Pub Date : 2024-11-14DOI: 10.1016/j.gexplo.2024.107628
Xiaojun Hu , Huan Li , Thomas J. Algeo , Biao Liu , Fan Kang , Yiming Xie , Dapeng Zhu
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 εNd(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 (<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.
{"title":"Differentiating Triassic W–Sn ore-bearing and ore-free plutons in the Xitian Ore Field (South China) using apatite geochemistry","authors":"Xiaojun Hu , Huan Li , Thomas J. Algeo , Biao Liu , Fan Kang , Yiming Xie , 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<sub>Nd</sub>(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 (<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 <sup>147</sup>Sm/<sup>144</sup>Nd 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}
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 ca. 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 syn- to post-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.
{"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 , Davood Raeisi , M. Santosh , Miao Zhao , 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 δ<sup>65</sup>Cu 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}
Pub Date : 2024-11-03DOI: 10.1016/j.gexplo.2024.107613
David Calisto , Daniel Moncada , Eric Sonnenthal , Lorena Ortega , Darío Chinchilla
<div><div>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.</div><div>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.</div><div>To identify the most relevant geochemical and transport parameters controlling the formation of this fossil geothermal system >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.</div><div>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.</div><div>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.</div><div>The results of both models are validated by replicating the system evolution, reproducing the sa
{"title":"Numerical simulation of a base metal deposit related to a fossil geothermal system","authors":"David Calisto , Daniel Moncada , Eric Sonnenthal , Lorena Ortega , Darío Chinchilla","doi":"10.1016/j.gexplo.2024.107613","DOIUrl":"10.1016/j.gexplo.2024.107613","url":null,"abstract":"<div><div>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.</div><div>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.</div><div>To identify the most relevant geochemical and transport parameters controlling the formation of this fossil geothermal system >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.</div><div>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.</div><div>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.</div><div>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}
Pub Date : 2024-11-01Epub Date: 2022-03-09DOI: 10.1080/08869634.2022.2048225
Jeong-Seung Kwon, Sang-Ho Han, Yeong-Gwan Im
Objective: To investigate the surface electromyography (EMG) activity of the temporalis, masseter, digastric, and infrahyoid muscles during passive jaw opening in healthy adults.
Methods: The EMG activity of the masseter, temporalis, digastric anterior belly, and infrahyoid muscles on the right side was recorded during the four jaw-opening tasks: active opening to 20 mm (AO20); active opening to 40 mm (AO40); passive opening to 40 mm with a rubber mouth prop on the right posterior teeth (POR40); and passive opening to 40 mm with a mouth prop on the left posterior teeth (POL40).
Results: The EMG amplitude of the digastric anterior belly and infrahyoid muscles in either POL40 or POR40 was significantly less than that in AO20 or AO40, respectively.
Conclusion: Passive jaw opening reduces the EMG activity of the digastric and infrahyoid muscles significantly and could help reduce the load on these muscles during prolonged mouth-opening conditions.
{"title":"Effect of passive jaw opening on the electromyographic activity of the temporalis, masseter, digastric, and infrahyoid muscles in healthy adults.","authors":"Jeong-Seung Kwon, Sang-Ho Han, Yeong-Gwan Im","doi":"10.1080/08869634.2022.2048225","DOIUrl":"10.1080/08869634.2022.2048225","url":null,"abstract":"<p><strong>Objective: </strong>To investigate the surface electromyography (EMG) activity of the temporalis, masseter, digastric, and infrahyoid muscles during passive jaw opening in healthy adults.</p><p><strong>Methods: </strong>The EMG activity of the masseter, temporalis, digastric anterior belly, and infrahyoid muscles on the right side was recorded during the four jaw-opening tasks: active opening to 20 mm (AO20); active opening to 40 mm (AO40); passive opening to 40 mm with a rubber mouth prop on the right posterior teeth (POR40); and passive opening to 40 mm with a mouth prop on the left posterior teeth (POL40).</p><p><strong>Results: </strong>The EMG amplitude of the digastric anterior belly and infrahyoid muscles in either POL40 or POR40 was significantly less than that in AO20 or AO40, respectively.</p><p><strong>Conclusion: </strong>Passive jaw opening reduces the EMG activity of the digastric and infrahyoid muscles significantly and could help reduce the load on these muscles during prolonged mouth-opening conditions.</p>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"174 1","pages":"736-744"},"PeriodicalIF":2.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86959825","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}
Pub Date : 2024-11-01DOI: 10.1016/j.gexplo.2024.107610
Xueqing Zhang , Jiahong Chen , Tiancai Ye , Hulong Yi , Shan Lei , Xiangxiang Cui , Dinggui Luo , Tangfu Xiao , Jinli Cui
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 (n = 5, 61.1–248.6 mg As/kg) and As-contaminated groundwater-impacted soil including yellow soils (n = 6, 23.2–32.1 mg As/kg) and chestnut soils (n = 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.
