Omid Javariani, Farhad Ehya, Mohammad Ali Aliabadi, Abbas Asgari, Mohammad Mehri
Supergene copper mineralization occurs at the Kuh Toto deposit, located 25 km to the west of Torud village in the Semnan Province, Iran. Mineralogical, fluid inclusion and stable isotopic (C and O) studies, as well as rare earth element (REE) geochemistry of whole rock and minerals are used to unravel the conditions under which the Cu ores formed. Malachite is the only copper ore mineral, and it is present as veinlets, coatings and small patches in Eocene volcanic rocks. Malachite is accompanied by minor calcite, manganese and iron oxides and oxyhydroxides, clay minerals, epidote, quartz and chrysocolla. Argillic and, to a lesser extent, propylitic hydrothermal alteration partially affected the basic volcanic host rocks. The chondrite-normalized REE patterns of malachite and calcite are similar to those of the volcanic host rocks. They are enriched in LREEs. The volcanic host rocks are enriched in Cu (187 ppm on average). Fluid inclusions hosted in calcite reveal that calcite precipitated from hydrothermal fluids at low temperatures (69–150°C) and low to moderate salinities (7.17–11.10 wt% NaCl equivalent). The oxygen isotopic geothermometry yielded an average temperature of 41°C for malachite formation. Geochemical and fluid inclusion evidence strongly support that mineral-forming elements, including Cu, originated from the associated volcanic rocks. Available data support the view that Cu was likely leached as mobile aqueous Cu2+ from the volcanic rocks by oxidizing surface waters. When Cu-enriched fluids entered the underlying groundwater environment, Cu was precipitated as malachite in fractures, via recombination with carbonate ions dissolved as CO2 in meteoric fluids.
{"title":"The Kuh Toto volcanic-hosted copper deposit, Semnan Province, Iran: geochemical, fluid inclusion, and C and O isotopic studies","authors":"Omid Javariani, Farhad Ehya, Mohammad Ali Aliabadi, Abbas Asgari, Mohammad Mehri","doi":"10.1144/geochem2021-018","DOIUrl":"https://doi.org/10.1144/geochem2021-018","url":null,"abstract":"Supergene copper mineralization occurs at the Kuh Toto deposit, located 25 km to the west of Torud village in the Semnan Province, Iran. Mineralogical, fluid inclusion and stable isotopic (C and O) studies, as well as rare earth element (REE) geochemistry of whole rock and minerals are used to unravel the conditions under which the Cu ores formed. Malachite is the only copper ore mineral, and it is present as veinlets, coatings and small patches in Eocene volcanic rocks. Malachite is accompanied by minor calcite, manganese and iron oxides and oxyhydroxides, clay minerals, epidote, quartz and chrysocolla. Argillic and, to a lesser extent, propylitic hydrothermal alteration partially affected the basic volcanic host rocks. The chondrite-normalized REE patterns of malachite and calcite are similar to those of the volcanic host rocks. They are enriched in LREEs. The volcanic host rocks are enriched in Cu (187 ppm on average). Fluid inclusions hosted in calcite reveal that calcite precipitated from hydrothermal fluids at low temperatures (69–150°C) and low to moderate salinities (7.17–11.10 wt% NaCl equivalent). The oxygen isotopic geothermometry yielded an average temperature of 41°C for malachite formation. Geochemical and fluid inclusion evidence strongly support that mineral-forming elements, including Cu, originated from the associated volcanic rocks. Available data support the view that Cu was likely leached as mobile aqueous Cu2+ from the volcanic rocks by oxidizing surface waters. When Cu-enriched fluids entered the underlying groundwater environment, Cu was precipitated as malachite in fractures, via recombination with carbonate ions dissolved as CO2 in meteoric fluids.","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44307956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Meuzelaar, Pablo Núñez-Fernández, A. Martín-Izard, D. Arias-Prieto, Fernando Díaz-Riopa
Characterization of metamorphic rocks to evaluate waste material acid rock drainage potential is particularly challenging as commonly used laboratory methods can result in its significant underprediction. Static tests were conducted for over 300 samples from the Touro copper project and indicate that carbon-based methods frequently overestimate acid neutralization potential due to the presence of both graphite and manganese–iron carbonates. The Modified Sobek method more accurately accounts for the buffering capacity of carbonates and does not account for graphite, although aluminosilicate dissolution kinetics need to be evaluated in the context of sulfide oxidation rates. Historic sulfur assays for the project relied on methods insufficient to fully digest metamorphosed sulfides and required correction. The more aggressive Leco method provides accurate sulfur estimates and has now been adopted for the project. Static test metrics such as the net neutralization