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By P Audet, D R. Mulligan, D Doley

This analysis attempts to reconcile existing ecological theories, rehabilitation planning goals and implementation constraints in the form of a rehabilitation paradigm that considers potential and pragmatic ecosystem transformation pathways. The framework prioritises multiple developmental scenarios for post-disturbed landscapes within a continuum of ecological outcomes. A feature of the framework is that ænovelÆ ecosystems and agro-ecosystems, having a range of commercial and societal values, are valid outcomes spanning the conceptual divide between the ecological functions of under-rehabilitated versus re-instated ænaturalÆ landscapes, especially in a changing environment. Landscape suitability analyses are considered to be fundamental to the incorporation of regional landscape and climate in the implementation of land rehabilitation and management strategies. Altogether, the paradigm could facilitate the identification of widely pertinent rehabilitation goals having direct implications at the regional scale of restoration ecology and acceptance of the need for ongoing commitment to the management of disturbed environments.CITATION:Audet, P, Doley, D and Mulligan, D R, 2012. Can ænovelÆ ecosystems offer suitable rehabilitation alternatives for post-mined landscapes?, in Proceedings Life-of-Mine 2012 , pp 135-142 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By H. I. Smith

WHEN Spain established colonies on the North American continent, some of her land grants, in what is now the United States, reserved to the Crown deposits of gold, silver, and mercury. Later mineral rights were reserved under some of the English Crown charters involving land in the eastern part of North America, with provisions for the payment of royalties thereon to the Crown. Reservation of mineral deposits to the United States Government was instituted by an ordinance of Congress on May 20, 1785, which applied to such deposits in the Northwest Territory, then north of the Ohio River and east of the Mississippi River, and provided that there should be reserved "one third of all gold, silver, lead, and copper mines, to be sold or otherwise disposed of as Congress shall hereafter direct." Little was known then of the mineral resources of the country; the Great Lakes copper region had just come into the possession of the United States by treaty and much of the western mineral land still belonged to France and Spain. The policy of leasing mineral deposits was enacted by Congress under the act of March 3, 1807, which provided that "the President of the United States shall be, and is hereby, authorized to lease any lead mine which has been or may hereafter be discovered in the Indiana Territory, for a term not exceeding five years," and in the same year the Government reserved 345,600 acres of land in northern Illinois, valuable for lead. In 1816 Congress provided that in all cases where a tract of public land containing a lead mine or salt spring was applied for by settlers on the public domain, no permission to work the mine or spring would be granted without the approbation of the President of the United States. By the act of March 1, 1847 (9 Stat. 146), the control of mineral lands was transferred, with all records, from the War Department to the Treasury Department, and by the act of March 3, 1849 (9 Stat. 395), supervisory powers over lead and other mines of the United States were transferred to the Secretary of the Interior. Following the discovery of gold in California in 1848, President Polk advocated the leasing of mineral lands acquired from Mexico under the treaty of 1848. However, owing to the lack of communication and transportation facilities and the consequent difficulty of checking on production and operations, leasing was found impracticable. Mining was permitted to be carried on in each district under rules made by the miners themselves and patterned after the Mexican mining system. To meet the situation, Congress enacted mining laws in 1866, 1870, and 1872, which provided for possession by location and for private ownership, after discovery, by patent of essentially all mineral deposits belonging to the United States, except coal. Many other acts were passed by Congress applying to specific regions and states, reserving salt, lead, or other minerals, some of which provided for the leasing of such deposits. However, very few if any leases were issued thereunder. Not until 1901 (31 Stat. 745) were the mining laws extended to include salt, and in 1910 they were revised to specify salines and associated products. At the turn of the century, it became more and more evident that the mining laws developed for metallic minerals were not practical for the development and conservation of oil and gas, coal, potash, phosphate, or oil shale. Following withdrawals by the Secretary of the Interior as authorized by the act of June 25, 1910, the Department of the Interior recommended leasing legislation; however, it was not until February 25, 1920, that the Mineral Leasing Act was passed by Congress. This act authorized leasing all public lands potentially valuable for oil, gas, coal, phosphate, sodium, or oil shale. The Organic Act, creating the Geological Survey in 1879, imposed upon its director the duty of classifying the public lands.' The early years of the Survey were devoted largely to the accumulation of fundamental data and, with only minor exceptions, land classification was not seriously undertaken until 1906. Since that year, it has been actively pursued with respect particularly to leasable minerals and water power values. On March 3, 1873 (17 Stat. 607) Congress authorized the sale of coal lands of limited acreage to individuals at $10 to $20 an acre, depending on the distance from a railroad, and in 1907 a new scale of prices was adopted by the Secretary of the Interior, based, more logically, on the quality and thickness of the coal deposits, their depth below the earth's surface, and their accessibility. At that time it was much cheaper and easier to obtain incidental title to coal rights under the homestead laws at $1.25 an acre. On March 3, 1909, the first separation act (35 Stat. 844) became a law. It authorized patents, with a reservation of the coal and mining rights involved to the United States, to persons who in good faith had entered public lands under the non-mineral land laws prior to withdrawal, classification, claim, or report that such lands were valuable for coal. It solved the problem only partially, and the practice thereupon adopted by the department of making coal withdrawals "from all forms of entry" instead of "from coal entry" expedited the more complete solution effected by later acts. By the act of June 22, 1910 (36.Stat. 583) withdrawn and classified coal lands were declared subject to entry under the homestead, desert land, and Carey acts, provided a waiver of the coal rights accompanied the application, and by the act of April 30, 1912 (37 Stat. 105) the same privilege was extended to State selections and isolated tracts. The act of August 24, 1912 (37 Stat. 496) extended the separation policy to lands withdrawn for oil and gas in Utah, and finally the act of July 17, 1914 (38 Stat. 509) extended it to all nonmineral filings on public lands theretofore or thereafter

Jan 1, 1955

By P. Tittes, M. Deal, M. Spicher, S. McDaniel, J. Wickens

"Haile Gold Mine is located near Kershaw, South Carolina, approximately 50 miles south of Charlotte, North Carolina. Gold was first discovered at the site in 1827, and the property has been through several operating periods since. The relatively low grade and refractory nature of the deposit has been a challenge for efficient processing since the start of mining on the property. Early processing techniques included gravity separation and barrel chlorination. The last operation employed heap leaching in 1985 through 1992. After being closed and reclaimed for over 20 years, the property is poised to re-open and produce once again. In this chapter of the Mine’s legacy, flotation and ultra-fine grinding will be employed to achieve economic extraction of gold and silver from the pyrite. This paper briefly reviews some of the mine’s history, the metallurgical testing, the flowsheet and discusses design considerations.INTRODUCTIONHaile Gold Mine is located near Kershaw, South Carolina, approximately 50 miles south of Charlotte, North Carolina. Gold was first discovered at the site in 1827, and the property has been through several operating periods since. The last operation employed heap leaching in 1985 through 1992. Since then, the property has been closed and fully reclaimed. Romarco Minerals acquired the property in 2007, and began an exploration program that has delineated over 62 tonnes (+2M ozs.) of gold in reserve at an overall grade of 2 ppm (0.06 opt). This paper provides a brief history of the property, a summary of metallurgical testing, description of the process flowsheet and discusses design considerations.HISTORY1827 – 1837Gold was discovered in creek beds on the Haile property in 1827. The property was owned by Benjamin Haile, and the first few years of production came from placer mining. After gold was discovered in schist beds to the sides of the streams, Haile expanded the operation by leasing 18 meter-square (50 ft.) plots to local planters. These planters used slaves to work the small excavations in the agricultural offseason. The gold ore was taken to arrastras where the free gold was liberated and recovered. The excavations were above the water table, generally less than 18 meters (60 ft.) down, and it was noted then that gold could be found embedded in sulfides and difficult to extract."

