Pliocene intraplate-type volcanism in the Andean foreland at 26°10′S, 64°40′W (NW Argentina): Implications for magmatic and structural evolution of the Central Andes

Abstract

The Antilla magmatic complex (26°10′S, 64°40′W, NW Argentina) attests to magma eruption at ca. 4.7 Ma in the Central Andes backarc region, 300 km E of the active arc. The Antilla lavas have an alkaline, predominantly mafic composition and record the most primitive isotopic ratios (87Sr/86Sr = 0.704360 and 143Nd/144Nd = 0.512764) of Central Andes Neogene backarc volcanism between 24°S and 27°S. They show trace-element patterns recalling backarc Pliocene-Quaternary intraplate mafic rocks, but they show lower silica and higher alkali contents, and are interpreted to derive from the depleted subcontinental mantle.