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Research about Leadville, Colorado

Source-linked reports with geographic coverage including Leadville, Colorado.

11 recordsLinked to original sources
USGS2026

Sackung at Bald Eagle ridge, central Colorado: An updated interpretation of ridge-spreading movement, structures, and mechanisms from 50 years (1975–2025) of U.S. Geological Survey research

Slow gravitational failures of mountain peaks and ridges are poorly understood. Herein, we report on 50 years of studies at a slowly spreading castellate ridge in the Sawatch Range in central Colorado. The orientations of geomorphic-structural features indicate that the fractured Precambrian granitic rock underlying the ridge has extended and spread northwestward toward the formerly glacier-covered Busk Creek valley. Results from surveying, field-based geomorphic-structural mapping using lidar, rock mass quality measurements, a passive seismic survey, and satellite radar provide a major update to research started by U.S. Geological Survey researchers in the 1970s and 1980s. New insights include a recognition that the entire ridge has slowly moved by concurrent sliding along an inferred northwest dipping, compound basal-slip surface (or zone), and through the formation of multiple grabens by normal faulting and flexural toppling along sets of pre-existing fractures that dip moderately (∼45°) to the southeast. We were unable to distinguish the presence of a sudden and strong contrast in seismic velocity across the inferred slip surface. Movement during the 50-year study period has been episodic and gradually decreasing, in correspondence with decreasing cumulative annual precipitation and increasing mean annual air temperatures. The fastest moving area, just upslope from the glacier trimline, had an average horizontal velocity of 3 – 4 mm/yr. Evidence suggests that movement started as a paraglacial response mechanism, but because of the site’s proximity to the Rio Grande Rift, we cannot exclude earthquake shaking as a mechanism for initiation or enhancement of slope movement. An estimate of longer-term horizontal movement from the exposed basal-slip surface at the uphill side of the ridgetop graben is ∼1.1 mm/yr for the 13 – 14 ky post-glacial period. Broad implications of our work are that: (1) long-term measurements (decades or longer) of slope movement can add insights into how sackungen form and evolve through time; (2) the identification of thrust faults and toes in zones of compression near valley bottoms can be crucial for interpreting sackung failure mechanisms, and (3) the use of passive-seismic techniques to identify the depth to a slip surface may not be successful in granitic terrain dominated by planar fractures and subtle changes in rock-mass characteristics.

Colorado↗
USGS2011

Hydrogeologic setting and simulation of groundwater flow near the Canterbury and Leadville Mine Drainage Tunnels, Leadville, Colorado

