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By Quast K. B

Samples of limestone and micaceous hematite have been ground in a laboratory batch mill using equal weights of either rods or balls. Values of the Schuhmann distribution modulus, a, have been shown to depend on grind time and do not remain constant as often reported. The linear reduction in a with grind time was attributed to a change in grinding mechanisms with time. The product sizing from ball milling limestone showed a bimodal distribution, but rod milling produced a unimodal size distribution. The product sizing from milling micaceous hematite was difficult to interpret due to the major influence of the shape factor on the transition from screen sizing to cyclosizing.

Jan 1, 1995

The great variety of geological conditions in French coal deposits has obliged the industry to develop different thick seam mining methods. In very steep seams in a dense deposit where stowing is necessary to avoid spontaneous combustion, surface subsidence and water problems, a rising horizontal slice method is used, the coal being hard enough and the seams regular (Lorraine). In very thick and irregular steep seams where the stowing is not necessary, a sub-level horizontal slicing is used; a third method has to be used in Dauphine.

Jan 1, 1976

By L Torckler, J Hobbins

Favona is a blind low-sulfidation epithermal vein deposit in the Waihi Vein System approximately two kilometres east of the world class Martha Hill deposit that has produced nearly 6.8 M oz Au to date. The Favona epithermal system has surface expression in variously altered and mineralised hydrothermal eruption breccias forming a series of low hills that are windows through post mineral dacites and ignimbrites. The tip line of the Favona vein is about 50 û 100 m below surface with a steeply east dipping principal vein structure carrying numerous hanging wall splays in the upper flatter section and thickening down dip where the vein steepens. Host rocks comprise feldspar phyric andesite flows with minor pyroclastics. Although Favona has a strike length in excess of 1000 m and vein widths up to 25 m over a vertical range in excess of 400 m it was only recently discovered after nearly thirty years of exploration by various companies involved in the Martha Hill joint venture that operates the Martha Mine. Since discovery in 2001 a feasibility study based on 27.5 km of diamond drilling in 83 holes has been completed reporting a reserve of 1 Mt @ 10 g/t Au against a resource of 1.8 Mt @ 10.3 g/t Au. Exploration is continuing with a further 20.5km of diamond drilling completed to date on nearby prospects.

Jan 1, 2004

The Mt Muro gold and silver deposit in Central Kalimantan has been in production since December 1994. The geology is characterised by narrow high-grade lodes containing gold and significant amounts of silver. From a largely untrained workforce in the grade control department, production per crew and per geologist has tripled during the three years of production. Grade control drilling evolved from blast hole sampling to reverse circulation sampling. National geologists are trained in basic modeling procedures. A fully integrated reporting and reconciliation system was programed and implemented.

Jan 1, 1997

By Toivanen R-M, Leinonen O, Pekkarinen H

This paper presents developments in designing an integrated mine control system at Kemi mine. The aim of this paper is to present the general structure of the system and to outline some features of the process control strategies. The results o

Jan 1, 1998

By Matthew SP, Hayes PC

The product morphologies formed on the reduction of dense wustite crystals are classified into three types,A) porous iron, B) porous wustite covered with dense iron and C) dense wustite covered with dense iron. The mechanisms of formation of these structures and the effects of impurity elements on the product morphologies are discussed

Jan 1, 1984

By Cullen JF

Australia has a large resource of manganese at BHP's Groote Eylandt mine which has been progressively developed over the last two decades. While much of the product is marketed internationally to the iron and steel industry, substantial quantities are processed in Australia at the Company's ferro alloy works in Tasmania. In addition, small but increasing quantities of ore are being consumed by the non-metallurgical industry. Fluctuating fortunes in the steel industry produce similar trends in the marketing of manganese. The increasing cost of freight and power together with strict environmental control is further affecting the market balance. Mine operators are expanding into the alloy making field. Reduction in usage in less developed countries is occurring.

Jan 1, 1982

By Keele R. A

The Cambrian structure in the Mt Read Volcanics was produced by four deformational events: obduction of forearc-derived mafic/ultramalic complexes in the early Middle Cambrian, a middle Middle Cambrian extensional phase related to the post-collisional Mt Read volcanism and VHMS mineralisation, Middle Cambrian E-W folding, and Late Cambrian N-S folding and basin inversion. The major phase of VHMS mineralisation in western Tasmania is restricted to the very brief period of extensional tectonics within the middle Middle Cambrian. Within this period a N-S graben was produced with a complex series of transfer zones, largely striking E-W. Most VHMS mineralisation is restricted to the top of massive volcanic successions, with several mines close to Cambrian transfer structures. Many of the transfer structures continued to be active until the Devonian. The later compressional Cambrian events are not significant in localising orc formation. Within the Rosebery mine a complex pattern of minor Cambrian normal faults has a second order control on the distribution of the mineralisation.

