The Precambrian supracrustal rocks in the Naternaq (Lersletten) and Ikamiut areas, central West Greenland

Abstract

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article.
 Østergaard, C., Garde, A. A., Nygaard, J., Blomsterberg, J., Møller Nielsen, B., Stendal, H., & Thomas, C. W. (1). The Precambrian supracrustal rocks in the Naternaq (Lersletten) and Ikamiut areas, central West Greenland. Geology of Greenland Survey Bulletin, 191, 24-32. https://doi.org/10.34194/ggub.v191.5080
 Naternaq, or Lersletten, in central West Greenland is an extensive Quaternary outwash plain characterised by light grey, silty sediments. Scattered low hills with outcrops of crystalline Precambrian basement rocks protrude from the outwash plain and form the northern part of the Nagssugtoqidian orogen (e.g. Connelly et al. 2000). The prominent Naternaq supracrustal belt, at least 25 km long and up to c. 2 km wide, occurs along the north-western margin of Lersletten, bordered on both sides by Archaean orthogneisses and granitic rocks; the supracrustal rocks outline a major fold structure with an irregular and sporadically exposed hinge zone (Fig. 1). The supracrustal rocks, including the fold closure, exhibit a negative signature on the regional aeromagnetic map (Fig. 2). The belt is known for its disseminated and massive iron sulphide mineralisation with minor copper and zinc, which is common in the south-eastern part of the belt.

Pre-Nagssugtoqidian crustal evolution in West Greenland: geology, geochemistry and deformation of supracrustal and granitic rocks north-east of Kangaatsiaq

“…Supracrustal assemblages are common, and have been mapped in many places in the Kangaatsiaq, Aasiaat and Kangersuneq map sheet areas (Marker et al 1995;Mengel et al 1998;Østergaard et al 2002; van Gool et al 2002a;Garde 2004;Hollis et al 2006, this volume). They are of two main types, either amphibolites or metasedimentary rocks, that may be either aluminous, biotite ± muscovite ± sillimanite ± garnet-bearing metapelites, or quartz-rich, psammitic rocks.…”

“…The age of the supracrustal rocks is, however, poorly constrained. Whilst some of them are of demonstrated Palaeoproterozoic age (c. 1.95 Ga, the Naternaq supracrustal belt, Østergaard et al 2002;Thrane & Connelly 2002, others are likely to be of Archaean age, for instance anatectic metapelites in Saqqarput fjord in the southern part of the Kangaatsiaq map sheet area (Thrane & Connelly 2006, this volume).…”

Evolution of Neoarchaean supracrustal belts at the northern margin of the North Atlantic Craton, West Greenland

“…A Neoarchaean depositional age is furthermore in agreement with the Rb-Sr isotopic data for 12 metasedimentary samples from Ikamiut reported by Kalsbeek & Taylor (1999), which likewise show that their source was Archaean. Finally, the Ikamiut belt has experienced a more complex structural history than the Naternaq supracrustal belt of Palaeoproterozoic age to its south (Østergaard et al 2002;Garde 2004;Thrane & Connelly 2006, this volume). This likewise points to an Archaean age of the Ikamiut belt.…”

²⁰⁷Pb-²⁰⁶Pb dating of magnetite, monazite and allanite in the central and northern Nagssugtoqidian orogen, West Greenland

“…The depositional environment is of a sedimentary type comprising true sediments, submarine volcanic rocks and exhalites. A range of variably altered conformable horizons of very fine-grained siliceous and sulphide rich lithologies associated with either amphibolite or marble are interpreted as volcanogenic-exhalitic rocks (Østergaard et al 2002;Stendal et al 2002).…”