The Leadville mining district is historically one of the most heavily mined regions in the world producing large quantities of gold, silver, lead, zinc, copper, and manganese since the 1860s. A multidisciplinary investigation was conducted by the U.S. Geological Survey, in cooperation with the Colorado Department of Public Health and Environment, to characterize large-scale groundwater flow in a 13 square-kilometer region encompassing the Canterbury Tunnel and the Leadville Mine Drainage Tunnel near Leadville, Colorado. The primary objective of the investigation was to evaluate whether a substantial hydraulic connection is present between the Canterbury Tunnel and Leadville Mine Drainage Tunnel for current (2008) hydrologic conditions. Altitude in the Leadville area ranges from about 3,018 m (9,900 ft) along the Arkansas River valley to about 4,270 m (14,000 ft) along the Continental Divide east of Leadville, and the high altitude of the area results in a moderate subpolar climate. Winter precipitation as snow was about three times greater than summer precipitation as rain, and in general, both winter and summer precipitation were greatest at higher altitudes. Winter and summer precipitation have increased since 2002 coinciding with the observed water-level rise near the Leadville Mine Drainage Tunnel that began in 2003. The weather patterns and hydrology exhibit strong seasonality with an annual cycle of cold winters with large snowfall, followed by spring snowmelt, runoff, and recharge (high-flow) conditions, and then base-flow (low-flow) conditions in the fall prior to the next winter. Groundwater occurs in the Paleozoic and Precambrian fractured-rock aquifers and in a Quaternary alluvial aquifer along the East Fork Arkansas River, and groundwater levels also exhibit seasonal, although delayed, patterns in response to the annual hydrologic cycle. A three-dimensional digital representation of the extensively faulted bedrock was developed and a geophysical direct-current resistivity field survey was performed to evaluate the geologic structure of the study area. The results show that the Canterbury Tunnel is located in a downthrown structural block that is not in direct physical connection with the Leadville Mine Drainage Tunnel. The presence of this structural discontinuity implies there is no direct groundwater pathway between the tunnels along a laterally continuous bedrock unit. Water-quality results for pH and major-ion concentrations near the Canterbury Tunnel showed that acid mine drainage has not affected groundwater quality. Stable-isotope ratios of hydrogen and oxygen in water indicate that snowmelt is the primary source of groundwater recharge. On the basis of chlorofluorocarbon and tritium concentrations and mixing ratios for groundwater samples, young groundwater (groundwater recharged after 1953) was indicated at well locations upgradient from and in a fault block separate from the Canterbury Tunnel. Samples from sites downgradient from the Canterbury Tunnel were mixtures of young and old (pre-1953) groundwater and likely represent snowmelt recharge mixed with older regional groundwater that discharges from the bedrock units to the Arkansas River valley. Discharge from the Canterbury Tunnel contained the greatest percentage of old (pre-1953) groundwater with a mixture of about 25 percent young water and about 75 percent old water. A calibrated three-dimensional groundwater model representing high-flow conditions was used to evaluate large-scale flow characteristics of the groundwater and to assess whether a substantial hydraulic connection was present between the Canterbury Tunnel and Leadville Mine Drainage Tunnel. As simulated, the faults restrict local flow in many areas, but the fracture-damage zones adjacent to the faults allow groundwater to move along faults. Water-budget results indicate that groundwater flow across the lateral edges of the model controlled the majority of flow in and out of the aquifer (79 percent and 63 percent of the total water budget, respectively). The largest contributions to the water budget were groundwater entering from the upper reaches of the watershed and the hydrologic interaction of the groundwater with the East Fork Arkansas River. Potentiometric surface maps of the simulated model results were generated for depths of 50, 100, and 250 m. The surfaces revealed a positive trend in hydraulic head with land-surface altitude and evidence of increased control on fluid movement by the fault network structure at progressively greater depths in the aquifer. Results of advective particle-tracking simulations indicate that the sets of simulated flow paths for the Canterbury Tunnel and the Leadville Mine Drainage Tunnel were mutually exclusive of one another, which also suggested that no major hydraulic connection was present between the tunnels. Particle-tracking simulations also revealed that although the fault network generally restricted groundwater movement locally, hydrologic conditions were such that groundwater did cross the fault network at many locations. This cross-fault movement indicates that the fault network controls regional groundwater flow to some degree but is not a complete barrier to flow. The cumulative distributions of adjusted age results for the watershed indicate that approximately 30 percent of the flow pathways transmit groundwater that was younger than 68 years old (post-1941) and that about 70 percent of the flow pathways transmit old groundwater. The particle-tracking results are consistent with the apparent ages and mixing ratios developed from the chlorofluorocarbon and tritium results. The model simulations also indicate that approximately 50 percent of the groundwater flowing through the study area was less than 200 years old and about 50 percent of the groundwater flowing through the study area is old water stored in low-permeability geologic units and fault blocks. As a final examination of model response, the conductance parameters of the Canterbury Tunnel and Leadville Mine Drainage Tunnel were manually adjusted from the calibrated values to determine if altering the flow discharge in one tunnel affects the hydraulic behavior in the other tunnel. The examination showed no substantial hydraulic connection. The multidisciplinary investigation yielded an improved understanding of groundwater characteristics near the Canterbury Tunnel and the Leadville Mine Drainage Tunnel. Movement of groundwater between the Canterbury Tunnel and Leadville Mine Drainage Tunnel that was central to this investigation could not be evaluated with strong certainty owing to the structural complexity of the region, study simplifications, and the absence of observation data within the upper sections of the Canterbury Tunnel and between the Canterbury Tunnel and the Leadville Mine Drainage Tunnel. There was, however, collaborative agreement between all of the analyses performed during this investigation that a substantial hydraulic connection did not exist between the Canterbury Tunnel and the Leadville Mine Drainage Tunnel under natural flow conditions near the time of this investigation.

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USGS2009

Investigating hydraulic connections and the origin of water in a mine tunnel using stable isotopes and hydrographs

Turquoise Lake is a water-supply reservoir located north of the historic Sugarloaf Mining district near Leadville, Colorado, USA. Elevated water levels in the reservoir may increase flow of low-quality water from abandoned mine tunnels in the Sugarloaf District and degrade water quality downstream. The objective of this study was to understand the sources of water to Dinero mine drainage tunnel and evaluate whether or not there was a direct hydrologic connection between Dinero mine tunnel and Turquoise Lake from late 2002 to early 2008. This study utilized hydrograph data from nearby draining mine tunnels and the lake, and stable isotope (δ 18 O and δ 2 H) data from the lake, nearby draining mine tunnels, imported water, and springs to characterize water sources in the study area. Hydrograph results indicate that flow from the Dinero mine tunnel decreased 26% (2006) and 10% (2007) when lake elevation (above mean sea level) decreased below approximately 3004 m (approximately 9855 feet). Results of isotope analysis delineated two meteoric water lines in the study area. One line characterizes surface water and water imported to the study area from the western side of the Continental Divide. The other line characterizes groundwater including draining mine tunnels, springs, and seeps. Isotope mixing calculations indicate that water from Turquoise Lake or seasonal groundwater recharge from snowmelt represents approximately 10% or less of the water in Dinero mine tunnel. However, most of the water in Dinero mine tunnel is from deep groundwater having minimal isotopic variation. The asymmetric shape of the Dinero mine tunnel hydrograph may indicate that a limited mine pool exists behind a collapse in the tunnel and attenutates seasonal recharge. Alternatively, a conceptual model is presented (and supported with MODFLOW simulations) that is consistent with current and previous data collected in the study area, and illustrates how fluctuating lake levels change the local water-table elevation which can affect discharge from the Dinero mine tunnel without physical transfer of water between the two locations.

