[en] The existence of radioactive rocks in the area south of the Igdlerfigssalik centre of the Igaliko nepheline syenite complex has been known since 1962. Reconnaissance radiometric investigations on the ground and from a helicopter in 1979 and 1980 revealed a large number of occurences of radioactive mineralisation. The characteristics of the mineralisation are briefly described. (author)

[en] About 600 one-metre drill core sections from lujavrites and country rock xenoliths of northern Kvanefjeld were analysed for Li, Be, F, Na, K, Ca, Ti, Mn, Fe, Cu, Zn, Y, Zr, Nb, Pb, Th and U. The samples were taken from 7 of the 23 drill cores of the 1977 drilling operations. The analysed rocks were divided into seven rock groups: (1) Naujakasite lujavrite, (2) naujakasite lujavrite with visible villiaumite, (3) arfvedsonite lujavrite, (4) arfvedsonite lujavrite with visible villiaumite, (5) volcanic rocks (lava and gabbro), (6) sheared volcanic rocks, and (7) sheared volcanic rocks with visible Nb minerals. Naujakasite lujavrite (both groups) has high concentrations of Th, U and Y at relatively low Zr contents. Arfvedsonite lujavrite (both groups) has high Zr contents but lower contents of Th, U and Y than naujakasite lujavrite. Thorium, U and Y generally accumulate at upper levels of lujavrites, mostly at the contact to xenoliths. This is thought to be caused by temperature gradients at the contacts. Zirconium enrichement occurs at lower levels of mainly arfvedsonite lujavrites expressing gravity settling of eudialyte during crystallisation. Naujakasite lujavrite is regarded as the youngest and most differentiated lujavrite. Microscopic and chemical investigations of two transition zones of lava and gabbro at contacts with lujavrites revealed typical features of metasomatic action, i.e. formation of aegirine, arfvedsonite, albite, microline, pectolite and other minerals. A general increase of sodium from the unaffected volcanic rocks towards the lujavrite contact is accompanied by a depletion of silicon and other elements. Niobium mineralisation is confined to sheared marginal zones of country rock xenoliths. Resource evaluation for Zr, Nb, Zn, Be, F, Li and rare earth elements of the rocks of northern Kvanefjeld suggest Nb and rare earth elements as potential by-products of a possible uranium extraction process of the Kvanefjeld ore, while F should be extracted for mainly environmental reasons. (author)

[en] A short review is given of reconnaissance work in South Greenland. The work has demonstrated that there are areas in the Motzfeldt centre of at least 1 km² with continuously high radioactivity. If the uranium content of these radioactive zones are sufficiently high, then potential ore tonnages could prove to be substantial. The reconnaissance exploration has proved that uranium mineralization is widely distributed in the Narssaq-Narssarssuaq district. It is, no doubt, responsible for the high uranium values in the exploration geochemical samples. Although the size of the pitchblende occurences which have been found so far are small, the high grade of the mineralisation, the great frequency of the fracturing and the evidence for an all pervasive mineralising event over a wide area indicate that there is a good possibility of finding economic mineralisation within the Narssaq-Narssarssuaq area. The area as a whole may, perhaps, be termed a ''uranium mineral district''. As the potential targets are small, only detailed follow-up exploration will establish this. At the same time more detailed work on individual showings, and geological mapping to demonstrate the relative ages of the various petrological and mineralising events, will establish the possible origin of this uranium mineralisation. (author)

[en] As part of the uranium extraction research programme carried out at the Risoe National Laboratory, geochemical and mineralogical investigations of the Kvanefjeld area were conducted at the Geological Survey of Greenland. Principal conclusions on the distribution of uranium and the mineralogy of the potential uranium ore from Kvanefjeld are summarised: Uranium is primarily distributed in the lujavrite varieties and in deformed lavas. The radioactive grains may show homogeneous, layer- (vein-) like, nest-like or single-crystal, coarse-grained types of distribution in the rocks. Steenstrupine of two types (generations), A and B, represents the main uranium-bearing mineral. It is generally metamictized or altered into secondary in situ phases. The metamictization and alteration of steenstrupine are primarily dependent on its U-Th content and not on the rock type or on the degree of hydration of the primary felsic minerals. (author)

[en] This study is part of a more detailed investigation of the stability and the natural decomposition process of steenstrupine, initiated to help delineate the conditions during the later stages of solidification of the Ilimaussaq rocks. Interest in steenstrupine also arises from the potential importance regarding Kvanefjeld as a uranium ore reserve, steenstrupine being the most important uranium-bearing mineral in the Kvanefjeld area. Major emphasis has been placed on the decomposition of steenstrupine in Na²CO³ solution in the 200 deg to 600 deg C range at pressures up to 1000 bars. (author)

[en] As part of the geological investigation of the Ilimausaaq intrusion, South Greenland, trace-element analyses have been performed on carefully chosen rock samples. Material was selected on the basis of detailed field mapping and with particular attention paid to its fresh and representative nature; in every case more than 15 kg was obtained by blasting. The samples have already been used for the separation of accessory ore minerals and for analysis of fluid inclusions. To date, the rocks have been analysed for trace elements by neutron activation and X-ray fluorescence analysis. Average trace-element analyses are presented for seven agpaitic rocks types from the Ilimaussaq intrusion. Future work will extend the multi-element analysis of Ilimaussaq rocks and minerals, and integrate the results with the physical-chemical history of the intrusion. (B.P.)

[en] The Kap Washington Group, Peary Land, North Greenland, is a bedded suite of rhyolitic lavas and tuffs that forms the northernmost rock province of Greenland. The volcanic group borders on the north the Palaeozoic North Greenland fold belt from which it is separated by the sourtherly-dipping Kap Cannon thrust. K/Ar whole-rock age determinations of 34.9+-5.3 m.y. and 32.3+-3.2 m.y. on somewhat mylonitised lava samples were earlier regarded as giving an approximate minimum age volcanic consolidation and a maximum age of the Kap Cannon thrusting. This note reports on Rb/Sr isotopic work that dates the Kap Washington Group, the five samples processed suggesting an age of about 63 m.y. Thus the general age of extrusion and consolidation of the volcanic pile is considered to be earliest Tertiary. (author)

[en] The field activity in 1977 completed a 5-year programme of exploration for uranium in norhtern East Greenland from 72deg to 76degN. An account is given of the field activities of 1976 and 1977. The field activities comprised 1) follow-up of the aerial gamma-spectrometric survey of 1973 and 1974, 2) completion of the geochemical sampling programme commenced in 1975 in Hudson Land and Gauss Halvoe, and 3) detailed field work in selected areas. (author)

[en] Regional exploration for uranium was carried out in South Greenland in 1979 and 1980. From the planning stage the area between the fjords Tasermiut and Soendre Sermilik was considered a favourable target because deposits from geological environments of similar age, structure and lithology are known, e.g. the Makkovik Bay area in Labrador. The deposits sought were mainly pegmatitic or vein type deposits related to a Proterozoic unconformity. During the South Greenland uranium exploration project the area was covered in 1979 by a regional reconnaissance gamma-spectrometric survey and by drainage geochemistry (stream sediments and stream waters). Several areas of anomalous radioactivity were recorded, and on the basis of this and short field visit in 1979 it was decided to undertake a more systematic follow-up in 1980. The preliminary results of this work are reported below. (author)

[en] The development of a relatively rapid neutron activation technique, involving fast-transfer of samples from the reactor followed by Cerenkov counting, has allowed us to extend analytical coverage of Li and F in the Ilimaussaq lujavrites and their minerals. On geological grounds the lujavrites have been regarded as crystallising from the final agpaitic magmas at Ilimaussaq. In agreement with this, contents of Li and F - which are normally maximal in residual magmas - have been shown to attain their highest levels within the lujavrites. However, these studies failed to agree on the absolute contents of Li in the lujavrites. For aegirine lujavrite and arfvedsonite lujavrite, Gerasimovsky reported averages of 155 and 791 ppm, respectively, whereas Ferguson found only 90 and 266 ppm. Hamilton only reported 80 ppm Li in a single sample of arfeedsonite lujavrite. More recent mapping within the intrusion has revealed further divisions within the lujavrite sequence. These subdivisions provide an increased geological control for the interpretation of Li and F data. Samples of the various lujavrite varieties were taken from the drill cores obtaned in 1958, 1962 and 1969. (author)