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By A. A. Burgoyne

"The McDame chrysotile asbestos deposit located near Cassiar in northern British Columbia isfound at depth and on trend to the southeast of the currently mined open-pit Cassiar asbestos deposit. The ultramafic rock hosting the McDame is serpentinized peridotite of the Upper Paleozoic Sylvester Group contained in an ophiolitic sequence preserved within a lower thrust sheet of the Sylvester Allochthon. The Sylvester stratigraphic package is a series of thrust slices composed of argillite, tuff and volcanic flows, diorite and serpentinite. Contacts between units are often fault-controlled.The McDame asbestos-bearing ultramafite is considered to represent a separate interleaved fault-bounded slice of rock distinct from the Cassiar asbestos deposit.Asbestos mineralization of the McDame deposit was discovered in /978. Exploration during /980 and /98/ focused on extensive underground drilling of the deposit and in /983 on geological mapping, airborne and ground magnetic surveys. In /984 a 622.5 m borehole was drilled with a 242 m intersection of McDame ultramafite of which the lower 15/ metres contain potentially economic chrysotile asbestos. The McDame deposit averages 90 m thick, trends north-south, dips easterly and plunges southeasterly. The deposit is estimated to contain geological reserves in the order of 62 million tonnes containing asbestos fibre similar in value to the Cassiar deposit.The McDame is considered a major world-class asbestos deposit. A decision to develop and mine the deposit will require further substantial underground exploration and evaluation. A + 1200 m exploration adit driven to the hanging wall of the deposit was undertaken in 1985 in anticipation of bulk sampling and diamond drilling in 1986."

Jan 1, 1986

By Sabine Noelte, Mikko Petteri Rantamäki, Christopher Robben, Anssi Takala, Karl-Erik Rånman

"Sensor-based ore sorting is on its way to establish as a standard option for physical separation. The increasing number of installations in coal, iron ore, industrial minerals and hard-rock metal mining segments underlines the technological and financial potential that is beginning to be untapped. The Ma’aden Phosphate installation with 1.650 t/h sensor-based ore sorter feed sets a new benchmark for the possible capacity of stationary installations. Besides stationary installations, including multiple sorters parallel in different size ranges and multiple stages, containerised semi-mobile plants are applied. These offer two advantages, first being the reduction of transport costs when applied close to the mining face. The second is that semi-mobile systems enable processing of tens of thousands of tonnes of ore in a piloting phase with an approximate duration of 0.5 to six months, verifying the results laboratory mini-bulk tests on 5–10 tonnes of sample. This is especially important for low-grade metal ores because of the inherent Fundamental Sampling Error, as well as the Grouping and Segregation Error. The paper elaborates the results achieved within the I2MINE project, treating polymetallic ore at the Boliden Concentrator in Sweden.INTRODUCTIONSensor-based ore sorting (SBS) is becoming a standard option for physical separation, applied in all segments of mineral production. The Umm Wu’al project sets the bar for stationary SBS installations with 1,650 t/h feed (TOMRA, 2015). TOMRA Sorting Solutions has finalised an agreement in cooperation with Outotec to supply Outotec-branded sorting solutions for the mining and metallurgical industry (TOMRA, 2014). Especially for low-grade hard rock metal ores, an interdisciplinary approach is necessary applying experts for all aspects of mineral production. Due to the impact on the whole process stream, it is important on the end user side to have high level managerial support and involve all disciplines to ensure that all stake holders are involved in the analysis."

