Precise in situ zircon U-Pb dating and Lu-Hf isotopic measurement using an LA-ICP-MS system,whole-rock major and trace element geochemistry and Sr-Nd isotope geochemistry were conducted on the volcanic host rocks of t...Precise in situ zircon U-Pb dating and Lu-Hf isotopic measurement using an LA-ICP-MS system,whole-rock major and trace element geochemistry and Sr-Nd isotope geochemistry were conducted on the volcanic host rocks of the Tongyu copper deposit on the basis of further understanding of its geological characteristics.Three zircon samples from the volcanic host rocks yielded 206Pb/238 U weighted average ages ranging from 436±4 Ma to 440±5 Ma,which are statistically indistinguishable and coeval with the ca.440 Ma northward subduction event of the Paleo-Qinling oceanic slab.The volcanic host rocks were products of magmatic differentiation that evolved from basalt to andesite to dacite to rhyolite,forming an integrated tholeiitic island arc volcanic rock suite.The primitive mantle-normalized trace element patterns for most samples show characteristics of island arc volcanic rocks,such as relative enrichment of LILE(e.g.Th,U,Pb and La)and depletion of HFSE(e.g.Nb,Ta,Ti,Zr and Hf).Discrimination diagrams of Ta/Yb vs Th/Yb,Ta vs Th,Yb vs Th/Ta,Ta/Hf vs Th/Hf,Hf/3 vs Th vs Nb/16,La vs La/Nb and Nb vs Nb/Th all suggest that both the volcanic host rocks from the Tongyu copper deposit and the volcanic rocks from the regional Xieyuguan Group were formed in an island arc environment related to subduction of an oceanic slab.Values of ISr(0.703457 to 0.708218)andεNd(t)(-2 to 5.8)indicate that the source materials of volcanic rocks from the Tongyu copper deposit and the Xieyuguan Group originated from the metasomatised mantle wedge with possible crustal material assimilation.Most of the volcanic rock samples show good agreement with the values of typical island arc volcanic rocks in the ISr-εNd(t)diagram.The involvement of crustal-derived material in the magma of the volcanic rocks from the Tongyu copper deposit was also reflected in the zirconεHf(t)values,which range from-3.08 to 10.7,and the existence of inherited ancient xenocrystic zircon cores(2616±39 Ma and 1297±22 Ma).The mineralization of the Tongyu copper deposit shows syn-volcanic characteristics such as layered orebodies interbedded with the volcanic rock strata,thus,the zircon U-Pb age of the volcanic host rocks can approximately represent the mineralization age of the Tongyu copper deposit.Both the Meigou pluton and the volcanic host rocks were formed during the ca.440 Ma northward subduction of the Paleo-Qinling Ocean when high oxygen fugacity aqueous hydrothermal fluid released by dehydration of the slab and the overlying sediments fluxed into the mantle wedge,triggered partial melting of the mantle wedge,and activated and extracted Cu and other ore-forming elements.The magma and ore-bearing fluid upwelled and erupted,and consequently formed the island arc volcanic rock suite and the Tongyu VHMS-type copper deposit.展开更多
The Dashuigou tellurium deposit is the world’s only known independent tellurium deposit.By restoring metamorphic rocks’protolith,we seek to understand not only the development and evolution trajectory of the region ...The Dashuigou tellurium deposit is the world’s only known independent tellurium deposit.By restoring metamorphic rocks’protolith,we seek to understand not only the development and evolution trajectory of the region but also the origin of the relevant deposits.While there are many ways to restore metamorphic rocks’protolith,we take the host metamorphic rocks of Dashuigou tellurium deposit and leverage various petrochemical eigenvalues and related diagrams previously proposed to reveal the deposit’s host metamorphic rocks’protolith.The petrochemical eigenvalues include molecular number,Niggli’s value,REE parity ratio,CaO/Al_(2)O_(3)ratio,Fe^(3+) /(Fe^(3+) -+Fe^(2+) )ratio,chondrite-normalized REE value,logarithmic