Although the term orogenic gold deposit has been widely accepted for all gold-only lode-gold deposits,with the exception of Carlin-type deposits and rare intrusion-related gold systems,there has been continuing debate...Although the term orogenic gold deposit has been widely accepted for all gold-only lode-gold deposits,with the exception of Carlin-type deposits and rare intrusion-related gold systems,there has been continuing debate on their genesis.Early syngenetic models and hydrothermal models dominated by meteoric fluids are now clearly unacceptable.Magmatic-hydrothermal models fail to explain the genesis of orogenic gold deposits because of the lack of consistent spatially- associated granitic intrusions and inconsistent temporal relationships.The most plausible,and widely accepted,models involve metamorphic fluids,but the source of these fluids is hotly debated.Sources within deeper segments of the supracrustal successions hosting the deposits,the underlying continental crust,and subducted oceanic lithosphere and its overlying sediment wedge all have their proponents.The orogenic gold deposits of the giant Jiaodong gold province of China,in the delaminated North China Craton,contain ca.120 Ma gold deposits in Precambrian crust that was metamorphosed over 2000 million years prior to gold mineralization.The only realistic source of fluid and gold is a subducted oceanic slab with its overlying sulfide-rich sedimentary package,or the associated mantle wedge.This could be viewed as an exception to a general metamorphic model where orogenic gold has been derived during greenschist- to amphibolite-facies metamorphism of supracrustal rocks：basaltic rocks in the Precambrian and sedimentary rocks in the Phanerozoic.Alternatively,if a holistic view is taken,Jiaodong can be considered the key orogenic gold province for a unified model in which gold is derived from late-orogenic metamorphic devolatilization of stalled subduction slabs and oceanic sediments throughout Earth history.The latter model satisfies all geological,geochronological,isotopic and geochemical constraints but the precise mechanisms of auriferous fluid release,like many other subduction-related processes,are model-driven and remain uncertain.展开更多
The reservoirs of the Upper Triassic Xujiahe Formation in Sichuan Basin have the characteristics of low compositional maturity, low contents of cements and medium textural maturity. The general physical properties of ...The reservoirs of the Upper Triassic Xujiahe Formation in Sichuan Basin have the characteristics of low compositional maturity, low contents of cements and medium textural maturity. The general physical properties of the reservoirs are poor, with low porosity and low permeability, and there are only a few reservoirs with medium porosity and low permeability in local areas. Based on the diagenetic mineral association, a diagenetic sequence of cements is established: early calcites (or micrite siderites) →first quartz overgrowth→chlorite coatings→dissolution of feldspars and debris→chlorite linings→ second quartz overgrowth (quartz widen or filled in remain intergranular pores and solution pores)→dissolution→third quartz overgrowth (quartz filled in intergranular and intragranular solution pores)→intergrowth (ferro) calcites→dolomites→ferro (calcites) dolomites→later dissolution→veins of quartz and calcites formation. Mechanical compaction is the main factor in making the reservoirs tight in the basin, followed by the second and third quartz overgrowth. In a long-term closed system, only feld-spars and some lithic fragments are dissolved by diagenetic fluids, while intergranular cements such as quartz and calcit are not dissolved and thus have little influence on the porosity of the Xujiahe Formation. This is the third factor that may have kept the sandstones of Xujiahe Formation tight finally. The hydrocarbon was extensively generated from organic materials after the second quartz overgrowth, and selectively entered favorable reservoirs to form tight sandstone gas reservoirs.展开更多
