C. Rissmann, M. Leybourne, C. Benn, J. Kidder, L. Pearson
Groundwaters recovered from the Salar de Punta Negra and Monturaqui basins in the Atacama Desert of northern Chile exhibit distinctly different isotopic, major, trace, and porphyry copper elemental compositions related to contrasting morphostructural, geochemical, and hydrodynamic settings. Comparison of these distinct groundwater signatures with groundwaters from known porphyry copper deposits (Salar de Hamburgo and Spence Deposit), can be used to determine if either basin might be prospective for porphyry copper mineralization. Groundwaters within the Punta Negra Basin exhibit geochemical characteristics consistent with other closed basin settings throughout the arid Andes. Elemental and isotopic compositions within the Punta Negra Basin reflect closed basin evaporitic processes consistent with the hyperarid, volcanic setting of the central Andes. Pathfinder metals and isotopic compositions are not consistent with porphyry copper type mineralization as described for groundwaters within the Salar de Hamburgo Basin, and the Spence Deposit. Within the Monturaqui Basin the geochemical composition of groundwaters are characteristic of diffuse hydrothermal activity. Sulfur isotopic composition within the waters of the northern Monturaqui Basin exhibit δ34SCDT isotopic signatures that fall within the range for sulfide mineralization as reported for groundwaters in and around the Spence Deposit and the Salar de Hamburgo. However, porphyry copper related elements within the Monturaqui Basin are impoverished relative to groundwaters of the Spence and Escondida Deposit. Such impoverishment in porphyry related elements, taken in conjunction with enriched δ13CPDB compositions, elevated groundwater temperatures, groundwater compositions dominated by HCO3, SO4, and Si, and the proximity of the Monturaqui Basin to the current magmatic arc are consistent with a volcanic hydrothermal origin. In summary, the groundwater geochemistry of the Monturaqui and Punta Negra Basins are not indicative of porphyry copper-type mineralization. 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
从智利北部阿塔卡马沙漠的Salar de Punta Negra和Monturaqui盆地开采的地下水显示出明显不同的同位素、主铜、微量铜和斑岩铜元素组成，这与对比鲜明的形态结构、地球化学和流体动力学环境有关。将这些不同的地下水特征与已知斑岩铜矿床（Salar de Hamburgo和Spence矿床）的地下水进行比较，可以用来确定任何一个盆地是否具有斑岩铜矿化的前景。Punta Negra盆地内的地下水表现出与整个干旱安第斯山脉其他封闭盆地环境一致的地球化学特征。Punta Negra盆地内的元素和同位素组成反映了封闭盆地蒸发过程，与安第斯山脉中部的超干旱火山环境一致。探路者金属和同位素组成与Salar de Hamburgo盆地和Spence矿床地下水中描述的斑岩铜型矿化不一致。在Monturaqui盆地内，地下水的地球化学成分具有扩散热液活动的特征。Monturaqui盆地北部水域的硫同位素组成显示出δ34SCDT同位素特征，该特征属于Spence矿床和Salar de Hamburgo及其周围地下水的硫化物矿化范围。然而，相对于Spence和Escondida矿床的地下水，Monturaqui盆地内的斑岩铜相关元素贫乏。斑岩相关元素的这种贫化，再加上富集的δ13CPDB成分、升高的地下水温度、以HCO3、SO4和Si为主的地下水成分，以及Monturaqui盆地靠近当前岩浆弧，都与火山热液成因一致。总之，Monturaqui和Punta Negra盆地的地下水地球化学并不表明斑岩铜型矿化。主题集：本文是与勘探和环境问题相关的水化学集的一部分，可在以下网站获取：https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issues
{"title":"Comparison of groundwater composition from the Monturaqui and Punta Negra Basins, northern Chile: implications for porphyry copper exploration","authors":"C. Rissmann, M. Leybourne, C. Benn, J. Kidder, L. Pearson","doi":"10.1144/geochem2021-056","DOIUrl":"https://doi.org/10.1144/geochem2021-056","url":null,"abstract":"Groundwaters recovered from the Salar de Punta Negra and Monturaqui basins in the Atacama Desert of northern Chile exhibit distinctly different isotopic, major, trace, and porphyry copper elemental compositions related to contrasting morphostructural, geochemical, and hydrodynamic settings. Comparison of these distinct groundwater signatures with groundwaters from known porphyry copper deposits (Salar de Hamburgo and Spence Deposit), can be used to determine if either basin might be prospective for porphyry copper mineralization. Groundwaters within the Punta Negra Basin exhibit geochemical characteristics consistent with other closed basin settings throughout the arid Andes. Elemental and isotopic compositions within the Punta Negra Basin reflect closed basin evaporitic processes consistent with the hyperarid, volcanic setting of the central Andes. Pathfinder metals and isotopic compositions are not consistent with porphyry copper type mineralization as described for groundwaters within the Salar de Hamburgo Basin, and the Spence Deposit. Within the Monturaqui Basin the geochemical composition of groundwaters are characteristic of diffuse hydrothermal activity. Sulfur isotopic composition within the waters of the northern Monturaqui Basin exhibit δ34SCDT isotopic signatures that fall within the range for sulfide mineralization as reported for groundwaters in and around the Spence Deposit and the Salar de Hamburgo. However, porphyry copper related elements within the Monturaqui Basin are impoverished relative to groundwaters of the Spence and Escondida Deposit. Such impoverishment in porphyry related elements, taken in conjunction with enriched δ13CPDB compositions, elevated groundwater temperatures, groundwater compositions dominated by HCO3, SO4, and Si, and the proximity of the Monturaqui Basin to the current magmatic arc are consistent with a volcanic hydrothermal origin. In summary, the groundwater geochemistry of the Monturaqui and Punta Negra Basins are not indicative of porphyry copper-type mineralization. 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":"2022-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44478768","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}
