The Classical Pb-Zn Deposits of the Eastern Alps (Austria/Slovenia) Revisited: MVT Deposits Resulting From Gravity Driven Fluid Flow in the Alpine Realm
AbstractThe stratabound East Alpine lead-zinc deposits in south Austria and northeast Slovenia are hosted by platform carbonates of Triassic age. Ore textures interpreted to be synsedimentary supported the model of syngenetic/synsedimentary ore formation, favored by many authors for a long time. These „synsedimentary“ ore textures represent in our interpretation internal cavity infills. Ore-formation commenced after the precipitation of shallow burial carbonate cements. The deep burial diagenetic stage includes two types of saddle dolomite and three types of blocky calcite. The Zn-rich first ore-phase occurred coeval with the first generation of saddle dolomite and shows a distinct succession of different sphalerite-types which can be distinguished by petrographical and geochemical characteristics. The mineralization of sphalerite is accompanied by pyrite, galena, fluorite, and barite. The second ore-phase was Pb-dominated and appears distinctly after the precipitation of the first generation of saddle dolomite and before precipitation of the first generation of blocky calcite. This second ore phase contains only one type of sphalerite, which shows a characteristic yellow color in transmitted light. Sphalerite with the same optical characteristics and geochemical composition is also related to younger carbonate cements. Fluid inclusion studies indicate formation temperatures of 122 to 159 °C for saddle dolomite and sphalerite of the first ore phase. Formation temperatures of fluorite decreases from the first to the third generation. The first generation of sphalerite and of saddle dolomite can be followed upsection into Late Triassic/Early Jurassic sedimentary rocks, giving a maximum age of ore emplacement for the first phase of Pb-Zn ore. Geochemical data for the ore and the host rock indicate the origin of the metals in the crystalline basement rocks. It is suggested that fluids originating in the hinterland to the north (Vindelician-Bohemian massif) migrated southward by gravity driven flow. These fluids leached the metals from the crystalline basement rocks and ascended, supported by a high heat flow resulting from the onset of rifting in the Alpine realm. Ores formed within the areas of high porosity under distinct geochemical conditions, e.g. the presence of Triassic sulfur.
How to Cite
Zeeh, S., Kuhlemann, J., & Bechstädt, T. (1998). The Classical Pb-Zn Deposits of the Eastern Alps (Austria/Slovenia) Revisited: MVT Deposits Resulting From Gravity Driven Fluid Flow in the Alpine Realm. Geologija, 41(1), 257–273. https://doi.org/10.5474/geologija.1998.014