Journal of Geochemical Exploration最新文献

{"title":"Differentiating Triassic W–Sn ore-bearing and ore-free plutons in the Xitian Ore Field (South China) using apatite geochemistry","authors":"Xiaojun Hu ,&nbsp;Huan Li ,&nbsp;Thomas J. Algeo ,&nbsp;Biao Liu ,&nbsp;Fan Kang ,&nbsp;Yiming Xie ,&nbsp;Dapeng Zhu","doi":"10.1016/j.gexplo.2024.107628","DOIUrl":"10.1016/j.gexplo.2024.107628","url":null,"abstract":"<div><div>Though the metallogenic process of the Xitian W–Sn deposit has been established, the key factors distinguishing Triassic W–Sn ore-bearing granites from ore-free granites remain uncertain, leaving an important gap in understanding the controls on Triassic W–Sn mineralization. In this study, we present a comprehensive investigation of apatite from the Triassic Longshang W–Sn ore-bearing and Goudalan ore-free granites, to trace the nature of parental magma and to provide constraints on the processes related to Triassic W–Sn mineralization in Xitian Ore Field (South China). Apatites from ore-bearing (AOB) granites and apatites from ore-free (AOF) granites exhibit distinct Cathodoluminescence (CL) images: AOB samples feature darker cores and brighter rims, with concentric oscillatory growth zoning in the rim sections, whereas AOF samples exhibit chaotic textures in CL images. The U–Pb age dating of AOB and AOF yield a lower intercept age of 227.3 ± 4.3 Ma (1σ, MSWD = 3.9) and 227.1 ± 7.8 Ma (1σ, MSWD = 2.4) on the Tera-Wasserburg diagrams, respectively. The similar ε_Nd(t) values (−10.91 to −9.82 for AOB; −10.42 to −8.77 for AOF) (expressed as deviation in parts per 10,000 from CHUR composition), relatively low Cl contents (&lt;0.05 wt%), and high F (~3 wt%) of studied apatites, suggest that W–Sn ore-bearing and ore-free granitic magmas were both generated by melting of old continental crust. The texture and high concentration of REE + Y and Th in AOB could be assumed as the result of fluid exsolution. The chaotic texture, broad variation in ¹⁴⁷Sm/¹⁴⁴Nd ratios, may imply that AOF might have experienced metasomatic modification. Lower Eu/Eu* value together with higher Ce/Ce* value in AOB suggests a more reduced environment for W–Sn ore-bearing granites. Lower Sr, Mg content, and higher Y contents suggest that W–Sn ore-bearing granites have a higher degree of fractionation than ore-free granites. We propose that the mobilization and transport ability of W and Sn by hydrothermal fluids play an important role in the enrichment of W and Sn, and redox state of magma and the degree of magma differentiation determine the final enrichment level of tungsten and tin.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"268 ","pages":"Article 107628"},"PeriodicalIF":3.4,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664303","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":"Recycled mantle source for porphyry mineralization: U−Pb and Re−Os geochronology, and S–Pb–Cu isotopic constraints from the Urumieh-Dokhtar magmatic arc, central Iran","authors":"Shahrouz Babazadeh ,&nbsp;Davood Raeisi ,&nbsp;M. Santosh ,&nbsp;Miao Zhao ,&nbsp;Massimo D'Antonio","doi":"10.1016/j.gexplo.2024.107630","DOIUrl":"10.1016/j.gexplo.2024.107630","url":null,"abstract":"<div><div>The Urumieh−Dokhtar magmatic arc (UDMA) hosts some of the world-class porphyry copper deposits in Iran. Here, we present high-resolution geochronological and stable isotope data to gain insights into the timing and source of the metallogeny of Kahang porphyry Cu deposit. Zircon U−Pb data show crystallization age of <em>ca.</em> 15 Ma age for the host porphyry intrusion and Re−Os geochronology yields 14.5 Ma from the molybdenite associated with the ores. Sulfur isotope values on the sulphide minerals range from −1.6 ‰ to + 2.1 ‰, indicating a magmatic source for sulfur. Lead isotopic compositions of the S-bearing minerals are akin to those of the intrusive rocks, suggesting that the metal was likely sourced from mantle reservoirs. We propose a model for the UDMA involving slab break-off during the maturity of arc magmatism from the <em>syn</em>- to <em>post</em>-collisional stages of orogenesis. The δ⁶⁵Cu data trace a systematic change from the barren to the fertile magmas. We suggest that partial melting of the sub-continental lithospheric mantle that has previously been refertilized of Cu through time as the potential source for the formation of ore-bearing magmas.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"268 ","pages":"Article 107630"},"PeriodicalIF":3.4,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664323","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":"Numerical simulation of a base metal deposit related to a fossil geothermal system","authors":"David Calisto ,&nbsp;Daniel Moncada ,&nbsp;Eric Sonnenthal ,&nbsp;Lorena Ortega ,&nbsp;Darío Chinchilla","doi":"10.1016/j.gexplo.2024.107613","DOIUrl":"10.1016/j.gexplo.2024.107613","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Fossil and active geothermal systems that produce ore deposits are sites of complex physicochemical processes and a favorable combination of factors related to the amount of metal-bearing fluid that flows through the system, ore fluid metal concentrations, depositional efficiency, and the duration of ore deposition. Of all these factors, the length of the mineralizing event is one of the least understood aspects of ore genesis.&lt;/div&gt;&lt;div&gt;We used fluid inclusion data, chemical compositions of base metal sulfides, and fluid flow rates to constrain a reactive-transport model of a fossil geothermal system - the Patricia Zn-Pb-Ag deposit in northern Chile. The Patricia deposit consists of quartz and base metal sulfide veins of hydrothermal origin with structural control, hosted in a volcanic succession with intense propylitic alteration. The fluid inclusions are liquid-rich, with homogenization temperatures ranging from 250 to 150 °C and salinities between 22 and 1 wt% NaCl equiv., with an early fluid mixing trend and no evidence of boiling in the system. Sulfide mineralogy indicates intermediate sulfidation conditions.&lt;/div&gt;&lt;div&gt;To identify the most relevant geochemical and transport parameters controlling the formation of this fossil geothermal system &gt;1000 simulations were performed using the reactive-transport code TOUGHREACT. The paragenesis of the deposit is mimicked by a model of successive stages of fluid circulation consistent with the observed mineral assemblage distribution, the fluid inclusion data, and the estimated resources in the deposit.&lt;/div&gt;&lt;div&gt;The entire geothermal activity of the system was modeled considering 10,000 years of fluid-rock interaction, with periods of circulation of metal-barren fluids followed by metal-rich fluids driving the ore formation. In the initial model, base metal solubility with predominant chloride complexing suggests that the most efficient ore-forming mechanism for the Patricia deposit was the result of the interaction of two different fluids, one fluid transporting metals and another fluid transporting reduced sulfur, mixing in a rock volume of high permeability. Mass balance estimations with this model give a period of 3500 to 5000 years for the ore stage duration in which all the ore resources of the Patricia deposit could have been precipitated by fluid mixing.&lt;/div&gt;&lt;div&gt;In a second model, the previous estimates for the duration of the main ore stage were used to simulate the fluid-rock interaction during the ore stage for 3500 years. The results indicated the importance of the permeability of the host rock enhanced by fractures to concentrate the volume of the mineralization and the role of the hydrothermal alteration assemblage in controlling the circulating fluid acidity. A higher efficiency in forming sulfide minerals appears to coincide with pH values ranging from 5.1 to 5.3.&lt;/div&gt;&lt;div&gt;The results of both models are validated by replicating the system evolution, reproducing the sa","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"268 ","pages":"Article 107613"},"PeriodicalIF":3.4,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664311","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":"Iron and phosphate species regulates arsenic speciation and potential mobility in contaminated soils","authors":"Xueqing Zhang ,&nbsp;Jiahong Chen ,&nbsp;Tiancai Ye ,&nbsp;Hulong Yi ,&nbsp;Shan Lei ,&nbsp;Xiangxiang Cui ,&nbsp;Dinggui Luo ,&nbsp;Tangfu Xiao ,&nbsp;Jinli Cui","doi":"10.1016/j.gexplo.2024.107610","DOIUrl":"10.1016/j.gexplo.2024.107610","url":null,"abstract":"<div><div>Arsenic in soils poses a high environmental risk. The understanding of arsenic geochemical speciation, mobility, and other potential factors in contaminated soils is crucial for appropriate remediation strategy development and environmental assessment. The