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By Gooday PE, Brech GE

Ore reserve categories used by Pancontinental Mining fall into one of three fundamental groupings: Geological In Situ Reserves Mining Reserves Production Estimates The first of these describes the total reserve within stated parameters without implication as to its mineability. The second is that part of the Geological In Situ Reserve which is considered mineable under a specific mining plan. The third is the Mining Reserve adjusted with appropriate dilution and recovery factors and thus represents the best estimate of the tonnage and grade of production. This practical three category system mirrors the standard steps traditionally taken in ore reserve estimation and readily conveys the basis of the estimates. An important, but secondary classification can be added to qualify the level of confidence in these estimates using the terms: Proved (or Measured) Probable (or Indicated) Possible (or Inferred) These terms can be applied to any of the fundamental groupings, but it is generally implicit that the level of detail required to produce meaningful Mining Reserves or Production Estimates would require the basic Geological Reserve to be at a Proved or at least Probable level of confidence. The application of these classification systems by Pancontinental is illustrated by reference to the Paddington Gold Project. The methods of calculation are described including the use of geostatistics. Reconciliations of actual production with predictions from reserves are carried out monthly and annually. To date there has been an excellent correlation with Production Estimates, based on both manual and geostatistical calculations.

Jan 1, 1987

By Johnson RW, Rogerson R

New perceptions of the nature of volcanic hazards on Bougainville Island have resulted from a recent remapping of the geology of the island. Ignimbrites and calderas have been identified at six Quaternary centres (Emperor Range, Tore, Kunua, Billy Mitchell, Loloru, and Laluai), and large-scale explosive activity now must be identified as a significant volcanic hazard on the island. Billy Mitchell and Loloru volcanoes are identified as the most likely sites of future, major, explosive activity. Billy Mitchell was recognised formerly as an extinct volcano, but is now known to have produced major eruptions 370 and 918 years BP. Five ignimbrite units recognised at Loloru range in age from about 12 700 to 3200 years BP. Bagana is an active volcano in central Bougainville, but its explosive activity is relatively minor and does not significantly affect areas beyond the uninhabited area of the volcano itself. Balbi is the largest volcano on Bougainville and has an extensive geothermal area at its summit. It was thought to have been in eruption last in the early nineteenth century. However, 370 and 940 year BP plinian ashfalls from Billy Mitchell cover the central area of Balbi, so the latest significant activity from Balbi may have been at least 1000 years ago.

Jan 1, 1990

By Nightingale R, Johnson B, Bensley C, Vince A, Keast-Jones R

In order to counter the massive increase in the level of near gravity material that would follow the reduction in dense-medium cyclone separation density at B.H.P. Slab and Plate Product Division's B and C coal preparation plants, "wing tank" systems to control medium density to within ¦0.005RD units have been installed. However, despite very precise density control, cyclone metallurgical performance has been less than satisfactory. The approaches taken to identify the causes of this poor performance and to justify alterations in operational and maintenance practices are presented.

Jan 1, 1987

THE filter-press, which has done so much for the successful-treatment of the sulpho-telluride ores of Kalgoorlie, has a serious rival in the vacuum process, and this paper is written with a view to arousing more interest in the cheaper working of the press, it being doubtful whether its efficiency in extraction can be improved upon. Before proceeding with the actual working of the press, it may be as well to make brief mention of the character of the ore treated at the Associated Northern Blocks, where these notes were compiled. A sample from several weeks' run was taken of the raw ore, with the following analysis...

Jan 1, 1911

The elements of consistent structural de sign models for underground structures are explained. Such models should comprise at least ground properties, excavation and support methods, computational models for analysis, failure hypotheses, and in-situ monitoring. The fundamental characteristics of the interaction between ground and support are investigated. Then, plane strain models for soft ground tun- nelling and design models for rock tunnelling employing stress release at the tunnel face are elaborated. Some numerical evaluations are gi- ven in diagrams, comparing approaches of dif- ferent authors. Comments are presented on nume- rical three-dimensional models (visualized by structural models for mining in rock salt), on the interaction of in-situ monitoring and design, on structural safety for underground structures, and finally on the general develop- ment of structural design models in geo- Techniques.

