Search Documents

By I D. Hair

A numerical groundwater model was used to predict the nature of interactions between heavy mineral sands mining operations and the groundwater regime at North Stradbroke Island, Southeast Queensland. North Stradbroke Island is formed mainly of massive vegetated Cainozoic aged dune sands. Since the 1950s, a number of operations have mined rutile, zircon and ilmenite on North Stradbroke Island. In such mining operations, a dredge and an associated processing plant are floated in a pond either above or below the prime groundwater table The numerical model was based on the North Stradbroke Island Groundwater Management Model, developed in 2001 by the Department of Natural Resources and Mines (NR&M). This model was constructed using the modular, cell-centred, finite-difference groundwater flow model, MODFLOW, developed by the United States Geological Survey (USGS). The NR&M model was refined to improve model resolution and detail for simulating dredge mine paths. Of particular interest were: water table fluctuations induced by mining for the identification of slope stability risk; the optimisation of sand spear arrays supplying mine make-up water requirements; inflow and outflow rates to the dredge pond for overall mine water balance; and interactions with Eighteen Mile Swamp and water supply bores controlled by the Redland Shire Council (RSC). Depending on the water level in the dredge pond compared with the surrounding groundwater table, water either flows out of the dredge pond into the groundwater regime or from the groundwater system into the dredge pond. The MODFLOW river package (RIV) was utilised for the modelling study. Dredge pond movement was simulated using specialised software developed by Watermark Numerical Computing (WNC) to interpolate pond positions and map the dredge path to the model grid both spatially and temporally. As tailings placement affects the groundwater system through increased recharge, the MODFLOW recharge package (RCH) was utilised to simulate different recharge efficiencies. Long-term model predictions were made for the period from July 2002 to May 2021. Results of the modelling showed that exchanges of flow between mining operations and the groundwater regime could be effectively managed. The study provided valuable information which was used to develop an appropriate mine water management plan.

Jan 1, 2003

By Tuite M. J, Woolcock L. J

The Awak Mas gold project is located in the Province of South Sulawesi, Republic of Indonesia. It is situated 300 km by road north of the provincial capital of Ujung Pandang. The capital is readily accessible by air from Australia via Denpasar on Bali or the Indonesian capital, Jakarta (Figure 1). Elevations at Awak Mas range from 850 to 1400 metres above sea level in reasonably rugged terrain. The area is covered by primary and secondary (regrowth) rain forest. The region is subject to an equatorial-type tropical climate. The annual rainfall is a high 3000 mm most of which falls in the rainy season between March and June. In the lower valleys rice, cloves and chocolate crops are cultivated. Title to the project area is secured by a Contract of Work (COW) issued to PT Masmindo Eka Sakti (MES) on 23 October 1987 by the Government of Indonesia. MES was controlled at the time by New Hope Industries group of Brisbane. After New Hope had completed initial reconnaissance exploration of the area, Battle Mountain Gold Company (BMGC) farmed-in in 1991 and earned a 60 per cent beneficial interest in MES.

Jan 1, 1996

By L Lagoeiro

The samples studied in this paper were derived from the iron oxide facies of iron formations (IFs) of the Quadrilßtero Ferrffero, south-eastern Brazil. The rich-iron oxide varieties of the IFs can be regarded as Fe-O systems because they consist predominantly of aggregates of haematite and magnetite crystals. The study was based on carefully selected samples in which magnetite crystals occur as isolated large crystals set in a matrix of haematite grains. Optical microscopy and an electron microscope equipped with an electron backscattered diffraction (EBSD) system were used to investigate the microstructural and crystallographic relationships involved in the phase transformation between magnetite and haematite. The magnetite crystals in the IF samples are partially transformed to haematite and this process is also known as martitisation. This transformation occurs along the crystallographic planes {111} of the magnetite producing a characteristic triangular pattern of interlocking lamellae of transformed haematite crystals that are oriented parallel to octahedral plane {111}. This new generation of haematite is referred to martite because of the martitisation process. EBSD analyses show that the magnetite and the new haematite crystals, martite, share crystallographic planes of highest atomic density, eg {111} and (0001), respectively, possibly due to the ccp and hcp atomic arrangement of the two crystals. Stereographic projections of these two planes therefore coincide when the maxima of their poles are plotted. However, the crystallographic orientation of the haematite crystals in the matrix shows maxima of (0001) poles that do not coincide with those of {111} planes of magnetite. Consequently, it is concluded that the direct transformation to haematite crystals retains the crystallographic orientation memory of the former magnetite crystals, possibly due to the similar manner whereby their atoms are packed together in the crystal structures. On the other hand, no such relationships are observed between magnetite and haematite crystal in matrix. This suggests that haematite grains in the matrix may have been formed by other processes rather than those involved in the iron oxide transformation observed within the magnetite grains.

Jan 1, 2008

By W Stange

Assessing the risks in a mining project is a key aspect of project evaluation. This is an exacting and demanding task because of the complexity due to the need to deal with uncertainty over long time periods. The way risks are assessed and managed is critical to the long-term success of the projects and the business. Discounted cash flow (DCF) analysis is commonly used for project and risk evaluation. A discount rate is selected that accounts for uncertainties in the cash flows. However, it is difficult to determine an appropriate discount rate due to the large number of factors that need to be considered and the complex relationships between risk sources. Using a proven framework, ævalue at riskÆ (VaR), this paper proposes to rigorously model and quantify ærisk at sourceÆ. The approach was first employed to assess financial market risks and is now widely used in the banking sector for risk assessment. In project evaluation, all risk sources are identified and estimated separately to ensure the overall project risk is quantified accurately. A bottom-up approach has been proposed. Estimates are first carried out for risk factors at the bottom of the project structure. The assessment is then applied at increasingly higher levels until the overall project risk is estimated. Value at risk is a versatile methodology and can be used in a local or integrated manner. The final value is objective and the calculation steps can be easily justified and followed. Four case studies have been included to illustrate how the proposed approach can assist management in decision-making.

Jan 1, 2009

By Purvis A. H, Greenwood-Smith R, Sowerby B. D

A nuclear technique for the determination of copper and nickel in bulk samples and drill core has been developed at Lucas Heights andfield-tested at Mount Isa. The technique, which is highly specific to the element being measured, utilises the gamma-ray resonance scallering process.A bulk mineral analyser was installed in mid-1976 for the routine assay of copper in bulk samples and drill cores, and remained in operation until late 1981. The operation of the analyser over this five-year period is reviewed with particular emphasis on reliability, accuracy and principal usage.The main application of this analyser was in stope planning and design whereby several thousand drill-core and Wall-chip samples were analysed. It was also used as an aid to underground grade control of stopes where ore dilution by supporting barren backfill was a problem.

Jan 1, 1984

By Nag D. K

The Dolphin Scheelite orebody is located near the old mining town of Grassy on the south-east comer of King Island in Tasmania. Surface open cut mining of the Dolphin deposit was conducted for a number of years, then the proximity of the sea and adverse stipping ratio led to underground mining. As a result of the variable orientation and dimensions of parts of the orebody a number of mining methods were practiced at the Dolphin mine until 1990 when a combination of high processing and surface site costs coupled with low tungsten prices led to the cessation of operations. In this paper the different mining methods practised are examined and critically reviewed. The more successful mining methods were developed with experience and improving equipment technology to the extent that the underground operation produced ore at the lowest unit cost during the final years of operation.

Jan 1, 1995

THE South Mine. owned by the Broken Hill South Limited, occupies mineral leases 7 and 8 on the Broken Hill lode. The ore reserves are 4,250,000 tons, and the ore hauled for the year ended June, 1930, was 387,000 tons, the total to date being 7,840,000.The mine, down to the 1070-ft. level, is naturally divided into two sections, the northern and southern ends. Ore extraction is practically completed in the northern end to this horizon, while the southern end is developed ready for a concentrated attack.Fig. 1 shows the state of the 8215-ft. level, after connection to the new shaft.The levels above and below to the 1070-ft. level are in a similar condition, while below the 1070-ft. level the stoping has been confined to the north end, but not completed. The south end on these levels is also partially developed.The ore at present is hauled up No. 1 shaft, which is centrally situated to the present workings. This shaft was put into use in 1909, and in 20 years has had approximately 5,000,000 tons of ore pulled through it.The company, having proved the existence of large ore-bodies in the southern end of the mine, decided to sink No. 7 shaft. This is a six-compartment frame-set shaft (see Fig. 2) equipped with two cages and two 5-ton skips, the remaining compartments being utilised for electric cables, pipes, and ladders. The surface arrangements will include a steel head frame, electric winders, and breaker station.

Jan 1, 1930

To gain further understanding of the operating efficiency of the BHP Slab and Plate Products Division (SPPD) RH vacuum degasser, physical and mathematical model studies of the process have been undertaken. The purpose was to investigate how the various process parameters affect the liquid circulation rate, to visualise the flow patterns, and to identify and eliminate the cause of localised wear in the downleg. In the physical model mixing times were measured using an acid tracer technique. The results were applied to predicting trends in times required to obtain homogenous melt composition under varying conditions. A 2-dimensional mathematical model describing the liquid metal flow has been developed using the PHOENICS fluid-flow package. The physical model results were simulated and incorporated into the mathematical treatment and an improved design for vessel geometry is proposed. The effect of rounding the downleg entrance or installing a baffle between the legs is discussed.

Jan 1, 1987

Hamersley Iron Pty. Limited has maintained an interest in the screening of iron ore fines (nominally -6 mm). However, no dry screening process had successfully demonstrated acceptable separating efficiencies at high tonnage rates, low operating costs, and mechanical reliability when screening iron ore fines (containing up to 6% free moisture) at sizes of around 1 to 2 mm. A new type of vibrating inclined screen has recently been developed which is claimed to have a non-blinding screening surface. It was decided to test a pilot scale unit in an existing pilot plant located at Hamersley's facilities at Dampier, Western Australia. The appropriate operating parameters such as vibration speed and feed rate were determined using one fine ore type. Mats with different aperture sizes, and different feed moisture contents were also tested. Trials were then conducted on various fine ore types to indicate the effect of different size distributions on separating efficiencies. The effects of feed moisture content were determined with these ore types, and a blend of lump (nominally -30+6 mm) and fines was tested to compare the screen's performance with that of the bottom deck of the minesite product Screens.

Jan 1, 1991

By Sandenbergh RF

The debate on the mechanism of adsorption of gold and silver di-cyanide onto activated carbon could be divided into two schools of thought. On the one hand, it has been proposed that the combined effects of electrostatic and chemical interaction between the activated carbon surface and adsorbing gold di-cyanide anion results in the adsorption of the latter. On the other hand the `ion-pair' adsorption reaction mechanism has been vigorously advocated as the dominant mechanism responsible for the adsorption of gold di-cyanide onto activated carbon. It is maintained that gold is adsorbed onto the carbon surface as the neutral ion-pair [M"+][Au(CN)z ]". Adsorption is viewed as the result of mainly the chemical interaction while electrostatic interactions are neglected. The validity of the `ion-pair' adsorption mechanism may be challenged on a number of counts. However, the alternative mechanism (based on aqueous surface chemistry principles) has not gained general acceptance yet, because it has not been applied widely enough to explain the different adsorption phenomena associated with gold di-cyanide on activated carbon. In the present study the case in favour of an adsorption mechanism based on general aqueous surface chemistry principles is presented. A model framework is developed for the adsorption reaction mechanism of gold di-cyanide onto activated carbon which incorporates the effects of chemical and electrostatic interactions between the dissolved species, the aqueous solution and the carbon surface. This model is then employed to explain a wide variety of reported adsorption phenomena for gold di-cyanide on activated carbon, such as the effects of pH, the adsorption of different metal cyano complexes, ionic strength, and type and concentration of cations in solution. In addition the effects of cyanide and dissolved oxygen concentration were investigated. No ready explanation, in terms of aqueous surface chemistry principles, is yet available for the switch in adsorption behaviour that agrees with ion exchange to ion-pair adsorption with increasing ionic strength.

Jan 1, 1997

By Wright J

Large scale cut and fill mining in narrow silver-lead-zinc orebodies began at Mount Isa in 1964. Initially each orebody was one stope and access was via raises from the level above. Upholing was the principal mining method, although flatbacking was employed where ground conditions were more difficult. Developments since have included access via footwall inclines and connection of all stopes with major crosscuts. Flatbacking is the principal method. The most recent cut and fill operation is now fully mechanised using drilling jumbos, rockbolting jumbos and load-haul-dump units. Improved ground support and drilling and blasting practices have enhanced safety, recovery and productivity in all cut and fill operations.

