Historias eruptivas de volcanes cuaternarios en la zona del Paso San Francisco, Puna Sur.

GUZMÁN, S.; GROSSE, P.

Congreso; XX Congreso Geológico Argentino, Tucumán; 2017

Eruptive histories of Quaternary volcanoes in the Paso San Francisco region, Central Andes. We reconstruct the eruptive histories of Incahuasi, Falso Azufre, El Cóndor and Peinado Quaternary volcanoes from the Paso San Francisco region (at ~27ºS, within the southern Central Volcanic Zone of the Andes: CVZ), based on field- and satellite image-based mapping, whole-rock geochemistry and unspiked K-Ar geochronology. Incahuasi consists of a main mostly andesitic conical edifice constructed between 1.6?0.7 Ma at a growth rate of 0.07 km3/ky. At 0.8?0.7 Ma activity shifted to the eastern flank, with the emplacement of a trachydacitic dome and a trachyandesitic lava field. At 0.35 Ma scoria cones and basaltic andesite lava flows were emplaced on the NE flank. Falso Azufre is anarcuate-shaped massif containing a Pliocene andesitic edifice remnant on its NW flank. The bulk of the massif is (trachy)-andesitic and was constructed between 0.9?0.5 Ma at a growth rate of 0.20 km3/ky. More recent activity (< 0.4 Ma) comprises mostly dacitic flows, coulées and domes restricted to the summit regions and the eastern flank. The overall Quaternary growth rate is 0.10 km3/ky. El Cóndor is a NW-SE elongated (trachy)-andesitic to (trachy)-dacitic massif with two distinct stages of activity, Pliocene and recent. Recent activity (< 0.13 Ma) is among the youngest recorded in the region and the estimated eruption rate of 0.37 km3/ky is one of the highest of the CVZ. Peinado, of basaltic trachyandesite to (trachy)-andesitic composition, is formed by a steep cone of lava, scoria and pyroclastic deposits surrounded by a lava flow ring emitted from five vents located around the base of the central cone. An age of 0.04 Ma evidences its youth. Incahuasi can be considered a young extinct volcano, Falso Azufre may be ongoing a minor felsic phase and can be considered potentially active, whereas El Cóndor and Peinado are possibly still in their main constructive phases and can be considered dormant active volcanoes.