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By Blockley J. G, Laeter J. R

The history of the Ph-Cu-Zn mineralisation in the orthampton Block of Western Australia has been further investigated. It was hoped that (1) Rh-Sr studies on partially-remelled granulites, wall-rocks to the dolerite dykes, should date the dolerite intrusion, (2) Rh-Sr data on hydrothermally-altered dolerite should date the sulphide mineralisation, (3) Pb model ages on the galenas might provide an independent dating of the mineralisation, in addition to any geochemical information that might be derived. Only the second dating aim was fulfilled, but the Pb isotope data, when combined with the Rh-Sr data, have permitted deductions about U, Th and Pb abundance changes during the regional metamorphism, and about a possible source of the ore Pb. In detail the following has been found. (1) The partially-remelted granulitic wall rocks yield a scattered whole-rock Rh-Sr isochron which seems not to have been reset by the dyke intrusion (age 1037 ± 146 Ma, with initial Sr ratio 0.7171 ± 0·0054, MSWD = 111). This date agrees well with that reported previously for granulites from another locality; together theyestablish the time the metamorphic period closed. (2) The hydrothermally-altered dolerites yield a Rh-Sr whole-rock date 434 ± 16 Ma, with initial Sr ratio 0.7072 ± 0·0029 and MSWD = 31, taken as referring to the time of Ph-Zn mineralisation. This contrasts with a report of much older palaeomagnetic and K-Ar datings of the dolerite (not less than 550 Ma, possibly older) and suggests that neither the dolerites nor their heat have had any connection with the mobilisation of the Pbscavenging solutions. (3) The Pb isotope ratios of galenas from the ores yield a well-correlated regression which is not amenable to any of the model-age calculations. (4) The Pb-isotopic trends negate any genetic connection between dolerite and mineralisation, but the country-rock granulites could be the Pb source. (5) Combination of the Rh-Sr dates and the Pb data in a "simultaneous isochrons" construct permits the inference of major losses from the system during the regional metamorphism, in the order U>Pb>Th, with substantial homogenisation of the remaining Pb. This left a wide range in local UlPb and Th/U among the source rocks which eventually were scavenged by the mineralising solutions. (6) These geochemical deductions are shown to be compatible with previously-published information on the abundance ofU and Th in the Northampton Block granulites, which are thus seen to be credible as source rocks for the ore lead.

Jan 1, 1985

By Cocker J, Urosevic M

Seismic methods have become common for the detection of low-throw faults ahead of underground coal mining. Surface seismic methods cannot theoretically be used where dykes occur, because seismic waves transmit from the surface down to the seams, and reflect back to the surface. Consequently, where sub-vertical structure such as dykes occurs, the surface seismic method fails.The ability of seismic methods to image dykes depends on the geometry used, the dyke thickness and the seismic wave propagation mode in relation to dyke composition and internal structure. Surface seismic methods find it difficult to distinguish between faults/fractures and very thin dykes (1-2m in thickness) when the dyke's thickness is less than the seismic wavelength. Consequently, borehole seismic methods have to be used to detect the presence of such thin dykes.

Jan 1, 1998

Perhaps the only thing certain about an address that purports to look into the future of any human endeavour is that time will prove it :.o be inaccurate. In undertaking the dubious, but oft-times necessary business of prediction, thr, historian will base his/her forecasts on tr-ands of the past, the speculator on current events, and the politician on what he/she would dearly like to see happen. The thoughts expressed in this address seem to have arisen through exercising a combination of all three of those philosophies but, hopefully, with a smat- tering of pragmatism.

Jan 1, 1988

By Wright G. A

The objective of refining in steelmaking is to reduce the concentration of impurity atoms, e.g. sulphur, phosphorus, from an initially high level to a specified low concentration. A two-film theory of refining is presented in which the rate of

Jan 1, 1980

The phenomenon of Instantaneous Outbursts, although not new to Australia, was sharply drawn to the attention of the local coal-mining industry by two isolated fatal occurrences on widely separated fields, both late in 1954. An outburst is the eruption of apparently solid coal from the face, aided by vast quantities of gas released from the coal, as the coal fails under mining stresses additional to its natural stressing.The gases involved are principally methane and carbon dioxide. The various factors which combine to produce outburst conditions range from external factors such as stresses arising from depth of cover and other causes, to inherent factors such as strength of coal,and its capacity to retain gases (sorption). Of the localities where instantaneous outbursts occur the Gard Basin in Southern France has had the greatest number and the most serious occurrences. By contrast, local outbursts have been minor.Experimental work into some influencing factors has been carried out by various overseas authorities and some research has been accomplished in Australia. Practices used in some overseas areas to improve safety of working are largely empirical, as are the local rules and recommendations for work in affected areas.The appearance of further outburst areas is anticipated as mining becomes more extensive and deeper.INTRODUCTION"Instantaneous Outbursts" can be described as violent eruptions of coal from the solid accompanied by considerable gas evolution. The projected coal is usually of small size, and a high proportion is pulverized, and may be carried and deposited over great distances by the gases, liberated from the outburst. This outburst coal is of bituminous to anthracitic rank, and the gas involved is essentially methane or carbon dioxide, or a mixture of both. Outbursts involving carbon dioxide are usually more violent and dangerous. The phenomenon is relatively unusual, being confined to probably sixteen known areas in the entire world, these areas comprising only portion of the coalfields in which they occur. Usually only one or two mines on each field are affected.

