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By Lifeng Yang, Xiang Zhang, Liang Yuan, Yonghui Wang, Bing Hou, Mian Chen, Rixing Zhang

Large-scale hydraulic fracturing technique has been widely applied to the development of shale gas reservoirs, where the interaction between natural fractures and critical fracture zones has substantial impact on the propagation of hydraulic fractures. Therefore, it is of significant importance to understand and experimentally verify such mechanism. To reach this end, tri-axial fracturing tests were implemented on 400mm×400mm×400mm block samples collected from Longmaxi shale outcrops. The interplay between hydraulic and natural fractures was investigated during the tests, factoring in the role of pump rate in affecting the created fracture network. Based on the experimental results, the critical fracture zone, defined as the weak formation zone nearby the wellbore created by staged pressure implementation that is observed rapid fracture propagation upon next stage of pressure increase, was thoroughly investigated. The analysis illustrates that given the high brittleness of the shale formation, abundant critical fracture zones are generated around natural fractures with pressure building up at a relatively low pump rate. As the pump rate increases, hydraulic fractures initiate and come into play with critical fracture zones, implying emergence of a large number of micro-cracks. A changing pump rate modifies the way of interaction between hydraulic and natural fractures and the subsequent formation of fracture network. Long term fracturing fluid injection with relatively low pump rate below the activation of critical zones is suggested. Also proposed is appropriate timing when applying a specific pump rate that will contribute to the improvement of hydraulic fracture propagation.

Jan 1, 2015

By Alexander Smith

Surf Point and Edye Pass mines are on the northwestern part of Porcher island; 25 miles southwest of Prince Rupert. During the 1930's they produced about $750; 000 in gold from ore averaging better than one-half ounce a ton. The deposits are quartz veins; containing auriferous pyrite; concentrates average about 8 oz. gold a ton. The veins occur in a quartz diorite; stock. Their distribution shows an apparent control by primary flow structures; for the principal deposits lie on the axis of an arch of flow layers. The technique used in mapping the structures in the intrusive is that known as the Cloos method and described by Balk.

Jan 1, 1954

By A. A. Brant

BECAUSE of its simplicity, the dip needle is widely used for locating magnetic rock formations in drift-covered areas. Although it responds only to strong magnetic disturbances, it has the advantage that surveys with it can be carried out rapidly, at relatively low cost, by untrained operators. More accurate surveys can be made with a much more sensitive instrument known as the magnetometer, but this must be operated by a specialist and the resulting survey costs are much higher. Mining men use the dip needle for the location of magnetic ores or mineral deposits associated with magnetic rocks. In certain districts, a survey with the dip needle may aid in solving geological structure. In the Little Long Lac and Crow River gold camps of Ontario, it has recently been used for these purposes. In interpreting the results of a dip needle survey, an understanding of the chief magnetic and mechanical factors determining the dip recorded by the needle is definitely necessary. For example, many observers locate a magnetic body by the highest dip values, apparently unaware that these frequently may not lie directly above the body. It should also be realized that a careful dip needle survey may yield information regarding the dip, breadth, and perhaps depth, of the magnetic body. Moreover, the observer should know when numerous closely-spaced dip readings are necessary, and when the dip may be measured at more widely separated intervals. The purpose of the following article is primarily to describe the factors affecting the registration of the dip needle, with a view to aiding investigators in a more accurate and complete interpretation of their results. To explain the cause of magnetic disturbances (anomalies) and the action of the dip needle, a knowledge of certain fundamental magnetic terms is necessary.

Jan 1, 1938

By T. Bhambhani, Mukund Vasudevan, Partha Patra, D. R. Nagaraj, P. Somasundaram

Selective Ni separation from ultramafic ores rich in serpentines has been a huge challenge in the mineral processing industry, and therefore highly inefficient. Analysis of the root causes of the challenges and consequent development of robust processing solutions were the main goals of the Cytec-Columbia. University-Vale Joint Development Program. In this context, the subject of this paper is limited to one of the key findings of this research program which is the influence of fibrous serpentines on grade-recovery characteristics. Specifically, the poor flotation behavior is characterized by an atypical reverse C-shaped grade-recovery curve.

