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Permian ultramafic and associated rocks form a belt in East Nelson and contain widespread, but minor, chromite and copper mineralisation and some mining was carried out last century. Since mining ceased, about 1910, little mapping of the belt has been carried out although its origin has been debated vigorously. Recently it has been inferred to form part of a ophiolite sequence, which has been tectonically disrupted to form a melange, and several 'plate -tectonic' models have been proposed. Mapping in the central part of the belt has shown that mTlanges are to the east of the ophiolite sequence. Faulting is widespread so that in anyone section part of the sequence may be absent. Some of the faulting is difficult to recognise and probably took place during or soon after the sequence accumulated. Other faulting is clearly of Cenozoic age and includes major NNE striking faults, with large horizontal displacement, and approximately east-west striking faults with almost entirely vertical movement. The writer agrees that 'plate tectonics' could provide an acceptable explanation for the origin of the ophiolite sequence but the models so far proposed do not take into account the nature and field relationships of the rock units present. Copper Mineralisation is largely controlled by the younger faults, particularly those striking about north-east, and is largely confined to the western part of the ultramafic rocks particularly where slivers of the volcanics of the adjacent Lee River Group are enclosed. Mineralisation, along NNE striking shear zones, has recently been found in the volcanics some distance from the ultramafic rocks. The chromite mineralization is in the form of primary layering in the basal part of the ultramafic belt although in places it has been concentrated into lenses probably during serpentinisation.

Jan 1, 1977

By C McMahon, S G. Walters

Mineral maps of æintactÆ and large particle textures have been produced routinely from optical microscope images. Polished thin sections of large particles (1 - 3 mm) provide a balance between representative sampling and the preservation of primary rock textures. Optical microscopy is an efficient way to generate mineral maps suitable for geometallurgical applications. The automated optical mineral identification was carried out using a Leica DM6000¬ microscope with a high precision stage suitable for direct tiling of image frames and good registration of multiple image layers. Standard images collected were 10 x 10 frames (20 mm x 16 mm). Four image layers were recorded: ætransmitted light plane polarisedÆ, ætransmitted light crossed polarsÆ, ætransmitted light crossed polars with 1l tint plateÆ and æreflected lightÆ. All image analysis was carried out using Definiens Professional V5¬. The four image bands were read directly in 12 greyscale bands. A segmentation algorithm produced objects based on homogeneity across all bands. These objects were then classified using a complex set of rules (Process Tree) that are based on image brightness in all 12 bands. Opaque and non-opaque minerals were classified in the same sample. Using this protocol up to 12 minerals can be satisfactorily classified in one sample. The opaque minerals were recognised using colour ratio and reflectance intensity in the reflected light image. Non-opaque minerals are more difficult because of the complex variable colours of many minerals and the complexity of interference colours. However, object-oriented classification using three transmitted light image layers and multiple rules is a powerful technique for recognition of these minerals.

Jan 1, 2008

Present value maximisation studies are a useful aid in enhancing the economic performance of open pit mining operations. Maximising present value helps to reduce the risk of financial failure. Maximisation of present value also means that the capital invested is being used most efficiently. A characteristic step in determining the present value of an open pit mining operation is to set out the sequence in which increments of material (ore of various grades and waste rock) are mined. Traditionally, present value maximisation has been performed by selecting a cut-off grade for each increment so as to maximise the present value of the total operation, by an iterative process using computers. Kenneth F Lane has developed a method and applied it to many mining operations. An alternative method for determining the maximum present value of an open pit mining operation is given. In this method the maximum present value is determined by working backwards from the end of the operation life, progressively asking the question of each increment `what cut-off grade maximises the the present value at the start of mining of that increment?' The method allows calculations to be performed by a `spreadsheet' package. Present value determinations are characteristically performed under constant conditions (eg prices, costs) throughout the operation life. Unfortunately real life circumstances are rarely constant, with the costs of mining inputs rising at variable rates. The prices received for mineral products have been shown to broadly trend downwards with time in real terms. Treatment of such changes in the determination of the maximum present value of an operation is discussed.

Jan 1, 1994

Statistical frequency distributions may be used to characterize the overall variation of grade in orebodies. Special types of distribution (e.g. lognormal, log-type A) are necessary to describe skewness inthe case of rare metals. Also needed (but for the most part hitherto neglected) is the serial correlation function which describes the tendency for grades near together in an orebody to be closer together than grades at points relatively far apart.The sampling problem for orebodies is interpreted in statistical terms. Different methods are reviewed, and the effect of serial correlation discussed.A discussion is given, based on experiments and observations made by the author, of biases arising in the minei:l material by such methods as chip sampling and grab sampling due to such causes as nonrepresentative selection by the sampler.INTRODUCTIONMiners have always recognized the large element of chance in their operations. Chance is the raw material of statistical theory and, provided there is some recognizable pattern or underlying regularity in a set of data arising from the operation of chance events, statisticians are able to formulate mathematical models to study them. Mining engineers, geologists, and statisticians have gone a long way between them towards finding general statistical rules which describe the distribution of minerals and metals in orebodies, and even the distribution of orebodies over the earth's surface.These rules do not have the force of physical laws, though they obviously derive from them and have been used to throw light on them. From statistical theory it is possible to find methods of estimating from sampling some of the characteristics of orebodies which are of importance to...

Jan 1, 1962

By L E. Setiawan

The mining and milling groups at Batu Hijau are tasked with increasing SAG mill throughput by approximately ten per cent. Avenues used for this process are blasting and crushing optimisation, ore blending and predicting SAG mill throughput in relation to the geological model. This is in line with traditional æMine to MillÆ studies. At Batu Hijau, mill and mine sequencing cannot readily be configured to perform the surveys traditionally required by a æMine to MillÆ study while meeting the daily production target of 140 000 tonnes per day and processing from varying ore types in one pit. A program called BOCCOST (blasting optimisation crushing conveying optimising SAG throughput) has been implemented to capture approximately 200 variables from blasting, mining and milling operations and assign them to a common point in space in the geological model in real time. Interpretive analysis of data from BOCCOST is used to model relationships between the 200 variables to determine which and how these factors affect SAG throughput. Once these relationships are determined, the blasting, ore blending and crushing process can be optimised to generate a product that maximises mill throughput. The relationships modelled from BOCCOST are also used to generate a SAG mill throughput estimator, which can be coded into the production block model. The block model can be reconciled with the geological block model for correlation by geological domain. Once this relationship is established, SAG mill throughput domains can then be established for predicting SAG mill throughput. This SAG mill throughput estimator is then used in conjunction with revenue calculations to determine an ore cut-off, which combines these two elements to maximise metal production.

Jan 1, 2002

By R M. Tosdal

The Manantial Espejo district (Argentina) hosts a low-sulfidation epithermal Ag (-Au) deposit with a proven and probable reserve of 38 Moz Ag and 0.55 Moz Au. The district lies along the southern rim of the Deseado Massif in the Middle to Late Jurassic Chon Aike Province, a large bimodal igneous province dominated by silicic volcanic rocks that were formed during the initial extension leading to the opening of the South Atlantic Ocean. The district stratigraphy consists of 162 to 161 Ma old rhyodacitic to rhyolitic volcaniclastic rocks of the Chon Aike and La Matilde Formations, followed by 160 to 157 Ma old andesites and dacites of the informally called intermediate formation. The main stage of normal faulting post-dates the volcanic activity and coincides with the formation of the precious metal veins that were dated by 40Ar/39Ar on hydrothermal adularia with ages between 152.8 ¦ 0.8 Ma and 156.6 ¦ 0.8 Ma. Economically important hydrothermal veins show characteristic features of a low-sulfidation epithermal deposit with crustiform and colloform banding, bladed calcite replaced by quartz and abundant adularia. In the Maria Vein, the major orebody of the district, six hydrothermal stages are identified, but only stages one and four contributed metal. Lead isotope ratios in hydrothermal sulfides show a close relationship to ratios in feldspars from the district Chon Aike Formation, suggesting a common source for the Pb and possibly the precious metals in both the magmatic and hydrothermal products, or that the Pb in the hydrothermal veins was derived from the volcanic rocks. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By D M. Aranha, A R. Cabral

Theories on the origin of the Itabira iron formation (itabirite) in Quadrilßtero Ferrffero (QF), as elsewhere in the world, are restricted by the apparent lack of adjoining volcanic units, severe syndeformational metamorphism and deep weathering. Besides the three types of iron formations at QF (siliceous, dolomitic and amphibolitic; Dorr, 1969) we include a fourth type initially described as ocherous, goethitic, limonitic or even yellow iron formation. Considering its high magnetite content, it has been described as yellow magnetite itabirite (Pires, 1979). It was reported as formed by the alteration of the dolomitic itabirite (Dorr, 1969) although the anomalous Al2O3 contents are high for normal weathered itabirite. The yellowish magnetitic itabirite occurs at the bottom of the Itabira Iron formation, along the contact with the Batatal schists, and at the top units of the Itabira, within the Gandarela Formation. Within the magnetitic itabirite at the Tamanduß iron ore mine there are metric zones, concordant to the bedding of pillow-like structures, exhibiting a porous core, surrounded by an intermediate, more granular zone with numerous, minute rounded cavities grading to an external, fine-grained zone with much less minute cavities. In the external portions of some pillows a breadcrust type structure, derived by quenching with the water can be observed. In some other zones, such as the Barreiro hill, an outer, vesicular, whitish yellow, 5 - 10 mm thick, band grades to an aphanitic, isotropic band. The vesicles are slightly flattened against the band surfaces. The existence of fragmental layers showing flowage and fragment alignment, kaolinitic laminas and vesicles filled with kaolinite at Barreiro Hill and Capitpo do Mato Mine represent mesoscopic structures, indicators of a possible volcanic origin. Chemical compositions of the magnetitic itabirite from a wide area in QF revealed a relatively high Al2O3 content, consistent with a volcanic origin.

