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By Penttila V

The Paleoproterozoic Hitura Ni-Cu deposit in western Finland is in an ultramafic igneous complex composed of two subvertical plug-shaped bodies embedded in intensely migmatised felsic gneisses. The ultramafic complex is not far from a north-south trending graphitic and sulphidic gneiss zone interpreted to be a primary sulphide-graphite unit in the metasedimentary sequence. The sulphide accumulation exists as a zone parallel to the contact of the northern ultramafic body. The ultramafic rock types, now mainly serpentinites, have primarily been olivine adcumulates in the core grading to olivine orthocumulates and pyroxenites towards the margins. Coarse-grained felsic pegmatite veins injected serpentinite where they now exhibit prominent zoned alteration rims of chlorite, antophyllite and talc. The serpentinite core of the body was primarily an olivine adcumulate derived from a tholeiitic or high-Mg basalt parental magma with about 11 wt % MgO. Metamorphism and alteration have totally changed the igneous mineral compositions and the rock types are serpentinites (from olivine adcumulates), ambhibole-bearing serpentinites and amphibole-chlorite rocks (from pyroxenites). As the result of CO2 alteration talc is an accessory mineral throughout the serpentinite. Like silicates, also sulphide minerals are altered. In the core of the body the low-grade sulphide dissemination still reveals primary igneous interstitial forms. The core sulphides are now mackinawite, pentlandite and valleriite instead of primary igneous pyrrhotite and pentlandite derived from Mss. At the marginal zone the heavy dissemination and net-textured sulphides display pyrrhotite-pentlandite-magnetite intergrowths with magnetite films along cleavage of sulphides, mackinawite in pentlandite and exsolution textures of different low-temperature pyrrhotite phases as the result of alteration processes. Mechanically weak rocks, complicated structures and textures of the ore, magnetite and mackinawite intergrowths in pentlandite and readily-floating MgO silicates cause problems in exploitation of the deposit. Solution to problems come from selective stoping, three-step classification in grinding, froth-washing technique and on-line process control based on ore type determination from process data using an expert System

Jan 1, 1996

By Craw D

Quaternary warping and uplift of antiformal schist ranges in Central Otago, New Zealand, has resulted in recycling of alluvial gold from widespread, generally weakly auriferous, Miocene fluvial gravels that unconformably overlie the schist, into aprons of fan sediments along the range margins. Basement erosion during uplift has been limited and so gold input from sparse gold-bearing quartz veins in the schist has been relatively minor. In an eluvial cycle on the slopes of the ranges, chemical remobilization of gold occurs during oxidation and erosion of the Miocene sediments. The typically fine-grained (300-400¦m) gold undergoes chemical modification and grain size enhancement of up to two orders of magnitude, and much of it is redeposited in a large number of relatively small alluvial fans along the range margins. Groundwater mobility within the fans results in minor additional gold mobility and grain size Enhancement.

Jan 1, 1995

By Hagan T. N

Quite apart from economic considerations, the following performance parameters must be considered when selecting an explosive for a particular blasting operation. 1. total energy yield/kg, and more particularly, strain energy/kg and bubble energy/kg of charge 2. charge weight/m of blasthole 3. sensitivity of the charge 4. water resistance of the charge The effective division of an explosive's total energy into strain energy (SE) and bubble energy (BE) is explained as is the influence of each energy component on blast results. Because some rocks require a high strain energy for effective breakage, while others are most satisfactorily fragmented by bubble energy, values of SE and BE are more meaningful than those of total energy. Unfortunately, our extensive knowledge of the effects of certain variables on total energy has not yet been completely supplanted by the influence of these variables on SE and BE values. Relative SE/kg and BE/kg values are presented for a range of explosives. The 'charge density of ammonium nitrate/ fuel oil (ANFO)-type explosives is essentially constant throughout the length of the charge; because of their compressibility, slurry

Jan 1, 1974

By Fukui M

An increase in pig iron output by 50 per cent was aimed at after re-lining No.2 blast furnace of NAKAYAMA STEEL WORKS. This had to be achieved by increasing both the furnace volume (from 673 to 757 m3) and its productivity, Without equipment for high top pressure operation, high productivity was mainly attained by the following three measures; (1) improving the gas flow characteristics by maintaining a high ratio of agglomerated ores, increasing the strength of sinter and coke, and optimizing the charge distribution, (2) decreasing the fuel ratio by low Si operation and the use of hot blast, and (3) oxygen enrichment. In addition, the tapping controls for pig iron and slag were intensified. As a result of the above measures an excellent hot metal output of 2.7 tonne/m3/day was attained in April 1979 (monthly average).

Jan 1, 1980

By Little T. N, Bettess D

For many mining operations the challenge of equalling World Best Practices has become the key motivator for increasing mine productivities and for lowering total costs. In most instances this will only be achieved if mines optimise their total system rather than minimising specific costs within unit operations. In the past, drilling and blasting have been viewed as a cost to be minimised rather than operations which should have their impacts fully leveraged. Once a hardrock orebody is defined the activity which has the most substantial impact in determining the efficiency of a mining operation is the blasting. The output from a blast affects every downstream operation; only by understanding the extent and interactions can the mine be optimised. Substantial improvements to hardrock mining, quarrying and excavation operations are achievable. Instead of seeking the regular one to three per cent improvements based on reduction of consumables, mine operators would be well advised to go for much bigger targets of ten to 30 per cent by fully leveraging the drill and blast operations.

Jan 1, 1995

Ulan Coal Mines Limited operates an underground and open cut mine near Mudgee in the Central West of NSW. The mines are part of a Joint Venture managed by Exxon Coal and Minerals Australia Limited (ECMAL). Currently all the mines output of over five million tonnes per annum is sold into the export market predominantly as a steaming product.

Jan 1, 1993

By Schmidt CG

Parameters affecting gold elution using the AARL process are reviewed and critically analyzed in an attempt to optimise metallurgical efficiency and minimise costs in both current and future carbon adsorption operations. Such factors as acid washing, column geometry, elution temperatures and pretreatment reagents are discussed together with eluant water quality and eluate flowrates. Hot acid washing of carbon prior to gold elution has many benefits. Besides improving elution efficiency when eluting with regional water, a hot acid treatment preheats the carbon without causing any gold leakage. Laboratory data indicated that hot acid washing reduces the mass loss of carbon during thermal regeneration. The eluate going to either zinc precipitation or electrowinning is also relatively free of troublesome impurities (organic contaminants and ferrocyanides in particular). Because of the chromatographic character of the AARL elution where an ionic strength gradient is used to inhibit the readsorption of gold, column geometry plays a significant role. While practical considerations and capital costs may restrain the length of the elution column, high length/diameter ratios are advocated in order to promote the plug flow of column eluate. From both a metallurgical and costing viewpoint, the two significant factors affect- ing the AARL gold elution are temperature and cyanide addition. High temperature and high reagent additions within prescribed limits will improve metallurgical efficiencies, but a balance between energy and reagent costs is required in order to minimise overall elution costs. As pretreatment reagents constitute a considerable portion of the total elution costs, both the addition and consumption of sodium cyanide must be carefully considered. Lower cyanide additions may be effective in certain instances, but the more practical use of 0,6 bed volume of a 2-3 per cent NaCN reagent containing 2 per cent NaOH is advocated. This is equivalent to an addition of 20-30 kg NaCN and 20 kg NaOH per ton carbon Treated.

Jan 1, 1986

By Thompson M

The humble gabion basket is to mine development what the light bulb and safety pin are to eir-ryday life. Gabions provide a flexible, easy to assemble and cost efficient solution for "101" mine and civil engineering development applications.In some instances gabion baskets are still efficiently in use after many years of faithful, maintenance-free service. In other situations, the baskets have been demolished or made redundant within days, either having served their temporary usefulness or negligently destroyed by the operator of heavy equipment. Either way, the gabion basket must surely rate among the top 10 cost efficient engineering construction materials.

