黑龙江省翠宏山钨钼多金属矿床辉钼矿Re-Os同位素定年及其地质意义

翠宏山钨钼多金属矿床是小兴安岭-张广才岭成矿带内一个重要的矽卡岩型矿床，钨、钼、锌均达大型规模。为确定该矿床的形成时代，对取自岩体内接触带钨钼矿体的7件辉钼矿样品进行了Re-Os同位素测年研究。结果表明:辉钼矿中Re质量分数为（0.376 9～0.973 7）×10^-6，Os质量分数为（1.272～3.234）×10^-9;获得的模式年龄为(199.0±3.1)～(203.9±3.8) Ma，加权平均年龄为（201.6±1.4）Ma(MSWD=0.80)，等时线年龄为（198.9±3.7）Ma(MSWD=0.83)。结合区域成矿作用分析认为:翠宏山多金属矿床的形成时代为早侏罗世，与成矿带内的霍吉河和鹿鸣等斑岩型（细网脉型）钼矿床同属燕山早期大规模构造-岩浆-成矿事件的产物。根据本次辉钼矿Re-Os定年结果，结合前人在矿区内所测多个花岗岩体的锆石U-Pb年龄认为:与翠宏山多金属矿床具成因联系的岩体应为二长花岗岩、碱长花岗岩，成岩成矿作用与古太平洋板块俯冲有关。辉钼矿中Re质量分数、成矿岩体的物质源区综合研究表明，翠宏山多金属矿床的成岩成矿物质具有壳幔混源特征。

Re-Os Isotopic Dating of the Molybdenite from the Cuihongshan W-Mo Polymetallic Deposit in Heilongjiang Province and Its Geological Significance

The Cuihongshan deposit is one of important polymetallic deposits in the Lesser Xing’an Range-Zhangguangcai Mountain polymetallic metallogenic belt. The tungsten, molybdenum and zinc resources in this deposit are over large-scale. To determine the metallogenic age of the deposit, Re-Os dating of 7 molybdenite samples from W-Mo ore bodies in the inner contact zone has been completed. The Re content in the molybdenite varies from (0.376 9-0.973 8)×10^-6 and Os content varies from (1.272-3.234)×10^-9. The model age of the molybdenite ranges from (199.0±3.1) Ma to (203.9±3.8) Ma, the weighted mean age is (201.6±1.4) Ma (MSWD is 0.80), and the isochron age is (198.9±3.7) Ma (MSWD is 0.83). Combined the isotopic dating with the regional mineralization characteristics, it’s suggested that the Cuihongshan polymetallic deposit be formed in Early Jurassic period, contemporary with some large-scale porphyry molybdenum deposits as Huojihe and Luming in the Lesser Xing’an Range-Zhangguangcai Mountain metallogenic belt, and they are all resulted from the Early Yanshanian large-scale tectonic-magma-metallogenetic events. According to the molybdenite Re-Os ages and zircon U-Pb ages of some granitic rock bodies in the mine, we can conclude that the monzonite and alkali-feldspar granite were closely related to the W-Mo polymetallic mineralization. The content of Re in molybdenite minerals, together with data on material source of associated intrusion, suggests that the ore-forming materials should be derived mainly from the mixing source of the crust and the upper mantle.