Nd isotope systematics of 1.8 Ga volcanic rocks within the Transscandinavian Igneous Belt, south-central Sweden

Abstract

Mafic to felsic volcanic rock suites dated at c. 1.8 Ga within the southern part of the Transscandinavian Igneous Belt have been analysed for Sm and Nd isotopes. Primitive, basaltic parts are interpreted to be derived from mildly depleted mantle (DM)-derived magmas with ϵ_Nd values around +2, similar to those for other mafic intrusive rocks of the same age. Felsic-intermediate parts, with somewhat lower initial ϵ_Nd values, probably resulted from a combination of fractional crystallisation of the basaltic magmas and mixing with two different crustal components, one consisting of juvenile felsic material and another of intermediate composition containing somewhat older crustal material. These components were probably of regional importance and may have been involved in the formation of other extrusive and intrusive TIB-1 rocks in southern and central Sweden as well.

Keywords:

• Transscandinavian Igneous Belt
• volcanic rocks
• Sm–Nd isotopes
• active continental margin
• Sweden

Acknowledgements

This work was financed by the Department of Earth Sciences, University of Gothenburg. David Cornell made constructive comments on an earlier version of this manuscript. Marina Fischerström and Hans Schöberg at the Laboratory for Isotope Geology in Stockholm are thanked for help during the isotope work, and Tom Andersen and Stefan Jung for helpful reviews.