Journal of Geochemical Exploration最新文献

{"title":"Sulfur isotope and trace element geochemistry of sulfides from the unique Yaojialing Zn-Au-Cu deposit, Lower Yangtze River Metallogenic Belt, China: Implications for ore-forming process and exploration","authors":"Yu Wang ,&nbsp;Xiaoyong Yang ,&nbsp;Xuanyang Feng ,&nbsp;Huishan Zhang ,&nbsp;Shasha Liu ,&nbsp;Fangyue Wang","doi":"10.1016/j.gexplo.2024.107477","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107477","url":null,"abstract":"<div><p>The Yaojialing Zn-Au‑Cu deposit is a porphyry-skarn-epithermal vein-type compound deposit that consists of epithermal vein-type lead‑zinc‑silver orebodies, skarn Zn-Cu-Au orebodies, and porphyry Cu<img>Au orebodies from shallow level to depth. We decipher the source and metallogenic mechanism by studying the trace element and S isotopic compositions of sulfides (pyrite, sphalerite, chalcopyrite, and galena) from three types of orebodies. The collected pyrite can be divided into two types. PyI coexists with chalcopyrite, and PyII coexists with sphalerite or galena. In addition, PyI was further divided into PyIa (collected from porphyry copper bodies) and PyIb (collected from skarn copper bodies). PyII can be further divided into PyIIa (collected from skarn-type lead‑zinc ore body) and PyIIb (collected from vein lead‑zinc ore body in strata). Sphalerite and galena from skarn-type Pb<img>Zn ore bodies and shallow vein-type Pb<img>Zn ore bodies are named SpI and GnI, and SpII and GnII, respectively.</p><p>Pyrite and sphalerite trace element thermometers revealed that the temperature of the ore-forming fluids decreased from 500 to 600 °C in the porphyry ore body to 300– 360 °C in the skarn ore body and then to 240– 280 °C in the shallow vein ore body. The decrease in the Co and Ni contents of pyrite collected from deep to shallow depths may indicate that meteoric water precipitated in the late ore-forming hydrothermal system. Rapid crystallization and variations in the physicochemical states (such as temperature, pH, fO₂, and geochemical composition) of the fluids resulted in an obvious oscillating zone of euhedral PyI pyrite particles. It also affects the solubility of trace metal elements and leads to the selective entry of these elements into pyrite. PyII also shows obvious zonation characteristics rather than oscillating zonation, indicating that the growth rate of pyrite is relatively slow. Moreover, the relationships between the Au and As contents in the two types of pyrite are different. PyI is coupled, while PyII shows decoupling. We believe that this phenomenon is due to the high content of As in ore-forming fluid systems, which may inhibit the absorption of Au on the surface of pyrite rather than the decoupling of Au and As caused by rapid crystallization, based on the rapid increase in As content and non-oscillating zonation in PyII. According to the analysis of the sulfur isotopes of various sulfides, the solid evidences suggest that the ore-forming materials of each type of orebody in the Yaojialing deposit were mainly derived from magmatic-hydrothermal processes and that the fractionation of sulfur isotopes was the result of variations in physicochemical conditions caused by magma-hydrothermal evolution rather than the addition of foreign sulfur sources.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140542583","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":"Integrate physics-driven dynamics simulation with data-driven machine learning to predict potential targets in maturely explored orefields: A case study in Tongguangshan orefield, Tongling, China","authors":"Liangming Liu ,&nbsp;Feifu Zhou ,&nbsp;Wei Cao","doi":"10.1016/j.gexplo.2024.107478","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107478","url":null,"abstract":"<div><p>The physics-driven dynamics simulation (DS) and data-driven machine learning (ML) are two general approaches to predict complex systems whose complexity is a hardship impediment to prediction. Based on the 3D geological modeling (GD), we embedded the DS into ML to predict high potential targets and to evaluate ore-controlling and ore-indicating factors in the Tongguangshan (TGS) skarn orefield that has undergone intensive exploration and 4 Cu and Au deposits discovered. The 3D geological models show that the heterogeneous distribution of orebodies around intrusions is associated with the wall rock lithology and contact zone (CZ) characteristics of