The Valley of Lakes is approximately a 500-km elongate depression in Central Mongolia, where Eocene to Miocene continental sediments are long known for their outstanding fossil richness. The palaeontological record of this region is an exceptional witness for the evolution of mammalian communities during the Cenozoic global cooling and regional aridification. In order to precisely elucidate the climatic evolution of the region, we studied the mostly siliciclastic sediments with several levels of paleosols for their sedimentology, mineralogy, major and trace element composition and δ13C and δ18O composition. The obtained results show that temperate hydrothermal fluids induced a strong illitization of the fluvial and lacustrine sediments. This finding contradicts the current conceptual view that the fine fraction of the sediments is of aeolian origin. Moreover, the diagenetic growth of illite resulted in a strong overprinting of the sediments and, subsequently, largely disturbed the pristine mineralogical and geochemical composition of the sediments that could have carried any palaeo-climatic information. An exception is the δ13C (and δ18O) isotope values of authigenic carbonate found in calcrete horizons that still record the ambient climatic conditions prevailing during paleosol formation. Our novel δ13C and δ18O record suggests an early Oligocene aridification in Central Asia at ∼31 Ma, whereas the Oligocene glacial maximum shows no increase in aridification. A second, regional-scale aridification occurs at ~25 Ma and corresponds to a late Oligocene marked mammalian turnover in the Valley of Lakes sediments.

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The drainage systems of several tunnels in Austria are heavily clogged with calcite precipitates. Cleaning and water conditioning are cost-intensive for the operating company. The results of the case study Koralm tunnel show that the dissolved calcium in the drainage solutions derives from the ground water and especially from the dissolution of portlandite at the shotcrete. Accordingly, the drainage solutions are often strongly alkaline and as sufficient supersaturation with respect to calcite is reached, calcite precipitates. The carbonate in the calcite sinter is obtained from the ground water or from the absorption of atmospheric CO 2 . Extensive chemical, mineralogical, and isotopic analyses as well as hydrogeochemical modelling permit to decipher the effective parameters in order to develop recommendations for retaliatory action. In-situ experiments in the Koralm tunnel simulate the conditions for the designed drainage system, which should provide an appropriate evaluation of the sinter formation in the drainage and the application of inhibitors. Sinter formation will be reduced by using tailored construction materials. Koralmtunnel als Fallbeispiel für Versinterungen in Dränage-systemen -Ablagerungsmechanismen und GegenmaßnahmenIn den Dränagesystemen mehrer Tunnel in Österreich werden enorme Mengen an Kalzit abgelagert. Die Reinigung und Wasserkonditionierung sind für den Betreiber mit erheblichen Kosten verbunden. In dieser Arbeit konnte anhand der Fallstudie Koralmtunnel gezeigt werden, dass das gelöste Kalzium in dem Dränage-wasser aus dem Bergwasser selbst und insbesondere aus der Auflösung von Portlandit im Spritzbeton bereitgestellt wird. Die so erhaltenen Lösungen sind häufig stark alkalisch. Hierdurch kommt es zu einer Übersättigung an Kalzit, wodurch in weiterer Folge die Abscheidung von Kalzit eingeleitet werden kann. Das Karbonat im Kalksinter kann entweder aus dem Grundwasser oder aus der Absorption von atmosphärischem CO 2 erhalten werden. Durch umfangreiche chemische, mineralogische und isotopenchemische Analysen sowie hydrogeochemische Modellierungen wurden die jeweils wirksamen Faktoren identifiziert, um auf deren Basis Ansätze für Gegenmaßnahmen entwickeln zu können. In-situ-Experimente im Koralmtunnel simulieren die Bedingungen in der geplanten Dränage. Hierüber soll eine Beurteilung der Versinterungen im Dränagesystem und der Anwendung von Inhibitoren ermöglicht werden. Versinterungen werden auch durch den Einsatz maßge-schneiderter Baustoffe verringert werden. IntroductionThe formation of carbonate sinter is a natural phenomenon as well as a challenge in the fields of engineering [3] [4]. Carbonate precipitation in drainage systems may cause serious problems due to the reduction of the cross section of drainage tubes (Figure 1) and the pollution of receiving streams by suspended carbonates and ongoing sinter formation.The Koralm tunnel will be the longest tunnel in Austria and special effort is given to minimize costs for maintenance action such as cleaning of the drainage system and wat...

The formation of secondary sulphate minerals such as thaumasite, ettringite and gypsum is a process causing severe damage to concrete constructions. A major key to understand the complex reactions, involving concrete deterioration is to decipher the cause of its appearance, including the sources of the involved elements. In the present study, sulphate attack on the concrete of two Austrian tunnels is investigated. The distribution of stable sulphur isotopes is successfully applied to decipher the source(s) of sulphur in the deteriorating sulphate-bearing minerals. Interestingly, δ(34)S values of sulphate in local groundwater and in the deteriorating minerals are mostly in the range from+14 to+27 ‰. These δ(34)S values match the isotope patterns of regional Permian and Triassic marine evaporites. Soot relicts from steam- and diesel-driven trains found in one of the tunnels show δ(34)S values from-3 to+5 ‰, and are therefore assumed to be of minor importance for sulphate attack on the concretes. In areas of pyrite-containing sedimentary rocks, the δ(34)S values of sulphate from damaged concrete range between-1 and+11 ‰. The latter range reflects the impact of sulphide oxidation on local groundwater sulphate.