Microstructural and deformational studies on mylonite in the detachment faults of Yalashan

Microstructural and deformational studies on mylonite in the detachment faults of Yalashangbo

dome, North Himalayan domes zone

ZHANG Bo;ZHANG Jinjiang ;GUO Lei;WANG Weiliang

【期刊名称】《自然科学进展（英文版）》 【年(卷),期】2005(015)011

【摘要】The Yalashangbo dome, located at the eastern end of North Himalayan domes zone, has a geometry and structure similar to those of a metamorphic core complex. Ductile shear zones formed the detachment system around the dome and these zones are composed of garnet-bearing phyllonite, mylonitic schist, mylonitic gneiss and mylonitic granite. Ductile shear fabrics developed well in mylonitic rocks, and penetrative lineation and foliation were formed by stretched quartz and feldspar and preferred orientation of mica. Polar Mohr diagram method is used to calculate the kinematic vorticity numbers of the shear zones in the detachment system. Results indicate that the shear zone is a thinned shear zone (thinning of 23 % )in an extensional setting which underwent a general shear dominated by simple shear. Comparison of the vorticity numbers between the northern and southern flanks of the Yalashangbo dome shows that the dome is an asymmetric system formed by a north-northwest-directed detaching unanimously. Statistical fractal analysis shows that the shapes of