| Title | Indicator mineral and till geochemical dispersal patterns associated with the Ranch Lake kimberlite, Lac de Gras region, NWT, Canada
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| Author | McClenaghan, M B ;
Ward, B C; Kjarsgaard, I M; Kjarsgaard, B A; Kerr, D E; Dredge,
L A |
| Source | Geochemistry: Exploration, Environment, Analysis vol. 2, 2002 p. 299-320, https://doi.org/10.1144/1467-787302-004 |
| Year | 2002 |
| Alt Series | Geological Survey of Canada, Contribution Series 2001041 |
| Publisher | Geological Society of London |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Northwest Territories |
| NTS | 76E/03; 76E/04; 76E/05; 76E/06 |
| Area | Lac de Gras; Ranch Lake |
| Lat/Long WENS | -112.0000 -111.0000 65.5000 65.0000 |
| Subjects | economic geology; geochemistry; kimberlites; till analyses; till geochemistry; tills; dispersal patterns; diamond; mineral exploration; drift prospecting; drift geochemistry |
| Illustrations | sketch maps; tables; graphs; plots |
| Released | 2002 11 01 |
| Abstract | The Ranch Lake kimberlite, in the Contwoyto Lake area of the northwest Territories, consists of volcaniclastic crater facies kimberlite which contains thousands of kimberlite indicator mineral grains in
a 10 kg sample. Cr-diopside and pyrope are the most abundant indicator minerals in the kimberlite, accompanied by much less abundant chromite and rare Mg-ilmenite. Indicator minerals in till samples collected around the Ranch Lake kimberlite define a
spectacular ribbon-shaped glacial dispersal train trending west for 70 km. At its head, the train is 500 m wide and gradually widens 2 km at 20 km down-ice. The lateral edges of the train are sharply defined by the presence or absence of indicator
minerals in till. Background (up-ice) concentrations of all indicator minerals are zero. Patterns for Cr-diopside and pyrope abundance are similar and concentrations increase down-ice, reaching their highest levels between 15 and 19 km down-ice. Of
the two size fractions of heavy minerals examined, most indicator minerals occur in the finer, 0.25 to 0.5 mm, size fraction. The <0.063 mm fraction of the till matrix displays weak geochemical signatures of the kimberlite down-ice, most notably for
Ba, Cr, Ce and Th. The results of this study of indicator mineral and geochemical methods around a known kimberlite will aid in the design of mineral exploration programs for kimberlite-hosted diamond deposits in glaciated terrain around the world.
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| GEOSCAN ID | 212598 |
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