scholarly journals Descriptive text to the Geological map of Greenland, 1:100 000, Kangaatisiaq 68 V.1 Syd and Ikamiut 68 V.1 Nord

2010 ◽  
pp. 1-41
Author(s):  
Adam A. Garde ◽  
Julie A. Hollis
Keyword(s):  
Sea Water ◽  
Ocean Floor ◽  
Iron Formation ◽  
Second Phase ◽  
Banded Iron Formation ◽  
Mafic Dykes ◽  
West Greenland ◽  
North East ◽  
Basement Rocks ◽  
Supracrustal Belt

The two adjacent Kangaatsiaq and Ikamiut map sheets cover a coastal area of central West Greenland in the northern part of the Palaeoproterozoic Nagssugtoqidian orogen. The map area is part of the Aasiaat domain, which almost entirely consists of Neoarchaean orthogneisses with intercalated metamorphosed volcano-sedimentary belts. The Aasiaat domain was partially reworked during the Nagssugtoqidian orogeny, but Palaeoproterozoic components are restricted to mafic dykes, the ≤1904 ± 8 Ma (2σ) Naternaq supracrustal belt east of Kangaatsiaq, and remnants of a c . 1850 Ma Palaeoproterozoic ocean-floor – arc-trench association on small islands north-east of Aasiaat. Undated, lithologically similar rocks occur on Hunde Ejlande north of Aasiaat. The Archaean volcano-sedimentary belts are up to 2 km thick and comprise fine-grained mafic and minor, intermediate amphibolite of ex- and intrusive origin, gabbro, leucogabbro-anorthosite, and biotite-garnet schist with common sillimanite pseudomorphs after andalusite. The c . 2.8 Ga Archaean orthogneiss is largely tonalitic besides minor dioritic and granodioritic components, and preserves intrusive relationships with some of the supracrustal belts. Sheet-like bodies of late-kinematic crustal melt granites are up to about 10 km in length and 2 km thick. One of these has yielded a zircon Pb-Pb age of 2748 ± 19 Ma (2σ). Up to kilometre-thick units of quartzo-feldspathic and locally garnet-bearing paragneisses also occur, some of which are younger than the orthogneisses. The Aasiaat domain has undergone two Archaean orogenic episodes, separated by injection of mafic dykes and sedimentation at its margins. Archaean deformation resulted in kilometre-scale, tight to isoclinals folds refolded by upright to overturned folds, and its southern part reached granulite facies P–T conditions with widespread partial melting. The Aasiaat domain also underwent heating during the Nagssugtoqidian orogeny, but only its northern part was tectonically reworked, resulting in an intense E–W- to NNE–SSW-trending structural grain associated with subhorizontal extension lineation. The Palaeoproterozoic Naternaq supracrustal belt in the eastern part of the Kangaatsiaq map area has a complex synformal structure and displays a prominent structural discordance against the underlying Archaean rocks; the belt also contains a second phase of SE-plunging, overturned folds. The Palaeoproterozoic ocean-floor – arc trench association on islands north-east of Aasiaat comprises pillow lava, manganiferous chlorite schist, chert, banded iron formation, graded aluminous schist, and siliceous sandstone, and points to the existence of a palaeosuture in this area. A Palaeogene picritic sill complex and a small exposure of sandstone form the c . 15 km long island group of Kitsissunnguit / Gronne Ejland in the north-eastern Ikamiut map area. Two contem-poraneous, N–S-trending mafic dykes were emplaced into the basement rocks south-west of the islands. One of these was hydraulically chilled and fractured during its emplacement, presumably due to contact with meteoric or sea water. Widespread hydrothermal alteration occurs along faults and joints in the basement rocks in the northern archipelago. The alteration may have been caused by circulation of magmatically heated meteoric or sea water during the development of the Cretaceous–Paleocene basalt province in West Greenland. No deposits of economic interest have been found in the Archaean rocks within the map area. A massive sulphide deposit in the Naternaq supracrustal belt was discovered and explored in the 1960s by Kryolitselskabet Oresund A/S, and a VHMS-style copper-gold-zinc mineralisation was reported in 2004 from Kitsissuarsuit / Hunde Ejlande by a local inhabitant. The potential for ornamental rocks is largely unexplored.

