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Microstructures of Mylonites Along the Karakoram Shear Zone, Tangste Valley, Pangong Mountains, Karakoram


Affiliations
1 Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee - 247 667, India
2 Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee – 247 667, India
     

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The Karakoram Shear Zone is a northwest-southeast trending dextral ductile shear zone, which has affected the granitic and granodioritic bodies of the southern Asian Plate margin in three distinct episodes. The ductile shearing of the granitic bodies at Tangste and Darbuk has resulted in the development of mylonites with mylonitic foliation and stretching lineation. More intense deformation is noted in the Tangste granite grading up to orthomylonite, as compared to the Darbuk granite. Kinematic indicators include S-C foliation, synthetic C' and C" antithetic shear bands, Type A s-mantled porphyroclasts, oblique quartz foliation, micro-shears with bookshelf gliding, mineral fishes including Group 2 mica fishes, and Type 1 and 2a pull-apart microstructures, and exhibit strong dextral sense of ductile shearing towards southeast. The textural features of the minerals, especially that of quartz and feldspar, indicate temperature of mylonitisation ranging between 300 and 500°C in the upper greenschist facies, and appear to have been evolved during exhumation as a consequence of oblique strike-slip movements along the Karakoram shear zone.

Keywords

Karakoram Shear Zone, Mylonites, Texture, Kinematic Indicators, Karakoram, Uttarakhand.
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  • Microstructures of Mylonites Along the Karakoram Shear Zone, Tangste Valley, Pangong Mountains, Karakoram

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Authors

Priyom Roy
Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee - 247 667, India
A. K. Jain
Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee – 247 667, India
Sandeep Singh
Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee – 247 667, India

Abstract


The Karakoram Shear Zone is a northwest-southeast trending dextral ductile shear zone, which has affected the granitic and granodioritic bodies of the southern Asian Plate margin in three distinct episodes. The ductile shearing of the granitic bodies at Tangste and Darbuk has resulted in the development of mylonites with mylonitic foliation and stretching lineation. More intense deformation is noted in the Tangste granite grading up to orthomylonite, as compared to the Darbuk granite. Kinematic indicators include S-C foliation, synthetic C' and C" antithetic shear bands, Type A s-mantled porphyroclasts, oblique quartz foliation, micro-shears with bookshelf gliding, mineral fishes including Group 2 mica fishes, and Type 1 and 2a pull-apart microstructures, and exhibit strong dextral sense of ductile shearing towards southeast. The textural features of the minerals, especially that of quartz and feldspar, indicate temperature of mylonitisation ranging between 300 and 500°C in the upper greenschist facies, and appear to have been evolved during exhumation as a consequence of oblique strike-slip movements along the Karakoram shear zone.

Keywords


Karakoram Shear Zone, Mylonites, Texture, Kinematic Indicators, Karakoram, Uttarakhand.