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A Himalayan-type indentor-escape tectonics model for the southern part of the Late Neoproterozoic-Early Paleozoic East African-Antarctic Orogen

By J. Jacobs and Robert James Thomas

Abstract

The East African–Antarctic orogen is one of the largest orogenic\ud belts on the planet. It resulted from the collision of various parts of\ud proto–East and West Gondwana during late Neoproterozoic–early\ud Paleozoic time (between 650 and 500 Ma). We propose that the\ud southern part of this Himalayan-type orogen can be interpreted in\ud terms of a lateral-escape tectonic model. Modern Gondwana reconstructions\ud show that the southern part of the East African–\ud Antarctic orogen can best be reassembled when a number of microplates\ud (the Falkland, Ellsworth-Haag, and Filchner blocks) are\ud positioned between southern Africa and East Antarctica. This microplate\ud assemblage is unusual. The microplates probably represent\ud shear-zone–bounded blocks, produced by tectonic translation\ud during lateral escape, similar to those currently evolving in Southeast\ud Asia. One of the escape-related shear zones is exposed as the\ud 20-km-wide Heimefront transpression zone in western Dronning\ud Maud Land. Coats Land, a crustal block within the orogen, probably\ud represents a block of older crust that was not subjected to\ud tectonometamorphic reworking ca. 500 Ma by lateral tectonic escape.\ud The southern part of the orogen is also typified by very large\ud volumes of late-tectonic A2-type granitoids, intruded ca. 530–490\ud Ma, probably as a consequence of delamination of the orogenic\ud root and the subsequent influx of hot asthenospheric mantle during\ud tectonic escape. Erosional unroofing of the orogen is documented\ud by the remnants of originally massive areas covered by Cambrian–\ud Ordovician molasse-type sedimentary rocks throughout Africa,\ud Arabia, and Antarctica, testifying to the past extent and size of this\ud largest of orogens

Topics: Earth Sciences
Publisher: Geological Society of America
Year: 2004
DOI identifier: 10.1130/G20516.1
OAI identifier: oai:nora.nerc.ac.uk:5586
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