Terrain characterization and structural control of the Auca Mahuida volcanism (Neuquen Basin, Argentina)
Geomorphometric parameters (slope, aspect, valley depth, and areal density of cones) derived from a moderate resolution digital elevation model with a grid spacing of 100m are used in an attempt to interpret the tectonic/structural features related to surface deformation in the Auca Mahuida volcanic terrain (Neuquen Basin, Argentina). The Auca Mahuida (2.03-0.88Ma) is the southernmost volcanic field of the Payenia volcanic province, in the Andean foreland. The foreland is subjected to an E-W compression related to the eastward migration of the N-S striking thrust front of the Andes. The geomorphometric analysis indicates that the Auca Mahuida consists of a basal, E-W elongated lava field with monogenic vents and a summit, polygenic, also E-W elongated, cone. A N100 degrees E striking fault controls the southern flank of the field, which is also affected by scarps related to erosional and gravity-controlled processes. The drainage network shows a pseudo-radial pattern around the summit cone, and the Auca Mahuida's deepest valley is structurally controlled by a NNW-SSE striking fault affecting the sedimentary basement. The volcanic field lies on a NE to E dipping substratum. The areal distribution of the monogenic cones is consistent with ascent of magmas along E-W striking fractures, and with elastic models of a pressurized hole (magma chamber) subjected to an E-W compression. At Auca Mahuida, the ascent of melts from the mantle is controlled, in the overriding crust, by tectonic structures formed in response to the E-W compression of the Andes.
volcanism tectonics geomorphology