Nephelinite, olivine nephelinite, melilitite, phonolite and carbonatite are found in the vicinity of Frederikshabs Isblink as 0.5-2 m thick, vertical, north-south-trending dykes as well as some flat-lying sheets. A carbonate breccia occupies a 'blow' along one dyke (Hansen, 1980, p.145).
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There is no general review available of all the alkaline rocks of Greenland, but the important concentration of the Kangerdlugssuaq area has been described by Deer (1976) and Brooks and Nielsen (1982). The Gardar Province is reviewed by Upton (1974) and Emeleus and Upton (1976), while a full Rb-Sr study of this area was made by Blaxland et al. (1978).
In an area southwest of Frederikshab a swarm of northwest-trending, Mesozoic dolerite dykes is paralleled by fewer and generally thinner lamprophyric carbonatite dykes which range from a few mm to about 1 m in thickness.
Figs 101 and 102. Emplaced in Precambrian Ketilidian quartzofeldspathic gneisses, the Kungnat Fjeld intrusion, covering about 15 km2, is one of the smaller Gardar intrusions.
Figs 101 and 106. At about 4x2 km Puklen is one of the smallest Gardar intrusions and lies 3 km east of the much larger but petrographically similar Nunarssuit complex (No. 34).
Among the concentration of Gardar dykes in the Isortoq area are five giant dykes, four of which are multiple and consist of alkali gabbro, augite syenite and granite whilst one is essentially larvikite (Bridgwater and Coe, 1970).
Figs 101 and 107. The island of Tugtutoq and the numerous small islands and skerries adjacent to it are composed of Precambrian granites and granite gneisses, which are cut by intensive swarms of dykes trending predominantly north-northeast-south-southwest.
Figs 101 and 108. This is one of the least known Gardar intrusions, no full account having yet been published. It lies on the northwest margin of Ilimaussaq and appears to have been torn into two parts by one of the major east-west-trending sinistral faults (Emeleus and Upton, 1976, p. 171).
Figs 101 and 109. The best known of the Gardar intrusions and one of the most remarkable alkaline complexes in the world, with its spectacular layered rocks of unparalleled mineralogy, Ilimaussaq is oval in plan, measuring 16 by 7 km and is separated into two parts by the Tunugdliarfik Fjord.
Figs 101 and 110. The uppermost parts of a number of diatremes and associated effusives interstratified with sandstones have been preserved in a downfaulted area of approximately 2 km2 south of Qagssiarssuk.
North of Narssarssuaq and north and northwest of the North Qoroq centre of the Igaliko complex, sills, dykes and plugs of carbonatite occur, with a number of diatremes, up to 300 m across, having carbonatitic affinities.