Erratum to "High-Ti and low-Ti mafic potassic magmas: Key to plume--lithosphere interactions and continental flood-basalt genesis" [Earth Planet. Sci. Lett. 136 (1995) 149-165] *1

Details Erratum to "High-Ti and low-Ti mafic potassic magmas: Key to plume--lithosphere interactions and continental flood-basalt genesis" [Earth Planet. Sci. Lett. 136 (1995) 149-165] *1 Erratum to "High-Ti and low-Ti mafic potassic magmas: Key to plume--lithosphere interactions and continental flood-basalt genesis" [Earth Planet. Sci. Lett. 136 (1995) 149-165] *1

Jun 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996e%26psl.141..325g&link_type=abstract

Earth and Planetary Science Letters, vol. 141, Issue 1-4, pp.325-341

Physics

14

Scientific paper

The role of mantle plumes in the genesis of continental flood-basalts (CFB) remains controversial, primarily due to our limited knowledge of the composition of the subcontinental lithospheric mantle (SCLM). In this study we use the widespread Cretaceous mafic potassic magmatic rocks, emplaced around the margins of the Paraná sedimentary basin, to probe large-scale compositional variations of the SCLM beneath southern Brazil and Paraguay. On the basis of Ti contents, together with major-, trace-element and isotopic ratios, these mafic potassic rocks may be subdivided into high-Ti and low-Ti groups. The former have relatively high average TiO 2 (4.64), CaO/Al 2 O 3 (1.74) and 143 Nd/ 144 Nd i (0.51232), together with low La/Nb (1.1) and 87 Sr/ 86 Sr i (0.7050). The latter are characterised by much lower average TiO 2 (1.77), CaO/Al 2 O 3 (0.72) and 143 Nd/ 144 Nd i (0.51182), together with higher La/Nb (2.01) and 87 Sr/ 86 Sr i (0.7068). These high-Ti and low-Ti groups are spatially separate and their distribution correlates with tectonic setting; the low-Ti magmas are associated with cratonic regions, whereas the high-Ti magmas are in Proterozoic mobile belts. The distribution of the subgroups of mafic potassic magmatic rocks correlates closely with the geochemical provinciality of the Early Cretaceous high-Ti and low-Ti Paraná flood-basalts. This is the first reported occurrence of extensive low-Ti mafic potassic magmatism associated both spatially and temporally with the low-Ti region of a major CFB province. Our study further reveals similar relationships between tectonic setting and the geochemical provinciality of mafic potassic magmas and continental flood-basalts across Gondwana. We use the bulk-rock compositions and radiogenic isotopic ratios of both the high-Ti and low-Ti mafic potassic magmatic rocks as end members in models of CFB genesis. Mixing calculations involving Sr and Nd isotopic ratios indicate that the flood-basalts may contain up to 50% of mafic potassic lithosphere-derived melts. Overall, the results of our geochemical modelling agree with geophysical arguments that the convecting asthenosphere is the predominant source of CFB magmas.

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