Abstract

The islands of Ios and Naxos in the Cycladic archipelago, Greece, contain elongate domes over which a pervasive north- to north-northeast–stretching lineation is warped. These islands may be metamorphic core complexes of Cordilleran type, involving middle-crustal rocks drawn upward and outward from underneath the sedimentary basins now 100 km to the south. From ca. 25 Ma onward, during uplift, the crystalline rocks now exposed on the islands were deformed noncoaxially in the deeper levels of a major shallow-dipping ductile shear zone. This shear zone may have connected with low-angle normal faults in its upper levels, because it is probable that its later history involved the metamorphic complexes being dragged out from under a stretching and fracturing upper plate composed mainly of unmetamorphosed sedimentary and ophiolite suite rocks. This model can be extended to explain the exhumation of the high-pressure–low-temperature metamorphic rocks on Crete, which, with the Cyclades, forms a distended paired metamorphic belt separated by an active sedimentary basin.

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