Alkaline Rocks and Carbonatites of the World

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Ivigtut

stripes

Occurrence number: 
063-00-032
Country: 
Greenland
Location: 
Longitude: -48.02, Latitude: 61.02

Figs 101 and 103. There is no comprehensive study available for the famous cryolite deposit at Ivigtut, the best account probably being the brief survey by Berthelsen and Henriksen (1975, p. 133) and the mineralogically orientated account of Karup-Moller (1973). The cryolite ore body, which has now been entirely removed by mining, originally formed an irregular mass of 50x115 m extending to a depth of 70 m. Together with a pegmatite on its western side the cryolite body lay within a stock of peralkaline granite containing a little biotite, aegirine-augite and sodic amphibole. The granite is almost entirely surrounded by an intrusive breccia zone up to 60 m wide, and another breccia body, the 'bunkebreccia', outcrops to the east, both being composed dominantly of somewhat altered country rock fragments. Several sets of doleritic and peralkaline dykes occur which are both earlier and later than the central Ivigtut intrusion. The main portion of the cryolite body consisted of cryolite-siderite rock with about 20% siderite and 1-2% of quartz and sulphides, but varying widely. To the east a siderite-rich zone underlay the cryolite and to the west a fluorite-rich zone. At deeper levels the cryolite body was separated from the granite by sulphide-bearing quartz rocks. The adjacent granite is strongly greisenized. More than 80 minerals have been identified from the cryolite body including many sulphides. Pauly (1960) estimated the temperature of formation of the cryolite-siderite rock at between 510° and 590° C, but its genesis is still unclear; origins involving foyaitic, granitic, basaltic and carbonatitic sources have all been suggested.

Economic: 
3.5 million tons of cryolite were mined between 1854 and 1962, and 50-60 000 tons were shipped annually from stockpiles during closure of the mine between 1962 and 1982. The flooded pit has now been drained and is being reworked. Galena, with 0.75% Ag and 1.5% Bi, chalcopyrite, sphalerite and siderite have been recovered as by-products (Sorensen et al., 1978, p. 259;Nielsen, 1976, p. 481).
Age: 
A Rb-Sr whole rock isochron for the Ivigtut granite gave 1248±25 Ma (Blaxland, 1976).
References: 
BERTHELSEN, A. 1962. On the geology of the country around Ivigtut, SW-Greenland. Geologische Rundschau, 52: 269-80. BERTHELSEN, A. and HENRIKSEN, N. 1975. Geological map of Greenland 1:100 000. Ivigtut 61 V. 1SYD. The orogenic and cratogenic geology of a Precambrian shield area. Descriptive text. Meddelelser om Gronland, 186(1): 1-169. BLAXLAND, A.B. 1976. Rb-Sr isotopic evidence for the age and origin of the Ivigtut granite and associated cryolite body, South Greenland. Economic Geology, 71: 864-9. BERTHELSEN, A. 1962. On the geology of the country around Ivigtut, SW-Greenland. Geologische Rundschau, 52: 269-80. BERTHELSEN, A. and HENRIKSEN, N. 1975. Geological map of Greenland 1:100 000. Ivigtut 61 V. 1SYD. The orogenic and cratogenic geology of a Precambrian shield area. Descriptive text. Meddelelser om Gronland, 186(1): 1-169. BLAXLAND, A.B. 1976. Rb-Sr isotopic evidence for the age and origin of the Ivigtut granite and associated cryolite body, South Greenland. Economic Geology, 71: 864-9. KARUP-MOLLER, S. 1973. A gustavite-cosatite-galena-bearing mineral suite from the cryolite deposit at Ivigtut, South Greenland. Meddelelser om Gronland, 195(5): 1-40. NIELSEN, B.L. 1976. Economic minerals. In A. Escher and W.S. Watt (Eds). Geology of Greenland. Gronlands Geologiske Undersogelse: 461-86. PAULY, H. 1960. Paragenetic relations in the main cryolite ore of Ivigtut, South-Greenland. Neues Jahrbuch fur Mineralogie Abhandlungen, 94: 121-39. SORENSEN, H., NIELSEN, B.L. and JACOBSEN, F.L. 1978. Denmark and Greenland. In S.H.U. Bowie, A. Kvalheim and H.W. Haslam (Eds). Mineral deposits of Europe, 1: 251-61. The Institution of Mining and Metallurgy and The Mineralogical Society, London
Fig. 101 The Gardar Province, Southwest Greenland. Fig. 103 Ivigtut (after Berthelsen, 1962, Fig. 1).
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