Petrography and Mineral Chemistry of Monte Epomeo Green Tuff, Ischia Island, South Italy: Constraints for Identification of the Y-7 Tephrostratigraphic Marker in Distal Sequences of the Central Mediterranean

The 56 ka Monte Epomeo Green Tuff (MEGT) resulted from the largest volume explosive eruption Ischia island (south Italy). Its tephra is one of main stratigraphic markers central Mediterranean area. Despite its importance, a detailed characterisation petrography and mineral chemistry MEGT lacking. To fill this gap, we present petrographic description electron microprobe data on samples collected on-land MEGT. Juvenile clasts include pumice, scoria, obsidian fragments with porphyritic/glomeroporphyritic, vitrophyric, fragmental textures. porphyritic index 13–40 vol.%, phenocryst phases alkali-feldspar, plagioclase, clinopyroxene, ferrian phlogopite, titano-magnetite, in order decreasing abundance; accessory sphene, hydroxy-fluor-apatite, rare edenite. Plagioclase varies predominant andesine to subordinate oligoclase, whereas alkali-feldspar more variable sanidine anorthoclase; quasi-pure commonly occurs as either rim or recrystallisation overgrowth large phenocrysts due hydrothermal alteration. Secondary minerals veins patches carbonate minerals, Fe-Mn oxyhydroxides, clay zeolites. Clinopyroxene ferroan diopside (En45–29Fs7–27) never reaches Na-rich compositions. This feature allows discrimination aegirine-bearing, distal layers erroneously attributed MEGT, implications for areal distribution deposits.