Blueschist-to-Greenschist Transition and the P-T Path of Prasinites from the Lavrion Area, Greece

Abstract 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 (Xmg=0.48–0.53). Albites are almost pure Ab100. The Kfeldspar 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°C. Pressures of 4.0–4.5 kbar and temperatures around 340–360°C are estimated for the subsequent overprint in the greenschist facies. The path EBS to GS conditions followed under nearly isothermal uplift.