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By Sterns UJ, Weller KR

Grinding to sizes less than 80 per cent passing 20 ¦m in both primary and regrind circuits is becoming increasingly important in processing metalliferous ores, as many of the remaining orebodies are very fine-grained and refractory. The process of very fine grinding, however, is expensive, and neither the performance nor the design criteria are well understood. This paper presents some findings from a collaborative research program, one of the objectives of which has been to better understand and improve the performance of very fine grinding circuits. Data from surveys of an industrial tower mill grinding circuit are reviewed and analysed using the population balance models of the CS]RO and 7KMRC. The performance of both models with regard to changes in feed size distribution, ball load and feedrate is assessed using these data. From comparisons between pilot and full scale tower mill operation a prototype scaling methodology is also presented which shows promise in allowing the models to be used to predict the effect of changes in mill Design.

Jan 1, 1993

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 Corbett GJ, Leach TM

ABSTRAC'T' Although hosted within an Ordovician magmatic arc, the Peak Hill high sulphidation system displays features typical of younger Pacific Rim high sulphidation epithermal gold deposits. Regional NW trending transfer structures are inferred to localise the magmatic source at their intersection of the NS trending arc. Fluids have migrated from the magmatic source along NW structures and thence exploited permeable horizons, which have become silicified. Alteration displays typical zonation from silicification through assemblages characterised by alunite, pyrophyllite and kaolinite and is followed by breccia/fracture controlled sulphide and gold deposition. Sinistral rotation on the NS arc has dilated NW trending fractures to produce the WNW to EW dilational fractures which host the higher grade ore. Mineral assemblages are typical of formation distal to the magmatic source in an epithermal environment. The combination of alteration and mineralisation zonation with structure provide fluid vectors which target a magmatic source to the SE of Peak Hill.

Jan 1, 1995

By Fulton B, Stewart R, Leach T

Gold mineralisation at Porgera is inferred to have been derived from a deep differentiated magmatic source which is capped by a series of (now tilted) inward dipping sills and stocks, which comprise the Porgera Intrusive Complex. An arc normal transfer structure provides a conduit, at the intersection with an arc parallel structure, into which basic magma derived from the deep melting of mantle material has been emplaced. Two phases of mineralisation display an association with late stage feldspar porphyry intrusives. Stage I carbonate-base metal-style gold mineralisation occurs as early quartz-sericite, then massive sulphide and late zoned Mn-Fe-Mg-Ca carbonate vein/breccias. Magmatic fluids derived from the deep magma source, are interpreted to have migrated along the margin of a feeder stock to the sills, and south to Waruwari. Stage II epithermal Au-Ag quartz-style gold mineralisation occurs as early fluidised breccias and carbonate veining, followed by zoned quartz-roscoelite-carbonate-gold vein/breccias, and late carbonate and/or sulphate open space infill. Magmatic fluids are interpreted to have utilised the same plumbing system as the late stage feldspar porphyry intrusive, and then migrated into the Roamane Fault which was dilated by; dextral rotation on elements of the transfer structure, normal faulting, and refraction around the competent footwall hornblende diorite. Bonanza gold is localised in a jog in the Roamane Fault, hangingwall splits and at intersections with cross structures. Bulk low grade Stage I gold has been deposited by the mixing of magmatic fluids with cool gas condensate waters, whereas high grade Stage II gold mineralisation resulted from the rapid quenching of mineralised magmatic fluids by oxygenated groundwaters.

Jan 1, 1995

High interest to basic-ultrabasic rocks is ex-plained by their specific, sutural, geotectonic po-sition and by deep level of generation of ultraba-sic magmas. These two factors allow us to treat this group of rocks as valuable source of informa-tion about the lower crust and upper mantle of the Earth. Basic-ultrabasic xenolith series is another source of information about the interior of the Earth. Detailed studies of the xenolith series give valuable material to geologists as to how endogenic deposits are fed and what is their source.Besides, the interest is explained by attempts to understand the relationship between basic-ultra-basic complexes and deposits of metalliferous and non-metalliferous mineral material.Absence of genetic boundaries in manifestation of metalliferous and non-metalliferous minerals, their temporal and spatial relationship allow us to treat the minerogenesis of ultrabasic complexes as a result of one ore-forming process manifested in Koryak-Kamchatsky, Sakhalin-Japanese, Ryukyu-Korean and Taiwan-Philippines island arc systems which re-present, in the opinion of the authors, one eastern Asian chain of the Pacific ore belt (Radkevich, 11)87).

Jan 1, 1990

This paper presents the findings from an experimental study of the effects of shock and gas penetration breakage mechanisms in rick blasting. A blasthole liner method, which realistically seperated these two basic sources of energy in blasting, was developed and utilized. The use of four different explosives with contrasting detonation behaviour produced a wide variation in the nature of explosive energy transfer to the rock. Through extensive field experiments it was found that, relative to low VOD dynamite, the high VOD emulsion imparted greater shock to the rock and therefore produced finer fragmentation and greater back damage. The comparatively lower heave energy of the emulsion caused less immediate blast results were obtained with watergel and ANFO explosives, which have detonation behaviour and energy partitioning charecteristics lying between emulsions and dynamite.

