The Ailaoshan-Red River（ASRR） shear zone is one of the major Southeast Asian tectonic discontinuities that have figured the present tectonic framework of the eastern Tibet.Several metamorphic massifs are distributed...The Ailaoshan-Red River（ASRR） shear zone is one of the major Southeast Asian tectonic discontinuities that have figured the present tectonic framework of the eastern Tibet.Several metamorphic massifs are distributed linearly along the shear zone,e.g.Xuelongshan,Diancangshan, Ailaoshan and Day Nui Con Voi from north to south.They bear a lot of lines of evidence for the tectonic evolution of the eastern Tibetan at different crustal levels in different tectonic stages.Controversy still exists on the deformation structures,microstructures and their relationship with metamorphisms along the ASRR.In this paper detailed microstructural and EBSD（Electron Backscattered Diffraction） fabric analysis of some highly sheared granitic rocks from different massifs along the ASRR are conducted.High temperature structures and microstructures are preserved in unsheared gneisses,in weakly sheared xenoliths or in some parts of the highly sheared rocks（mylonites）.Several types of high temperature quartz c-axis fabrics show symmetrical patterns or transitions from symmetrical to asymmetrical patterns.The former are attributed to coaxial deformation during regional shortening in an early stage of the Indian-Eurasian tectonic interaction and the latter are related to the transitions from coaxial compression to noncoaxial shearing during the post-collisional ASRR left lateral shearing.展开更多
The quartz fabric variation and the operation of slip systems were governed by the deformation flow. A new concept named quartz fabric slip flow pattern is to be considered thourgh this relation. On the other hand, st...The quartz fabric variation and the operation of slip systems were governed by the deformation flow. A new concept named quartz fabric slip flow pattern is to be considered thourgh this relation. On the other hand, strain path, quartz fabric variation and strain fabric development are inter related events which controlled by the deformation flow pattern. These events and related structures were analyzed in the Kazdag （IDA） stack antiform. The quartz fabric variation and the strain path analysis reveal mainly three distinct tectonic stages. These are initial vertical extrusion tectonic and following horizontal spreading tectonics. The beginning stage vertical extrusion represented by the quartz Y maxima fabric in rounded pattern and constructional strain and lengthening strain facies. The latest stage of the vertical extrusion also represented by the quartz fabric, constructional strain but proximating to plane strain and lengthening-widening strain facies. The vertical extrusions governed by the steeply dipping reverse faulting at the initial stage and then fallowed by the gently dipping thrusting at the latest stage. The flattening deformation was developed during the horizontal spreading stage. Typical incomplete single girdle quartz fabric, flattening type oblate strain and thinning--widening strain facies are characteristic features of the nappe tectonics.展开更多
基金supported by the National Key Basic Research and Development(973) Project (2009CB421001)National Natural Science Foundation of China(40872139)+2 种基金China Geological Survey (1212010661311)Ministry of Land and Resources (200811008)the Ministry of Education,Proiect 111 (B07011)
文摘The Ailaoshan-Red River（ASRR） shear zone is one of the major Southeast Asian tectonic discontinuities that have figured the present tectonic framework of the eastern Tibet.Several metamorphic massifs are distributed linearly along the shear zone,e.g.Xuelongshan,Diancangshan, Ailaoshan and Day Nui Con Voi from north to south.They bear a lot of lines of evidence for the tectonic evolution of the eastern Tibetan at different crustal levels in different tectonic stages.Controversy still exists on the deformation structures,microstructures and their relationship with metamorphisms along the ASRR.In this paper detailed microstructural and EBSD（Electron Backscattered Diffraction） fabric analysis of some highly sheared granitic rocks from different massifs along the ASRR are conducted.High temperature structures and microstructures are preserved in unsheared gneisses,in weakly sheared xenoliths or in some parts of the highly sheared rocks（mylonites）.Several types of high temperature quartz c-axis fabrics show symmetrical patterns or transitions from symmetrical to asymmetrical patterns.The former are attributed to coaxial deformation during regional shortening in an early stage of the Indian-Eurasian tectonic interaction and the latter are related to the transitions from coaxial compression to noncoaxial shearing during the post-collisional ASRR left lateral shearing.
文摘The quartz fabric variation and the operation of slip systems were governed by the deformation flow. A new concept named quartz fabric slip flow pattern is to be considered thourgh this relation. On the other hand, strain path, quartz fabric variation and strain fabric development are inter related events which controlled by the deformation flow pattern. These events and related structures were analyzed in the Kazdag （IDA） stack antiform. The quartz fabric variation and the strain path analysis reveal mainly three distinct tectonic stages. These are initial vertical extrusion tectonic and following horizontal spreading tectonics. The beginning stage vertical extrusion represented by the quartz Y maxima fabric in rounded pattern and constructional strain and lengthening strain facies. The latest stage of the vertical extrusion also represented by the quartz fabric, constructional strain but proximating to plane strain and lengthening-widening strain facies. The vertical extrusions governed by the steeply dipping reverse faulting at the initial stage and then fallowed by the gently dipping thrusting at the latest stage. The flattening deformation was developed during the horizontal spreading stage. Typical incomplete single girdle quartz fabric, flattening type oblate strain and thinning--widening strain facies are characteristic features of the nappe tectonics.
