SEDIMENT-HOSTED MINERALIZATION IN NEOPROTEROZOIC TO PALEOZOIC PLATFORM AND PLATFORM MARGIN CARBONATES AND SILICICLASTICS IN THE STIBNITE-YELLOW PINE MINING DISTRICT: A NORTHERN NEVADA ANALOG (?)

 

The Stibnite-Yellow Pine Mining District, in central Idaho, has produced significant gold, silver, antimony, tungsten and mercury and been the focus of nearly continuous mining activity for over 90 years. Past production occurred from underground and open pit operations in intrusive- and sediment-hosted deposits. Sediment-hosted mineralization, as typified by the West End deposit, has long been enigmatic in respect to its origins and relationship to the better studied intrusive-hosted deposits. Ongoing studies indicate similarities between the District’s precious metals deposits to those found farther south within the Great Basin.

Carbonate- and siliciclastic-hosted gold mineralization occurs in a roof pendant of Neoproterozoic to lower Paleozoic platform to platform margin facies rocks situated along the eastern edge of the Idaho Batholith and western margin of the Thunder Mountain Caldera. Age-correlative and facies equivalent rocks extend discontinuously in a belt southeast and northwest and are highly prospective for similar types of deposits. A regional-scale horst and graben complex (Stewart, et al., 2013) extends through the district and is probably related to the District’s metal endowment. This feature, associated with dike swarms, shallow intrusive stocks and volcanic centers provides evidence of large scale Eocene-age heat flow coeval with extensional tectonics and is similar in scale and style to other precious metal endowed Eocene-age features in the Republic District in north-central WA, the Challis region of south-central ID and extensional domains in northern Nevada.

Disseminated gold and antimony mineralization occurs within metamorphosed limestones, dolomites, quartzites, siltites and schists and exhibits primary structural and secondary stratigraphic controls. Unconformities in the section may also have acted as flow pathways for hydrothermal fluids. Isotopic dating indicates the sedimentary sequence likely spans the Cambro-Ordovician boundary which is the focus of mineralization in many sediment-hosted gold districts in the Great Basin.