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摘要:
通过大量数据统计，表明较高比例的辉钼矿中存在普通锇。普通锇可能以类质同像形式存在于辉钼矿样品中，理论上辉钼矿中可能含有较高含量普通锇。辉钼矿样品含有较高含量普通锇可能对Re-Os定年结果产生很大影响，从原理上并结合实例证实了普通锇含量对辉钼矿Re-Os年龄影响程度。对于一般辉钼矿样品来讲，如果187Os总量(放射成因187Os与非放射成因187Os之和)与普通锇比值小于20，需要考虑普通锇对Re-Os模式年龄的影响，并提出了对于含有普通锇辉钼矿模式年龄的计算方法。先做出187Os/188Os-187Re/188Os等时线，求得初始187Os/188Os值，再根据初始187Os/188Os值和单个样品的普Os含量求得非放射成因的普Os中187Os的量。最后根据Re含量以及放射成因187Os含量得到模式年龄。
Abstract:A number of statistics indicate that high content common Os universally occur in the molybdenite which is different from the previous study results. The common Os may occur in molybdenite as substitution atoms, therefore the molybdenite containing high content common Os has possibility in principle. Many analysis results demonstrate that high content common Os in the molybdenite may significantly affects the Re-Os model age. For most of molybdenite, the influence of common Os on the Re-Os model age cannot be ignored in case of OsCommon /187Os Total＜20, and the Re-Os model age should be calculated based on the method given in the paper rather than directly using the decay formula. 187Os/188Os-187Re/188Os isochron is made to obtain the initial187Os/188Os value, then the non-radiogenic 187Os in total Os is obtained according to the initial 187Os/188Os value and single sample common Os content. Model age is got according to the Re content and radiogenic 187Os content finally.
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Key words:
- Molybdenite /
- Re-Os isotopic system /
- Dating /
- Common Os
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图 1
Log(187Os/普Os)-辉钼矿组数(每组样品为采自同一矿区大约6件样品)的关系表明含普通Os辉钼矿出现比例
Figure 1.
The relationship between Log(187Os/common Os)and the frequency of molybdenite samples
图 2
Os同位素初始比值(187Os/188Os)变化对Re-Os模式年龄的影响(普Os占187Os总量五分之一条件下)
Figure 2.
A diagram show the influence of the initial Os isotope ratios on the molybdenite Re-Os model age(Oscommon/ 187Os total=0.2)
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