关于辉钼矿中Re含量示踪来源的讨论

Discussion on significance of Re content of molybdenite in tracing source of metallogenic materials

对近年来国内已发表的744个辉钼矿Re-Os同位素测年数据进行了汇总,发现所有样品辉钼矿中的Re含量具有混合分布的特征。按照岩性和共生矿物种类对所有数据进行了分类统计分析,结果显示辉钼矿中Re含量（质量分数,下同）与岩性和共生矿物种类存在密切的关系：长英质脉和花岗岩中辉钼矿的Re含量最低,几何平均值分别为7.41×10^-6和7.99×10^-6,多在n×10^-6-n×10^-5;矽卡岩中辉钼矿Re含量中等,几何平均值为58.1×10^-6,多在n×10^-5^-n×10^-4;碳酸岩中辉钼矿Re含量最高,几何平均值为231×10^-6,多在n×10^-4左右。辉钼矿的共生矿物种类影响其Re含量的变化,仅与白钨矿（或黑钨矿）和（或）方铅矿、闪锌矿、自然金和自然银共生时辉钼矿Re含量最低,几何平均值为n×10^-7,多在n×10^-8-n×10^-6;仅与黄铜矿和（或）磁铁矿（或磁黄铁矿）共生时辉钼矿Re含量最高,几何平均值为n×10-4,多在n×10^-5-n×10^-3;同时与黄铜矿（磁铁矿或磁黄铁矿）和白钨矿（或黑钨矿、方铅矿、闪锌矿、自然金和自然银）共生时辉钼矿Re含量处在前两者之间,几何平均值为n×10^-6,多在n×10^-7-n×10^-5。综合分析说明,辉钼矿与白钨矿（或黑钨矿、方铅矿、闪锌矿、自然金和自然银）共生或产在长英质脉和花岗岩中可能促使其Re含量降低,与黄铜矿、黄铁矿和磁铁矿（或磁黄铁矿）共生或产在矽卡岩和碳酸岩中可能促使其Re含量升高,辉钼矿Re含量的级数变化可能与其产出状态（岩性和共生矿物种类）密切相关,以及结合近年来辉钼矿Re含量示踪和其他同位素示踪结果间矛盾的存在,认为辉钼矿Re含量的级数变化似乎不能有效地反映出其成矿物质来源。

744 pieces of molybdenite Re-Os isotopic dating data published in China in recent years were collected and the authors found that the Re content of all the samples is characterized by mixed distribution.Classification and statistical analysis of all the data were based on the lithology and associated mineral types.The results show that the Re content of molybdenite has a close relationship with the lithology and associate minerals,i.e.,pure molybdenite in the felsic veins and granite has the lowest Re content with the geometric mean of 7.41×106 and 7.99×10^-6 respectively,and most of the values range from n×10^-6 to n×10^-5;the Re content of pure molybdenite in the skarn is medium with the geometric mean of 58.1×10^-6,and most of the values range from n×10^-5 to n×10^-4;molybdenite in the carbonatite has the highest Re content with the geometric mean of 231×10^-6,and most of the values are n×10^-4.The Re content of molybdenite is also affected by its associated mineral type： the Re content of molybdenite has the lowest value when molybdenite is only associated with scheelite（or wolframite） and/or galena,sphalerite,native gold and native silver with the geometric mean of n×10^-7,and most of the values range from n×10^-8 to n×10^-6;when it is only associated with chalcopyrite and/or magnetite（or pyrrhotine）,the molybdenite has the highest Re content with the geometric mean of n×10^-4,and most of the values range from n×10^-5 to n×10^-3;the medium Re content occurs when molybdenite is associated with chalcopyrite（magnetite or pyrrhotine） and scheelite （or wolframite,galena,sphalerite,native gold and native silver） with the geometric mean of n×10^-6,and most of the values range from n×10^-7 to n×10^-5.A comprehensive analysis shows that molybdenite associated with scheelite（or wolframite,galena,sphalerite,native gold and native silver） or produced in the felsic veins and granite may reduce the Re content,whereas molybdenite associated with chalcopyrite and/or magnetite（or pyrrhotine） or produced in the skarn and carbonatite may increase the Re content.The magnitude changes of Re content may be related to the modes of occurrence of molybdenite in combination with the contradiction of isotopic tracing between the Re content of molybdenite and other isotopic methods published in recent years.It seems that the magnitude changes of Re content of molybdenite could not effectively represent the source of metallogenic material.