Structure of a fossil ridge–transform intersection in the Troodos ophiolite

Abstract

RECENT palaeomagnetic studies of sheeted dykes adjacent to the east-west trending Southern Troodos transform fault of Cyprus have demonstrated significant clockwise block rotations, which are most easily interpreted as being due to drag induced by dextral strike-slip faulting along the transform1–6. We show here that such rotations have not occurred along the entire length of the transform; instead, to the west of the areas previously studied the sheeted dykes have been subjected to simple tilting only, indicating normal faulting but no strike slip. The changeover between these two domains of differing structural styles, near the village of Mandria, is approximately in line with the centre of the Solea graben, a north–south trending structure within the Troodos massif which has previously been interpreted as a fossil ridge axis7. We suggest that the Mandria area represents a fossilized ridge–transform intersection, and present the results of a detailed field investigation of the area, together with preliminary palaeomagnetic data, to determine the relationship between tectonism and magmatism at such plate boundary zones. We use our findings to test a recent theoretical model8 of deformation processes at ridge-transform intersections, and show that distributed deformation due to block rotation is largely confined to the ridge–transform corner itself.