MARBLES, MAGMAS, AND MINERALS: UNDERSTANDING MINERAL POTENTIAL IN THE STRUCTURALLY DISMEMBERED, MULTI-GENERATIONAL GOLD HILL MINING DISTRICT, UTAH (Invited Presentation)

The Gold Hill mining district is located in the North American Cordilleran orogenic system retroarc hinterland of western Utah along the Uinta–Cortez axis, an east-west-trending structural zone that is a deep crustal suture between Precambrian blocks that also hosts the Bingham Canyon and Park City mining districts. The Paleozoic rock units in Gold Hill comprise Mississippian to Permian marine basinal to carbonate platform facies that underwent compressional deformation in the Jurassic, lower crustal thickening and upper crustal shortening during development of the Nevadaplano in the Cretaceous, extension in multiple events from the Eocene to the Miocene, and Basin and Range extension from Miocene to the present. The complex brittle deformation of the Paleozoic units means there is no intact section anywhere in the district, and unit identification is complicated by bleaching, marbleization, and jasperoid development associated with magmatism. Three distinct magmatic pulses are recorded at Gold Hill, including a 155 Ma quartz monzonite pluton, a 40 Ma granite stock, and a series of 16–17 Ma dikes cutting the quartz monzonite pluton, varying from basaltic to rhyolitic in composition. Multiple smaller magmatic bodies such as diorite and aplite have been identified in the district, but lack detailed mapping and characterization.

As part of USGS-funded EarthMRI research at Gold Hill, new mapping and geochemistry were combined with literature, previous exploration results, geophysics, and geochemistry to understand the metallogenic potential of Gold Hill and how this area fits into regional geologic architecture. Gold Hill has been a target of mineral exploration activity for many decades and at least three mineralizing events with distinct metallogenic profiles are identified. A holistic interpretation of the district through a mineral systems understanding demonstrates potential for additional blind magmatic-hydrothermal systems. However, the structural complexity of the district and the multi-generational magmatic/metallogenic history requires a deep understanding of the framework geology to translate general mineral system models to practical exploration targets. This talk demonstrates the link between evolution of the underlying geology and the processes that prepared, controlled, and subsequently affected mineralization events.