Jan 1, 2016

By J. A. Finch, G. Labonté

"A long-standing objective has been to obtain interpretable measurements of the oxidation-reduction potential in mineral slurries. For this purpose several sensing electrodes (black platinum wire, platinum foil and spiral, gold foil and spiral, and sulphide minerals such as chalcopyrite and galena) were investigated to determine their response to the presence of sulphide minerals in the pulp, and to the addition of reagents commonly used in flotation. The observed discrepancies between the electrodes may be explained using a combination of the classical mixed potential model for complex solutions and the probability of contact between the mineral particles and the sensing electrode. It is shown from laboratory testwork that gold spirals are preferred over platinum electrodes. Finally, some of the practical aspects of using the electrochemical measurements in a plant environment are discussed.IntroductonThe interpretation of flotation of sulphide minerals in terms of electrochemical (electron transfer) processes has brought new possibilities for process control of selective flotation. Investigations on massive and compacted particulate bed electrodes have shown that the flotation of a given mineral in the presence of a collector can be controlled by the potential induced on the mineral surface. Also, phenomena such as collector less (self-induced) flotation, activation by heavy metal ions, and natural selectivity sustained by galvanic coupling during flotation might also be controlled by electrochemical means.The technique for measuring electrochemical potential in slurries is an adaptation of that used for solutions. The measurement of the oxidation-reduction potential of a solution (ORP , Redox, Eh) is usually carried out by immersing a noble metal electrode (platinum, gold or silver) and a non-polarizable reference electrode: Standard Hydrogen Electrode (SHE), Standard Calomel Electrode (SCE), or silver/silver chloride (Ag/AgCl) in the solution. (The abbreviation Eh implies the SHE is the reference electrode.) The potential difference between the two electrodes is measured using a high impedance electrometer. ASTM standard D 1498-76 (revised 1981)(1) covers the practical details of such measurements; however, it does not deal with their meaning either in complex solutions or in mineral slurries ."

Jan 1, 1988

By J. F. Hazzard, R. J. Chalaturnyk, C. Khazaei

"Various measurement, monitoring and verification (MMV) techniques are used to ensure the safety of operations in petroleum projects. One of these techniques is microseismic (MS) monitoring of the caprock. A challenge in MS monitoring of caprock is that unlike projects such as tunnelling in hard rocks, the number of recorded events are much smaller and also wide spread through the rock mass which makes interpretation of the physical meaning behind the events very difficult.In this paper, a numerical technique is introduced and validated for coupling a finite difference code, FLAC3D (Fast Lagrangian Analysis of Continua), with a discrete element code, PFC3D (Particle Flow Code). Then, a similar approach is adopted for modeling microseismic events in the caprock. For this purpose, the underburden, reservoir and overburden layers are modeled by FLAC3D. A rather small section of caprock above the reservoir is nulled in the FLAC3D model and substituted by a PFC3D inclusion. The reservoir pressures are then applied to the reservoir section of FLAC3D. Once the FLAC3D cycles, there will be induced pressures in the caprock due to its undrained response to the change in pressures within the reservoir. These induced pressures are transferred to PFC3D as boundary velocities. Then the PFC3D cycles and sends back the boundary forces to FLAC3D. This back and forth process continues until equilibrium is reached. During this process, there will be bond breakages within the PFC3D inclusion that can be regarded as MS events. An algorithm for recording the microseismic energies based on a change in local strains is also implemented. The results are then compared with real data. The effect of injection fluid temperature is also studied. No significant appearance of microseismic events was observed due to injection of CO2 in both cases (i.e. with or without considering temperature). However, this continuum/discontinuum approach seems promising for understanding the microseismic response of caprock in more detail and also using the MS data for validation of geomechanical models."

Jan 1, 2015

By J. M. Beeckmans, S. G. Butcher, M. Goransson

"The counter-current fluidized cascade is a novel and potentially efficient pneumatic gravity separation device. Data are presented on over 150 runs of cleaning Alberta thermal coals, covering several size ranges. The coarser sizes of coal were processed in admixture with a fluidizing medium consisting of 0.5-by 0.1-mm hematite (or magnetite) and limestone particles. The partition curves for coal particles larger than about 3 mm, mixed with fluidizing medium, showed that the sharpness of separation achievable with the cascade approaches that of wet heavy medium processes, whereas with particles in the size range of 3 by 0.6 mm the sharpness of separation was comparable to that of a Baum jig. Useful cleaning was also achieved with particles smaller than 0.6 mm , Throughput rates of up to 11 tonnes per metre width of cascade per hour were achieved, with no indication of a deterioration in performance.IntroductionPneumatic coal beneficiation has steadily lost ground vis-a-vis hydraulic beneficiation during the past quarter century, primarily because of the sharper separations achievable with the latter methods. Nevertheless, there are certain inherent advantages of pneumatic separation methods which would give them an advantage in the market place were it possible to increase their efficiency to be technically competitive with those of hydraulic processes. These advantages are a dry product, resulting in a higher calorific value per ton, and avoidance of the problems associated with treatment and storage of process waste waters. Also, although it may be necessary to dry the raw coal prior to pneumatic processing, the dry rejects produced constitute an ideal fuel for a fluidized-bed combustor, which could provide heat both for drying the coal and for other purposes."

