The Kallianos Au-Ag-Te mineralization, Evia Island, Greece: a detachment-related distal hydrothermal deposit of the Attico-Cycladic Metallogenetic Massif

The Kallianos Au-Ag-Te deposit in Evia Island (Greece) comprises sixteen syntaxial veins that intersect the schists and marbles of the Cycladic Blueschist Unit. The veins are filled with quartz-I and quartz-II, contain two hypogene ore stages (stages I and II), and are surrounded by infrequent muscovite-chlorite alteration zones. A magmatic origin is deduced for the Kallianos Au-Ag-Te mineralization, based on stable (S, C, Si, O, and H) and radiogenic (Pb, Sr, and Rb) isotopes, and fluid chemistry. The veins were deposited under pressures of ~ 220 to ~ 145 bars and temperatures of ~ 260 to 120 °C, from almost neutral H2Te-bearing hydrothermal fluids with a salinity of 2.2 to 15.8 wt.% NaCl equivalent. The telluride mineralization related to stage II was deposited at ~ 180 °C and evolved from Au- through Bi- to Ag-bearing tellurides. The vein minerals precipitated by simple cooling of almost non-reactive fluids that retained their initial magmatic signature. Taking into account the magmatic origin of the Kallianos deposit, we examine two proximal areas with granodioritic and leucogranitic intrusions similar to those associated with base and precious metal mineralization at Lavrion (~ 8.3 to ~ 7.1 Ma) and Tinos Island (~ 15 to ~ 13 Ma), as potential sources for the Kallianos fluids. Rb-Sr geochronology dating of the distal Kallianos Au-Ag-Te veins gave an age range of 8.1 to 7.6 Ma, implying that an overlapping and channelized hydrothermal system was active at the northern part of the Attico-Cycladic Metallogenetic Massif, utilizing the CBU detachment zones as fluid pathways.