Descriptive text to the Geological map of Greenland, 1:100 000, Kangaatisiaq 68 V.1 Syd and Ikamiut 68 V.1 Nord

2010 ◽  
pp. 1-41
Author(s):  
Adam A. Garde ◽  
Julie A. Hollis
Keyword(s):  
Sea Water ◽  
Ocean Floor ◽  
Iron Formation ◽  
Second Phase ◽  
Mafic Dykes ◽  
West Greenland ◽  
North East ◽  
Basement Rocks ◽  
Supracrustal Belt ◽  
Geological Map

NOTE: This Map Description was published in a former series of GEUS Bulletin. Please use the original series name when citing this series, for example: Garde, A. A., & Hollis, J. A. (2010). Descriptive text to the Geological map of Greenland, 1:100 000, Kangaatisiaq 68 V.1 Syd and Ikamiut 68 V.1 Nord. Geological Survey of Denmark and Greenland Map Series 5, 1-41. https://doi.org/10.34194/geusm.v5.4580 _______________ The two adjacent Kangaatsiaq and Ikamiut map sheets cover a coastal area of central West Greenland in the northern part of the Palaeoproterozoic Nagssugtoqidian orogen. The map area is part of the Aasiaat domain, which almost entirely consists of Neoarchaean orthogneisses with intercalated metamorphosed volcano-sedimentary belts. The Aasiaat domain was partially reworked during the Nagssugtoqidian orogeny, but Palaeoproterozoic components are restricted to mafic dykes, the ≤1904 ± 8 Ma (2σ) Naternaq supracrustal belt east of Kangaatsiaq, and remnants of a c. 1850 Ma Palaeoproterozoic ocean-floor – arc-trench association on small islands north-east of Aasiaat. Undated, lithologically similar rocks occur on Hunde Ejlande north of Aasiaat. The Archaean volcano-sedimentary belts are up to 2 km thick and comprise fine-grained mafic and minor, intermediate amphibolite of ex- and intrusive origin, gabbro, leucogabbro-anorthosite, and biotite-garnet schist with common sillimanite pseudomorphs after andalusite. The c. 2.8 Ga Archaean orthogneiss is largely tonalitic besides minor dioritic and granodioritic components, and preserves intrusive relationships with some of the supracrustal belts. Sheet-like bodies of late-kinematic crustal melt granites are up to about 10 km in length and 2 km thick. One of these has yielded a zircon Pb-Pb age of 2748 ± 19 Ma (2σ). Up to kilometre-thick units of quartzo-feldspathic and locally garnet-bearing paragneisses also occur, some of which are younger than the orthogneisses. The Aasiaat domain has undergone two Archaean orogenic episodes, separated by injection of mafic dykes and sedimentation at its margins. Archaean deformation resulted in kilometre-scale, tight to isoclinals folds refolded by upright to overturned folds, and its southern part reached granulite facies P–T conditions with widespread partial melting. The Aasiaat domain also underwent heating during the Nagssugtoqidian orogeny, but only its northern part was tectonically reworked, resulting in an intense E–W- to NNE–SSW-trending structural grain associated with subhorizontal extension lineation. The Palaeoproterozoic Naternaq supracrustal belt in the eastern part of the Kangaatsiaq map area has a complex synformal structure and displays a prominent structural discordance against the underlying Archaean rocks; the belt also contains a second phase of SE-plunging, overturned folds. The Palaeoproterozoic ocean-floor – arc trench association on islands north-east of Aasiaat comprises pillow lava, manganiferous chlorite schist, chert, banded iron formation, graded aluminous schist, and siliceous sandstone, and points to the existence of a palaeosuture in this area. A Palaeogene picritic sill complex and a small exposure of sandstone form the c. 15 km long island group of Kitsissunnguit / Gronne Ejland in the north-eastern Ikamiut map area. Two contem-poraneous, N–S-trending mafic dykes were emplaced into the basement rocks south-west of the islands. One of these was hydraulically chilled and fractured during its emplacement, presumably due to contact with meteoric or sea water. Widespread hydrothermal alteration occurs along faults and joints in the basement rocks in the northern archipelago. The alteration may have been caused by circulation of magmatically heated meteoric or sea water during the development of the Cretaceous–Paleocene basalt province in West Greenland. No deposits of economic interest have been found in the Archaean rocks within the map area. A massive sulphide deposit in the Naternaq supracrustal belt was discovered and explored in the 1960s by Kryolitselskabet Oresund A/S, and a VHMS-style copper-gold-zinc mineralisation was reported in 2004 from Kitsissuarsuit / Hunde Ejlande by a local inhabitant. The potential for ornamental rocks is largely unexplored.