Jan 1, 1982

By G. S. Dobby, J. A. Finch

"A significant development in froth flotation technology has been the emerging industrial acceptance of column flotation during the past few years. Flotation columns are being employed now in several Canadian base metal concentrators and they are being considered f or a wide range of flotation applications throughout North and South America. Since the operating principles of a column differ markedly from those of conventional flotation machines, and have been poorly understood, scale-up of columns has been difficult. This paper describes a methodology f or translating laboratory column data to industrial operation.The scale-up model utilizes kin etic data that is obtained from a series of laboratory column experiments; the laboratory column can be as short as 2 m. For modelling purposes the column is considered to consist of two zones: the collection zone, where particle recovery occurs, and the cleaning zone, a packed bubble bed generated by downward flowing wash water. Mixing conditions in the collection zone have been characterized using the results of tracer experiments on plant columns at Mines Gaspe. The same experiments demonstrated the nearly complete suppression of entrained gangue minerals that is attained in the cleaning zone. The model explicitly accounts for both the collection zone and cleaning zone recoveries and allows for the effects of bubble overloading. Results of column scale-up experiments at Gibraltar Mines are presented."

Jan 1, 1986

"One of the workhorses of the minerals industry is the autogenous grinding (AG) mill and its derivative the semi-autogenous (SAG) mill. These are relatively well understood, but not so Scrubbers. Scrubbers are mechanically of the same appearance/function, so what is the difference between an AG mill and a scrubber? When, or under what conditions should a scrubber be used and when should an AG mill be used? Can the processes within be mathematically modelled?In the past decades, the minerals industry has focused most of its attention on the modelling of unit processes such as cone crushers, HPGR’s, AG/SAG mills and ball mills within conventional processing circuits. Less attention has been placed on the modelling of scrubbers. This paper reviews the difference between scrubber and AG mill modelling, highlighting some of the similarities, with a view to confident comminution circuit designs.Engineering practitioners should be comfortable with these circuit designs and not shy away from considering AG mills for both small and large scale plants. AG mills can treat both harder or softer ore and scrubbers are for only softer ores. This paper differentiates scrubber and AG mill modelling in a similar way that overflow ball mills and grate discharge ball mills are analysed. Smaller scrubbers (600 kW) are suited to small scale soft ore (100-300 t/h) operations. Larger scrubbers up to 2,500 kW have the capability of very high throughput, in excess of 1,750 t/h with soft fine feed ore. AG mills are scalable up to 28 MW and are capable of treating harder ores at rates exceeding 2,000 to 4,500 t/h. Observations are that the specific energy requirements for the mill grinding duty is wide and varied. This is to a large degree the crux of the matter in sizing, as well as, differentiating, scrubbers from AG mills.INTRODUCTIONAG milling is a mature technology that has been used in minerals processing applications for more than 100 years. In the last 50 years, harder metalliferous ores have seen the introduction of steel balls to assist in the grinding/milling action. Tumbling mills used in such a configuration are called semiautogenous mills (SAG). The greater minerals industry is no newcomer to the use of fully autogenous (AG) mills. Perhaps scrubbers are. What is the difference? When should a scrubber be used versus an AG mill? How are they mathematically modelled?"

