The Irish continental crust revealed by potential field methods

Aeromagnetic and Bouguer gravity data from onshore Ireland have been compiled in order to analyse regional data sets with conventional wavenumber domain techniques. The results from this analysis have defined major geophysical lineaments which represent terrane boundaries in Ireland. A coherence analysis of gravity and topography using a maximum entropy spectral estimation technique was used to investigate the flexural strength (equivalen t the effective elastic thickness T_e) of the Irish lithosphere. Large scale (~50 km) variations in flexural rigidity broadly correspond to the terranes which were delineated by the wavenumber domain analysis. The spatial configuration of flexural rigidity, and the major crustal faults that it controls, allows only three terranes to be distinguished with certainty . The Central Terrane, encompassing the Iapetus Suture Zone, is a zone of low crustal strength with T_e values ~20-45 km. It hosts major fault-controlled lead - zinc mineralisation.