Using microstructures to analyze the deformationistory Taimali area, southeastern Taiwan
Date Issued
2008
Date
2008
Author(s)
Hsu, Yi-Chun
Abstract
Since the geometries of syn-tectonic fibers in pressure shadows are considered to be closely related to the deformation paths of host rocks, syn-tectonic fibers have been used to determine fold kinematics and the kinematics of deformation in accretionary prism and fold-and-thrust belt. This study uses pressure shadows to analyze rock deformations in five outcrops of folds with flat-lying foliation (Sh) at Taimali, Taiwan.he study region, which is located at the subduction-collision conjunction, southeastern Taiwan, consists of overturned Miocene deposits having undergone lowest-grade metamorphism and ductile-brittle deformation during the Late Cenozoic Penglai Orogeny. There lies a set of flat-lying foliation (Sh) and ESE-trending stretch lineation ( L ). The deformation history was evaluated using incremental strain indicators and microstructures. bserved phenomena are described as follows: (1) the antitaxial overgrowths of fibrous quartz are developed in pressure shadows of pyrite object; (2) non-coaxial strain was indicated by fibers on both cleavage plane (XY) and cleavage-perpendicular plane (XZ); (3) in the XY plane, the radial fibers over the pyrite are prominent and are of the last deformation stage; (4) the rotation directions of pressure shadows in rocks of different limbs were the same on the XY plane, which indicated the pressure shadows have not been affected by folding; (5) the deformation recorded by pressure shadows on the YZ plane in rocks of different limbs of the Jinlun antiform was symmetrical with respect to the fold axial plane. These results show that the deformation history was triclinic deformation and vertical flattening is strong during exhumation in this region.
Subjects
pressure shadows
strain history
flat-lying foliation
subduction-collision conjunction
Taimali
Type
thesis
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