Nature and origin of Palaeozoic volcanic rocks of the Seeberg area (Karawanken/Austria) |
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| Authors: | Dr Jörg Loeschke |
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| Institution: | 1. Institut für Geologie und Pal?ontologie, Sigwartstr. 10, 74 Tübingen
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| Abstract: | In the Seeberg area (Karawanken/Austria) intermediate to acidic pyroclastic rocks of Palaeozoic age are found. These rocks are partly of upper Ordovician age and partly as yet undated. 12 complete chemical analyses of these tuffs and their corresponding modal mineral content are presented. The tuffs differ chemically from the average composition of intermediate to acidic volcanic rocks by their lower alkali and higher H2O and CO2 values. It is assumed that the originally glassy parts of the tuffs took up H2O and CO2 and lost alkalies and possibly also SiO2 during diagenesis and tectonic stress. In addition, two other complete chemical analyses of a basic dyke which cuts across Devonian limestones are given. The dyke has a spilitic mineral content which is of secondary origin. The petrographic character of the analysed tuffs is discussed in comparison with Palaeozoic and Tertiary to recent trachytes, alkali rhyolites and rhyolites. |
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