Tectonic deformation of the southeastern tip of the Indochina Peninsula during its southward displacement in the Cenozoic time
Tectonic deformation of the southeastern tip of the Indochina Peninsula during its southward displacement in the Cenozoic time
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DOI：
10.1016/j.gr.2011.09.015
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发表时间：
2012-09
影响因子：
6.1
通讯作者：
Y. Otofuji;V. D. Tung;M. Fujihara;Masayuki Tanaka;M. Yokoyama;K. Kitada;H. Zaman
中科院分区：
文献类型：
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作者：
Y. Otofuji;V. D. Tung;M. Fujihara;Masayuki Tanaka;M. Yokoyama;K. Kitada;H. Zaman
印度与亚洲大陆的碰撞末期，亚洲大陆发生了明显的构造变形。为了描述印度支那半岛东南缘的这些变形特征，在越南Kontum Bagraf的达拉特地区（11.7°N，108.3°E）采集了晚白垩世Dak Rium组红层。热退磁过程揭示了在大多数样品中存在特征剩磁（具有约680°C的解除阻断温度）。通过正褶试验确定了这种磁化的基本性质。Dak Rium组经倾斜校正后的平均方向为Dec/Inc=11.4°/35.4°（ks=331.7 α95=1.7°，N=21），对应的古极点为76.5° N，161.2° E（A95=1.7°）。与欧洲的APWP相比，Kontum Baglif自晚白垩世以来向南位移了9.2° ± 4.9 °，倾角为负变平（−15.2° ± 4.9 °）。由于在印支地块和汕泰地块的16个地点都报告了相当数量的向南位移，因此，预测印支半岛作为一个复合单元（包括汕泰地块、印支地块和Kontum Bagarf）经历了5.1°±2.4°（570 km ± 270 km）的向南位移似乎是一个合理的假设。相反，Kontum板块相对于印支地块逆时针旋转27.0°±9.8°，表明沿南移的印支半岛尖端沿着有明显的内部变形。Kontum Bagf的这种旋转归因于沿东越边界断裂沿着的32- 17 Ma的左旋运动，该断裂构成哀牢山-红河剪切带的1000 km长的向海延伸。因此，印度支那半岛的构造变形部分是由局部块体旋转（如板块旋转）所调节的。例如，在一个实施例中，Kontum的逆时针旋转，并在一定程度上由内部构造变形的Shan-Thai块。
The terminal collision of India with Asia brought about significant tectonic deformation into the Asian Continent. In order to depict these deformational features in the southeastern margin of the Indochina Peninsula, Late Cretaceous red beds of the Dak Rium Formation were sampled from Da Lat area (11.7°N, 108.3°E), the Kontum massif, Vietnam. Thermal demagnetization procedure revealed the presence of characteristic remanent magnetization (with unblocking temperatures around 680°C) in most samples. Primary nature of this magnetization is ascertained through positive fold test. A tilt-corrected mean direction calculated for the Dak Rium Formation is Dec/Inc=11.4°/35.4° (ks=331.7 α95=1.7°, N=21), with a corresponding paleopole at 76.5° N, 161.2° E (A95=1.7°). Compared with the European APWP, a negative inclination flattening (−15.2°±4.9°) is observed, indicating southward displacement of the Kontum massif by 9.2°±4.9° since Late Cretaceous. Since, comparable amount of southward displacement has been reported from 16 localities of the Indochina and Shan–Thai blocks, it seems a reasonable assumption to predict that the Indochina Peninsula underwent a southward displacement of 5.1°±2.4° (570km±270km) as a composite unit (including the Shan–Thai Block, Indochina Block and Kontum massif). On the contrary, 27.0°±9.8° counter-clockwise rotation of the Kontum massif with respect to the Indochina Block indicate a significant amount of internal deformation along the tip of south moving Indochina Peninsula. This rotation of the Kontum massif is attributed to 32–17Ma left lateral motion along the East Vietnam Boundary Fault, which makes up the 1000km long seaward continuation of the Ailao Shan–Red River shear zone. Tectonic deformation of the Indochina Peninsula was, thus, partly accommodated by local block rotation (e. g., counterclockwise rotation of the Kontum massif) and to some extent by internal tectonic deformation of the Shan–Thai Block.