Jan 1, 2013

The Nena high sulphidation-type copper-gold deposit is composed of andesitic pyroclastic units with minor interstratified lava flows. Epiclastic sandstone and conglomerate, and siliciclastic rocks consisting of mudstone, shale, lithic and bioclastic sandstone and conglomerate are locally present. Pre-mineral diorite intruded and domed the volcano-siliciclastic sequence. Economic copper-gold is hosted by vuggy quartz altered lapilli tuff and tuff breccia. The early hydrothermal alteration stage involved deposition of epithermal banded quartz and chalcedonic silica in localised environments. This alteration stage was locally superimposed by a hydrothermal breccia event. Following the breccia event, magmatically-derived volatiles were channelled through a NW striking dilational fault zone and generated the high sulphidation alteration. The high sulphidation alteration is zoned from a vuggy quartz core with local massive replacement silica through a broad pyritic quartz-alunite halo and finally to a thin illite-smectite zone. This is surrounded by regional chlorite-epidote-smectite alteration. A gangue mineral phase consisting of quartz, alunite and baryte overprinted the zoned high sulphidation alteration and preceded the main copper-gold-arsenic mineralisation. Early sulphide deposition is characterised by marcasite, arsenical pyrite and melnicovenite. Main-stage copper-gold mineralisation involved sequential deposition of hypogene bladed covellite+chalcocite, enargite-luzonite and luzonite+stibioluzonite respectively. The copper sulphides are zoned from bladed covellite-chalcocite in the north (cross-sections 5000 - 5600 N) through enargite-luzonite (cross-sections 4700 - 5000 N) and to luzonite????stibioluzonite in the south (cross-sections 4400 - 4700 N). A late phase of minor acicular covellite and enargite+luzonite overprinted the zoned copper sulphides and associated gold mineralisation. Gold mineralisation commenced at the transition from enargite to luzonite, and continued through the deposition of luzonite-stibioluzonite in both stages. Most gold was deposited during the main-stage mineralisation. Yellow native sulphur was deposited in the remaining vugs and defines the waning stage of the hydrothermal system. Post-mineral dioritic intrusives and feldspar porphyries intruded the volcano-siliciclastic sequence. Finally, supergene chemical processes with associated erosion and uplift generated a 40 - 50 m thick oxide-hosted gold cap. The oxide gold cap is underlain by a 35 - 45 m thick blanket of supergene chalcocite+covellite mineralisation which overlies and occurs throughout the main hypogene copper-gold zone. Supergene gold is related to the distribution of primary gold-bearing sulphides. Therefore, remobilisation and redeposition of gold are considered to be insignificant and very localised.

Jan 1, 1999

By A. Zarei-Hanzaki, S. M. Fatemi-Varzaneh, M. Haghshenas

The microstructure in modified semi-solid ALTHIX (A356) alloy consists of aAl phase with Al/Si eutectic structure. Silicon phase in eutectic structure is coral like with fine fibers. The lack of good ductility in this alloy is related to the presence of silicon fibers. Accordingly many investigations have been recently conducted to modify the Si morphology through Thermomechanical processing on this alloy. In the present work an ALTHIX (A356) alloy was deformed at 450°C, 500°C and 540°C through different strain rates. Consequently the silicon fibers were broken into small particles. The results indicated that the Si particles may coarsen according to Ostwald ripening mechanism at 540°C deformed by rate of0.0005 sec-1 & 0.0001 sec-1-

Jan 1, 2006

By M. Andrews, B. J. Göhre, G. Strong, C. Terblanche

Mechanized mining can be experienced as a symphony by substituting the instruments for the different machines that each perform their own function and thus have different sounds. The drill-rig is the soloist around which all the other machines must play their part in harmony. Each machine can function on its own, but productivity is achieved only when all of the machines function in a holistic manner, as the different sounds of instruments form a symphony when playing together. To produce a symphony is to have the ability to put together all the pieces. It is the capacity to synthesize rather than to analyse. Today?s managers have to apply this harmonic way of thinking to make the system of mechanized mining work. In other words each of these people must have the ability of a conductor, whose job involves corralling a diverse group of notes, instruments and performers, and producing a unified and pleasing sound. At Modikwa Mine the introduction of the MAPS (Mine Activity Performance System) has allowed management to obtain a clear view of all the activities associated with the equipment. Through synthesis the issues that hampered productivity were identified and addressed to improve production and reduce costs.

