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Deformation Characteristics And Rheological Parameter Estimation Of Motianling Ductile Shear Zone

Posted on:2018-06-11Degree:MasterType:Thesis
Country:ChinaCandidate:S Y LiuFull Text:PDF
GTID:2370330620957701Subject:Geology
Abstract/Summary:PDF Full Text Request
On the basis of detailed field geological investigation,a systematic finite strain measurement,kinematic vorticity number and EBSD quartz fabrics analysis have been conducted throughout the Motianling ductile shear zone,the main results show that:The Motianling ductile shear zone outcrops over 65 kilometers long and 10-16 km wide mylonites and granitic mylonites,which develop dipping at 200-330°at dip angles from 10°to 74°.Shear sense macroscopic indicators,including mylonitic foliation,lineation,rotated porphyroclast,S-C fabric and book inclined structure;while microcosmic indicators,including undulatory quartz,recrystallization,mechanical twin,pressure shadow,myrmekitic texture,mica fish as well as mica strip.Moreover,some typical macroscopic deformation signs such as tectonic schist zone,a fold and shear deformed quartz vein are also observed in the Neoproterozoic Sibao Group and Danzhou Group country rocks.Both macroscopic and microcosmic signs indicate that the Motianling ductile shear zone is a dextral strike-slip ductile shear zone.According to granitic mylonites finite strain measurement and kinematic vorticity number analysis results,we noted that the deformation in the central part of the Motianling ductile shear zone is characterized by elongated strain,whereas the edge of the ductile shear zone is characterized by compressed strain.Both strain intensities?r?and compression rates????data indicates that the deformation intensity in middle part of the shear zone is stronger than in edges.Moreover,our research results also suggest that the shear zone is dominated by simple shear,but coexistence with pure shear.Combined with metamorphic mineral assemblage,quartz recrystallization,fractal method and EBSD quartz fabrics analysis,we noted that there clearly exists a temperature gradient within the shear zone so that the deformation temperatures decrease from the middle?550-630??toward the edge?300-480??.In the aspect of dynamics,the differential stress of the ductile shear zone is between 19.17 and 55.07 MPa,while the strain rates range from3.99×10-14s-1to 8.68×10-13s-1.
Keywords/Search Tags:the Motianling ductile shear zone, finite-strain analysis, rheological parameter, Electron Backscattered Diffraction, northern Guangxi
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