Significado de fábricas magnéticas en rocas volcánicas cuaternarias de la Isla Decepción (Shetland del Sur, Antártida)

Abstract

This work deals with the magnetic fabric (AMS technique) of different lithotypes related to quaternary volcanism of Deception Island (South Shetland Islands). The studied rocks include lava flows from basaltic to basaltic-andesitic composition, mafic dykes and several types of pyroclastic deposits. By combining the analysis of parametric aspects of the magnetic ellipsoids and their directional pattern, four types of magnetic fabrics have been recognized. Type I fabrics are related to laminar magma flow in both lava flows and dykes. The second one is related to magma reology in lava flow and tractive streams in pyroclastic deposits. Type III only identified in dikes, characterizes the imbrications of the magma flow against the dyke wall. Type IV reflects an isotropic rock-fabric and has been related to the presence of large anisotropic grains in lavas and particle fall without later modifications in pyroclastic deposits. The obtained results demonstrate the utility of AMS technique for petrogenetic model development linked to rock-fabric acquisition