Thomas Lake

A strong nearly circular aeromagnetic anomaly 3-4 km in diameter occurs some 3 km north of Thomas Lake. Exposure is poor, only three outcrops having been sampled. Two proved to be a moderately foliated nepheline syenite of orthoclase, nepheline, cancrinite and a little albite, green biotite, sphene, apatite and rare arfvedsonite, aegirine-augite and magnetite. The rock of the third outcrop comprises andesine with abundant inclusions, particularly of epidote, rimmed by clear oligoclase, oligoclase anhedra and porphyroblastic perthite, with lesser amounts of biotite, blue-green amphibole, apatite, epidote, magnetite and carbonate. This is possibly a fenite.