potential or neutralization potential ratio, therefore, can give misleading results when incorrect characterization methods are employed. Such metrics should be considered as screening level, used with caution, and complemented with careful field and laboratory kinetic tests. Preliminary humidity cell testing of five Touro samples suggests that terminal pH values for cells that have become acidic closely match predicted net acid generation (NAG) pH values. The NAG pH test avoids some of the challenges associated with sulfur and carbon predictions in metamorphic rocks as it directly buffers sulfide oxidation acidity with available material neutralization potential. As such, NAG pH has been adopted as the accepted project metric for segregating acid-generating from non-acid-generating waste. Supplementary material: All Touro project static and kinetic test data are available at https://doi.org/10.6084/m9.figshare.c.5389948 Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issues
{"title":"The waste rock of the Touro copper deposit in Galicia, Spain: challenges for its environmental characterization","authors":"T. Meuzelaar, Pablo Núñez-Fernández, A. Martín-Izard, D. Arias-Prieto, Fernando Díaz-Riopa","doi":"10.1144/geochem2020-081","DOIUrl":"https://doi.org/10.1144/geochem2020-081","url":null,"abstract":"Characterization of metamorphic rocks to evaluate waste material acid rock drainage potential is particularly challenging as commonly used laboratory methods can result in its significant underprediction. Static tests were conducted for over 300 samples from the Touro copper project and indicate that carbon-based methods frequently overestimate acid neutralization potential due to the presence of both graphite and manganese–iron carbonates. The Modified Sobek method more accurately accounts for the buffering capacity of carbonates and does not account for graphite, although aluminosilicate dissolution kinetics need to be evaluated in the context of sulfide oxidation rates. Historic sulfur assays for the project relied on methods insufficient to fully digest metamorphosed sulfides and required correction. The more aggressive Leco method provides accurate sulfur estimates and has now been adopted for the project. Static test metrics such as the net neutralization potential or neutralization potential ratio, therefore, can give misleading results when incorrect characterization methods are employed. Such metrics should be considered as screening level, used with caution, and complemented with careful field and laboratory kinetic tests. Preliminary humidity cell testing of five Touro samples suggests that terminal pH values for cells that have become acidic closely match predicted net acid generation (NAG) pH values. The NAG pH test avoids some of the challenges associated with sulfur and carbon predictions in metamorphic rocks as it directly buffers sulfide oxidation acidity with available material neutralization potential. As such, NAG pH has been adopted as the accepted project metric for segregating acid-generating from non-acid-generating waste. Supplementary material: All Touro project static and kinetic test data are available at https://doi.org/10.6084/m9.figshare.c.5389948 Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issues","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46729208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mojtaba Shamseddin Meigooni, M. Lotfi, P. Afzal, N. Nezafati, M. Razi
The present study was conducted to determine different geochemical anomalies of rare-earth elements (REEs) using a combined approach of stepwise factor analysis (SFA), sequential Gaussian simulation (SGS), and concentration–area (C-A) fractal modeling based on surface lithogeochemical samples obtained from the Esfordi phosphate mine (Central Iran). The Esfordi mine is one of the important mines in the Bafq metallogenic zone due to average and maximum grades of 0.5 and 1.7%, respectively for REEs. With SFA operating in two steps, the REEs were placed in the first factor of the second stage (F1-2). Then, SGS and C-A fractal modeling were performed on F1-2 factor scores for classification of anomalies. A log-ratio matrix was used to evaluate the correlation of these results with anomalous lithogeochemical samples, as well as to determine the relationship of anomalies with rock types and mineralized units and, finally, to validate the results of the SGS–fractal modeling. The results confirmed an appropriate correlation between F1-2 anomalies and high concentration in further rock samples. The main anomalies were found to have good correlation with an apatite–iron unit and in general with other apatite-bearing units based on overall accuracy values. The apatite-bearing units with high values of REEs were located in the northern and central parts of the mine. The results of the SFA, SGS and C-A fractal modeling show that this hybrid approach can be useful in determining anomalies with high accuracy.
