- S. M. Naqvi
- P. Rama Rao
- S. M. Ahmad
- B. Uday Raj
- D. V. Subba Rao
- P. K. Govil
- D. Rameshwar Rao
- S. N. Charan
- S. Nirmal Charan
- H. K. Gupta
- R. K. Chadha
- M. N. Rao
- P. Mandal
- M. Ravi Kumar
- N. Kumar
- H. C. Tewari
- V. Divakar Rao
- M. M. Dixit
- N. Madhav Rao
- A. S. N. Murty
- B. Rajendraprasad
- P. R. Reddy
- N. Venkateswarlu
- V. Vuaya Rao
- D. C. Mishra
- S. B. Gupta
- S. H. Jafri
- S. Moeen
- N. Charan
- V. Divakara Rao
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
Narayana, B. L.
- The Mode of Occurrence, Petrography, Metamorphism and Origin of Amphibolites of Devgad Baria Panchmahals District, Gujarat State
Authors
1 School of Studies in Geology, Vikram University, Ujjain, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 15, No 3 (1974), Pagination: 246-255Abstract
Amphibolites occur towards south and south-east of Devgad Baria town in the Panchmahals district of Gujarat State, in the form of disconnected bands showing concordant relationship with the rocks of the Banded gneissic complex and passing into striped varieties, and also as caught-up patches in the granitic intrusive bodies. Mineralogically, the former type is a quartz and plagioclase bearing amphibolite, while the latter is only plagioclase-bearing.
The quartz-amphibolites are shown to be para-amphibolites on the basis of their intimate association with the impure calcareous metamorphosed sedimentary rocks, lack of relict igneous textures, absence of sphene and plagioclase, high modal percentage of quartz, and low weight percentage of TiO2 and Al2O3 showing a near concordance with the alumina content of marbles of the area. On the other hand, the plagioclase-amphibolites show, in addition to the disconnected sill-like form, relic sub-ophitic texture, high proportion of sphene and high weight percentage of TiO2 and Al2O3 indicating their primary igneous nature.
- Geochemistry of Spinifex-Textured Peridotitic Komatiites from Ghatti Hosahalli, Karnataka, Indi
Authors
1 National Geophysical Research Institute, Hyderabad-500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 21, No 4 (1980), Pagination: 194-198Abstract
Spinifex-textured peridotitic komatiites (STPK) of Ghatti Hosahalli have low CaO/Al2O3 ratio (< 1), low TiO2, K2O and high MgO. These STPK have comparable Ni and Co contents with those of the Australian and Canadian shields. These characters support the view that the spinifex-texture observed in these rocks is primary and not the result of later metamorphism. The Al2O3/TiO2 ratios are comparable to those of Chondrites indicating that the STPK are products of partial melting of the Archaean mantle. The STPK of Ghatti Hosahalli arc overlain by exhalative chemical precipitates and argillaceous metamorphosed sediments like bedded-barytes, fuchsite-quartzites and kyanite-mica schists. It is suggested that Ghatti Hosahalli band is a relic of an early Archaean greenstone belt.- Geology and Geochemistry of Paragneisses from the Javanahalli Schist Belt, Karnataka, India
Authors
1 National Geophysical Research Institute, Hyderabad-500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 21, No 12 (1980), Pagination: 577-592Abstract
The lowermost member of the Javanahalli schist belt consists of meta-arkoses/ paragneisses with interbedded epidote-quartzite and calc-silicate bands. These meta-arkoses exhibit relict current-bedding, arkosic texture and grain-to-grain variation in anorthite content within the same sample. Plagioclase is subordinate to K-feldspar and is relatively more weathered and sericitized. Orthoclase predominates over microcline in the total K-feldspar content and the quartz/feldspar ratio is generally very low. The meta-arkoses appear to be first-cycle sediments.
