Search Documents

By Bilodeau M. L

The paper describes a model which has been developed to assess the economic charac- teristics of base metal investment in Canada and the effects of past, present and possible future sharing systems, particularly mining taxation systems, thereon. The model is illustrated by applying the 1976 Canadian tax system to the economic characteristics of base metal discoveries made in Canada during the 1951-1974 period.

Jan 1, 1977

By R Benton

Since commencement of underground production in March 2006 the Kencana K1 orebody has delivered over 0.9 Mt of ore containing 1.18 Moz Au until April 2009. The Kencana deposits are part of the Gosowong goldfield located on the island of Halmahera in eastern Indonesia. The district has produced over 2.3 Moz since mining commenced in 1999 with the first two deposits extracted by open pit methods. The K1 deposit is technically challenging being a vein style deposit with poor to very poor ground conditions and a relatively low overall dip of around 45 degrees to mine grid east. It is mined under geological control by underhand cut and fill methods utilising cemented paste backfill aiming for 100 per cent extraction. With these conditions the operation was mine limited in the initial two years of production resulting in low stockpile levels for mill feed blending and hand-to-mouth mine to mill production. Mill feed rates have increased from 30 t/h to 55 t/h over this period following business improvement projects while mine production has escalated to match this increase as deeper levels of the deposit are accessed. The operation has now become mill limited. Monthly mill gold production from Kencana has ranged up to 50 000 oz with head grades ranging between 8 g/t and 122 g/t Au on a daily basis. As individual grade control assays can extend into the per cent Au range there are challenges in sampling, modelling, mining, blending and milling the Kencana orebody. At the time of commencement of ore driving in K1 the national geology team had little prior experience in underground mining and systems were in early development. The variances in feed grade and tonnages have been reduced with time as the operation evolves and business improvement initiatives are undertaken to smooth peaks and troughs in ore supply. Two such initiatives in the geology department have added over US$20 M of additional revenue per annum.

Jan 1, 2009

The Golden Valley Volcanic Centre has been recently interpreted as being a combination diatreme breccia pipe and rhyo-dacite flow dome complex of Permo-Carboniferous age that intrudes basement granitoids and sediments of Ordovician-Devonian age. Exceptionally good exposure at the Centre has enabled the relationships between different lithologies to be determined. This, along with petrological studies, has led to a detailed understanding of the geological environment in which the complex formed. Gold, silver and base metal mineralisation have been recently shown to be associated with the Marginal Breccia at the perimeter of the diatreme. Comparisons have been made between the geology and mineralisation in this system and several similar diatremes which also contain gold-base metal sulphide mineralisation.

Jan 1, 1990

This paper is based on studies made intermittently from 1937 to 1950. Its object is to describe the surface geology and the tin lodes, and to relate the lodes to the structure of the field.PREVIOUS REFERENCESR L. Jack made his first report on the field in 1880, but his principal report was made in 1883. W. E. Cameron described the Great Northern lodes in 1904. Numerous later reports on various mines were made by L. C. Ball, J. H. Reid and C. C. Morton, the most important of which were on the Black King, Good Friday, St. Patrick and the Great Northern Gully Shaft.GENERAL GEOLOGYJensen maps the Herberton area as part of a granite massif intruding rocks of two ages, the Younger Metamorphics of Silurian-Devonian age, and the Older Metamorphics of Older Palaeozoic age. The distinction is apparently based on lithological data. The Older Metamorphic rocks occur as inliers in the granite massif to the west and east of Herberton (Fig. 1).The area described consists of granite traversed by numerous dykes. West of the area, approaching the Older Metamorphic rocks, the granite becomes finer grained as if chilled towards its contact, and the dykes more numerous. To the east, passing from the Nova Scotia mine to Mount Lavery there are numerous dyke rocks, but the outcrops are poor and knowledge of the geology indefinite. The area is the main tin-producing area. To the west there are comparatively small tin lodes in the granite, and the "Copper Firing Line" occurs in the Older Metamorphic...

Jan 1, 1951

By Quast K

A series of laboratory flotation tests were conducted to evaluate the effectiveness of various depressants as arsenic (and zinc) depressants in the lead cleaner stage of the NBHC mill at Broken Hill. The depressants used included potassium cyanide, ferrous sulphate, sodium hypochlorite, potassium ferricyanide and two Cyanamid commerical depressants, Aerodepressants 610 and 633. A standard roughing stage was completed before the addition of the reagents in the cleaning stage. All reagents tested produced significant arsenic depression, with the best results being obtained with the addition of potassium cyanide and sodium hypochlorite. Some of the depressants activated the zinc in the process of arsenic depression. The best result was obtained with the addition of 90 g/t potassium cyanide at a pH of 10 when arsenic recovery was only 1/4 that of the value obtained for the standard test.

Jan 1, 1991

Since 1958 there have been 16 major coal mine explosions in the U.S. claiming 323 lives. Whilst the exact cause of a number of these incidents has not been determined, the majority has involved gas ignitions in one way or another. In addition there have been fatal gas explosions in salt mines and vapor explosions in oil mines. Furthermore, many of the oil shale mines in the U.S. have proven to be gassy giving cause for concern. Compounding these problems is the fact that frictional ignition of methane in coal mines has dramatically increased over the past several years; over 100 such ignitions were reported in 1979. While, no fatalities have been attributed to frictional ignition in the U.S. since early 1978, a recent mine explosion in Nova Scotia which resulted in 11 fatalities was attributed to a frictional face ignition. Research being conducted at the Bureau of Mines is aimed at the prevention and suppression of gas explosions. Emphasis is placed on new coal cutter bits for reducing ignition frequency, machine-mounted water sprays for preventing frictional face ignitions and automatic devices for quenching incipient ignitions and fully developed gas explosions.

Jan 1, 1981

By Jepsen L, Gifford M, Thomas G. S

Mine planning requires careful prediction of both the head grade and tonnage of mineralisation. As part of the planning process, operators of the Murrin Murrin nickel/cobalt orebodies (located in the Eastern Goldfields province of the Yilgarn

Jan 1, 1998

By Laage L. W

line fires pose a serious threat to the safety of all underground personnel. Early knowledge of the location of a fire in a complex underground mine would greatly reduce the associated risks by enabling miners to choose the safest escape routes, rescue teams to concentrate searches where survivors would most likely be found, and fire fighters to select the most efficient route to the fire and the most effective fire fighting strategy. Once'the fire's location is known, other related aspects of the fire can also be inferred, such as intensity, fuel, and growth Rate.

Jan 1, 1988

Economic conditions dictated the lead time from concept to commissioning of the Kambalda C.I.P. Plant. The high gold price prevailing at the time the Victory ore-body was discovered provided the impetus to establish a treatment plant with the utmost haste. Consequently only limited metallurgical testing was possible. Fortunately the Kambalda Metallurgical Department had experienced gold metallurgists among its' staff. This enabled a rapid assessment to be made of the ore types to be treated. Flexibility was the keynote in the plant design. Overseas practice and experience was drawn upon extensively, but it was known that problems uniquE to the Kambalda Plant would be encountered due to the high nickel content of the C.I.P. Plant feed and the difficult clays in some of the areas. These fears were well founded and problems have been experienced. However the plant design has enabled these problems to be absorbed, if not overcome, and design production rates were achieved and maintained within three month; of start-up.

Jan 1, 1982

The Honeymoon Well nickel sulphide deposits are located in the Agnew-Wiluna greenstone belt, about 45 km south of Wiluna. Both disseminated and massive sulphide nickel deposits are hosted by komatiitic rocks within the deformed and metamorphosed Honeymoon Well ultramafic complex. Fresh ultramafic bedrock is covered by up to 50 m of highly conductive transported material which greatly hampers both exploration and understanding of the bedrock geology. In the early-1970s, mineralisation was discovered by diamond drilling geochemical anomalies defined by wide-spaced percussion drilling over ultramafics that had been outlined by ground magnetics. Subsequent drilling has defined a resource of 158 Mt at 0.71 per cent nickel (based on 0.4 per cent nickel cut-off, 300 m below surface, December 1995) in four deposits. Over the life of the project a wide range of geophysical techniques have been used including airborne and ground magnetics, time domain clectromagnetics (EM), induced polarisation (IP)/resistivity, gravity and downhole techniques including EM, IP and physical property Measurements.

Jan 1, 1996

By Williams D. J

The boundary element method is one of a number of tools that have found wide application in geomechanics for mine design and stress analysis. Two examples are presented in this paper, illustrating the use of the boundary element method to find potential problem regions in large-scale excavations. These examples are from a Papua New Guinea open cut mine and an Australian sub-level caving operation. Because of the scale of the mines and the complexity of the excavations, the boundary element method is the only practical numerical modelling technique to account for the major influences. Although the boundary element method uses only linear elastic models of the rock mass, the paper illustrates techniques for dealing with non-homogenous and anisotropic rock masses, as well as clasto-plastic effects associated with an excavation.

