈sup〉34〈/sup〉S〈sub〉CDT〈/sub〉= –1.1 to 0.7‰). Type-I calcite (in skarn) and type-II calcite (in quartz-sulfide vein) have δ〈sup〉13〈/sup〉C〈sub〉PDB〈/sub〉 and δ〈sup〉18〈/sup〉O〈sub〉SMOW〈/sub〉 values of –8.4 to –7.8‰, –6.3 to –6.1‰ and 10.1 to 12.3‰ and 12.0 to 13.0‰, respectively. Type-III calcite from calcite-sulfide veins has δ〈sup〉13〈/sup〉C〈sub〉PDB〈/sub〉 = –5.6 to 0.2‰ and δ〈sup〉18〈/sup〉O〈sub〉SMOW〈/sub〉 = 12.5 to 16.3‰. Biotite, garnet and pyroxene, syn-ore quartz, and chlorite yielded δ〈sup〉18〈/sup〉O〈sub〉SMOW〈/sub〉 values of 6.9‰, 4.1–5‰, 13.2–15.3‰, and 6.8‰, respectively. Sulfur, carbon and oxygen isotopic features of these hydrothermal minerals and the FIs microthermometric data suggest that the ore-forming fluids were magmatic sourced and contaminated by meteoric/formation water during ascent and/or fluid/wallrock interactions. Low δ〈sup〉34〈/sup〉S (= –5.3 to –4.6‰) in sulfides and the CH〈sub〉4〈/sub〉 in the FIs are interpreted to reflect the reaction between the magmatic fluids and the carbonaceous slate in Qugasi Fm. The methane likely expanded the vapor/liquid immiscibility field and reduced the sulfates (SO〈sub〉4〈/sub〉〈sup〉2–〈/sup〉) to sulfides (S〈sup〉2–〈/sup〉). And extensive water/rock reaction and fluid mixing may have occurred, leading to the high-grade Cu mineralization at Langdu.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819309746-ga1.jpg" width="277" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Jingya Cao, Qianhong Wu, Xiaoyong Yang, Xuantong Deng, Huan Li, Hua Kong, Xiaoshuang Xi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Xitian and Dengfuxian ore fields, located in the middle Qin-Hang Belt, are known for hosting large-scale W–Sn polymetallic deposits. The Xitian ore field hosts a series of small to large scale Sn–W deposits, including skarn-, quartz vein- and structurally altered rock-type, whereas the Dengfuxian ore field mainly contains a medium-scale quartz vein-type W deposit. These granitic rocks are composed of ore-barren Triassic and ore-related Jurassic granites. In this study, LA–ICP–MS zircon U–Pb dating of three representative samples from Dengfuxian Triassic granites (DTG), Xitian Jurassic granites (XJG) and Dengfuxian Jurassic granites (DJG) yields weighted mean 〈sup〉206〈/sup〉Pb/〈sup〉238〈/sup〉U ages of 231.2 ± 2.5 Ma, 152.5 ± 1.2 Ma and 155.9 ± 1.6 Ma, respectively. Chemical compositions of the Xitian Triassic granites (XTG) and DTG indicate that they belong to relatively lower fractionated granites, whereas the XJG and DJG are highly fractionated granites. The XTG and DTG have similar Lu–Hf isotopic compositions, which have peak ε〈sub〉Hf〈/sub〉(t) values of ca. −5.9 and T〈sub〉DMC〈/sub〉 ages of ca. 1.57 Ga, and peak ε〈sub〉Hf〈/sub〉(t) values of ca. −5.7 and T〈sub〉DMC〈/sub〉 ages of ca. 1.57 Ga, respectively. However, the XJG have higher peak ε〈sub〉Hf〈/sub〉(t) values of ca. −5.4 and younger T〈sub〉DMC〈/sub〉 ages of ca. 1.52 Ga than those of the DJG with peak ε〈sub〉Hf〈/sub〉(t) values of ca. −7.6 and T〈sub〉DMC〈/sub〉 ages of ca. 1.70 Ga, respectively. Furthermore, the XTG have ε〈sub〉Nd〈/sub〉(t) values of −10.5 to −9.40 and Nd model ages (T〈sub〉DM2〈/sub〉) of 1.86 to 1.76 Ga, which are similar to those of the DTG with ε〈sub〉Nd〈/sub〉(t) values of −11.7 to −9.67 and Nd model ages (T〈sub〉DM2〈/sub〉) of 1.95 to 1.79 Ga (Wu et al., 2016, Cai et al., 2015). The XJG have ε〈sub〉Nd〈/sub〉(t) values of −11.0 to −9.1 and younger T〈sub〉DM2〈/sub〉 ages of 1.69–1.84 Ga, which are fairly distinct to the reported Nd isotopes of the DJG (Cai, 2013). It is proposed that the XTG and DTG were originated from the similar magma chamber and formed from partial melting of the Proterozoic basement rocks of the South China Block (SCB) at low temperatures (ca. 690 °C) and oxygen fugacity (log(〈em〉f〈/em〉O〈sub〉2〈/sub〉) values of ca. −17), involved with a certain amount of mantle derived magma; Magmas of the XJG and DJG might be mainly originated from the partial melting of Proterozoic basement rocks of the SCB. In contrast, the formation of XJG and DJG are involved with a considerable and little mantle-derived magma, respectively. In addition, the magma temperatures and log(〈em〉f〈/em〉O〈sub〉2〈/sub〉) values of XJG are of ca. 856 °C and ca. −15, respectively, which are higher than those of the DJG (ca. 716 °C and ca. −17). That the Xitian and Dengfuxian Triassic granites did not induce W–Sn mineralization is likely attributed to their low fractionated signatures. The key factors leading to the Sn–W mineralization in the Xitian ore field and W mineralization in the Dengfuxian ore field might be magma source and temperature, since additional Sn could be provided by the mantle and/or released by melting of those Sn-bearing minerals at high temperatures (over than 780 °C).〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S016913681930277X-ga1.jpg" width="272" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Gülcan Bozkaya, Ömer Bozkaya, David A. Banks, Ahmet Gökçe〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Koru deposit is a typical intermediate sulfidation base-metal (± Au) example of volcanic-volcaniclastic hosted mineralization in the Biga Peninsula and northwestern Turkey. Ore deposition was associated with the collisional and post–collisional tectonics related to the closure of the Tethys Ocean. Galena, baryte and quartz are main minerals, accompanied by minor amounts of sphalerite, pyrite, chalcopyrite, covellite and marcasite. The homogenization temperature of fluid inclusions indicates two distinct fluid pulses, one at a temperature commensurate with epithermal mineralization and boiling/near boiling conditions at c. 350 °C, with the second approximately 150-200 °C lower. Salinity in both instances was from 11.0 to 0.2 wt. % NaCl. The δD and δ〈sup〉18〈/sup〉O values of water in equilibrium with early quartz and fluid inclusions plot close to the magmatic water box indicating the source of the high temperature fluid was magmatic. δD and δ〈sup〉18〈/sup〉O values from early and late baryte trend towards the meteoric water line (MWL), but this is not due to mixing with meteoric water, rather equilibration with alteration assemblages at decreasing temperature. LA-ICP-MS analyses of fluid inclusions reveal high Cu–Zn–Pb concentrations in the fluids, despite their low salinity, transported as chloride complexes. The range of temperatures within the early quartz and sphalerite mineralization can be explained by pressure variations during vein and fracture opening.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136818307649-ga1.jpg" width="293" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 118〈/p〉 〈p〉Author(s): Sinan Akıska〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Biga Peninsula (NW Turkey) is an important sector of the Tethyan Metallogenic Belt. In addition to Au and Ag, this region hosts several Pb, Zn, Cu, Fe, and Mo deposits. Pb-Zn skarn mineralizations in the Biga Peninsula (Biga Pb-Zn skarn) are bounded by carbonate lenses in the metamorphic rocks and localized along the regional faults and at the contact between carbonate units and igneous-metamorphic rocks. The primary ore minerals are galena, sphalerite, chalcopyrite, pyrite, arsenopyrite, magnetite, and hematite. Ore-bearing altered rocks are composed primarily of calc-silicate alteration minerals, including both prograde (grossular-andradite garnets and johannsenite-hedenbergite pyroxenes) and retrograde (epidote, chlorite, quartz, and calcite) assemblages. The garnet composition is a solid solution with 〈96% andradite and 1.4% to 94.4% grossular content. Some garnet grains exhibit zonings because of fluctuations in the content of Al〈sup〉3+〈/sup〉 and Fe〈sup〉3+〈/sup〉. Mn/Fe ratios are high, and the outermost grains have a high MnO content, up to 3 wt%. The pyralspite content is 〈10 wt%. The proportions of johannsenite and hedenbergite in clinopyroxenes range from 0.35 to 94.69 mol% and 2.13 to 77.90 mol%, respectively. Clinopyroxenes have high Mn/Fe values, with Mn content up to 10 wt%. The epidote-group minerals with a high Al〈sup〉3+〈/sup〉 and Fe〈sup〉3+〈/sup〉 content belong to the epidote-clinozoisite series (Ep〈sub〉37-21〈/sub〉Czo〈sub〉78-63〈/sub〉Pie〈sub〉1-0〈/sub〉). Mineral chemistry data indicate that Biga Pb-Zn skarn deposits and distal Pb-Zn skarn deposits throughout the world have similar characteristics. The abundance of graphite in the metamorphic host rocks and the andradite-hedenbergite content of the skarns imply that the studied mineralizations were formed under reducing conditions. The ranges of crystallization depth and pressure values calculated from the chemistry of garnet-clinopyroxene pairs are 1.3–1.6 km and 10–12 MPa, respectively. Because these values are less than those of plutons hosting the Biga Pb-Zn skarn deposits, the mineralizations likely formed in the distal zones of plutons.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136818305511-ga1.jpg" width="275" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 20 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Jingya Cao, Xiaoyong Yang, Gaofeng Du, Huan Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Waterfall tin deposit, located in the south Peninsular Malaysia, is one of the earliest exploited tin deposit of the giant Southeast Asian Tin Belt (SATB) which is a world-class tin metallogenic belt and holds the largest tin resource and reserves in the world. It is a skarn-type deposit genetically associated with the Waterfall granites. Samples from the Waterfall biotite granites were analyzed using the LA–MC–ICPMS zircon U–Pb dating techniques, and the results show that these ages range from 241.2 ± 2.5 Ma (MSWD = 1.3) to 239.0 ± 3.4 Ma (MSWD = 1.2). In addition, these ages are consistent with weighted average age of 238.5 ± 1.7 Ma (MSWD = 0.23), using the LA–ICPMS cassiterite U–Pb dating techniques, indicating a coeval granitic magmatism and tin mineralization event. These granites are characterized by high contents of SiO〈sub〉2〈/sub〉, Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, Na〈sub〉2〈/sub〉O and K〈sub〉2〈/sub〉O, low contents of P〈sub〉2〈/sub〉O〈sub〉5〈/sub〉, enrichment in Th, U, Nb, Zr and Hf and depletion in Ba, Nb, Sr, P and Ti, indicating that they likely belong to I-type granites with high-K calc-alkaline and metaluminous to peraluminous signatures. The Sr–Nd isotopes show that the Waterfall granites are characterized by relatively low initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios of 0.706131–0.707291, slightly negative ε〈sub〉Nd〈/sub〉(t) values of –5.63 to –5.30, and old two-stages Nd model ages of 1.28–1.26 Ga. The zircon ε〈sub〉Hf〈/sub〉(t) values of the zircon grains from the Waterfall biotite granites vary from –2.4 to 0.5, with average crustal Hf model ages of 1.42–1.24 Ga. Based on the elemental and Sr–Nd isotopic compositions of the meta-igneous rocks in the Kontum massif, Indochina Block, a model using the amphibolite and gneiss as two endmembers indicates that the magma for the Waterfall granites were possibly originated from the partial melting of the meta-igneous rocks of the Kontum massif. The Waterfall granites were likely emplaced in a syn-collision setting, triggered by the subduction of the Paleo-Tethys ocean floor beneath the Indochina Block. These granitic rocks, enriched in tin, are in favor of the tin mineralization, resulting in the giant tin mineralization in the SATB.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819302112-ga1.jpg" width="278" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 20 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Jyoti Priyam Sharma, Prabodha Ranjan Sahoo, Haraman Mahanta, A.S. Venkatesh, E.V.S.S.K. Babu, Manish M. John〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The copper mineralization at the southeastern fringe of the Khetri copper belt in western India is primarily hosted within the metapelites and dolomite units of the Mesoproterozoic Ajabgarh Group of rocks. The copper mineralization is well exposed along a NE-SW trending basinal part around Nim ka Thana area where a few of the prospects namely Dokan, Baniwala-ki-Dhani, Dariba, and Nanagwas primarily consist of abundant bornite, chalcopyrite, covellite, digenite, and chalcocite as disseminated phases hosted within a wide-ranging litho units and along quartz-calcite-barite veins. An integrated approach has been adopted to understand the metallogenetic evolution of this bornite dominated copper mineralization. δ〈sup〉13〈/sup〉C〈sub〉V-PDB〈/sub〉 and δ〈sup〉18〈/sup〉O〈sub〉V-SMOW〈/sub〉 results of the carbonate veins ranging from 0.57‰ to -3.75‰ and δ〈sup〉18〈/sup〉O range from 15.01‰ to 20.74‰ respectively suggest the influx of hydrothermal fluid in shaping up the deposit. δ〈sup〉13〈/sup〉C (CO〈sub〉2〈/sub〉) of the ore-bearing fluid ranges from -1.67‰ to 2.65‰ and δ〈sup〉18〈/sup〉O (H〈sub〉2〈/sub〉O) from 7.11‰ to 12.84‰ respectively also suggest the input of hydrothermal source. The S-isotopic values of Cu-mineralized barite samples range between 16‰ and 20‰, which are lower than that of seawater (δ〈sup〉34〈/sup〉S‰= 20–22‰). This provides the evidence that the barite mineralization could have formed from the hydrothermal fluid that is cogenetic with the late-stage mineralization in a phase-wise separation as an associated mineral assemblage in the system progressively enriching the bornite-rich copper deposit.〈/p〉 〈p〉Based on the field data and evidences, petrographic characteristics, mineral chemistry, fluid inclusion, and stable isotopic signatures, a three-stage mineralization event is proposed as 1) syngenetic precipitation of dispersed bornite-pyrite in a euxinic environment; 2) hydrothermal vein-type mineralization dominated by chalcopyrite-bornite phase, and 3) supergene enrichment of the vein filled mineralization with the development of wide-scale chalcocite-digenetite-covellite mineral phases. Fluid inclusion microthermometry suggests a temperature range from 225〈sup〉o〈/sup〉-320°C with moderate salinity fluid representing epithermal mineralization which is coherent with the stable isotope data (C, O and S isotopes) of the mineralized carbonate and barite veins suggesting the involvement of large scale hydrothermal fluid influx. Te content of various Cu-bearing sulfide phases shows a gradual change in the concentration from chalcopyrite (2.21% to 2.31%), bornite (2.31% to 4.50%), chalcocite (2.77% to 2.87%), digenite (2.57% to 3.70%) and covellite (2.53% to 3.13%) suggesting their evolution from hydrothermal to supergene process. The studied area has experienced wide-scale alterations and Na-metasomatism with the development of associated minerals such as scapolite, tremolite, and sericite. Occurrence of primary and secondary copper sulfides in the metasedimentary sequence, alteration assemblages affected by Na-metasomatism, association of magnetite and specularite in the study area is affiliated to the hydrothermal system akin to IOCG clan as noted from the adjoining Khetri Copper Deposit.