GEOCHEMICAL SURVEY FOR ASSESSING THE ECONOMIC POTENTIAL OF THE MOUNT BELKNAP VOLCANICS, SOUTH-CENTRAL UTAH

The Marysvale Volcanic Field (MVF) in south-central Utah is a historic gold, silver, and uranium mining district. An initial reconnaissance survey carried out earlier this year revealed that much of the historic mining was surficial and didn’t utilize modern exploration or drilling techniques. There is evidence that there is still potential for hidden ore bodies that can be profitably and environmentally extracted. Numerous surface indicators of hidden ore deposits, like intensely weathered outcrops of precious and base metal sulfides know as gossan, are widely observed. As well as siliceous cappings caused by hydrothermal fluids that may have contained ore elements.

Surface water is an underutilized mineral exploration tool and with the advent of new analytical technology shows great promise. We are currently investigating the economic potential of the MVF by analyzing surficial water samples from 36 sites along a 30-km stretch of the Sevier River that cuts through the Mount Belknap Volcanics beginning at the outlet of Piute Reservoir northward through the MVF. Samples have currently been carried out for Ag, Cu, As, and nine other chalcophile elements commonly associated with base metal ore deposits. With pending analysis of Au, U, Th, and the Au-­pathfinder elements (Bi, Sb).

The spatial distribution and concentrations of these elements were correlated with drainage pathways associated with gossan and siliceous caps. All sites contained concentrations of (SO₄)^2-, Cu and Fe with Co, Ag, and Cr completely absent. The site with the most promise (site 17) contained concentrations of Zn and Cu at ~18 and ~4 mg/L respectively. These elevated concentrations of select elements coupled with mapped alunite, kaolinite and gossan within the drainage basin of site 17 are strong evidence for a hidden ore body of the kaolinite-alunite epithermal type gold deposit. Future geochemical and geophysical techniques will be used to further investigate the drainage basin of site 17. Surficial aqueous exploration techniques offer advantages to sediment analyses, due to the lower concentration thresholds of aqueous analyses and the greater homogeneity of water. Since sediment analyses are the most common geochemical exploration technique for minerals, a comparison of the techniques will help to advance the field of mineral exploration.