REE value,various REE eigenvalues including scandium,Eu/Sm ratio,total REE amount,light and heavy REEs,δEu,Eu anomaly,Sm/Nd ratio,and silicon isotope δ^(30) SiNBS-29‰,etc.The petrochemical plots include ACMs,100 mg-c-(al+alk),SiO_(2)-(Na_(2)O+K_(2)O),(al+fm)-(c+alk)versus Si,FeO+Fe_(2)O^(3+) TiO)-Al_(2)O_(3)-MgO,c-mg,Al_(2)O_(3)-(Na_(2)O+K_(2)O),chondrite-normalized REE model,La/Yb-REE,and Sm/Nd ratio,etc.On the basis of these comprehensive analyses,the following conclusions are drawn,starting from the many mantle-derived types of basalt developed in the study area of different geological ages,combined with the previously published research results on the deposit s fluid inclusions and sulfur and lead isotopes.The deposit is formed by mantle degassing in the form of a mantle plume in the late Yanshanian orogeny.The degassed fluids are rich in nano-sc ale substances including Fe,Te,S,As,Bi,Au,Se,H_(2),CO_(2),N_(2),H_(2)O,and CH_(4),which are enriched by nano-effect,and then rise to a certain part of the crust in the form of mantle plume along the lithospheric fault to form the deposit.The ultimate power for tellurium mineralization was from H_(2)flow with high energy,which was produced through radiation from the melted iron of the Earth’s outer core.The H,flow results in the Earth’s degassing,as well as the mantle and crust’s uplift.展开更多
The western Tianshan high-pressure(HP) metamorphic belt represents the paleosubduction mélange of paleozoic south Tianshan ocean between the Yili-central Tianshan and Tarim plates. High-pressure veins are extensi...The western Tianshan high-pressure(HP) metamorphic belt represents the paleosubduction mélange of paleozoic south Tianshan ocean between the Yili-central Tianshan and Tarim plates. High-pressure veins are extensively developed in this HP belt. Compared with normal mid-ocean ridge basalt(N-MORB), the high-pressure veins and host rocks are enriched in light rare earth elements(LREE) and incompatible elements. But high-pressure veins show a larger variation than host rocks in total REE abundance. On the trace element spidergram, all the samples are enriched in incompatible elements and show strong positive Pb anomaly relative to N-MORB. The array tendency lines of plots of the HP rocks have apparent slopes on diagram of m(Sr) vs m(Sr)/m(Zr), m(Li) vs m(Li)/m(Y) and (m(Ce)) vs m(Ce)/m(Pb), which indicates that the enrichment in LREE and incompatible elements relative to N-MORB of the HP-metamorphic rocks from western Tianshan is not attributed to magma evolution process of the protolith. High field strength elements, such as Nb, Ta, Ti, Zr and Hf, do not show negative anomaly relative to N-MORB, which is dissimilar to that of island arc basalts. Therefore, the enrichment in LREE and incompatible elements of the HP rocks is not attributed to the enrichment of the source of the protolith. The mass ratios of Rb to Ba, Ce to Pb, Nb to U and Ta to U of high-pressure veins and host rocks are intermediate of mid-ocean ridge basalt or oceanic island basalt and continental crust. The fluids in western Tianshan paleosubduction zones are mixtures of two sources, dehydration or devolatilization of host rocks and of subducted sediments.展开更多
Fluids in the deep subduction zones play an important role in crust-mantle ex-change related to the subduction process. Identification of fluids origin, internal or external, can help us to evaluate the contribution o...Fluids in the deep subduction zones play an important role in crust-mantle ex-change related to the subduction process. Identification of fluids origin, internal or external, can help us to evaluate the contribution of crust materials to mantle during this process. High-pressure veins, which developed in the western Tianshan HP-metamorphic belt extensively, are the direct products of the fluids in subduction zones. In western Tianshan, high-pressure veins and host rocks have overall Pb- and Sr-isotope compositions. At t = 340 Ma, the high-pressure metamorphic time, the ratios of 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb and 87Sr/86Sr of high pressure veins are 17.122―18.431, 15.477―15.611, 37.432―38.689 and 0.70529―0.70705, and are 17.605―17.834, 15.508―15.564, 37.080―38.145 and 0.70522―0.70685 for host rocks. However, high-pressure veins show a much larger variation in Pb-isotope composi-tions than host rocks. Plots of samples are distributed roughly along a line parallel to and far away from the Northern Hemisphere reference line (NHRL) on the plot of 206Pb/204Pb vs 207Pb/204Pb. On the plot of 206Pb/204Pb vs 208Pb/204Pb, plots of data are distributed nearby mid-ocean-ridge basalts (MORB) area or along a line parallel to and not far away from NHRL, which shows that the data plots are farther away from MORB and ocean island basalts (OIB) areas on the plot of 206Pb/204Pb vs 207Pb/204Pb than on the plot of 206Pb/204Pb vs 208Pb/204Pb. The compositions of Pb- and Sr-isotopes of these high-pressure metamorphic rocks are between that of enriched mantle 1(EMI) and of sediments or upper crust. A notable characteristic can be seen from plots of Pb-isotope ratio vs Pb-isotope ratio and 206Pb/204Pb vs 87Sr/86Sr that array of plots shows an evident tendency of mixture of two end members. Ratios of Rb/Ba, Ce/Pb, Nb/U and Ta/U of high-pressure veins and host rocks are between that of OIB or MORB and that of conti-nental crust, which indicates that continental crust materials probably have been incorporated into the rocks. The fluids in the paleosubduction zones in western Tianshan are mixtures of two sources, one originating from the devolatilzation of the host rocks with protolithes similar to ocean basalts from enriched mantle 1 (EMI), the other from the dehydration of subducted sediments.展开更多
The Lannigou deposit is a large-sized sedimentary rock-hosted disseminated gold （SRHDG） deposit located in the Youjiang Basin. It is hosted by the Middle Triassic turbidite. Wall rock alterations, including silicifi...The Lannigou deposit is a large-sized sedimentary rock-hosted disseminated gold （SRHDG） deposit located in the Youjiang Basin. It is hosted by the Middle Triassic turbidite. Wall rock alterations, including silicification, pyritization, arsenopyritization, carbonatization and argillization, commonly occur along fractures. PGE study demonstrates that either Permian basalts or Triassic ultrabasic intrnsives are unlikely to be the main source of gold mineralization. Coupled with the lack of other nmgmatic activity in the vicinity of the mining area, an amagmatic origin is proposed. Organic matter compositions and GC-MS analysis of the ores and host rocks show that the organics in the ores and the host rocks have a common source; the organic matter in the ores was mainly indigenous. The positive correlation between S2 and Au contents, along with the common occurrence of organic inclusions, suggest involvement of organic matter in the ore-forming process in terms of promoting Au leaching from the source rocks, making colloidal Au migration possible, as well as hydrocarbon reduction of sulphate. Geological and geochemical characteristics of the Lannigou deposit suggest that it was formed through circulation of meteoric water and probably less importantly organic bearing formation water driven by high geothermal gradient caused by late Yanshanian extension, which leached Au from the source bed, and then migrated as Au-bisnlfides and colloidal Au, culminating in deposition by reduction-adsorption and surface complexation of gold onto the growth surface of arsenlan pyrite.展开更多