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819304020-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 118〈/p〉 〈p〉Author(s): C.J. Kelly, W.J. Davis, E.G. Potter, L. Corriveau〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tourmaline crystallized during iron oxide and alkali-calcic alteration and IOCG mineralization in the Great Bear magmatic zone, Canada. Within the samples analyzed, tourmaline occurs as small crystals in the groundmass of hydrothermal breccias (Southern Breccia and Contact Lake), or as large prismatic crystals in quartz (±ore-mineralogy) veins (Contact Lake, DeVries Lake, and NICO). The tourmaline from these localities is predominantly shorlitic in composition, with minor dravitic, uvitic and feruvitic components. The boron isotopic composition ranges from −15‰ to −5‰, with the majority of values between −15‰ and −10‰. The lack of variation among samples supports a common fluid source across the belt for the metasomatic-hydrothermal systems. These results are isotopically similar to global magmatic and non-marine evaporitic reservoirs, and lighter than seawater and marine sedimentary rocks. The δ〈sup〉11〈/sup〉B results support a single-fluid IOCG deposit model for the systems studied, wherein metasomatic-hydrothermal fluids derived by magmatism ascend and evolve over time through fluid-rock interactions.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819302756-ga1.jpg" width="376" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Bingyu Gao, Lianchang Zhang, Xindi Jin, Zhiquan Li, Wenjun Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The rhenium-osmium (Re-Os) isotopic system preserved in ancient seafloor hydrothermal sulfide deposits can be used to gain insight into the Os composition of ancient seawater. In particular, the age of sedimentary exhalative (SEDEX) deposits can be determined by measuring Re-Os isotopes in syn-depositional pyrite, a common constituent of SEDEX deposits. Here we report on the Gaobanhe sediment-hosted, polymetallic pyrite deposit which is hosted within the Gaoyuzhuang Formation in the central part of the northern margin of the North China Craton (NCC). Re-Os isotopic data from syn-depositional pyrite yield an isochron age of 1505 ± 55 Ma, constraining the timing of primary mineralization, as well as the minimum age of the host sediments to the Mesoproterozoic. Analyzed pyrite grains indicate an initial 〈sup〉187〈/sup〉Os/〈sup〉188〈/sup〉Os (Os〈sub〉i〈/sub〉) value of 0.181 ± 0.066, suggesting that the mineralizing fluids were an admixture of seawater and submarine hydrothermal fluids, with the Os being primarily derived from seawater. The Os〈sub〉i〈/sub〉 value is slightly higher than that of Paleoproterozoic seawater (~0.13), suggesting that there was a radiogenic riverine flux to the oceans and that atmospheric oxygen must have been sufficiently high at that time to drive this increased, continental radiogenic Os input to the oceans. We propose that the Re-Os isotopic system, as recorded by these SEDEX deposits, may provide key insights when examining changes in the Os isotopic composition of seawater throughout the Precambrian.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819303762-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 18 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Eduardo T. Mansur, Cesar F. Ferreira Filho, Denisson P.L. Oliveira〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Luanga Complex, located in the eastern portion of the Carajás Mineral Province, is part of a cluster of PGE-mineralized layered intrusions, grouped into what is known as the Serra Leste magmatic suite. The Luanga deposit, the largest PGE deposit in South America, has two distinct styles of PGE mineralization. The first type, termed as Sulfide Zone, consists of a 10-50 m thick interval with disseminated base metal sulfides (pentlandite 〉 pyrrhotite 〉〉〉 chalcopyrite) located along the upper contact of the intrusion's Ultramafic Zone. The Sulfide Zone extends along the entire length of the intrusion (∼ 3 km) and hosts the bulk of PGE resources of the Luanga Complex (i.e., 142 Mt at 1.24 ppm Pt+Pd+Au and 0.11% Ni). The second type of PGE mineralization, termed as low-S-high-Pt-Pd zones, consists of 2-10 m thick stratabound PGE mineralization within a sequence of interlayered ultramafic and mafic cumulates located above the Sulfide Zone. Host rocks of the low-S-high-Pt-Pd zones consist mainly of sulfide- and chromite-free harzburgite and orthopyroxenite. These mineralized rocks do not show any distinctive texture or change in modal composition. The Sulfide Zone and low-S-high-Pt-Pd zones have distinct PGE distribution. The Sulfide Zone has Pt/Pd ratios of 0.52 and a positive correlation between PGE and S. The low-S-high-Pt-Pd zones have Pt/Pd ratios of 1.2 and depletion in IPGE relative to primitive mantle. The platinum-group minerals (PGM) observed in the Sulfide Zone are predominantly Pt-Pd-bismuthtellurides, stanides and arsenides, mainly enclosed within sulfide minerals. On the contrary, the PGM found at low-S-high-Pt-Pd zones are mainly Pt-arsenides, stannides and antimonides, mostly enclosed within alteration silicates. Differences in texture, geochemistry and PGM assemblage between these mineralization styles suggest that they originated from distinct geological processes. The Sulfide Zone was formed by a major event of segregation of an immiscible sulfide liquid, whereas the low-S-high-Pt-Pd zones formed by a sulfide liquid saturation followed by sulfur loss during post-magmatic alteration. The identification of PGE-rich layers in rocks without sulfides or chromite at the Carajás Mineral Province is important as these may have been overlooked during previous exploration programs.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819301404-ga1.jpg" width="263" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 17 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Fatma Nuran Sönmez, Hüseyin Yılmaz, Mustafa Çiçek, Osman Ersin Koralay, Samuel Niedermann, Jason Kirk〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Menderes Massif (MM) is considered to be one of the principal regions hosting vein-type quartz-arsenopyrite orogenic gold deposits and occurrences in Turkey. Gold mineralizations in the MM can be grouped into: (i) schistosity-conformable E-trending veins and (ii) shear-controlled NW-trending veins. Arsenopyrite is one of the major gold-bearing minerals in these deposits or occurrences. Rhenium–Osmium isotopic dating of two types of arsenopyrite from the schistosity-conformable and vein-type Küre (Ödemiş) gold deposit has yielded two groups of model ages (maximum ages) at 557-574 Ma and 246-250 Ma, respectively. The data suggested that the quartz-arsenopyrite gold deposit formed in the Neoproterozoic and Early Triassic, with the former and the latter corresponding to Pan-African compressional orogenesis and Palotethys rifting, respectively. Fluid inclusions in Küre arsenopyrite have 〈sup〉3〈/sup〉He/〈sup〉4〈/sup〉He ratios of ∼0.08-0.09 Ra (Ra=1.39x10〈sup〉-6〈/sup〉, the 〈sup〉3〈/sup〉He/〈sup〉4〈/sup〉He ratio of air) being within the range of middle to upper crustal values〈strong〉.〈/strong〉 A minor helium contribution of mantle fluids to the Küre gold deposit is possible because the 〈sup〉4〈/sup〉He concentrations in arsenopyrite are enriched 170 to 9520 times relative to argon and typical atmospheric values, indicating that contribution of atmospheric He to the mineralizing fluids is negligible, and 0.08-0.09 Ra is slightly above typical crustal 〈sup〉3〈/sup〉He/〈sup〉4〈/sup〉He ratios. Arsenopyrite yields relatively non-radiogenic initial Os isotopic compositions, also indicating possiblecontribution from mantle fluids. Carbonic fluid inclusion type-2 (H〈sub〉2〈/sub〉O-CO〈sub〉2〈/sub〉-NaCl ± CH〈sub〉4〈/sub〉) in quartz of NW-trending veins at Küre are gas-liquid-hydrate-crystal-rich and their homogenization temperatures (T〈sub〉h〈/sub〉) range from 244 to 387 °C. Salinity values range from 0.2 to 5.7 wt.% NaCl equiv. The homogenization temperatures (T〈sub〉h〈/sub〉) of aqueous fluid inclusions type 1 (H〈sub〉2〈/sub〉O-NaCl) in quartz from NW-trending veins at Küre vary between 237 and 358 °C whereas salinity values range from 1.7 to 7.7 wt.% NaCl equiv. Quantitative EPMA spot analyses on arsenopyrite minerals have shown that As concentrations in EW-trending and NW-trending veins range from 32.5 to 33.8% and 32.3-33.8%, respectively. Based on a phase diagram for the Fe–As–S system along with the arsenopyrite geothermometer, the ranges of temperature and corresponding log〈em〉f〈/em〉 S2, at which arsenopyrite is in equilibrium with pyrite are between 380 and 480 °C, and -7.4 and -4.3 for Apy-1, respectively. These values are between 390 and 475 °C, and -7.0 and -4.5 for Apy-2, respectively.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136818305377-ga1.jpg" width="140" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 116〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: Available online 17 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Grzegorz Gil, Bogusław Bagiński, Piotr Gunia, Stanisław Madej, Michał Sachanbiński, Petras Jokubauskas, Zdzislaw Belka〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nephrites belonging to both the dolomite-related and serpentinite-related genetic types, from the Złoty Stok deposit, and Jordanów Śląski and Nasławice prospects in the Ślęża Ophiolite, respectively, were analyzed for Fe and Sr isotope compositions. These deposits in the Central Sudetes (SW Poland), are unusually situated relatively close to each other. This study is a first attempt to perform combined Fe and Sr isotope study of nephrites. Our results show that Fe in the Fe-As-Au-bearing skarn samples from Złoty Stok (2.77-7.00 wt.% Fe, δ〈sup〉56〈/sup〉Fe +0.07 to +0.14‰, and δ〈sup〉57〈/sup〉Fe +0.12 to +0.21‰), to which the dolomite-related nephrite belongs, is not inherited from the host dolomitic marbles (ca. 0.4 wt.% Fe; δ〈sup〉56〈/sup〉Fe -0.08 to -0.07‰, and δ〈sup〉57〈/sup〉Fe -0.12 to -0.09‰), but derived from the nearby, ca. 340 Ma granite intrusion (2.64-5.64 wt.% Fe). In contrast, iron in the serpentinite-related nephrites (2.06-3.88 wt.% Fe, δ〈sup〉56〈/sup〉Fe +0.41 to +0.45‰, and δ〈sup〉57〈/sup〉Fe +0.59 to +0.66‰) was likely inherited from host serpentinites (5.27-4.81 wt.% Fe), rather than metasomatically derived from adjacent granite intrusions (0.13-0.45 wt.% Fe). Moreover, both the marble transformation into a dolomite-related nephrite (and Fe-As-Au-bearing skarn), and the abyssal serpentinite – through ophiolite – towards serpentinite-related nephrite transformation, are accompanied by a progressive increase of δ〈sup〉56〈/sup〉Fe and δ〈sup〉57〈/sup〉Fe. This increase is regardless of changes in the bulk Fe content, increasing during the dolomite-related nephrite formation, and decreasing during serpentinite-related nephrite formation. This phenomena may be caused by one of the below listed factors, or combinations: a) preferential incorporation of heavy iron by tremolite and diopside; b) preferential incorporation of the heavy iron in the Fe〈sup〉3+〈/sup〉-bearing phases, crystallizing during nephrite formation; c) preferential incorporation of the heavy Fe from migrating granite-derived fluids (positive fractionation between aqueous Fe-bearing fluid, and tremolite/diopside); d) positive isotope fractionation between dolomite/antigorite precursor, and newly formed amphibole/clinopyroxene; e) change of the Fe oxidation state. Furthermore, Fe in the rock-forming tremolite from the serpentinite-related nephrites is isotopically heavier than Fe in tremolite from the dolomite-related ones. In contrast to the iron, the isotopic composition of strontium, combined with its content and structural evidence, suggest multiple sources for this element. In the case of the dolomite-related nephrite (ca. 3-4 ppm Sr; initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr = 0.7085), Sr inheritance from the host-dolomitic marble (ca. 90 ppm Sr; initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr = 0.7081), as well as its derivation from intrusions of both the syn- to late-tectonic, ca. 340 Ma granites (ca. 400-440 ppm Sr), and post-tectonic ∼305 Ma granites (86.4 ppm Sr), is suggested. In the case of the serpentinite-related nephrite (6.3-61.7 ppm Sr; initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr 0.7037 to 0.7081), the situation is similar, i.e., Sr in the most primitive samples tends to be sourced from ophiolitic rocks (up to 2.4 ppm Sr in serpentinite), whereas in the more evolved types, it was likely delivered from the adjacent, ca. 340 Ma (8.8-102.6 ppm Sr) partially rodingitized granites, as well as ∼305 Ma granites (ca. 80 ppm Sr). Moreover, these granites caused the fluid-flow, responsible for Sr-bearing clinozoisite vein formation; these veins are likely related with nephrite formation, and with a metallic mineralization.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819300939-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 17 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Jingya Cao, Xiaoyong Yang, Youyue Lu, Jianming Fu, Lizhi Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Guposhan ore field, located in the central part of the Nanling Range and close to the giant Central South Peninsula tin ore belt, is well-known for its large-scale Sn (W) mineralization and hosts a series of middle to large scale Sn (W) deposits. In this study, medium to fine grained biotite granite, outcropped in the mining area, have zircon U–Pb ages of 162.8 ± 1.3 Ma (MSWD = 0.54) and 162.7 ± 1.2 Ma (MSWD = 0.66), respectively. These zircon ages are consistent to the Sm–Nd isotopic age of minerals (garnet, hornblende, clinopyroxene and orthopyroxene) from the skarn-type ores, which is 160.4 ± 4.8 Ma (MSWD = 1.3). These granites are characterized by high content of SiO〈sub〉2〈/sub〉, K〈sub〉2〈/sub〉O, Na〈sub〉2〈/sub〉O and REEs, and high Ga/Al ratios, indicating that they belong to highly fractionated A-type granites with high-K calc-alkaline and aluminous-peraluminous signatures. The zircon Lu–Hf isotopes of these granites have ε〈sub〉Hf〈/sub〉(t) values and T〈sub〉DMC〈/sub〉 ages of –2.66 to –1.71 and 1.32–1.38 Ga, respectively. Combined with the previous studies, it was proposed that the magma was formed by the mixing of crust-mantle components (ca. 50 and ca. 50%, respectively). In addition, magmas are characterized by low temperatures of ca. 710°C and oxygen fugacity (log(〈em〉f〈/em〉O〈sub〉2〈/sub〉) values of –18.5 to –16.4. Formation of these granites were likely related to an intraplate extensional tectonic setting, triggered by roll-back of the subducted Paleo-Pacific plate beneath the South China Block (SCB). These granites are in favor of the Sn (W) mineralization, making the Guposhan ore district a large-scale Sn (W) mineralization ore field in the Nanling Range.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819300617-ga1.jpg" width="273" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 14 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Guotao Sun, Qingdong Zeng, Lingli Zhou, Yongbin Wang, Peiwen Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Trace elements distribution in minerals and formation mechanism of visible gold are poorly understood in intrusion-related gold systems. Here, we choose the Baiyun gold deposit, which is hosted within the Paleoproterozoic metamorphic rocks in the Liaodong Peninsula, NE North China Craton (NCC), as a case study, to address these issues. The ore deposit geology characteristics and paragenesis are described in details; 〈em〉In situ〈/em〉 geochemical and sulfur isotopic compositions of pyrite and bulk Pb isotopic ratios of pyrite were presented to define the genesis of pyrite that is closely associated with gold mineralization. Three generations of pyrite were recognized based on petrographic studies: metamorphic pyrite (Py0), hydrothermal pyrite (Py1) coexisting with milky quartz, and hydrothermal pyrite (Py2) coexisting with smoky quartz. 