MINERALOGICAL CONTRAINTS TO THE FORMATION OF VEIN-TYPE ZEOLITES FROM KIZARI AREA, THRACE NORTHERN GREECE

Abstract

Vein-type zeolites in Kizari area, (western Thrace) are found within fresh to zeolitic altered volcanic rocks of andesitic to dacitic composition. The zeolites stilbite-Ca, Sr-bearing heulandite-Ca and laumontite occur in epithermal-style crustiform quartz/chalcedony-calcite veins crosscuting lavas and volcanic breccias. Open-space filling is common and well-shaped crystals (up to 3cm) were observed. Smectite, feldspar, magnetite, pyrite and rutile occur in minor amounts in the veins. Halite and barite grains are included in stilbite-Ca. SEM EDS data indicate high Sr (up to 4.4 wt. % SrO) and Ba (up to 2.9 wt. % BaO) contents for heulandite-Ca. It is suggested that the studied zeolites are intergral parts of the porphyry-epithermal mineralizing systems which operated in the area during the Oligocene. Their formation took place in the outmost transitional propylitic to fresh zones of the porphyry-epithermal systems and in a submarine environment as indicated by the geological and mineralogical evidence.