Permian palaeomagnetism of East Kazakhstan and the amalgamation of Eurasia
Permian palaeomagnetism of East Kazakhstan and the amalgamation of Eurasia
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DOI：
10.1046/j.1365-246x.2003.01879.x
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发表时间：
2003-03
影响因子：
2.8
通讯作者：
N. M. Levashova;K. Degtyarev;M. Bazhenov;A. Collins;R. Voo
中科院分区：
文献类型：
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作者：
N. M. Levashova;K. Degtyarev;M. Bazhenov;A. Collins;R. Voo
哈萨克斯坦的大部分地区属于乌拉尔-蒙古带，其构造演化至今仍知之甚少，因为迄今为止提出的不同构造模型证明了这一点。我们进行了古地磁研究的上二叠统玄武岩和安山岩从两个地方在哈萨克斯坦东部，以评估该带的演化和欧亚合并的最后阶段。热退磁揭示了一个单一的预倾斜特征组件的无处不在的极性从所有样品。其中一个地点的剩磁的平均递减率与二叠纪欧洲古子午线的结果相当一致，而另一个地点的剩磁的平均递减率则顺时针旋转了28 <$± 8 <$。总体平均倾角为−49 ± 4，与我们计算的参考倾角相差9.7 ± 4.2，参考倾角来自欧亚平均极245 - 260 Ma的时间间隔，与260 - 275 Ma的数据一致。我们占观察到的模式，无论是一个稍微错误的岩石年龄（岩性有点老比地质数据）或非偶极子（八极）地磁场的组成部分。由于研究区相对于欧亚大陆的显著相对运动没有得到证明，我们得出结论，哈萨克斯坦，欧洲和西伯利亚的焊接基本上是在中二叠世完成的。
SUMMARY Most of Kazakhstan belongs to the Ural‐Mongol belt, the tectonic evolution of which is poorly understood as demonstrated by disparate tectonic models suggested thus far. We undertook a palaeomagnetic study of Upper Permian basalts and andesites from two localities in east Kazakhstan in order to evaluate the final stages of the evolution of this belt and Eurasian amalgamation. Thermal demagnetization revealed a single pre-tilting characteristic component of ubiquitously reversed polarity from all samples. The mean declination of this remanence from one locality agrees rather well with the Permian European palaeomeridian, whereas that from the other is clockwise rotated by 28 ◦ ± 8 ◦ . The overall mean inclination of −49 ◦ ± 4 ◦ differs by 9.7 ◦ ± 4.2 ◦ from the reference inclination calculated, for our localities, from the Eurasian mean pole for the 245‐260 Ma interval and is in agreement with 260‐275 Ma data. We account for the observed pattern by either a slightly erroneous rock age (lithologies are somewhat older than indicated by geological data) or non-dipole (octopole) components of the geomagnetic field. Because significant relative motion of the study area with respect to Eurasia is not demonstrated, we conclude that welding of Kazakhstan, Europe and Siberia was essentially completed by Mid-Permian time.