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By T. Shellhammer, A. Park

Among all pure metals, copper has the second highest thermal and electrical conductivity, next to silver. These properties coupled with a reasonable cost, make copper ideal for use in metallurgical vessels as a conductor of electrical current, as well as a lining material and protector of refractories and steel superstructures. Treatments of copper to address it’s softness and low melting point, specifically hard surfacing and calorizing, will be discussed. This paper will cover the evolution of copper to its current form, offer comparisons to other materials, and theoretical and empirical evidence on its superior performance in metallurgical vessels such as blast furnaces, basic oxygen converters and electric arc furnaces. Some case studies will be provided and finally a brief summary.

Jan 1, 2015

By James A. Lewis

It is the purpose of this paper to show the importance of sand characteristics, when combined with other physical data, in evaluating production obtained by secondary recovery operations, and to indicate the benefits to be gained from the application of these principles to primary production. Introduction During the past 10 years there has been a growing interest within the industry regarding the movement of fluids through oil reservoirs. A number of research projects have been directed toward the development of the physical laws governing this movement. In the period 1933 to the present, correlations between laboratory analysis of cores, reservoir fluids and well performance have been established and have been applied to successful secondary water-flooding recovery operations; and to the completion, production, reconditioning and evaluation of wells in new fields. The application of these data to water-flooding, either natural or artificial, is comparatively new, but the principlcs involved were set forth in 1880 by John F. Carll,1 who said: The flooding of an oil district is generally viewed as a great calamity, yet it may be questioned whether a larger amount of oil cannot be drawn from the rocks in that way than by any other, for it is certain that all the oil can-not be drawn from the reservoir without admission of something to take its place. If one company owned all of the wells drawing upon a pool, and had accurate records of the depth and characteristics of the oil producing stratum in each well, it is quite possible that some system might be devised by which water could be let down through certain shafts, and thus the rocks be completely voided of oil and left full of water. As it is, however, no systematized plan of action can be adopted. The careless handling of one well. by which water is let down to the oil rock, may spoil several others belonging to different parties. A clashing of interests at once arises and is likely to result in disaster to the whole district. In judging of the probable effects of the intro-duction of water into any particular oil district several things are to be considered. (1st) The time of flooding—whether early in the progress of development, while yet a large percentage of oil remains unexhausted or at a later period after the supply has suffered from long continued depletion. (2nd) The structure of the rock—whether regular and homogeneous throughout, or composed of fine sand inter. bedding connected and irregular layers of gravel, sometimes lying near the top and at others near the bottom. (3rd) The shape of the area being flooded. (4th) The position of the point at which water is admitted. in relation to the location of the surrounding wells still pumping oil. (5th) The height (which governs the pressure) of the column of water obtaining admittance. (6th) The duration of the water supply. Although we may take exception to part of Carll's reasoning, particularly " and thus the rocks be completely voided of oil and left full of water," we must give him credit for pointing out the increased effectiveness of water encroachment in displacing oil from a sand and for his recording six of the present seven considerations necessary for evaluation of production of oil by water

Jan 1, 1942

By James A. Lewis

It is the purpose of this paper to show the importance of sand characteristics, when combined with other physical data, in evaluating production obtained by secondary recovery operations, and to indicate the benefits to be gained from the application of these principles to primary production. Introduction During the past 10 years there has been a growing interest within the industry regarding the movement of fluids through oil reservoirs. A number of research projects have been directed toward the development of the physical laws governing this movement. In the period 1933 to the present, correlations between laboratory analysis of cores, reservoir fluids and well performance have been established and have been applied to successful secondary water-flooding recovery operations; and to the completion, production, reconditioning and evaluation of wells in new fields. The application of these data to water-flooding, either natural or artificial, is comparatively new, but the principlcs involved were set forth in 1880 by John F. Carll,1 who said: The flooding of an oil district is generally viewed as a great calamity, yet it may be questioned whether a larger amount of oil cannot be drawn from the rocks in that way than by any other, for it is certain that all the oil can-not be drawn from the reservoir without admission of something to take its place. If one company owned all of the wells drawing upon a pool, and had accurate records of the depth and characteristics of the oil producing stratum in each well, it is quite possible that some system might be devised by which water could be let down through certain shafts, and thus the rocks be completely voided of oil and left full of water. As it is, however, no systematized plan of action can be adopted. The careless handling of one well. by which water is let down to the oil rock, may spoil several others belonging to different parties. A clashing of interests at once arises and is likely to result in disaster to the whole district. In judging of the probable effects of the intro-duction of water into any particular oil district several things are to be considered. (1st) The time of flooding—whether early in the progress of development, while yet a large percentage of oil remains unexhausted or at a later period after the supply has suffered from long continued depletion. (2nd) The structure of the rock—whether regular and homogeneous throughout, or composed of fine sand inter. bedding connected and irregular layers of gravel, sometimes lying near the top and at others near the bottom. (3rd) The shape of the area being flooded. (4th) The position of the point at which water is admitted. in relation to the location of the surrounding wells still pumping oil. (5th) The height (which governs the pressure) of the column of water obtaining admittance. (6th) The duration of the water supply. Although we may take exception to part of Carll's reasoning, particularly " and thus the rocks be completely voided of oil and left full of water," we must give him credit for pointing out the increased effectiveness of water encroachment in displacing oil from a sand and for his recording six of the present seven considerations necessary for evaluation of production of oil by water