Jan 1, 1987

The design of mine ventilation systems for the BHP Steel Division Collieries is based on the acquisition of ventilation survey data for the establishment of a realistic computer net- work model. The branches which form the net- work for the computer models are calculated from a range of resistance factors incorporat- ing both a frictional and shock loss component. Since shock losses can account for up to 30 per cent of the total energy losses in mine airways the use of friction factors alone without accounting for shock losses will result in the choosing of an insufficiently performing fan. Published tables of friction factors have in- variably been taken from metalliferous or single entry studies and consequently are not reliable for Australia's mining conditions where multiple entries with regularly spaced cut-throughs are the normal practice. Typical resistance factors for roadways of rectangular cross-section 5.5 m x 2.0 m, with coal sides, have been found to vary from 0.11 Ns2/m8/km where no timber supports are used, to 0.98 Ns2/m8/km where double centre legging together with wooden chocks is used. In addition to the range of resistance factors due to varying support methods, the nature of use for a roadway is very significant because of the condition of repair and upkeep maintained.

Jan 1, 1983

By Black LP, Law SR, Oversby BS, Mackenzie DE, Wyborn D

Three volcanic sequences of different ages occur close together in the Burdekin Falls area, southeast of Charters Towers in northeastern Queensland. The oldest is equated with the Cambro-Ordovician Mt Windsor Volcanics, and consists mostly of strongly deformed, regionally metamorphosed rhyolitic lava and minor feldspathic to quartzose sandstone. This unit is overlain by folded but unmetamorphosed Upper Devonian-Lower Carboniferous volcanics (DCv) of the lowermost Drummond Basin sequence. The primary volcanic facies of (DCv) principally comprises andesitic and rhyolitic lavas, and dacitic ignimbrites. Similar volcanics are widespread in the lowest formations of the Drummond Basin sequence elsewhere, and dominate that sequence east of the Anakie Inlier. The youngest volcanic sequence is Late Carboniferous and composed of lower, more deformed, compositionally diverse ignimbrites, lavas and conglomerates, overlain by generally less deformed rhyolitic ignimbrite sheets. The upper part is equated with the Bulgonunna Volcanics which extend 90km south to the Mt Coolon area. The Burdekin Falls area contains an ignimbrite stratigraphy different from that in the south. However, one of the most voluminous ignimbrites (Locharwood Rhyolite) in the southern stratigraphy is also present in the north, enabling the two to be correlated.Each of the three volcanic sequences reflects proximity to eruptive sources. Both the volcanics at the base of the Drummond Basin sequence and the Late Carboniferous volcanics are largely the products of subaerial eruptions. The former were erupted from several intermediate-composition volcanoes, and the latter from multiple-vent silicic calderas. All three sequences are considered to be prospective for precious and/or base metal mineralisation. Polymetallic massive sulphide deposits occur in the Mt Windsor Volcanics farther west, and many epithermal gold prospects and mines are hosted by the volcanics at the base of the Drummond Basin, especially east of the Anakie Inlier. The Late Carboniferous volcanic sequence is deeply eroded, and co-magmatic high-level plutons are widely exposed; this sequence may therefore be more prospective for deeper-than-epithermal mineral deposits.

Jan 1, 1990

The calibrated thermal IR data of part of Cambay Basin is used to determine surface temperatures and to detect the heat flow. Applying the conductive heat flow continuation technique, the three dimensional configuration of the hydrocarbon bearing reservoir was defined. The zone delineated by the present study coincides with the oil-bearing structures inferred by seismic survey. The results indicate the possibility of the technique as an effective tool in hydrocarbon exploration.

