Natural Versus Mining-Related Water Quality Degradation to Tributaries Draining Mount Moly, Silverton, Colorado

Yager, Douglas B. ; Mast, M. Alisa ; Verplanck, Philip L. ; Bove, Dana J. ; Wright, Winfield G. ; Hageman, Philip L.
Organization: Society for Mining, Metallurgy & Exploration
Pages: 14
Publication Date: Jan 1, 2000
Geological, hydrological, and geochemical information synthesized in a Geographical Information System (GIS) for water and rock surrounding South and Middle Forks of Mineral Creek, northwest of Silverton Colorado, was analyzed to distinguish between the natural and the mining-related sources of metals to dace waters in the watershed An important natural source of metals to surface water emanates from a porphyry molybdenum deposit south and upslope from the Middle Fork of Mineral Creek. Interaction of surface and ground water with fractured, altered rocks and permeable, Quatemay-age surficial deposits produces downstream water quality that does not meet current State of Colorado water quality standards for metals and pH. GIS site characterization and three-dimensional modeling distinguish surficial deposits as volumetrically substantial, significant sources of naturally occurring metals that strongly influence water quality and complicate ongoing mine-site mitigation efforts. Our findings indicate that regional hydrologic and geologic information needs to be evaluated before realistic water quality guidelines are established and mitigation recommendations are confidently implemented.
Full Article Download:
(1067 kb)