Jan 1, 1942

By Shenxu Bao, Ying Bian, Xiang Liu, Liuyi Ren, Yimin Zhang, Chun Liu

Efficient enrichment of high-carbon low-grade mica stone coal containing vanadium is a key problem in the mineral processing field, and the mature beneficiation process is yet to be developed and applied. In this paper, a special mineral mica type of stone coal containing vanadium from Tongshan, Hubei Province, China was selected as the research object. Chemical analysis results show that this mineral contains V2O5 0.71%, SiO2 49.28%, C 13.44%, and CaO 6.26%. Scanning electron microscope (SEM) shows that vanadium generally exists in all kinds of mica minerals in 20 µm to 50 µm fractions. Mica stone coal containing vanadium must be ground to a particular fineness (approximately 45 µm). To reduce acid consumption during vanadium extraction from stone coal through acid leaching, a pretreatment process was proposed to enrich micas by using shaking table and flotation methods. A new combined technology process was implemented, resulting in a 0.96% improvement in the vanadium grade of raw materials in the succeeding process. Vanadium losses were controlled to 4.57% through the pre-concentration process, which reduced the burden of the subsequent procedure. The content of high acid consuming minerals was also diminished, such that approximately 6612 CNY was saved from producing 1 t V2O5. Therefore, stone coal containing vanadium should be pre-concentrated by using an appropriate combined process to reduce costs.

Jan 1, 2014

Jan 1, 1925

By Jacqueline A. McClaskey

The U.S. Bureau of Mines Information and Analysis Directorate collects worldwide data on virtually every commercially important non fuel mineral commodity. These data form the base for tracking and assessing the health of the minerals sector of the U.S. economy. The Bureau's data collection activity was instituted by the 47th Congress in an appropriations act of August 7, 1882 (22 Stat. 329), which placed the collection of mineral statistics on an annual basis. The most recent authority for the U.S. Bureau of Mines survey activity is the National Materials and Minerals Policy, Research and Development Act of 1980 (Public Law 96-479, 96th Congress). This act strengthens protection for proprietary data provided to the U.S. Department of the Interior by persons or firms engaged in any phase of mineral or mineral-material production or consumption.

Jan 1, 1993

By H. C. Cooke

THE gold mining industry, in Canada as in other countries, has passed through trying times in the past year. The strains and stresses of war have drawn away much of its man-power, both from the labour and the management. The urgent needs of the war machine have greatly curtailed the amounts of steel and explosives that can be allotted to the mines; and the loss, by enemy action, of supplies of such essential things as rubber, bids fair to reduce operations still further, if not cripple them entirely in time. And, as if these difficulties were not enough, war on the psychological front has been declared on the gold mines. Earnest supporters of the war effort, well-meaning theorists, and perhaps others whose intent is less disinterested, have all combined to clamour against the continuance of gold mining. We have been asked, what is the use of taking gold out of one hole in Canada to put it into another in Kentucky. We have been assured that gold will never again have any value, except for filling teeth. We have been repeatedly adjured to look at Germany, how well it has got along without gold. We have been told that it is unthinkable, when this nation is girding her loins for war, that labour and materials should be diverted to this useless effort. Gold miners should be diverted to the base-metal mines, where they can produce something of real value to the war effort; or to war factories; or, in fact, almost anywhere, so long as they are got out of the gold mines. And, what has made the situation even more disturbing, it has seemed as if all this clamour might be convincing governments. In fact, as you all know, the government of the United States did actually take the step of ordering its gold mines to cease operations. Fortunately, however, for Canada, the facts that no large favourable effects resulted from that action, and that, in Canada, gold mining is a much larger part of the national economy than in the United States, have caused our government, so far at least, to avoid this drastic step. In talking about this, however, let me emphasize that I have no more inside information on the subject than any of you. Like Will Rogers, all I know is what I see in the papers.

