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By Winfield G. Wright, Greg P. Meeker, Philip L. Verplanck, Douglas B. Yager, Dana J. Bove, M. Alisa Mast

A really extensive acid sulfate-altered and mineralized rock in the southeast Red Mountains area is noted for its association with naturally occurring and mine-related acidic and metal-rich waters. Integrated geologic and aqueous geochemical studies demonstrate that the degree of metal mobilization and acid production in natural waters correlates well with the type of hydrothermally altered rock and structural features in which these water interact. Quartz-sericite-pyrite, quartz-alunite, and argillic alteration assemblages are associated with some of the most naturally acidic, high-metal waters in the study area; calcite-bearing propylitic rocks are related to the most pristine waters and buffer sulfate-rich, acidic waters produced by pyrite oxidation. Trace metals in natural waters are mostly derived from enargite, zinc-rich tetrahedrite and sphalerite. Pyrite oxidation contributes very little with respect to base-metals in these natural waters.

Jan 1, 2000

By Mark Van Dyke, Ted Klemetti, Joe Wickline

"The identification and mitigation of adverse geologic conditions are critical to the safety and productivity of underground coal mining operations. To anticipate and mitigate adverse geologic conditions, a formal method to evaluate geotechnical factors must be established. Each mine is unique and has its own separate approach for defining what an adverse geological condition consists of. The collection of geologic data is a first critical step to creating a geological database to map these hazards efficiently and effectively. Many considerations must be taken into account, such as lithology of immediate roof and floor strata, seam height, gas and oil wells, faults, depressions in the mine floor (water) and increases in floor elevation (gas), overburden, streams and horizontal stress directions, amongst many other factors.Once geologic data is collected, it can be refined and integrated into a database that can be used to develop maps showing the trend, orientation, and extent of the adverse geological conditions. This information, delivered in a timely manner, allows mining personnel to be proactive in mine planning and support implementations, ultimately reducing the impacts of these features. This paper covers geologic exploratory methods, data organization, and the value of collecting and interpreting geologic information in coal mines to enhance safety and production.The implementation of the methods described above have been proven effective in predicting and mitigating adverse geologic conditions in underground coal mining. Consistent re-evaluation of data collection methods, geologic interpretations, mapping procedures, and communication techniques ensures continuous improvement in the accuracy of predictions and mitigation of adverse geologic conditions. Providing a concise record of the work previously done to track geologic conditions at a mine will allow for the smoothest transition during employee turnover and transitions. With refinements and standardization of data collection methods, such as those described in this paper, along with improvement in technology, the evaluation of adverse geologic conditions will evolve and continue to improve the safety and productivity of underground coal mining."

Jan 1, 2019

By C. McLean, S. G. Kolb, A. J. Erickson, S. C. Moore

The Grossschloppen vein-uranium deposit, Bavaria, West Germany, was examined with underground workings during 1980-82 by Esso Erz GmbH, an affiliate of Exxon Minerals Company (EMC). Geologic evaluation entailed dense drilling of a portion of the deposit from workings constructed specifically for the program. Discovered in 1977, the deposit was initially explored by surface diamond drillholes which allowed definition of a 30-60 m wide vein system discontinuously mineralized along a 1000 m strike length and to at least a 450 m depth. The underground program was conceived as a cost-effective procedure to answer questions on vein correlation, grade continuity and variability. A 1200 m decline allowed access for detailed sampling of approximately 10% of the known area of mineralization. Fanned drillholes, logged by gamma probe, were spaced to provide intersections of veins at 10 to 20 m intervals. Six cross-cuts also penetrate the pitchblende and uranophane mineralization which occurs in 0.1 to 2.5 m thick quartz veins. Detailed cross-sections and level plans were constructed for resource estimates of the intensively studied portion of the vein system. The program resulted in the discovery of local, high grade areas and an average grade in the evaluated area nearly double that expected from surface drilling.

Jan 1, 1992

By K. N. Santini

The evaporite deposit at Searles Lake consists of alternating brine-saturated saline beds and saline-bearing mud beds. Three major subsurface brine-saturated saline horizons have been identified by private companies and the U.S. Geological Survey. They have been termed, from bottom to top, the Mixed Layer, Lower Salt, and Upper Salt. The important water-soluble components (Na, K, Mg, CO3, HCO3 , SO4, Cl, and B407) are either in brines or have combined to form the following minerals: halite, hanksite, trona, nahcolite, burkeite, borax, thenardite, northupite, sulfohalite, glaserite, etc. Kerr-McGee Chemical Corp., the current operator at the lake, selectively pumps interstitial brines from each of the major horizons to feed its three chemical plants. As the pumping continues, brines are continuously replenished within the deposit by dissolution of the minerals through natural recharge or artificial fluid injection (solution mining). The brines are processed to produce a variety of chemical products, which include sodium carbonate and sulfate, potassium chloride and sulfate, sodium borate, and boric acid. The Anaconda Minerals Co. has been evalua¬ting potential domestic trona acquisition since 1981. We have evaluated various properties in the Green River, Wyoming trona district, and Owens Lake and Searles Lake in southern California. In 1983, we purchased with our joint-venture partner, Leslie Salt Co., the southern portion of Searles Lake from Occidental Petroleum Corp. Since mid-1983, Anaconda has been conduct¬ing a small exploration-drilling program at the property. The initial core holes were drilled along and adjacent to the existing access road. In 1984 we used an all-terrain drill rig to gain access to drill sites on the playa where no roads exist. The use of this equipment proved to be highly successful. The drill program consists of coring to an average depth of 450 feet and collecting brine samples from potentially commercial horizons. The brine samples are collected by setting a packer and swabbing the hole. The core is logged and split lengthwise; one-half is submitted to our Tucson Geoanalytical Laboratory for semi-quantitative mineralogy by X-ray diffraction and the following suite of chemical analyses: Na, K, Mg, C03, HCO3, SO4, Cl, B407, Li, H20 insolubles, and acid insolubles. Additional test work for selected core samples will include effective porosity and horizontal permeability determinations. The brine samples are subjected to the same suite of chemical analyses (minus insolubles) as the core samples. In addition, specific gravity is also determined. Both cross sections and isopach maps are being constructed. The hydrological characteristics of the potentially commercial horizons are also being investigated.

Jan 1, 1987

By Charles E. Robertson

As it becomes more and more apparent that our nation must place a great deal of reliance on coal as an energy source in the coming decades, prospecting for new reserves Un Missouri and other states in the Western Interior Region is increasing. As more and more of the known reserve becomes committed to existing or planned projects operators will be forced to look beyond the fringes of existing coal fields for additional reserves. Perplexing geologic problems invariably confront all prospectors and are particularly bothersome to those new to a particular area. It is the purpose of this paper to alert prospective operators to geologic problems likely to be encountered and to offer guidance in the recognition and solution of these problems. Particular emphasis is placed upon geologic structure and washouts. Other geologic problems have been discussed in a previous paper.

Jan 1, 1977

By Joseph R. Wojcik

Introduction Placer deposits account for one-half to two-thirds of the total gold produced worldwide. As many as 311 t (10 million oz) have been produced from some major districts. Several others are credited with 155 t (5 million oz). All the major districts and many lesser ones have similar characteristics. Consideration of these characteristics offers insight into the origin of gold in the deposit. Knowing the gold deposit's geologic history leads to useful conclusions in exploring for placer deposits and for deposits in consolidated areas. Placer Deposit Characteristics Table 1 lists 17 placer gold districts around the world and their characteristics. These include type and age of, mineralized source rocks, associated intrusive rocks, and age of intermediate sedimentary cycles. Although quartzite or sandstone occurs in the bedrock sequence in four of the 17 districts, slates, phyllites, or schists are present in all of the districts. Additionally, in all but three, the slates are pre-Mesozoic. And, in six of the remaining 14, the slates are Precambrian. Rocks intrusive into the slates are all of intermediate to acidic composition and are emplaced as stocks, dikes, or sills, rather than being batholithic in proportions. Intermediate interceptors have not been recognized in only three of the 17 districts. Data from China and Mongolia are inconclusive as to this characteristic. Black Shale Gold Higher than average gold values are found in modern sedimentary rocks in coarse granulites, conglomerates, sandstones, and gray-wackes. Not so predictably, higher than average gold values also occur in black shales and carbonaceous argillities. Li and Shokena (1974) found that, in the Proterozoic sedimentary and equivalent metamorphic rocks of the Enisei Ridge, carbonaceous and graphitic phyllites and schists were particularly enriched in gold. Korotayeva and Polikarpochkin (1969) reported gold content in organic rocks to be enriched up to 15 times more than the organic free shales and siltstones of the Nerchinsk Zavod region of eastern Transbaikal. Black shales can be gold interceptors as are rocks of the granulite facies. Gold occurs in shales in particulate, free form, in pyrite, adsorbed on clays, and precipitated on carbon. In copper-bearing shales of Poland's Fore-Sudetic monocline, Kucha (1973) reported gold present in organic compounds as well as in silver bearing minerals. Anoshin (1969) found a strong correlation between gold and the pelitic fraction of sediments in certain rocks of the Atlantic Ocean basin. Heavy metal absorption on clays results in agglomeration to the extent that the particles settle with the heavy mineral fraction in enriched strata. Piper and Graef (1974) think that gold in sediments on the flank of the East Pacific rise is of lithogenic origin. Crockett (1973), however, proposed a volcanogenic exhalative origin. A strong correlation between gold and volcanic activity exists in rocks of the Canadian Shield where tuffaceous sediments and porphyries are more frequently enriched in gold than rocks with no volcanic components. Volcanic rocks of intermediate to acidic composition are considered here to be the primary source of gold in black shales. Gold is concentrated in shales as detrital free grains with diameters less than 50 µm (270 mesh), as precipitates, and in pyrite or other sulfide minerals. This is the first step in the history of gold placer deposits. Grain Size Modification Gold, as free grains with diameters less than 50 µm (270 mesh), is too light to be concentrated hydraulically into placer deposits. Some process has increased the average size of the gold grains. Mobilization during regional metamorphism converts most of the gold into particulate grains or entrains it in microfractures in the sulfide minerals. With moderate folding, small, white, vitreous quartz veins develop. As deformation continues, larger, more conspicuous quartz veins are formed. The larger veins are folded and faulted and contain native gold as minute specks and flakes not visi-

