GSA Connects 2021 in Portland, Oregon

Paper No. 101-12
Presentation Time: 4:35 PM


WETZEL, Matthew, Tucson, AZ 85711

The Southwest Tintic porphyry system is a blind porphyry Cu-(Mo-Ag) deposit, located in the Tintic mining district in the East Tintic mountains, west-central Utah. Reported combined production from various veins, breccias, and carbonate replacement deposit (CRD) ore bodies in the Tintic district is an estimated 25 million tons of ore containing 2.85M oz of Au, 291M oz of Ag, 278M lbs of Cu, 2.4G lbs of Pb, and 575M lbs of Zn. The undeveloped Southwest Tintic deposit has a reported historic non-compliant (to any regulatory institution) mineralized volume of >6G lbs of Cu, within an estimated 1.5G tons of mineralized material at 0.21% Cu, 0.01% Mo.

Recent deep exploratory drilling intersected three distinct, spatially-related deposit types: 1) pyrite ± enargite, high-sulfidation epithermal veins; 2) CRD-style mineralization that contains chalcopyrite-pyrite-pyrrhotite-sphalerite mineralization; and 3) porphyry copper-style alteration and mineralization. The porphyry (Southwest Tintic) is hosted in the 34.9-32.8 Ma aged caldera complex principally consisting of three volcanic units: an upper air fall latite tuff, a middle andesite, and lower welded latite tuff. Porphyry copper-style mineralization and alteration are associated with various intrusive phases chiefly composed of monzonite (33.5 ± 0.3) and monzodiorite (34.4± 0.3Ma) porphyry dikes and plugs, and cut by sparsely mineralized, megacrystic monzonite porphyry dikes. Evidence from mineral textures, and cross cutting relations indicate that the distal epithermal and CRD mineralization are connected to the development of the blind porphyry system. This has led to the development of a refined geologic-paragenetic model for the district.

Through the study of the Tintic district we have a better understanding for the systems that influence the distribution and timing of the mineralization events that drive the formation of diverse deposit types present throughout the East Tintic Mountains. Porphyry copper and related satellite deposits contain significant amounts of the metals which are necessary for the green economy. An increased understanding of how these mineral systems develop and relate to one another in time and space will aid us in providing those critical metals that will power the incoming global economic shift in energy production.