Biological Fe oxidation controlled deposition of banded iron formation in the ca. 3770Ma Isua Supracrustal Belt (West Greenland)

2013 ◽  
Vol 363 ◽  
pp. 192-203 ◽  
Author(s):  
Andrew D. Czaja ◽  
Clark M. Johnson ◽  
Brian L. Beard ◽  
Eric E. Roden ◽  
Weiqiang Li ◽  
...  
Keyword(s):  
Iron Formation ◽  
Banded Iron Formation ◽  
West Greenland ◽  
Fe Oxidation ◽  
Supracrustal Belt ◽  
Controlled Deposition

A new volcanic province: evidence from glacial erratics in western North Greenland

2000 ◽  
pp. 35-41 ◽  
Author(s):  
Peter R. Dawes ◽  
Bjørn Thomassen ◽  
T.I. Hauge Andersson
Keyword(s):  
Volcanic Rocks ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Common Component ◽  
Volcanic Province ◽  
North West ◽  
North East ◽  
The North ◽  
Surficial Deposits ◽  
North Greenland

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Dawes, P. R., Thomassen, B., & Andersson, T. H. (2000). A new volcanic province: evidence from glacial erratics in western North Greenland. Geology of Greenland Survey Bulletin, 186, 35-41. https://doi.org/10.34194/ggub.v186.5213 _______________ Mapping and regional geological studies in northern Greenland were carried out during the project Kane Basin 1999 (see Dawes et al. 2000, this volume). During ore geological studies in Washington Land by one of us (B.T.), finds of erratics of banded iron formation (BIF) directed special attention to the till, glaciofluvial and fluvial sediments. This led to the discovery that in certain parts of Daugaard-Jensen Land and Washington Land volcanic rocks form a common component of the surficial deposits, with particularly colourful, red porphyries catching the eye. The presence of BIF is interesting but not altogether unexpected since BIF erratics have been reported from southern Hall Land just to the north-east (Kelly & Bennike 1992) and such rocks crop out in the Precambrian shield of North-West Greenland to the south (Fig. 1; Dawes 1991). On the other hand, the presence of volcanic erratics was unexpected and stimulated the work reported on here.

scholarly journals Early (3700 Ma) Archaean rocks of the Isua supracrustal belt and adjacent gneisses

1983 ◽  
Vol 112 ◽  
pp. 5-22
Author(s):  
A.P Nutman ◽  
D Bridgwater ◽  
E Dimroth ◽  
R.C.O Gill ◽  
M Rosing
Keyword(s):  
Amphibolite Facies ◽  
Iron Formation ◽  
Ultramafic Rocks ◽  
Banded Iron Formation ◽  
Sedimentary Structures ◽  
The North ◽  
Gneiss Complex ◽  
Supracrustal Belt ◽  
Silicate Rocks

