- S. Vyshnavi
- P. Srivastava
- D. K. Misra
- K. K. Purohit
- V. C. Thakur
- K. S. Bist
- B. K. Chaudhuri
- B. S. Rawat
- Subhajit Sinha
- Sumit K. Ghosh
- Rohtash Kumar
- P. Sanyal
- S. J. Sangode
- Y. P. Sundriyal
- K. H. Sachan
- R. J. Bodnar
- Cs. Szabo
- R. D. Lawi
- Himanshu K. Sachan
- J. John
- V. Thamarai
- M. M. Mehra
- Teena Choudhary
- M. S. Giridhar
- Ashwini Jambhalikar
- Gogulapati Supriya
- Gaurav Saxena
- K. V. Shila
- B. Ramesh
- T. K. Pratheek
- Deepak Kumar Sharma
- P. Selvaraj
- A. Kalpana
- S. Ajith Kumar
- K. V. Sriram
- A. S. Laxmiprasad
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Islam, R.
- Elemental Behaviour in the Soil Profile of the Humid Northeastern Himalaya
Authors
Source
Himalayan Geology, Vol 34, No 1 (2013), Pagination: 65-75Abstract
Soil profiles are generally developed on stable landform in an erosion limited area with the interaction of water (rainfall). The development of the soil profile on granodioritic lithology at Anini village of Arunachal Pradesh, at an altitude of 1644 m in the NE Himalaya provides us some opportunity to understand the elemental behavior in the highly eroded and humid region, where rainfall is as high as ~2600 mm/a. The study area is geodynamically active resulting in many landslides and other mass movements. Therefore, physical and chemical weathering processes, have played a major role in its geomorphic development. The exposed least altered rock is noted with high features indicating the play of tectonics (physical weathering), which further promotes chemical weathering due to water-rock interaction substantiated by the increase of loss of ignition (Lo1) percentage from least altered rock to regolith. Due to rain water interaction, the profile shows the change of pH from alkaline to acidic, i.e., from least altered rock (pl-l-9) to regolith (pH-5). Depletion of major oxides such as SiO,, MgO, CaO, Na,O, P20, and enhancement of TiO,, Al,O_ Fe2O, l(,O are noticed in the profile. Continuous enhancement of chemical index of alteration (CIA) is observed from least altered rock to regolith (56-85) with the progression of weathering. Chemical index of alteration (CIA), chemical index of weathering (CIW) and plagioclase index of alteration (PIA) of soil profile show identical behaviour in sap rock and saprolith, however during the advancement of weathering, the leaching of Ko resulted in deviation of CIW and PIA value from CIA parameter. Trace elements show enrichment from least altered rock to regolith (except Sr). The study infers that the variable geochemical proxies in soil profile are resultant of high precipitation in the tectonically active northeastern Himalaya.Keywords
Soil Profile, Northeastern Himalaya, Geochemical Proxies, Climate-tectonic Interaction- 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.- Comparative Study of Soil Profiles Developed on Metavolcanic (Basaltic) Rocks in Two Different Watersheds of Garhwal Himalaya
Authors
1 Wadia Institute of Himalayan Geology, Dehradun 248 001, IN
2 H.N.B. Garhwal University (Srinagar), Srinagar 246 174, IN
Source
Current Science, Vol 108, No 4 (2015), Pagination: 699-707Abstract
Soil profiles are rarely preserved in the Himalaya due to active tectonics and erosion. We have studied two rarely well-preserved soil profiles developed on metavolcanic rocks namely Alaknanda soil profile (ASP) and Bhilangna soil profile (BSP) in Alaknanda and Bhilangna watersheds of the Garhwal Himalaya. Geochemical studies were carried out to understand the elemental mobility with reference to the least altered rock (LAR) in both the profiles and are compared. Differences in major element behaviour noticed are depletion of Ca and K in ASP, and depletion of Ca and Na in BSP. Trace elements also show variable mobility such as leaching of Rb, U and enrichment of Sr, Ni in ASP. In BSP, behaviour of these elements is just the opposite. Accumulation of ΣREEs in saprolitic layer and depletion in regolith of ASP suggest that rare earth element (REE) mobility took place during advanced stages of weathering. In BSP, increase in REE content from LAR to regolith suggests dominance of chemical weathering over physical weathering. This is also reflected in chemical index of alteration values which suggest variation of climatic parameters such as rainfall in the region.Keywords
Climate–Tectonic Interaction, Geochemical Behaviour, Lesser Himalaya, Physical and Chemical Alterations, Weathering.- 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
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 60, No 1 (2002), Pagination: 91-105Abstract
The shallow marine Nagthat siliciclastics of the Jaunsar Group show extensive development of medium to thickly bedded arenites and wackes, and represent the terminal Proterozoic siliciclastic episodes of the Lesser Himalaya. Chemical variation between arenites and wackes of Nagthat siliciclastics is related to the elemental distribution within the different mineralogical phases. Inverse correlation of most of the major oxides and trace elements (Ni, Cr, Co and Nb) with SiO2, indicate quartz dilution effect. The majority of arenites show the common presence of plagioclase, K-feldspar and clay minerals, but lack ferromagnesium minerals and therefore indicate minimal decomposition of felspar and greater decomposition of ferromagnesian minerals. This phenomenon is well documented by the positive correlation of Fe2O2(t) Ni, CO, K2O, Rb, Sr, Th, Nb and Y with Al2O3 hereby suggesting that elemental distributions are mainly controlled by clay minerals. A moderate correlation exists between Al2O3 and La and Yb suggesting that REEs are similarly controlled in part by clays or micas. The plots of Nagthat siliciclastics in A-CN-K diagram, along with their enriched K2O contents suggest variable degree of post-depositional K-metasomatism. Presence of higher amounts of monocrystalline quartz than the polycrystalline quartz, characteristic major and trace element contents, and enriched LREE pattern with negative Eu anomaly indicate a source of granite or granitic gneiss. High Eu/Eu ratio, low Ni concentration and low La/Co, Th/Co and Cr/Th ratios corroborate the acidic source. Granite or granitic gneiss source signature, along with indicative palaeocurrent directions, suggest that the detritus for Nagthat siliciclastics may have been derived from the southerly direction where Banded Gneissic Complex (BGC) of Aravalli-Bundelkhand craton is widely developed.Keywords
Neoproterozoic, Nagthat Siliciclastics, Source Rock, Geochemistry, Banded Gneissic Complex (BGC), Kumaun Lesser Himalaya.- Instrument for Lunar Seismic Activity Studies on Chandrayaan-2 Lander
Authors
1 Laboratory for Electro-Optics Systems, Indian Space Research Organisation, Peenya 1st Stage, 1st Cross, Bengaluru 560 058, IN
Source
Current Science, Vol 118, No 3 (2020), Pagination: 376-382Abstract
Instrument for Lunar Seismic Activity Studies (ILSA) is a science payload with the objective of studying seismic activities at the landing site of Vikram, the Lander of Chandrayaan-2. ILSA will be deployed to the lunar surface by a specially built mechanism. It is an indigenously developed instrument based on microelectro mechanical systems technology. High sensitivity silicon micro-machined accelerometer is the heart of the instrument that measures ground acceleration due to lunar quakes. The instrument has the capability of resolving acceleration better than 100 nano-g Hz–1/2 up to a range of 0.5 g over bandwidth of 40 Hz. This paper presents the basic concepts in the design, realization, characterization and the performance test results of the space qualified strong motion seismic sensors.Keywords
Lunar Quakes, MEMS, Seismometer, Strong Motion Sensors.References
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