Jan 1, 2011

By W. S. Szolga, M. Moser, M. D. Soderstrom, L. Cohen

"CYANEX® 272 is a phosphinic acid-based solvent extraction reagent used commercially since the early 80’s to recover and purify cobalt from sulfate solutions. Historically, the design of CYANEX 272 circuits has involved the selection of an optimal pH profile during pilot-scale testing using mixbox pH control. The desired pH profile is required to be carefully controlled in the same manner during commercial operation. To assist operators in the design and optimization of their circuits, Solvay developed CYANEX 272-specific solvent extraction modeling software, which has enabled determination of the ideal pH profile and staging configuration. Solvay’s recent advances in modeling capabilities have allowed the simulation of circuits without direct mixbox pH control. Modeling has indicated that circuits operated without direct pH control can achieve the desired metal separation while simplifying the commercial operation significantly. This paper reviews a number of potential circuit configurations for the use of CYANEX 272 and demonstrates the separations achievable under the right design and operational conditions, some of which have historically been considered too difficult.INTRODUCTION CYANEX® 272 is a phosphinic-acid based reagent designed specifically for the separation of cobalt from nickel by solvent extraction from weakly acidic sulfate solutions (Rickelton, Robertson, & Burley, 1982; Rickelton, Flett, & West, 1984; Rickelton & Nucciarone, 1997). Following commercial introduction in the 1980’s, CYANEX 272 has been used in a number of hydrometallurgical flowsheets for cobalt purification and/or recovery. CYANEX 272 metal extraction occurs by means of a cation exchange mechanism. Extraction of a divalent metal ion M2+ is represented by the following equation where RH represents the CYANEX 272 ligand and MR2 represents the ligand-metal complex."

Jan 1, 2017

By N. Ogbonna, D. G. Dixon

Although heap bioleaching has been recognized as an economic alternative for treating low grade mineral ores, the underlying physical, chemical and biological processes involved are complex. A detailed investigation into the dynamics of heap bioleaching processes has provided much insight into the underlying complexities, and has led to the development of a sophisticated modelling tool - HeapSim. This tool can be of great help in the design and operation of heap bioleaching processes. In this paper, the mathematical model implemented in HeapSim is examined. The model takes into account mineral kinetics, particle level effects, bacterial growth, oxidation and adsorption, gas absorption, pore diffusion, bulk advection, gas balance and heat conservation. Three case studies where the model has been applied are briefly discussed. Computational Analysis in Hydrometallurgy 35th Annual Hydrometallurgy Meeting held in conjunction with the 44th Annual Conference of Metallurgists of CIM Calgary, Alberta, Canada Edited by

Jan 1, 2005

By P. T. Bloomer

Introduction Mining of the orebody of the Sullivan mine, which is owned and operated by the Consolidated Mining & Smelting Company of Canada, Limited, has reached a point where pillar extraction is rapidly becoming a major part of the operation. Very few of the larger pillars have been completely extracted; consequently, this paper contains much that is theory and expectation. Due to early mining methods and the physical characteristics of the Sullivan deposit, similar conditions may not exist in other older mines facing the problems of pillar extraction, but it is thought that the methods employed and those contemplated may be of general interest. History The Sullivan orebody, which is at Kimberley in the Fort Steele mining division of the East Kootenay district of British Columbia, was discovered in May, 1892, by Messrs. Sullivan, Smith, Cleaver, and Burchett. After passing through the hands of several owners the property was optioned in 1909, and purchased in 1910, by The Consolidated Mining and Smelting Company of Canada, Limited. Early mining was highly selective, the objective being a clean, high-grade silver-lead ore. By 1923 the difficulties of milling the very complex ore had been overcome and the first unit of a concentrator was completed with a capacity of 2,500 tons daily. Capacity was increased by stages to the present rate of 8,500 tons per day. Concentrates are shipped over the Canadian Pacific railway ? to the Company smelter at Tadanac, British Columbia, for final treatment. Approximately 45,000,000 tons of ore has been mined to date.

