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Supercritical fluids are gases compressed to near liquid densities and, as such, have unique properties compared to liquids: low viscosity; zero latent heat; high diffusivity and pressure-dependent, solvation characteristics. These properties are being utilised in new processes and current research is delineating areas where such processes may be applicable to extractive metallurgy. The processes and areas of interest are as follows: Supercritical Fluid Extraction in which substrates are dissolved at high pressure and fractionated at successively lower pressures. Areas of interest include extraction of organic materials for regeneration of activated carbon for the CIP process and for upgrading alumina industry products and, separation of transition metal chlorides. ò Supercritical Water Oxidation in which high pressure gaseous water acts as a medium in which substrates are oxidised while suspended or dissolved. This process may be of use for oxidation of organics in Bayer liquor and oxidation of mine waters etc. ò Supercritical Fluid Reactions where reactions occur in a supercritical fluid medium, particularly when the medium itself is a reactant. This may be of use in treating refractory or carbon-aqueous auriferous ores and in lower-temperature chlorination of transition metal oxides. Research is described which is aimed at chlorination and separation of transition metal oxides by two supercritical operations.

Jan 1, 1991

By Lawson F

A rotating disc geometry has been used to provide a uniformly accessible surface for a kinetic study of the cementation of the metals cadmium, lead and silver from dilute aqueous solutions. This work is an extension of studies carried out on the Cu/Zn and Cu/Fe systems for which the rection rate was found to be completely solution-phase mass-transfer controlled. When the amount of material deposited was greater than 0.2 to 0.4 mg/cm2 there was an apparent enhancement in e which is attributed to the formation of a roughened deposit. This same phenomeon was obseived in the Cu/Zn Cu/Fe systems. Again, the rate of reaction of each system investigated was found to be solution-phase mass ,..~sfer controlled.

Jan 1, 1970

By Derham DW, Newcombe LA

The operations of the Mount Morgan gold tailings retreatment plant were significantly improved in 1984 by the desliming of the CIP plant feed, which reduced cyanide consumption and increased percent gold dissolution. Subsequently, the development of slimes treatment, incorporating gold leaching from slimes solids by copper cyanide complexes in the process water, and gold adsorption on to carbon in an environment lacking free cyanide was successfully implemented. Mount Morgan was initially mined for gold commencing in 1882 on the auriferous ironstone cap to the sulphide ore body. During the history of mining and processing at Mount Morgan the operations have developed through numerous phases of gold and copper production, operating almost continuously through until the final closure in late 1990. The final phase of processing was the retreatment of tailings, predominantly flotation tailings accumulated since the 1930s, for the recovery of gold and minor silver. Tailings retreatment commenced in 1982 with the commissioning of a 10 000 tonnes per day CIP plant to treat some 40 million tonnes of tailings at an average grade of 1.08 g/t Au. The initial operations were hampered by high cyanide consumption and poor gold dissolution on the mixed siliceous/pyritic tailings. The successful development and implementation of the desliming of the CIP plant feed in 1984 (as described by Parsons and Hampshire, 1986) reduced cyanide consumption by 40 per cent, and raised gold extraction by 13 per cent points by virtue of significantly higher dissolved oxygen levels. The finer portion of the reclaimed tailings were deslimed by eighty 100 mm diameter AKW cyclones, with the desliming cyclone overflow thickened in a Warman 30 in diameter thickener for water recovery and slimes disposal. Operation of the desliming plant involved the discarding of a slime fraction representing about 15 per cent of the reclaimed feed. Although gold-bearing, the high content of cyanicides and oxygen consumers within the slime negated any conventional treatment of this stream with free cyanide for gold recovery. The natural lixiviant behaviour of the soluble copper cyanide complexes for gold, which was extremely evident at Mount Morgan, directed efforts in this area. Enhancement of gold leaching with a deficiency or near absence of detectable free cyanide, but with significant levels of copper cyanide complex from recycled process water were examined. Adsorption of this solubilised gold onto carbon in a similarly difficult environment required close examination.