S. Xie, Ning Huang, J. Deng, Songle Wu, Mingguo Zhan, E. Carranza, Yuepeng Zhang, Fanxing Meng
One significant geochemical data processing aim is to delineate anomalies associated with mineral deposits. In areas with strong surface weathering, the accumulation centres of surface geochemical anomalies are often not completely matched with locations of mineral deposits. This affects anomaly interpretation and mineral prospectivity prediction. In order to solve this challenging problem, quantitative prediction of mineral prospectivity based on multi-information fusion techniques has been one of the research hotspots in the field of data analysis in recent years. This study first summarized the geological background and metallogenic control factors of each tectonic unit in Guangxi, and then analysed the relationship between Pb–Zn deposits and Pb–Zn geochemical anomalies from 60 767 geochemical stream sediment samples. Based on the re-classified geochemical element contents, gravity, aeromagnetic data and fault, magmatic rock, magmatic rock and fault intersection buffer data as input layers, together with 302 Pb–Zn ore occurrences selected as training data sets, quantitative prediction of prospectivity for Pb–Zn ore deposits in the study area was carried out using back-propagation neural network and fuzzy weights-of-evidence methods. It was found that the Pb–Zn mineral prospectivity prediction areas based on multi-information fusion techniques can eliminate effectively the influence of secondary accumulation of elements during weathering of carbonate rocks on the recognition of deposit-associated stream sediment geochemical anomalies, and identify effectively the mineral resources closely related to rock mass and structure distribution. These analyses reveal the metallogenic regularity of Pb–Zn deposits from the perspective of data mining based on machine learning and geographical information system multi-information fusion for delineation of prospective metallogenic target areas. The purpose here was to provide new ideas for reducing the effects of secondary weathering of extensive carbonate rocks in Guangxi, and in other regions with similar landscapes, on mineral prospectivity prediction. Thematic collection: This article is part of the Applications of innovations in geochemical data analysis collection available at: https://www.lyellcollection.org/cc/applications-of-innovations-in-geochemical-data-analysis
{"title":"Quantitative prediction of prospectivity for Pb–Zn deposits in Guangxi (China) by back-propagation neural network and fuzzy weights-of-evidence modelling","authors":"S. Xie, Ning Huang, J. Deng, Songle Wu, Mingguo Zhan, E. Carranza, Yuepeng Zhang, Fanxing Meng","doi":"10.1144/geochem2021-085","DOIUrl":"https://doi.org/10.1144/geochem2021-085","url":null,"abstract":"One significant geochemical data processing aim is to delineate anomalies associated with mineral deposits. In areas with strong surface weathering, the accumulation centres of surface geochemical anomalies are often not completely matched with locations of mineral deposits. This affects anomaly interpretation and mineral prospectivity prediction. In order to solve this challenging problem, quantitative prediction of mineral prospectivity based on multi-information fusion techniques has been one of the research hotspots in the field of data analysis in recent years. This study first summarized the geological background and metallogenic control factors of each tectonic unit in Guangxi, and then analysed the relationship between Pb–Zn deposits and Pb–Zn geochemical anomalies from 60 767 geochemical stream sediment samples. Based on the re-classified geochemical element contents, gravity, aeromagnetic data and fault, magmatic rock, magmatic rock and fault intersection buffer data as input layers, together with 302 Pb–Zn ore occurrences selected as training data sets, quantitative prediction of prospectivity for Pb–Zn ore deposits in the study area was carried out using back-propagation neural network and fuzzy weights-of-evidence methods. It was found that the Pb–Zn mineral prospectivity prediction areas based on multi-information fusion techniques can eliminate effectively the influence of secondary accumulation of elements during weathering of carbonate rocks on the recognition of deposit-associated stream sediment geochemical anomalies, and identify effectively the mineral resources closely related to rock mass and structure distribution. These analyses reveal the metallogenic regularity of Pb–Zn deposits from the perspective of data mining based on machine learning and geographical information system multi-information fusion for delineation of prospective metallogenic target areas. The purpose here was to provide new ideas for reducing the effects of secondary weathering of extensive carbonate rocks in Guangxi, and in other regions with similar landscapes, on mineral prospectivity prediction. Thematic collection: This article is part of the Applications of innovations in geochemical data analysis collection available at: https://www.lyellcollection.org/cc/applications-of-innovations-in-geochemical-data-analysis","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":"22 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2022-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41446009","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. Leybourne, D. Layton-Matthews, J. Peter, J. Kidder
Understanding the controls on the behaviour of metalloids (Se, As) and metals (Cu, Zn, Pb) in natural aqueous systems is vital to interpreting hydrogeochemical data in environmental and mineral exploration applications. Geochemical, isotopic and redox measurements of a suite of groundwaters sampled from around the ABM zone of the Kudz Ze Kayah (KZK) volcanogenic massive sulfide (VMS) deposit in the Yukon, Canada are presented and contrasted with other case studies from a variety of mineral deposit types. This deposit has atypically high As (up to 4.3 wt%, average 2457 ppm) and Se (up to 2620 ppm, average 157 ppm) contents in the sulfide mineralization. As a relatively undisturbed deposit (unmined), it is an ideal site to study the mobility and solubility of trace metals in groundwaters. Herein we present field measurements (pH, dissolved oxygen, specific conductance, oxidation–reduction potential and temperature), major ion, trace element, anion (Cl, Br, SO4, PO4), and stable isotope (δ2H, δ13CDIC, δ18O, δ18OSO4, δ34S) data. Waters are dominantly low-salinity HCO3 to HCO3–SO4-type waters with variable sulfate (4.83 to 601 mg l−1), Ca (23–235 mg l−1) Mg (3.1–96.8 mg l−1), Na (0.30–66.9 mg l−1) and K (0.55 to 6.25 mg l−1) concentrations. These waters also have variable trace element concentrations that include As (0.01 to 148 µg l–1), Se (<0.02 to 1.01 µg l–1), Fe (0.01 to 3.84 mg l−1), Zn (<0.2 to 1070 µg l–1), Pb (<0.01 to 8.4 µg l–1), Cu (0.03 and 24.5 µg l–1) and Sb (0.01 to 54.4 µg l–1). Some waters also have elevated concentrations (compared to most meteoric waters) of Nb (up to 0.3 µg l–1), Y (up to 1.42 µg l–1), Zr (up to 18 µg l–1), and the rare-earth elements (REEs) (ΣREE up to 2.04 µg l–1). The δ18O (−22.8 to −20.9 ‰) and δ2H (−174 to −158 ‰), together with the δ13CDIC (−10.6 to +1.9 ‰), δ34S (+10 to +12 ‰) and δ18OSO4 (15.5 to −4.75 ‰) all suggest that local meteoric water has interacted with massive sulfide mineralization at the ABM zone. Our results demonstrate the requirement for the use of multiple techniques in hydrogeochemical studies, with dissolved concentrations of major and trace elements coupled with a suite of stable isotopes that help define a larger geochemical footprint for the KZK deposit. Water–mineral interaction between groundwater aquifers and VMS deposits like the ABM zone are distinctly different from dispersion halos described from other deposit types (i.e. Cu porphyry, unconformity U). 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":"Controls on groundwater selenium, arsenic and base metals in groundwater around a selenium-bearing volcanogenic massive sulfide deposit: constraints from stable isotopes, trace elements and redox controls","authors":"M. Leybourne, D. Layton-Matthews, J. Peter, J. Kidder","doi":"10.1144/geochem2021-063","DOIUrl":"https://doi.org/10.1144/geochem2021-063","url":null,"abstract":"Understanding the controls on the behaviour of metalloids (Se, As) and metals (Cu, Zn, Pb) in natural aqueous systems is vital to interpreting hydrogeochemical data in environmental and mineral exploration applications. Geochemical, isotopic and redox measurements of a suite of groundwaters sampled from around the ABM zone of the Kudz Ze Kayah (KZK) volcanogenic massive sulfide (VMS) deposit in the Yukon, Canada are presented and contrasted with other case studies from a variety of mineral deposit types. This deposit has atypically high As (up to 4.3 wt%, average 2457 ppm) and Se (up to 2620 ppm, average 157 ppm) contents in the sulfide mineralization. As a relatively undisturbed deposit (unmined), it is an ideal site to study the mobility and solubility of