The slip-fiber chrysotile asbestos deposit in the Zidani area, northern Greece

Abstract

The chrysotile asbestos deposit of Zidani in northern Greece is an example of a slip-fiber deposit associated with alpine-type peridotites. The deposit occurs in the northern part of an antigorite serpentinite and peridotite body, tectonically emplaced on the Pelagonian basement of the area.

A continuous retrograde alteration event is recognizable along the thrust fault between a metaclastic and carbonate sequence and the serpentinite body. A phase of ductile deformation that formed antigorite mylonites was followed by a brittle one, which formed schistose serpentinite. The sense of shear of the overthrusting metaclastic mylonite coincides with that of the immediate underlying schistose and mylonite serpentinites; thus retrogression of both groups of rocks is assumed to be the result of the thrust event.

The numerous altered amphibolite dikes crosscutting the ore created planar anisotropies during the thrust-related deformation. These planar anisotropies localized the deformation and consequently the formation of the schistose serpentinite and the asbestos ore in the northern part of the serpentinite body.

Slip-fiber chrysotile asbestos was formed along anastomosing non-penetrating shear surfaces in the schistose serpentinite. The chrysotile fibers replaced antigorite “in situ” in shear planes, most likely at a transitional stage of deformation exhibiting both ductile and brittle fabrics. However, syntectonic filling of “shear veins” at the brittle stage is the major cause of the origin of the asbestos deposit.