Jan 1, 1943

By L. C. IlsLey

Cooperation between the United States Bureau of Mines and the Safety in Mines Research Board of Great Britain, continuous, since 1924, s made possible this and other papers on safety subjects. Grateful acknowledgment is made to representatives of the board for their assistance in arranging visits to several mine-safety stations, and to F. R. Wynne, Deputy Chief Inspector of Mines, for arranging visits to mines in Great Britain and certain other countries in Europe. During the summer of 1927 the writer had the privilege of visiting the mine-safety testing stations An Great Britain, Belgium, Germany, and France, in the order named. All of these countries have large coal mines, many of which are rated as gassy. Therefore, a the installation of electrical equipment is contemplated each of these countries is confronted with the same safety problem as is the United States that is, the development of electrical equipment that will not, ignite gassy atmospheres should they through neglect or accident surround the equipment. The means employed by these countries in safeguarding gassy mines should therefore be of general interest to safety engineers of American coal mines, and a brief survey is given for each of the four countries mentioned. The fourth or last of these surveys covers conditions in France.

Jan 1, 1929

By J. A. Dos Santos

"INTRODUCTION Dramatic reduction in energy use and environmental impact can be achieved with sandwich belt high angle conveyors that serve as the vital link in any IPCC (In-pit Crushing and Conveying) system. These high angle conveyors are not new at all, but have not found wide use in IPCC systems where they can realize the greatest advantage. Reduced energy consumption and environmental impact, with IPCC systems, was already realized in the 1970s. With the bulk material haulage limited to conventional open trough conveyors the most direct path out of the open pit was precluded, requiring low angle spiral ramps and/or deep slots and/or tunnels through the high wall of the open pit. These excavations, to accommodate the low angle limitations, represented undesirable impact on cost and on the environment. Against this backdrop, a major study in 1979 sought to develop high angle conveying systems that could continuously haul the mined bulk material directly out of the pit, along the high wall – the shortest distance between the two end points. Between 1979 and 1982, that study developed sandwich belt high angle conveying systems that utilized all conventional conveyor equipment including smooth surfaced rubber belts that could be continuously scraped clean. These systems had all of the positive features of conventional conveyors but overcame the angle limitation. By hugging the bulk material between two belts, the material’s internal friction could be developed to facilitate conveying at any high angle up to 90 degrees (vertical). After an intense testing period (about one year) on the first large scale prototype system, commercialization began in 1983 with the installation of a 60 degree incline system at a western United States coal mine, elevating 2000 t/h of coal to a train load out system. It did not take a long period of scrutiny and acceptance before this high angle conveyor found use in the most rugged requirements of an IPCC system. This was only the second commercial sale, and after more than 150 commercial installations, it remains arguably the most significant high angle conveying system. In 1984, a copper mine in Serbia, already using pit perimeter crushing and conveying, decided to move their primary crusher deep into the pit and to use a sandwich belt high angle conveying system to elevate the ore continuously, directly out of the pit, along the high wall to the pit perimeter where it then transferred to a conventional conveyor for the remaining haul to the plant. The system had significant features including 2000mm wide belts that elevated 250mm coarse ore, at 4000 t/h, over six 15-meter high benches for a total 90 meters of net lift. The system was able to reduce the truck haulage fleet by ten 200 ton trucks realizing great cost savings, zero emissions to the air and greatly reduced traffic congestion in the pit. The system operated successfully until 2002 when the mine shut down. Many successful sandwich belt high angle conveyors followed with the current count of commercial installations at more than 150. Despite the great success with this system, its use has not been repeated as part of an IPCC system."

