Mesoproterozoic continental growth: U–Pb–Hf–O zircon record in the Idefjorden Terrane, Sveconorwegian Orogen

• Novel U–Pb, O and Hf isotopic data, from the Idefjorden Terrane are presented.
• A refined model of crustal growth of the Idefjorden Terrane is suggested.
• The Idefjorden Terrane formed in a predominantly retreating arc system.
• Our data opens for a possible Sveconorwegian amalgamation of the Idefjorden Terrane.

The Idefjorden Terrane of the Sveconorwegian Orogen, Fennoscandia, is known to be an area of comparatively juvenile Mesoproterozoic continental growth. Here we provide an improved model of crustal growth based on new coupled zircon U–Pb–O–Lu–Hf isotopic data on thirteen samples of mafic to intermediate plutonic rocks from different domains of the Idefjorden Terrane. The new data support a retreating volcanic arc system, with shorter pulses of accretion. A gradual increase of radiogenic Hf (mean ɛHf from 3.5 to 5.4) in plutonic rocks intruded between ca. 1630 Ma and 1560 Ma reflects an increase in juvenile mantle-derived magma in the genesis of the plutonic suites. This trend is consistent with development of an extensional back-arc rift geotectonic setting, accommodating deposition of the Stora Le-Marstrand greywacke dominated metasediment sequence. Combined isotopic information and the detrital zircon record of the Stora Le-Marstrand Formation support the interpretation that the Idefjorden Terrane was separated from the Fennoscandian Shield before the Sveconorwegian Orogeny.