Late Proterozoic charnockites in Orissa, India: A U-Pb and Rb-Sr isotopic study

Journal Article · Tue Nov 01 00:00:00 EST 1988 · Journal of Geology; (USA)

DOI:https://doi.org/10.1086/629269· OSTI ID:7104132

Aftalion, M; Bowes, D R; Dash, B; Dempster, T J ^[1]

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1. Scottish Universities Research and Reactor Centre, Glasgow (Scotland)

Charnockite formation in the Angul district of Orissa took place between 1088 + 26/ -17 Ma, the U-Pb zircon upper intercept crystallization age of a leptynite neosome, and 957 +8/ -4-956 {plus minus} 4 Ma, the U-Pb zircon-monazite upper intercept and U-Pb monazite crystallization ages of a granite. Confirmation of the Proterozoic age of the charnockites is given by (1) a U-Pb zircon upper intercept 1159 + 59/ -30 Ma age and a Rb-Sr whole-rock 1080 {plus minus} 65 Ma age for an augen gneiss which pre-dates the leptynite, and (2) U-Pb monazite ages of 973 {plus minus} 5,964 {plus minus} 4, and 953 {plus minus} 4 Ma for a gray quartzofeldspathic gneiss, the augen gneiss, and the leptynite, respectively: these late Proterozoic dates are interpreted as representing ages recorded during charnockitization. The ca. 950-980 Ma charnockite- and granite-forming events are related to the evolution of mantle-derived, CO{sub 2}-bearing basic magma emplaced into the deeper levels of an extensional tectonic-transcurrent fault regime. The ca. 1100-1150 Ma tectonothermal and igneous events represent compressional tectonism in reactivated crystalline basement in the late mid-Proterozoic Eastern Ghats orogenic belt.

• OSTI ID: 7104132
• Journal Information: Journal of Geology; (USA), Vol. 96:6; ISSN 0022-1376
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
GEOLOGIC DEPOSITS
AGE ESTIMATION
INDIA
CARBON DIOXIDE
CRYSTALLIZATION
GRANITES
ISOTOPE DATING
ISOTOPE RATIO
LEAD
MAGMA SYSTEMS
MONAZITES
RUBIDIUM
STRONTIUM
TECTONICS
URANIUM
ACTINIDE COMPOUNDS
ACTINIDES
ALKALI METALS
ALKALINE EARTH METALS
ASIA
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
DEVELOPING COUNTRIES
ELEMENTS
GEOTHERMAL SYSTEMS
IGNEOUS ROCKS
MATERIALS
METALS
MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PLUTONIC ROCKS
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
RARE EARTH COMPOUNDS
ROCKS
THORIUM COMPOUNDS
THORIUM MINERALS
THORIUM PHOSPHATES
580000* - Geosciences