Journal of Geochemical Exploration最新文献

{"title":"Hydrogeochemical process and coal mining-motivated effect on the hydrochemistry for the groundwater system in mining area of Western China","authors":"Yifan Zeng ,&nbsp;Qiang Wu ,&nbsp;Aoshuang Mei ,&nbsp;Lu Wang ,&nbsp;Wenbin Yin ,&nbsp;Lei Yang ,&nbsp;Di Zhao ,&nbsp;Shihao Meng ,&nbsp;Hongfei Gao","doi":"10.1016/j.gexplo.2024.107516","DOIUrl":"10.1016/j.gexplo.2024.107516","url":null,"abstract":"<div><p>The Jurassic coalfield in the mining area of western China exhibits a multi-layered groundwater system. However, it is subject to an arid and semi-arid climate with limited water resources. Consequently, the ecological environment is highly vulnerable, and the chemistry and quality of groundwater may be influenced by multiple factors. This study systematically the coal mining-motivated effect on the hydrochemistry and water quality of the groundwater system, using the Caojiatan Coal Mine as a case study. The analysis incorporates a combination of the self-organizing maps (SOM), entropy-weighted water quality index (EWQI), and traditional hydrochemical analysis methods. After coal mining, there was an increase in the proportion of HCO₃-Ca and HCO₃-Mg in the groundwater samples of J₂z, J₂y⁴, and J₂y⁵. The groundwater is controlled by cation exchange as a whole. The J₂y⁴ and above groundwater is influenced by both the dissolution of carbonate and silicate rocks before coal mining. After coal mining, the Quaternary and J₂a groundwater in the western wing is primarily influenced by the dissolution of carbonate rocks; the J₂z, J₂y⁴ and J₂y⁵ groundwater is primarily governed by the dissolution of silicate rocks and the oxidation of FeS₂; the J₂y³ and below groundwater is primarily controlled by the dissolution of evaporate rocks. The resulting dilution effect after coal mining and the implementation of measures for the discharge of treated mine water make the groundwater quality of the J₂y⁴ and higher aquifers tend to be better. The research findings serve as a valuable reference for promoting the sustainable development and protection of groundwater resources not only in the study area but also in other coal mines.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141130888","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":"Exploration indication of hidden gold deposits using the fine-grained soil prospecting method and its nano-micron metal migration evidence in the alluvial soil covered area, Jiaodong","authors":"Hanliang Liu ,&nbsp;Bimin Zhang ,&nbsp;Xueqiu Wang ,&nbsp;Qiang Wang ,&nbsp;Yude Du ,&nbsp;Baoyun Zhang ,&nbsp;Yubin Cui ,&nbsp;Jian Zhou ,&nbsp;Bin Liu ,&nbsp;Jie Li","doi":"10.1016/j.gexplo.2024.107514","DOIUrl":"10.1016/j.gexplo.2024.107514","url":null,"abstract":"<div><p>Jiaodong stands out among three global provinces boasting gold reserves surpassing 5000 tons. As geological exploration in the region continues to rise, the significance of deep and covered areas in Jiaodong for ore prospecting becomes increasingly evident. In this study, a Fine-grained soil prospecting method was employed in the Qujia hidden gold deposit and its surrounding region, situated in Yantai City, Shandong Province, and concealed by alluvial soil. The gold (Au) content exhibited a high enrichment level, and the range of Au and silver (Ag) geochemical anomalies demonstrated a robust correlation with known hidden orebodies. Furthermore, transmission electron microscopy and nano-CT were utilized to identify nano-micron metal particles and micro-fractures in the wall rock. A hereditary relationship between the nano-micron metal particles of ore-forming elements present in surface media and the deep orebody was observed. A migration model detailing the movement of deep ore-forming materials in the form of nano-micron metal particles, governed by a multi-agent relay dominated by ascending geogas flow, was established in the Qujia gold deposit in Jiaodong. These findings contribute theoretical support for the fine-grained soil prospecting method in geochemical exploration within alluvial soil covered areas.