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By Leandro Echavarría

El presente texto describe el sistema epitermal de Arcata, situado en Arequipa, Perú. Arcata es un distrito epitermal de sulfuración intermedia rico en plata y metales base, cuya mineralización se hospeda en vetas de rumbo predominante noroeste y movimiento principal paralelo a la inclinación que forman una estructura de fosa (graben). Las vetas poseen texturas de relleno de espacios abiertos como bandeados costriformes, en cucarda, crecimientos en peine y brechas, con ganga de cuarzo, calcita, rodonita y rodocrosita. Por su parte, los minerales de mena más comunes son galena, esfalerita, calcopirita, con los metales preciosos hospedados en sulfosales de plata (pirargirita y tetrahedrita). Asimismo, se ha identificado una compleja secuencia paragenética con varios pulsos responsables de la mineralización económica.

Apr 22, 2003

By T. R. Paquin

Powerful, easy to manipulate, ventilation modeling software is readily available to most mining engineers. Too often when preparing an initial ventilation model, engineers will go overboard in their design, creating a complex model with hundreds of branches. When, in practice, the creation of a less complicated ?to the point? model, containing a few well-constructed branches, would have delivered the same results. In this paper the author will demonstrate, by using actual feasibility report examples, that when designing a ventilation model, engineers should make more use of the K.I.S.S. (?Keep It Simple, Stupid?) Principle. As mining industry consultants we must continue to improve on, and deliver timely and cost-effective results to our customers.

Jan 1, 2009

By J. C. Bayles

Jan 1, 1885

By I. Liebman

A Bureau of Mines study is in progress to determine the effectiveness of passive water barriers in suppressing coal-dust explosions. A 2.9-ft3-capacity water-filled plastic tub was found effective in suppressing dust explosions propagating at speeds of 250 to over 1,000 ft/sec. Work directed at determining the limitations of water barriers showed that the passive water barrier technique is also feasible for the suppression of weak dust explosions propagating at speeds of 100 to 250 ft/sec. For relatively slow accelerating flames, dynamic wind forces appear to be the important quantity governing fragmentation of the plastic tub and subsequent water release and dispersion, whereas dynamic impulse appears to be the significant quantity for rapidly accelerating flames. The acoustic approximation (relation between static pressure and flame or wind speed) is shown to be valid in a long single mine entry. This relationship appears to be useful in predicting the regions within a long single entry where passive water barriers are effective in quenching a dust explosion.

Jan 1, 1974

Large quantities of combustible materials are often found in underground metal and nonmetal mines, with support timber most often the predominant combustible material. Oils, lubricants, paper, cartons, and rags are additional combustible materials and are commonly found in maintenance shop areas. Welding and cuting, shorted or overloaded electrical cables, spontaneous combustion, and careless smoking are some of the common fire ignition sources. Inexpensive, reliable fire detection and suppression systems are available to provide early warning of such fires and to isolate and extinguish fires that originate in underground maintenance shop areas. Technology developed and demonstrated under Bureau of Mines Contract H024216, Mine Shaft Fire and Smoke Protection System, may be applied to protect underground maintenance shop areas. The mine area described in this report is a representative ex-ample only; the fire protection system described considers costs, benefits, equipment performance and includes the concepts of: ? Early warning and alarm ? Isolation ? Extinguishment ? Control. Each fire protection system application requires analysis of numerous variables including total mine profile (depth, personnel, escape routes, hazards, etc.).

Jan 1, 2011

By ?. ?ivkovic

The silicate slag and copper matte that are the byproducts of smelting copper in a reverberatory furnace contain SiO2, FeO, Fe3O4, CaO and Al2O3, and Cu, Fe and S, respectively. These components influence the oxide (Cuox), sulfide (Cusul) and total (Cutotal) copper content lost in the waste slag. This paper uses multiple linear regression analysis (MLRA) to determine the degree of influence. The results of calculations obtained using MLRA were compared to actual measured results and found to have a large degree of correspondence, with the coefficient of determination R2 = 0.975. These results indicate that slag composition and copper content in the matte influence the copper losses in the waste slag with a probability of above 97%. It was determined that, of the total copper content of the slag, 74% is in sulfide and 26% in oxide form, and that this ratio is not dependent on the slag or matte composition.

