NJG74-1-04
1994
The rift-related mafic dyke complex of the Rohkunborri Nappe,Indre Troms, northern Norwegian Caledonides
74
1
pp. 35-47

Well-preserved dyke complexes are found within the Seve Nappe Complex, Upper Allochthon, in the easternmost part of Indre Troms, Norway. They form a separate thrust sheet, the Rohkunborri Nappe, and are best exposed in two low-strain units in the Rohkunborri and Njunis areas. In these areas the dolerite swarm intrudes a succession of carbonate rocks and subordinate sandstones, siltstones and quartzites. The sedimentary rocks, the Njunis Group, are supposed to represent the outermost part of the clastic wedge deposited during Neoproterozoic-earliest Palaeozoic time on the thinned outermost part of the Baltoscandian margin. A complex structural evolution can be recognized within the dyke complexes involving early block rotation during intrusion, rotation of both dykes and bedding due to simple shear deformation during thrusting and subsequent imbrication of the dyke complex. The Indre Troms dykes are part of the Neoproterozoic-Early Palaeozoic rifted Baltoscandian margin and represent the transition zone between the continent Baltica and the Iapetus ocean. The Rohkunborri Nappe can be correlated with the Vaivvancohkka Nappe and the Sarektjåkkå Nappe of the Seve Nappe Complex in the northemmost Swedish Caledonides.

Lars Kristian Stølen, Department of Mineralogy and Petrology, Institute of Geology, University of Lund, Solvegatan 13, S- 223 62 Lund, Sweden.

0029-196X