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141134648","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":"Inferring arsenic anomalies indirectly using airborne hyperspectral imaging – Implication for gold prospecting along the Rise and Shine Shear Zone in New Zealand","authors":"Rupsa Chakraborty ,&nbsp;Gabor Kereszturi ,&nbsp;Reddy Pullanagari ,&nbsp;Dave Craw ,&nbsp;Patricia Durance ,&nbsp;Salman Ashraf","doi":"10.1016/j.gexplo.2024.107510","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107510","url":null,"abstract":"<div><p>Well-exposed mineral deposits are scarce at a global level and presently potential mineral-rich sites are underlying vegetation cover and topsoil, which are suboptimal for direct remote sensing based exploration techniques. This study aims to implement an indirect approach to arsenic (As) distribution mapping using the surface manifestations of the subsurface geology and link it to the known gold mineralisation in the study area. Rise and Shine Shear Zone (RSSZ) in New Zealand is broadly a part of the Otago schist hosting lower to upper green-schist facies rocks manifesting mesothermal gold mineralisation. The area has several surficial geological imprints separating mineralised and non-mineralised zones, but these are dominated by topographic ruggedness, soil moisture and vegetation (mainly grass/tussock) spectra in the hyperspectral data. Initially, a band selection using Recursive Feature Elimination (RFE) was executed. The bands generated were tallied with the field and geological understanding of the area. The resultant 85 bands were then further put through Orthogonal Total Variation Component Analysis (OTVCA) to concise the information in 10 bands. OTVCA output was then classified using Random Forest classifier to map three levels of As concentration (&lt;20 ppm, between 20 and 100 ppm and &gt;100 ppm). The potentially high As concentration zones are likely to be related to the gold mineralisation. The geology of the area correlates with soil exposure which is captured by the classification in some parts, this increases the accuracy but also makes the classification analysis challenging.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141077659","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":"Factor analysis of geogas data for concealed lithium deposits detection and false anomalies identification in Jiajika area","authors":"Zhiqiang Xu,&nbsp;Bin Liang,&nbsp;Hui Jiang,&nbsp;Ting Liu,&nbsp;Qiubo Wang,&nbsp;Jiaxin Duan,&nbsp;Bangqiao Chen,&nbsp;Yangpiao He","doi":"10.1016/j.gexplo.2024.107511","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107511","url":null,"abstract":"<div><p>The Jiajika hardrock-type rare metal deposit in western Sichuan, China, is considered the largest spodumene deposit in Asia. The quaternary overburden of this area leads to ineffectiveness for ore prospecting using geochemical soil and geochemical stream sediment surveys. Although geogas prospecting has been proven to be effective in exploring buried orebodies, it is seldom deployed to explore concealed lithium deposits. In this work, the geogas samples were collected using the dynamic collection technique along the traverses over three concealed lithium deposits, namely, V-804, V-X03 (Line 7 and Line 35 were selected for sampling, denoted as V-X03–7 and V-X03–35, respectively), and V-STG. The samples were also collected from a Li-poor pegmatite (V-CLZ). The concentrations of Li, Be, Rb, Cs, Nb, Ta, Sn, B, Sr, Ba, and W in the nitric acid collector were measured by performing inductively coupled plasma-mass spectrometry (ICP-MS) measurements. The nanoparticles in geogas were analysed by using a transmission electron microscope coupled with performing energy dispersive spectroscopy (TEM-EDS) measurements. Apparent anomalies of Li, Be, Rb, Cs, B, and Sr were observed on all the traverses. These elements are regarded as pathfinders for the detection of concealed lithium deposits. Clear anomalies of Li, Be, Rb, Sn, B, and Sr were also found over V-CLZ. The concentrations of these elements in the nitric acid solutions were close to those over V-X03–35 and V-STG. The pathfinders are thus not effective in accurately recognizing the false anomalies over Li-poor pegmatite. The TEM-EDS measurements are not suitable for the characterization of nanoparticles in the Jiajika area because the particles from Li-rich and Li-poor pegmatites exhibited similarities in their morphologies. In addition, Li and Be