The Abrolhos Magmatic Province (AMP), situated along the southeastern Brazilian passive margin, comprises a Paleocene–Eocene transitional basalt series of alkaline affinity. Despite the lack of mineral chemistry and thermobarometric estimates, it has long been linked to a classical deep-mantle plume model. This study integrates mineral chemistry, calculations of intensive parameters (P, T, H2O), geochronology, and geochemical modeling to evaluate an alternative explanation for AMP magmatism. Whole-rock and clinopyroxene compositions from different AMP localities are consistent with parental magmas derived from fertile, pyroxenite-enriched mantle sources that melted under ambient mantle potential temperatures (~1300–1400 °C). Inverse petrological modeling using alphaMELTS and MeltPT, together with trace-element systematics, suggests low degrees of partial melting within asthenospheric domains. These results indicate that shallow (upper-mantle) processes and high mantle fertility were important controls on melt generation. New 40Ar/39Ar ages of 24.3–28.4 Ma for southern AMP rocks are also difficult to reconcile with a simple age-progressive evolution of the previously proposed plume model. Taken together, the data support ambient-temperature melting of a fertile mantle as a plausible explanation for Abrolhos magmatism and reduce the need to invoke a classical high-temperature mantle plume as the sole model. Here, we favor a tectonically controlled model, involving localized shallow mantle processes such as edge-driven convection and/or lithospheric delamination as triggers for intraplate magmatism along the South Atlantic margins.
Lima et al. (Thu,) studied this question.
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