Lac Rouge is an approximately circular body of 25 km2 forming a depression corresponding to a positive aeromagnetic anomaly. It is poorly exposed. Nepheline-bearing rocks occur in a north- south trending ridge about 1.6 km in length by 250-300 m wide. The rocks are coarse, mesocratic syenites of orthoclase microperthite and towards the centre of the occurrence nepheline forms large porphyroblasts essentially replaced by cancrinite, thomsonite, natrolite and sodalite. Biotite and lesser hastingsitic amphibole are present with large euhedral zircons. Nepheline-rich pegmatites occur (Currie, 1976a, p. 199). Corriveau (1984, p. 305) reports the fenitization of country rock amphibolite and quartzite, and gives an exposure map (Corriveau, 1985, Fig. 22.5).
C CORRIVEAU, L. 1984. Account of field observations on rock units and structural features of the syenitic complexes of the Mont-Laurier area, central metasedimentary belt of the Grenville Province. Paper, Geological Survey of Canada, 84-1A: 303-6.
CORRIVEAU, L. 1985. Precambrian syenitic plutons, central metasedimentary belt, Grenville Province of Quebec. Paper, Geological Survey of Canada, 85-1A: 165-74.
CURRIE, K.L. 1976a. The alkaline rocks of Canada. Bulletin, Geological Survey of Canada, 239: 1-228.
WYNNE-EDWARDS, H.R., GREGORY, A.F., HAY, P.W., GIORANELLA, C.A. and REINHARDT, E.W. 1966. Mont Laurier and Kempt Lake map-areas, Quebec. Paper, Geological Survey of Canada, 66-32: 1-32.