{"title":"Application of multivariate geostatistical simulation and fractal analysis for detection of rare-earth element geochemical anomalies in the Esfordi phosphate mine, Central Iran","authors":"Mojtaba Shamseddin Meigooni, M. Lotfi, P. Afzal, N. Nezafati, M. Razi","doi":"10.1144/geochem2020-035","DOIUrl":"https://doi.org/10.1144/geochem2020-035","url":null,"abstract":"The present study was conducted to determine different geochemical anomalies of rare-earth elements (REEs) using a combined approach of stepwise factor analysis (SFA), sequential Gaussian simulation (SGS), and concentration–area (C-A) fractal modeling based on surface lithogeochemical samples obtained from the Esfordi phosphate mine (Central Iran). The Esfordi mine is one of the important mines in the Bafq metallogenic zone due to average and maximum grades of 0.5 and 1.7%, respectively for REEs. With SFA operating in two steps, the REEs were placed in the first factor of the second stage (F1-2). Then, SGS and C-A fractal modeling were performed on F1-2 factor scores for classification of anomalies. A log-ratio matrix was used to evaluate the correlation of these results with anomalous lithogeochemical samples, as well as to determine the relationship of anomalies with rock types and mineralized units and, finally, to validate the results of the SGS–fractal modeling. The results confirmed an appropriate correlation between F1-2 anomalies and high concentration in further rock samples. The main anomalies were found to have good correlation with an apatite–iron unit and in general with other apatite-bearing units based on overall accuracy values. The apatite-bearing units with high values of REEs were located in the northern and central parts of the mine. The results of the SFA, SGS and C-A fractal modeling show that this hybrid approach can be useful in determining anomalies with high accuracy.","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47356663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Lou, Xinghai Lang, Xuhui Wang, Yulin Deng, Qing He, Chao Huang, Haihui Liang, Na Lv, Min-Gang Dong, Kai Jiang, Zhong Zhang
This paper describes the discovery of porphyry Cu–Au ore bodies (No. 2 and No. 3) in Xiongcun, Tibet, China, through the investigation of stream sediments, soils and rocks. The study area (Xiongcun), located in the city of Xigaze, has a complex topography due to its complicated geological background. The Xiongcun No. 1 ore body will soon be mined, 15 years after its discovery. However, recent research on stream sediments, soils and rocks around the No. 1 ore body has revealed notable Cu anomalies on the periphery. With the successful application of exploratory geochemistry data in the anomaly locations, the No. 2 and No. 3 ore bodies have been revealed. The ore reserves of the No. 2 and No. 3 ore bodies are estimated to reach 1.64 million tons of Cu, more than 80 tons of Au and 200 tons of Ag. We expect that our findings will not only enhance the understanding of the reanalysis of anomalies surrounding the discovered deposits but also contribute to the evaluation of the ore-prospecting potential of this plateau region.
{"title":"Application of exploration geochemistry data to identify anomalies in the plateau region: a case study from the Xiongcun district in the Gangdese metallogenic belt, Tibet, China","authors":"Y. Lou, Xinghai Lang, Xuhui Wang, Yulin Deng, Qing He, Chao Huang, Haihui Liang, Na Lv, Min-Gang Dong, Kai Jiang, Zhong Zhang","doi":"10.1144/geochem2020-083","DOIUrl":"https://doi.org/10.1144/geochem2020-083","url":null,"abstract":"This paper describes the discovery of porphyry Cu–Au ore bodies (No. 2 and No. 3) in Xiongcun, Tibet, China, through the investigation of stream sediments, soils and rocks. The study area (Xiongcun), located in the city of Xigaze, has a complex topography due to its complicated geological background. The Xiongcun No. 1 ore body will soon be mined, 15 years after its discovery. However, recent research on stream sediments, soils and rocks around the No. 1 ore body has revealed notable Cu anomalies on the periphery. With the successful application of exploratory geochemistry data in the anomaly locations, the No. 2 and No. 3 ore bodies have been revealed. The ore reserves of the No. 2 and No. 3 ore bodies are estimated to reach 1.64 million tons of Cu, more than 80 tons of Au and 200 tons of Ag. We expect that our findings will not only enhance the understanding of the reanalysis of anomalies surrounding the discovered deposits but also contribute to the evaluation of the ore-prospecting potential of this plateau region.","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47638807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper presents results of investigations of the chemical composition of iron sulphides contained in dust from the pyrometallurgical production process of zinc and lead. The main mineral components of these dusts are sphalerite, galena, iron sulphide – pyrite, zincite, anglesite and probably kirchsteinite. The tests performed have demonstrated that the chemical composition of iron sulphide grains was not close to stoichiometric, the grains were non-uniform in terms of phase composition and they always included admixtures in the form of inclusions of other sulphides, i.e. zinc sulphide and lead sulphide, and accompanying elements (Ca, Mn, Se, As, Ag, Cu, Cd).
