Abundant melt-and fluid inclusions occur in corundum megacrysts of alkaline basalt from the Changle area,Shandong province,eastern China.One type of melt inclusions,i.e.muhiphase melt inclusions(glass+bubbles+daughter...Abundant melt-and fluid inclusions occur in corundum megacrysts of alkaline basalt from the Changle area,Shandong province,eastern China.One type of melt inclusions,i.e.muhiphase melt inclusions(glass+bubbles+daughter minerals)were identified,which occur along growth zones of host corundum megacrysts.Microthermometry and laser Raman microprobe analysis were performed on the melt inclusions.The bubbles within the melt inclusions are confirmed to be CO_2-rich phase and the daughter minerals are probably silicates,such as augite and okenite.The results of high temperature homogenization experiment strongly suggest that two immiscible melts,i.e.a H_2O-and CO_2-rich melt and an anhydrous and CO_2-poor melt were trapped by melt inclusions in corundum megacryst.展开更多
The Wangjiazhuang Cu(-Mo)deposit,located within the Zouping volcanic basin in western Shandong Province,China,is unique in this area for having an economic value.In order to expound the metallogenetic characteristics ...The Wangjiazhuang Cu(-Mo)deposit,located within the Zouping volcanic basin in western Shandong Province,China,is unique in this area for having an economic value.In order to expound the metallogenetic characteristics of this porphyry-like hydrothermal deposit,a detailed fluid inclusion study has been conducted,employing the techniques of representative sampling,fluid inclusion petrography,microthermometry,Raman spectroscopy,LA-ICP-MS analysis of single fluid inclusions,as well as cathode fluorescence spectrometer analysis of host mineral quartz.The deposit contains mainly two types of orebodies,i.e.veinlet-dissemination-stockwork orebodies in the K-Si alteration zone and pegmatiticquartz sulfide veins above them.In addition,minor breccia ore occurs locally.Four types of fluid inclusions in the deposit and altered quartz monzonite are identified:L-type one-or two-phase aqueous inclusions,V-type vapor-rich inclusions with V/L ratios greater than 50%-90%,D-type multiphase fluid inclusions containing daughter minerals or solids and S-type silicate-bearing fluid inclusions containing mainly muscovite and biotite.Ore petrography and fluid inclusion study has revealed a three-stage mineralization process,driven by magmatic-hydrothermal fluid activity,as follows.Initially,a hydrothermal fluid,separated from the parent magma,infiltrated into the quartz monzonite,resulting in its extensive K-Si alteration,as indicated by silicate-bearing fluid inclusions trapped in altered quartz monzonite.This is followed by the early mineralization,the formation of quartz veinlets and dissemination-stockwork ores.During the main mineralization stage,due to the participation and mixing of meteoric groundwater with magmatic-sourced hydrothermal fluid,the cooling and phase separation caused deposition of metals from the hydrothermal fluids.As a result,the pegmatitic-quartz sulfide-vein ores formed.In the late mineralization stage,decreasing fluid salinity led to the formation of L-type aqueous inclusions and chalcopyrite-sulfosalt ore.Coexistence of V-type and D-type inclusions and their similar homogenization temperatures with different homogenization modes suggest that phase separation or boiling of the ore-forming fluids took place during the early and the main mineralization stages.The formation P-T conditions of S-type inclusions and the early and the main mineralization stages were estimated as ca.156-182 MPa and 450-650℃,350-450℃,18-35 MPa and 280-380℃,8-15 MPa,respectively,based on the microthermometric data of the fluid inclusions formed at the individual stages.展开更多
