Dora Bay

Dora Bay, located in the south of Prince of Wales Island, Alaska, is host to peralkaline intrusive complex. The complex intrudes volcaniclastics and metasedimentary rocks of the Wales Group, the latter includes andesitic to basaltic marine volcanics, mudstones, shales, and marble. Structurally, the complex is sinuous and sheet-like in shape, trending and conformable with a north-south oriented fault. The main body itself is composed of medium-grained peralkaline (riebeckite?) granite and hornblende syenite, with minor alkaline granite and diorite. Cutting both country rock and the main intrusive body are late-stage aplite and pegmatite dykes, which can be spilt into three types: 13 ft thick coarse-grained tabular bodies; 0.3-0.9 m thick vein dykes; and 0.3-0.6 m thick siliceous, manganese stained, radioactive veins. Vein dykes are restricted to the country rock, whereas coarse-grained pegmatites cut across both the main body and the country rock. Minerals found in these dykes include quartz, rhodochrosite, plagioclase, aegirine, riebeckite, calcite, and chlorite. REE and Nb bearing phases have also been identified including major thalenite-(Y), bastnäsite, and minor monazite, eudialyte, and euxenite. Resource estimation and geochemical data including whole rock major and trace element can be found in Barker and Mardock (1990).