Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Obedjiwan (Gouin Reservoir)


Occurrence number: 
Longitude: -75.17, Latitude: 48.68

An approximately circular complex 7 km in diameter with a smaller, separate intrusion to the north, Obedjiwan consists of a core of nepheline syenite surrounded by aegirine syenite, which may be in the form of a ring dyke. The few outer contacts exposed are steep. A small plug of ijolite is probably only about 100 m in diameter and lies within the nepheline syenite. Nepheline syenite pegmatites with calcite cores are widespread. The aegirine syenite consists of perthite, aegirine and minor magnetite. A few boulders of biotite-calcite rocks on the flanks of the northern satellite intrusion may represent sheets in the intrusion. The nepheline syenite of this satellite reaches a grain size, in its uppermost part, of about 10 cm.

Rocks of the complex have been tested for the manufacture of ceramics but appear to contain too much iron.
K-Ar on biotite gave 1050 Ma for nepheline syenite and 890 Ma for biotite-calcite rock.

CURRIE, K.L. 1976a. The alkaline rocks of Canada. Bulletin, Geological Survey of Canada, 239: 1-228.
GITTINS, J. 1971. The Obedjiwan alkaline complex, Gouin Reservoir, Toussaint Township, Abitibi County, Quebec. Quebec Department of Natural Resources, Service de la Documentation Technique, No. 27357.
Gittins, J. personal communication, 1984.

Fig. 1_72 Obedjiwan (after Gittins, 1971).
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith