. “Gondwana” magmatism of Patagonia: inner cordilleran calc-alkaline batholiths and bimodal volcanic provinces

RAPELA, C.W.; PANKHURST, R.J; LLAMBÍAS, E.J.; LABUDÍA, C.; ARTABE, A.E.

Saint Malo

Simposio; Third International Symposium on “Andean Geodynamics; 1996

ORSTOM

The Permian Lo Jurassic silicic igneous provinces of southern South America are characteristic of the Gondwana supercontinental stage in this region. “Gondwana” magmatism exhibits distinctive composition, geological setting and spatial distribution compared with those typical of the Cretaceous to modern Andes. Whereas the large rhyolite provinces of Permian-Triassic and Middle Jurassic age have attracted much attention (e.g. Kay et al., 1989; Pankhurst & Rapela, 1995), the role of the intraplate batholiths has usually been overlooked. The precise timing and complete compositional characterization of both episodes are crucial to an understanding of the early stages that lead to “Andean type subduction” and the mechanisms that triggered the breakup of the supercontinent. New Rb-Sr geochronological and geochemical data are reported for three key localities of northern Patagonia that, together with results from previous studies, allow us to reach a broader view of the “Gondwana” magmatic episode and its possible tectonic scenario.