The Yueguang gold deposit is located in Fengjia,Xinhua County,Hunan Province,South China.It represents a recently discovered small-scale gold deposit situated in the southwestern region of the Jiangnan Orogenic Belt,w...The Yueguang gold deposit is located in Fengjia,Xinhua County,Hunan Province,South China.It represents a recently discovered small-scale gold deposit situated in the southwestern region of the Jiangnan Orogenic Belt,west of the Baimashan granitic batholith.In order to discern the characteristics of the ore-formingfluids,the underlying mineralization processes,and establish a foundation for the origin of the Yueguang gold depositfluid inclusion micro-thermometry,as well as quartz hydrogen and oxygen isotope analysis,have been carried out on samples obtained from various stages of mineralization.The hydrothermal miner-alization stages within the Yueguang gold deposit can be categorized into three stages:(i)the barren,pre-ore quartz-pyrite stage(Stage Ⅰ),the quartz-pyrite-gold stage(Stage Ⅱ),and the post-ore quartz-carbonate stage(Stage Ⅲ),with the second stage being the main mineralization stage.Thefluid inclusions identified in samples from the main min-eralization stage can predominantly be described with the NaCl–H_(2)O and CO_(2)–NaCl–H_(2)O systems.These inclusions display homogenization temperatures ranging from 158.8 to 334.9℃,and thefluid salinity ranges from 0.3%to 4.0%(wt.%NaCl equiv.).Laser Raman spectroscopy analysis of individual inclusions further reveals the presence of gas-phases such as CO_(2),CH_(4),and N_(2).Isotopic analysis indicatesδ^(18)Ofluid values ranging from 3.95 to 6.7‰ and δDH_(2)O values ranging from-71.9 to-55.7‰.These results indi-cate that the ore-formingfluid of the Yueguang gold deposit belongs to metamorphic hydrothermalfluids of middle-low temperature and low salinity.In the process of ore formation,gold is transported in the form of Au(HS)2-complexes,with gold deposition being driven byfluid immiscibility.Therefore,the Yueguang gold deposit is categorized as an orogenic gold deposit dominated by metamorphic hydrother-malfluid.It may become a new target for gold exploration in the Baimashan region,central Hunan Province.展开更多
Igneous topazites found recently in South China are closely associated with F-rich granites in time and space. They have a typical igneous porphyritic texture. The phenocrysts are topaz and quartz, while the groundmas...Igneous topazites found recently in South China are closely associated with F-rich granites in time and space. They have a typical igneous porphyritic texture. The phenocrysts are topaz and quartz, while the groundmass consists mainly of prismatic or acicular topaz microlites and anhedral quartz. Compared with granites, topazites are rich in SiO2 (65.06%-81.12% ) and Al2O3 (13.01%-18.09%) but poor in MgO and Na2O and strongly peraluminous with A/NKC = 3.204-37.313. Geochemically, the rocks are evidently depleted in Sr and Ba, but enriched in Sn, W, Nb and F. The concentrations of Sn and partial W in the topazites are 1-2 orders of magnitude higher than the average of acid rocks. The F-riched granites related to the topazites in the area usually have much higher ISr (0.7103-0.7460) and δ18OQ‰ (9.5-14.24), but lower INdCT) (-4.8- 9.4). It suggests that the topazite is similar to S-type granites in genesis. Hydroxylated silicate melt inclusions, consisting of several grains of quartz and aqueous fluids, have been found in the quartz phenocrysts. The entrapment temperature of these inclusions is about 520℃.展开更多
Although the involvement of hydrous fluids has been widely invoked in formation of podiform chromitites in ophiolites, there is lack of natural evidence to signify the role and mechanism of fluids. In this study, a ne...Although the involvement of hydrous fluids has been widely invoked in formation of podiform chromitites in ophiolites, there is lack of natural evidence to signify the role and mechanism of fluids. In this study, a new model for the genesis of podiform chromitite is proposed on basis of revisits of comprehensive petrological, mineralogical and geochemical results of the well-preserved K?z?lda? ophiolite and the well-characterized Luobusa chromite deposit. In this model, ascending magmas intruding oceanic lithospheric mantle would presumably form a series of small magma chambers continuously connected by conduits. Tiny chromite nuclei would collect fluids dispersed in such magmas to form nascent droplets. They tend to float upward in the magma chamber and would be easily transported upward by flowing magmas. Chromite-rich droplets would be enlarged via coalescence of dispersed droplets during mingling and circulation in the magma chamber and/or transport in magma conduits. Crystallization of the chromite-rich liquid droplets