Deformation and metamorphism of Wuliangshan area, western Yunnan
Hou Quanlin1, Zhong Dalai2, Guo Qianqian1
1. Key Laboratory of Computational Geodynamics, CAS; University of Chinese Academy of Sciences, Beijing 100049;
2. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029
The Wuliangshan metamorphic belt is a striking NNW-SSE anticlinorium,with both limbs limited by faults.In the middle part of the anticlinorium,there is a striking NNW-SSE sinistral ductile shear zone.The metamorphic grade of the middle shear zone reaches to kyanite zone of epidote amphibolite facies,which is obviously higher than the biotite zone of greenschist facies in the surrounding rocks.Using the biotite-garnet thermobarometry,the P-T conditions are yielded at 600 ℃～650 ℃ and 5.6 kbar at the western edge,as 550 ℃～600 ℃ and 5 kbar at the eastern edge,respectively.It is first advanced in Western Yunnan that this shear zone is a progressive metamorphic zone according to the compositional zone of contemporaneous garnet and the b0 value of phengites.The metamorphism of the shear zone has the characteristics of inhomogeneity and uncontinuative isograde,which is different from the regional metamorphism of homogeneity and isograde.The theory of deformation energy is first used to discuss the mechanism of the shear-metamorphic zone in this paper.The metamorphism of the ductile shear zone in Wuliangshan area has a relation with the deformation of the rocks,namely the stronger the formation,the higher the metamorphic grade.This is reduced to the heat,transformed from the deformation energy and then causing higher-grade metamorphism with the strengthening of the formation.