objective of this study was to investigate the arsenic oxidation state and its form in each step of sequential extraction applied to different types of contaminated soils, and to analyze the impact of sequential extraction forms of soil Fe and phosphate. Soil samples were collected from three agricultural regions: acid mine drainage (AMD)-impacted red soils (<em>n</em> = 5, 61.1–248.6 mg As/kg) and As-contaminated groundwater-impacted soil including yellow soils (<em>n</em> = 6, 23.2–32.1 mg As/kg) and chestnut soils (<em>n</em> = 5, 9.0–13.3 mg As/kg). The results of sequential extraction revealed that As was primarily associated with Fe(III) oxyhydroxides. The highest proportion of amorphous Fe(III) oxyhydroxide-bound As was observed in the southern red soils, which was attributable to the coprecipitation/immobilization of high Fe and As concentration levels in AMD during irrigation. The amount of adsorbed As (mass fraction) increased linearly with increasing amounts of As and is related to the presence of both amorphous and crystalline Fe phases in the soils. This demonstrates the immobilization role of reactive Fe phases in controlling the potential mobility of As in contaminated soils impacted by As-contaminated groundwater and AMD. Soil phosphate, with mass concentrations 2–4 orders of magnitude higher than those of As, occupied most of the Fe(III) oxyhydroxide reactive sites. Phosphate-extractable As was 4.3–80.7 mg/kg, accounting for 18.3–76.0 % (median of 33.5 %) of total As, indicating the competitive effect of phosphate on the desorptive release of As. The AMD-impacted paddy soil exhibited much higher proportions of phosphate-extractable As and a predominance of As(III) in the water-soluble extract, revealing the high potential mobility and toxicity of As in flooded soil. The dominant occupation of Fe adsorption sites by soil phosphate likely contributes to low efficiency of soil Fe in immobilizing As. To reduce As mobility, it is imperative to develop future strategies for phosphates used as sustainable fertilizer to support crop culture.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"268 ","pages":"Article 107610"},"PeriodicalIF":3.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664304","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":"Mapping hydrothermal alteration in regolith using white micas and chlorite as vectors towards gold mineralization","authors":"Walid Salama,&nbsp;Naina Goswami,&nbsp;Heta Lampinen,&nbsp;Michael Verrall,&nbsp;Louise Schoneveld","doi":"10.1016/j.gexplo.2024.107603","DOIUrl":"10.1016/j.gexplo.2024.107603","url":null,"abstract":"<div><div>Mineral exploration through regolith-dominated terrains poses a significant challenge to cost-effective exploration techniques. Due to missing surface expression, undercover mineral exploration relies on understanding ore-forming processes and characterizing alteration regimes to decipher suitable vectors towards ore deposits. The work presented focuses on the Archean granite-greenstones of the Yilgarn Craton, east of the Meekatharra area in Western Australia, and characterizes the weathering profiles by understanding metal dispersion mechanisms and identifying mineralogical vectors towards gold mineralization within regolith. Mineral mapping of gold mineralization using TESCAN Integrated Mineral Analyzer and laser ablation ICP-MS shows gold is associated with multiple generations of pyrite, and base metal sulfides and sulfosalts hosted in felsic to intermediate volcanics and volcaniclastics. Intensive weathering generated a thick regolith profile dominated by a leached zone of kaolinitic and micaceous saprolite underlain by a supergene Au-Cu deposit blanket at the base. The supergene deposit is dominated by colloform and framboidal pyrite, with pure microcrystalline Au, chalcocite, bornite, malachite, and alunite. Hyperspectral analyses were used to trace the composition and abundance of chlorite and white mica variations in the host rock and the weathering profile. The mineral assemblage in the hydrothermal alteration halo proximal to and intersecting gold mineralization is dominated by Fe-rich chlorite and Na-rich white mica (paragonite). Fe-rich chlorite and paragonite are spatially tied to elevated Au concentration and trends to Fe-Mg-rich chlorite and K-rich white mica (muscovite) distal to the alteration. The variations in chlorite chemistry were detected mainly in bedrock and saprock. Conversely, the white mica chemistry variations were detected in bedrock and the regolith profile, in which white micas resist intensive weathering. The spectral signatures identified through short-wave and thermal infrared data are verified through X-ray diffraction, mineral chemistry, and bulk geochemical analyses. This distinctive spectral signature of white mica and chlorite is a cost-effective exploration method for regional mapping of mineral systems to identify hydrothermal alteration footprints in the regolith developed over felsic and intermediate rocks.