Paleomagnetic Constraints From the Baoshan Area on the Deformation of the Qiangtang‐Sibumasu Terrane Around the Eastern Himalayan Syntaxis
Paleomagnetic Constraints From the Baoshan Area on the Deformation of the Qiangtang‐Sibumasu Terrane Around the Eastern Himalayan Syntaxis
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DOI：
10.1002/2017jb015112
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发表时间：
2018-02
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影响因子：
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通讯作者：
Shihu Li;D. V. Hinsbergen;C. Deng;E. Advokaat;R. Zhu
中科院分区：
文献类型：
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作者：
Shihu Li;D. V. Hinsbergen;C. Deng;E. Advokaat;R. Zhu
东南亚的思茅 - 马来亚地块是羌塘地块向东的延伸。在此，我们对思茅 - 马来亚北部的中侏罗世和古新世岩石进行了详细的岩石磁学和古地磁研究，以记录自古新世以来印度 - 亚洲碰撞期间的地壳变形，并重建印度 - 亚洲碰撞前羌塘/思茅 - 马来亚地块的整体走向。尽管仅依据我们的数据褶皱检验结果不明确，但正向倒转检验、结合先前古地磁结果的正向区域褶皱检验以及扫描电子显微镜显示的红层中赤铁矿的碎屑成因表明，从侏罗纪和古新世岩石中获得的磁化很可能是原生的，显示出自古新世以来约80°的顺时针旋转。这些结果与先前发表的古地磁数据一起表明，思茅 - 马来亚北部和思茅北部地块自古新世以来经历了约60 - 80°的顺时针旋转。这种大的顺时针旋转也与地表GPS速度场和东北 - 西南向断层网络一致，表明在新生代晚期西藏东南部地壳物质存在旋转运动。我们推断，这种大的顺时针旋转是始新世到中中新世与印支挤出相关的旋转以及中中新世之后与西藏中部东西向伸展相关的旋转的总和。这表明中中新世之后藏地壳物质沿鲜水河 - 小江断裂的向东运动向西南传递至缅甸。侏罗纪和白垩纪的古地磁结果表明，羌塘/思茅 - 马来亚北部原本是一个在西藏呈N60°W方向的弯曲构造，在思茅 - 马来亚南部变为N10°W方向。
The Sibumasu Block in SE Asia represents the eastward continuation of the Qiangtang Block. Here we report a detailed rock magnetic and paleomagnetic study on the Middle Jurassic and Paleocene rocks from northern Sibumasu, to document the crustal deformation during the India‐Asia collision since the Paleocene and reconstruct the overall strike of the Qiangtang/Sibumasu elements before the India‐Asia collision. Although the fold test is inconclusive based solely on our data, a positive reversal test, a positive regional fold test with previous paleomagnetic results, and a detrital origin of hematite in the red beds as indicated by scanning electron microscopy suggest that the magnetizations obtained from the Jurassic and Paleocene rocks are most likely primary, showing an ~80° clockwise rotation since Paleocene. These results, together with previously published paleomagnetic data, suggest that the northern Sibumasu and northern Simao elements experienced a ~60–80° clockwise rotation since Paleocene. This large clockwise rotation is also consistent with the surface GPS velocity field and NE‐SW fault networks, suggesting a rotational motion of crustal material from southeastern Tibet during late Cenozoic. We infer that the large clockwise rotation is a sum of rotation in the Eocene to Middle Miocene time associated with Indochina extrusion and rotation after the Middle Miocene associated with the E‐W extension in central Tibet. This suggests that the eastward motion of Tibetan crustal material along the Xianshuihe‐Xiaojiang fault after Middle Miocene is transmitted to the southwest toward Myanmar. Jurassic and Cretaceous paleomagnetic results suggest that the Qiangtang/northern Sibumasu was originally a curved structure with an orientation of N60°W in Tibet and changes to N10°W in southern Sibumasu.