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Part II <br />Works Aiter Cessation <br />of Significant Mining (1926-1953) <br />VANDERWILT REPORT <br />1. W. VANDERWILT, REVISION OF STRUCTURE AND $TRATICRAPRY OP THE ASPEN DISTRICT, <br />COLORADO, AND ITS BEARING ON THE ARE DEPOSITS, 30 Economic Geology <br />223-241 (1935) ("VANDERWILT REPORT"~ <br />Vanderwilt generally questions Spurr's interpretation of <br />purely fault control - Silver and Contact faults - of the <br />Aspen ore deposits,'0 and presents a revised theory that <br />Aspen ores occur at the intersections of cross-cutting <br />faults and certain sedimentary horizons. <br />General occurrence of Aspen ores, p. 226. In the Aspen <br />district, virtually all metal production has come from two <br />horizons: on Smuggler mountain, along or near the contact <br />between the [Leadville) dolomite and the overlying shaly <br />members of the weber [Belden] formation, and on Aspen <br />mountain, between the dolomite and limestone members of the <br />Leadville. <br />Character of deposits in Smucgler mountain, p. 234. The <br />mine workings of Smuggler mountain are on the northward <br />continuation of beds that form the east limb of the Aspen <br />mountain syncline, but whether the syncline itself extends <br />to Smuggler mountain is not known. Cross-faults on Smuggler <br />mountain dip 35-40° southwest, while they are nearly <br />vertical on Aspen mountain. in general the footwalls have <br />moved upward, a few to over 200 feet. The faults are <br />commonly brecciated or shattered throughout the zones that <br />are up to 50 ft. thick with no clean-cut fault plane. <br />Breccias, pp. 235-238. Breccia found in the Aspen district <br />is evidence against the presence of large bedding faults. <br />Brecciated and shattered rock is very common and usually <br />present in the walls of stopes. There are two types of <br />breccias, those related to cross-faults and those related to <br />bedding. <br />Breccia related to cross-faults, pp. 235-236. On Smuggler <br />mountain sedimentary beds strike N. ±45° E. and dip 50° <br />northwest, and are cut by faults striking N. 45° W. and <br />~0 $e@ generally SPURR MONOGRAPH and SPURR REPORT. <br />Bruce A. Collins - 14 - BIeLIOCRAPHY <br />