1 Geological setting of the deposit THE Qiaogashan gold deposit is located at contact zone of middle Tianshan terrance and south Tianshanback-arc basin, and near the latter side. The orebodies are controlled by middle...1 Geological setting of the deposit THE Qiaogashan gold deposit is located at contact zone of middle Tianshan terrance and south Tianshanback-arc basin, and near the latter side. The orebodies are controlled by middle Tianshan brittle-ductileshear zone. The main ore types are auriferous quartz veins and fractured and alterated rocks. The southpart of the deposit is hosted in striking sheared Devonian rocks, while the north part in a diorite body,which was deformed by a nape shear zone. 2 Geology and geochemistry of host rocks The host rocks of south part of the deposit are Devonian detrital stone of terrigenous origin, interlayering volcanic detrial stone of back-arc basin facies, which locally suffered intensive ductile-brittle shearing. The rock type is composed mainly of gray-green siltstone, poststone, metasiltstone, etc., and a se-展开更多
Most gold deposits in intrusive rocks were formed as a result of reworking processes.The intrusive rocks containing gold deposits and consisting of ultramafic-mafic, intermediate-acid and alkaline rocks of the Archean...Most gold deposits in intrusive rocks were formed as a result of reworking processes.The intrusive rocks containing gold deposits and consisting of ultramafic-mafic, intermediate-acid and alkaline rocks of the Archean, Proterozoic, Caledonian, Hercynian and Yenshanian periods occur in cratons, activated zones of cratons and fold belts. Among them, ultramafic-mafic rocks, diorite, alkaline rocks, and anorthosite are products of remelting in the mantle or mantle-crust or mantle with crustal contamination. However, auriferous intermediate-acid rocks are products of metasomatic-remelting in auriferous volcanic rocks or auriferous volcano-sedimentary rocks in the deep crust.展开更多
Standard laboratory procedures and remote sensing techniques were employed in the characterization of gold bearing rocks of the Paishanlou area. Results indicate that, the rocks were formed in an alteration complex of...Standard laboratory procedures and remote sensing techniques were employed in the characterization of gold bearing rocks of the Paishanlou area. Results indicate that, the rocks were formed in an alteration complex of medium temperature and pressure. The area was under intense polymetamorphism (ductile shearing, and hydrothermal metamorphism), which occurred along the deformation zone stretching from Jinzhou to Fuxin. The area bears some propylitic, phyllic (or sericitic) and argillic alteration styles. Gold minerals are contained in fine grained pyrite in silicified zones, and associated with metamorphosed Precambrian rocks. The host rock is composed of gneiss, mylonite and trondhjemite granite, and has a distinctive gold lead geochemical affinity.展开更多
基金jointly supported by the National Natural Science Foundation of China(Grant Nos.41272092,41421002 and 41072068)Program for Changjiang Scholars and Innovative Research Team in University(Grant IRT1281)+1 种基金Natural Science Basic Research Program of Shaanxi Province,China(Grant No.2013JZ013)Graduate Innovation Funds of Northwest University,China(Grant No.YZZ12006)
文摘Precise in situ zircon U-Pb dating and Lu-Hf isotopic measurement using an LA-ICP-MS system,whole-rock major and trace element geochemistry and Sr-Nd isotope geochemistry were conducted on the volcanic host rocks of the Tongyu copper deposit on the basis of further understanding of its geological characteristics.Three zircon samples from the volcanic host rocks yielded 206Pb/238 U weighted average ages ranging from 436±4 Ma to 440±5 Ma,which are statistically indistinguishable and coeval with the ca.440 Ma northward subduction event of the Paleo-Qinling oceanic slab.The volcanic host rocks were products of magmatic differentiation that evolved from basalt to andesite to dacite to rhyolite,forming an integrated tholeiitic island arc volcanic rock suite.The primitive mantle-normalized trace element patterns for most samples show characteristics of island arc volcanic rocks,such as relative enrichment of LILE(e.g.Th,U,Pb and La)and depletion of HFSE(e.g.Nb,Ta,Ti,Zr and Hf).Discrimination