Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Chipman Lake


Occurrence number: 
Longitude: -86.2, Latitude: 49.97

The Chipman Lake intrusion has been suggested to be a circular stock of syenite about 3 km in diameter associated with dykes of syenite and carbonatite (Ferguson, 1971, p. 43). A strong, approximately circular aeromagnetic anomaly of this size does occur, but Sage (1975 and 1985) shows that this is caused by a metamorphosed early Precambrian syenodiorite to diorite stock. Along the southern shore of Chipman Lake dykes of carbonatite, generally less than 1 m thick, are numerous and cause extensive fenitization. Carbonate, which is essentially dolomitic, is also abundant along joints and cracks in the fenites. Spectacular brecciated fenites with secondary amphibole and phlogopite concentrated along block margins is illustrated by Sage (1985, Photo 8). A few probe analyses of carbonate, phlogopite and amphibole, analyses of carbonatite and fenite and a geological map will be found in Sage (1985).

Two zones of massive and disseminated sulphides running to over 0.3% Cu have been defined, but these are associated with basement metavolcanics, and are unlikely to be petrogenetically related to the alkaline rocks.
FERGUSON, S.A. 1971. Columbium (niobium) deposits of Ontario. Mineral Resources Circular, Ontario Department of Mines and Northern Affairs, 14: 1-58. SAGE, R.P. 1975. Carbonatite-alkalic complexes. Miscellaneous Paper, Ontario Geological Survey, 63: 58-66. SAGE, R.P. 1985. Geology of carbonatite-alkalic rock complexes of Ontario: Chipman Lake area, Districts of Thunder Bay and Cochrane. Study, Ontario Geological Survey, 44: 1-40.
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