Genesis Of Fluorite Deposit In Xiong'er Mountain Area,Southwestern Henan Province

The Xiong'ershan district,located in Western Henan Province of Central China,is belongs to the junction of the southern part of the North China Craton and the Eastern part of the Qinling orogenic belt.The oldest unit in the region is the Paleoproterozoic Taihua Group,covered by the the lowest cover of the Mesoproterozoic Xiong'er Group.This region experienced several periods of subduction-collision-accretion processes.After the collision between the North China Craton and the Yangtze Craton,the land-continuation orogeny,multi-stage thrust nappe and demolition,a large number of metal and nonmetal deposits were formed.In recent years,a large number of large-medium sized fluorite deposits have been discovered in this area.This study aims to gain insights into ore genesis based on a systematic analysis of geological,geochemical and fluid inclusions properties of typical fluorite deposits(e.g.,the Angou and Shimenzhai deposits).This paper obtained the following achievements:1.This paper elaborates on the nature of the ore deposit including wall rocks,structures,mineralization and alteration.The surrounding rocks of the Angou fluorite deposit are Taihua Group;.The ore-bearing strata of the Shimenzhai fluorite deposit is the Jiuping group of the Xiong'er group.The fluorite vein systems in this regional are fault-controlled.2.The fluid inclusions of fluorite deposits in the study area are mainly composed of liquid-rich and/or vapor-rich two-phase inclusions.The inclusions have many and large features.The ore-forming fluids are featured by low-temperature and low-salinity,and the ore-forming fluid are dominantly of meteoric water origin.The homogenization temperatures of fluid inclusions in the Angou fluorite deposit range from 140 °C to 160 °C,and the salinity is concentrated in 0.1% NaCleqv-0.6% NaCleqv.The fluid inclusions in the Shimenzhai fluorite deposit homogenize to the liquid phase at 150 °C-165 °C,with corresponding salinities less than 0.2% NaCleqv.3.The trace element compositions of different samples from the the Angou and shimenzhai deposits are consistent.Furthermore,fluorite samples share similar chondrite-normalized REE patterns.4.The geochemical characteristics of rare earth elements,the typical fluorite deposits are mainly characterized by the enrichment trend of light rare earth elements,and the similarity pattern of rare earth elements is similar to the ore-bearing strata.Among them,the Angou and Shimenzhai fluorite deposits are both negative anomalies,and the anomalies of Angou are consistent with the anomalous conditions of the Taihua Group in the ore-bearing strata.5.The ore-forming materials of the fluorite deposits are derived from the ore-bearing strata.The atmospheric precipitation causes leaching of the surrounding rocks,enriching the minerals,and the ore-forming hydrothermal fluid is filled in the fissures to precipitate the fluorite through the water-rock reaction.