Characterization of the Cerrito Banco de Arizaro formation and its relationship with Cenozoic magmatism in the Southern Puna.

Abstract

The Cerrito Blanco de Arizaro Formation is part of the widespread Cenozoic volcanism in the Southern Puna region. It comprises three lava domes (Domes 1, 2, and 3) with subcircular to slightly elliptical shapes, emplaced on gentle slopes. Domes 1 and 2 lie east of the Aracar volcano, while Dome 3 is located east of the Vega de Arizaro. Dome 1 consists solely of coherent lava, whereas Domes 2 and 3 display both coherent lava and autobreccia facies. Petrographically, the rocks contain plagioclase, quartz, and biotite crystals within a glassy groundmass. All three domes exhibit flow foliation, marked by variations in vesicle abundance and distribution, indicating emplacement under laminar flow conditions. Geochemically, the domes are high-silica rhyolites with a calc-alkaline signature
and features suggesting intraplate magmatic affinity. Their silica-rich composition and low rare earth element (REE) enrichment imply advanced fractionation of phases such as hornblende, pyroxene, and accessory minerals. Compared to other rhyolitic bodies in the region, these domes are distinguished by a subtle negative Eu anomaly and moderate Sm/Yb ratios, consistent with crystallization at intermediate depths in the crust.