Jan 1, 2010

By C. Navalkar

Systematic drilling & blasting techniques are currently being viewed in the mining & construction industry as a correct 8z scientific approach for optimization process in rock excavation, as drill & blast costs usually represent major share in total cost of production and also the environmental impacts plays an important role in designing of the operations. Designing a blast is a complex planning task, which for optimization, includes deciding the bench geometry with respect to the rock properties & geology of the area, capacity of the excavators, choice of explosives & detonation method, tiring sequence, etc. Optimization of blast design needs a detailed comprehensive study of all the above intersecting elements. Preblast & Post blast surveys are required for further improvements in blast designs. However, the choice of blast design depends upon the the requisite blasting results opted for and the cost you are ready to pay for the same. The blasting operation, in general, also involves numerous side effects namely, ground vibrations, fly rocks, dust, noise & gas pollution, air blast effect etc. Again these effects can be made tolerable up to a certain extent depending upon the limitations of the environmental obligations as may be specified by the concerned authorities.

Jan 1, 2001

By George J. Tamara

The urban environment presents special challenges for the design and construction of earth retention systems. Complications arising from difficult subsurface conditions are compounded by the presence of urban infrastructure and existing and prior construction. The proximity of adjacent structures as well as intense prior use can cause special concerns including the potential for archeological artifacts or contaminated ground or ground water. Utilities and structures may be particularly vulnerable to the effects of ground movement, dewatering and vibrations. Difficulty of access, congestion and limited work areas may severely restrict means and methods of construction. Dewatering may be limited or prohibited because of concerns for disposal of clean or contaminated water, depletion of aquifers, drawing of contaminants to the site or dewatering induced settlements.

Jan 1, 2003

By S. L. Gerhard

In the United States the performance characteristics of permissible explosives are controlled by routine tests, which include firing the explosive into a gallery filled with a methane-air mixture. These tests are made by the staff-of the Explosives Division of the Bureau of Mines and are similar, in general, to those employed in other countries. This control has helped to reduce the frequency of accidents involving the ignition of firedamp by explosives but has not clarified the basic causes of the ignition. To advance this control and to minimize potential hazards further, this fundamental knowledge is needed. Some of the results of recent research on the causes of the ignition are described herein. NATURE OF THE PROBLEM When an explosive ignites firedamp in the gallery tests, the source of the ignition must be one or more of the emissions from the steel borehole. It has been accepted generally that these emissions are (1) particles, (2) the shock wave, and (3) hot gases and flames. Photographs show that the shock wave emerges from the borehole first, followed closely by hot gases. At first the velocities of these are high and approximately equal, but the velocity of the gases decreases more rapidly than that of the shock wave, and by the time the reactions causing the flame are complete the shock wave travels in an otherwise undisturbed medium. The particles are originally enveloped in the hot gases but some soon begin to break through and eventually out-distance the shock wave. The approximate geometry of these emissions about 1 millisecond after the shot is fired is illustrated in figure

Jan 1, 1939

A shortage of technical skills in all areas of the mining industry is being experienced worldwide. This has significant consequences for design, operations, productivity and safety and, therefore, needs to be seriously addressed, both in the short and longer term. It is therefore both a strategic and a tactical issue. Importantly, however, since mining is a long-term business, the shortage of skills must be dealt with from a strategic point of view to ensure the supply of the necessary skills for future mining. This paper will deal specifically with the provision of high level technical skills, that is, university graduates in mining engineering, and the outlook for the institutions that are currently producing such graduates.

Jan 1, 2009

By M. Peshko, J. C. Gingerich, L. W. Matthews

"Noranda has successfully developed and implemented two leading-edge mineral exploration technologies — hyperspectral remote sensing and 3-D seismic surveying. Airborne hyperspectral imaging provides detailed geological and mineralogical mapping capability at both a regional and project scale that facilitates improved selection of prospective terrain and an accelerated exploration cycle. Noranda, in partnership with Falconbridge, has licensed the exclusive use of the Earth Search Sciences Inc. (ESSI) Probe-1 hyperspectral scanners (128- channel, 0.43 µm to 2.5 µm spectral range) that are capable of mapping in excess of 3500 km2 per day at 10 m pixel resolution. The technology has been successfully deployed on four continents over a broad range of terrain from desert to boreal forest and the high Arctic.To augment the company’s deep search initiatives, Noranda has successfully modified and implemented existing 3-D seismic technology to help targeting massive sulphides located at depths ranging from 500 m to 2000 m. In the fall of 1998 and early 1999, Noranda completed an 18 km2, 3-D seismic program in eastern Canada by successfully drill testing acoustic impedance anomalies locating massive sulphides at depths in excess of 1100 m."

