Variscan deformation in Ireland (Fig. 1) can be divided into subareas (Gill, 1962). Deformation in Upper Paleozoic rocks in the south of the country is dominated by tight folding and strong development of a slaty cleavage. This style of deformation is the product of reactivation of early extensional faults (Price and Todd, 1988). The fold belt has been interpreted both as a thick-skinned dextral transpression zone (Sanderson, 1984) and a thin-skinned fold and thrust belt (Cooper et al., 1984). As pointed out by Ford (1987), although the belt is part of the Rhenohercynian belt of Europe its geometry differs from a classic thin-skinned belt in that the shortening is largely accommodated by ductile folding and cleavage development with relatively minor faulting. Using sequential section balancing, Ford (1987) estimated a total of approximately 50% shortening. Gravity data (Ford et al., 1991) constrain any putative detachment to depths of the order of 10- 12km. Throughout the Munster Basin, especially in the southwest, Sanderson (1984) documented evidence of along strike extension (boudinage, shear bands and veins). In addition, horizontal fibres in pyrite pressure fringes and fold-cleavage transection are also common throughout much of the southwest.
Figures & Tables
Irish Carbonate-Hosted Zn-Pb Deposits
This paper describes the stratigraphy, basin evolution, and structural geology of Ireland so that the hydrothermal processes which formed the deposits can be placed in a geological context. Informal regional nomenclature are used throughout this paper to provide a clearer overview, rather than the myriad of existing local formation names (see Jones and Earls, this volume). The stratigraphy, together with series and stage designation and available radiometric ages, is presented in Figure 1.