Strain and kinematic vorticity analysis:An indicator for sinistral transpressional strain-partitioning along the Lancangjiang shear zone,western Yunnan,China  

作　　者：Bo Zhang  JinJiang Zhang  DaLai Zhong Lei Guo 

机构地区：[1] State Key Laboratory Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China [2] The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, Peking University, Beijing, 10

出　　处：《Science China Earth Sciences》2009年第5期602-618,共17页中国科学（地球科学英文版）

基　　金：Supported by National Natural Science Foundation of China (Grant Nos. 40802050, 49802020, 40172074);China Postdoctoral Science Foundation (Grant No. 20070440065)

摘　　要：This work deals with the preliminary relationship between strain path and strain partitioning pattern in a sinistral transpressional zone, Lancangjiang shear zone, located to the southeast of Tibet. Various ductile rocks provide an opportunity to investigThis work deals with the preliminary relationship between strain path and strain partitioning pattern in a sinistral transpressional zone,Lancangjiang shear zone,located to the southeast of Tibet.Various ductile rocks provide an opportunity to investigate quantitative finite strain(Rs),kinematic vorticity values(Wm),and proportions of simple and pure shear components.The mean kinematic vorticity values(Wm) were evaluated based on three methods,such as Rs-θ,prophyroclast hyperbolic distribution method(PHD),and polar Mohr diagram construction(PMD).Wm for mylonitic metasediments of the low-grade schist belt ranged from 0.19 to 0.54.Protomylonites,mylonites,and ultramylonites recorded differential Wm values,0.19―0.73,0.11―0.8,and 0.84―0.95(even 0.99) respectively in the high-grade gneiss belt.Based on classical strain analysis and these kinematic vorticity evaluations,the shear zone is classified as a preliminarily bulk monoclinic symmetry.The pattern of vorticity path suggests that a previously undocumented transpressional setting and strain partitioning pattern in the southeast region of Tibet Plateau,characterized by steep-narrow domain of simple-shearing(Tertiary strike-slip shearing) deformation and wider domain of mostly pure-shearing(Tertiary contraction) to accommo-date intracontinental deformation.

关 键 词：STRAIN KINEMATIC VORTICITY TRANSPRESSION STRAIN partitioning Lancangjiang SHEAR zone 

分 类 号：P313[天文地球—固体地球物理学]