would proceed from the margin of the droplet inward, leaving liquid entrapped within grains as precursor of mineral inclusions. With preferential upward transportation, immiscible chromite-rich liquids would coalesce to a large pool in a magma chamber. Large volumes of chromite would crystallize in situ, forming podiform chromitite and resulting in fluid enrichment in the chamber. The fluids would penetrate and compositionally modify ambient dunite and harzburgite, leading to significant fractionations of elemental and isotopic compositions between melts and fluids from which dunite and chromitite respectively formed. Therefore, fluid immiscibility during basaltic magma ascent plays a vital role in chromitite formation.展开更多
Low saline aqueous carbonic fluids are considered to be the ore forming solutions for orogenic lode gold deposits.Phase separation/fluid immiscibility of the ore fluid is quite common and is one of the major reasons f...Low saline aqueous carbonic fluids are considered to be the ore forming solutions for orogenic lode gold deposits.Phase separation/fluid immiscibility of the ore fluid is quite common and is one of the major reasons for deposition of gold in these deposits.Abundant carbonic fluid inclusions have been observed in quartz grains of Hira-Buddnini Gold Deposit.Theoretical estimation indicates that more volume of H2O compared to CO2 is likely to be trapped in inclusions at different P-T conditions.Preferential loss of H2O from fluid inclusions during ductile deformation of quartz grains have been attributed as the suitable reason for abundance of carbonic fluid inclusions.展开更多
Based on results of microscopic observation and laser Raman analysis about fluid in-clusions,multiple special forms of immiscible inclusions that contain sulphur,liquid hydrocarbon,bi-tumen,etc.were discovered in samp...Based on results of microscopic observation and laser Raman analysis about fluid in-clusions,multiple special forms of immiscible inclusions that contain sulphur,liquid hydrocarbon,bi-tumen,etc.were discovered in samples collected from the H_(2)S gas reservoir-containing carbonates in the Lower Triassic Feixianguan Formation in the Jinzhu-Luojia area,Kai County,Sichuan Province.Based on the lithology and burial history of the strata involved as well as measurement results of homogenization temperature of fluid inclusions,bitumen reflectivity,etc.,it is concluded that the H_(2)S in the gas reservoir resulted from the thermal reaction between hydrocarbons in reservoir and CaSO_(4)in the gypsum-bearing dolostone section at the high temperature(140℃―170℃)oil-cracked gas for-mation stage in Late Cretaceous.Thereafter,research on a great number of immiscible inclusions in the reservoir reveals that elemental sulphur resulted from oxidation of part of the earlier-formed H_(2)S and further reaction between sulphates,hydrocarbons and H_(2)S in geological fluids in H_(2)S-bearing gas reservoir at a temperature of 86℃―89℃and a pressure of 340×10^(5)Pa and during the regional uplift stage as characterized by temperature decrease and pressure decrease in Tertiary.Meanwhile,gyp-sum,anhydrite and calcite formed at this stage would trap particles like elemental sulphur and result in a variety of special forms of immiscible inclusions,and these inclusions would contain information concerning the complexity of the fluids in the reservoir and the origin of H_(2)S and natural sulphur in the gas reservoir.展开更多
基金National Natural Science Foundation of China （ Grant No. 402213101）.
文摘Abundant melt-and fluid inclusions occur in corundum megacrysts of alkaline basalt from the Changle area,Shandong province,eastern China.One type of melt inclusions,i.e.muhiphase melt inclusions(glass+bubbles+daughter minerals)were identified,which occur along growth zones of host corundum megacrysts.Microthermometry and laser Raman microprobe analysis were performed on the melt inclusions.The bubbles within the melt inclusions are confirmed to be CO_2-rich phase and the daughter minerals are probably silicates,such as augite and okenite.The results of high temperature homogenization experiment strongly suggest that two immiscible melts,i.e.a H_2O-and CO_2-rich melt and an anhydrous and CO_2-poor melt were trapped by melt inclusions in corundum megacryst.
