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By B Leisemann, M Watkinson

Coal augering is an ideal method for recovering coal from the highwalls of open cut coalmines. Coal augering is a simple process whereby additional flights are added to the auger cutting head and auger holes are drilled at 1.9 m diameter up to 200 metres deep. Traditional monitoring was located at the mouth of the hole and if methane was encountered above two per cent, inert gas was delivered into the mouth of the hole to deplete the oxygen content at the auger cutting head below 12 per cent. The auger operator was asked the question ‘how do you know that this is the case?’ Trials were undertaken to prove that the oxygen content at the cutting head did drop below 12 per cent (the lowest limit for methane to ignite, also known as the oxygen nose point). Initial trials showed that the oxygen content in the mouth of the hole did not drop below 12 per cent and modifications were made to hold the inert gases in the mouth of the hole so that the auger flights could take this inert gas into the hole. In-hole monitoring, after completion of mining and after extracting the auger flights, showed that the atmosphere quickly returned to fresh air. In-hole monitoring was also tried during the augering process and yielded valuable results. This paper will discuss the results of the monitoring, information on the gas results obtained and the methodologies used to optimise the oxygen content at the auger face.CITATION:Watkinson, M and Leisemann, B, 2017. Inertisation of coal augering holes, in Proceedings Australian Mine Vent Conference 2017, pp 293–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

Validation of the JKMRC Rotary Breakage Tester (JKRBT) Ore Breakage Characterisation Device

Sep 13, 2010

By Cadman S. J

( The central part of the Gippsland Basin is surrounded by existing major Petroleum accumulations and although six exploration wells have been drilled in the area, none are significant petroleum discoveries. Post drilling analyses indicate that the wells were drilled off structure due to the presence of high-velocity Miocene channels. These channels contain carbonates of significantly higher interval velocity than the surrounding sediments. Problems with seismic interpretation were thus encountered in the development of prospects in the central part of the Gippsland Basin as part of a BMR prospectivity study. The seismic interpretation problems associated with the Miocene channels are two-way time pull-ups at the underlying top of Latrobe Group and deeper levels on the seismic sections. Interpreted seismic sections passing through some of the exploration wells and the Miocene channels are presented to illustrate the configurations of these channels and the pullup effect associated with them. Two different methods of depth conversion were applied, one for the area below the high velocity channels and the other for the area away from the channel. The application of these two methods of depth conversion were found to be reasonably successful in correcting for the pull-ups caused by the high velocity Miocene channels. Mapping of the events near the top of Latrobe Group and near Base Lower L balmei seismic horizons has led to the identification of several potential structural closures. Further exploration efforts are necessary in this area to test these closures.

Jan 1, 1992

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

By R J. Worland, D Bowyer, J L. Mauk

The TerraSpec is a compact field portable mineral analyser that uses non-destructive reflectance spectroscopy for mineral identification. The instrument uses and measures infrared and visible light that is absorbed by certain covalent and molecular bonds (AlOH, FeOH, MgOH, CO32-, OH, H2O and NH4) within the lattice of a mineral at specific wavelengths producing an absorption spectral profile. A variety of minerals can be detected including clays, micas, carbonates, and hydroxides as well as some sulfates and silicates. However, not all minerals are detectable, such as quartz and feldspar. Alteration minerals replacing volcanic rocks have been studied for several epithermal prospects in the lower Waitekauri Valley (Sovereign, Jubilee, Scotia and Jasper Creek) and a geothermal field in the Taupo Volcanic Zone. At the Sovereign, Jubilee, Scotia and Jasper Creek prospects previous XRD investigations determined well developed clay mineral zonation with illite in the west (Sovereign and Jubilee) grading into interstratified illite-smectite (Scotia) and smectite (Jasper Creek) to the east. Although the percent of illite within interstratified illite-smectite could not be determined and some illite-rich illite-smectite (>90 per cent illite) and some smectite-rich illite-smectite (>90 per cent smectite) could be misidentified as illite or smectite respectively, the TerraSpec survey determined the same zonation of illite to illite-smectite and smectite. Common chlorite, rare calcite and local kaolinite were also detected. At the geothermal field, the TerraSpec was primarily used to determine the occurrence of kaolinite, dickite and alunite, which form in acid conditions. Widely spaced (every 50 to 100 m) XRD results are in excellent agreement with closely spaced (every 5 to 10 m) TerraSpec results that further determined the occurrence of these minerals in previously unrecognised intervals. It also determined the occurrence of zoned smectite, illite-smectite, illite, and chlorite alteration. Overall, the TerraSpec is a rapid mineral identification technique that is very useful in delineating the occurrence and distribution of certain minerals in both epithermal deposits and geothermal fields. Although the TerraSpec cannot detect as many minerals as XRD, the TerraSpec allows data collection at a sampling scale and speed (real time) that is not practical by XRD.

