Characterizing volcanic features using a frequency-domain Electromagnetic Induction System

A. OSELLA; M. DE LA VEGA; E. LOPEZ; E. ROVERE; R. VIOLANTE

Foz de Iguazu

Congreso; The meeting of tha Americas, American Geophysical Union; 2010

AGU

Geophysical methods were used to characterize volcanic features in the western lacustrine plain of the Llancanelo Lake, in Mendoza Province (Argentina). At a first stage, electromagnetic induction (EMI) and geoelectricity (Multielectrode Resistivity Meter) methods, as well as short drillings, were performed along a 2.5 km long transect perpendicular to the lake's western-shoreline. The combined analysis of geophysical and sedimentological information, supported by lab analysis, microfaunistic and petrographic/EDAX studies, indicates the presence of a lacustrine sequence at least 30 m thick, mainly composed of volcaniclastic Sediments. Also, a particular anomaly feature, located at approximately 1 km from the coast (centered at 35º33´53´´S69º11´28´´W), was detected. It has very low electrical resistivity (less than 1 ohm/m) partially fringed by a higher resistivity zone (up to 15 ohm/m). The maximum depth at which the anomaly was evidenced is up to 12 m depth due to the fact that the geoelectrical method was conditioned by the uppermost highly conductive layers (saline soils) which consume most of the current injected into the soils.