Quecksilbermobilität in der Rannach-Decke des Grazer Paläozoikums
Research output: Thesis › Master's Thesis › Research
Within the Rannach-Nappe of the Graz Palaeozoic almost monomineralic cinnabar mineralisations occur in quartz-calcite veins and stocks of sparry carbonates within the Kanzel-Member of the Kollerkogel-Formation around Gratwein/Gratkorn. The goals of this work are focused to the source and mobility of mercury in this area. Due to the mobilisation of Hg during weathering of the rocks and adsorption to clay-minerals of the soils, there are some mercury-anomalies in soils above Paleozoic limestones. Soils above mineralized limestones have high contents of mercury (up to 8000 ppb). The anomalies are situated in an E-W corridor from Gratkorn – St. Pankrazen where non mineralized Givetian limestones (Kanzel-Member and equivalents) show high contents of mercury, antimony and cobalt compared to the other carbonatic formations. Some alkaline volcanic tuffs with high contents of these elements were also found in Givetian limestones. The linking of the Hg-anomalies and the tuffs to the Givetian limestones suggests a primary non-visualisable volcanic Hg-enrichment in some parts of the Givetian carbonate shelf. The type of the mineralisation and the results of the microthermometry and cation-geothermometers indicate a low-temperature hydrothermal formation (80-160°C) for the mercury mineralisation and ± simultaneously formation of the coarse-grained carbonates and quartz-calcite veins with cinnabarite mineralisations. The position of the mineralisations and the character of the C/O-isotopes constrain, that the fluid-movement and the mass transport are only restricted to the area of the Kanzel-Member. The time for the mineralisation is not known exactly. Two models are open for discussion. One possibility is an early formation due to the general availability of intraformational fluids during the diagenetic stage. The other model is related to late Alpine fluid activities after the uplift of the Gleinalm metamorphic dome during Neogene escape-tectonics along E-W fault zones and formation of the Neogene Rein basin at the margin of the Hg-anomaly. As mercury and cinnabar have a very low water solubility a contamination of the groundwater, as also indicated by the hydrochemistry, can be excluded.
|Translated title of the contribution||Hg-mobilisation in the Rannach-Nappe of the Graz Palaeozoic|
|Award date||14 Dec 2012|
|Publication status||Published - 2012|