There are few modern isotopic ages of igneous rocks and polymetallic (Pb-Zn-Ag-Cu-Au) hydrothermal mineral veins of the Mt. Thompson quadrangle in southwestern Montana. Lithology ages of this region vary from approximately 85-80 Ma Butte granite(Kbg) (Lund et al. 2002) to 48.6 Ma of Lowland Creek Volcanic Field (LCVF) (Dudas et...