Search Documents

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

By V Chamberlain, M Appeah Owusu, M Aniawu-Asumakah, A Anyimadu, R Peattie

This is an integrated geology and plant improvement study arising from the heterogeneity seen in mineralogy and gold association at the Obuasi goldmine in Ghana. This heterogeneity comes from the two ore types mined, the one being a sulphide ore, mainly composed of gold-bearing arsenopyrites. This gold is refractory and exhibits a strong relationship between gold and As. The other is quartz veins, that are high grade and free milling. The installed circuit consists of comminution – Gravity -Flotation – BIOX – Leaching and Adsorption processes. The opportunity tested involved improved mass pull - related flotation recovery of Au in the Sulphide stream; while balancing the need for a minimum Sulphide grade for the Bio-oxidation process, occasioned by the removal of 25 to 30 % of the (quartz) stream through preconcentration by Ore sorting. The current circuit is then utilized for the sulphide route, while a smaller grind-gravity circuit is utilised for the quartz stream in a relatively inexpensive way, followed by a common leaching and adsorption circuit. Added advantages of the strategy includes faster recovery of gold from the quartz stream, with less consumption of reagents from saving on flotation and BIOX reagents for this stream. Screening and Ore sorting was successfully tested with laser technology, achieving over 98% separation of quarts (containing up to 40% of the gold). The plant schedule of Ore, the suggested circuit design for the Ore sorting, the results obtained from the different flotation regimes, as well as consequent financial modelling have been presented and discussed in this paper. This illustrates the opportunity that arises out of a detailed analysis of material versus installed circuits, even if the gains in pre-concentration do not necessarily involve rejection of gangue material. An added opportunity for future investigation, briefly discussed but not tested in this paper, would be to maintain current mass pulls but with increase in throughput (by the space created by the sorted material). This will of course require the mining ability. It could also add LOM value by altering the cut-off grade.

Nov 10, 2020

The segment of the Upper Cenozoic volcanic chain (CVZ) located on the western border of South America (16-28¦S lat.) is constituted by an association of strato- volcanoes and ignimbrite sheets, with high K calco-alkaline affinities. Strata-bound volcanoes, mainly of andesitic and dacitic composition, present along the whole chain, and various hydrothermal alteration zones, on the slopes and in the cores of eroded volcanic structures. Some of these altera- tion zones bear epithermal precious metal ores and sulphur deposits, which at present are being exploited. The studied Salar de Gorbea area, located in the Andes of northern Chile (25-26¦S lat.) contains a numer- ous group of Miocene to Quaternary stratovolcanoes, with advanced argillic and extreme silicification hydrothermal alteration in their cores and on their slopes, favoring the formation of great volumes of alunite within altered zones and sulphur deposits in the higher parts of the volcanic edifices. Simultaneously, siliceous hydrothermal breccia of the phreato-magmatic type, with evidences of hydromag- matic explosions are recognizable, allowing, in some cases, the ascent towards the surface of rock fragments belonging to the Paleozoic pre volcanic basement. Radiometric ages obtained in some of the hydro- thermal alteration zones (K-Ar in alunite) are slighty young- er than the unaltered rocks which constitute the strato- volcano. Trace element (Hg, As, Sb, S, Au, Ag, Cu, Pb, Zn, Mo) patterns in orientative rock samplings show that the studied alterations zones correspond to high sectors of the cpithermal system, without evidences of metallic minerali- zation on surface. The weak erosive action due to the ex- tremely and climatic conditions in this segment of the Andes, has not allowed the cropping out of deeper areas of the hydrothermal alteration zones, in contrast to other Miocene more eroded volcanic edifices and Miocene vol- canic terranes of the Andean Range.

