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By H. Warren Newcomen, Dennis C. Martin

"This paper describes the investigation of a large, progressive slope failure on the southeast wall of the east pit at Highmont Mine, British Columbia Geotechnical investigation s consisted of geological and structural mapping, assessment of blasthole drilling records, review of rock core information, slope movement monitoring and back analysis of various possible failure modes. Climate records and mining history were also assessed to determine their relationship to slope movement.Analysis of movement monitoring records and geotechnical information indicates that the failure is deep seated. The upper portion of the failure surf ace occurs along clay filled discontinuities. The lower portion of the failure surf ace appears to occur through the highly altered rock mass. High groundwater pressures and mining at the toe of the slope are documented to have had a major influence on stability at various times during the failure. Stability analyses results are presented and possible remedial measures are discussed.IntroductionHighmont Mine is located near Logan Lake in the Highland Valley approximately 50 km southwest of Karnloops, British Columbia (Fig. I). Mining of the porphyry copper and molydenum ore bodies began in 1980. In May, 1983, when mining in the east pit had progressed to a depth of about 60 m (200 feet) , a failure (designated the Southeast Failure) began to develop in the southeast corner of the east pit. Subsequent mining to a depth of 110m (360 feet) was accompanied by frequent and substantial slope movements involving between 500000 and I 000 000 m3 of rock . The slope was monitored extensively to assess short-term movement trends for operational safety. Geological mapping, core logging and rock mechanics testing were used in conjunction with the long-term monitoring information to determine the failure mechanism, conduct stability analyses, assess the effects of instability on pit design and enable design and installation of remedial measures."

Jan 1, 1988

By N. W. Xu, C. Sha, F. Dai, Y. G. Zhu, B. Li

Underground caverns stability and excavatability of rock masses are of significance in geotechnical engineering, in both design and construction stages. Risks associated with underground group caverns of Houziyan hydropower station in southwestern China are growing as a result of continuous excavation-induced unloading. To improve our understanding of the underground caverns instability and resolve the complex subsurface conditions of the highly fractured rock mass, a high resolution microseismic monitoring system was established in the deep underground caverns, pursuing the relationship between the measured data about microseismic activity and excavation damage zones of surrounding rock mass. Through analyzing the tempo-spatial distribution of microseismic activity, excavation damage zones and potential risk regions in underground caverns were identified. Furthermore, the correlation between microseismic activity and pre-existing geological structures, as well as traditional monitoring was analyzed. In order to validate the correlation between seismicity and potential slip surface of underground caverns, a model was implemented into numerical code to further evaluate the deformation and stability of surrounding rock mass. The monitoring results demonstrate that microseismic events mainly occur at high stress concentration regions, which coincides with the results obtained from numerical analysis. Therefore, the comprehensive method incorporating microseismic monitoring and numerical analysis, as well as traditional monitoring and filed observation has been proven to be very promising in deformation and even instability prediction of surrounding rock mass in underground caverns subject to delineation of potential slip surfaces and excavation damage zones.

Jan 1, 2015

By G. Swan

"The selection of material comprising a backfill is, of economic necessity, site dependent. Nevertheless, given the existing range of typical components-coarse waste, alluvial sand, tailings a balanced or optimal choice is no straightforward matter. A new design approach toward deciding what constitutes an optimum combination of backfill material promises to be useful. In particular a 'binder ' number, based on the mean distance between aggregate particles, specific surface and cement content, is proposed. Using this number, related empirically to compressive strength, the expected mechanical performance of any cemented fill can be predicted.IntroductionOver the years a considerable volume of information has accumulated on mine backfill material design. The principal aggregate component has been deslimed mill tailings, though more recently admixtures of rock waste, sand and tailings are quite common. For these materials uniaxial compressive strength and percolation rate properties are known to be controlled by, among other things, aggregate grading. While empirical formulae exist for relating grading to percolation rates, considerable uncertainty exists concerning strength development."

