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Electromagnetic and Tomographic Research of Melt below EPR

EPR 下熔体的电磁和层析成像研究

基本信息

批准号：
07041089
负责人：
HAMANO Yozo
金额：
$ 11.07万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

项目摘要

As for geophysical measurements around the East Pacific Rise (EPR four Ocean Bottom Electro Magnetometers (OBEMs) were successfully retrieved during a research cruise from the end of May/'97 through the beginning of July/'97 by R/V Melville of Scripps Institution of Oceangraphy, US,to yield electromagnetic (EM) time series at the seafloor for more than one year. The OBEMs have been installed at 17ﾟS of EPR during a previous research cruise from the middle of May/'96 through the beginning of July/'96, which was also an international cruise coordinated by Mantle ELectromagnetic and Tomography (MELT) Project. The EM data from these seafloor units are now being analyzed together with those simultaneously collected by US and Australian groups. The goal of the analyzes and subsequent modellings/inversions is reveal the EM structure of melt bodies just below the super spreading center. Specifically, this research aims at quantifying the geometry, melt fraction and connectedness of the melt bodies by a joint observation of seismics and magnetotellurics at the seafloor.In terms of study of the very old oceanic crust in Archaen, rock sampling was conducted in South Africa and Zimbabwe this year. The samples collected are either igneous or sedimentary rocks as old as 2,500 to 3,500 Ma. These samples are in the course of petrological, geological and paleomagnetic analyzes to yield estimates of the tectonic activity at the seafloor and Earth's geomagnetic field in Archaen, which will be combined with the results from the samples collected in Australia ('95) and in Canada ('96) to give reconstruction of a worldwide view of the Earth in Archaen.

至于东太平洋海隆周围的地球物理测量(EPR)，美国斯克里普斯海洋研究所的R/V Melville在1997年5月底至1997年7月初的一次研究巡航期间成功地探测到了四个海底电磁磁强计，以得出一年多来海底的电磁(EM)时间序列。在96年5月中旬至96年7月初的前一次研究巡航期间，OBEM已安装在EPR的17ﾟS，那也是由地幔电磁和层析成像(MELT)项目协调的国际巡航。来自这些海底单元的EM数据现在正与美国和澳大利亚小组同时收集的数据一起进行分析。分析和后续模拟/反演的目标是揭示位于超级扩展中心下方的熔体的电磁结构。具体地说，这项研究旨在通过在海底进行地震和大地电磁联合观测来量化熔体的几何形状、熔体比例和连通性。在研究太古宙非常古老的洋壳方面，今年在南非和津巴布韦进行了岩石采样。采集的样品要么是火成岩，要么是沉积岩，年龄在2500至3500 Ma之间。这些样品正在进行岩石学、地质学和古地磁分析，以估计太古代海底的构造活动和地球的地磁场，这些估计将与在澳大利亚(‘95)和加拿大(’96)收集的样品的结果相结合，以重建太古宙地球的世界观。