Blue River Area
North and northeast of the town of Blue River several sheets of carbonatite have been delineated which are conformable, and commonly sheared and boudinaged.
Canadian occurrences of alkaline rocks have previously been listed and described in some detail in the monograph by Currie (1976a), although a significant number that have come to light since that publication will be found here. These new localities notably include extensive areas of peralkaline granites in Newfoundland, and of alkaline volcanics and intrusives in British Columbia, and it seems likely that many future discoveries will be concentrated in the latter area.
Many of the more northerly carbonatite occurrences are only poorly known and have not been dated. Although generally badly exposed, many have been drilled but rarely have findings been published. Many Canadian occurrences have been investigated for their economic potential (see, for instance, Ferguson, 1971) and important mining operations for nepheline syenite at Blue Mountain and Nb at St-Honore are taking place, with active exploration and appraisal for phosphate and vermiculite elsewhere. A number of occurrences in Ontario is described by Parsons (1961) and nearly 30 Ontario carbonatites have recently been re-investigated by R.P. Sage, although his internal reports were not available when the present accounts were compiled. K-Ar ages on numerous carbonatites in eastern Canada are given by Gittins et al.(1967) and of a broader range of alkaline rocks by Doig and Barton (1968). Rb-Sr ages and Sr isotopic ratios for many Ontario occurrences have been published by Bell et al. (1982).
North and northeast of the town of Blue River several sheets of carbonatite have been delineated which are conformable, and commonly sheared and boudinaged.
A number of bands and lenses of carbonatite up to 35 m thick lies conformably in mica and hornblende gneisses, and are cut by feldspar-rich pegmatites. An outcrop of sodalite syenite occurs just to the northeast of the area.
Alkaline rocks are found in a number of small outcrops along the Rayfield River, but are completely surrounded by younger Miocene- Pliocene plateau olivine basalts.
A northeast-southwest-trending dyke of alnoite, averaging 1.2 m in thickness, cuts sedimentary and volcanic rocks of the Nicola Group (Triassic).
Alkaline rocks occur in an elliptical pluton 3x1.5 km elongated east-west, and a smaller crescent-shaped body to the south.
Nepheline syenite gneisses are found as a conformable horizon 15- 300 m thick on the west flank of the Frenchman's Cap Dome. Beneath are quartzites, which overlie migmatitic gneisses forming the core of the Dome, and above are pelitic schists, paragneisses and calc-silicate gneiss.
On the southeast side of the Frenchman's Cap Dome lies a series of nepheline-bearing gneisses complexly folded within a sequence of biotite, diopside and sillimanite schists and gneisses, amphibolites, quartzites and some calc-silicate rocks. The alkaline gneisses comprise three units.
Nepheline syenite gneiss occurs in the core of a recumbent nappe, where it forms a conformable lenticular body with the central thickest portion high on Trident Mountain. The gneiss, in addition to nepheline, includes perthitic K-feldspar, albite, biotite and aegirine.
Two occurrences of nepheline syenite are reported either side of the lower reaches of the Sullivan River, and a third possible occurrence some 13-15 km to the southeast.
Sodalite veins are reported by Currie (1976a, p. 101) to occur at Mount Laussedat, 77 km northwest of the Ice River Complex.