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USGS2005

Mass loading of selected major and trace elements in Lake Fork Creek near Leadville, Colorado, September-October 2001

A mass-loading study of Lake Fork Creek of the Arkansas River between Sugarloaf Dam and the mouth was completed in September-October 2001 to help ascertain the following: (1) variation of pH and aqueous constituent concentrations (calcium, sulfate, alkalinity, aluminum, cadmium, copper, iron, manganese, lead, and zinc) and their relation to toxicity standards along the study reach; (2) location and magnitude of sources of metal loading to Lake Fork Creek; (3) amount and locations of metal attenuation; (4) the effect of streamside wetlands on metal transport from contributing mine tunnels; and (5) the effect of organic-rich inflow from the Leadville National Fish Hatchery on water quality in Lake Fork Creek. The study was done in cooperation with the Bureau of Land Management, U.S. Department of Agriculture Forest Service, and U.S. Fish and Wildlife Service. Constituent concentrations and pH showed variable patterns over the study reach. Hardness-based acute and chronic toxicity standards were exceeded for some inflows and some constituents. However, stream concentrations did not exceed standards except for zinc starting in the upper parts of the study reach and extending to just downstream from the inflow from the Leadville National Fish Hatchery. Dilution from that inflow lowered stream zinc concentrations to less than acute and chronic toxicity standards. The uppermost 800 meters of the study reach that contained inflow from the Bartlett, Dinero, and Nelson mine tunnels and the Dinero wetland was the greatest source of loading for manganese and zinc. A middle section of the study reach that extended approximately 2 kilometers upstream from the National Fish Hatchery inflow to just downstream from that inflow was the largest source of aluminum, copper, iron, and lead loading. The loading was partially from the National Fish Hatchery inflow but also from unknown sources upstream from that inflow, possibly ground water. The largest sources for calcium and sulfate load to the stream were the parts of the study reach containing inflow from the tribu-taries Halfmoon Creek (calcium) and Willow Creek (sulfate). The Arkansas River and its tributaries upstream from Lake Fork Creek were the source of most of the calcium (70 percent), sulfate (82 percent), manganese (77 percent), lead (78 percent), and zinc (95 percent) loads in the Arkansas River downstream from the Lake Fork confluence. In contrast, Lake Fork Creek was the major source of aluminum (68 percent), copper (65 percent), and iron (87 percent) loads to the Arkansas River downstream from the confluence. Attenuation was not important for calcium, sulfate, or iron. However, other metals loads were reduced up to 81 percent over the study reach (aluminum, 25 percent; copper, 20 percent; manganese, 81 percent; lead, 30 percent; zinc, 72 percent). Metal attenuation in the stream occurred primarily in three locations (1) the irrigation diversion ditch; (2) the beaver pond complex extending from upstream from the Colorado Gulch inflow to just downstream from that inflow; and (3) the stream reach that included the inflow from Willow Creek. The most likely attenuation mechanism is precipitation of metal oxides and hydroxides (primarily manganese), and sorption or coprecipitation of trace elements with the precipitating phase. A mass-balance calculation indicated that the wetland between the Dinero Tunnel and Lake Fork Creek removed iron, had little effect on zinc mass load, and was a source for, or was releasing, aluminum and manganese. In contrast, the wetland that occurred between the Siwatch Tunnel and Lake Fork Creek removed aluminum, iron, manganese, and zinc from the tunnel drainage before it entered the creek. Inflow from the National Fish Hatchery increased dissolved organic carbon concentrations in Lake Fork Creek and slightly changed the composition of the dissolved organic carbon. However, dissolved organic carbon loads increased in the stream reach downs