{"title":"Iron and phosphate species regulates arsenic speciation and potential mobility in contaminated soils","authors":"Xueqing Zhang , Jiahong Chen , Tiancai Ye , Hulong Yi , Shan Lei , Xiangxiang Cui , Dinggui Luo , Tangfu Xiao , 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}
Pub Date : 2024-11-01DOI: 10.1016/j.gexplo.2024.107603
Walid Salama, Naina Goswami, Heta Lampinen, Michael Verrall, Louise Schoneveld
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.
通过以碎屑岩为主的地形进行矿产勘探，对具有成本效益的勘探技术提出了重大挑战。由于地表表达缺失，地下矿产勘探有赖于了解矿石形成过程和蚀变机制特征，以破译通往矿床的合适路径。本文介绍的工作重点是西澳大利亚米卡塔拉地区以东 Yilgarn 克拉顿的 Archean 花岗岩-绿岩，通过了解金属弥散机制和确定碎屑岩中金矿化的矿物学载体，描述风化剖面的特征。使用 TESCAN 集成矿物分析仪和激光烧蚀 ICP-MS 绘制的金矿化矿物图显示，金与长英质至中英质火山岩和火山碎屑岩中的多代黄铁矿、贱金属硫化物和硫化物有关。强烈的风化作用产生了厚厚的风化岩剖面，该剖面以高岭土和微粒灰质吸水岩浸蚀带为主，底部则是超生金-铜矿床毯。该超生矿床主要由胶状黄铁矿和框架黄铁矿组成，并伴有纯微晶金、黄铜矿、辉铜矿、孔雀石和褐铁矿。高光谱分析用于追踪主岩和风化剖面中绿泥石和白云母的成分和丰度变化。热液蚀变晕中接近金矿化并与之相交的矿物组合主要是富含铁的绿泥石和富含 Na 的白云母（paragonite）。富铁绿泥石和副皂石在空间上与金浓度的升高有关，在热液蚀变远端则向富铁镁绿泥石和富钾白云母（白云母）的方向发展。绿泥石化学成分的变化主要在基岩和边岩中发现。相反，白云母化学变化则在基岩和沉积岩剖面中检测到，其中白云母可抵抗强烈的风化作用。通过短波和热红外数据确定的光谱特征通过 X 射线衍射、矿物化学和块体地球化学分析得到了验证。白云母和绿泥石的这种独特光谱特征是一种具有成本效益的勘探方法，可用于绘制区域矿物系统图，以确定在长英岩和中间岩上形成的残积岩中的热液蚀变足迹。
{"title":"Mapping hydrothermal alteration in regolith using white micas and chlorite as vectors towards gold mineralization","authors":"Walid Salama, Naina Goswami, Heta Lampinen, Michael Verrall, 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}
Pub Date : 2024-10-30DOI: 10.1016/j.gexplo.2024.107616
Zhi-Lin Cheng , Pei Ni , Jun-Yi Pan , Liang Han , Wen-Sheng Li , Stefano Albanese , Zhe Chi , Jun-Ying Ding , Jian-Ming Cui
<div><div>Sn and Cu are proposed to have their mineralization potential predetermined by their contents in initial fluids of granite-related magmatic-hydrothermal systems. However, it remains ambiguous whether the giant Sn-mineralized skarn system is applicable, and whether the Sn-Cu association in some deposits is predominantly determined by their initial metal contents. The Gejiu orefield is one of the most essential Sn-polymetallic districts worldwide, with proven resources of 3.27 million tons of tin, 3.25 million tons of copper, 4.29 million tons of lead and zinc, and >20 other metals with economic significance. Sn-polymetallic mineralization at Gejiu constitutes a composite skarn ore system that includes proximal skarn and related cassiterite-sulfide, greisen, and tourmaline-vein types. The Laochang Sn-polymetallic deposit hosts several largest skarn and cassiterite-sulfide orebodies in the eastern part of Gejiu. Recent exploitation at Laochang discovered Sn-mineralized quartz veins hosted in the concealed granite, providing a valuable opportunity to characterize the proximal magmatic-hydrothermal process of the mineralizing granitic system. Here, fluid inclusion analysis is carried out on these veins to discuss the fluid evolution, cassiterite precipitation mechanism and whether metal content in early proximal magmatic fluids determines the metal association and endowment in the deposit.</div><div>Based on the paragenesis of ore and gangue minerals, three hydrothermal stages are distinguished, including quartz-tourmaline stage (Stage I), cassiterite-arsenopyrite-quartz stage (Stage II) and late sulfide stage (Stage III). Fluid evolution controlling vein formation is constrained by microthermometry and LA-ICP-MS analysis of four fluid inclusions generations successively entrapped in quartz and cassiterite. The fluids involved during vein formation show an interplay between single-sourced magmatic fluids and meteoric water. The intermediate-density single phase fluid recorded at stage I quartz is derived from initial fluids directly exsolving from granitic magma. At stage II, fluid immiscibility occurred and the separated brines were entrapped in quartz and early-formed cassiterite. Along with cassiterite precipitation, brines were mixed with low-salinity and cooler meteoric water, leading to entrapment of low-salinity aqueous fluid in outer growth zones of cassiterite at stage II. The constructed fluid evolution history suggests that fluid immiscibility may have facilitated the nucleation of cassiterite crystals at the onset of deposition while mixing of magmatic fluid with meteoric water likely dominate later cassiterite mineralization.</div><div>Compared with the fluid dataset of barren and mineralized granitic systems worldwide, pre-ore fluids of the studied quartz veins are enriched in Sn, confirming that high Sn content in the initial magmatic fluid can serve as indicator to distinguish mineralized system. In contrast, although Cu m