Jan 1, 2006

Drilling at Ipswich during the last twelve years by the Queensland Department of Mines has proved large quantities of reserves which have assured the security of the field for many years to come. This is perhaps the greatest contribution to the development of the field since its discovery in 1827.The drilling campaign commenced in 1950 and by the end of 1961 comprised 242 holes totalling 180,220 ft.Intersections of formations and seams, accompanied by detailed surface mapping, led to more precise knowledge of the geology of the field than was previously possible, and clarified many problems of correlation. Productive formations are part of the Middle Triassic Ipswich Coal Measures, a 4,300 ft sequence of fresh-water sediments with some interbedded volcanics. They are overlain by the Upper Triassic Bundamba Group and the Lower Tertiary Booval Group.Reserves disclosed by drilling amount to 171,487,000 tons, comprising 109,407,000 tons "measured" and 62,080,000 tons "indicated". The security of these reserves encouraged many collieries to instal modern efficient mining machinery and washing plants.The climax of recent development of the resources of the field will be the commissioning in 1966 of a £33 million 360 MW power station in the Swanbank district which will consume 14 million tons of coal during its 30 year life and will have a peak demand of some 20,000 tons per week.Drilling is continuing and is expected to prove additional reserves which will justify further development of the field.INTRODUCTIONUntil 1949 there had been no concerted effort to test systematically the resources of the whole Ipswich field. Fifty two known holes totalling 30,500 ft had been drilled, eight of them by the Department of Mines, but because of poor core recovery and inadequate records most of them were of little use in a comprehensive assessment.Development of the field was being retarded by uncertainty regarding reserves and by the general state of the coal mining industry. Numbers of comparatively small independent companies and owner groups were operating coal...

Jan 1, 1963

Owing to improvements in computer capacity, it is now possible to undertake fully coupled or partially coupled, three-dimensional (3D) hydromechanical Finite Element (FE) simulation of mines, including explicit representations of large numbers of discontinuities. The analysis requires fewer assumptions than uncoupled analysis or two-dimensional (2D) analysis, but may require a change in how hydrological data is collected. The way hydrological data is incorporated in stability assessment and the approach to uncertainty in hydrological information also requires discussion. The current procedures for this type of analysis are discussed, along with some practical difficulties and teachings from early applications. A work flow for integration of 3D hydromechanical modelling with pit planning and some considerations for the management of uncertain data are also proposed.

May 1, 2010

By D M. Hunter, S M. Iveson, K P. Galvin

For low density materials such as coal, density-based fractionation of particles via the sink-float method is relatively simple due to the availability of liquids of suitable density; however, for high density minerals, suitable heavy liquids are less available and those that are available are expensive and pose significant hazards. At best, sink-float separation can be performed up to densities of 4400 kg/m3 with the use of Clerici’s solution at elevated temperatures. Hence the direct measurement of grade-recovery and density-partition curves is problematic. Therefore, in most cases, beneficiation plants must rely on methods such as QEMSCAN, density tracer particles or very limited information to guide them in the design and optimisation of their plants.This paper describes a density-fractionation method utilising laminar flow through a system of parallel inclined channels to generate a series of overflow fractions at different flow velocities. Here the particles are subject to precise hydrodynamic forces with minimal dispersion or mixing. The size distribution of each overflow fraction at a given flow velocity is obtained using a laser particle size analyser, and combined with a laminar flow model to deduce the corresponding density distribution. The paper describes the application of the method to measure the separation achieved using a REFLUX Classifier to obtain the corresponding feed, product and reject ‘washability curves’, and in turn the full partition surface. Approaches used to corroborate the findings are discussed.CITATION:Hunter, D M, Iveson, S M and Galvin, K P, 2017. A batch elutriation technique for the density-based fractionation of iron ore, in Proceedings Iron Ore 2017, pp 195–104 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

Updraft sintering of lead concentrates was introduced at Port Pirie in 1955 and since that time a considerable amount of investigational work has been carried out in the laboratory and on the plant with the objective of improving both the understanding of the process and its practical application.From this work it is now possible to predict trends in design and operation, which should result in capital savings and increased efficiency of future updraught plants.INTRODUCTIONOver the last 70 years a remarkable advance has been made in the method of preparing lead concentrates for smelting in the Port Pide blast furnaces of The Broken Hill Associated Smelters Pty. Ltd. (RH.A.S.). Beginning in 1889 with heap roasting, the process progressed to Ropp roasters and Huntington-Heberlein pots in various combinations, then to multiple small Dwight Lloyd (D.L.) downdraught machines. In 1940 two large 10 ft by 50 ft D.L. downdraught machines were installed, and finally in 1955 updraught sintering was ,introduced with the installation of the present 10 ft by 99 ft sinter machine.At the time this last machine was built it was the first unit of its type and thus, of necessity, an experimental machine. During the eight years it has been operating a considerable amount of investigational work on sintering has been carried out both on the plant and in the laboratory.It is now felt that sufficient information is on hand to predict at least tentatively, some of the future developments in lead sintering, whereby both the quality of the sinter and the rate of production may be improved. This will result in a considerable reduction in smelting costs.

Jan 1, 1964

By G de Jong, W Sunyoto, K Sari, P Silalahi

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Big Gossan mine is operated by PT Freeport Indonesia and is one of the largest stope-and-fill mining systems in the world. The Big Gossan deposit is a ~200 m wide, 1200 m long and 500 m high steeply north-east-dipping to subvertical skarn body at the Cretaceous-Tertiary Ekmai-Waripi contact. The copper-gold mineralisation, with a 1.3 per cent copper equivalent cut-off grade, occurs mainly proximal to the Ekmai-Waripi contact in the garnet-clinopyroxene prograde skarn at the base of the Tertiary Waripi formation and partly distal to the contact in the tremolite-actinolite retrograde skarn of the Tertiary Waripi formation.The Big Gossan stope mine is designed from 2540 m to 3020 m above sea level. Present active stoping operations occur at level 2540 mL to level 2640 mL and are done in a primary and secondary stoping sequence. The width and length of the stopes is 15 m and 20 m respectively, while the height of the stope varies between 20 m and 40 m, depending on the ground conditions. The stability of the stopes is visualised in the Mathew’s Stope Stability graphs. These graphs and actual Cavity Measurement Scanner measurements on the stope will predict and show the overbreak and underbreak, which affect the reconciliation of the mined stope and also the pillar stability between the primary stopes. Geological factors like major structures, joints, veins and alteration intensity are important factors that correlated with the stability of the Big Gossan stopes.CITATION:Sari, K, de Jong, G, Silalahi, P and Sunyoto, W, 2015. Stope stability at the Big Gossan skarn deposit, Papua, Indonesia, in Proceedings PACRIM 2015 Congress, pp 139–146 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Burns W. G, Muceniekas E, Whitcher I. G, Hughes F. E

