Author(s):
P.V.N. Rao, A.T. Rao
Email(s):
Email ID Not Available
Address:
Department of Geology, Nagarjuna University, Nagarjunanagar-522510, Guntur, A.P
Department of Geology, Andhara University, Waltair-530 003, A.P.
Published In:
Volume - 5,
Issue - 1,
Year - 1992
Cite this article:
Rao and Rao (1992). Radioelement distribution in Leptynites from Eastern Ghat Granulite Terrain. Journal of Ravishankar University (Part-B: Science), 5(1), pp.77-83
Journal
of Ravishankar University Vol. 4-5
No. B (Science) 1991-92 pp.77-83
ISSN
0970 5910
Radioelement distribution in Leptynites from Eastern Ghat
Granulite Terrain
P.V.N. Rao and A.T. Rao
Department
of Geology, Nagarjuna University, Nagarjunanagar-522510,
Guntur, A.P.
*Department
of Geology, Andhara University, Waltair-530 003, A.P.
Ms: Received 16.6.92; Revised 26.11.92.
Abstract: Leptynites are important rock type
in the Visakhapa1nam area and they are categorised into grey and cream
varieties. At a glance it is noticed from the data that the radioelement concentrations
in grey leptynites are lower while they are higher in the
cream leptynites. The concentrations of U,
Th, K and Th/U
ra1ios of grey leptynites do not represent the primary distribution
but indicate their expulsion in a hydrous
partial melt from the
destabilised mineral sites/
dislocations of k-feldspar, biotite
and other accessory phases. The expelled
U, Th, K and other LIL elements during granulite facies metamorphism were
carried
up in hydrous granitic partial
melts
along weak shear
planes/zones and crystallized in surrounding cream leptynites. The enrichment of
radioelements in the cream leptynites may be po5$ible by two reascne: 1. Crystallization
of radioelement bearing partial melts in
the cream leptynites. 2. The radioelement
already resided in the accessory phases present in cream leptynites.
The expulsion of U, Th and K from
grey leptynites during granulite facies metamorphism is simultaneously followed
by the crystalization of partial melts in the cream variety. The higher rediogenic heat generatlon (2.17) values
of leptynites reveals that the Precambrian crust of the Eastern Ghats Granulite
Terrain characterised
by high radioactivity.
Keywords: Leptynites, VisaKhapamacn,
Radioelements, Metamorphism-partial melting, Radiogenic Reat Generation.
NOTE:
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