在东北太平洋上升下被动地幔上升的电图
Kerry Key1, Steven Constable, Lijun Liu
1Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, USA. kkey@ucsd.edu
Nature
|March 30, 2013
概括
板块构造驱动地幔上升,在中洋山脊上形成海洋地. 新的地质物理数据显示,在东太平洋上升处主导的是被动上升,融化聚焦发生在多孔融化区域.
科学领域:
- 地质物理学 地质物理学
- 地幔动力学地幔动力学
- 海洋地的形成
背景情况:
- 地幔上升会在中洋山脊上产生海洋地,但其驱动力仍在争论中.
- 被动流模型预测对称的上游,而活跃模型则建议聚焦的对流流.
- 地质物理观测显示了对称和不对称的上游模式.
研究的目的:
- 在东北太平洋上升的地幔电结构图像使用海底磁探测.
- 为了研究控制地幔上升和融化的力量,专注于快速扩散的山脊.
- 为了区分被动和主动地幔流量模型.
主要方法:
- 海底磁 (MT) 探测是在东太平洋北部的海拔上进行的.
- 使用MT数据,绘制了大约160公里深的地幔电结构图像.
- 分析了电导率和异构性,以推断地幔特性和流动动力学.
主要成果:
- 一个对称的,高导电性区域 (20-90公里深) 表明被动上游地幔的部分融化.
- 这种导电性融区域与融聚焦的被动流预测保持一致.
- 在山脊以东的更深的导体 (深度超过100公里) 表明与转变断层相关的不对称上升.
- 浅层地幔 (10-20公里) 中的电异质性指向局部的,浅层岩输送管道.
结论:
- 板块驱动的被动上升是这个快速扩散的山脊段的主导机制.
- 融化聚焦发生在多孔融化区域内,而不是在石质层底部.
- 在这个位置控制上游的动力力量似乎可以忽略不计.
- 浅的岩运输道,而不是更深的离轴上升,可能解释地震异常.
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