Epithermal beryllium deposits in water-laid tuff, western Utah

Abstract

Epithermal beryllium deposits in western Utah have distinctive geological and geochemical associations that provide guides to exploration for new resources of beryllium and associated metals. Beryllium deposits at Spor Mountain and the Honeycomb Hills are uniquely associated with topaz-bearing rhyolite of Late Tertiary age and are restricted to porous water-laid tuff and breccia that contains carbonate clasts. The beryllium deposits are near both local and regional faults that probably provided conduits for mineralizing fluids.The beryllium deposits contain sizable but uneconomic concentrations of fluorite, lithium (in smectite), manganese oxides, zinc (in smectite and manganese oxides), and uranium, as well as many trace elements. Distinctive zones of argillic and feldspathic alteration enclose the beryllium deposits and generally are parallel to the original stratification of the host tuff. Anomalous concentrations of fluorine, beryllium, cesium, lithium, gallium, niobium, and yttrium occur in relatively unmineralized tuff nearby; these elements form extensive but discontinuous halos around the Spor Mountain beryllium and fluorspar district.The mineralized areas at Spor Mountain and the Honeycomb Hills may be the tops of extensive altered zones that contain deep ore deposits. Anomalous molybdenum, lead, tin, and tungsten in beryllium deposits at Spor Mountain may indicate such leakage. Consideration of possible zonation of ore deposits suggests that if ore deposits do exist at depth, they are in greisens, banded tactites, and medium to high temperature veins similar to the tin-beryllium deposits in the York Mountains of Alaska.