Crustal contaminants in the Permian Oslo Rift, South Norway: constraints from Precambrian geochemistry

During the late Paleozoic Oslo rifting event, the SW part of the Baltic Shi eld was penetrated by mantle-derived magmas from a depleted lithospheric or sublithospheric source. Along the way to their final emplacement, these ma gmas may have interacted with a heterogeneous continental crust, consisting of a mosaic of continental terranes, each with its unique composition and internal crustal history. Information on radiogenic isotope ratios and trac e element distributions in the Precambrian terranes surrounding the rift ca n be used to define characteristic crustal components. These components may be used as endmembers in petrogenetic modelling of the Oslo Rift magmatic system. Based on available data, six endmember components can be identified , and (semi) quantitatively characterized in terms of Sr, Nd and Pb isotope s and selected trace elements. Data on the distribution of rock-types along the rift flanks allow estimates to be made of the relative importance of t he components in different parts of the rift. Combining these data with pet rological information may allow a realistic understanding of crust-magma in teraction in the Oslo Rift magmatic system. (C) 2000 Elsevier Science B.V. All rights reserved.