Geochemistry of the porphyry-related intrusions of the Wasatch Mountains, Utah: implications for porphyry mineralization

The central Wasatch Mountains of Utah are host to a number of mineralized intrusions including the White Pine Fork and Park Premier porphyry deposits. The older intrusions to the west have been interpreted to have been emplaced at greater depths than those to the east. Recent advances in geochronology and new geochemical data show that the western stocks evolved to more felsic compositions with higher degrees of crustal contamination over time, whereas the eastern stocks show no significant variations. The greater contamination in the western stocks is consistent with magma ponding at greater depths, whereas the shallower emplacement depths of the eastern porphyries can account for the reduced contamination. The lack of pronounced geochemical evolution trends seen in other well-endowed porphyry districts, where they are explained by tectonic perturbations, may account for the small size of the deposits in the Wasatch Mountains.