巨大的撞击以及大陆的起源和演变
Tim E Johnson1,2, Christopher L Kirkland3, Yongjun Lu4,5
1School of Earth and Planetary Sciences, the Institute for Geoscience Research, Timescales of Mineral Systems Group, Curtin University, Perth, Western Australia, Australia. tim.johnson@curtin.edu.au.
Nature
|August 10, 2022
概括
地球的大陆形成的三个阶段,受巨大的冲击和热水变化的影响. 分析古老的晶揭示了形成皮尔巴拉坑的早期过程.
科学领域:
- 地质科学,特别是前剑桥时期的地质学和地化学.
- 专注于早期地球条件和大陆的形成.
背景情况:
- 地球在拥有大陆方面是独一无二的,但它们的起源和演变仍然不太清楚.
- 西澳大利亚的皮尔巴拉坑是地球早期大陆地的重要,保存良好的残余物,起源于远古时代 (4.0-2.5亿年前).
研究的目的:
- 阐明皮尔巴拉地的形成和演变,提供早期大陆地发展的见解.
- 研究巨大的冲击和水热过程在新兴大陆的形成中的作用.
主要方法:
- 在Pilbara Craton中测定日期的岩石石晶体中分析氧同位素组成 (δ18O).
- 与地质事件如巨大的撞击和地变化相关的石年龄群和同位素特征.
主要成果:
- 从36-340亿年前 (Ga) 的石显示下层 δ18O,表明由水热改变的玄武岩地相互作用而形成的结晶,可能是由巨大的冲击引发的.
- 在3.4亿年前的第二个石团与巨大撞击的证据一致,表明它们的持续影响.
- 后期的石 (3.4-3.0 亿年和<3.0 亿年) 显示出由不断演变的大陆核和随后的地岩的循环形成的晶体.
结论:
- 皮尔巴拉地形成发生在三个不同的阶段,受到石撞击和海洋热水变化的强烈影响.
- 早期阶段涉及冲击驱动的浅层融化,导致地形-超地形核的形成.
- 后来的阶段涉及表面岩石的回收,有助于现代大陆地的发展.
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