Alkaline Rocks and Carbonatites of the World

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Kaminak Lake

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Occurrence number: 
031-00-010
Country: 
Canada
Region: 
Northwest Territories, Keewatin
Location: 
Longitude: -94.07, Latitude: 62.05

This is an ellipsoidal body of 7x2 km lying along the north shore of an arm of Kaminak Lake beneath which 35% of the complex lies. It is intruded between Archaean greenstones and tonalite, both of which are fenitized for up to 300 m from the contact. The southern part of the complex is occupied by pyroxenite and melteigite which grade northwards into ijolites and leucocratic rocks composed essentially of nepheline and nepheline-orthoclase intergrowths. The northern and northeastern parts of the intrusion consist of syenite and nepheline syenite which also form dykes cutting the ijolites and pyroxenites. Carbonatite is present as lenses and dykes in all the other rock types, including the fenites. The ijolites and pyroxenites contain varying proportions of nepheline and aegirine-augite, melanite, magnetite, biotite, cancrinite and apatite, and they display a vague, steeply dipping layering sub- parallel to the margins. The rocks containing vermiform nepheline-orthoclase intergrowths may be solely composed of this, or it may form only a small proportion of the rock Descriptions, illustrations and analyses of nepheline and feldspar are given by Davidson (1970b). The syenites are principally coarse-grained K- feldspar leucosyenites with less common varieties containing nepheline, melanite, biotite, cancrinite, vishnevite, calcite and sphene, with accessory apatite, magnetite and pyrite. The carbonatites consist of calcite and varying proportions of apatite, biotite, magnetite, pyrite, a blue amphibole and pyroxene. The fenites are syenitic rocks with aegirine and a blue amphibole.

Age: 
Biotite from an alkali syenite gave 1820+-60 Ma. (Davidson, 1970c, Table 4) but a Rb-Sr isochron gave an age of 2686 Ma. (Wanless, pers.comm., 1973, in Currie, 1976a, p.103).
References: 
CURRIE, K.L. 1976a. The alkaline rocks of Canada. Bulletin, Geological Survey of Canada, 239: 1-228. RIDLER, R.H. 1972. Volcanic stratigraphy and metallogeny of the Kaminak Group. Paper, Geological Survey of Canada, 72-1, Part A: 128-34
Fig. 8 Kaminak Lake (after Davidson, 1970?a,b or c?, Fig.1.).
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