Tectonic deformation of the Indochina Peninsula recorded in the Mesozoic palaeomagnetic results
Tectonic deformation of the Indochina Peninsula recorded in the Mesozoic palaeomagnetic results
复制标题
DOI：
10.1111/j.1365-246x.2009.04274.x
复制
发表时间：
2009-10
影响因子：
2.8
通讯作者：
K. Takemoto;S. Sato;Kongkham Chanthavichith;Thongpath Inthavong;H. Inokuchi;M. Fujihara;H. Zaman
中科院分区：
文献类型：
--
作者：
K. Takemoto;S. Sato;Kongkham Chanthavichith;Thongpath Inthavong;H. Inokuchi;M. Fujihara;H. Zaman
摘要为了描述印度支那半岛的构造变形特征，在珊泰和印度支那地块的三个地点采集了早侏罗世至早白垩世红砂岩样品。大多数样品的分步热处理揭示了特征剩磁的存在，其通常在680 °C下未被阻断。来自Phong萨利的组件（21.6°N，101.9°E）和Borikhanxay（18.5°N，103.8°E）地点产生正褶皱测试，晚侏罗世-早白垩世方向为Dec/Inc = 28.8°/32.1°（ks= 15.4，α95= 8.8°，N= 22）和Dec/Inc = 42.1°/46.9°（ks= 20.1，α95= 7.9°，N= 18）。此外，在Muang Phin地区（16.5°N，106.1°E）的样品中观察到一个同折叠的白垩纪中期特征磁化，其平均方向为Dec/Inc = 30.8°/39.9°，k= 102.6，α95= 3.0°，N= 23。这可靠的晚侏罗世到白垩纪中期的古地磁方向从三个不同的地方被纳入古地磁数据库的山泰和印度支那块。在此基础上，对陕泰地块和印支地块的构造变形进行了总结：（1）在印度-亚洲碰撞早期，作为一个复合单元，汕泰地块和印支地块发生了约10°的顺时针旋转;（2）此后，汕泰地块发生了内部构造变形，而印支地块在同一时期表现为刚性构造单元。我们的古地磁结果与地震层析成像的比较表明，这些块体之下的大陆岩石圈的强度在变形过程中发挥了重要作用，而不是任何其他构造体制。与陕泰地块相反，印度支那地块之下的大陆根的存在阻止了其内部变形。
SUMMARY In order to describe features of tectonic deformation in the Indochina Peninsula, Early Jurassic to Early Cretaceous red sandstones were sampled at three localities in the Shan-Thai and Indochina blocks. Stepwise thermal treatment of most samples revealed the presence of characteristic remanent magnetization, which is generally unblocked by 680 °C. This component from Phong Saly (21.6°N, 101.9°E) and Borikhanxay (18.5°N, 103.8°E) localities yield positive fold tests with Late Jurassic–Early Cretaceous directions of Dec/Inc = 28.8°/32.1° (ks= 15.4, α95= 8.8°, N= 22) and Dec/Inc = 42.1°/46.9° (ks= 20.1, α95= 7.9°, N= 18), respectively. Additionally, a syn-folding mid-Cretaceous characteristic magnetization is observed in the samples of Muang Phin locality (16.5°N, 106.1°E), which gave a mean direction of Dec/Inc = 30.8°/39.9°, k= 102.6, α95= 3.0°, N= 23. This reliable Late Jurassic to Mid-Cretaceous palaeomagnetic directions from three different localities are incorporated into a palaeomagnetic database for Shan-Thai and Indochina blocks. Based on these compilations, tectonic deformation of the Shan-Thai and Indochina blocks is summarized as follows: (1) the Shan-Thai and Indochina blocks experienced a clockwise rotation of about 10° as a composite unit in the early stage of India–Asia collision and (2) following this, the Shan-Thai Block underwent an internal tectonic deformation, whereas the Indochina Block behaved as a rigid tectonic unit during the same period. Comparison of our palaeomagnetic results with seismic tomographic images suggests that the strength of continental lithosphere beneath these blocks played an important role in the process of deformation rather than any other tectonic regime. In contrast to the Shan-Thai Block, an existence of continental roots beneath the Indochina Block prevented its internal deformation.