Hydrogeochemical Investigations of Historic Mining Districts, Central Western Slope of Colorado, Including Influence on Surface-Water Quality By J. Thomas Nash U.S. Geological Survey Digital Data Series DDS-73 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey Charles G. Groat, Director February 2002, version 1.0 For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225 For more information about the USGS and its products: Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov/ This publication is also available online at: http://geology.cr.usgs.gov/pub/dds/dds-073/ Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government III Contents Abstract .......................................................................................................................................................... 1 Introduction ................................................................................................................................................... 1 Methods ......................................................................................................................................................... 4 Rock and Mine-Waste Geochemical Studies ................................................................................. 4 Water Geochemical Studies .............................................................................................................. 4 Laboratory Leach Tests of Mineralized Samples ........................................................................... 4 Geographic Setting and Climate ................................................................................................................ 5 Introduction to Ore-Deposit Types and Their Environmental Signatures ........................................... 5 Polymetallic Deposits.......................................................................................................................... 8 Gold-Quartz Vein Deposits ............................................................................................................... 14 Massive Sulfide Deposits................................................................................................................. 14 Sediment-Hosted Copper Deposits ................................................................................................ 15 Uranium Deposits .............................................................................................................................. 15 Porphyry Cu-Mo Deposits ................................................................................................................ 15 Geochemistry of Mined Mineralized Rocks .................................................................................. 16 Mining, Mills, and Mill Tailings: An Introduction ................................................................................... 17 Mobility of Metals: Leach Tests of Mineralized Rocks......................................................................... 28 Water Quality: Introduction to Standards and Ratings......................................................................... 32 Threats to Aquatic Life by Metals: A Copper-Zinc Index ..................................................................... 33 Surface-Water Quality Relative to Historic Mining...............................................................................34 Geochemical Concepts for Water Quality ..................................................................................... 38 Risks During Extreme Storms: Failure of Tailings Impoundments ...................................................... 42 Geochemical Investigations of Historic Mining Districts .................................................................... 43 Mining Districts of the Gunnison River Watershed............................................................................... 44 Cochetopa District (Gunnison Gold Belt)....................................................................................... 44 Vulcan Subdistrict (within Cochetopa District) ............................................................................ 47 Los Ochos Subdistrict (within Cochetopa District) ...................................................................... 52 Marshall Pass District....................................................................................................................... 54 Gold Brick District.............................................................................................................................. 56 Quartz Creek District ......................................................................................................................... 60 Ruby District (Irwin)........................................................................................................................... 64 Tincup District .................................................................................................................................... 71 Tomichi District (Whitepine)............................................................................................................. 74 Mining Districts of the Lake Fork Watershed......................................................................................... 79 Burrows Park District (Whitecross, including Sherman)............................................................ 81 Galena District (Henson Creek)....................................................................................................... 82 Lake Fork District (Lake San Cristobal) .......................................................................................... 87 Mining Districts of the Uncompahgre River Watershed ...................................................................... 88 Ouray District (Uncompahgre)......................................................................................................... 88 IV Sneffels District.................................................................................................................................. 93 Mineral Point District (including Upper Uncompahgre)............................................................ 100 Red Mountain District ..................................................................................................................... 103 Mining Districts of the Upper San Miguel River Watershed ............................................................. 117 Telluride District ............................................................................................................................... 118 Iron Springs District (Ophir) ........................................................................................................... 125 Mount Wilson District ..................................................................................................................... 134 Placerville District (Lower San Miguel) ....................................................................................... 135 Mining Districts of the Lower San Miguel River Watershed............................................................. 135 Uravan District ................................................................................................................................. 135 Cashin District (La Sal Creek) ........................................................................................................ 139 Discussion and Summary ........................................................................................................................ 140 References Cited ...................................................................................................................................... 143 Appendix I: Water-Sampling and Analysis Methods .......................................................................... 149 Appendix 2: Tables 1–3............................................................................................................................. 152 Figures 1. Location of mining districts studied, central Western Slope, Colorado.............................. 3 2. Composition of mined materials by deposit type, central Western Slope, Colorado ....................................................................................................................................... 12 3. Composition of mineralized rocks by sample type, central Western Slope, Colorado ....................................................................................................................................... 13 4. Location of mill tailings and mill sites, central Western Slope, Colorado......................... 17 5. Compositions of leachate solutions by deposit type ............................................................ 29 6. Compositions of leachates from mineralized rocks as a function of pH........................... 30 7. Copper-zinc index (CZI) values for surface waters, central Western Slope, Colorado........................................................................................................................... 34 8. Comparison of mine drainage and stream water compositions, central Western Slope, Colorado .......................................................................................................... 40 9.