A study of mylonites from parts of the Salem-Attur shear zone (Tamil Nadu) and its tectonic implications |
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| Authors: | T K Biswal V Thirukumaran Kamleshwar Ratre Krishanu Bandyapadhaya K Sundaralingam Amit Kumar Mondal |
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| Institution: | (1) Department of Lithospheric Research, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria;(2) Department of Geodynamics and Sedimentology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria |
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| Abstract: | The E-W running Salem-Attur shear zone demarcates the tectonic boundary between Archaean Dharwar Craton in the north and Proterozoic
Southern granulite terrane in the south. This study reveals that the shear zone is a low angle thrust. The thrust zone is
around 10 m thick and it merges with the main shear zone along the strike. The thrust is developed on charnockite near Odyarpatti,
which is retrograded into schists. Further, it is marked by gently dipping mylonitic foliation and subhorizontal lineation.
The S-C fabric, mantled porphyroclasts and intragranular faults indicate northeasterly slip along the thrust. Recumbent shear
folds SF1 are developed within the thrust zone. The thrust has been folded by late stage F2 fold which has brought variation in the orientation of the mylonitic foliation from subhorizontal to vertical attitude; the
mylonitic lineations have been rotated to subvertical orientation also. Additionally, the F2 crenulations and shear cleavages and intersection lineations are superimposed on the mylonitic fabric. Thrusting along the
Salem-Attur shear zone is probably the cause for upliftment of the charnockites to the upper crust. Post-upliftment stage
has witnessed brittle deformation in the form of development of shear fractures in NNE-SSW and E-W directions. Pseudotachylites
are emplaced along these fractures. |
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