trace metals in groundwaters. Herein we present field measurements (pH, dissolved oxygen, specific conductance, oxidation–reduction potential and temperature), major ion, trace element, anion (Cl, Br, SO4, PO4), and stable isotope (δ2H, δ13CDIC, δ18O, δ18OSO4, δ34S) data. Waters are dominantly low-salinity HCO3 to HCO3–SO4-type waters with variable sulfate (4.83 to 601 mg l−1), Ca (23–235 mg l−1) Mg (3.1–96.8 mg l−1), Na (0.30–66.9 mg l−1) and K (0.55 to 6.25 mg l−1) concentrations. These waters also have variable trace element concentrations that include As (0.01 to 148 µg l–1), Se (<0.02 to 1.01 µg l–1), Fe (0.01 to 3.84 mg l−1), Zn (<0.2 to 1070 µg l–1), Pb (<0.01 to 8.4 µg l–1), Cu (0.03 and 24.5 µg l–1) and Sb (0.01 to 54.4 µg l–1). Some waters also have elevated concentrations (compared to most meteoric waters) of Nb (up to 0.3 µg l–1), Y (up to 1.42 µg l–1), Zr (up to 18 µg l–1), and the rare-earth elements (REEs) (ΣREE up to 2.04 µg l–1). The δ18O (−22.8 to −20.9 ‰) and δ2H (−174 to −158 ‰), together with the δ13CDIC (−10.6 to +1.9 ‰), δ34S (+10 to +12 ‰) and δ18OSO4 (15.5 to −4.75 ‰) all suggest that local meteoric water has interacted with massive sulfide mineralization at the ABM zone. Our results demonstrate the requirement for the use of multiple techniques in hydrogeochemical studies, with dissolved concentrations of major and trace elements coupled with a suite of stable isotopes that help define a larger geochemical footprint for the KZK deposit. Water–mineral interaction between groundwater aquifers and VMS deposits like the ABM zone are distinctly different from dispersion halos described from other deposit types (i.e. Cu porphyry, unconformity U). 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":"2022-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44152343","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}
Geothermal water resources are being exploited widely in many areas to relieve pressure on water resources generally. Excessive Mn2+ concentration in geothermal water will seriously reduce its utilization rate. Therefore, this study investigated the removal of Mn2+ from simulated geothermal water by manganese sand. The Mn2+ removal rate from simulated water with a concentration of 10 mg l−1 by 2 g manganese sand at 298, 323, 343 and 363 K was more than 90%. The removal efficiency of Mn2+ is influenced by adsorbent dosage, adsorbent particle size, initial Mn2+ concentration and competing ions, and less so by a pH of 5–9. A pseudo-first-order kinetic model fits the adsorption data better than a pseudo-second-order model. The pseudo-first-order adsorption rate constants (K1) ranged from 0.14 to 0.5 h−1 as the temperature increased from 298 to 363 K. The Langmuir isotherm model fits the adsorption data better than the Freundlich and Temkin isotherm models. The maximum monolayer adsorption capacities (qm) obtained by the Langmuir isotherm model fitting were 0.91/1.02/1.22/1.23 mg g–1 at 298/323/343/363 K. Thermodynamic studies revealed that the adsorption was endothermic and physical in nature. These findings suggest that the potential of manganese sand for removing Mn2+ in geothermal water is considerable. 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":"Removal of Mn2+ in geothermal water by manganese sand: process and mechanisms","authors":"Wen Feng, Jun Wu, Jian Lu","doi":"10.1144/geochem2021-071","DOIUrl":"https://doi.org/10.1144/geochem2021-071","url":null,"abstract":"Geothermal water resources are being exploited widely in many areas to relieve pressure on water resources generally. Excessive Mn2+ concentration in geothermal water will seriously reduce its utilization rate. Therefore, this study investigated the removal of Mn2+ from simulated geothermal water by manganese sand. The Mn2+ removal rate from simulated water with a concentration of 10 mg l−1 by 2 g manganese sand at 298, 323, 343 and 363 K was more than 90%. The removal efficiency of Mn2+ is influenced by adsorbent dosage, adsorbent particle size, initial Mn2+ concentration and competing ions, and less so by a pH of 5–9. A pseudo-first-order kinetic model fits the adsorption data better than a pseudo-second-order model. The pseudo-first-order adsorption rate constants (K1) ranged from 0.14 to 0.5 h−1 as the temperature increased from 298 to 363 K. The Langmuir isotherm model fits the adsorption data better than the Freundlich and Temkin isotherm models. The maximum monolayer adsorption capacities (qm) obtained by the Langmuir isotherm model fitting were 0.91/1.02/1.22/1.23 mg g–1 at 298/323/343/363 K. Thermodynamic studies revealed that the adsorption was endothermic and physical in nature. These findings suggest that the potential of manganese sand for removing Mn2+ in geothermal water is considerable. 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":"2022-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45803625","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}
