Long-term convergence along SW Fennoscandia:330 m.y. of Proterozoic crustal growth [Precam Res 161 (2008) 452-472] (DOI:10.1016/j.precamres.2007.09.007)

• Published in: Precambrian Research
• Main Authors: Åhäll, Karl Inge, Connelly, James N.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2008
• Subjects: Convergent margin; Crustal growth; Fennoscandia; Idefjorden terrane; Proterozoic; Sweden; U-Pb geochronology
• Online Access: https://curis.ku.dk/portal/da/publications/longterm-convergence-along-sw-fennoscandia(2f087c13-e107-4be6-98b8-a8e77442196a).html; https://doi.org/10.1016/j.precamres.2008.02.002; http://www.scopus.com/inward/record.url?scp=43049164321&partnerID=8YFLogxK

The core of Fennoscandia formed during Svecofennian 1.91-1.86 Ga orogenesis that included amalgamation of Archean micro-continents in the northeast and extensive arc accretionary growth toward the southwest. Post-Svecofennian crustal growth persisted southwestwards and later westwards, mainly by subduction-related magmatism that lasted another ∼330 m.y. By integrating mapping and geochemistry with new U-Pb geochronology from 31 igneous and 4 metasedimentary rocks in the Idefjorden terrane, we have defined major growth-related crustal units in this southwestern segment of Fennoscandia. Available constraints permit definition of nine lithotectonically distinct, semi-continuous stages of crustal growth between 1850 and 1522 Ma. The first stages included 1.85 Ga continental arc magmatism along the southwestern Svecofennian margin and recurring, 1.83-1.82 Ga growth further south. Voluminous continental arc magmatism at 1.81-1.77 Ga (TIB 1 rocks) and 1.72-1.66 Ga (TIB 2-3 rocks) resulted in large batholithic domains with a high proportion of rejuvenated material. The sixth stage (∼1.66 Ga) marks a transition in the south from continental arc magmatism to island arc magmatism that created the Horred supracrustal rocks. After accretion of the Horred sequence, a seventh magmatic stage (1.63-1.59 Ga) represents the return to a fully continental arc system. A short-lived eighth stage (∼1.59 Ga) returned to an oceanic arc system represented by an early package of volcano-sedimentary Stora Le-Marstrand formation rocks (SLM 1). Accreted SLM 1 rocks were intruded by stage nine rocks (1.59-1.52 Ga) that represent the last convergent arc magmatism in the Idefjorden terrane. A younger ca. 1.57-1.55 Ga package of volcano-sedimentary Stora Le-Marstrand formation rocks (SLM 2) is recognised in the Koster segment, demonstrating a return to an oceanic arc system in the north, coeval with continued continental arc magmatism in the south. This near-continuous, oceanward-stepping growth of Fennoscandia over this 330 m.y. period ...