Jan 1, 1990

The Nickel Rim Depth Cu-Ni-PGE deposit, discovered by Falconbridge Limited in 1993, illustrates several trends in exploration in the Sudbury area. Recent discoveries tend to be deep, high grade, footwall hosted, close to or straddle property boundaries and made using a multi-disciplinarian exploration approach that integrates economic considerations with geology, metal geochemistry and geophysics (borehole EM). The Nickel Rim deposit occurs down dip of Inco's Victor Deep deposit (4.2 million tonnes at 2.25 per cent Ni, 7.30 per cent Cu) in the eastern margin of the Sudbury Igneous Complex (SIC) at a depth of 2650 m. Before commencing drilling an economic evaluation was done to determine the minimum size needed to be economic at the expected depths and determine the expected value of an exploration venture. The subsequent surface exploration program discovered a drill indicated, undiluted mineral inventory of 1.6 million tonnes of 1.58 per cent Ni, 10.13 per cent Cu, 4.17g/t Pt and 3.50 g/t Pd including 519 000 tonnes of 4.13 per cent Ni, 25.53 per cent Cu, 9.76 g/t Pt and 8.42 g/t Pd. The deposit is hosted by gneiss, migmatite, gabbro and pseudotachylite (Sudbury Breccia) 100 m below the base of the SIC.

Jan 1, 1996

This paper describes a plant built at The Broken Hill Associated Smelters, Port Pirie to sample lead sinter automatically. As the plant is still in the commissioning stage results on the precision and accuracy of the sampling are not yet available, but some of the difficulties experienced during commissioning are discussed.

Jan 1, 1976

By Artone E

screening equipment installed in e Hamersley Iron operation is described, and tails of operating parameters and screening - Iia in use are given. Tests were carried out on full-size reens in the operating plants to study the Meets of mat aperture size, feed size distri 1,ution, feed rate, screen speed and throw, angle of inclination, and feed moisture content n screen performance. Sampling equipment was signed so that undersize samples could be htained from various locations along the length of the screen, thus providing information pout the quantity and size of particles passing òhro gh the screen at any point. Conclusions derived from the testwork and relevance of these to the Hamersley Iron aeration are discussed.

Jan 1, 1984

The Elgas Underground Storage Facility at Port Botany, Sydney, is the first purpose-built cavern of its kind in Australia and provides large capacity, safe and environmentally benign storage of Liquefied Petroleum Gas (LPG). The facility will provide Elgas with the flexibility to source product at competitive prices and ensure long-term security of supply. Construction has provided Orica Australia, formerly ICI Explosives, with a unique opportunity to provide a bulk explosive delivery system specifically designed to meet the exacting demands of the site and of the project.

Jan 1, 1999

By D Manhire, G Hogan, M Ryan, S Whiteley

Site restoration at the L&M Mining Limited alluvial gold mining project at Waikaka near Gore, Southland is described. In 2000 mining operations started to recover alluvial gold beneath historical dredge tailings over 244 hectares in the flood plain of the Waikaka Stream. The project had an eight to nine year mine life but was prematurely closed in 2002 because of economic considerations. Restoration of the site back to pastoral farming, with shelter-belt and amenity tree, shrub, and wetland plantings is described. Dealings with the landowners and regulating authorities are addressed in the paper.

Jan 1, 2003

By Witkowski A

I have the pleasure to present 6 excellent papers in this section all of major relevance to the mining environment of today where competing social, legal and monetary interests and their often complex interaction require serious consideration. This is particularly true today where huge fluctuations in commodity prices makes mining a perilous undertaking while the world increasingly are becoming aware of the serious threat that mans activities has on his environment. The 6 papers deal with such complex issues as safety in an underground environment; How to protect sensitive wetlands well into the next century; The enormeous waterproblems in China and conflicting dewatering/water supply needs; Disposal of contaminated water in sensitive areas and the dynamic interaction between mining companies and legislation.

Jan 1, 1988

The late Carboniferous to early Permian Featherbed Volcanics cover an area of about 3000km near the western margin of the Hodgkinson Basin, in northeastern Queensland. The dominantly ignimbritic volcanic rocks are mostly confined to a single, composite, volcano-tectonic depression, but, along with the associated intrusive rocks, may be divided into two main groups: late Carboniferous I- type rocks and early Permian A-type rocks. Late Carboniferous I-type andesitic to rhyolitic ignimbrites and minor andesite lava crop out in the southeastern, southern, and southwestern parts of the complex, mostly confined to a basin-like depression, or "sag" structure, and are associated with coeval dioritic (and rare gabbroic) to granitic intrusive rocks. Extensive Sn, W and base- metal, and some Au, mineralisation are associated with these rocks, particularly in the southeast. The main part of the complex is of early Permian age, and consists almost entirely of A-type rhyolitic ignimbrite and relatively minor volumes of lava intruded by a peripheral ring dyke of porphyritic microgranite and by resurgent-type plutons of porphyritic microgranite and microgranodiorite. These rocks are associated with sparse base-metal, Au, U, W, and Sn mineralisation.