Jan 1, 2016

Objectives ? New deposits can be found in mature Mining CampsNew Camps ? Volcanogenic Massive Sulfide (VMS) deposits ? polymetallicpolymetallicexamples are desirable exploration targets examples ? Genetic and exploration models for VMS deposits are robustrobust ? subtle but important differences exist between deposits and districts ? sometimes ??neglectedneglected??in resource modeling and exploration efforts ? ReRe-evaluation of a prominent existing camp is rewarding ? update on the exploration strategies currently being applied on a practical level The Falconbridge-Alexis approach includes GoCAD modelling

May 1, 2006

By R. L. Guerguerian, Eugene Bercel

"Grinding mill hydrostatic trunnion bearings require an external pumping source to provide and maintain the oil film between the bearing members. In order to guarantee a predetermined minimum film thickness, the lubrication system tends to be oversized. The oil film is ""indirectly"" controlled by flow, pressure and temperature monitors with fixed settings on the conservative side. This can lead to excessive maintenance and abbreviated life for the lubrication system components. A reliable method of monitoring actual film thickness would not only provide greater mill availability, but also minimize maintenance costs.This paper describes the instrumentation installed in Dominion hydrostatic bearings, and presents results of field tests where the output of that instrumentation was recorded under various operating conditions.IntroductionThe trend toward larger and more sophisticated grinding mills has made the operators of these machines increasingly vulnerable to financial loss, as the cost of downtime and repairs has increased directly with machine size. In order to guard against such losses, it is becoming imperative that large, sophisticated grinding mills be equipped with protective instrumentation to monitor some of the critical operating parameters and to identify events and trends which, if they go unnoticed, can lead to excessive maintenance costs and machine downtime. The idea of protective monitoring systems is not new. The operators of certain types of machinery where a high degree of safety is required or where machinery health can deteriorate very rapidly, as in the case of high-speed turbo-machinery, have long been using protective instrumentation on their machines. The increased awareness of the benefits of monitoring machinery conditions and the availability of reliable and relatively low-cost instrumentation of a large range of sophistication is making the practice now widespread. Traditionally, grinding mills have not been considered as high-risk machinery requiring instrumented protection. However, the trend, mentioned earlier, toward employing fewer, but larger capacity, mills increases the risk of significant disruption of production, and therefore measures to minimize the risks are desirable."

Jan 1, 1981

By Ken Wood, Luc Duval

"The development and operation of the milling circuits treating the different Selbaie orebodies are discussed in this paper. The project is reviewed from metallurgical evaluation through construction to present operating status. The current flowsheets are described, with discussion of some unusual features.IntroductionThe Selbaie concentrator commenced initial production in August 1981, treating underground B zone copper ore in a single 1500 t/d circuit. Throughput was increased to 1650 t/d in 1985. The mill was expanded in 1986 to treat ore from the A-I zone open pit; an independent circuit was added to selectively treat 5000 t/d of copper-zinc ore. Current total mill throughput through both circuits averages 7200 t/d with the production of approximately 270 t/d of copper concentrate and 230 t/d of zinc concentrate.This paper describes the stages involved in bringing the project from initial laboratory testing to its current status as one of the most important producers of silver, copper and zinc in Quebec and a major employer in the region."

Jan 1, 1990

By R. S. Nichols

"During 1973 to 1978, Canadaka Mines Limited, a subsidiary of St. Joseph Explorations Ltd., undertook an extensive exploration and development program in the Cobalt area. This program resulted in the delineation of previously unknown stratigraphic units in the Archean volcanic sequence. During this time period, significant are controls related to area silver deposits were also identified.The Archean geology is comprised of a volcanic pile conformably overlain by sediments. The volcanics contain at least two felsic volcanic centres near the stratigraphic top of the pile. The bulk of the pile consists of mafic flows and interflow sediments. lnterflow sediments around silver are shoots contain mineralized halos of base metal sulphides. The halos exhibit lateral and vertical metal zoning with Cu, Pb and Zn mineralization decreasing away from an are shoot.Silver mineralization controls determined during the Canadaka program agree with the historically well established importance of Coleman sediments as well as Archean contacts for hosting silver deposits. The vertical extent of are shoots is typically 150to 250ft. A strong correlation was found to exist in the Cobalt area between Archean strike and the strike of are veins. Finally, al/ Cobalt area are deposits appear to be associated with a distinct volcanic pile at the top of a sequence of Archean flows."

