The Bangbu gold deposit is a large orogenic gold deposit in Xizang formed during the AlpineHimalayan collision.Ore bodies(auriferous quartz veins)are controlled by the E-W-trending Qusong-Cuogu-Zhemulang brittle-ducti...The Bangbu gold deposit is a large orogenic gold deposit in Xizang formed during the AlpineHimalayan collision.Ore bodies(auriferous quartz veins)are controlled by the E-W-trending Qusong-Cuogu-Zhemulang brittle-ductile shear zone.Quartz veins at the deposit can be divided into three types:pre-metallogenic hook-like quartz veins,metallogenic auriferous quartz veins,and postmetallogenic N-S quartz veins.Four stages of mineralization in the auriferous quartz veins have been identified:(1)Stage S1 quartz+coarse-grained sulfides,(2)Stage S2 gold+fine-grained sulfides,(3)Stage S3 quartz+carbonates,and(4)Stage S4 quartz+greigite.Fluid inclusions indicate the oreforming fluid was CO_2-N_2-CH_4 rich with homogenization temperatures of 170–261°C,salinities 4.34–7.45 wt%Na Cl equivalent.δ^(18)Ofluid(3.98‰–7.18‰)and lowδDV-SMOW(-90‰to-44‰)for auriferous quartz veins suggest ore-forming fluids were mainly metamorphic in origin,with some addition of organic matter.Quartz vein pyrite hasδ^(34)SV-CDT values of 1.2‰–3.6‰(an average of 2.2‰),whereas pyrite from phyllite hasδ^(34)SV-CDT 5.7‰–9.9‰(an average of 7.4‰).Quartz vein pyrites yield 206Pb/204 Pb ratios of 18.662–18.764,207Pb/204 Pb 15.650–15.683,and^(208)Pb/204 Pb 38.901–39.079.These isotopic data indicate Bangbu ore-forming materials were probably derived from the Langjiexue accretionary wedge.40Ar/39 Ar ages for sericite from auriferous sulfide-quartz veins yield a plateau age of 49.52±0.52 Ma,an isochron age of 50.3±0.31 Ma,suggesting that auriferous veins were formed during the main collisional period of the Xizang-Himalayan orogen(-65–41 Ma).展开更多
基金funded by the National Basic Research Program of China(No.2011CB403104)Geological Survey Project of China(No.12120113037901)
文摘The Bangbu gold deposit is a large orogenic gold deposit in Xizang formed during the AlpineHimalayan collision.Ore bodies(auriferous quartz veins)are controlled by the E-W-trending Qusong-Cuogu-Zhemulang brittle-ductile shear zone.Quartz veins at the deposit can be divided into three types:pre-metallogenic hook-like quartz veins,metallogenic auriferous quartz veins,and postmetallogenic N-S quartz veins.Four stages of mineralization in the auriferous quartz veins have been identified:(1)Stage S1 quartz+coarse-grained sulfides,(2)Stage S2 gold+fine-grained sulfides,(3)Stage S3 quartz+carbonates,and(4)Stage S4 quartz+greigite.Fluid inclusions indicate the oreforming fluid was CO_2-N_2-CH_4 rich with homogenization temperatures of 170–261°C,salinities 4.34–7.45 wt%Na Cl equivalent.δ^(18)Ofluid(3.98‰–7.18‰)and lowδDV-SMOW(-90‰to-44‰)for auriferous quartz veins suggest ore-forming fluids were mainly metamorphic in origin,with some addition of organic matter.Quartz vein pyrite hasδ^(34)SV-CDT values of 1.2‰–3.6‰(an average of 2.2‰),whereas pyrite from phyllite hasδ^(34)SV-CDT 5.7‰–9.9‰(an average of 7.4‰).Quartz vein pyrites yield 206Pb/204 Pb ratios of 18.662–18.764,207Pb/204 Pb 15.650–15.683,and^(208)Pb/204 Pb 38.901–39.079.These isotopic data indicate Bangbu ore-forming materials were probably derived from the Langjiexue accretionary wedge.40Ar/39 Ar ages for sericite from auriferous sulfide-quartz veins yield a plateau age of 49.52±0.52 Ma,an isochron age of 50.3±0.31 Ma,suggesting that auriferous veins were formed during the main collisional period of the Xizang-Himalayan orogen(-65–41 Ma).