Jan 1, 1997

By Enever JR

In-situ rock stress measurements conducted in the Phillipines and on Bougainville have revealed stress fields significantly different from expectations based on intraplate experience. The results have potential significance in regard to both engineering practice in the Pacific Rim region as well as in helping to understand the geological processes occuring near subduction Zones.

Jan 1, 1987

By LaBrooy SR

A number of gold processing plants in Western Australia have nickel in their ores, leading to significant levels of nickel on their loaded carbon. The presence of nickel during leaching, adsorption and elution'may have detrimental effects on cyanide consumption, carbon inventory requirements, stripping costs, electrowinning efficiencies and may contaminate the gold bullion.This paper discusses the competitive adsorption of gold and nickel cyanides onto activated carbon and investigates changes in solution parameters that may improve gold adsorption and/or inhibit nickel adsorotion.

Jan 1, 1997

By Guerney P. J

A suspension of finely powdered ferrosilicon in water is the dense medium used in the gravity upgrading of iron ore, diamonds and other minerals. Ferrosilicon can he lost in the plant through corrosion. The greatest corrosion losses occur when

Jan 1, 1997

By Weller KR, Restarick CJ, Stewart PSB

Following a detailed assessment of concen trator performance at Broken Hill South Limited which was reported in a previous paper, the fine grinding section was changed from a parallel arrangement of the two grinding circuits to a series arrangement, and the concentrator per- formance re-assessed. The change to series grinding had virtually no effect on the actual or potential capacity of the circuit to make a final product with 80% passing 100 mesh. However, the fresh flotation feed contained significantly less +150 mesh lead and +65 mesh zinc (material which was shown to float poorly), without an increase in the quantity of poor-floating ultra-fine lead and zinc. From the size-by-size flotation recovery data, it was shown that overall recoveries of both lead and zinc were approximately 1% higher than they would have been without this change in size distribution and it was concluded that this was a direct result of the change in grind- ing procedure.

Jan 1, 1972

This paper describes operational experience with seam gas and spontaneous combustion management, gained during ten years of production history (1993 to 2003) in the Wynn seam at Dartbrook Coal mine. In addition, comparisons are made with more recent operational experience in the overlying Kayuga seam. Development and retreat longwall operations were undertaken in a 4.0 m thick working section of the Wynn seam, contained within the lower quarter of a circa 24 m thick mega seam, from 1993 until mining operations were relocated to the overlying Kayuga seam in 2004. Production from the first block of the Kayuga seam is currently underway with seam gas and spontaneous combustion management requirements being refined as further operational experience is gained. Seam gas management techniques, including pre-drainage with pressurised fracturing, surface to underground goaf drainage of a carbon dioxide rich seam gas and novel, high capacity ventilation circuits, were employed in the Wynn seam. Ventilation strategies included operating up to carbon dioxide STEL concentrations of 3.0 per cent in segregated return airways rather than being limited to the TWA-TLV concentration of 1.25 per cent. The spontaneous combustion experience at Dartbrook Coal has, to some degree, resulted in a change in the way the risk is managed in Australian coal mines. Values of carbon monoxide make and hydrogen concentrations are profoundly different from previously recommended management plan trigger levels and those used elsewhere in the industry. However, the detection of higher hydrocarbons together with rising oxygen depletion ratios and absolute hydrogen concentrations remain as indicators of advancing spontaneous combustion events. In this respect, experience gained in the Wynn seam was important in the initial management of the shallower Kayuga seam, an essentially greenfield site with no prior operational experience being available.

Jan 1, 2005

By A van As

This paper serves to outline the circumstances and causes of the air-blast that occurred at Northparkes Mines in November 1999. It describes the design of the mine, the geotechnical issues surrounding cave propagation and the cave monitoring systems that were in place prior to the event. A short description of the air-blast that followed a sudden collapse is given. Details of the risk assessment process that evolved during the rectification process are provided with their subsequent modification to form the core of a major hazard monitoring process. The system is in line with the recommendations given by the Coroner resulting from the inquest into the deaths of the four people who lost their lives during the air-blast.

Jan 1, 2005

By Nickelsen J, Theisen KG, Hansen PH

The use of stationary calciners in the processing of aluminium hydroxide has emphas- ized the importance of Bayer hydrate properties with respect to particle breakdown during calcination and subsequent treatment. Test results from calcination of several Bayer hydrates to sandy alumina in the FLS Gas Suspension Calciner (GSC) were obtained in a 250 kg/h pilot plant unit. Particle breakdown during calcination was influenced by content of solid sodium oxalate, trapped in the hydrate particles and operating gas velocities. Owing to the design and operational principles of the GSC it is possible to reduce particle breakdown to at least the same as what is found in long rotary kilns. Other major advantages reviewed are obtained through simplifications in plant design and operation, pointing to low specific power and heat consumption, and generally low production costs, thereby providing an attractive alternative to fluid-bed calciners.

