The Pinion Deposit lies at the southeastern end of the Carlin gold trend along the Bullion Fault Corridor and is hosted by a sequence of Paleozoic sedimentary rocks exposed within large structural horst blocks in which the sedimentary rocks have been broadly folded into a southward plunging asymmetric anticline. The apparent dip of the western fold limb ranges from 10 to 25 degrees and the steeper eastern limb dips 35 to 50 degrees. Carlin-type mineralization at the Pinion Deposit is hosted in dissolution collapse breccia developed along the contact between the underlying Devonian Devils Gate Limestone Formation and the overlying Mississippian Webb Formation fine grained clastic sediments and Tripon Pass Formation silty micrite. The Pinion thrust occurs beneath or along the base of the deposit and emplaced Devonian Devils Gate Limestone on top of Mississippian Chainman sandstone. An additional zone of mineralization has been identified at the Pinion Deposit hosted within the Sentinel Mountain dolomite and the top of the underlying Oxyoke sandstone below the Devils Gate Limestone. Gold deposition is thought to have occurred contemporaneous with breccia development and with late silica flooding and quartz veining. Barite-rich breccias can also be observed associated with jasperoid bodies at surface.
Gold deposition is thought to have occurred during the Eocene at the same time as formation of the dissolution collapse breccia. Significant control on the distribution of gold appears to have been exerted by folding/horst development in that the highest grades and thickest mineralization occurs in the apical hinge portion of the coincident Pinion anticline and main horst block. Breccias and gold zones thicken noticeably towards high angle faults, which likely acted as conduits for the gold-bearing hydrothermal fluids.