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By L. J. Buchanan

The relationship between hydrothermal ore deposits and hot spring systems has received intensive study in recent years, particularly as a consequence of interest in the energy potential of geothermal systems. Base and precious metal deposition in surface pools and at shallow depths in modern geothermal systems has been recorded in numerous publications (1, 2, 3) Theoretical studies of hydrothermal fluid flow at depth, connected to surficial hot springs systems, have been presented by White and others (1), Cathles (2) , Henley and McNabb (3). As a result of these and additional studies, numerous hydrothermal ore deposits are thought to have originated as genetic parts of larger geothermal systems. In particular, it appears that metal precipitation is greatly enhanced in zones of boiling where volatiles and steam are escaping (4). High grade, near surface concentrations of base and precious metals, deposited as a result of partial vaporization of rising fluids, are such a common aspect of modern not spring systems that ore deposition models are becoming based on what may be called a geothermal model. In its most general terms, this model requires an anomalously high thermal gradient which acts as the driving force behind a convecting hydrothermal system. The water may be entirely meteoric or may be In part at least of other origins. The water migrates towards the higher temperature area, becomes heated, and picks up alkalies and metals by dissolving minerals along the fluid path. As water exits to the surface above the heat source, a mass balance requires the incoming hot water to rise to replace the lost water. As the water rises past the elevation where the hydrostatic pressure is insufficient to prevent boiling, then boiling will occur. Depending on the salinity and the temperature of the water, boiling can occur anywhere from great depths to near surface. Boiling results in a loss of volatiles, a pH rise in the fluid phase, cooling of the remaining fluid, a rise in oxygen fugacity, a concentration of salts in the remaining liquid, and precipitation of ore and gangue minerals.

Jan 1, 1980

The Colorado portion of the Rio Grande rift is clearly defined physiographically from the south in the San Luis valley northward to the latitude of Leadville where sediments of the Dry Union Formation (Tweto, 1961) accumulated within the subsiding rift zone. To the north of Leadville is a system of faults active in the late Tertiary, including the Mosquito fault that offset a portion of the Climax mineralization (Wallace et al., 1968). Tweto (197B) describes remnants of Dry Union Formation against the Mosquito fault north of Dillon in the Blue River valley, so it is apparent that the rift and associated sediments extended well to the north of Leadville. Kelley (1952, 1954, 1956) and Chapin (1971) have noted in New Mexico that the Rio Grande rift is a series of en echelon basins, offset to the east, with constrictions connecting them (Fig. 1). In Colorado the structural basins are offset to the west. The net effect of all the rift zone basins in New Mexico and Colorado is an arcuate pattern (Fig. 1) abutting the Colorado Plateau and Sari Juan Volcanic Province on the west. The width of the rift system gradually decreases northward to about Leadville where rift definition is not apparent.

Jan 1, 1987

By J. C. Gathje

The Robinson copper ores were mined for many years from pits containing varying ore grades, sulfide and oxide ore types, and differing mineralogy. The ores also contain gold and molybdenum values, and their recoveries are an integral part of the flowsheet development. Metallurgical responses were characterized using a standard flotation procedure. Further studies investigated primary and regrind particle sizes, reagents, and other variables. The metallurgical testing was supported by mineralogical studies. Results demonstrated a high degree of metallurgical success for flotation. Final copper concentrates ranged in grade from approximately 28 to 30% copper and copper recoveries were 89 to 95% based on laboratory and pilot plant data.

Jan 1, 1992

In recent years, Computational Fluid Dynamics, CFD, has been commonly utilized in the mining industry to model the fluid flow behavior in underground mine workings. This paper uses CFD modeling to simulate the airflow behavior in underground crosscut regions, where brattice sails are used to direct the airflow into these regions. Brattice sails are cost effective ventilation control devices for temporary or permanent use in underground mining. They can be used to deflect air into the unventilated areas such as crosscut regions. Their design and installation is a fundamental issue for maintaining a sufficient supply of fresh air and achieving effective air circulation and contaminant removal. At the same time, they should have little impact on the mine ventilation system. This paper presents the results of a two-dimensional CFD model, which examines the effects of brattice length on fluid flow behavior in the crosscut regions. The results of this study will assist in understanding the ventilation air behavior and in determining the optimum size of brattice curtain (sails), which provide a highly effective contaminant removal from the unventilated mine areas. This, in turn, helps the mine ventilation designers to meet the mine safety requirements.

