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Age of magnetization of Mesoproterozoic rocks from the Natal sector of the Namaqua-Natal belt, South Africa

By Robert James Thomas, W. Gose and S.T. Johnston

Abstract

We report paleomagnetic results from Mezoproterozoic rocks from the Margate and Mzumbe terranes of the Natal belt,\ud KwaZulu-Natal, South Africa. The Port Edward pluton, a member of the Oribi Gorge Suite, yields a pole position at 7.4S,\ud 327.8E, A95 = 4.2. The magnetic remanence of these magnetite-bearing rocks was not acquired soon after crystallization at\ud 1025 Ma but only when the sampling area cooled below 500 C at about 1005 Ma. Similar results have been reported from the\ud western (Namaqualand) sector of the Namaqua-Natal Belt which suggests that the entire belt underwent a similar tectono-metamorphic\ud history. The tonalitic Mzumbe Gneiss was intruded by a swarm of porphyroblastic metadolerite dykes. The magnetization of\ud these Equeefa dykes and the gneissic wall rock is carried by titano-maghemite with Curie temperatures between 330 and 400 C.\ud Their magnetization was reset at about 530 Ma after burial and exhumation and they yield a pole position at 24.7N, 17.4E,\ud A95 = 10.6. These results demonstrate the difficulty in finding rocks on the Kalahari craton that would yield pole positions to fill\ud the data gap in the apparent polar wander path between 1.1 and 1.0 Ga, a critical time span for Rodinia reconstructions, and\ud provide the first dated Cambrian pole position for the Kalahari craton

Topics: Earth Sciences
Publisher: Elsevier
Year: 2005
DOI identifier: 10.1016/j.jafrearsci.2004.11.003
OAI identifier: oai:nora.nerc.ac.uk:5584
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