Eclogite-Blueschist Relationships as Evidenced by Mineral Equilibria in the High-Pressure Metabasic Rocks of Sifnos (Cycladic Islands), Greece   总被引：1，自引：0，他引：1  

SCHLIESTEDT  MANFRED 《Journal of Petrology》1986,27(6):1437-1459

The northern part of the Cycladic island of Sifnos (Greece)is formed by a coherent sequence of interlayered acid and basicmetavolcanic rocks and metasediments, which underwent a high-pressureblueschist facies metamorphism during the Eocene. The metabasicrocks, including eclogites, blueschists, and actinolite-bearingrocks, are discussed in terms of their mineral assemblages,and bulk-rock and mineral chemistries. Metamorphic conditionsof 470 ? 30 ?C and 15 ? 3 kb are indicated by garnet-omphacitegeothermometry and by the development of deerite in meta-ironstonesand jadeite +quartz in meta-acidites.Mineral textures and systematicelement distributions between coexisting minerals suggest attainmentof chemical equilibrium. A new projection from garnet, epidote,quartz and vapour onto the NaAlO₂-Al₂O₃-CaMgO₂ plane is usedto illustrate equilibrium phase relations between omphacite,glaucophane, actinolite, paragonite, and chloritoid. It is demonstratedthat eclogites, blueschists, and actinolite-bearing metabasitesrepresent different bulk-rock compositions that recrystallizedunder the same fluid pressure and temperature conditions. Eclogitescontaining hydrous minerals such as glaucophane, actinolite,phengite, or paragonite in equilibrium with garnet and omphacitecan occur together with blueschists in high-pressure terraneswithout indicating different metamorphic conditions.  相似文献