diagrams of Ta/Yb vs Th/Yb,Ta vs Th,Yb vs Th/Ta,Ta/Hf vs Th/Hf,Hf/3 vs Th vs Nb/16,La vs La/Nb and Nb vs Nb/Th all suggest that both the volcanic host rocks from the Tongyu copper deposit and the volcanic rocks from the regional Xieyuguan Group were formed in an island arc environment related to subduction of an oceanic slab.Values of ISr(0.703457 to 0.708218)andεNd(t)(-2 to 5.8)indicate that the source materials of volcanic rocks from the Tongyu copper deposit and the Xieyuguan Group originated from the metasomatised mantle wedge with possible crustal material assimilation.Most of the volcanic rock samples show good agreement with the values of typical island arc volcanic rocks in the ISr-εNd(t)diagram.The involvement of crustal-derived material in the magma of the volcanic rocks from the Tongyu copper deposit was also reflected in the zirconεHf(t)values,which range from-3.08 to 10.7,and the existence of inherited ancient xenocrystic zircon cores(2616±39 Ma and 1297±22 Ma).The mineralization of the Tongyu copper deposit shows syn-volcanic characteristics such as layered orebodies interbedded with the volcanic rock strata,thus,the zircon U-Pb age of the volcanic host rocks can approximately represent the mineralization age of the Tongyu copper deposit.Both the Meigou pluton and the volcanic host rocks were formed during the ca.440 Ma northward subduction of the Paleo-Qinling Ocean when high oxygen fugacity aqueous hydrothermal fluid released by dehydration of the slab and the overlying sediments fluxed into the mantle wedge,triggered partial melting of the mantle wedge,and activated and extracted Cu and other ore-forming elements.The magma and ore-bearing fluid upwelled and erupted,and consequently formed the island arc volcanic rock suite and the Tongyu VHMS-type copper deposit.
基金supported by Orient Resources Ltd.College of Earth Sciences,Jilin University。
文摘The Dashuigou tellurium deposit is the world’s only known independent tellurium deposit.By restoring metamorphic rocks’protolith,we seek to understand not only the development and evolution trajectory of the region but also the origin of the relevant deposits.While there are many ways to restore metamorphic rocks’protolith,we take the host metamorphic rocks of Dashuigou tellurium deposit and leverage various petrochemical eigenvalues and related diagrams previously proposed to reveal the deposit’s host metamorphic rocks’protolith.The petrochemical eigenvalues include molecular number,Niggli’s value,REE parity ratio,CaO/Al_(2)O_(3)ratio,Fe^(3+) /(Fe^(3+) -+Fe^(2+) )ratio,chondrite-normalized REE value,logarithmic REE value,various REE eigenvalues including scandium,Eu/Sm ratio,total REE amount,light and heavy REEs,δEu,Eu anomaly,Sm/Nd ratio,and silicon isotope δ^(30) SiNBS-29‰,etc.The petrochemical plots include ACMs,100 mg-c-(al+alk),SiO_(2)-(Na_(2)O+K_(2)O),(al+fm)-(c+alk)versus Si,FeO+Fe_(2)O^(3+) TiO)-Al_(2)O_(3)-MgO,c-mg,Al_(2)O_(3)-(Na_(2)O+K_(2)O),chondrite-normalized REE model,La/Yb-REE,and Sm/Nd ratio,etc.On the basis of these comprehensive analyses,the following conclusions are drawn,starting from the many mantle-derived types of basalt developed in the study area of different geological ages,combined with the previously published research results on the deposit s fluid inclusions and sulfur and lead isotopes.The deposit is formed by mantle degassing in the form of a mantle plume in the late Yanshanian orogeny.The degassed fluids are rich in nano-sc ale substances including Fe,Te,S,As,Bi,Au,Se,H_(2),CO_(2),N_(2),H_(2)O,and CH_(4),which are enriched by nano-effect,and then rise to a certain part of the crust in the form of mantle plume along the lithospheric fault to form the deposit.The ultimate power for tellurium mineralization was from H_(2)flow with high energy,which was produced through radiation from the melted iron of the Earth’s outer core.The H,flow results in the Earth’s degassing,as well as the mantle and crust’s uplift.
