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Geofluids
Volume 2017 (2017), Article ID 2410504, 19 pages
https://doi.org/10.1155/2017/2410504
Research Article

Nature and Evolution of the Ore-Forming Fluids from Nanmushu Carbonate-Hosted Zn-Pb Deposit in the Mayuan District, Shaanxi Province, Southwest China

1State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Resources and Collaborative Innovation Center for Exploration of Strategic Mineral Resources, China University of Geosciences, Wuhan 430074, China
2State Key Laboratory for Mineral Deposits Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, China

Correspondence should be addressed to Shao-Yong Jiang

Received 5 May 2017; Revised 21 August 2017; Accepted 24 October 2017; Published 21 November 2017

Academic Editor: Sabina S. Palinkas

Copyright © 2017 Suo-Fei Xiong et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The Nanmushu carbonate-hosted Zn-Pb deposit is located in the Mayuan district of Shaanxi Province, a newly discovered metallogenic district next to the Sichuan Basin, in the northern margin of the Yangtze Block, which is the largest and the only one that is currently mined in this district. The δ34S values of sulfides are characterized by positive values with a peak around +18, and the reduced sulfur may have derived from reduction of from paleoseawater or evaporitic sulfates that have possibly been leached by basinal brines during mineralization stage. Detailed fluid inclusion study shows two types of fluids in the sphalerite, quartz, dolomite, calcite and barite, that is, aqueous-salt dominant inclusions (type I) and hydrocarbon-bearing inclusions (type II). The Laser Raman spectroscopy study shows occurrence of certain amount of CH4, C4H6, and bitumen. The salinities show similar values around 6 to 12 wt% NaCl equivalent but a decreasing temperature from early to late stages (typically 200° to 320°C in stage I, 180° to 260°C in stage II, and 140° to 180°C in stage III). These features may be related to basinal brines mixing between an external higher salinity CaCl2  ±  MgCl2-rich fluid and a local H2O-NaCl methane-rich fluid.