{"title":"Chemical composition of iron sulphides contained in dust from pyrometallurgical Zn and Pb production","authors":"K. Nowińska, Z. Adamczyk","doi":"10.1144/geochem2020-073","DOIUrl":"https://doi.org/10.1144/geochem2020-073","url":null,"abstract":"The paper presents results of investigations of the chemical composition of iron sulphides contained in dust from the pyrometallurgical production process of zinc and lead. The main mineral components of these dusts are sphalerite, galena, iron sulphide – pyrite, zincite, anglesite and probably kirchsteinite. The tests performed have demonstrated that the chemical composition of iron sulphide grains was not close to stoichiometric, the grains were non-uniform in terms of phase composition and they always included admixtures in the form of inclusions of other sulphides, i.e. zinc sulphide and lead sulphide, and accompanying elements (Ca, Mn, Se, As, Ag, Cu, Cd).","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45894128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Schmidt, M. Leybourne, J. Peter, D. Petts, S. Jackson, D. Layton-Matthews
There is increasing acceptance of the presence of variable magmatic contributions to the mineralizing fluids in the formation of volcanogenic massive sulfide (VMS) deposits. The world-class Windy Craggy Cu-Co-Au deposit (>300 MT @ 2.12 wt% Cu) in northwestern British Columbia is of interest because, unlike most VMS deposits, fluid inclusions in quartz from within the deposit range from relatively low to intermediate salinity (most 6–16 wt% equivalent). In this study we used an excimer (193 nm) laser ablation system interfaced to a quadrupole inductively coupled plasma mass spectrometer to quantify key metals and metalloids that are considered by many to be indicative of magmatic contributions to hydrothermal ore deposits. Although LA-ICP-MS signals from these low-salinity inclusions are highly transient, we were able to quantify Na, Mg, K, Ca, Mn, Fe, Co, Cu, Zn, Sr, Sn, Ba, Ce, Pb and Bi consistently – of the 34 elements that were monitored. Furthermore, Cl, Sb, Cd, Mo, Rb, Br and As were also measured in a significant number of inclusions. Comparison of the fluid inclusion chemistry with unaltered and altered mafic volcanic and sedimentary rocks and mineralized samples from the deposit indicate that enrichment in the main ore metals (Cu, Zn, Fe, Pb) in the inclusions reflects that of the altered rocks and sulfides. Metals and metalloids that may indicate a magmatic contribution typically show much greater enrichments in the fluid inclusions over the host rocks at the same Cu concentration; in particular Bi, Sn and Sb are significantly elevated when compared to the host rock samples. These data are consistent with the ore-forming fluids at Windy Craggy having a strong magmatic contribution. Supplementary material: fluid inclusion data for temperature of homogenization and salinity, and full analytical results for laser ablation ICP-MS analyses of individual inclusions for the two analytical sessions are available at https://doi.org/10.6084/m9.figshare.c.5443094
{"title":"Development of a laser ablation ICP-MS method for the analysis of fluid inclusions associated with volcanogenic massive sulfide deposits","authors":"M. Schmidt, M. Leybourne, J. Peter, D. Petts, S. Jackson, D. Layton-Matthews","doi":"10.1144/geochem2020-043","DOIUrl":"https://doi.org/10.1144/geochem2020-043","url":null,"abstract":"There is increasing acceptance of the presence of variable magmatic contributions to the mineralizing fluids in the formation of volcanogenic massive sulfide (VMS) deposits. The world-class Windy Craggy Cu-Co-Au deposit (>300 MT @ 2.12 wt% Cu) in northwestern British Columbia is of interest because, unlike most VMS deposits, fluid inclusions in quartz from within the deposit range from relatively low to intermediate salinity (most 6–16 wt% equivalent). In this study we used an excimer (193 nm) laser ablation system interfaced to a quadrupole inductively coupled plasma mass spectrometer to quantify key metals and metalloids that are considered by many to be indicative of magmatic contributions to hydrothermal ore deposits. Although LA-ICP-MS signals from these low-salinity inclusions are highly transient, we were able to quantify Na, Mg, K, Ca, Mn, Fe, Co, Cu, Zn, Sr, Sn, Ba, Ce, Pb and Bi consistently – of