Metallogensis of the Xiadian gold deposit in Shandong Province has been a question under dispute for a long time. There are many points such as metamorphic hydrothermal, magamatic hydrothermal and meteoric water. Deta...Metallogensis of the Xiadian gold deposit in Shandong Province has been a question under dispute for a long time. There are many points such as metamorphic hydrothermal, magamatic hydrothermal and meteoric water. Detailed study shows that mantle-rooted fluids were involved in the ore-forming processes. Evidence for this argumentation comes from: (1) discordogenic fault; (2) intersecting and accompanying of basic veins and lodes; (3) geochemistry of stable isotopes; (4) geochemistry of fluid inclusions; and (5) multi-level circulation and exchanging of mantle-rooted fluids. Based on the characteristics of the circulation system of mantle-rooted fluids and its close relation to magmatic hydrothermal fluids and meteoric water, ore-bearing fluids are divided into three subsystems: (1) C-H-O-rich fluid circulation subsystem in mantle, (2) Si-rich fluid circulation subsystem in the middle and lower crust; and (3) S-rich fluid circulation subsystem in shallow and surface crust. Ore-forming functions of these subsystems are controlled respectively by their different geodynamic settings.展开更多
Stable carbon isotope geochemistry provides important information for the recognition of funda- mental isotope exchange processes related to the movement of carbon in the lithosphere and permits the elab- oration of m...Stable carbon isotope geochemistry provides important information for the recognition of funda- mental isotope exchange processes related to the movement of carbon in the lithosphere and permits the elab- oration of models for the global carbon cycle. Carbon isotope ratios in fluid-deposited graphite are powerful tools for unravelling the ultimate origin of carbon （organic matter, mantle, or carbonates） and help to constrain the fluid history and the mechanisms involved in graphite deposition. Graphite precipitation in fluid-deposited occurrences results from C02- and/or CH4-bearing aqueous fluids. Fluid flow can be considered as both a closed （without replenishment of the fluid） or an open system （with renewal of the fluid by successive fluid batches）. In closed systems, carbon isotope systematics in graphite is mainly governed by Rayleigh precipi- tation and/or by changes in temperature affecting the fractionation factor between fluid and graphite. Such processes result in zoned graphite crystals or in successive graphite generations showing, in both cases, isotopic variation towards progressive 13C or 12C enrichment （depending upon the dominant carbon phase in the fluid, C02 or CH4, respectively）. In open systems, in which carbon is episodically introduced along the fracture systems, the carbon systematics is more complex and individual graphite crystals may display oscillatory zoning because of Rayleigh precipitation or heterogeneous variations of 613C values when mixing of fluids or changes in the composition of the fluids are the mechanisms responsible for graphite precipitation.展开更多
The composition of gases trapped in olivine, orthopyroxene and clinopyroxene in Iherzolite xenoliths collected from different locations in eastern China has been measured by the vacuum stepped-heating mass spectrometr...The composition of gases trapped in olivine, orthopyroxene and clinopyroxene in Iherzolite xenoliths collected from different locations in eastern China has been measured by the vacuum stepped-heating mass spectrometry. These xenoliths are hosted in alkali basalts and considered as residues of partial melting of the upper mantle, and may contain evidence of mantle evolution. The results show that various kinds of fluid inclusions in Iherzolite xenoliths have been released at distinct times, which could be related to different stages of mantle evolution. In general, primitive fluids of the upper mantle (PFUM) beneath eastern China are dominated by H2, CO2 and CO, and are characterized by high contents of H2 and reduced gases. The compositions of PFUM are highly variable and related to tectonic settings. CO, CO2 and H2 are the main components of the PFUM beneath cratons; the PFUM in the mantle enriched in potassic metasomatism in the northern part of northeastern China has a high content of H2, while CO2 and SO2 are the dominant components of the PFUM in the Su-Lu-Wan (Jiangsu-Shandong-Anhui) region, where recycled crustal fluids were mixed with deeper mantle components. There are several fluids with distinct compositions beneath eastern China, such as primitive fluids of upper mantle (CO, CO2 and H2), partial melting fluids (CO2 and CO) and metasomatic fluids mixed with recycled crustal fluids (CO2, N2, SO2 and CH4) etc. Fluids of the upper mantle beneath the North China craton are different from that of the South China craton in total gases and chemical compositions: the contents of the reduced gases of the PFUM in the NCC are higher than those in the SCC.展开更多
