Pub Date : 2023-08-01DOI: 10.5382/econgeo.118.5.ip01
{"title":"Interesting Papers in Other Journals","authors":"","doi":"10.5382/econgeo.118.5.ip01","DOIUrl":"https://doi.org/10.5382/econgeo.118.5.ip01","url":null,"abstract":"","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135717145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Elias Martins Guerra Prado, C. R. de Souza Filho, Emmanuel John Muico Carranza
Acquiring information about the spatial distribution of ore grade in the subsurface is essential for exploring and discovering mineral resources. This information is derived commonly from the geochemical analysis carried out on drill core samples, which allows the quantification of the concentration of ore elements. However, these surveys are generally time-consuming and expensive, usually leading to information at a low spatial resolution due to large sampling intervals. The use of hyperspectral systems in the mining industry to characterize and quantify minerals in drill cores is increasing due to their efficiency and fast turnaround time. Here, we propose the use of convolutional neural networks on hyperspectral data to estimate Cu concentration in drill cores at the Olympic Dam iron oxide copper-gold deposit. The Cu concentration data obtained by drill core geochemical analysis and the mean spectra between the analyzed intervals obtained from hyperspectral data were used to train the machine learning model. The trained model was then used to estimate the Cu concentration of a test drill core, which was not used to train the model. In addition, the trained model was used to extrapolate the Cu concentration, at a centimetric spatial resolution, to the drill core intervals without geochemical analysis. Qualitative and quantitative evaluations of the results demonstrate the capabilities of the proposed method, which provided a root mean squared error of 0.48 for the estimation of Cu percentage along drill cores. The results indicate that the method could be beneficial for determining the spatial distribution of ore grade by supporting the selection of zones of interest where more detailed analyses are appropriate, reducing the number of samples needed to characterize and identify the ore zones, and assisting in the estimation of the volume with commercially viable ore, thereby potentially reducing the geochemical assays needed and decreasing the data acquisition time.
{"title":"Ore-Grade Estimation from Hyperspectral Data Using Convolutional Neural Networks: A Case Study at the Olympic Dam Iron Oxide Copper-Gold Deposit, Australia","authors":"Elias Martins Guerra Prado, C. R. de Souza Filho, Emmanuel John Muico Carranza","doi":"10.5382/econgeo.5023","DOIUrl":"https://doi.org/10.5382/econgeo.5023","url":null,"abstract":"\u0000 Acquiring information about the spatial distribution of ore grade in the subsurface is essential for exploring and discovering mineral resources. This information is derived commonly from the geochemical analysis carried out on drill core samples, which allows the quantification of the concentration of ore elements. However, these surveys are generally time-consuming and expensive, usually leading to information at a low spatial resolution due to large sampling intervals. The use of hyperspectral systems in the mining industry to characterize and quantify minerals in drill cores is increasing due to their efficiency and fast turnaround time. Here, we propose the use of convolutional neural networks on hyperspectral data to estimate Cu concentration in drill cores at the Olympic Dam iron oxide copper-gold deposit. The Cu concentration data obtained by drill core geochemical analysis and the mean spectra between the analyzed intervals obtained from hyperspectral data were used to train the machine learning model. The trained model was then used to estimate the Cu concentration of a test drill core, which was not used to train the model. In addition, the trained model was used to extrapolate the Cu concentration, at a centimetric spatial resolution, to the drill core intervals without geochemical analysis. Qualitative and quantitative evaluations of the results demonstrate the capabilities of the proposed method, which provided a root mean squared error of 0.48 for the estimation of Cu percentage along drill cores. The results indicate that the method could be beneficial for determining the spatial distribution of ore grade by supporting the selection of zones of interest where more detailed analyses are appropriate, reducing the number of samples needed to characterize and identify the ore zones, and assisting in the estimation of the volume with commercially viable ore, thereby potentially reducing the geochemical assays needed and decreasing the data acquisition time.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"14 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81381446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Cernuschi, J. Dilles, J. Osorio, J. Proffett, K. Kouzmanov
The timing and temperature at which copper-iron and molybdenum sulfide deposition occurs in porphyry deposits remain controversial. Petrologic estimates indicate that veins and wall-rock alteration zones containing copper-iron sulfides form in a wide temperature range from ~350° to 650°C. Most sulfides are hosted in potassium(K)-silicate–altered rock and quartz A veins or in early-halo alteration selvages formed above ~450°C. In contrast, cathodoluminescence (CL) imaging of A veins indicates that copper-iron sulfides are contained within a primary lucent (bright and gray)-CL quartz and are crosscut by microfractures filled with younger dull (dark and medium-gray)-CL quartz in direct contact with copper-iron sulfides. These observations have been interpreted as supporting late copper-iron sulfide introduction together with dull-CL quartz at moderate temperatures of ~300° to 450°C, based on fluid inclusion estimates. We provide new CL, QEMSCAN, and petrographic