Jan 1, 1988

By H. Utsunomiya, Mehdi Sanjari, Abu Kabir, Steve Yue, Jing Su, L. Kestens, In-ho Jung

The microstructure and texture evolution of low temperature rolled AZ31 magnesium alloy during annealing were investigated. The specimens were rolled at the temperature of 100? at a high rolling speed of 1000m/min with a reduction of 30% in one pass. Annealing was conducted at various temperatures ranging from 200? to 500? for different time. To study the effect of fast speed rolling, the same annealing procedures have been applied for the specimens rolled at a significantly lower speed of 15m/min. The microstructure was characterized by optical microscopy and scanning electron microscopy, while the texture was analyzed by X-ray diffraction analysis and electron backscattered diffraction analysis. Texture weakening occurred during annealing at both fast and slow rolling speeds. However, at the same annealing condition, fast rolled specimens always had weaker intensity of basal texture than slow rolled ones.

Jan 1, 2014

By G. Harper

The Sustut Copper deposit, 230 miles northwest of Prince George, B.C., was discovered in August of 1971. Subsequent exploration has included 56,417 feet of surface diamond drilling in 139 holes. The deposit occurs in gently dipping volcanic rocks of the Upper Triassic Takla Group, which outcrops as rugged mountains. The general Mesozoic sequence comprises some 20,000 feet of green and red basaltic to andesitic rocks. The Lower Formation is characterized by subaqueous basalt, andesite and augite porphyry flows with interbedded breccias. They were rapidly deposited in tectonic depressions of limited extent and steep gradients. Fades changes are abundant. The Middle Formation consists of volcaniclastic rocks made up of fragments from the underlying formation. Two cycles are discernible, both with basal turbiditic, tuf-faceous sandstone and shale units overlain by massive, volcanic conglomerates exhibiting graded and cross bedding. A broader, shallower-water basin is indicated. The top of the uppermost unit was subaerially deposited. The Upper Formation is a variable sequence of volcanic sedimentary rocks. Detritus was supplied from a wide source area and included multiple reworked fragments of the lower formations and material from other rock groups known in the region. Zeolite fades metamorphism is recognized throughout the entire sequence. Epidote is particularly abundant in the Middle Formation, demonstrating the results of metasomatism. The mineralized zone is approximately concordant with the strata over 100-200 feet of the Middle Formation succession. It lies just below the zone of transition from subaqueous to subaerial deposition in the top unit. Hematite, chalcocite, pyrite, bornite, chalcopyrite and native copper are disseminated throughout all sizes of lithic fragments and matrix. Concentration into the specific zone is believed, to be due to upward leaching of copper during low-grade metamorphic and metasomitic reaction. Precipitation occurred in the zone of hydration characterized by prehnite-pumpellyite below the oxidized subaerial rocks.

Jan 1, 1977

By S. Dallaire

"RÉSUMÉLes revêtements céramiques ont une moins grande visibilité que les revêtements métallurgiques. Ils ont cependant jour un role significatif dans noire développement technologique. Les procédés de revêtement ont permis de s'affranchir de barrières technologiques importantes dans le domaine de l'optique, de l'électronique, de l'usure, des hautes temperatures. L'introduction de nouvelles technologies ou la mise en service de nouveaux matériaux peut nécessiter l'adaptation de certain procédés actuels ou le recours a des procédés qui ont peu percé jusqu’ à maintenant.ABSTRACTApplications concerned with ceramic coatings are not as well known as those with metallic coatings. However, ceramic coatings have played a tremendous role in the development of technology. Ceramic coating processes made it possible to overcome technological barriers in the areas of optics, electronics, wear resistance and high temperature applications. Ceramic coatings can provide new properties to materials never considered for demanding applications. They can also open new frontiers and revitalize materials which are maturing or in decline."