Jan 1, 2009

By D. Scott Scovira, Karl Dufresne

Blasting in geothermally high temperature ground and/or extremely reactive ground is an increasing common challenge for surface and underground mines. Many current PETN based non-electric and electronic detonators have manufacturer published in-hole temperature limits ranging from 55°C to 65°C (131°F to 150°F). When confronting blasthole temperatures above the manufacturer published limits, operations may request site-specific guidance and qualification for use. The advised safe loading window for in-hole PETN based detonators is often too short to be practicable for production blasting. To overcome limitations of PETN based initiation systems, surface mines with high temperature ground and/or reactive ground are known to load blastholes with a qualified high temperature bulk emulsion that are top primed with a cartridge of temperature qualified detonator sensitive emulsion plus an RDX detonating cord downline. As there is no in-hole delay detonator in this system, blasthole timing is accomplished with surface delays. Although this system is safe, top priming and surface delaying does influence floor quality and top size fragmentation, and safe loading windows times reduce blast block size and increase blasting frequency. A mining company with a site characterized by geothermally high temperature ground plus highly reactive ground employed a blasting system like the one described above. The site desires to improve blasting performance by moving to an in-hole delay initiation system that can withstand the site ground conditions. At the request of the mining house, DynaEnergetics developed an electronic initiation system for application in geothermally high temperature ground and/or extremely reactive ground conditions. The DynaEnergetics IGNEO high temperature electronic initiation system is rated for in-hole use in ground up to 150°C (302°F) for 48 hours. The detonator consists of a high strength detonator with an HMX base charge and thermally resistant downline. To make up a primer, the detonator is inserted into a booster charge assembly that is fitted with a small HMX shape charge. This high energy primer is designed to be compatible and reliable for firing bulk emulsions, including those with high percentages of urea inhibition to combat reactive ground. Up to 1000 detonators may be programmed in 1 ms increments up to 1500 ms. The system is controlled by a digital firing panel that can be used with either a wired or wireless trigger. The system enables high temperature and/or reactive ground sites to utilize in-hole delay initiation and realize the associated performance benefits.

Feb 1, 2024

By W. H. Renison

This paper will discuss the operation and maintenance of Molycorp's Quests Mine ore conveyor system. The 1.2 m wide, steel cable-reinforced conveyor belts are capable of transporting 1089 kt/h of ore over a belt line distance of 3124 m with a vertical rise of 518 m. A portion of the conveyor runs in a 2057 m long underground decline on a 10° slope. Six 448 kW motors power the main 1.2 m wide belts.

Jan 1, 1984

By L. A. Henry

The island of Jamaica consists predominantly of Carbonate rocks which vary in chemical & physical characteristics. Currently these rocks are used for construction and road aggregate, landfill and as a raw material in the manufacture of cement. Over the past fifteen years the Geological Survey of Jamaica with assistance from a number of international aid agencies and the private sector have identified deposits of high calcium/high brightness limestones which have the potential to be utilized as a high quality filler and a number of other commercial applications. Geologically, these limestones are formed within the Eocene Swanswick Formation, the Oligocene Walderston-Browns Town Formation and to a lesser extent the Miocene Montpelier and Newport Formations.

Jan 1, 1998

By J. M. Mutmansky

Procedures for the determination of the operating point that results when a fan is connected to a mine and placed in operation have been a source of confusion for decades. A variety of techniques has been proposed, often to the detriment of the practicing ventilation engineer trying to apply the techniques to the multitudinous mine/fan matching problems encountered in the engineering of mine ventilation systems. This paper proposes some different assumptions and definitions that simplify the solution of problems in determining the operating point. As a result, a set of procedures is provided for determining the operating point of a mine/fan system when the outlet areas of the mine and fan are known. To establish a major simplification in the development of procedures for the determination of the operating point for a mine/fan combination, the authors suggest that the mine pressures be redefined and then used in such a manner that the conservation of energy is ensured. This provides the basis for the recommendation that the fan operating point be determined using the fan total pressure and the system total pressure characteristics. This procedure can be applied to fans in the blower, booster, and exhaust positions equally well and to both single-fan and multiple-fan networks. Another advantage is that the method is applicable to fans with or without an evase.

