East Greenland Caledonides—an extension of the British Caledonides

Abstract

Summary The major part of the Caledonian fold belt in East Greenland comprises gneiss complexes, which in the south have yielded Archaean and early Proterozoic isotopic ages; their features may be compared to those of the Scourian and Laxfordian divisions of the Lewisian. They are overlain by middle Proterozoic supracrustal sequences, which in some areas are involved in migmatitic activity and granite emplacement of Grenville age; parallels may be drawn with events recorded in the Morar Division of the Moine in Scotland, and in Ireland with those in the Annagh gneiss complex in N Mayo and perhaps in the Ox Mountains sequence. The late Precambrian lower Eleonore Bay Group is similar in development to the Grampian Group (Dalradian) of the British Isles, and the upper Eleonore Bay Group bears comparison with the Appin Group of the Dalradian. The Vendian glacial event is well represented in both regions. The early Palaeozoic succession in Greenland shows marked similarities with the Durness Limestone succession. The pattern of Caledonian deformation, metamorphism and plutonic activity show many similarities but also differences. The marked marginal thrust zone in the west of the E Greenland fold belt is the logical continuation of the Moine thrust belt. Late Palaeozoic continental deposits overlie Caledonian folded units in both regions.

Resistance of zircons to U–Pb resetting in a prograde metamorphic sequence of Caledonian age in East Greenland

“…Thus, these rocks have the typical characteristics of the Krummedal supracrustal sequence (Higgins et al 198 1) but are considered in this study to be in structural continuity with the lower EBG succession. Caledonian metamorphism has affected all the formations of the East Greenland fold belt: witness the majority of mineral ages (372-510 Ma total range in Higgins and Phillips 1979). The main phase of Caledonian metamorphism is dated by granite emplacement ages at between 475 and 400 Ma ago (Steiger et al 1979).…”

The offshore continuation of the Moine Thrust north of Shetland as deduced from basement isotopic ages

“…1 and 2), Shetland (Pringle 1970;Flinn et al 1979) and in the intervening offshore areas (Brewer and Smythe 1984;Andrews 1985), is not continuous with the western thrust belt margin observed on east Greenland, as favoured by many workers (e.g. Nicholson 1979;Shackleton 1979;Higgins and Phillips 1979;Hanisch 1984;Brewer and Smythe 1984). The Scotland-Norway cratonic basement block would effectively separate the east and west margins of the Caledonian orogenic fold belt (Fig.…”

Scandian-Acadian-Caledonian sensu strictu metamorphism in the age range 430–360 Ma

“…It exposes the apparent western margin of the Caledonide orogen, as does the NW part of the British Isles (Higgins & Phillips 1979) which lie 600 km to the south in a palaeogeographic reconstruction (Figs 1 and 2).…”

“…As discussed by Hailer (1971) and Higgins & Phillips (1979), Caledonian metamorphism and deformation overprinted one or more preCaledonian episodes in rocks ranging from Archaean and Proterozoic gneiss complexes to Cambro-Ordovician sediments, and it is difficult to separate the relative effects of the different episodes. Many of the deeper levels of the fold belt seem to be characterized by amphibolitefacies metamorphism, but the metamorphic grade decreases rapidly upward.…”