A model for stratigraphic and metamorphic inversions at Sulitjelma, central Scandes

Abstract

AbstractThe relationship between disposition of metamorphic isograds and early strain history is examined for the Sulitjelma Fold Nappe of the central Scandes. Evidence for stratigraphic inversion and the widespread inversion of the garnet isograd is reviewed, and new evidence for the nature of early Scandian deformation is presented. A two-stage model is presented which explains the inversions by (i) an initial phase of horizontal compression resulting in crustal thickening by vertical stretching during closure of a marginal basin, followed by (ii) continued horizontal compression and crustal thickening by eastward-directed nappe emplacement. The emplacement of the Sulitjelma Fold Nappe during the latter phase of progressive simple-shear-dominated deformation was accompanied by the development of sheath fold geometries and the overturning of isotherms to produce the widespread inversion of the garnet isograd.