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By Peter E. Price

Salt dome hosted metallic sulfide deposits are the product of a complex evolutionary system involving halokinesis, cap rock development and diagenesis, and the generation, migration, and accumulation of basinal brines and hydrocarbons. Hydrocarbons play an important role in: (1) the production of calcite cap rock which hosts some of the metallic sulfide and sulfur concentrations, and (2) the generation of the reduced sulfur available for metallic sulfide precipitation and sulfur formation. Hydrocarbons and related fluids also are involved in the transporta¬tion and remobilization of the metals. Hydrocarbon consumption, in the course of cap rock development and sulfide mineralization at Hockley dome, is estimated to have been 6.4 million barrels of oil or 114 million cubic feet of methane. Mineral textures, including cap-rock banding, sulfide bands in anhydrite, and fine sulfide mineral banding indicate both episodic fluid influx and fluid compositional differences through time. Features such as pyrite "shells" and sphalerite and marcasite hemispheres may have been localized by hydrocarbon droplets and /or bacterial colonies. Marcasite mineralization in shallow strata above and flanking Hockley dome is best developed over the western and southern parts of the dome. This pattern mimics the known distribution of sulfide mineralization, which is dominantly marcasite, in the underlying cap rock. The iron sulfide paragenetic sequence in the sediments is pyritohedral and cubic + pyrithohedral pyrite followed by marcasite which is encrusted by cubic pyrite. Sulfur isotopic averages for the three stages are +20.8, -20.2, and +6.4 per mil, respectively. These values generally coincide with cap rock sulfate (+20 per mil), cap rock hosted metallic sulfides (-20 to +4 per mil), and sulfur in hydrocarbons (+5.8 per mil). Hydrocarbon compositions indicate provincial variations in oil composition and generation history. Long Point and Boling domes, which have an intergrown sulfide-sulfate-sulfur mineral assemblage indicative of mixed reducing-oxidizing environment, contain oils that are less mature than Hockley dome which appears to be more mineralogically segregated. Sterane biomarker compositions of the oils at Hockley, Long Point and Boling domes indicate a local, dominantly terrestrial source. An oil sample from supracap sandstones on the northeast flank of Hockley dome contained over 750 ppm combined Fe, Zn, Pb, and Co, indicating that hydrocarbons are carrying or remobilizing metals. Cap rock calcite and anhydrite also exhibit provincial variations in strontium isotopic ratios. Calcite and anhydrite cap rocks from several sulfide mineralized domes in the Houston diapir province have strontium isotopic ratios that are more radiogenic than Jurassic sea water (>0.7078). A calcite sample within massive sulfides at Winnfield dome also has a high 87Sr/86Sr ratio (0.7085). Variations in strontium isotopic ratios with strontium content indicate the mixing of at least three Sr-bearing fluids in the cap rock environment, one of which may have been the metal carrier. Anhydrite residues from diapiric salt have strontium ratios up to 0.7100, considerably more radiogenic than Jurassic seawater. These high ratios indicate either that salt and anhydrite recrystallized sometime post-Jurassic in the presence of a fluid with a high 87Sr/86Sr ratio, or that they precipitated in the Jurassic from a fluid with a higher 87Sr/86Sr ratio than Jurassic seawater. Salt domes with cap rocks containing metallic sulfides have only been found in basins that have geopressured zones. Waters from geopressured zones in the vicinity of mineralized salt domes have salinities that are two or more times higher and iron and base metal concentrations that are three to one thousand times higher, than geopressured fluids from other parts of the basin.

Jan 1, 2013

By K. I. Cunningham, C. S. Spirakis

Two types of native sulfur deposits have been found in Lechuguilla Cave: thin late-stage crusts and massive early- formed deposits. Most, if not all, of the crusts appear to have formed by remobilization of native sulfur contained within gypsum and sulfur masses. The process is occurring today and is slowly converting the sulfur to gypsum. The absence of primary gypsum or reductants in the cave indicates that the early-formed massive sulfur deposits did not form by in-place reduction of sulfate, which is the process that formed the commercial sulfur deposits in the Delaware basin. Instead, it appears that H2S dissolved in basinal brines was oxidized by oxygen in near-surface ground waters in the cave. Fluid- inclusion data, which suggest the presence of both fresh water and saline water as the sulfur formed, support this interpretation. Although individual sulfur deposits in Lechuguilla Cave are no more than several tens of metric tons, the abundance of secondary gypsum (as much as 10 meters thick) indicates that native sulfur may once have been much more extensive.

