湘西花垣地区铅锌矿床流体包裹体显微测温与特征元素测定

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

花垣铅锌矿床的成矿流体演化特点和铅锌矿物沉淀机制存有分歧,为了总结矿床成因并建立成矿模式,指导该地区铅锌矿的下一步找矿勘探工作.对闪锌矿、主成矿期方解石和萤石中的流体包裹体进行岩相学观察、显微测温、拉曼光谱分析以及同步辐射X射线荧光微探针分析,结果显示花垣地区铅锌矿床成矿流体温度主要为150~220℃,总盐度一般为13%~23%NaCl_(eqv),多>15%NaCleqv,密度多>1g/cm^3,成矿流体为NaCl-CaCl_2-MgCl_2-H_2O卤水体系.成矿流体均一温度具有由北而南降低的趋势.流体液相组分中主要为Ca^(2+)、Mg^(2+)、Na^+、Cl^-,具有盆地热卤水体系特点.流体包裹体气相中发育CO_2、CH_4,方解石、萤石中流体包裹体均有成矿元素Pb、Zn的存在.花垣矿集区成矿流体属于低温度、中-高盐度、中-高密度,成分以钠和钙氯化物为主的含矿热水溶液,流体运移方向为由北向南,流体来源于封层水、大气降水和少量变质水.铅锌矿物的沉淀与热化学硫酸盐还原作用有关.闪锌矿、方铅矿等矿石矿物与方解石、萤石等脉石矿物应属同一富含Pb、Zn、Mn、Fe、As、Cr等成矿元素的成矿流体在同一成矿期次相同条件下沉淀的产物.

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% NaCleqv（mostly15% NaCleqv）Density1 g/cm^3.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 Ca^2＋,Mg^2＋,Na^＋,Cl^-,and have the characteristics of hot brine system in the basin.CO2 and CH_4 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 fluidis 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.