Jan 1, 1948

By L. Price, R. Hortie

Movement of ore and waste from the Hilton Mines pit is accomplished by truck haulage. With the aim of reducing costs, a study of truck fleet replacement was initiated. The study included on-site short-term tests and longer-term rental purchase agreements for haulage trucks. The operation and maintenance characteristics of different trucks, along with projected haulage conditions, were used to prepare cash flows, from which the most advantageous trucks were selected. The results of the study and implementation of the recommendations gave a cost saving greater than had been estimated. The study also indicated areas where improvements could be made, and resulted in much more attention being paid to road conditions, the training of operators and mechanics, and the development of a practical preventative maintenance scheme.

Jan 1, 1971

By J. Tuzo Wilson

"AT ANY TIME, it is a pleasure to me to be invited to address The Canadian Institute of Mining and Metallurgy because it represents an industry and men with whom I have been happily, if peripherally, associated continuously for forty years. This year, it is a particular pleasure because I believe that an important subject has arisen which I propose to discuss.This is a major discovery in the earth sciences, first fully revealed this winter, but already widely accepted. The basis of this revolution, for it is no less, is that measurements of three different features of the earth all change in exactly the same ratios. These ratios are the same in all parts of the world. The results from one set are thus being used to make precise numerical predictions about all the sets in all parts of the world. No such accurate correlations and predictions have ever been found before in geology or areal geophysics. The whole subject of earth science has thereby been radically altered.The first of these measurements is that of the direction of magnetic polarity in lava flows. When piles of young lavas are examined with the aid of a pocket compass, it is noted that some flows are magnetized in the direction of the earth's field and some in the reverse direction (Figure 1). By accurately dating enough flows, a time scale of the dates of reversals has been established. During the past four million years, nine reversals have occurred synchronously all over the world (Cox, Darymple and Doell, 1967, McDougall and Chamalaun, 1966) (Figure 2). It appears that the scale can be extended back to Precambrian times (McMahon and Strangway, 1967). This time scale is the first of the 'three identical ratios."

Jan 1, 1968

By David R. Lentz

Abstract -At True Hill in southwestern New Brunswick, low-grade porphyry-style Bi-Sn-Mo greisen mineralization is associated with the cupola of an epizonal granite porphyry (granite) that also exhibits three episodes of brecciation. The first episode of brecciation is an in situ, 8 m to 10 m wide transitional zone of net-veined to coarse-grained "blocky" endogranitic mesobreccia that is chloritized and greisenized and hosts weak disseminated mineralization. ln a zone doser to the host rock­ granite contact, angular fine- to coarse-grained endogranitic mesobreccia with greisenized matrix is superimposed on the earlier transitional breccia. The latest episode is fault-controlled and consists of quartz- and chalcedony-hosted subangular to rounded fine-grained "pebble" mesobreccias that crosscut and brecciate the other breccia types, as well as the adjacent altered metasedimentary country rocks. The first two episodes of brecciation are magrnatic-hydrothermal in origin related to hydrofracturing of the granite carapace and are accompanied by greisenization and mineralization, whereas the post-mineralization, silica-hosted, "pebble" mesobreccias related to hydromagrnatic, low­ temperature fluid circulation and/or boiling along faults near the contact. These magmatic­ hydrothermal and hydromagmatic mesobreccias are similar to those associated with W-Mo-Bi porphyry-greisen mineralization at the Mount Pleasant deposit.

Jan 1, 1994

By John B. Hodgeson

AMMONIA is an essential constituent in the production of the ammonium-sulphate and ammonium-phosohate soil fertilizers manufactured by the Consolidated Mining and Smelting Company of Canada, Limited. The fertilizer plant, built in 1930 at Warfield, near Trail, provides a means of utilizing the large amount of sulphuric acid produced from the sulphur dioxide which is removed from the smelter smoke. The plant has an avail-able source of cheap power which makes the production of fertilizer economically possible. The fundamental operations involved in the production of ammonia at the Warfield plant are, first, the manufacture of hydrogen by the electrolytic dissociation of water; next, the recovery of nitrogen by the fractional distillation of liquid air; and finally, the combination of hydrogen and nitrogen in proper proportions and under suitable conditions to form ammonia.