The first marine gas hydrate expedition in China has been conducted by Guangzhou Marine Geological Survey in the Shenhu Area, northern continental slope of the South China Sea. Previous study has analyzed the P-T cond...The first marine gas hydrate expedition in China has been conducted by Guangzhou Marine Geological Survey in the Shenhu Area, northern continental slope of the South China Sea. Previous study has analyzed the P-T conditions, geophysical anomalies and saturation calculations of these gas hydrates, but has not documented in detail the migration of gas-bearing fluids in the study area. Based on the interpretations of 2D/3D seismic data, this work identified two types of migration pathways for gas-bearing fluids in the Shenhu area, i.e., vertical and lateral pathways. The vertical pathways（largescale faults, gas chimneys and mud diapirs） presented as steep seismic reflection anomalies, which could be traced downward to the Eocene source rocks and may penetrate into the Late Miocene strata. The deeper gases/fluids might be allowed migrating into the shallower strata through these vertical conduits. However, the distributions showed distinct differences between these pathways. Large-scale faults developed only in the north and northeast of the Shenhu area, while in the drilling area gas chimneys were the sole vertical migration pathways. Since the Pliocene, normal faults, detachment faults and favorable sediments have constituted the lateral pathways in the Shenhu gas hydrate drilling area. Although these lateral pathways were connected with gas chimneys, they exerted different effects on hydrate formation and accumulation. Gas-bearing fluids migrated upward along gas chimneys might further migrate laterally because of the normal faults, thereby enlarging the range of the chimneys. Linking gas chimneys with the seafloor, the detachment faults might act as conduits for escaping gases/fluids. Re-deposited sediments developed at the early stage of the Quaternary were located within the gas hydrate stability zone, so hydrates would be enriched in these favorable sediments. Compared with the migration pathways（large-scale faults and mud diapirs） in the LW3-1 deep-sea oil/gas field, the migration efficiency of the ve展开更多
The genesis of giant gold provinces is an international scientific frontier,in which the source of a huge amount of gold and the drive for mineralization are key challenges.The mineralization intensity of the Jiaodong...The genesis of giant gold provinces is an international scientific frontier,in which the source of a huge amount of gold and the drive for mineralization are key challenges.The mineralization intensity of the Jiaodong gold province in eastern China is a rare occasion in the world,because it owns gold reserves of~5500 tons within an area of less than 10,000 km^(2).The Jiaodong gold province formed in the superimposed domain of diverse tectonic regimes in an intracontinental setting.Paleoproterozoic regional peak metamorphism and Triassic continental collision are followed by the tectonic transition and gold mineralization at ca.120 Ma with time intervals of 1.9 billion years and about 100 million years,respectively.The Jiaodong gold deposits are different from orogenic and intrusion-related gold deposits in terms of the tectonic background,types of host rocks,and oreforming mechanism.These gold deposits show close spatial-temporal and genetic relationships to mafic igneous rocks,implying the derivation of ore-forming fluids from the metasomatic mantle domains.Mafic dykes in Jiaodong have negativeε_(Hf)(t)values of-29.9 to-9.1,Os content of 0.002-0.16 ppb,heavyδ^(18)O up to 8.23‰,and high initial^(187)Os/^(188)Os ratios of 0.1352-0.8858.These indicate that the lithospheric mantle was metasomatized by ancient crust-derived components.The lithospheric mantle in the western Jiaodong shows generally more enriched isotope features than that in the eastern part,which is explained to be an important reason for its huge gold resources.The mafic dykes show lighter Mg isotope characteristics(averageδ^(26)Mg of-0.33‰,n=50)and high Ca O content(overall greater than 6.5 wt%),indicating that the lithospheric mantle would also record the metasomatism by the carbonate rocks from the subducting oceanic slab.Under the background of the rollback of the subducting paleo-Pacific slab and the destruction of the North China Craton,partial melting of the lower crust would produce granitic magmas that led to the enrichment of gold i展开更多
