Magnetic fabric analysis of deformed rocks in the Riiser-Larsen Main Shear Zone, East Antarctica
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Anisotropy of magnetic susceptibility (AMS) in deformed rocks in the Riiser-Larsen Main Shear Zone (RLMSZ) was analyzed in order to demonstrate the changes in rock magnetic properties due to deformation. Sixty-nine samples were collected at six sites from sheared gneisses and sheared dolerites. Experimental results of stepwise acquisition of isothermal remanence, demagnetization of a composite IRM and thermomagnetic measurement indicate the presence of Ti-poor titanomagnetite. Pyrrhotite also occurs characteristically in specimens with mylonitic textures. Magnetic foliations of AMS for the mylonite at three sites show good agreement with mylonitic foliation at each site. The mylonites showed enhancement of anisotropy degree from protoliths, indicating overprinting of the original magnetic fabrics. Their maximum susceptibility axes are well defined within each site, and dip about 50-60° northward. The magnetic lineation probably indicates the maximum stretching direction in the RLMSZ.
- Polar geoscience
Polar geoscience 18, 15-25, 2005-10
National Institute of Polar Research