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Geology of the Sivorg Terrane, Heimefrontfjella, (East Antarctica), and new U-Pb zircon provenance analyses of metasedimentary rocks.

By Joachim Jacobs, Wilfried Bauer, Klaus Weber, Gerhard Spaeth and Robert J. Thomas

Abstract

The Sivorg Terrane is the largest crustal block of the Heimefrontfjella.\ud It consists of a thick supracrustal sequence of metavolcanic and metasedimentary\ud rocks that are intruded by a wide range of predominantly granitic\ud plutonic rocks. The protolith ages of the metavolcanic rocks have been dated\ud at ~1170-1140 Ma and the granitoid intrusions at ~1110-1050 Ma. The best\ud estimate for Grenville-age metamorphism in the Sivorg Terrane is 1090-1060\ud Ma. Unlike the other two terranes in the Heimefrontfjella, the Sivorg Terrane\ud records intense reworking of Mesoproterozoic rocks during the Late Neoproterozoic-\ud Cambrian East African – Antarctic Orogeny. U-Pb detrital zircon\ud provenance analyses from two samples indicate that at least two age-groups of\ud different supracrustal sequences crop out in the Sivorg Terrane. The older,\ud preorogenic sequence gave youngest detrital ages of ~1140 Ma, which are\ud interpreted as dating the maximum deposition age of the original sediment.\ud These rocks also provide evidence of a Palaeoproterozoic to Archaean foreland.\ud The second sample is dominated by Mesoproterozoic to late Neoproterozoic\ud detrital zircons, with a significant proportion of ages ranging from 1100\ud to 980 Ma. The youngest ages significantly postdate the Grenville-age metamorphism,\ud so the sediments must have been deposited after or during the Late\ud Mesoproterozoic orogenesis and, as such, might represent remnants of a\ud molasse deposit of the orogen

Topics: Earth Sciences
Publisher: Deutschen Gesellschaft für Polarforschung
Year: 2009
OAI identifier: oai:nora.nerc.ac.uk:8954

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