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USGS1970

Nature and origin of early and late cherts in the Leadville Limestone, Colorado

Two generations of chert have been observed in the Mississippian Leadville Limestone of west-central Colorado: (1) an early chert inferred to have precipitated from hypersaline marine waters of high pH after those waters seeped into carbonate muds prior to final burial and lithification of the carbonate; and (2) a late chert that appears to have precipitated from ground waters as amorphous silica after initial lithification but prior to or during karst erosion of the formation in Late Mississippian (?) and Early Pennsylvanian time. A third type of microcrystalline quartz, hydrothermal jasperoid, is associated with ore deposits of Laramide age in the Leadville, but it is not discussed here. Conditions in west-central Colorado at the time that the early cherts formed in the Leadville were probably similar to those associated with the formation of early diagenetic chert in modern sediments, and the early chert in the Leadville is believed to have formed in a manner similar to the modern early cherts. The silica of the late chert appears to have come from Paleozoic sandstones below the Leadville. It was carried by slightly acid artesian waters into the formation, probably in concentrations of less than 60 ppm SiO 2 Super-saturation of amorphous silica occurred within the Leadville and probably was obtained by evaporative concentration at the water-air interface during dry seasons. Dissolution of the limestone by the slightly acid waters may account for the removal of the calcite that is replaced by chert.

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USGS1934

Zoning of ore deposits in and adjoining the Leadville District, Colorado

The ore deposits in the heart of the Leadville district , Colorado , are divisible, as shown by Emmons, Irving, and Loughlin,2 into two main classes on the basis of mineral composition: "contact-metamorphic" silicates accompanied by iron oxides, which adjoin an obscure igneous stock, and mixed sulphides accompanied by manganosiderite and quartz gangue, which cut the "contact-metamorphic" deposits and form a broad zone extending for 2 1/2 miles to the west and for shorter distances in other directions. A detailed consideration of the mineralogy of the mixed sulphide ore deposits clearly shows that they in turn are divisible into groups, referred to as hotter and intermediate mesothermal deposits . These groups, however, because of complications in structural control, are not ideally arranged from the standpoint of zoning .Emmons, Irving, and Loughlin noted that barite was a conspicuous gangue mineral in certain outlying deposits on the west slope of the Mosquito Range. The junior author during 1928-1931 had an opportunity to study the outlying deposits over an area of twenty square miles, which includes mines near the heads of Iowa Gulch and Empire Gulch, and the Weston Pass district (Fig. 1), and found that these baritic deposits form a somewhat distinct outer zone in which the primary ore consists of galena and light-colored zinc blende, with small amounts of silver and practically no gold, in a gangue of barite, jasperoid, and crystalline quartz. There is also recognized a still more remote though poorly defined zone in which the same sulphides are present but jasperoid is less conspicuous and barite is practically absent, whereas dolomite is the characteristic gangue mineral. The deposits in these two outer zones are fissure-fillings and comparatively small replacement bodies. They contrast strongly with the sulphide deposits in the heart of the Leadville district and are assigned to the outer mesothermal and epithermal zones. As they have not been described before, general features of these deposits are given in some detail, followed by their relations to the deposits within the Leadville district . Analogies are also drawn with similar deposits in other districts. In the preparation of this paper the authors have been impressed with the confusion that may result from too simple a conception of zoning . For a proper conception of Leadville , the geologist must have sufficient regard for structural conditions, must make due allowance for successive stages of mineral deposition within a small block of ground or even within a single ore shoot, and must also allow for the reactions between minerals formed at an early stage and solutions introduced during a late stage. The effects of such complications in the Leadville district might give the impression that certain minerals found in one of the inner zones were formed at relatively high temperatures, but close study of paragenesis indicates late deposition at relatively low temperatures. Again, as already stated, there is sufficient inconsistency in the distribution of certain varieties of deposits to give a confused impression of zonal arrangement unless the influence of structure on the circulation of ore -forming solutions is appreciated. The field facts give a far more complex picture than might be anticipated from a simple statement of the theory of zoning .

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USGS1927

Geology and ore deposits of the Leadville mining district, Colorado

Adequate treatment of so large and so extensively developed a district as that of Leadville necessitates a voluminous report, in which the practical questions of prime interest to the commercial world can not be systematically answered until the data on which they depend are discussed. Many readers will no doubt wish to turn at once to the chapter on ore reserves, which will give them an appraisal of the district, without bothering with geologic detail. For those who wish a brief general account, a summary of the principal chapters of the report is presented below.

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USGS1886

Geology and mining industry of Leadville, Colorado, with atlas

The present work was undertaken at the instance of the Ron. Clarence King, first Director of the United States Geological Survey, in 1879. It was his intention that it should form part of a series of monographs which would in time include all the important mining districts of the country, and thus furnish an accurate and permanent record of the manner of occurrence and geological relation of the metallic deposits of the United States, as well a of all substantial improvement in the methods of obtaining the metals from their ores.

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