Jan 1, 1938

By J. Ouellet

The design of hydrostatic liner for a deep potash mine shaft in Saskatchewan poses tremendous technological challenges. Technology has evolved to a point where one could consider a new innovative approach to hydrostatic liner design. But there is still a place for conventional technologies such as cast iron tubbings. As will be discussed in this paper, improvement to manufacturing process, installation procedures and even new materials can bring this technology to an excellent level of performance. With the spur of new projects in the potash industry of Saskatchewan, the authors worked in various shaft liner designs from the conceptual stage through to the construction phase. They were either directly leading the design work on some of these projects or acting as an external reviewer on others. Most of these shaft liner designs involved cast iron tubbing technology and ground freezing. The major challenge in sinking potash shafts in Saskatchewan is to go through a water-bearing ground formation under high pressure, known as the Blairmore or Manville fm. The only proven stabilizing technology for these formations is ground freezing. For a potash shaft, dry shaft conditions are highly desired, so a fully waterproof hydrostatic liner is required. All the existing potash mine shafts in Saskatchewan, except for two with composite steelconcrete lining, used the cast iron tubbing technology. Two new shaft tubbing liners have been constructed recently, one in the Athabasca Basin and one for a potash mine in Saskatchewan. When the authors began working on these new projects, what became quickly evident is that the technological knowhow for designing and constructing tubbing liners was no longer available within Canada and that the past construction methods used to sink tubbing lined shafts was obsolete. The tubbing liner for the shafts sunk in the sixties were designed either by German or British companies. In both of these countries only few tubbing lined shafts were sunk in last 40 years and the technology used in the sixties was not improved. There are only few countries where tubbing is routinely produced and installed: China, Russia, Ukraine and Poland. Out of these countries Poland is the one where this technology is the most advanced. The authors, working in close collaboration with engineers from Poland, attempted to rebuild this knowledge for the mining industry in Canada. This process involved thorough analysis of old technical reports, literature review and study of current polish design and construction practices as well as site visits of existing shafts. Through actual construction experience, some lessons were learned as well as ideas for improvements. In this paper, the authors will present a succinct review of design and procurement process. But, the practical aspects of the construction and installation methodology will be treated with more emphasis, more specifically the practice leading to good liner performance. Some of the poorly understood technical aspects of tubbing installation will be discussed more thoroughly and some currently accepted myths dispelled.

Aug 1, 2013

By A. Ojaghi, A. R. Mohammadi

"The Marvast monazite deposit is located 35 kilometres south - southwest of Marvast in Yazd province of Iran. A representative sample weighing approximately 10 tons was prepared to study the amenability of the ore to physical beneficiation. The size fraction of +1000 µm was removed due to low monazite content and the –1000 µm size fraction was concentrated by the gravity-classification-magnetic methods. According to the results of sample characterization, the representative sample contains 220 ppm REO that is contained in monazite. It was concentrated to 41.5% REO by the above mentioned methods. The recovery of REO in the monazite concentrate was 41.5%.INTRODUCTIONRare earth elements are critical metals in many countries (Gupta, 2005; UK Geological Survey, 2011). Increasing application of these metals in hi-tech industries and price fluctuation caused by Chinese production policy has led other countries to focus on their local resources (UK Geological Survey, 2011). In this case, Iran is not an exception.REE mineralization in Iran is mainly located in the central zone. Regarding the exploration data, these deposits are divided into two categories. The first group is iron ore deposits in which the REE are carried by phosphate minerals. The other group is placer deposits where monazite is the major mineral of the deposit. The Marvast placer deposit is one of these types of deposit (Daliran, 1990; Mokhtari, 2008; Torab, &Lehmann, 2007; Alipour, 2014)."