Jan 1, 1987

Ferromanganese metasediments in the immediate vicinity of the Mid-Proterozoic Broken Hill Pb-Zn-Ag lodes, have undergone high grade (upper amphibolite facies) metamorphism,to form Mn-pyroxenoid (rhodonite,pyroxmangite) and garnet-rich lithologies. Such lithologies bear compositional (bulk rock,rare earth element)and morphological similarities to recent and ancient ferromanganese hydrothermal sediments of the Pacific.The non-metasomatic,stratiform garnetites are predominantly composed of magnesia-rich, calcium-poor almandine spessartine and quartz, which possess a bulk chemistry comparable to alumina-rich ferrommanganese oxide deposits of the Pacific. Such sediments are attributed to a mixed protolith comprised of clay and ferro-manganese oxides (mainly amorphous goethite with lesser todorockite-birnessite). Manganiferous pyroxenoid rocks are probably derived from alumina-poor ferromanganese cherts,similar to Japanese tetsusekiei.Rare earth element compositions ofBroken Hill garnetites are very similar to those of recent ferromanganese seafloor accumulations, suggestive of some genetic link.

Jan 1, 1990

By Jena, Anand S, Das R. P

Leaching studies were carried out on Indian Ocean manganese nodules using sulphuric acid as the lixiviant. By leaching the nodules with 8 per cent sulphuric acid for 12h at 100°C, copper and nickel could be completely extracted along with 50 per cent cobalt and 6.2 per cent manganese.94.2 per cent of the iron was also dissolved. To increase manganese and cobalt extraction, charcoal was used as a reductant. The role of charcoal was to reduce the manganese dioxide and render it soluble as manganese sulphate as well as to facilitate solution of the cobalt minerals associated with the manganese dioxide. Various leaching parameters were studied including acid concentration, amount of reductant, leach time, pulp density and leach temperature. It was found that by leaching the nodules with 10 per cent sulphuric acid at 100°C for 4h using 5 wt/wt per cent charcoal (0.05g of charcoal per g of nodule) almost complete extraction of copper, nickel, cobalt and manganese could be achieved. However, under these conditions all the iron present in the nodules was also leached.

Jan 1, 1989

By E S. B Santiago, C P. N Moreto, L V. S Monteiro, G H. C Melo, R P. Xavier

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Iron oxide-copper-gold (IOCG) systems of the Carajás mineral province (Amazon craton, Brazil) are structurally controlled by regional-scale shear zones and have formed by multiple episodes of fluid circulation and hydrothermal alteration in the Neoarchean (2.71–2.68 Ga and 2.56 Ga) and Palaeoproterozoic (1.90–1.87 Ga).Collectively, fluid inclusion, boron, oxygen and hydrogen isotope data and Cl/Br–Na/Cl ratios in fluid inclusions reveal that regional circulation of non-magmatic brines (eg evaporative fluids/evolved sea water) and mixing with other fluid sources (eg meteoric or magmatic) is an important attribute in the genesis of the Carajás IOCG systems. The ?33S and d34S compositions of sulfides from the Neoarchean and Palaeoproterozoic IOCG systems suggest that the ore-bearing fluids have assimilated sulfur from crustal reservoirs. Nevertheless, most ?33S measurements have indicated mass independent fractionation (MIF) effect for both systems which points to the possible involvement of surface sulfur sources.CITATION:Xavier, R P, Monteiro, L V S, Moreto, C P N, Melo, G H C and Santiago, E S B, 2015. Non-magmatic versus magmatic fluids in the genesis of Archean and Palaeoproterozoic iron oxide-copper-gold systems of the Carajás Mineral Province (Brazil), in Proceedings PACRIM 2015 Congress, pp 281–288 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Fewings JH

When the mining and milling of 1100 Copper Orebody commenced, difficulties were experienced in producing a satisfactory grade of copper concentrate. The major concentrate contaminants were fine pyrite and silica, particularly in the minus 10 microns fraction. Studies of the 1100 Orebody showed that much of the fine grained pyrite and a proportion of the silica present in the ore contained carbonaceous matter in the form of complete or partial rims and as internal carbon films disseminated throughout grains. The hydrophobic surface property of the carbonaceous material resulted in an inherently flotable fine pyrite and silica fraction. The addition of a 60:40 mixture of nigrosine and dextrine, initially to a prefloat concentrate of the inherently flotable carbonaceous material and finally to'the total copper flotation feed, successfully controlled the flotation rates of the carbonaceous pyrite and silica. The objective of a 25 per cent Cu concentrate grade was then achieved without decreasing copper recovery.

