The northern half of the Jennings River (104O) and southern half of the Wolf Lake (105B) map areas include polydeformed and metamorphosed rocks of the eastern Big Salmon Complex (Yukon-Tanana Terrane) and a succession of mostly Paleozoic rock assemblages currently grouped in Dorsey Terrane.
On the northeast side of Dorsey Terrane, siliceous grits and mafic metavolcanic rocks of the Dorsey assemblage are thrust over the Ram Creek assemblage. Dorsey assemblage is in turn structurally overlain by thin mafic volcanic rocks and limestone (Klinkit (?) assemblage), and by dark phyllitic rocks and quartzites of the Swift River assemblage.
Extensive stratabound pyrrhotite-sphalerite mineralization occurs along a 6.5 km structural trend in calc-silicate rocks and rhyolite of the Ram Creek assemblage. Similar mineralization also occurs several kilometres southwest of that trend, within or adjacent to the Dorsey assemblage. Both assemblages contain quartz +/- feldspar -phyric layers with potential for volcanogenic massive sulphide showings.