J. Kidder, M. McClenaghan, M. Leybourne, M. McCurdy, P. Pelchat, D. Layton-Matthews, A. Voinot
The Casino Cu–Au–Mo deposit is one of the largest and highest-grade porphyries of its kind in Canada, residing in an unglaciated region of west-central Yukon. A batch of 22 stream water samples and eight groundwater samples were collected proximal to the deposit for the purpose of identifying the most diagnostic trace element and isotopic pathfinders associated with the hydrothermal mineralization, as well as establishing natural hydrogeochemical baselines for the area. Water chemistry around this deposit was investigated because: (i) the deposit has not yet been disturbed by mining; (ii) the deposit was known to have metal-rich waters in local streams; and (iii) the deposit has atypically preserved ore zones. Surface and ground waters around the Casino deposit are anomalous with respect to Cd (up to 5.4 µg l–1), Co (up to 64 µg l–1), Cu (up to 1657 µg l–1), Mo (up to 25 µg l–1), As (up to 17 µg l–1), Re (up to 0.7 µg l–1) and Zn (up to 354 µg l–1) concentrations. Sulfur and Sr isotopes are consistent with proximal waters interacting with the Casino rocks and mineralization; a sulfide-rich bedrock sample from the deposit has δ34S = −1.2‰ and proximal groundwaters are only slightly heavier (−0.3 to 3.1‰). These geochemical and isotopic results indicate interaction and dispersion of porphyry-related solutes in ground and surface waters and point to the suitability of hydrogeochemistry as a medium for mineral exploration for porphyry-style mineralization in the Yukon, and elsewhere in Canada. Supplementary material: Dissolved concentration data for major and trace elements for the ground and stream water samples from Casino are available at https://doi.org/10.6084/m9.figshare.c.5778911 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":"Hydrogeochemistry of porphyry-related solutes in ground and surface waters; an example from the Casino Cu–Au–Mo deposit, Yukon, Canada","authors":"J. Kidder, M. McClenaghan, M. Leybourne, M. McCurdy, P. Pelchat, D. Layton-Matthews, A. Voinot","doi":"10.1144/geochem2021-058","DOIUrl":"https://doi.org/10.1144/geochem2021-058","url":null,"abstract":"The Casino Cu–Au–Mo deposit is one of the largest and highest-grade porphyries of its kind in Canada, residing in an unglaciated region of west-central Yukon. A batch of 22 stream water samples and eight groundwater samples were collected proximal to the deposit for the purpose of identifying the most diagnostic trace element and isotopic pathfinders associated with the hydrothermal mineralization, as well as establishing natural hydrogeochemical baselines for the area. Water chemistry around this deposit was investigated because: (i) the deposit has not yet been disturbed by mining; (ii) the deposit was known to have metal-rich waters in local streams; and (iii) the deposit has atypically preserved ore zones. Surface and ground waters around the Casino deposit are anomalous with respect to Cd (up to 5.4 µg l–1), Co (up to 64 µg l–1), Cu (up to 1657 µg l–1), Mo (up to 25 µg l–1), As (up to 17 µg l–1), Re (up to 0.7 µg l–1) and Zn (up to 354 µg l–1) concentrations. Sulfur and Sr isotopes are consistent with proximal waters interacting with the Casino rocks and mineralization; a sulfide-rich bedrock sample from the deposit has δ34S = −1.2‰ and proximal groundwaters are only slightly heavier (−0.3 to 3.1‰). These geochemical and isotopic results indicate interaction and dispersion of porphyry-related solutes in ground and surface waters and point to the suitability of hydrogeochemistry as a medium for mineral exploration for porphyry-style mineralization in the Yukon, and elsewhere in Canada. Supplementary material: Dissolved concentration data for major and trace elements for the ground and stream water samples from Casino are available at https://doi.org/10.6084/m9.figshare.c.5778911 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":"2022-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47648836","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}
V. Gallagher, E. Grunsky, Mairéad M. Fitzsimons, Margaret A. Browne, Sophie Lilburn, J. Symons
