stripes
Occurrence number:
031-00-135
Country:
Canada
Region:
Montreal area
Location:
Longitude: -73.2, Latitude: 45.37
Carbonatite:
No
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.
References:
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.
Map:
Fig. 1_61 Distribution of alkaline rocks in the area of Montreal.
Location: