Journal of Geochemical Exploration最新文献

{"title":"Secondary mineral formation and trace-element reservoirs in weathered waste rock: Integration of quantitative mineralogy and conventional mineralogical techniques","authors":"Lianna J.D. Smith ,&nbsp;Dogan Paktunc ,&nbsp;David W. Blowes","doi":"10.1016/j.gexplo.2024.107563","DOIUrl":"10.1016/j.gexplo.2024.107563","url":null,"abstract":"<div><p>Sulfide minerals and secondary minerals associated with sulfide oxidation were characterized using automated quantitative mineralogy techniques in samples of weathered and freshly blasted waste rock from the Detour Lake Mine, Ontario, Canada. Associations and mineral habits of secondary minerals suggest heterogeneous and dynamic geochemical conditions within the historical waste-rock pile, and the formation of secondary minerals in microenvironments associated with oxidizing sulfide minerals. Electron-probe microanalyses of sulfide grains and alteration rims applied to the modal mineralogy determined by quantitative mineralogy permitted a calculation of trace elements in these reservoirs. The calculations revealed an under-estimation of trace elements by quantitative mineralogy when mass-balance calculations were considered.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"266 ","pages":"Article 107563"},"PeriodicalIF":3.4,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142041088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temporal–spatial variations of soil respiration and the controlling factors on global scale (1991–2015)","authors":"Mi Tian ,&nbsp;Jian Zhou ,&nbsp;Xueqiu Wang ,&nbsp;Bimin Zhang ,&nbsp;Binbin Sun ,&nbsp;Wei Wang ,&nbsp;Hanliang Liu ,&nbsp;Qinghai Hu ,&nbsp;Qinghua Chi ,&nbsp;Chao Wu ,&nbsp;Futian Liu ,&nbsp;Yu Qiao","doi":"10.1016/j.gexplo.2024.107562","DOIUrl":"10.1016/j.gexplo.2024.107562","url":null,"abstract":"<div><p>Temporal–spatial variations of soil respiration and the controlling factors is important for understanding the global carbon cycle process. In this research, the Global Soil Respiration Database (SRDB) and Global Geochemical Baseline (GGB) dataset were used, temporal–spatial variations of soil respiration from 1991 to 2015 and the controlling factors in soils developed from different soil parent materials were analyzed. We found, for the first time, soil respiration was significantly varied in soils developed from different soil parent materials on a global scale, which was mainly controlled by geochemical indexes such as Al/Si, MnO, CaO and P₂O₅. We also found that temporal variations of soil respiration during 1991–2015 in acidic plutonic rocks, acidic volcanic rocks, metamorphic rocks, siliciclastic sedimentary rocks and unconsolidated sediments–developed soils was significantly controlled by temperature, while that of basic plutonic rocks, basic volcanic rocks, intermediate volcanic rocks, mixed sedimentary rocks and carbonate rocks–developed soils was less sensitive to temperature relatively. We conclude that temporal–spatial variations of soil respiration were correlated with soil geochemistry, which mainly depends on the stability difference caused by the bonding between soil organic carbon and soil minerals. The findings may be helpful to understand the temporal–spatial pattern of global soil respiration, moreover reveal the importance of soil geochemistry in influencing soil respiration on global scale.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"266 ","pages":"Article 107562"},"PeriodicalIF":3.4,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of spatiotemporal variations and mixed patterns for a multi-aquifer system in the Sulin mining area based on analyses of hydrochemical and isotopic characteristics","authors":"Miao Zhang ,&nbsp;Luwang Chen ,&nbsp;Xiaowei Hou ,&nbsp;Yongsheng Hu ,&nbsp;Jie Zhang ,&nbsp;Yuanyuan Zhang ,&nbsp;Xinyue Cai","doi":"10.1016/j.gexplo.2024.107561","DOIUrl":"10.1016/j.gexplo.2024.107561","url":null,"abstract":"<div><p>Determining the hydrochemical variations and groundwater mixing is crucial for mining safety