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...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 yield δ18Ofluid values of 0.15‰-10.45‰, low δDv-SMow values （-173%o to -96%o）, and the δ13C 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 has δ34SV-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 microcontin展开更多
The Zedong Terrane forms a discontinuous belt of volcanic and volcaniclastic rocks adjacent to the Yarlung Zangbo River in south eastern Tibet. It extends from Luobusa to 20km west of Zedong. The Zedong Terrane lies w...The Zedong Terrane forms a discontinuous belt of volcanic and volcaniclastic rocks adjacent to the Yarlung Zangbo River in south eastern Tibet. It extends from Luobusa to 20km west of Zedong. The Zedong Terrane lies within the Indus—Yarlung Zangbo suture zone and may represent an intra\|oceanic island arc that once lay between the Lhasa (Asian) and Himalayan (Indian) terranes. Rare fossils within the terrane indicate active volcanism during the Early Cretaceous.Ultramafic rocks of the Dazhuqu Terrane, including harzburgite and gabbro are thrust over the southern margin of the Zedong Terrane along a steep south\|dipping thrust fault. To the west of Zedong, this fault is marked by a distinctive zone of serpentinite. East of Zedong, the northernmost rocks of the terrane are thrust onto Oligocene molasse deposits of the Luobusa Formation and Cretaceous plutonic rocks of the Gangdese batholith (Lhasa Terrane). These thrusts form part of a northward directed thrust stack \| the Renbu\|Zedong thrust system of Yin et al.., (1994, 1999).展开更多
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 yield δ18Ofluid values of 0.15‰-10.45‰, low δDv-SMow values （-173%o to -96%o）, and the δ13C 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 has δ34SV-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 microcontin
文摘The Zedong Terrane forms a discontinuous belt of volcanic and volcaniclastic rocks adjacent to the Yarlung Zangbo River in south eastern Tibet. It extends from Luobusa to 20km west of Zedong. The Zedong Terrane lies within the Indus—Yarlung Zangbo suture zone and may represent an intra\|oceanic island arc that once lay between the Lhasa (Asian) and Himalayan (Indian) terranes. Rare fossils within the terrane indicate active volcanism during the Early Cretaceous.Ultramafic rocks of the Dazhuqu Terrane, including harzburgite and gabbro are thrust over the southern margin of the Zedong Terrane along a steep south\|dipping thrust fault. To the west of Zedong, this fault is marked by a distinctive zone of serpentinite. East of Zedong, the northernmost rocks of the terrane are thrust onto Oligocene molasse deposits of the Luobusa Formation and Cretaceous plutonic rocks of the Gangdese batholith (Lhasa Terrane). These thrusts form part of a northward directed thrust stack \| the Renbu\|Zedong thrust system of Yin et al.., (1994, 1999).
