Abstract A comprehensive look at the closely spaced blast hole samples, exploration drill data, and a resource model interpolated from diamond exploration drilling data show that the distinct molar tooth shape of the Bingham Canyon orebody has strong lithologic controls at depth. At and below the level of current mining Cu occurs in the Bingham stock as a ring approximately 4000 feet in diameter, centered on a barren core located at the eastern end of the quartz monzonite porphyry (QMP). A smaller ring of Cu (about 2500 feet in diameter) is centered on the southwest end of the QMP. The mineralized cylinders are broken where chemical and physical differences between the mineralized intrusive rocks and the barren quartzites on the south and west sides of the Bingham stock cause gaps in the regular Cu distribution, leading to the distinctive root zones of the Bingham porphyry system. These root zones are artifacts of favorable host rock and not products of multiple mineralization centers or structural control. Blasthole and diamond drill hole assay data show broadly continuous grade through monzonite (MZ), QMP and latite porphyry (LP) dikes, though locally grade changes occur across LP contacts. A drop in grade within quartz latite porphyry (QLP) dikes is common. The overall consistency of grade across intrusive contacts including the LP suggests that the main pulse of mineralization, associated with the QMP, spanned the period of subsequent LP intrusion. Mineralization had notably waned by the time of QLP emplacement, leading to lower Cu grades in the QLP throughout the system.

Integrated geological and geochemical studies of the Barneys Canyon gold deposit in the Oquirrh Mountains of north-central Utah suggest that compressional tectonism and metamorphism are Jurassic in age. Detailed geologic mapping, clay mineralogy, and fluid-inclusion analyses together with Jurassic K/Ar age determinations indicate that deformation at Barneys Canyon was contemporaneous with regional Jurassic metamorphism recognized in the southern Oquirrh Mountains by Wilson and Parry (1990b). The Barneys Canyon gold deposit occurs on the crestal region of the Copperton anticline which is interpreted as a fault-bend fold. Bedding-plane gouges formed within the Barneys Canyon sedimentary sequence during flexural slip folding. Clay minerals formed in the gouges and in the Barneys Canyon gold deposit are kaolinite, illite, and some minor interstratified illite-smectite. The distribution of illite and kaolinite shows that the orebody is associated with illite alteration surrounded by a halo of more kaolinitic material. Illite crystallinity suggests that a lower-temperature (retrograde) zone is associated with the orebody. Fluid-inclusion analyses from quartz and barite show a range of homogenization temperatures from 130–400 °C with two weak modes at 225 °C and 345 °C. Kaolinite and quartz are unstable with respect to pyrophyllite at the higher temperatures. No pyrophyllite has been observed at Barneys Canyon restricting the kaolinitic alteration to the lower-temperature range. The formation temperature of illite is not constrained. The bedding-plane gouges contain illite, kaolinite (minor), quartz, carbonate, and as much as 1.5 ppm Au. The illites yielded K/Ar ages of 147 Ma and 159 Ma consistent with K/Ar ages of heavy metal bearing illite veins in the southern Oquirrh Mountains described by Wilson and Parry (1990b). This interpretation extends Jurassic deformation to north-central Utah from areas to the west where Jurassic magmatism and tectonics have previously been described.