scholarly journals Tectonostratigraphic terranes within Archaean gneiss complexes: examples from Western Australia and southern West Greenland

1991 ◽  
Vol 39 ◽  
pp. 199-211
Author(s):  
Allen P. Nutman
Keyword(s):  
Western Australia ◽  
Field Work ◽  
Ion Microprobe ◽  
Late Archaean ◽  
West Greenland ◽  
Tectonic Processes ◽  
Gneiss Complex ◽  
Northwestern Margin ◽  
Geological Boundaries ◽  
Orogenic Belts

New field work and isotopic data show that the Godthabsfjord region of West Greenland consists of a collage of tectonostratigraphic terranes, which evolved separately prior to tectonic juxtaposition in the late Archaean. In Western Australia the Narryer Gneiss Complex, which lies on the northwestern margin of the Yilgarn Craton, is, unlike the Godthabsfjord region, very poorly exposed (less than 1 % ). In consequence it is impossible to follow geological boundaries in this complex, and instead the complex has been studied by a very extensive use of within-grain zircon U-Pb geochronology on the ion microprobe SHRIMP. The zircon geochronology suggests that the Narryer Gneiss Complex also consists of several discrete terranes of early to mid Archaean gneisses. In both the Godthabsfjord region and the Narryer Gneiss Complex, late Archaean juxtaposition of terranes was accompanied by intrusion of crustally­derived granites, deformation, and amphibolite facies metamorphism. Thus some Archaean high grade gneiss complexes consist of terranes that underwent independent evolution until they were brought together at a later time. In this respect their anatomy resembles post-Archaean orogenic belts that formed as a consequence of plate tectonic processes.

scholarly journals The Archaean gneiss complex of northern Labrador A review of current results, ideas and problems

1991 ◽  
Vol 39 ◽  
pp. 153-166
Author(s):  
D. Bridgwater ◽  
L. Schiøtte
Keyword(s):  
Major Part ◽  
Granulite Facies ◽  
High Grade ◽  
Late Archaean ◽  
West Greenland ◽  
Metamorphic History ◽  
Gneiss Complex ◽  
History Of ◽  
Augen Gneiss ◽  
Dominant Phase

1. The early Archaean rocks in northern Labrador can be subdivided into the ea. 3.78 Ga Nulliak supracrus­tal association, the migmatitic Uivak I gneisses, the dominant phase of which was emplaced at ea. 3.73 Ga, and the Uivak II augen gneiss. Inherited low-U rounded inclusions within igneous zircons in the Uivak I gneisses have ages between 3.73 and 3.86 Ga and are more likely to have been derived from a pre-existing high-grade metamorphic gneiss complex than from the Nulliak association. In the early Archaean there were probably several rapid cycles of sedimentary deposition and volcanism followed by emplacement of major plutons. Mid Archaean gneisses are more abundant in northern Labrador than previously realised. The late Archaean metamorphic history of these gneisses is different from the history of the early Archaean gneisses. Whereas an important part of the mid Archaean suite was emplaced in granulite facies and retrogressed at the time of granitoid veining at ea. 2.99 Ga, the major part of the early Archaean rocks were reworked under granulite facies conditions in a sequence of closely spaced events between 2. 7 and 2.8 Ga. The two groups of gneisses had different metamorphic histories until ea. 2.7 Ga, but late and post-tectonic granites of 2.5- 2. 7 Ga age cut across both. It is suggested that the terrane model in southern West Greenland can be extended to Labrador and that tectonic intercalation of early and mid Archaean gneisses took place around 2.7 Ga. Correlation between the Maggo gneisses around Hopedale, mid Archaean gneisses in northernmost Labrador and gneisses from the Akia terrane in West Greenland is suggested. Like the Malene supracrustals in West Greenland the Upernavik supracrustals in Labrador are composite associations, the youngest of which are thought to have been deposited around 2. 7 Ga.

scholarly journals Noritic rocks and associated nickel-copper-sulphide occurrences in Sukkertoppen district, central West Greenland

1983 ◽  
Vol 115 ◽  
pp. 30-34
Author(s):  
K Secher
Keyword(s):  
Mineral Resources ◽  
Field Work ◽  
General Description ◽  
Copper Sulphide ◽  
West Greenland ◽  
Gneiss Complex ◽  
Nickel Copper ◽  
Geophysical Investigations ◽  
Geochemical Investigation ◽  
Rock Suite

