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6.4.21(8)(c)
<br />The regional and local geological structure can be described as follows (excerpt from USGS Professional Paper 359,
<br />ECONOMIC GEOLOGY OF THE CENTRAL CITY DISTRICT. GILPIN COUNTY COLORADO. Sims, P. K.,,
<br />Drake, A. A., and Tooker, E. W., 1963):
<br />Upper Russell Gulch Area
<br />"The upper Russell Gulch area includes the mines in or near the village of Russell Gulch, south of State
<br />Highway 279 [Virginia Canyon Rd.] and west of the head of Willis Gulch. Several mines are large and have
<br />been substantial producers; the Old Town, Iron, and Pewabic have each produced more than $1 million.
<br />"Most of the area is on the southeast limb of the Central City anticline. The axis of a minor open syncline, the
<br />Russell Gulch syncline, is east of the Pewabic mine. The contact between microcline-bearing gneiss, which
<br />crops out along the axis of the Central City anticline, and overlying interlayered biotite gneisses trends east-
<br />northeast through the area, generally following the south side of Russell Gulch. At least one layer of biotite-
<br />quartz-plagioclase gneiss, an estimated 250 feet thick, occurs within the microcline-bearing gneiss layer; this
<br />layer of biotite gneiss probably is the equivalent of the layer that occurs in the microcline-bearing gneiss under
<br />Quartz Hill.
<br />"The veins are mainly pyrite veins, most of which contain moderate quantities of copper minerals (type B). In
<br />the mines south of Russell Gulch much of the gold ore, particularly the higher grade material, occurs as so-
<br />called talc ore, an argillized rock probably of supergene origin, which is enriched in gold.
<br />"Most of the ore shoots plunge nearly vertical or steeply to the west. They are localized by deflections in strike
<br />of the veins on the steep parts of the veins, and on or near vein junctions or intersections. The veins are
<br />markedly stronger in the microcline-bearing gneiss than in the biotite gneisses, and ore shoots are rarely found
<br />in the latter."
<br />(USGS Professional Paper 359, ECONOMIC GEOLOGY OF THE CENTRAL CITY DISTRICT
<br />GILPIN- COUNTY. COLORADO, Sims, P. K.,, Drake, A. A., and Tooker, E. W., 1963, pg. 117-
<br />118).
<br />A more detailed analysis can be found within the referenced citation, but has not been included here. Since no
<br />underground development or no newly proposed surface impoundments are proposed; but rather removal of a pre-
<br />existing waste rock dump, this geologic summary shall suffice.
<br />6.4.21(8)(d)
<br />The only major, identifiable fault know to exist in the area is the Idaho Springs Fault which is illustrated in USGS
<br />Bulletin 1208, Plate 2, Generalized Geologic Map and Sections of the Idaho Springs District Colorado attached to
<br />this Exhibit U.
<br />This fault is located approx. 2 miles to the south of the proposed operation and does not impact the underlying
<br />geology.
<br />Detailed above in 6.4.21(8)(b-c) is a description of the vein and fracture systems that underlie this area and provide
<br />a hydraulic drainage connection to the Argo Tunnel.
<br />6.4.21(8)(e)
<br />Detailed above in 6.4.21(8)(b-c) is a description of the vein and fracture systems that underlie this area and provide
<br />a hydraulic drainage connection to the Argo Tunnel.
<br />Refer to a map from USGS Professional Paper 359, ECONOMIC GEOLOGY OF THE CENTRAL CITY
<br />DISTRICT GILPIN COUNTY COLORADO, Sims, P. K.,, Drake, A. A., and Tooker, E. W., 1963 at the end of
<br />Exhibit C detailing this.
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