基金financially supported by the Natural Science Foundation of China(Grant Nos.42272104,42172094 and 41772076)。
文摘The Wangjiazhuang Cu(-Mo)deposit,located within the Zouping volcanic basin in western Shandong Province,China,is unique in this area for having an economic value.In order to expound the metallogenetic characteristics of this porphyry-like hydrothermal deposit,a detailed fluid inclusion study has been conducted,employing the techniques of representative sampling,fluid inclusion petrography,microthermometry,Raman spectroscopy,LA-ICP-MS analysis of single fluid inclusions,as well as cathode fluorescence spectrometer analysis of host mineral quartz.The deposit contains mainly two types of orebodies,i.e.veinlet-dissemination-stockwork orebodies in the K-Si alteration zone and pegmatiticquartz sulfide veins above them.In addition,minor breccia ore occurs locally.Four types of fluid inclusions in the deposit and altered quartz monzonite are identified:L-type one-or two-phase aqueous inclusions,V-type vapor-rich inclusions with V/L ratios greater than 50%-90%,D-type multiphase fluid inclusions containing daughter minerals or solids and S-type silicate-bearing fluid inclusions containing mainly muscovite and biotite.Ore petrography and fluid inclusion study has revealed a three-stage mineralization process,driven by magmatic-hydrothermal fluid activity,as follows.Initially,a hydrothermal fluid,separated from the parent magma,infiltrated into the quartz monzonite,resulting in its extensive K-Si alteration,as indicated by silicate-bearing fluid inclusions trapped in altered quartz monzonite.This is followed by the early mineralization,the formation of quartz veinlets and dissemination-stockwork ores.During the main mineralization stage,due to the participation and mixing of meteoric groundwater with magmatic-sourced hydrothermal fluid,the cooling and phase separation caused deposition of metals from the hydrothermal fluids.As a result,the pegmatitic-quartz sulfide-vein ores formed.In the late mineralization stage,decreasing fluid salinity led to the formation of L-type aqueous inclusions and chalcopyrite-sulfosalt ore.Coexistence of V-type and D-type inclusions and their similar homogenization temperatures with different homogenization modes suggest that phase separation or boiling of the ore-forming fluids took place during the early and the main mineralization stages.The formation P-T conditions of S-type inclusions and the early and the main mineralization stages were estimated as ca.156-182 MPa and 450-650℃,350-450℃,18-35 MPa and 280-380℃,8-15 MPa,respectively,based on the microthermometric data of the fluid inclusions formed at the individual stages.
基金support from several sources,including the Backbone Teacher Training Program(10912-SJGG2021-04233)the Teaching Reform Project of Chengdu University of Technology(JG2130131)+1 种基金the University-Industry Collaborative Education Project,Ministry of Education,China(22097130210756)National Natural Science Foundation of China(42272129).
文摘The Yueguang gold deposit is located in Fengjia,Xinhua County,Hunan Province,South China.It represents a recently discovered small-scale gold deposit situated in the southwestern region of the Jiangnan Orogenic Belt,west of the Baimashan granitic batholith.In order to discern the characteristics of the ore-formingfluids,the underlying mineralization processes,and establish a foundation for the origin of the Yueguang gold depositfluid inclusion micro-thermometry,as well as quartz hydrogen and oxygen isotope analysis,have been carried out on samples obtained from various stages of mineralization.The hydrothermal miner-alization stages within the Yueguang gold deposit can be categorized into three stages:(i)the barren,pre-ore quartz-pyrite stage(Stage Ⅰ),the quartz-pyrite-gold stage(Stage Ⅱ),and the post-ore quartz-carbonate stage(Stage Ⅲ),with the second stage being the main mineralization stage.Thefluid inclusions identified in samples from the main min-eralization stage can predominantly be described with the NaCl–H_(2)O and CO_(2)–NaCl–H_(2)O systems.These inclusions display homogenization temperatures ranging from 158.8 to 334.9℃,and thefluid salinity ranges from 0.3%to 4.0%(wt.%NaCl equiv.).Laser Raman spectroscopy analysis of individual inclusions further reveals the presence of gas-phases such as CO_(2),CH_(4),and N_(2).Isotopic analysis indicatesδ^(18)Ofluid values ranging from 3.95 to 6.7‰ and δDH_(2)O values ranging from-71.9 to-55.7‰.These results indi-cate that the ore-formingfluid of the Yueguang gold deposit belongs to metamorphic hydrothermalfluids of middle-low temperature and low salinity.In the process of ore formation,gold is transported in the form of Au(HS)2-complexes,with gold deposition being driven byfluid immiscibility.Therefore,the Yueguang gold deposit is categorized as an orogenic gold deposit dominated by metamorphic hydrother-malfluid.It may become a new target for gold exploration in the Baimashan region,central Hunan Province.
基金the China National Natural Science Foundation Grant No.49272100
文摘Igneous topazites found recently in South China are closely associated with F-rich granites in time and space. They have a typical igneous porphyritic texture. The phenocrysts are topaz and quartz, while the groundmass consists mainly of prismatic or acicular topaz microlites and anhedral quartz. Compared with granites, topazites are rich in SiO2 (65.06%-81.12% ) and Al2O3 (13.01%-18.09%) but poor in MgO and Na2O and strongly peraluminous with A/NKC = 3.204-37.313. Geochemically, the rocks are evidently depleted in Sr and Ba, but enriched in Sn, W, Nb and F. The concentrations of Sn and partial W in the topazites are 1-2 orders of magnitude higher than the average of acid rocks. The F-riched granites related to the topazites in the area usually have much higher ISr (0.7103-0.7460) and δ18OQ‰ (9.5-14.24), but lower INdCT) (-4.8- 9.4). It suggests that the topazite is similar to S-type granites in genesis. Hydroxylated silicate melt inclusions, consisting of several grains of quartz and aqueous fluids, have been found in the quartz phenocrysts. The entrapment temperature of these inclusions is about 520℃.