data and images of vein quartz as well as petrologic data of altered wall rock from Haquira East (Peru), Encuentro (Chile), and Batu Hijau (Indonesia) porphyry deposits, which were formed at conditions ranging from deep to shallow (~2–10 km). At all three deposits, dull-CL quartz in microfractures is ubiquitously observed crosscutting all generations of high-temperature lucent-CL quartz veins. Each lucent-CL vein type hosts distinct sulfide populations, crosscuts the others, and coexists in space within the copper and molybdenum ore zones. Within this ore zone, the dull-CL quartz only contains copper-iron sulfides where it transects old A veins and early halos, molybdenite where it transects young molybdenite-bearing quartz veins, and both copper-iron sulfides and molybdenite in younger B veins. Furthermore, where the dull-CL quartz crosscuts igneous or barren (deep) quartz veins, it typically lacks copper and molybdenum. Therefore, dull-CL quartz has no particular spatial or genetic affinity with copper-iron sulfides or molybdenite. We propose that copper was introduced and precipitated at high temperatures in stability with K-silicate alteration. In shallow porphyry deposits, most copper was introduced with lucent-CL quartz in A veins, likely formed via adiabatic decompression from magmatic lithostatic to hydrostatic conditions at ~450° to 600°C. In deep deposits, most copper is introduced with quartz-poor early halos, likely formed at a temperature range similar to that of A veins but during an early stage of retrograde silica solubility. The inferred timing and temperature of copper precipitation are consistent with available solubility experiments for copper-bearing solutions that suggest copper precipitation may start at a high temperature of ~600°C, and ~90% precipitates before it cools down to ~400°C. Much of the molybdenum is introduced and precipitated with discrete pulses of molybdenite-bearing quartz veins that crosscut and postdate copper-bearing A veins and early halos and,
{"title":"A Reevaluation of the Timing and Temperature of Copper and Molybdenum Precipitation in Porphyry Deposits","authors":"F. Cernuschi, J. Dilles, J. Osorio, J. Proffett, K. Kouzmanov","doi":"10.5382/econgeo.5032","DOIUrl":"https://doi.org/10.5382/econgeo.5032","url":null,"abstract":"\u0000 The timing and temperature at which copper-iron and molybdenum sulfide deposition occurs in porphyry deposits remain controversial. Petrologic estimates indicate that veins and wall-rock alteration zones containing copper-iron sulfides form in a wide temperature range from ~350° to 650°C. Most sulfides are hosted in potassium(K)-silicate–altered rock and quartz A veins or in early-halo alteration selvages formed above ~450°C. In contrast, cathodoluminescence (CL) imaging of A veins indicates that copper-iron sulfides are contained within a primary lucent (bright and gray)-CL quartz and are crosscut by microfractures filled with younger dull (dark and medium-gray)-CL quartz in direct contact with copper-iron sulfides. These observations have been interpreted as supporting late copper-iron sulfide introduction together with dull-CL quartz at moderate temperatures of ~300° to 450°C, based on fluid inclusion estimates.\u0000 We provide new CL, QEMSCAN, and petrographic data and images of vein quartz as well as petrologic data of altered wall rock from Haquira East (Peru), Encuentro (Chile), and Batu Hijau (Indonesia) porphyry deposits, which were formed at conditions ranging from deep to shallow (~2–10 km). At all three deposits, dull-CL quartz in microfractures is ubiquitously observed crosscutting all generations of high-temperature lucent-CL quartz veins. Each lucent-CL vein type hosts distinct sulfide populations, crosscuts the others, and coexists in space within the copper and molybdenum ore zones. Within this ore zone, the dull-CL quartz only contains copper-iron sulfides where it transects old A veins and early halos, molybdenite where it transects young molybdenite-bearing quartz veins, and both copper-iron sulfides and molybdenite in younger B veins. Furthermore, where the dull-CL quartz crosscuts igneous or barren (deep) quartz veins, it typically lacks copper and molybdenum. Therefore, dull-CL quartz has no particular spatial or genetic affinity with copper-iron sulfides or molybdenite.\u0000 We propose that copper was introduced and precipitated at high temperatures in stability with K-silicate alteration. In shallow porphyry deposits, most copper was introduced with lucent-CL quartz in A veins, likely formed via adiabatic decompression from magmatic lithostatic to hydrostatic conditions at ~450° to 600°C. In deep deposits, most copper is introduced with quartz-poor early halos, likely formed at a temperature range similar to that of A veins but during an early stage of retrograde silica solubility. The inferred timing and temperature of copper precipitation are consistent with available solubility experiments for copper-bearing solutions that suggest copper precipitation may start at a high temperature of ~600°C, and ~90% precipitates before it cools down to ~400°C. Much of the molybdenum is introduced and precipitated with discrete pulses of molybdenite-bearing quartz veins that crosscut and postdate copper-bearing A veins and early halos and,","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"58 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90054041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. S. Mohammedyasin, J. Magnall, S. Gleeson, H. Schulz, A. Schleicher, J. Stammeier, Bodo-Carlo Ehling
