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EnglishThe eastern border of the Sa˜o Francisco craton is characterized by widespread Mesoproterozoic (1.0 Ga) tholeiitic dykes and minor analogues of Early Cretaceous age (130 Ma). The Mesoproterozoic dykes (Salvador, Olivenc¸a, Espinhac¸o, Diamantina) show large elemental and Sr–Nd isotopic variations that suggest different parental melts related to a small-scale heterogeneous mantle of depleted residua and enriched components (Statistical Upper Mantle Assemblage, SUMA), responsible for plume- and crust-type signatures. The Mesoproterozoic intrusions, compatible with early stages of Rodinia breakup, may represent the initial breakup of the Sa˜o Francisco– Congo junction. Early Cretaceous dykes (Espinhac¸o) reveal normal and reversed polarities, indicating two distinct intrusive periods. These intrusions have elemental and Sr–Nd isotopic compositions similar to those of the coeval (132 Ma) high-TiO2 tholeiites from southern Parana´ Basin (Urubicı´-type, Brazil) and northern Etendeka (Khumib-type, Namibia). The genesis of these tholeiites requires lithospheric mantle components, as represented by K-alkaline (and carbonatitic) rocks from the Asuncion-Sapucai graben (Paraguay), that highlight the intriguing Pb-isotope relationships involving the Urubicı´-Khumib tholeiites. The essential role of the Tristan plume is difficult to determine. The spatial distribution of such uncommon high-TiO2 tholeiites reveals that similar lithospheric components may exist in different cratonic blocks and associated mobile belts.
| Titolo: | Genesis and Geodynamic Significance of Mesoproterozoic and Early Cretaceous Tholeiitic Dyke Swarms from the São Francisco Craton (Brazil). | |
| Autori: | ||
| Data di pubblicazione: | 2007 | |
| Rivista: | ||
| Abstract: | The eastern border of the Sa˜o Francisco craton is characterized by widespread Mesoproterozoic (1.0 Ga) tholeiitic dykes and minor analogues of Early Cretaceous age (130 Ma). The Mesoproterozoic dykes (Salvador, Olivenc¸a, Espinhac¸o, Diamantina) show large elemental and Sr–Nd isotopic variations that suggest different parental melts related to a small-scale heterogeneous mantle of depleted residua and enriched components (Statistical Upper Mantle Assemblage, SUMA), responsible for plume- and crust-type signatures. The Mesoproterozoic intrusions, compatible with early stages of Rodinia breakup, may represent the initial breakup of the Sa˜o Francisco– Congo junction. Early Cretaceous dykes (Espinhac¸o) reveal normal and reversed polarities, indicating two distinct intrusive periods. These intrusions have elemental and Sr–Nd isotopic compositions similar to those of the coeval (132 Ma) high-TiO2 tholeiites from southern Parana´ Basin (Urubicı´-type, Brazil) and northern Etendeka (Khumib-type, Namibia). The genesis of these tholeiites requires lithospheric mantle components, as represented by K-alkaline (and carbonatitic) rocks from the Asuncion-Sapucai graben (Paraguay), that highlight the intriguing Pb-isotope relationships involving the Urubicı´-Khumib tholeiites. The essential role of the Tristan plume is difficult to determine. The spatial distribution of such uncommon high-TiO2 tholeiites reveals that similar lithospheric components may exist in different cratonic blocks and associated mobile belts. | |
| Handle: | http://hdl.handle.net/11368/1693394 | |
| Digital Object Identifier (DOI): | http://dx.doi.org/10.1016/j.jsames.2007.02.002 | |
| Appare nelle tipologie: | 1.1 Articolo in Rivista |
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