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This paper reviews some of the factors thought to control the formation of supergene gold in the Pacific and its Rim. Discussion of these should lead to reassessment of the economic potential of many areas. In several parts of the world many gold-bearing veins display rich gold values only in the oxidized zone, whereas beneath the present (or ancient) watertable the unaltered vein commonly holds only sub-economic refractory low grade sulphides or arsenides. In the Eastern Highlands of Australia some of the most spectacular concentrations of - gold have been found at shallow depths. For example, Harper (1918) describes the Canton mine in New South Wales which was stoped over a length of 180 metres from the 45 metre level to the surface. The reef yielded gold at 300 g/t in the upper levels, but became gradually poorer at depth. Present geologists of N.S.W. Geol. Survey, G.R. Mcllveen and B.P.J. Stevens, believe that many similar Australian enrichments were formed between the surface and its ancient water table level during the extended period of weathering in the Eocene or pre-Eocene. They concede, however, that further supergene movement of gold may have occurred since the early Tertiary. Large quantities of Mesozoic supergene gold of extreme fineness (Au 99.7%, Cu +òFe 0.3%; Leibius 1885) was found at Mt. Morgan near the Tropic of Capricorn in Queensland. Lower Jurassic sediments cover part of the gossan in a small depression caused by oxidation and collapse of the Main Pipe, thus showing that the supergene gold is pre-Lower Jurassic (Cornelius, 1968). Because the Lower Jurassic landscape around Mt. Morgan was mature with a surface slope of less than 10 (Playford and Cornelius, 1967), erosion would have been very slow. Moreover, once all sulphides had been removed from the ore body the Lower Jurassic environment would have reverted from highly acid to alkaline as it is at present. Accordingly, gold, goethite and 1. Dept. of Geology & Mineralogy, University of Queensland, St. Lucia, Australia,

Jan 1, 1987

The Central Extended Orebody is located within the Cracow Goldfield approximately 360 km northwest of Brisbane and approximately 220 km west of Bundaberg. It is an epithermal gold deposit hosted by the Late Carboniferous to Early Permian Camboon Andesite. The lode was mined by open cut methods and produced 170 458 tonnes of ore at 5.62 g/t gold.The geology of the rit is relatively simple, comprising two rock types, trachyandesite and rhyolite which have been sub-divided into several units. The trachyandesite is sub-divided into three rock types: brecciated trachyandesite which is the most widespread, hydraulically fractured trachyandesite hosts the mineralisation and the third sub-unit is chloritised hydraulically fractured trachyandesite and has no associated mineralisation. The mineralisation is confined to quartz veins in hydraulically fractured trachyandesite. Several phases of brecciation and subsequent quartz and quartz/adularia vein injection are evident although not all phases are mineralised. Two rhyolite dykes intrude the trachyandesite one is monolithic, the other is sub-divided into hydraulically fractured rhyolite (barren), silicified rhyolite and auto-brecciated rhyolite.

Jan 1, 1993

The development of the Australian uraniumindustry over the last decade has been subjectto socio-political controversy, but the industryis now beginning to emerge onto the world scene.The socio-political controversies which haveexisted over developing Australian uranium arediscussed and suggestions put forward as topossible changes in the relationship of themining industry to the pplitical and socialstructure of Australian Society.The rate of growth in energy consumptionis considered and on the basis of a growth rateof 3% by the year 2000 the world will beconsuming twice the amount of energy that itdoes today. It is anticipated that the growthin generation of electrical power will begreater than the growth rate fQr energy.The dominant part played by coal and nuclearpower in the generation of electrical power isdiscussed. Nuclear power at present, contributesabout 4% of the world's electricityrequirements and by the turn of the centurythis could be nearer to 30%.

Jan 1, 1981

By Fraser RJ

A Robbins Raise Drill Model 61R was used to provide one 7' diameter shaft 1050' deep in Clutha Development's exploratory mine at Blackwater in Central Queensland and two 7' diameter shafts 1450' deep at their South Clifton mine on the Illawarra Coast of New South Wales.

Jan 1, 1972

Iron from the blast furnace constitutes the starting point in steel production and any increase that can be made in iron production will bring about important repercussions in a long line of processes. Coke constitutes a major item in furnace operation and consumption at the Port Kembla Works of Australian Iron & Steel Ltd. has been approximately 1,850 lb. per ton of iron produced on ore practice, or 3,000 tons per day.For many years coke quality has been subject to much criticism by furnace operators throughout the world, sometimes with little real grounds. Whatever the merits of previous arguments, and they were no doubt two-sided, the development of bigger furnaces has focused attention on coke strength. At the same time a decrease in the quantity of good quality coking coals available to many plants has stimulated research in this field.Extensive coke research has been carried out overseas, and in Australia the.B.H.P. Organization is now actively doing likewise in its Central Research Laboratories at Shortland near Newcastle, N.S.W., and works research groups at Newcastle and Port Kembla Steelworks. Similar work has been initiated in the beehive coking industry. Such work is in its infancy and this paper will outline the direction of the activities at Port Kembla rather than propound specific solutions.At Port Kembla good quality coking coals are readily available from the IIIawarra coalfield. The seams generally mined for coking are Bulli and Wongawilli and to a much smaller extent Tongarra. Characteristics of these coals appear in Table 1.

Jan 1, 1958

By Linge H. G

The effect of the presence of ore pulp on the adsorption rate of gold on activated carbon has been studied. A substantial reduction in the rate occurs when the pulp is present. The reduction in rate appears to be caused by two effects: permanent carbon pore blocking by ore particles and temporary shielding of the carbon particle surface, slowing gold access to the carbon due to the physical presence of the fine pulp. There is no significant effect arising from the presence of a pulp viscosity modifier even for conditions when mass transport dictates the loading rate of carbon in clear Solution.

Jan 1, 1987

By L Crew, S Jackson

A trial of an Adept Online Ore Sizer (OOS) was undertaken at the WMC Leinster Nickel Operation (LNO) in the first half of 2000. During this time the On Line Ore Sizer has been shown to be a robust and accurate instrument for measuring mill feed ore size. Data collected during the trial indicates significant variation in the F80 of the SAG mill feed. The effects of feed size on milling parameters such as mill weight, mill power draw and mill efficiency appears to be dependent on the ore blend treated. With some ore blends a weak positive correlation was found between ore size and mill weight and milling efficiency but with others no correlation is evident. It is believed that the OOS will become a vital piece of equipment in the future as LNO continues to optimises its milling circuit.

Jan 1, 2000

By Schofield N. A

The cross-sectional method of stope grade estimation at Cobar Mines has consistently had several shoneomings, me most imponant of which being mat stope grade is significantly overestimated in the high grade lenses.The use of mree-dimensional ore lens modelling improved the grade estimation and ore waste definition but significant overestimation still occurred in me high grade stopes, particularly those wim extremely variable grade distribution. The implementation of an indicalor kriging based method for mapping of me high grade copper mineralization has significantly improved the quality of copper grade estimates and provides a mineralisation geometry similar to that generated manually by me mine geologists. This paper presents the results of a test case study in the application of indicator kriging to the mapping of the copper grade in two stopes in the QTS North mineralisation. The results are encouraging in that they prov ide coofi rmation of the geometrical model developed by the geologists and much improved estimates of the grades of me stopes whencompared to me grade reponed from mining these stopes.

Jan 1, 1993

By L C. Thompson

BioLix is the term for a new class of biologically-derived lixiviants for precious metals (gold and silver) recovery. BioLix can be used as an alternative to cyanide on virgin and spent ores. The BioLix process is based on inducing microbial enzymatic reactions that generate organo-lixiviant chemicals. The bioprocess involves a two-stage culture strategy. First, specialty microorganisms are cultured to generate a high biomass. Then, a food-grade quality amendment is introduced that forces the microorganisms to produce the organo-lixiviant. The second-stage culture is applied to the ore where the microbial/lixiviant system acts on mineral surfaces to extract precious metals. The process operates at ambient temperatures and near neutral pH. This paper will examine the BioLix process through an extensive laboratory development and demonstration project. Laboratory development consisted of identifying and isolating specialty microorganisms and inducing agents for the production of the organo-lixiviant solutions. A demonstration was performed on low-grade and high-grade oxidised ore from the Buffalo Valley mine in Nevada, USA. Results indicate that the BioLix process was comparable to cyanide in terms of gold recovery and operated at near neutral pH and ambient temperatures. Applications for the BioLix process will be discussed including spent-ore re-leaching, cyanide replacement for virgin ore, and in situ mining.

