Intrusive age and geochemistry of the Kebne Dyke Complex in the Seve Nappe Complex, Kebnekaise Massif, arctic Sweden Caledonides

Abstract

The Seve Nappe Complex of the Scandinavian Caledonides is predominately metamorphosed rift-related igneous and sedimentary rocks formed during Rodinia breakup in the Neoproterozoic. The Kebne Dyke Complex of the Kebnekaise Massif, arctic Sweden, is one such unit within the Seve Nappe Complex and is mostly composed of dolerite dykes metamorphosed and thrust onto Baltica during the Caledonian orogeny. Structurally adjacent to the dyke complex are geochemically similar amphibolites that have a common origin as the metadolerite dykes. Collectively, these rocks have transitional mid-ocean ridge basalt geochemistry similar to correlative Seve Nappe Complex rocks to the north (Indre Troms dykes) and south (Sarek Dyke Swarm). U–Pb single-crystal chemical abrasion–thermal ionization mass spectrometry of zircon from a metagabbro and a metagranitoid, showing co-mingling magmatic textures with the metadolerite, produced 11 concordant analyses with 206Pb/238U ages ranging from 608 to 596 Ma, which includes the magmatic age of the dyke complex. These results support the idea that the Kebne Dyke Complex, Sarek Dyke Swarm and Indre Troms dykes constitute the tholeiitic continent–ocean transition subdivision within the Seve Nappe Complex. However, the Kebne Dyke Complex differs from the Sarek Dyke Swarm and Indre Troms dykes as it is the least enriched among these, nearly lacks rift-related metasedimentary rocks, and may be younger than the Sarek Dyke Swarm by up to 14 Myr.