Jan 1, 1986

By Sjaw WJ

Conditional simulation is a set of geostatistical tools that is becoming popular as powerful personal computers make the use of these tools less costly. The more familiar set of tools for spatial estimation has a number of varieties (eg Ordinary Kriging, Simple Kriging, Multiple Indicator Kriging, etc) each suited to particular solutions of the problem of estimation, for example predicting the average grades of blocks in a region from more or less sparse data. Similarly, conditional simulation has a number of varieties, discussed in this paper, which in various ways address the problem of characterising the variability of a deposit between the known data locations.Conditional simulation can provide a number of equiprobable images of a deposit, at a finer resolution than would be economic or practical to sample, and that can be constrained by various criteria (which may be geological, statistical and geostatistical), to ensure that the images reasonably represent the deposit. These images can then be used to assess the risk involved in various practical mining decisions. Examples are provided where conditional simulation has been used for validating resource estimate parameters, optimising grade control sampling grids, and for ore block optimisation for mining grade control.

Jan 1, 1997

Various aspects concerning gold are mentioned below. These have no common theme but suggest points of interest any one of which, if warranted, could lead to development later and elsewhere. 'High level' auriferous gravels The gold deposits of Victoria are commonly classified as being either primary or secondary. Most primary occurrences comprise gold present in quartz reefs, together with other lode-like occurrences in which gold is associated with various sulphides, with or without quartz. Secondary occurrences are derived by physical release of primary gold and subsequent concen- tration of it as a constituent of sediments. Secondary gold deposits may be themselves eroded so leading to third or even fourth generation gold.

Jan 1, 1982

In 1972, metallurgical testwork on Renison ore indicated a significant proportion of low specific gravity, tin-barren material ideally suited to heavy medium separation (HMS). Further technical and financial studies provided adequate economic justification and in December 1974 the Renison HMS plant was cannissioned. Initial operations were interrupted by the imposition of tin production quotas for three months in 1976; they were also beset with difficulties particularly with regard to mechanical wear. During the first two operating years much develognent work was carried out including installation of a pyrrhotite flotation bank in the medium recovery circuit, investigations into various wear-resistant materials and the use of atanised rather than milled ferro-silicon. By 1977/78 financial year satisfactory performance had been achieved and since then the average floats rejection has been 18.8% of the total ore treated with an associated tin loss of 2.96%. Developnent has nevertheless continued during the last three years, principal modifications being the installation of larger aperture desliming screens and improvements to the overdense cyclone circuit.

Jan 1, 1978

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 Sarracino R. S

A number of ideal detonation codes are used internationally for estimating the strength of explosives compositions. Important and far reaching decisions by explosives users are ofen based on the predictions of these codes, but since different codes can deliver very different answers for the same composition, there is a strong possibility of decision makers being misled. In order to both provide a sensible basis for comparing the theoretical energy from explosives from different manufacturers and to prevent the entire rating system from slipping into disrepute, it is in the interests of all to reach agreement on fundamental criteria used by detonation codes for detemtining strength. The problem is illustrated by a case history and basic conventions are proposed, specifically the adoption of energy of reaction as a fundamental and code independent indicator of explosive energy, and agreement on disclosure by suppliers of key non-proprietary information. These measures would assist explosives customers in assessing the true strengths of explosives from the strengths calculated by the different ideal Codes.

Jan 1, 1990

Western Mining Corporation, managing partner of the Windarra Nickel Project are in- stalling a raise-bored haulage shaft and under- ground crushing system at the Mt. Windarra Nickel Mine. The system will be the second of its type installed by W.M.C., the first being in- stalled at the Otter-Juan mine in Kambalda in 1976/77. Both haulage systems became necessary as a result of the increasing production limi- tations, and escalating costs of a deep decline mine. The Windarra haulage system required a single 3m diameter vertical raise drill hole to a depth of 470 metres. Two five tonne skips in balance will hoist crushed ore and mullock to the surface, at a design rate of 200 tonnes per hour, effectively reducing truck haulage leads by up to 50%. It is expected the project will be in full operation by mid 1982 and will enable the mine to achieve an annual production rate of 600,000 t.p.a. by 1983.

