Preliminary U-Pb geochronology in the West Troms Basement Complex, North Norway: Archean and Palaeoproterozoic events and younger overprints.

Abstract

This paper reports new U-Pb ages for zircon and titanite in four magmatic units of the West Troms Basement Complex. A granite, present as a megalens within the NNW-trending Senja Shear Belt at the southwestern tip of Kvaløya, yields a zircon age of 2689+-6 Ma showing that the unit is an integral part of the Archean basement in the region rather than a Palaeoproterozoic intrusion. By contrast, a Palaeoproterozoic origin of the Ersfjord granite is well confirmed by a zircon age of 1792+-5 Ma. This age shows at the granite is coveal with the main gemeration of mangerites in Lofoten and formed during one of the dominant plutonic episodes across the Baltic Shield. Zircon in a smaller, late-synkinematic granitic dyke at Oervika yields 1774+-5Ma, indicating that deformation along major NW-SE-striking, block-bounding shear zones of the Senja Shear Belt was in the waning stages at this time.