The Southern Permian basin in central Europe contains a number of important high-grade sediment-hosted Cu deposits. Laterally extensive stratabound Cu and Zn-Pb sulfide mineralized rocks are located at a major stratigraphic redox boundary, where coarse-grained continental sandstones of the uppermost Rotliegend Group are overlain by carbonaceous mudstones (T1) and limestones (Ca1) of the Zechstein Formation. This study investigates the diagenetic evolution and style of sulfide mineralization in three drill cores that intersect Cu and Zn-Pb sulfide mineralized rocks at three locations (Sangerhausen, Allstedt, and Wallendorf) in the Saale subbasin (Eastern Germany), which is located at the southern margin of the Southern Permian basin. We combine macro- to microscale petrographic data (binocular, transmitted and reflected light, and scanning electron microscopy) with quantitative X-ray diffractometry and bulk-rock geochemical analyses. Petrographic results show extensive, primary-porosity-occluding, early diagenetic calcite cementation that predates both the diagenetic alteration of detrital clasts and sulfide mineralization. The highest-grade Cu and Zn-Pb sulfides (bornite, sphalerite, and galena) replace the calcite cement, with subordinate replacement of dolomite and detrital clasts. Quantitative mineralogical and geochemical data demonstrate that the highest base metal (Cu, Zn, and Pb) concentrations are associated with carbonate-rich samples, mostly as disseminated mineralization in the middle T1. Bulk-rock geochemical results show enrichment and covariation of redox-sensitive trace elements (RSTEs, e.g., Mo) with total organic carbon content toward the lower T1, consistent with highly reducing depositional conditions. Overall, the distribution and dissolution of calcite cement across this stratigraphic redox boundary provided the main control on the lateral migration of base metal-bearing fluids and high-grade Cu and Zn-Pb sulfide mineralization in the Saale subbasin.
{"title":"Diagenetic History and Timing of Cu and Zn-Pb Sulfide Mineralization in the Permian Kupferschiefer System, Saale Subbasin, Eastern Germany","authors":"M. S. Mohammedyasin, J. Magnall, S. Gleeson, H. Schulz, A. Schleicher, J. Stammeier, Bodo-Carlo Ehling","doi":"10.5382/econgeo.5015","DOIUrl":"https://doi.org/10.5382/econgeo.5015","url":null,"abstract":"\u0000 The Southern Permian basin in central Europe contains a number of important high-grade sediment-hosted Cu deposits. Laterally extensive stratabound Cu and Zn-Pb sulfide mineralized rocks are located at a major stratigraphic redox boundary, where coarse-grained continental sandstones of the uppermost Rotliegend Group are overlain by carbonaceous mudstones (T1) and limestones (Ca1) of the Zechstein Formation. This study investigates the diagenetic evolution and style of sulfide mineralization in three drill cores that intersect Cu and Zn-Pb sulfide mineralized rocks at three locations (Sangerhausen, Allstedt, and Wallendorf) in the Saale subbasin (Eastern Germany), which is located at the southern margin of the Southern Permian basin. We combine macro- to microscale petrographic data (binocular, transmitted and reflected light, and scanning electron microscopy) with quantitative X-ray diffractometry and bulk-rock geochemical analyses. Petrographic results show extensive, primary-porosity-occluding, early diagenetic calcite cementation that predates both the diagenetic alteration of detrital clasts and sulfide mineralization. The highest-grade Cu and Zn-Pb sulfides (bornite, sphalerite, and galena) replace the calcite cement, with subordinate replacement of dolomite and detrital clasts. Quantitative mineralogical and geochemical data demonstrate that the highest base metal (Cu, Zn, and Pb) concentrations are associated with carbonate-rich samples, mostly as disseminated mineralization in the middle T1. Bulk-rock geochemical results show enrichment and covariation of redox-sensitive trace elements (RSTEs, e.g., Mo) with total organic carbon content toward the lower T1, consistent with highly reducing depositional conditions. Overall, the distribution and dissolution of calcite cement across this stratigraphic redox boundary provided the main control on the lateral migration of base metal-bearing fluids and high-grade Cu and Zn-Pb sulfide mineralization in the Saale subbasin.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"38 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91009627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-01DOI: 10.5382/econgeo.118.4.ip01
{"title":"Interesting Papers in Other Journals","authors":"","doi":"10.5382/econgeo.118.4.ip01","DOIUrl":"https://doi.org/10.5382/econgeo.118.4.ip01","url":null,"abstract":"","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135575419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Dana, A. Agangi, A. Idrus, C. Chelle-Michou, Chunkit Lai, Mizuki Ishida, M. Guillong, I. González-Álvarez, R. Takahashi, Moei Yano, K. Mimura, J. Ohta, Y. Kato, Doly R. Simbolon, X. Xia
The Ruwai skarn deposit is the largest polymetallic skarn deposit in Borneo and is located in the Schwaner Mountains. The skarns and massive orebodies are hosted in marble of the Jurassic Ketapang Complex, which was intruded by Cretaceous Sukadana granitoids. The prograde-stage garnet and retrograde-stage titanite yielded U-Pb ages of 97.0 ± 1.8 to 94.2 ± 10.3 Ma and 96.0 ± 2.9 to 95.0 ± 2.0 Ma, respectively. These ages are similar to Re-Os ages obtained on sulfides (96.0 ± 2.3 Ma) and magnetite (99.3 ± 3.6 Ma). The U-Pb zircon ages reveal that magmatism at Ruwai occurred in three phases, including the Early Cretaceous (ca. 145.7 and 106.7–105.7 Ma; andesite-dacite), Late Cretaceous (ca. 99.7–97.1 Ma; diorite-granodiorite), and late Miocene (ca. 10.94–9.51 Ma; diorite-dolerite). Based on geochemical and stable isotopic data (C-O-S) the Ruwai skarn ores are interpreted to have formed from oxidized fluids at ca. 160 to 670°C. The ore-forming fluids and metals were mostly magmatic in origin but with significant crustal input. Ruwai skarn mineralization occurred in the Late Cretaceous, associated with Paleo-Pacific subduction beneath Sundaland after the Southwest Borneo accretion. Ruwai is the first occurrence of Cretaceous mineralization recognized in the Central Borneo metallogenic belt.