Jan 1, 1994

By Cox SJD, Kramadibrata S

One of the major causes of accidents and loss of production in underground mines is falls of ground.As mines go deeper, higher stresses are encountered and strain energy stored in the rocks is more likely to be released dynamically. This results in bumping in the rock mass around a stope or development face. Such noises and increasingly difficult ground conditions are obviously a warning of more serious problems ahead. The activity is collectively referred to as rock bursting.In Australia the mining of metalliferous deposits is taking place at increasing depths at Mt Isa, Broken Hill and the Eastern Goldfields and ground control problems with rock bursts has already been experienced at all three sites.

Jan 1, 1990

By Grinenko VA

Mineralogical, chemical, and isotopic data have been obtained for samples from 11 volcanoes and 4 kortlandite intrusives on Kamchatka.Similarities and differences in ore-bearing and barren intrusives are discussed. Differences in sulphide mineralization and sulphur isotope compositions of intrusives are explained in terms of the "auto-sulphurization" hypothesis which involves the redox conditions of the host rocks. possible role for carbon in nickle sulphide ore formation is also considered.

Jan 1, 1990

Both as an energy source and as a raw material, natural gas is playing an increasingly important role as a catalyst for the development, continuation and rebirth of mining projects in Australia. Pipelines are the vital link in making natural gas available to a region and to individual mines. This paper will cover the role of pipelines in supplying mining projects in Australia, the development and status of the Ballera to Mount Isa gas pipeline and the future prospects for gas pipelines in the Carpentaria Mineral Province.

Jan 1, 1998

Since 1969, a substantial number of geophysical methods have been applied in the search for porphyry copper and mesothermal type -sulpha-de deposits. These have assisted with geological mapping as well as the definition of various sulphide depos-its. The application of these methods at the Frieda-Nena deposits, Papua New Guinea, can be used as a case study for exploration in other parts of New Guinea.In 1993, Highlands Gold Limited carried out an intensive geophysical program over the Nena deposit. The methods employed included, CSAMT (controlled-source audio magneto-tellurics), airborne and ground elect-romagnetics, IP/resistivity and ground magnetics. The magnetic method was used as a regional mapping tool as well as a way of mapping alteration zones over both the Nena and Frieda River copper deposits. Electromagnetics, in part-icular FLAIRTEM, is a rapid reconn-aissance tool as well as a detailed mapping tool for the location of Nena-style massive sulphide deposits. IP/ resistivity is an expensive but most useful tool for mapping out Frieda porphyry copper style disseminated sulphides as well as Nena style deposits. It can be used to define drill targets in areas of difficult Access.a

Jan 1, 1994

By Pate W. T

This paper describes the development of a dynamic flowsheet simulator for comminution operations. Object oriented software design allows the handling of multiple ore types, blended into multicomponent feed streams. Software objects have been c

Jan 1, 1998

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

The large rotary blast hole drills for hole sizes of 250 to 375 mm in diameter have been utilized by large open pit metal and coal mines for production drilling all over the world. The design of such rotary drills is in most cases about two decades old and it has not been done much in order to apply a modern technology on rotary drilling. The most modern large rotary drill, Tamrock RI 10, consists of an advantageous rotary head with a squirrel cage AC motor controlled by a frequency converter, a beneficial mast structure with a possibility for inclined drilling, hydraulic driven, independent crawlers, and a modern ergonomic cabin to provide a comfortable working condition for the oper- ator. Several automatic features are available as options. The rig has been designed to be operated by one man only. With this modern rig the produc- tion rate can be increased and production cost kept on a low level.