Jan 1, 2018

By E. V. Manlapig, M. C. Harris

"The complexity of the flotation process has made the identification of an appropriate model structure, for use in the prediction of flotation circuit performance, far from obvious. Work performed under the auspices of the AMIRA P9 flotation program has indicated that the metallurgical performance achieved from a flotation cell arises from the interaction of two essentially independent property classes, namely the cell operating conditions and the properties of the cell feed stream. These observations have led to the development of a model structure that associates a constant set of flotation parameters to the streams of the circuit, which are transformed into a flotation response depending on the operating conditions within the flotation cell.A variety of alternative model structures exist within the literature which do not make this distinction between cell and stream flotation properties, and many of these models are in widespread use for flotation optimisation and design studies, both in industry and academia.In this paper, data collected from an industrial flotation circuit is used to derive the parameters associated with two different types of flotation models. Simulations performed using these models demonstrate the need to differentiate between cell and feed properties. A model that does not differentiate between these two properties fails to successfully predict the metallurgical performance of a flotation circuit after a disturbance."

Jan 1, 2003

By J F. Penrose

To obtain cost-efficient financing by way of securing an optimal credit rating, the operating and market risks of a single-asset mining project should be accommodated in the financial structure. Weak financing structures can cause projects to fail, as evidenced by the Murrin Murrin and Bulong examples; these can be compared to the investment-grade structure of Straits (Nifty), which managed operational, market, and financing risks well. Most mining projects are capital-intensive, and have heavy dependency on debt financing. A weak financial structure may result in the early failure of an otherwise sound and economically viable project. Appropriate management of technology, construction, and management risks generally will get a project built; of the project failures that occur, most are caused by a liquidity crisis as the project goes through ramp-up (the transition period between completion of construction and full operation). A projectÆs viability can be enhanced through sound hedging practices, while poor hedging can increase the likelihood of financial default.

Jan 1, 2003

By Milford L. Skow

This report summarizes the principal activities and results of 15 years of research by the Bureau of Mines, U.S. Department of the Interior, on methane control in coal mines. This research has investigated fundamental factors regarding the occurrence and movement of methane in coal beds, removal of methane prior to mining, and control of methane during mining. The report includes a bibliography listing the more than 150 publications resulting from the Bureau's methane control program as well as numerous other references, a section on methane recovery and use, a look at the upcoming Bureau of Mines research program, and a brief review of methane drainage practices in other coal-producing countries.

Jan 1, 1980

The annual meeting of the Woman's Auxiliary was held on February 19, at 10 a. m. The president, Mrs. Sidney Jennings, said in her greeting "it is a matter of congratulation that during the past year when the demands upon women for work of all kinds has been so large our membership has grown from the 50 enrolled at the first meeting a year ago to over 300 today. Some women, when. asked to join the organization, say that they are doing so much work in other ways that they have no time for work in a new organization, but the director for Canada struck the right note in her report when she told us of the splendid work the wives of mining engineers are doing in Canada, as individuals and as leaders and members of various organizations doing patriotic work. We do not want to divert such women from the work they are now doing, but we do want them to enroll as members of the Woman's Auxiliary and let us know what they are doing, that they play give inspiration to others." Reports were made by the directors of the following sections: Canada, Chicago, Colorado, Columbia, New York, Puget Sound and St. Louis, in some of which sections excellent progress has been made in food conservation, foreign war relief, including the adoption of fatherless French children, and in work for our own engineering regiments. These reports were read, accepted, and placed on file. The reports of the corresponding secretary, of the recording secretary, and of the treasurer, were read, accepted, and placed on file. Various amendments to the Constitution were proposed and accepted, and copies of the Constitution, as amended, will be mailed to all the members of the Woman's Auxiliary.

Jan 4, 1918

By WILFRED SYKES

THE story of the rolling of strip steel is not limited to any one plant or individual or group of individuals. It is a story with many ramifications. First of all, it should be understood that the strip mills we are considering are continuous mills, in that the steel passes directly from one mill to the other in a more or less straight line. Continuous mills are not new; in fact, they have been used for many years in the rolling of a few simple shapes. They were, however, driven by one motor through jackshafts, and as a result the speed of each roll stand had a fixed relation to that of every other stand in the series. This in turn fixed the reduction that could be made in each stand. The mill could produce simple things, but was not satisfactory for the production of the variety of strip now required. It was, therefore, necessary to get away from the restrictions of that kind of drive. To accomplish this, the designer could either separate

