The geochemistry, genesis, and geotectonic setting of Proterozoic mafic dyke swarms in southern and central Sweden
Title:
The geochemistry, genesis, and geotectonic setting of Proterozoic mafic dyke swarms in southern and central Sweden
Author:
Solyom, Zoltan Lindqvist, Jan-Erik Johansson, Ingrid
Appeared in:
GFF
Paging:
Volume 114 (1992) nr. 1 pages 47-65
Year:
1992-03-10
Contents:
Ideas on the genesis and magmatectonic setting of three prominent Proterozoic, Grenvillian mafic dyke swarms in southern and central Sweden are presented. Two of the linear dyke swarms are associated with the Protogine Zone, a zone currently interpreted as a taphrogenic complex. The third dyke swarm represents very extensive mafic magmatism in central Sweden and forms large sheets and feeder dykes. The first two consist of the c. 1180 Ma old alkaline Protogine Zone Dolerite Group (PZDG) and the early Late Proterozoic, Late Grenvillian c. 930 Ma old Blekinge Dalarna Dolerite Group (BDDG), composed of olivine and quartz tholeiites. The third consists of the c. 1220 Ma old weakly alkaline to transitional Central Scandinavian Dolerite Group (CSDG). Petrogenetic modelling of the REE distribution patterns of the dyke swarms indicates partial batch melting followed by fractional crystallization. It is shown that the dyke swarms have been generated by low to moderate degrees of partial melting of a garnet-Iherzolitic mantle. The emplacement of the mafic dyke swarms can be interpreted as a response to the early stage of continental rifting in the Baltic Shield. Similarities in age, geochemistry, and geotectonic setting indicate a linkage between the CSDG and PZDG of Sweden and the Abitibi and Sudbury dyke swarms of Canada. The BDDG, on the other hand, has age equivalence to the c. 900 Ma old Borden and Kingston swarms in Canada.