Jan 1, 1985

By Fred A. Curtis, Kathryn E. Moore

"The past 14 years have brought an increased awareness of environmental problems. Surface mining for mineral aggregates has been one o f the issues which ha s sparked fierce controversy and debate. Various level s of government, industry, and the public have engaged in an unending battle for adequate planning, regulation, and rehabilitation of pits and quarries. Agreement has seldom been reached and, as a result, few standards, guidelines or policies have been established, or enforced province-wide.Surface mining ca uses a number of environmental problems including noise, dust, water table disturbances, aesthetic degradation, increased traffic, and health and safety hazards. These problems are particularly serious in urbanizing area s, where people are exposed to the mining operations. Associated with the operational phase of surface mining are the issues generated by the multiplicity of abandoned pits and quarries which dot the countryside. These large, gaping, often dangerous waterfilled holes are a blight o n the landscape, and represent a misuse of land.The environmental problems connected with pit s and quarries are compounded by the fact that accessible reserves of mineral aggregates are being lost through the process o f urbanization. In addition, restrictive zoning at the municipal level is restricting access to even more aggregate rich land. This results in the paradox that the very urbanizing process which creates the demand for aggregates is rapidly reducing the available supply. These problems have stimulated the Ontario Ministry of Natural Resources to call for a province-wide program of inventory, assessment and planning for the protection o f high-quality reserves in Official Plans. These proposals have met with strong opposition from municipal leaders, who are jealously protecting their autonomy.Environmental management education is a prerequisite for all parties involved in pit and quarry planning, regulation or rehabilitation. To this end the following bibliography of selected articles with attention given to the Ontario experience, should provide helpful information on these topics."

Jan 1, 1985

By E. G. Bazeley

The paper reviews the scope, timing and financial impact of this significant project, which involves the supply and transportation of nearly 4 million tons per year of bituminous coal and lignite from sources in British Columbia. Alberta and Saskatchewan to Ontario Hydro's generating stations. The critical factors involved in the selection and utilization of these coals are discussed in relation to the three types of coal to be utilized initially. The paper then deals with each of the significant project elements to be undertaken by the various companies involved in the mining and movement of the coal, beginning with production at the mine through rail shipment to Thunder Bay, train-to-ship terminalling, shipment by lake vessel from there to the generating station, and finally blending the bituminous coal with United States coal prior to combustion. The review discusses the key features of the facilities involved in each case and the status and timing of the project elements , which are phased for the start of coal shipment by mid-1978. The paper concludes with some observations on the capability of the project to handle increased tonnage s and the challenges facing the movement in terms of quality , quantity and cost.

Jan 1, 1978

By Dogan Paktunc, Larry J. Hulbert, Robert C. Carne, D. Conrad Gregoire

A thin layer of stratiform Ni-Zn-PGE sulfide mineralization of sedimentary-diagenetic origin was deposited during the Middle to Upper Devonian in the euxinic "Nick basin". The mineralized unit (=3 cm thick), which seems to have been developed over the entire sedimentary basin of > 80 km2, consists of pyrite, vaesite (NiSz), and sphalerite. The average grade of the mineralization is about 5.30/0 Ni, 0.73% Zn, =770 ppb (pGE+Au), and up to 61 ppm Re. Anomalous Se, As, Mo, P, Ba and U are present. A minimum of 0.90 x 106 tonnes of Ni were deposited in the basin (based on a bed thickness of 3 cm) during the Devonian. The unique metal association, extensive lateral distribution, persistent metal grade, mineralogical makeup, and stratigraphic control demonstrate that this is a new deposit type and a new geological environment for Ni and PGE + Au. The sulfide layer occurs at the base of a Phosphatic Chert Member which is underlain by a distinctive marker unit consisting of concretionary limestone structures. The limestone spheroids may represent a vent-specific carbonate facies developed adjacent to faults that emanated nutrientrich hydrothermal discharges just prior to the main mineralizing event. The suite of elements associated with the Nick mineralization suggests that the ore-forming metals were originally bound to organic matter derived from decaying marine organisms. Discharge of hot brines bearing organic matter-bound metals took place along numerous conduits within basin faults that are now manifest as bitumen veins. Our syndiagenetic model proposes that these fluids were discharged laterally from the conduits into the unconsolidated bottom sediment (ooze). The introduction of this metalliferous fluid, rich in organic matter, stimulated biological activity and bacterial reduction of its contained 804 to sulfide. Hot, dense, laterally migrating hydrothermal fluid precipitated thin sulfide-rich larninae within bottom sediment. Published thermodynamic studies suggest that the diagnostic vaesitepyrite assemblage crystallized at approximately 138°C. The 034S values range from -14.7 0/00 to -10.00/00 and are up to 340/00 lighter than locally surrounding sulfides and age-equivalent mineralized strata elsewhere in the Selwyn Basin. The Ol3C values of calcite in the footwall of the mineralized unit (- 12 0/00 to -6 0/00) are isotopically much lighter than regional values. The lighter isotopic character is attributed to the hydrothermal discharge of fluids enriched in organic compounds. Although geochemical profiles of the lower Earn Group sediments that host the Nick mineralization reveal that these black shales are not distinctive, the unusual Ni, Zn, PGE, U, Ba, and P elemental associations and their anomalous concentrations in stream sediments can be used to explore for this deposit type.

Jan 1, 1992

By Nicola Robjohns, Kenneth A. Grace, Jane Spooner

"The important volume end use sectors for the rare earth elements and yttrium continue to be in steelmaking, petroleum cracking catalysts and glass polishing. The market sectors which may provide future high volume demand, to replace the older sectors where demand has declined over the past decade, include magnets, automobile catalysts, ceramics and superconductors. Increases in production capacity in all major rare earth producing countries are expected to restrain large price increases for high purity rare earth oxides over the short term. A sharp increase in demand for yttrium in advanced ceramics and superconductors would lead to a shortage in separation capacity, however, and to a corresponding rise in prices for separated rare earths.IntroductionWhile visiting the Geology Department of the University of Toronto in 1981, Professor Lu from the Institute of Geochemistry of Academia Sinica at Gweiyang in China introduced one of his seminars with the observation that in China, rare earths are not rare at all.Indeed, while being rare in terms of abundance as measured by, say, the Clarke scale, the rare earth elements, like many other low abundance elements, are subject to geological, geochemical and mineralogical concentration.The rare earth elements comprise the fifteen inner transition elements of Group IIIB, Period 6, of the periodic table, from lanthanum to lutetium (the lanthanides), as set out in Table 1. The rare earths constitute a distinct group as they have extremely similar chemical characteristics due to the uniformity of their outer electron shells. The element yttrium is usually, by convention, included in the rare earth group as it occurs with the rare earths in nature and has properties very similar to them.The rare earths are divided into two subgroups, the ""light"" rare earths, made up of the first seven elements of the series, lanthanum to europium, and the ""heavy"" rare earths, comprising the remaining eight elements, gadolinium to lutetium, plus yttrium. These two subgroups are also referred to as the cerium subgroup and the yttrium subgroup, respectively. The subdivision is based on differences in the atomic radii resulting in somewhat different properties for the two subgroups."