the 34 elements that were monitored. Furthermore, Cl, Sb, Cd, Mo, Rb, Br and As were also measured in a significant number of inclusions. Comparison of the fluid inclusion chemistry with unaltered and altered mafic volcanic and sedimentary rocks and mineralized samples from the deposit indicate that enrichment in the main ore metals (Cu, Zn, Fe, Pb) in the inclusions reflects that of the altered rocks and sulfides. Metals and metalloids that may indicate a magmatic contribution typically show much greater enrichments in the fluid inclusions over the host rocks at the same Cu concentration; in particular Bi, Sn and Sb are significantly elevated when compared to the host rock samples. These data are consistent with the ore-forming fluids at Windy Craggy having a strong magmatic contribution. Supplementary material: fluid inclusion data for temperature of homogenization and salinity, and full analytical results for laser ablation ICP-MS analyses of individual inclusions for the two analytical sessions are available at https://doi.org/10.6084/m9.figshare.c.5443094","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48001811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Li Zhang, Wei Han, M. Peng, Fei Liu, Yuntao Song, Xiu-jin Liu, Qiaolin Wang, Kuo Li, Dongjie Zhao, Wei Yang, Y. Qin, Hangxin Cheng
The geochemistry of rare earth elements (REEs) was studied in rock samples from host formations, ore samples from two mineral deposits (the Hetaoping Cu-Pb-Zn mine: HTP and the Heiyanao Fe-Cu-Pb-Zn mine: HYA) and the overlying or nearby soils to better understand REE concentrations, distributions and behaviour during weathering from different parent materials at the regional scale, Baoshan area, Yunnan Province, SW China. The mudstone and sandstone formations have the highest total REE (ΣREE) contents. Chondrite-normalized diagrams for rocks and ores show significant light REEs (LREEs) enrichments and Eu depletion (except for ores in HYA). Cerium displays an obvious negative anomaly in carbonate rocks (Є-3-R, C-R, D-R, T-1-R and T-2-R). Soils overlying carbonate rock formations (T-1-S, C-S and Є-3-S) have the highest ΣREE contents, while soils overlying basalts have the lowest ΣREE contents. Soils show enrichments in LREEs with negative Eu anomalies and slight Ce anomalies in the studied soils. Soils with high ∑LREE/∑heavy REE (HREE) values may result from the preferential absorption of LREEs by organic matter. Negative Eu anomalies in soils occur for parent materials in the study area lacking feldspar, especially soils developed from carbonates. Compared to the parent materials, most soils show REE enrichment because alkali metals are removed and REEs are concentrated by low mobility in surficial processes and positive Ce anomalies because of weathering dissolution of other trivalent REEs with ionic radii similar to that of Ca2+. Supplementary material: Additional data (Tables S1 and S2) and sample locations (Fig. S1) are available at https://doi.org/10.6084/m9.figshare.c.5303140
{"title":"Geochemical characteristics of rare earth elements (REEs) in soils developed on different parent materials, in the Baoshan area, Yunnan Province, SW China","authors":"Li Zhang, Wei Han, M. Peng, Fei Liu, Yuntao Song, Xiu-jin Liu, Qiaolin Wang, Kuo Li, Dongjie Zhao, Wei Yang, Y. Qin, Hangxin Cheng","doi":"10.1144/geochem2019-082","DOIUrl":"https://doi.org/10.1144/geochem2019-082","url":null,"abstract":"The geochemistry of rare earth elements (REEs) was studied in rock samples from host formations, ore samples from two mineral deposits (the Hetaoping Cu-Pb-Zn mine: HTP and the Heiyanao Fe-Cu-Pb-Zn mine: HYA) and the overlying or nearby soils to better understand REE concentrations, distributions and behaviour during weathering from different parent materials at the regional scale, Baoshan area, Yunnan Province, SW China. The mudstone and sandstone formations have the highest total REE (ΣREE) contents. Chondrite-normalized diagrams for rocks and ores show significant light REEs (LREEs) enrichments and Eu depletion (except for ores in HYA). Cerium displays an obvious negative anomaly in carbonate rocks (Є-3-R, C-R, D-R, T-1-R and T-2-R). Soils overlying carbonate rock formations (T-1-S, C-S and Є-3-S) have the highest ΣREE contents, while soils overlying basalts have the lowest ΣREE contents. Soils show enrichments