Geology and ore deposits of the Rico District, Colorado

McKnight, Edwin Thor

doi:10.3133/pp723

Cited by 12 publications

(23 citation statements)

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“…The upper part also contains fossilbearing beds that have a greater proportion of mollusks to brachiopods as compared to fauna in the lower and middle parts of the formation. A similar ratio of mollusks to brachiopods is typical of the Rico Formation of Pennsylvanian age, a transitional unit between marine Hermosa below and continental Cutler above, as mapped in the Rico area about 25 mi to the south west (McKnight, 1974). Comparison of the fauna from the two areas found that each contained a considerable number of species in common, but also that each had a considerable num ber of species peculiar to itself (Burbank, 1930, p. 165).…”

Section: Hermosa Formationmentioning

confidence: 93%

“…The lack of large replacement deposits in this formation is due either to unfavorable lithic characteristics of its beds or to some unfavorable structural conditions. It is significant, however, that the major massivesulfide replace ment ore deposits characteristic of the middle Hermosa in the Rico mining district are not present at Ouray (Ransome, 1901;McKnight, 1974).…”

Section: Hermosa Formationmentioning

confidence: 99%

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Geology and ore deposits of the Uncompahgre (Ouray) Mining District, Southwestern Colorado

Burbank¹,

Luedke²

2008

Professional Paper

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Section: Hermosa Formationmentioning

confidence: 93%

Section: Hermosa Formationmentioning

confidence: 99%

Geology and ore deposits of the Uncompahgre (Ouray) Mining District, Southwestern Colorado

Burbank¹,

Luedke²

2008

Professional Paper

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“…The potential for considerable amounts of non-AMD water entering the system along the St. Louis Tunnel may also be explained by the regional hydrogeology. The drainage tunnel extends several thousand feet into the Rico dome, which is comprised of a thick series of interbedded sandstone, arkose, shale, limestone and dolomite of the Pennsylvania age Hermosa formation [51]. One of the units of this formation is the Leadville Limestone, which is locally 75 m thick and the top of the unit exhibits widespread karst and related erosional features [52].…”

Section: The St Louis Tunnel Portal Dischargementioning

confidence: 99%

Use of Natural and Applied Tracers to Guide Targeted Remediation Efforts in an Acid Mine Drainage System, Colorado Rockies, USA

Cowie

Williams

Wireman

et al. 2014

Water

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Stream water quality in areas of the western United States continues to be degraded by acid mine drainage (AMD), a legacy of hard-rock mining. The Rico-Argentine Mine in southwestern Colorado consists of complex multiple-level mine workings connected to a drainage tunnel discharging AMD to passive treatment ponds that discharge to the Dolores River. The mine workings are excavated into the hillslope on either side of a tributary stream with workings passing directly under the stream channel. There is a need to define hydrologic connections between surface water, groundwater, and mine workings to understand the source of both water and contaminants in the drainage tunnel discharge. Source identification will allow targeted remediation strategies to be developed. To identify hydrologic connections we employed a combination of natural and applied tracers including isotopes, ionic tracers, and fluorescent dyes. Stable water isotopes (δ 18 O/δD) show a well-mixed hydrological system, while tritium levels in mine waters indicate a fast flow-through system with mean residence times of years not decades or longer. Addition of multiple independent tracers indicated that water is traveling through mine workings with minimal obstructions. The results from a simultaneous salt and dye tracer application demonstrated that both tracer types can be successfully used in acidic mine water conditions. OPEN ACCESSWater 2014, 6 746

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“…1) consists of a thick sequence of Paleozoic and Mesozoic sedimentary rocks that has been uplifted more than 1 km (Pratt et al, 1969;McKnight, 1974;Pratt, 1976). 1) consists of a thick sequence of Paleozoic and Mesozoic sedimentary rocks that has been uplifted more than 1 km (Pratt et al, 1969;McKnight, 1974;Pratt, 1976).…”

Section: Geologymentioning

confidence: 99%

“…Two contemporaneous and cogenetic intrusive rocks, hornblende latite porphyry and augitc monzonite, were intruded at about 65 Ma (McKnight, 1974; Naeser et al, 1980). Hydrothermal mineralization resulted in the formation of several ore deposits (Ransome, 1901;McKnight, 1974;Barrett et al, 1985;Larson, 1987 Larson, 1987) and are similar to veins at the Sunnyside mine within the Silverton caldera, western San Juan volcanic field (Casadevall and Ohmoto, 1977). These rocks appear to be petrologically and structurally similar to the laccoliths of the Colorado Plateau.…”

Section: Geologymentioning

confidence: 99%

Large-scale alteration effects in the Rico paleothermal anomaly, Southwest Colorado

Larson

Cunningham²,

Naeser³

1994

Economic Geology

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A major 4 Ma palcothermal anomaly is present around the Silver Creek stockwork Mo deposit near Rico, southwestern Colorado. The anomaly extends at least 8 km outward from the deposit and was formed from heated, meteoric water circulating around an intrusion related to the deposit. The top of the 4 Ma Mo deposit is located near the center of the anomaly, more than 1 km beneath the present ground surface. Near-surface contemporaneous vein and replacement base and precious metal deposits are peripheral to the Mo system; they were the source of historic production in the Rico mining district.The thermal and chemical effects of the palcothermal anomaly are well developed in 65 Ma hornblende latite sills that extend throughout the district. They provided an essentially uniform material in which to measure the effects of water-rock interaction. Hydrothermal alteration in the latite resulted in several alteration facies. A texturally destructive facies proximal to the center of the system consists of quartz-illite-calcite and chlorite-epidote assemblages and is restricted to a vertical cylindrical zone, 3 km in diameter, directly above the stockwork Mo deposit. Peripheral to this, the latite is altered to a propylitic assemblage, with primary textures preserved. Temperature gradients in the altered latite, measured from tetrahedralsite AI in hydrothermal chlorite and the degree of partial annealing of fission tracks in apatite and zircon, are symmetrically distributed about the stockwork Mo deposit and show that temperature increased gradationally toward the heat source. The chlorite tetrahedral AI geothermometer indicates that temperatures were less than 200øC in the distal part of the system and greater than 300øC in the center of the palcothermal anomaly, directly over the stockwork Mo system. Whole-rock b•sO values of the latite decrease from near fresh-rock values of about 9.0 per mil to as low as -4.0 per mil above the Mo deposit. Mass exchange between fluid and latite is extensive above the Mo deposit, where nearly all of the Na•O has been removed from the rocks. The extent and distribution of thermal and chemical effects in a vertical cylindrical volume of rock above the heat source suggests that this marks the pathway for an upwelling geothermal plume, 3 km wide and at least 2 km high. A horizontal outflow plume moved laterally away from the rising plume 1.5 to 2 km above the stockwork Mo system. Water/rock ratios within the plume area are greater than 0.5 on a molar oxygen basis, but are less than 0.45 in the propylitized latite outside the plume. All mineralization in the Rico district is related to this 4 Ma meteoric-magmatic hydrothermal system. The deep stockwork Mo deposit is beneath the plume and the shallower veins and replacement deposits are at the margins of the plume.

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Geology and ore deposits of the Rico District, Colorado

Cited by 12 publications

References 0 publications

Geology and ore deposits of the Uncompahgre (Ouray) Mining District, Southwestern Colorado

Geology and ore deposits of the Uncompahgre (Ouray) Mining District, Southwestern Colorado

Use of Natural and Applied Tracers to Guide Targeted Remediation Efforts in an Acid Mine Drainage System, Colorado Rockies, USA

Large-scale alteration effects in the Rico paleothermal anomaly, Southwest Colorado

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