The Early Proterozoic Karasjok Greenstone Belt, Norway. A preliminary description of lithology, stratigraphy and mineralization.

Abstract

The Karasjok Greenstone Belt of Finnmark, Norway, is a sequence of medium-grademetmorphic supracrustal rocks in the northernmost part of the Baltic Shield.Regional mapping has revealed a tectonostratigraphy with the greenstone beltresting on Archaean sialic basement, dipping away under the Tanaelv MigmaticComplex with the Levajok Granulite Complex on top. Major thrust zones separatethe lowermost part of the greenstone belt, the clastic Skuvvanvarri Formation,from the mixed volcanic-sedimentary Iddjajav'ri Group. High grade thrust zonesalso separate the migmatic and granulitic complexes feom the greenstone belt.Pyroclastic komatiites constitute an important part of the Issjaja'ri Group,suggesting volcanism in a shallow-water environment. A plate-tectonic conceptis applied to describe the evolution of the greenstone belt which is probablyof Earth to Middle Proterozoic age. Mineralizations within the Karasjok Green-stone Belt are classified and briefly described. Thw two most important typesare manganiferous banded iron-formations of Algoma type and large low-gradedisseminated copper-gold mineralizations of uncertain origin.