Jan 1, 1995

By Donchak PJ, Lang SC, Hammond RL, Bultitude RJ

The Hodgkinson and Broken River Provinces form the northern part of the Tasman Orogen. They are separated by a broad belt of Late Palaeozoic igneous rocks, but were probably originally continuous. They are bounded to the west by a system of major faults (Fig. 1) which separate them from the Georgetown Province. Although largely Precambrian, the Georgetown Province includes probable Siluro- Devonian granitoids, and in the south adjacent to the Broken River Province, metamorphosed Early Palaeozoic(?) volcanics and sediments of the Greenvale Subprovince. South of the Broken River Province, the Lolworth-Ravenswood Province includes probable Precambrian rocks, Cambro-Ordovician volcanics and sediments, and voluminous Ordovician to Early Devonian granitoids. The first systematic studies of the provinces were the 1:250 000 scale mapping programs by the Bureau of Mineral Resources and Geological Survey of Queensland (White, 1965; de Keyser and Lucas, 1968). These and subsequent regional studies were reviewed by Arnold and Fawckner (1980). Remapping by the Geological Survey of Queensland since 1982, and a concurrent regional study of the deformation by Hammond (1986) have provided much new data. We acknowledge the contribution of other members of the GSQ field parties - L. Cranfield, J. Domagala, B.G. Fordham, P. Green, R. Halfpenny, R. Hegarty, L. Hutton, S. Law, D. Macansh, T. McLennan and M. Scott.

Jan 1, 1987

The traditional concept of optimum drill and blast is that it is achieved when ore is produced at the lowest unit cost and, because of the complexities of most mining operations, represents a band which extends either side of an overall cost m

Jan 1, 1998

The major coalfields of Australia are almost unique in the occurrence in some areas of CO partly or almost completely replacing CH4,t1e normal seam gas from metamorphism of coal due to time and depth of burial. This CO2 situation has some benefits but mostly it introduces particular safety problems result- ing from the high density of CO2 relative to air, magnifying problems of gas dilution in ventilation, and the greater affinity which coal has for CO2 than for CH4 increasing proneness to gas-dynamic phenomena. The occurrence of most CO2 seam gas can be directly related to igneous intrusion and to its associated pneumatolytic injections. Whilst intrusions locally increase the rank of coal by their contact metamorphic effect, normal coal metamorphism due to time and depth of burial continues after intrusion and injection together with the ongoing metamorph- ic production of CH . This new CH slowly displaces any CO to leave some present-day intruded coals with seam gas with reduced CO2 or even without any significant CO2 associat- ions. The seam gas maps of the Bowen and Sydney Basins and more detailed maps of specific areas exemplify these situations. Mining progress, plus more searching studies of igneous-coal relationships provide improved understanding of the factors involved.

Jan 1, 1986

Mining companies in order to compete and succeed in being viable business propositions must look to the future and select mining methods which guarantee improved efficiency and productivity as well as lower costs.A mining company in adopting a method of mining must now select the equipment most compatible. To some mines compatible equipment may mean the use of drilling jumbos to replace hand held rock drills or the use of load haul dump units to replace scrapers. To other more mechanized mines compatible equipment may mean the use of raise borers and road heading machines. The right decision will be where equipment compliments method in such a way that the working environment is improved, productivity is maximized, cost if reduced and all profit opportunities are optimized. An example of such is where the use of improved mining techniques in underground operations may see cut off grades reduced. By selectively mining these lower grade orebodies, smaller operation's ore reserves improve and the capacity for continued growth is enhanced.

Jan 1, 1990

By A Kuras

Segmental tunnel linings are becoming more common in Australia. One current project employing a segmental lining is the City West Cable Tunnel (CWCT) in Sydney. The project has been commissioned by Energy Australia and is currently being constructed by Thiess Pty Ltd. The project includes 1.6 km of tunnel boring machine (TBM) driven, segmentally lined tunnel. The majority of the CWCT will be excavated through Hawkesbury Sandstone. The tunnel is required to carry a 132 kV electrical circuit under SydneyÆs central business district (CBD), between Haymarket and Energy AustraliaÆs City North Substation on Sussex Street. The segmental lining has been designed as a 3.2 m internal diameter, 200 mm thick universal ring with six trapezoidal segments. The design and detailing of this segmental lining presents some noteworthy challenges, including exposure to saline groundwater, and the exclusive use of steel fibres for flexural and tensile concrete reinforcement. This paper describes some of the key elements of the segmental lining design. These include:the case for choosing segmental linings over other forms of tunnel construction;the major design checks required of a segmental lining including ground loading, hydrostatic loading, joint bearing, joint rotation, ram loading and the early strength lifting case;the benefits of using steel fibres over conventional steel reinforcement;the design approach used for steel fibre reinforced concrete;the application of 3D computer modelling in the design;the provision for components including connector dowels and gaskets;the design for passive fire resistance; andthe design for durability of steel fibre reinforced concrete in a saline environment. Segmental lining design requires the application of specialist design approaches. Input is required by the construction team, as the methods of demoulding, handling, transportation and installation impact on the lining design. As the segmental lining is functioning as immediate ground support and also a permanent lining, high standards of manufacture and construction quality control are required to ensure that the 100-year design life is met. The requirement for a watertight tunnel means that detailing and installation of the EPDM gaskets is of importance.