Jan 1, 1990

By L. C. Galloway, G. L. Tiley

"Mine hoist brakes must meet the following statutory performance criteria:- There should be two independent braking systems; at least one should act directly on the hoist drum.-If one brake fail s, the others should be able to retard and stop the hoist safely before the descending conveyance, carrying the rated load, reaches any obstruction.- When all brakes apply, decelerations should not be so violent that men travelling in the conveyance are injured.- The brakes shall not overheat and fade during an emergency stop.This paper discusses design principles and capacities of caliper and disc type brakes, when applied to double drum and friction hoists of equivalent capacity.IntroductionThis paper is about the brakes that are used on mine hoists; their functions, especially in emergencies, typical design, and how they are operated, controlled, tested, and adjusted.There are two basic types of mine hoists:1. Drum hoists, where the ropes are attached to, and coil on drums. The simplest system has only one drum. Most such hoists, however, have two drums, attached to a common shaft. Ropes are wound on each drum in opposite directions, so that when one conveyance is being raised, the other is lowered. The conveynaces may travel in vertical or inclined shafts. In the latter case, the hoist s are referred to as slope hoists.2. Friction hoist s, where the headropes are not attached to the wheel, but are in contact with it for an angle of lap of, typically, between 180 and 195 degree s. Forces are transmitted from the hoist wheel to the head ropes by friction.The lower ends of the conveyances are connected to balance ropes , approximately the same weight per foot as the headropes."

Jan 1, 1986

By W. K. Muwais, R. G. Cuddy

"The Lower Cretaceous McMurray Formation contains the bitumen reserves of the Syncrude Mine in northeastern Alberta. This formation comprises sediments deposited sequentially in fluvial, estuarine and marine depositional environments. The Syncrude Base Mine area consists mostly of estuarine sediments, as much of the original marine sediments have been eroded away. These estuarine deposits consist of channel-fill sediments and interchannel tidal flat sediments with the channel-fills comprising most of the orebody.Channel-fills contain, among other lithologies, interbedded sand, silt and clay rich layers that often occur as sequences of inclined beds with dips up to 25 degrees or more. A detailed knowledge of the distribution of these inclined beds, their lithological characteristics and their continuity is very important in assessing the risk of mine highwall instability . Techniques used to identify and characterize adverse structures are reviewed. INTRODUCTIONGeneralThe Syncrude Canada Ltd. oil sand mine is located within the surface mineable portion of the Athabasca Oil Sands area about 40 kilometres north of Fort McMurray in northeastern Alberta, Canada (Fig. I). The company commenced large-scale strip mining of oil sands in June 1977in the area, referred to as the Base Mine, situated in the southeast corner of the company's two lease areas (Fig. 2).The mining method (Fig. 3) utilizes large electric drag lines operating on a single bench with highwall depths up to 60 metres. Feed grade oil sand (= 6 wt.% bitumen) is mined by draglines and windrowed parallel to the highwall crest. Lower grade oil sand « 6 wt. 0J0 bitumen) occurring as waste bands is selectively mined by the draglines and cast back into the mined out pit or placed on the bench and hauled by truck. The windrowed feed is delivered to the extraction plant by a bucket wheel reclaimer and conveyor system. Stripping of Recent, Pleistocene and Cretaceous overburden units is done outside the conveyor systems by mobile equipment. The 4.5 kilometre long mine is split into four quadrants for planning and scheduling purposes, with each quadrant having an individual dragline-bucketwheel-conveyor system.Surface mining of oil sand at Syncrude requires the removal of vast quantites of material. The design of the open pit mine relies heavily on knowledge of the distribution of ore and waste materials, and on the physical characteristics of these materials.The geology of the oil sand below the dragline bench at the Syncrude Mine is complex. Geological, geotechnical and hydrogeological factors play an important role in the design and operation of the mine. This paper describes aspects of the geology that impact on the design and operation of the mine. Some of the methods and procedures adopted by Syncrude to successfully overcome difficulties that the complex geology creates are discussed."

