Isotopic dating of very early Precambrian amphibolite facies gneisses from the Godthaab district, West Greenland

1971 ◽  
Vol 12 (3) ◽  
pp. 245-259 ◽  
Author(s):  
Oxford isotope geology laboratory ◽  
L.P. Black ◽  
N.H. Gale ◽  
S. Moorbath ◽  
R.J. Pankhurst ◽  
...  
Keyword(s):  
Amphibolite Facies ◽  
Isotopic Dating ◽  
Early Precambrian ◽  
West Greenland

A Discussion on the evolution of the Precambrian crust - The early Precambrian gneisses of the Godthåb district, West Greenland

1973 ◽  
Vol 273 (1235) ◽  
pp. 343-358 ◽  
Keyword(s):  
Amphibolite Facies ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Early Precambrian ◽  
West Greenland ◽  
Metasedimentary Rocks ◽  
Parent Rocks

Intensely metamorphosed and deformed basic dykes, the Ameralik dykes, have been used to divide the amphibolite-facies gneisses of the Godthåb district into the Amitsoq gneisses (older) and the Nuk gneisses. Metavolcanic and metasedimentary rocks (the Malene supracrustals), and stratiform meta-anorthosites are also present and are probably younger than the Amitsoq gneisses, but are older than the Nuk gneisses. The Amitsoq gneisses contain abundant fragments of Ameralik dykes. They appear to have been derived from homogeneous granitic (s.l.) parents, but most of them have been intensely reworked before and/or after the intrusion of the Ameralik dykes and are now banded gneisses. They range from dioritic to granitic in composition and potassic varieties are common. Isotopic data indicate that the parent rocks of the gneisses were emplaced or metamorphosed about 3750 Ma ago. Ameralik dykes are absent from the Nuk gneisses, which are the most abundant rocks in the area. These gneisses are derived from intrusive calc-alkaline parents, mainly tonalites and granodiorites, and represent a massive addition of granitic material to this level of the crust about 3080 Ma ago, after the first supracrustal rocks had been laid down.

scholarly journals Mapping in the Fiskefjord area, southern West Greenland

1982 ◽  
Vol 110 ◽  
pp. 55-57
Author(s):  
A.A Garde ◽  
V.R McGregor
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
Isotopic Age ◽  
Supracrustal Rock ◽  
Granulite Facies Metamorphism ◽  
West Greenland ◽  
Facies Metamorphism ◽  
Geological Work ◽  
Age Determinations

Previous geological work on the 1:100000 map sheet 64 V.l N (fig. 15) includes published maps of smaller areas by Berthelsen (1960, 1962) and Lauerma (1964), mapping by Kryolitselskabet Øresund A/S (Bridgwater et al., 1976) and mapping by GGU geologists for the 1:500000 map sheet Frederikshåb Isblink - Søndre Strømfjord (Allaart et al., 1977, 1978). The Amltsoq and Niik gneisses and Malene supracrustal rock units south and east of Godthåbsfjord have not so far been correlated with rocks in the Fiskefjord area. Godthåbsfjord separates the granulite facies gneisses in Nordlandet from amphibolite facies Nûk gneisses on Sadelø and Bjørneøen; the granulite facies metamorphism occurred at about 2850 m.y. (Black et al., 1973), while no published isotopic age determinations from the Fiskefjord area itself are available.

scholarly journals Palaeomagnetic sampling of basic dykes and remnant magnetisation studies on old gneisses from West Greenland

1973 ◽  
Vol 55 ◽  
pp. 28-28
Author(s):  
W.F Fahrig
Keyword(s):  
Field Work ◽  
Geological Survey ◽  
Early Precambrian ◽  
Correlation Parameter ◽  
West Greenland

A joint programme has been embarked upon with the Geological Survey of Canada to use the palaeomagnetism of basic dykes as a possibie correlation parameter between rocks of north-eastem Canada and those of West Greenland. As part of this, programme field work during the summer was concentrated within the early Precambrian craton of West Greenland where sampling of Precambrian basic dykes was undertaken in three areas, namely the Fiskenæsset, Søndre Strømfjord and Godthåb areas.

scholarly journals Fe-Ti oxides in the Malene supracrustals and the occurrence of Nb-rich rutile

1983 ◽  
Vol 112 ◽  
pp. 83-94
Author(s):  
R.F Dymek
Keyword(s):  
Amphibolite Facies ◽  
Fe2o3 Content ◽  
West Greenland ◽  
Ti Oxides

Data are presented on Fe-Ti oxide compositions and assemblages in Malene supracrustal rocks from the Godthåb District and surrounding territory, West Greenland. Amphibolite facies samples contain ilmenite ± rutile, in which the ilmenite has a low Fe2O3-content (

scholarly journals Field mapping of Bjørneøen and the adjacent coast of Nordlandet, Godthåbsfjord, southern West Greenland