Jan 1, 2004

By J-H Shin, Y-S Jung, D-J Youn, G-J Bae

This research is to grope for a method to reduce high pore pressure taking place on tunnel shotcrete lining, especially in underwater tunnels, effectively by utilising a new concept of patternised pin drain. Accordingly, the patternised pin drain system is investigated numerically in order to confirm to the effect of reduction of pore pressure by the pin drain and its effective application. Installation of pin drain shows considerable reduction in the figure of pore pressure. It is found through 2D numerical modelling that the change of pore pressure, according to the shape and the location of pin drain, is sensitive by the sequences of the change of location > the change of length > the change of angle degree. In the results of investigation in 3D modelling, the pore pressure is the largest in the centre of the interval among pin drains, and it is possible to obtain an ideal degree of longitudinal angle and an interval by investigating pore pressure taking place on the lining.

Jan 1, 2008

Sluice-boxes are by far the most widely used concentrating devices by small-scale operators in PNG who work alluvial gold deposits. The sluice-box designs and their operating conditions used are known to vary widely. The selection of sluice-box configuration and the operating parameters such as the water flow rate is purely based on past experience. Some use small flowrates to increase the fine gold recovery at the expense of efficient separations and capacity while others use high flow rates resulting in increased fine gold losses but with high throughput rates. Recent work has revealed that the combination of riffle height, their spacing and wash water flow rate are the most important parameters that determine the success or failure of such operations. This combination has been shown to depend on the in situ gold and gangue size distributions of the deposit being processed. This paper describes a design procedure which uses a non-linear optimisation method to determine the optimal combination of the above parameters to maximise the metallurgical efficiency of such operations.

Jan 1, 1993

By Markic S, Subelj A

Long-term plan for lignite mine Velenje has been made by using technical parametrisation method where the basis for periodical, middle- term and short-term plans as well as for scheduling has been already fixed. For a certain time period a plan

Jan 1, 1998

The extinction of zinc from steelmaking dusts has been studied with a laboratory scale reduction-vapour deposition (RVD) process in the absolute pressure and temperature ranges of 13 - 1300 Pa and 1333 - 1513 K respectively. This process consists of pre-reduction of iron oxide by carbonaceous agent, carbothermic reduction of zinc oxide under reduced pressure to produce zinc deposits and subsequent re-evaporation of the deposits to liquedify the zinc. In the RVD, the gas mixture of Zn and CO quenched from the hot zone is separated into Zn deposit and CO which is transferred to the pumping system. The Zn are a layer of fine metallic zinc powders accumulated on the cold wall and removed to the vacuum distillation chamber. The experimental works have been carried out according to the following items: carbothennic reduction of zinc oxide under vacuum, carbothermic reduction o zinc ferrite under vacuum, and 3. distillation of the Zn deposits. It has been concluded from these experimental results that the recovery of metallic zinc from the EAF dusts is successful by this process, and a new concept for a practical zinc winning process has been proposed.

Jan 1, 1993

By G Partington

A regional scale prospectivity model was developed for Papua New Guinea (PNG) to identify areas of porphyry Cu-Au mineralisation. Weights of evidence modeling techniques were used to determine spatial correlations between porphyry Cu-Au mines and predictive maps created from available spatial data. These predictive maps were then combined into a final prospectivity map. Despite limited regional scale data the model has successfully identified areas of known porphyry mineralisation as prospective and has also identified areas where new mineralised systems may be discovered with further exploration. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By Maidl B

A tunnel operations analyser is a new high technol- ogy instrument for use in underground work. By remotely sensing the acoustic emissions from operating machines and processes in a tunnel or shaft and by applying sophis- ticated computer processing to them individual process cycles and other detailed information about the operating processes can be collected. Detailed analyses and dissec- tions of the work in progress can be made and a variety of action oriented management reports produced. The pro- cess is fully automatic. Results of applying this device to two full scale tunnel projects are presented. The hardware and software that comprise the instrument are discussed in detail. Processes by which this device can be used to sub- stantially reduce tunnel costs are presented. It is concluded that this type of technology has great potential.

