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
Joshi, A.
- Granites of Petermann Ranges, East Antarctica and Implications on their Genesis
Authors
1 Antarctica Division, Geological Survey of India, Faridabad-121 001, Haryana, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 38, No 2 (1991), Pagination: 169-181Abstract
The hypersolvus granitic rocks of the Petermann Ranges in East Antarctica reveal high alkali content, generation from a relatively dry magma as shown by the field and petrological characters and development in an anorogenic selling as indicatcd by an indirect genetic linkage with the spatially associated Gruber anorthosite massif. Hence, their resemblance to A-type granites and generation in a tensional tectonic environment is suggested.
The petrochemical characters indicate that the partial melting of a heterogenous but largely metasedimentary source generated the melt for crystallisation of the Petermann granite. The heat required for melting was possibly released by the fractionating basic magma which produced the juxtaposed Gruber anorthosite massif.
Keywords
Petermann Granite, East Antarctica.
- Deformational History and Shape Analysis of Folds in the Metamorphic Rocks of the Petermann Ranges, East Antarctica
Authors
1 Antarctica Division, Geological Survey of India, NH-5P, N.I.T., Faridabad - 121001, Haryana, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 40, No 6 (1992), Pagination: 487-500Abstract
Considered earlier to be very little defonned, the granulite facies rocks of the Petennann Ranges, East Antarctica, reveal three phases of folding and two episodes of ductile shearing. These metamorphic rocks preserve the F1 folds as small scale, ischolar_mainless, intrafolial features with tight to isoclinal profiles, and F2 folds as mesoscopic features with close to tight profiles. F1 and F2 folds are coaxial and broadly coplanar having axial surfaces marked by pervasive NW-SE striking foliation. F3 folds are open, upright with N-S to NNW-SSE axial planes and impart local swings in the regional foliation. The early ductile shears produce a strong mylonitic fabric and are synchronous to F1, while occurring as thin wavy zones, the later shears are post F2.Shape and geometric analyses of representative folds show that F1 folds belong to class 2 and 1C at low and high limb dips respectively and are fonned dominantly by flexural flow. F2 folds exhibit geometric features of class 1C at low as well as high limb dips and owe their origin to buckling with a flexural slip component and flattening.
Keywords
Folds, Mylonitisation, Petermann Ranges, Antarctica.- High-Al Gabbro in Proterozoic Anorthosite Massifs of Orissa: Implications for Anorthosite Genesis
Authors
1 A-2, Pushpa Bhavan, Geological Survey of India, New Delhi - 110 049, IN
2 EPMA Laboratory, Geological Survey of India, Faridabad - 121 001, IN
3 PPOD, A M S E Wing, Geological Survey of India, Bangalore - 560 078, IN
4 OP Orissa, Geological Survey of India, Bhubaneshwar - 75 1 012, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 68, No 1 (2006), Pagination: 59-71Abstract
High-Al gabbro is reported here for the first time from three anorthosite complexes of Orissa sector of Eastern Ghats Granulite Belt (EGGB). It has distinctly different textural, mineralogical and chemical characters from the anorthosite within which it occurs, and also from the spatially associated Fe, Ti and REE enriched ferrodiorite suite.
The high-Al gabbro of EGGB is comparable to similar rocks from other anorthosite complexes in major, trace element compositions and Mg# range (50-58). However, in contrast to the high-Al gabbro of the Laramie Anorthosite Complex (LAC), it does not form the most primitive rock of this association and exhibits negative Eu anomaly (Eu/EU* 0 2 0 6). The Mg enriched composition of the silicates of the high-Al gabbro and higher MgO contents of the associated anorthosite and ferrodiorite of the LAC are other critical differences.
Variable composition of the parental melts for these rocks at EGGB and LAC is interpreted Derivation of these aluminous melts by partial melting of basalt under high pressure i s suggested.
Keywords
Petiogenesis, High-Al Gabbio, Anorthosite, Ferrodiorite, Eastern Ghats Granulite Belt, Orissa.- Mid-Late Cretaceous Stratigraphy of the Cauvery Basin and the Development of the Eastern Indian Ocean
Authors
1 Department of Geological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, GB
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 58, No 3 (2001), Pagination: 217-229Abstract
Planktonic foraminifera are widely used in Cretaceous stratigraphy and have a well-Established zonation for low latitude regions. The most recently published version includes some of the proposals for the Cretaceous stage boundaries introduced at the meeting of the International Sub-Commission on Cretaceous Stratigraphy held in Brussels in 1995.
This zonation is identified in the sediments of the Cauvery basin and correlated with the ODP boreholes on the Exmouth plateau and in Western Australia. The maximum diversity of planktonic foraminifera in the Cauvery basin can be correlated with the highest temperatures in the Cretaceous and the Mesozoic sea-Level maximum. Both of these appear to relate to enhanced rates of ocean crust production. The distribution of planktonic foraminifera in the developing eastern Indian Ocean can also be used in palaeogeographical reconstructions that confirm the predicted palaeotemperatures.