Jan 1, 2006

By Donald E. Steif

The Tower Mill is a vertical stirred mill using steel balls or pebble grinding media. This device is designed for fine grinding at significant power savings when compared to conventional tumbling mills. This paper describes the machine, its operation, application, and performance for wet grinding.

Jan 1, 1984

Sifto Salt Div. of Domtar Chemicals Ltd. has developed a new method for installing roof bolts in the high backs of its 1-million-tpy rock-salt mine at Goderich, Ontario, on the east shore of Lake Huron. The method teams a telescoping- boom hydraulic crane with a specially developed combination auger-drill and bolt-tightening ma- chine. One man, controlling all operations from a basket supported at the end of the crane's telescoping boom, installs an average of 100 5-ft roof bolts per shift, at heights to 45 ft. The mine has very long backs that are not as stable as might be expected. The result has been that roof scaling has occupied an unusually high percentage of the underground work force. About six years ago, company officials decided to go to 100% roof bolting of all backs as a safety measure. The present roof-bolting equipment is the result of a development program instituted at that time to find a faster and more economical method for doing the job.

Jan 9, 1967

By Shaohua Ju, Feng Jiang, Jian Jian, Hongying Xia, Jinhui Peng, Libo Zhang

Microfluidic solvent extraction of zinc from sulfate solution was studied using di-2-ethyl hexyl phosphoric acid, D2EHPA, in sulfonated kerosene as diluent. The influence of different parameters on the extraction of zinc, such as flow rate, temperature, flow rate ratio, extraction concentration, and saponification ratio of extractant were investigated and the conventional and micro fluidic extraction were compared. Under the optimized conditions, micro fluidic extraction efficiency of zinc is up to 97.1%. It is better than that conventional extraction. Therefore, microfluidic solvent extraction can achieve high efficiency and low consumption of extraction process.

Mar 1, 2018

By Duan Xin-hui, Wang Xin, Peng Jin-hui, C. Srinivasakannan, Zhang Li-bo

The work attempts to optimize the process of preparation of modified semi-coke from semi-coke using phosphoric acid (H3P04) as the activating agent using the response surface methodology (RSM). The influences of three major dependent variables, the impregnation ratio, activation time, and activation temperature were assessed on the independent variables yield and the iodine number. The empirical relationship between the dependent and the independent variables were established using the quadratic response surface models, which were utilized to optimize the process parameters. The significance of each of the parameters and interaction among the parameters on the independent variable was assessed based on analysis of variance (ANOVA). The process variables were varied within the range of impregnation ratio (IR) from 1.5 to 4, activation time from 30 to 90 min and activation temperature from 550 'C to 650 'C. The optimized process conditions were estimated to be an IR of 2.29, activation time of 32 min, and an activation temperature of 605°C respectively using the process optimization tool. The BET surface area of modified semi-coke of the optimized sample was estimated to be 915m2/g, with the pore volume of0.71cm3/g, with an average pore diameter of 3.09 nm, with micropore volume fraction being 52.36%. The scanning electron microscope (SEM) images were utilized to visualize the surface pore structure.

Jan 1, 2013

By Klaus-Markus Peters, James G. Hemrick, John Damiano

"Work was performed by Oak Ridge National Laboratory (ORNL), in collaboration with industrial refractory manufacturers, refractory users, and academic institutions, to employ novel refractory systems and techniques to reduce energy consumption of molten material processing vessels found in industries such as aluminum, glass and pulp and paper. The energy savings strategies discussed are achieved through reduction of chemical reactions, elimination of mechanical degradation caused by the service environment, reduction of temperature limitations of materials, and elimination of costly installation and repair needs. Key results of several case studies resulting from US Department of Energy (DOE) funded research programs are discussed with emphasis on applicability of these results to high temperature processing industries.IntroductionRefractory materials are limited in their application by many factors including chemical reactions between the service environment and the refractory material, mechanical degradation of the refractory material by the service environment, temperature limitations on the use of a particular refractory material, and the inability to install or repair the refractory material in a cost effective manner or while the vessel is in service. All of these limitations reduce the energy efficiency of the process as degraded refractory materials lead to loss of process heat (reduced insulation by refractories) and the need for maintenance through repair or replacement of refractory linings.This situation is conceptualized in Figure 1 which shows that when the thickness of the refractory wall is reduced by chemical or mechanical degradation, the heat losses through the wall increase exponentially. The subsequent maintenance to repair such conditions often requires cooling of the furnace or refractory lined vessel which entails loss of energy due to cooling and consumption of energy due to reheating. Additionally, production time and capability are sacrificed.Additionally, in most applications where refractories are used (metal melting furnaces, glass furnaces, steel making furnaces, gasifiers, etc.) wear of the refractory lining is not uniform. Very often, specific areas will wear (become thinner) more rapidly due to exposure to more corrosive or erosive conditions. This concept is illustrated in Figure 2, through the example of excessive metal line corrosion."