No iron ore deposits were reported before 1961 from the Hamersley Ranges, Western Australia, although low-grade bedded iron formations, associated with ferruginous jaspers and cherts, were known to occur in the local Nullagine Series of Precambrian age.In January-March 1961 preliminary investigations in the area drained by the Turner River, Duck Creek and Serpentine Creek revealed the presence of over 1000 million tons of dense botryoidal or pisolitic limonite, forming flat-lying orebodies with 50-57 per cent iron.Large bedded hematitic orebodies were also discovered in the same area in August-October 1961. These have a porous, biscuity texture and an iron content of 60-61 per cent. They occur at a welldefined stratigraphic level (Brockman Iron Formation), normally in synclines where they have been upgraded by circulating meteoric waters during an old cycle erosion.In 1962 systematic geological studies and mapping, together with sampling and scout drilling, indicated larger reserves of biscuity hematitic ore and led to the discovery of massive hematite deposits at Mt. Tom Price. These were extensively drilled in 1963, proving the persistence of' high-grade mineralisation to a depth of 200 ft and over.To date the total indicated reserves of the Hamersley deposits, within the area held by Hamersley Iron Pty. Limited, are of the order of 4960 million tons and thus rank among the more important of the world. The reserves are composed of 600 million tons of bedded dense hematite ore with 64-66 per cent iron, 2900 million tons of bedded biscuity hematite-limonite with 60-61 per cent iron, 1360 million tons of limonite (goethite) ranging in grade from 50 to 57 per cent, and 100 million tons of canga (conglomerate) iron ore containing 53-63 per cent iron. In all cases harmful impurities are comparatively low.

Jan 1, 1964

Vein swarms in metamorphic terranes such as the Otago Schist Belt, New Zealand provide evidence of past hydrothermal flow systems leading to fault initiation and reactivation. A major episode of hydrofracturing and fluid redistribution occurred during early Cretaceous exhumation of the schist belt. As a result, presently exposed lower greenschist facies greyschists in NW Otago are pervaded by abundant quartz-filled hydraulic extension fractures with associated normal faults hosting quartz¦scheelite¦gold mineralisation. Once the effects of Cenozoic folding have been removed, a regional subhorizontal schist foliation contains an aligned array of subvertical hydrofractures striking NNW, striking parallel to a set of low-slip conjugate normal faults; the array extends over an area >1500 km2 and over a depth interval >5 km. The hydrofracture array comprises a mesh of interlinked extensional-shear and pure extension veins. These veins show mutually cross-cutting relations. Extensional hydrofracturing apparently preceded the development of major throughgoing normal faults. Low-displacement normal faults are infilled with laminated quartz (¦ scheelite) veins (

Jan 1, 2002

By P Illig, R Newberry

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Recent exploration efforts in Eastern Interior, Alaska have discovered significant ca 72 Ma Au-Cu-Ag sulfide-amphibole skarn mineralisation within metamorphic rocks of the Yukon Tanana Terrane, 20 km SE of Tok, Alaska. Contango ORE, Inc’s 1.1 Moz Au-equivalent Peak deposit skarn discovery is hosted by an argillaceous marble layer in quartzite and micaceous quartz schist. This skarn mineralisation is both younger and much more Cu-rich than the typical ca 90 Ma Au intrusive-related gold deposits in the Tintina Gold Belt (eg Ft Knox and Pogo). Silicates at the Peak skarn are predominantly high Cl-, randomly oriented, Fe-rich amphibole, lesser chlorite and minor (<1 per cent) residual clinopyroxene (Hd80–90). Amphibole is ferroedenite to hastingsite and contains up to 4.2 wt per cent Cl-. Pb-Zn-Sb veins are most distal and cut schist wall rocks and amphibole skarn. The predominant sulfide mineral is pyrrhotite, with subordinate arsenopyrite and lesser chalcopyrite, native gold, minor pyrargyrite (Ag3SbS3), trace Jonassonite (AuBi5S4) and maldonite (Au2Bi). Native bismuth, galena, hedlyite (Bi7Te3) and Joseite-A (Bi4TeS2) are also present.Unmineralised garnet (Ad38–43) + pyroxene (Hd60–63) and pyroxene-rich (Hd76–80) skarn occurs in different fault blocks from the Peak skarn and represent proximal skarn related to different intrusive centres. Amphibolites in the region are true metabasites, display metamorphic fabrics and lack the high Fe-Cl compositions of the amphiboles in mineralised skarn. Residual clinopyroxene in the Peak skarn is rare, and most of the hornblende is coarse radial splays that shows no evidence for replacement of pyroxene. Consequently, we propose that the sulfides and hornblende were mostly direct replacements of argillaceous marble and not formed by retrograde alteration of pyroxene-rich skarn. The high-Cl amphiboles indicate that the fluids were Cl-rich and presumably carried Cu via Cl complexing, unlike the Cl-poor fluids associated with ca 90 Ma Cu-poor deposits of the region.CITATION:Illig, P and Newberry, R, 2015. Amphibole Au-Cu skarn and massive sulfide replacement at the Peak deposit, Eastern Interior, Alaska, Peru , in Proceedings PACRIM 2015 Congress, pp 415–422 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Greenwood J. N

