The uppermost unit of the Cretan nappe system consists of ophiolites on the top, and an ophiolitic m61ange at the base.
Among the various constituents of the m61ange, there are slices of low-P/high-T metamorphics. They form a variegated series consisting of tholeiitic ortho-amphibolites, para-amphibolites, andalusite and sillimanite-cordierite-garnet bearing mica schists, calcsilicate rocks, and marbles. The metamorphic sequence is locally intruded by early tectonic magmatites of gabbroic, dioritic and granitic composition. Critical mineral assemblages lead to a maximmn temperature of about 700 ~ C reached during metamorphism, at a total pressure of 4 5 kilobars. K-Ar dating on 6 hornbtendes, 7 biotites and 1 muscovite yielded cooling ages of 75-66 m.y. and confirmed earlier results according to which the metamorphism and related magmatism took place in Late Cretaceous times.
In order to evaluate the age relationships between the hightemperature metamorphics within the ophiolitic m61ange and the ophiolites, hornblendes from uttramafic and mafic rocks of the ophiolite complex were dated by the K-Ar method. Hornblende from one schistose hornblendite forming a constituent of the ophiolites proper yielded 156 m.y. and thus provides a middle Jurassic minimum age for the formation of this piece of oceanic lithosphere. Four hornblendes of calc-alkaline gabbrodiorite dikes within the ophiolite complex gave distinctly lower K-Ar dates of about I40 m.y.. The dikes probably intruded after the detachment of the ophiolites in an island-arc or continental-margin environment.
As a consequence, the high-temperature metamorphics and related intrusives in the ophiolitic m61ange of Crete are genetically unrelated to the overlying ophiolites. The paleogeographic position of the crystalline terrane, slices of which are now incorporated into the ophiolitic m~lange is still open to discussion. phics, the L6ndas area, Asterofisia mountains. In the meantime we collected K-Ar data on other localities in Crete which shall be presented in this paper and discussed in the light of recent literature.
In addition we will present and discuss first radiometric results on hornblendes from the ophiolites themselves.