Paleomagnetic study on the Early Devonian Pingshagou Formation limestone from the the North Qiangtang Terrane in the Tibetan Plateau
The paleogeographic reconstructions of the plates lack of reliable paleomagnetic data,so that the evolution of the Paleo-Tethys Ocean in the Devonian is controversial,and high-quality paleomagnetic data quantitatively qualifying the paleolatitudinal position of the plates is the key to solving the above problem.In this paper,we conducted a paleomagnetic study on the limestone from the Lower Devonian Pingshagou Formation of the North Qiangtang Terrane to provide a relative reliable paleomagnetic data.The results of microscopic observation and rock magnetic experiments show that the main magnetic minerals in samples are magnetite and hematite,and there is no remagnetization characteristic.The results of systematic and alternating field demagnetization curves show that the Natural Remanent Magnetization(NRM)intensity of the samples is low.This stable Characteristic Remanent Magnetization(ChRM)is separated from 54 samples and passes the C-class reversal test at the sample level.The tilt-corrected mean direction for the Early Devonian rocks from North Qiangtang Terrane is Ds=8.8°,Is=-0.9°,ks=18.1,α95=4.5°,n=54,which yields a corresponding paleomagnetic pole at 54.8° N,251.2° E(dp/dm=2.3°/4.5°).This paleopole does not resemble to younger paleopoles from the North Qiangtang Terrane,indicating that the ChRM is very likely to be the primary remanence.Our results,together with the evidence of paleontology,imply that the North Qiangtang Terrane was located near the paleo equator(0.5°S)during the Early Devonian,in which,the North Qiangtang Terrane may be closely related to the South China Block.The Paleo-Tethy Ocean may have existed.
万方数据
维普
