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
Gupta, L. N.
- Studies on Zircons from the Central Gneisses of the Dhauladhar Range, North of Dharmsala
Authors
1 Department of Geology, Panjab University, Chandigarh, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 9, No 2 (1968), Pagination: 124-137Abstract
Zircons from the Central Gneisses of the Dhauladhar range, north of Dharmsala have been separated and studied to establish the stability of zircons during metamorphism and migmatization of the sediments; field and petrological studies indicate that the rocks have formed by migmatization of the metasediments. Crystal habit, colour, clouding, corrosion, overgrowth and outgrowth, length and breadth, elongation ratio and the (reduced major axis of zircons separated from several rock types have been studied in detail. The number of euhedral zircons increases during the migmatization apparently due to the recrystallization of the zircons. The zircon data corroborates with the structural and petrographic observations. The zircon study is useful as a criterion in deciphering the petrogenesis of the granitic rocks.- Petrochemical Studies of the Lansdowne Granite Gneiss, Lesser Himalaya, India
Authors
1 Department of Geology, University College, Belfield, Dublin 4, IE
2 Centre of Advanced Study in Geology, Panjab University, Chandigarh 160014, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 22, No 11 (1981), Pagination: 505-516Abstract
Petrochemical studies on fourteen representative samples of the Lansdowne Granite Gneiss indicate close compositional uniformity. Most of the analyses fall within the field of granodiorite, and lie close to the low-pressure ternary minimum in the system Qz-Or-Ab-H2O. Inter-element relationships indicate an initial magmatic origin, with pronounced gneissosity due to later deformation.- Electron Microscopic Investigations of Perthite, Myrmekite and Rapakivi Structures in Feldspars Occurring in the Granitic Rocks of the Doda Area
Authors
1 Geological Survey of India, Jaipur, IN
2 Centre of Advanced Study in Geology, Panjab University, Chandigarh, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 2 (1986), Pagination: 220-222Abstract
Patchy, vein, film, and crypto types of perthites, rapakivi structure, and myrmekite texture are commonly developed in the potash-feldspar augen of the granitic gneisses of the Doda area, Jammu and Kashmir State.
The scanned perthites show an interlamination of microc1ine and albite resulting in a criss-cross pattern. Islands of soda-feldspar in potash-feldspar show embayed margins. These interrelationships appear to be the result of exsolution phenomenon.
Segregated sodic-calcic components replace the host potash-feldspar releasing blebs and globules of quartz which are present in the form of myrmekite texture.
- Secondary and Primary Growths in the Zircons from Paragneisses and Migmatites of Arvika (Sweden) and Nelaug (Norway) Regions
Authors
1 Central of Advanced Study in Geology, Panjab University, Chandigarh, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 28, No 4 (1986), Pagination: 320-324Abstract
Secondary growths which include overgrowths, outgrowths, and multiple growths are formed during metamorphism and partial melting. Primary growths include growth twins and parallel growths. Twinning may occur during the early crystallization of zircon in magmatic rocks. The process of synneusis may result in parallel growths or attachment of zircons that have initially undergone separate growth histories.
The occurrence of primary growths in paragneisses and migmatites is due to their derivation from magmatic sources and their survival during mechanical transportation and crushing of the samples at the time of separation.
- Petrochemistry of Basics and Metabasics, Mandi-Pandoh Area, Himachal Pradesh, India
Authors
1 Centre of Advanced Study in Geology, Panjab University, Chandigarh, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 31, No 6 (1988), Pagination: 565-574Abstract
Basic and metabasic rocks occur in the form of an oval-shaped, plug-like body. intrusive into the granitic gneisses and metasediments belonging to the Chail Formation. The core is made of fresh olivine gabbro metamorphosed to varying degrees at the margins. Chemical data suggest that the basic and metabasic rocks are co-magmatic and the parent magma was of alkali olivine basalt composition. The observed diversity in physical and textural parameters exhibited by different rocks are considered to be the expressions of varying rates of cooling and effects of autometamorphism. These are more pronounced at the margins than in the central parts of the body.- Zoning in Plagioclase (Normal and Oscillatory) in the Feldspar Porphyries of Karsog Area, Lesser Himalaya, Himachal Pradesh, India
Authors
1 Centre of Advanced Study in Geology, Punjab University, Chandigarh, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 33, No 3 (1989), Pagination: 223-227Abstract
Growth of plagioclase crystals accompanied by rapid cooling and contemporaneous crystallisation with falling temperature is considered to cause disequilibrium due to incomplete reaction between the growing crystal and the residual sodic melt. This causes the formation of normal zoning. Regular oscillatory zoning has been explained mainly due to the process of diffusion of An-molecules towards the crystal face of growing plagiolcase in a magma. Growth of zoned plagioclase was accompanied by fractional crystallisation and accumulation of magma of trondhjernitic composition. During this process, zoned plagioclases came in contact with one another and resulted in synneusis. Partial resorption resulted in truncated zones followed by crystallisation of a more calcic rim.- Zircons from the Granitic Rocks of the Malani Igneous Suite : Morphological and Chemical Studies