intrusions, and the resistivity can only provide some ambiguous clues for interpretation of underground geological architectures rather than a direct ore-indicator. The DS results show heterogeneous distribution of temperature, pore pressure, differential stress, volume strain and shear strain, among which the volume strain is closest associated with ore formation. Based on the prediction of Random Forest (FR) model of which the feature variables are combination of DS and 3D modeling results, the SHAP valuing results show a descending importance rank of ore-controlling factors and ore-indicators as lithology, volume strain, distance to CZ, distance to Devonian-Carboniferous interface, curvature of CZ, pressure, temperature, CZ azimuth, resistivity, differential stress, shear strain and CZ dip. The DS results are more important than the resistivity. We have run 6 RF models, consisting of different feature variables which were assigned by DS and 3D modeling, to predict ore-formation favor spaces. The prediction performances on test data sets suggest that, integrating of geological features with dynamics features can enhance performance of RF prediction, the RF model consisting of pure dynamics features can predict mineralization different from the training samples. All RF models' predictions support that there are no significant high potentials at the depth of the orefield, except one small target at its eastern south corner.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140555347","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":"Source, distribution patterns and resources potential of selenium in soil of north Pakistan: Revealed by a national-scale geochemical mapping","authors":"Jing Zhang ,&nbsp;Yasir Shaheen Khalil ,&nbsp;Tianhu Li ,&nbsp;Xueqiu Wang ,&nbsp;Weili Guo ,&nbsp;Lei Wang ,&nbsp;Jun Hong ,&nbsp;Huishan Zhang","doi":"10.1016/j.gexplo.2024.107470","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107470","url":null,"abstract":"<div><p>During national scale geochemical mapping in Pakistan, 69 elements including selenium were analyzed in 2563 stream sediment samples, which filled the gap of selenium distribution in the middle section of Tethyan metallogenic belt. The sampling density was 1–2 sites /100 km². The geochemical concentration of selenium in the samples range from 0.008 to 6.849 mg/kg with an average value of 0.306 mg/kg. The highest average concentration of Se was found in the Suleiman Fold and Thrust Belt (anomaly III3), whereas the lowest is in WKLT Kohistan-Ladakh Island Arc. The type of soil in Pakistan with the highest Se concentration is entisol. The high selenium anomalies are delineated in the northeast of Quetta, near Muslim Bagh, in Mekhtar-Musa Khel area and its southwest region, north of Quetta and Khushab. Three strong selenium anomalies have also been identified in the northeast of Islamabad, northwest of Rawalpindi and the east of Dargai, respectively. It is suggested that selenium anomalies, having a correlation with elements of Mo, CaO, S, Sr, are mainly caused by geological background of shale, coal and coal-bearing formations. Negative anomalies are mainly distributed in the northern Pakistan, which is mostly consists of bedrocks with no or very thin layer of soil. The product of anomaly intensity and variance are defined as prospecting favorable degree (Pfd). The product of Pfd and area (S) are defined as Quantity of Mineral (Qm). There are two anomalies with the highest Pfd in the east of Quetta city, and the anomaly in the southwest of Kundian ranks third. The selenium anomalies indicate the areas of potential Se enrichment and supply basic data and information for geochemical investigation on a larger scale or selenium relevant research.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140540642","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":"Chemical and boron isotopic compositions of tourmaline from the pegmatite in Ke'eryin rare metal orefield, Eastern Tibet: Implications for pegmatitic evolution","authors":"Deshui Yu ,&nbsp;Haibo Yan ,&nbsp;Shoujing Wang ,&nbsp;Deru Xu ,&nbsp;Zhilin Wang ,&nbsp;Chi Ma ,&nbsp;Fushuai Wei","doi":"10.1016/j.gexplo.2024.107475","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107475","url":null,"abstract":"<div><p>Pegmatites occur widely in the Ke'eryin rare metal orefield. The genesis and evolution of the Ke'eryin pegmatites are still in dispute, and morphological and geochemical studies