[SCG69-P04] Magnetic Fabrics Analysis across the Central Region of the Chimei Fault in the Coastal Range of Eastern Taiwan
Keywords:Anisotropy of Magnetic Susceptibility, Chimei Fault, Coastal Range, Taiwan
Results of AMS across the central part of the Chimei fault show that the direction of kMAX changed from N-S orientation to sub-vertical and the orientation of kMIN switched from 270/70 to N-S orientation when samples of the footwall were approaching to the fault zone. At the same time, anisotropy was increasing and susceptibility ellipsoid changed from oblate in the fractured zone through prolate in the folded zone to oblate in the faulted zone. Based on identification experiments of magnetic minerals, the major magnetic carrier is magnetite with pseudo-single domain, suggesting paramagnetic minerals control the AMS. With increasing deformation, oblate ellipsoids with strong anisotropy developed within the fault zone highlighted the strain history of the central part of the Chimei fault. As a result, it strongly speculated that stress altered from sub-vertical sedimentary loading to horizontally NW-SE compression during collision stage and current N-S compression orientation could be resulted from 30 degree clockwise rotation during accretion stage.
This study demonstrates that AMS pattern across the Chimei fault is the consequence of finite deformation. Our results of magnetic fabrics evolution across the Chimei fault can provide insights into understanding the tectonic history of Chimei fault.