Permo-Triassic and Jurassic 40Ar-39Ar ages from Greek ophiolites and associated rocks

Determinations are reported of 40Ar-39Ar age spectra for hornblende separates from two unaltered samples of igneous rocks that are interpreted as the intitial igneous products of rifting in the Othris region of central Greece. A third hornblende has been analysed from amphibolites believed to have been formed during tectonic emplacement of the Pindos ophiolite. The ages suggest that the initial rifting began in Othris in the Permo-Triassic (approximately 248 Myr), while tectonic emplacement of the Pindos ophiolite occurred in the middle Jurassic time (approximately 180 Myr). (U.K.)