Blueschist-to-greenschist transition and the P-T path of prasinites from the Lavrion area, Greece

The Lavrion area is part of the Attic-Cycladic massif. Blue amphibole analyses revealed that they are glaucophane or ferroglaucophane. Ca-amphiboles are characterized as actinolite or actinolitic hornblende. The Ps component of epidotes from the glaucophane-bearing rocks varies from 25.42-30.89%, whereas the Ps component of epidotes from the greenschist assemblages ranges from 23.81-26.88%. Chlorites show narrow compositional variations of ferromagnesian ratios (X(mg)=0.48-0.53). Albites are almost pure Ab(100). The K-feldspar present has a low Ab content. The evolution of the prasinites studied is characterized by the progressive transformation of eclogite facies (?) rocks through epidote blueschists into greenschists. A P-T path for the prasinites is presented indicating epidote blueschist facies at P-T conditions of around 7.0-7.5 kbar and 300-340 degrees C. Pressures of 4.0-3.5 kbar and temperatures around 340-360 degrees C are estimated for the subsequent overprint in the greenschist facies. The path EBS to GS conditions followed under nearly isothermal uplift.