Mixing in Two Types of Fluids Responsible for Some Carbonate-Hosted Pb–Zn Deposits, SW China: Insights from the Maoping Deposit

Abstract

Carbonate-hosted Pb–Zn deposits are of major economic importance. The Sichuan–Yunnan–Guizhou metallogenetic belt (SYGMB), located on the western margin of the Yangtze Block, comprises over 400 carbonated-hosted Pb–Zn deposits. However, ore-forming fluids recorded in these deposits have led to controversy regarding ore genesis. We investigated a fluid system for the Maoping deposit in the SYGMB, based on fluid inclusions, and H–O–He–Ar isotopic studies. The results showed that ore-forming fluids in the Maoping deposit are characterized by mixing of high-temperature and low-salinity metamorphic fluids and low-temperature and high-salinity basinal brines. The Precambrian basement is considered to produce metamorphic fluids, while the basinal brines are said to originate from the Youjiang Basin. The mineralization at the depositional site appears to reflect the coincidence of the metamorphic fluids, basinal brines, Carboniferous coal seams, and structural-stratigraphic traps. Regional-scale data show large-scale heterogeneity in fluid properties, including basinal brines, metamorphic fluids, and organic fluids. Furthermore, the data suggest a precipitation model for some high-grade Pb–Zn deposits in the SYGMB. These findings will contribute to an understanding of deposit types in the SYGMB.