Jan 1, 1982

By Zhen Y. Y, Cook A, Jell J. S, Fleming P. J G

Remapping of the Burdekin Basin has resulted in subdivision of the three interfingering basin-wide megafacies previously recognised in the Early to Middle Devonian Fanning River Group. Eleven carbonate and siliciclastic facies are now identified within the three megafacies, representing coastal plain, shoreline, nearshore, and shallow marine shelf depositional environments. The facies reflect two phases of a major transgression. An initial phase, in the Early Devonian, was confined to the far north of the basin, whereas a second, main phase, resulted in the encroachment of the sea from the east or southeast in the Middle Devonian.The proposed depositional model begins with the drowning of a coastal plain and the transgression of shoreline and nearshore facies between granitic and metamorphic headlands and/or islands. This was followed by the deposition of a patch reef and fringing reef complex including stromatoporoid and coral bioherms, biostromes, and oncolitic, crinoidal, and brachiopod-dominated banks/shoals, together with foreslopes and submarine channels, carbonate rubble deposits and terrigenous sediments. Sedimentation during the peak of the transgression was dominated by sheltered carbonate shelf facies, the maximum, flooding surface being recognisable across most of the Burdekin Basin. Progradation of muddy and sandy nearshore bay and shoreline facies soon followed, terminating carbonate deposition.

Jan 1, 1990

The Woodlawn base metal sulphide deposit, located 50km S of Goulbum, New South Wales, was mined as an open pit operation for 10 years from 1977, producing 8 million tonnes of ore. Underground development began in 1985 and reached full production of 500,000t/yr as open pit mining ceased in mid 1987. Underground development highlighted the extensive deformation and intense alteration associated with the deposit and the host rocks.The deposit occurs above an acid volcanic pile in a sequence of interbedded and interfingering shales, cherts, volcanogenic sediments and pyroclastics of mid to late Silurian age intruded by dolerite sills.

Jan 1, 1990

By Culshaw MG, Deaves AP, Bell FG

The accurate prediction both of the water ingress into sub-surface excavations and the nearby groundwater pressures is of fundamental importance to the control of the stability and flooding of tunnels or mines constructed below the water table. Predic- tions are usually based on laboratory and in situ permeability determinations together with observations of groundwater conditions in boreholes. Although established theoretical methods provide a basis for prediction, the actual ingress depends on many factors. The objective of this paper is to explore the geological controls on groundwater conditions, and the available methods of prediction of both groundwater flow and pressure are outlined. Salient points are emphasised by reference to a case history involving the construc- tion of a tunnel in a faulted and mixed sequence of sandstones, siltstones, shales and coals. Water ingress quantities have been monitored for a variety geological and geotechnical conditions including heavily faulted and mine disturbed ground. The overall results are discussed with reference to the relevant hydrological and geologi- cal conditions in terms of the geological structure, lithology and rockmass condition as well as the construction methods.

Jan 1, 1988

Industrial and telecommunications organizations around the world are now turning to optical fibres to satisfy their growing needs for data, voice and video communications and to solve transmission problems in noisy and hazardous environments. Already, coaxial cables have been made obsolete for intermediate and long distance applications and fibres are making in-roads on other copper cable and microwave system techniques.The idea of optical fibres is not new, but techniques to manufacture the high quality cable and components required have only recently been developed. Nonetheless, the technology is now advanced, reliable and mature, and costs are plummeting with increased production and market competition.The mining industry has benefited greatly from developments in electronics and communications over the years. Optical fibres are to have a further significant impact and the time is now right for the industry to begin to exploit the many advantages of this new medium. Applications include data transmission, long distance telecommunications, measurement and control systems, surveillance, computer networks, etc.This paper briefly describes the characteristics of optical fibres, current status of the technology, applications and possibilities for future development.

