Diamond, former coesite and supersilicic garnet in metasedimentary rocks from the Greek Rhodope: a new ultrahigh-pressure metamorphic province established

We report here the first discovery of ultrahigh-pressure (UHP) indicator minerals and textures from the Rhodope Metamorphic Province (RMP), northern Greece. In particular, we document the exsolution of quartz, rutile and apatite in sodic garnet from metapelites (garnet¯biotite¯kyanite gneisses), which attests to the presence of a Si¯Ti¯Na¯P-rich precursor garnet phase. Similar textures in garnet have been reported in the literature only once before for eclogites from the Su Lu UHP metamorphic province, China. We also document the presence of microdiamonds and multicrystalline quartz pseudomorphs after coesite, included in garnet from both eclogites and metapelites. We then argue that these rocks had once been transported to depths exceeding 220 km, well into the upper mantle, thus establishing the RMP as another important UHP metamorphic belt in the world.