Jan 1, 1989

By C. R. Lattanzi, M. J. Davie, L. D. Smith, J. R. Goode

"The feasibility study determines the technical and economic viability of a project at the level of accuracy required by the owner to make an investment decision. The economic analysis usually includes calculation of the discounted cash flow. Key components of the cash flow include the project capital cost, the operating costs, construction schedule, production rate, product prices and financial details.This paper examines the feasibility study for a typical mining project. The paper discusses acceptable methods for the determination of the geological and mineable are reserves. The prerequisites for the development of suitable designs, and the calculation of capital and operating costs for the mine, processing plant, and infrastructure are reviewed. Important features of the cash flow analysis and its interpretation are presented.IntroductionThe commercial development of a mineral deposit invariably requires the investment of capital in preparing the deposit for production. It has always been necessary, therefore, to demonstrate to the investor of capital that production of a saleable commodity is both technically feasible and economically viable. The instrument typically used to make these determinations is the feasibility study .Traditionally, mining companies have been rather conservative in their approach to financial management. Until about thirty years ago, the capital required to develop a new mine was most frequently provided by internal corporate cash now and virtually all of the necessary technical and economic studies were performed 'in house'. Under these circumstances, there was little standardization as to what constituted an acceptable feasibility study, and even less as to what constituted an acceptable measure of economic viability."

Jan 1, 1991

By N. D. MacFarlane, D. J. Mossman

"The Nemeiben Lake ultramafic complex, in the Churchill Province of the Canadian Shield in north-central Saskatchewan, is a small I. 6-km circular plug largely composed of high-alumina pyroxene cumulates forming a series of grossly concentric layers of clinopyroxenite, websterite and wehrlite. Minor dunite and gabbro are present in the northwestern part of the pluton.Disseminated primary magmatic pyrrhotite, pentlandite, chalcopyrite, magnetite and chromite occur throughout the intrusion. Sulphides occur in proportions of economic interest in the northern outcrops. A secondary assemblage of fine-grained oxides, sulphides and native metals occurs in serpentinized and uralitized peridotites and pyroxenites. Primary opaque minerals are largely altered to marcasite, violarite and hematite. The ores represent a primary magmatic assemblage extensively modified by metamorphism and, to a lesser extent, by supergene alteration.The complex intruded an Early Aphebian supracrustral succession during the waning stages of the Hudsonian orogeny. The metamorphic peak during Hudsonian time reached middle to upper amphibolite facies, granitized the country rocks and contributed to the partial amphibolitization of the ultramafic pluton.The Nemeiben complex has a number of features in common with the zoned intrusions of southeastern Alaska, including: the diopsidic composition of clinopyroxene, highly magnesian olivines, ubiquitous primary magnetite, relatively high alumina content of clinopyroxenes and the unlikelihood that associated gabbroic rocks are derived from a magma common to the ultramafic rocks. However, at Nemeiben, orthopyroxene occurs as a widespread postcumulus phase and, to a lesser extent, as a cumulus mineral. This fact, together with geochemical data on whole-rock and mineral compositions, indicates a tholeiitic parentage.The nickel-copper deposits of the Nemeiben Lake ultramafic complex are not currently economic, although standard technology for recovery of sulphide minerals in the clinopyroxenite (and websterite) would probably be adequate. Most ore minerals in the altered peridotites belong to the fine-grained secondary assemblage of opaques due to the formation of retrograde hydrous silicates and are probably too fine grained for standard recovery methods."

