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By Marquez W

Trace fossils have been found in Bolivian Silurian sediments in "La Iumhre" area close to La Paz-Bolivia.Tracks, are good indicators of depth and environment. A detailed study of the ichnogenus is made.The depth and environmental deposits are analyzed to determine the facies. It was shown that the trace fossils of Silurian sediments in La Paz belong to the Zoophvcos and Nereites facies.

Jan 1, 1990

By Hammond J. R, Ward T. A

The Tom Price orebody, in the Hamersley Ranges of North West of Western Australia, is mined by Hamersley Iron Pty. Limited. The orebody is a folded sequence of hematite and shale bands capped with goethite, with a con- sequential variable iron content. The overall grade is below that required to yield spec- ification product, necessitating selective mining, 'Zone Plans' based on geological structure have been developed to yield forward information on material types and grades. Short and medium term mine plans - the initial stage of quality control - are based upon these 'zone plans'. Blasts are laid out to break to the grade boundaries, thus minimising dilution, and the samples taken from the blasthole cuttings provide blast grades. Blending of shovel out- put from different blasts forms the operational basis of grade control. Shales, being more friable than hematite, produce fines that are lower in iron grade than lump. Quality control in the mine centres around maintaining the target fines grade, compensation being applied in the mine if the fines grade lies outside the target range.

Jan 1, 1973

The standard charge weight scaling laws imply that only one particular delay (that possessing the maximum instantaneous charge) contributes to the ppv. However, the present analysis clearly demonstrates that a varying number of blastholes contributes to the ppv. This number also increases with distance, x, between the blast source and the detector, and is caused by waveform broadening due to attenuation. Thus the operative charge weight, itself, is also a function of the distance, and so makes the standard charge weight laws difficult to implement. If the delay time scatter is neglected, then, under certain conditions, relatively simple expressions can be derived for the ppv magnification, FN, as a function of the number, N, of blastholes. When the influence of delay scatter and random fluctuations in each blasthole vibration is included using Monte Carlo simulations, then, to a first approximation, the condition FN=KNx applies, where KN is a constant dependent upon N. Unfortunately, however, for any particular blast this condition cannot be distinguished from the standard charge weight scaling law. The dependence of ppv on N would only be apparent if blasts of differing N were to be compared in an otherwise identical environment. Since this situation is very difficult (if not impossible) to realise, then the influence due to N, although significant, goes largely undetected. Another problem associated with standard charge weight scaling laws is the difficulty of accurately assessing the appropriate charge weight, even if attenuation broadening is neglected. For example, if a number of blastholes are very close, then they experience a vibration interaction which is non-linear. However, if the same blastholes were to be widely spaced, then the separate vibration signatures add linearly. The standard charge weight scaling law fails to distinguish between such linear and non-linear regimes. Unfortunately, in many production blasts, both regimes exist throughout various portions of the blast spatial pattern and so makes it difficult to determine the operative charge weight. The solution to the combined influence of waveform broadening and linear/non-linear interactions will obviously require substantial future research. A possible solution may be found in the use of numerical dynamic codes.

Jan 1, 1990

By Quinlan M. J, Ratcliffe J. S

Chemical kinetics is a dependent process which usually correlates the rate at which a reaction proceeds with the mechanism descriptive of the manner by which reactive particles interact. Given the latter, the object gen- erally is to find the reaction rate dependency in terms of an intensive property of the system - number of reactive particles present, and of the energetics of the system - usually temperature. Chemical kinetics depend on a dem- onstration that reaction considerations alone control the phenomenological process under study. For these rea- sons, chemical kinetics are usually involved in homogeneous gaseous systems. Even in liquid homogeneous sys- tems earliness or lateness of reactant mixing rather than chemical kinetics may be controlling. Considerations of transport phenomena are involved in heterogeneous systems and often control the observable rate:an additional problem in such systems is to apportion the rate due to mass transfer - usually a linear process - and that due to reaction which may be linear or non-linear. Experimentally, conditions are often chosen so that only one consideration controls but this becomes more difficult where solid phases are involved. Kinetic modelling involves considerations of chemical kinetics, transport phenomena, and factors attributable to the physical environment in which the process takes place. The latter two considerations may be quite different as between experiment and plant. The kinetic model may be a mathematical representation of a conceptual mech- anistic model of the reaction. Alternatively, it may be an empirical relationship resulting from, for example, some curve fitting procedure applied to experimental data. The latter approach may be necessary where the system is particularly complicated.

Jan 1, 1975

By Lunt D

Arsenic is classified chemically as a metalloid. That is, it has properties intermediate between those of metals and non-metals. Like non-metals, it combines with many metals to form arsenides (eg arsenopyrite FeAsS, niccolite NiAs, sperrylite PtAs2), but like metals it forms sulphides and oxides (eg realgar AsS, arsenolite As203). Arsenic is distributed widely in the Earth's crust at an average concentration of 1.5 mg/kg and is present in more than 150 minerals.

Jan 1, 1991

By Romanovsky N. P

The Pacific Mobile Belt (PMB) is characterized by old origin and complex evolution both in time and space. As the global structure, the PMB is a narrow tectonic region dividing two plan-etary hemispheres, viz. the Pacific and IndoAfro-Atlantic ones, the relative shifting of which defines the character of many geodynamic processes in this belt. The PMB features inhomogeneity of structure, special matter composition characteristics, sharply broken-out topography, and intensive fields. Generalized anomalies of the gravitational field closely correspond to the PMB boundaries defined by the real features, i.e. the andesite line and distribution areals of Mesozoic-Cenosoic granitoids. The belt boundary position is controlled also by seismic velocity anomalies at a depth of down to 200 km. The modern PMB deformation is defined by the left-hand equatorial shift and rotation of the Pacific Ocean counterclockwise. This rotation is non-uniform in time and of an oscillating character. The motive forces of the phenomenon are considered.

Jan 1, 1990

By Armstrong AB

It has been identified that particulate matter in the form of suspended solids and bed load has the ability to adsorb heavy metals. Each year Ranger Uranium Mines Pty Ltd (RUM) identifies potential danger areas which could become major sediment sources during the wet season. Methods of suppressing sediment uptake such as hydromulching and coating areas with Poly Vinyl Acetate (PVA) glue are used. Other methods of reducing the sediment load after uptake such as diversion bunds, filters across drains, stone filters, minor sumps and settling ponds are also used. The 1983/84 wet season saw drain sediment loads reduced to acceptable levels before the water reached the outside environment. Studies to qualify and quantify flows from minor drains are still underway.

Jan 1, 1984

By Drain P, Dibdin T. R

THE completion of the Linda incline man and supply haft at the Mount Morgan Gold Mining Oompany's mine led to an investigation of the various safety gears in general use in mining shafts. One of these gears completely fulfilled the necessaryconditions. This paper endeavours to give a description of the man car and safety gears now operating in the before mentioned shaft, together with the main considerations leading to their design and sub equent adoption. Fig 1 diagramatically shows a longitudinal section of this shaft.

Jan 1, 1911

The paper, one of two papers on the Queensland Railways Brunswick Street tunnels presented at the VIII Australian Tunnelling conference, describes documentation, tendering and construction aspects.Tender documents were written to reduce the risk taken by the contractor. Details of tenders received are analysed and the changing industrial situation at that time described.Construction aspects covered include mobilisation, major equipment, tunnelling equipment and manning. Program and progress are reported including industrial relations and advance rates for Mitsui-Miike S-200 and S-65 roadheaders. Cycle times and performance in terms of cutting rate and pick wear are provided for the roadheaders.

