Paleomagnetism Rscearch On Nayixiong Layer’s Extrusive Rock Of Permian In Qamdo Block

Qiangtang and Qamdo Blocks are divided by a NW-SE distributed Lantsang fault now, and argument exists whether the two blocks formed by later separation of a togethered block or the collision of Qiangtang and Qamdo Blocks. Therefore, the research of the Palaeogeographic position and structural evolution of the two blocks is an important issue, in which the geological evolution of the two blocks during late Paleozoic and Mesozoic is particularly important, but the paleomagnetic data is inadequate so far. The subject investigated in this article is the Nayixiong Layer’s extrusive rock of Permian in Zhouqiongmalu, Tanggulashan Xiang, Golmud City of Qinghai Province, we get 30 sample sites and 252 samples from the layer and the paleomagnetic data of this area by research.Most magnetite, some hematite and magnetite-hematite are the three types of Magnetic minerals existed in the stratum. The systematically thermal demagnetization experiments are used to get the high temperature characteristic remanence component which cleaned every sample and applies center components anaylsis methods and average statistics standard by Fisher.99% confidence level fold test has been through by the data of Nayixiong Layer and Jiushidaoban Layer, which likely represents the original residual information of rock. Most samples show the characteristic of negative polarity, this further proves the age of the layer studied is Late Permian.The average direction of originally residual magnetization in Nayixiong layer is Ds=272.9°, Is=20.4°, ks=32.3, α95=4.7°, correspondingly the position of paleomagnetic is λ=-8.2°, φ=189.1°, dp/dm=4.9/2.6,Φ=-10.5°.Comparative analysis of the data our group have got before, we can come to the conclusion that though Qamdo Block situated in the southern hemisphere,8.5±13° northword drift with clockwise rotation of 14.9±13.5° happened between Middle Permian and late Permian, and it was 5° faraway with Qiangtang Block. The two blocks drifted northward with clockwise rotation from late Permian to late Triassic, and involved in the continent-continent collision stage in the late Permian-early Triassic periods, which built a consolidated northen Qiangtang-Qamdo block.