Jan 11, 1984

By L. P. Johnson

Longwall mining has gained acceptance as a safe method of maintaining coal production where conventional systems were unsuccessful or uneconomic due to bad roof conditions (Kuti8). One of the major problems confronting American operators involves the correct choice of equipment which should be selected to suit the local mining and geologic conditions for optimum productivity. To achieve this, factors such as rock strengths, local geology, panel geometry, and panel orientation must be examined to optimize production and minimize down time due to ground control problems. Little quantitative information is available in the literature regarding the effects of geologic conditions on American longwall operations, and past implementations of longwall systems appear to have been based largely on experience. When mining engineers are able to assess the geologic conditions both quantitatively and qualitatively, they can more fully optimize equipment selection and panel design.

Jan 1, 1977

By M. Fustic, A. H. Paul

The geology of the Muskeg River Oil Sands Mine is described to demonstrate how geologic modeling aided in resource evaluation and material characterization during the feasibility and construction stages. Bitumen is hosted in the clastic sediments of the Cretaceous McMurray Formation which is informally divided into members representing the fluvial, estuarine and marine environments of this transgressive sequence. Lithofacies mapping of drill core provides further detail to classify materials as resource type, for extraction suitability and for construction suitability. Geologic interpretation provides tools for the engineers to produce effective mine plans and for the operators to execute them during mine development.

Jan 1, 2002

By M. Saidman, R. Pizzuti, R. Hirschfeld, A. J. Desai, J. Rand

Two bedrock tunnels, 170 to 250 feet deep and with a length of about 17,000 feet each, will be used to convey cooling water from the Atlantic Ocean to the Seabrook, N.H., Nuclear Power Plant. Seismic reflection and refraction surveys were used to obtain preliminary information about overburden and bedrock conditions. A major boring program, including core orientation and water-pressure testing, was undertaken to provide detailed geologic data. The results of the geotechnical investigation were summarized in terms of rock type, frequency and character of joints, degree of weathering, modified core recovery (RQD), pressure-test results and strength and hardness. These parameters were used as a basis for evaluating the feasibility of using a tunnel-boring machine, for designing and estimating the initial support systems, and for evaluating the grouting and tunnel lining requirements.

Jan 1, 1976

By Jack G. Quade

During the summer and fall of 1973 a series of Skylab and high-altitude aircraft overflights provided excellent hard-copy photographs of the Great Basin. These photographs, with a wide range of ground resolution were used by the NASA Project of the University of Nevada, Reno, to conduct specific geologic studies. The principal objectives of these studies were to: select individual areas covered by Skylab photography for detailed studies, develop mapping techniques using varied film-filter products with a wide range of ground resolution, compare the results of the mapping techniques to existing geologic maps at comparable scales, verify the results wherever possible by direct field observations. These studies were conducted by Jack Quade and Dennis Trexler and by graduates and undergraduates of the Reno campus under a contract with the Manned Spacecraft Center Houston, Texas.