Field work in 1982 included detailed mapping and collection of samples of sulphide occurrences in the so called 'norite belt', Sukkertoppen district. Several nickel-copper-sulphide mineralisations related to norite rocks are known from the work of Kryolitselskabet Øresund A/S who mapped this rock suite and carried out exploratory investigations of the sulphides (Nielsen, 1976). The earlier mapping has revealed a suite of metabasic plutonic rocks of mainly noritic composition which are situated in an arcuate belt, approximately 15 x 75 km, curving around the Finnefjeld gneiss complex east of Sukkertoppen (fig. 8). Metanorites are embedded in quartzo-feldspathic gneisses and rarely in amphibolitic rocks, and they occur as a series of irregular pods up to 6 km Iong within the arcuate belt. The present investigation was carried out as part of GGU's mineral resources mapping and evaluation programme in central West Greenland, which this year focussed on the area covered by the 1:250000 map sheet 65 V.2. The fieId work was carried out in dose cooperation with teams doing systematic reconnaissance geochemical stream-sediment and water sampling (to be discussed elsewhere), detailed soil geochemical investigation (Jensen & Secher, this report) and experimental geophysical investigations (Thorning, this report). The present work aimed at a general description of the structure and the metallogenetic behaviour of the known norite-related sulphide occurrences in order to reach an understanding of the mineral genesis within this section of the Archaean environment.

scholarly journals Border relations between the amphibolite facies Finnefjeld gneiss complex and granulite facies grey gneisses in the Fiskefjord area, southern West Greenland

1988 ◽  
Vol 140 ◽  
pp. 49-54
Author(s):  
M Marker ◽  
A.A Garde
Keyword(s):  
Granulite Facies ◽  
Field Work ◽  
Geological Mapping ◽  
Amphibolite Facies ◽  
The South ◽  
West Greenland ◽  
South Eastern ◽  
Gneiss Complex ◽  
Eastern Boundary ◽  
The 1950S

The authors carried out geological mapping in August 1987 at the south-eastern boundary of the Finnefjeld gneiss complex around 65°N. The field work was supported by the GGU cutter 'J. F. Johnstrup'. Based on reconnaissance mapping in the 1950s Berthelsen (1951, 1957,1962) divided the Archaean gneiss terrain in the southem Sukkertoppen district between Godthåbsfjord and Søndre Isortoq into three major tectonic units: the Nordland, the Finnefjeld and the Alangua complexes. This division was also followed by Noe-Nygaard & Ramberg (1961).

scholarly journals Malene stratigraphy and late Archaean structure: new data from Ivisârtoq, inner Godthåbsfjord, southern West Greenland

1986 ◽  
Vol 130 ◽  
pp. 74-85
Author(s):  
B Chadwick
Keyword(s):  
Field Work ◽  
Main Thrust ◽  
Late Archaean ◽  
West Greenland ◽  
Preliminary Results ◽  
Critical Areas ◽  
Basaltic Magmas ◽  
Bad Weather ◽  
The University

This report summarises the principal results of a six-week study of some critical areas in Ivisârtoq (part of the Ivisârtoq region, 65 V. 2 Nord; fig. 1) by a two-man expedition (the writer and his undergraduate assistant) during the summer of 1985, a period of exceptionally good weather. Our objective was to complete the field programme of a team from the University of Exeter (Chadwick et al., 1983; Brewer et al., 1984) which had been seriously disrupted by bad weather in 1983. The main thrust of the field work in 1985 was to investigate the geometry of the late Archaean system of dornes of gneisses and intervening synclinal cusps of Malene supracrustal rocks which dominates the structure of Ivisârtoq (figs 1,2). The fjeld mapping revealed important new details, not only of the structure but also of the Malene stratigraphy and the emplacement of granitic and basaltic magmas during the development of the system of dornes and synclines. Systematic geological investigations in the Ivisårtoq region began in 1976 (Allaart et al., 1977) and important contributions have been made by Hall & Friend (1979, 1983), Hall (1980, 1981) and Friend et al. (1981). Some preliminary results of investigations by the Exeter team have been reported by Brewer et al. (1984), Chadwick (1985), and Coe & Robertson (1984). Details of isotopic ages and petrogenesis of the gneisses and late Arehaean granites have been reported by Robertson (1985, in press).

scholarly journals Mapping of the Isukasia sheet, southern West Greenland

1983 ◽  
Vol 115 ◽  
pp. 20-29
Author(s):  
A.A Garde ◽  
R.P Hall ◽  
D.J Hughes ◽  
S.B Jensen ◽  
A.P Nutman ◽  
...  
Keyword(s):  
Field Work ◽  
Late Archaean ◽  
West Greenland ◽  
North East ◽  
The North ◽  
Base Camp ◽  
Geophysical Investigations ◽  
Set Up

