Mineralogical and geochemical study of hydrothermal dolomite from the Daliang zinc deposit in Guizhou, Southwest China: new evidence for the genesis

The Daliang zinc deposit occurs in the southwestern Xiangxi-Qiandong Zn-Pb metallogenic belt and is located on the southeastern margin of the upper Yangtze block. In this study, we present results from petrographic observations, rare earth elements, C-H-O isotopes, and fluid inclusions. The zinc deposit is hosted by middle Cambrian dolomite. The ore-forming process is divided into three stages from early to late: pyrite-galena, sphalerite-pyrite-dolomite, and dolomite. The characteristics of the REEs suggest that multiple fluids were involved in hydrothermal dolomite precipitation under low-temperature conditions. Two types of hydrothermal dolomite fluid inclusions were identified: pure liquid phase inclusions and liquid-rich phase inclusions. The fluid inclusions of hydrothermal dolomite yield homogenization temperatures of 108–192 °C (average 153 °C), with salinities of 12.3–26.4 wt% (average 23.0 wt%) NaCl equiv. The δ 13 C fluid , δD fluid and δ 18 O fluid values for ore-forming fluids range from −4.2 to −3.5‰ (mean −3.8‰), −38.8 to −34.3‰ (mean −36.0‰), and 6.2–6.4‰ (mean 6.3‰), respectively. This study demonstrates that ore-forming fluid was sourced from a moderate- to high-salinity basinal brine and leached metals from metasedimentary rocks of the basement in the Yangtze block. The main transportation of ore-forming fluid occurred in the form of chlorine complexes along well-developed faults, and sulfides precipitated with decreases in pressure and temperature, as well as pH changes. Studies of the Daliang zinc deposit suggest that it is a medium- to low-temperature MVT-like deposit.