Jan 1, 2016

By J. Lee, K. B. Min, J. Rutqvist

Shear slip of fractures in fractured rock masses is a critical issue for many geological engineering applications, such as the design of underground nuclear waste repositories, enhanced geothermal systems (EGS), and geosequestration of CO2. This paper presents new development of the TOUGH-UDEC simulator for analysis of coupled thermal-hydraulic-mechanical (THM) processes in fractured porous media. As an alternative to developing a single coupled THM code in discontinuum, two existing wellestablished codes, namely TOUGH2 and UDEC, are coupled to cover coupled THM analysis of multiphase fluid flow, heat transfer, and deformation in fractured porous media. TOUGH2 is widely used for modeling heat transfer and multiphase, multicomponent fluid flow, and UDEC is a well-known discrete element code for rock mechanics, which have been verified and used by many groups all over the world. Although a sequential coupling of two codes is less efficient than having a single code in principal, a big advantage with coupling of TOUGH2 and UDEC is that both codes are well tested and widely applied in their respective fields. When linking two codes, the coupled equations cannot be solved simultaneously; they should be solved sequentially, with coupling parameters passed to each equation at specific intervals. After solving thermal-hydraulic equations through the TOUGH2 model, pressure (P) and temperature (T) information is delivered to UDEC model. Pressure information is directly stored at the center of each UDEC zone and domain, however, temperature information is interpolated from zone-centers to the corners nodes. After solving the mechanical equation through the UDEC model—considering new pressure and temperature—calculated fracture apertures are converted to equivalent permeability and porosity for TOUGH2 flow analysis. The solution was calculated by iteratively following an explicit sequence for numerical efficiency. Verification examples are presented to demonstrate the capabilities of the coupled TOUGH-UDEC simulator.

Jan 1, 2015

By G. Chi, W. J. Davis, S. Watters, D. Hoy, S. Castonguay

"The Poplar Mountain gold occurrence in western New Brunswick is hosted in the Poplar Mountain volcanic complex (PMVC), which is located along the southern segment of the regional Woodstock fault zone. The PMVC consists of three principal units including, in ascending order, a porphyritic felsic volcanic unit, a volcaniclastic unit, and a mafic volcanic unit. U-Pb dating of zircon indicates that the age of the volcanic rocks is younger than 459 ± 3 Ma, and 40Ar/39Ar dating of mineralization-associated sericite indicates that the age of mineralization is 411 ± 3.7 Ma. Gold-mineralized zones occur in all the lithologic units but mainly in the porphyritic felsic volcanic unit. Gold zones are not controlled by individual faults but are characterized by high-density brittle fracturing, thin carbonate-quartz veining, and intensive ankerite-sericite alteration, superimposed on an earlier chlorite-calcite- quartz alteration. Gold is associated with arsenopyrite, which mostly occurs as disseminations in the host rocks, and to a lesser extent with quartz-carbonate-sericite veins and quartz-cemented breccias.Geochemical data indicate that mineralization-associated alteration is characterized by enrichment of K, Rb, Cs, Ca, Sr, Ba, As, Sb, W, C, and S. Fluid inclusion data indicate that the mineralizing fluids are composed of H2O, salts, and CO2 with variable amounts of N2 and CH4; salinities range from 2.3 to 10.6 eq. wt.% NaCl, but mainly from 2.3 to 5.6 eq. wt.% NaCl, and homogenization temperatures lie mainly between 220° and 270°C. Fluid pressures at the site of mineralization are estimated to have been 770 to 1200 bars, corresponding to a depth of 2.9 to 4.6 km at lithostatic pressure. The d18OSMOW and d13CPDB values of mineralization-related ankerite range from +14.5‰ to +16.5‰, and -6.8‰ to -8.3‰, respectively. The d18O values of the ore-forming fluids are estimated to be 6.4‰ to 8.3‰ at a temperature of 250°C. These carbon and oxygen isotope data fall in the field of magmatic fluids and in part the field of metamorphic fluids.Considering the geological setting of the region, abundant granitic intrusions, the similarity between the age of mineralization (411 ± 3.7 Ma) and the nearby Pokiok batholith (402-415 Ma), and the enrichment of granophile elements in mineralization-related alteration, the ore-forming fluids were probably derived from a granitic intrusion underneath the PMVC. These fluids were focused along structures related to the Woodstock fault. The Poplar Mountain gold occurrence might be compared to some granitic intrusion-related gold systems based on the geochemical data presented herein. L’indice aurifère de Poplar Mountain dans l’ouest du Nouveau Brunswick est contenu dans le complexe volcanique de Poplar Mountain (CVPM), lequel est situé le long du segment sud de la zone de faille régionale de Woodstock. Les trois unités principales du CVPM sont, de la base au sommet, une unité volcanique felsique porphyrique, une unité volcaniclastique et une unité volcanique mafique. La datation U-Pb de zircons indique que les roches volcaniques sont plus jeunes que 459 ± 3 Ma, et la datation par la méthode 40Ar/39Ar de séricite associée à la minéralisation assigne à la minéralisation un age de 411 ± 3.7 Ma. Bien que les zones minéralisées en or soient présentes dans toutes les unités lithologiques, on les retrouve surtout dans l’unité felsique porphyrique. Les zones aurifères ne sont pas contrôlées par des failles individuelles mais sont caractérisées par une grande densité de fractures cassantes, de minces veines de quartz-carbonate, et par une altération en ankérite-séricite intense qui se superpose à une altération antérieure en chlorite-calcite-quartz. L’or est associé à l’arsénopyrite, laquelle est principalement présente à l’état de disséminations dans la roche hôte, et à un moindre degré avec des veines de quartz-carbonate-séricite et des brèches à ciment de quartz.Les données de géochimie indiquent que l’alté"