Jan 1, 1976

By W. J. Nelson

Detailed underground geologic map- ping at a scale of 1:1200 has been carried out at the Crown II Mine of Freeman United Coal Mining Company, which operates in the Herrin (No. 6) Coal Member. The roof sequence, upward from the coal, includes (1) soft, medium- to dark-gray shale; (2) hard, black, fissile shale; (3) argillaceous nodular-bedded limestone, and (4) fine-grained, shaly, water-bearing sandstone. The first unit is highly lenticular, and any or all may be missing at a given locality. The sand- stone has a sheet facies and a channel facies. The Herrin Coal is eroded in channels near the Crown II Mine. Structural features mapped at Crown II include normal and strike-slip faults of small displacement, "slips" and clay dikes, and limestone "bosses." Less stable roof and wet con- ditions are encountered where the limestone is thin or missing or where it is broken by natural fractures or by artificial openings that inter- sect the water-bearing strata above the limestone. Geologic mapping of the underground workings has allowed us to predict faults, fracture zones, and channels ahead of the face for this mine. Some lithologic and structural patterns apparently are random and cannot now be projected. Conventional exploratory drilling is entirely inadequate to map faults or lithology of the roof, but it does indicate the range of lithologic variability, which can be used to project needs for roof sup- ports. Drilling also is useful In locating channels and in mapping regional variation in thickness and facies of the sandstone.

Jan 1, 1980

By Wilbur H. Smith

Geologic mapping techniques at the Bingham Mine have evolved as rapidly expanding applications of geological data have caused new methods to be utilized. The most significant changes in method have been in the preparation of the base map and in computer application of collected data. Formerly maps were prepared by surveying with transit or plane table. Currently a photogrammetric map, on the scale of 1-inch equals 200-feet, is prepared semi-annually and continuously updated to keep pace with the removal of more than 350,000 tons of material daily. Larger scale bases for specific problems, such as areas having unstable slopes, are prepared by use of aerial and terrestial photography and photo mosaics. Note sheets designed for computer application enable fast processing of the data. Application of geology at the Bingham Mine has been increasing rapidly in recent years. The effect of structure, rock type, and alteration on slope stability, the relationship of sulfide mineral distribution to concentrating results, the effect of rock and mineral types on waste dump leaching, and requirements of a reliable internal source of silica flux for smelting are a few of the problems which require the collection and application of geologic data.

Jan 1, 1968

By Malcolm Heyburn

Airborne and ground magnetic surveys were made over and in the vicinity of the Sanford Hill ore body at Tahawus, Essex County, New York. These geophysical surveys served to: l. delineate, lithologic and structural features associated with the ore bodies; 2. indicate a major extension of the Sanford Hill ore body; and 3. guide a drilling program to prove this extension. The titaniferous magnetite ore body at Sanford Hill is associated with gabbro occurring in anorthosite. The contrast in the magnetic susceptibilities of these rock types, reflected in the magnetic measurements, allows geologic-mapping showing rock types and inferred structural features. The anomalous magnetic high of the airborne magnetometer survey indicated a southern extension of the Sanford Hill ore body. Diamond drilling, guided by the airborne and specifically the ground magnetic results, substantiated this interpreted ore extension to be of major magnitude.

Jan 1, 1961

By Steven G. Vick, Herbert H. Einstein

1. INTRODUCTION The Tunnel Cost Model (TCM) is a computer based model whose objective is to quantify the risks of hard rock tunneling in terms of cost and time to completion. The main feature of the TCM is the simulation of the tunnel construction. The simulation makes it possible to incorporate in the time and cost computations the effect of uncertainties in geologic conditions and in productivity rates and costs. The cost and time computed with the TCM will be in form of distributions that allow a quantitative risk assessment. The TCM will be useful as an estimating tool permitting the estimator to rigorously relate uncertainties of individual factors to the end result. The TCM will also make it possible to evaluate technological innovations and to identify problem areas in existing technologies. The TCM consists of three interacting submodels: the geologic submodel, the construction operations submodel and the tunnel simulator. The goal of this paper is to describe the geologic submodel, whereas the construction operations submodel and the tunnel simulator will be described in the following paper by Moavenzadeh et al. First it will be shown how interactions between the geologic submodel and other parts of the TCM will impose certain requirements on the geologic submodel. These requirements, which relate primarily to the description of geologic conditions by a set of problem-oriented parameters and the quantification of uncertainty associated with geologic conditions, will then be discussed. This is followed by the description of the special structuring techniques -- decision tree and segmentation -- that are necessary to handle the great number of

Jan 1, 1974

By Robert W. Elayer

For the design of a coal mine and process plant, a comprehensive foundation of geologic information is essential. Historically, the development, collation, and use of this information for design have been costly and time consuming. With the application of a digital computer, however, the effort expended can be reduced and maximum effective use of the geologic information realized. The purpose of this paper is to demonstrate the feasibility and convenience of using a computer to Store and manipulate geologic data for use in mine and process plant design.

