Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Rajinder Parshad ¹, Nand Lal ², K. K. Nagpaul ¹

Affiliations
1 Department of Physics, Kurukshetra University, Kurukshetra-132119, IN
2 Electrologging Section, Oil and Natural Gas Commission, Ahmedabad-380005, IN

Abstract

Fission track ages of two cogenetic minerals viz., garnet and apatite collected from the pegmatites of Nellore Mica. Belt of India, emplaced during the closing stages of the Eastern Ghats Orogeny (1500-1600 Ma) are found to be 1065 Ma and 440 Ma respectively. The data has been interpreted in terms of tectonic uplift of the pegmatites. The average rate of uplift for this region has been calculated as 0.04 mm/year.

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Ashok Kumar ¹, Nand Lal ², A. K. Jain ³, R. B. Sorkhabi ⁴

Affiliations
1 Department of Physics, Kurushetra University, Kurukshetra - 132 119, IN
2 Department of Geophysics, Kurukshetrauniversity, Kurukshetra - 132 119, IN
3 Department of Earth Sciences, University of Roorkee, Roorkee - 247 667, IN
4 Department of Geology, ArizonaState University, Tempe, Arizona 85287-1404, US

Abstract

Fission Track (m) ages of apatite and zircon from the Higher Himalayan Crystalline (HHC), SE - Jammu and Kashmiralong Chenab-Suru-Dodarivers and their tributaries provide constraints on the cooling (<250°C) and exhumation history of these rocks. FT ages of apatite/zircon versus the topographic elevations of the host samples from different traverses provide linear relationships, indicating differential and secular nature of exhumation in the Himalaya. The HHC belt is exhumedat a rate of about 0.27 mm/a during Middle to Late Miocene. However, regional exhumation rate near the base along the Main Central Thrust and in central parts of the HHC from FT apatite ages is faster upto 0.35 mm/a since Late Miocene. Exhumation has considerably slowed down to 0.11 mm/a along its northern boundary and 0.02 mm/a along the Zanskar Shear Zone. No apparent faster exhurnationis discernible either along thee MCT or the Zanskar ShearZone (ZSZ). On the other hand, three large fold structures namely the Suru Dome, the Chisoti Dome and the Kishtwaranti formal window have indicated very young and fast exhumation of 0.33 mm/a, 1.1 mm/a and 3.6 mm/a respectively during the last 1 to 5 Ma.

Keywords

Fission Track Ages, Geochronology, Crystallines, NW Himalaya.

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R. C. Patel ¹, Vikas Adlakha ¹, Paramjeet Singh ¹, Yogesh Kumar ², Nand Lal ¹

Affiliations
1 Department of Geophysics, Kurukshetra University, Kurukshetra - 136 119, IN
2 RITES, New Delhi, IN

Abstract

The crystallines in the Kumaon Himalaya, India are studied along Goriganga, Darma and Kaliganga valleys and found to be composed of two high-grade metamorphic gneiss sheets i.e. the Higher Himalayan Crystalline (HHC) and Lesser Himalayan Crystalline (LHC) zones. These were tectonically extruded as a consequence of the southward directed propagation of crustal deformation in the Indian plate margin. The HHC and its cover rocks i.e. the Tethyan Sedimentary Zone (TSZ) are exposed through tectonic zones within the hinterland of Kumaon Himalaya. The HHC records history of at least one episode of pre-Himalayan deformation (D₁), three episodes of Himalayan deformation (D₂, D₃, D₄). The rocks of the HHC in Kumaon Himalaya are thoroughly transposed by D₂ deformation into NW-SE trending S_m (S₁+S₂). The extent of transposition and a well-developed NE-plunging L₂ lineation indicate intense strain during D₂ throughout the studied portion of the HHC. Ductile flow continued, resulting in rotation of F₁ and F₂ folds due NE-direction and NW-SE plunging F₃ folds within the HHC. The over thickened crystalline was finally, superimposed by late-to-post collisional brittle-ductile deformation (D₄) and exposed the rocks to rapid erosion.

Apatite Fission Track (AFT) and Zircon Fission Track (ZFT) studies from the Kumaon Himalaya suggest reactivation of the Main Central/Munsiari Thrust (MCT/MT) and Vaikrita Thrust (VT), rapid exhumation and a system that has been in topographic and exhumation steady-state since at least ₄ Ma.

Keywords

Higher Himalayan Crystallines, Deformation, Exhumation, Kumaon Himalaya.

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Nand Lal ¹, Promila Batra ²

Affiliations
1 Kurukshetra University, IN
2 Principal Senior Secondary Model School, Kurukshetra, IN

Abstract

No Abstract.

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