Jan 1, 1992

By C. L. Karr, D. E. Goldberg

This paper considers optimization of the design and operation of an air-injected hydrocyclone (AIHC) via a genetic algorithm (CAI. The AIHC is a mineral separating device, developed by the U.S. Bureau of Mines, that combines the selectivity of flotation with the capacity and simplicity of hydrocyclones. GA's are search procedures based on the mechanics of natural genetics. Computer results demonstrate the ability of a GA to rapidly locate design and operating parameters that improve AIHC performance. A computer model of the GA-designed AIHC predicts improved recovery over that currently being obtained with an AIHC in operation at the U.S. Bureau of Mines Tuscaloosa Research Center.

Jan 1, 1990

By J. Frenzel

The computation of hydrometallurgical equilibria is very difficult because of the many complex species in solution, the precipitates, condensed species, or solids, and the activity coefficient corrections necessary to non-ideal thermodynamics. Our objective was to tryout recently developed genetic algorithms to minimize free energy and solve the equilibrium computation. We selected test problems that were seemingly unsolvable with more traditional algorithms, and we applied genetic algorithms to them. We were pleased to find that genetic algorithms succeeded where other algorithms did not. We concluded that they are an effective tool for hydrometallurgical equilibria.

Jan 1, 1992

By S. Peng, N. Vayenas, A. Farah

"While genetic algorithms have been widely adopted in ore grade estimation and optimization, mine design, and production scheduling in the mining engineering field, reliability and maintainability analysis of mining equipment using genetic algorithms has been a relatively new research area in recent years. This paper presents an application of genetic algorithms using case studies with seven underground scoop trams whose maintenance records have been collected over a period of 12 months from an underground mine in the Sudbury mining area. Based on the assumption that various factors that contribute to machine failures resemble the biological evolution process, the authors have developed an in-house PC software application called GenRel which adopts genetic algorithms in its programming. In this study, the authors feed the historical maintenance data into GenRel in order to predict future maintenance characteristics of mining equipment in a time period of three months. Then the predicted maintenance characteristics are compared to the actual maintenance records in the same time period. A statistical study is then used to examine the similarity between the predicted data and the recorded data.INTRODUCTION Today maintenance costs of sophisticated engineering systems are so high that maintainability draws great attention from scientific researchers to operations managers. For instance, a study by [1] shows that American manufacturers spend more than 300 billion U.S. dollars on plant maintenance and operations. Therefore it is understandable that the main objectives of applying maintainability principles to engineering systems are to reduce projected maintenance costs, to use maintainability data to estimate system or equipment availability/unavailability and to determine labor-hours and other related resources needed to perform the projected maintenance. A system with better maintainability would inherently provide the benefit of lower maintenance costs, less time to recover with lower breakdown frequency (design for simplicity), less complexity of maintenance tasks and relatively reduced man-hours [2]. Most maintainability functions use the Time To Repair (TTR) as the independent variable. It is common to use probabilistic or statistical concepts to define a maintainability function, for example, the probability density function. Let t denote the time. Assuming a repair starts at t=0 and completes at time T, the maintainability can be mathematically defined [3] as in Equation (1)."

Jan 1, 2015

By W. F. Hahnert, P. A. S. Ralston

In off-line training of a rule-based controller, the significant measure of successful training is the quality of control provided by the generated rule set. In an adaptive or on-line control environment, performance is also measured by the ability to accurately maintain a satisfactory rule set, but within constraints on speed and/or resource availability. Very small population genetic algorithms, or microGAs, have been proposed as a means of capitalizing on the hill climbing characteristics of faster local optimization techniques while requiring less memory and retaining much of the robustness of traditional, larger population genetic search. A traditional genetic algorithm and a similar microGA are developed and applied to two control problems. The performance of these algorithms is analyzed with respect to (1) the quality of the rules learned, (2) the rate at which learning occurs, and (3) the memory resources required during learning.

Jan 1, 1993

By Q. X. Yun, S. H. Liu

This paper provides a new approach to determine the opening layout in underground mining methods by means of genetic programming. Based on a set of random combination of openings, the layout of openings will gradually improve with the help of genetic operations, including reproduction, crossover, mutation and fitness calculation. The optimal solution will finally emerge according to Darwinian principle: "the survival of the fittest ".

