Relics of the Mozambique Ocean in the central East African Orogen: Evidence from the Vohibory Block of southern Madagascar

Jöns, N. and Schenk, V. (2008) Relics of the Mozambique Ocean in the central East African Orogen: Evidence from the Vohibory Block of southern Madagascar Journal of Metamorphic Geology, 26 (1). pp. 17-28. DOI 10.1111/j.1525-1314.2007.00745.x.

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Abstract

The Vohibory Block of south-western Madagascar is part of the East African Orogen, the formation of which is related to the assembly of the Gondwana supercontinent. It is dominated by metabasic rocks, which have chemical compositions similar to those of recent basalts from a mid-ocean ridge, back-arc setting and island-arc setting. The age of formation of protolith basalts has been dated at 850-700 Ma by U-Pb SHRIMP analysis of magmatic cores in zircon, pointing to an origin related to the Neoproterozoic Mozambique Ocean. The metabasic rocks are interpreted as representing components of an island arc with an associated back-arc basin. In the early stage of the Pan-African orogeny, these rocks experienced high-pressure amphibolite to granulite facies metamorphism (9-12 kbar, 750-880 degrees C), dated at 612 +/- 5 Ma from metamorphic rims in zircon. The metamorphism was most likely related to accretion of the arc terrane to the margin of the Azania microcontinent (Proto-Madagascar) and closure of the back-arc basin. The main metamorphism is significantly older than high-temperature metamorphism in other tectonic units of southern Madagascar, indicating a distinct tectono-metamorphic history.

Document Type: Article
Keywords: East African Orogen Gondwana assembly Mozambique Ocean Pan-African suture zone high-grade metamorphism u-pb geochronology zircon geochronology northern madagascar tectonic evolution trace-element west gondwana mautia hill lu-hf garnet
Research affiliation: Kiel University
DOI etc.: 10.1111/j.1525-1314.2007.00745.x
ISSN: 0263-4929
Date Deposited: 12 Jan 2012 05:59
Last Modified: 08 Oct 2012 10:14
URI: http://eprints.uni-kiel.de/id/eprint/15846

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