Jan 1, 1958

By Collins DN, Hollick CT

Conventional processing of heavy mineral deposits containing radioactive rare earth minerals such as monazite and xenotime may cause industrial hygiene problems through atmospheric dust and contamination of product concentrates. An alternative procedure has been developed in which such minerals are removed from bulk heavy mineral concentrates by flotation with little loss of other economic minerals. With fine ores, recoveries of over 95% have been achieved and with coarse ores over 80%,in both cases at high grade. Several flotation regimes have proven effective. The potential for generation of radioactive dust or product contamination is subsequent processing -is correspondingly reduced.

Jan 1, 1990

By Doyle R

Underground operations commenced at Tower Colliery in late 1978 and the early prevailing mining conditions in the worked seam were considered poor as a result of high stress and geological disturbances. This suggested that outbursting activity may be a possibility. The colliery has since recorded a total of 13 individual outburst incidents, all of which have been associated with the same dyke and strike-slip fault zone. This paper depicts the geological conditions and presents the results of investigations undertaken at the time of these outbursts.

Jan 1, 1986

By Leahy G. J, Moxon N. T, Nicol S. K

Experimental work is described in which extremely dilute aurocyanide liquors are treated with novel surface-active complexing agents to produce a hydrophobic aurocyanide species. Subsequent aeration of these liquors causes accumulation of such species at the air-water interface and the aurocyanide complex is transferred to a froth concentrate. A detailed performance assessment of this process is made and this knowledge used in the design of a pilot plant facility. Early results indicate the feasibility of the selective recovery of aurocyanide ions from reclaimed residue dam water (approximately 0.2ppm Au) with upgrade ratios of the order 180:1. A further study was made applying ion flotation to the recovery of gold from a carbon-in-pulp (CIL) feed liquor (approximately 1.0ppm Au). The probable economics of this process compared to conventional CIL processing is also described. Successful development of countercurrent ion flotation for concentrating solids-free gold solutions may offer a lower cost alternative to existing gold ore processing technologies, or in more secondary applications such as concentrating dilute gold solutions or heap leach runoff. The technology may also have more generalised applications to other heavy metal process- Ing.

Jan 1, 1991

By Huntington J. F, Green A. A

The quality of a photointerpreter's anno- tation of an image may be displayed by writing maps in which the pixels are shaded according to the number of times a pixel was seen to be on a feature. The map of grey tones is more valuable, if, for each grey level, a measure of quality is determined, which is the probability that a feature exists in a pixel of a given grey tone. From repeated annotations (at least four) of the same image by a single observer, it is possible to formulate a perception model which describes stochastic processes in the observer. From that model, it is possible to assign estimates of data quality for each observer to each grey tone. For two observers on the same scene, the 'mean' method of quantifying the grey levels is to assign a value equal to the mean of the ii,:lities for each of the two observers separately. For this example, the grey tones arr thus quantified at probability levels of 0.70, 0.80, 0.90 and 0.95.

Jan 1, 1977

By Brinkmann J. R

In the narrow stopes of South African gold mines, rockbreaking is carried out by drilling and blasting with safety fuse and igniter cord being used as the initiation system. The fuse/gniter cord system is used primarily because of its low cost, however several limitations of this method include: inaccurate delay time, unreliable firing, inflexible application to varied configurations, and the absence of dynamic interaction between holes. Alternative initiation systems that incorporate millisecond timing are being developed to overcome the limitations of fuse(tgniter cord systems. Current investigations by the Stoping Technology Division of the Chamber of Mines Research Organization (COMRO) into the effects of millisecond initiation are being conducted at a deep test site. Experimental blasts using various millisecond delays and the independent firing of holes with fuse/igniter cord are being studied in order to quantify the influence of delay time on the blasting process and to identify the best methods of applying millisecond initiation systems. The effect of design variables such as delay time, hole firing pattern, stemming, and panel layout are discussed. Blast results including throw distance and direction, muckpile profile and rock cleaning times are used in the discussion of different combinations of blasting variables.