Jan 1, 1993

By Coppock BW

Sintering of lead and zinc concentrates is practised by Sulphide Corporation Pty. Limited to provide both desuiphurised lump sinter feed, for simultaneous reduction to zinc and lead in the Imperial Smelting Process blast furnace, and sulphur dioxide gas for sulphuric acid manufacture. From November, 1969 a 20 percent increase in production rate has been obtained through improvements in operating technique. A gradual increase in bed permeability was achieved by modifications to the feed mix conditioning equipment and by improving moisture control. However advantage could not be taken of the higher permeability to increase sulphur elimination because the hardness of the lump sinter decreased. Higher throughput, better quality sinter and more stable sintering conditions were however made possible by simultaneously: 1. reducing segregation and compaction in the sinter bed, by narrowing the discharge opening of the main layer feed hopper, 2. reducing the sizing of sinter returns to give a closer size spectrum of particles in the feed mix, and 3. increasing the sulphide sulphur content of the feed mix to give higher bed Temperatures.

Jan 1, 1972

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

The relevant characteristic of the evolution of the Pacific continental margin of South America during the Mesozoic-Early Cenozoic has been tectonic segmentation. This has controlled suc-cesive episodes of sedimentary accumula-tion, extrusive and intrusive magmatism and deformation that ocurred at conver-vergent plate edges. During this inter-val, at least three main transverse boundaries played an important role conditioning the existence of paleo-segments of different longitudinal extent at various Periods. These probably correspond to deep-seated faults in the Huancabamba Deflection and at the Arica-Santa Cruz Line; the third boundary projects westward to the Chile Ridge. Tectonic activity appears to have been continous at the Huancabamba Deflection at least since the Triassic. The Arica-Santa Cruz Line was probably an active boundary during the Triassic and Cretaceous; the southernmost boundary may have started to be active at the end of the Jurassic. This tectonic activity has determined the subsidence - uplift and paleogeographic conditions of the paleosegments.

Jan 1, 1990

By Thompson AG, Cadby GW

The New Austrian Tunnelling Method (NATM) is a proven concept for the safe and economic construction of underground facilities. This is especially true for tunnelling activity where changing ground conditions are often encountered. However, the principles central to the NATM have gained only limited use within Australia, presumably due to the measurement process inter- fering with tunnel driving and the cost associated with instrumentation and interpre- tation expertise. The design and operating principles of two basic instruments are explained together with laboratory simulated test results and suggest- ions for use in an integrated NATM style approach to underground excavation and construc- tion. The two instruments monitor load in rock reinforcement and deformation in rock or primary and secondary linings. The instruments may be fitted with a miniature display module which outputs the measured parameter in engineering units directly. The design of the sensing components allows the instruments to be installed in various configurations suitable for routine performance monitoring, quality control, support element testing or detailed investigations. The display module which reduces the need for instrumenta- tion expertise should suit contractors and allow performance data to be obtained which quickly may be used to modify support procedures to suit ground conditions. When complemented by convergence measurements the devices enable most facets of the NATM to be implemented.

Jan 1, 1987

By Parsons A. E

The application of known pelletizing tech- nology was successful in the agglomeration of zinc concentrate into pellets of minus 6mm siz- ing using fine zinc calcine and sulphuric acid as binder. Subsequent roasting trials conducted in a 0.3 m diameter fluid bed reactor, showed that the pellets satisfactorily withstood hot physical abrasion during fluidization. Fines generation was low and the pellet calcine was hard, possessing excellent handling properties. Results of laboratory scale static pellet sinter- ing tests showed conclusively that the deterior- ation in sinter physical quality experienced with fine calcine was not apparent when the calcine was added to the mix in pellet form. Based on the results of small scale exper- imental work, a one tonne per hour pilot plant was constructed and operated. Several thousand tonne of pellets were produced-for fluid bed roasting in Badische Analin and Soda Fabrik (B.A.S.F.) turbulent layer (T.L.) roasters previously designed for roasting iron pyrite concentrate. Continuity of the T.L. fluid bed roasting operations was achieved when the waste heat boilers were replaced with atmospheric coolers and thus eliminated the problems of gas flow restrictions. Sinter plant trials were conducted over a period of two weeks with the addition of pellet calcine to the sinter feed. Results showed a marked improvement in sinter plant performance, and as a result of better bed permeability, increased sinter production was achieved, with- out significant deterioration in sinter quality.