This work was commenced at a time when information on the manufacture of cemented tungsten carbide was urgently needed in Australia. Much information of a general type has been published, but many of the details of the processes used are still undisclosed. The aim of this research was to determine a satisfactory way in which cemented tungsten carbide could, be made, and to investigate the problems which are associated with the process. As the work proceeded, its ramifications grew continually, and it was necessary to limit the possible lines of investigation. After much experimental work, a 9% cobalt-tungsten carbide alloy was developed which had satisfactory properties when used as a cutting tip. The effect of certain variables on the properties of this particular alloy was investigated.The tungsten carbide was prepared in stages from King Island scheelite concentrates under strict laboratory control, whilst the cobalt (1) used was made from cobalt oxide prepared from crude cobalt oxide obtained from Eisdon.In order to clarify the detailed experimental work, a brief summary of the method used for the preparation of cemented tungsten carbide follows.Tungsten carbide and cobalt are prepared in a very finely powdered state, and are then thor,oughly mixed by a ball milling operation. The resultant mixture is pressed in a suitably shaped die into small compacts which are subsequently '''presintered,'' i.e., heated' in hydrogen between 800°C. and 1000°C. The final sintering is carried out in hydrogen between 1,400°C.and 1,600°C. for about half an hour. These "alloys" may contain from 3 to 13% cobalt, depending on the particular properties required of them.PREPARATION OF MATERIALSThe tungsten oxide prepared as described by Smithells (2) was extremely finely divided, and after a few hours' grinding in a ball mill, the powder consisted of material below 10 microns iJ;l size. The oxide was reduced to tungsten metal with hydrogen in a tube furnace. The reduction was carried out at 800-900° C., a rapid flow of hydrogen being maintained in order to remove the water vapour' formed as a result of the reactions:

Jan 1, 1942

The material presented in this paper describes experimental work to determine the effect of variations in suction nozzle design upon inlet flow conditions. Four entrance profile shapes were examined under controlled conditions of slurry flow and it was found that the straight ended nozzles had consistently higher entrance losses than the straight taper or the ellipse, and that the circular arc profile nozzles were the most efficient. Subordinate considerations were the measurement of the quantities and the forces involved.As the work progressed, three distinct phases in the pattern of flow were apparent and the static pressures in each were carefully examined. An inlet zone was found to be unstable in changing boundary conditions, a transition zone was largely independent of slurry density and in a zone of stability the pressures were found to be directly related to the characteristics of the flowing pulp. In this zone pressure measurements were reproducible within ± 2 per cent regardless of changing boundary conditions.The effect of varying the "1" parameter of nozzles with a part circular entrance profile was examined and it was found that flow conditions approaching the ideal were obtained when the radius of curvature was between 0·40 and 0·550.