Regional stream water geochemistry acquired as part of the Tellus programme in Ireland has been analysed to assess its potential for application to environmental assessment and mineral exploration. Interpolated geochemical maps and multivariate statistical analysis, including principal component analysis and random forest classification, demonstrate broad geogenic control of stream water chemistry, with both bedrock and subsoil contributing to the patterns observed. Surface water regulations set Environmental Quality Standard values for individual Priority Substances and Specific Pollutants that may depend on background concentrations and/or water hardness. The high resolution of Tellus stream water data and their location on low-order streams have allowed estimation of background concentrations and water hardness in the survey area, with significant implications for water monitoring programmes. Anthropogenic inputs to stream water in the survey area come mainly from agricultural sources and Tellus data suggest few catchments are unaffected. Comparison of Tellus stream water geochemistry with stream sediment and topsoil geochemistry suggest that stream water geochemistry has strong potential for use in mineral exploration, with the same base metal and gold pathfinder anomalies apparent in all three data sets. Cluster analysis indicates that base metals in stream water are associated with organic matter but statistical analysis may be employed to distinguish mineralization-related signatures. Supplementary material: Comparison of cation/anion associations using Piper plots and principal component analysis is available at https://doi.org/10.6084/m9.figshare.c.5683094 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":"Tellus regional stream water geochemistry: environmental and mineral exploration applications","authors":"V. Gallagher, E. Grunsky, Mairéad M. Fitzsimons, Margaret A. Browne, Sophie Lilburn, J. Symons","doi":"10.1144/geochem2021-050","DOIUrl":"https://doi.org/10.1144/geochem2021-050","url":null,"abstract":"Regional stream water geochemistry acquired as part of the Tellus programme in Ireland has been analysed to assess its potential for application to environmental assessment and mineral exploration. Interpolated geochemical maps and multivariate statistical analysis, including principal component analysis and random forest classification, demonstrate broad geogenic control of stream water chemistry, with both bedrock and subsoil contributing to the patterns observed. Surface water regulations set Environmental Quality Standard values for individual Priority Substances and Specific Pollutants that may depend on background concentrations and/or water hardness. The high resolution of Tellus stream water data and their location on low-order streams have allowed estimation of background concentrations and water hardness in the survey area, with significant implications for water monitoring programmes. Anthropogenic inputs to stream water in the survey area come mainly from agricultural sources and Tellus data suggest few catchments are unaffected. Comparison of Tellus stream water geochemistry with stream sediment and topsoil geochemistry suggest that stream water geochemistry has strong potential for use in mineral exploration, with the same base metal and gold pathfinder anomalies apparent in all three data sets. Cluster analysis indicates that base metals in stream water are associated with organic matter but statistical analysis may be employed to distinguish mineralization-related signatures. Supplementary material: Comparison of cation/anion associations using Piper plots and principal component analysis is available at https://doi.org/10.6084/m9.figshare.c.5683094 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":"2022-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47860060","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}
P. Négrel, A. Ladenberger, C. Reimann, A. Demetriades, M. Birke, M. Sadeghi
Carbonate rocks are very soluble and export elements in dissolved form, and precipitation of secondary phases can occur on a large scale. They leave a strong chemical signature in soil that can be quantified and classified by geochemical indices, and which is useful for evaluating chemical weathering trends (e.g. the Chemical Index of Alteration (CIA) or the Mafic Index of Alteration (MIA)). Due to contrasting chemical compositions and high Ca content, a special adaptation of classical weathering indices is necessary to interpret weathering trends in carbonate-derived soil. In fact, this adaptation seems to be a good tool for distinguishing weathering grades of source-rock types at the continental scale, and allows a more robust interpretation of soil parent-material weathering grade and its impact on the current chemical composition of soil. An increasing degree of weathering results in Al enrichment and Mg loss in addition to Fe loss and Si enrichment, leaching of mobile cations such as Ca and Na, and precipitation of Fe-oxides and hydroxides. The relation between soil weathering status and its spatial distribution in Europe provides important information about the role played by climate and terrain. The geographical distribution of soil chemistry contributes to a better understanding of soil nutritional status, element enrichment, degradation mechanisms, desertification, soil erosion and contamination.
