Strain Pattern Analysis of Mylonites From Sitampundi-Kanjamalai Shear Zone, Thiruchengode, South India

  • Thirukumaran V Department of Geology, Government Arts College, Salem-636 007, Tamil Nadu, India
  • Biswal T.K Department of Earth sciences, IIT Bombay, Poway, Mumbai, India.
  • Sundaralingam K Department of Geological Survey of India, Hyderabad, India.
  • Sowmya V Department of Geology, Government Arts College, Salem-636 007, Tamil Nadu, India
  • Boopathi S Department of Geology, Government Arts College, Salem-636 007, Tamil Nadu, India
  • Mythili R Department of Geology, Government Arts College, Salem-636 007, Tamil Nadu, India
Keywords: Mylonite, SASZ, Strain pattern, Vorticity, Kinematic analysis, Pure shear, Bulk strain

Abstract

This study aims to investigate the petrography and strain pattern of mylonites from parts of N-S trending Sitampundi-Kanjamalai Shear Zone (SKSZ) around Thiruchengode. The petrographic study indicates the presence of recrystallized quartz, K-feldspar, plagioclase, biotite and some hornblende. The kinematic analysis of Mylonites was done with the help of shear sense indicators such as recrystallized type quartz (quartz ribbon) around the cluster of feldspar, S-C fabric shows dextral shear sense and some sinisterly shear sense in some parts of SASZ which can be considered as a product of partitioning of both strain and vorticity between domains. These all indicates the simple shear extension along E-W direction and the mylonitic foliation shows the pure shear compression along N-S direction. Further the study of bulk strain analysis by Flinn plot method using L and T section of mylonite shows k<1 which lies in the field of flattening zone of finite strain. The kinematic vorticity number is calculated by Rxz/β method which gives the value of 0.36 indicating the general shear. The rigid grain graph shows that the pure shear component is more ­­­­dominant than the simple shear component. The analysis leads to the conclusion that the mylonite has experienced a high temperature shearing of above 700°cat deep crustal level.

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Published
2019-05-30