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Panda, P. K.
- Nepheline Syenite from Rairakhol, Sambalpur District, Orissa
Authors
1 Geological Survey of India, Operations Orissa, Nuapalli, Unit-8, Bhubaneswar, Orissa 751 012, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 41, No 2 (1993), Pagination: 144-151Abstract
A newly identified body of nepheline syenite with associated non-feldspathoidal syenites from the Rairakhol area of Sambalpur district in the Eastern Ghat belt of Orissa sector adds to the present population of such complexes in this segment of Precambrian crust of Indian Peninsula. Recent researches have emphasized the significance of these bodies as a major Late-Proterozoic tectonothermal marker event in this belt.
The Rairakhol syenitc complex consists mainly of nepheline syenite, syenite and minor quartz syenite. Biotite and hornblende are the chief mafic constituents which occur as accessories in varying proportions. This body is emplaced within an interbanded sequence of quartzite, khondalite and charnockite. Syenitic rocks have a flow banding/foliation well-developed at many localities. A pink pegmatitic K-feldspar sycnite possibly represents a late-magmatic product. Occurrences of a few relatively smaller bodies of similar composition are also recorded.
Keywords
Nepheline Syenite, Rairakhol, Sambalpur Dist., Orissa.
- Petrogenesis of Pal Laharha Granitic Gneiss in Eastern Indian Craton: Evidence from Field Relations and Petrochemistry
Authors
1 Geological Survey of India, Laitumkrah, Shillong-793003, IN
2 Geological Survey of India, Laitumkrah, Bhubaneswar-751012, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 72, No 3 (2008), Pagination: 415-431Abstract
A large segment of the southcentral part of the Eastern Indian Craton proximal to the contact of the Eastern Ghats Mobile belt is occupied by the Pal Laharha gneiss. Spatially associated with the lithoensemble of greenstone belts. This segment is a zone of high strain traversed by regional faults. The granite gneiss is mainly represented by stromatic migmatite having supracrustal rocks constituting the immobile components. Three different varieties of granite VIZ (i) fine to medium grained mesocratic, horriblende-magnetite bearing granite, (ii) banded, pink, leucocratic granitic gneiss, and (iii) muscovite-biotite±garnet bearing medium to coarse grained granitic gneiss have been identified in this segment.
The granitic gneiss has a granite to monzogranite range of composition and compares well with anorogenic, metalummous A-type granite (A/CNK<1). Highly fractionated REE, LREE enrichment, flat HREE pattern and a -ve Eu-Anomaly characterize the granites. From field, petrographic and geochemical attributes, it is suggested that the Pal Laharha granitic gneiss does not form a discrete plutonic body. It possibly evolved by the synkinematic mid-crustal anatexis of the supracrustal sequences now occuring either as megaenclaves or as immobile components.