Sandstone or Revett-type Cu-Ag–bearing occurrences in the Belt Supergroup may have formed as a result of upward migration of metal-bearing solutions through syndepositional, basement-controlled faults. Upon encountering permeable horizons, the solutions moved laterally; mineralization occurred in zones containing pyrite and/or H2S. The model is supported by the alignment of the deposits that occur in different stratigraphic positions in north-northwest–trending belts, host-rock permeability control of the epigenetic sulfides, sulfide zonation, repetition of mineralization in different stratigraphic intervals, and association of the mineralization at Spar Lake, Rock Creek, Emma Peak, Ross Point, and Minton Pass(?) with faults trending north-northeast to northwest. Additional deposits may be discovered along known and/or subsequently discovered fault trends and below known and discovered deposits, and similar type deposits may occur elsewhere in other Belt deltaic units.