New Late Permian paleomagnetic results from Qaidam Block and tectonic implications

Paleomagnetism can provide quantitative information about paleoposiotion of the terranes during geological period. However, previous studies on the late Paleozoic formations for Qaidam block have been hampered by the scarce paleomagnetic data. We present paleomagentic results on the Late Permian rocks in the Qaidam block near localities of Zuhema (37.49N/99.07E). A total 13 sites have been sampled from Late Permian sediments. Stepwise thermal demagnetizating has revealed a characteristic remanent magnetization(ChRM). Both normal and reversal polarities were observed in studied section, and the high-temperature components pass reversal tests at the 95% confidence level. This indicates the possibly primary magnetization. The tilt-corrected mean directions for the Late Permian is D/I=333.9/41.7 with a95=6.2 and N=9 sites, corresponding to a paleopole at 64.0N, 345.4E, dp/dm=4.7/7.6. Compared with the Late Carboniferous and Late Permian poles from the Tarim block, insignificant post- Late Permian northward motion may have occurred between the Qaidam block and the Tarim block. Also. On the basis of the similarity of rocks of basement and the paleontology for the Qaidam block and Tarim block, the Qaidam block may be a part of the Tarim block, or the two blocks were in close proximity since the Late Permian. This Late Permain paleogeographic reconstruction indicates that the Altyn Tagh fault between the Tarim and Qaidam blocks may begin to form, at least until Late Permian. Key words: Late Permian, Qaidam block, Paleomagnetic, Paleogeographic reconstruction