Abstract: The properties of sandstones are strongly affected by formation of minerals in the pore space during diagenesis. In many sandstones, quartz overgrowths are the most important pore-filling cements and show a characteristic trace element composition. The most important impurities are Al, Li, H and Ge. The Al concentration of quartz may reach up to several 1000 µmol mol −1 and is assumed to reflect the composition of the porewater. Geochemical modelling of the activity ratio of Al and Si revealed a minimum at nearly neutral to slightly acid conditions. This minimum shifts to lower pH with increasing temperatures. Due to complexing, organic acids may strongly affect the Al solubility especially in acidic water at low temperatures. There is a linear correlation between Al and Li, indicating their incorporation in a combined [AlO 4 |Li] centre. Since Li only accounts for 10–30% of the Al concentration, the remaining Al needs to be balanced by H. The ratio of Li/H-compensated Al centres seems to depend on the Li activity and the pH in the aqueous solution. Germanium concentrations in quartz cements are slightly higher than the crustal average and they show a weak correlation with Al. The excess of Ge in authigenic quartz requires pre-enrichment, probably by formation of kaolinite. Possible applications of trace element analyses of authigenic quartz include discrimination of different sources that contribute to the supply of silica, enhanced understanding of inhomogeneities that are related to cementation and possible tracking of fluid migration.

Abstract The career of the Austrian-born landscape painter Eugene von Guérard (1811–1901) was defined by his travels, which took him to Italy and Germany in the 1830s and 1840s and to Australia and New Zealand between 1852 and 1882. Today he is recognized as one of Australia’s greatest nineteenth-century landscape painters. His formative years coincided with the emergence of geology as an independent scientific discipline and a growing awareness in the wider community of the role played by volcanic activity and other geological processes in the formation of the Earth’s geomorphology. This new understanding was particularly pertinent to landscape painters, whose very subject was the form of the land; in Germany, where von Guérard trained and worked between 1838 and 1852, its relevance for landscape painters was emphasized by the influential natural scientist Alexander von Humboldt and the scientist, landscape painter and art theorist Carl Gustav Carus. They argued that the artist should paint from a geologically informed perspective. Von Guérard’s interest in volcanic geology was sparked by his experiences in southern Italy, consolidated in Germany on expeditions through the Harz and Eifel regions and then fully realized in response to the landscapes of southeastern Australia. Through his informed portrayal of sites of geological significance in each hemisphere and through the cultural value invested in them as a consequence of his depiction of them, von Guérard epitomized that recently conceived construct: the geotourist.