Structural controls of volcanism in transversal chains : resheared faults and neotectonics in the Cordon Caulle-Puyehue area (40.5 degrees S), Southern Andes

The nature of the relationship between tectonics and volcanism in a specific area is the result of the interaction between the crustal structures of the basement and ongoing regional stress field. In the Southern Andes, different kinematic environments represented by two nearly orthogonal active fissure systems show apparently incompatible arrays of volcanic chains. Moreover, a local Quaternary compressive regime is inferred from basement faults. However, these mutually orthogonal chains, which are also oblique to the volcanic front, have contrasting magma evolution and eruptive styles that can be related with their tectonic setting. Whereas northeast-trending monogenetic cones (Carran-Los Venados) can be interpreted as resulting from magma upwelling along regional tension cracks in a Quaternary dextral transpressive/compressive domain, northwest-striking fissure system (Cordon Caulle Volcanic Complex) can be the result of extensional fault reactivation and long magma residence in the upper crust. Different kinematic environments cause contrasting magma evolution and eruptive styles. A two-way coupling mechanism is suggested for to explain local depart of the regional stress field, geometric array of extensional features, and final magmatic evolution in these volcanic domains of the Southern Andes. (c) 2006 Elsevier B.V. All rights reserved