Field work for the Isukasia map sheet north of Godthåbsfjord, started in 1981 (Allaart et al., 1982), was continued in 1982. A tent base camp was set up at the fjord Kangiussaq both summers. In 1982 seventeen fjeld teams and the glaciological station Qamanârssup sermia were supplied from the base by the GGU cutter J. F. Johnstrup and by a Jet Ranger helicopter based in Kangiussaq. Twelve mapping geologists worked on the two map sheets Ivisartoq and Isukasia, and five teams carried out ore geological, geochemical and geophysical investigations (see Appel, Chadwick et al., Jensen & Secher, and Secher, this volume). The field work was carried out from June 20th to August 28th. The Isukasia map sheet is situated north-east of the head of Fiskefjord, around the lake Taserssuaq. To the east it is bounded by the Inland lee, from which the glacier Sarqap sermia enters Taserssuaq. Most of the area is a lake strewn, undulating plateau at elevations between 500 and 800 m. Outcrops are generally good aIthough there are some Quaternary boulder fields, the largest of whieh extends over some 25 km2 in the north-east corner of the map sheet. The north-north-east trending Ataneq fauIt zone (see below), which oeeurs some 25 km east of Taserssuaq, separates an area of early Archaean rocks (induding the Isua supracrustals) from rocks to its west of probable late Archaean age. The younger rocks make up the bulk of the Isukasia map sheet.

Ketilidian structure and the rapakivi suite between Lindenow Fjord and Kap Farvel, South-East Greenland

2000 ◽  
pp. 50-59
Author(s):  
Brian Chadwick ◽  
Adam A. Garde ◽  
John Grocott ◽  
Ken J.W. McCaffrey ◽  
Mike A. Hamilton
Keyword(s):  
Coastal Region ◽  
Field Work ◽  
Natural Environment Research Council ◽  
East Greenland ◽  
The North ◽  
Tectonic Processes ◽  
Field Investigations ◽  
North Eastern ◽  
Bad Weather ◽  
North Eastern Part

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Chadwick, B., Garde, A. A., Grocott, J., McCaffrey, K. J., & Hamilton, M. A. (2000). Ketilidian structure and the rapakivi suite between Lindenow Fjord and Kap Farvel, South-East Greenland. Geology of Greenland Survey Bulletin, 186, 50-59. https://doi.org/10.34194/ggub.v186.5215 _______________ The southern tip of Greenland is underlain by the Palaeoproterozoic Ketilidian orogen (e.g. Chadwick & Garde 1996; Garde et al. 1998a). Field investigations in the summer of 1999 were focused on the structure of migmatites (metatexites) and garnetiferous granites (diatexites) of the Pelite Zone in the coastal region of South-East Greenland between Lindenow Fjord and Kap Farvel (Figs 1, 2). Here, we first address the tectonic evolution in the Pelite Zone in that region and its correlation with that in the Psammite Zone further north. Then, the structure and intrusive relationships of the rapakivi suite in the Pelite Zone are discussed, including particular reference to the interpretation of the controversial outcrop on Qernertoq (Figs 2, 8). Studies of the structure of the north-eastern part of the Julianehåb batholith around Qulleq were continued briefly from 1998 but are not addressed here (Fig. 1; Garde et al. 1999). The field study was keyed to an interpretation of the Ketilidian orogen as a whole, including controls of rates of thermal and tectonic processes in convergent settings. Earlier Survey field work (project SUPRASYD, 1992–1996) had as its principal target an evaluation of the economic potential of the orogen (Nielsen et al. 1993). Ensuing plate-tectonic studies were mainly funded in 1997–1998 by Danish research foundations and in 1999 by the Natural Environment Research Council, UK. The five-week programme in 1999 was seriously disrupted by bad weather, common in this part of Greenland, and our objectives were only just achieved. Telestation Prins Christian Sund was the base for our operations (Fig. 2), which were flown with a small helicopter (Hughes MD-500).

Upernavik 98: reconnaissance mineral exploration in North-West Greenland

1999 ◽  
pp. 39-45 ◽  
Author(s):  
Bjørn Thomassen ◽  
Johannes Kyed ◽  
Agnete Steenfelt ◽  
Tapani Tukiainen
Keyword(s):  
Mineral Exploration ◽  
Mining Industry ◽  
Field Work ◽  
Geological Survey ◽  
Original Series ◽  
West Greenland ◽  
North West ◽  
One Year

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Thomassen, B., Kyed, J., Steenfelt, A., & Tukiainen, T. (1999). Upernavik 98: reconnaissance mineral exploration in North-West Greenland. Geology of Greenland Survey Bulletin, 183, 39-45. https://doi.org/10.34194/ggub.v183.5203 _______________ The Upernavik 98 project is a one-year project aimed at the acquisition of information on mineral occurrences and potential in North-West Greenland between Upernavik and Kap Seddon, i.e. from 72°30′ to 75°30′N (Fig. 1A). A similar project, Karrat 97, was carried out in 1997 in the Uummannaq region 70°30′–72°30′N (Steenfelt et al. 1998a). Both are joint projects between the Geological Survey of Denmark and Greenland (GEUS) and the Bureau of Minerals and Petroleum (BMP), Government of Greenland, and wholly funded by the latter. The main purpose of the projects is to attract the interest of the mining industry. The field work comprised systematic drainage sampling, reconnaissance mineral exploration and spectroradiometric measurements of rock surfaces.

