VARNET MT: Interpretation of Magnetotelluric Data over the Killarney–Mallow Fault Zone in South-West Ireland

Abstract

The south-west of Ireland is an area in the European Variscides where the surface geology can provide constraints on geophysical models of deep Variscan (and Caledonian) tectonic structures. The VARNET (VARiscan NETwork) project has acquired new wide-angle seismic reflection, magnetotelluric (MT) and gravity data collected in south-west Ireland in order to integrate these with surface geological observations and tectonic models from Ireland and other parts of the European Variscides. This paper is concerned with the interpretation of VARNET MT data collected across the major tectonic structure seen at the surface: the Killarney-Mallow Fault Zone. The MT data have identified a near-surface conductive zone associated with the east-west-trending Killarney-Mallow Fault Zone. The inversion of these data along three profiles across the Killarney-Mallow Fault Zone and the eastern end of Dingle Bay indicates the presence of steep, probably north-dipping structures, extending to depths of at least 2km. There is also prima facie MT evidence for a steep structure near the Cork-Kenmare Line and a steep, north-dipping structure associated with the Dingle Bay-Galtee Mountains Line. The locations of these structures appear to be consistent with those interpreted from the wide-angle seismic reflection data.