Jan 1, 1989

General Gold was discovered in quartz veins at Wiluna in 1896, and the first lode was discovered in 1904. Since 1896, some 2.5 million ounces of gold have been produced from the Wiluna area. The mining operations at Wiluna are 100 per cent owned by Wiluna Gold Pty Ltd, a wholly owned subsidiary of Wiluna Mines Ltd. Oxide and sulphide gold ore is extracted by conventional open pit mining techniques, and ran-of-mine ore is processed through two separate circuits. The oxide circuit has a capacity to treat 600 0(X) tonnes per annum and the sulphide circuit has a capacity to treat 400 (XX) tonnes per annum. Additional gold is won by dump leaching sub-grade oxidised ore and by retreating of primary ore flotation tailings from previous operations. Testwork carried out in 1990 indicated the viability of leaching dumps of run-of-mine oxide ore, and in June 1991 Signet Engineering of Perth, WA, was awarded an EPCM contract to construct a nominal 2.5 million tonne dump leach facility, for a total construction estimate of 51.75 million.

Jan 1, 1994

By Nelson G

The construction and placement of tunnels by means of jacking is continually advancing. This paper presents an outline of the construction of a major highway tunnel placed by a combination of mining and progressive placement by hydraulic jacking of precast units. Features of the project were the relatively shallow ground cover between rail and road routes over the tunnelling and jacking operations and also the weight of tunnel sections to be moved into position.

Jan 1, 1993

By Barnes GJ

The gabbroid-hosted nickel sulphide deposits of the East Kimberley constitutes one of Australia's most prospective emerging nickel provinces. Sally Malay Nickel NL (SMN), a wholly owned subsidiary of Gindalbie Gold NL, has established the East Kimberley Nickel Project (EKNP). The EKNP project tenements cover about 2000 sq km. The tenements cover the northern potion of a corridor containing mineralised or potentially mineralised layered mafic-ultramafic intrusions which includes the Ni-Cu-Co sulphide deposits at Sally Malay and Keller Creek. The Sally Malay deposit is located 225 km south-south-west of Kununurra (Figure 1). The sealed Great Northern Highway passes 3 km to the east of the deposit.

Jan 1, 1996

To help meet the challenge of mine finding at the start of the 21st century, the exploration geophysicist will have at his command a powerful range of tools, some new, some improved, and some which already exist today but are as yet little used. Remote sensing, using satellite and aircraft-based multi-spectral scanners, will provide the means for routinely mapping the surface distribution of certain carbonate rocks, clay and ferrous alteration minerals, based on the analysis of solar reflectance spectra. Time and emission-spectral resolved laser-induced fluorescence will likewise map the distribution of certain ore and pathfinder minerals, as well as certain skarn zones, all potentially related to ore deposits. The GPS (Global Positioning System), based on 18 orbitting satellites, will provide a universal, three dimensional, all weather navigation system which will completely supplant all existing aerial navigation systems, and greatly facilitate aerial surveying and automated processing and presentation of the data. Aeromagnetic gradiometer measurements will provide higher geometric resolution which will yield better definition of individual geological units. Multi-method ground geophysical surveys will be greatly expedited through the use of portable microcomputer-based, multi-sensor instruments. These instruments will interface with other intelligent devices for automated processing, presentation and interpretation of the ground field data. Borehole geophysics will come into more general use, both for at-hole measurements, especially using active nuclear techniques for grade determination, and for remote detection using a variety of electrical, magnetic, seismic and other methods.

Jan 1, 1986

By Weller K. R, Trahar W. J

The Mount Lyell Company treats some 2.3 million tonnes of ore annually, mined from a number of orebodies on the field. Blended ore is essentially a quartz-sericite schist containing about eight per cent of pyrite and three per cent of chalcopyrite. Four-stage crushing and two-stage ball milling are followe by selective flotation for copper. Pyrite is recovered from the coarse fraction of dopper circuit tailings. A detailed survey involving examination. of 82 samples provided information on the size- by-size behaviour of the principal ore constituents throughout the grinding, copper flotation and pyrite flotation sections of the circuit. Results for the copper and pyrite flotation sections are presented in the paper, and it is shown that over half the copper reporting to the final tailing (5% of copper in the feed) is plus 100 microns and that the major pyrite loss is in the desliming cyclone overflow. These data proVide a basis for assessing potential methods of circuit optimisation.

Jan 1, 1977