{"title":"GEMAS: adaptation of weathering indices for European agricultural soil derived from carbonate parent materials","authors":"P. Négrel, A. Ladenberger, C. Reimann, A. Demetriades, M. Birke, M. Sadeghi","doi":"10.1144/geochem2021-059","DOIUrl":"https://doi.org/10.1144/geochem2021-059","url":null,"abstract":"Carbonate rocks are very soluble and export elements in dissolved form, and precipitation of secondary phases can occur on a large scale. They leave a strong chemical signature in soil that can be quantified and classified by geochemical indices, and which is useful for evaluating chemical weathering trends (e.g. the Chemical Index of Alteration (CIA) or the Mafic Index of Alteration (MIA)). Due to contrasting chemical compositions and high Ca content, a special adaptation of classical weathering indices is necessary to interpret weathering trends in carbonate-derived soil. In fact, this adaptation seems to be a good tool for distinguishing weathering grades of source-rock types at the continental scale, and allows a more robust interpretation of soil parent-material weathering grade and its impact on the current chemical composition of soil. An increasing degree of weathering results in Al enrichment and Mg loss in addition to Fe loss and Si enrichment, leaching of mobile cations such as Ca and Na, and precipitation of Fe-oxides and hydroxides. The relation between soil weathering status and its spatial distribution in Europe provides important information about the role played by climate and terrain. The geographical distribution of soil chemistry contributes to a better understanding of soil nutritional status, element enrichment, degradation mechanisms, desertification, soil erosion and contamination.","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49272839","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. McClenaghan, W. Spirito, S. Day, M. McCurdy, R. McNeil, S. Adcock
The Geological Survey of Canada carried out reconnaissance-scale to deposit-scale geochemical and indicator-mineral surveys and case studies across northern Canada between 2008 and 2020 as part of its Geo-mapping for Energy and Minerals (GEM) program. In these studies, surficial geochemistry was used to determine the concentrations of up to 65 elements in various sample media including lake sediment, lake water, stream sediment, stream water, or till samples across approximately 1 000 000 km2 of northern Canada. As part of these surficial geochemistry surveys, indicator mineral methods were also used in regional-scale and deposit-scale stream sediment and till surveys. Through this program, areas with anomalous concentrations of elements and/or indicator minerals that are indicative of bedrock mineralization were identified, new mineral exploration models and protocols were developed, a new generation of geoscientists was trained, and geoscience knowledge was transferred to northern communities. Regional- and deposit-scale studies demonstrated how transport data (till geochemistry, indicator mineral abundance) and ice-flow indicator data can be used together to identify and understand complex ice flow and glacial transport. Detailed studies at the Izok Lake Zn–Cu–Pb–Ag VMS, Nunavut, the Pine Point carbonate-hosted Pb–Zn in the Northwest Territories, the Strange Lake REE deposit in Quebec and Labrador as well as U–Cu–Fe–F and Cu–Ag–Au–Au IOCG deposits in the Great Bear magmatic zone, Northwest Territories demonstrate new suites of indicator minerals that can now be used in future reconnaissance- and regional-scale stream sediment and till surveys across Canada.
2008年至2020年间，加拿大地质调查局在加拿大北部进行了按矿床规模的地球化学和指示矿物调查以及案例研究，作为其能源和矿产地质测绘（GEM）计划的一部分。在这些研究中，表层地球化学用于确定各种样品介质中多达65种元素的浓度，包括湖泊沉积物、湖水、溪流沉积物、溪流水或大约1 000 000 加拿大北部平方公里。作为这些表层地球化学调查的一部分，指示矿物方法也用于区域规模和矿床规模的河流沉积物和沉积物调查。通过该项目，确定了指示基岩矿化的元素和/或指示矿物浓度异常的地区，开发了新的矿产勘探模型和协议，培训了新一代地球科学家，并将地球科学知识转移到北方社区。区域和矿床规模的研究表明，运输数据（直到地球化学、指示矿物丰度）和冰流指示数据可以一起用于识别和理解复杂的冰流和冰川运输。对努纳武特Izok Lake Zn–Cu–Pb–Ag VMS、西北地区的Pine Point碳酸盐岩型Pb–Zn、魁北克和拉布拉多的Strange Lake REE矿床以及大熊岩浆带的U–Cu–Fe–F和Cu–Ag–Au–Au-IOCG矿床的详细研究，西北地区展示了一系列新的指示矿物，这些矿物现在可以用于未来的勘察和区域范围的河流沉积物以及加拿大各地的调查。
{"title":"Overview of surficial geochemistry and indicator mineral surveys and case studies from the Geological Survey of Canada's GEM Program","authors":"M. McClenaghan, W. Spirito, S. Day, M. McCurdy, R. McNeil, S. Adcock","doi":"10.1144/geochem2021-070","DOIUrl":"https://doi.org/10.1144/geochem2021-070","url":null,"abstract":"The Geological Survey of Canada carried out reconnaissance-scale to deposit-scale geochemical and indicator-mineral surveys and case studies across northern Canada between 2008 and 2020 as part of its Geo-mapping for Energy and Minerals (GEM) program. In these studies, surficial geochemistry was used to determine the concentrations of up to 65 elements in various sample media including lake sediment, lake water, stream sediment, stream water, or till samples across approximately 1 000 000 km2 of northern Canada. As part of these surficial geochemistry surveys, indicator mineral methods were also used in regional-scale and deposit-scale stream sediment and till surveys. Through this program, areas with anomalous concentrations of elements and/or indicator minerals that are indicative of bedrock mineralization were identified, new mineral exploration models and protocols were developed, a new generation of geoscientists was trained, and geoscience