cannot be detected by studying the EDS spectra, and the disturbance from the high background was non-negligible. To effectively address these issues, factor analysis (FA) was conducted on the concentrations of Li, Be, Rb, Cs, Nb, Ta, and Sn in geogas. The synthesis score (SSC) was computed based on three factors extracted by FA. At some sampling sites over V-804, V-X03, and V-STG, the SSC values were larger than 0.25, whereas the maximum SSC over V-CLZ was 0.15. Therefore, FA of geogas data is arising as a feasible method to detect concealed lithium deposits and identify false anomalies in the Jiajika area. The elemental concentrations in the samples from V-X03–7 were much higher than those from the other veins. This effect was attributed to the migration of the elements from buried orebodies to the ground surface, which was possibly promoted by the tourmalinized hornfels.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141090951","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":"Accurate and precise in situ determination of beryllium contents in beryllium minerals using ablation spot size of 13 μm by LA–ICP–MS","authors":"Wen-Kai Jin ,&nbsp;Xu-Dong Che ,&nbsp;Ru-Cheng Wang ,&nbsp;Huan Hu ,&nbsp;Can Rao ,&nbsp;Wen-Lan Zhang ,&nbsp;Xiao-Feng Li","doi":"10.1016/j.gexplo.2024.107512","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107512","url":null,"abstract":"<div><p>Beryllium is a strategically critical metal, and its accurate <em>in situ</em> analysis in beryllium minerals is challenging in the field of earth science. High spatial resolution is also a difficult point in the analysis. A new analysis approach for the accurate and precise determination of beryllium contents in beryl using an ablation spot size of 13 μm by LA–ICP–MS was first achieved in this study. The control variables were used to optimise the instrument conditions and determine the laser ablation parameters suitable for determining beryl under an ablation spot size of 13 μm. The energy density was set at 5.5 J/cm² with a repetition rate of 4 Hz, and the ablation time was 50 s. A new concept, the Relative Fractionation Index (<em>RFI</em>), was proposed to measure fractionation and matrix effects. Two potential beryl reference substances (B4–2 and Brl-3) were also assessed by determining their homogeneity to further improve the measurement accuracy. Other common beryllium minerals, including phenakite, chrysoberyl, and herderite, were identified in this study. By comparing the <em>RFI</em> values of different minerals and reference materials, appropriate reference materials and determination conditions were selected, and ideal analysis results were obtained. Therefore, the accurate and precise determination of beryllium contents in common beryllium minerals was achieved using an ablation spot size of 13 μm by LA–ICP–MS.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141095996","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":"The Lac à l'Orignal phosphate deposit and constraints on high-quality phosphatic ore in massif-type anorthosite, Grenville Province, Canada","authors":"Sandeep Banerjee ,&nbsp;Peir K. Pufahl ,&nbsp;Fred J. Longstaffe","doi":"10.1016/j.gexplo.2024.107499","DOIUrl":"10.1016/j.gexplo.2024.107499","url":null,"abstract":"<div><p>Phosphate is an indispensable component in the fertilizer industry. It has recently become a critical part of the green energy transition because of the demand for lithium ferro phosphate in rechargeable batteries. A significant amount of phosphate ore (∼90 %) is globally produced from sedimentary rocks. High-quality phosphate ore containing low amounts of toxic elements, however, is mostly produced from igneous carbonatite.