Paraná Magmatic Province–Tristan da Cunha plume system: fixed versus mobile plume, petrogenetic considerations and alternative heat sources

Paleomagnetic reconstructions demonstrate that the Tristan da Cunha (TC) plume, which is usually related to the genesis of the high- and low-Ti flood tholeiites of the Paraná Magmatic Province (PMP), was located ∼1000 km south of the Paraná Province at the time of the magma eruptions. Assuming plume mobility, and considering the low-velocity zone identified in the northern portion of the PMP as the TC ‘fossil’ plume (∼20° from the present TC position), the plume migrated southward from 133–132 (main volcanic phase) to 80 Ma at a rate of about 40 mm/yr. From 80 Ma to Present the plume remained virtually fixed, leaving a track (Walvis Ridge) compatible with the African plate movement. However, geochemical and Sr–Nd–Pb isotopic data do not support that the tholeiites from Walvis Ridge, Rio Grande Rise and Paraná can result from mixing dominated by the TC plume and mid-ocean ridge basalt components. The similarity among the high-Ti basalts from Rio Grande Rise, part of Walvis Ridge (525A) and the Paraná Province suggests that delaminated subcontinental lithospheric mantle must be considered in their genesis. Regional thermal anomalies in deep mantle mapped by geoid and seismic tomography data offer an alternative non-plume-related heat source for the generation of intracontinental magmatic provinces.