Jan 1, 2002

By John F. Burst

For several generations now, the high alumina clayey sediments of Southeastern Alabama and Southwestern Georgia have supplied those regions with steady, mineral-based income although the impact of that income has been relatively minor until recently. Since World War II, mining activity has increased algebraically with over half of the total ore value in the Alabama area having been recovered since that time. The Georgia area production increases are even more dramatic. The trends are continuing and the next decade should see ore winning figures which will dwarf all previous production. It's time for the mining engineers to take note of this development as the mining methods, similar to the production, have developed rapidly and now offer challenges for the most competent professional. The development of mining techniques has followed a classic pattern. Beginning almost a hundred years or so ago, with the loading of weather-resistant surface boulders into mule-drawn wagons, mining methods have progressed to discovery of limited surface exposures in outcrop and eventually to stripping and development of non-obvious, subsurface deposits. Little by little, the overburden thickness of new pits has increased until, at present, pits with 100' -125' of overburden are being actively worked. Ground water problems in the Eufaula District are particularly challenging. At A. P. Green's J. W. Baker Pit, #l, in Barbour Co., Alabama, it is necessary to continually pump groundwater at the rate of about 400 gallons per minute from wells on the periphery of this large pit in order to keep the water table low enough to allow mining of the ore body.

Jan 1, 1972

By D. W. Dew, D. M. Miller, P. C. van Aswegen

The bacterial oxidation (BIOX®) process for pre-treatment of refractory ores for gold recovery is marketed by BIOMIN Technologies S.A. The process was originally developed by GENMIN who are still providing testwork, design and commissioning assistance to BIOMIN. This process offers an alternative to the more conventional roasting or pressure oxidation techniques with the following advantages: • Greatly reduced capital costs for small to medium size plants. • A relatively flexible and easily controllable process requiring relatively unskilled labour for operation. • Improved gold recovery. • A process that is environmentally friendly. The principal disadvantage of bacterial oxidation is the relatively slow kinetics compared to pressure oxidation and roasting, a plant residence time of 4 to 5 days typically being required to obtain complete liberation of gold from refractory sulphide minerals. Bacterial activity is also slow to recover from disruptions such as air supply failure or contamination by toxic species such as cyanide. Optimum plant performance depends on judicious management and sound training of operators.

Jan 1, 1993

By Guido Venturini, Giorgio Martinotti, Luca Delle Piane, Paolo Perello

This paper presents a critical review of geo-structural mapping methodologies applied to deep tunneling projects in complex mountain chains such as the Alps. Geological forecastings are often a crucial part of tunneling projects, which should allow contractees or contractors to assume their own risks. Despite this, often adequate methodological criteria are not applied in the realization of these studies, with consequent increase of costs and delays. A discussion should hopefully start in the world of tunneling in order to define a correct approach.

Jan 1, 2003

By N. M. Cheimanoff

GEOCAD is an ambitious research program aimed at the development of a computer based system assisting the geologist and the production or planning engineer. BONANZA, its mining part, is a computer production scheduling tool (short to medium term) of particular relevance to complex orebodies. The principle is to simultaneously use a powerful information management system (CAD potentialities) and small expert modules integrating the exploitation context and the engineer's knowledge (Artificial Intelligence tecniques). As an illustration, a module of mineable block determination for underground exploitation is discussed.

Jan 1, 1989

By Rolland L. Blake

The Bureau of Mines is investigating the potential for in situ leach mining "(ISM) of gold and silver mineralization. This preliminary study examined samples from several types of deposits using light optical microscopy and the electron microprobe to characterize the ore and gangue minerals and their microscopic characteristics, including the spacial relations between the target minerals and likely natural fluid channelways. Low grade disseminated deposit types from the western U.S. were found to contain fracture-hosted or matrix-hosted gold and silver minerals, some of which are encapsulated by quartz or pyrite. Geologic features readily observed microscopically include ore and gangue mineral identity, size, and their association with each other and with fractures. Successful ISM application to gold and silver deposits needs this data to: (1) select the proper lixiviant based on chemical reactivity of the host rock, ore, and gangue minerals, (2) determine potential permeability characteristics when designing lixiviant flow patterns, and (3) understand potential problems of the lixiviant reaching encapsulated ore minerals. Careful examination of the geologic characteristics of each ore body is required because of the observed diversity of characteristics in deposits from the same "class" and even within the deposit itself.

Jan 1, 1989

By D. III Earley, R. L. Blake

The Bureau of Mines is investigating the potential for in situ mining (ISM) of gold and silver mineralization. This preliminary study examined samples from several types of deposits. It used light optical microscopy and the electron microprobe to characterize the ore and gangue minerals and textural features of these samples. This included the spacial relations between the target minerals and likely natural fluid channel ways. Low-grade disseminated deposit types from the western US were found to contain fracture- hosted or matrix-hosted gold and silver minerals, some of which are encapsulated by quartz or pyrite. Successful ISM application to gold and silver deposits needs this data in order to understand potential problems of the lixiviant reaching the ore minerals.