</p><p>The Lac à l'Orignal deposit (∼1069–993 Ma), Canada, in the central Grenville Province, contains a large amount of fluorapatite (≤ 20 %) hosted in oxide-bearing norite-gabbronorite-anorthosite layered intrusions. The deposit is hosted in the Vanel Anorthosite (1080 ± 2 Ma) near the northern border of the Mattawa Anorthosite (1016 ± 2 Ma). The major host rock oxide-apatite-gabbronorite (OAGN) is primarily composed of plagioclase, orthopyroxene, clinopyroxene, fluorapatite, ilmenite, and magnetite. The Al contents of the OAGN orthopyroxene indicate that the magmatic deposit was emplaced at mid-low crustal levels (∼2.0–3.6 kbar) and reverse zoning in the OAGN plagioclase suggests &lt;2.5 kbar of pressure change during their crystallization. An overall increase of REE + Y concentrations in the OAGN fluorapatite with decreasing their fluorapatite contents indicates that the magma went through fractional crystallization. This study suggests that high abundances (ca. &gt; 8 %) of fluorapatite in some OAGN were produced from crystal avalanching after initial crystal settling. Antithetic correlation between the Cl content of fluorapatite and the Mg# [Mg/(Mg + Fe²⁺)] of coexisting orthopyroxene suggests that phosphate ores with low Cl contents are expected for OAGN that formed at the initial stages of magma crystallization. Therefore, the Mg# of the OAGN orthopyroxene provides an exploration tool for targeting phosphate ore with low Cl content, which is preferred in the production of phosphoric acid, a major intermediate feedstock for the fertilizer and green energy industries. Apatite contents in carbonatite and average P₂O₅ content in carbonatite melt are generally similar to those of the Lac à l'Orignal OAGN. The average concentrations of REE, and toxic metals, such as Pb, Th, and U, in the OAGN fluorapatite are, however, lower than those in apatite from carbonatite worldwide. Therefore, the apatite of the OAGN appears to be of high quality and more environmentally-friendly as a source of phosphate ore.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141025238","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":"Reactive transport numerical modeling of intermediate sulfidation epithermal deposit: A case study of Haopinggou Ag-Au-Pb-Zn deposit, Henan province, China","authors":"Cheng Chang ,&nbsp;Keyan Xiao ,&nbsp;Guanhong Feng ,&nbsp;Li Sun ,&nbsp;Junsheng Yang","doi":"10.1016/j.gexplo.2024.107500","DOIUrl":"10.1016/j.gexplo.2024.107500","url":null,"abstract":"<div><p>The Haopinggou Ag-Au-Pb-Zn deposit is the only deposit that simultaneously contains Au and Ag-Pb-Zn vein-type ores at the Xianyu ore field in Xiong'ershan District, Henan Province, China. The early-stage gold-bearing pyrite-quartz veins are cut or surrounded by late-stage silver-bearing Pb-Zn-sulfide veins. However, there is controversy whether these two-stage veins were formed from distinct fluid systems associated with discrete mineralization events or via hydrothermal evolution processes of individual mineralization events. To study the metallogenic dynamics of how the Au and Ag-Zn-Pb veins were formed at the same depth in the Haopinggou deposit under these two distinct metallogenic models, we established a series of reactive transport numerical models. We studied the influence of the temperature of the hydrothermal fluid, fault permeability, and HS⁻, Au⁺, and Ag⁺ concentrations on the mineralization of Au, Ag, Pb, and Zn. Based on the model results, two distinct mechanisms causing Au and Ag to precipitate at the same depth has been established: (1) Under the assumption of the single hydrothermal fluid metallogenic model, the deep part of the early Au precipitation will be overlapped by the shallow part of the late Ag precipitation due to temperature and permeability decreases, causing Au and Ag to precipitate at the same deep depth; (2) Under the assumption of the distinct hydrothermal fluids metallogenic model, the shallow part of the early Au precipitation will be overlapped by the late Ag precipitation due to high concentration of HS⁻, causing Au and Ag to precipitate at the same shallow depth. The metallogenic mechanisms behind these two controversial understandings indicate that the deeper parts of the Haopinggou deposit have a high metallogenic potential for gold or silver.