Strontium and oxygen isotopes in igneous rocks from a 35 000-km2 region of the Serra Geral (Paraná) continental flood-basalt province, southern Brazil, indicate that certain mantle-derived magmas that formed during the rifting and breakup of Gondwana incorporated continental crust. Sr-O and trace-element assimilation–fractional crystallization models point to variable amounts and types of “warm” Archean granulitic crust, δ18O 11 > 15 and 87Sr/86Sr(I) ∼0.735, having contaminated ascending mafic magmas. Resulting products include evolved rocks, basaltic andesite to rhyolite, that have δ18O 11 to 15 and 87Sr/86Sr(I) 0.714 to 0.729, and basaltic rocks that have δ18O 8 to 10 and 87Sr/86Sr(I) ∼0.710.

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