Tectonic deformation around the eastern Himalayan syntaxis: constraints from the Cretaceous palaeomagnetic data of the Shan-Thai Block
Tectonic deformation around the eastern Himalayan syntaxis: constraints from the Cretaceous palaeomagnetic data of the Shan-Thai Block
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DOI：
10.1111/j.1365-246x.2008.03885.x
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发表时间：
2008-11
影响因子：
2.8
通讯作者：
Kenji Tanaka;Chuanlong Mu;Ken Sato;K. Takemoto;D. Miura;Yuyan Liu;H. Zaman;Zhenyu Yang;M. Yokoyama;H. Iwamoto;K. Uno;Y. Otofuji
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文献类型：
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作者：
Kenji Tanaka;Chuanlong Mu;Ken Sato;K. Takemoto;D. Miura;Yuyan Liu;H. Zaman;Zhenyu Yang;M. Yokoyama;H. Iwamoto;K. Uno;Y. Otofuji
摘要对山泰地块兰品—思茅褶皱带中、下白垩统4个地点的红砂岩进行了采样，描述了其区域变形特征。大多数样品在解封温度约为680°C时显示出特有的剩余磁化。通过正折试验确定了磁化的主要性质。在距哀老山—红河断裂带25 km处的京东地区（24.5°N, 100.8°E），经倾斜校正后的地层平均方向显示出偏北倾角大（dec /Inc.）。= 8.3°/48.8°，α95= 7.7°，n = 13)。而正原（24.0°N, 101.1°E）、正原西（24.0°N, 101.1°E）和勐腊南（21.4°N, 101.6°E）的平均方向显示偏东偏斜；例如dec /Inc.。= 61.8°/46.1°，α95= 8.1°（N= 7）， dec /Inc。= 324.2°/ - 49.4°，α95= 6.4°（N= 4）， dec /Inc。= 51.2°/46.4°，α95= 5.6°（N= 13）。从这四个地点获得的古地磁方向被合并到山泰地块的古地磁数据库中。结合地质、年代和GPS资料，山泰地块的变形过程描述如下：在印度-亚洲碰撞早期，山泰地块顺时针旋转了约20°，在32 Ma之前，山泰地块沿着红河断裂经历了一次连贯的向南移动。在32-27 Ma期间，该地块受到了南北向的压应力作用，这对崇山兰江-清迈带的构造形成起了关键作用。在此之后的上新世至第四纪期间，山泰地块中部发生了局部的顺时针旋转运动，这是由于内部地块沿着重新激活的断层网络运动的结果。
SUMMARY Lower to Middle Cretaceous red sandstones were sampled at four localities in the Lanpin-Simao fold belt of the Shan-Thai Block to describe its regional deformational features. Most of the samples revealed a characteristic remanent magnetization with unblocking temperatures around 680 °C. Primary natures of magnetization are ascertained through positive fold test. A tilt-corrected formation-mean direction for the Jingdong (24.5°N, 100.8°E) locality, which is located at a distance of 25 km from the Ailaoshan–Red River Fault, revealed northerly declination with steep inclination (Dec./Inc. = 8.3°/48.8°, α95= 7.7°, N= 13). However, mean directions obtained from the Zhengyuan (24.0°N, 101.1°E), West Zhengyuan (24.0°N, 101.1°E) and South Mengla (21.4°N, 101.6°E) localities indicate an easterly deflection in declination; such as Dec./Inc. = 61.8°/46.1°, α95= 8.1° (N= 7), Dec./Inc. = 324.2°/−49.4°, α95= 6.4° (N= 4) and Dec./Inc. = 51.2°/46.4°, α95= 5.6° (N= 13), respectively. The palaeomagnetic directions obtained from these four localities are incorporated into a palaeomagnetic database for the Shan-Thai Block. When combined with geological, geochronological and GPS data, the processes of deformation in the Shan-Thai Block is described as follows: Subsequent to its rigid block clockwise rotation of about 20° in the early stage of India–Asia collision, the Shan-Thai Block experienced a coherent but southward displacement along the Red River Fault prior to 32 Ma. This block was then subjected to a north–south compressive stresses during the 32–27 Ma period, which played a key role in shaping the structure of Chongshan-Lancang-Chiang Mai Belt. Following this some local clockwise rotational motion has occurred during the Pliocene-Quaternary time in central part of the Shan-Thai Block as a result of internal block movements along the reactivated network of faults.