The Jinding superlarge lead and zinc deposit has attracted the attention of geologists of the world and its metallogenesis has long been in dispute. This paper takes the Jinding deposit and the Baiyangping Cu-Ag-Co de...The Jinding superlarge lead and zinc deposit has attracted the attention of geologists of the world and its metallogenesis has long been in dispute. This paper takes the Jinding deposit and the Baiyangping Cu-Ag-Co deposit which was recently found at about 30 km north of Jinding as one ore belt, and, based on researches on the helium, argon, and xenon isotopic compositions of primary inclusions in ore-forming solutions of the main stage, the authors have found that the 3He/4He ratio of the ore-forming fluid is 2.7×10?6 (varying from 0.19 to 1.97 Ra), the 4He/40Ar ratio (0.24–3.12) is close to the mantle characteristic ratio, and the xenon isotopic composition and evolution show characters of the mantle xenon. The above results reveal the characteristics of mantle source and crust-mantle fluid mixing (mantle helium reaching 32%) and the metallogenic contributions of the deep processes in the Jinding-Baiyangping ore belt.展开更多
We synthesize significant recent results on the deep structure and origin of the active volcanoes in China's Mainland. Magmatism in the western Pacific arc and back-arc areas is caused by dehydration of the subduc...We synthesize significant recent results on the deep structure and origin of the active volcanoes in China's Mainland. Magmatism in the western Pacific arc and back-arc areas is caused by dehydration of the subducting slab and by corner flow in the mantle wedge, whereas the intraplate magmatism in China has different origins. The active volcanoes in Northeast China （such as the Changbai and Wudalianchi） are caused by hot upwelling in the big mantle wedge （BMW） above the stagnant slab in the mantle transition zone and deep slab dehydration as well. The Tengchong volcano in Southwest China is caused by a similar process in the BMW above the subducting Burma microplate （or Indian plate）. The Hainan volcano in southernmost China is a hotspot fed by a lower-mantle plume which may be associated with the Pacific and Philippine Sea slabs＇ deep subduction in the east and the Indian slab＇s deep subduction in the west down to the lower mantle. The stagnant slab finally collapses down to the bottom of the mantle, which can trigger the upwelling of hot mantle materials from the lower mantle to the shallow mantle beneath the subducting slabs and may cause the slab-plume interactions.展开更多
文摘Although the term orogenic gold deposit has been widely accepted for all gold-only lode-gold deposits,with the exception of Carlin-type deposits and rare intrusion-related gold systems,there has been continuing debate on their genesis.Early syngenetic models and hydrothermal models dominated by meteoric fluids are now clearly unacceptable.Magmatic-hydrothermal models fail to explain the genesis of orogenic gold deposits because of the lack of consistent spatially- associated granitic intrusions and inconsistent temporal relationships.The most plausible,and widely accepted,models involve metamorphic fluids,but the source of these fluids is hotly debated.Sources within deeper segments of the supracrustal successions hosting the deposits,the underlying continental crust,and subducted oceanic lithosphere and its overlying sediment wedge all have their proponents.The orogenic gold deposits of the giant Jiaodong gold province of China,in the delaminated North China Craton,contain ca.120 Ma gold deposits in Precambrian crust that was metamorphosed over 2000 million years prior to gold mineralization.The only realistic source of fluid and gold is a subducted oceanic slab with its overlying sulfide-rich sedimentary package,or the associated mantle wedge.This could be viewed as an exception to a general metamorphic model where orogenic gold has been derived during greenschist- to amphibolite-facies metamorphism of supracrustal rocks：basaltic rocks in the Precambrian and sedimentary rocks in the Phanerozoic.Alternatively,if a holistic view is taken,Jiaodong can be considered the key orogenic gold province for a unified model in which gold is derived from late-orogenic metamorphic devolatilization of stalled subduction slabs and oceanic sediments throughout Earth history.The latter model satisfies all geological,geochronological,isotopic and geochemical constraints but the precise mechanisms of auriferous fluid release,like many other subduction-related processes,are model-driven and remain uncertain.