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S037567422400116X/pdfft?md5=a45a35c1107dcbad39ac82c1ae58c9f7&pid=1-s2.0-S037567422400116X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141027886","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":"Machine learning prediction of health risk and spatial dependence of geogenic contaminated groundwater from the Hetao Basin, China","authors":"Peng Xia ,&nbsp;Yifu Zhao ,&nbsp;Xianjun Xie ,&nbsp;Junxia Li ,&nbsp;Kun Qian ,&nbsp;Haoyu You ,&nbsp;Jingxian Zhang ,&nbsp;Weili Ge ,&nbsp;Hongjie Pan ,&nbsp;Yanxin Wang","doi":"10.1016/j.gexplo.2024.107497","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107497","url":null,"abstract":"<div><p>Geogenic contaminated groundwater (GCG), characterized by elevated arsenic, fluoride, and iodine levels, present a significant challenge to public health and government management. Conventional survey-based approaches of collecting groundwater samples, conducting physicochemical tests, and performing spatial interpolation to obtain regional groundwater chemical component maps are inefficient and costly. More importantly, it does not take into account the actual hydrogeological conditions or the characteristics of pollutant transport and enrichment. To address this issue, we utilized Support Vector Machine (SVM), Random Forest (RF), Adaptive Boosting (AdaBoost), and Extreme Gradient Boosting (XGBoost) to analyze the likelihood of occurrence of arsenic, fluoride, and iodine as well as their spatial distribution in shallow groundwater from the Hetao Basin. Our study incorporated 20 indicators related to meteorology, soil physicochemical properties, and groundwater conditions, along with 1505 labeled samples consisting of groundwater arsenic, fluoride, and iodine concentrations and their corresponding coordinates. Subsequently, the study automatically analyzed the meteorological, soil physicochemical properties and groundwater conditions by constructing a machine learning model using the available data. In order to optimise and select the best prediction model, this paper presents a quantitative evaluation of the prediction performance of various machine learning models. The accuracy (AC), area under curve (AUC) and mean squared error (MSE) were calculated to predict the spatial distribution of CGC. Subsequently, the optimized model for predicting the spatial distribution of GCG was selected. The results showed that the XGBoost algorithm provided optimal predictions for groundwater with arsenic concentrations above 10 μg/L and fluoride concentrations exceeding 1.5 mg/L, whereas the RF model provided the best predictions for groundwater with arsenic concentrations surpassing 50 μg/L and iodine concentrations exceeding 100 μg/L. Subsequently, groundwater health risk zones were delineated based on an optimal prediction model, and demographic analysis was conducted in both the direct and potential groundwater risk zones. Model predictions indicated that hundreds of thousands of people in the Hetao Basin were facing a public health crisis caused by high concentrations of arsenic, fluoride and iodine in groundwater. These findings underscore the significant health challenge in the study area. Considering the agricultural development and increasing groundwater use in the area, our findings can guide local governments in managing the extent of groundwater development, establishing control zones, and enhancing protection measures for populations at risk from groundwater contamination.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140905421","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":"Apatite-rich zones in the Uppermost Upper Zone, Northern Limb, Bushveld Complex: Possible non-conventional source of REE and TiO2","authors":"Hakundwi Mandende ,&nbsp;Themba Mothupi","doi":"10.1016/j.gexplo.2024.107498","DOIUrl":"10.1016/j.gexplo.2024.107498","url":null,"abstract":"<div><p>The uppermost Upper Zone of the Bushveld Complex is known as a potential host of significant apatite-ilmenite resources. Recent exploration studies have delineated two apatite-rich zones representing a huge potential resource of phosphate. A detailed mineralogical and geochemical study of the two apatite-rich zones is undertaken to demonstrate that in addition to phosphate, apatite and ilmenite could be important saleable by-products for REE and Ti. In the Lower Apatite Zone (LAZ), the average concentrations of apatite, ilmenite, and titano-magnetite are 11%, 6%, and 18%, respectively. Grades of about 30 wt% combined apatite, ilmenite, and titano-magnetite can be recovered from the Upper Apatite Zone (UAZ), of which apatite and granular ilmenite constitute 9 and 10%, respectively. There is an association between diamagnetic (apatite), paramagnetic (mostly silicates and ilmenite), ferromagnetic (titano-magnetite) minerals and, to a lesser