| 辉钼矿亚晶粒范围内Re和187Os的失耦现象 |
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| 引用本文：.2007.Subgrain-size decoupling of Re and 187Os within molybdenite[J].Mineral Deposits,26(5):572~580 |
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| 基金项目:国家自然科学基金项目（No. 40572062）、中国地质调查局“中国成矿体系综合研究”项目（编号1212010733803）及“我国重要矿产和区域成矿规律研究”项目（编号1212010535804） |
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| 中文摘要:对于一些粗颗粒辉钼矿样品，取样量小时，不能产生准确且重现性好的结果；取样量大时，则重现性好。这是因为Re和187Os在辉钼矿亚晶粒（微米级）范围内出现了失耦现象，也就是由于放射性成因187Os的迁移使Re和187Os在空间上不再保持连接。失耦的程度随辉钼矿年龄的增加和颗粒度的增大而更加明显。地质年龄年轻的自然细颗粒样品的失耦现象不明显，使用1～3 mg样品就有可能取得准确且重现性好的结果。而地质年龄老的粗颗粒样品，则可能需要大约100 mg甚至更多的样品才能得到重现性好的数据。增大取样量以及将样品研磨至粒度< 0.1 mm，以增加样品的均匀性，可有效克服失耦现象对准确定年的影响。 |
| 中文关键词:地球化学 辉钼矿 Re-Os 同位素年龄 失耦现象 |
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| Subgrain-size decoupling of Re and 187Os within molybdenite |
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| Abstract:For some coarse_grained molybdenites, the analysis of small sample aliquants may fail to yield accurate or reproducible Re-Os ages, whereas the analysis of larger aliquants from the same mineral separate does yield reproducible Re-Os ages. Such an observation can be best explained if Re and 187Os are internally decoupled within molybdenite grains. The degree of decoupling between Re and 187Os seems to increase as a function of both increasing grain size and increasing age of molybdenite. Geologically younger and natural fine_grained molybdenite samples seem not to show obvious Re and 187Os decoupling, and reproducible ages can be determined from some samples with merely 1～3 mg of aliquant. Geologically old and coarse-grained molybdenite samples may require as many as 100 mg or more of aliquant from a much larger mineral separate to overcome the effect of Re and 187Os decoupling. Grinding sample into homogeneous powder (grain size <0.1 mm) could reduce the effect of decoupling. |
| keywords:geochemistry, molybdenite, Re-Os isotopic age, decoupling |
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