Rock Creek

A syenite intrusion, probably sheet-like in form (referred to as a chonolith by Daly, 1912), covers about 10 km2 along Rock Creek, just above its confluence with the Kettle River. The syenite is crowded with rhomb-shaped feldspar phenocrysts 2-5 mm in length, phenocrysts of pale-green augite, biotite and rare altered olivine, in a groundmass of alkali feldspar, augite, biotite, sphene, large apatite prisms, magnetite and occasional stout prisms of nepheline, usually altered. Two other smaller intrusions, apparently of identical composition, occur in the vicinity and dykes and sheets containing nepheline are widespread. Northwards the Rock Creek intrusion appears to pass into an extrusive phase, and this in turn is followed by analcime-phyric lavas named "shackanite" by Daly (1912, p. 415), which lie in Canada (Canada, No. 36).