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S PURR MONOGRAPH <br />Aspen ores are common in igneous rocks, rare in <br />sediments. <br />Changes in Ore since Deposition, pp. 236-242 <br />Mechanical chances, p. 236. Mechanical changes are <br />limited to crushing and grinding ["trituration"] along <br />fault planes where ores were deposited by subsequent <br />movement, as demonstrated continuously along the Silver <br />fault in the Smuggler mine, and offset of the deposits <br />themselves (and attendant faults) by new, post- <br />deposition, faults, such as Clark fault in the Smuggler. <br />Chemical chanoes, pp. 236-242. Formation of native <br />silver, mainly in the Smuggler and Mollie Gibson mines, <br />is the principal post-depositional chemical change in <br />the Aspen district ores. The silver is generally <br />associated with the Weber [Belden] shales, and is <br />sometimes massive but usually "spun into wires and <br />delicate threads, which occur in crevices and vugs." A <br />further reduction of polybasite/tennantite occurs, <br />producing a crumbly ore consisting essentially of barite <br />held together by silver. This ore occurs along fracture <br />zones and watercourses" in the vicinity of the Weber <br />[Belden] shales. <br />Oxidation of ores, pp. 237-239. In near surface areas, <br />sulfide ores have been oxidized to oxides, sulfates and <br />carbonates, although barite is not altered. A <br />calculated composition from a sample from the Buckhorn <br />No. 2 mine in Tourtellotte Park showed lead as the <br />sulfate at 19.18 (anglesite), as the sulfide at 2.28 <br />(galena), and silver as the sulfide <br />(acanthite/argentite). Magnesium sulfate occurs in idle <br />or abandoned areasls as long, silky, hair-like masses of <br />delicate crystals leached from slow decomposition of <br />sulfides adjacent to mine openings (epsomite). <br />Watercourse alteration, pp. 291-242. The general <br />alteration of rocks along underground watercourses <br />[faults and breccias], producing soft, clay-like areas <br />(and areas where in fact clay minerals are all that <br />remain), is described. <br />Surface changes since ore deposition, pp. 243-250. <br />Total erosion in the immediate Aspen area based on post <br />Weber [Belden] rocks to the west is at least 15,000 ft. <br />Essentially one and the same. <br />is For example the Anaconda crosscut in the Smuggler mine. <br />Bruce A. CO111R5 - S - BIBLIOGAAPBY <br />