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New geochemical, isotopic and age data from igneous rocks complement earlier models of a long-lived and complex accretionary history for East African Orogen lithologies north of the Blue Nile in western Ethiopia, but throw doubt on the paradigm that ultramafic complexes of the region represent ophiolites and suture zones. Early magmatism is represented by a metavolcanic sequence dominated by pyroclastic deposits of predominantly basaltic andesite composition, which give a Rb-Sr wholerock errorchron of 873 ± 82 Ma. Steep REE patterns and strong enrichments of highly incompatible trace elements are similar to Andean-type, high-K to medium-K calc-alkaline rocks; ε Nd values between 4.0 and 6.8 reflect a young, thin continental edge. Interlayered basaltic flows are transitional to MORB and compare with mafic rocks formed in extensional, back-arc or inter-arc regimes. The data point to the significance of continental margin magmatism already at the earliest stages of plate convergence, in contrast with previous models for the East African Orogen. The metavolcanites overlap compositionally with the Kilaj intrusive complex dated at 866 ± 20 Ma (U-Pb zircon) and a related suite of dykes that intrude thick carbonate-psammite sequences of supposedly pre-arc, continental shelf origin. Ultramafic complexes are akin to the Kilaj intrusion and the sediment-hosted dykes, and probably represent solitary intrusions formed in response to arc extension. Synkinematic composite plutons give crystallization ages of 699 ± 2 Ma (Duksi, U-Pb zircon) and 651 ± 5 Ma (Dogi, U-Pb titanite) and testify to a prolonged period of major (D 1 ) contractional deformation during continental collision and closure of the 'Mozambique Ocean'. The plutons are characterized by moderately peraluminous granodiorites and granites with ε Nd values of 1.0-2.0. They were coeval with shoshonitic, latitic, trachytic and rare trachybasaltic intrusions with very strong enrichments of highly incompatible trace elements and ε Nd of 0.4-8.0. The mafic end-member is ascribed to partial melting of enriched sub-continental mantle that carried a subduction component inherited from pre-collision subduction. Contemporaneous granodiorite and granite formation was related to crustal underplating of the mafic magmas and consequent melting of lower crustal material derived from the previously accreted, juvenile arc terranes of the East African Orogen.

The Karasjok Greenstone Belt of the northwestern Baltic/Fennoscandian Shield forms the westernmost unit in a Palaeoproterozoic tectonic belt, recording crustal mobilization, tectonic reworking and metamorphism of the Archaean and Palaeoproterozoic lithosphere during a 2.1-1.7-Ga tectonic episode. In northern Norway, this 100 km-wide tectonic belt consists of linear segments of highly strained rocks that are separated by N-S-striking thrust zones. The lowest unit, the Karasjok Greenstone Belt, consists of lowto medium-grade volcanogenic and sedimentary rocks. Excellent exposures in the northern part of the greenstone belt reveal a continuous lithostratigraphic section towards the core of a major recumbent synform, which is related to the regional D 1 deformation episode. This episode is responsible for transposition of primary features and formation of an east-dipping penetrative foliation and banding, with a well-developed east-plunging stretching lineation. Major D 1 shear zones, marked by mylonites and blastomylonites, are found (i) locally at the base of the belt, (ii) at high tectonostratigraphic levels, and (iii) at the upper boundary of the greenstone belt. Shear-sense indicators support west-directed displacement along the thrusts. The superimposed D 2 episode is evident as eastplunging folds, whereas a major D 2 thrust with top-to-the-SSW shear occurs near the base of the greenstone belt. The younger D 3 episode is manifested by N-S-trending folds of the former (D 1 and D 2 ) structures. All fold systems are truncated by steep NE-SWstriking brittle faults of D 4 affinity. The polyphase deformation seen in the Karasjok Greenstone Belt supports a model in which the assembling of the Karasjok Greenstone Belt, the Tanaelv Migmatite Complex and the Levajok Granulite Complex occurred from major orogen-normal E-W contraction (collision) during the D 1 episode. At this stage the greenstone belt was isoclinally folded and welded to overlying units during west-directed overthrusting of the medium-to high-grade complexes. From then on the greenstone belt acted as a basal detachment zone. The D 2 episode of NNE-SSW shortening and SSW-directed thrust emplacement suggest dextral and orogen-oblique movement patterns, prior to continued orogen-perpendicular E-W shortening during the D 3 episode. The final faulting (D 4 ) may relate to a post-orogenic, shield-scale strike-slip event.

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