Jan 1, 2008

By H. W. Fleming

In 1955, the results of a regional, geological interpretation of the northern portion of New Brunswick were used as a basis for selecting, for intensive exploration, three areas in which structural and stratigraphic conditions were believed to be favourable. Airborne electromagnetic work, in one of these areas, provided the justification for acquiring the Murray group. Even though the initial results were discouraging, this geological interpretation, combined with the fortuitous discovery of cop• per-bearing float, was sufficient reason for carrying out further work using geochemical methods. This work finally resulted in the discovery of the Murray massive-sulphide deposit, after about eighteen months of coordinated exploration on the property. While this deposit is a typical New Brunswick-type base-metal occurrence, extensive leaching has produced a fossil gossan that rendered it an elusive target for exploration techniques of limited penetration Full credit for localizing the target area is given to the geochemical techniques, but geophysical surveys were needed to provide the necessary

Jan 1, 1961

By H. A. Pearse

The history of the flotation process, as applied to the practical field of ore dressing, dates back somewhat less than twenty years; yet this fact may be overlooked in view of the present universal dependence on this process in the concentration of almost all classes of ore. It is therefore interesting to recall that Britannia was the scene of some of the earliest experiments with flotation on a commercial scale. In 1911, sixteen years ago, an Elmore vacuum machine was operated for several months with encouraging results. In 1913, some time before flotation was very generally adopted elsewhere, a Minerals Separation plant, capable of treating 600 tons daily, was operating successfully at Britannia. Considering how little was known of the theory and practice of flotation at that time, the recovery was remarkably good, but it was not until the present mill was completed in 1923 that any attempt was made to raise the concentrate grade by differential flotation, or, in other words, to float the chalcopyrite while rejecting the then worthless pyrite with the tailings. The first ore passed through the present concentrator in March, 1923. As originally designed, the rated capacity was for 2,000-2,500 tons, but this has been increased year by year, until at the present time 4,000 tons daily can be treated economically. During the first few months of operation the concentrate grade averaged only 10-11 per cent Cu, but by the end of 1923 this had been raised to over 20 per cent, due to the elimination of the pyrite by differential flotation. In 1923 the tailings averaged approximately 0.25 per cent Cu, but also in the matter of recovery a considerable improvement has been effected, for during the year 1926 an average tailing of 0.15 per cent Cu was maintained.

Jan 1, 1927

By M. P. Sinha, Rashmi, Tata Steel Ltd., S. Jaiswal, A. Bhatnagar, P. Garg

Reagents form a crucial part of flotation process as they have the power to control the surface properties of minerals. In case of coal flotation, collectors and frothers are two the important and commonly used reagents. But other types of reagents such as promoters, modifiers and depressants are also finding wide applications because of their availability to improve selectivity and increase recovery. Because of these chemicals the scenario has changed from flotation being used mostly for high rank hydrophobic coals to low rank, oxidised or inferior coals. In the present work a case is presented in which two non-ionic surfactants (abbreviated as A & B) known to act as emulsifier have been studied to get a better flotation performance for a preparation plant with varying feed characteristics. Laboratory flotation tests were conducted with both the surfactants using three feed samples of the plant by varying the dosage at three different levels. The highest combustible matter recovery (more than 80%) was obtained for surfactant B at a dosage of 75 ppm (parts per million) for feed 1. But at the same dosage the recovery decreased by 21% and 10.2 % respectively for feed 2 and 3. On the other hand surfactant A showed a consistent result for all the three feed samples giving the highest value at a dosage of 50 ppm followed by a decrease beyond this point. The tests were complemented by contact angle measurements that demonstrated the same trend. In addition to this the reproducibility of data for Surfactant A was checked and found that the standard deviations for both separation efficiency and combustible matter recovery were within the permissible range (less than 5%). Finally an in-plant process optimization study to evaluate the performance and applicability of surfactant A at industrial level was done and has been discussed.