and water resource management in the Sulin mining area in North China, especially after mining activities. In this study, 94 groundwater samples were collected from the main aquifers in the Sulin mining area during the early and late stages of mining. Water-rock interactions, spatiotemporal variations in hydrochemistry, and groundwater level characteristics during the early and late stages of mining were determined by analyzing data on major ions, hydrogen and oxygen isotopes, and groundwater level. Analytical methods included Piper diagram, principal component analysis, ionic ratio analysis, and Kriging interpolation. A comprehensive conceptual model was proposed to describe the spatiotemporal variations and mixed patterns of the multi-aquifer systems. Results showed that groundwater level in the study area remained relatively consistent before and after mining, with no significant changes observed. The distribution of regional geological structures significantly affects on the groundwater distribution characteristics, which, in turn, determines the spatial variations in groundwater hydrogeochemistry and mixing patterns of groundwater under natural conditions. Moreover, there was significant temporal variation in hydrochemistry in areas of strong drainage. Mining activities led to a decrease in groundwater level, resulting in regional differences in water-rock interactions and groundwater mixing patterns. The Bayesian isotope mixing model (MixSIAR) and the hydrogeological conceptual model can be applied to quantitatively verify the groundwater mixing and the hydrogeochemical process. The study offers insights into the spatiotemporal variations and mixing patterns of groundwater under the impact of exploitation.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"266 ","pages":"Article 107561"},"PeriodicalIF":3.4,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141954098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genesis and evolution of Late Oligocene to Late Miocene syn-rift Pb-Zn deposits along the Red Sea coast, Egypt: Inference from a petrographic and geochemical investigation","authors":"El Sayed Ahmed Saber ,&nbsp;Ashraf Embaby ,&nbsp;Ashraf Ismael ,&nbsp;Ahmed E. Radwan ,&nbsp;Ahmed Abd El Aal ,&nbsp;Ahmed El Sheikh","doi":"10.1016/j.gexplo.2024.107560","DOIUrl":"10.1016/j.gexplo.2024.107560","url":null,"abstract":"<div><p>Lead‑zinc deposits on the Egyptian Red Sea coast are hosted within a <em>syn</em>-rift system's carbonate platform; however, their origin is still under discussion. This study has used an integrated geological, petrographic, and geochemical analysis of these deposits along seven localities to investigate the record of the main processes that controlled their onset and evolution. Two main zones of mineralization are distinguished: an exposed upper zone composed essentially of smithsonite, hydrozincite, hemimorphite, goethite, and hematite with relics of galena, and a lower zone composed mainly of galena, sphalerite, and pyrite with minor amounts of marcasite. Geochemically, these deposits are depleted in Na, K, Al, Ti, and Nb but are enriched in Mo, Cd, and As. The chondrite-normalized patterns of Pb-Zn-bearing samples show pronounced negative Ce and Eu anomalies, whereas the pattern of the host rocks shows a distinctive pattern with pronounced negative Ce and positive Eu anomalies. The isotope geochemistry analysis of the present lead‑zinc-host rocks shows negative values of δ¹⁸O and δ¹³C in the saddle dolomite-II, dolomite-III, and Zn-dolomite, all of which reflect the effects of dolomitization by hydrothermal fluids. Based on mode of occurrence, texture, mineralogy, and geochemistry, the studied lead‑zinc deposits were formed in two stages: an early stage marked by the participation of primary sulfide ores from hydrothermal solutions, and a late stage involving the replacement of the precursor primary sulfides by means of surface water. These Pb-Zn ore deposits hosted in carbonate rocks are genetically considered to be of Mississippi Valley-type and could constitute important clues, taking into account their wide distribution, for the exploration of new targets of lead‑zinc in addition to a better understanding of the origin of lead‑zinc deposits in the Middle East area and provides important information to improve future mining in the area.