Jan 1, 2009

By XUEWEN WANG, Xingming Wang, Xuehui Liu, Mingyu Wang

The Panzhihua titanium concentrate contains high contents impurity of Mg and Al, and it is difficult to prepare high grade titanium slag. To solve this problem, a sodium salt roasting-acid leaching process was proposed for removing the impurities in titanium concentrate. Na2CO3 and titanium concentrate were mixed with the proportion of 1:4, and then the mixture was roasted at 700 for 2h. After roasting, the calcine was leached with HCl solution. The experimental results showed that the removal rate of silicon and aluminum can reach more than 85% and 80%, respectively, at leaching temperature of 70 , leaching time of 4h, HCl addition of 5ml and liquid-solid ratio of 4:1.

Jan 1, 2016

By D. Saramak, T. Gawenda, Z. Naziemiec, A. Saramak

"Crushing and grinding operations are burdensome to the environment due to generating large amounts of dust, noise and waste during course of comminution operations. An indirect negative contribution of industrial crushing processes is an increase of carbon dioxide emissions, which is a byproduct in energy production processes. On the other hand comminution processes in ore enrichment technology are essential due to liberation the useful minerals from the gangue, and producing the demanded particle size fractions of products. The article concerns investigation over negative influence of comminution devices on environment in terms of dust and noise emissions. Several various crushing devices were under investigations, both in laboratory and in industrial scale.The obtained results were analyzed in terms throughput and energy consumption achieved in various crushing devices. The test results allow to conclude that an intensity of dust generation for individual types of crushing devices is varied. An additional aim of this article is to link the aspect of mineral processing with its environmental impact and hence an influence of raw materials beneficiation industry on the quality of life of residents in immediate and close vicinity.INTRODUCTIONMineral raw materials beneficiation processes are an integral part of multi-stage processing of coal, iron ore and non-ferrous metals, production of aggregates, cement, or precious metals and stones. One of the common features of all beneficiation operations is their high energy consumption, which is mainly connected with various operations of feed particle size reduction. Comminution processes in ore enrichment technology are essential to expose and liberate the useful minerals from the gangue, while in aggregate production processes – to obtain the demanded particle size fractions of products. Crushing operations are characterized by a high degree of negative impact to the environment and humans, mainly due to:• High electricity consumption, which indirectly contributes to the increased emissions of carbon dioxide into the atmosphere, since CO2 is often one of the byproducts of energy production;• Relatively rapid wear of device working parts, what forces a production of spare parts and involvement of steel industry;• Intense dust pollution generated during crushing and grinding processes. This is one of the factors affecting the air quality and the consequent deterioration of the living conditions of inhabitants near mines and processing plants; and • Excessive noise emissions."

Jan 1, 2016

By Claudio Toro, Alex Moyano, Rodrigo Díaz, Hugo Jara, Carlos Caballero, Pedro Morales, Leandro Guzmán

"During 2007, Codelco-Chile carried out industrial tests to validate the Continuous Converting Process in the Teniente Converter of the Codelco Norte smelter.For planning and starting up the tests, a predictive, analytical and dynamic model was developed to support operational decisions. The dynamic model was developed using the METSIM® platform and dynamic data exchange (DDE) to operate smoothly with MS Excel®. The main feature of this real-time model was the on/off-line ability to work and gather data from either the smelter’s PI system® or database, and simulate the operation with or without scheduled events and controls.The main model development aspects, which include thermodynamics, metallurgical and kinetic considerations, slag-type and on-line mass and heat balances of the process, as well as the successful validation of the model, are presented and discussed in the present paper."

