Abstract Exposures in and around the mid-Tertiary Wasatch Igneous Belt (WIB) provide an opportunity to investigate the mechanisms associated with the emplacement of the stocks. They are associated in time and place with northeast-trending dikes, indicating that the area was undergoing extension at the time. Studies elsewhere show that at best, distortion of the country rock around igneous intrusions can only account for 40 percent of the space required. We propose a model in which part of the space is made available where faults associated with the extension change strike (releasing bends) or dip (releasing steps). Evidence for this is in the form of kinematic indicators associated with minor intrusions, the map scale geometry of the stocks and the pattern of dikes. The Little Cottonwood, Alta, and Clayton Peak stocks are chemically distinct, lending support to the concept of separately generated and separately emplaced magma bodies. The eastern stocks and the Keetley Volcanics have some similarities with the Alta stock. The stocks and volcanic rocks of the WIB are all high-K calc-alkaline rocks with K 2 O, ε Sr and ε Nd values that are difficult to generate from the mantle wedge overlying a subducting plate, but are consistent with magmas derived by partial melting of the lower crust (Proterozoic meta-igneous). The intrusive and volcanic rocks in the WIB range in age from 30.5 ± 0.6 Ma (Little Cottonwood) to 35.5 ±1.5 Ma (Clayton Peak) with most of the intrusions and volcanic deposits occurring in the 32 to 36 Ma range.