岩石圈板块漂移引起岩石古剩磁偏角变化规律

The rule of variation of residual paleomagnetic declination by the drift of lithospheric plate.

依据古地磁基本原理,结合岩石圈板块在地球表面的欧拉旋转,通过赤平投影作图,探讨了岩石圈板块漂移引起古剩磁偏角的变化规律,得出古剩磁偏角的变化与岩石圈板块所处的半球、欧拉极所处的区间以及岩石圈板块东西向运动分量相关,在现今地理坐标下的古剩磁偏角是地质历史时期岩石圈板块多期活动引起古剩磁偏角变化的综合结果。由于欧拉极主要分布在绝对占优的两个区间,因此,岩石圈板块运动主要是欧拉极分布在这两个区间的旋转运动,而当欧拉极分布在这两个区间且当岩石圈板块所处的半球的东西向运动分量方向相同时,古剩磁偏角的变化规律较一致。进而可依据欧拉极分布在这两个区间岩石圈板块旋转引起古剩磁偏角变化规律,结合相邻两个时代形成的岩石古剩磁偏角和倾角之差,以及相对较老岩石形成时所处的半球,可定性确定岩石圈板块在这一地质历史时期的运动方向,为构造应力场演化提供一定的依据,使古地磁数据在大地构造研究中发挥出更大作用。

Based on the basic principle of paleomagnetism, combined with the study of Euler rotation of lithospheric plate on the earth surface, and through drawing diagram of stereographic projection, we have investigated the rule of variation of residual paleomagnetic declination by the drift of the lithospheric plate. We conclude that the variation of residual paleomagnetic declination is related to the hemisphere where the lithospheric plate is located, the zone of the Euler pole, and the transmeridional component of the lithospheric plate movement. The residual paleomagnetic declination in present geographic coordinates is a comprehensive result of the variations of residual paleomagnetic declination caused by many periods of lithospheric plate activities. Since the Euler pole is mainly confined in two dominant zones, the movement of the lithospheric plate is mainly the rotation within these two zones. When the Euler pole is located in these two zones, and the hemisphere that the lithospheric plate is located at and the direction of the transmeridional movement of the lithospheric plate are the same, the rules of variations of residual paleomagnetic declination would be coincident. Thus, according to the variation of residual paleomagnetic declination by the rotation of the lithospheric plate with the Euler pole confined in the two dominant zones, combined with the differences of the rock＇s residual paleomagnetic declinations and paleomagnetic inclinations in two adjacent ages, and knowing in which hemisphere was the relative older rock formed, then the motion direction of the lithospheric plate during this geological period could be determined qualitatively. This may provide evidences for the evolution of tectonic stress field and make the best use of the paleomagnetic data in the research of tectonics.