Jan 1, 1984

By Santhanam Sundaram

The potential for the utilization solar energy for the production of industrial process steer in mineral processing industries is discussed briefly. To advance the technical and economic feasibility of solar-thermal systems applications, U.S. Department of Energy has funded several projects. NL industries of Newberry Springs, California is one among them and has been chosen as a case study. The NL Industries solar system consists of 950 square meters of Del, single-axis, tracking, parabolic-trough, concentrating collectors. It was designee to produce a portion of the 420°. 530°k. steam utilized in a trying operation reduce the moisture content of hectorite ore from 10 percent to 4 percent. (Hectorite is an hydrous magnesium silicate which, when refined, is of significant commercial interest because of its applications in various chemical and food processes.) is estimated that implementation or this solar system could result an annual savings of 3.545 billion KJ ,3.360 billion BTUs), or the equivalent of 90 cubic meters (600 barrels) of oil and a net reduction of 1,860 kilograms (4100 pounds) of air pollutants annually. The technical, economic and institutional issues encountered in the course of this project are also discussed. Finally, the impact of the commercialization of solar energy applications in mineral processing industries is evaluated.

Jan 1, 1981

By William R. Bond

The pressure/vacuum lysimeter is being used as an effective vadose zone monitoring device for mining heap leach facilities, tailing disposal ponds and tailing waste sites. Their use has proven reliable for baseline data collection, early warning leakage detection and analyzing geochemical variations in the vadose zone. The lysimeter structure utilizes a closed cylindrical chamber made of PVC or inert material. The soil water intake portion of the cylinder is made of a porous material of low permeability. The application of vacuum or pressure to the unit is via two access tubes from the ground surface. Available soil moisture is drawn by vacuum through porous material into the lysimeter chamber and then collected from the access tubes. Case studies show their usefulness for monitoring around a uranium tailing pond constructed in glacial till material, under heap leach pads and pregnant, barren, and overflow ponds, and investigating the movement of contaminant moisture through old tailing deposits. Relatively easy to install and sample, regulatory agencies and facility operators are accepting and negotiating for their application as a site integrity monitoring device and unsaturated zone research tool. Their use at heap leach facilities lends credibility to solution balance calculations when considering a leachate loss of 5 or 10 percent can make or break a mine's profitability.

Jan 1, 1984

By Bijan Taheri, Behrouz Maghsodi, Monireh Heshami, Reza Kohan

A common problem recently encountered with the increase in the rate of input feed at Enrichment Plant 2 of the Sarcheshmeh Copper Complex is the loss of value to the tails, translating to lower recoveries. The feasibility of the direct transfer of part of the high-grade concentrate from rougher stages to an appropriate position along the circuit was studied, and two positions were proposed for direct transfer of the concentrate. One position was the feed flow into cleaner cells, and the other was the feed flow into the recleaner cell. The results indicated that transferring the concentrate from the first unit of the rougher stage to the feed flow into the cleaner cells was feasible, with no limitations, while the second position required the installation of a set of hydrocyclones. It was found that the transfer of concentrate to the proposed positions not only addressed the problem of limited cell capacity, resulting in debottlenecking of the circuit, but also improved metallurgical separation efficiency up to 1.4%.

By Yi Luo

Bolting the mine roof is one of the noisiest underground mining operations. The main contribution to the noise is the drilling of the roof bolt holes, especially drilling in hard rock. Previous research shows that the specific energy consumed in drilling bolt holes is inversely proportional to the bite depth (i.e., penetration per drill revolution). Less specific energy at a reasonably high bite depth means less energy is wasted in the drilling process for producing heat, bit wear and noise. Therefore, proper control of the drilling operation to achieve a reasonably higher bite depth can reduce drilling noise from its sources as a proactive noise control approach. In order to explore the feasibility and develop the proactive technology for reducing drilling noise, drilling tests have been conducted in laboratory settings. The preliminary results show that significant reduction in noise dose can be achieved by drilling in medium hard rock with uniaxial compressive strength of about 276 bars (4,000 psi) and at a reasonably high bite depth of about 4.6 mm/rev (0.18 in./rev). This paper presents the findings from laboratory experimental studies.

