PENG Yi-wei¹，GU Xue-xiang¹，LIU Li¹，CHENG Wen-bin²，ZHANG Yong-mei¹，WU Cheng-yun¹，LV Peng-rui¹

（1. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;
2. College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China)

Abstract：The Zimudang gold deposit is a typical example of micro-disseminated (Carlin-type) gold deposits in Southwest Guizhou Province, China. The petrographic observation and microthermometric study were carried out on the fluid inclusions from main stage (Ⅱ) quartz and calcite as well as late stage (Ⅲ) calcite from the deposit. Major types of fluid inclusions include aqueous inclusions, pure CO2 inclusions, CO2-H2O inclusions, CH4 inclusions, and CH4-H2O inclusions. The pure CO2 inclusions and CO2-H2O inclusions were only recognized in the main stage (Ⅱ) quartz. The homogenization temperatures, salinities and densities of the main stage (Ⅱ) range 180–220 ℃, 0.35%–7.45% of NaCl, and 0.745–0.969 g/cm3, respectively, while those of the late stage (Ⅲ) vary in the ranges of 100–180℃, 0.18%–5.71% NaCl, and 0.868–0.993 g/cm3,respectively. The ore-forming fluids were characterized by a H2O-NaCl-CO2 system with medium to low temperature, low salinity, and medium density. The fluid inclusiondata indicate that the gold mineralization was a process of decrease in temperature and salinity and slight increase in density of the ore-forming fluids. Immiscibility of the H2O-NaCl-CO2 fluidsystem occurred during the main mineralization stage (Ⅱ), resulting precipitation of Au and formation of the ore deposit. The CO2 - and CH4-bearing fluid played an important role in the formation of the deposit.

Key words：CO2 fluid; CH4-bearing fluid; fluid inclusion; immiscibility; Zimudang gold deposit

E-mail: xuexiang_gu@cugb.edu.cn

ACTA MINERALOGICA SINICA Vol. 32, No. 2, 2012, Page 211-220