Genesis of the gold deposit in the Indus-Yarlung Tsangpo suture zone, southern Tibet

evidence from geological and geochemical data

Xiong Zhang, Xueguo Deng, Zhusen Yang, Zengqian Hou, Yuanchuan Zheng, Yingchao Liu, Xiaoyan Zhao*, Bo Xu, Yingru Pei, Jinsheng Zhou, Miao Zhao, Jianfei Yuan

*Corresponding author for this work

Research output: Contribution to journalArticle

5 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)947-970
Number of pages24
JournalActa Geologica Sinica
Volume91
Issue number3
DOIs
Publication statusPublished - Jun 2017

Keywords

  • geology
  • gold mineralization
  • Nianzha Deposit
  • lndus-Yarlung Tsangpo suture zone
  • Tibet

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