By Ademar Lopes, Victor Silva, Heitor Silva, Gustavo Usero, Roberto Rolo, Lucas Pereira, Gabriel Moreira, João Lague, Arthur Endlein, Matheus Feitosa

Grade control models are supposed to provide a higher resolution than long-term or interim models. However, available grids from diamond or reverse circulation drilling do not provide that required resolution. In this study, a geostatistical workflow is proposed to integrate available grade data from production blastholes with its operational parameters taken when drilling downhole. The step of geological logging can be replaced by machine learning models for classifying blastholes into lithologies and hardness classes. Next, indicator and ordinary kriging use the classified blastholes and previous data for estimating the model domains and the grades within each one. The workflow is applied in a world class iron ore mine in Brazil.

Jun 25, 2023

By J. A. Domenico

A safe and precise mineral separation alternative to heavy liquids is being used for mineral sands exploration on large scale orebodies. The separation process, Magstream®, uses ferro-fluids and magnetic and centrifugal forces to produce precise split points over a range of specific gravities from 1.5 to 18.0 g/cc. This paper describes a commercial scale exploration program treating, roughly, 90 samples per day in Senegal (West Africa). Separation results comparing Magstream® and conventional heavy-liquid separation are presented.

Jan 1, 1994

Your assessment of the minerals business. The global mining industry is strong. I am convinced it will continue meeting the mineral needs of the world population for the foreseeable future. Two developments have greatly enhanced the industry’s ability to produce low-cost minerals. Technological innovations have resulted in increased productivity. And there has also been a dramatic expansion of the number of favorable countries in which to explore and mine. Capital expenditures have flowed to the low-production-cost mines and development projects as well as to the exploration projects and stable countries having the best potential for valuable mineral discoveries.

Jan 1, 2000

By Dirk van Zvl

The design of cover systems for reclamation schemes in tailings requires estimation or determination of tailings materials properties such as compressibility, shear strength and consolidation characteristics. It is very difficult and expensive to obtain truly undisturbed tailings samples for laboratory testing. In situ testing methods have been developed for economically obtaining large amounts of information. Two of these methods are described, the piezocone and the flat plate dilatometer. Both of these methods provide a rapid means of detailed material identification in a nearly continuous fashion for the entire depth investigated. The equipment is described and typical data from a uranium tailings impoundment is presented. The results are compared and the advantages and disadvantages of these methods are discussed.

Jan 1, 1984

By A. Choudhury

Deep open-pit mines are becoming increasingly common in the highly mineralized arctic and sub-arctic regions. Air inversion is a frequent occurrence in these regions, and is exacerbated by the natural topography of an open-pit mine. Due to such inversions, the air quality in open-pit mines deteriorates very rapidly. Transport of gaseous pollutants under arctic air inversion is complex and involves an interaction between flow, thermal and convective transport systems. This paper discusses the construction and validation of a three-dimensional model that simulate the flow of air and the transport of gaseous contaminants in an arctic open-pit mine and the effect of low influent velocity and large gust velocities on the contaminants profiles in the mine. It was found that while higher velocities may remove contaminants from the pit bottom, they may not remove the contaminants from the pit entirely, necessitating artificial mitigation measures.

Jan 1, 2012

By G. Biles

The Eskay Creek Mine, a high-grade gold and silver underground mine in northwestern British Columbia started operations in late 1994. For the first three years of operation, ore was crushed to minus 2 inch; blended to satisfy smelter terms and direct shipped to smelters in Japan and Canada. Before commencing the above operations, preliminary evaluations had indicated that an extremely complex metallurgical facility, requiring a large capital investment, would be required to recover the precious and other economic metals. Subsequently markets for raw ore were identified and underground mining and ore transportation operations, at a nominal production rate of 300 tonnes per day, were commenced. Exploration diamond drilling in 1995 and 1996 discovered additional lower grade mineralized zones, which are less economic or uneconomic as direct shipping ore. Testwork demonstrated that these lower grade zones could be upgraded to marketable concentrates in a simple flotation mill. The mill was built in 1997 and has been in operation since late 1997. The mining rate now has increased to 400 tonnes per day including 250 tonnes per day of the direct shipping ore and ISO tonnes per day of the mill ore. Prime Resources Group Inc. wholly owns the Eskay Creek Mine. Homestake Canada Inc. owns 50.6% of Prime's shares and manages and operates the mine on Prime's behalf. This paper discusses the mining and milling operations as well as ore shipment and smelter contracts' administration.