Jan 1, 1990

By Merry N, Cocks T

The mineral exploration industry is increasingly aware of the importance of the relationship between mineralogical data and geochemical assay results. However, until recently, the cost and time constraints of most techniques for analysing alteration mineralogy have precluded detailed alteration studies. These impediments have been reduced by the development of the Portable Infrared Mineral Analyser (PIMA), a field portable infrared spectrometer that allows rapid (in field) and cost effective analysis of alteration minerals including subtle variations in mineral crystallinity and Composition.

Jan 1, 1995

By Mankosa MJ, Yoon R-H

A reliable scale-up procedure for column flotation must address three important areas of column design, ie column geometry, sparging system and wash water distribution network. The column geometry is dictated by the maximum froth carrying capacity (which determines column diameter) and the bubble-particle attachment rate and particle retention time (which determines column length). The most important factor in the scale-up of an air sparging system is the ability to produce small bubbles in both laboratory and full-scale columns. Other factors, such as energy consumption and maintenance requirements, should also be considered in the scale-up of bubble generators. It is also important to design a wash water distribution system that can properly control the froth stability and maximise the column throughput. Based on these criteria, a successful scale-up example is given.

Jan 1, 1993

The blasting process involves a complex interaction of a delayed sequence of moving sources of seismic energy which produce nonlinear behaviour near the blast holes. A deterministic description of this nonlinear behaviour represents a formidable problem. The modelling of blast vibrations remote from the blast source may use some of the primary features of the blast design such as charge type, charge weight and initiation sequence. Such modelling of blast vibrations usually assumes linear behaviour remote from the blast holes. Site specific charge weight scaling laws may be used to predict the blast vibration levels with relatively poor accuracy. An important ingredient which is missing from charge weight scaling laws is the seismic source wavelet emanating from each blast hole. The present paper considers some approaches which may be used to determine a suitable source wavelet. The wavelets are suitable for use in the region where linearity may be assumed. In that region, it is possible to model the attenuation and scattering of the seismic wave as it propagates from the blast source to the measurement location.

Jan 1, 1990

Tourmaline-bearing rocks are a rare rock type of Suites 3, 4 and 5 at Broken Hill. Minor laminated plagioclase-quartz-tourmaline rocks occur in association with the quartz- magnetite rocks of Suite 3 with the greatest abundance of tourmaline-bearing rocks present in Suite 4 intimately associated with lode horizon, scheelite mineralisation and zinc mineralistion - all approximate strike equivalents of the Broken Hill Pb-Zn-Ag deposit. Bedded quartz-tourmaline rocks, tourmalinites, tourmaline-rich pelite and tourmaline-bearing lode horizon have been recorded from suite 4. The bedded tourmaline rocks rarely display cross bedding, graded bedding, slump structures and small scale intraformational breccias. Minor tourmaline-gahnite-bearing pelites are present in Suite 5. The sedimentary structures, metamorphic textures, the stratigraphic position of the tourmaline-rocks and the presence of quartz-tourmaline-gahnite-spessartine (-fluorapatite) lode rocks indicates that the mineralisation at Broken Hill and the tourmaline-rich rocks are all products of submarine exhalative hot spring systems which were most active during deposition of Suite 4 rocks. Tourmaline is chemically different from that associated with granitic activity and from other submarine exhalative tourmaline-rich rocks because the premetamorphic alteration at Broken Hill involved addition of Fe, Ti and F and subtraction of Mg - a feature reflected in the chemistry of tourmaline from Broken Hill.

Jan 1, 1983

Probabilistic seismic hazard analyses (PSHA) have now gained wide acceptance in the development of design criteria for major projects. When used with regional criteria the procedures have also allowed the preparation of more rational seismic zoning maps. Seismic zoning maps using various levels of results from PSHA studies around the Pacific Rim now include Canada, Indonesia, New Zealand and the United States. Some Pacific Rim countries such as Chile where the seismic exposure is dominated by subduction events have no subdivision into separate zones.Approaches to risk based zoning are being considered in several Pacific Rim countries including Australia. Australian studies must face problems similar to parts of the Eastern United States where seismic activity is low with irregular and infrequent occurrences of moderately large earthquakes. The perception of the seismic exposure by both regulatory agencies and the public at large is different when considering areas of low seismicity. There is therefore a need to make different interpretations of the results of PSHA studies in these areas of low seismicity. The aim of this paper is to explore some of these differences by comparing the results from two site specific studies from areas with widely differing seismic activity rates.

