The Stockton quadrangle is on the west side of the central Oquirrh Mountains, about 50 km west-southwest of Salt Lake City, Utah. The quadrangle is the site of two historically important Utah base-and precious-metal mining districts at Ophir and Stockton. The Oquirrh Mountains here are composed of allochthonous folded and faulted Paleozoic sedimentary rocks of the Bingham and South Mountain nappes, which are part of the Sevier thrust belt of Late Mesozoic age. The plates are differentiated on the basis of their structural and stratigraphic characteristics. Sedimentary rocks in both plates are intruded by distinctive Tertiary rhyolite porphyry, quartz monzonite, and quartz monzonite porphyry stocks, dikes, and sills. The ore deposits are spatially associated with the igneous rocks. Although the mining districts occur in different nappes, the styles of mineralization replacement of carbonate rocks and fissure fillings are similar. The upper parts of ore bodies are largely oxidized, grading downward into sulfides. Ore production at Stockton exceeded that at Ophir and contained more gold, lead and zinc. Ophir ores contained more silver and copper than those at Stockton.