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187↑Os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187↑Os的迁移使Re和187↑Os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1～3mg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100mg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〈0.1mm,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。

英文摘要：

For some coarse-grained molybdenhes, 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 187↑Os are internally decoupled within molybdenite grains. The degree of decoupling between Re and 187↑Os 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 187↑Os 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 nag or more of aliquant from a much larger mineral separate to overcome the effect of Re and 187↑Os decoupling. Grinding sample into homogeneous powder （grain size d0.1 mm） could reduce the effect of decoupling.