MINERALOGY AND MINERAL PARAGENESIS OF THE DOTSON RIDGE HREE DEPOSIT, BOKAN MOUNTAIN, PRINCE OF WALES ISLAND, ALASKA
The veins are composed mainly of quartz and albite with variable amounts of phlogopite, magnetite, hematite, and zircon. The dominate HREE-bearing minerals at Dotson Ridge are fergusonite, various Ti-Nb-Y-oxides (mainly polycrase), pyrochlore, an unidentified Ti-Y-HREE-oxide, an unidentified HREE-Nb-Y-oxide, gadolinite, hingganite, Y-Mg-fluosilicate (magnesiorowlandite?), xenotime, and iimoriite. The dominant LREE minerals are bastnaesite, parisite, synchysite, allanite, monazite, and multiple types of Ca-±Y-LREE-silicates. The proportion of LREE and HREE minerals is highly variable from sample to sample. Other minerals present in more than trace amounts include thorite, fluorite, cassiterite, ilmenite, pyrophanite, ilmenorutile, Ti-oxide (rutile?), Nb-oxide, fluocerite and cerianite. Sulfides are present in trace amounts in most samples and include galena, FeS, sphalerite, and chalcopyrite. Uranium-rich minerals are lacking or in trace amounts. In addition, a very complex hydrothermal alteration suite of REE-Th-U Silica-enriched Ti-, Nb-, Y-, Th-oxides, silicates, carbonates and fluocarbonates is present. A volumetrically small suite of low-temperature hydrothermal minerals is also present that consists of chlorite, zincian-chlorite, calcite, and complex inhomogeneous Fe-Mn-Zn-carbonates.