The Agios Georgios argentiferous galena deposit on Antiparos Island, Cyclades, Hellas and its relationship to the Paros leucogranite
Kevrekidis, Elias; Seymour, Karen St.; Tombros, Stylianos; Zhai, Degao; Liu, Jiajun; Zouzias, Dimitrios
published: Jul 1, 2015
ArtNo. ESP154019203008, Price: 29.00 €
The Agios Georgios argentiferous galena deposit on Antiparos island lies ~12 km from the Miocene Paros pluton and is hosted by mineralized quartz veins in marbles of the Cycladic Blueschist Unit. Argentiferous galena and clear quartz were deposited in the epithermal stage in veins armoured by higher temperature milky quartz. The Paros pluton is a mesozonal volatile-rich tourmaline and Li-bearing muscovite leucogranite emplaced at ca. 700 °C and 4–5 kbars. Fluid inclusion microthermometry of vein quartz yielded ore fluid temperatures from 130° to 400 °C, salinities from 4.8 to 15.7 NaCl wt. percent equivalent and pressures of 100 to 135 bars. CO2-effervescence of the ore fluid at the high end of the temperature range is suggested by Raman data along with CO2 clathrate formation. Closure and boiling and reopening of the mineralized quartz veins occurred between 240° to 290 °C. Raman spectroscopy of fluid inclusions showed significant contents of Cu2+ and SO4 2– indicative of the mineralization and of Li+ and B3+ indicative of magmatic fluid contribution. Raman ratios, i.e., logXO2/XH2O indicate mixing with meteoric water. Stable isotope analyses of vein quartz yielded δ18OH2O and δDH2O values of the hydrothermal fluid from 1.2 to 11.6 and –73.2 to –52.4 per mil, respectively and δ 30Si from –0.6 to 0.0 per mil. All are consistent with a dominant magmatic origin of ore fluids. The physicochemical conditions of the ore deposition were pH = 3.6–5.5, logfS2 = –9.7 to –7.3 and logfO2 = –31.3 to –34 for 330° and 210 °C and pressures of 135 bars. The volatile–rich nature of the Paros pluton, the presence of granitophile elements such as Li+ and B3+ in fluid inclusions in the vein quartz, the high salinities of the fluid inclusions, the initial high T (> 400 °C) of the mineralizing event and the magmatic signature of stable isotopes in mineralized vein quartz suggest that mineralizing fluids were derived from the leucogranite.