〈em〉In situ〈/em〉 laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) spot analysis suggests that both Py0 and Py1 contain low contents of invisible gold (mean 0.19 ppm and 0.17 ppm, respectively). However, Py1 is low in most other trace element contents and contains Au-Ag-Cu-Pb-Bi micro-inclusions. In contrast, Py2 contains both invisible gold (mean 0.50 ppm) and Au-Ag-Cu-Pb-Bi micro-inclusions. Furthermore, LA-ICP-MS mapping reveals the distributions of Ag, Cu, Pb, Bi and Te closely mimic that of Au, indicating an episode of ore-forming fluid rich in Au, Ag, Cu, Pb, Bi and Te. 〈em〉In situ〈/em〉 sulfur isotope analysis of pyrite shows that Py0 has significantly positive δ〈sup〉34〈/sup〉S values (+11.74 to 17.33‰), suggesting that sulfur was derived from sedimentary sources. Py1 and Py2 have negative δ〈sup〉34〈/sup〉S values (–8.53 to –6.19‰, –10.44 to –6.86‰, respectively), indicating that sulfur was derived from oxidized magmatic fluids. The magmatic fluids are concluded to be released from the early Cretaceous microdiorite magmas, providing most of the sulfur and ore-forming metals. Proofs include the close spatial association of the ore bodies and the dykes, as well the uniform Pb isotopic ratios of Py1 and the early Cretaceous microdiorite. Lines of geological, mineralogical, geochemical and isotopic evidence consistently suggest that the gold mineralization in the Baiyun deposit is intrusion-related, and was resulted from the ∼126 Ma magmatic-hydrothermal activities in the region. Visible gold precipitating in pyrite and fractures was from metal-rich magmatic fluids rather than being remobilized from the metamorphic pyrite.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819306948-ga1.jpg" width="263" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Bjorn P. von der Heyden〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Geology researchers commonly confront critical research questions that require microscopic and sub-microscopic level observations (e.g., distribution of chemical elements of economic interest, nature of mineralising fluid) in order to explain the macroscale phenomena related to the characterisation of and controls on ore mineralisation. The emergence and technological evolution of fourth generation synchrotron radiation light sources render these facilities as important, but still largely under-utilised tools for advancing the frontiers of ore related research. To this end, the present contribution seeks to critically review and highlight the power and affordances of synchrotron X-ray techniques specifically to the fields of fundamental- and applied ore geology. The review introduces a range of commonly applied synchrotron X-ray techniques, before comprehensively highlighting past applications of synchrotron X-rays to a range of commodities and ore deposits types. A synthesis of this information highlights the historical importance of synchrotron X-ray techniques towards (1) understanding ore textures and chemical relationships at high (µm) spatial resolutions; (2) understanding coordination chemistry of metals in aqueous fluids at geologically relevant P-T conditions; (3) in situ evaluation of the chemistry and speciation of fluid inclusions; (4) evaluating the coordination environment of deleterious and economic trace metal substitutions in major mineral structures; and (5) understanding the biogeochemical behaviour and transformations of metals in the low temperature (supergene) mineralising environment. These applications as well as recommendations for future work are described in the hope that a greater diversity of ore geology researchers will incorporate synchrotron X-ray tools into their existing suite of analytical and experimental techniques.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819302173-ga1.jpg" width="225" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Cheng Wang, Yongjun Shao, Xiong Zhang, Chunkit Lai, Zhongfa Liu, Huan Li, Chao Ge, Qingquan Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Hengjiangchong gold deposit is located in northeastern Hunan of the central Jiangnan Orogen, South China. Distribution of auriferous sulfide–calcite–quartz vein-type orebodies are controlled by NW-/WNW-trending ductile shear zones, and hosted in the Lengjiaxi Group (Gp.) low-grade metamorphic sequences and the Hengjiangchong granite. Ore minerals include mainly pyrite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite, galena, and native gold, whilst the major alteration styles include silicic, sericite, carbonate and chlorite. Alteration/mineralization can be divided into three stages: quartz–calcite–pyrite–arsenopyrite mineralization (Stage 1), quartz–calcite–polymetallic sulfide mineralization (Stage 2), and quartz–calcite ore-barren alteration (Stage 3). Two types of fluid inclusion (FI) are present in the auriferous sulfide–calcite–quartz ore veins: CO〈sub〉2〈/sub〉-bearing (C) and H〈sub〉2〈/sub〉O-rich (W) type. Petrographic and microthermometric analyses of the FIs yielded homogenization temperatures for Stage 1, 2, and 3 to be 254–377, 191–339, and 134–223 °C, respectively, with corresponding salinities of 2.22–10.37, 2.23–9.98, and 1.56–4.94 wt.% NaCl〈sub〉equiv〈/sub〉. Pressures of Stage 1 and 2 mineralization are estimated to be 280–370 and 170–300 MPa, respectively. δ〈sup〉18〈/sup〉O and δD values are determined to be 9.8–10.1‰ and −70.2 to −68.7‰ (Stage 1), 7.4–8.1‰ and −72.4 to −71.2‰ (Stage 2), and 2.7 to 2.9‰ and −79.1 to −73.0‰ (Stage 3), respectively. These results indicate that the primary ore-forming fluids were derived from a metamorphic source. For the auriferous sulfides, their δ〈sup〉34〈/sup〉S values are of −15.4 to −7.5‰, whilst their 〈sup〉208〈/sup〉Pb/〈sup〉204〈/sup〉Pb, 〈sup〉207〈/sup〉Pb/〈sup〉204〈/sup〉Pb, and 〈sup〉206〈/sup〉Pb/〈sup〉204〈/sup〉Pb values are of 38.663−44.861, 15.637−15.769, and 18.301−20.936, respectively. Both the stable and radiogenic isotopic data indicate that ore-forming fluids and metals were derived from a deeper and higher metamorphic grade source (e.g. underlying metamorphosed rocks). Fluid immiscibility and fluid–rock interactions were likely critical for the gold ore precipitation. The Hengjiangchong deposit exhibits many features of orogenic gold deposits, such as the structural control on orebody distribution, alteration and mineralization styles, and FI microthermometric and H–O–S–Pb isotopic features. Therefore, the Hengjiangchong is best classified as an orogenic gold deposit.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819304639-ga1.jpg" width="190" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): A.D. Titisari, D. Phillips, I.W. Warmada, Hartono, A. Idrus〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Pongkor gold deposit located approximately 90 km southwest of Jakarta is well known as the typical low sulfidation (LS) epithermal gold deposit and the largest gold vein deposit in Indonesia. The Pongkor gold mineralisation has been the subject of several geological studies. Determination of the duration of gold mineralisation events, however, is less well understood. The mineralisation events are important for understanding the genesis of ore deposits. This study presents 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar age results for four adularia samples from Ciguha gold-bearing quartz vein yielding plateau ages of 1.80 ± 0.03 Ma, 2.33 ± 0.32 Ma, and 1.88 ± 0.02 Ma, plus one weighted mean age of 1.95 ± 0.04 Ma. Adularia from the Kubang Cicau gold-bearing quartz veins yielded a 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar plateau age of 2.02 ± 0.03 Ma. The period of adularia growth in the Ciguha vein may have extended from ca. 2.07 to 1.77 Ma that includes the ages of 1.95 ± 0.04 Ma and 1.88 ± 0.02 Ma. The time interval indicates multiple generations of the adularia. The data suggest that mineralisation of Ciguha may have continued episodically or continuously. The age of adularia from the Kubang Cicau gold-bearing quartz vein (2.02 ± 0.03 Ma) is within the error of the Ciguha vein age and the adularia growth of Kubang Cicau vein reveals at the beginning of Ciguha’s adularia growth. The data suggest that gold mineralisation in the Pongkor deposit for Kubang Cicau and Ciguha veins was initiated at the relatively similar time. The 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar adularia ages of this study are within error of the previously reported 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar results (Milesi et al., 1999) but significantly younger than the previously reported K-Ar adularia dating result (Kageyama, 1999 in Rosana and Matsueda, 2002).〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉The data suggest that gold mineralisation in the Pongkor deposit for Kubang Cicau and Ciguha veins was initiated at the relatively similar time.〈/p〉 〈p〉The 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar adularia ages of this study are within error of the previously reported 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar results (Milesi et al., 1999) but significantly younger than the previously reported K-Ar adularia dating result (Kageyama, 1999 in Rosana and Matsueda, 2002).〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819303798-ga1.jpg" width="209" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 18 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): José M. González-Jiménez, Joaquin A. Proenza, Miriam Pastor-Oliete, Edward Saunders, Thomas Aiglsperger, Núria Pujol-Solà, Joan Carles Melgarejo, Fernando Gervilla, Antonio Garcia-Casco〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Moa-Baracoa ophiolite in eastern Cuba is one of the few known ophiolites that display sulfide mineralization attributable to a magmatic origin in association with podiform-chromite ores hosted in the mantle-crust transition. These sulfide ores chiefly consist of Fe-Ni-Cu sulfides, namely pyrrhotite, pentlandite, chalcopyrite and cubanite partly altered to valleriite. The sulfide mineralization is located along the contact between the podiform-like chromite ores and intruding pegmatitic gabroic dykes. The detailed mineralogical study of the sulfide mineralization coupled with the first ever laser ablation ICP-MS analysis reveals that this sulfide mineralization show contents of the precious metals (Os, Ir, Ru, Pt, Re, Au, Ag) and other (semi)-metals (Co, Ni, Cu, Se, Te, Bi, Pb, As Sb) comparable to those sulfides from the magmatic sulfide deposits associated with mafic complexes hosted in the continental crust. The results obtained from this study confirm that Fe-Ni-Cu sulfides at Potosí are magmatic in origin, and very likely derived from the solidification of droplets of sulfide melt segregated by immiscibility from the intruding mafic melts once they interacted with the pre-existing chromitite at the mantle-crust transition zone of the ophiolite. The immiscibility of sulfide melt was achieved as a result of a progressive increase of 〈em〉f〈/em〉S〈sub〉2〈/sub〉, very likely triggered by a set of circumstances, including the progressive fractionation of the intruding mafic melt leading to increase of 〈em〉a〈/em〉SiO〈sub〉2〈/sub〉 and accumulation of volatiles as well as the crystallization of oxides. Two main generations of pentlandite were observed. One generation is primary in origin and it was locally exsolved along with pyrrhotite from monosulfide solid solution (〈em〉MSS〈/em〉) during low-temperature cooling. The second type of pentlandite resulted from the reaction of 〈em〉MSS〈/em〉 with coexisting droplets of Cu-and Ni-rich sulfide melt. LA-ICP-MS analysis reveals that most precious metals (Ru, Os, Ir, Re, Au, Ag) were concentrated along with the base-metal sulfides (BMS), although their distribution among the different BMS (pyrrhotite, pentlandite, chalcopyrite and cubanite) does not strictly follow the expected distribution according to the known melt-solid and solid-solid partition coefficients. Unlike the other analyzed PGEs, Pt was not preferentially concentrated in BMS but as discrete micrometer-sized sperrylite grains. The crystallization of sperrylite took place before and contemporaneous to sulfide segregation, and Pt-As nanoparticles probably played an important role in the Pt uptake as nucleation seeds for the formation of micron-sized sperrylite grains. These observations highlight the open-system nature of the ore forming system as well as the important role of arsenic in concentrating PGE in high-temperature silicate and sulfide melts.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819310583-ga1.jpg" width="266" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 18 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Kun-Yue Ling, Hao-Shu Tang, Zheng-Wei Zhang, Han-Jie Wen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Carboniferous karstic bauxite-bearing rock series in central Guizhou Province in southwest (SW) China is rich in trace elements, particularly Li, Ga, V, and rare earth elements (REEs), which have potential for comprehensive utilization as independent deposits or associated resources. However, the host minerals of Li, Ga, V, and REEs are not well-constrained because the sedimentary rocks are characteristics by complex mineral composition and fine mineral particles. This situation considerably hinders the compressive utilization of these trace elements in bauxite. Herein, laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) was successfully applied to element geochemistry analysis of hydrous minerals (diaspore/boehmite, kaolinite, and illite) in karstic bauxite samples, based on the principle that laser ablation data of all oxides were normalized to the sum of 100% minus the total volatile components of the mineral chemical formula. The analysis showed signal stabilization. Results indicated that the bivariate plots of selected elements had characteristics similar to statistical results of whole-rock samples from global bauxites, thereby indicating that the LA–ICP–MS analysis data were reliably but artificially herein. Combined with whole-rock geochemistry studies, the analysis results revealed that smectite may be the main host minerals of Li. Furthermore, Ga was enriched in diaspore/boehmite; V was mainly enriched in iron-bearing minerals, particularly chlorite; and REE-independent minerals, such as monazite, were the main host minerals of REEs in the Carboniferous karstic bauxite in SW China. This study contributed to the knowledge on the use of in-situ method for the element geochemistry investigation of hydrous minerals and sedimentary rocks.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S016913681930349X-ga1.jpg" width="295" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 11 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Allan Trench, Rebecca Gordon, John Sykes〈/p〉