The composition of these paragneisses is unusual for Archaean metasediments. They are enriched in K, Si, Fe, Mg, Th, Rb, Ni, Cr and Co and depleted in Na, AI, Sr and often in Ca. The meta-arkoses of Javanahalli schist belt may be the product of strong and/or rapid chemical disintegration of Archaean tonalitic gneisses and basic and ultrabasic rocks. all of which were prominent components of the continental crust at the time the Javanahalli belt formed. If the meta-arkoses have not undergone major metasomatism, then their high abundance of K and Rb may indicate intense chemical leaching of these tonalitic source areas. Most of the saIt of the primitive oceans might have been derived from this intense leaching of the ancient cratonic tonalite gneisses.
- High Alumina-Magnesium Sedimentation in the Javanahalli Schist Belt, Karnataka, India
Authors
1 National Geophysical Research Institute, Hyderabad 500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 23, No 4 (1982), Pagination: 175-182Abstract
High alumina, magnesium and iron-bearing sediments represented by cordierite-anthophyllite rocks occur in association with amphibolites. calc silicate rocks and banded magnetite quartzites, within the Javanahalli schist belt, Karnataka. Their chemical composition is anomalous. The abundance levels of elements like Fe, Mg, AI, Ni, Cr, Co, Rb and Sr indicate that probably they represent metamorphosed chemical sediments generated by volcanogenic exhalative activity.- Mineralogical and Petrological Studies of Gneisses and Charnockites of Dharmapuri District, Tamil Nadu
Authors
1 National Geophysical Research Institute, Hyderabad 500007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 35, No 1 (1990), Pagination: 55-69Abstract
Detailed mineralogical studies of amphibolite to granulite facies transition zone rocks and granulite facies rocks in Dharmapuri district, Tamil Nadu, were carried out in order to know the gneiss-charnockite relations, nature of protolith, and metamorphic conditions.
The studies show that the rocks are of magmatic origin. and show a gradual decrease in modal composition of hornblende and biotite and gradual increase of hypersthene and iron oxide in a north to south traverse. Breakdown of hydrous minerals to anhydrous minerals is evident with the release of iron oxide suggesting progressive transformation of gneisses to charnockite, Biotite occurs in two generations, an earlier one is of massive type and breaks down to anhydrous minerals, while the latter one occurs as tabular flakes and likely to have formed during the waning stages of amphibolite to granulite facies metamorphism, and forms a zone of concentration just above the stage or CO2 migration. The mineralogy of pyroxene, plagioclase, hornblende, biotite and iron oxides also suggests that the pressure-temperature conditions in the transition zone are lower than those of the granulite zone.
Keywords
Petrology, Igneous and Metamorphic, Charnockites, Dharmapuri District, Granulites, Tamil Nadu.- Symplectites in High-Grade Pelitic Gneisses of Usilampatti, Tamil Nadu: P-T Conditions and Geochemistry
Authors
1 National Geophysical Research Institute, Hyderabad-500 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 46, No 1 (1995), Pagination: 37-45Abstract
Occurrence of fine-grained, fingerprint-like symplectic intergrowths of cordierite, K-feldspar and quartz formed due to the retrogressive, garnet breakdown reactions following decompression during uplift, is reported here from metapelites of Usilampatti area. These metapelites consisting of cordierite, garnet, hypersthene, biotite, hercynitic spinel, sillimanite, K-feldspar assemblage were metamorphosed at 6.5-7.5 Kb and 750-800°C. The symplectites were formed at 600-670°C and 5 Kb pressure. The textural and mineralogical evolutions in these metapelites indicate a rapid decompressional P-T evolution. Petrological and geochemica1 data suggest that these metasediments were derived mostly from an evolved basement source of granodiorite-granite composition with a minor basic component.Keywords
