Paleomagnetic Records Of Tectonic Thermal Events In Huinan Area, Jilin Province

Northeast China is located between the North China plate,the South Siberia plate and the East Pacific plate.The geotectonic position belongs to the eastern end of the Central Asia Mongolia orogenic belt and the superimposed part of the Pacific tectonic domain.The tectonic magmatic activity is complex and active,which has become a hot area to study the process of regional tectonic evolution and plate movement.Based on the U/Pb dating results of zircon in volcanic rocks,it has been found that there are at least six stages of volcanic activity in Mesozoic.In addition,it has been found that a large number of strata suffer from different degrees of late remagnetization.Whether there are records of Mesozoic and Cenozoic volcanic activities in Paleozoic sedimentary rocks in Northeast China,and whether the evolution law of time and space are discussed,is worth further investigation and study.The study of paleomagnetism can provide a basis for tectonic evolution and magmatic thermal events.246 samples were collected from 31 mining sites of Middle Cambrian in Huinan area of Jilin Province for petrology,rock magnetism and systematic thermal demagnetization experiments.The main magnetic minerals in the limestone of Zhangxia formation are magnetite and pyrite with smaller particles,while the main magnetic minerals in the sandy mudstone of Xuzhuang formation are hematite and magnetite,all of which were Remagnetizationed,and the stable middle temperature component is recorded.The average direction of the former is D/I=29.1°/59.0°,?95=6.5°,corresponding pole position is 68°N,213.7°E,A95=8.4°;the average direction of the latter is D/I=10.9°/50.8°,?₉₅=11.7°,corresponding pole position is 76°N,264.6°E,A₉₅=13°.Based on the comprehensive analysis,the following conclusions are obtained:1.The Middle Cambrian Zhangxia formation limestone and Xuzhuang formation sandy mudstone in Huinan area of Jilin Province were both remagnetizationed,because of the different magnetic minerals,the influence of volcanic activity is also different;2.Based on the paleomagnetic records,it can be inferred that there have been at least two strong tectonic thermal events since the early Cretaceous in Huinan area,Jilin Province,respectively,in the early Cretaceous and Quaternary,providing a basis for the study of the tectonic thermal events in this area.3.Huinan area of Jilin Province is located in the northeast edge of North China plate,and the magmatic activity recorded by paleomagnetism can be inferred to be the response of West Pacific plate subduction in the context of global dynamics,which to some extent provides the evidences for the destruction of North China Craton.