Jan 1, 2016

By I. R. Muirhead, A. L. Craven

The trend in mining thermal coal is only to mine coal with the lowest sulphur content. In many coal seams, bands of coal with high sulphur content are often present, generally occurring either at the roof or floor level. Methods of selective mining are, therefore, necessary to recover only the low sulphur coal. This paper examines the methods currently in use in mines and the alternative methods that are able or have potential to offer control of shearers and continuous miners where greater thicknesses of coal have to be left in the roof and floor. These alternative methods rely on such characteristics as neutron gamma radiation; electromagnetic waves; vibration; infrared; infrared; optical; pick force; X-ray fluorescence; conductivity; gyroscopes and laser systems.

Jan 1, 2000

By Richard W. Hutchinson, Robert W. Hodder

"Pyritic massive sulphide deposits lie conformably above submarine volcanic rocks, and beneath siliceous and manganiferous iron formations. The massive bodies are often zoned, with a barren pyritic top grading downward into pyrite with sphalerite, and occasionally galena, and a chalcopyrite-rich base. They are frequently brecciated, like the lavas beneath them, which contain pyrite and chalcopyrite as coatings on joints and fractures and as dispersed grains. The lavas also exhibit propylitic, argillic and silicic alteration. These sulphide deposits appear to have formed on sea bottom from fluids escaping through the lavas during periods of exhalative and sometimes explosive volcanism. The process may be comparable to the present deposition of base metals from hot brines in the Red Sea. Some porphyry copper deposits resemble the altered, sulphide-impregnated lavas which lie beneath bodies of pyritic massive sulphide. In porphyry copper deposits, pyrite and chalcopyrite occur as veinlets and dispersed grains in intensely fractured tuffs, flows, sub-volcanic intrusions or other host rocks, characterized by propylitic, argillic and silicic alteration. Metal zoning is present; sphalerite and galena often occur in manganiferous veins peripheral to a shell of pyritic veinlets which encloses the mineable zone of chalcopyrite-bearing veinlets. This sulphide distribution appears to have formed from hydrothermal fluids escaping, either passively or violently, from solidifying magma. The fluids may be comparable to hot brines encountered by drilling in the Salton Sea area of California.There are also important differences between massive sulphide and porphyry copper deposits. The former usually occur in differentiated, mafic-to-felsic subaqueous volcanic rocks, whereas porphyry copper deposits are often associated with shallow plutons and subaerial volcanic rocks of intermediate to felsic composition. Calcic-sodic metasomatism accompanies the massive sulphides, whereas potassic metasomatism characterizes the porphyry cop.per deposits. Further, ages of massive sulphides range from Archean (Keewatin) to Tertiary, but porphyry coppers are Triassic to Tertiary in age. These similarities and differences suggest that massive sulphide and porphyry copper deposits are related tectonically and metallogenetically. The former were generated during early stages of crustal evolution, particularly in Archean time, and were repeatedly derived during early stages of younger, individual tectonic cycles. In contrast, the porphyry coppers developed during the later stages of crustal evolution - later in terms of both absolute age and relative age within younger individual tectonic cycles. They appear in younger rocks generally, and specifically in rocks involved in events of the middle and late tectonic stages of orogenic belts. The massive sulphide deposits are of early-magmatic eugeosynclinal affiliation, whereas the porphyry deposits formed in late-magmatic, predominantly subvolcanic settings at the edge of continental plates, where contemporaneous exhalative volcanism was mainly a subaerial phenomenon. Transitional types of deposits exist and are found on continental margins with flanking eugeosynclinal sequences."

Jan 1, 1972