U-Th-total Pb dating of monazite from orthogneisses and their ultra-high temperature metapelitic enclaves: implications for the multistage tectonic evolution of the Madurai Block, southern India

Braun, I. and Appel, P. (2006) U-Th-total Pb dating of monazite from orthogneisses and their ultra-high temperature metapelitic enclaves: implications for the multistage tectonic evolution of the Madurai Block, southern India European Journal of Mineralogy, 18 (4). pp. 415-427. DOI 10.1127/0935-1221/2006/0018-0415.

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Abstract

Electron microprobe dating of monazite was performed on enclaves of sapphirine-bearing granulites and their host granites from the southeastern part of the Madurai Block in India. The granulites are strongly migmatitic and comprise quartzofeldspathic leucosome veins and restitic domains of sapphirine, garnet, orthopyroxene, sillimanite and cordierite. Inclusions of sapphirine-quartz intergrowths in garnet testify to an UHT stage of metamorphism which was followed by a stage of decompression during which garnet was replaced by coronitic opx-sill intergrowths. Monazite inclusions in garnet, orthopyroxene and quartz often yield a bimodal age distribution of Mid- to early Neoproterozoic (1500-850 Ma) ages in the cores which are rimmed by late Neoproterozoic age domains (630-580 Ma). Monazites in the granite and the charnockite exclusively yield Pan-African values. The occurrence of sapphirine-quartz intergrowths and the early Neoproterozoic age population in the same petrographical position infers that the crystalline basement of the Madurai Block already experienced a stage of UHT metamorphism prior to the Pan-African orogenic event.

Document Type: Article
Keywords: southern India UHT metamorphism U-Th-total Pb dating monazite polymetamorphism electron-microprobe analysis kerala khondalite belt metamorphism granulites gneisses zircon ganguvarpatti decompression geochronology evaporation
Research affiliation: Kiel University > Faculty of Mathematics and Natural Sciences > Institute of Geosciences
DOI etc.: 10.1127/0935-1221/2006/0018-0415
ISSN: 0935-1221
Date Deposited: 12 Jan 2012 05:19
Last Modified: 08 Oct 2012 10:23
URI: http://eprints.uni-kiel.de/id/eprint/15977

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