Jan 1, 2009

By John Cory, Ran Tamir

Blasting data analytics are being increasing used to increase mining productivity, reduce mining costs, maximize high margin aggregate products, and to reduce fines. Three examples will be illustrated using simple models to maximize the percentage of blasted rock within established dimensions and reduce fines-one from video fragmentation distribution information, the second from sieved crusher fragmentation data, and the third from plant production data. In addition, the use of sieved crusher results to determine blasting related fines and the use of mine productivity data to maximize aggregate sizes when pattern (burden and spacing) areas are changed will be illustrated

Jan 1, 2012

A good deal of experimental work has been done from time to time on the application of compressed air to the elevation of wet pulp. On account of the flat nature of most of our mill sites elevation of the pulp has to be provided for, and the various methods in vogue show considerable loss of time, in the replaceing of wearing parts. During the last two years the writer has carried out a great many experiments with a view of devising an elevator that will give continuous work with a minimum of wear.The results do not show a high efficiency for the power employed, but the lift is continuous in operation, very cheaply installed, and possesses no wearing parts. The lift was tried working in a bore hole of 8 in. diameter, but in many cases it is more convenient to sink a small well for the purpose. The result to date showed that the most efficiency was obtained when the depth of the wellwas not less than the height of the lift required. The pressure of air required in pounds per square inch was (approximately) half the number of feet to be lifted.In the majority of cases the lift required varied between 20 ft. and 50 ft. and the air pressure required between 10 lbs. and 25 lhs. per square inch. In most existing installations the air compressors in use were delivering air to the receivers at about four times that pressure, and when air so compressed was expanded to perform its work at a reduced pressure, it was apparent that the power exerted in origInally compressing the air above the working pressure required at the lift was absolutely lost.

Jan 1, 1901

By Edmund J. Cardoza

The paper describes the design, construction and quality control aspects of the installation of a cement-bentonite (CB) cut off wall to impede seepage through a flood control dike. Special emphasis is placed upon the development of a proper specification, distinguishing the CB method from the Soil-Bentonite technique. The importance of the pre-construction laboratory testing program and field quality control procedures is emphasized by the fact that the in-place properties and characteristics of the CB cut off may not be known until after a majority of the work is complete. Sections are included which describe the construction method, the specialty equipment and personnel requirements and the quality control/quality assurance aspects of the project.

Jan 1, 1992

By Stephan Buys, Dan Curry, Chris Rule

"The use of fine grinding (FG) in mineral processing is well established. The application of FG in the South African platinum industry is more recent and it’s use in the recovery of PGM’s from dormant tailings dams is unique. Anglo Platinum uses IsaMill FG technology at their Western Limb Tailings Retreatment project (WLTR) near Rustenburg in the North West Province of South Africa.In December 2003, Anglo Platinum commissioned the first purpose built tailings re-treatment facility for PGM recovery in South Africa. The concentrator re-treats Merensky ore tailings from concentrators that operated early last century. The WLTR facility takes advantage of modern technology, such as FG, to economically recover PGM’s from material historically considered as waste. The WLTR concentrator has a capacity of 4.8 Mtpa, and has been designed to easily expand to 10.8 Mtpa. The flow sheet includes recovery of tailings by high pressure water monitoring, ball milling, rougher flotation, rougher concentrate regrinding and cleaner /recleaner flotation.The rougher concentrate is reground in an IsaMill, which is a stirred mill that operates with inert silica sand grinding media. For this project, Anglo Platinum required a stirred mill of a unit size not previously available. Xstrata Technology and Anglo Platinum collaboratively developed the largest wet, fine grinding mill available; the M10,000, 2.6 MW IsaMill.The use of IsaMill technology was enabling for the WLTR project, as it allowed smeltable concentrate grades to be produced from the oxidised, slow floating tailings. The economics and practicality of fine grinding has fundamentally changed with the M10,000 IsaMill. Flotation is transformed by high intensity attritioning in the inert media environment, and the narrow size distribution of product in open circuit configuration. The use of conventional steel media grinding to improve fine particle flotation is limited due to the oxidation of liberated mineral surfaces inherent in these environments."

