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
The Nianzha gold deposit,located in the central section of the Indus-Yarlung Tsangpo suture(IYS)zone in southern Tibet,is a large gold deposit(Au reserves of 25 tons with average grade of 3.08 g/t)controlled by a E-W ...The Nianzha gold deposit,located in the central section of the Indus-Yarlung Tsangpo suture(IYS)zone in southern Tibet,is a large gold deposit(Au reserves of 25 tons with average grade of 3.08 g/t)controlled by a E-W striking fault that developed during the main stage of Indo-Asian collision(-65-41 Ma).The main orebody is 1760 m long and 5.15 m thick,and occurs in a fracture zone bordered by Cretaceous diorite in the hanging wall to the north and the Renbu tectonic melange in the footwall to the south.High-grade mineralization occurs in a fracture zone between diorite and ultramafic rock in the Renbu tectonic melange.The wall-rock alteration is characterized by silicification in the fracture zone,serpentinization and the formation of talc and magnesite in the uitramafic unit,and chloritization and the formation of epidote and calcite in diorite.Quartz veins associated with Au mineralization can be divided into three stages.Fluid inclusion data indicate that the deposit formed from H20-NaCl-organic gas fluids that homogenize at temperatures of 203℃-347℃and have salinities of 0.35wt%-17.17wt%NaCI equivalent.The quartz veins yieldδ18Ofluid values of 0.15‰-10.45‰,lowδDv-SMow values(-173%o to-96%o),and theδ13C values of-17.6‰to-4.7‰,indicating the ore-forming fluids were a mix of metamorphic and sedimentary orogenic fluids with the addition of some meteoric and mantle-derived fluids.The pyrite within the diorite hasδ34SV-CDT values of-2.9‰-1.9‰(average-1.1‰),206pb/204pb values of 18.47-18.64,207pb/204pb values of 15.64-15.74,and 208pb/204pb values of 38.71-39.27,all of which are indicative of the derivation of S and other ore-forming elements from deep in the mantle.The presence of the Nianzha,Bangbu,and Mayum gold deposits within the IYS zone indicates that this area is highly prospective for large orogenic gold deposits.We identified three types of mineralization within the IYS,namely Bangbu-type accretionary,Mayum-type microcontinent,and Nianzha-type ophiolite-associated orogenic Au deposits.The three types formed at different depths in an aeeretionary orogenic tectonic setting.The Bangbu type was formed at the deepest level and the Nianzha type at the shallowest.展开更多
Objective The Shangxu gold deposit is located in the south of the middle Bangong-Nujiang suture zone in northern Tibet. The origin of this deposit as an orogenic gold deposit is debatable. The study of the Shangxu de...Objective The Shangxu gold deposit is located in the south of the middle Bangong-Nujiang suture zone in northern Tibet. The origin of this deposit as an orogenic gold deposit is debatable. The study of the Shangxu deposit has a profound implication on gold exploration in the Bangong- Nujiang metallogenic belt and can also improve our understanding of gold mineralization in northern Tibet.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).
基金provided by the National Key Research and Development Program of China"Deep Structure and Ore-forming Process of Main Mineralization System in Tibetan Orogen"(2016YFC0600300)the National Basic Research Program of China(2011CB403104)+1 种基金the China Geological Survey(12120113037901)the National Natural Science Foundation of China(41320104004)and(41503040)
文摘The Nianzha gold deposit,located in the central section of the Indus-Yarlung Tsangpo suture(IYS)zone in southern Tibet,is a large gold deposit(Au reserves of 25 tons with average grade of 3.08 g/t)controlled by a E-W striking fault that developed during the main stage of Indo-Asian collision(-65-41 Ma).The main orebody is 1760 m long and 5.15 m thick,and occurs in a fracture zone bordered by Cretaceous diorite in the hanging wall to the north and the Renbu tectonic melange in the footwall to the south.High-grade mineralization occurs in a fracture zone between diorite and ultramafic rock in the Renbu tectonic melange.The wall-rock alteration is characterized by silicification in the fracture zone,serpentinization and the formation of talc and magnesite in the uitramafic unit,and chloritization and the formation of epidote and calcite in diorite.Quartz veins associated with Au mineralization can be divided into three stages.Fluid inclusion data indicate that the deposit formed from H20-NaCl-organic gas fluids that homogenize at temperatures of 203℃-347℃and have salinities of 0.35wt%-17.17wt%NaCI equivalent.The quartz veins yieldδ18Ofluid values of 0.15‰-10.45‰,lowδDv-SMow values(-173%o to-96%o),and theδ13C values of-17.6‰to-4.7‰,indicating the ore-forming fluids were a mix of metamorphic and sedimentary orogenic fluids with the addition of some meteoric and mantle-derived fluids.The pyrite within the diorite hasδ34SV-CDT values of-2.9‰-1.9‰(average-1.1‰),206pb/204pb values of 18.47-18.64,207pb/204pb values of 15.64-15.74,and 208pb/204pb values of 38.71-39.27,all of which are indicative of the derivation of S and other ore-forming elements from deep in the mantle.The presence of the Nianzha,Bangbu,and Mayum gold deposits within the IYS zone indicates that this area is highly prospective for large orogenic gold deposits.We identified three types of mineralization within the IYS,namely Bangbu-type accretionary,Mayum-type microcontinent,and Nianzha-type ophiolite-associated orogenic Au deposits.The three types formed at different depths in an aeeretionary orogenic tectonic setting.The Bangbu type was formed at the deepest level and the Nianzha type at the shallowest.
基金supported by the National Natural Science Foundation of China(grant No.41320104004)the Ministry of Science and Technology of China(973 Project,grant No.2011CB403104)
文摘Objective The Shangxu gold deposit is located in the south of the middle Bangong-Nujiang suture zone in northern Tibet. The origin of this deposit as an orogenic gold deposit is debatable. The study of the Shangxu deposit has a profound implication on gold exploration in the Bangong- Nujiang metallogenic belt and can also improve our understanding of gold mineralization in northern Tibet.