基金the National Basic Research Program of China (Grant No. 2007CB209500)the Eleventh Five Year Key Science and Technology Item of PetroChina (Grant No. 07-01A-01)
文摘The reservoirs of the Upper Triassic Xujiahe Formation in Sichuan Basin have the characteristics of low compositional maturity, low contents of cements and medium textural maturity. The general physical properties of the reservoirs are poor, with low porosity and low permeability, and there are only a few reservoirs with medium porosity and low permeability in local areas. Based on the diagenetic mineral association, a diagenetic sequence of cements is established: early calcites (or micrite siderites) →first quartz overgrowth→chlorite coatings→dissolution of feldspars and debris→chlorite linings→ second quartz overgrowth (quartz widen or filled in remain intergranular pores and solution pores)→dissolution→third quartz overgrowth (quartz filled in intergranular and intragranular solution pores)→intergrowth (ferro) calcites→dolomites→ferro (calcites) dolomites→later dissolution→veins of quartz and calcites formation. Mechanical compaction is the main factor in making the reservoirs tight in the basin, followed by the second and third quartz overgrowth. In a long-term closed system, only feld-spars and some lithic fragments are dissolved by diagenetic fluids, while intergranular cements such as quartz and calcit are not dissolved and thus have little influence on the porosity of the Xujiahe Formation. This is the third factor that may have kept the sandstones of Xujiahe Formation tight finally. The hydrocarbon was extensively generated from organic materials after the second quartz overgrowth, and selectively entered favorable reservoirs to form tight sandstone gas reservoirs.
基金supported by the National Natural Science Foundation of China(Nos.40172036 and 40272051)the Science and Technology Research Key Project of the Ministry of Education(Grant No.01037)the Foundation for University Key Teachers by the Ministry of Education and the National Key Basic Research Project(Grant No.1999043206).
文摘Metallogensis of the Xiadian gold deposit in Shandong Province has been a question under dispute for a long time. There are many points such as metamorphic hydrothermal, magamatic hydrothermal and meteoric water. Detailed study shows that mantle-rooted fluids were involved in the ore-forming processes. Evidence for this argumentation comes from: (1) discordogenic fault; (2) intersecting and accompanying of basic veins and lodes; (3) geochemistry of stable isotopes; (4) geochemistry of fluid inclusions; and (5) multi-level circulation and exchanging of mantle-rooted fluids. Based on the characteristics of the circulation system of mantle-rooted fluids and its close relation to magmatic hydrothermal fluids and meteoric water, ore-bearing fluids are divided into three subsystems: (1) C-H-O-rich fluid circulation subsystem in mantle, (2) Si-rich fluid circulation subsystem in the middle and lower crust; and (3) S-rich fluid circulation subsystem in shallow and surface crust. Ore-forming functions of these subsystems are controlled respectively by their different geodynamic settings.
基金contribution from project CGL2010-16008 (Spanish Ministry for Science and Innovation)
文摘Stable carbon isotope geochemistry provides important information for the recognition of funda- mental isotope exchange processes related to the movement of carbon in the lithosphere and permits the elab- oration of models for the global carbon cycle. Carbon isotope ratios in fluid-deposited graphite are powerful tools for unravelling the ultimate origin of carbon （organic matter, mantle, or carbonates） and help to constrain the fluid history and the mechanisms involved in graphite deposition. Graphite precipitation in fluid-deposited occurrences results from C02- and/or CH4-bearing aqueous fluids. Fluid flow can be considered as both a closed （without replenishment of the fluid） or an open system （with renewal of the fluid by successive fluid batches）. In closed systems, carbon isotope systematics in graphite is mainly governed by Rayleigh precipi- tation and/or by changes in temperature affecting the fractionation factor between fluid and graphite. Such processes result in zoned graphite crystals or in successive graphite generations showing, in both cases, isotopic variation towards progressive 13C or 12C enrichment （depending upon the dominant carbon phase in the fluid, C02 or CH4, respectively）. In open systems, in which carbon is episodically introduced along the fracture systems, the carbon systematics is more complex and individual graphite crystals may display oscillatory zoning because of Rayleigh precipitation or heterogeneous variations of 613C values when mixing of fluids or changes in the composition of the fluids are the mechanisms responsible for graphite precipitation.
基金the Natural Science Foundation of China(grant 40273009).