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"266 ","pages":"Article 107560"},"PeriodicalIF":3.4,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141993569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dissolution behavior of mixed calcium‑cobalt carbonates at 25 °C in contact with different gas phases","authors":"Fei LUO ,&nbsp;Chengyou MA ,&nbsp;Zongqiang ZHU ,&nbsp;Xiaoke NONG ,&nbsp;Peijie NONG ,&nbsp;Shen TANG ,&nbsp;Lihao ZHANG ,&nbsp;Huan DENG ,&nbsp;Yinian ZHU","doi":"10.1016/j.gexplo.2024.107558","DOIUrl":"10.1016/j.gexplo.2024.107558","url":null,"abstract":"<div><p>The potential immobilization of cobalt in various environments can be achieved through the incorporation of Co into carbonate minerals, forming solid solutions of (Ca_1-xCo_x)CO₃. However, the thermodynamic properties of these minerals are not well-understood due to conflicting data from natural observations and experiments. In this work, a series of mixed calcium‑cobalt carbonates were prepared and their interaction with aqueous solution was investigated. Depending on the Co/(Ca + Co) mol ratio (X_Co) of the mixed solution, ranging from 0.00 to 1.00, pure calcite, Co-bearing calcite, Co-bearing aragonite, Ca-bearing spherocobaltite and pure spherocobaltite were successively synthesized using a precipitation method. Upon dissolution of the Co-bearing solids (X_Co = 0.10–1.00) in N₂-degassed water (NW) and air-saturated water (AW), the Co concentration of the aqueous solutions increased gradually to a stable state of 0.017–0.191 and 0.018–0.186 mmol/L after 240–360 d dissolution, respectively. When the dissolution occurred in CO₂-saturated water (CW), the Co concentration initially spiked to 0.372–2.258 mmol/L within 6 h ∼ 15 d and then decreased to a stable range of 0.030–0.559 mmol/L after 240–360 d. The Co/(Ca + Co) mol ratio in the aqueous solution (X_Co2+,AS) was significantly lower than the Co/(Ca + Co) atomic ratio in the solids (X_Co,SS), particularly when dissolved in NW and AW. During these dissolution processes in NW, AW and CW at 25 °C, the average log IAP values at the final stable state were determined as follows: for calcite (CaCO₃), the values were −8.25 ± 0.03 in NW, −8.34 ± 0.11 in AW, and −8.10 ± 0.08 in CW; for spherocobaltite (CoCO₃), they were −9.24 ± 0.26 in NW, −9.39 ± 0.23 in AW, and −9.38 ± 0.09 in CW. Furthermore, the log IAP values increased from those typical for calcite to −7.89 ± 0.01 ∼ −7.84 ± 0.10 for the solid with X_Co,SS = 0.187 as X_Co,SS increased, eventually aligning with those typical of spherocobaltite. Lippmann diagrams, constructed using the Guggenheim parameters <em>a</em>₀ = 2.30 and <em>a</em>₁ = 0.265 for the “subregular” calcite-spherocobaltite solid solutions [(Ca_1-xCo_x)CO₃] with a miscibility gap ranging from X_Co,SS = 0.251 to 0.858, highlighted the “peritectic” point at X_Co₂₊_,AS = 0.0538 on the <em>solutus</em>. This analysis revealed that the solids dissolved non-stoichiometrically in water. Consequently, the Co-poor aqueous solution would reach equilibrium with the Co-rich calcite-structure phase at the solid surface.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"265 ","pages":"Article 107558"},"PeriodicalIF":3.4,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trace element signatures in scheelite associated with various deposit types: A tool for mineral targeting","authors":"Ana Carolina R. Miranda ,&nbsp;Georges Beaudoin ,&nbsp;Bertrand Rottier ,&nbsp;Jan Pašava ,&nbsp;Petr Bohdálek ,&nbsp;Jan Malec","doi":"10.1016/j.gexplo.2024.107555","DOIUrl":"10.1016/j.gexplo.2024.107555","url":null,"abstract":"<div><p>Scheelite is a widespread mineral in several geological settings and its trace element composition provides valuable information about the source and composition