Jan 1, 1987

By Huajun W, Long LZ

The composition of fly ash and formation mechanism of cennospheres are introduced in this paper. The signification of using this potential new mineral processing resource is emphasised. The beneficiation properties of the components of fly ash, such as susceptibility, specific gravity, size, shape and flotability etc have been examined in detail. A technique was designed to process fly ash from the XiGaoJing power plant in Beijing, and a flowsheet is also presented. Flotabld cennospheres, magnetic beads, sinkable beads, carbon and advanced pozzolamics can be obtained as separate products through this flowsheet. It is emphasised that the beneficiation of fly ash is an efficient means of totally utilising the resource. Examination of the products show that they have good physico-chemical properties. Possible areas of their application are also Suggested.

Jan 1, 1993

By Glatthar J. W, Lauder D. W, Manlapig E. V, Mackinnon I. R

The Ok Tedi copper orebody consists of porphyry and skarn orebodies. The skarn orebodies, identified by different mineralogies, are the source of high intermittent fluorine levels in the mill concentrates. This paper discusses the results of t

Jan 1, 1998

By Hagan T. N, Tucker A. J

The Cumnock Open Cut Mine (COCM) is located in the Hunter coalfield in New South Wales. Five coal seams are being mined, mostly by drilling and blasting, loaders and excavators, and trucks. The annual production of coal is 1.3 million tonnes. Overburden and interburdens consist mostly of siltstones and medium to thickly bedded sandstones. The strata dip to the south-east at approximately four degrees. There are no major faults in the rock mass.

Jan 1, 1995

Discovered in 1896, the Sons of Gwalia orebody is located in a ductile mylonite zone within a sequence of Archaean pillow metabasalts and minor metasediments of greenschist facies which are variably sheared.The ore zone has good continuity, being 110 m wide and 500 m long, dipping 45 degrees east and plunging 70 degrees to the south to a depth of 1500 m downplunge. A strongly-developed foliation is present together with a prominent lineation paralleling the plunge. The mylonite zone consists of unmineralised chlorite schist and a 'U' shaped mineralised zone of chlorite-sericite schist with varying amounts of quartz-carbonate as veins parallel to foliation, boudins, and locally as massive quartz-carbonate. Pyrite is the dominant sulphide present.Grade control utilises RC holes on a 10 m x 10 m pattern, with infill blast rig holes 5 m deep where necessary.Some visual control of ore boundaries is present and, combined with good ore continuity and a knowledge of the structure of the orebody, enables cost-effective grade control to be achieved. To-date, over three million ounces of gold have been produced from the orebody.

Jan 1, 1993

By M D. Rosengren, G Gregor, M F. Young

Over the last 15 years the silver/lead/zinc ore treated at Mount Isa became increasingly complex and lower grade. Metal recoveries dropped dramatically, causing a serious decline in profitability. The ætraditionalÆ response of increasing tonnage to reduce unit cost was unsuccessful, since the additional tonnage was even lower quality ore. A major technical and capital program in the 1990s restored metallurgical performance, but business return was still too low and ore quality continued to decline. In 1996 a new, holistic approach integrated the steps of geology, mining, concentrating, smelting, and refining. Previous assumptions about æfixedÆ and æmarginalÆ costs in mining and processing were shown to be wrong. Detailed analysis showed that some ore sources were reducing profit. This led to a fundamental redesign and downsizing of both Mount Isa and Hilton mines. The result was dramatic increases in head grades, metallurgical performance and plant stability without any capital expenditure. The business is now smaller, but more profitable.

Jan 1, 1998

By Brown GA

Results are presented which demonstrate the feasibility of employing electrolytic membrane technology to process leach liquors derived from alkaline pressure leaching of scheelite concentrates and to recover and recyle sodium carbonate. Thus the problem of disposal of sodium sulphate is avoided. In a further application of the technique sodium tungstate is converted to tungstic acid which can be further processed by three possible routes to crystalline or amorphous tungstic acid or tungsten powder. In each route sodium hydroxide is produced which on carbonation can be recycled as soda ash to the pressure leach stage. Further testwork is required to determine long term operational conditions in the membrane cell and to confirm the effect and deportment of impurities on products. The process has been patented.

Jan 1, 1986

By Corner NG

A sea bed sampling programme by CRA Exploration Pty. Limited over an area of 12000 km offshore from Westland, Southland and Otago, New Zealand, led to the discovery of the Harvester Prospect, an area of some 67 km2 which averaged 189 mg/m3 gold in surface samples. This area was in water depths of 70 to 100 m and contained a high grade core of 33 km2 which averaged 283 mghn3 gold. The gold recovered was fine grained, averaging 124 microns, and indicated a potential resource of approximately 10 t of gold per metre of thickness. Interpretation of existing seismic and geological data suggested that the gold anomaly may be associated with a unit of sediments 10-40 m thick, probably deposited during a lower sea level stand. Two initial attempts at vibrocoring the anomaly produced inconclusive results. In 1989 a much more powerful vibrocorer with scaled up support facilities and a dedicated 24 It turnaround laboratory were employed. The final results clearly showed that the gold was from an uneconomic surface enrichment.

Jan 1, 1990