The basal gneisses and basement contact of the Hestbrepiggen area, North Jotunheimen, Norway.

Abstract

Pethographic, modal, chemical, X-ray and structural studies have been made on rocks from a mapped area of Basal Gneisses and Basement contact in a glaciated region in the North Jotunheim mountains. Precambrian Basal Gneisses were deposited, intruded by basic bodies, folded about E-W axes, metamorphosed in the almandine-amphibolite faces, pegmatised, intruded by foliated granite, elevated and eroded before the deposition of Eocambrian (and younger) sediments. Subsequently, these sediments were thrust (gravity glided?) from the W-WNW, folded and lineated and metamorphosed in the greenschist facies (Caledonian events.). Retrograde metamorphism of the underlying Basal Gneisses occured at this time. Latterly, the area has been dislocated by tear faults, especially the 40-trending, sinistral, Briedalen tear fault, with which are associated sheared, retrograded, schistose gneisses, quartzite bodies, joints and a quartz-epidote-clinochlore vein mineral assemblage.