Mantle xenoliths from Tertiary lavas and dykes on Ubekendt Ejland, West Greenland

1998 ◽  
pp. 152-154
Author(s):  
Stefan Bernstein ◽  
C. Kent Brooks
Keyword(s):  
Field Work ◽  
Mantle Xenoliths ◽  
Alkaline Basalt ◽  
Basalt Flow ◽  
Volcanic Province ◽  
East Greenland ◽  
Original Series ◽  
West Greenland ◽  
Ultramafic Xenoliths ◽  
Extensive Collection

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Bernstein, S., & Brooks, C. K. (1998). Mantle xenoliths from Tertiary lavas and dykes on Ubekendt Ejland, West Greenland. Geology of Greenland Survey Bulletin, 180, 152-154. https://doi.org/10.34194/ggub.v180.5099 _______________ Mantle xenoliths were found in Tertiary alkaline (basanitic) lavas on Ubekendt Ejland in West Greenland in the mid 1970s by J.G. Larsen. Microprobe analyses of olivine, pyroxene and spinel in two mantle xenoliths, suggested that the xenoliths on Ubekendt Ejland are highly depleted and have high modal olivine contents, and low modal orthopyroxene and clinopyroxene (Larsen 1982). In this respect the mantle xenoliths from Ubekendt Ejland are very similar to the spinel harzburgites from Wiedemann Fjord, in the Tertiary volcanic province of East Greenland (Brooks & Rucklidge 1973; Bernstein et al. 1998). Larsen (1981) also reported dykes containing mantle nodules and a varied suite of cumulates and megacrysts, one of which has subsequently been dated to 34.1 ± 0.2 Ma (Storey et al. 1998) The basalt flow that carries the xenoliths is from what is defined as the Erqua Formation which occurs at the top of the lava succession in western Ubekendt Ejland (Fig. 1; Drever & Game 1948; Larsen 1977a, b). The basalts have not been dated, but are younger than 52.5 Ma, which is the date obtained for the underlying formation (Storey et al. 1998). During July 1997, we spent three weeks collecting xenoliths and prospecting for xenolith-bearing dykes in the Uummannaq district of central West Greenland. The field work resulted in an extensive collection of xenoliths from an alkaline basalt flow described by Larsen (1977a, b), as well as the discovery of a dyke carrying a large number of ultramafic xenoliths of various origins. 

Qaanaaq 2001: mineral exploration reconnaissance in North-West Greenland

2002 ◽  
pp. 133-143
Author(s):  
Bjørn Thomassen ◽  
Peter R. Dawes ◽  
Agnete Steenfelt ◽  
Johan Ditlev Krebs
Keyword(s):  
Mineral Exploration ◽  
Mining Industry ◽  
Field Work ◽  
Original Series ◽  
West Greenland ◽  
North West ◽  
Ice Caps ◽  
High Plateau ◽  
Set Up ◽  
Inland Ice

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Thomassen, B., Dawes, P. R., Steenfelt, A., & Krebs, J. D. (2002). Qaanaaq 2001: mineral exploration reconnaissance in North-West Greenland. Geology of Greenland Survey Bulletin, 191, 133-143. https://doi.org/10.34194/ggub.v191.5141 _______________ Project Qaanaaq 2001, involving one season’s field work, was set up to investigate the mineral occurrences and potential of North-West Greenland between Olrik Fjord and Kap Alexander (77°10´N – 78°10´N; Fig. 1). Organised by the Geological Survey of Denmark and Greenland (GEUS) and the Bureau of Minerals and Petroleum (BMP), Government of Greenland, the project is mainly funded by the latter and has the overall goal of attracting the interest of the mining industry to the region. The investigated region – herein referred to as the Qaanaaq region – comprises 4300 km2 of ice-free land centred on Qaanaaq, the administrative capital of Qaanaap (Thule) municipality. Much of the region is characterised by a 500–800 m high plateau capped by local ice caps and intersected by fjords and glaciers. High dissected terrain occurs in Northumberland Ø and in the hinterland of Prudhoe Land where nunataks are common along the margin of the Inland Ice.

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