Fluid inclusion thermometric and stable isotope (δ180-δD) evidence for "cryptic boiling" in the Profitis Ilias epithermal gold deposit, Milos: a potential exploration tool for epithermal gold

"Cryptic boiling" has been disclosed throughout the vertical extent of the Profitis Ilias epithermal system ('450 m) by assessing systematic variations in fluid inclusion and stable isotope (δ180-δD)data in relation to elevation. Highest gold grades (Au: 2-57.9 g/t) are preferentially concentrated in the upper 200-250 m of the system in a "steam-dominated zone" that is separated from a lower "liquid-dominated zone" (Au < 2 g/t). This distribution of gold may be due to colloidal transport in a boiling epithermal system. The identification of the base of the "steam-dominated zone" using fluid inclusion and stable isotope data may potentially guide exploration drilling to depths with high-grade gold ore in productive epithermal systems.