{"title":"Fluid inclusion LA-ICP-MS constraint on hydrothermal evolution of proximal cassiterite-bearing quartz veins in the giant Gejiu orefield: Implications for controls on metallogenic potential of granite-related skarn system","authors":"Zhi-Lin Cheng , Pei Ni , Jun-Yi Pan , Liang Han , Wen-Sheng Li , Stefano Albanese , Zhe Chi , Jun-Ying Ding , Jian-Ming Cui","doi":"10.1016/j.gexplo.2024.107616","DOIUrl":"10.1016/j.gexplo.2024.107616","url":null,"abstract":"<div><div>Sn and Cu are proposed to have their mineralization potential predetermined by their contents in initial fluids of granite-related magmatic-hydrothermal systems. However, it remains ambiguous whether the giant Sn-mineralized skarn system is applicable, and whether the Sn-Cu association in some deposits is predominantly determined by their initial metal contents. The Gejiu orefield is one of the most essential Sn-polymetallic districts worldwide, with proven resources of 3.27 million tons of tin, 3.25 million tons of copper, 4.29 million tons of lead and zinc, and >20 other metals with economic significance. Sn-polymetallic mineralization at Gejiu constitutes a composite skarn ore system that includes proximal skarn and related cassiterite-sulfide, greisen, and tourmaline-vein types. The Laochang Sn-polymetallic deposit hosts several largest skarn and cassiterite-sulfide orebodies in the eastern part of Gejiu. Recent exploitation at Laochang discovered Sn-mineralized quartz veins hosted in the concealed granite, providing a valuable opportunity to characterize the proximal magmatic-hydrothermal process of the mineralizing granitic system. Here, fluid inclusion analysis is carried out on these veins to discuss the fluid evolution, cassiterite precipitation mechanism and whether metal content in early proximal magmatic fluids determines the metal association and endowment in the deposit.</div><div>Based on the paragenesis of ore and gangue minerals, three hydrothermal stages are distinguished, including quartz-tourmaline stage (Stage I), cassiterite-arsenopyrite-quartz stage (Stage II) and late sulfide stage (Stage III). Fluid evolution controlling vein formation is constrained by microthermometry and LA-ICP-MS analysis of four fluid inclusions generations successively entrapped in quartz and cassiterite. The fluids involved during vein formation show an interplay between single-sourced magmatic fluids and meteoric water. The intermediate-density single phase fluid recorded at stage I quartz is derived from initial fluids directly exsolving from granitic magma. At stage II, fluid immiscibility occurred and the separated brines were entrapped in quartz and early-formed cassiterite. Along with cassiterite precipitation, brines were mixed with low-salinity and cooler meteoric water, leading to entrapment of low-salinity aqueous fluid in outer growth zones of cassiterite at stage II. The constructed fluid evolution history suggests that fluid immiscibility may have facilitated the nucleation of cassiterite crystals at the onset of deposition while mixing of magmatic fluid with meteoric water likely dominate later cassiterite mineralization.</div><div>Compared with the fluid dataset of barren and mineralized granitic systems worldwide, pre-ore fluids of the studied quartz veins are enriched in Sn, confirming that high Sn content in the initial magmatic fluid can serve as indicator to distinguish mineralized system. In contrast, although Cu m","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"267 ","pages":"Article 107616"},"PeriodicalIF":3.4,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571904","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}
Pub Date : 2024-10-30DOI: 10.1016/j.gexplo.2024.107615
Long-Jiao Li , Xian-Cheng Mao , Zhan-Kun Liu , Xin-Ming Duan , Yun-Qi Wang , Qi-Xing Ai , De-Xian Li
The western intrusion of the world-class Jinchuan NiCu 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.