Authors
1 Department of Geology, Panjab University, Chandigarh, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 38, No 6 (1991), Pagination: 561-576Abstract
Zircons are hydrothennal or late-magmatic. The high UO2 contents of the Tosham zircons reflect the high UO2 of the host rocks. The Siwana granites, though high in Zr values, have very poor zircon yield. This is probably due to the pcralkalinity of the Si wana magma.Keywords
Malani Igneous Suite, Zircon, Siwana Granite, Geochemistry, Rajasthan.- Petrogenesis of the Mandi Gabbroic Rocks, Lesser Himalaya, India
Authors
1 Centre of Advanced Study in Geology, Panjab University, Chandigarh - 160 014, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 50, No 1 (1997), Pagination: 49-59Abstract
The gabbroic rocks of Mandi area occur as an oval-shaped, 500 m thick intrusive body within the Mandi granite. The central zone of the body is made up of fresh gabbro and it grades into metagabbro and epidiorite towards the margins. The relatively high abundances of Ti, AI, Ca and Mg in clinopyroxenes of the central part as compared to the clinopyroxenes of the marginal part suggest different rates of cooling within the Mandi gabbroic body. The zoned plagioclases have calcic-rich cores and calcic-poor rims. The Al - (Fe+Ti) - Mg values and incompatible trace element ratios of the rocks indicate tholeiitic nature of the body. The discrimination diagrams based on major elements as well as immobile minor and trace elements suggest that these rocks are of MORB type. However, the chemical characteristics like negative Nb, Ti and P anomalies in the primordial mantle-normalised spiderdiagram together with low TiN and ZrN ratios testify that the Mandi gabbroic rocks are akin to low-Ti continental flood basalts. [Mg]-[Fe] modelling, incompatible versus compatible trace element data and lower Ni abundances for the given Mg contents suggest 10-15 % fractional crystallisation of olivine after the rocks were generated by partial melting under pressure conditions ranging between 25 and 40 kb. The intrusive appears to have formed by low degree of partial melting of a non-pyrolitic metasomatised mantle source that was heterogeneous with respect of Zr and Fe/Mg ratios.Keywords
Geochemistry, Petrology, Mandi Gabbro, Himalaya.- Earthquake-Induced Structures in Pinjor formation of Nadah Area, Haryana
Authors
1 Centre of Advanced Study in Geology, Panjab University, Chandigarh - 160 014, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 65, No 3 (2005), Pagination: 346-352Abstract
Soft sediment deformational structures have been observed in three sections of the basal Pinjor Formation exposed in the frontal Himalayan foothills in northern Haryana. The Nadah Choe section (A) shows contortion, Thinning-Thickening and faulting within 5 m thick sequence of sandstone, sandy shale and calcareous siltstone. The section (B) in a stream in the southwest of Nadah shows autoclasts, contortions around clay ball and faulting about 2 m thick Fluvio-Lacustrine sequence. The third section © is exposed in the Ghaggar river shows diapiric, Flame-Like intrusion of mud into the overlying beds of siltstone. The three sections are about 1.5 km strike length of gently dipping beds of basal Pinjor Formation. These structures were formed by liquefaction attending shear stress and can be related to major seismic events in this region during the deposition of the basal Pinjor Formation.Keywords
Earthquakes, Pinjor Formation, Nadah, Haryana.- "Ash Beds" in the NW Himalaya
Authors
1 Centre of Advanced Study in Geology, Panjab University, Chandigarh - 160014, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 59, No 5 (2002), Pagination: 485-486Abstract
No Abstract.- Study of Muscovite from Pelitic Schist of Doda Area, District Doda, Jammu and Kashmir, India
Authors
1 Centre of Advanced Study in Geology, Panjab University, Chandigarh, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 34, No 3 (1989), Pagination: 255-262Abstract
Muscovites separated from pelitic schists of the Dada area show a limited range of composition between ideal muscovite and ferrimuscovite. The paragonite content in the muscovites ranges between 14 and 21 %. The tetrahedral Aliv increases with the increase in the grade of metamorphism though this increase is more for the muscovite of the aureole rock, i.e., in the andalusite to staurolite zone than in the kyanite-staurolite zone. Similar results are also shown by the (FeO+Fe2O3) and Na/(Na+K) with respect to AI2O3 and total Al respectively.- A Contribution to the Geology of Lansdowne Area, Garhwal Himalayas, India
Authors
1 Centre of Advanced Study in Geology, Punjab University, Chandigarh, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 17, No 4 (1976), Pagination: 449-460Abstract
Lansdowne granite gneiss shows a tectonic contact with the underlying Lansdowne metamorphites. The metamorphites show repeated and superposed progressive regional metamorphism. Three phases of deformation and folding are noticed. The rare assemblage, chloritoid, staurolite, kyanite, andalusite and quartz is present in the area.
Granite is metamorphosed into augen gneiss, mylonites and phyllonites. Muscovitisation, tourmalinisation and greisening indicate chemical alteration in the granitic rocks. Textural features are correlated with deformation and folding.
- Mineral Chemistry of Biotites from Jalor, Tosham and JhunJhunu Ring Complexes: Malani Igneous Suite, India
Authors
1 PG Department of Geology, H.P. University, Regional Centre, Dharamsala, (H.P.) - 176 2 15, IN
2 Department of Geology, Panjab University, Chandigarh, 160 014, IN
3 HCC Ltd., C-1 Works, Tala Hydroelectric Project, PB# 390, Phuentsholing, BT