Jan 1, 1999

Throughout the 1970s, the US Bureau of Mines rode an ebb tide in Washington political circles. In rapid fire succession, the agency lost its mine health and safety enforcement responsibility (1973), a large portion of its energy research responsibility (1975), and then its fuel statistics functions plus a sizable portion of its coal R&D (1977). By 1978, johnny-come-latelies in the Energy, Labor, and Interior Departments had siphoned away from the Bureau some $125 million in program responsibilities as well as 900 of its employees. The bruising decade came to a close with a Department of Natural Resources proposal that, in its original form, would have scattered the Bureau's responsibilities to the winds. "There is no doubt in my wind," said Lindsay Norman, acting director of the Bureau of Mines (see box), "that were the Bureau to continue down the path it was on, the next step was closing the doors and going out of business." The doors are still open, but erosion of responsibilities had a devastating effect on the resources available to fulfill the Bureau's mission. Devastating, too, in terms of internal morale, considering the Bureau had six directors in a 10-year span. "When the troops are in the trenches and are being shot at," Norman said, "they need a leader-hopefully, a permanent one- that can get them advancing. This is something the Bureau did not consistently have in the 1970s." In September 1978, Roger Markle climbed aboard as director of the Bureau to rejuvenate the 70-year-old agency. He resigned only six months later* but the program Markle set in motion is being carried through by Lindsay Norman. Since Norman's appointment as acting director, he has spent considerable time on the road explaining his agency's redefined goals. At one such stop in Duluth, Norman and his two deputy directors, Charles Kenahan and Mike Kaas, answered the following questions. Lindsay, you were the principal architect in the Bureau's 1979 reorganization. How about a glimpse of what that entailed? Toward the end of the 1970s, after almost a decade of steady dismemberment, we reached what we felt was a critical point in the Bureau's history-we had the choice of redefining and strengthening our organization to meet the mineral challenges ahead, or continuing down the path toward the agency's eventual demise. We felt the Bureau's mission too important to abandon, so in 1978 with Roger Markle as director we initiated a six-month, no-holds-barred intro spection of just what the Bureau should be doing, why, and toward what ultimate national needs. And what did this self-reflection reveal? That there is, indeed, a unique federal role for the Bureau of Mines-that of a lead agency for influencing mineral decisions and pioneering tomorrow's technologic advances. Don't confuse us with policymakers, we're not. But we are policy analysts; we're scientists, engineers, and mineral professionals who can offer a sorely needed source of objective, accurate information to decision makers in both the public and private sectors. I feel there is no better brain trust in government than the Bureau when it comes to mineral expertise-of course, I'm biased. Do I understand you to say the Bureau of Mines is an advocate agency for the minerals industry? We plead no parochial interests, nor ought we, but from our viewpoint a sound minerals industry is extremely important to the broader national goals of security and a healthy economy. US dependence on foreign sources for critical minerals, the increasing noncompetitiveness of some US mineral sectors, and the array of land use issues surrounding mineral-rich lands all have much more serious implications than many otherwise informed people seem to recognize. In your estimation, how vulnerable is the US to foreign mineral suppliers? Let me make a distinction between dependency and vulnerability. The

Jan 4, 1980

By D. E. Ranta, William B. Ryan, Ronald W. May

The Lower Cretaceous McMurray Formation in northern Alberta contains bituminous sands interbedded with other sediments which form the reject encountered during mining operations. Grade prediction is based on a combination of geological interpretation, computer modelling and past mining experience. In addition to estimates for ore, an accurate estimate of "waste" or "reject," are required for Mine Planning. This study investigates the ability of point-kriging using geostatistics, to augment the existing data base of drill-holes in a study area on Syncrude's leases. This approach enables the assessment of potential "worst" case - "best" case scenarios within the context of Mine Planning.

Jan 1, 1992