The Origin of a New Pargasite-schist Hosted Ruby Deposit from Paranesti, Northern Greece

摘要: Gem-quality (cabochon) ruby-bearing occurrences (here termed PAR-1 and PAR-5) located near Paranesti, north eastern Greece have been systematically studied for the first time in this paper. Tectonically, are within Nestos Shear Zone (NSZ). The NSZ separates two distinct geological units. Rhodope Terrane is a heterogeneous unit of gneisses, mafic, ultramafic, meta-sedimentary rocks hanging wall. footwall Pangaion-Pirin Complex consists marbles acid gneisses Mesozoic carbonate platform on pre-Mesozoic continental basement. In paper, range petrographic geochemical techniques were used to determine (1) any similarities differences other mafic-ultramafic hosted ruby deposits worldwide; (2) distinctive fingerprints Paranesti; (3) likely P-T conditions formation. Detailed whole-rock analyses utilizing ICP-MS, XRF, XRD found Paranesti corundum be mafic/ultramafic protolith with approximately 40 wt.% SiO2, 16 Mg, 11000 ppm Cr, 440 Ni. EMPA major element analysis determined mineral inclusions grains picotite hercynite spinels. Pargasite dominant amphibole corundum-bearing schist host. surrounding non-corundum bearing chlorite mainly comprises clinochlore. Petrographic examination assemblages schists revealed strong fracturing alignment (parallel main regional foliation) margarite reaction rims around corundum. amphibolites also contain anorthite, along relict sillimanite, kyanite, chlorite/muscovite/epidote overprinting. Detailed LA-ICP-MS trace color from showed metamorphic origin, though pale rubies PAR-5 suggest some metasomatic influence. The displays locality signatures, combination high Cr (average 2300 15% sample points core positions >5000 maximum 8600 ppm); Si 1400 40% over 1500 2500 ppm), low Mg 30 very V, Ti, Ga. Based literature similar occurrences, observed at estimated formation <7 kbar <750 °C, mafic African amphibolite-hosted rubies. This study has most Winza, Tanzania deposit, whilst there high-Cr deposits, primarily Fiskenaesset, Greenland amphibolitic deposits. formed during amphibolite facies metamorphism which created Zone, lesser influence (primarily occurrence) more localized metasomatism. Subsequent multiple greenschist retrogression resulted current-day host amphibole-chlorite assemblages.