The interplay between hydrothermal mineralizations and element redistribution processes related to young tectonic activity - case studies from SW Germany
Final Report Abstract
Different aspects of element transport and mobility in hydrothermal systems were investigated. The combination of different studies on active and fossil hydrothermal systems with experimental work provides a better understanding of the development of such systems from mobilization of elements in the source aquifers over formation of the hydrothermal minerals to remobilization by post-hydrothermal alteration. Using isotopic and trace element compositions, the source aquifers in an active hydrothermal system in the northern Upper Rhine Graben were constrained and compared to fossil hydrothermal ore deposits in the Schwarzwald. Different concurrent precipitation mechanisms for barite could be identified from the same system. A large scale mixing model is proposed for hydrothermal fluids ascending along the Taunus border fault. It is demonstrated that strontium and barium are derived predominantly from the Variscan basement, whereas NaCl is contributed by shallow sedimentary aquifers. Rare earth element patterns of hydrothermal fluorite from a fluorite-barite deposit (Clara mine, Schwarzwald) were obtained with LA-ICP-MS. Formation constants of Y fluoride complexes at 100-250°C have been determined experimentally to allow interpretation of Y anomalies typically observed in hydrothermal fluorites. It was found that the fluoride speciation of Y differs from that of the REE. Yttrium is complexed as di-fluoride complex at elevated temperatures and fluoride activities, whereas the REE are complexed as mono-fluoride complexes. This difference causes fractionation of the geochemical twin pair Y and Ho. Fractionation of Y and Ho was modeled for hydrothermal fluorite formation using the new thermodynamic data. Rare earth element remobilization during supergene weathering was also investigated in the hydrothermal fluorite-barite deposit Clara. Therefore, primary (fluorite and carbonate) and secondary minerals (fluorite, goethite, Mn oxides, calcite) were investigated as well as water samples from different levels in the mine. The analyses demonstrate that the secondary minerals obtain their REE content from dissolving primary minerals and that this process usually takes place on a small scale (μm to mm). Moreover, unusually high mobility of Ce compared to the other REE was found. This observation can be explained by oxidation of Ce during precipitation of Mn oxides and subsequent complexation of Ce 4+ with siderophores or other siderophore-like organic ligands.
Publications
- (2009) Remobilization of REE in F-rich, low temperature environments. Geochim. Cosmochim. Acta, 73, Suppl., A788
Loges, A., Göb, S., Barth, M., Bau, M., Wagner, T., Markl, G.
- (2009) Trace elements in young fluorites, goethites and Mn oxides. Hallesches Jahrb. Geowiss., 31, 145
Loges, A., Barth, M., Wagner, T., Markl, G.
- (2010) REE fractionation during lowtemperature water-mineral interaction. Geochim. Cosmochim. Acta, 74, Suppl., A628
Loges, A., Göb, S., Barth, M., Bau, M., Wagner, T., Markl, G.
- (2011) Fluoride complexation of yttrium under hydrothermal conditions. Min. Mag. 75, 1353
Loges, A., Migdisov, A. A., Wagner, T., Williams-Jones, A. E., Markl, G.
- (2011) The redistribution of rare-earth elements in secondary minerals of hydrothermal veins, Schwarzwald, southwestern Germany. Can. Mineral., 49, 1305-1333
Göb, S., Wenzel, T., Bau, M., Jacob, D.E., Loges, A., and Markl, G.
- (2012) Element Mobility in Hydrothermal Systems. Dissertation, Universität Tübingen, 137 p.
Loges, A.,
- (2012) Negative Ce anomalies in Mn oxides: The role of Ce 4+ mobility during water–mineral interaction. Geochim. Cosmochim. Acta 86, 296-317
Loges, A., Wagner, T., Barth, M., Bau, M., Göb, S., and Markl, G.
(See online at https://doi.org/10.1016/j.gca.2012.03.017) - (2012) Source and origin of active and fossil thermal spring systems, northern Upper Rhine Graben, Germany. App. Geochem. 27, 1153-1169
Loges, A., Wagner, T., Kirnbauer, T., Göb, S., Bau, M., Berner, Z., and Markl, G.
(See online at https://doi.org/10.1016/j.apgeochem.2012.02.024)