of the hydrothermal fluids. In this study, scheelite from 22 magmatic-hydrothermal deposits and 2 orogenic Au deposits (Hangar Flats and Corcoesto) were analyzed by EPMA and LA-ICP-MS. Magmatic-hydrothermal scheelite, together with literature data are investigated using partial least square-discriminant analysis (PLS-DA) and Random Forest (RF) classifier, to evaluate the use of scheelite as a robust indicator mineral for W-bearing deposit targeting. Cathodoluminescence images show that scheelite is texturally homogeneous in reduced intrusion-related gold systems (RIRGS) and varies from homogeneous to heterogeneous in other magmatic-hydrothermal and orogenic Au deposits. Scheelite displays six REE chondrite-normalized patterns, which are a function of the source and composition (mainly salinity) of the mineralizing fluids and partitioning with co-genetic minerals (e.g., garnet, clinopyroxene). The PLS-DA highlights that scheelite trace element composition from magmatic-hydrothermal deposits varies following different deposit types (e.g., oxidized and reduced skarns, porphyry W<img>Mo, RIRGS, quartz-vein/greisen Sn<img>W), and that such compositional variation reflects mainly the difference of <em>f</em>O₂ and composition of mineralizing fluids. Additionally, scheelite from magmatic-hydrothermal deposits are chemically distinct to those formed dominantly by metamorphic fluids in orogenic settings as shown by their higher Mo, Nb and Mn, and lower Sr contents and predominantly negative Eu anomalies. Metamorphic scheelite can be discriminated from that of orogenic Au deposits by their lower Pb, As and REE contents and LREE/HREE ratios, which are related to local host rock composition and metamorphic grade. Using Na, Mg, Mn, As, Sr, Y, Nb, Mo, Pb, ΣREE concentrations and Eu anomaly as predictors, the RF model yields an overall prediction accuracy of 97 % for test data as function of deposit types (89.2 % for RIRGS, 100 % for porphyry W<img>Mo, 97.8 % for quartz-vein/greisen Sn<img>W, 96.9 % for oxidized skarn, 98.1 % for reduced skarn and 99.3 % for orogenic Au deposits). Application of RF classifier to scheelite composition from orogenic Au and skarn- and greisen-type W deposits from literature yields an overall prediction of ∼79 % (91 % for oxidized skarn, 71.4 % for quartz-vein/greisen Sn<img>W and 74.2 % for orogenic Au deposits) showing that scheelite is an efficient indicator mineral for Au and W deposits targeting. Metamorphic scheelite is predicted mostly as orogenic Au scheelite (83 %), reflecting the genesis of metamorphic fluids and similar geological setting, suggesting that RF classifier can be also used to predict the fluid sources.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"266 ","pages":"Article 107555"},"PeriodicalIF":3.4,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0375674224001717/pdfft?md5=4ac787e7aeccc4b9dadebc23cbf3656b&pid=1-s2.0-S0375674224001717-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141978564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical simulation-based targeting of the Au mineralization within the Hongbu Altered Rock type gold deposit, Eastern Shandong Peninsula, China","authors":"Xunyu Hu ,&nbsp;Ruyi Chen ,&nbsp;Guangxian Liu ,&nbsp;Kun Wang ,&nbsp;Hui Yang ,&nbsp;Yuhua Chen ,&nbsp;Jie Zhou ,&nbsp;Guoyu Zhou","doi":"10.1016/j.gexplo.2024.107557","DOIUrl":"10.1016/j.gexplo.2024.107557","url":null,"abstract":"<div><p>Altered rock type deposits are significant gold deposits widely distributed throughout the world, having important economic and industrial value. The Eastern Shandong Peninsula is the third largest gold mining camps in the world with known gold reserves of more than 5300 tons. The majority of the gold deposits here are located in three main orefields, namely the northwest Jiaodong (Laizhou-Zhaoyuan), the Qixia-Penglai-Fushan, and the Muping-Rushan orefields. The Hongbu deposit is a medium-sized altered rock type deposit within the northwest Jiaodong orefield. With decades of mining, the Hongbu deposit faces the dilemma of resource