Caledonian structural geology and tectonics of East Hinnøy, North Norway.

Abstract

Rocks of east Hinnøy comprise three Caledonian tectonic elements: (1) parautochthonous pre-Caledonian crystalline basement (Lofoten block); (2) allochtonous Precambrian gneisses, probably derived from the Lofoten block, and metasedimentary rocks of the Storvann Group, which are interpreted to represent the Vendian\/Cambrian(?) sedimentary cover of the Lofoten block; and (3) Caledonian cover allochtons (Narvik Group, Stangnes amphibolite and Evenes Group). The Lofoten block probably belonged to the Baltic craton in pre-Cambrian time, and its interpreted to lie presently at a lower structural level than the Caledonian allochtons. Four Caledonian deformation phases are identified. D1 og D2 occurred prior to or synchronous with amphibolite-facies metamorphism, whereas D3 and D4 post-dated the metamorphic peak. D1 emplaced the Caledonian allochtons upon the Lofoten block and at least some of its sedimentary cover (Storvann Group). During D2, thrust sheets were detached from the upper surface of the Lofoten-block basement, imbricating and infolding these sheets together with the structural cover, which comprised both the Storvann Group and the D1 cover allochthons. This resulted in further transport of the composite nappe stack relative in the Lofoten basement. Analysis of minor structures indicates ESE-directed transport during D2. D3 and D4 formed upright to overtuned folds which redeformed the tectonic stack, but probably caused no major tectonic displacement. Cross-foldings during D3 may reflect left-lateral transpression at a late stage of orogenesis, perhaps related to late-to post-orogenic left-lateral movements which have been interferred in other parts of the Appalachian-Caledonian orogen.