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3.0 GENERAL HYDROGEOLOGY OF THE SUNNYS/DE M/NE <br />The general hydrogeology in the vicinity of the Sunnyside Mine was covered in <br />"Preliminary Characterization of the Hydrology and Water Chemistry of the Sunnyside <br />Mine and Vicinity, San Juan County, Colorado" by Simon Hydro-Search (1992). <br />Selected aspects of that discussion are excerpted below. <br />3.1 Geology Pertinent to Ground-Water Flow and Chemistry <br />Rocks in the vicinity of the Sunnyside Mine are pyroclastics and flows which erupted <br />from local calderas approximately 28 million years ago (Steven and Lipman, 1976). <br />The Sunnyside Mine is principally located within the Burns Formation, which generally <br />consists of massive silica-rich latite flows which have locally been altered and <br />mineralized (Langston, pp. 34-391. The highest mine workings (above A level) extend <br />1 into the overlying interbedded lava flows and air-fall tuffs of the Henson Formation, <br />an alkali-rich andesite (Langston, p. 49). <br />The Burns Formation was erupted from vents within the San Juan caldera (Steven and <br />Lipman, 1976, p. 11-12). The degree of welding of the upper Burns formation <br />generally increases towards the west in the direction of the vent source (Langston, <br />1978, p. 11). The Henson Formation also was derived from vents located within the <br />San Juan caldera, but typically is less welded than the Burns Formation and contains <br />more pyroclastic units. <br />cunnylwpltmci122511Mer1993.Rpt 1 <br />N:0 SItT1011 HYDRO-SEARCH <br />