1975 ◽  
Vol 75 ◽  
pp. 58-62
Author(s):  
P.R James
Keyword(s):  
East Coast ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Field Mapping ◽  
West Greenland ◽  
Structural Relationships ◽  
Field Season ◽  
The Relationship

Mapping at a scale of 1:50 000 was carried out on the gneisses and supracrustals of Bjørneøen and the granulites of the adjacent east coast of Nordlandet; the area has previously been described by Noe-Nygaard & Ramberg (1961) and Bridgwater & McGregor (1974). During the present study special emphasis was placed on the structural relationships of the various rock units and also on the relationship and contact between the amphibolite facies and granulite facies areas. A short excursion was made at the beginning of the field season around Godthåbsfjord and Arneralik with the helpful guidance of V. R. McGregor whose kind assistance is especially acknowledged.

scholarly journals Stratigraphy and structural development of the Precambrian rocks in the area north-east of Disko Bugt, West Greenland

1967 ◽  
Vol 13 ◽  
pp. 1-28
Author(s):  
A Escher ◽  
M Burri
Keyword(s):  
Transition Zone ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Structural Development ◽  
West Greenland ◽  
Precambrian Rocks ◽  
The Third ◽  
North East ◽  
Area North

The Precambrian rocks in the area north-east of Disko Bugt can be divided into a lower gneiss group and an upper supracrustal group. The lower part of the supracrustal group consists of quartzites, amphibolites and garnet-staurolite schists, while the upper part is mainly semipelitic schist. The gneisses were affected by three successive phases of deformation, while in the supracrustals only the two latest phases of folding can be recognized. Evidence is given in support of the idea that the supracrustals were deposited on a gneiss basement after the first phase of folding, the basement being later reactivated mainly during the third and last deformation. Two main tectonic compLexes can be distinguished in the area mapped: a southern complex characterized by a predominarit ENE direction of the fold axes and a northern complex in which the main fold axes are strongly curved around a central gneiss dorne. The transition zone between the southern and northern complex is marked by the presence of severaL important faults and mylonites. The gneiss dorne is flanked in its northern part by a thick granite sheet. The dorne structure appears to have been forrned by a combination of diapiric movements and the interference between two successive deformations. The gneisses and lower supracrustals recrystallized under amphibolite facies conditions, while greenschist facies conditions prevaiLed during the recrystallisation of the upper supracrustals.

scholarly journals Stratabound scheelite and stratiform tourmalinites in the Archaean Malene supracrustal rocks, southern West Greenland

1987 ◽  
Vol 156 ◽  
pp. 1-26
Author(s):  
P.W.U Appel ◽  
A.A Garde
Keyword(s):  
West Coast ◽  
Stream Sediment ◽  
Amphibolite Facies ◽  
The West ◽  
Late Archaean ◽  
Sea Floor ◽  
West Greenland ◽  
Sediment Sampling ◽  
Geological Map ◽  
Boron Complexes

The Malene supracrustal rocks form large enclaves in the late Archaean Nûk gneisses within an area of at least 36 000 km2 on the west coast of Greenland and have been repeatedly deformed and metamorphosed under amphibolite facies conditions. Stream sediment sampling has shown that scheelite occurs in the supracrustal enclaves throughout the area. It occurs stratabound in amphibolites, micaceous quartzites, siliceous cordierite-bearing metasediments and tourmalinites. A detailed geological map has been made of the central part of Store Malene mountain close to Nuuk. Banded metavolcanic Malene amphibolites and siliceous cordierite-bearing metasediments contain stratiform tourmalinites, often with appreciable scheelite, in addition to common accessory tourmaline. The tourmaiinites predate the earliest recognisable phase of deformation as well as prominent simple pegmatites. The tourmaline probably originated as primary sea floor precipitates, and the primary or diagenetic tourmaline crystals were later overgrown with tourmaline during metamorphism. The scheelite and tourmaline are probably syngenetic and of submarine exhalative origin, and boron complexes may have played a role in transporting tungsten in hot brines.

scholarly journals Dykes and deformation in the Ikertoq zone of the Nagssugtoqidian at S0ndre Str0mfjord Airport, West Greenland

1984 ◽  
Vol 32 ◽  
pp. 101-106
Author(s):  
I. van der Molen
Keyword(s):  
Amphibolite Facies ◽  
Two Stage ◽  
West Greenland

The geology of the southern part of the Nagssugtoqidian of W Greenland is examined in a traverse of the amphibolite facies Ikertoq zone at S0ndre Str0mfjord Airport. The continuous fanning of the foliation, shallow· dips near the Archaean - Nagssugtoqidian boundary and steeper dips further north, is not indicative of a two-stage history for the zone. The structures of the deformed Kangamiut dykes and the gneisses in which they occur have been studied in some detail. It is concluded that deformation synchronous with and postdating the intrusion of the dykes has been intense enough to rejuvenate the fabric of the gneisses to a post-intrusive age.

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