Jan 1, 1990

By Merwin RA

The recent development of rare earth permanent magnets has revolutionised the field of magnetic separation. The advent of rare earth permanent magnets in the 1980s provided a magnetic energy product an order of magnitude greater than that of conventional ferrite magnets. This has allowed the design of high-intensity magnetic circuits operating energy free and surpassing the strength and effectiveness of electromagnets. New applications and design concepts focusing on the mineral and metal processing industries have evolved. This technology also led to the development of various magnetic separators specifically designed for mineral processing applications. Applications which were not previously considered are now being applied to primary mineral upgrading and recycling and secondary recovery.

Jan 1, 1993

The Kennedy Siltstone Open Cut provides graded rock for stope filling. Rotary drilling of 310 mm blastholes with a Gardner Denver GD120 is used, and the successful application of an equilateral triangular drilling pattern is described. Charging practices and the development of bulk slurry handling are outlined. Blast monitoring plays an important role in K.S.O.C. drilling and blasting operations. The proximity of nearby residential areas (1300 m) and the Mount Isa Airport (4500 m) necessitates special attention with regard to the minimisation of both air blast and ground vibration levels. The application and control of drilling and blasting parameters has had a direct bear- ing on success of the mining operations and also played an important role in reducing the disturbance to the community.

Jan 1, 1978

By Cotton R. E, Cox R

Digger Rocks is one of several nickel-bearing sulphide deposits localised within komaLiitic volcanics of the Forrestania Greenstone Bell within the Archaean YiIgam Block of Western Australia. Exploration and evaluation to April 1990 have delineated a resource, at a nominal cut-off grade of 0.5 per cent Ni, of 1.9 Mt at 1.1 per cent Ni within a lensoid sulphide body which strikes NW, dips 50°SW, and occurs at a depth of 30 - 110 m below surface. There has been no production from any of the Forrestania nickel deposits to-date. The deposit, comprising both disseminated and massive sulphides, has maximum dimensions of 400 m strike, 115 m vertically and 90 m true width. Generally the massive sulphides occur at the base of the disseminated sulphides, on or close to the base of the Digger Rocks dunite. The two main massive sulphide lenses have maximum dimensions of 120 m strike, 75 m vertically and 16 m true width (northern lens) and 60 m strike, 25 m vertically and 4 m true width (southern lens). The average grades of the massive and disseminated sulphides are 5.9 per cent i and 1.2 per cent i respectively. The massive sulphides generally have sharp hangingwall and fOOlwall contacts and display strong internal grade anisolropy.The massive sulphides are mainly within the supergene zone and consist of violarite, pyrite and marcasite. The disseminated sulphides are mainly within the primary zone and consist of pentlandite, pyrrholite, pyrite and minor chalcopyrite. Alteration zones, up to six in number, are complex in detail. The sulphides are capped by an average of 30 m of sub-economic, leached, siliceous, oxidised material.A genetic model for the deposit is described which places Digger Rocks in Category 2 (sulphides in large layered dunite bodies) of the latest classification of komatiitic nickel sulphide deposits in the Yilgam Block of Western Australia by Hill and Gole (1990).

Jan 1, 1992

By Plumridge C. L, Lynch J. E, Forresty R. J

The Amanda Bel Goldfield (new name) is an area of approximately 1000 sq. km centred 65km WSW of Ingham and 150km due east of Kidston (Camel Creek homestead to Ryeburn homestead area). Gold mineralisation has been located in tightly folded sediments of the Silurian Greenvale Formation as well as in the Early Devonian Kangaroo Hills Formation and the Early Carboniferous Clarke River Formation. The area is traversed by a major NW-SE structural corridor, with many of the numerous basaltic, andesitic and rhyolitic dykes of the region sharing a similar trend. So far fourteen gold-bearing zones have been located, all of which are new discoveries delineated by bulk cyanide leach sampling and subsequent geological reconnaissance. The region has undergone three periods of deformation with gold mineralisation introduced syn-D1, post D1 - pre D , syn-D and post-D2/D , thereby revealing an involved metall~genic history. Mineralisation types include Sb, Sb-Au, Sb-Au-As, Sb-Au-As (-Pb-Zn) and Au-As. Minor occurrences of W, Pb-Zn-Ag and Pb-Zn-Ag-As-Sn are also present as are alluvial (deep lead) tin Drosoects.

Jan 1, 1989

With the sinking of the No. 3 Shaft at North Broken Hill Limited, it was necessary to construct adjacent to the shaft a new changehouse for mining and surface personnel.It was also probable that as the older sections of the North and British leases were worked out, all employees at present working in these sections would be transferred to the No. 3 Shaft area. This could ultimately result in all personnel employed by North Broken Hill Limited being concentrated in this area, requiring the construction of new administration offices, workshops, mine store, etc., also in this area.

Jan 1, 1957