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Comparisons between the northwestern Borborema Province, NE Brazil, and the southwestern Pharusian Dahomey Belt, SW Central Africa

By
T. J. S. Dos Santos
T. J. S. Dos Santos
1
Instituto de Geociências
,
Universidade Estadual de Campinas (UNICAMP)
,
PO Box 6152, CEP 13081-970, Campinas, SP, Brazil
(e-mail: ticiano@ige.unicamp.br)
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A. H. Fetter
A. H. Fetter
2
U.S. Nuclear Regulatory Commission, 11555 Rockville Pike, Rockville, MD 20852
,
USA
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J. A. N. Neto
J. A. N. Neto
3
Universidade Federal do Ceará
,
Campus do Pici, CEP 60455-760 Fortaleza, CE
,
Brazil
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Published:
January 01, 2008

Abstract

Geological and geochronological data for the northwestern part of the Brasiliano Borborema Province are described and compared with their counterparts in the Pan-African Dahomey (Pharusian) belt that flanks the southeastern margin of the West African Craton, where outcrops are sufficiently continuous to discern the nature of the collision during West Gondwana assembly. In the Médio Coreaú domain, NW Borborema Province, U–Pb and Sm–Nd data have revealed unusual basement rocks representing 2.35–2.30 Ga juvenile crust, along with large tracts of 2.15–2.10 Ga juvenile gneisses in the Ceará Central domain. These basement blocks were affected by two pulses of intracratonic extension at 1785 and 775 Ma. Prior to West Gondwana collision, a continental arc (the Santa Quitéria batholith) developed between 665 Ma and 620 Ma. The presence of this arc strengthens the hypothesis that convergence between the Borborema Province and the São Luis craton involved closure of an oceanic basin. New geochronological data are presented showing that Palaeoproterozoic orthogneisses (U–Pb upper intercept 2288±2 Ma) were affected by a major late Neoproterozoic event (554±4 Ma U–Pb lower intercept, 558±3 Ma Sm–Nd whole-rock and mineral isochron). Exhumation and cooling of granulite rocks between 568 and 550 Ma in the Médio Coreaú domain and between c. 587 and 576 in the West African Dahomey Belt indicate that the final tectonic phase was not simultaneous along this front of the orogen.

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Geological Society, London, Special Publications

West Gondwana: Pre-Cenozoic Correlations Across the South Atlantic Region

R. J. Pankhurst
R. J. Pankhurst
British Geological Survey, UK
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R. A. J. Trouw
R. A. J. Trouw
Universidade Federale do Rio de Janeiro
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B. B. de Brito Neves
B. B. de Brito Neves
Universidade de São Paulo, Brazil
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M. J. de Wit
M. J. de Wit
University of Cape Town, South Africa
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Geological Society of London
Volume
294
ISBN electronic:
9781862395428
Publication date:
January 01, 2008

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