概括
由于-187的衰变,行星系统中的-187/-186比率随着时间的推移而演变. 地球 地球 地球 地球 地球 地球
科学领域:
- 地质化学 地质化学
- 宇宙化学 宇宙化学
- 同位素地质学的同位素.
背景情况:
- -187 (4.6 x 10^10年) 到-187的放射性衰变影响行星系统中的-187/-186比率.
- 这个比率是时间和最初的-187/-186比率的函数,在不同的行星储库 (如地幔和地) 中有所不同.
研究的目的:
- 为了研究各种地球和海洋样本中的-187/-186比率.
- 评估奥斯在地质构成中的起源,特别是在白纪-地球界边界.
主要方法:
- 分析-187/-186的比例在石,地球的地幔,大陆地,海洋结,和白纪-第三纪的边界层.
- 利用同位素特征来追踪的来源和演变.
主要成果:
- 典型的石和地球地幔-187/-186比率约为3.2,使得当今的-187/-186比率约为1.1.
- 地球的大陆地 (-187/-186比率~400,年龄2×10^9年) 预计-187/-186比率为~10.
- 海洋块的比例 (6-8.4) 与大陆输入和地幔相一致.
- 甲-第三纪的边界层表现出低的-187/-186比率 (1.65海洋,1.29大陆).
结论:
- 在白-第三纪边界层中观察到的-187/-186比率表明的主要起源是石.
- 同位素分析为了解行星进化过程中材料的来源和混合提供了一个强大的工具.
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