A coherent stratigraphy is recognised in the highly deformed, amphibolite facies early Archaean Isua supracrustal belt. The supracrustal belt consists of layered rocks (in which sedimentary structures are locally preserved), ultramafic rocks and units of garbenschiefer (a massive Mg-Al rich, leucoamphibolite). The layered supracrustal rocks form two sequences, which are separated from each other tectonically. When folding is taken into account, these sequences are now less than 200 m thick. Sequence A forms most of the belt. In it there is a transition upwards from predominantly layered amphibolites with banded iron formation horizons to calc-silicate rocks, carbonates and layered felsic metasediments. Sequence B is restricted to the western edge of the eastern part of the supracrustal belt. It changes upwards from predominantly layered felsic metasediments to ferromagnesian mica schists. The supracrustal belt is regarded as a thin fragment from a thicker, more extensive volcanosedimentary pile. The early Archaean gneisses adjacent to the supracrustal belt consist of early multiphase tonalites which were first intruded by mafic dioritic dykes and then by granitic sheets. The granitic sheets were originaIly horizontal to gently inciined and form up to 40 per cent of the gneiss complex. Interdigitation of supracrustal rocks and gneisses in the Isukasia area is due to both the style of intrusion ofthe gneisses and to tectonic intercalation. Archaean basic dykes that cut the supracrustal belt and adjacent gneisses are ofseveral generations. Within and south of the supracrustal belt they are generally strongly deformed and have been recrystallised under amphibolite facies conditions; but in the north of the area they are generally better preserved. The dykes cut across several generations of structures in the supracrustal belt and the adjacent gneisses.

scholarly journals Further work on the early Archaean rocks of the Isukasia area, southern West Greenland

1982 ◽  
Vol 110 ◽  
pp. 49-54
Author(s):  
A.P Nutman
Keyword(s):  
Field Work ◽  
Regional Mapping ◽  
West Greenland ◽  
North East ◽  
The North ◽  
Starting Point ◽  
Supracrustal Belt ◽  
Geochemical Studies

Work in 1981 on the early Archaean rocks of the Isukasia area (Ailaart, 1976) was an integral part of GGU's mapping programme of northern Godthåbsfjord, Fiskefjord and adjacent areas to the north-east. Within the Isukasia area, there was dose co-operation with Minik Rosing who was making detailed studies of certain aspects of the Isua supracrustal belt. The object of this summer's field work was to complete the study of the supracrustal belt and the central gneisses that was started last year (Nutman et al., in press), and to see as much as possibIe of the gneisses between the supracrustal belt and 65°N (fig. 18). For the mapping of the supracrustal belt, manuscript maps drawn by J. H. Allaart were an invaluable starting point. Besides regional mapping, detailed studies were made of the nature of the lithological units and the relationships between them; see Table 4 for chronology. Suites of rocks were collected for isotopic and geochemical studies. In connection with this, H. Baadsgaard spent 10 days working with the author in the area, as a guest of GGu. The results reported here supplement those given by Nutman et al. (in press).

scholarly journals The early Archaean to Proterozoic history of the Isukasia area, southern West Greenland

1986 ◽  
Vol 154 ◽  
pp. 1-80
Author(s):  
A.P Nutman
Keyword(s):  
Volcanic Rocks ◽  
Amphibolite Facies ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Stratigraphic Sequence ◽  
Supracrustal Belt ◽  
History Of ◽  
High Grade Metamorphism ◽  
Polyphase Metamorphism ◽  
Chemical Sediments

