Paleomagnetism of the Bonin Islands and its tectonic significance
Paleomagnetism of the Bonin Islands and its tectonic significance
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小笠原群岛的古地磁及其构造意义
DOI：
10.1016/0040-1951(83)90257-3
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发表时间：
1983
期刊：
影响因子：
2.9
通讯作者：
C. Helsley
中科院分区：
文献类型：
--
作者：
K. Kodama;B. Keating;C. Helsley
古地磁样品采集于菲律宾海东北缘(27°N，142°E)的6个博宁群岛。这些火山岛的时代是始新世。熔岩流和岩堤都是在34个地点分别采集的，其中最大的岛屿奇奇-吉马岛的采样范围最广。在95%的置信度水平上，集集-吉马上27个点的平均方向可分为两组，显示出反极关系。2 7个测点中有2 2个测点的平均倾角为ISI=7°，D=110°，α95=14°，其余测点的平均测向为ISI=10°，D=2 73°，α95=32°。其他三个小宁岛上的七个站点作为一个整体，似乎很好地聚集在OFI=3°，D=213°和95=19°的平均方向附近，这与确定的奇奇-吉马的两个平均方向有很大的不同。波宁群岛的低倾角和偏斜被解释为是由于构造旋转造成的。这些岛屿从赤道区向北迁移了至少30°，同时围绕垂直轴旋转(可能是顺时针)30°至90°以上。由于北向漂移和顺时针旋转与前人研究推断的菲律宾西部盆地的构造运动相一致，因此，在中新世四国盆地和帕雷斯贝拉盆地开放之前，博宁群岛似乎是盆地的一部分。
Paleomagnetic samples were collected from six of the Bonin Islands located on the northeastern margin (27°N, 142°E) of the Philippine Sea. These volcanic islands are of Eocene age. Both lava flows and dikes were collected at each of 34 sites with Chichi-jima the largest island being sampled most extensively. Mean directions of the 27 sites on Chichi-jima are divisible into two groups showing antipolar relationships at the 95% confidence level. A between-site mean direction after tilt correction of 22 of the 27 sites isI= 7°,D=110°,α95= 14° while that of the remaining sites isI= 10°,D= 273°,α95= 32°. The seven sites on the other three Bonin Islands, as a whole, seem to cluster well around the mean ofI= 3°,D= 213° witha95= 19°, which differs significantly from both mean directions determined for Chichi-jima. The low inclinations and deflected declinations of the Bonin Islands are interpreted as being due to tectonic rotation. The islands have undergone a northward migration of at least 30° from the equatorial region together with (possibly clockwise) rotation of 30° to over 90° around the vertical axis. Since the northward drift and clockwise rotation are consistent with the tectonic movement inferred for the West Philippine Basin by previous studies, the Bonin Islands appear to have been part of the basin before opening of the Shikoku and Parece Vela basins during the Miocene.