The Ice River igneous complex, exposed in the southern part of Yoho National Park in the Field area, British Columbia, is an asymmetrical laccolith made up of several varieties of undersaturated alkaline igneous rooks. Nepheline- sodalite syenite and urtite, two of the major types, are described. Several theories on the origin of undersaturated alkaline igneous rocks are discussed and it is concluded that Daly’s limestone syntexis theory best explains the origin of the Ice River complex. In the vicinity of Garnet Mountain and Aquila Ridge, the north-west extension of the laccolith has contact metasomatised enclosing limestone and limestone inclusions. The mineralogy and petrology of several extensive skarn zones which carry pyrochlore and radioactive minerals are described. The concentration of certain elements in alkaline igneous rooks is considered and the, addition of Na, K, Cb, Zr and others to Ice River limestone is described. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate