Table of Contents Author Guidelines Submit a Manuscript
Geofluids
Volume 2017, Article ID 2417209, 22 pages
https://doi.org/10.1155/2017/2417209
Research Article

The Au-Hosting Minerals and Process of Formation of the Carlin-Type Bojitian Deposit, Southwestern China

1State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
2Institute of Karst Geology, Karst Dynamics Laboratory, Ministry of Land and Resources, Chinese Academy of Geological Sciences, Guilin 541004, China
3School of Geosciences, China University of Petroleum (East China), Qingdao 266580, China
4Key Laboratory of Nuclear Resources and Environment, Ministry of Education, College of Earth Sciences, East China Institute of Technology, Nanchang 330013, China

Correspondence should be addressed to Kai Hu; nc.ude.ujn@uhiak

Received 26 February 2017; Accepted 24 May 2017; Published 9 July 2017

Academic Editor: Weidong Sun

Copyright © 2017 Kai Hu 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 recently discovered middle-sized Bojitian Carlin-type Au deposit is located in southwestern Guizhou Province, China, near the well-known Shuiyindong super-large-sized deposit. To improve the understanding on this deposit, here we investigate the minerals that host Au and the occurrence of Au in the deposit, using a combination of microscopic work and electron probe microanalysis (EPMA). Based on the results, the formation of the deposit was addressed. Results indicate that the dominant minerals that host Au include arsenian pyrite and arsenopyrite. Au in the cores of zoned pyrite exists mainly as natural nanoscale Au (Au0), while Au in the rims exists mainly as solid solution Au (Au+), but it likely also exists in the rims as natural nanoscale Au. The framboidal, coarse-grained, and banded pyrite types contain both natural nanoscale Au0 and solid solution Au+. The arsenopyrite is of hydrothermal origin, and Au within the arsenopyrite exists as gold solution Au+. The Bojitian deposit was formed from As-bearing, H2S-rich, low-to-medium-temperature fluids that migrated along faults and other channels. Au that was already present in the strata or source beds migrated with the fluids in the form of Au(HS) and ore-forming fluids were then formed in the reducing environment. The ore-forming fluids interacted with Fe-rich carbonates to form an abundance of Au-hosting arsenian sulfides.