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
Kanungo, D. N.
- Paleocurrent Studies in the South-Eastern Part of Gangpur Series
Authors
1 National Geophysical Research Institute, Hyderabad, IN
2 Regional Engineering College, Rourkela, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 11, No 1 (1970), Pagination: 68-73Abstract
Paleocurrent analysis of the south-eastern part of the Gangpur series, made from cross-bedded structures in the quartzites of Raghunathpalli and Birmitrapur stages, shows that during the deposition of the older Raghunathpalli stage, the currents were flowing in a north-north-east direction and at a later period during the deposition of upper Birmitrapur stage the current direction was predominantly north-north-west.
A new method has been suggested for correction of tectonic tilt of paleocurrent data.
- Metamorphism in the Eastern Part of Gangpur Series
Authors
1 National Geophysical Research Institute, Hyderabad, IN
2 Regional Engineering College, Rourkela, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 13, No 2 (1972), Pagination: 122-130Abstract
Metamorphism in the eastern part of Gangpur series and its relation to stratigraphy. structure, tectonics and granitic intrusion has been discussed. Three phases of metamorphic recrystallisation are observed. The early low grade metamorphic phase (M1) belonging to the green schist facies is related to the main movement phase (F1) which deformed the Gangpur series into a major synclinorium. The early phase was followed by the main phase of metamorphism (M2) belonging to the lower amphibolite facies. This phase represents the highest grade of metamorphism for this area. This phase is mainly post-tectonic in relation to the main movement phase (F1). It is believed to be a result of the granitic intrusion into the adjoining area, and has no relation to depth of burial or tectonic level. The progressive metamorphism of the early and main phase was followed by a late phase retrograde metamorphism (Ms) belonging to the greenschist facies.- Anorthosite Body in the Nellore Mica-Pegmatite Belt of Eastern India
Authors
1 National Geophysical Research Institute, Hyderabad-7, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 19, No 2 (1978), Pagination: 87-90Abstract
Anorthosites from Nellore mica belt include pure anorthosites, gabbroic anorthosites and anorthositic gabbros. The anorthosite intrusives are deformed and metamorphosed along with the host rocks. The structural setting of the host rocks and similar association of anorthosites in other parts of Eastern Ghats, suggest that these rocks belonged to the Eastern Ghat Orogeny. On the basis of the field set-up and the chemical analyses, the anorthosites of Nellore mica belt show similarity to the anorthosites of Adirondack.Full Text
- Structures in the Tethys Himalayas and their Tectonic Significance
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 22, No 8 (1981), Pagination: 357-367Abstract
Structural studies of Tethys sediments between Malari and Lapthal show development of many minor structures e.g. - 'cleavages, tension and shear fractures' - which have been utilised to deduce the stress fields responsible for the deformation of these rocks. The primary sedimentary structures such as bedding, current bedding suggest shallow deposition conditions. The shape of folds, the fracture cleavages, quartz and calcite filled tension gashes and other fractures, and the thrusts are all taken as evidence for 'shallow-level' deformation of these rocks in which 'brittle deformation' was dominant.
The study suggests that major compressive stress responsible for the deformation of these rocks was always directed northeast-southwest and was lying sub-parallel to the earth's surface, the P-intermediate was directed NW-SE and was also horizontal, while the P-minimum was always invariably perpendic:ular to the earth's surface. Hence, it is concluded that these rocks have been deformed by horizontal compression and it appears that the major push was from the SW in this part of the ranges.
- Anorthosites and Associated Rocks of Nellore-Gudur, South 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 27, No 5 (1986), Pagination: 428-439Abstract
Structural, petrographic and geochemical characters of several anorthosite bodies exposed over a length of eight km in the eastern margin of India are presented. From the asymmetry of parasitic folds and cleavage/bedding relationship in the host rocks, it is concluded that these were emplaced into anticlinal cores of isoclinally folded Precambrian schistose formations.
Textural variation from centre to border, mafic enrichment towards the margins. alignment of linear structures combined with steeply dipping foliation of arcuate nature parallelling the boundaries. suggest that anorthositic bodies are plug-shaped and viscous magmatic fluid moved vertically upwards. The progressive variation in mineralogy. grain-size and some of the major oxides is attributed to flow differentiation.
- Geochemistry of Amphibolites from the Nellore Schist Belt, Andhra Pradesh, India: An Example of Back-Arc Basin Low-K Tholeiitic Magmatism
Authors
1 Atomic Minerals Division, Department of Atomic Energy, Hyderabad-500016, IN
2 Atomic Minerals Division, Department of Atomic Energy, Bangalore-560072, IN
3 Atomic Minerals Division, Department of Atomic Energy, Bhubaneswar-751002, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 44, No 3 (1994), Pagination: 253-265Abstract
Geochemistry of ortho-amphibolites from the Degapudi-Kalichedu area of the Nellore Schist Belt (NSB), an Archaean greenstone belt in southeastern India, has indicated their affinity to a low-K tholeiitic magma derived from an LIL-enriched, apatite-bearing mantle by about 5-20% partial melting, followed by fractional crystallization. Amphibolites range from high-Mg-type early differentiates (massive amphibolite and actinolite schist) to low-Mg-type middle-stage differentiates (schistose amphibolite, hornblende schist and related gametiferous hornblende schist). During and subsequent to the generation of their parental magma, the early crystallizing mineral phases are oli vine-clinopyroxene-plagioclase-magnetite-apatite. A back-arc or marginal basin palaeotectonic setting is indicated for NSB by geochemistry of these amphibolites, with precursors of high-Mg-type emplaced in a narrow basin associated with mature subduction zone system and of low-Mg-type in a wider basin associated with youthful subduction zone system.Keywords
Amphibolites, Tholeiites, Igneous Rocks, Nellore Schist Belt, Andhra Pradesh.- Basement Structure as Inferred from Geophysical Data Around Karaikudi, Tamil Nadu
Authors
1 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 14, No 1 (1973), Pagination: 12-22Abstract
Rocks of the sedimentary belt in the south-east coast of Peninsular India, popularly known as the Cauvery basin, have been deposited in basin like troughs on the basement. Because of the probable existence of favourable structures for oil and gas accumulations, the interest in this thick sedimentary sequence created among geoscientists has led to the collection of a lot of geological and geophysical data over this area.
This paper discusses the basement structure around Karaikudi, based on the results of electrical soundings taken along an eight kilometre long NW-SE profile nearly perpendicular to the regional geologic and structural trend. The available gravity and magnetic data of ONGC are also interpreted for corroboration. Results obtained from seismic studies of Geological Survey of India are also cited. From a synthesis of all the geophysical results, it appears that the Archaean basement exposed at Kunnakkudi becomes deeper successively through step-wise block faulting as one proceeds southeastwards, and reaches a maximum depth of one kilometre at Karaikudi, and then it rises up again further east in a similar fashion.
- Inference of Granitic Batholiths by Gravity Studies in South India
Authors
1 National Geophysical Research Institute, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 17, No 1 (1976), Pagination: 45-53Abstract
Three well-defined gravity 'lows' in Kodaikanal, Gudalur and Erode regions are explained as due to granitic batholiths at depth. The scattered outcrops of granitic bodies exposed in these regions are suggested to be interconnected at depth, and, therefore, are merely the surface expressions of the three concealed batholiths. Although the exposures of the individual granitic bodies in the Kodaikanal-Coimbatore region are elongated in an east-west direction, it is surmised, from structural evidences, that the main batholith is elongated in a roughly NNW-SSE direction.
A striking correspondence between the isoseismals for the Coimbatore earthquake of February 8, 1900 and the gravity contours is noticed. It is suggested that the Coimbatore earthquake (and the reported seismicity near Kottayam and 'Palghat Gap') could be the result of some minor readjustments of the boundaries of the batholith along fault planes.