knowledge was transferred to northern communities. Regional- and deposit-scale studies demonstrated how transport data (till geochemistry, indicator mineral abundance) and ice-flow indicator data can be used together to identify and understand complex ice flow and glacial transport. Detailed studies at the Izok Lake Zn–Cu–Pb–Ag VMS, Nunavut, the Pine Point carbonate-hosted Pb–Zn in the Northwest Territories, the Strange Lake REE deposit in Quebec and Labrador as well as U–Cu–Fe–F and Cu–Ag–Au–Au IOCG deposits in the Great Bear magmatic zone, Northwest Territories demonstrate new suites of indicator minerals that can now be used in future reconnaissance- and regional-scale stream sediment and till surveys across Canada.","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48827367","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}
E. Potter, C. J. Kelly, W. Davis, G. Chi, S-Y. Jiang, M. Rabiei, B. McEwan
The Patterson Lake corridor is a new uranium district located on the southwestern margin of the Athabasca Basin. Known resources extend almost 1 km below the unconformity in graphite- and sulfide-bearing shear zones within highly altered metamorphic rocks. Despite different host rocks and greater depths below the unconformity, alteration assemblages (chlorite, illite, kaolinite, tourmaline and hematite), ore grades and textures are typical of unconformity-related deposits. This alteration includes at least three generations of Mg-rich tourmaline (magnesio-foitite). The boron isotopic composition of magnesio-foitite varies with generation: the earliest generation, which is only observed in shallow samples from the Triple R deposit (Tur 1), contain the heaviest isotopic signature (δ11B ≈ 19–26‰), whereas subsequent generations (Tur 2 and Tur 3) yield lighter and more homogeneous isotopic signatures (δ11B ≈ 17.5–19.9‰). These results are consistent with precipitation from low-temperature, NaCl- and CaCl2-rich brine(s) derived from an isotopically heavy boron source (e.g. evaporated seawater) that interacted with tourmaline and silicates in the basement rocks and/or fluids derived from depth (with low δ11B values). The lower δ11B values in paragenetically later magnesio-foitite reflect greater contributions of basement-derived boron over time, whereas minor compositional variations reflect local metal sources (e.g. Cr, V, Ti) and evolving fluid chemistry (decreasing Na and Ca, increasing Mg) over time. The δ11B and chemical variation in magnesio-foitite over time reinforce the strong interactions with basement rocks in these systems while supporting incursion of basinal brines well below the unconformity contact. Supplementary material: Complete analytical dataset including reference materials are available at https://doi.org/10.6084/m9.figshare.c.5727555 Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways
{"title":"Fluid sources in basement-hosted unconformity–uranium ore systems: tourmaline chemistry and boron isotopes from the Patterson Lake corridor deposits, Canada","authors":"E. Potter, C. J. Kelly, W. Davis, G. Chi, S-Y. Jiang, M. Rabiei, B. McEwan","doi":"10.1144/geochem2021-037","DOIUrl":"https://doi.org/10.1144/geochem2021-037","url":null,"abstract":"The Patterson Lake corridor is a new uranium district located on the southwestern margin of the Athabasca Basin. Known resources extend almost 1 km below the unconformity in graphite- and sulfide-bearing shear zones within highly altered metamorphic rocks. Despite different host rocks and greater depths below the unconformity, alteration assemblages (chlorite, illite, kaolinite, tourmaline and hematite), ore grades and textures are typical of unconformity-related deposits. This alteration includes at least three generations of Mg-rich tourmaline (magnesio-foitite). The boron isotopic composition of magnesio-foitite varies with generation: the earliest generation, which is only observed in shallow samples from the Triple R deposit (Tur 1), contain the heaviest isotopic signature (δ11B ≈ 19–26‰), whereas subsequent generations (Tur 2 and Tur 3) yield lighter and more homogeneous isotopic signatures (δ11B ≈ 17.5–19.9‰). These results are consistent with precipitation from low-temperature, NaCl- and CaCl2-rich brine(s) derived from an isotopically heavy boron source (e.g. evaporated seawater) that interacted with tourmaline and silicates in the basement rocks and/or fluids derived from depth (with low δ11B values). The lower δ11B values in paragenetically later magnesio-foitite reflect greater contributions of basement-derived boron over time, whereas minor compositional variations reflect local metal sources (e.g. Cr, V, Ti) and evolving fluid chemistry (decreasing Na and Ca, increasing Mg) over time. The δ11B and chemical variation in magnesio-foitite over time reinforce the strong interactions with basement rocks in these systems while supporting incursion of basinal brines well below the unconformity contact. Supplementary material: Complete analytical dataset including reference materials are available at https://doi.org/10.6084/m9.figshare.c.5727555 Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways","PeriodicalId":55114,"journal":{"name":"Geochemistry-Exploration Environment Analysis","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45430853","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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