Nachicapau Lake
A cancrinite-arfvedsonite pegmatite occurs on two small islands in a narrow arm along the north side of Nachicapau Lake. Arfvedsonite crystals up to 2x0.2 cm lie in a groundmass of cancrinite and very fine grained magnetite.
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).
A cancrinite-arfvedsonite pegmatite occurs on two small islands in a narrow arm along the north side of Nachicapau Lake. Arfvedsonite crystals up to 2x0.2 cm lie in a groundmass of cancrinite and very fine grained magnetite.
The Hecla-Kilmer complex is completely covered by muskeg and glacial deposits, but aeromagnetic data indicate a complex of 18 km2. Drilling has proved the presence of essexite, ijolite, pyroxenite and nepheline syenite.
Sills up to 20 m thick intrude Lower and Middle Devonian sediments at Sextant Rapids on the Abitibi River and 3 km downstream at Coral Rapids where a 30 m thick dyke also outcrops.
Two drill holes intersected carbonatites and syenitic rocks at depths of about 130-160 m beneath Palaeozoic sediments and overburden.
Currie (1976a, p. 130) says that the Goldray occurrence is almost identical to Argor. There is no outcrop, the whole being covered with Pleistocene deposits. An aeromagnetic map and location is given by Ferguson (1971, Map P.452 - revised). Further information has not been located.
Said to be identical to Argor (031-00-059) by Currie (1976a, p. 130) and to occur 50 km south of that locality. No other information located.
An approximately circular intrusion of aegirine syenite about 13 km in diameter is intruded in its southeastern part by an arcuate mass of carbonatite some 900x100 m. The carbonatite consists of carbonate, garnet, amphibole and disseminated magnetite (10- 80%).
This is a northeast-trending 10 m thick dyke of calcite carbonatite with phlogopite, sodic amphibole and pyroxene.
This complex is intruded into Precambrian granite gneisses and quartz gabbros. Outcrop is scarce but there is a strong, double aeromagnetic anomaly.
This intrusion of 11x7 km emplaced in Precambrian high grade metamorphic rocks consists of syenites and alkaline diorites, but no descriptions are available.