New Late Permian Paleomagnetic Data From The Qaidam Block And Tectonic Implications

The Qaidam block is located in a special tectonic position and has a complex evolution. Based on the information of paleontology, lithofacies, many scholars have explored the late Paleozoic paleogeography and tectonic affiliation of the Qaidam block. However, there are some disputes which have an impact on the deployment and progress of the oil and natural gas resources exploration in the Qaidam Basin. Due to the lack of reliable Permian paleomagnetic data of the Qaidam block, the paleolatitude of the Qaidam block can not be quantitatively determined and tectonic relationship between the Tarim block and the Qaidam block can not be identified.We present paleomagentic results on the Late Permian rocks in the Qaidam block near localities of Zuhema (37.49°N/99.07°E). A total13sites 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 the studied section, and the high-temperature components pass reversal tests at the95%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=9sites, corresponding to a paleopole at64.0°N,345.4°E, dp/dm=4.7/7.6. Compared with the 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 during Late Permian. Accompanied with previous studies, a Late Permain paleogeographic reconstruction including the major Chinese blocks is constructed.