Paleomagnetic study of Cretaceous rocks from Pu'er, western Yunnan, China: Evidence of internal deformation of the Indochina block
Paleomagnetic study of Cretaceous rocks from Pu'er, western Yunnan, China: Evidence of internal deformation of the Indochina block
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DOI：
10.1016/j.epsl.2007.02.043
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发表时间：
2007-06
影响因子：
5.3
通讯作者：
Ken Sato;Yuyan Liu;Yongbiao Wang;M. Yokoyama;S. Yoshioka;Zhenyu Yang;Y. Otofuji
中科院分区：
文献类型：
--
作者：
Ken Sato;Yuyan Liu;Yongbiao Wang;M. Yokoyama;S. Yoshioka;Zhenyu Yang;Y. Otofuji
为定量研究思茅地体在印度-亚洲碰撞作用下的构造变形，对云南西部普洱地区（23.0°N，101.0°E）景兴组和南新组31个测点的白垩纪红砂岩和粉砂岩进行了古地磁研究。在逐步热退磁之后，具有680 °C左右的解阻塞温度的高温分量磁化被隔离。正场试验表明，25个测点的高温磁化分量是白垩系地层的主要磁化分量。倾斜校正后的平均方向为D=59.9°，I=45.2°，α95=5.1°，对应于35.8°N，173.1°E的古极点，A95=5.6°。与整个中国块体白垩纪古地磁极的对比表明，普洱地区相对于整个中国块体的顺时针旋转量为46±9°，这与思茅地体中部的勐腊和景谷地区的大旋转量（47°和66°）相一致。思茅地体中部的自转角比北方的云龙、永平地区大20°以上，说明思茅地体经历了内部变形。普洱地区相对于川滇地块的南向位移为7.5±6.6°，与思茅地体和印支地块的其他地区的南向位移基本一致。思茅地体向南位移800 km，整体顺时针旋转30°，中部进一步发生顺时针旋转。
Cretaceous red sandstones and siltstones were collected at 31 sties for paleomagnetic investigation from the Jingxing and Nanxin Formation around Pu'er (23.0°N, 101.0°E), western part of Yunnan province, China, in order to examine quantitative amount of tectonic deformation of the Simao Terrane due to collision of India with Asia. After stepwise thermal demagnetization, the high-temperature component magnetization with unblocking temperature of around 680 °C is isolated. Positive field tests show that the high-temperature component magnetization from 25 sites is primary for the Cretaceous formations. A tilt-corrected mean direction is D=59.9°, I=45.2° with α95=5.1°, corresponding to a paleopole at 35.8°N, 173.1°E with A95=5.6°. Comparison with Cretaceous paleomagnetic pole of the whole China block indicates that amount of clockwise rotation in the Pu'er area is evaluated to be 46±9° with respect to the whole China block, which is consistent with large amount of rotation in the Mengla and Jinggu areas (47° and 66°) in the central part of the Simao Terrane. Clockwise rotation of the central part is larger by more than 20° compared to the Yunlong and Yongping areas of northern part of the Simao Terrane, suggesting that the Simao Terrane experienced internal deformation. The southward displacement of the Pu'er area expected from inclination data is 7.5±6.6° with respect to the Chuan Dian fragment, which is a similar estimate to other areas in the Simao Terrane and the Indochina block. While the Simao Terrane displaced southward by 800 km together with clockwise rotation of 30° as a whole, further clockwise rotation occurred in the central part.