盘古山钨矿成矿流体特征及其地质意义

Fluid inclusion characteristic and its geological implication of the Pangushan tungsten deposit

盘古山钨矿是一个石英脉型钨多金属矿床,在赣南地区的钨矿床中尤为著名.本文在详细的流体包裹体岩相学研究的基础上,对该矿床主成矿阶段黑钨矿-黄铁矿-石英脉和黑钨矿-辉铋矿-石英脉中含矿石英脉中的流体包裹体做了显微测温及拉曼探针分析.结果显示,该矿床流体包裹体类型复杂,不同类型包裹体均一温度及盐度差异较大,反映了复杂的流体特征;包裹体组合复杂,各类型包裹体常叠加在一起,不同分布特征的包裹体组合的均一温度存在明显区别.其中NaCl-H2O气液（Ⅰ型）包裹体均一温度分布范围为100 ～ 370℃,大致可划分为三个温度区间,即270～ 370℃高温区、230～270℃中温区及100～210℃低温区;盐度均＜10wB％NaCleq.,主要集中在＜1wB％ NaCleq.和4～ 6wB％NaCleq.之间.相对而言,含CO2三相（Ⅱ型）包裹体的均一温度普遍高于Ⅰ型包裹体,主要集中在220 ～ 250℃、260～ 350℃之间;而盐度相对较低,集中在2～5 wB％NaCleq.之间.所有这些包裹体特征都表明成矿流体具有多期次性,可能反映本区存在多期次的矿化作用.利用含CO2三相包裹体的部分均一温度与最终均一温度计算出成矿流体的捕获压力36.3～ 97.8Mpa,平均压力72.2 Mpa,按静岩压力换算成最小成矿深度为1.4 ～ 3.76 km,平均为2.78 km.对各类包裹体的激光拉曼探针测试表明：成矿流体中除水、CO2外,还含有少量的CH4和N2.盘古山钨矿的各类流体包裹体的综合特征研究表明,流体的不均一捕获作用可能是盘古山钨矿床石英脉型钨矿形成的主要机制.

After detailed fluid inclusions petrographic study, we have done microthermometric and Raman microspectroscopic analysis to the fluid inclusions in the wolframite-bearing quartz from the major mineralizing stage of wolframite-pyrite-quartze veins and wolframite-bismuthinite-quartz veins in Pagushan tungsten deposit, southern Jiangxi province. Analysis results show that the types of fluid inclusions are extremely complicated, different types fluid inclusions homogenization temperature（Th） and salinity are also complex, which reflect complex fluid characteristics. Furthermore, the fluid inclusion assemblage （FIA） complexity can also revealed in the phenomenon, that more than one type fluid inclusions are superimposed in one FIA, FIAs, which have different distribution characteristics, are not alike in Ths. Among them, NaC1-H20 gas liquid （type I ） inclusions with Th distributed in the range of 100-370℃, can be roughly divided into high, medium and low temperature intervals, re- spectively 270-370℃, 230-270℃and 100-210℃; as even salinity 〈 10 ws%NaCleq, mainly concentrated in section〈 lwB%NaCleq as well as 4-6 Ws %NaCleq. Relatively, the Ths of type II inclusions containing CO2 are generally higher than that of type I inclusions, mainly concentrated between 220-250℃ and 260-350℃ ,while relatively show low salinity, focused between 2-5 wB%NaCleq. All of these fluid inclusions features indicated that the mineralizing fluid has multi-stage, and there may be existing multiple episodes of mineralizing. According to the Thco2 and ultimate Th of the type II fluid inclusions, this paper got ore-forming fluid trapping pressure ,which was 36.3 - 97.8 Mpa, an average pressure of 72.2 Mpa, converted into ore-forming depth of 1.4 - 3.76 km, an average of 2.78 km. Raman microspectroscopic studies of the various type fluid inclusions presented that, the fluid inclusions contain not only water and CO2, but also small amounts of CH4 and Nz. It is concluded from the characteristic of all types fluid inclusions that the fluid may uneven when capturing, which is probably the major mechanism of formation of wolframite-quartz-vein type ore in the Pangushan tungsten deposit.