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Geofluids
Volume 2018, Article ID 4261795, 19 pages
https://doi.org/10.1155/2018/4261795
Research Article

Physiochemical Restrictions of Mineral Zoning of Sediment-Hosted Stratiform Copper Deposit in SW China

1Southwest Institute of Geological Survey, Geological Survey Center for Non-Ferrous Mineral Resources, Kunming University of Science and Technology, Kunming 650093, China
2State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, China
3Kunming Geological Prospecting Institute, China Metallurgical Geological Bureau, Kunming, Yunnan 650024, China

Correspondence should be addressed to Runsheng Han; moc.qq@240076455

Received 4 November 2017; Accepted 22 January 2018; Published 26 February 2018

Academic Editor: Andri Stefansson

Copyright © 2018 Yan Zhang 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 Chuxiong basin, located in southwest China, is well known as a mineralization area of red-bed type copper deposits in China. These deposits are characterized by mineral zoning, which is especially true for the Dayao deposits. The mineral zoning is consistent for both horizontal and vertical zoning; from the base (center) of the ore body to the top (outermost), the mineral zones are from hematite, chalcocite, chalcocite + bornite, and bornite + chalcopyrite to pyrite. We studied the mineral zoning in detail using a thermodynamic phase diagram method, such as -, pH-, and pH-Eh, and discussed the constraints on the order of the minerals precipitation under different physiochemical conditions. It is indicated that changes in temperature have little effect on pH and Eh in the formation of minerals. S2− is stable only below 473 K, and the forming temperature of chalcocite must be below 473 K. In this paper, we also explain the mineral zoning formation mechanism and propose that the main controlling factor of mineral zoning is pH. Because this mineral zoning is widespread in sediment-hosted deposits, studies on this mechanism can considerably promote better understanding of the genesis of ore deposits in order to guide the exploration.