Alkaline Rocks and Carbonatites of the World

Funded by HiTech AlkCarb - New geomodels to explore deeper for Hi-Tech critical raw materials in Alkaline rocks and Carbonatites



Occurrence number: 
Montreal area
Longitude: -73.2, Latitude: 45.37

A small, circular, magnetic anomaly detected 4 km west of Mt Johnson has proved to be a Monteregian intrusion, probably some 900 m in diameter. Unlike other Monteregian intrusions it produces very little topographic expression, only rising about 20 m above the surrounding plain. Outcrop is confined to two small areas in both of which the main rock type consists of 70% plagioclase, hastingsitic amphibole, biotite and accessories. This is cut by dykes up to 5 cm thick of porphyritic nepheline syenite. A possible outcrop and numerous boulders of rougemontite occur on the western side of the intrusion.

KUMARAPELI, P.S., COATES, M.E. and GRAY, N.H. 1968. The Grand Bois anomaly: the magnetic expression of another Monteregian pluton. Canadian Journal of Earth Sciences, 5: 550-3.
Fig. 1_61 Distribution of alkaline rocks in the area of Montreal.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith