The Ammarnas Complex in the central Scandinavian Caledonides: an allochthonous basin fragment in the foreland of the Sveconorwegian orogen?

作者：Grimmer J C^*; Greiling R O; Gerdes A

来源：Terra Nova, 2011, 23(4): 270-279.

DOI：10.1111/j.1365-3121.2011.01009.x

The Ammarnas Complex is a tectonic unit in the Middle Allochthon of the central Scandinavian Caledonides and consists of several hundred metres of thick uniform meta-grey-wacke successions of greenschist metamorphic grade containing kilometre-scale lenses of pre-Caledonian crystalline basement rocks. Meta-greywacke samples were analysed for major and trace elements and U-Pb isotopes. Lithoclasts and geochemical data indicate that the greywackes were derived from granitic-granodioritic rocks. Detrital zircon dating yielded 7% Neoproterozoic, 52% Mesoproterozoic and 41% Palaeo-proterozoic (207)Pb/(206)Pb ages with two prominent age peaks at 1.64 and 1.5 Ga and a broad distribution of Sveconorwegian (1140-900 Ma) and 'pre-Sveconorwegian' (1340-1140 Ma) ages. We interpret the Ammarnas Complex as a former Neoproterozoic basin in the foreland of the Sveconorwegian orogen, which escaped major pre-Caledonian magmatism-metamorphism and which was most likely deposited between c. 920 and 630 Ma.

• 出版日期2011-8