Microthermometry and Characteristic Elements Determination of the Fluid Inclusions of the Huayuan Lead-Zinc Deposit in Western Hunan

To understand the evolution of ore-forming fluids and the mechanism of lead-zinc mineral deposition in the Huayuan lead-zinc deposit, summarize the genesis of the deposit and establish a metallogenic model to guide the prospecting and exploration of lead-zinc deposits in the region, petrophysical observation, micro-temperature measurement, Raman spectroscopy and synchrotron radiation X-ray fluorescence microprobe analysis were carried out on the fluid inclusions in sphalerite, calcite and fluorite in the main mineralization stage. In this paper The results show that the ore-forming fluid temperature of lead-zinc deposit in the Huayuan area is mainly 150-220℃, and the total salinity is generally 13%-23% NaCl_eqv (mostly > 15% NaCl_eqv) Density > 1 g/cm³. The ore fluid is NaCl-CaCl₂-MgCl₂-H₂O brine system. The homogenization temperature of the ore-forming fluid has a tendency to decrease from north to south. The main components of the fluid are Ca²⁺, Mg²⁺, Na⁺, Cl^-, and have the characteristics of hot brine system in the basin. CO₂ and CH₄ are commonly observed as gas phase of fluid inclusions. Pb and Zn contents above determination limits were examined in the fluid inclusions of both calcite and fluorite. The ore-forming fluids in the Huayuan ore field belong to the low-temperature, medium-high salinity, medium-high density hydrothermal solution, the composition is sodium and calcium chloride-based basin brine. The direction of fluid flow is from north to south. the fluid is derived from formation water, atmospheric precipitation and a small amount of metamorphic water. The precipitation of lead-zinc minerals is related to the thermochemical reduction of sulfate. Sphalerite, galena, calcite and fluorite may have precipitated from the same ore-forming fluid rich in Pb, Zn, Mn, Fe, As, Cr, in the same ore-forming period and under the same conditions.