Jan 1, 1974

By Morrison RD, Peberdy NJ

Simulator training provides a cost effective method of training operators in both the process and control aspects of a metallurgical plant. The components and requirements of a training simulator are described along with the benefits to be gained from simulator training. A table summarizing some applications of metallurgical training simulators is Given.

Jan 1, 1991

By Howarth W. J, Sowerby B. D, Watt J. S

On-line analysis systems have found widespread application in the metalliferous mineral and coal industries. The continuous analysis and rapid response of these systems has led to improved control of mining, processing and blending operations, with increased recovery of valuable minerals and coal combustibles.The paper reviews developments in on-line analysis by CSIRO and Mineral Control Instrumentation Ltd which led to the award of the Australia Prize 1992. These commercialised systems analyse mineral and coal slurries; determine the ash and moisture contents of coal on conveyors, and the moisture content of coke on conveyors; and determine the carbon content of fly ash. These gauges are estimated to have resulted in productivity increases valued at $50 million per year to Australia.

Jan 1, 1993

The paper describes the geotechnical as- pects of design and construction of two 12 m diameter concrete lined tunnels from the start of design to completion of construction. Prob- lems occurred due to delay in supply of essen- tial rock support materials from overseas and alternative methods using locally available materials were developed. Several major rock- falls and rock movements occurred and remedial measures are outlined.

Jan 1, 1981

Lightweight polymer grids have recently been introduced to the mining industry. They are currently being used for roof and rib control, longwall shield recovery, safety guarding or barricade, highwall screening, internal reinforcement of gunnite/shotcrete applications, sub-base reinforcement, construction of steepened slopes, retaining walls, mine reclamation (i.e. erosion control, turf reinforcement), and in numerous mining waste related projects. These polymer mining grids utilize a strong, lightweight polymer, usually special grades of polypropylene or polyethylene. High tensile strengths are achieved by molecular orientation of these polymers in the manufacturing process. The first step in the manufacturing process is to extrude the polymers into thick continuous sheets. These sheets are then punched, and drawn into open grid structures. Aperture size and configuration are controlled by the geometry of the punched hole and the degree to which the grids are stretched. The drawing process is the key to the molecular orientation required for the tensile strengths. These long chain polymer molecules in their natural state have a random orientation. When stretched, the molecules are pulled into a parallel alignment, thus creating a lightweight product with tensile strength comparable to Steel.

Jan 1, 1992

By Selischop F, Tredoux M

The distribution of platinum-group elements (pGEs) has been investigated in matte and slag samples from Waterval Smelter (Rustenburg Platinum Mines). The study showed that a strong preference of PGEs for alloy phases in matte represents a concentration mechanism that commenced in the furnace but can be considered a continuum from natural processes. Metal losses to fayalite (converter) slag occur by matte entrainment due to the mechanical capture of liquid sulphide droplets from the matte layer, and the exsolution of dissolved metal sulphide resulting from changes in the oxidation state of the slag. The latter is comparable to immiscible sulphide in basic magmas. However, the observed distribution of PGEs shows enrichment in metal phases of the matte. A mechanism is proposed whereby naked PGEs in silicate melts coalesce to form clusters which are stabilised by surface attachment of sulphur atoms. This envelope acts to 'draw the cluster into sulphide melts. Small particle melting effects permit PGE clusters to remain as liquids at magmatic and smelter temperatures.

Jan 1, 1994

In any strip coal mining operation the aosL important single operating unit is the dragline. Because the capital and operating costs of a dragline are high, it is desirable to operate these machines at their maximum efficiency. Thiess Bros. Pty. Limited operate a Bucyrus-Erie 1350 Walking dragline at their Callide coal mine. The operating conditions at the Callide Mine are different from those of other coal mines situated in Central Queens ,nd. The topography is rugged, the coal seam is thick, and the overburden is hard and inter- HH,inded. Several different operating techniques for a large dragline working under these con- ditinns arc discrossmd it tt

Jan 1, 1978