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TitleLamprophyre dykes of the Christopher Island Formation, Thirty Mile Lake, District of Keewatin, Northwest Territories
DownloadDownload (whole publication)
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorJones, A L; Miller, A R; Armitage, A E; MacRae, N D
SourceCanadian Shield/Bouclier canadien; by Geological Survey of Canada; Geological Survey of Canada, Current Research no. 1995-C, 1995 p. 187-194, Open Access logo Open Access
PublisherNatural Resources Canada
Lang.English; French
Mediapaper; on-line; digital
RelatedThis publication is contained in Canadian Shield
File formatpdf
AreaThirty Mile Lake
Lat/Long WENS-97.0000 -96.7500 63.6667 63.5000
Subjectsigneous and metamorphic petrology; economic geology; dykes; lamprophyres; igneous rocks; mineral assemblages; mineral potential; diamond; mylonites; metamorphic rocks; gneisses; Archean; paleosols; xenoliths; Churchill Province; Christopher Island Formation; South Channel Formation; Baker Lake Group; Precambrian
Illustrationssketch maps; photographs
Released1995 01 01
AbstractThe Thirty Mile Lake area is underlain by upper amphibolite to granulite grade para- and orthogneiss and by Archean megacrystic alkali feldspar megacrystic granite. Paleoproterozoic gabbro, lamprophyre, and feldspar porphyry dykes intrude basement rocks. A thick hematitic saprolite was developed in the gneiss prior to deposition of South Channel Formation sharpstone conglomerate. The lamprophyre dykes, equated to the Christopher Island Formation of the Baker Lake Group, are of two types. The first contains phlogopite phenocrysts in a groundmass consisting of phlogopite, alkali feldspar, and apatite; the second contains phlogopite±amphibole in a groundmass consisting of amphibole, alkali feldspar, and apatite. The lamprophyre dykes intrude along a northwest-trending joint set and east-trending mylonite zones. Oblate xenoliths of granitoid and less abundant mafic-ultramafic compositions occur in the dykes; some xenoliths display recessive rims indicating reactions with the host rock. The lamprophyres are being thoroughly studied in order to evaluate their diamond potential.

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