印支地块思茅地区早白垩世古地磁结果及其构造意义
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国家地球深部探测计划


Early Cretaceous paleomagnetic results from Simao araea of the Indochina block and its tectonic implication
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    摘要:

    对印支地块思茅地区的早白垩世红层开展详细的岩石磁学和古地磁学研究,获得镇沅剖面特征剩磁方向Ds=52.4°,Is=45.5°,κ= 77.9,α95=6.3°;普洱剖面特征剩磁方向Ds=46.2°,Is=46.6°,κ= 50.9,α95=5.6°;江城剖面特征剩磁方向Ds=8.6°,Is=42.2°,κ= 117.1,α95=4.0°。普洱和江城剖面进行E–I磁倾角偏低检验,江城剖面不存在磁倾角偏低,普洱剖面由于偏角较分散,导致其伸展方向出现假象,理论磁倾角偏大,出现磁倾角偏低的假象。思茅地区各采样剖面之间的磁偏角差异表明,块体内部发生过差异性旋转变形,其变形过程不仅受控于边界深大断裂,也与内部小断裂活动关系密切。若进一步考虑华南地块白垩纪可能存在的磁倾角偏低现象,该结果表明印度支那地块思茅地区白垩纪以来相对于华南地块向南滑移量为570±310km,接近构造地质研究的推测值。

    Abstract:

    Rock magnetic and paleomagnetic studies were carried out on the Early Cretaceous red beds at Simao area of Indochina Block, the characteristic remanent magtization (ChRM) directions obtained from Zhenyuan, Pu’er and Jiangcheng, such as Ds=52.4°,Is=45.5°,κ= 77.9,α95=6.3°, Ds=46.2°,Is=46.6°,κ= 50.9,α95=5.6° and Ds=8.6°,Is=42.2°,κ= 117.1,α95=4.0°. The elongation/inclination (E/I) correction model was applied to evaluate the inclination error from the Pu’er and Jiangcheng sections, results of the correction model indicate that inclination shallowing was negligible within the uncertainty in Jiangcheng, however there's the illusion of inclination shallowing in Pu’er, as the declinations are scattered, resulting in the illusion of elongation and the corrected inclination is too large. The differences of declination between all the sample sections at Simao area suggest that differential rotation has taken place within the block, the deformation process is not only controlled by boundary faults, is also closely related with activities of the internal small faults. Taken the Cretaceous shallow inclination in the South China block into consideration, the Simao area has been subjected to south displacement by 570±310km with respect to the South China block since Cretaceous, presumably close to the estimation of structural geology evidences. Key words: Indochina Block; Cretaceous; block movement; intracontinental deformation

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张海峰,仝亚博,王恒,杨振宇.2012.印支地块思茅地区早白垩世古地磁结果及其构造意义[J].地质学报,86(6):923-939.
Zhang Haifeng.2012. Early Cretaceous paleomagnetic results from Simao araea of the Indochina block and its tectonic implication[J]. Acta Geologica Sinica,86(6):923-939.

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历史
  • 收稿日期:2011-11-14
  • 最后修改日期:2011-12-30
  • 录用日期:2012-01-04
  • 在线发布日期: 2012-05-31