Description: 〈p〉Publication date: Available online 9 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): H.G. Dill〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The Central European Variscides and their epicontinental basins and grabens (Mesoeurope 〈em〉sensu〈/em〉 Stille) subsided into the uplifted basement as well as the Alpidic Orogens, encompassing the Alpine Mts. Range, the Dinarides, the Northern Carpathians and the depressions in between (Neoeurope) are rife with a great variety of clay mineral assemblages. In many places the clay mineral deposits reach economic grade and several phyllosilicates can be used as an ore guide to non-clay mineral deposits. Time, climate and the geodynamic setting are the decisive parameters for the clay mineral accumulation. Time constitutes the x-axis for the plots illustrating the global climate change and the regional geodynamic crustal variation. It is also some kind of a yardstick to measure the preservation potential and the stability of phyllosilicates. The geological time scale is equivalent to a depth of a drill hole which penetrates different geological units characterized by various zones of post-depositional alteration. As such the geological age of formation is synonymous with an increase of the P-T regime where important boundaries concerning the micaceous phyllosilicates, kaolinite-, smectite-group minerals and the composition of glauconite are observed.〈/p〉 〈p〉The Mg-bearing phyllosilicates are marker for the Permo-Carboniferous to early Triassic and for the Middle to Late Jurassic extensional regimes in Central Europe. They indicate an ensialic geodynamic regime in Mesoeurope and an ensimatic regime in Neoeurope. This is also true for the presence and absence of Li-bearing phyllosilicates and Li-bearing tourmaline and spodumene which are a mirror image of the Permo-Carboniferous compressive regime in the Variscides and the extensional regimes in the Alpides and indicative of an ensialic and ensimatic regime, respectively. In the ensimatic geodynamic setting of the Neo- and Paratethys during the Miocene and Pliocene a felsic volcanic activity in an interarc-to back arc environment brought about an Fe-poor clay mineral assemblage in an ensimatic setting. In the ensialic Variscides only small-sized kaolinite deposits can be taken as an equivalent. Some ferroan saponite and chlorite represent the basic branch of the bimodal rift magmatic activity. Bentonitic clays and bentonites in the Alpine and Carpathian Foredeeps are marker beds for rift-related explosive volcanic activity sourced particularly in the North Atlantic Province and important mineral deposits.〈/p〉 〈p〉Fe-bearing phyllosilicates, e.g. chamosite, in the Early Ordovician and Jurassic ironstones were emplaced in a marginal and epicontinental basins, locally with restricted circulation. The Alpine extensional regimes saw the formation of celadonite in a calcareous depositional environment open to ocean. They act as facies indicators.〈/p〉 〈p〉Some phyllosilicates act as a natural multifunction display. Corrensite and mixed-layer chlorite-corrensite are not only in altered basic magmatic rocks marker for basement rocks but also affected by extraterrestrial impacts. The glauconite-kaolinite-illite-smectite-chlorite assemblages are efficient tools for the depositional environment and the post-depositional alteration, all in one. There exists an antagonism 〈em〉par excellence〈/em〉 in terms of the sedimentary environment of formation between glauconite and kaolinite The clay mineral catena together with palygorskite and sudoite can be used as a proximity indicator from land to sea from the various subenvironments, e.g., from a coastal sabkha to the alluvial fan. Chromium muscovite, Cr smectite, and Cr chlorite formed at the brink from hypogene to supergene alteration and pave the way from the geodynamic/ lithofacial - to the climate-induced clay mineralization. They are the most recent clay mineral assemblages in Central Europe proved by radiometric age dating (Mio-Pliocene).〈/p〉 〈p〉The humid-tropical paleoclimate zone occurred from the Late Triassic to the Late Cretaceous, the Late Cretaceous to the Eocene, and during the Miocene. In Central Europe these paleoclimates and the resultant weathering conditions were most effective in the formation of residual clay deposits dominated by kaolin and Ni-Co laterites (garnierites) enriched in Al-, Fe- and Mn-duricrusts of economic grade. The climax of formation was reached around the Paleocene-Eocene Temperature Maximum (PETM).〈/p〉 〈p〉The tropical wet and dry paleoclimate zone in Central Europe was widespread during the Jurassic and Cretaceous leading to similar residual clay deposits impoverished in duricrusts. Residual clays in the tropical arid and semi-arid paleoclimate zones have palygorskite, corrensite and sudoite as typical phyllosilicates which denote the widespread occurrence of evaporates with the precipitation level reaching the K salt and even bittern stages. These clay minerals appeared episodically from the Late Permian through the Late Triassic. It is a paleoclimatic zone still under-explored as to Al-rich Li-Mg-bearing phyllosilicates.〈/p〉 〈p〉The high economic potential of clay minerals in Central Europe may be discovered among construction and non-construction raw materials from cement-making materials to structural clay products. Second to none are clay minerals in the construction sector used for all kinds of bricks and tiles. The majority of clay deposits is allocated to the Cenozoic, mainly Paleogene, followed by Mesozoic, Paleozoic and Precambrian rocks which is a manifesto for the expression “Clay & Time”.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819309321-ga1.jpg" width="268" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Yongzhen Long, Anhuai Lu, Xiangping Gu, Guoxiang Chi, Lin Ye, Zhongguo Jin, Dongliang Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cobalt can be enriched in a variety of different geologic settings, while it is mainly produced as a by-product of sediment-hosted stratiform Cu deposits and magmatic Ni-Cu deposits associated with mafic and ultramafic rocks. In this study, we report elevated Co concentrations in a paleo-karstic bauxite deposit at Yunfeng, Guizhou Province. Whole-rock chemical analyses indicate that Co is concentrated in carbonaceous ferruginous clay layers (167–962 ppm, average 383 ppm, n = 5) and siderite layers (47–439 ppm, average 213 ppm, n = 7) within the bauxite deposit. The positive correlation between Co and S, together with petrographic and EPMA analyses, suggests that Co occurs primarily as Co-rich/bearing sulfides/sulfoarsenides rather than cobaltiferous oxides/hydroxides as in most lateritic Ni-Co deposits. Many of the Co concentrations measured in this study are higher than the minimum grade (300 ppm) or cut-off grade (200 ppm) for economic exploitation of Co from sulfides or arsenides. Basing on these results, we put forward the scientific significance of Co enrichment in paleo-karstic environments and the potential importance of Co resources (as by-products of aluminum production) in bauxite deposits.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819308546-ga1.jpg" width="462" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 26 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Jiancheng Xie, Likai Ge, De Fang, Quanzhong Li, Lin Qian, Zhensheng Li, Jun Yan, Weidong Sun〈/p〉