Jan 1, 1987

By Boyce WH

Earthquakes are the most frightening and devastating natural phenomena known to mankind. They strike without warning and their consequences can be disastrous in terms of the toll of human life, financial crises related to the damage or destruction of man-made structures and the social and economic effects on a wide spectrum of the affected communities in the aftermath of the event. Such situations can be widely attested to by most areas around the Pacific Rim. Indeed, the threat of earthquakes is always imminent because of the geological-tectonic nature of the region as manifested by past experiences. It is patently obvious that earthquake occurrences are not only a geological hazard but also pose a serious social danger. When one considers the 19 September 1985 Mexico (Michoacan) earthquake (Mitchell at al., 1986), the necessity of continuing research is of paramount importance. An estimation . of earthquake risk encompasses both qualitative and quantitative aspects and demands a multidisciplinary research effort integrating seismology, tectonics, geology, enginering, sociology, economics, insurance and governmental policies (Bolt, 1978; Booth, 1984). These roles in mitigating such a hazard have been aptly discussed by Press (1985). A series of discussion papers based on an intergovernmental conference covering the whole scenario were published by UNESCO (1978). A comprehensive case history was provided through a workshop on the 1886

Jan 1, 1987

The thick coal seams of the South Maitland field are the only ones in New South Wales which have been worked extensively to heights beyond 3.8 m (nominal "thin" seam height). Under shallow cover only minor difficulties were experienced in developing first workings but later the widespread occurrence of incidents of spontaneous combustion and the growth of "creeps" extending over large areas gave the field its own peculiar problems. As the mines have driven under deeper cover extreme difficulties in forming development roadways have been experi- enced. Various methods have been adopted in an attempt to overcome the problems of the field.

Jan 1, 1976

The application of modern sciences prior to nineteenseventies have resulted in the placing of Continental Drift theory into broader concept of Plate Tectonics. The concept is applied to explain the Cenozoic Tectonics of North Sumatera.Oceanic crust flooring the Indian Ocean is moving northeasterly and being obliquely subducted at a Benioff zone along the western margin of Asian Plate, marked by the Sunda Trench in the west coast of Sumatera. This phenomenon was generated since late Mesozoic, continued during Cenozoic era up to present day, resulted an exellent example of arc-trench system which can be traced along SW - NE transect of North Sumatera.The oblique-subducting plate of Indian Ocean beneath Asian Plate, together with spreading of Andaman seafloor beginning in Pliocen epoch, have led to the origin of Sumateran Fault System; the System extends throughout the length of Sumatera island. In the region under review it comprises almost contiguous set of broadly SE-trending. Evidences for transcurent-dextral displacement have been observed.

Jan 1, 1990

Recovery of Precious Metals from Chloride Solution by Magnetite The development of environmental-friendly lixiviants as alternatives to cyanide and the increasing recycling activities to recover precious metals from waste materials have prompted researchers to find efficient methods and alternative sorbents to recover precious metals, such as Au and Pt, from aqueous solutions. This study explored the use of magnetite (Fe3O4) as a sorbent to recover Au and Pt from chloride solutions. Magnetite is a semiconductor and has the capability of transferring electrons both within the solid state and across the solid-liquid interface and has the ability to reduce metal species on its surface. The sorption of AuCl4- and PtCl62- from NaCl solution on commercial grade magnetite powder was investigated by batch-sorption experiments. The effects of pH, contact time, NaCl concentration and precious metal concentration on the recovery were studied. Sorption experiments revealed that magnetite exhibited selectivity towards other metals with the strongest affinity for Au. Both Au and Pt recoveries showed similar pH dependence curves, with peaks at pH 6 - 7. At this pH range, a maximum of 4.4 ¦mol Au/g Fe3O4 and 3.0 ¦mol Pt/g Fe3O4 were recovered after 24 h at an initial metal concentration of 0.05 mol/m3. Increasing the initial precious metal concentration increased the Au and Pt uptake amount by magnetite. It was also observed that the recovery decreased with high NaCl concentrations. The SEM images of the magnetite particles after the treatment showed that gold, which was confirmed by the EDX analysis, agglomerated and were deposited on Fe3O4 surface.

Sep 13, 2010

Bubble Load Measurements in Flotation - A Critical Review of Current Practice

Sep 13, 2010