Mafic igneous rocks and mineralisation in the Palaeoproterozoic Ketilidian orogen, South-East Greenland: project SUPRASYD 1996

Abstract

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example:
 Stendal, H., Mueller, W., Birkedal, N., Hansen, E. I., & Østergaard, C. (1997). Mafic igneous rocks and mineralisation in the Palaeoproterozoic Ketilidian orogen, South-East Greenland: project SUPRASYD 1996. Geology of Greenland Survey Bulletin, 176, 66-74. https://doi.org/10.34194/ggub.v176.5064
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 The multidisciplinary SUPRASYD project (1992–96) focused on a regional investigation of the Palaeoproterozoic Ketilidian orogenic belt which crosses the southern tip of Greenland. Apart from a broad range of geological and structural studies (Nielsen et al., 1993; Garde & Schønwandt, 1994, 1995; Garde et al., 1997), the project included a mineral resource evaluation of the supracrustal sequences associated with the Ketilidian orogen (e.g. Mosher, 1995). The Ketilidian orogen of southern Greenland can be divided from north-west to south-east into: (1) a border zone in which the crystalline rocks of the Archaean craton are unconformably overlain by Ketilidian supracrustal rocks; (2) a major polyphase pluton, referred to as the Julianehåb batholith; and (3) extensive areas of Ketilidian supracrustal rocks, divided into psammitic and pelitic rocks with subordinate interstratified mafic volcanic rocks (Fig. 1). The Julianehåb batholith is viewed as emplaced in a magmatic arc setting; the supracrustal sequences south of the batholith have been interpreted as either (1) deposited in an intra-arc and fore-arc basin (Chadwick & Garde, 1996), or (2) deposited in a back-arc or intra-arc setting (Stendal & Swager, 1995; Swager, 1995). Both possibilities are plausible and infer subduction-related processes. Regional compilations of geological, geochemical and geophysical data for southern Greenland have been presented by Thorning et al. (1994). Mosher (1995) has recently reviewed the mineral exploration potential of the region. The commercial company Nunaoil A/S has been engaged in gold prospecting in South Greenland since 1990 (e.g. Gowen et al., 1993). A principal goal of the SUPRASYD project was to test the mineral potential of the Ketilidian supracrustal sequences and define the gold potential in the shear zones in the Julianehåb batholith. Previous work has substantiated a gold potential in amphibolitic rocks in the south-west coastal areas (Gowen et al., 1993.), and in the amphibolitic rocks of the Kutseq area (Swager et al., 1995). Field work in 1996 was focused on prospective gold-bearing sites in mafic rocks in South-East Greenland. Three M.Sc. students mapped showings under the supervision of the H. S., while an area on the south side of Kangerluluk fjord was mapped by H. S. and W. M. (Fig. 4).

Mineral exploration in Greenland in the 1990s

“…Drill-core information indicates a potential for more than 60 000 000 t at an average palladium concentration of 2.5-3 g/t. The best intersections show 5 g/t Pd over 1 m and more than 0.5 g/t over 10 m. 19 As an outcome of the SUPRASYD project in South Greenland 35,37,38,41 all the currently known gold occurrences in the Ketilidian Mobile Belt, e.g. at Nalunaq, Kangerluluk and Niaqornaarsuk (Fig.…”

Geochemical signatures of gold provinces in South Greenland

“…In the Batholith Zone mesothermal gold mineralization occurs along a major shear zone at Niaqornaarsuk peninsula close to the boundary with the Psammite Zone (occurrences 4, 5 and 6 40,41 ). The gold is located in quartz veins in zones of shearing, aplite veining and alteration that transect batholitic granodiorite and amphibolite dykes within the batholith.…”

“…5,19 Mesothermal gold mineralization occurs at several localities within the Psammite Zone. 42 The gold is found in quartz or aplite veins hosted by mafic metavolcanic rocks. The most important is Nalunaq (occurrence 9), which has been investigated at prospect scale.…”

“…Analyses of boulder samples of quartz-and carbonate-veined, epidotized volcanic and sedimentary rocks have returned up to 9 ppm gold and 4% copper. 42 Gardar province A considerable part of the Batholith and Border Zones was subjected to rifting and intrusion of alkaline magmas during the Gardar event (1350-1150 m.y.). Three major phases of rifting have been recognized and intrusions of dyke swarms and central complexes of alkaline syenites and granites are associated with each.…”

“…More sites of gold mineralization were discovered during the Survey's SUPRASYD project (1992-96) 14,15,42 and a much improved understanding of the plate-tectonic setting of South Greenland was obtained during geological mapping, age-dating and structural studies. 12,13 At present, 15 sites of gold mineralization have been identified in South Greenland, and their locations are examined here in relation to element distribution patterns displayed by stream-sediment geochemical maps.…”