on tourmalines from the Ke'eryin pegmatites are limited. In this study, in-situ analyses of major and trace elements and B isotope were conducted to uncover the origin of tourmaline and the evolution of related pegmatites. Three types of tourmaline from the Ke'eryin barren pegmatite were identified: elongated columnar or needle-columnar tourmaline (Tur-1 type), isolated, disseminated, irregular, and massive tourmaline (Tur-2 type), and long columnar tourmaline (Tur-3 type). Petrographically, the Tur-1 type crystallized at the early stage of pegmatitic crystallization sequence, the Tur-2 type possibly formed at the early- and/or <em>syn</em>-pegmatitic crystallization sequence, whereas the Tur-3 type likely formed at the relatively late crystallization sequence. Compositionally, most tourmalines belong to the alkali group with a few falling in the vacancy group. All the tourmalines show a schorl composition and are of magmatic origin. Chemical variations from the Tur-1 to Tur-3 tourmalines are controlled by magma fractionation and melt compositions rather than crystal chemical effects. Most tourmalines follow the (Na, Mg)(X_vac, Al)₋₁, (Mg, OH)(Al, O)₋₁, and (Ca, Mg₂)(X_vac, Al₂)₋₁ exchange vectors. The higher contents of Zn, Sn, Li, Be, Nb, and Ta and negative Eu anomalies in the Tur-3 type indicate that it was likely crystallized at a more evolved stage. In combination with textural evidence and tourmaline chemistry, we suggest that the Tur-1 and Tur-2 types were formed at the relatively earlier stage of pegmatite-forming magma and the Tur-3 type was likely formed closer to the end-stage of barren pegmatite crystallization. The B isotopic compositions are relatively homogeneous and display slightly higher in the Tur-3 type, which were likely caused by fractional crystallization during B-rich magma evolution. It can be inferred that the tourmaline in more evolved and/or Li-mineralized pegmatite with magma evolution should have higher Li, Be, Nb, Ta, and Sn contents, implying that tourmaline chemistry may be used as a potential exploration indicator for rare metal mineralization.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140546221","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":"Pyrite geochemical fingerprinting on skarn ore-forming processes: A case study from the Huangshaping W–Sn–Cu–Pb–Zn deposit in the Nanling Range, South China","authors":"Lianjie Zhao ,&nbsp;Yongjun Shao ,&nbsp;Yu Zhang ,&nbsp;Liangyu Liu ,&nbsp;Shitao Zhang ,&nbsp;Hongtao Zhao ,&nbsp;Hongbin Li","doi":"10.1016/j.gexplo.2024.107474","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107474","url":null,"abstract":"<div><p>Pyrite geochemistry has been extensively used to reveal ore-forming processes in diverse ore deposits, but its application in skarn systems is not well understood. The Huangshaping deposit in the Nanling Range (South China) uniquely develops W–Sn–Pb–Zn and Cu–Pb–Zn skarn mineralization systems, and both two systems have formed multi-types of pyrite, which provides a good window to reveal the mineralization histories of different skarn systems using pyrite trace element geochemistry. In the Cu–Pb–Zn system, texturally homogeneous Py1 mainly occurs in calcite veins within the host rock, whereas texturally homogeneous Py2 in the calcite-sulfide stage mainly occurs in skarn orebodies. Py3 in the siderite-sulfide stage replaces Py2 and commonly develops abundant pores or fractures, resembling the “bird's eye” texture. In the W–Sn–Pb–Zn system, Py4 in calcite veins can be divided into the oscillatory-zoned Py4a and irregular Py4b under BSE, and Py4b commonly replaces Py4a as veins or overgrowth. Texturally homogeneous Py5 in the calcite-sulfide stage occurs in skarn orebodies and is replaced by Py6 with a “bird's eye” texture in the siderite-sulfide stage.</p><p>In the Cu–Pb–Zn system, Py1 may have formed by fluid cooling during its ascent along the hydraulic fractures indicated by its enrichment of Co, Ni, As, Sb, and Tl, whereas Py2 is likely formed under higher temperature and pH conditions caused by intense fluid-rock interactions evidenced by its depletion of Co, Ni, As, Sb, and Tl as well as its enrichment of Zn and Ag. In the W–Sn–Pb–Zn system, Py4b has higher contents of Co, Ni, As, Sb, and Tl than Py4a and similar contents of Ag, Zn, and Mo with Py4a, suggesting that decreasing temperature may have controlled the formation of Py4b. Py5 is featured by the depletion of As, Sb, Tl, and Mo as well as the enrichment of Zn and Ag, indicating that Py5 is likely formed under higher temperature and pH conditions resulting from the intense fluid-rock interactions. Marcasite replaces pyrrhotite and then is replaced by pyrite may be an important precipitation mechanism for pyrite with a “bird's eye” texture (Py3 and Py6) in both two skarn systems at Huangshaping. This study demonstrates that fluid-rock interaction is an important mechanism for sulfide precipitation at Huangshaping, which shows that pyrite geochemistry has good potential to reveal mineralization histories in skarn systems.