The Kvanefjeld area is situated in the northernmost part of the nimaussaq intrusion. The area represents a section through the roof zone of this intrusion. The roof is composed of sandstone, basaltic lavas, sheets of gabbro and dykes of dolerite and trachyte. Large masses of anorthosite are also found in the roof zone, The oldest members of the intrusion are augite syenite and alkali syenite which together with large masses of naujaite (poikilitic sodalite syenite) are enclosed in various types of fine-grained lujavrite. The lujavrite also intrudes the lavas of the roof. The bodies and veins of lujavrite are mainly located in zones of deformation in the rocks of the roof zone. The lavas of the roof are strongly altered in contact with the lujavrite and are locally enriched in epistolite-murmanite minerals. The latest member of the intrusion is a medium- to coarsegrained lujavrite which forms sheets and veins in most of the abovementioned rocks. The earlier fine-grained lujavrites and the contactmetasomatized lavas have concentrations of steenstrupine, monazite and thorite (?) in contact with the medium- to coarse-grained lujavrite and may contain up to 0.3 % U and three to four times this amount of thorium. This mineralization has been studied by mineralogical, geochemical and radiometric methods and in a number of drill holes. Analcime-rich veins rich in niobium and beryllium minerals are of widespread occurrence. The present paper gives a preliminary account of the geology of this region with special reference to the structural geology. A detailed examination of the economic geology of the Kvanefjeld area is currently being undertaken.
The geological setting of organic remnants from well preserved Ketilidian rocks of SW Greenland is presented. The absolute age (2000? m. y.) of the rocks is discussed and compared to that of other regions. Many types of organic remnants have been found in these low-metamorphic rocks. Most of the organic remnants are microscopic globules and fragments with cell-like structures. The type which is best preserved is a complex globular structure on about 1/2mm in diameter. This structure is established as a new monotypic form genus Vallenia erlingi (Raunsgaard Pedersen) n. gen. et sp. Stromatolithes and other macro-structures of possible organic origin are also found. A coal-graphite layer indicates that large-scale accumulation of organic matter has taken place. The organic remnants are so well preserved that it has been possible to extract small amounts of paraffines (n-C11 to n-C31 with maximum about n-C18 to n-C20) and other organic compounds. The carbon-isotope composition from carbonaceous matter and carbonates from a number of samples has been determined. The analytical procedure is described. The result of this investigation shows δ C13-values which indicate that the carbonaceous material is probably of organic origin.
The development of research in the Ivigtut region leading to the establishment of a pre-Ketilidian supracrustal sequence is briefly outlined. The stratigraphy of the Ketilidian supracrustals, the nature of the pre-Ketilidian supracrustals and the uncomformable relationship of the two sequences are described. The older supracrustals, the Tartoq Group, are shown to have suffered deformation, metamorphism and migmatisation in pre-Ketilidian time.
The Grænseland area exhibits a middle Precambrian (Ketilidian) succession of unusually well preserved sediments, basic volcanics, and intrusives. A Ketilidian type lithostratigraphy is established and the evolution of the sedimentary basins is reconstructed. The sedimentation began on a weathered gneiss surface with residual gravel and arkoses. An early carbonate sedimentation led to a severe alteration of the gneiss substratum. Varved pelites and a magnetite-conglomerate with chert pebbles transgressed the earlier deposited sediments and the gneiss substratum; orthoquartzites were thereafter deposited in two basin structures. The deposition of dolomitic shales and pelites appears to indicate progressively increasing depth. Large amounts of graded greywackes, interpreted as turbitides, bear witness of unstable tectonic conditions and a subaqueous tallus indicates nearby fault activity. Filled with greywackes the basins appear to have stabilized, and a comparatively uniform euxenic facies of carbonaceous shales and dolomites with preserved organic remnants prevailed independent of the earlier basins in a period of tectonic quiescence. A considerable thickness of pillow lavas then appears to have been extruded under conditions of quiet subsidence during the euxenic conditions shown by the existence of an anthracite-carbonaceous shale layer and the local facies relations on top of the pillow lavas. A new phase of sedimentation appears to have taken place under conditions of tectonic activity and explosive volcanism. The total thickness of the Ketilidian strata in Grænseland is approximately 4400 m. This succession is compared with other areas of Ketilidian deposits in SouthWest Greenland. The Ketilidian deposits were deformed in two periods of folding, accompanied by thrusting and metamorphism under low greenshist facies conditions. The first deformation is a local drag in incompetent horizons and is possibly related to the tilting and twisting of the basement surface. The second deformation is of regional importance but of very different development depending on the material affected and its position in relation to the sedimentary basins and earlier formed structures. Some areas are virtually undeformed. The basement reacted to the deformations by brecciation and faulting. An analysis of lineations in a thrust zone indicates that the initially formed lineations were twisted and bent towards the direction of tectonic transport. A correlation, based on deformation of metadykes, is attempted with other areas of Ketilidian activity and it is suggested that the second deformation occurred close to 1635 m.y. and corresponds thus to the Sanerutian plutonic episode. The Ketilidian (1800 m.y.? -1500 m.y.) is envisaged as an orogenic cycle of deposition, folding and metamorphism beginning at and ending with major uncomformities. The basement gneisses are shown to contain evidence for two older (pre-Ketilidian) orogenic cycles.
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