Alkaline Rocks and Carbonatites of the World

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Montreal Area

Montreal Area

Apart from the major complex of Mount Royal, Montreal Island is also cut by numerous alkaline dykes and many, though fewer, sills. The dykes encompass many varieties and are most abundant in the vicinity of Mount Royal. Although the majority of the sills are only some 0.5 m or less in thickness, and will not be dealt with individually, others are considerably thicker, more extensive and have often been named and described individually so that they are afforded separate entries and brief descriptions in the catalogue. They are not confined to Montreal Island but also occur to the west and east (see Fig. 61). For general accounts see Clark (1952, p. 84) and Gold and Marchand (1969); Eby (1985c) gives ages and detailed chemistry for mafic dykes. There are several dykes, pipes and diatremes of monticellite- and melilite- bearing alnoitic rocks in the vicinity which are included in the catalogue, but bodies of (?)kimberlitic rock such as the pipes on Ile Bizard, which do not contain melilite, are excluded, as are breccia diatremes lacking alkaline rock fragments or matrix such as those on Ile Ronde and Ile Ste-Helene.
A line of ten intrusions extending eastwards from Oka via Mount Royal to Mount Megantic is known as the Monteregian Hills and has been the subject of numerous papers. Eby (1984a, 1984b, 1985a and 1985b) has made the most recent comprehensive study and much of the earlier work is cited by him.

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