Sulfur is closely associated with various types of ore deposits,particularly orogenic gold(Au)systems,where sulfur-bearing melts and fluids play a critical role in transporting oreforming elements essential for ore fo...Sulfur is closely associated with various types of ore deposits,particularly orogenic gold(Au)systems,where sulfur-bearing melts and fluids play a critical role in transporting oreforming elements essential for ore formation.The widely accepted metamorphic devolatilization model suggests that compositionally fertile sedimentary rocks serve as potential gold sources.Therefore,understanding sulfur behavior during prograde metamorphism is essential for elucidating the mechanisms underlying metal activation and mobility.In this study,we conducted in-situ sulfur isotope(δ^(34)S)analyses using secondary ion mass spectrometry(SIMS)on samples from the Hongshankou area,a representative Barrovian-type metamorphic sequence characterized by intermediate pressure-temperature(P-T)conditions.This sequence comprises the biotite,garnet,staurolite,and kyanite zones.Our results show a systematic increase in δ^(34)S values(from 3.1‰ to 5.5‰)coupled with a progressive decrease in total sulfur content(from 320 ppm to 165 ppm)as metamorphic grade increases.The most pronounced sulfur mobilization occurs between the garnet and staurolite zones.In all analyzed samples,Au or Au-bearing minerals predominantly occur along the edges or within pyrite grains,highlighting the critical role of pyrite breakdown in controlling gold mobility.Thus,sulfur isotope fractionation provides robust constraints for quantitatively assessing sulfur mobility during metamorphism.These findings reinforce the concept that metasedimentary rocks and their metamorphic fluids represent fertile sources of Au and other metals enriched in orogenic gold deposits.展开更多
In igneous-intruded coal seams,coal undergoes significant metamorphism,which critically alters its pore structure and oxygen consumption dynamics,thereby elevating its spontaneous combustion tendency.This study invest...In igneous-intruded coal seams,coal undergoes significant metamorphism,which critically alters its pore structure and oxygen consumption dynamics,thereby elevating its spontaneous combustion tendency.This study investigates the specific surface area,pore volume,structure complexity/connectivity,heterogeneity/local features of pore size distribution,and oxygen consumption dynamics of igneous metamorphic coal through N_(2)/CO_(2) isothermal adsorption tests and low-temperature oxidation experiments,and elucidates the influence mechanisms of pore structure evolution on oxygen consumption dynamics during low-temperature oxidation.With increasing metamorphic degree,igneous metamorphic coal exhibits a more pronounced reduction in specific surface area during oxidation,while the increase in structure complexity due to coal-oxygen reactions is suppressed.Thermally metamorphic coal demonstrates accelerated oxygen consumption,with oxidation amplifying the difference in reaction rates compared to raw coal.Key mechanisms include oxidation-induced reduction in mesopore complexity and micropore volume,decreased dominance of small-pore-volume apertures,and increased heterogeneity,collectively leading to a lower half-oxygen-consuming temperature and steeper oxygen consumption curves.Simultaneously,increased pore volume/complexity and reduced uniformity/connectivity act synergistically to enhance oxygen consumption capacity,highlighting the coupling between pore structure evolution and oxidation behavior in igneous metamorphic coal.This study provides theoretical insights into the pore-oxygen coupling mechanisms governing coal spontaneous combustion in igneous intrusion areas.展开更多
Debate has persisted over whether the metamorphic basement of the Zhoushan Islands,easternmost Cathaysia Block,is Precambrian.Here,representative metamorphic rocks from the Qushan Islands were investigated using petro...Debate has persisted over whether the metamorphic basement of the Zhoushan Islands,easternmost Cathaysia Block,is Precambrian.Here,representative metamorphic rocks from the Qushan Islands were investigated using petrography,mineral chemistry,phase equilibria modeling and SHRIMP zircon U-Pb dating to constrain their metamorphic evolution and tectonic significance.Both the pelitic granulites(garnet-kyanite-perthite-biotite-quartz)and the mafic granulites(garnet-clinopyroxene-amphibole-plagioclase-quartz)reached high-pressure granulite-facies conditions of 1.2-1.4 GPa/820-900℃,and recorded three metamorphic stages along a clockwise P-T path with post-peak isothermal decompression.This trajectory indicated rapid exhumation of thickened continental crust during collisional orogeny.Metamorphic ages of 254±3 Ma,262±4 Ma and 259±3 Ma were obtained for mafic granulite,pelitic granulite and marble,respectively,and were consistent with the emplacement age of 259±4 Ma for a pegmatite vein.Detrital zircons in metasediments spanned 2706-330 Ma,which constrained the latest deposition to~330 Ma;thus represented mid-Paleozoic sediment metamorphosed during the late Paleozoic rather than Precambrian basement.We conclude that the Indosinian tectonothermal event in the Cathaysia Block had originated from late Paleozoic-early Mesozoic collisional orogeny between the South China Plate to the north and the Indochina Block to the south.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42225301 and 42330304)。
文摘Sulfur is closely associated with various types of ore deposits,particularly orogenic gold(Au)systems,where sulfur-bearing melts and fluids play a critical role in transporting oreforming elements essential for ore formation.The widely accepted metamorphic devolatilization model suggests that compositionally fertile sedimentary rocks serve as potential gold sources.Therefore,understanding sulfur behavior during prograde metamorphism is essential for elucidating the mechanisms underlying metal activation and mobility.In this study,we conducted in-situ sulfur isotope(δ^(34)S)analyses using secondary ion mass spectrometry(SIMS)on samples from the Hongshankou area,a representative Barrovian-type metamorphic sequence characterized by intermediate pressure-temperature(P-T)conditions.This sequence comprises the biotite,garnet,staurolite,and kyanite zones.Our results show a systematic increase in δ^(34)S values(from 3.1‰ to 5.5‰)coupled with a progressive decrease in total sulfur content(from 320 ppm to 165 ppm)as metamorphic grade increases.The most pronounced sulfur mobilization occurs between the garnet and staurolite zones.In all analyzed samples,Au or Au-bearing minerals predominantly occur along the edges or within pyrite grains,highlighting the critical role of pyrite breakdown in controlling gold mobility.Thus,sulfur isotope fractionation provides robust constraints for quantitatively assessing sulfur mobility during metamorphism.These findings reinforce the concept that metasedimentary rocks and their metamorphic fluids represent fertile sources of Au and other metals enriched in orogenic gold deposits.
基金supported by the National Natural Science Foundation of China(No.52374247)the Joint Funds of the National Natural Science Foundation of China(No.U24B2042).
文摘In igneous-intruded coal seams,coal undergoes significant metamorphism,which critically alters its pore structure and oxygen consumption dynamics,thereby elevating its spontaneous combustion tendency.This study investigates the specific surface area,pore volume,structure complexity/connectivity,heterogeneity/local features of pore size distribution,and oxygen consumption dynamics of igneous metamorphic coal through N_(2)/CO_(2) isothermal adsorption tests and low-temperature oxidation experiments,and elucidates the influence mechanisms of pore structure evolution on oxygen consumption dynamics during low-temperature oxidation.With increasing metamorphic degree,igneous metamorphic coal exhibits a more pronounced reduction in specific surface area during oxidation,while the increase in structure complexity due to coal-oxygen reactions is suppressed.Thermally metamorphic coal demonstrates accelerated oxygen consumption,with oxidation amplifying the difference in reaction rates compared to raw coal.Key mechanisms include oxidation-induced reduction in mesopore complexity and micropore volume,decreased dominance of small-pore-volume apertures,and increased heterogeneity,collectively leading to a lower half-oxygen-consuming temperature and steeper oxygen consumption curves.Simultaneously,increased pore volume/complexity and reduced uniformity/connectivity act synergistically to enhance oxygen consumption capacity,highlighting the coupling between pore structure evolution and oxidation behavior in igneous metamorphic coal.This study provides theoretical insights into the pore-oxygen coupling mechanisms governing coal spontaneous combustion in igneous intrusion areas.
基金supported by the National Natural Science Foundation of China(42072223)Geological Survey project(DD20221649,DD20231429).
文摘Debate has persisted over whether the metamorphic basement of the Zhoushan Islands,easternmost Cathaysia Block,is Precambrian.Here,representative metamorphic rocks from the Qushan Islands were investigated using petrography,mineral chemistry,phase equilibria modeling and SHRIMP zircon U-Pb dating to constrain their metamorphic evolution and tectonic significance.Both the pelitic granulites(garnet-kyanite-perthite-biotite-quartz)and the mafic granulites(garnet-clinopyroxene-amphibole-plagioclase-quartz)reached high-pressure granulite-facies conditions of 1.2-1.4 GPa/820-900℃,and recorded three metamorphic stages along a clockwise P-T path with post-peak isothermal decompression.This trajectory indicated rapid exhumation of thickened continental crust during collisional orogeny.Metamorphic ages of 254±3 Ma,262±4 Ma and 259±3 Ma were obtained for mafic granulite,pelitic granulite and marble,respectively,and were consistent with the emplacement age of 259±4 Ma for a pegmatite vein.Detrital zircons in metasediments spanned 2706-330 Ma,which constrained the latest deposition to~330 Ma;thus represented mid-Paleozoic sediment metamorphosed during the late Paleozoic rather than Precambrian basement.We conclude that the Indosinian tectonothermal event in the Cathaysia Block had originated from late Paleozoic-early Mesozoic collisional orogeny between the South China Plate to the north and the Indochina Block to the south.