Jan 1, 1991

By Nobuyoshi Yabuki

Building Information Modeling is a prevailing methodology in the building industry and half (by length) of the world's shield tunnels are in Japan. Accordingly, for shield tunnels from 2005 to 2007, we developed a product model called IFC-ShieldTunnel, which is based on Industry Foundation Classes (IFC), in order to meet the future demand for such a product model. IFC-ShieldTunnel was developed by adding new elements that are specific to shield tunnels and that are not included in the original IFC. The added elements include shafts, segments (A, B, and K types), waterproofing elements, segment joint elements, and ring joint elements. Furthermore, soil layers and void elements were created. Recently, we updated the product model by re-organizing the entities and correcting errors. We deployed the updated IFCShieldTunnel model in the construction of an actual shield tunnel in Tokyo for about a year from August 2010 in order to check its feasibility. In the verification process, first, segments were modeled using Autodesk Revit Structure 2011 and property data were assigned to each segment element. Next, a mapping between the original attributes of the entities of IFC and properties of IFC-ShieldTunnel segments was developed. Using this mapping and IFC?s IfcBuildingElementProxy function, we were able to convert the IFC data from Revit Structure 2011 to IFC-ShieldTunnel automatically. Segment data were also converted from Revit Structure to Google SketchUp by IFC-ShieldTunnel. Furthermore, the construction scheduling and cost data were converted from Revit Structure to EXCEL for 4D and 5D analyses of construction. We interviewed engineers who used IFC-ShieldTunnel and received positive comments about the utilization of the product model. Overall, our test demonstrated the feasibility of IFC-ShieldTunnel. In future work, we plan to apply IFC-ShieldTunnel to more projects and test its practicality.

Aug 1, 2013

By Ming’an Wei, Qifu Duan, Chengtie Wang, Jianmin Wu, Erdenet Mining Corporation, Lusheng Zhou, Wenjian Wu

"The development and industrial applications of magnetic liners have been around for decades. A Swedish company SKEGA first introduced the rubber magnetic liner, and then followed by the Chinese metal magnetic liners. Traditionally, both liners were used in secondary and regrind ball mills, especially for ores containing magnetic materials. Mostly steel balls or equivalent forged balls, usually below 60 mm in diameter, were used as grinding media. With the development of mineral resources over the years, SAG mills and larger ball mills have become the dominating components for comminution circuit design globally. Due to the larger ball mills and thus larger grinding balls (up to 80 mm) especially in non-ferrous metal industry, the application of magnetic liners has been very limited. Based on the new development of materials, the HMR Group Limited has been exploring new designs of magnetic liners which led to the invention of the Nano Steel Magnetic Liner (NSML). Recently, NSML had a successful application in a 5.5m x 6.5m ball mill with 80 mm balls at the Erdenet Copper Mine in Mongolia. Although the first set of liner had a service life of 12 months, the design of the second set was modified and improved to accommodate the operating conditions, which is expected to reach least 24 months service life. The original manganese steel liner only had about 8 months liner life.1. IntroductionMineral processing is an essential operation for the development and utilization of mineral resources. The effective concentration of various useful minerals depends on sufficient liberation of the mineral particles in the ore. The crushing and grinding process such as ball milling are the most common way to achieve proper liberation size. Mill liner is an eternal topic for the operations, not only because it protects the equipment, but also affects the mill grinding efficiency and availability. In recent years, magnetic mill liners have been developed that can easily meet the production targets with numerous benefits, such as zero maintenance, reducing specific energy consumption and improving grinding efficiency."

Jan 1, 2016

By C. O. Campbell

THE recognition by C. W. McKee, field engineer for Springer Sturgeon Gold Mines, Limited, in the fall of 1940, of the economic possibilities of a small outcrop of baryres near Pembroke, in Hants county, Nova Scotia, followed by aggressive exploration and development by the Company, has placed Canada for the first time in its history in the position of becoming a major producer of barytes and its products. In past years, production of this mineral in Canada has been unimportant. Thus the coral output from 1885 ro 1933, inclusive, amounted to only 41,027 short tons, following which there was no production until 1939. Deposits in Nova Scotia, and particularly in the Lake Ainslie district, Cape Breton, have been the main source of supply, with a production between 1866 and 1925 of 31,689 tons. Following the examination of the outcrop of baryres near Pembroke by Mr. C. W. McKee in October, 1940, the area surrounding it was trenched, and, as this work gave encouraging results, a diamond drilling programme was commenced. A grid system was laid our and sixteen holes aggregating 2809.3 feet were put down, spaced at 100-foot intervals, the deepest hole being 300 feet. This drilling outlined a body of high-grade baryres over 600 feet long and 200 to 250 feet wide, with an average depth of 120 feet and estimated to contain well over one million tons of ore. The limits of the body were reached on the west, north, and southwest, but the drilling was suspended before the eastern limit was determined. Quarrying operations, and construction of a 100-ton mill, were commenced in February, 1941. The mill was placed in operation on May 29th, and on June 15th, eight months after the initial discovery, the first shipment of 2,500 long rons of milled baryres was made to Trinidad, British West Indies.

Jan 1, 1942

By R. E. G. Caines, P. Alport

"Operating heavy equipment in Labrador, where the winters are 8 months long and the temperature frequently drops below -40°F (-40°C) for days and sometimes weeks presents unique problems in both the operation and maintenance junctions. Winterization programs must be well designed and implemented at the proper time. These programs must include the proper selection of fuel oil, engine oil, hydraulic oils, greases, cooling system fluids, etc. More often than not, modifications have to be made to the original equipment in order that it can be operated safely and economically in the Canadian North. Manufacturers usually design equipment for a less harsh environment and the user makes adaptations by trial and error.Operators have to be trained for the proper operation on ice- and snow-covered roads in an open-pit mine. Special emphasis must be put on haulage road conditions. In this paper, the authors will cover some specific maintenance procedures, equipment modifications and operator training problems experienced by the Iron Ore Company of Canada in its open-pit operation in Labrador.IntroductionT he Iron Ore Company of Canada is engaged in open-pit mining , concentrating and pelletizing of iron ore. The company operates in two provinces, Quebec and Newfoundland (Fig . 1) . The Knob Lake operation "", based in Schefferville, Quebec, has mine sites located both in Labrador and Quebec . The Caro l Lake Project is situated in Labrador, 25 kilometres east o f the Quebec border at Labrador City. The Carol operation mines, concentrates and pelletizes it s o re before rail transportation to the seaport o f Sept-lies via the Quebec North Shore and Labrador Railway."

Jan 1, 1984

By William F. Caley, A. MacKinnon, P. W. Kingston

"The purpose of this paper is to identify a number of currently available opportunities for exploration and/or mine development in the industrial minerals field in southeastern Ontario. The paper is not intended as a complete review of the industrial minerals industry in southeastern Ontario, but highlights what are seen by the authors as areas where there are immediate opportunities for investment and growth.Traditional exploration targets in the Grenville Supergroup in southeastern Ontario have been vein-hosted gold deposits, industrial minerals, and base metals. In recent years, emphasis has increasingly shifted to industrial minerals, in response to changing technologies in the minerals-consuming manufacturing industries, and to an increasing awareness of the industrial mineral potential in this area.This paper examines the resurgence of interest in exploring for and developing a wide variety of industrial minerals, and it examines the work the Ontario Ministry of Northern Development and Mines has done under the current Canada-Ontario Mineral Development Agreement. Specific development opportunities are identified in various commodity areas. Use oj the industrial minerals wollastonite and nepheline as substitutes for fluorspar in the formulation of synthetic steelmaking slags is also discussed."

Jan 1, 1990

By Robert B. Parsons

"A joint federal/provincial/industry subcommittee of the Intergovernmental Working Group on the Mineral Industry (IOWG) has published an informative and readable report on taxation matters concerning Canada's mining industry. The report, which was presented to the federal and provincial mines ministers in September 1986, identifies and discusses key tax issues relating to this industry. The report is mandatory reading for anybody with an interest in mineral exploration or production in Canada.IntroductionIn 1986, Canada's federal and provincial mines ministers were presented with an important report concerning the taxation of this country's mining industry. This document is important for a number of reasons, two of the reasons being: first, the report contains an objective analysis of the key mineral taxation issues of the day; and, second, the report is the product of a cooperative exercise involving representatives of various facets of the industry and government. The report should be regarded as compulsory reading for anybody who has an interest in fiscal matters affecting mineral exploration and production.The ""Report on Fiscal Proposals"" was prepared by a subcommittee of the Intergovernmental Working Group on the Mineral Industry (IOWO). IOWO is a group of senior federal, provincial, and territorial government officials concerned with the analysis of mineral policy issues in Canada."