Jan 1, 2002

By M. Hermanus

1. INTRODUCTION It gives me great pleasure to extend my warmest greetings to everyone attending the 30th International Conference of Safety in Mines Research Institutes. I would also like to bid a special welcome to all of the international delegates who have travelled to Johannesburg to take part in what surely be a most rewarding session of deliberations. As you come together over next four days, you will have a wonderful opportunity to exchange ideas and information on strategies and practices for the implementation of sustainable patterns of development. The objectives of this meeting are both timely and far-reaching, as countries around the globe work towards the sustainable use of the world resources. Each of you brings a high level of expertise to these deliberations. I know that you will make the most of this opportunity to address the challenges and opportunities to highlight the most innovative and technologically efficient methods of social protection in order to ensure an increase in the quality of life, health, safety and living environment for the peoples of the Africa. Our country, although endowed with an immense and diverse array of mineral deposits, is perhaps best known in the mining industry for the fact that it is the world’s biggest producer of gold. Although South African gold production has declined over the past years and the industry faces serious problems, it is a myth that the South African industry is moribund. There is a new energy coursing through the South African producers which will ensure their powerful presence for many years to come, based not only on their domestic production but also and probably increasingly on their external operations. Africa features prominently in the latter category.

Jan 1, 2003

By M Watson, A V. Engelbrecht, E Murray-Hayden

Whereas mine reconciliation is a well-established month-end process for most modern mining operations, the resource sector has yet to endorse uniform reporting factors against which model accuracy and metal recovery can be formally assessed. Logically, any comprehensive reconciliation framework should facilitate comparison between period reserve, mine and mill and production figures. Historically, Parker’s F Series ratios (Parker, 2012) are often used in some form by mine operators, although they are rarely shared externally, as formal definitions have yet to be accepted. This paper presents a structural extension to the reconciliation process, wherein resource ratios (R Series factors) are used to quantify the long-term impact of the information effect, together with dilution and ore loss. A case study from the El Limón Guajes (ELG) Mine Complex in Mexico is used to demonstrate how an R Factor Series can be implemented to facilitate operation optimisation, over and above conventional F Series reconciliation treatments. This approach is applicable to any mining operation.

Mar 22, 2022

By Shanti Arangala

Several improvements were made to the single strand rod mill at Laverton to increase production, reduce maintenance and improve several aspects of product quality. With changes to the water cooling line and control system, cobbles could be significantly reduced, more consistent properties obtained and yield improved. An upgrade of the laying head enabled vibrations to be reduced and thus allowed for higher speeds on small sizes. With potential for dramatically increased pipe life, a new pipe support and laying pipe system provided for improved laying pattern on small sizes and thus more uniform cooling on the conveyor and better coil package. This paper discusses details of these equipment and control system upgrades and the resulting benefits that have been realized from the project.

Aug 16, 2017

By Y. Duraisamy

This paper presents the compressibility of tropical peat reinforced with cylindrical cement column. When a cement column installed vertically in peat, its compressibility was reduced because of the hardened skeleton matrix formed by cement particles bonding with adjacent soil particles in the presence of pore water. The effects of diameter, number of columns and cement proportions in cement columns on the compressibility have been investigated in this study. The results indicated that compressibility index Cc and Ca decreased with the increase in diameter of the cement column. Specimens with 45 mm and 60 mm diameter of cement column were cured for 28 days, after which they were subjected to Rowe Cell Consolidation test. Based on the results obtained, it shows that cement columns can successfully reduce the compressibility of tropical peat.

