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      https://www.ias.ac.in/article/fulltext/jess/126/04/0046

    • Keywords

       

      Pseudotachylyte; clast; Power law distribution; roundness; Gangavalli Shear Zone.

    • Abstract

       

      Gangavalli (Brittle) Shear Zone (Fault) near Attur, Tamil Nadu exposes nearly 50 km long and 1–3 km wide NNE–SSW trending linear belt of cataclasites and pseudotachylyte produced on charnockites of the Southern Granulite Terrane. Pseudotachylytes, as well as the country rock, bear the evidence of conjugate strike slip shearing along NNE–SSW and NW–SE directions, suggesting an N–S compression. The Gangavalli Shear Zone represents the NNE–SSW fault of the conjugate system along which a right lateral shear has produced seismic slip motion giving rise to cataclasites and pseudotachylytes. Pseudotachylytes occur as veins of varying width extending from hairline fracture fills to tens of meters in length. They carry quartz as well as feldspar clasts with sizes of few mm in diameter; the clast sizes show a modified Power law distribution with finer ones (<1000 μm2) deviating from linearity. The shape of the clasts shows a high degree of roundness (<0.4) due to thermal decrepitation. In a large instance, devitrification has occurred producing albitic microlites that suggest the temperature of the pseudotachylyte melt was >1000∘C. Thus, pseudotachylyte veins act as a proxy to understand the genetic process involved in the evolution of the shear zone and its tectonic settings.

    • Author Affiliations

       

      Bhuban Mohan Behera1 V Thirukumaran2 Aishwaraya Soni1 Prasanta Kumar Mishra3 Tapas Kumar Biswal1

      1. Department of Earth Sciences, Indian Institute of Technology Bombay, Mumbai 400 076, India.
      2. Department of Geology, Govt. Arts College, Salem 636 007, India.
      3. Geological Survey of India, Raipur, Chhattisgarh 492 010, India.
    • Dates

       
  • Journal of Earth System Science | News

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