EVIDENCE FOR A COMPLEX, MULTI-PHASE AND ZONED OLIGO-MIOCENE MAGMATIC-HYDROTHERMAL SYSTEM WITHIN THE STRATONI FAULT ZONE, NORTHERN GREECE

Extensional tectonics in the north Aegean have been active since the middle Eocene. Normal and transtensional brittle-ductile faults that constitute the Stratoni Fault Zone (SFZ) in the Kassandra Mining District of northern Greece localized Oligo-Miocene magmas and hydrothermal fluids. Extending >12 Km, this strongly mineralized corridor is a complex mélange consisting of amphibolite, marble, and gneiss. Footwall marble and lenses contained within the SFZ host the Madem Lakkos and Mavres Petres Au-Ag-Pb-Zn-Cu replacement massive sulfide deposits, respectively. Overprinting structural relationships evident in drill core, outcrop, and underground exposures demonstrate the influence of pre-existing metamorphic structures on orebody morphology, with ductile to semi-ductile extensional faults controlling late Oligocene intrusions and hydrothermal fluids that formed the massive sulfide orebodies. Early Miocene porphyry dikes, quartz-rich replacement sulfide and crustiform-textured quartz-rhodochrosite vein-breccias are associated with brittle faults, all of which crosscut earlier structures and the massive sulfide orebodies. Post-mineral extensional faults dissect and partially expose the ore deposits.

Massive sulfide orebodies contained within the SFZ display a generalized metal zonation pattern from Cu-W (skarn) in the east with Ag-Pb-Zn-Cu and Ag-Mn becoming progressively more important to the west. Late quartz-rich replacement sulfide also shows a zonation pattern with Fe-Zn-Pb prevalent in the east with increasing As-Pb-Sb-Au contents toward the west, typically associated with quartz-rhodochrosite veins and breccias. Carbon and oxygen isotopes (carbonate) indicate that the massive sulfide orebodies were deposited from a magmatic fluid that equilibrated with marble wallrock, whereas the quartz-rhodochrosite veins in the west were sourced from a magmatic fluid with a meteoric water component. Minimum trapping temperatures determined from primary fluid inclusions in quartz associated with replacement-style sulfide and quartz-rhodochrosite veins display a broad cooling gradient from east to west. These data support an evolving, multi-phased magmatic-hydrothermal system centered on the eastern segment of the SFZ associated with Oligo-Miocene magmatic activity.