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140542584","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":"Modelling the paleopedological development of loess/palaeosol sections using discriminant function analysis of compositional geoscience data, case study in Eastern Croatia","authors":"Lidija Galović,&nbsp;Ajka Šorša,&nbsp;Zoran Peh","doi":"10.1016/j.gexplo.2024.107473","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107473","url":null,"abstract":"<div><p>Previous studies on the mineralogical differentiation of Pleistocene loess/palaeosol sections focused on the description and source material of four loess/palaeosol sections located on the eastern border of Croatia along the Danube: Zmajevac, Zmajevac I, Erdut and Šarengrad. The authors demonstrated the decreasing influence of the Danube and the increasing influence of the rivers draining the Central Bosnian Mountains of the Dinaric Ophiolite Zone both important source areas for aeolian sediments at the southern edge of the Carpathian Basin that transport material from the Central Bosnian Mountains. The aim of this research is to identify the palaeoclimatic factors that influenced the pedogenetic development of the studied palaeosols. The model was created based on the research results of the same four loess/palaeosol sequences in Eastern Croatia. This model can also be applied in other locations to determine the influence of certain climatic factors on the degree of pedogenetic development of individual palaeosols. The loess/palaeosol sequences were divided into eight comprehensive groups (horizons) based on their genesis, degree of pedological development and/or position in the soil profiles. The explanation of the typical patterns occurring between the studied horizons is based on the construction of a Discriminant Function Model (DFM) resulting from the analysis of the compositional data (CoDa) of the geochemical (major and trace elements) and granulometric (grain size) data of the loess/palaeosols in combination with external variables such as weathering coefficients and chemical soil properties. In the final phase, the DFM was transformed from structural (mathematical) to functional (process) terms. This revealed that three main themes dominate the formation of Pleistocene loess/palaeosol sequences: 1) the separation of well-developed palaeosols from parent material; 2) the separation of automorphic palaeosols from hydromorphic soils exposed to post-pedogenic waterlogging conditions; and 3) the differentiation of horizons (soils and alluvium) formed by the redeposition (by water or mudflows) of previously deposited aeolian material, regardless of whether and to what extent it was exposed to post-sedimentary pedogenesis.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140549592","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":"Molybdenum and gold distribution variances within Iranian copper porphyry deposits","authors":"Seyed Mehran Heidari ,&nbsp;Peyman Afzal ,&nbsp;Behnam Sadeghi","doi":"10.1016/j.gexplo.2024.107471","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107471","url":null,"abstract":"<div><p>This study aims to differentiate between Cu-Mo and Cu-Au porphyry deposits within Iran through fractal modeling, utilizing the Mo/Au geochemical index as a primary determinant. Employing the Concentration-Number (C-N) fractal model, the Mo and Au values within Iranian copper porphyry deposits were comprehensively classified. The findings from the fractal modeling reveal distinct criteria for separating these deposits. Cu-Mo porphyry deposits are identified by Mo concentrations ≥141 ppm, while Cu-Au porphyry deposits are characterized by Au concentrations ≥398 ppb. The pivotal threshold for the Mo/Au ratio stands at 1585, facilitating the division between these distinct types of porphyry deposits. Within the Urumieh-Dokhtar magmatic arc, numerous Cu-Mo porphyry deposits, exemplified by globally recognized sites like Sarcheshmeh and Sungun, are prevalent. Conversely, Cu-Au porphyry deposits are found in the NW and SW regions of the Urumieh-Dokhtar magmatic arc and eastern Iran, typified by occurrences like Dalli. The study's findings reveal a correlation between geological characteristics and the ages of porphyry deposits, indicating that those formed during the Miocene period and later are predominantly of the Cu-Mo (Copper-Molybdenum) porphyry type.