基金Preoject(2001CB409803) supported by the National Key Fundamental Research and Development Program of China
文摘The western Tianshan high-pressure(HP) metamorphic belt represents the paleosubduction mélange of paleozoic south Tianshan ocean between the Yili-central Tianshan and Tarim plates. High-pressure veins are extensively developed in this HP belt. Compared with normal mid-ocean ridge basalt(N-MORB), the high-pressure veins and host rocks are enriched in light rare earth elements(LREE) and incompatible elements. But high-pressure veins show a larger variation than host rocks in total REE abundance. On the trace element spidergram, all the samples are enriched in incompatible elements and show strong positive Pb anomaly relative to N-MORB. The array tendency lines of plots of the HP rocks have apparent slopes on diagram of m(Sr) vs m(Sr)/m(Zr), m(Li) vs m(Li)/m(Y) and (m(Ce)) vs m(Ce)/m(Pb), which indicates that the enrichment in LREE and incompatible elements relative to N-MORB of the HP-metamorphic rocks from western Tianshan is not attributed to magma evolution process of the protolith. High field strength elements, such as Nb, Ta, Ti, Zr and Hf, do not show negative anomaly relative to N-MORB, which is dissimilar to that of island arc basalts. Therefore, the enrichment in LREE and incompatible elements of the HP rocks is not attributed to the enrichment of the source of the protolith. The mass ratios of Rb to Ba, Ce to Pb, Nb to U and Ta to U of high-pressure veins and host rocks are intermediate of mid-ocean ridge basalt or oceanic island basalt and continental crust. The fluids in western Tianshan paleosubduction zones are mixtures of two sources, dehydration or devolatilization of host rocks and of subducted sediments.
基金supported by the State Key Basic Research Project of China(Grant No.2001CB409803)the National Natural Science Foundation of China(Grant No.49972079).
文摘Fluids in the deep subduction zones play an important role in crust-mantle ex-change related to the subduction process. Identification of fluids origin, internal or external, can help us to evaluate the contribution of crust materials to mantle during this process. High-pressure veins, which developed in the western Tianshan HP-metamorphic belt extensively, are the direct products of the fluids in subduction zones. In western Tianshan, high-pressure veins and host rocks have overall Pb- and Sr-isotope compositions. At t = 340 Ma, the high-pressure metamorphic time, the ratios of 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb and 87Sr/86Sr of high pressure veins are 17.122―18.431, 15.477―15.611, 37.432―38.689 and 0.70529―0.70705, and are 17.605―17.834, 15.508―15.564, 37.080―38.145 and 0.70522―0.70685 for host rocks. However, high-pressure veins show a much larger variation in Pb-isotope composi-tions than host rocks. Plots of samples are distributed roughly along a line parallel to and far away from the Northern Hemisphere reference line (NHRL) on the plot of 206Pb/204Pb vs 207Pb/204Pb. On the plot of 206Pb/204Pb vs 208Pb/204Pb, plots of data are distributed nearby mid-ocean-ridge basalts (MORB) area or along a line parallel to and not far away from NHRL, which shows that the data plots are farther away from MORB and ocean island basalts (OIB) areas on the plot of 206Pb/204Pb vs 207Pb/204Pb than on the plot of 206Pb/204Pb vs 208Pb/204Pb. The compositions of Pb- and Sr-isotopes of these high-pressure metamorphic rocks are between that of enriched mantle 1(EMI) and of sediments or upper crust. A notable characteristic can be seen from plots of Pb-isotope ratio vs Pb-isotope ratio and 206Pb/204Pb vs 87Sr/86Sr that array of plots shows an evident tendency of mixture of two end members. Ratios of Rb/Ba, Ce/Pb, Nb/U and Ta/U of high-pressure veins and host rocks are between that of OIB or MORB and that of conti-nental crust, which indicates that continental crust materials probably have been incorporated into the rocks. The fluids in the paleosubduction zones in western Tianshan are mixtures of two sources, one originating from the devolatilzation of the host rocks with protolithes similar to ocean basalts from enriched mantle 1 (EMI), the other from the dehydration of subducted sediments.
