evolutionary model of the meliata blueschists

The Meliata blueschists are subdivided into four groups which are characterized by different litholo-gies and metamorphic histories: (1) Marbles, intercalated with metabasalts and glaucophane-bearing phyllites. Phengite from this group metabasalts and phyllites records the Middle Jurassic age which is interpreted to date the high-pressure metamorphism; (2) Metabasites and micaschists, devoid of marbles contain relic muscovite and newly formed high-Si phengite. The relic muscovite gives Palaeozoic age; (3) Quartz phyllites indicate a polyphase evolution characterized by greenschist facies metamorphism followed by blueschist-facies over-print; the high-Si micas provide evidence of an early Middle Jurassic age of the high-pressure metamorphism; (4) Amphibolite-facies slices and blocks, overprinted by blueschist-facies metamorphism, represent old base-ment rocks. Lithological and metamorphic characteristics together with radiogenic ages of high-pressure micas indicate a subduction of a continental wedge prior to that of oceanic crust can be assumed.