世界级金川硫化镍铜矿床的西部侵入体由细粒和粗粒二元岩性单元组成。然而，最近的勘探在金川侵入体西端的细粒单元中发现了两层净纹理硫化物，增加了硫化物成矿的复杂性。我们测量了亲铝元素并收集了铜和镍含量的勘探数据，以研究其成因和找矿潜力。下部细粒亚单元由底部的浸染状硫化物层（DS-1）和块状硫化物（MS）及橄榄石硫化物积层（NTS-1）组成，上部细粒亚单元为浸染状硫化物层（DS-2），核心为净纹理硫化物（NTS-2）。粗粒蛭石与浸染状硫化物（DS-3）尖锐地切割了上亚单元。所有浸染状样品的铜/钯比率（11,414-128,626）都超过了地幔范围。此外，DS-1（1.26-13.2）的钯/钌比值最低，DS-2（3.69-13.5）次之，DS-3（2.80-33.6）最高。勘探数据表明，DS-3 中的 Ni 和 Cu 含量以及 Cu/（Cu + Ni）比值明显高于 DS-2，而 DS-1 则更为分散。NTS-1表现出明显的Ir和Ru贫化，Cu/（Cu + Ni）随深度降低，最终遇到Ir和Ru富集的MS。此外，NTS-2 显示部分 Ir 贫化，但 Ru 未贫化，Cu/（Cu + Ni）随深度增加。这些特征表明，下亚单元和上亚单元以及粗粒度单元是在日益贫化的岩浆中由铂族元素（PGE）形成的，很可能是在成岩之前硫化物偏析造成的。此外，NTS-1和NTS-2之间Ir和Ru贫化程度的差异以及Cu/（Cu + Ni）随深度变化的趋势，可以用硫化物分馏过程中分馏硫化物液体的迁移方向来解释。我们认为金川侵入体西端是由多级岩浆喷发形成的。勘探数据（镍、铜和铜/（铜+镍））与各硫化物矿化层之间的强相关性表明，划分各硫化物矿化层的空间范围可为深部找矿制图提供有价值的信息。
{"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 , Xian-Cheng Mao , Zhan-Kun Liu , Xin-Ming Duan , Yun-Qi Wang , Qi-Xing Ai , 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}
Pub Date : 2024-10-30DOI: 10.1016/j.gexplo.2024.107611
Li Chen, Nannan Zhang, Jinyu Chang, Shibin Liao, Jintao Tao, Hao Zhang, Siyuan Li
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, 2D3D 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.
{"title":"Indicator element selection and lithological mapping using deep learning methods in the Dahongliutan area, NW China","authors":"Li Chen, Nannan Zhang, Jinyu Chang, Shibin Liao, Jintao Tao, Hao Zhang, 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}
Pub Date : 2024-10-29DOI: 10.1016/j.gexplo.2024.107607
Chaokun Luo, Ruidong Yang, Junbo Gao, Jun Chen, Hongcheng Mo
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.
{"title":"Metallogenic model of the carboniferous karst bauxites in Central Guizhou Province, Southwest China","authors":"Chaokun Luo, Ruidong Yang, Junbo Gao, Jun Chen, 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}
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