Variation in vorticity of flow during exhumation of lower crustal rocks (Neoproterozoic Ambaji granulite, NW India)

Sudheer Kumar Tiwari*, Anouk Beniest, Tapas Kumar Biswal

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The exhumation of the Neoproterozoic Ambaji granulite in the Aravalli-Delhi mobile belt, NW India, took place along NNW-SSE trending D2-shear zones. The shear zones evolved from a high temperature (>700 °C) thrust-slip shearing event in the lower-middle crust to a low temperature (450 °C) retrograde sinistral top-to-NW shearing event at the brittle-ductile-transition (BDT). The vorticity of flow (Wm) along the shear zones is estimated with the Rigid Grain Net and strain ratio/orientation techniques. The Wm estimates of 0.32–0.40 and 0.60 coincide with the high temperature event and suggests pure shear dominated deformation. The low temperature phase coincides with Wm estimates of 0.64–0.87 and ~1.0 implying two flow regimes. The shear zone was first affected by general non-coaxial deformation and gradually became dominated by simple shearing. We interpreted that the high temperature event happened in a compressive tectonic regime which led to horizontal shortening and vertical displacement of the granulite to the BDT. The low temperature event occurred in a transpressive tectonic setting that caused the lateral displacement of the granulite body at BDT depth. The Wm values indicate a non-steady strain during exhumation of granulite. This tectonic evolution is comparable with that of the Himalayas.

Original languageEnglish
Article number103912
Pages (from-to)1-14
Number of pages14
JournalJournal of Structural Geology
Volume130
Early online date15 Oct 2010
DOIs
Publication statusPublished - Jan 2020

Keywords

  • Exhumation of lower crustal rocks
  • Neoproterozoic Ambaji granulite
  • Non-steady strain
  • Shear zones
  • Vorticity analysis

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