Macro-and Microstructural, Textural Fabrics and Deformation Mechanism of Calcite Mylonites from Xar Moron-Changchun Dextral Shear Zone, Northeast China  

作　　者：LIANG Chenyue LIU Yongjiang ZHENG Changqing LI Weimin Franz NEUBAUER ZHANG Qian 

机构地区：[1]College of Earth Sciences,Jilin University,Changchun 130061,China [2]Key laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources,Jilin University,Changchun 130061,China [3]Key Lab of Submarine Geosciences and Prospecting Techniques,Ministry of Education Institute for Advanced Ocean Study,College of Marine Geosciences,Ocean University of China,Qingdao,Shandong 266100,China [4]Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao,Shandong 266237,China [5]Department of Geography and Geology,University of Salzburg,Salzburg,A-5020,Austria

出　　处：《Acta Geologica Sinica(English Edition)》2019年第5期1477-1499,共23页地质学报（英文版）

基　　金：financially co-supported by the National Key R&D Program of China (Grant No.2017YFC0601401 and 2017YFC0601300-01);the National Natural Science Foundation of China (Grant no. 41602211 and 41230206)

摘　　要：The calcite mylonites in the Xar Moron-Changchun shear zone show a significance dextral shearing characteristics. The asymmetric(σ-structure) calcite/quartz grains or aggregates, asymmetry of calcite c-axes fabric diagrams and the oblique foliation of recrystallized calcite grains correspond to a top-to-E shearing. Mineral deformation behaviors, twin morphology, C-axis EBSD fabrics, and quartz grain size-frequency diagrams demonstrate that the ductile shear zone was developed under conditions of greenschist facies, with the range of deformation temperatures from 200 to 300°C. These subgrains of host grains and surrounding recrystallized grains, strong undulose extinction, and slightly curved grain boundaries are probably results of intracrystalline deformation and dynamic recrystallization implying that the deformation took place within the dislocation-creep regime at shallow crustal levels. The calculated paleo-strain rates are between 10-7.87s-1 and 10-11.49s-1 with differential stresses of 32.63-63.94 MPa lying at the higher bound of typical strain rates in shear zones at crustal levels, and may indicate a relatively rapid deformation. The S-L-calcite tectonites have undergone a component of uplift which led to subhorizontal lifting in an already non-coaxial compressional deformation regime with a bulk pure shear-dominated general shear. This E-W large-scale dextral strike-slip movement is a consequence of the eastward extrusion of the Xing’an-Mongolian Orogenic Belt, and results from far-field forces associated with Late Triassic convergence domains after the final closure of the Paleo-Asian Ocean.The calcite mylonites in the Xar Moron-Changchun shear zone show a significance dextral shearing characteristics. The asymmetric（σ-structure） calcite/quartz grains or aggregates, asymmetry of calcite c-axes fabric diagrams and the oblique foliation of recrystallized calcite grains correspond to a top-to-E shearing. Mineral deformation behaviors, twin morphology, C-axis EBSD fabrics, and quartz grain size-frequency diagrams demonstrate that the ductile shear zone was developed under conditions of greenschist facies, with the range of deformation temperatures from 200 to 300°C. These subgrains of host grains and surrounding recrystallized grains, strong undulose extinction, and slightly curved grain boundaries are probably results of intracrystalline deformation and dynamic recrystallization implying that the deformation took place within the dislocation-creep regime at shallow crustal levels. The calculated paleo-strain rates are between 10–7.87s–1 and 10–11.49s–1 with differential stresses of 32.63–63.94 MPa lying at the higher bound of typical strain rates in shear zones at crustal levels, and may indicate a relatively rapid deformation. The S-L-calcite tectonites have undergone a component of uplift which led to subhorizontal lifting in an already non-coaxial compressional deformation regime with a bulk pure shear-dominated general shear. This E-W large-scale dextral strike-slip movement is a consequence of the eastward extrusion of the Xing’an-Mongolian Orogenic Belt, and results from far-field forces associated with Late Triassic convergence domains after the final closure of the Paleo-Asian Ocean.

关 键 词：CALCITE MYLONITES EBSD analysis finite-strain determination kinematic vorticity paleopiezometry Solonker- Xar Moron-Changchun-Yanji SUTURE Belt 

分 类 号：TG1[金属学及工艺—金属学]