depletion and loss of undigitized data. Therefore, prospecting and exploration have to focus on deep and peripheral areas of known Au mineralization. This study built a three-dimensional model of the Hongbu deposit and sliced it to obtain nine cross-sections to conduct multi-field coupled numerical simulation (including heat conduction, fluid migration, chemical reaction, and material migration). Locations with relatively developed Au mineralization (the top 15 % within the concentration range of Au) are defined as having metallogenic potential, which are highlighted and projected to the geological map of the Hongbu district. The results also show that the spatial distributions of Au mineralization within these nine sections are different, indicating that the formation of Au mineralization is controlled by the morphology of the Hexi fault (other simulation parameters of these nine sections are the same) and the pyrite sericite cataclasite. This research proves that numerical simulation methods is effective in mineral exploration, especially for those areas with insufficient data to use data-driven prospectivity modeling approaches. Future development into both mathematical geosciences and computational science will provide more detailed answers for remaining hot issues related to mineral exploration.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"265 ","pages":"Article 107557"},"PeriodicalIF":3.4,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141844748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization and stable isotopic fingerprinting of mine seepage in hyperarid environments: An example of the Namib Lead & Zinc mine, Namibia","authors":"Ondra Sracek ,&nbsp;Vojtěch Ettler ,&nbsp;Bohdan Kříbek ,&nbsp;Martin Mihaljevič ,&nbsp;Ben Mapani ,&nbsp;Vít Penížek ,&nbsp;Tereza Zádorová ,&nbsp;Aleš Vaněk","doi":"10.1016/j.gexplo.2024.107554","DOIUrl":"10.1016/j.gexplo.2024.107554","url":null,"abstract":"<div><p>Mine drainage at the Namib Lead &amp; Zinc mine in the hyperarid environment of the Namib Desert close to Swakopmund, Namibia, has been investigated using mineralogical, hydrochemical, and isotopic methods. The principal ore minerals are galena and sphalerite. Mine drainage is neutral due to the reactions with the marble gangue rock. Mine water seepage is of the Na-Ca-Cl-SO₄ type and sources of dissolved ions are likely halite and gypsum in the unsaturated zone above the mine. Concentrations of dissolved metals are relatively low, and the principal attenuation mechanism of metals is probably their adsorption on ferric minerals because equilibrium of the seepage water with secondary minerals that host the metals is not attained. Based on strongly enriched δ²H (up to 13.27 ‰) and δ¹⁸O (up to 4.5 ‰) values, seepage water originates from advective fog and is strongly evaporated after the fog deposition. The high δ¹³C(DIC) values indicate equilibrium with carbonates and CO₂ de-gassing. The δ³⁴S(SO₄) values are enriched in shallower depths, probably because of pedogenic gypsum dissolution and then the δ³⁴S values decrease with depth, probably due to the increasing input of sulfur from sulfides. Mine drainage at the Namib Lead &amp; Zinc mine does not represent any risk for the environment due to its neutral character and relatively low seepage water volumes caused by high degree of aridity.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"265 ","pages":"Article 107554"},"PeriodicalIF":3.4,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ore mineralization in the Mofete and San Vito geothermal fields, Campi Flegrei volcanic complex, Naples, Italy","authors":"Harvey E. Belkin ,&nbsp;Ryan J. McAleer ,&nbsp;Benedetto De Vivo","doi":"10.1016/j.gexplo.2024.107556","DOIUrl":"10.1016/j.gexplo.2024.107556","url":null,"abstract":"<div><p>The Mofete and San Vito geothermal fields, located west of Naples, Italy, are part of the Campi Flegrei volcanic complex. In the 1970s, exploratory wells were drilled to a depth of ~3000 m in an attempt to locate high-enthalpy fluids for potential power