Jan 1, 1970

Early efforts to control the dust necessarily produced during dry crushing operations, took the form of venturis at loading chutes and other places where dust was most evident. These venturis discharged to the atmosphere and for obvious reasons were not very satisfactory.Attempts to collect the dust drawn off by the venturis, using dry cyclones, were not successful, the cyclones catching only the coarser particles. Further, no satisfactory method of continuously discharging the dust catchment was evolved. Water sprays were also used, and will be referred to later.In 1940, a single discharge fan of 3,000-4,000 cu. ft. per minute capacity, was installed to draw the dust-laden air from the Symons crushers and ·screening sections with their attendant conveyors. Suction was through two 15 in. ducts which branched off into 10 off-takes situated over the conveyers at points of discharge from crushers and screens.A dry cyclone was installed in front of the fan, which exhausted into a bag-house.The cyclone suffered from the defects of the smaller units mentioned earlier. When the collected dust reached a certain level in the cone, no more collection would take place until the cone was emptied. This objectionable feature was overcome by introducing a jet of water ahead of the cyclone. The water and dust collected overflowed a weir and were pumped to the mill.

Jan 1, 1948

By C McIntosh, M Carder, P M. J Durance

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Disseminated, gold-bearing sulfide minerals hosted in sheared, wall rock metasediments and clay alteration zones comprise one of the dominant styles of Palaeozoic orogenic gold mineralisation within the Reefton Goldfield, and is exemplified by OceanaGold’s Globe Mine. This study begins the exploration and characterisation of the gold-arsenic-antimony mineralisation hosted within the dominant lithologies of the Globe-Progress shear zone. The main gold-bearing sulfides are pyrite, arsenopyrite and stibnite. Pyrite and arsenopyrite are not compositionally uniform across the Globe-Progress shear zone. Pyrite from the mineralised greywacke and argillite has higher As contents than pyrite in the host rock and pug breccia. Furthermore, the mineralised greywacke and argillite pyrite are enriched in As from core to rim. The 3D models based on bulk assays reveal a significant correlation in the distribution of Au, As and Sb. The interpolant for Sb envelops those for Au and As, which in turn are very similar to each other in their vertical and lateral extents across the shear zone. This result is consistent with earlier findings that the occurrence of stibnite represents a separate and likely later phase of mineralisation relative to that represented by the formation of disseminated pyrite and arsenopyrite both of which exert a stronger control on the distribution of As.CITATION:Durance, P M J, Christie, A B, McIntosh, C and Carder, M, 2015. The composition of disseminated, gold-bearing sulfides within the three-dimensional framework of bulk Au, As and Sb in the Globe-Progress orogenic gold deposit, Reefton Goldfield, New Zealand, in Proceedings PACRIM 2015 Congress, pp 327–334 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Wernick B. J

Recently, the Environmental Engineering Laboratory of the Chamber of Mines of South Africa Research Organization has made signifi- cant progress in the development of more accurate algorithms for assessing heat flow in gold mines. These algorithms have been incor- porated into an overall computer program, ENVIRON, which enables the complete thermo- dynamic analyses of mine ventilation and cool- ing systems to be carried out. Recently, efforts have concentrated on the development of an expert computer system which will guide engineers in the process of selecting the most appropriate environmental control strategy.

Jan 1, 1988

The paper examines the current status of risk and accepted practice in mining geomechanics. It explores some deficiencies in human capital, risk analysis and our future technical needs, and suggests ways of improving our estimates of slope reliability through knowledge sharing and research.

