Role of basaltic magmatism within the Parnaíba cratonic basin, NE Brazil
Marthe Klöcking, Nicky White, John MacLennan, 2018. "Role of basaltic magmatism within the Parnaíba cratonic basin, NE Brazil", Cratonic Basin Formation: A Case Study of the Parnaíba Basin of Brazil, M. C. Daly, R. A. Fuck, J. Julià, D.I.M. MacDonald, A. B. Watts
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The sedimentary fill of the Parnaíba basin in NE Brazil is punctuated by two episodes of basaltic magmatism in Jurassic and Cretaceous times, known as the Mosquito and Sardinha formations, respectively. A quantitative understanding of the depth and degree of melting that generated these basalts should provide useful constraints on the history of vertical motions in this cratonic basin. We carried out forward and inverse modelling of major, trace and rare earth element concentrations for primitive melts from both igneous provinces. We calculated the melt fraction as a function of depth to determine the melt volumes and mantle potential temperatures. Our results suggest that both episodes of magmatism resulted from shallow decompression melting within the asthenospheric mantle. The Mosquito basalts record an excess temperature of 55–75°C and are probably related to the widespread Central Atlantic Magmatic Province associated with the initial break-up of Gondwanaland. By contrast, the Sardinha basalts record localized lithospheric thinning to less than half its original thickness with excess temperatures of 15–25°C. This younger activity is probably part of the Paraná–Etendeka large igneous province, which is linked to rifting between South America and Africa. We suspect that these magmatic episodes are associated with phases of regional epeirogenic uplift affecting the Parnaíba basin.
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Cratonic Basin Formation: A Case Study of the Parnaíba Basin of Brazil
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Cratonic basins are large, distinctive features of the continental crust. They are preferentially developed on thick continental lithosphere, are typically sub-circular in shape and subside over periods of hundreds of millions of years. They are also endowed with significant resources. However, in spite of their location in continental interiors and often well-known geology, the subsidence driving mechanism and tectonic setting of these basins remains controversial.
This volume presents both lithospheric and basin scale datasets acquired specifically to interrogate the tectonic process of cratonic basin formation. Focused on the Silurian to Triassic Parnaíba cratonic basin of Brazil, the papers discuss the results of a multidisciplinary basin analysis project comprising new geophysical, geological and geochemical data. This unique dataset enables the characterization of the lithospheric crust and mantle beneath the Parnaíba Basin, constrains the detailed evolution of the basin itself, and enables comparisons with cratonic basins globally. Several convergent themes emerge providing new and powerful constraints for models of the driving mechanisms of these enigmatic basins.