Jan 1, 1991

By W. C. Shanks

The Pioche District of Lincoln County in southeastern Nevada (Figures 1 and 2) has been an historically important producer of silver, zinc, and lead. Economic geology of districts in the Pioche area is summarized most adequately in recent reports by Tschanz and Pampeyan (1) and Gemmill (2) and only a few major aspects will be discussed here. Production in the Pioche District began in 1869 and early mining concentrated on silver-bearing fissures in lower Cambrian quartzites. In the early 1870's the Pioche District was second only to the Comstock Lode in world silver production (3). More recent mining activities have centered on the other major ore type in the area, bedded replacement of lower Cambrian carbonates by Ag-Zn-Pb sulfide ore. Production of replacement ore peaked around 1950. The present study is focused on the Pan American Mine because it is an excellent example of low grade carbonate replacement deposits, because there is little structural dismemberment, and because access was readily available. Most previous workers have suggested that both the fissure vein deposits and the bedded replacement deposits of the Pioche districts are a result of spatially related Laramide igneous activity. The purpose of this study is to determine whether ore genesis is a result of igneous activity or if mineralization might be related to late diagenetic processes such as formed Mississippi Valley "type" deposits. Stable isotopes of sulfur, carbon, and oxygen in ore and gangue minerals have been studied to determine the probable isotopic composition of the ore fluid and paleomagnetic studies of the carbonate rocks have been utilized to determine timing of mineralization. Additionally, petrographic and field studies of carbonate lithologies were undertaken in an attempt to delineate non-structural controls on ore localization. These studies are still proceeding and the results presented herein are, therefore, preliminary in nature.

Jan 1, 1979

By Jeffrey A. Holcomb

INTRODUCTION The passage of Comprehensive Environmental Response Compensation and Liability Act (CERCLA/Superfund) as well as the Resource Conservation and Recovery Act (RCRA) and state laws, have placed added regulatory pressures on the mining industry. These laws which focus on the regulation of hazardous substances and wastes for the protection of the public health and welfare and the environment, present the potential for tremendous financial impacts and liabilities on existing mine operators and owners and/or potential mine operators/owners. This paper takes a brief look at these laws and presents an environmental audit procedure to identify environmental liabilities prior to mine land transactions. The environmental audit approach presented is an overview of the procedures that could be used to document, evaluate and inventory existing and/or potential environmental concerns. This audit procedure can be applied to developed or undeveloped properties and at active or inactive mining sites. REGULATORY OVERVIEW Mining environmental liabilities have been addressed in RCRA, Superfund, the Clean Air Act (CAA) and the Clean Water Act (CWA). Even though the U.S. Environmental Protection Agency (EPA) has determined that mining wastes will be treated as solid wastes under RCRA and not as hazardous wastes, these wastes could still bring about a great deal of financial liability under Superfund. The catch is if the mine wastes generated contain hazardous substances such as the heavy metals arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium, zinc and others as well as cyanide. Thus, it is not only important for a mine operator/owner or a potential mine operator/owner to know if the mine wastes generated are hazardous, but it is important to know if the wastes contain hazardous substances. Following is a brief overview of RCRA and Superfund and their potential implications. RCRA RCRA, which provides the basis for the regulation of solid and hazardous wastes, is applicable to active mining and milling sites. Within RCRA the definition of a hazardous waste is provided. This definition applies to owners and operators of mining and milling sites if the operator has stored, disposed or treated hazardous wastes on-site. If this is the case and if strict process control and waste management activities are not adhered to, environmental liabilities may be associated with the site. Superfund The 1980 Superfund law can be applicable to inactive mining sites or to inactive sections of an active facility. The provisions of Superfund call for the regulation of hazardous wastes and hazardous sub- stances disposal and release not only by the existing owner, but also for any previous owner. This concept of joint and several liability means that one party, as among many, can be held totally responsible for the costs of hazardous waste cleanup (Haller, 1987). Furthermore, liabilities under Superfund have also been applied back to past acts; thus, several mining properties, active or inactive prior to the 1980 Superfund law, are at risk of being placed on the EPA's National Priority List (NPL) for cleanup. Last years amendments to Superfund, known as the Superfund Reauthorization Act of 1986 (SARA), provided some significant developments for the mining industry. The major requirement of the amendments as it pertains to owners or operators of mining sites is that the EPA must revise its present Hazard Ranking System (HRS). This is important be- cause in most cases the primary reason for several mining sites having been included on the NPL was due to the large volume of wastes generated. As is typical at most mining sites, large volumes of low toxicity wastes are generated and the current HRS model prejudices against this. It should be noted that this provision only applies to sites that are not already on the NPL or have not been proposed for inclusion on the list.

