HR: 0800h
AN: V41C-0713    [Abstracts]
TI: Microfabric Characteristics and Rheological Importance of UHP Jadeite-Quartzite from Shuanghe, Dabie Mountains
AU: * Wang, L
EM: wanglucug@163.com
AF: Dept. of Marine Geology, Ocean Univ. of China, Qingdao, 266100, China
AU: * Wang, L
EM: wanglucug@163.com
AF: Faculty of Earth Sciences, China Univ. of Geosciences, Wuhan, 430074, China
AU: Jin, Z
AF: Faculty of Earth Sciences, China Univ. of Geosciences, Wuhan, 430074, China
AU: Liu, X
AF: Faculty of Earth Sciences, China Univ. of Geosciences, Wuhan, 430074, China
AU: Li, S
AF: Dept. of Marine Geology, Ocean Univ. of China, Qingdao, 266100, China
AB: Jadeite-quartzite is one of the important UHP rock types occurring in the Dabie Mountains ultrahigh-pressure metamorphic belt. It is significant to study the structural evolution of jadeite-quartzite in order to understand more completely the formation and evolution of UHP orogenic belts. Moreover, to understand the jadeite-quartzite's deformation mechanisms and geodynamical parameters (stress, strain, strain rate) the study of the microstructure and LPO (lattice preferred orientation) of deformed jadeite and quartz is essential; until now this kind of study has not been performed extensively. Petrofabric data and preliminary TEM work on six representative jadeite-quartzite samples from Shuanghe (Dabie Mountains) are presented. Petrofabric data obtained by EBSD (Electron Backscattered Diffraction) show that the jadeite LPOs patterns are similar to those of omphacite and vary between L- and S-type, which correlate with prolate and oblate grain shape fabrics; quartz LPOs are monoclinic; garnet has no crystallographic preferred orientation. TEM study shows that dominant slip systems of jadeite in one sample are (100)[001], (110)[001] and (-110)1/2[110], while in another sample no dislocation is observed. Abundant dislocations in quartz are operated by the dominant slip system (0001)[11-20] which is basal glide and represents regional shearing during the exhumation process. This suggests that dislocation creep is the dominant deformation mechanism in jadeite. Further study is needed to determine whether other factors such as diffusion creep, grain boundary migration, cation ordering and strain symmetry play an important role in deformation mechanism of jadeite in the jadeite- quartzites of Shuanghe, Dabie Mountains.
DE: 3613 Subduction zone processes (1031, 3060, 8170, 8413)
DE: 3625 Petrography, microstructures, and textures
DE: 3654 Ultra-high pressure metamorphism
DE: 3902 Creep and deformation
DE: 3904 Defects
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting