Alkaline Rocks and Carbonatites of the World

Funded by HiTech AlkCarb - New geomodels to explore deeper for Hi-Tech critical raw materials in Alkaline rocks and Carbonatites

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. 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