Sm-Nd isotopic data from Archean metavolcanic rocks at Holenarsipur, South India

Journal Article · Sun Nov 01 04:00:00 EST 1987 · J. Geol.; (United States)

DOI:https://doi.org/10.1086/629182· OSTI ID:5516374

Drury, S A; Van Calsteren, P C; Reeves-Smith, G J

Results of a Sm-Nd isotopic analysis of Archean metavolcanics in the Holenarsipur greenstone belt, Karnataka, South India, give a whole-rock isochron age of 2.62 Ga for lightly deformed metabasaltic amphibolites in the northern part of the belt. This is within error of the age of high-grade metamorphism and crustal thickening which affected areas further to the south during the late Archean. Together with the geochemical affinities of these and other metavolcanics in Karnataka, and results of regional structural analysis, this unexpected age supports a model relating volcanism and crustal thickening to northward subduction and crustal accretion during the late Archean. Data from basic and ultrabasic metavolcanics from the more strongly deformed and higher-grade southern arm of the Holenarsipur belt do not permit an age greater than 3.0 Ga. Previously, these rocks were regarded as part of an older supracrustal sequence that predated the local 3.0 to 3.3 Ga gneissic complex. The new dates therefore considerably simplify attempts at accounting for greenstone evolution in South India.

• Research Organization: Open Univ., Milton Keynes, England
• OSTI ID: 5516374
• Journal Information: J. Geol.; (United States), Journal Name: J. Geol.; (United States) Vol. 95:6; ISSN JGEOA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
AGE ESTIMATION
ASIA
CONTINENTAL CRUST
DEVELOPING COUNTRIES
DIMENSIONS
EARTH CRUST
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGIC MODELS
IGNEOUS ROCKS
INDIA
ISOTOPE DATING
ISOTOPES
METAMORPHISM
NEODYMIUM ISOTOPES
RARE EARTH ISOTOPES
ROCKS
SAMARIUM ISOTOPES
THICKNESS
VOLCANIC ROCKS
VOLCANISM