贡德瓦纳的洪水玄武岩在地震上与风诱导的石质层不稳定性有关
1Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
概括
在冈德瓦纳下方的大陆石质层地幔分层,在地幔中部造成了快速的地震异常. 这些受地幔羽毛影响的分层碎片解释了大陆洪水玄武岩及其地化学特征.
科学领域:
- 地质物理学 地质物理学
- 地力学是什么?地力学是什么?
- 构造学 构造学 构造学 构造学
背景情况:
- 大陆石质层地幔分层是公认的,但被移除的石质层的命运是不太了解的.
- 沉积板块的图像很好,但分层石灰岩层的深层地幔行为在很大程度上仍然没有特征.
- 以前的研究还没有完全将分层事件与深层地幔结构和随后的地质现象联系起来.
研究的目的:
- 为了调查分层大陆石化层的命运和深层地幔表达.
- 为了确定分层,地幔羽毛和大陆洪水玄武岩 (CFB) 起源之间的关系.
- 为了解释在前贡德瓦纳地区下方观察到的地震异常.
主要方法:
- 分析地震断层模型以识别深层地幔结构.
- 数字建模以模拟分层过程和羽毛-石灰岩相互作用.
- 地震异常与已知的地质事件的相关性,如帕拉纳和德坎陷.
主要成果:
- 在前贡德瓦纳下面600公里深处识别多个水平快波速度异常,与潜水无关.
- 这些异常位于缓慢的地震波速干的上方,与地幔羽毛上方停滞不前的分层岩层相一致.
- 数字实验表明,分层石化层可以产生相当大的融体积 (~2-4 x 10^6 km^3),与CFB体积相匹配.
结论:
- 观察到的中层地幔高波速异常代表了分层的大陆石化层碎片.
- 石层分层,与次大陆羽毛结合,在冈多瓦兰的分裂期间引发了主要的CFB事件.
- 随后的羽毛活动可能会引入分层石化层,将其地化学特征运送到中洋山脊.
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