Spurenelement-Daten von paläozoischen Spiliten aus den Ostalpen und ihre Bedeutung für geotektonische Interpretationen

The Ti, Zr, Y, Cr, Sr and Rb contents of 36 Palaeozoic spilites (pillow lava and sills) from the Karawanken (Austria) have been analysed. During devitrification and metamorphism of the spilites the Ti, Zr, Y and Cr contents have hardly been changed. But Sr and Rb show strong variations caused by secondary alterations. With the help of the Ti, Zr and Cr contents it can be proved that these spilites are differentiation products of alkali olivine basalts (hawaiites, mugearites). The original geotectonic setting of the area in which the spilites erupted, is not known exactly. Two possible interpretations are discussed: The spilites are either similar to hawaiites or mugearites occurring in island arcs on the continental side of deep sea trenches (subcontinental crust, e. g. Japan Sea) or they are similar to hawaiites or mugearites found on ocean islands on the flanks of mid-ocean ridges (oceanic crust). A similarity with continental alkali basalts is less probable because the accompanying sediments and the appearance of the pillow lava seem to suggest that the eruption took place in very deep water.