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The Neoproterozoic Quatipuru ophiolite and the Araguaia fold belt, central-northern Brazil, compared with correlatives in NW Africa

By
M. A. P. Paixão
M. A. P. Paixão
1
Department of Mineralogy and Petrology
,
Institute of Geosciences, University of Brasília
,
Brasília, DF 70910-900
,
Brazil
(e-mail: pires_paixao@ig.com.br)
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A. A. Nilson
A. A. Nilson
1
Department of Mineralogy and Petrology
,
Institute of Geosciences, University of Brasília
,
Brasília, DF 70910-900
,
Brazil
(e-mail: pires_paixao@ig.com.br)
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E. L. Dantas
E. L. Dantas
2
Geochronology Laboratory, Institute of Geosciences, University of Brasília
,
Brasília, DF 70910-900
,
Brazil
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Published:
January 01, 2008

Abstract

The Araguaia Belt, the northern branch of Neoproterozoic Tocantins tectonic province, developed during West Gondwana amalgamation as a result of collision between the Amazon and West African and/or São Francisco/Congo cratons. The external zone of the belt consists of ophiolitic slices and fragments, sedimentary rocks derived from magmatic arc sources, volcanic rocks, and part of a passive continental margin with low-grade metamorphic rocks, while the internal zone corresponds to a pile of low- to medium-grade metasedimentary rocks. The largest and best preserved ophiolitic bodies occur in the southern part of the belt, where the Quatipuru and Morro do Agostinho ophiolites are composed predominantly of mantle peridotites (mainly residual harzburgite) representing the base of the Moho transition zone. They contain chromitite pods, dunitic lensoid bodies and a suite of mafic–ultramafic dykes and/or sills resulting from partial melting, magma impregnation and diapiric up-rise. A Sm–Nd isochron age of 757±49 Ma indicates oceanic crust formation during the Early Neoproterozoic. NW African correlatives of the Araguaia Belt, the Mauritanide–Bassaride–Rokelide belt, show similarities with respect to lithostratigraphic units, the ages of basement and supracrustal rocks, the presence of Neoproterozoic ophiolitic slices and fragments, suture zones characterized by high gravity anomalies and centrifugal tectonic vergence. We conclude that these belts were probably formed around the same Neoproterozoic ocean or several small coeval oceans.

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Contents

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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