The fluid conduit at the Schönbrunn fluorspar mine, SW Saxony: Geology of conduit and hydro-, gas- and isotope chemistry of thermal water

To explore fault-bound hydrothermal systems, knowledge about fluid conduits and the (isotope-) geochemical composition of the geothermal water is necessary. At the hydrothermal vein deposit of the former Schönbrunn fluorspar mine, fluid conduits in the depth between the 293 and the 533 m level were outcropped. Attempts at utilization for deep geothermal energy failed in 1997, because the mine was flooded. The thermal water outflow of the most active fluid conduit, outcropped at the 533 m level was 1 m³ min^-1 and the temperature was 35,7°C. The fluid conduit is controlled by the intersection of a fault bundle of several NNW-SSE and NW-SE striking faults. The horizontal length of the intersection area is about 400 m. A geothermal anomaly exists at the segment of the intersection. The quartz-fluorite bearing mineralization (primary) was redeposited by carbonate-sulfide mineralization with depth.

Research on unpublished water and gas samples (96 and 115 data sets, respectively) from the so called “spa” at the 453 m level of the Schönbrunn mine was carried out by time-series measurements (weekly sampling rate) to investigate 1) composition and origin of the thermal water, 2) reservoir temperature via geothermometry, and 3) potential hydro- and gas-chemical effects of regional swarm seismicity. We revaluated the results and collated them with new findings of the Neumühle thermal water (Prause et al., session 4b) in order to develop deep geothermal energy projects at crystalline rock areas in Western Saxony.