Jan 1, 2003

The Taupo Volcanic Zone in New Zealand and the Philippine Mobile Belt in the Philippines are characterized by active subduction, active volcanism and high seismicity. The main factors affecting characteristics of geothermal systems in both countries are: tectonic setting, source magmas, maturity of the systems, and depth to the degassing magma body. Within New Zealand, geothermal systems are grouped into arc- and rift-type. Fluids in arc-type systems contain high amounts of volatiles (40%) and higher Cl contents (3,000-10,000 mg/kg). Maximum temperatures are also higher, reaching up to >400¦C. Arc-type alteration assemblages in New Zealand and the Philippines are similar. Because Philippine geothermal systems are less mature, have higher temperatures and steeper geochemical gradients than New Zealand ones, advanced argillization is more widespread occurring down to depths of 2000 m. Mineral phases are more varied due to the active input of magmatic waters and the formation of vapor conditions at depth, forming P04-, B-, Li-, Ce-, F-, and Cl-bearing minerals at high temperatures. In the Philippines, high temperature magmatic-hydrothermal to contact metamorphic assemblages containing biotite, amphiboles and pyroxenes are relatively common, but rare in New Zealand.

Jan 1, 1995

By Dif A. E N, Abdalla MH

The effect of multiple tunnels /cavities on the stress and deformation field of the soil media was investigated by using a two dimen- sional plane strain boundary element model. The soil was considered as an elastic, isot- ropic and homogenous media. The interaction of two circular and parallel tunnels/cavities was investigated. Depth of burial, tunnel spacing and surface load width were the system variables considered. The results of this study indicated that the vertical displacements of the soil media increases by decreasing the distance between the adjacent openings, the interaction between the two tunnels/cavities can be neglected for K/D > 5, while the load width has a minor effect except in the dis- tance of D from the center line of the load and for a depth of 2D.

Jan 1, 1987

By B P. Voutharoj, R A. Dutch, M Paknezhad, T Ostersen

With the proliferation of new sensor technologies, acquiring multiple data sets over the same ground is becoming cheaper and easier than ever. This new, higher resolution multivariate data provides a significant resource for exploration and resource geologists but comes with the added complexity of effectively integrating the various data sets in useful and meaningful ways to elucidate new geological understanding. Both geophysical data sets and hyperspectral data are extensively used for exploration targeting, providing different information at different resolutions and crustal scales. One of the biggest challenges comes from trying to effectively integrate data sets that record very different physical properties, across the different scales these data are captured at, in a way which can allow for a data-driven analysis of these combined data sets.

Sep 1, 2024

By D J. Cronin

Alcoa World Alumina AustraliaÆs Huntly and Willowdale bauxite mines are located in the Darling Range of South Western Australia, which places their operations within PerthÆs surface water supply catchments. These catchments supply Perth with its highest quality drinking water. With the decreasing rainfall trend of recent years catchment yields to water supply reservoirs have reduced to such an extent that water use restrictions were necessary in Perth for 2001, 2002 and 2003. Protection of catchment water quality and water use conservation are crucial issues for AlcoaÆs operations within the Darling Range. Alcoa has been conducting bauxite mining activities in water supply catchments since the mid-1960s. During that time Alcoa has worked closely with the relevant State Government water and environmental agencies to ensure that its operations do not adversely impact catchment water yield and water quality. Monitoring and research have shown that Alcoa has the necessary environmental management systems in place to ensure it can continue to operate in a sustainable manner within water supply catchments. AlcoaÆs mines reduced the volume of water taken from public water supply catchments by 24 per cent in 2002, compared with 2000. This success has had an added benefit; Alcoa does not need to develop a new water source for its Huntly Mine. The conservation measures implemented to reduce water use include: increasing water recycling, using chemical additives for haul road dust suppression, conducting water audits, reducing water demand, monitoring water use, promoting water use targets and training staff in water conservation.

Jan 1, 2003

By M F. Navarrete

During 2003, different plastic stemming plugs (Cats«, Stemtite«, and Taponex«) were tested in EscondidaÆs Mina Sur, to determine the effect on gas retention time when used in conjunction with drill cuttings in production shots with a blasthole diameter of 10 5/8ö. Longer retention times were expected to provide greater fragmentation and muckpile looseness. In order to determine which plug showed the greatest enhancement of stemming retention, 17 trials were carried out û in the first seven tests, only the Cats were used, in the following five tests, a combination of Cats, Taponex and Stemtite were used, and in the last three tests, only the Taponex plug was used. In the last two blasts, drill cuttings were used without stemming plugs as a benchmarking exercise. Blasts were filmed with a high-speed camera, which could record the detonation times of holes using rolls of shock tube tied to stakes at the hole collars, to act as flash indicators. The camera allowed measurement of the time between charge detonation and the commencement of stemming ejection. In order to obtain the statistical parameters of each one of the stemming plugs used in the 17 trials carried out, the Minitab software was used and a data base was created for it, corresponding to each stemming configuration with the retention time obtained from the filming. Once it was determined which stemming plug provided the greatest enhancement of stemming retention, the impact on the fragmentation was analysed using the WipFrag image analysis software to estimate the muckpile size distribution.