The c. 3800 Ma Isua supracrustal belt and associated smaller bodies of supracrustal rocks are intruded by >3600 Ma orthogneisses. A coherent stratigraphic sequence is recognised consisting of interlayered metabasic rocks, metasediments derived from volcanic rocks, chemical sediments, and metabasic and ultramafic intrusions. Despite repeated deformation and high-grade metamorphism sedimentary structures are locally preserved. The depositional environment was probably an immersed volcanic region remote from areas of significantly older crust. Conglomeratic structures in a metachert and banded iron formation unit suggest shoaling and shallow water conditions. Felsic sediments locally preserve evidence of deposition from turbidite flows. The Isua supracrustal rocks are regarded as thin fragments of a thicker, more extensive sequence. The orthogneisses that intrude the supracrustal rocks consist of 3750-3700 Ma multiphase tonalites (the grey gneisses) which were first intruded by the basic Inaluk dykes, then by abundant shallow-dipping swarms of c. 3600 Ma granite sheets (the white gneisses) and finally by c. 3400 Ma pegmatitic gneiss sheets. These early Archaean rocks were metamorphosed under amphibolite facies conditions and repeatedly deformed prior to intrusion of the Tarssartôq basic dykes in the mid Archaean. In the late Archaean (3100-2500 Ma) there was polyphase metamorphism up to amphibolite facies grade and two or more stages of deformation and local intrusion of granitic gneiss sheets and pegmatites. However, despite general strong deformation there is a large augen of low deformation preserved within the arc of the Isua supracrustal belt. During the Proterozoic there was intrusion of basic dykes, major faulting with associated recrystallisation under uppermost greenschist to lowermost amphibolite facies conditions, followed by heating and intrusion of acid dykes at c. 1600 Ma. No profitable mineralisations have been located.

Early Archaean Isua supracrustal belt,West Greenland: pilot study of the Isua Multidisciplinary Research Project

1998 ◽  
pp. 94-99 ◽  
Author(s):  
Peter W. U. Appel ◽  
Christopher M. Fedo ◽  
Stephen Moorbath ◽  
John S. Myers
Keyword(s):  
Pilot Study ◽  
Minor Component ◽  
Science Research ◽  
Pilot Project ◽  
Multidisciplinary Research ◽  
Research Project ◽  
West Greenland ◽  
North East ◽  
Gneiss Complex ◽  
Supracrustal Belt

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Appel, P. W. U., Fedo, C. M., Moorbath, S., & Myers, J. S. (1998). Early Archaean Isua supracrustal belt,West Greenland: pilot study of the Isua Multidisciplinary Research Project. Geology of Greenland Survey Bulletin, 180, 94-99. https://doi.org/10.34194/ggub.v180.5092 _______________ The Isua belt of 3.8–3.7 Ga metavolcanic and metasedimentary rocks, is located 150 km north-east of Nuuk, within the Archaean gneiss complex of West Greenland. Most of this gneiss complex consists of late Archaean rocks with a minor component of early Archaean age, including the oldest known supracrustal rocks on Earth. The Isua belt contains the best preserved of the oldest supracrustal components and is therefore of vital importance in providing information on the oldest known terrestrial environments and a prospective locality in which to search for the earliest traces of life on Earth (Mojzsis et al. 1996). The Isua Multidisciplinary Research Project (IMRP) aims to coordinate a reinvestigation of the geology of the Isua belt and adjacent tonalitic gneisses with a broad-based, diversely skilled, international research team. IMRP is supported by the Danish Natural Science Research Council, the Commission for Scientific Research in Greenland and the Minerals Office of the Greenland Government (from 1998, the Bureau of Minerals and Petroleum). The project began in 1997 with a pilot study of the north-east sector of the Isua belt to test the feasibility of reinvestigating the early Archaean geology on the basis of new mapping. Five weeks of field work were carried out by a core of four geologists (P.W.U.A, C.M.F., S.M., J.S.M.) augmented by visits of shorter duration by G. Arrhenius, A. Hofmann, V.R. McGregor, S. Mojzsis, R.K. O’Nions and H.K. Schønwandt. This report outlines the geological background to the current study and the results of the 1997 pilot project.

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