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"268 ","pages":"Article 107603"},"PeriodicalIF":3.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664310","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":"Multi-stage magma emplacement in the western end of the Jinchuan NiCu sulfide deposit, NW China, and mineral exploration strategy based on exploration data","authors":"Long-Jiao Li ,&nbsp;Xian-Cheng Mao ,&nbsp;Zhan-Kun Liu ,&nbsp;Xin-Ming Duan ,&nbsp;Yun-Qi Wang ,&nbsp;Qi-Xing Ai ,&nbsp;De-Xian Li","doi":"10.1016/j.gexplo.2024.107615","DOIUrl":"10.1016/j.gexplo.2024.107615","url":null,"abstract":"<div><div>The western intrusion of the world-class Jinchuan Ni<img>Cu sulfide deposit consists of fine-grained and coarse-grained binary lithofacies units. However, recent exploration has revealed two layers of net-textured sulfides in the fine-grained unit at the western end of the Jinchuan intrusion, adding complexity to the genesis of sulfide mineralization. We measured chalcophile elements and collected exploration data on Cu and Ni content to investigate their genesis and prospecting potential. The lower fine-grained subunits, comprising a layer of disseminated sulfides (DS-1) in the bottom and overlain by massive sulfide (MS) and olivine-sulfide cumulates (NTS-1), were overlain by the upper fine-grained subunits disseminated sulfides (DS-2) with a core of net-textured sulfides (NTS-2). The coarse-grained lherzolite with disseminated sulfides (DS-3) sharply cut through the upper subunit. All disseminated samples have Cu/Pd ratios (11,414–128,626) that exceed the mantle range. Additionally, the Pd/Ru ratios of DS-1 (1.26–13.2) are the lowest, followed by DS-2 (3.69–13.5), and highest in DS-3 (2.80–33.6). The exploration data indicate that the Ni and Cu contents and Cu/(Cu + Ni) ratios are significantly higher in DS-3 than in DS-2, while DS-1 shows more dispersed. The NTS-1 exhibits significant Ir and Ru depletion, with Cu/(Cu + Ni) decreasing with depth, eventually encountering Ir and Ru-riched MS. In addition, NTS-2 shows partially Ir depletion but Ru non-depletion, and Cu/(Cu + Ni) increases with depth. These signatures suggest that the lower and upper subunits, along with the coarse-grained unit, formed from platinum-group elements (PGE) in increasingly depleted magma, likely resulting from prior sulfide segregation before emplacement. Furthermore, the differences in Ir and Ru depletion and the variation in the Cu/(Cu + Ni) trend with depth between NTS-1 and NTS-2 were explained by the migration direction of fractional sulfide liquid during sulfide fractionation. We propose that the western end of the Jinchuan intrusion was formed by multi-stage magma emplacement. The strong correlation between exploration data (Ni, Cu, and Cu/(Cu + Ni)) and various sulfide mineralization layers suggests that delineating the spatial range of each sulfide mineralization could provide valuable information for deep mineral prospectivity mapping.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"268 ","pages":"Article 107615"},"PeriodicalIF":3.4,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664325","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":"Indicator element selection and lithological mapping using deep learning methods in the Dahongliutan area, NW China","authors":"Li Chen,&nbsp;Nannan Zhang,&nbsp;Jinyu Chang,&nbsp;Shibin Liao,&nbsp;Jintao Tao,&nbsp;Hao Zhang,&nbsp;Siyuan Li","doi":"10.1016/j.gexplo.2024.107611","DOIUrl":"10.1016/j.gexplo.2024.107611","url":null,"abstract":"<div><div>Rare metal resources are extensively used in the emerging energy field, making the security and sustainability of rare metal supply chains critical issues. Pegmatite-type rare metal deposits are a significant source of rare metal resources. Geochemistry is one of the most