Jan 1, 1986

There are many inherent risks in creating a mine plan for a new ore zone in an underground mine; one of such risks is the redistribution of stresses that could be a cause of instability. Using numerical modelling tools, it is possible to model the planned stope extraction sequence and evaluate the influence of mining induced stresses on the stability of remnant pillars, and use this information to remedy potential setbacks. This paper demonstrates this approach through a case study of the short-term mine plan of the Lapa mine of Agnico Eagle Mines Ltd., an underground gold mining operation near Val d?Or. Three-dimensional boundary element modelling is used to compute the stresses induced by the stope extraction sequence as planned with a longitudinal retreat mining method. The proposed methodology can be generalized to other mines that require an understanding of the stress concentrations at the pre-feasibility stage of mine design.

May 1, 2009

By L. Voisin, G. Damm

"In order to develop a new pyrometallurgical process for eliminating detrimental arsenic and antimony from the impurity-rich matte produced from copper concentrate, and for treating the occasionally generated speiss in nonferrous smelting processes, the phase relations in the Fe-Cu-S-As-Sb system saturated with carbon at 1473 K were investigated. The distribution of elements between the condensed phases at the miscibility gap, where three equilibrated phases of iron-rich alloy, copper-rich alloy, and matte coexist, were also studied. The investigation was carried out by performing a series of laboratory scale experiments in an electrical furnace at 1473 K, followed by a quenching method on the final stage. The samples obtained from the experiments were analyzed by using Inductively Couple Plasma (ICP), Atomic Absorption Spectroscopy (AAS) and Carbon Infrared Spectrometry (CIS) techniques.The results were compared with previous investigations for the Fe-Cu-S-As-C and Fe-Cu-S-Sb-C systems and discussed on the basis of the molar fraction distribution for both arsenic and antimony in the matte phase at five different matte grades. It is expected that by using this phase separation technique it might be feasible both, the cleaning of a complex copper matte and the elimination of arsenic and iron together with an acceptable amount of antimony into the iron-rich alloy phase, which can be discarded as a harmless and smaller deposit."

Jan 1, 2014

By M. L. Jeremic, G. J. P Delaire

"The mechanical aspects of cable bolt failure are considered from the point of view of properties of grout and cable, as well as of the rock in which it is anchored. The results from recent investigations made in-situ as well as in the lab are combined and presented with reference to other work done in the area. An attempt is made to stimulate the thinking along these lines so as to initiate further research which may enhance the design of cable bolting as it applied to mining operations.IntroductionIn the past twelve year s systematic cable bolting has found application in many areas. In civil engineering rock anchors have been used to provide tension at the heel of a dam permitting the reduction of its cross section. They have been used in retaining walls to reduce construction time and costs by eliminating the need for struts and braces which complicate pouring the foundation walls. It is also possible to use rock anchors in providing reactions where tall buildings are subjected to uplift on one side due to wind forces. Cantilever bridges may be constructed by implementing rock anchors to provide anchorage requirements. Anchorage piles or dolphins or mooring ships have also been built using these. In the mining area rock anchors, commonly known as cable bolts because they are made of hoist cable may be implemented in the reinforcement of hanging walls or to retain rock slopes.In order to sustain de-pressurized ground where rock separation developed along the pressure arches, cable bolts were utilized at the Tsumeb Mine in South-West Africa and also at the Strathcona Mine in Sudbury, Ontario, In both places old degreased hoist ropes were installed in downholes from crosscuts above a given stope and then grouted without tensioning. Jeremic and Cassidy described the use of cable bolts to increase hanging wall stability and postpone fracturing, in addition to producing pre-support for improvement of stope back stability."