{"title":"The Age and Origin of the Ruwai Polymetallic Skarn Deposit, Indonesia: Evidence of Cretaceous Mineralization in the Central Borneo Metallogenic Belt","authors":"C. Dana, A. Agangi, A. Idrus, C. Chelle-Michou, Chunkit Lai, Mizuki Ishida, M. Guillong, I. González-Álvarez, R. Takahashi, Moei Yano, K. Mimura, J. Ohta, Y. Kato, Doly R. Simbolon, X. Xia","doi":"10.5382/econgeo.5009","DOIUrl":"https://doi.org/10.5382/econgeo.5009","url":null,"abstract":"\u0000 The Ruwai skarn deposit is the largest polymetallic skarn deposit in Borneo and is located in the Schwaner Mountains. The skarns and massive orebodies are hosted in marble of the Jurassic Ketapang Complex, which was intruded by Cretaceous Sukadana granitoids. The prograde-stage garnet and retrograde-stage titanite yielded U-Pb ages of 97.0 ± 1.8 to 94.2 ± 10.3 Ma and 96.0 ± 2.9 to 95.0 ± 2.0 Ma, respectively. These ages are similar to Re-Os ages obtained on sulfides (96.0 ± 2.3 Ma) and magnetite (99.3 ± 3.6 Ma). The U-Pb zircon ages reveal that magmatism at Ruwai occurred in three phases, including the Early Cretaceous (ca. 145.7 and 106.7–105.7 Ma; andesite-dacite), Late Cretaceous (ca. 99.7–97.1 Ma; diorite-granodiorite), and late Miocene (ca. 10.94–9.51 Ma; diorite-dolerite). Based on geochemical and stable isotopic data (C-O-S) the Ruwai skarn ores are interpreted to have formed from oxidized fluids at ca. 160 to 670°C. The ore-forming fluids and metals were mostly magmatic in origin but with significant crustal input. Ruwai skarn mineralization occurred in the Late Cretaceous, associated with Paleo-Pacific subduction beneath Sundaland after the Southwest Borneo accretion. Ruwai is the first occurrence of Cretaceous mineralization recognized in the Central Borneo metallogenic belt.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"19 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85147850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Skarn ores have recently been identified beneath the historically mined placer Sn deposit at Kanbauk of the Dawei region, southern Myanmar. A large-tonnage skarn ore reserve at Kanbauk is estimated to be over 100 million tonnes, with reported ore grades of 0.17% WO3, 0.26% Sn, and 15.4% CaF2, potentially making it one of the largest W-Sn skarn deposits in the Southeast Asian tin belt. The mineralized skarns lie between marbles to the east and metasediments of the Mergui Group to the west. The timing of the mineralization is unclear, and thus the genetic relationship with regional magmatic events is not known. We report laser ablation-inductively coupled plasma-mass spectrometry U-Pb ages of garnet and cassiterite from the mineralized skarns. Garnet grains from the massive prograde skarns are typically subhedral to euhedral and show both sector and oscillatory zoning. They have 15 to 23% andradite (Ad), 55 to 67% grossularite (Gr), and 16 to 30% pyralspite (Py) (Ad15-23Gr55-67Py16-30) and contain 0.08 to 306 ppm U with a lower intercept 206Pb/238U age of 56.0 ± 1.5 Ma. Cassiterite grains from retrograde veinlets are subhedral to anhedral and have U contents from 110 to 12,000 ppm with a lower intercept 206Pb/238U age of 54.2 ± 1.7 Ma. Garnet and cassiterite have ages consistent within error and can be taken to indicate the formation of the Kanbauk W-Sn(-F) skarn deposit at around 55 Ma. Together with published ages of primary Sn-W deposits in the Dawei region, our study confirms a westwardly younging trend of mineralization toward the coast and provides support for rollback of the Neo-Tethyan subducting slab since the Late Cretaceous, which is considered as the main mechanism for the regional, extensive Sn-W mineralization.