文摘The composition of gases trapped in olivine, orthopyroxene and clinopyroxene in Iherzolite xenoliths collected from different locations in eastern China has been measured by the vacuum stepped-heating mass spectrometry. These xenoliths are hosted in alkali basalts and considered as residues of partial melting of the upper mantle, and may contain evidence of mantle evolution. The results show that various kinds of fluid inclusions in Iherzolite xenoliths have been released at distinct times, which could be related to different stages of mantle evolution. In general, primitive fluids of the upper mantle (PFUM) beneath eastern China are dominated by H2, CO2 and CO, and are characterized by high contents of H2 and reduced gases. The compositions of PFUM are highly variable and related to tectonic settings. CO, CO2 and H2 are the main components of the PFUM beneath cratons; the PFUM in the mantle enriched in potassic metasomatism in the northern part of northeastern China has a high content of H2, while CO2 and SO2 are the dominant components of the PFUM in the Su-Lu-Wan (Jiangsu-Shandong-Anhui) region, where recycled crustal fluids were mixed with deeper mantle components. There are several fluids with distinct compositions beneath eastern China, such as primitive fluids of upper mantle (CO, CO2 and H2), partial melting fluids (CO2 and CO) and metasomatic fluids mixed with recycled crustal fluids (CO2, N2, SO2 and CH4) etc. Fluids of the upper mantle beneath the North China craton are different from that of the South China craton in total gases and chemical compositions: the contents of the reduced gases of the PFUM in the NCC are higher than those in the SCC.
基金supported by the National Natural Science Foundation of China (grants No.41576048,41202080 and 41176052)the Open Fund of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology) (grant No.PLC201402)+1 种基金the Youth Innovation Promotion Association CAS (2016312)the Scientific Cooperative Project by CNPC and CAS (2015A-4813)
文摘The first marine gas hydrate expedition in China has been conducted by Guangzhou Marine Geological Survey in the Shenhu Area, northern continental slope of the South China Sea. Previous study has analyzed the P-T conditions, geophysical anomalies and saturation calculations of these gas hydrates, but has not documented in detail the migration of gas-bearing fluids in the study area. Based on the interpretations of 2D/3D seismic data, this work identified two types of migration pathways for gas-bearing fluids in the Shenhu area, i.e., vertical and lateral pathways. The vertical pathways（largescale faults, gas chimneys and mud diapirs） presented as steep seismic reflection anomalies, which could be traced downward to the Eocene source rocks and may penetrate into the Late Miocene strata. The deeper gases/fluids might be allowed migrating into the shallower strata through these vertical conduits. However, the distributions showed distinct differences between these pathways. Large-scale faults developed only in the north and northeast of the Shenhu area, while in the drilling area gas chimneys were the sole vertical migration pathways. Since the Pliocene, normal faults, detachment faults and favorable sediments have constituted the lateral pathways in the Shenhu gas hydrate drilling area. Although these lateral pathways were connected with gas chimneys, they exerted different effects on hydrate formation and accumulation. Gas-bearing fluids migrated upward along gas chimneys might further migrate laterally because of the normal faults, thereby enlarging the range of the chimneys. Linking gas chimneys with the seafloor, the detachment faults might act as conduits for escaping gases/fluids. Re-deposited sediments developed at the early stage of the Quaternary were located within the gas hydrate stability zone, so hydrates would be enriched in these favorable sediments. Compared with the migration pathways（large-scale faults and mud diapirs） in the LW3-1 deep-sea oil/gas field, the migration efficiency of the ve
基金supported by the National Natural Science Foundation of China(Grant Nos.42130801,42125203,42261134535,41230311,42272071)the National Key Research and Development Program(Grant No.2019YFA0708603)+1 种基金the 111 Project of the Ministry of Science and Technology(Grant No.BP0719021)the Fundamental Research Funds for the Central Universities(Grant Nos.2652023001,3-7-8-2023-09)。