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0375674224000876/pdfft?md5=5f485919a9db7626eb21c16c2d447adc&pid=1-s2.0-S0375674224000876-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140537250","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":"Evaluating the application of texture and chemistry of detrital tourmaline as an indicator of porphyry Cu mineralization: A case study from the Casino porphyry Cu-Au-Mo deposit, Yukon, Canada","authors":"Christopher E. Beckett-Brown ,&nbsp;Andrew M. McDonald ,&nbsp;M. Beth McClenaghan ,&nbsp;Martin W. McCurdy","doi":"10.1016/j.gexplo.2024.107469","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107469","url":null,"abstract":"<div><p>Tourmaline is an effective indicator mineral for porphyry Cu-Au-Mo exploration because the compositional and morphological features of tourmaline in such systems are distinct from those found in non-mineralized environments. The texture and chemistry of detrital tourmaline was investigated using local stream sediment samples in the vicinity of the Casino calc-alkalic porphyry Cu-Au-Mo deposit (Yukon, Canada) to identify prospective grains by comparing them to grains in bedrock samples from the deposit. Bulk stream sediment samples were collected up to 18 km downstream of the Casino deposit and as far as 30 km away in a drainage basin that does not contain any known porphyry Cu mineralization. Overall, a method combining the physical and chemical characteristics is effective in discriminating detrital tourmaline, including morphology (<em>i.e.,</em> grain clusters), inclusion populations (<em>i.e.,</em> lack of inclusions), crystal chemistry (<em>i.e.,</em> Na-dominant <em>X</em>-site, Mg/Fe dominant <em>Y</em>-site, and OH⁻/O²⁻ dominant <em>W</em>-site), and trace-element compositions (<em>i.e.,</em> high Sr/Pb values and relatively low Zn/Cu values). Detrital tourmaline was evaluated on the basis of these parameters. Detrital grains are light brown to brown, sub- to euhedral, and range in texture from individual isolated grains to clusters of radiating aggregates. Tourmaline in the Casino deposit compositionally ranges from Fe-rich; 0.03–2.54 <em>apfu</em>, <em>avg.</em> 0.61 to Mg-rich, <em>avg.</em> 2.00 <em>apfu</em>, with a minor povondraite (Fe³⁺) component. Detrital tourmaline is similar in composition with Fe-rich; 0.03–3.73 <em>apfu, avg.</em> 1.04 to Mg-rich, 0.14–2.93 <em>apfu</em>, <em>avg.</em> 1.83 to tourmaline in bedrock at Casino. In both bedrock and detrital tourmaline, alkali- and alkaline-earth element concentrations are similar with Na &gt; Ca &gt; vacancy. The most relevant distinctions between tourmaline groups comes from grain morphology (<em>i.e.,</em> clustered <em>versus</em> individual grains) and trace-element chemistry. A significant abundance of prospective porphyry Cu tourmaline grains (14 % of total recovered tourmaline in one sample) can be observed up to 18 km downstream from the Casino deposit (the current limit of sampling), while in drainages where there are no known porphyry Cu systems, tourmaline fitting these criteria is absent and reflect grains sourced from other geologic environments (<em>e.g.,</em> pegmatitic, granitic, and metamorphic). This method provides a new addition to the indicator mineral toolbox for the exploration of porphyry Cu systems.