production. Drill core samples from Mofete wells (MF1, MF2, and MF5) and from San Vito wells (SV1 and SV3) contain authigenic ore mineralization. Pyrite, pyrrhotite, and galena are abundant. Less common are chalcopyrite, sphalerite, arsenopyrite, and scheelite; rare are millerite, violarite, native bismuth, tellurobismuthite, cassiterite, molybdenite, and acanthite. Mineral chemistry was determined by electron microprobe wavelength dispersive spectroscopy aided by a scanning electron microscope equipped with energy-dispersive spectroscopy. The mineral assemblage suggests a low sulfidation environment and the absence of pyrrhotite in the MF1 well and upper part of the SV1 well indicates variable sulfur activity. Both molybdenite and scheelite were identified in samples SV1–2860 and SV3–2353 and scheelite in the SV3 well is zoned with variable Mo⁶⁺ content; low Mo⁶⁺ zones show blue cathodoluminescence, whereas, zones with high Mo⁶⁺ content are yellow to brown. Zoned scheelite and the occurrence of both Mo-bearing minerals attest to the variability of ƒO₂ and ƒS₂ in the geothermal fluid.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"265 ","pages":"Article 107556"},"PeriodicalIF":3.4,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141853904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magmatic-hydrothermal evolution of the Dangba rare-metal granitic pegmatites in the Songpan–Ganzê orogenic belt, Eastern Tibet: Insights from muscovite and columbite-group minerals","authors":"Lin Xu ,&nbsp;Lei Chen ,&nbsp;Jingyu Zhao ,&nbsp;Jie Li ,&nbsp;Shuilong Wang ,&nbsp;Wenguo Yang ,&nbsp;Jian Li ,&nbsp;Bo Yang ,&nbsp;Hai Wang ,&nbsp;Yongsheng Yang ,&nbsp;Zufei Zhang ,&nbsp;Wenning Lu","doi":"10.1016/j.gexplo.2024.107559","DOIUrl":"10.1016/j.gexplo.2024.107559","url":null,"abstract":"<div><p>Rare-metal granitic pegmatites are commonly considered to be the results of a combination of magmatic and hydrothermal processes. Although magmatic crystallization and fractionation, and magmatic-hydrothermal transition have been extensively investigated, the processes related economically valuable mineralization of rare-metals and strong fractionation of geochemical twins remain controversial. This study presents a comprehensive analysis of the geochemical evolution of rare-metal mineralized pegmatites, focusing on the mineral chemistry of muscovite and columbite-group minerals (CGM) from the Dangba rare-metal granitic pegmatites in the Songpan–Ganzê orogenic belt. Our findings suggest that the random orientation growth of spodumene crystals and widespread distribution of disordered columbite-group minerals crystals are indicative of lithium saturation in the initial melt at the Dangba No. VII dike. Magmatic fractionation is indicated by gradually increasing ratios of alkali metals (K/Rb ratios) and Ta# (Ta/(Ta + Nb)) in muscovite and CGM, and is proposed to be an important factor for enrichment of rare-metals. During the magmatic-hydrothermal transition, muscovite from metasomatism of spodumene exhibits similar or slightly higher levels of Li, Rb, and Cs, compared to primary muscovite, but shows strong depletion of Ta, Nb, Sn, and W. Alteration of primary minerals (e.g., spodumene, alkali feldspar, and columbite-group minerals) results in the release of these elements into the reactive media (melt/fluid) during the metasomatism. This process ultimately leads to the depletion of rare metals in the early crystallized minerals. However, this process is advantageous for the subsequent mineralization of Ta and Nb, as well as their fractionation. The chemical compositions of exsolved aqueous fluid are influenced by the mineralogy of pegmatites and the partitioning behavior between melt and fluid. Furthermore, pervasive albitization serves as an exploration criterion for Li–Ta–Nb in the Ke'eryin Orefield.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"265 ","pages":"Article 107559"},"PeriodicalIF":3.4,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141847803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}