Jan 1, 1984

The purpose of this paper is to discuss briefly the problems encountered in designing and sinking No 7 shaft, and to present the methods employed in the operation.The illustrations accompanying the paper show the details of the construction of the equipment used in completing No 7 shaft, consequently the descriptions appearing in the text are brief outlines only. Mineral leases Nos 7 and 8, held by the Broken Hill South Limited, comprise an area of 69.5 acres. The length of the holding is approximately 2500 ft.The western orebodies, which are the main producing masses, enter the property at the northern bonndary. Generally, the dip of the orebody is to the west, and the pitch to the south, but local variations occur and even a reversal of pitch has been noticed. The angle of dip is approximately 70 degrees and the angle of pitch 45 degrees.

Jan 1, 1932

By M Skead, H Michael, R Chase, A Davidson

Ashanti Goldfields CompanyÆs (AshantiÆs) most recent development is the Geita Project in the Lake Victoria Goldfield of NW Tanzania. It comprises six distinct gold deposits within two mineralised trends: Nyankanga, Lone Cone, Geita Hill (Geita trend) and Matandani, Kukuluma and Area 3 West (Kukuluma trend). Between 1936 and 1966, the Geita area produced an estimated 5.5 M tonnes of ore from five underground deposits at an average recovered grade of 5.3 g/t. The discovery of Nyankanga was made by Ashanti in 1996 from RAB drilling of a +100 ppb Au anomaly in laterite soil above ferricrete cover. The Kukuluma trend was discovered by SAMAX Resources (taken over by Ashanti in 1998) between 1996 and 1997 from RC drilling of a +80 ppb Au laterite soil anomaly. Oxide facies banded iron formation (BIF) of the Upper Nyanzian System forms prominent topographic ridges and is the dominant host lithology for gold mineralisation. The ridges are flanked by felsic tuff units which lie stratigraphically above. Syn-genetic lamprophyre (vogesite) and post-genetic felsic dykes are also seen in the Geita trend. At Nyankanga a granodiorite-diorite suite has intruded as dykes and sills into BIF from a plug centred on a WNW fault and has produced wallrock alteration assemblages similar to those seen in Cu-porphyry systems (potassic, propylitic, etc) as well as sulphide and gold deposition. However, the main ore-grade mineralisation (as in the rest of the Geita trend) is controlled by low-to-medium angle structures dipping north-west and north with numerous splays in the hanging wall. High-grade shoots at Nyankanga plunge to the west and to the north-west, being lithologically and fault-controlled respectively. At Geita Hill the higher grade shoots are controlled by fold noses in BIF dipping to the north. Free gold occurs within fractures of sulphides. The deposits of Kukuluma and Matandani occur on an ancient (possibly Cretaceous) erosional plateau and are related to two WNW to NW trending shear zones, discordant to the local strike of the BIF sequence. Complete oxidation occurs up to 120 m depth and there is a strong supergene component to the gold distribution. Primary gold mineralisation is divisible into two distinct assemblages: arsenopyriteûpyrrhotiteûmagnetiteûchlorite associated with brecciated cherts and pyrite associated with shaley banded ironstones. Area 3W is most likely the fault-displaced extension of the same mineralised trend and comprises thin, intermittent zones of high-grade gold mineralisation occurring adjacent to a ridge in banded cherts and minor BIF. Current resources (measured, indicated and inferred) for the project are estimated at 89.24 Mt at an average grade of 4.17 g/t (11.97 Moz of contained gold) at a 1.0 g/t cut-off grade. Of this 9.83 Moz is within the Geita trend and 2.14 Moz is within the Kukuluma trend. A resource of 2.74 Moz is from an inferred resource at depth at Nyankanga where the viability of an underground operation is being studied. Proven and probable reserves are 49.77 Mt @ 3.46 g/t (5.54 Moz) based on a $325/oz gold price providing a mine life of ten years at an average production rate of 500 000 oz per year. Reserve estimation was carried out using mineable polygons to select resource blocks based on a series of mining and costs parameters. In addition key cost parameters were tested to provide sensitivities for pit optimisations and pathfinders for negotiations with suppliers and contractors. Construction began in March 1999 and first gold is expected to be poured in the second-quarter 2000.

Jan 1, 2000