Description: 〈p〉Publication date: Available online 25 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): F. Putzolu, I. Abad, G. Balassone, M. Boni, P. Cappelletti, S.F. Graziano, M. Maczurad, N. Mondillo, J. Najorka, L. Santoro〈/p〉

Description: 〈p〉Publication date: Available online 21 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Sangita Chowdhury, Dipak C. Pal, Dominic Papinue, David R. Lentz〈/p〉

Description: 〈p〉Publication date: Available online 20 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Lin-Gang Xu, Zhi-Gang Kong, Jian-Fei Qu, Bao-Long Li, Zhi-Yin Qiu, Paul Olin, Leonid Danyushevsky〈/p〉

Description: 〈p〉Publication date: Available online 20 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): C.M. Lesher〈/p〉

Description: 〈p〉Publication date: May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 120〈/p〉 〈p〉Author(s): Xiang Liu, Jianjin Cao, Wanqiang Dang, Zixia Lin, Junwei Qiu〈/p〉

Description: 〈p〉Publication date: May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 120〈/p〉 〈p〉Author(s): Jiuyang Jiang, Yongfeng Zhu〈/p〉

Description: 〈p〉Publication date: May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 120〈/p〉 〈p〉Author(s): Rosaline C. Figueiredo e Silva, Lydia M. Lobato, Marcia Zucchetti, Steffen Hagemann, Torsten Vennemann〈/p〉

Description: 〈p〉Publication date: Available online 15 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Lei Zhao, Shifeng Dai, Victor P. Nechaev, Evgeniya V. Nechaeva, Ian T. Graham, David French〈/p〉

Description: 〈p〉Publication date: May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 120〈/p〉 〈p〉Author(s): Munir M.A. Adam, Xinbiao Lv, A.A. Abdel Rahman, Robert J. Stern, Asma A.A. Abdalrhman, Zaheen Ullah〈/p〉

Description: 〈p〉Publication date: April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 119〈/p〉 〈p〉Author(s): Hua-Wen Cao, Guang-Ming Li, Zhi Zhang, Lin-Kui Zhang, Sui-Liang Dong, Xiang-Biao Xia, Wei Liang, Jian-Gang Fu, Yong Huang, An-Ping Xiang, Cheng-Shi Qing, Zuo-Wen Dai, Qiu-Ming Pei, Yun-Hui Zhang〈/p〉

Description: 〈p〉Publication date: April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 119〈/p〉 〈p〉Author(s): Qingmin Zhu, Yongfeng Zhu〈/p〉

Description: 〈p〉Publication date: April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 119〈/p〉 〈p〉Author(s): Erika Tanaka, Kentaro Nakamura, Kazutaka Yasukawa, Kazuhide Mimura, Koichiro Fujinaga, Koichi Iijima, Tatsuo Nozaki, Yasuhiro Kato〈/p〉

Description: 〈p〉Publication date: April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 119〈/p〉 〈p〉Author(s): Gaofeng Du, Xiaoyong Yang, Jingya Cao, Jasmi Hafiz Abdul Aziz〈/p〉

Description: 〈p〉Publication date: Available online 4 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Christopher J.L. Wilson, David H. Moore, Stefan A. Vollgger, Harry E. Madeley〈/p〉

Description: 〈p〉Publication date: April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 119〈/p〉 〈p〉Author(s): Rhys S. Davies, David I. Groves, Allan Trench, Michael Dentith〈/p〉

Description: 〈p〉Publication date: May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 120〈/p〉 〈p〉Author(s): Isaac S. Malta, Frederico M. Faleiros, Lena V.S. Monteiro, Marcelo B. Andrade, Bruna Coldebella, Melina C.B. Esteves〈/p〉

Description: 〈p〉Publication date: Available online 1 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Saleh Ibrahim Bute, Xiaoyong Yang, Cheo Emmanuel Suh, Musa Bala Girei, Musa Bappah Usman〈/p〉

Description: 〈p〉Publication date: April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 119〈/p〉 〈p〉Author(s): Yuzhou Feng, Yu Zhang, Youliang Xie, Yongjun Shao, Huajie Tan, Hongbin Li, Chunkit Lai〈/p〉

Description: 〈p〉Publication date: April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 119〈/p〉 〈p〉Author(s): Junchen Liu, Yitian Wang, Qiaoqing Hu, Ran Wei, Shikang Huang, Zhenghao Sun, Jiaolong Hao〈/p〉