in LREEs with negative Eu anomalies and slight Ce anomalies in the studied soils. Soils with high ∑LREE/∑heavy REE (HREE) values may result from the preferential absorption of LREEs by organic matter. Negative Eu anomalies in soils occur for parent materials in the study area lacking feldspar, especially soils developed from carbonates. Compared to the parent materials, most soils show REE enrichment because alkali metals are removed and REEs are concentrated by low mobility in surficial processes and positive Ce anomalies because of weathering dissolution of other trivalent REEs with ionic radii similar to that of Ca2+. Supplementary material: Additional data (Tables S1 and S2) and sample locations (Fig. S1) are available at https://doi.org/10.6084/m9.figshare.c.5303140","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42185180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The accurate characterization of mafic and ultramafic rocks is a challenging but necessary task given the spatial and genetic relationship of mineralization with specific lithologies (e.g. komatiite hosted nickel-sulfides preferentially associated with cumulate-rich ultramafic rocks). Rock classification is further complicated as most mafic and ultramafic rocks have undergone varying degrees of alteration. The accuracy and reproducibility of characterization can be significantly improved by using portable energy dispersive X-ray fluorescence (pXRF) chemical data with portable visible and near-infrared (pVis-NIR) mineralogical data. A new workflow using pXRF and pVis-NIR is presented and used to reliably characterize mafic and ultramafic rocks from the Yilgarn Craton, Western Australia. The workflow involves six steps: (1) Mitigate and identify compound processing and closure issues. For example, we used a pXRF with helium flush to reliably and rapidly measure light elements and mitigate closure, i.e. problems related to data failing to sum to 100%. (2) Identify and exclude geochemically heterogeneous samples. Heterogeneity may be unrelated to alteration and caused by veining or small-scale structure interleaving of different rock types. Geochemical heterogeneity was evaluated using skewness and kurtosis of SiO2 data. (3) Relate rocks from similar magmatic, weathering and alteration events. This was achieved by interpreting data grouping of Vis-NIR ferric and ferrous iron data via a 852 nm/982 nm reflectance v. 651 nm/982 nm reflectance plot and the ferrous abundance index. Unrepresentative data were omitted. (4) Correct XRF iron data, and characterize lithology and alteration. Values ascribed to regions in the TAS (total alkali silica) diagram were used to approximate FeO and Fe2O3. Subsequently, geochemical indices (e.g. Mg#) were used to characterize the alteration box plot. (5) Characterize fractionation in detail. Fractionation variation diagrams were used to interpret fractionation, e.g. MgO v. Al2O3, Ca/Al v. Al2O3, Ni/Cr v. Ni/Ti, and MgO v. Cr. (6) Identify and quantify talc alteration and serpentinization. This included the use of a new alteration plot (Mg# v. 1410 nmRAD/Albedo) to estimate serpentinization and identify relationships between serpentine, carbonate, chlorite and talc abundances. The results and observations contained in this contribution have important implications for progressive technologies such as core logging platforms that are equipped with pXRF and pVis-NIR instruments.
考虑到成矿与特定岩性的空间和成因关系(例如，含镍硫化物的科马地岩优先与富集的超基性岩相关)，基性岩和超基性岩的准确表征是一项具有挑战性但又必要的任务。由于大多数基性岩和超基性岩都经历了不同程度的蚀变，岩石分类更加复杂。将便携式能量色散x射线荧光(pXRF)化学数据与便携式可见和近红外(pVis-NIR)矿物学数据相结合，可以显著提高表征的准确性和再现性。提出了一种使用pXRF和pVis-NIR的新工作流程，并用于可靠地表征西澳大利亚Yilgarn克拉通的基性和超基性岩石。工作流包括六个步骤:(1)减轻和识别复合处理和关闭问题。例如，我们使用带有氦气冲洗的pXRF来可靠、快速地测量轻元素，并减轻封闭，即与数据无法求和到100%相关的问题。(2)识别和排除地球化学非均质样品。非均质性可能与蚀变无关，由不同岩石类型的脉状或小尺度结构交错引起。利用SiO2数据的偏度和峰度评价地球化学非均质性。(3)对比类似岩浆、风化和蚀变事件的岩石。这是通过通过852 nm/982 nm反射率和651nm /982 nm反射率图和铁丰度指数来解释Vis-NIR铁和亚铁数据的数据分组来实现的。不具代表性的数据被省略。(4)校正XRF铁元素数据，进行岩性和蚀变表征。TAS(总碱二氧化硅)图中区域的值被用来近似FeO和Fe2O3。随后，利用地球化学指标(如mg#)对蚀变盒区进行表征。(5)详细描述分馏过程。分馏变化图用于解释分馏，例如MgO与Al2O3、Ca/Al与Al2O3、Ni/Cr与Ni/Ti和MgO与Cr。(6)识别和量化滑石蚀变和蛇纹石化。这包括使用新的蚀变图(Mg# v. 1410 nmRAD/Albedo)来估计蛇纹石化，并确定蛇纹石、碳酸盐、绿泥石和滑石丰度之间的关系。这一贡献中包含的结果和观察结果对诸如配备pXRF和pVis-NIR仪器的岩心测井平台等先进技术具有重要意义。