文摘The Lannigou deposit is a large-sized sedimentary rock-hosted disseminated gold （SRHDG） deposit located in the Youjiang Basin. It is hosted by the Middle Triassic turbidite. Wall rock alterations, including silicification, pyritization, arsenopyritization, carbonatization and argillization, commonly occur along fractures. PGE study demonstrates that either Permian basalts or Triassic ultrabasic intrnsives are unlikely to be the main source of gold mineralization. Coupled with the lack of other nmgmatic activity in the vicinity of the mining area, an amagmatic origin is proposed. Organic matter compositions and GC-MS analysis of the ores and host rocks show that the organics in the ores and the host rocks have a common source; the organic matter in the ores was mainly indigenous. The positive correlation between S2 and Au contents, along with the common occurrence of organic inclusions, suggest involvement of organic matter in the ore-forming process in terms of promoting Au leaching from the source rocks, making colloidal Au migration possible, as well as hydrocarbon reduction of sulphate. Geological and geochemical characteristics of the Lannigou deposit suggest that it was formed through circulation of meteoric water and probably less importantly organic bearing formation water driven by high geothermal gradient caused by late Yanshanian extension, which leached Au from the source bed, and then migrated as Au-bisnlfides and colloidal Au, culminating in deposition by reduction-adsorption and surface complexation of gold onto the growth surface of arsenlan pyrite.
文摘1 Geological setting of the deposit THE Qiaogashan gold deposit is located at contact zone of middle Tianshan terrance and south Tianshanback-arc basin, and near the latter side. The orebodies are controlled by middle Tianshan brittle-ductileshear zone. The main ore types are auriferous quartz veins and fractured and alterated rocks. The southpart of the deposit is hosted in striking sheared Devonian rocks, while the north part in a diorite body,which was deformed by a nape shear zone. 2 Geology and geochemistry of host rocks The host rocks of south part of the deposit are Devonian detrital stone of terrigenous origin, interlayering volcanic detrial stone of back-arc basin facies, which locally suffered intensive ductile-brittle shearing. The rock type is composed mainly of gray-green siltstone, poststone, metasiltstone, etc., and a se-
文摘Most gold deposits in intrusive rocks were formed as a result of reworking processes.The intrusive rocks containing gold deposits and consisting of ultramafic-mafic, intermediate-acid and alkaline rocks of the Archean, Proterozoic, Caledonian, Hercynian and Yenshanian periods occur in cratons, activated zones of cratons and fold belts. Among them, ultramafic-mafic rocks, diorite, alkaline rocks, and anorthosite are products of remelting in the mantle or mantle-crust or mantle with crustal contamination. However, auriferous intermediate-acid rocks are products of metasomatic-remelting in auriferous volcanic rocks or auriferous volcano-sedimentary rocks in the deep crust.
基金This study was supported by the China Scholarship Council(GrantNo.160)National Nature Science Foundation of China(Grant No.400722006)the Key Task Project of Science and Technology of Liaoning Province(GrantNo.2001230001).
文摘Standard laboratory procedures and remote sensing techniques were employed in the characterization of gold bearing rocks of the Paishanlou area. Results indicate that, the rocks were formed in an alteration complex of medium temperature and pressure. The area was under intense polymetamorphism (ductile shearing, and hydrothermal metamorphism), which occurred along the deformation zone stretching from Jinzhou to Fuxin. The area bears some propylitic, phyllic (or sericitic) and argillic alteration styles. Gold minerals are contained in fine grained pyrite in silicified zones, and associated with metamorphosed Precambrian rocks. The host rock is composed of gneiss, mylonite and trondhjemite granite, and has a distinctive gold lead geochemical affinity.