extent, sulphides. In addition, the majority of the targeted minerals; apatite, ilmenite, and titano-magnetite are relatively coarse, with a median value ranging between 270 μm and 931 μm. In-situ trace element data obtained on apatite demonstrate an increase in Light Rare Earth Elements (LREE) stratigraphically, grading from an average of 3180 ppm Total Rare Earth Elements (TREE+Y) in the LAZ to an average of 4068 ppm TREE+Y in the UAZ, indicating a sub-economic potential of REE that may be economically viable as by-product to phosphate. Preliminary resource estimations show that ~1,405,560 t and ~1,798,056 t of TREE can be exploited from the LAZ and UAZ, respectively. The discrete ilmenite grains are an attractive additional by-product considering their higher average &gt;50% TiO₂ and lower concentration of impurities such as &lt;1.06% MgO, &lt;1.21% MnO, &lt;0.08% Al₂O₃, &lt;0.02% V₂O₅ and &lt;0.01% Cr₂O₃. These results suggest that apatite-rich layers in mafic layered intrusions are viable prospects for economic extraction of REE in conjunction with titanium as other by-products that can be recovered from phosphate rocks.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141057424","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":"New insights into the origin and depositional setting of the Haerdaban PbZn deposit, Chinese western Tianshan: Evidence from geology, chert geochemistry, and detrital zircon UPb geochronology","authors":"Jialin Wang ,&nbsp;Xuexiang Gu ,&nbsp;Jingchi Xu ,&nbsp;Yongmei Zhang ,&nbsp;Yiwei Peng ,&nbsp;Liangtao Lu","doi":"10.1016/j.gexplo.2024.107496","DOIUrl":"https://doi.org/10.1016/j.gexplo.2024.107496","url":null,"abstract":"<div><p>The Haerdaban Pb<img>Zn deposit (with an ore reserve of 10.93 Mt. at 1.0–25.65 % Zn and 0.7–12.29 % Pb) is hosted in weakly metamorphosed clastic‑carbonate rocks from the Proterozoic Haerdaban Group. It represents a significant addition of the sediment-hosted Pb<img>Zn deposits in the Yili block, Chinese western Tianshan. Currently, there are ongoing debates regarding its genesis, with a particular focus on the crucial metallogenic mechanism (syngenetic sedimentary exhalation or epigenetic reworking) responsible for the primary sulfide mineralization. Mineralization at Haerdaban primarily occurs as banded to stratiform ore layers or lenses conformably sandwiched in their host rocks. Vein and stockwork ores occur locally below the stratiform ore layers. A <em>syn</em>-sedimentary fault trending S<img>N was identified based on abrupt lateral changes in lithofacies and thickness of the stratigraphic units. The ore mineralogy is dominated by sphalerite, galena, quartz, and dolomite, with a small amount of pyrite, barite, and organic matter. Detrital zircon LA-ICP-MS U<img>Pb dating of the Haerdaban siltstones obtained a maximum depositional age of about 604 Ma. Their geochemical composition similar to the passive continental margin signatures, with rare earth element (REE) patterns enriched in LREE and negative Eu anomalies (Eu/Eu* = 0.50–1.14). Stratiform beds of chert that host disseminated ores have relatively high contents of hydrothermal components (e.g., Ba, Zn), with apparent positive Eu anomalies (Eu/Eu* = 7.38–49.34) and negligible negative Ce anomalies (Ce/Ce* = 0.85–0.98). They are thus interpreted to be hydrothermal sedimentary rocks (exhalites) deposited in a suboxic-anoxic environment proximal to the hydrothermal vents. Integrated geological and geochemical evidence indicates that the Haerdaban Pb<img>Zn deposit is a typical vent-proximal sedimentary exhalative (SEDEX) deposit formed in a Neoproterozoic Sinian (Ediacaran) passive continental margin rift basin. Post-depositional metamorphism and deformation in the Paleozoic may have caused partial remobilization of primary ores but did not significantly alter the morphology of the orebodies. Furthermore, establishing a genetic model for the Haerdaban deposit has important implications for the exploration of similar deposits preserved in the equivalent stratigraphy within the Chinese western Tianshan region.</p></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":null,"pages":null},"PeriodicalIF":3.9,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140950911","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}