Jan 1, 1966

By Misra V. N, Cheng C. Y

Two types of Mt Tom Price hematite iron ore from Hamersley Iron P/L were tested using a Humboldt Wedag Jones P40 wet high intensity magnetic separator (WHIMS). The parameters tested were magnetic intensity (7000, 9000 and 11 000 Gauss), groove plate type (8R and 12R) and gap width (2.5 and 1.8 mm). It was found that at 9000 gauss magnetic intensity, reasonably high-grade and recovery in the concentrate were obtained. At 2.5 mm plate gap width, the 12R groove plate performed slightly better than the 8R groove plate. Further testwork is recommended to optimise the magnetic intensity, feed flowrate and pulp density, wash water pressure and flowrate with 12R and 8R groove plates at 2.5 mm gap width.

Jan 1, 1999

By B W. Riddol1s

The 1983 Energy Plan calls for an increase in North Island coal production from both underground and opencast sources from the 1982/1983 production of 843 000 tpa to approximately 3.4 Mtpa within the ten year period to March 1993. This increased production is scheduled to come from the following sources: Huntly West No 1 underground mine reaching full production of 1.26 Mtpa. Huntly East underground mine increasing production to 750 000 tpa. The proposed new Huntly West No 2 mine producing 100 000 tpa in its first year of operation û 1992. The proposed Ohinewai opencast producing 920 000 tpa for supply to the steelmaking plant at Glenbrook, replacing Weavers opencast which will be worked out in 1990. Rotowaro opencast producing at 220 000 tpa (currently being achieved). Two additional sources of supply which are not scheduled to begin production for at least ten years, and both of which have been designated for coal fired thermal power generation, are the Maramarua and Mokau coalfields. It was originally envisaged that development of both coalfields would be a combination of underground and opencast mines. The form of development is yet to be confirmed by detailed feasibility studies. The location of the Maramarua, Ohinewai (Waikare Coalfield) and Mokau deposits is shown on Figure 1. Worley Consultants Limited, in conjunction with their partners Rheinbraun Consulting GmbH (Germany) and Longworth McKenzie Pty Limited (Australia) have been involved with investigations and mining assessments for the Maramarua, Mokau and Ohinewai prospects. The Maramarua and Mokau studies form part of the New Zealand Coal Resources Survey programme of updating information to the Pre-Feasibility Mining Assessment level before proceeding to detailed feasibility studies. The Ohinewai study was commissioned directly by Mines Division to investigate the feasibility of mining coal by 1989 before reserves at Weavers opencast are depleted. This paper describes typical studies which are now being commissioned by Mines Division to investigate large-scale mining development and the effect geotechnical-conditions may have on coal recovery. The magnitude of these projects is reflected in the proposed outputs û up to2 Mtpa from individual mines û and the introduction of new continuous mining systems for both underground and opencast mines on a scale which has not previously been contemplated.

Jan 1, 1984

By J Cahill, D Holden, R Stuart, G Cryan, W Power, W Stratford, S Garwin

The combination of Stage 1 Geoinformatics legacy data intervention processes with the Stage 2 ultra-detailed airborne geophysical prospecting demonstrates a new approach to converting data to information to knowledge, and converting that knowledge into exploration results.   The Coromandel region of the North Island of New Zealand has long been know to host gold deposits of economic viability (Hauraki Gold Fields). To the SE of this area lies the Taupo Volcanic Region (TVR) where the geology and structural setting mirror the Hauraki Gold Fields, however mineral exploration in the past has been hindered by the blanketing volcanic ash deposits. Glass Earth Limited recognised that this whole potential epithermal gold province could be effectively explored utilising rapid, risk orientated processing to review legacy geoscience data: The Geoinformatics Data Intervention Process; which in turn directed ultra detailed airborne geophysical surveys over the TVR. Results have outlined 21 new drillable potential epithermal gold targets; and a plethora of other targets with high prospectivity.

