Thermal history of the Pan-African/Brasiliano Borborema Province of northeast Brazil deduced from 40Ar/39Ar analysis
1998; Elsevier BV; Volume: 285; Issue: 1-2 Linguagem: Inglês
10.1016/s0040-1951(97)00192-3
ISSN1879-3266
AutoresMichel Corsini, L. Lambert de Figueiredo, Renaud Caby, Gilbert Féraud, Gilles Ruffet, Alain Vauchez,
Tópico(s)High-pressure geophysics and materials
ResumoDetailed step heating 40Ar/39Ar analyses were performed on different minerals from magmatic and metamorphic rocks of the Borborema Province. This region, located in northeast Brazil, belongs to the Pan-African/Brasiliano belt which is about 1000 km wide and 600 km long. Twenty-six single grains of amphibole, muscovite and biotite were extracted from eighteen samples selected in an area of about 17,500 km2 (250 km by 70 km) in the Patos region. This region has been affected by a continental-scale shear zone system. Well-defined 40Ar/39Ar plateau ages and an UPb analysis on zircon [Leterrier, J., Jardim de Sà, E.F, Bertrand, J.M. and Pin, C., 1994. Ages UPb sur zircon de granitoïdes brasilianos de la ceinture du Serido (Province Borborema, NE brésil). C.R. Acad. Sci., Paris, 318: 1505–1511] allow the definition of a homogeneous and unusual slow cooling history (3–4°C/Ma) and suggest a rather slow uplift rate between 580 and 500 Ma, followed by a fast cooling of the whole studied area around 500 Ma. Rapid cooling is suggested by concordant plateau ages on muscovite and biotite. The existence of such an event at the end of the belt history is in agreement with data obtained on other major belts such as the Alpine-Himalayan system or the Hercynian belt.
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