Jan 1, 2007

By J. Douglas Causey

In 1984, at the request of the Bureau of Land Management, the Bureau of Mines studied 9,600 acres of the 12,350-acre Antelope Creek Wilderness Study Area (MT-065-266) in order to evaluate its mineral resources. Within this report, these 9,600 acres are referred to as the study area. The Antelope Creek Wilderness Study Area, Phillips County, MT, adjoins the north end of the Charles M. Russell Wildlife Refuge. Considered part of the Missouri River Breaks, the area straddles the edge of a thrust fault zone that has deformed the Mesozoic strata in the west half of the area. Shale, siltstone, and sandstone of Cretaceous Age are exposed in the area. Coal beds averaging 3.0 ft thick occur in the Judith River Formation. About 0.20 million short tons of coal were mined from the Judith River Formation adjacent to the west boundary of the area; no production is known in the study area.

Jan 1, 1986

By J. F. Breedis

The stabilization of austenite in Fe-Ni alloys against martensitic transformation after reversion has been attributed' to the lattice imperfections remaining from previous transformation. More recently, however, such stabilization has been associatedzy3 with compositional changes which occur in martensite during slow heating. Dislocation arrangements in deformed austenitic stainless steels strongly influence transformation to martensite on quenching.4 Therefore, it is of interest to observe the transformation behavior of stainless steel after reversion, especially since previous studies have been confined to Fe-Ni alloys. The transformation-product morphology also differs in the two iron-alloy systems;6 plate martensite forms in the latter while stainless steel transforms to lath-type martensite. Samples of Fe-16 wt pct Cr-12 wt pct Ni (maximum C + N = 0.005 wt pct, 0 = 0.02 wt pct), prepared by vacuum melting and casting from high-purity components, were annealed at 900°C for 24 hr, after cold rolling to produce a 40-p grain diameter. The M, temperature of this alloy is -80°C and samples are fully austenitic after annealing. The amount of martensite present after quenching, annealing, and requenching was determined magnetically, to within 0.01 wt pct, using a vibrating specimen magnetometer. Nearly 14 pct of martensite forms during the initial quench in 1 min at -196°C. Two-min and 2-hr anneals were done in air and in evacuated quartz capsules, respectively. All specimens were electro-polished before making the magnetic measurements.

Jan 1, 1967

Evaluation of the Iron Blast Furnace Process using Heat and Material Balances of the Flame-Zone

Sep 13, 2010

By Sheridan A. Glen

As the Federal government along with individual states continue to grapple with the job of refining a comprehensive energy policy, coal continually stands out as an energy source which heralds a combination of old and new capabilities like an energy planners prophecy, but which is plagued with serious environmental constraints. To determine what level of coal utilization is ultimately possible for states East of the Mississippi, whose high sulfur content coal presents the most paramount of challenges, one must consider product availability, via existing transportation modes, the developing industrial markets and the ability of coal to meet the challenge of becoming an environmentally acceptable fuel. Gasification is emerging as a form of utilization, which during the next twenty years stands a good chance of being able to meet the challenge of making coal an environmentally clean, easily transport-able and usable fuel. It can be argued that, of all the potential ways of utilizing high sulfur coal, coal gasification is perhaps the most expensive, the most financially risky and carries environmental liabilities of its own. Synthetic gas and oil markets will undeniably be a function of price and demand, which, for the purposes of this paper, I'm assuming will begin to merge in the late 1980's and into the 1990's. This is also presuming that public utility commissions will allow favorable price structure ruling so that gasified coal products can be rolled into their respective rate base, much the same as synthetic natural gas from petroleum by-products are currently being priced. The comparative economic markets of coal to gas pro-duct have plenty of time to mature. There is an approximate twelve-year lead time needed to bring coal gasification plants on line which will be able to compete in the market place for natural gas and oil customers.

Jan 1, 1977

By L. R. MacLead

Delivery of tailing to any part of the area by gravity from the ridge was found practicable. Experiments with asbestos-cement pipe proved it possible to use level pipe across the dams if it is fed through an inclined section in which pressure could be developed. Use of pipe to transfer the tailing to the dams was not favored because of the possibility that choking might occur. Metal flume was not believed to have sufficient wear resistance on this material and wooden flume would not withstand damage by the weather so well- Flume -action made- of 26-in diameter asbestos-cement pipe, split before curing and molded to a specified cross section, were finally approved. The flume is connected to the 24-in. diameter tail in distribution pipe by heavy concrete lateral launders. Cascades of horizontal and vertical pipe sections are used at the top of the pressure leg where scouring by high-velocity flow of tailing might occur.

Jan 1, 1942