Geology of the Trial Harbour district

A Devonian (?) granite complex intrudes Cambrian (?) volcanics, serpentinised dunite (olivine Fo,), and siltstones and quartzites of the Precambrian (?) Oonah Quartzite and Slate and the Silurian Crotty Quartzite and Amber Slate Formations. The general trends of these country rocks are parallel to the granite margins.
The complex is composed of grey, pink and white granites all with the same mineralogical composition (quartz, orthoclase dominant, plagioclase subordinate). The white granite commonly contains tourmaline nodular segregations, Emplacement began with the pink and grey granites, followed closely by the white granite, and finally the intrusion of minor bodies (porphyritic aplite, micro-granite, aplite, pegmatite, quartz-tourmaline dykes, pyroxene dyke) . Tourmaline is abundant in the later intrusions and is sometimes accompanied by cassiterite.