Jan 1, 1983

By D. F. Machuca-Mory

The new algorithm for high-order simulation of ore deposit grades termed HOSIM is based on the concept of spatial cumulants. The algorithm is tested using data from Apensu, a structurally controlled gold deposit in Ghana. The required high-order spatial structures are obtained from a training image or analogue of the deposit. Using the available drillhole data and training image, HOSIM realizations are able to model well the grades and geometry of the large and well sampled mineralized structures. However, under-sampled small structures remain difficult to model. HOSIM offers a promising alternative for the spatial simulation of complex non-Gaussian orebody attributes of interest.

Jan 1, 2011

By J. Schmidt

Cold drawing of copper wire rod is usually combined with an in-line annealing process to adjust the ductile microstructure of the wire again. One important key factor for successful annealing is the quality of the copper itself. Rod producers can check the recrystallization behaviour of the rod by different methods: chemical analysis, Spiral Elongation Test (SEN) as well as the Rapid Elongation Test (AR) are some examples of common testing methods. The comparison of the results of these methods does not always show sufficient correlations. The paper introduces firstly the SEN and AR-Tests and their different approaches to the mentioned task. The second step is to compare some results of the SEN-Test with the results of the AR-Test and identify causes of deviations. Thirdly, the effect of pre-annealing is discussed, which is especially common for wire rod with diameters of more than 8 mm.

Jan 1, 2007

By A. A. Bakke

"The Fort Knox gold deposit is hosted within the Fort Knox Pluton, a Cretaceous multiphase granitic body that intrudes the Fairbanks schist. Gold occurs along the margins of stockwork veins and veinlets, quartz-filled shear zones, and along fractures within the granite. The mineralization is generally sulphide-poor and closely associated with trace amounts of bismuth, tellurium and to a lesser extent with molybdenum and tungsten. At present, proven/probable reserve estimates, based on a cutoff grade of 0.39 g/t Au, are 158.3 million tonnes grading 0.83 g/t Au.The Fairbanks schist comprises the bulk of the country rock. The dominant lithologies present include muscovite-quartz schist and micaceous quartzite. Immediately north and south of the main orebody, mixed metamorphic lithologies of the Cleary sequence, a subunit of the Fairbanks schist, have been mapped. Development of local zones of weakness, most likely due to a broad regional warping event, resulted in brittle-ductile deformation and activation of a northwest-southeast shear couple between contrasting lithologies.The Fort Knox Pluton consists of at least three phases based primarily on textural differences. Intrusion of a fine-grained granite was followed by a medium-grained porphyritic granite. The youngest intrusive phase is a coarse-grained, seriate porphyritic granite, the Vogt Stock. The Vogt Stock forms an elongate dome with the axis in the east-west direction. Structures displayed in the overlying units, believed to be the result of doming, include tension fiSSUres and longitudinal fractures.Premineralization fractures, the result of the magmatic doming, provided conduits for initial stockwork quartz vein development and quartz enrichment in shear zones. Weak development of vein-controlled phyl/ic, potassic, albitic, and argillic alteration styles are present. Evidence of a late thermal event resulting in a low-temperature alteration assemblage of calcite + zeolite (stilbite) + chalcedony + clay occupies breccia zones, joint surfaces, and fractures within the granite."

Jan 1, 1995

By Brian Putland, Fred Kock, Leigh Siddall

Single stage semi-autogenous / autogenous (S/AG) milling has become a common design for a variety of ore types with the advantages of being comparatively low capital cost and flexible for future expansion. The single stage SAG/AG milling option is ideal for starter projects with significant exploration and expansion potential. Currently a number of the largest SAG mills designed are installed in single stage configuration. This paper discusses the challenges associated with the process design of single stage SAG/AG milling circuits, the design flexibility required to ensure a robust circuit and the operating techniques adopted at successful installations.

Jan 1, 2012