Jan 1, 1987

By K. O. Johnson

Contaminant transport of mine and mill tailings is controlled by the hydrologic flow regime and the geochemical mobility of the contaminants. Contaminant' mobility is primarily determined by chemical reactions occurring within an interface zone between the tailings and soil The large geochemical differences between tailings and groundwater create a disequilibrium in the groundwater with respect to the soils when seepage from tailings enters the groundwater. Precipitation and dissolution reactions involving the major chemistry occur to return the perturbed system to chemical equilibrium between groundwater and minerals. Retardation of trace elements depends upon the chemical character of the groundwater and the adsorption substrates. In the case of uranium mill tailings, the mobility of contaminants is controlled primarily by precipitation/dissolution reactions which neutralize the pH, modify the Eh (redox potential), and produce highly adsorptive substrate for retardation of trace elements.

Jan 1, 1988

By Roman Pyrih, Jim V. Rouse

Because cyanide is a naturally-occurring chemical, geochemical and biogeochemical mechanisms exist to retard or attenuate the movement of cyanide and its compounds in the subsurface and to degrade such compounds into low-hazard reaction products. The attenuation capacity of subsurface earth materials can be measured, predicted, and enhanced by simple and inexpensive procedures. The paper describes methods of testing the geochemical and biogeochemical attenuation capacity of the subsurface and offers general suggestions for methods of enhancing such capacity. It also presents examples of data which documents such attenuation.

Jan 1, 1991

By C. Ptacek, D. Hiller, J. L. Janbor, H. Mccreadie

Between 1991 and 1994, metallurgical residues from a pressure-oxidation autoclave at the Campbell Au-quartz mine at Red Lake, northern Ontario, were neutralized with dolomite-rich flotation tailings and were deposited in a polyethylene-lined disposal area. Mineralogical analysis indicates that most of the As occurs as a crystalline ferric sulfarsenate, and some is associated with Fe oxides and with K-H3O jarosite. Field pore-water geochemical data from 1994 and 1995 showed increases in Fe(II) and As(III) concentrations, suggesting that the sulfarsenate and jarosite are dissolving; none of the discrete As phases included in a thermodynamic database limit dissolved-As concentrations, and these concentrations may continue to increase. These results demonstrate the potential for Fe and As loading through groundwater systems.

Jan 1, 1998

By Daryl R. Tweeton

The Bureau of Mines measured the geochemical changes as H2S04 was used for in situ uranium leaching by Rocky Mountain Energy Company near Casper, Wyoming. Cores and ground water were analyzed before leaching. Water samples were taken from observation wells located between injection and production wells as the leach solution was brought up to full strength in several steps. Measurements were made of pH, Eh, temperature, conductivity, total dissolved solids, dissolved oxygen, HC03, U, V, Na, K, Ca, Mg, SO4, C1, Mo, Mn, Fe, Al, Si, F, P, As, and Se. The data were gathered to assist in geochemical modeling of leaching and to study the potential environmental effects of acid leaching. Environmental considerations appear favorable. For example, the concentration of Se, a toxic element often found in uranium deposits, stayed below the EPA standard for drinking water.

Jan 1, 1979

By Eli Curiel, Ingar F. Walder, Patrizia P. Schuster, Walt Keyes

Mansfield Canyon, of the Wrightson Mining District, Santa Cruz County, Coronado National Forest, Arizona, was actively mined in the late 1800's and early 19001s, with minor activity until 1953. The main products were lead, silver, copper, zinc, and gold occurring in polymetallic quartz veins. The canyon contains numerous adits and waste dumps, some of which generate metal-loaded acid. Samples of seeps, waste dumps and bedrock have been collected for various analyses: metal concentrations, acid base accounting (ABA), and water quality to evaluate the extent of oxidation and metal release from the start of mining until present, the potential impact, and reclamation options. Although the waste-rock piles within the canyon are small (2,000-10,000 tons), they have a high sulfide content with little or no neutralizing capacity. It is planned, therefore, to move the waste piles either to a constructed repository site within the canyon or to a copper leach facility to be used as an acid generator.

Jan 1, 2000