Cerro Blanco Volcanic Complex, youngest caldera system in the southern Central Antes. A multidisciplinary earth science project

JOSÉ VIRAMONTE; J.M. ARNOSIO; PABLO EUILLADES; MAURO BLANCO; G. ASH; B. HEIT; M. POODTS; S. CASTRO GODOY; R. BECCHIO; G. GROPELLI; J. KLOTZ; M. DIFILIPPO; A. COLOMBÍ

Postdam, Alemania

Workshop; 19th Colloquium on Latin American Geosciences; 2005

Terra Nostra

The Cerro Blanco volcanic complex (S 26° - W67° 45´) is the youngest (200.000 -150.000 years) caldera in the Southern Central Andes. A perfect piston-like 5 km in diameter caldera is associated to a large (45 km long) piroroclastic flow, post caldera domes with assocoated block and ash flow with big pumice fragments (up 5 Km in diameter) that fill the caldera. However, several previous collapse structures d rock units can be recognized forming a neasted caldera complex. The youngest pyroclastic flow (Campo de la Piedra Pómez flow) is rylotic in composition (70-74.4 %SiO2) and shows a variation from co-lag ignimbritic proximal facies to a pumice rich distal facies. A thermal anomaly (~ 100° C) was detected in the central part of the caldera associated with a freatomagmatic explosión structure. Pritchard & Simons (2002, 2004), from radar interferometry reported a subsidence of 2.5 cm/year for an area 10 km in diameter related to the Cerro Blanco Caldera. In order to valídate this data, and model the possible collapse of the caldera, a high precision 5 benchmarks GPS network was monunted and measured for the first time in April 04 and remeasured in February 2005. A fíve passive broad band digital continuous seismometer network was installed in February 2004 and Checked in December 2004. During February 2005 the fisrt gravimetric detail data was recorded. Geological mapping using ÁSTER images, petrological, geochemical, and isotopic studies was carried out. First muítidisciplinary integrated interpretation from geological, geochemical, geodetic and geophysical data is presented.