Description: 〈p〉Publication date: Available online 1 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Benedict Kinshasa Pharoe, Alexander Nikolaevich Evdokimov, Irina Mikhailovna Gembitskaya, Yakov Yurievich Bushuyev〈/p〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 118〈/p〉 〈p〉Author(s): Liam Courtney-Davies, Cristiana L. Ciobanu, Max R. Verdugo-Ihl, Nigel J. Cook, Kathy J. Ehrig, Benjamin P. Wade, Zhi-Yong Zhu, Vadim S. Kamenetsky〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Spatial associations between banded iron formation and iron-oxide Cu-Au (IOCG) style mineralization are well documented in the Gawler Craton (South Australia), but the possible genetic relationships between these two distinct types of mineralization are hitherto unclear. A texturally conspicuous generation of coarse-grained silician magnetite, intergrown with carbonates and quartz, is observed in drillholes intersecting the ‘outer shell’ of the Olympic Dam IOCG-type deposit. This magnetite is characterised by high U-content (~50 ppm), siliceous chemistry, and unusual zonal textures with respect to Si-Fe-nanoprecipitates. Direct dating of this magnetite by laser ablation inductively coupled plasma mass spectrometry yields reproducible 〈sup〉207〈/sup〉Pb/〈sup〉206〈/sup〉Pb dates (1761 ± 16 Ma) that are significantly older than the granite hosting the deposit (1593 Ma), or the mineralized breccias constituting the Cu-U-Au-Ag resource (~1592–1589 Ma). The older, Fe-rich crustal material can be correlated with the ~1.76–1.74 Ga (meta)sedimentary Wallaroo Group, host to Fe-rich horizons across the Gawler Craton, including locations ~15 km NW of Olympic Dam. A generation of granitic rocks, which intruded bedrock at ~1.75 Ga are present ~30 km NE of Olympic Dam, and likely exsolved hydrothermal fluids that enriched pre-existing magnetite-bearing protoliths in both U and REE. Such material was physically, and likely chemically, incorporated into the ‘outer shell’ at Olympic Dam some ~150 Ma later, during granite uplift along faults. The coincidence between Fe-rich horizons/BIF and ~1750 Ma granitoids may have provided IOCG systems with an additional source of both Fe and U that predates the ~1.59 Ga craton-scale metallogenic event. The uranium concentrations in some South Australian IOCG systems represent major global anomalies in the element. A combination of the fortuitous geological circumstances outlined here, may help explain the highly anomalous accumulation of uranium found at Olympic Dam.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819309242-ga1.jpg" width="250" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 118〈/p〉 〈p〉Author(s): Liang Yue, Yangquan Jiao, Liqun Wu, Hui Rong, Mostafa Fayek, Huili Xie〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pyrite is an abundant mineral throughout the uranium-bearing Middle Jurassic Zhiluo Formation, northern Ordos Basin. Three different morphologies of pyrite are identified: framboidal, euhedral and cement. Based on textural and geochemical results from optical microscopy, secondary electron (SE) and back scattered electron (BSE) imaging, energy-dispersive spectroscopy (EDS), electron probe microanalysis (EPMA), and laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS), three evolutionary models are proposed as follows: aggregation of framboids to form polyframboids as a result of the bacterial sulfate reduction (BSR) processes, the formation of cement pyrite under the addition of thermal fluids with numerous framboids and microcrystals inside, and euhedral pyrite evolving from framboids. The analytical data show that there is a minor increase in major and trace element contents in transformed pyrite, and each pyrite morphology has a distinct sulfur isotopic composition (−9.9‰ to −8.0‰ for framboids, −19.1‰ to −14.2‰ for polyframboids, +18.7‰ to +20.3‰ for euhedral pyrite, and +15.7‰ to +21.2‰ for cement pyrite). This indicates that the sulfur was derived from more than one source, compared with the original framboids. The association between uranium and different types of pyrite indicates that different processes (e.g., BSR and thermogenic sulfate reduction (TSR)) were involved in the precipitation of uranium mineralization and are important to the formation of the precipitation of uranium in the Zhiluo Formation, northern Ordos Basin.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract:〈/h5〉 〈div〉 〈p〉In the sandstone-type uranium deposits in northern Ordos Basin, the micromorphologies of pyrite are categorized as framboidal, euhedral and cement. Three evolutionary models are suggested to interpret the evolution and origins of the pyrite based on petrological observations and chemical documents. The occurrence characteristics between uranium and different transformed pyrite indicate the different process of uranium mineralization, and the origins of pyrite from bacteria to thermal fluids have a certain significance for the study of metallogenic law of uranium in the sandbodies of the Zhiluo Formation in northern Ordos Basin.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819301623-ga1.jpg" width="170" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Zakaria Adiri, Rachid Lhissou, Abderrazak El Harti, Amine Jellouli, Mohcine Chakouri〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thanks to their wide coverage and the valuable spectral information, remote sensing data constitute a popular instrument in the mineral exploration toolbox. In recent times, the remote sensing community has witnessed the launch of the new and improved Landsat-8 and Sentinel-2 multispectral sensors. The former constitutes the eighth sensor of the Landsat series launched by the National Aeronautics and Space Administration (NASA), while the latter is linked to the Sentinel-mission launched by the European Space Agency (ESA). The main objective of our contribution is to provide a comprehensive review of the use of the Landsat-8 and Sentinel-2 multispectral sensors in mineral exploration. The free and open access to these data and their enhanced spectral and spatial characteristics (compared to the existing multispectral sensors) has clearly promoted the use of remotely sensed in mineral exploration. In addition, as illustrated by the case studies presented in this paper, Landsat-8 and Sentinel-2 data present effective and accurate mapping tools for mineral exploration. Both sensors identified iron oxides and Al-OH absorption features, in addition to silicate and carbonate minerals. Our review indicated that Landsat-8 is by far the more popular sensor in mineral exploration applications. Greater uptake of Sentinel-2 and further case studies will be necessary to better demonstrate its capabilities and potential.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819305517-ga1.jpg" width="268" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 118〈/p〉 〈p〉Author(s): Vivek K. Sengar, A.S. Venkatesh, P.K. Champati ray, P.R. Sahoo, Israil Khan, Shovan L. Chattoraj〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper discusses the effectiveness of spectroscopic techniques for identifying hydrothermal alteration zones associated with the Mundiyawas-Khera copper deposit, Alwar Basin, western India, and assesses implications for mineral exploration targeting in the greater Alwar basin. Mineral specific SWIR bands of ASTER were spectrally enhanced to highlight areas of anomalous Al-OH and Mg-OH responses, representing key mappable expressions of the Mundiyawas-Khera copper deposit. The hydroxyl-bearing mineral zones were identified at 98% and 95% threshold pixels, respectively. Kaolinite ± scapolite, sericite (muscovite), tremolite and dolomite, contained in the felsic volcanic and dolomitic copper host rocks, were identified from spectroscopic data and corroborated with petrographic and XRD data. On this basis, distinct argillic, phyllic and propylitic hydrothermal alteration zones could be identified at Mundiyawas-Khera. The integrated approach presented here (i) identified a well defined phyllic alteration pattern in the felsic volcanic rocks, (ii) resulted in a comprehensive remotely sensed hydrothermal alteration map illustrating the spatial distribution of the copper-related hydrothermal alteration zones (i.e., an eastern argillic, a central phyllic, and a western propylitic zone), (iii) helped to delineate potential copper-rich zones coincident with a known lithostructural trend, and (iv) has implications for copper exploration in the greater Alwar basin.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Simplified remotely sensed hydrothermal alteration map of the Mundiyawas-Khera copper deposit and photomicrographs of the mineralized rocks comprising sericite (Ser) and scapolite (Scp), the major constituents of the phyllic alteration zone.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819301829-ga1.jpg" width="244" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 11 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Xiang-Guo Guo, Jin-Wen Li, De-Hui Zhang, Fei Xue, Han-biao Xian, Shuai-Jie Wang, Tian-Long Jiao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Dongbulage porphyry Mo deposit is a recently discovered deposit located in the Huanggang–Ganzhuermiao polymetallic metallogenic belt of Inner Mongolia, NE China. Here, we present zircon U–Pb ages and Hf isotopic compositions, and whole-rock geochemical and Sr–Nd–Pb isotopic data, for magmatic rocks associated with Mo mineralisation to constrain the age and petrogenesis of these rocks. The rocks are dominated by mineralised granite porphyries, quartz-monzonites, and rhyolite. Zircon U–Pb dating shows that the ore-bearing granite porphyries have ages of 154.4 ± 3.5, 155.4 ± 1.1, and 158.7 ± 0.6 Ma, the quartz-monzonites have ages of 157.8 ± 1.6 and 166.5 ± 1.3 Ma, and the rhyolite has an age of 172.9 ± 3.0 Ma. The granite porphyries and rhyolites are characterised by high K〈sub〉2〈/sub〉O and SiO〈sub〉2〈/sub〉 contents, enrichment in light rare-earth elements, strong negative Eu anomalies, and pronounced depletion in Ba, Nb, Ta, Sr, P, and Ti. The quartz-monzonites show enrichment in large-ion lithophile elements (Rb and K), are depleted in heavy rare-earth elements, Nb, Ta, Sr, P, and Ti, and exhibit weak negative Eu anomalies. All of the rocks have low initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr (0.7022–0.7064) and ε〈sub〉Nd〈/sub〉(〈em〉t〈/em〉) values (−3.62 to +3.99), positive ε〈sub〉Hf〈/sub〉(〈em〉t〈/em〉) values (+1.1 to +13.8), and young two-stage Nd and Hf model ages (〈em〉T〈/em〉C DM(Nd) = 623–1240 Ma and 〈em〉T〈/em〉C DM(Hf) = 305–1108 Ma, respectively). Whole-rock Pb isotopic compositions show a narrow range of values, with 〈sup〉206〈/sup〉Pb/〈sup〉204〈/sup〉Pb = 18.314–19.116, 〈sup〉207〈/sup〉Pb/〈sup〉204〈/sup〉Pb = 15.573–15.595, and 〈sup〉208〈/sup〉Pb/〈sup〉204〈/sup〉Pb = 38.731–39.296, which, together with their Sr–Nd–Hf isotopic compositions, indicate the dominance of a mantle source component. The isotopic data suggest that the Dongbulage magmatic rocks were derived from partial melting of juvenile lower crust. The granite porphyries are highly evolved I-type magmas with geochemical characteristics similar to those of porphyry granitoids associated with Mo mineralisation in the Great Hinggan Range. On the basis of the regional geology and geochemistry, we suggest that the Dongbulage porphyry Mo deposit formed in a subduction setting associated with southward subduction of the Mongol–Okhotsk oceanic plate.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819306043-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Lei Xu, Jin-Hui Yang, Qing-Dong Zeng, Lie-Wen Xie, Yu-Sheng Zhu, Rui Li, Bin Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sr-Nd-Fe isotopes are reported for pyrites and whole rocks of ores and associated rocks for the Qingchengzi Pb-Zn deposits in the northeasern China, to investigate the age, sources and processes of the Pb-Zn mineralization. Rb-Sr leaching isotopic dating of pyrites that crystallized coeval with galena and sphalerite from five subsamples of ores yields isochron ages of 143 ± 12 Ma to 159 ± 12 Ma with a weighted mean age of 151.8 ± 5.2 Ma. This age can be interpreted to be the timing of Pb-Zn mineralization, coeval with the emplacement of Late Jurassic granites in the region. The pyrites have negative ε〈sub〉Nd〈/sub〉 (152 Ma) values of −17.6 to –22.0, among the Neoarchean TTG rocks, Paleoproterozoic meta-sedimetary rocks (i.e., wall rocks) and granites, and Mesozoic mafic dykes and granites. However, the initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratio of 0.7188 ± 0.0004 is similar to those of Late Jurassic granites and Paleoproterozoic rocks (0.7082–0.7183), distinct from those of mafic dykes (0.7069–0.7110), indicating the ore-forming materials (i.e., Pb and Zn) were mainly derived from wall rocks and Late Jurassic granites. Combined with the previously-published H-O isotopes, the new age and Sr-Nd isotopic data indicate that the mineralizaing fluids were mainly derived from dehydration of granitic magmas, interacted with meteoric water that extracted Pb and Zn from the wall rocks. The δ〈sup〉56〈/sup〉Fe values of pyrites in the Pb-Zn ores and Paleoproterozoic meta-sedimentary rocks range from +0.23‰ to +1.09‰ and −0.49‰ to +0.17‰, respectively, distinct from those of Paleoproterozoic basement rocks and Mesozoic rocks (−0.03‰ to +0.28‰). Combined with Nd isotopes, the large range of δ〈sup〉56〈/sup〉Fe values for pyrites would be the result of rapid precipitation of pyrites in the wall rocks and contemperal deposition of pyrites in the residual fluids during interaction between wall rocks and ore-forming fluids. Collectively, our new Sr-Nd-Fe isotopes of pyrites not only constrain the age and sources of Pb and Zn mineralization, but also reveal the detailed mineralization processes, providing a new method to constrain the genesis of hydrothermal Pb-Zn deposits.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819306134-ga1.jpg" width="352" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 11 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Gert Heuser, Gloria Arancibia, Eugenio Veloso, José Cembrano, Pedro Cordeiro, Mathias Nehler, Rolf Bracke〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Fe-Cu Dominga deposit (2082 Mt at 23% Fe, 0.07% Cu), located in the Coastal Cordillera of northern Chile, is hosted by volcanic rocks of the Punta del Cobre Formation (131.5±1.5 Ma zircon U-Pb) and into subvolcanic units (Dioritic Complex, 131.6±1.0 Ma zircon U-Pb). The Fe-Cu mineralization is controlled by three structural systems which developed from a transtensional to a transpressional tectonic regime and can be divided into three groups: Early iron, Late iron and Early copper ores. Early iron ores are comprised of magnetite+pyrite+biotite breccia (1A ore), veins (1B ores), layers (1C ores) and disseminated ores (1D ores). Late iron ores are characterized by two groups of magnetite-apatite-actinolite hydrothermal breccias (2A, 2C ores) and syntaxial/antitaxial veins (2B, 2D, 2E ores). Early copper ores occur as syntaxial K-feldspar and quartz+epidote+chalcopyrite veins (3A ores), and as anhydrite+chalcopyrite-rich matrix breccia and veins (3B ores). This work presents a detailed mineral texture study of veins, hydrothermal breccias and disseminated iron-rich layers of the Dominga deposit which aims to determine fluid flow mechanisms associated with both iron and copper ores. The description of vein and breccia textural and internal structures was conducted in thin/polished sections perpendicular and parallel to the wall using optical and Scanning Electron Microscope techniques. In addition, two oriented surface samples were analyzed by computerized X-ray microtomography and numerical fluid flow simulations through the Lattice-Boltzmann method to obtain (3D) permeability anisotropy associated with early iron ores. Microtextures associated with Dominga iron and copper ores suggest that the main mass transfer fluid flow mechanism corresponds to advection (channelized and pervasive fluid flow), regardless of the tectonic regime. However, early copper ores have more complex mineral textures and internal structure due to the recurrence of crack-seal episodes. We propose that the various mineral textures and structures indicate changes in fluid flow direction over time, controlled by the permeability anisotropy of each tectonic regime. Results from numerical fluid flow simulations of early iron ore (1B) veins show a higher value of structural permeability in the vertical direction (k〈sub〉Vz〈/sub〉), which is consistent with a transtensional tectonic regime and the formation of vertical veins. Moreover, permeability related to 1C layered ore is higher in horizontal directions (k〈sub〉Hx〈/sub〉, k〈sub〉Hy〈/sub〉) rather than vertical (k〈sub〉Vz〈/sub〉) because of the natural permeability anisotropy of volcaniclastic rocks parallel to bedding. However, the k〈sub〉Vz〈/sub〉 value suggests that the development of such layered ores also exhibits a degree of structural control at several length scales consistent with a transtensional regime. These results indicate that the occurrence of early iron ores as veins and layers may be controlled by both primary permeability anisotropy related to each lithology present at the Dominga Fe-Cu deposit and to the tectonic regime at the time. Finally, the Dominga Fe-Cu deposit attests to long lived hydrothermal activity with a transition from early fluids capable of precipitating iron ores under a transtensional system to later-stage fluids which precipitated copper ores under a transpressional regime that generated multiple crack and seal episodes.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819305773-ga1.jpg" width="284" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Z. Alaminia, M. Tadayon, F. Finger, D.R. Lentz, M. Waitzinger〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The Abbas-Abad volcano-sedimentary-hosted Fe-Cu skarn deposit, NE Isfahan, is one of the most important skarns in the central Urumieh-Dokhtar magmatic arc. It was formed along the contact with the Dorojin granitoid massif next to the Zefreh Fault. The plutonic rocks are of I-type, volcanic arc affinity with normal-K, metaluminous, calc-alkaline to calcic quartz diorite, tonalite, and granodiorite, similar to many other Fe-type skarn-related granitoids worldwide. The parent magma involved in this skarn system is high temperature and relatively oxidized. Amphibole geobarometery in quartz diorite yielded a crystallization pressure lower than 200 MPa (2 kb, ~7 km) at 724° to 785 °C. Granitoid compositions around the ore deposit are mainly granodiorite. U-Pb zircon dating yields Early Miocene ages of 23.0 ± 1.6 Ma for a quartz dioritic rock and 21.3 ± 1.5 Ma for a tonalitic sample. The injection and cooling of the granodiorite produced a hornblende hornfels aureole with endoskarn.〈/p〉 〈p〉Paragenetic relationships and microprobe data indicate that Abbas-Abad calcic skarn evolution can be subdivided into three stages as follow: (I) Prograde skarn associated andradite-rich garnet (Adr〈sub〉93-98〈/sub〉Grs〈sub〉0-4〈/sub〉Spe〈sub〉1-2〈/sub〉) and pyroxene, (II) Retrograde skarn starting with garnet (Adr〈sub〉53-69〈/sub〉Grs〈sub〉28-43〈/sub〉Spe〈sub〉2-4〈/sub〉), magnetite, and sulfide minerals associated with calcic-alteration, and (III) Post-ore with pyrite, chalcedony, epidote, quartz, calcite, and zeolite veinlets. Textural and compositional studies of garnet and magnetite from the garnet-bearing exoskarn zone reveal the multiple events associated with skarn formation. Garnets are characterized by low TiO〈sub〉2〈/sub〉 and relatively high CaO that are indicative of a calcareous wall-rock among Eocene volcaniclastic rocks. They are grouped into garnet-1 (low w/r) and garnet-2 (inverse zoning at high w/r) with notable Cu-contents (up to 743 ppm). Petrographically, magnetite morphology is divided into fine-grained granular, needle-like, and polycrystalline aggregates. Mineral chemistry of needle-like type reveals impure components (Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, CaO, and SiO〈sub〉2〈/sub〉). This type formed from dissolution-reprecipitation processes during a stage of reequilibration in the skarn system. Mixing with cooler external fluid (rich in oxygen and poor in Fe〈sup〉2+〈/sup〉) is reflected in individual features during infiltration metasomatism during garnet and magnetite growth, such as oscillatory zoning and needle-like textures. Thus, we infer increasing pH (decreasing acidity) and decreasing T related to carbonate neutralization reactions affecting Fe- and Cu-chloride complexing as the main controls on mineralization.〈/p〉 〈p〉The structural studies of the area show that movement of the dextral transtensional Zefreh Fault provide local zones for emplacement of Dorojin granitoid during the Early Miocene. Consequently, the dextral transtensional Zefreh Fault and dextral transpression associated with the Marbin-Rangan Fault uplifted the skarn and host units and Dorojin body under the roughly N-S directed maximum compression direction. Furthermore, the interplay of Zefreh and Marbin-Rangan faults within the N-S regional compressional regime formed an anticlinal structure that exposed the Dorojin body within the core.