Deformation of Asian continent

印度-亚洲碰撞是新生代最重要的构造事件之一。印度大陆在52 Ma左右碰撞到亚洲，并继续向亚洲大陆渗透。印度板块的北侵引起了亚洲大陆的构造变形，本文从古地磁的角度探讨了亚洲大陆东部的构造变形。我们选择了中国的云南和四川地区作为印度大陆碰撞变形的可能地区。中国内蒙古和俄罗斯锡霍特阿利姆地区被认为是没有任何变形的地区，我们在这四个地区进行了古地磁研究。我们重点研究了侏罗纪熔结凝灰岩、侏罗纪红砂岩、上白垩统红砂岩和古新世熔结凝灰岩，因为晚中生代地层保留了印度碰撞后52 Ma以后的变形证据。从这四个地区收集了750多个样本。三到十个手的样本，用磁罗盘定位，分布在一个网站的距离高达15米。地点的位置是由便携式导航仪确定的。利用1994年国际地磁参考场计算出采样点的现今衰减值。在实验室制备了直径25 mm、长23 mm的样品。用2G低温磁力仪测量了天然反射磁化强度。每个样品中的一个样品经受高达690* 710* 的逐步热退磁。现在对测量数据进行分析。

Collision of India and Asia is one of the most prominent tectonic events in Cenozoic time. The Indian continent collided to Asia at about 52 Ma and continued to penetrate into the Asian continent. The northward penetration of the India gave rise to tectonic deformation in the Asian continent.The present program of investigation aims to detect tectonic defonriation on eastern part of Asian continent from paleomagnetic view points. We chose the Yunnan and Sichuan in China areas as possible areas which was subjected to deformation due to collision of Indian continent. Inner Mongolia of China and Sikhote Alim area in Russia are regarded as areas without any deformation.We carried out our paleomagnetic study in these four areas. We focused the Jurassic welded tuffs, the Jurassic red sandstones, the Upper Cretaceous red sandstones and the Paleocene wefded tuffs, because late Mesozoic formation preserves evidence of deformation later than 52 Ma when India collided. More than 750 samples were collected from these four areas. Three to ten hand samples, oriented with a magnetic compass, were distributed over a distance ranging up to 15m in a site. Localities of sites were determined by a portable navigational instrument. The present declination value at the sampling point was estimated from the calculation using the International Geomagnetic Reference Field of 1994.In the laboratory, individual specimens, 25mm in diameter and 23mm long, were prepared from samples. Natural remanent magnetizations were measured with a 2G cryogenic magnetometer. One specimen from each sample was subjected to stcpwise thermal demagnetization up to 690* 710*. Measurement data are now analyzed.