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
Banerji, P. K.
- Inverted Metamorphism in the Sikkim-Darjeellng, Himalaya, India
Authors
1 Geological Survey of India. Orissa Circle (N) 31, Budha Nagar, Bhubaneshwar 14, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 21, No 7 (1980), Pagination: 330-342Abstract
Inverted metamorphic sequences from chlorite zone phyllites grading progressively upwards into staurolitc/kyanite zone schists and gneisses with associated granitic bodies occur intermittently in the Lower Himalaya from Kumaon to Sikkim. In Sikkim-Darjeeling area, this progressive metamorphism is broadly late-kinematic with respect to the polyphase fabric elements in the metasedimentaries and is broadly coeval with the emplacement of metasomatic/anatectic granitic masses, which occur as low to moderately dipping sheets within both greenschist and amphibolite facies metasediments and carry I-type enclaves. Locally, strong, gravity induced polarity has concentrated metasomatic transformations along the hanging wall sections of the granite.
This 'inverted' metamorphism, as well as positive gravity anomaly gradients and shallow focus seismicity in this sector, are correlative with differential vertical displacements, which have exposed the naturally inverted metamorphic sequences along footwall sections of moderately dipping intrusive masses. LANDSAT and air photo interpretations of various types of linears and lineaments with supporting indications from the location of hot springs, lakes, water falls, abrupt changes in river gradient, truncation of marker bands and erraticity in terrace distribution, suggest that the area has been witnessing differential uplift along a number of regional and local sub-vertical fault surfaces including a number of geofaults, some of which are transverse to the axis of the range in a crypto-aulacogen style. This tectonic regime appears to be an integral part of postorogenic processes in Sikkim-Kumaon Himalaya possibly extending eastwards up to Arunachal Pradesh.
- The Khondalites of Orissa, India - A Case Confusing Terminology
Authors
1 Geological Survey of India, Orissa Circle, Bhubhaneswar 751 014, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 23, No 4 (1982), Pagination: 155-159Abstract
The paper traces the progressive metamorphosis of the term 'Khondalite' from 1902 to 1975 from a specific rock name to the collective group name of a suite of high grade metamorphic and metasomatic rocks and presents examples of the extent of compositional variations of these rocks from Dhenkanal, Angul and Tikarpara areas of Orissa. It is recommended that prevalent usage of the term 'Khondalite' as a mapping unit should be discontinued by general consensus, since the term can now be used only in the sense of a 'group'.- Behaviour of Elements in Tropical Weathering Profiles
Authors
1 Geological Survey of India, Orissa Circle, Bhubaneswar 751 012, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 25, No 12 (1984), Pagination: 809-809Abstract
No Abstract.Full Text
- Secondary Geochemical Dispersion in the Lateritic Tracts Over Two Copper Sulphide Deposits in Orissa, India
Authors
1 Geological Survey of India, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 31, No 4 (1988), Pagination: 404-416Abstract
Host rocks are kyanite-quartzite at Kesarpur and uralitised garnet-diopside granulite (± scapolite) at Adash. Primary sulphides include chalcopyrite, pyrite and pyrrhotite with small but variable amounts of bornite. The ore bodies are lenticular and carry variable trace constituents of Ag. Au, Ni and Co. Supergene minerals occur only in thin stretches and include covellite, marcasite and violarite. No discrete zone of supergene enrichment is noted in the boreholes. Oxidised zones at the top are 15-45m. thick and analyse in Adash up to 2.27% Cu plus 0.4% Zn over 3-4 m width. Goethite, haematite, malachite, azurite and chrysocolla are the constituent minerals.
Feeble to strong anomalies are present in pedogenetic laterites over orc bodies. but spurious anomalies locally with 1 % Mn are common. Laterites in Adash are polycyclic and anomaly values are locally erratic. Over groundwater laterites of Kesarpur. very feeble secondary anomalies are confined to only 100 m from the ore zone.
Stream sediment signals are confined to first order seasonal drainge courses and are traceable for only 2-3 km from the source down stream. Such limited anomaly dispersion is due to differential block movements in this area.
Landforms developing under this dynamic system have not given rise to widespread and strong stream sediment dispersion patterns of chalcophile elements. Systematic search for small ore bodies in such tracts has, therefore, to be hased only on sampling the sediments of first order drainage courses.