Metamorphic Petrology, Gneiss, Tamil Nadu.- The Jabalpur Earthquake of May 22, 1997
Authors
1 National Geophysical Research Institute, Hyderabad - 560 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 50, No 1 (1997), Pagination: 85-91Abstract
The Jabalpur earthquake of magnitude 5.8 occurred on May 22, 1997 along seismically active Narmada-Son Lineament (NSL) in central India, with its epicenter about 30 km southeast of Jabalpur. A maximum intensity Io = VIII on MM scale was observed in Jabalpur and surrounding region. The isoseismal map prepared for this earthquake shows NE-SW trend which in general agrees with the focal mechanism solution indicating thrust faulting along a ENE-WSW fault with minor strike-slip component. Several ground cracks mapped in meizoseismal area show a dominant N75° E trend. The damage pattern of the constructions clearly shows a strong correlation with lithology, structures and soil cover of the area. There are no foreshocks reported for this earthquake and only a few aftershocks are recorded. which warrant a close monitoring of this region.Keywords
Earthquake, Seismology, Jabalpur.- Nagaur-Jhalawar Geotransect Across the Delhi/Aravalli Fold Belt in Northwest India
Authors
1 National Geophysical Research Institute, Hyderabad-500007, IN
2 National Geophysical Research Institute, Hyderabad-500007
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 52, No 2 (1998), Pagination: 153-161Abstract
Lithological, gravity, magnetic, and seismic data within 100 Km corridor of the 400 km long seismic reflection profile are compiled to constitute the NW-SE Nagaur-Jhalawar Geotransect. The transect sequentially cuts across the Neo-Proterozoic Marwar Basin (MB) on the northwest, the Palaeo/Mesoproterozoic Delhi Fold Belt (DFB), the middle/late Archaean Bhilwara Gneissic Complex (BGC) and the MesolNeoproterozoic to early Palaeozoic Vindhyan Basin (VB) at the southeast. The BGC and DFB belts show polyphase deformation and metamorphism.
The BGC within the transect, consists of Sandmata Granulite Complex, followed by amphibolite facies Mangalwar Complex and Greenschist facies Hindoli/Sawar groups. The BGC show evidence of crustal reworking at c.3.0 Ga. The DFB is represented by amphibolite facies metavolcanic-metasedimentary shallow marine sequences and is tectonically highly disturbed. The DFB deposits (c. 2.0 - 1.5 Ga.) were subjected to tectonic deformation during Delhi orogeny (c. 1.5 Ga.), which is marked by syntectonic granitic plutonism. Both, the BGC and OFB also appear to have been affected by Neoproterozoic thermal events and granitic plutonism. The Neoproterozoic MB consists of clayevaporite sequences of shallow oscillatory basin deposits.
Seismic, gravitylmagnetic and magneto-telluric techniques could delineate a number of shallow to deep faults, intrusive bodies and a high conductivity zone. The total magnetic intensity shows a regional increase towards southeast. The Bouguer anomaly values show a steep rise of upto 80 mGal towards the boundary of OFB and BGC. Based on the seismic studies, doubling of the crust under the OFB and vertical intrusion of high density material under the BGC are inferred. The upper crust is, in general, transparent in its reflectivity while the lower crustal reflectivity is high in the transect area, except in the BGC and the VB. A thrust boundary, dipping NW, is present at the eastern margin of the BGC and could be traced up to 30 km depth. The Moho is at a depth of 36-38 km under the MB. Multiple Moho reflections are identified in the DFB crust, the deepest being at 45-50 km depth. In some part of the BGC the Moho can not be identified but in parts it is traced at about 50 km depth, with southeast up dip, before becoming subhorizontal at depth of 41-42 km. It becomes shallower to about 30 km depth at the SE end under the VB.
Keywords
Delhil Aravalli Fold Belt, Geotransect, Northwest India.- Occurrence of Quench Olivine Crystals in a Basaltic Dyke from Schirmacher Oasis, Queen Maud Land, East Antarctica
Authors
1 National Geophysical Research Institute, Hyderabad - 500 007, IN