40Ar/39Ar dating of metamorphic soles from the Albanian ophiolites: implications for their emplacement models

The metamorphic soles of the Albanian ophiolites, 0.5 km thick, highly deformed, show an inverted metamorphic gradient, formed during the early stages of intra-oceanic thrusting. Twenty-four 40Ar/39Ar radiometric ages were obtained on amphiboles and micas from the different soles and ophiolitic igneous genesis rocks. The main results are the Middle Jurassic age (160-174 Ma) of the metamorphic soles, an important north-south diachronism (up to 14 Ma) over 150 km, and a synchronism between the metamorphism and the late magmatic events. The closure of the triangular oceanic basin, cut by ENE-WSW transform faults, can explain these results. (authors)