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140552784","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":"Fluctuations of trace elements and Sr isotopes of the multi-stage scheelite in the reduced polymetallic Yupo tungsten skarn deposit, South China: Implications for ore-forming process","authors":"Jiahao Chen ,&nbsp;Qingfei Wang ,&nbsp;Qihai Shu ,&nbsp;David R. Lentz ,&nbsp;Chao Li ,&nbsp;Jun Deng","doi":"10.1016/j.gexplo.2024.107476","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107476","url":null,"abstract":"<div><p>The Yupo scheelite (Sch)-bearing deposit is hosted in the external contact zones between the Yupo granodiorite and Cambrian Huangdongkou Formation of South China. The stratiform ore bodies contain hedenbergitic pyroxene (Hd_23–69) and andradite-poor garnet (Ad_0–22) assemblages, indicating that Yupo is a typical reduced W skarn deposit. The garnet compositions are zoned in a deposit scale inwardly from the periphery of the grossular-rich skarn reaction front to more subcalcic compositions. Scheelite occurs mainly as disseminated grains in the skarn coeval with retrograde alteration (Sch I) and in quartz veins crosscutting skarns (Sch II-1, -2, and -3). Sch II-1 occurs as cores rimmed by Sch II-2, and Sch II-3 as veinlet cutting both of them. The Sch I and Sch II-3 show weak Eu anomalies different from the pronounced positive Eu anomalies of Sch II-1 and -2. All the scheelite contains low Mo contents (&lt;0.1 wt%), together with the subordinate precipitation of molybdenite, indicating a reduced ore-forming fluid system. The Mo content and Eu anomaly jointly reveal that the reducing condition enhanced from Sch I to Sch II-1 and alleviated from Sch II-1 to Sch II-3. The four scheelite generations show gradually increased initial ⁸⁷Sr/⁸⁶Sr ratios from 0.7144 to 0.7242, which are higher than that of the magmatic apatite (0.7082–0.7127) and the carbonate rocks (0.7104–0.7109). The Cambrian carbonaceous shale is a high (⁸⁷Sr/⁸⁶Sr)_i endmember that interacted with the initial ore-forming fluid; continuing interaction was deemed to enhance the reduction of the ore-forming fluid from Sch I to Sch II-1. Weakening of the intensity of fluid-rock interaction with carbonate rocks during vein-type mineralization caused the (⁸⁷Sr/⁸⁶Sr)_i values of the scheelite to increase gradually. The input of meteoric water decreased the fluid reduction capability during the formation of Sch II-1 to Sch II-3. Fluid-rock interaction dominated the scheelite mineralization of the reduced W skarn deposit.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140537251","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":"Geochemistry of scandium in pelagic sediments from the Pacific Ocean: Implication to the resource assessment of deep-sea REE-rich mud","authors":"Yanhui Dong ,&nbsp;Huan Zhang ,&nbsp;Tianyi Wang ,&nbsp;Yuwei Liu ,&nbsp;Xiaohan Gong ,&nbsp;Zhiming Zhu ,&nbsp;Weiyan Zhang ,&nbsp;Xiaohu Li ,&nbsp;Huaiming Li ,&nbsp;Fengyou Chu","doi":"10.1016/j.gexplo.2024.107465","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107465","url":null,"abstract":"<div><p>With the rapid development and wide use of fuel cells and scandium (Sc)-aluminum (Al) alloy, the demand for Sc may increase significantly in the future. Due to the lack of independent deposits, Sc is mainly derived from comprehensive utilization at present, which may cause a potential resource risk for the green economy in the future. It has been reported that deep-sea rare earth elements (REE)-rich mud is also enriched in Sc, but the geochemical properties of Sc in pelagic sediments are still poorly understood. In this study, bulk sediments geochemical data of China Ocean Mineral Resources R&amp;D Association cruises at the Western Pacific and the Clarion-Clipperton Fracture Zone combined with <em>in-situ</em> chemical composition of fish teeth (ichthyoliths or bioapatite) and ferromanganese micronodules are used to reveal the geochemical characteristics of Sc in pelagic sediments. The frequency distribution of Sc contents in sediments from the Western Pacific and the CCFZ showed regional variability, with median values of ∼19 ppm and ∼ 24 ppm, respectively. Scandium is commonly enriched in REE-rich sediment layers unassociated with hydrothermal activity, with a median content of ∼38.4 ppm. The Sc contents of the pelagic clay are generally higher than that of calcareous ooze and siliceous ooze. Compared to REE-rich sediments, Sc is concentrated in bioapatites (up to ∼250 ppm) but deficient in micronodules (∼2–20 ppm). Based on the <em>in-situ</em> geochemical results and the correlations between Sc and other major elements, clay minerals and bioapatites are likely to be the main Sc host phases in deep-sea sediments. Considering the high commercial price of Sc and its highest value proportion (&gt;20 %) among REEs, Sc should not be ignored in the resource assessment of REE-rich sediments.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140558518","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}