Palaeoproterozoic age of a basement gneiss complex in the Charcot Land tectonic window, East Greenland Caledonides

Abstract

The Charcot Land tectonic window exposes crystalline basement gneisses, which form part of the foreland of the East Greenland Caledonides. These gneisses were previously believed to be Archaean in age, on the basis of imprecise K-Ar analyses carried out in the early 1980s on hornblende from amphibolitic bands and inconclusive Rb/Sr isotope data. New U-Pb singlezircon ion microprobe analyses on the gneisses of the window yield upper intercept ages of 1916 ± 21 and 1928 ± 11 Ma, and are interpreted to represent the age of crystallisation of the igneous protolith. The foreland gneisses of the Charcot Land window are similar in age to parts of the allochthonous gneiss complexes of structurally overlying thrust sheets, but the two terranes have different lithological and structural characteristics. No Archaean rocks have been identified with certainty in any of the East Greenland Caledonian foreland windows.

U–Pb zircon geochronology and tectonostratigraphy of southern Liverpool Land, East Greenland: Implications for deformation in the overriding plates of continental collisions

“…Furthermore, zircons from the Tvaerdal complex orthogneisses indicate protolith magmatic ages of ~1670 Ma, which coincide with ~1660 Ma zircon inheritance in a Tvaerdal complex eclogite that is interpreted to represent the original timing of mafic dike emplacement (Augland, 2007). Protolith ages younger than 1750 Ma have not been found elsewhere in Greenland, and the basement gneisses of North-East Greenland, the NSTS, HBTS and the Foreland are exclusively Paleoproterozoic-Archean (Thrane, 2002;Thrane, 2004;Kalsbeek et al, 2008). The ~1670-1660 Ma protolith ages from the Tvaerdal complex are more similar to Gothian plutonism from 1690 to 1630 Ma that is widespread throughout the Western Gneiss Region of Norway (Tucker et al, 1990;Skår, 2000;Austrheim et al, 2003), and once again suggests a direct correlation between the Tvaerdal complex and the western margin of Baltica.…”

Discovery of an Eo-Meso-Neoarchean terrane in the East Greenland Caledonides

“…The Gletscherland orthogneisses are also exposed within the Niggli Spids thrust sheet structurally beneath Krummedal sequence, and are likely correlative to the Hjørnedal rocks. Furthermore, these Archean rocks within the East Greenland Caledonides are apparently isolated from the Archean rocks of the Greenland shield by Paleoproterozoic basement gneisses exposed in the parautochthonous foreland Thrane, 2004). Taken together, the EGAD can be characterized as an isolated Meso-Neoarchean terrane that includes fragments of Eoarchean crust, is relatively undisturbed by Paleoproterozoic events, and stretches a minimum of 300 km along the coast of East Greenland (Fig.…”