{"title":"Characterization of altered mafic and ultramafic rocks using portable XRF geochemistry and portable Vis-NIR spectrometry","authors":"C. Adams, M. Dentith, M. Fiorentini","doi":"10.1144/geochem2020-065","DOIUrl":"https://doi.org/10.1144/geochem2020-065","url":null,"abstract":"The accurate characterization of mafic and ultramafic rocks is a challenging but necessary task given the spatial and genetic relationship of mineralization with specific lithologies (e.g. komatiite hosted nickel-sulfides preferentially associated with cumulate-rich ultramafic rocks). Rock classification is further complicated as most mafic and ultramafic rocks have undergone varying degrees of alteration. The accuracy and reproducibility of characterization can be significantly improved by using portable energy dispersive X-ray fluorescence (pXRF) chemical data with portable visible and near-infrared (pVis-NIR) mineralogical data. A new workflow using pXRF and pVis-NIR is presented and used to reliably characterize mafic and ultramafic rocks from the Yilgarn Craton, Western Australia. The workflow involves six steps: (1) Mitigate and identify compound processing and closure issues. For example, we used a pXRF with helium flush to reliably and rapidly measure light elements and mitigate closure, i.e. problems related to data failing to sum to 100%. (2) Identify and exclude geochemically heterogeneous samples. Heterogeneity may be unrelated to alteration and caused by veining or small-scale structure interleaving of different rock types. Geochemical heterogeneity was evaluated using skewness and kurtosis of SiO2 data. (3) Relate rocks from similar magmatic, weathering and alteration events. This was achieved by interpreting data grouping of Vis-NIR ferric and ferrous iron data via a 852 nm/982 nm reflectance v. 651 nm/982 nm reflectance plot and the ferrous abundance index. Unrepresentative data were omitted. (4) Correct XRF iron data, and characterize lithology and alteration. Values ascribed to regions in the TAS (total alkali silica) diagram were used to approximate FeO and Fe2O3. Subsequently, geochemical indices (e.g. Mg#) were used to characterize the alteration box plot. (5) Characterize fractionation in detail. Fractionation variation diagrams were used to interpret fractionation, e.g. MgO v. Al2O3, Ca/Al v. Al2O3, Ni/Cr v. Ni/Ti, and MgO v. Cr. (6) Identify and quantify talc alteration and serpentinization. This included the use of a new alteration plot (Mg# v. 1410 nmRAD/Albedo) to estimate serpentinization and identify relationships between serpentine, carbonate, chlorite and talc abundances. The results and observations contained in this contribution have important implications for progressive technologies such as core logging platforms that are equipped with pXRF and pVis-NIR instruments.","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47400814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Simandl, S. Paradis, Johnathan Savard, D. Miller, R. D'Souza, D. Araoka, C. Akam, M. Hoshino, Y. Kon
The Rock Canyon Creek carbonate-hosted REE-F-Ba deposit has tectonic, stratigraphic and structural similarities with Mississippi Valley-type and sparry magnesite deposits in the SE Rocky Mountains. The main REE-fluorite zone is a steeply dipping body, extending 1100 m along-strike, 50 m wide and 100 m deep. It spatially coincides with pre-existing crackle breccias in carbonate rocks, and consists of dolomite, fluorite, barite, pyrite, quartz, K-feldspar, calcite, porous apatite, REE-fluorocarbonates and REE-phosphates. The main fluorocarbonates are bastnaesite, parisite and synchysite. Monazite, crandallite group minerals and apatite are the main phosphates. Fluorite content varies from less than 1 to 13.5% (by weight) and ∑REE + Y concentrations vary from trace to 1.95% (by weight). The mineralized zone is heterogeneous on the deposit scale, as indicated by three-dimensional geochemical modelling combined with a geochemical assessment based on 89 mineralized samples and detailed downhole mineral and geochemical profiles of a key borehole. Chemical heterogeneity and key elemental co-variations are explained by strong mineralogical control and have implications for the design of exploration and development programmes for this type of deposit. The chondrite-normalized REE pattern of samples from the mineralized zone shows enrichment in LREE, similar to typical carbonatite-related mineralization; however, no carbonatite is exposed nearby.
