Geochemical analyses of surface water, groundwater and springs surrounding Mount Emmons near Crested Butte, Colorado (ver. 2.0, September 2020)

The U.S. Geological Survey (USGS), Colorado Division of Reclamation, Mining and Safety (DRMS), and Coal Creek Watershed Coalition (CCWC) working independently, have intermittently collected samples of surface- and groundwater and springs around Mount Emmons, near Crested Butte, Colorado. This data release is a compilation of the comprehensive inorganic chemical analyses conducted as a result of that sampling. The earliest samples were collected in the summer of 1997, and subsequent sampling has continued through 2017. Water samples collected in the Elk Creek basin, sample identifiers starting with EC, have been previously published in three U.S. Geological Survey reports; Verplanck and others, 2007, Manning and others, 2008, and Verplanck and others, 2010. These reports contain figures showing locations of samples including samples from underground in the Standard Mine. The geochemical analyses for this compilation were conducted by several analytical laboratories, so potential users of the data should be aware of uncertainties introduced by direct comparison of data from more than one lab. Nevertheless, these data serve as a record of potential changes and trends in water chemistry over a 20-plus year period that may be useful for evaluation of long-term environmental changes. Mount Emmons is interesting because it is host to a number of mineral deposits of various types, including polymetallic vein systems (primarily Pb-Zn deposits) and porphyry Mo deposit(s). If these deposits are exposed to the oxygenated weathering environment, they may produce acidic waters that are rich in heavy metals such as Zn, Cd, Pb, and other elements. The alteration halos surrounding the mineralized areas also can be weathered to mobilize heavy metals in the environment. Acidic, metal-rich waters typical of these environments are found around Mount Emmons, some of which are natural and some of which are of anthropogenic origin.