Jan 1, 1988

By R Skirrow, E Bastrakov, A Mauger, P

A new rapid spectroscopic core and chip logging and imaging system developed by CSIRO was evaluated by PIRSA and GA on a wide variety of mineralised properties in South Australia, including the Emmie Bluff, iron oxide copper-gold-style prospect on the Stuart Shelf. During a three-month campaign in South Australia in 2003 the system logged over 50 000 metres of core from the State Core Library, company prospects and mines. The new system uses automated core tray handling, continuous visible and infrared spectroscopy, and digital imaging, to characterise and identify dominant mineral species on core, chips and pulps, at spatial resolutions of ~1 cm (spectral data) and ~0.1 mm (image data). The system can log up to 1000 m of core per day and several thousand metres of drill chips. Mineralogy is pre-interpreted using specialised identification software trained on a selected suite of minerals showing characteristic absorption features within the measured spectral range. On core from the Emmie Bluff iron oxide copper-gold prospect, 470 km NW of Adelaide and 80 km SSE of the Olympic Dam Cu-U-Au deposit, the spectral mapping system was able to characterise a number of alteration zones enveloping the sub-economic Cu-Au mineralisation. These consist of distal white mica phases showing decreasing Al content towards mineralisation, a zone of increased iron oxide content in the hangingwall to mineralisation, and a zone proximal and coincident to Cu-Au mineralisation that is enriched in chlorite with variable Mg/Fe chemistry. Additionally the results show background spectral characteristics that mimic the magnetite distribution.

Jan 1, 2004

By Sneddon J

This Is not a highly technical paper, but rather an attempt to give a general outline of coal mining for the benefit of those present who may have little or no experience in the industry, and is intended to give some general knowledge which may help to a better understanding of the problems of the industry. A knowledge of the disposition of workable material is necessary to give a comparison with other mining practices. Coal Is usually found in comparatively fiat seams of varying thickness, whereas other minerals are generally found in highly inclined lodes of variable width. However, even in comparatively flat seams unaffected by faulting, grades can, and do, vary greatly over short distances.This variation causes many local problems in working the small area affected. Even very steep seams, and some are much steeper than 1 in 1, vary considerably not only in grade, but also in direction of grade and level course. This is probably caused by folding during alteration of the shape and form of the basins after deposition.These swellies are common to most coal seams and vary only in extent. This type of variation in grade and direction of grade, while common to most ore bodies, is a matter of great importance in coal mining when it is considered that roadways are driven in the seam itself and have to be graded and made suitable for haulage purposes.The area of ground involved in an individual coal mining operation is often very large; many times larger than most metal mining propositions, and often comprises many thousands of acres.When it is considered that the specific gravity of coal may be only one-fifth of that of some ores mined, and the coal seam may be five or six feet in thickness, the vastness of the area necessary for continuous mining operations over many years will be realised.To achieve comparable outputs, with about five times the bulk of material to handle, much more ground and working places must...

Jan 1, 1947

By Rogis J

The basic parameters causing outbursts are rock pressure, gas characteristics and the physico-mechanical properties of the coal. The three sets of factors are to some degree interdependent. At Collinsville, the gas characteristics coupled with the physico-mechanical properties of the coal appear to be the major factors contributing to outbursts. The relative importance of rock pressure is uncertain. The following geological parameters appear to be necessary before outbursts can occur. 1. A coal rank greater than 1.2% vitrinite reflectance. 2. Thrust faults with throws greater than 3.Om or strike- slip faults with coal gouge wider than 0.3m. 3. Seam gas emission values greater than 1.1 cm3 /g. Igneous intrusions are the likely source of the carbon dioxide seam gas. Outbursts have occurred at depths ranging from 215m to 265m. They occur at these relatively shallow depths due to: 1. the high rank of coal at the present topographic surface and the high coalification gradient; 2. the relatively high degree of tectonic deformation of the strata; 3. the seam gas characteristics; and 4. the extent of igneous intrusions.

Jan 1, 1980

By Doig ID, Phillips HR

As a prelude to studying the sorption desorption and permeability behaviour of coal cores in a triaxial stressing rig using sorb- able gases, the air permeability of typical cores was measured. Lump coal samples were obtained from three gas-troubled collieries in Queensland and New South Wales. These were cored in the laboratory and a simple laboratory permeameter employed which accepted 38 x 40 mm cores in a thick rubber sheath. Air pressure of 500 kPa was applied outside the sheath to provide suitable sealing between the rubber and the coal. Differential driving pressures up to 100 kPa were employed and the air flow measured by displacement of water columns in inverted graduated cylinders. Flow measurements accurate to + 2% could thereby be achieved. Coal lumps were cored both parallel and perpen- dicular to the bedding plane, and were observed prior to measurement for any notable features, in particular for the presence of fissures. Between samples an overall variation of from 100 milliDarcy was found in Appin, Westcliff and Leichhardt coals. Significant variation was observed both from section to section of a core and between regions of a

Jan 1, 1982

By Okura T, Hino J

Coal utilization for copper flash smelting in Japan was initiated due to the sudden upheaval in the price of oil in the last ten years. A major portion of the heavy fuel oil has already been replaced by coal resulting in a corresponding decrease in energy costs. In addition to energy cost savings, an interesting metallurgical phenomenon was observed in flash smelting operations. Unlike oil combustion, coal is not burned completely in the shaft. A considerable fraction of coal particles remain on the surface of slag and are burned at the settler. Chemical investigation has shown that oxygen potentials at the settler have consequently decreased, bringing the slag and matte phases into reducing conditions, thus oxidation and reduction can coexist in one flash smelting unit. As a result, a decrease in magnetite and copper contents in the slag, elimination of furnace hearth build-up and dissolution of intermediate layer between matte and slag have been observed. In general, these led to improvements of furnace operations. However, thermodynamic investigations have shown that some minor elements such as As, Sb, Bi and Pb concentrate from slag to matte. Results evaluated on the basis of thermodynamic data relatively agree with practical observa- tions. Consequently, for coal utilization in flash smelting operations it will be necessary to control oxygen potentials from the stand- points of copper loss in slag and minor element Distributions.

Jan 1, 1987

By Casale G

This paper discusses a long range mine plan development at the Santa Fe Pacific Gold Twin Creeks Mine based on the reserves of Mega pit. The key constraints of the schedule development included two types of mill ore targets (sulphide and oxide mill ore), consideration of blending of six chemical constituents (sulphide sulphur, carbonate, organic carbon, the ratio of iron/[arsenic, antimony]), and mining of acid generating and acid neutralizing waste at pre-defined proportions. Solution approaches, selected results, and project experiences are discussed.

Jan 1, 1995

The operators of the iron ore railroads in the Pilbara faced problems of excessive wear between rail and wheels as the tonnage hauled increased in the early 1970's. Joint research projects were begun between Hamersley Iron, Mt Newman Mining and the BHP Melbourne Research Laboratories to study these problems and recommend solutions. The particular problems of wheel rail interaction were solved by asymmetrical profile grinding of the rail and modifications to the machining of the wheels. Rail materials were improved through increasing yield strengths by alloying and by heat treatment. Wheel materials were improved by alloying. The economic benefits of these improvements have been demonstrated by much reduced re-rail requirements and other reduced maintenance costs.

Jan 1, 1986

By Haeussler P, Christie A, Bradley D, Skinner D

Mesothermal gold deposits of southern Alaska and Westland, New Zealand have both formed at the seaward edge of major collisional zones in the Pacific basin. In Alaska, production of large fluid volumes correlates in time with the addition of heat into the lower parts of the accreted terranes in the late stages of collisional orogeny. This heat was critical for driving both the metamorphic reactions that released the large volumes of fluid that carried the gold, and the contemporaneous widespread anatexis and magmatism. In Alaska's Chugach terrane, this heat was produced by subduction of a spreading ridge beneath the North America continental margin in the Eocene. The resulting products were the S-type granites and gold-bearing veins. The similar widespread S-type plutonism and gold veining in Westland's Buller terrane suggest that a similar tectonic event could have triggered ore formation along the southeastern edge of Gondwanaland. Based on the Alaskan model, a Devonian or Early Carboniferous age is favoured for high volume metamorphogenic fluid generation and gold vein formation in Westland.

Jan 1, 1995

By Jackson S

An investigation into different aspects of importance in the understanding of explosibility of hybrid mixtures of coal dust, air and gases potentially found within mine workings through a comprehensive laboratory program of explosibility tests was conducted. Plotting of test results revealed that conditions of potential explosibility could be described using two dimensional flammability limit surfaces- for coal dust/oxygen; methane/oxygen; and coal dust/methane mixtures. From these plots, the three dimensional flammability envelopes defining the explosibility of the coal dust/methane/oxygen mixtures can be defined and illustrated for a coal sample. The surfaces of the three dimensional envelope describe limits which separate inert mixtures of coal dust and methane at varying oxygen levels from those concentrations which are ignitable under defined conditions. It is considered appropriate to generalise that the geometric shapes of these limit regions are applicable to all type classifications of coal dust. There are practical applications of these results to the underground environment.The action of free radical initiators in the propagation of a methane gas explosion was examined for its applicability to the flammability of coal dust/gas/air mixtures. The oxides of nitrogen or NO x radicals have influence upon the lean limits of flammability of hybrid mixtures and this is illustrated by use of three dimensional coordinate geometry. Gases can be introduced to the underground environment through the exhaust gases of diesel equipment. It is concluded that radical species can substantially increase the flammability of gas and dust flames and as a consequence raise risk of mine atmosphere explosibility.

Jan 1, 1998