Rock Canyon Creek碳酸盐岩型REE-F-Ba矿床在构造、地层和结构上与落基山脉东南部的密西西比河谷型和亮镁矿矿床相似。主要的REE萤石带是一个陡峭的倾斜体，延伸1100 沿走向m，50 m宽，100 m深。它在空间上与碳酸盐岩中预先存在的裂纹角砾岩一致，由白云石、萤石、重晶石、黄铁矿、石英、钾长石、方解石、多孔磷灰石、REE氟碳酸盐和REE磷酸盐组成。含氟碳酸盐岩主要有氟碳铈矿、绿柱石和正长辉石。独居石、裂隙岩组矿物和磷灰石是主要的磷酸盐。萤石含量从小于1%到13.5%不等（按重量计），∑REE + Y的浓度从微量到1.95%（按重量计）不等。矿化带在矿床规模上是不均匀的，如三维地球化学建模和基于89个矿化样品的地球化学评估以及关键钻孔的详细井下矿物和地球化学剖面所示。强烈的矿物学控制解释了化学不均匀性和关键元素共变异，并对该类型矿床的勘探和开发计划的设计产生了影响。矿化带样品的球粒陨石归一化REE模式显示LREE富集，类似于典型的碳酸盐岩相关矿化；但附近无碳酸盐岩出露。
{"title":"Mineral control on the geochemistry of the Rock Canyon Creek REE-F-Ba deposit, British Columbia, Canada","authors":"G. Simandl, S. Paradis, Johnathan Savard, D. Miller, R. D'Souza, D. Araoka, C. Akam, M. Hoshino, Y. Kon","doi":"10.1144/geochem2020-010","DOIUrl":"https://doi.org/10.1144/geochem2020-010","url":null,"abstract":"The Rock Canyon Creek carbonate-hosted REE-F-Ba deposit has tectonic, stratigraphic and structural similarities with Mississippi Valley-type and sparry magnesite deposits in the SE Rocky Mountains. The main REE-fluorite zone is a steeply dipping body, extending 1100 m along-strike, 50 m wide and 100 m deep. It spatially coincides with pre-existing crackle breccias in carbonate rocks, and consists of dolomite, fluorite, barite, pyrite, quartz, K-feldspar, calcite, porous apatite, REE-fluorocarbonates and REE-phosphates. The main fluorocarbonates are bastnaesite, parisite and synchysite. Monazite, crandallite group minerals and apatite are the main phosphates. Fluorite content varies from less than 1 to 13.5% (by weight) and ∑REE + Y concentrations vary from trace to 1.95% (by weight). The mineralized zone is heterogeneous on the deposit scale, as indicated by three-dimensional geochemical modelling combined with a geochemical assessment based on 89 mineralized samples and detailed downhole mineral and geochemical profiles of a key borehole. Chemical heterogeneity and key elemental co-variations are explained by strong mineralogical control and have implications for the design of exploration and development programmes for this type of deposit. The chondrite-normalized REE pattern of samples from the mineralized zone shows enrichment in LREE, similar to typical carbonatite-related mineralization; however, no carbonatite is exposed nearby.","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46910914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The field-portable X-ray fluorescence (FPXRF) spectrometer has evolved significantly in the last decade and has become one of the most innovative tools for field geologists. Portability and ease of use of FPXRF systems have opened up new and unique applications for even novice technicians. Application of FPXRF in precious metals exploration and mining appears to be challenging due to their low concentrations (lower than detection limit by FPXRF) in nature and even in most ore deposits. This case study shows the success of FPXRF in identifying anomalous zones of platinum group elements (PGE) and Au (target elements) using pathfinder elements in the Pilanesberg PGE deposit, Bushveld Complex, South Africa. Sixty-three core samples were analysed using both FPXRF and laboratory methods. In these samples, Pt <8 ppm, Pd <5 ppm and Au <1 ppm, which were not detected by FPXRF; however, Ni and Cu are up to 6540 and 3560 ppm, respectively, which were easily detected by the same method. These elements show positive correlation with the precious metals indicating that they can be used as pathfinders. Both direct shot analyses of core samples and their pulverized specimen assays show correlation with lab assay data suggesting that both methods can be used in the field; however, the accuracy of direct shot data is lower due to the heterogeneity of samples.
{"title":"Use of field-portable XRF in exploration of PGE-enriched zones in the Pilanesberg PGE deposit, Bushveld Complex, South Africa","authors":"A. Somarin, Ingo Steinhage","doi":"10.1144/geochem2020-075","DOIUrl":"https://doi.org/10.1144/geochem2020-075","url":null,"abstract":"The field-portable X-ray fluorescence (FPXRF) spectrometer has evolved significantly in the last decade and has become one of the most innovative tools for field geologists. Portability and ease of use of FPXRF systems have opened up new and unique applications for even novice technicians. Application of FPXRF in precious metals exploration and mining appears to be challenging due to their low concentrations (lower than detection limit by FPXRF) in nature and even in most ore deposits. This case study shows the success of FPXRF in identifying anomalous zones of platinum group elements (PGE) and Au (target elements) using pathfinder elements in the Pilanesberg PGE deposit, Bushveld Complex, South Africa. Sixty-three core samples were analysed using both FPXRF and laboratory methods. In these samples, Pt <8 ppm, Pd <5 ppm and Au <1 ppm, which were not detected by FPXRF; however, Ni and Cu are up to 6540 and 3560 ppm, respectively, which were easily detected by the same method. These elements show positive correlation with the precious metals indicating that they can be used as pathfinders. Both direct shot analyses of core samples and their pulverized specimen assays show correlation with lab assay data suggesting that both methods can be used in the field; however, the accuracy of direct shot data is lower due to the heterogeneity of samples.","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2020-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43329897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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