文摘The genesis of giant gold provinces is an international scientific frontier,in which the source of a huge amount of gold and the drive for mineralization are key challenges.The mineralization intensity of the Jiaodong gold province in eastern China is a rare occasion in the world,because it owns gold reserves of~5500 tons within an area of less than 10,000 km^(2).The Jiaodong gold province formed in the superimposed domain of diverse tectonic regimes in an intracontinental setting.Paleoproterozoic regional peak metamorphism and Triassic continental collision are followed by the tectonic transition and gold mineralization at ca.120 Ma with time intervals of 1.9 billion years and about 100 million years,respectively.The Jiaodong gold deposits are different from orogenic and intrusion-related gold deposits in terms of the tectonic background,types of host rocks,and oreforming mechanism.These gold deposits show close spatial-temporal and genetic relationships to mafic igneous rocks,implying the derivation of ore-forming fluids from the metasomatic mantle domains.Mafic dykes in Jiaodong have negativeε_(Hf)(t)values of-29.9 to-9.1,Os content of 0.002-0.16 ppb,heavyδ^(18)O up to 8.23‰,and high initial^(187)Os/^(188)Os ratios of 0.1352-0.8858.These indicate that the lithospheric mantle was metasomatized by ancient crust-derived components.The lithospheric mantle in the western Jiaodong shows generally more enriched isotope features than that in the eastern part,which is explained to be an important reason for its huge gold resources.The mafic dykes show lighter Mg isotope characteristics(averageδ^(26)Mg of-0.33‰,n=50)and high Ca O content(overall greater than 6.5 wt%),indicating that the lithospheric mantle would also record the metasomatism by the carbonate rocks from the subducting oceanic slab.Under the background of the rollback of the subducting paleo-Pacific slab and the destruction of the North China Craton,partial melting of the lower crust would produce granitic magmas that led to the enrichment of gold i
基金supported by the Chinese postdoctoral research fund,Major State Basic Research Program of China(G1999143201)special project of geological sciences(9801)of the State Planning Commission
文摘The Jinding superlarge lead and zinc deposit has attracted the attention of geologists of the world and its metallogenesis has long been in dispute. This paper takes the Jinding deposit and the Baiyangping Cu-Ag-Co deposit which was recently found at about 30 km north of Jinding as one ore belt, and, based on researches on the helium, argon, and xenon isotopic compositions of primary inclusions in ore-forming solutions of the main stage, the authors have found that the 3He/4He ratio of the ore-forming fluid is 2.7×10?6 (varying from 0.19 to 1.97 Ra), the 4He/40Ar ratio (0.24–3.12) is close to the mantle characteristic ratio, and the xenon isotopic composition and evolution show characters of the mantle xenon. The above results reveal the characteristics of mantle source and crust-mantle fluid mixing (mantle helium reaching 32%) and the metallogenic contributions of the deep processes in the Jinding-Baiyangping ore belt.
基金partially supported by Grant-in-aid for Scientific Research(Kiban-B.11440134,Kiban-A 17204037) from Japan Society for the Promotion of Science and by some financial support from the Global Center of Excellence(G-COE) program of Tohoku University
文摘We synthesize significant recent results on the deep structure and origin of the active volcanoes in China's Mainland. Magmatism in the western Pacific arc and back-arc areas is caused by dehydration of the subducting slab and by corner flow in the mantle wedge, whereas the intraplate magmatism in China has different origins. The active volcanoes in Northeast China （such as the Changbai and Wudalianchi） are caused by hot upwelling in the big mantle wedge （BMW） above the stagnant slab in the mantle transition zone and deep slab dehydration as well. The Tengchong volcano in Southwest China is caused by a similar process in the BMW above the subducting Burma microplate （or Indian plate）. The Hainan volcano in southernmost China is a hotspot fed by a lower-mantle plume which may be associated with the Pacific and Philippine Sea slabs＇ deep subduction in the east and the Indian slab＇s deep subduction in the west down to the lower mantle. The stagnant slab finally collapses down to the bottom of the mantle, which can trigger the upwelling of hot mantle materials from the lower mantle to the shallow mantle beneath the subducting slabs and may cause the slab-plume interactions.