{"title":"IN SITU U-Pb DATING OF GARNET AND CASSITERITE FROM THE KANBAUK W-Sn(-F) SKARN DEPOSIT, DAWEI REGION, SOUTHERN MYANMAR: NEW INSIGHTS ON THE REGIONAL Sn-W METALLOGENY IN THE SOUTHEAST ASIAN TIN BELT","authors":"Wen Winston Zhao, Mei‐Fu Zhou, S. Dudka","doi":"10.5382/econgeo.5002","DOIUrl":"https://doi.org/10.5382/econgeo.5002","url":null,"abstract":"\u0000 Skarn ores have recently been identified beneath the historically mined placer Sn deposit at Kanbauk of the Dawei region, southern Myanmar. A large-tonnage skarn ore reserve at Kanbauk is estimated to be over 100 million tonnes, with reported ore grades of 0.17% WO3, 0.26% Sn, and 15.4% CaF2, potentially making it one of the largest W-Sn skarn deposits in the Southeast Asian tin belt. The mineralized skarns lie between marbles to the east and metasediments of the Mergui Group to the west. The timing of the mineralization is unclear, and thus the genetic relationship with regional magmatic events is not known. We report laser ablation-inductively coupled plasma-mass spectrometry U-Pb ages of garnet and cassiterite from the mineralized skarns. Garnet grains from the massive prograde skarns are typically subhedral to euhedral and show both sector and oscillatory zoning. They have 15 to 23% andradite (Ad), 55 to 67% grossularite (Gr), and 16 to 30% pyralspite (Py) (Ad15-23Gr55-67Py16-30) and contain 0.08 to 306 ppm U with a lower intercept 206Pb/238U age of 56.0 ± 1.5 Ma. Cassiterite grains from retrograde veinlets are subhedral to anhedral and have U contents from 110 to 12,000 ppm with a lower intercept 206Pb/238U age of 54.2 ± 1.7 Ma. Garnet and cassiterite have ages consistent within error and can be taken to indicate the formation of the Kanbauk W-Sn(-F) skarn deposit at around 55 Ma. Together with published ages of primary Sn-W deposits in the Dawei region, our study confirms a westwardly younging trend of mineralization toward the coast and provides support for rollback of the Neo-Tethyan subducting slab since the Late Cretaceous, which is considered as the main mechanism for the regional, extensive Sn-W mineralization.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"32 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72724585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The ABM deposit, Finlayson Lake district, Yukon, Canada, is a bimodal-felsic, replacement-style volcanogenic massive sulfide (VMS) deposit (19.1 Mt @ 6.6 wt % Zn, 0.9 wt % Cu, 2.0 wt % Pb, 1.4 g/t Au, and 148 g/t Ag) hosted by Late Devonian continental back-arc–related volcanosedimentary rocks of the Kudz Ze Kayah formation. The VMS-related hydrothermal alteration associated with the deposit extends >1 km beyond the mineralization. Zones of pervasive sericite and chlorite alteration occur proximal to the massive sulfide lenses (<50 m) both in the hanging wall and the footwall, and zones of pervasive sericite and moderate sericite ± chlorite alteration extend laterally from the mineralization and into the hanging wall and footwall for hundreds to thousands of meters. Geochemical data and petrographic observations indicate that feldspar destruction and formation of white mica and chlorite were the main alteration processes. In both the hanging wall and footwall to the mineralization, base (e.g., Zn, Cu, Pb) and trace metals (e.g., Sb, Tl, Mo) form halos with elevated values up to 100 and 200 m, respectively. The paragenesis and the formation conditions of the hydrothermal alteration were determined through petrography of hydrothermal alteration assemblages and their crosscutting relationships, electron microprobe analyses of the compositions of white mica, chlorite, and carbonate, and illite-chlorite geothermometry. These data suggest that the sericite ± chlorite assemblage was the earliest and most extensive phase of the hydrothermal alteration that formed at temperatures around 215° ± 30°C. Overprinting the sericite-chlorite assemblage is the pervasive sericite assemblage that formed at temperatures around 250° ± 15°C. The pervasive chlorite assemblage formed at temperatures around 320° ± 10°C and overprints the preceding sericite-rich assemblages. Microprobe analyses of white mica and chlorite generally show that Mg-rich varieties are more common proximal to mineralization and formed earlier in the deposit paragenesis than Fe-rich varieties. Mineralogy derived from short-wave infrared data for mica and chlorite, however, shows no clear spatial trends across the deposit due to complex overprinting relationships between alteration minerals.
