Volume 91, Issue 3 pp. 947-970
Original Articles
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Genesis of the Gold Deposit in the Indus-Yarlung Tsangpo Suture Zone, Southern Tibet: Evidence from Geological and Geochemical Data

Xiong ZHANG

Xiong ZHANG

School of Earth sciences and Resources, China University of Geosciences, Beijing 100083 China

MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037 China

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Xueguo DENG

Xueguo DENG

Institute of Metallurgical Geology and Exploration, Sichuan, Chengdu, 610000 China

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Zhusen YANG

Zhusen YANG

MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037 China

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Zengqian HOU

Zengqian HOU

Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037 China

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Yuanchuan ZHENG

Yuanchuan ZHENG

School of Earth sciences and Resources, China University of Geosciences, Beijing 100083 China

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Yingchao LIU

Yingchao LIU

Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037 China

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Xiaoyan ZHAO

Corresponding Author

Xiaoyan ZHAO

MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037 China

Corresponding author. E-mail: [email protected]Search for more papers by this author
Bo XU

Bo XU

ARC Centre of Excellence for Core to Crust Fluid System (CCFS) and GEMOC, Department Of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109 Australia

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Yingru PEI

Yingru PEI

School of Earth sciences and Resources, China University of Geosciences, Beijing 100083 China

MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037 China

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Jinsheng ZHOU

Jinsheng ZHOU

Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037 China

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Miao ZHAO

Miao ZHAO

MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037 China

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Jianfei YUAN

Jianfei YUAN

Institute of Metallurgical Geology and Exploration, Sichuan, Chengdu, 610000 China

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First published: 05 July 2017
Citations: 14

About the first author:

ZHANG Xiong: Male, born in 1988 in Guyuan City, Ningxia Hui Autonomous Region; doctoral student; study in School of Earth sciences and Resources, China University of Geosciences, Beijing; His research interests is mainly in orogenic gold deposits. Email: [email protected].

Abstract

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 mélange in the footwall to the south. High-grade mineralization occurs in a fracture zone between diorite and ultramafic rock in the Renbu tectonic mélange. The wall-rock alteration is characterized by silicification in the fracture zone, serpentinization and the formation of talc and magnesite in the ultramafic 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 H2O–NaCl–organic gas fluids that homogenize at temperatures of 203°C–347°C and have salinities of 0.35wt%–17.17wt% NaCl equivalent. The quartz veins yield δ18Ofluid values of 0.15‰–10.45‰, low δDV-SMOW values (−173‰ to −96‰), 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 microcontinent, and Nianzha-type ophiolite-associated orogenic Au deposits. The three types formed at different depths in an accretionary orogenic tectonic setting. The Bangbu type was formed at the deepest level and the Nianzha type at the shallowest.

 

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