Determining the Reference Frame for Kinematic Analysis in S-tectonites Using AMS
Authors
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Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur – 721302
Manish A. Mamtani -
Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur – 721302
V. Abhijith
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Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur – 721302
Sivaji Lahiri
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Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur – 721302
Virendra Rana
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Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur – 721302
Sandeep Bhatt
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Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur – 721302
Shalini Goswami
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Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur – 721302
A. R. Renjith
DOI:
https://doi.org/10.1007/s12594-017-0657-0Abstract
In this paper a methodology based on anisotropy of magnetic susceptibility (AMS) measurements is presented to identify XZ section of the strain ellipsoid in order to perform kinematic analysis in S-tectonites, which are rocks that lack stretching lineation on the foliation plane. The similarity between orientations of three principal axes of the AMS ellipsoid (K1>K2>K3) and strain ellipsoid (X>Y>Z) is demonstrated by discussing the case of a mylonite (LS-tectonite) that contains both foliation and stretching lineation. Subsequently, the case of S-tectonite from the peninsular gneiss (south India) is discussed, where the K1K3 plane of AMS ellipsoid is equated with XZ section of strain ellipsoid. Quartz crystallographic preferred orientations are investigated using SEM-EBSD studies in thin section prepared parallel to the K1K3 plane. Quartz c-axis patterns characteristic of rhomb slip and indicating top-to-325° sense of shear are recorded. This supports the movement sense inferred by earlier researchers from northern parts of the sampled locality. Thus the usefulness of AMS in determining the reference frame for kinematic studies in S-tectonites is documented.
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