{"title":"Evolution of the Hydrothermal System Associated with the ABM Replacement-Style Volcanogenic Massive Sulfide Deposit, Finlayson Lake District, Yukon, Canada","authors":"N. Denisová, S. Piercey","doi":"10.5382/econgeo.5004","DOIUrl":"https://doi.org/10.5382/econgeo.5004","url":null,"abstract":"\u0000 The ABM deposit, Finlayson Lake district, Yukon, Canada, is a bimodal-felsic, replacement-style volcanogenic massive sulfide (VMS) deposit (19.1 Mt @ 6.6 wt % Zn, 0.9 wt % Cu, 2.0 wt % Pb, 1.4 g/t Au, and 148 g/t Ag) hosted by Late Devonian continental back-arc–related volcanosedimentary rocks of the Kudz Ze Kayah formation. The VMS-related hydrothermal alteration associated with the deposit extends >1 km beyond the mineralization. Zones of pervasive sericite and chlorite alteration occur proximal to the massive sulfide lenses (<50 m) both in the hanging wall and the footwall, and zones of pervasive sericite and moderate sericite ± chlorite alteration extend laterally from the mineralization and into the hanging wall and footwall for hundreds to thousands of meters. Geochemical data and petrographic observations indicate that feldspar destruction and formation of white mica and chlorite were the main alteration processes. In both the hanging wall and footwall to the mineralization, base (e.g., Zn, Cu, Pb) and trace metals (e.g., Sb, Tl, Mo) form halos with elevated values up to 100 and 200 m, respectively.\u0000 The paragenesis and the formation conditions of the hydrothermal alteration were determined through petrography of hydrothermal alteration assemblages and their crosscutting relationships, electron microprobe analyses of the compositions of white mica, chlorite, and carbonate, and illite-chlorite geothermometry. These data suggest that the sericite ± chlorite assemblage was the earliest and most extensive phase of the hydrothermal alteration that formed at temperatures around 215° ± 30°C. Overprinting the sericite-chlorite assemblage is the pervasive sericite assemblage that formed at temperatures around 250° ± 15°C. The pervasive chlorite assemblage formed at temperatures around 320° ± 10°C and overprints the preceding sericite-rich assemblages. Microprobe analyses of white mica and chlorite generally show that Mg-rich varieties are more common proximal to mineralization and formed earlier in the deposit paragenesis than Fe-rich varieties. Mineralogy derived from short-wave infrared data for mica and chlorite, however, shows no clear spatial trends across the deposit due to complex overprinting relationships between alteration minerals.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"21 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86043436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Perelló, R. Sillitoe, Joaquín Rossello, Julián Forestier, Guido Merino, Diego Charchaflié
Filo del Sol is a composite porphyry-epithermal deposit, straddling the frontier between Argentina and Chile at latitude 28°29′ S, that has attracted a great deal of recent attention because of several drill intersections in excess of 1 km long with unusually high Cu, Au, and Ag grades. The deposit is part of the 8.5-km-long, N- to NE-trending Filo del Sol alignment of porphyry and high-sulfidation epithermal centers, which, in turn, is located in the newly defined Vicuña metallogenic belt that unites the well-known late Oligocene to middle Miocene Maricunga and El Indio belts. The deposit is hosted by Permian felsic volcanic rocks intruded by Triassic monzogranite and, nearer the surface, by shallowly dipping Late Cretaceous volcano-sedimentary rocks. These lithologic units were intruded by several generations of mafic dikes and high-level sills and, in the middle Miocene, by a parallel swarm of composite diorite porphyry dikes. An intermineral magmatic-hydrothermal breccia body is closely associated with the porphyry dikes and subsequently cut at shallow levels by a smaller, finer-grained breccia of phreatic and, possibly, phreatomagmatic origin. Early Cu-Au mineralization, mainly as chalcopyrite, is associated with K-feldspar- and biotite-bearing potassic alteration and accompanying A-type quartz-veinlet stockworks. The potassic zone was massively overprinted and extensively reconstituted by a zone of vuggy residual quartz and silicification in the core of the deposit, flanked by quartz-alunite as part of a more extensive lithocap. These alteration types host high-sulfidation Cu-Au-Ag mineralization as pyrite with early enargite and later bornite, chalcocite, covellite, and numerous Ag-bearing sulfosalts, with the highest grades typically confined to vuggy residual quartz. Largely barren, steam-heated alteration is preserved above and overprinted on the lithocap. The results of radiometric dating (six U-Pb and 22 Re-Os ages) show that porphyry intrusion and potassic alteration began at ~15 Ma and lasted for nearly 1 m.y., although most of the molybdenite samples reported ages from 14.7 to 14.4 ± 0.06 Ma. This short interval coincided with a pulse of regional compressive tectonism accommodated by high-angle, thick-skinned, reverse faulting of basement-cored blocks, and concomitant uplift and exhumation. This uplift gave rise to ~1 km of erosion during formation of the Filo del Sol deposit, thereby accounting for the extreme telescoping of high-sulfidation over porphyry mineralization. Spatial association of these middle Miocene intrusion centers with dated middle Permian and Eocene mineralization suggests deep-seated structural control of the Filo del Sol alignment. Ongoing supergene processes under low-pH conditions produced a near-surface resource dominated by chalcanthite, with minor underlying chalcocite enrichment, as well as partially oxidizing a shallow zone of high-grade Ag mineralization.
Filo del Sol是一个复合斑岩-浅成热液矿床，位于南纬28°29′S，横跨阿根廷和智利之间的边界，由于几个超过1公里长的钻孔交叉点具有异常高的Cu、Au和Ag品位，最近引起了人们的广泛关注。该矿床位于新近确定的Vicuña成矿带中，该成矿带连接着著名的晚渐新世至中新世中期Maricunga和El Indio带。该成矿带长8.5 km，由N- ne向Filo del Sol斑岩和高硫化浅成热液中心组成。矿床赋存于二叠纪长英质火山岩中，受三叠纪二长花岗岩侵入，近地表为浅浸的晚白垩世火山沉积岩。这些岩性单元被几代基性岩脉和高级岩脉侵入，在中新世中期，被平行的闪长斑岩岩脉群侵入。矿间岩浆-热液角砾岩体与斑岩岩脉密切相关，随后在浅层被较小的、细粒的潜水成因角砾岩切割，也可能是潜水成因角砾岩。早期铜金成矿以黄铜矿为主，与含钾长石和黑云母的钾蚀变有关，并伴有a型石英脉入口网。钾质带被大量叠印，并被矿床核心的空洞残余石英和硅化区广泛重建，两侧是石英明矾石，作为更广泛的岩盖的一部分。这些蚀变类型含有高硫化铜-金-银矿化，如黄铁矿、早期辉石矿和晚期斑铜矿、辉铜矿、钴岩矿和大量含银亚硫酸盐，最高品位通常局限于孔洞残余石英中。大部分贫瘠的、蒸汽加热的蚀变被保存在上面，并叠印在岩盖上。放射性测年(6个U-Pb年龄和22个Re-Os年龄)结果表明，斑岩侵入和钾蚀变始于~15 Ma，持续时间近1 Ma，而辉钼矿样品的年龄大多在14.7 ~ 14.4±0.06 Ma之间。这一短间隔与区域挤压构造运动的脉冲相吻合，该运动由基底核块体的高角度、厚皮、逆断裂以及伴随的隆升和掘出所适应。在Filo del Sol矿床形成过程中，这种隆起造成了约1公里的侵蚀，从而导致了斑岩矿化的高硫化物的极端伸缩。这些中中新世侵入中心与中二叠世和始新世成矿时间的空间关联表明，Filo del Sol走向受深层构造控制。在低ph条件下持续的表生作用形成了以辉铜矿为主的近地表资源，下伏辉铜矿少量富集，并部分氧化了浅层高品位银矿化带。
{"title":"Geology of Porphyry Cu-Au and Epithermal Cu-Au-Ag Mineralization at Filo del Sol, Argentina-Chile: Extreme Telescoping During Andean Uplift","authors":"J. Perelló, R. Sillitoe, Joaquín Rossello, Julián Forestier, Guido Merino, Diego Charchaflié","doi":"10.5382/econgeo.5029","DOIUrl":"https://doi.org/10.5382/econgeo.5029","url":null,"abstract":"\u0000 Filo del Sol is a composite porphyry-epithermal deposit, straddling the frontier between Argentina and Chile at latitude 28°29′ S, that has attracted a great deal of recent attention because of several drill intersections in excess of 1 km long with unusually high Cu, Au, and Ag grades. The deposit is part of the 8.5-km-long, N- to NE-trending Filo del Sol alignment of porphyry and high-sulfidation epithermal centers, which, in turn, is located in the newly defined Vicuña metallogenic belt that unites the well-known late Oligocene to middle Miocene Maricunga and El Indio belts. The deposit is hosted by Permian felsic volcanic rocks intruded by Triassic monzogranite and, nearer the surface, by shallowly dipping Late Cretaceous volcano-sedimentary rocks. These lithologic units were intruded by several generations of mafic dikes and high-level sills and, in the middle Miocene, by a parallel swarm of composite diorite porphyry dikes. An intermineral magmatic-hydrothermal breccia body is closely associated with the porphyry dikes and subsequently cut at shallow levels by a smaller, finer-grained breccia of phreatic and, possibly, phreatomagmatic origin. Early Cu-Au mineralization, mainly as chalcopyrite, is associated with K-feldspar- and biotite-bearing potassic alteration and accompanying A-type quartz-veinlet stockworks. The potassic zone was massively overprinted and extensively reconstituted by a zone of vuggy residual quartz and silicification in the core of the deposit, flanked by quartz-alunite as part of a more extensive lithocap. These alteration types host high-sulfidation Cu-Au-Ag mineralization as pyrite with early enargite and later bornite, chalcocite, covellite, and numerous Ag-bearing sulfosalts, with the highest grades typically confined to vuggy residual quartz. Largely barren, steam-heated alteration is preserved above and overprinted on the lithocap. The results of radiometric dating (six U-Pb and 22 Re-Os ages) show that porphyry intrusion and potassic alteration began at ~15 Ma and lasted for nearly 1 m.y., although most of the molybdenite samples reported ages from 14.7 to 14.4 ± 0.06 Ma. This short interval coincided with a pulse of regional compressive tectonism accommodated by high-angle, thick-skinned, reverse faulting of basement-cored blocks, and concomitant uplift and exhumation. This uplift gave rise to ~1 km of erosion during formation of the Filo del Sol deposit, thereby accounting for the extreme telescoping of high-sulfidation over porphyry mineralization. Spatial association of these middle Miocene intrusion centers with dated middle Permian and Eocene mineralization suggests deep-seated structural control of the Filo del Sol alignment. Ongoing supergene processes under low-pH conditions produced a near-surface resource dominated by chalcanthite, with minor underlying chalcocite enrichment, as well as partially oxidizing a shallow zone of high-grade Ag mineralization.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"170 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75997757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Declercq, R. Bowell, C. Brough, A. Barnes, R. Griffiths
Mineral carbonation reactions consume CO2 and thus have the potential for the long-term fixation of atmospheric CO2. This paper explores the possibility of integrating industrial-scale carbon storage into mining operations. Ultramafic rocks are typically considered to be one the most promising rocks for carbon capture and storage owing to their high content of Mg-bearing silicate minerals, such as forsterite (Mg2SiO4) and serpentine (Mg3Si2O5(OH)4). Beyond the thermodynamic considerations showing that magnesite (MgCO3) and quartz (SiO2) form from forsterite and serpentine alteration, the degree to which CO2 is carbonated depends on the kinetics of the reaction. For industrial carbon capture and storage to be viable, reasonable carbonation efficiency has to be achieved. To