Jan 1, 1993

By Woodcock J. T, Sparrow G. J

Activated carbon particles obtained from a number of Australian CIP operations were examined with an optical and a scanning electron micro- scope and an electron microprobe. External surfaces, and polished sec- tions through individual particles, were examined with special reference to materials on the surface and to calcium and gold distributions. Photographs are presented of surface contamination of the particles by salts precipitated from the pulp such as calcium carbonate (calcite), calcium sulphate (gypsum), and a magnesium salt; ore minerals such as quartz, hematite, pyrite, arsenopyrite, pentlandite, and various alumino- silicates; and other substances such as grinding media and a fungus. Calcite was very abundant but the other materials were less common. Contamination in the interior of carbon particles was almost exclu- sively calcium carbonate, and extensive contamination extended to the centre of some particles. A possible mechanism for the formation of cal- cium carbonate inside the carbon particles is noted. Gold X-ray dot maps of sections through carbon particles indicated that gold was distributed throughout coconut shell carbons and that although gold was more concentrated near the outer surfaces of extruded peat carbon particles, it was also present to depths of at least 500 ¦m. The gold distribution throughout the carbon particles was similar to that rf alrit~

Jan 1, 1988

By Kendall W. T C

This paper provides a brief overview of the history of the Chaffers Dewatering Project which was successfully commissioned in August 1993. Until the end of 1992 the `Superpit' and the deep mines of the Golden Mile had all been dewatered by a staged pumping system from the 28 level in the Lake View Shaft, which was removed at that time when the Lake View Mine was absorbed into the Superpit. Feasibility analysis had indicated that adaptation of oil industry technology offered the greatest potential for a low cost solution to the problem of dewatering the open pit and deep mines. A KCGM engineer and one of the authors visited the Jackson oilfields to look at the deep well pumping technology in use there in early-1991. In the final analysis a new dewatering station was established in the 23 level crushing station of the Chaffers Shaft using conventional plunger pumps, but the rising main was screwed 178 mm OD (7 inch) casing the suspended from the surface to a depth of 686 metres, and was installed using oilfield personnel and methods. Only the second installation of its kind in Australia, the project achieved the dewatering objective at about half of the capital cost of the more conventional approach and at lower operating costs as well.

Jan 1, 1995

By Arit I, Adisoma G

General Limit Equilibrium Method (GLE) and Janbu's Generalised Procedure of Slices (GPS) are two limit equilibrium methods in slope stability analysis which satisfy all equilibrium conditions. Numerical difficulties associated with these metho

Jan 1, 1998

By Nichol R

- PART A The Hoppers Crossing Pumping Station is one of the principal components of the Western Trunk Sewer Project which replaces the 90 year old Main Outfall Sewer and will convey 60% of Melbourne's sewage flow from Brooklyn to the Board's Farm at

Jan 1, 1987

By Christie AB, Bull VH

The geological environments of gold deposits are reviewed in relation to the strong resurgence in exploration for gold since 1979. The resurgence is due mainly to New Zealand's geological endowment with gold and its history as a gold producer. Major past production was from Cenozoic placers of Otago and Westland, late Cenozoic epithermal deposits of the Hauraki Goldfield, and the respective Paleozoic and Mesozoic lode deposits of the Reefton and Otago Goldfields. These same geological environments are the targets of current exploration, mainly in extensions of previously mined deposits. On the Westland and Otago Goldfields alluvial and fluvioglacial gravel placers, mainly representing lateral and depth extensions of previously worked ground, are being mined and prospected. Gold production in 1984 was exclusively from these deposits, and the development of mobile concentration plants has resulted in a great increase in mining activity. Mineralised zones adjacent to previously mined lodes in the Hauraki Goldfield, Reefton Goldfield, and at Macraes Flat (Otago Goldfield) are being intensively explored. At Waihi (Hauraki), an open-pittable resource of about 10 million tonnes of ore has recently been delineated. Some new deposit types and little explored environments are also receiving attention. They include: gold-sulphide quartz veins hosted in an alkaline granite dike in west Nelson; hot spring type gold deposits in fossil geothermal (epithermal) systems of Northland, the Hauraki Goldfield and the Taupo Volcanic Zone; and marine placers off the West Coast where an area of auriferous gravels has been outlined near Hokitika. There is potential in known deposits and prospects currently being evaluated for a large increase in gold production by the early 1990s.

Jan 1, 1986

Indigenous brown coals, which provide a readily available primary energy source, have played a significant part in the industrial development of Victoria. The deposits located in the Latrobe Valley compare in extent with other major deposits of brown coal in the world. Smaller but valuable deposits occur at Stradbroke, Gelliondale, Anglesea and Bacchus Marsh. Extensive drilling, aided by geophysical surveys, and detailed analyses of coal samples, have enabled the extent and quality of these Tertiary deposits to be Defined.

Jan 1, 1979

A brief review of the problems in ventilating and cooling deep and hot Australian mines is presented. An overview is given on the development of the controlled partial recirculation concept. The main part of this paper describes the first majo

Jan 1, 1994

By McDougall I, Claoue-Long J

A combination of high precision 40Ar/39Ar and U-Pb dating has been used to determine the age of hydrothermal minerals and host rocks in a number of Lachlan Fold Belt (LFB) gold deposits in New South Wales, Au4 ralii In particular, this investigation demonstrates that the UAr/ Ar technique of K-Ar dating can be used to determine the timing of mineralization in Palaeozoic systems.A close temporal link between mineralization and Late Ordovician to Early Silurian magmatism is indicated by the dating work. Hydrothermal sericite from the Goonumbla p8rph gy Cu deposit and Glendale Au prospect yieldsAt/ Ar step heating ages between 437.9 ¦ 1.1 and 441.2 ¦ 1.1 Ma (16), and4 minjrnum age of about 425 Ma has been obtained by Ar/ Ar dating of hydrothermal amphibole from the Browns Creek Au-Cu skarn deposit. Hydrothermal aluniI8 frog the Gidginbung epithermal Au deposit yields reset 44 Ar/ Ar ages of 401.0 ¦ 1.3 to 417.3 ¦ 1.3 Ma (16). U-Pb dating by ion microprobe on magmatic zircons from the vicinity of the Goonumbla and Gidginbung deposits gives ages of 438 ¦ 3.5 Ma (2 6), and 435 ¦ 2.5 Ma (2 (7) respectimly, W a minimum age of 435 Ma has been obtained by Ar/ Ar dating of magmatic phases from volcanic rocks adjacent to the Browns Creek skarn deposit. Magmatic episodes near the Sheahan-Grants gold skarnpost give ages of 479.2 ¦ 1.1 and 467.9 ¦ 4o1 by 'Ar/ 9Ar dating of magmatic amphibole. Most Ar/3yAr age spectra show the effects of partial Ar loss at between 360-420 Ma, probably due to heating caused by granitoid emplacement.The radiometric dating work in this paper suggests a restricted metallogenic epoch in the Late Ordovician-Early Silurian LFB, NSW, of similar duration to that found in the Andean margin and the western Pacific island arcs around the Pacific Rini.

Jan 1, 1990

By Erepan P. C

Flash flotation technology was introduced by Outokumpu in 1985. Considerable success was achieved in other plants with similar operations to OTML. Conclusions from site visits and amenability tests performed on plant samples were that the OTML

Jan 1, 1997

By de Lassar de Pressigny Y

IRSID has in its laboratories two experi mental counter-current reduction furnaces allo- wing the simulation of the physico-chemical conditions of reduction in any gas-solid coun- ter-current process, including the blast furnace and direct-reduction shaft-furnaces. The counter current is realized by an electric furnace mo- ving along a laboratory tube filled with the material to be tested. The reducing gas stream in the tube travels in the same direction as the furnace After reduction, twenty samples, with dif- ferent degrees of reduction and which can be related to different levels of an industrial furnace, are taken from the tube and subjected to various quality tests. Experiments were realized to determine the behaviour of various types of industrial pellets when reduced under either blast furnace or shaft furnace conditions. The results show the large influence of the reducing conditions on any pa- rameter characteristic of the quality of the pellets : reduction efficiency, swelling, cru- shing strength and disintegration.

Jan 1, 1974

In the stability assessment of open pit walls, geotechnical engineers have to deal with uncertainty related to structural geology, rock mechanical parameters, groundwater and so on. This uncertainty will immediately and significantly impact on wall stability assessment and therefore. influence mineral recovery and ultimately the financial return of open pit mining. However, the conventional factor of safety applied to measure the stability of slopes and the relevant analytical computer packages cannot quantitatively consider the variability or uncertainty of the input data. As a supplement, therefore, geotechnical engineers have begun to apply probability to the stability assessment of open pit walls over the last two decades. To-date unfortunately, no powerful computer package is available to geotechnical engineers to conduct the probability analysis of slope stability. This paper presents a computer package of probability analysis for rock and soil slope stability. In this computer package, the strength parameters of rock and/or soil material such as cohesion, friction angle and unit weight of the different rock and/or soil type domain in a complex structural geology environment can be considered as the basic input random variables. Groundwater level can also be taken into account as a random variable in this package. Two `rigorous' limit equilibrium solutions, the Morgenstern/Price method and the Sarma method, can be used to calculate the factor of safety during Monte Carlo Simulation applied in this program. Five types of probability distribution are included in this package for the user to simulate basic input random variables. Two realistic cases from BHP Iron Ore are used to illustrate this package.

Jan 1, 1997

Mining software systems have provided a basis for integration of resource, survey, and design functions. They can similarly provide a basis for incorporating ground conditions into the process.Exploration and mine geologists have a prime role to play in this process, extending their responsibilities further across the geological spectrum, into exploration of ground conditions, analyses of results, and assessments of their implications for mining. Ground conditions are as much a part of the geology of a prospect or mine as its mineralisation, and can have critical imnlicationa for mining.

Jan 1, 1993

A novel fracture-plane control blasting technique with particular application in wall-control blasts in mines employing medium to large diameter boreholes is described. It consists of a string of nested holes, each nest consisting of a large diameter charge-hole flanked on either side by a small diameter satellite hole. Each nest is shown to be an analog of a pressurized hole with diametral notches along its length. This 'equivalent-notched' hole concept for generating controlled fractures along preferred directions has been successfully investigated in the laboratory and in the field. The technique has been used to generate controlled fractures on a quarry bench in highly jointed limestone. The resulting blasts with a 250 mm diameter central charge-hole and 50-75 mm satellite holes show that two nests of such holes almost 5 m apart could be joined by a single co-linear fracture. The design range of diameter ratio between charge-hole and satellite hole is 3 to 6 and spacing is 3 to 5 charge-hole radii. With careful matching of explosives and decoupling, and combination of diameter ratio and spacing, it would be possible to connect two nests of such holes more than 20 charge diameters apart by a single controlled fracture plane. The relative merits of the technique against existing wall-control blasts are discussed, and guidelines for practical fracture-plane control blast designs are discussed.

Jan 1, 1990

By Das S. C

A detailed study was undertaken on the effect of Fe+3 in combination with LIX64N during copper electrowinning from sulphate electrolytes. The results show that the presence of Fe+3 not only affects the current efficiency during copper electrowinning but also affects the cathode quality. The effect is enhanced by electrolysis parameters like temperature, circulation rate, current density, etc. No significant effect was found from the presence of Fe+2. The presence of Fe+3 along with LIX64N causes a synergistic effect and results in a drastic fall in current efficiency. Moreover, cathode quality is also affected. A pyramidal structure is favoured in the presence of Fe+3 but the presence of LIX64N along with Fe+3 promotes a ridge structure. Addition of thiourea not only causes modification of cathode deposits, but also a rise in current Efficiency.

Jan 1, 1992

By Jeffery RI, Pollard CA, Fear NJ

The paper describes the detailed hydrogeological studies carried out prior to the sinking of twin shafts at British Coal's new mine at Asfordby, Leicestershire, UK. The test methods for assessing potential groundwater inflows to the shafts are discussed and details are given of the ground freezing scheme employed through the major aquifer zone in the Sherwood Sandstone at a depth of 375 metres. During shaft sinking pressure recovery tests were carried out to further assess potential inflows and the results are compared with those from the surface tests prior to sinking.

Jan 1, 1988

Traditionally trucks have dominated haulage in open pit mines. Only recently have conveyors begun to be used in the long haul and high lift duties of surface mines. Steep angle conveyors are proven versatile systems for elevating or lowering materials continuously at steep angles to 90¦. This paper describes the design of a bucket-type steep angle conveyor that was developed as a joint research project between the Western Australian School of Mines and the Maanshan Institute of Mining Research in China. The steep angle conveyor can be used as a viable option for transporting blocky ore from open pit mines. A pilot conveyor was constructed and tested to determine its technical and operational feasibility. Furthermore, a computer model based on Matlab mathematical modelling software was developed to simulate the performance of the pilot conveyor. The model enabled to determine the design parameters of industry-scale conveyors to yield satisfactory performance. These conveyors become very cost-effective for those mines having large mine lives and depths greater than about 500 metres.

Jan 1, 2003

By Rigby D, Gould K. W, Hart G. H

The variation in chemical and isotopic composition of hydrocarbon gases generated from humic source rocks in the Cooper Basin, the orth West Shelf, the agoorin oil shale deposit. ollinsville and the southern Sydney Basin is reviewed, discussed and interpreted.The primary composition of gases generated in and released from such source rocks appears to be very largely controlled by the degree of dispersion of the organic material. For example in eoaly shales, where the degree of dispersion may be high, products as generated may escape into surrounding inorganic structures where further maturational reactions may proceed. On the other hand, when the organic materials occur in massive form, as in coal seams, the hydrocarbons generated tend to be retained within the coal. Further cracking to the stage of methane generation is usually required before release of hydrocarbon products is significant.Secondary factors of importance in determining seam gas composition in the Bowen (Collinsville) and southern Sydney Basins are the invasion of coal measures by carbon dioxide from external magmatic sources and/or the vertical diffusion and loss from the surface ofgases generated at depth.Isotopic measurements of gas composition have been particularly valuable in determining the origins and histories of the gases examined, in demonstrating when gases are of mixed origins and in the prediction of gas quality in exploration.

Jan 1, 1985