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Islam, R.
- The Birth History of Two Granitic Plutons of the Bhilangna Valley of Garhwal Himalaya: A Geochemical Approach
Authors
1 Wadia Institute of Himalayan Geology, Dehra Dun - 248 001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 38, No 1 (1991), Pagination: 23-35Abstract
On the basis of geochemical study, two granitic plutons are identified in the Bhilangna valley of the Garhwal Himalaya, viz. the Chaili porphyritic granite gneiss (CPGG) and the Ingedinala granite gneiss (IGG). Both, CPGG and IGG rocks fall in the quartz rich zone (QRZ) of chemical-mineralogical typology of Dcbon and Le Fort, 1982. CPGG and IGG are strongly peraluminous, S-type granites and enriched in Si and K and depleted in Ca and Sr. The unusually high K2O suggests introduction of LILE during metasomatic processes. Both, CPGG and IGG are crustally derived and produced due to the partial melting of psammo-pelitic sediments. Probably the source materials for CPGG and IGG are same, attested by the geochemical similarities. The Q-Ab-Or plots of CPGG and IGG revealed that the temperature higher than that of the 'minimum' melt was attained during anatexis. During the Himalayan orogeny, intracontinental subduction took place along MCT and provided channels for the metasomatic fluids which induced K and Rb metasomatism and subsequently modified the nature of CPGG and IGG.Keywords
Anatexis, Granitic Pluton, Garhwal Himalaya, Subduction, Main Central Thrust, Metasomatism.- Geochemistry and Petrogenesis of Hanuman Tibba Granite of Kullu Valley, Himachal Himalaya
Authors
1 Wadia Institute of Himalayan Geology, Dehra Dun-248001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 49, No 1 (1997), Pagination: 13-21Abstract
A maiden attempt has been made to study the far-flung Hanuman Tibba Granites of Kullu valley, Himachal Pradesh. The granite has intruded the low grade Haimanta (-Lahaul) Formation which tectonically overlies the Rohtang Gneissic Complex. Integrated field, petrographic and geochemical studies have revealed that it is peraluminous S- type granite derived from sedimentary protolith. Compositional difference in terms of depletion of Fe, Mg, Ti, Ca, Sr, Zr and enhancement of Sit K and Rb from margin to core of the granite body is consistent with fractional crystallization process.
The emplacement of Hanuman Tibba Granite on the same tectonic level as Jispa and Ratilaman granite (500±ma) in adjacent Lahaul-Spiti region suggests a Cambro-Ordovician age for the Hanuman Tibba Granite.
Keywords
Petrology. Geochemistry, Hanuman Tibba Granite (HTG), Haimanta Formation, Kullu Valley, Himalaya.- Role of Tectono-Climatic Factors in the Neogene Himalayan Foreland Sediments: Petrology and Geochemical Approach, Kangra Sub-Basin
Authors
1 Sedimentology Group, Wadia Institute of Himalayan Geology, Dehradun - 248 001, IN
2 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur - 721 302, IN
3 Department of Geology, University of Pune, Ganeshkhind, Pune - 411 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 71, No 6 (2008), Pagination: 787-807Abstract
The Neogene Siwahk fluvial succession (12 77-4 48 Ma) of the NW Himalayan foreland basin, east of Ravi River, are deposited under varied Tectono-Climatic conditions. Petrography and geochemistry of the sediments were carried out to understand the relative roles of tectonics and climate in this basin.The sandstones are classified as sub-litharenites with subordinate arkosic-graywacke. The dental components particularly the rock fragments are consistent with the inferred source area presently disposed towards the north of the depocenter and suggest that the Higher, Lesser and Lower Tertiary formations supplied detntus since 12 77 Ma. The Th/Sc vs. Zr/Sc ratio indicates sediment recycling. The Cr and Ni, negative Eu anomaly, LREE enrichment and moderately flat HREE in the mudstones collectively suggest dominant contribution from felsic igneous rocks beside contribution from basic, sedimentary/metamorphic hithology. Near consistent nature of the dental modes and geochemical parameters through time suggest unvarying source since 12 77 Ma.The present study also infers that the source areas uplift owing to tectonic activity of Chad Thrust at least by 12 77 Ma with a perceptible activity of MBT after 8 Ma.
The 5180 variations in soil carbonates reveals ongoing intense monsoon system since 12 77 Ma followed by a phase of aridity at 91 Ma. Presence of fresh and weathered feldspar, limestone, basic volcamcs and mica, both in humid and arid phase indicate rapid deposition and preservation. Despite the climatic turnover from humid to arid, distinctive changes in the framework mineral compositions over time is not discernable.
The petrographic and geochemical data reveals that the near similar source area, relatively rapid transport, moderate chemical weathering and sediment recycling controlled the composition of the sediments of the HFB in response to tectonics and climate.
Keywords
Climate, Provenance, Tectonics, Himalayan Foreland Basin, Siwahk, Kangra.- Exhumation History of Eclogites from the Tso-Morari Crystalline Complex in Eastern Ladakh: Mineralogical and Fluid Inclusion Constraints
Authors
1 Wadia Institute of Himalayan Geology, Dehra Dun-248001, IN
2 Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA-24061, US
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 53, No 2 (1999), Pagination: 181-190Abstract
Eclogites from the Tso-Morari Crystalline Complex in Ladakh, India, preserve evidence for high P, low T metamorphism of subducted Indian continental crust in the presence of a moderate salinity aqueous fluid phase. The phengite barometry estimates a pressure range of 11-14 kbar for eclogitization whereas garnet-omphacite geothermometry reveals a temperature range of 530°-580°C. Following eclogitization at 530°-580°C at a minimum pressure of 14 kbar, the eclogites were tectonically exhumed along a nearly isothermal P-T path that brought them to within 10-30 kilometers of the surface. Final transport to the surface followed a more normal continental geotherm.Keywords
Tso-Morati, Eclogite, Fluid Inclusion, Mineral Geothermobarometry, Ladakh Himalaya.- Geochemical Characterisation of the Neoproterozoic Nagthat Siliciclastics, NW Kumaun Lesser Himalaya: Implications for Source Rock Assessment
Authors
1 Wadia Institute of Himalayan Geology, 33 General Mahadeo Singh Road, Dehra Dun - 248 001, IN