大颗粒辉钼矿Re-Os同位素失耦现象及187Os迁移模式研究

对采自西华山钨矿的大颗粒辉钼矿样品的不同部位进行了取样,并对其年龄分别进行精确厘定,得到了不同的Re-Os模式年龄值,验证了失耦现象的存在.从原理上对失耦现象及其成因进行了解释,并在前人成果的基础上,探索性地提出了187Os可能的迁移模型.取样方式的不同会对辉钼矿的模式年龄产生很大影响,因此,在实际应用中一定要严格遵循"多取样,细磨碎"的原则,这对于能获得科学真实的与地质背景相符的Re-Os同位素地质年龄,从而深入探讨矿床成矿作用具有重要意义.

Decoupling of Re and Os and migration model of 187Os in coarse-grained molybdenite

Different parts of coarse-grained molybdenite from the Xihuashan tungsten deposit were sampled and dated, which yielded different Re-Os apparent ages and hence confirmed the decoupling of Re and ~(187)Os within molyb-denite. The decoupling phenomenon and its cause were explained, and a tentative migration model of ~(187)Oswithin coarse-grained molybdenite was established. The results show that the difference in sampling methods might exert remarkable influence on the Re-Os apparent age. In order to reduce the influence of decoupling on Re-Os dating, more molybdenite samples should be collected, and the samples should be ground into homoge-neous powder (200 meshes). Only in this way can scientific and accurate Re-Os ages be obtained.