DAI De-rong¹, HE Xiao-hu², JIN Shao-rong¹, YANG De-zhi¹, DONG Shao-ji², ZHOU Jia-xi^2,3*

(1. Institute of Geophysical and Geochemical Prospecting, Bureau of Geology and Mineral Exploration and Development of Guizhou Province, Guiyang 5500018, China;
2. School of Resource Environment and Earth Sciences, Yunnan University, Kunming 650504, China;
3. Stake Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China)

Abstract: In this paper, the metallogenic characteristics and geochemistry of fluid inclusions within fluorite from four typical fluorite deposits in Puan, Qinglong, Zhenfeng, and Wangmo counties in Southwest Guizhou have been systematically studied. Orebodies of these fluorite deposits are mainly controlled by the “Dachang Bed”, which is sandwiched between the Permian basalt and Permian Maokou Formation, with minor orebodies developed in faults within the basalt and its overlying and underlying limestone strata. The geochemical characteristics of fluid inclusions within different types (colored) of fluorites from four typical fluorite deposits are quite different. Fluid inclusions in the purple fluorite have relatively high homogenization temperatures varying from 157 to 264 ℃ (average 190 ℃) and salinities varying from 4.03 to 5.26% NaCl equiv. Fluid inclusions in the light colored fluorite have relatively low homogenization temperatures varying from 100 to 176 ℃ (average 140 ℃) and salinities varying from 1.91 to 5.86% NaCl equiv.  Microscopic laser Raman spectroscopy analysis shows that the compositions of fluid inclusions within different types (colored) of fluorites are similar, with major gas phases of H₂, H₂S, and CH₄, minor gas phases of of CO₂ and hydrocarbon, and liquid phase components of H₂O (L), HCO^3-, and HS^-. The geochemical characteristics of fluid inclusions show that the ore-forming fluids of fluorite deposits in southwestern Guizhou are characterized with the medium-low homogenization temperatures and low salinities NaCl-H₂O system. Combined with previous research data, It is believed that the ore-forming fluids of the fluorite deposits could be sourced from the same original  fluids for the Sb  and even Au mineralization in the area, but the fluorite deposits were  formed, in forms of layered, lenticular fluorite orebodies in the “Dachang Bed” or veining orebodies in faults within the basalts and limestone, by the evolved fluids through the processes of fluids mixing at the early stage and water-rock interactions in the late mineralization stage.

Keywords: fluorite deposit; fluid inclusion; homogenization temperature; salinity; ore genesis; Southwest Guizhou