Mineralogy and (economic) geology of zeolite-carbonate mineralization in basic igneous rocks of the Troodos Complex, Cyprus

Zeolite carbonate mineralization in the extrusive sequence of the Troodos Ophiolite consists of various Ca-, Ca-Na- and Na zeolites associated in time and space with calcite and aragonite. Three different mineral associations have been established, each with a specific set of zeolites: (1) laumontite-stilbite/stellerite, (2) natrolite-thomsonite-heulandite, (3) analcime-gmelinite. The zeolite carbonate mineralization formed in the temperature range from 250 degrees C to 20 degrees C from seawater with variable amount of biogenic CO2. Calcium-selective zeolites at depth and sodium-selective zeolites near the surface of the eruptive complex reflect a diminishing impact of seawater on the geothermal system with depth and an increase of biogenic CO2 towards the seawater-rock interface. The mineralizing solutions may be characterized as near neutral to alkaline. Sulphides and oxidic ore minerals are associated with zeolites in metabasalts of the "Basal Group". In this stockwork-like mineralization, Cu- and Fe sulphides precipitated subsequently to laumontite and stilbite which are representative of mineral association I. Sulphides of this mineralization may have contributed to the build up of the massive sulphide deposits in the overlying "Pillow Lavas". Fault-related zeolite mineralization 11 is linked with Fe-Mn-oxide hydroxides and zeolite mineralization III may laterally grade into umber mineralization.