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136818309855-ga1.jpg" width="309" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 10 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Guopeng Wu, Guoxiong Chen, Detao Wang, Qiuming Cheng, Zhenjie Zhang, Jie Yang, Shuyun Xie〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Since the discovery of several large porphyry Mo deposits (〉0.1 Mt Mo) in the Jining region of Inner Mongolia, China, during the past decades, the area has been receiving wide interest for mining activities. However, mineral exploration in this area is challenging because most of it is thickly covered by Cenozoic sediments. Geophysical surveys, especially the seismic method, are becoming increasingly important for investigating deep-seated ore-controlling structures (e.g., porphyry granites, faults and even orebodies), supporting the discovery of buried ore deposits. Recently, potential field data and seismic reflection data have been acquired for the Hongniangyu area, south of Jining region. In this study, we mainly use seismic reflection and potential field data to obtain subsurface geological model in support of mineral exploration targeting. Gravity and magnetic data were firstly used for spatial analysis of mineral system by mapping the distribution of the faults, concealed granites, and the sedimentary basin (through wavelet analysis, tilt angle, and Euler deconvolution). To address the common problem of low signal-to-noise ratio of seismic reflection data obtained in hard-rock terranes, we applied a sophisticated workflow including refraction static correction, noise filtering, surface-consistent deconvolution, and velocity analysis. The obtained post-stack migrated seismic profile clearly imaged the geometry of the concealed graben located at the north end of the Datong Basin, and the South-East dipping Kouquan normal fault controls the depression of the graben and offsets Cenozoic sediments by several hectometers up to ∼500 m. Joint modeling of seismic, gravity and magnetic data further provided evidence of the three buried belts of granites. Intriguingly, one of the concealed granitic belts located in the north of Hongniangyu area was found to have both significant chargeability and Mo geochemical anomalies, indicating a high potential of hosting porphyry-type Mo ore deposits. As expected, Mo and W mineralized cores were discovered in this target area but limited to only one deep drilling hole. The presented results provide the geological framework of Hongniangyu district and guidelines for delineating new potential Mo mineralization in the Jining region.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S016913681930441X-ga1.jpg" width="190" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Guoxiang Chi, Kenneth Ashton, Teng Deng, Deru Xu, Zenghua Li, Hao Song, Rong Liang, Jacklyn Kennicott〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Many uranium deposits are related to granitic rocks, but the mineralization ages are much younger, thus excluding a direct magmatic-hydrothermal link between the mineralization and the granites. Two such examples are the Proterozoic “vein-type” uranium deposits in the Beaverlodge district in Canada and the Mesozoic granite-related uranium deposits in South China. Both areas have been extensively studied, but the critical factors that control the mineralization remain unclear.〈/p〉 〈p〉The uranium mineralization in the Beaverlodge district occurs in quartz – carbonate ± albite veins and breccias developed within and near major deformation zones, and are mainly hosted by ca. 2.33 – 1.90 Ga granitic rocks and ca. 2.33 Ga Murmac Bay Group amphibolite. These rocks are unconformably overlain by the Martin Lake Basin, which was formed during a period of regional extension in the later stage of the Trans-Hudson orogeny and is filled with red beds. A ca. 1820 Ma mafic magmatic event is manifested as volcanic rocks occurring within the Martin Lake Basin and as dikes crosscutting the basement rocks and lower Martin Group strata. Uraninite U-Pb and Pb-Pb ages range from ca. 2290 Ma to 〈300 Ma, with a peak overlapping the mafic magmatism.〈/p〉 〈p〉The granite-related uranium mineralization in South China occurs mainly as quartz – carbonate ± fluorite veins and as disseminations in the host rocks adjacent to fracture zones. The deposits are hosted by, or occur adjacent to, granitic rocks, and are spatially close to Cretaceous – Tertiary red bed basins that were formed in a Basin-and-Range like tectonic setting related to roll back of the Pacific plate. These red bed basins contain intervals of bimodal volcanic rocks and are crosscut by coeval mafic dikes. Uraninite U-Pb ages dominantly range from 100 to 50 Ma, which is much younger than the host granites (〉145 Ma) and broadly contemporaneous with development of the red bed basins and mafic magmatism.〈/p〉 〈p〉Comparison of the two study areas reveals striking similarities in geologic attributes related to uranium mineralization, specifically, the development of large volumes of granitic rocks that are relatively enriched in uranium, and the development of red bed basins with accompanying coeval mafic magmatism in extensional tectonic settings. It is proposed that oxidizing basinal fluids from the red bed basins circulated into the underlying fertile granitic rocks along high-permeability structural zones, acquired uranium in the path through fluid-rock interaction, and precipitated the uranium where they encountered reducing agents. Elevated geothermal gradients associated with the mantle-derived magmatism greatly enhanced the mineralization by facilitating the uranium extraction and transport processes. Thus, it is the coupling of shallow (red bed basin and oxidizing basinal fluid development) and deep-seated (mantle-derived magmatism and related thermal activity) processes, together with the pre-enrichment of uranium in basement rocks (particularly granitic rocks) and pre-existing deformation zones, that controlled the formation of the granite-related uranium deposits in both Beaverlodge and South China, and perhaps elsewhere in the world with similar geologic setting.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819308042-ga1.jpg" width="185" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 118〈/p〉 〈p〉Author(s): Xuanxuan Li, Taofa Zhou, Noel C. White, Yu Fan, Lejun Zhang, Jie Xie, Yinan Liu, Xin Xiao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lithocaps in island-arc settings are genetically related to porphyry-epithermal systems and can be used to guide exploration for porphyry deposits. The Fanshan area of the Luzong basin in the eastern China, hosts a large lithocap but no porphyry or epithermal deposits have been found. The Fanshan lithocap in the Luzong basin is centred on the Dafanshan alunite mining district with vuggy quartz–alunite–pyrite, quartz–dickite–kaolinite ± alunite, quartz–kaolinite and kaolinite–illite ± smectite from northeast to southeast. The alteration zoning reflects the gradual decrease in the temperatures and acidities of the fluids. Four types of alunite including bladed alunite, needle alunite, granular alunite, and powdery alunite suggest that the Fanshan lithocap formed in the magmatic-hydrothermal and supergene environment. From the southwest to the northeast of the Dafanshan district, Pb and 10〈sup〉6〈/sup〉Pb/(Na + K) in the alunite samples gradually decrease, Au content gradually increases, but the Cu content does not change significantly. The peak positions at 1480 nm and the Na content of the magmatic-hydrothermal alunite gradually increase, whereas Pb and 10〈sup〉6〈/sup〉Pb/(Na + K) in the alunite minerals gradually decrease. This suggests that the source of the hydrothermal fluids and a potential zone of precious metal mineralization area may be in the northeast of the Dafanshan district, and the potential area of copper mineralization may be in the Huangtun area northeast of the Luzong basin.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉In this paper, we present a case study of the Fanshan lithocap developing in the Luzong intracontinental volcanic basin to indicate the direction of mineralization because lithocaps are generally related to the porphyry-epithermal system. The Fanshan lithocap formed in the magmatic-hydrothermal environment and then superimposed by supergene environment. We predicted the direction of mineralization of Fanshan lithocap using the formation environment, alunite at 1480 nm peak positions, whole-rock geochemistry, magmatic-hydrothermal alunite geochemistry, and alteration zones. Precious metals mineralization may occur in the depth of Dafanshan alunite mining area (star position in figure), copper mineralization potential may be in the Huangtun area, which is located in the northeast of the Dafanshan alunite mining area.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819304536-ga1.jpg" width="279" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Haidong Zhang, Jian-Chao Liu, Qian Xu, Jin-Ya Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The Haoyaoerhudong gold deposit is the largest gold deposit in the north margin of the North China Craton gold province, and contains over 7 Moz of gold at an average grade of 0.62 g/t. The deposit is hosted in the carbonaceous and pyritic slate, phyllite, and schist and is controlled by a tight syncline and shear zones. The high-grade orebodies contains abundant pyrite veins and pyrite-quartz veins. Three stages of pyrite have been identified, including the diagenetic disseminated pyrite, pyrite veins caused by peak matamorphism, and pyrite-quartz veins forming during post-peak metamorphism. Native gold has been observed in pyrite veins and pyrite-quartz veins.〈/p〉 〈p〉The 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar plateau age of a biotite separate from a tails of boudinaged pyrite-quartz veins is 260.1 ± 2.9 Ma. Combined with previously published 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar mica age data and low closure temperature of mica, these results suggest that pyrite veins and pyrite-quartz veins were formed during the peak, to post-peak metamorphism during 285–260 Ma, respectively. The lower limit of the formation age of sedimentary disseminated pyrites has constrained to 1670–1560 Ma by the intruded mafic–ultramafic dikes.〈/p〉 〈p〉Disseminated pyrite separates have δ〈sup〉34〈/sup〉S values ranging from −39.40‰ to + 17.85‰, 〈sup〉206〈/sup〉Pb/〈sup〉204〈/sup〉Pb of 19.144–21.892, 〈sup〉207〈/sup〉Pb/〈sup〉204〈/sup〉Pb of 15.681–15.864, and 〈sup〉208〈/sup〉Pb/〈sup〉204〈/sup〉Pb of 37.502–38.925, suggesting they were formed from seawater sulfate and has experienced strong sulfur isotopic fractionation. In contrast, hydrothermal pyrites from pyrite veins and pyrite-quartz veins have δ〈sup〉34〈/sup〉S values ranging from +6.8‰ to +16.47‰, 〈sup〉206〈/sup〉Pb/〈sup〉204〈/sup〉Pb of 18.566–18.922, 〈sup〉207〈/sup〉Pb/〈sup〉204〈/sup〉Pb of 15.645–15.684, and 〈sup〉208〈/sup〉Pb/〈sup〉204〈/sup〉Pb of 38.924–38.983, which may reflect dissolution-reprecipitation of disseminated sulfides from the pre-existing organic-rich sediments. The mineral paragenetic, geometric, and cross-cutting relationships of pyrite veins and pyrite-quartz veins at Haoyaoerhudong suggest that gold was most likely introduced into pyrite, accompanying sedimentation of the organic-rich shales, and then became enriched during diagenesis. Subsequently, the hydrothermal fluids following metamorphism and shear zone activity make dissolution of the gold in the diagenetic pyrite and precipitated in the intersection of shear zone and tight syncline.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819307152-ga1.jpg" width="356" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Xiangping Zhu, Duoji, Guangming Li, Hongfei Liu, Huaan Chen, Dongfang Ma, Chaoqiang Liu, Lujie Wei〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The Naruo porphyry Cu-Au deposit is the third discovered large deposit in the Duolong metallogenic district. ‘Previous research has mainly focused on the geochemistry of the ore-bearing granodiorite porphyry; however, the metallogenesis is also poorly understood. Based on mapping using outcrops and geological drill cores, the alteration zones were outlined and the sequence of veins was also identified. Furthermore, fluid inclusion microthermometry and Raman composition analyses were conducted.〈/p〉 〈p〉A boiling fluid system is indicated by the coexisting aqueous, brine and vapor inclusions in all vein types. Daughter-metal minerals bearing brine inclusions are the major fluid inclusion types in all veins, suggesting that the Naruo porphyry Cu-Au deposit was formed by high-salinity fluids; thus, the measured data of the brine inclusions are mainly used for the interpretation of fluid evolution. In the early quartz-magnetite veins, brine fluid inclusions exhibit high homogenization temperatures (greater than 500 °C) and diverse salinities (30.1–61.5 wt% NaCl equiv), while in the later magnetite-absent, chalcopyrite-bearing quartz–sulfide veins, the homogenization temperatures of aqueous and brine inclusions are below 440 °C, suggesting that the magnetite mostly precipitated at temperatures higher than 440 °C. In the even later quartz–pyrite ± chalcopyrite veins, the homogenization temperatures of the brine inclusions are mainly below 300 °C, implying that the temperature range from 440 °C to 300 °C is the main copper mineralization interval. The precipitation temperature of chalcopyrite fits the fact that the copper ore-body is present within the potassic and early phyllic alteration zones.〈/p〉 〈p〉Hematite and magnetite are common within high-salinity inclusions in all vein types, indicating the high oxidation property of the ore-forming fluid. High oxidation facilitates the scavenging of sulfur and chalcophile metals into magmatic–hydrothermal systems. Moreover, hematite or magnetite deposition can facilitate the reduction of sulfate to sulfide and decrease pH values, ultimately affecting sulfide precipitation and hydrothermal alteration. The constant high oxidation is crucial for the metallogenesis of the Naruo porphyry Cu-Au deposit.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S016913681830862X-ga1.jpg" width="136" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Chang Yu, Richen Zhong, Ray Bai, Yanchao Wang, Yifan Ling〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Measuring homogenization temperature (T〈sub〉h〈/sub〉) is a basic work in fluid inclusion studies. However, the T〈sub〉h〈/sub〉 of some fluid inclusion is hard to obtain using the traditional microthermometric method, in particular those that is easy to decrepitate upon heating. Such inclusions are common when the host minerals have well-developed cleavages (e.g., calcite and fluorite) and the fluids are enriched in volatile components such as CO〈sub〉2〈/sub〉 or CH〈sub〉4〈/sub〉. In theory, upon heating of H〈sub〉2〈/sub〉O-NaCl and H〈sub〉2〈/sub〉O-CO〈sub〉2〈/sub〉-NaCl inclusions that tends to homogenize to the liquid phase, their bubble volumes (V〈sub〉g〈/sub〉) will decrease with increasing temperatures (T) following cubic and quartic polynomial V〈sub〉g〈/sub〉-T functions, respectively. A method that can predict inclusion T〈sub〉h〈/sub〉 without heating it to homogenization is proposed in this study. The core idea is to retrieve the V〈sub〉g〈/sub〉-T function of a given inclusion based on a series of (V〈sub〉g〈/sub〉, T) data points that were measured before total homo genization (or decrepitation of the inclusion), and then calculate the T〈sub〉h〈/sub〉 based on the function (the temperature at which V〈sub〉g〈/sub〉 equals to zero). To test the performance of this method, a total of 14 synthetic and natural fluid inclusions were heated to homogenization (at T〈sub〉h, real〈/sub〉) and their changes in V〈sub〉g〈/sub〉 were recorded with increasing temperature. It is assumed that the inclusions get decrepitated before homogenization, and their homogenization temperatures were predicted (T〈sub〉h, predicted〈/sub〉) using the method proposed by this study. If the inclusions were “decrepitated” at temperatures 40 °C below the T〈sub〉h, real〈/sub〉, the differences between the predicted and real homogenization are mostly smaller than 3 °C. This approach provides a quantitative estimation of the T〈sub〉h〈/sub〉 for inclusions that are easy to decrepitation, and is much more accurate than directly using the temperature of decrepitation as an approximation of T〈sub〉h〈/sub〉. This method was programed in two Microsoft EXCEL worksheets that are available in Supplementary Materials for T〈sub〉h〈/sub〉 calculations of H〈sub〉2〈/sub〉O-NaCl and H〈sub〉2〈/sub〉O-CO〈sub〉2〈/sub〉-NaCl inclusions, respectively.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819308832-ga1.jpg" width="173" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 117〈/p〉 〈p〉Author(s): Fuchuan Chen, Jun Deng, Qingfei Wang, Jan Marten Huizenga, Gongjian Li, Youwei Gu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Hetaoping deposit is one of the largest Fe-Zn-Pb skarn deposit in SW China, which is characterized by Zn-Pb mineralization in the upper part and the Fe mineralization in the deeper part. The Fe mineralization is dominated by magnetite and pyrite. Magnetite can be subdivided into four types: primary banded magnetite samples in clinopyroxene-actinolite skarn (Mt-1), primary disseminated magnetite in garnet skarn (Mt-2), primary disseminated magnetite in clinopyroxene-actinolite skarn (Mt-3), and altered magnetite in clinopyroxene-actinolite skarn (Mt-4). Pyrite can be subdivided into three types: pyrite in oxide-ore stage (Py-1), pyrite in early sulfide-ore stage (Py-2), and pyrite in late sulfide-ore stage (Py-3). The flat time-resolved signals of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) imply that trace elements exist mainly in the form of isomorphism in magnetite and pyrite with the exception some incompatible trace elements (e.g., Ca, K and Na in magnetite and Pb, Bi and Ag in pyrite). Trace element concentrations in magnetite and pyrite demonstrate that the ore-forming fluid in Hetaoping is of magmatic origin. Furthermore, compared to porphyry, IOCG, Kinuna and BIF type magnetite, the magnetite from Hetaoping has relatively low Ti, V and Ni concentrations but high Al, Mn and Ca concentrations, implying a typical skarn genesis. The variation of Ti concentrations in magnetite is an indication of the formation temperature and shows that banded magnetite (Mt-1) precipitated in a relatively high-temperature environment compared with disseminated magnetite (Mt-2 and Mt-3). Compared to Mt-1 and Mt-3, Mt-2 has a higher Si, Al, and W contents and a lower Mg and Mn contents. The Mn content increases from Py-1 to Py-2, and decreases from Py-2 to Py-3, suggesting that the fluid-rock interaction increased from the oxide-ore stage to the sulfide-ore stage, and decreased from sulfide-ore stage to post-ore stage. The variation of the V concentration in magnetite grains indicates a relatively higher oxygen fugacity of Mt-2 compared to Mt-1 and Mt-3, implying that the oxygen fugacity of the ore-forming fluid in the garnet skarn zone is higher than that in clinopyroxene-actinolite skarn zone. The variable oxygen fugacity probably caused spatial zoning of mineralization in Hetaoping Fe-Zn-Pb skarn deposit. The temperature and oxygen fugacity of the ore-forming fluid, and the extent of fluid-rock interaction, controlled the temporal order and spatial zonation of magnetite and sulfide precipitation, which led to the formation of the Hetaoping Fe-Zn-Pb skarn deposit.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819305360-ga1.jpg" width="219" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): N. Mondillo, M. Accardo, M. Boni, A. Boyce, R. Herrington, M. Rumsey, C. Wilkinson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Willemite is a common mineral mainly occurring in the so-called “hypogene” nonsulfide Zn-Pb mineralizations, deposited from what have been interpreted as high temperature hydrothermal or metamorphic fluids. Considering that a comprehensive compilation of geochemical data on willemite is currently lacking, the aim of this study is to provide evidence for specific geochemical signatures of willemites with contrasting genesis. For this work, we analyzed a range of specimens taken from the Mineralogy Collection of the Natural History Museum in London. The specimens are from several deposit-types:〈/p〉 〈dl〉 〈dt〉1.〈/dt〉 〈dd〉〈p〉Stratiform hypogene deposits: Franklin and Sterling Hill (USA);〈/p〉〈/dd〉 〈dt〉2.〈/dt〉 〈dd〉〈p〉Structurally-controlled hypogene deposits: Star Zinc, Excelsior, Surprise (Lusaka area, Zambia), Kabwe (Zambia), Berg Aukas and Tsumeb (Namibia);〈/p〉〈/dd〉 〈dt〉3.〈/dt〉 〈dd〉〈p〉Supposedly supergene deposits: Mumbwa area (Zambia), and Altenberg-Vieille Montagne (Belgium).〈/p〉〈/dd〉 〈/dl〉 〈p〉Textures and structures of the willemite-bearing specimens were initially investigated by scanning electron microscope energy dispersive analysis (SEM-EDS). Trace element concentrations were later measured 〈em〉in situ〈/em〉 on selected willemite crystals by laser ablation (LA)-ICP-MS. Statistical analyses (principal component analysis-PCA, multivariate analysis of variance, post hoc Tukey HSD test), conducted on the data obtained by LA-ICP-MS, showed that statistically significant differences exist between willemites derived from the various considered deposits. The high-T stratiform willemite samples contain significant amounts of Mn and Mg, and result statistically different from the all the other analyzed specimens. Structurally-controlled hypogene willemites, characterized by lower Mn and Mg concentrations, and by higher Pb, Cu, As, B, Ge contents, are statistically inhomogeneous, both at the district and at the deposit scale: high-T willemite from the Lusaka area contains more Mn than the low-T hydrothermal deposits, that show instead higher concentrations of other elements (e.g. Pb, Cu, Ge). Among the willemite generations associated with the supposedly supergene mineralizations, only the Mumbwa willemites form a cluster that is significantly displaced from the other deposits. The δ〈sup〉18〈/sup〉O isotopic compositions match the mentioned trace element distribution: willemites with similar origin are characterized by similar oxygen isotopic ratios. On the basis of the present work, willemite-types can be the distinguished as follows:〈/p〉 〈dl〉 〈dt〉•〈/dt〉 〈dd〉〈p〉High-T willemites are characterized by high Mn+Mg concentrations (between 100 ppm to unit wt.%) and by low and positive δ〈sup〉18〈/sup〉O compositions (around 3 to 5‰ V-SMOW);〈/p〉〈/dd〉 〈dt〉•〈/dt〉 〈dd〉〈p〉Low-T hydrothermal willemites show Mn+Mg concentrations below 50 ppm, associated with high Pb+Cu+As+Ge concentrations (above 100 ppm). They also have high and positive δ〈sup〉18〈/sup〉O compositions (between 9 and 15‰ V-SMOW);〈/p〉〈/dd〉 〈dt〉•〈/dt〉 〈dd〉〈p〉Willemites derived from (either cold or warm) meteoric fluids have possibly low concentrations of the above elements and negative δ〈sup〉18〈/sup〉O compositions (-3 and -9‰ V-SMOW).〈/p〉〈/dd〉 〈/dl〉The supposedly supergene Altenberg-Vieille Montaigne willemite, having low Mn+Mg and high Pb+Ge+As concentrations, and showing δ〈sup〉18〈/sup〉O compositions between 11 and 12.5‰, should have formed from low-T hydrothermal fluids.〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819307140-ga1.jpg" width="276" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 25 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Li-Qiang Feng, Xue-Xiang Gu, Yong-Mei Zhang, Jia-Lin Wang, Zhan-Lin Ge, Yu He, Ying-Shuai Zhang〈/p〉