Jan 1, 2008

In mineral asset valuation the use of any valuation method requires the input of competent and independent technical professionals. A resource valuation must be as transparent as possible to allow others to assess the validity of their underlying assumptions. Materiality is a dominant factor in all valuations and a valuer should set out the basis for the subjective decisions made in this regard. Any valuation methodology must comply with the requirements of the law, practice notes and guidelines issued by the various relevant authorities and professional bodies. The valuation methodology chosen to value a mineral asset depends upon the amount of data available on that asset and the reliance that can be placed upon those data. Mineral assets generally fall into one of three broad categories, depending upon their state of development, ie whether they are at the exploration, development or operating stage. Naturally there are transition phases. Hence, there are ""Grass Roots"" Exploration Areas and Advanced Exploration Prospects; Pre-Development Projects and Developing Mines; and Operating Mines. The features of each of these mineral asset status categories are described, mainly in terms of the confidence in the contained identified Resources/ Reserves. The various subjective methodologies available for the valuation of ""Grass Roots"" Exploration Areas and Advanced Exploration Prospects -are specifically reviewed. The pitfalls in adopting a ""recipe"" approach are noted. It is the author's view that the Expected Value Method (based on the probability adjustment of the output of a Discounted Cash Flow/ Net Present Value model) has little application in the valuation of exploration mineral assets, so it is only briefly addressed. The methodologies reviewed are listed below. ò Multiple of Exploration Expenditure Method (expenditure based). ò Joint Venture Terms Method (expenditure based). ò Geoscience Rating Methods (eg Kilburn - area based). ò Comparable Market Value Method (real estate based). ò Rules of Thumb (eg $/Resource or production unit; % of in situ value). Some recent Prospectuses are used to provide examples of their misinterpretation and misapplication.

Jan 1, 1994

The reasons for selecting two stage pebble milling in preference to conventional methods of grinding are discussed. Commissioning of the first section was completed in October, 1969. Improvements in both the operating and engineering aspects were then incorporated in the section commiss ioned in March, 1971.

Jan 1, 1975

By Wilson CJN

The central Taupo Volcanic Zone is a region of intense Quaternary silicic volcanism accompanying rapid crustal extension. Modem central TVZ is the most frequently active and productive silicic volcanic system on Earth, erupting rhyolite at c. 0.28 m' s'. The rhyolites show no major compositional changes with time, but the total extent of magma chamber zonation has changed with the advent of rifting and crustal extension at c.0.7 Ma. At least 34 caldera-forming ignimbrite eruptions have formed a complex sequence of relatively short-lived, nested and/or overlapping volcanic centres in central TVZ. Taupo contrasts with other large silicic magmatic systems in the exceptionally high frequency, but small size, of caldera- forming eruptions. This contrast reflects the thin, rifted nature of the TVZ crust, that precludes the development of long- term magmatic cycles at Taupo.Within central TVZ, non-rhyolitic compositions have been erupted apparently irregularly in time and space; in particular there is no evidence for a geographic separation of basalts from andesites. TVZ is a rifted arc, but its segmented nature, high thermal flux and voluminous rhyolitic volcanism make it unique on Earth.

Jan 1, 1995

A thick sequence of alkaline intrusions and volcanic rocks underlies a Quaternary caldera on Liliir Island. The sequence is host to a still active sub-aerial hydrothermal system and associated epithermal gold mineralisation. Sub-horizontal alteration horizons exhibit progressively increasing chondrite norma-lised (La/Lu) en and (La/Sm) cn ratios from unaltered shoshonites, to the potassic alteration zone, to the argillic altera-tion zone to the advanced argillic alte-ration zone. The increasing fractionation of HEE, and especially of LHEE, up the alteration sequence is the result of de-creasing pH, temperature and alkalinity of the hydrothermal fluids with increa-sing alteration intensity. HRE3 were especially mobile in argillic and advanced argillic alteration units characterised by acid fluid conditions and large fluid volumes. Abundant Cl, S and CO2 within the hydrothermal fluids and thus abundant REE complexing agents and large fluid volumes favoured the mobility of REE during hydro-thermal alteration of the volcanic rocks and intrusions. Steam escape, mixing of the gases with groundwater and a change from a magmatic neutral chloride hydro-thermal system to a meteoric acid sulphate system was accompanied by liquid/vapour ratio changes, pronounced alkalinity, pH and temperature decreases, and fluid/rock ratio increases. This caused the mobili-sation, fractionation and deposition of PF.F.

Jan 1, 1990