Jan 1, 1936

By J. A. Kinnaird, B. J. Youlton, K. L. Youlton

Methods for treating and processing refractory gold ores are well established. However, what is less well understood is how the formation of the gold-bearing deposits affects gold processing and extraction. In order to evaluate the effect of ore genesis on gold extraction a number of South African gold deposits were studied. These included complex Pilgrim’s Rest samples as well as refractory Fairview, Barbrook, and Consolidated Murchison samples. We found the refractory nature of gold ores is controlled by a limited number of well-understood mineralogical factors. Solid solution gold is linked to low temperature and pressure conditions in fine-grained sedimentary lithologies, while reactive pyrrhotite can form from hydrothermal fluids associated with mafic magmatic rocks. These formational controls can be used to identify and avoid complex deposits at a desktop study phase, or address and reduce complications further along the pipeline using early mineralogical studies.

Jun 1, 2021

By J. C. Bradley

THE relation of annealing temperature to conductivity of copper wire has been determined.1 Conductivity hard was 98.26 per cent. After a 10-min. heating at 200° C. it was 98.69. By annealing 10 min. at 300° C. a large increase, to 100.93, occurred. Maximum conductivity, 101.15, was attained after a 500° C. anneal; thereafter it decreased to 100.53 after a 950° C. anneal. If copper is gassed the decrease is much more than this. MATERIAL AND METHOD The work was done on high grade electrolytic copper, 99.942 per cent. copper-plus silver, silver 0.0008 per cent. It was hot-rolled to 3 in., then cold drawn to 0.080 in. The wire was cut into 25 5-ft. lengths and numbered 1 to 25 as cut. Four samples were tested hard. The others were wound into 5-in. diameter coils. For the 100° C. heating a coil was put into water, the water brought to boiling, and the wire kept at this temperature for 10 min. For the higher temperatures the coils were placed in envelopes of sheet copper, a little water added, and the envelopes sealed by folding over the edges twice, and hammering them together. This kept the air out very well. The envelope and wire were brought to the desired temperature; this was maintained for 10 min., then the whole was water-quenched.

Jan 1, 1927

By D. L. Sawyer

Aqueous C12-02 leaching procedures developed by the Bureau of Mines to produce zinc chloride from zinc sulfide bulk concentrates were effective in extracting 99 pct of the zinc and 97 pet of the silver contained in samples of massive seafloor sulfides from the southern Juan de Fuca Ridge. Zinc sulfide (sphalerite and wurtzite) mineralization comprised 55 and 88 pct of two specimens provided by the U.S. Geological Survey for this study. Minor occurrences of galena, chalcopyrite, and other minerals in the sulfides permitted the recovery of pregnant liquors that were low in metal values other than zinc, which were successfully purified by a two-step cementation procedure using zinc dust.