Description: 〈p〉Publication date: Available online 24 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): J.K. Porter, Neal J. McNaughton, Noreen J. Evans, Bradley J. McDonald〈/p〉

Description: 〈p〉Publication date: Available online 21 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Paula Montoya-Lopera, Gilles Levresse, Luca Ferrari, Andrea Luca Rizzo, Santiago Urquiza, Luis Mata〈/p〉

Description: 〈p〉Publication date: Available online 19 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Kun Wang, Zhong-Yuan Ren, Le Zhang, Quan Ou〈/p〉

Description: 〈p〉Publication date: Available online 20 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): S.I. Kostrovitsky, D.A. Yakovlev, A. Soltys, A.S. Ivanov, S.S. Matsyuk, S.E. Robles-Cruz〈/p〉

Description: 〈p〉Publication date: Available online 18 February 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Biao Wang, Tao-Fa Zhou, Yu Fan, Jing Chen, Yi-Nan Liu, Yang Chen〈/p〉

Description: 〈p〉Publication date: May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 120〈/p〉 〈p〉Author(s): Mohamed Zaki Khedr, Shoji Arai, Tomoaki Morishita〈/p〉

Description: 〈p〉Publication date: May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 120〈/p〉 〈p〉Author(s): Tushar Meshram〈/p〉

Description: 〈p〉Publication date: April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 119〈/p〉 〈p〉Author(s): Maurício L. Borba, Colombo C.G. Tassinari, Jason Kirk, Joaquin Ruiz〈/p〉