direct and effective methods of mineral exploration. In this study, whole-rock geochemical data from the Akesayi region, located in the Western Kunlun area of China, were used to identify the indicative elements of pegmatite automatically. Based on the stream sediment geochemical data, various deep learning models have been employed to achieve automatic lithological identification of the area. The results indicate that a novel interpretable model using SHapley Additive exPlanations (SHAP) and eXtreme Gradient Boosting (XGBoost) was employed to select indicative elements for the pegmatite in the Akesayi region, identifying Ta and Rb as key elements. The state-of-the-art application of deep-learning algorithms for lithological mapping has proven to be highly effective. Among the four approaches, the ensemble strategy integrating 1D convolutional neural networks, 2D<img>3D convolutional neural networks, and dual-branch neural networks yields the best lithological mapping results. This approach resulted in a total classification accuracy of 90.422 %, an average accuracy of 90.502 %, a Kappa coefficient of 89.643 %, and a user accuracy of 65.530 % for the pegmatite lithological unit. These results demonstrate that the proposed model can provide robust technical support for the exploration of rare metal pegmatites in regions with challenging natural conditions and limited research.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"268 ","pages":"Article 107611"},"PeriodicalIF":3.4,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664305","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":"Metallogenic model of the carboniferous karst bauxites in Central Guizhou Province, Southwest China","authors":"Chaokun Luo,&nbsp;Ruidong Yang,&nbsp;Junbo Gao,&nbsp;Jun Chen,&nbsp;Hongcheng Mo","doi":"10.1016/j.gexplo.2024.107607","DOIUrl":"10.1016/j.gexplo.2024.107607","url":null,"abstract":"<div><div>Karst bauxites, the dominant mineral resources of Guizhou Province, southwest China, are hosted in the Lower Carboniferous Jiujialu Formation and the Lower Permian Dazhuyuan Formation. Currently, the total bauxite resources in central Guizhou area (CGA) have exceeded 500 million tons. Herein, we present a detailed petrographic, mineralogical, and geochemical characterization of the Tanguanyao and Ganba bauxite deposits located in CGA, with a particular focus on the differences in mineral composition. The aim of this study is to discuss the genesis of major minerals, analyze the sedimentary environment of representative bauxite deposits, and further reveal the metallogenic model of the Jiujialu Formation. Mineralogically, the Tanguanyao bauxite is mainly composed of diaspore, chamosite, anatase, and pyrite, whereas the Ganba bauxite consists of diaspore, chamosite, anatase, boehmite, kaolinite, and illite. This is because the Tanguanyao and Ganba bauxite deposits are located in different paleo-elevation, and their mineral compositions are significantly different due to the fluctuation of groundwater level. Mineralogical evidence suggests that the diaspore in the Tanguanyao and Ganba bauxite deposits also includes supergene crystallization in addition to metamorphic processes. In terms of sedimentary environment, the Tanguanyao bauxite deposit belongs to the phreatic bauxite type characterized by a reducing environment, while the Ganba bauxite belongs to the transitional type between the vadose and phreatic facies.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"268 ","pages":"Article 107607"},"PeriodicalIF":3.4,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664324","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 geochemistry and zircon U-Pb geochronology of mafic sills from the Karagwe Ankolean Belt of northwestern Tanzania: Implications for petrogenesis and Ni-Cu-Co prospectivity","authors":"Gerald L. Chuwa ,&nbsp;Charles H. Kasanzu ,&nbsp;Emmanuel O. Kazimoto ,&nbsp;Francisco E. Apen","doi":"10.1016/j.gexplo.2024.107614","DOIUrl":"10.1016/j.gexplo.2024.107614","url":null,"abstract":"<div><div>In northwestern Tanzania, mafic sills intruded the Akanyaru and Kagera Supergroup rocks in the Mesoproterozoic Karagwe-Ankolean Belt (KAB). Trace element geochemistry and U<img>Pb geochronology results are reported to unravel petrogenetic and geochronological evolution of the sills in order to place constraints on Ni-Cu-Co prospectivity of the KAB. The sills