Jan 1, 1983

By Fritz Kleiner, Walter Meintrup

On Nov. 4, 1981 A/S Sydvaranger's 1-kt/h (1,100-stph) wet-process, iron ore ball mill completed its first four months of uninterrupted, full-load operation in Kirkenes, Norway. This 6.5-m-diam (21-ft-diam) mill is driven by a gearless ring or wraparound 8.1-MW (10,860-hp) motor at 13.1 rpm-a first of a kind in this segment of industry. This article examines reasons for selecting this type of drive over more conventional schemes, lists specific advantages of such large mills, and describes the installation in Norway. History For almost a decade, good operating experiences have been gained with 28 gearless ring motor drives in the cement industry, driving 2.5 to 4-m-diam (8.2 to 13-ft-diam) tube mills with drive powers ranging from about 3-4 MW (4,000 - 8,000 hp). Why then did the mineral ore processing industry hesitate until 1980 to adopt this successful concept for similar applications on ball, semiautogenous, and autogenous mills? There are a number of good reasons in the eyes of conservative mill builders and operators, the most commonly cited ones are: • No operating experience in this segment of specialized industry. • More severe environmental conditions in the wet ore grinding process. • An indifferent attitude of mill builders and electric motor manufacturers towards new drive technologies. • Limited confidence in solid-state power supply systems, such as frequency converters of the required size. There have been and still are numerous problems associated with low-speed geared mill drives of any kind, especially with individual motor/gear sizes approaching or exceeding about 4 MW (5,360 hp). Every mill builder knows about them, but operators learn to accept them as inevitable. The Decision to Change Three things combined to break this technological stalemate: the courage and progressive spirit of one major iron ore processor in Scandinavia, the cooperation of three experienced manufacturers, and an unusual application problem that could not be solved by any conventional approach. The last factor was surely the decisive one, but the first one does not come as a surprise either. The Swedes near Kiruna and the Norwegians around Kirkenes are experienced ore miners and processors, and much credit goes to them for technological breakthroughs in the industry. At A/S Sydvaranger in Kirkenes, above the Polar circle at about the latitude of Alaska's northern tip, the existing grinding facilities, with a total of 14 100 to 240-t/h (110 to 264-stph) ball mills, can not be expanded. Nevertheless, to increase mill throughput, only installing a larger mill in place of an existing smaller one was a practical alternative. For this replacement, the owners set requirements that seemed impossible to meet: • The old 100-t/h (110-stph) ball mill should be replaced with a new ball mill with 10 times the rated throughput, without significantly impairing the operation of the remaining mills, and without significantly changing the mill building. • The new mill should have a variable-speed drive to ultimately optimize the grinding process by means of a closed-loop process¬computer-controlled grinding cycle, and to minimize the specific energy consumption. • Availability, efficiency, and life expectancy of all new components must be higher than those being replaced. • Inrush-current and harmonic loads on the rather weak electric supply line must be minimized to ensure safe plant operation. All old ball mills at A/S Sydvaranger are the geared type, using single synchronous and wound-rotor, slow-speed motors with ring-and-pinion gears. Operators are familiar with the limitations and problems associated with such drives, and they are aware that the following items become major concerns when drive powers are drastically increased: • Gears are subject to wear and tear, require frequent maintenance, and eventual replacement of major parts. • Gears are sensitive to misalignment, overload, and thermal distortion, limiting their useful life. • On dual or quadruple drives, load-sharing and torque oscillations between motors can be a major reason for concern. • At these speeds, ring-and-pinion gears reach their torque transmission capabilities altogether at around 4 MW (5,360 hp) per motor/pinion. To obtain the desired variable-speed performance of the new drive, the only practical and economical conventional solution would have been a frequency-controlled, low- or medium-speed dual motor drive with about 8 MW (10,720 hp) of power. This, however, was not feasible because of limited floor space. Therefore, bids were solicited for the alternative drive method, the gearless ring motor. General Considerations Why are such large mills considered? After all, one could avoid all the problems by simply staying with smaller mill unit sizes. Under competitive pressures of free markets, however, grinding efficiencies and specific energy consumption become key factors in selecting new equipment. Specific energy consumption of ball mills decreases with increas-

Jan 9, 1982

The smoker, Monday evening, was an unusual success. It was held in the beautiful gold room of the Congress hotel, which was very elabo-rately decorated with American flags. More than 500 were present. The gallery was filled with ladies, who responded to the request of the song leader and helped in many ways to grace the occasion. The enter-tainment, was a varied one and was original with the Chicago Committee, which deserves great credit for the unusual success of the event. Al-though it was mostly funmaking, Dr. F. B. Cottrell and George S. Rice of the Bureau of Mines gave some very interesting talks, illustrated by flags and moving pictures, of their trip through Europe since the armis-tice. Mr. Rice's talk dealt particularly with the demonstrative coal and iron regions and Doctor Cottrell's was devoted almost solely to that part of his trip in Northern Italy where he was investigating the application of volcanic steam to power purposes. This steam is derived from boracic-acid springs and helium is secured as a byproduct.

Jan 11, 1919

Solution transport of gold and silver has occurred as a result of the chemical weathering of many Western Australian epigenetic gold deposits. Evidence for the remobilization of gold exists in the form of small crystalline octahedra, mustard gold, flake gold, and coatings on iron-oxide. This "secondary" gold is of high purity (low silver content). It is believed that the high chloride content of laterite profiles combined with the acid produced by the oxidation and hydrolysis (ferrolysis) of iron has caused dissolution of Au/Ag and Au/Te alloys. Gold, and less frequently silver, is subsequently reprecipitated in the profile nearby.Pyrite, which is a ubiquitous accessory of gold in vein or lode systems, is probably an important source of iron for the development of acidity. Where carbonate is abundant in the primary assemblage, neutralization directs the oxidation of sulphide to a path which produces thiosulphate, and an alternative type of Au/Ag oxidation process. Sulphide/carbonate ratios in the vein system, and adjacent wallrock are seen as important in determining the course and extent of remobilization in the oxidized zone of gold deposits.

Jan 1, 1984