Jan 1, 2005

By A. V. Nguye, P. A. Harvey

Previous studies have reported that inorganic electrolytes can enhance floatability of coal. The research has shown that the enhancement, if any, is highly dependent on changes in solution pH, type of electrolyte, and electrolyte concentration. The reasons for this are still not clear. In this study the floatability of coal particles in mono and divalent salt solutions was investigated. The zeta potential and hydrophobicity of the coal was measured experimentally, and a modified Hallimond tube was used to determine the floatability of coal particles by single bubbles, where the collision efficiency was equal to unity. The experimental information was used in conjunction with the Hogg-Healy-Fuerstenau equation to quantify the electrical double layer interaction. It was found that for low electrolyte concentration (less than 0.1 M) solutions the flotation recovery of coal particles was less than that for distilled water, and decreased with increase in concentration. Conversely, at electrolyte concentrations above 0.1 M, flotation recovery increased with increasing concentration. Both of these results are consistent with previous observations, but are inconsistent with expectations when considering the possible influence of electrical double layer interaction. A possible mechanism, based on the existence of the pre-existing submicron-sized gas bubbles, known as bubstons (i.e. bubbles stabilized by ions), present in water in close proximity to the hydrophobic coal surfaces is discussed in line with the early observation of flotation improvements by microbubbles “nucleating” on hydrophobic surfaces. In particular, the dependence of the bubble-particle attachment efficiency on electrolyte concentrations supports hypothesis on the salt-dependent and ion-specific existence of bubstons. However, a theoretical explanation of the transition salt concentration (at about 0.1M) is deficient at present. The existence of these submicrobubbles in close proximity to hydrophobic surfaces is not trivial. They can (as can individual gas molecules or other solutes) mediate and extend the range and magnitude of the attraction between hydrophobic macroscopic surfaces. These bubbstons may explain the curious phenomena of the socalled long-ranged hydrophobic attraction measured with the Surface Force Apparatus and Atomic Force Microscopy, and the slippage at hydrophobic surfaces. Finally, the coalescence of bubbstons affects the rupture of liquid films at a very large thickness (over 100 nm), observed, but unexpected, by flotation chemists.

Jan 1, 2003

By Michel Mellinger

This paper presents preliminary results of a project aimed at obtaining a better understanding of the genesis of gold mineralization in northern Saskatchewan using lithogeochemistry. The properties sampled were: Weedy Lake (B Zone), Waddy Lake (Komis Zone) and Wedge Lake (Twin Zone) in the La Range belt, and the Rio mine in the Flin Flon area. Although the three vein-type deposits rudied here (Weedy Lake. Waddy Lake, Rio deposit) occur in different geological situation . a common gold deposition mechanism appears to have been active at all three location . Hydrothermal fluids carrying sulphur in solution in exces of gold thio-complexes moved through fractured host-rocks until they reached a site where pyrite precipitation wa triggered. As pyrite precipitated, the a/ aAu activity ratio of the fluid decreased. until a critical thre hold was reached and gold thio-complexe were de tabilized . resulting in the co-precipitation of gold and pyrite. The conditions triggering the precipitation of pyrite appear to have been: the abundance of iron in host-rock ~ilicates at Waddy Lake. and temperature decrease upon the reaching of structural trap~ at both Weedy Lake and the Rio deposit. with additional involvement of carbonatizationrelated reactions between fluid and host-rocks for the latter. In addition to pyrite precipitation , potassic alteration of the mafic metavolcanics is observed at Waddy Lake. while at the Rio deposit, the extensive carbonatization of the host-rocks i coupled with the deposition of chlorite that may have been remobilized from the altered mafic host rocks. In both the B Zone at Weedy Lake and the Komis Zone at Waddy Lake, a di tinct vanadium signature give some clue about the direction in which the hydrothermal fluids have moved . and the interpretation made is con istent with the geological ituation in either case. As for the Wedge Lake deposits, the distinct base metals-precious metals a sociation within a sulphide-facies iron formation confirm the volcanic exhalative origin of this gold mineralization .

Jan 1, 1986