The region is underlain to the west by the Coast Crystalline belt and to the east by Mesozoic and Tertiary volcanic and sediment- ary rocks. A hybrid zone along the eastern margin of the Coast Crystalline Belt contains elements of both terranes. In this zone Mesozoic rocks have been incorporated into the plutons and are overlain by Tertiary volcanic rocks. The degree of metamorphism and deformation of the Intermontane Belt supracrustal rocks increases towards the Coast Crystalline Belt.

The Ada showing consists of minor amounts of copper, as dissem- inated chalcopyrite and bornite, within foliated granodiorite of the Coast Crystalline Belt.