延边杨金沟大型白钨矿矿床流体包裹体特征及成因探讨

延边杨金沟大型白钨矿矿床的成矿过程可划分为黄铁矿-毒砂阶段、石英-粗粒白钨矿阶段、石英-多金属硫化物-细粒白钨矿阶段以及碳酸盐阶段，其中，石英-粗粒白钨矿阶段为主成矿阶段。与粗粒白钨矿共生的石英中主要发育4种类型流体包裹体。Ⅰ型包裹体的气相组分主要由CO₂、CH₄和N₂组成，均一温度为278.5～336.4℃，盐度（w(NaCl)）为3.53%～7.72%；Ⅱ型气液两相包裹体均一温度为144.7~345.9℃,多数为190～220℃，w(NaCl)为3.05%～9.34%；Ⅲ型CO₂包裹体中的气相组分均为CO₂，液相中尚含少量CH₄等组分；Ⅳ型含CO₂三相包裹体由液态CO₂、气态CO₂、盐水溶液三相组成，CO₂相占10%～15%，完全均一化温度为301.6～305.1℃。综合地质条件及矿床特征、包裹体显微测温和成分分析结果认为：杨金沟石英脉型白钨矿矿床的成矿流体为中高温、低盐度的NaCl-H₂O-CO₂（-N₂）体系，初始流体主要来自酸性岩浆热液，并有地层组分的加入。成矿过程中流体发生过不混溶,并对钨的富集起到了重要作用。

Characteristics of Fluid Inclusions and Ore Genesis of Yangjingou Large Scheelite Deposit in Yanbian Area,NE China

The mineralizing process of the Yangjingou large scheelite deposit can be listed such four metallogenetic stages as pyrite-arsenopyrite, quart-coarse scheelite, quartz-sulphides-fine scheelite as well as carbonates stage. In order to analyze the source, features and evolution of ore-forming fluid, fluid inclusions in quartz minerals formed in the major metallogenetic stage are studied. Types of fluid inclusions include gas-rich (Ⅰ),gas-liquid (Ⅱ), pure-CO₂ (Ⅲ) and CO₂-bearing three phase (Ⅳ). The gas phase of typeⅠinclusions is proved to be mainly composed of CO₂, CH₄ and N₂, their homogenization temperatures vary from 278.5 to 336.4℃, with salinities (NaCl) from 3.53% to 7.72%. TypeⅡ inclusions, with ratios of gas to liquid in change from 10% to 45%, are homogenized to liquid during heating, their homogenization temperatures vary from 144.7 to 345.9℃, mainly from 190 to 220℃, salinities(NaCl) from 3.05% to 9.34%. Type Ⅲ is dominated by CO₂ with minor CH₄. Type Ⅳ fluid inclusions are composed of three phases (V_CO2+L_CO2+L_H2O), homogenization temperatures change from 301.6 to as 305.1℃.Comprehensive study on ore-forming condition,geological features of the deposit, compositional and microthermometric analysis of fluid inclusions leads to the conclusion that the ore-forming fluid of the Yangjingou deposit belongs to the NaCl-H₂O-CO₂(-N₂) hydrothermal system with medium-high temperature, low salinity. It is derived from deep crust to upper mantle and mixed by ore-forming materials from the Paleozoic metamorphic strata of the Wudaogou Group which hosts scheelite-quartz veins. The immiscibility of ore-forming fluid played an important role in the metallogenetic process of Yangjingou scheelite deposit.