are subalkaline gabbronorite and dolerite. They are relatively evolved Mg# = 43–69, with transitional metal contents lower than juvenile mafic-ultramafic rocks of the Kabanga-Musongati Alignment (KMA) intrusions. The sills can be subdivided into western and eastern swarms that display similar geochemical characteristics, including enrichment in LREE (Light Rare Earth Elements), LILE (Large Ion Lithophile Elements), Pb, Th, and U relative to HFSE (High Field Strength Elements). They are characterised by depletions of Nb-Ta-Ti in primitive mantle normalised spiderplots, enrichments in LREE and relatively flat MREE and HREE with negative Eu anomalies Eu/Eu* = 0.74–0.94 in chondrite normalised REE spiderplots. Together with elemental trace element ratios Nb/Yb, Th/Yb, Zr/Nb, Ba/Nb, and Nb-Yb-Ti index suggest derivation of the mafic sills from a sub-continental lithospheric mantle source followed by fractional crystallisation and crustal contamination.</div><div>Zircon U<img>Pb geochronology yields a concordant weighted age of 1424 ± 13 Ma for a gabbronorite in the western sills and an upper age intercept of 1411 ± 54 Ma for a dolerite in the eastern sills. The emplacement ages are similar to those of the KMA and the Lake Victoria Dolerite Dyke Swarm (LVDDS). Temporal and geochemical similarities with the KMA and LVDDS supports for emplacement of the mafic sills in an intracratonic rift setting. Although the KAB sills are relatively more geochemically evolved, they share similar evolutionary path with Ni-Cu-Co mineralised juvenile KMA intrusions, sensu stricto interaction with sulphur bearing country rocks. We suggest that trace elements geochemistry including chalcophile elemental ratios (Ni/Cr and Cu/Zn) of the sills be applied as vectors to locate prospective Ni-Cu-Co targets in the KAB.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"268 ","pages":"Article 107614"},"PeriodicalIF":3.4,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664309","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":"Distribution, enrichment characteristics and prospecting potential of lithium in Uzbekistan: Insights from 1:1 million geochemical mapping","authors":"Jifei Cao ,&nbsp;Wenyuan Li ,&nbsp;Maksud Isokov ,&nbsp;Jakhongir Movlanov ,&nbsp;Miraziz Mirkhamdamov ,&nbsp;Zhongping Ma ,&nbsp;Kai Weng ,&nbsp;Kai Cao ,&nbsp;Guanglu Meng","doi":"10.1016/j.gexplo.2024.107606","DOIUrl":"10.1016/j.gexplo.2024.107606","url":null,"abstract":"<div><div>With the world economy gradually shifting to alow‑carbon and greener model in recent years, there is a growing need for developing key metals like lithium in economic development. Economic growth has sped up the country's shift to a green economy along with Uzbekistan's reform and opening up, and the country's developing major mineral resources, such as lithium, have garnered a lot of attention. Owing to lithium resource protential of Uzbekistan is unclear, it is important to examine the possibility of lithium mineralization. The distribution and enrichment characteristics of lithium in the Uzbeksitan Tianshan are studied in this paper, based on geochemical mapping data at a 1:1000000 scale. It's concluded that stream sediments from the Tianshan region of Uzbekistan have higher concentration of lithium than the continental crust, and the South Tianshan has the highest lithium content. Lithium mineralization has been found in the lithium-geochemical anomaly areas in the eastern part of Uzbekistan South Tianshan through field investigation. Spodumene pegmatite, the first instance of pegmatitic type lithium mineralization in this region and even in the Tianshan orogenic belt of Central Asia. In conjunction with the geological background analysis, the metallogenic potential of lithium was assessed, resulting in the identification of four regions with lithium geochemical anomaly, and these sites will serve as target areas for Li deposits prospecting work in the future. This work has significant implications for the advancement of our understanding of the metallogenic theory of pegmatite-type Li deposits, as well as practical guiding significance for lithium ore prospecting in the Tianshan orogenic belt of Central Asia.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"268 ","pages":"Article 107606"},"PeriodicalIF":3.4,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664312","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}