Jan 1, 1982

By Jian Deng, Haitian Sun, Zengqian Hou, Shuhe Song

"Abstract - Volcanogenic massive sulfide (VMS) deposits, an important base-metal deposit type in China, occur widely in submarine volcanic districts of variable magmatic affinities. These VMS deposits range in age from Archean to Mesozoic, but most are in Proterozoic and Paleozoic sequences. More than 60% of VMS deposits formed in the Paleozoic, the most important metallogenic eon. Three important Paleozoic VMS-metallogenic provinces include Northern Qilian, Sanjiang and Altai provinces. The Proterozoic constitutes the next important era, but with no VMS deposits in the middle Proterozoic. VMS deposits associated with the Proterozoic volcanic rocks occur around the Yangtze Platform and in the western Kunlun-Qinling. The Triassic is third in importance, with VMS deposits concentrated in the Sanjiang Tethys. The Archean has only one VMS deposit, on the northern margin of the Sino-Korea Platform.Five distinct compositional classes of Chinese VMS deposits have been distinguished: Cu, Cu- Zn (or Zn-Cu), Cu-Fe, Zn-Pb-Cu, and Pb-Zn (-Cu). The Cu, Cu-Co, and Cu-Zn types of deposits occur sporadically from the Archean to Paleozoic, and are closely associated with mafic and ultramafic volcanic sequences. The Zn-Pb-Cu and some Cu-Zn type deposits are restricted to the Paleozoic and Triassic, and are hosted by calc-alkaline felsic rocks in bimodal basalt-rhyolite sequences, whereas Cu-Fe and Pb-Zn type (except for the Laochang deposit) deposits are restricted to the Proterozoic and occur in calc-alkaline volcanic sequences. As large quantities of marine mafic volcanic rocks were deposited in western China, Cu and Cu-Zn deposits are major types of Chinese VMS deposits.Chinese VMS deposits formed in a wide range of paleo-tectonic settings and depositional environments, such as island-arcs, rifts, aulacogens, and ocean ridge hot spots. Among these, the rift and back-arc environments are the most important, containing about 60% of Chinese VMS deposits. Aulacogens are a subordinate environment where most of the Proterozoic VMS deposits formed. The oceanic ridge and hot-spot systems are common in the tectono-magmatic domains in China, but contain only a few small Cu and Cu-Zn type VMS deposits.The Chinese VMS deposits have usually been influenced by both deformation and metamorphism to various degrees, resulting in changes in the shape and metal distribution. Seven representative deposit styles have been recognized: sheets, sheet plus strata-bound stringer, cyclically zoned deposits, mounds, mound-like deposits, strata-bound stringer-disseminated, and stockwork-disseminated deposits. The formation of these various styles of deposits is controlled by several key factors, such as lithology and permeability of the host rocks, focused or unfocused discharge, temperature and chemical composition (e.g., salinity) of hydrothermal fluids, as well as depth of seawater."

Jan 1, 1999

By Michael K. O’Leary, William D. Coplin

"Risks from political instability and government policies restricting equity ownership, local operations and transfers of payments affect the profitability of foreign mining ventures. More than seat-of-the-pants judgments and old-boy networks are required to anticipate these risks and to take actions appropriate to offsetting them. A system for making political forecasts, called the Prince System, and a series of charts relaying risk s to a production of key minerals will be presented.IntroductionFirm s with extractive operations outside their home country do not have to be told that political stability and government decisions play a big role in the success o f their operations. The takeover of copper firm s in Chile during the Allende administration in 1971 and the recent decision by Venezuela to reduce Reynolds Metals equity share in a smelting operation from 50% to 28% are two examples of hundreds of events that have determined the profitability of extractive operations over the past decade. Both risks and opportunities for international firms seeking to produce and market raw materials are heavily affected by political conditions. While news of political events travel much faster than in the past and host governments are more clever in shaping the risks as well as the opportunities, politics has always been part of the mining business.What has changed is the need to be more systematic in approaching the assessment of political conditions and how it affects business. The increasing costs of extractive operations, the need for long-range planning, the importance of financial arrangements and the world-wide scope of man y firm s' activities require that the assessment be updated continuously and be comparable across different countries and different types of investments. Political risk analysis, the assessment o f macro-political changes and specific governmental decision s on the operations of extractive industries needs to become as systematic and integrated into corporate decision -making as economic analysis has become over the past two decade s."

Jan 1, 1983