Jan 1, 1981

By Morland R

In the course of an exploration program aimed at increasing Pasminco Mining's ore reserves, an electromagnetic survey down one of the underground drillholes at the North Mine, Broken Hill, recorded a broad and persistent response. This paper demonstrates that the anomaly was not due to any geological feature, but rather was caused by 'self-response' of the sensing probe. The observed results are due to the surveyed hole lying within a resistive environment and having distinct, but not unusual, changes in dip.This phenomenon has not been widely reported and we believe that there are likely to be similar cases in company records where very genuine looking responses are due to self-response rather than sulphides. These false anomalies can be recognised by correlating the observed data with the calculated down-hole component of the transmitting loop's primary field.

Jan 1, 1994

By Wilkins C

The Browns Creek deposit is located 8 kin west of Blayney and 220 km west of Sydney (Figure 1), at lat 33¦32'S, long 149¦10'E on the Bathurst (SI 55-8) 1:250 000 scale map sheet. The total measured, indicated and inferred resource at 30 June 1997 was 1.29 Mt at 6.39 g/t gold and 0.45 per cent copper. During the 1996 - 97 year 263 557 t of ore at 6.30 g/t gold and 0.48 per cent copper was treated, to produce 47 496 oz of gold, and 1 169 t of contained copper in concentrate. As the result of an increase in the resources and reserves, because of underground exploration drilling and accelerated mine development, 1997 production at Browns Creek is predicted to expand from 240 000 to 390 000 tpa, to yield more than 70 000 oz of gold per year.

Jan 1, 1997

Surface and near surface particulate gold occurs sporadically over an area of some60 km2 between Vunda and Navilawa on the west coast of Viti Levu, Fiji.Background grades of 0.01 ppm can be found in the zone of weathering from 3 to ZQm but, at Vunda, attain significance within certain "localities" ranging from 1000 m2 to 35000 m2 in area. Intense and deep weathering renders geological interpretation difficult but the higher grades seem to relate to equally weathered dykes and apophyses which intrude the tuffaceous country rock.Both country rock (5.4 m.y.) and intru-sives (4.8 m.y.) are of shoshonitic composi-tion and all rocks are consanguineous. At Navilawa, on the eastern end of the zone, basic monzonite crops out as a sizeable stock carrying low grade porphyry-type copper and gold. Between Navilawa and Vunda intrusives are as large apophyses and dyke swarms, and at Vunda, on the western end, only the upper ends of dykes and small apophyses are exposed carry-ing various sulphides, magnetite and rutilein hair line fractures. The level of erosion is thus deeper to the east and shallower to-ward tha wPst_

Jan 1, 1984

The rocks of the Serranias Chilla massif of Bolivia are a suite of metamorphosed Palaeozoic basalts and associated continental sediments. Whole-rock trace element geochemistry of the basalts suggest a calc-alkaline affinity and indicate that subduction extended as far north as the Bolivian Altiplano during lower Palaeozoic time.

Jan 1, 1990

By Caress ME, Knight MD

The eruption 75,000 y ago of the Younger Toba Tuff ignimbrite and associated ash-fall ranks as the greatest known volcanic event of the past million years. The ignimbrite is known to cover 21,000 km2 (it may extend farther under alluvium of the coastal plain) and forms a low-angle depositional shield centered on the Lake Toba caldera. The ignimbrite is largely nonwelded and shows systematic outward decreases in lithic and crystal contents and clast sizes. Coarse lithic lag breccias that occur at places 85 km apart point to two or more vents on a fissure having this length. The extensive associated ash-fall traceable as far as Malaysia and India is evidently a co-ignimbrite ash but could have a phreatomag-matic component. The Lake Toba caldera measures95 x 35 km and is >1 kn deep. It is not a single caldera but comprises several contiguous depressions and grabens diversified by two re-surgent domes. Earlier parts of the caldera are related to at least two earlier ignimbrites including the Older Toba Tuff dated by Chesner at 0.5 Ma. The caldera is elongated parallel to, and is only 25 km from, the great Sumatra strike-slip fault, and it can be considered almost certain that the caldera is in part a kind of pull-apart structure. The ignimbrites are very crystal-rich. There is no reason to think basaltic magma was involved in their emplacement. Together with ash-falls they have a total volume of several thousand cubic kilometers. They can be categorized as originating from partially crystallized granitic magmas that erupted because tectonic pull-apart occurred several times across the pluton. Small rhyolitic lava domes on fault-lines comprise the youngest volcanic products.

Jan 1, 1990