The Studies Of Remagnetization Of Ordovician Carbonate In Yangdeng Area,Southeast Sichuan Province

Remagnetization phenomenon is common in sedimentary rocks,which could obscure the primary remanence.Thus,study the mechanism of remagnetization is significant on the separation of primary remanence,oil exploration and the determination of tectonic events,such as diagenesis,tectonic deformation in the area.The Yangtze block is an important part of the Chinese mainland.Its apparent polar wander path(APWP)cannot be completely determined due to the influence of remagnetization.In this paper,the Ordovician carbonate samples from the Yangdeng section in Zunyi City of Guizhou Province were studyed.Based on previous paleomagnetism studies,systematic rock magnetism and petrography studies were conducted to further clarify magnetic carriers,particle size and other rock magnetic information.By using the systematic rock magnetism analysis,combining with optical microscopy observations,we get the following preliminary conclusions:(1)The magnetic carriers of the Ordovician carbonate rocks in the Yangdeng are low to medium coercivity ferrimagnetic minerals such as magnetite and pyrrhotite,containing paramagnetic mineral pyrite.The main magnetic carriers for the A component(T_c<450?)are fine-grained authigenetic pyrrhotite,the minor magnetic carriers are magnetite,within pyrite.The main carriers of the B component(T_c ranges from450?~585?)are coarse(PSD)magnetite.(2)The mechanism for remagnetization is due to the fluids interaction within the Yangdeng Ordovician conbonates.The migration of orogenic fluids though the Yangdeng Ordovician conbonates prompt the growth of pyrrhotite/magnetite to acquire chemical remanence(CRM).