Tectonic evolution of a Paleoproterozoic diffuse cryptic suture zone in northern Fennoscandia and the correlation of northern Fennoscandia and southern Greenland

Abstract

The boundary between the Karelia and Norrbotten continental blocks in Fennoscandia is a diffuse cryptic suture zone recording c. 200 Ma of tectono-metamorphic evolution between 1.92 and 1.72 Ga. Syn-collisional deposition at 1.92–1.91 Ga was followed by post-collisional deposition at 1.88–1.87 and 1.85–1.84 Ga. The post-collision structural overprint in the suture starts with sinistral movements due to aulacogen inversion (D2) east of the suture. Late-D2 and D orocline extensional stages are followed by NE-vergent basin inversion (D3) of <1.88 Ga rocks and transpressional dextral shear in the suture zone. Nearly orthogonal D4 and D5 deformation events overprint earlier fabrics at c. 1.83 and c. 1.78 Ga, respectively. The youngest (D6, c. 1.73 Ga) structures include sinistral brittle–ductile movements. Northern Fennoscandia and southern Greenland are linked by coeval continent–continent collisions (D1, 1.92–1.89 Ga). The D orocline stage ( c. 1.87 Ga), responsible for oroclinal buckling in central Fennoscandia, is conceivably related to west-directed subduction and subsequent regional shortening in western Greenland. The D3–D4 events in Fennoscandia are comparable to, and the D5–D6 events correlate well with, tectonic events in the suture zone in the eastern Nagssugtoqidian orogen in Greenland. Supplementary material: Analytical methods, data, interpretations of U–Pb data, and structural data on detailed study areas and key locations are available at https://doi.org/10.6084/m9.figshare.c.6675191