this effect, the reaction rates have to be increased, which can be achieved either by increasing the reactive surface area, increasing the reaction temperature, or using reagents to drive the reactions. However, these approaches are usually energy demanding or not efficient enough. As part of its activities, the mining industry excavates tens or hundreds of million metric tons of rock per mine and in certain areas these mafic rock groups can represent a significant percentage of the waste material left on the surface. This could represent a locally important source of readily available material for carbon capture and storage if the conversion process is sufficiently efficient. To test and quantify the carbonation potential of mine waste, a sample of serpentine skarn waste rock obtained from an iron ore mine in Sweden was reacted for 60 weeks in a laboratory humidity-cell test (HCT) at 20°C. The results show the dissolution of olivine, the precipitation of serpentine, an increase in the neutralization potential of the sample, and the appearance of inorganic carbon during the 60 weeks of testing. At ambient temperatures the sluggish precipitation kinetics of secondary phases will favor the formation of more hydrous Mg silicate phases, such as serpentine (Mg3Si2O5(OH)4), in place of Mg-bearing carbonates. This reaction lowers considerably the efficiency of forsterite carbonation, as only 25% of the Mg released from forsterite dissolution to form carbonate minerals. This study aims to model the carbonation efficiency of Mg silicates through the use of models supported by laboratory testwork and taking the example of a mine site in northern Sweden. This study evaluates the reaction of CO2 with Mg-bearing silicate rocks and the demonstration that carbonation reactions occur with Mg silicate wastes consuming CO2. Consequently, weathering of waste rock may well represent an important sink for carbon in the environment.
{"title":"Role of Mg Gangue Minerals in Natural Analogue CO2 Sequestration","authors":"J. Declercq, R. Bowell, C. Brough, A. Barnes, R. Griffiths","doi":"10.5382/econgeo.4981","DOIUrl":"https://doi.org/10.5382/econgeo.4981","url":null,"abstract":"\u0000 Mineral carbonation reactions consume CO2 and thus have the potential for the long-term fixation of atmospheric CO2. This paper explores the possibility of integrating industrial-scale carbon storage into mining operations. Ultramafic rocks are typically considered to be one the most promising rocks for carbon capture and storage owing to their high content of Mg-bearing silicate minerals, such as forsterite (Mg2SiO4) and serpentine (Mg3Si2O5(OH)4). Beyond the thermodynamic considerations showing that magnesite (MgCO3) and quartz (SiO2) form from forsterite and serpentine alteration, the degree to which CO2 is carbonated depends on the kinetics of the reaction. For industrial carbon capture and storage to be viable, reasonable carbonation efficiency has to be achieved. To this effect, the reaction rates have to be increased, which can be achieved either by increasing the reactive surface area, increasing the reaction temperature, or using reagents to drive the reactions. However, these approaches are usually energy demanding or not efficient enough.\u0000 As part of its activities, the mining industry excavates tens or hundreds of million metric tons of rock per mine and in certain areas these mafic rock groups can represent a significant percentage of the waste material left on the surface. This could represent a locally important source of readily available material for carbon capture and storage if the conversion process is sufficiently efficient.\u0000 To test and quantify the carbonation potential of mine waste, a sample of serpentine skarn waste rock obtained from an iron ore mine in Sweden was reacted for 60 weeks in a laboratory humidity-cell test (HCT) at 20°C. The results show the dissolution of olivine, the precipitation of serpentine, an increase in the neutralization potential of the sample, and the appearance of inorganic carbon during the 60 weeks of testing. At ambient temperatures the sluggish precipitation kinetics of secondary phases will favor the formation of more hydrous Mg silicate phases, such as serpentine (Mg3Si2O5(OH)4), in place of Mg-bearing carbonates. This reaction lowers considerably the efficiency of forsterite carbonation, as only 25% of the Mg released from forsterite dissolution to form carbonate minerals. This study aims to model the carbonation efficiency of Mg silicates through the use of models supported by laboratory testwork and taking the example of a mine site in northern Sweden.\u0000 This study evaluates the reaction of CO2 with Mg-bearing silicate rocks and the demonstration that carbonation reactions occur with Mg silicate wastes consuming CO2. Consequently, weathering of waste rock may well represent an important sink for carbon in the environment.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"28 6 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88897326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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