基金supported by the National Natural Science Foundation of China (Grant Nos. 91755205, 41973012, and 41772055)。
文摘Although the involvement of hydrous fluids has been widely invoked in formation of podiform chromitites in ophiolites, there is lack of natural evidence to signify the role and mechanism of fluids. In this study, a new model for the genesis of podiform chromitite is proposed on basis of revisits of comprehensive petrological, mineralogical and geochemical results of the well-preserved K?z?lda? ophiolite and the well-characterized Luobusa chromite deposit. In this model, ascending magmas intruding oceanic lithospheric mantle would presumably form a series of small magma chambers continuously connected by conduits. Tiny chromite nuclei would collect fluids dispersed in such magmas to form nascent droplets. They tend to float upward in the magma chamber and would be easily transported upward by flowing magmas. Chromite-rich droplets would be enlarged via coalescence of dispersed droplets during mingling and circulation in the magma chamber and/or transport in magma conduits. Crystallization of the chromite-rich liquid droplets would proceed from the margin of the droplet inward, leaving liquid entrapped within grains as precursor of mineral inclusions. With preferential upward transportation, immiscible chromite-rich liquids would coalesce to a large pool in a magma chamber. Large volumes of chromite would crystallize in situ, forming podiform chromitite and resulting in fluid enrichment in the chamber. The fluids would penetrate and compositionally modify ambient dunite and harzburgite, leading to significant fractionations of elemental and isotopic compositions between melts and fluids from which dunite and chromitite respectively formed. Therefore, fluid immiscibility during basaltic magma ascent plays a vital role in chromitite formation.
文摘Low saline aqueous carbonic fluids are considered to be the ore forming solutions for orogenic lode gold deposits.Phase separation/fluid immiscibility of the ore fluid is quite common and is one of the major reasons for deposition of gold in these deposits.Abundant carbonic fluid inclusions have been observed in quartz grains of Hira-Buddnini Gold Deposit.Theoretical estimation indicates that more volume of H2O compared to CO2 is likely to be trapped in inclusions at different P-T conditions.Preferential loss of H2O from fluid inclusions during ductile deformation of quartz grains have been attributed as the suitable reason for abundance of carbonic fluid inclusions.
基金This research was supported by the State Brainstorm Science Program for the Tenth Five-Year Pkn Period(Grant No.2001BA605A-0404)the Frontier Research Program Sponsared by Guangzhou Institute of Geochemistry of Chinese Ac ademy of Sciences(Grant No.GiGCX-04-08).
文摘Based on results of microscopic observation and laser Raman analysis about fluid in-clusions,multiple special forms of immiscible inclusions that contain sulphur,liquid hydrocarbon,bi-tumen,etc.were discovered in samples collected from the H_(2)S gas reservoir-containing carbonates in the Lower Triassic Feixianguan Formation in the Jinzhu-Luojia area,Kai County,Sichuan Province.Based on the lithology and burial history of the strata involved as well as measurement results of homogenization temperature of fluid inclusions,bitumen reflectivity,etc.,it is concluded that the H_(2)S in the gas reservoir resulted from the thermal reaction between hydrocarbons in reservoir and CaSO_(4)in the gypsum-bearing dolostone section at the high temperature(140℃―170℃)oil-cracked gas for-mation stage in Late Cretaceous.Thereafter,research on a great number of immiscible inclusions in the reservoir reveals that elemental sulphur resulted from oxidation of part of the earlier-formed H_(2)S and further reaction between sulphates,hydrocarbons and H_(2)S in geological fluids in H_(2)S-bearing gas reservoir at a temperature of 86℃―89℃and a pressure of 340×10^(5)Pa and during the regional uplift stage as characterized by temperature decrease and pressure decrease in Tertiary.Meanwhile,gyp-sum,anhydrite and calcite formed at this stage would trap particles like elemental sulphur and result in a variety of special forms of immiscible inclusions,and these inclusions would contain information concerning the complexity of the fluids in the reservoir and the origin of H_(2)S and natural sulphur in the gas reservoir.
