PERMFILE60690 - Laserfiche WebLink

Home Browse Search

' '.k.. . .a ' ~ Location, History, Produdton:_ The Sungystde Hine is located 1n the Eureka 111n1ng District, San Juan County, Colorado. The tarn of Silverton (pop. 600) 11 es approximately 8 Hiles south of the mine (figure 1). Bold outcrops of the Sunnyside, No Name, Washington and 8e11e Creole veins were discovered in the early 1810s. Isolation and the law grade naturo of the ores prevented large scale development and production during the 1870s and 1880s. However, by the turn of the century, consolidation and the lntroducti~>n of capital transformed cony prooising lower grade properties, Sungystde Included, into mayor mining operations. A Mgh point in early day production was reached 'ln 1917 after the corpletlon of a 500 ton per day differential flotation atii. The corbined effects of declining ore grades, low metals prices and higher costs associated with greater depth forced Sungyside to close in 1930. Except for the year 1931, the mine remained closed until 1959 when Standard Uraniuo of Hoab, Utah leased i the nine and adfacent properties from U.S. Saelting and Refining Co. Standard ~ Uranium--soon to become Standard Metals Corp. rehabilitated the Gold King 'American' I Tunnel and then extended the tunnel beneath the old Sunnyside mine workings. During the 1960s, Standard Metals Corp. mined predominantly base metal ores from previously known veins. However, beginning in the early 1970s, a series of new veins rich in gold were discovered and developed. One of the gold bearing veins, Spur ~ Vein, lay beneath Lake Emma. a glacial tarn. Stoping inadverterrtly breached the lake bottom 1n 1978, flooding the mine. Fu11 production did not resume until 1982. In 1985, the mine was closed as a result of the bankruptcy of Standard tletals Corp. Sunnystde Goid Corp., a subsidiary of Echo Bay Nines, aswmed the Sungyside Hine lease in tlove~er, 1986. Echo Bay has formed a ,)oinL venture with +the following: Silver Kingiiines, Inc. and Pacific Silver Corporation. Recorded production for the Sunnyside nine is summarized in Table 1. In 1987 the mine produced at a rate of 757 tons of ore per day. District Geology: Resurgent doming of the San Juan-Uncompahgre caideras produced a wide zone of fracturing known as the Eureka Graben (figure 1) approximately 28 million years ago (Casadevall, 1973). The reins of the Sunnyside Cline are localized by this fracturing and are in part offset and disrupted by later faulting within the Graben. Amore detailed discussion of the regional structural history of the area aan be found in Burbank and Luedke, 1969 and Casadevall, 1973. Contenporaneous with the resurgent doping and graben formation, lava flows, pyroclastic flows and tuffacious sediments were deposited within rind around the caidera (Casadevall, 1913). The earlier of these accumulations, mostly lava flows (rhyolite) have been assigned to the Eureka Formation, while the later flows and tuffaceous deposits cake up the Burns and Henson Formations (lat:ite to quartz 62