Raman micro-spectroscopy on diamond, graphite and other carbon polymorphs from the ultrahigh-pressure metamorphic Kimi Complex of the Rhodope Metamorphic Province, NE Greece

Abstract

Raman micro-spectroscopy was applied on carbon inclusions in garnet porphyroblasts from kyanite–biotite–garnet schists of the Rhodope Metamorphic Province (RMP), NE Greece. Diamond and cuboids of poorly to highly ordered graphite were identified either as single phase inclusions or as polyphase inclusions along with CO2 and/or carbonates (calcite/magnesian calcite). Questionable Raman bands that may be assigned to other C-phases (?nanodiamond/?lonsdaleite/?a different C-polymorph) have been observed. The presence of diamond confirms beyond any doubt the ultrahigh-pressure (UHP) metamorphism reported by Mposkos and Kostopoulos [1] [E. Mposkos, D. Kostopoulos, Diamond, former coesite and supersilisic garnet in metasedimentary rocks from the Greek Rhodope: a new ultrahigh-pressure metamorphic province established, Earth Planet. Sci. Lett. 192 (2001) 497–506] in the RMP. Cuboid graphite showing variable degree of disordering most probably formed after diamond. The possible involvement of CO2 and or C–O–H fluids in the formation of diamond is discussed.