Jan 1, 1975

By T. E. Wayland

Bentonites are clay materials composed principally of minerals in the montmorillonite group. Distinctive physical properties of the montmorillonite minerals are responsible for selected bentonite deposits having become the raw materials source of industrial clay products which are virtually essential to the maintenance of high production standards in the petroleum, foundry, taconite and other basic industries. These versatile materials have no suitable substitutes in either their major applications or in hundreds of speciality products, The economics of the bentonite mining industry follows closely the established pattern of other non-metallic raw materials. Aggressive competition, advanced technologies, progressive marketing techniques, substantial reserves, and vast unmeasured resources insure the continued supply of high quality bentonite to industry at bargain prices. The purpose of this paper is to discuss the geology and economics of bentonite deposits, summarize both major domestic mining districts and foreign deposits, and report significant results of research and development.

Jan 1, 1970

By Dennis J. Lachel, Lloyd B. Underwood

In recent years a great number of papers have been presented at symposiums and have appeared in the literature relative to geologic prediction for rapid excavation and tunneling. Many of these papers describe research projects now underway to investigate tunnel site selection by remote sensing techniques, seismic holography, electro¬magnetic pulse sounding, optical scanning for structural features, and many other exotic geophysical techniques. While it is possible that this research will produce techniques that may prove to be very useful, it appears for the present at least, and perhaps for another decade, that there still will be no substitute for conventional exploration methods such as coring boring, geologic mapping, studies of existing wells, and proven geophysical techniques. Nevertheless, there is still room for tremendous improvement in the conventional techniques for geologic prediction in tunneling. These include: more rapid and accurately aligned coring borings drilled parallel to the tunnel alignment; improved geophysical surveys both prior and during construction; improved methods for predicting ground¬water inflows and water pressures, both of which can greatly influence the cost of driving tunnels. Geophysical techniques can also be ap¬plied to locate deeply incised glacial troughs or ancient buried stream channels that might cross the tunnel alignment. In the meantime, while some researchers continue their efforts to¬ward a breakthrough in new techniques for geologic prediction, it is recommended that other researchers direct their efforts toward sol¬ving specific problems such as accurately predicting ground-water conditions, determining locations of high geostatic stresses, and locations of major fault and shear zones.

Jan 1, 1997

By Andrew H. Merritt

INTRODUCTION The prediction of the engineering behavior of a rock mass depends upon the systematic analyses of the results of an exploration program, and upon the recognition of the significant rock properties in the early stages of excavation. The variations in rock properties in different geologic terrains and the state of the geotechnical art preclude complete success in the former case, and we therefore must rely heavily on the experience gained in the latter phase. The geotechnical information obtained from these two phases is only of value to the design engineer when applied to the rock behavior during excavation and subsequent plant operation. Pertinent questions which must be answered include: how does the joint orientation and frequency effect tunnel support and overall cavern stability; how does the depth of surficial soil or weathering effect foundations or slope stability for portal cuts; are there permeable zones within the rock mass that could lead to leakage problems around penstocks and is the material in these zones soluble or likely to pipe in the long term; and does the proposed engineering structure fit the terrain, or will it inevitably lead to problems requiring extensive remedial treatment. During the early stages of construction there are two types of geotechnical information required; actual rock behavior with respect to the original design assumptions,

Jan 1, 1997

By Alan C. Noble

Ore reserves are often less than 30% of geologic resource estimates that are initially prepared by exploration geologists. Differences of this magnitude between resources and reserves can lead to serious . problems in the early valuation of properties when the geologic resource estimates are interpreted to represent ore reserves and are later found to be misleading and gross overstatements of ore reserves. The geologist can avoid such difficulties by considering the implications of mining, metallurgical recovery, and economics early in the project and by using appropriate qualifiers in the resource statement Examples using typical deposit characteristics are used to demonstrate how cutoff grade, stripping ratio, dilution, mining extraction and metallurgical recovery affect ore reserve estimations.

Jan 1, 1992

By A. C. Noble

Ore reserves are often less than 30% of the geologic resource estimates initially prepared by exploration geologists. Differences of this magnitude can lead to serious problems in the early valuation of properties when the geologic resource estimates are interpreted to represent ore reserves but are later found to be misleading and gross overstatements of the actual ore tonnages. The geologist can avoid such difficulties by considering the implications of mining, metallurgical recovery and economics early in the project and by using appropriate qualifiers in the resource statement. Examples using typical deposit characteristics are used to demonstrate how the cutoff grade, stripping ratio, dilution, mining extraction and metallurgical recovery affect ore reserve estimations.

Jan 1, 1994