Jan 1, 2004

Computerisation of mine planning activities, specifically in the areas of geology, design and surveying, has been in progress for a number of years in underground metalliferous mines. The combined capabilities of hardware and software have only recently reached the levels necessary to fully support integrated mine planning computer systems in a graphical three dimensional environment. Despite the apparent capabilities of systems now on the market, many sites retain significant parts of their older paper based systems, and employ a mix of two or more software packages. This paper examines what underground metalliferous sites are doing in this area in Australia, and discusses the factors which are inhibiting full implementation of fully integrated computerised systems. Future directions for further developments in the field are also briefly discussed.

Jan 1, 1995

Goodenough and Fergusson Islands, in eastern PapuaNew Guinea, lie in an area of crustal extension on the western end of the Woodlark Basin seafloor spreading system. The islands are made up of a number of mountainous domes of complexely deformed basement, and these are intruded by large bodies of granodiorite. The domes are bounded by curved shear zones and faults dipping outwards at angles of around 25 to 45¦. The cores of the domes contain lower crustal rocks of eclogite and granulite facies, these rocks have undergone retrograde metamorphism in the outer sheared zones. Movement indicators on the shear zones indicate a complex moverm.-It geometry which does not fit the models proposed by earlier workers. These dome-like structures are similar to the metamorphic core complexes of the western United States Cordilleran region, however there are a number of aspects which do not fit with the models proposed for the development of metamorphic core complexes. Uplift of the metamorphic basement probably resulted from a combination of forces associated with the extension of the crust and the intrusion and emplacement of granodiorite plutons.

Jan 1, 1990

By M I. Pownceby, M A. Rhamdhani, S Purohit, G Brooks

The use of concentrated solar flux for high temperature metallurgical applications is a wellresearched area with several reported literatures on solar calcination and metal oxide reduction. This paper presents two such processes with potential to reduce the carbon footprint from ironmaking through using concentrated solar flux. The first process involves solar flux incorporation to the recently developed lime-magnetite pellet (LMP) route of magnetite ore agglomeration. The second process is a hybrid solar-smelting route for iron ore-coal composite pellets that utilises solar flux to provide process heat. Both the concepts of solar agglomeration and solar smelting process were investigated using a solar simulator-hybrid reactor set-up at Swinburne University of Technology. Results from solar agglomeration experiments at 950°C suggested no change in the reaction mechanism of the LMPs under solar irradiation compared to electrical heating. The percentage and morphology of the primary phases (mainly CaFe3O5) appeared similar for both solar and electric heated LMPs. The solar-smelting of magnetite concentrate-lignite coal composite pellets at 1130°C showed a maximum metallisation of 55 per cent after 1.5 hrs of reaction. The solar-smelt process has about 25 to 35 per cent lower CO2 emission compared to the blast furnace ironmaking. Technoeconomic analysis of implementing a CST facility in an existing composite pellet process suggested a payback period of about ten years at a heliostat cost of $A100/m2 and natural gas cost of A$10/GJ. The economics of CST implementation can be further enhanced by decreasing the thermal losses from the heliostat field and reactor.

Nov 8, 2021

By Hryniewicz M

The paper presents a sound critical estimate of mathematical models presently used for the process of compaction of fine-grained materials. It shows the mathematical model of compaction developed by the authors, which was used to formulate the program of computer simulation of the process. The examples of computer simulation experiments of compaction of selected fine-grained materials regard the results of the experiments made by the authors on variability of external friction occuring in this process. Simulation examination presented in the paper crucially contributed towards the original method of selection of rational compaction technologies of fine-grained materials developed by the authors.

Jan 1, 1993