Jan 1, 2005

By M P. Simpson, J L. Mauk

The Golden Cross, low-sulfidation, epithermal deposit shows a number of features that are directly or indirectly related to boiling hydrothermal fluids. Occurrences of lattice calcite and their quartz pseudomorph equivalents in veins, and occurrences of adularia in veins and in the surrounding altered rocks in the vicinity of ore, are both direct evidence of deposition in the presence of boiling hydrothermal fluids. Loss of carbon dioxide causes calcite deposition (platy variety) near the level of first boiling, while adularia deposits due to the attendant pH increase along the cooling flow path. Indirect evidence of boiling include crustiform-colloform quartz banding, late massive calcite veins, clay-carbonate alteration in the shallow and peripheral parts of the ore zone, and the restricted vertical interval of precious metal mineralisation. The colloform quartz banding strongly resembles the banding in amorphous silica deposits found in geothermal surface pipes. This implies that fluids ascending the Empire Vein structure were saturated in amorphous silica. If so, then they must have undergone phase separation, which initiated at considerable depth (e.g. =1000 m) and very hot temperatures (e.g. =300¦C). On the basis of stable isotope data, late massive calcite veins appear to have deposited from CO2-rich steam-heated waters. Calcite deposited along heating paths as these waters descended into the upflow zone during late stage collapse of the hydrothermal plume. In active systems, such steam heated waters form by deep boiling. The high CO2 contents of these waters promote hydrolytic alteration and the formation of clay-carbonate alteration. Reaction path modelling using CHILLER and a deep, Broadlands-Ohaaki water as an analogue, shows that minerals deposit along boiling flow paths over discrete spatial intervals. Calcite and adularia deposit near the site of first boiling, followed by gold and then by amorphous silica. For deep boiling starting at 300¦C, these minerals deposit over a path length that exceeds 1000 m. The distribution of banded quartz and gold at Golden Cross are consistent with such a boiling model. However, the elevation of first boiling must have fluctuated over 500 m to account for the coincidence of lattice quartz (pseudomorphs of platy calcite) and adularia, crustiform-colloform silica and gold over distances of a few centimeters in veins. We deduce that a downward propagating boiling front and expansion of two-phase flashing in a flowing water column occurred during episodes of high vertical permeability and fluid flux in the Empire vein structure.

Jan 1, 2000

By M P. Cipold, J F. Bachmann, C C. Bachmann, J Ha, H B. Wurst

In washability, the objective is to establish the set of maximum possible separation performance criteria for a given mineral feed. The method of choice for this has been the conventional sink–?float analysis. Using traditional sink–float method it is not possible to sample and automatically measure. This fact, as well as time, cost and safety aspects, as well as required and manageable sample size of the sink–float method have prompted the search for a new approach for establishing separation performance criteria. This is especially important as performance levels of separator plants can be maximised if reliable information based on an analysis of washability in conjunction with particle size distribution, elemental constituency becomes available in time. The new method to establish washability and associated performance information utilises at least two measurement technologies concurrently: single energy X-ray transmission and image processing. For porous or very inhomogeneous materials the results can be refined further by using dual energy X-ray transmission and image processing.If used as a standard laboratory device the continuous build-up of the washability curve allows to evaluate the statistical significance of the sample size during measurement.The measuring method can even be improved if it is combined with an automatic sampling system that feeds a continuous and representative particle stream to the analyser. Then the value of the collected data increases considerably since the washability data are additionally available in time to be considered in the control of the process plant. The washability curve can be derived and is continuously updated based on the particles measured during the past time interval. Older curves and results are stored in a database and can be retrieved for later reference. This technology now enables automated sampling and integrated automated measurement, which was previously not possible.This incorporation of an automated washability monitor at a representative sample gives near real-time data that would impinge positively on the profitability of the plant operation. The method was extensively tested using a range of samples with different densities, varying from 1 g/cm3 (coal) to 5 g/cm3 (iron ore).CITATION:Bachmann, C C, Bachmann, J F, Cipold, M P, Wurst, H B and Ha, J, 2017. Inline analysis of washability parameters for process control, in Proceedings Eighth World Conference on Sampling and Blending , pp 213–218 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017