Jan 1, 2005

This paper deals briefly with three of the more controversial aspects of the geology of the Mount Isa ore deposits namely the geologic structures, the method of ore deposition and the origin of the ore.In the section on geologic structures, an outline is first given of the purely tectonic deformation advocated by the early authors. The current interpretation, which differs in the proposed order of events and causal forces, is then discussed. Other concepts, which attribute all or part of the deformation to sedimentary features or preconsolidation movement, are outlined ilnd commented on.The remaining two sections deal mainly with the better known lead-zinc orebodies. In the first of these a brief description and criticism is given of the early interpretation which was based on the deposition of successive waves of mineralisation which replacedindividual beds in the shales. The current ideas, which visualise emplacement of the ore between the beds rather than replacement of them, is then discussed. The final section develops the case for a sedimentary origin of the lead-zinc ores and broadly outlines the author's ideas concerning the evolution of the Mount Isa ore deposits.INTRODUCTIONAny consideration of the geology of Mount Isa must begin with the work of Blanchard and continue with that of Hall. Individually, or as co-authors, they published various papers on the geology of Mount Isa. Of these, the best known is their "Rock Deformation and Mineralisation at Mount Isa" (1941) which gave a comprehensive account of all aspects of Mount Isa geology.It is necessary to appreciate the limits set on geological knowledge of the mine and environs in 1941 by the extent of mine development and regional geologic studies. Underground, 7 level (897 ft.) was the lowest producing level. Development on 8 (1073 ft.) and 9 (1247 ft.) levels consisted only of exploratory drives and crosscuts in the vicinity of the Davidson Shaft. The tops of the 650 and 750...

Jan 1, 1961

By Kuster D

Under humid conditions geochemical exploration for rare-metals is, at the reconnaissance level,usually carried out by stream sediment and soil sampling. As the secondary dispersion patterns are distinctly different in arid environ- ments, other exploration methods have to be applied (MATHEIS & KOSTER, 1985).

Jan 1, 1988

By Downs M

The use of a cutting machine designed to allow simultaneous cutting and setting of roof supports has numerous advantages few development roads in coalmines. The use of such a machine with the added ability to cut a curved roof profile is of considerable interest for longwall development in thick coal.

Jan 1, 1998

Instantaneous outbursts of coal and gas have occurred in Australia in the Sydney Coal Basin since 1895 and in the Bowen Coal Basin since 1954. The largest has been about 500 tonnes of coal and so their magnitude and character have not approached those experienced in some other countries. The occurrence of CO2 with some Australian cases provides some similarity with the worst affected areas in France and Poland.The proneness of seams depends on coal rank and seam gas composition, among other factors. The proneness of places depends on depth, structure, intrusion, tectonism and other factors affecting the geometric, physical and chemical uniformity as well as details of mining. As a phenomenon due to gas and stress, prevention can be achieved by relief of high gas and/or stress condition. Alternatively, controls can be applied to render mining safe for personnel. Unfortunately day-to-day prediction is not widely and reliably achieved to allow selective use of prevention or control. The initial rate of desorption is the most promising day-to-day indicator.Various researches include gas conditions and parameters, stress and failure conditions and parameters, coal variables and geological variables in relation to prediction, prevention and control. Some assistance in research may derive from study of analogous phenomena of instantaneous outbursts of salt and other rocks and gas. It is concluded that in the Sydney and Bowen Basins, any coals with less than 30 per cent Volatile Matter (VM) ash free dry (afd) at depths over 200 m could be prone. Proneness increases with depth, with lower volatile content, with geological disturbance including faulting, intrusion and recent tectonics, with increased CO2 in seam gas, with narrow work and with other factors. Much more research is needed.Unfortunately outbursts are needed too, to provide the research with realistic data. With the problems of mechanism and prediction still being unsolved much research remains to be done. No present aspect of research is satisfactorily resolved.

Jan 1, 1983

By Ryan CG, Cousens DR, Suter GF, Griffin WL

A novel method utilizing PIXE with microbeams following fire-assay has been developed to determine PGE and Au at sub-ppm levels suitable for application in exploration. Analyses of the prills from the lead and silver fire-assay yield Pt, Pd and Au concentrations readily. NiS must be used as collector if the complete suite of PGE is required, but this method is not as Convenient.

Jan 1, 1989

By R Williams, P Kohout, J Comins

The Northside Storage Tunnel (NST) is the largest tunnelling project ever undertaken in Sydney. The tunnel extends deep underground from the western bank of the Lane Cove river to the North Head sewage treatment plant (STP), with a branch tunnel from Scotts Creek connecting to the main tunnel under Tunks Park. The aim of the tunnel is to intercept wet weather overflows from four key points along the northernsuburbs ocean outfall sewer (NSOOS) and provide short-term storage and transfer of sewage to NorthHead STP for treatment prior to discharge to the ocean through the deep ocean outfall. The project was an ambitious undertaking by an alliance between the client Sydney WaterCorporationand the engineering firms of Montgomery Watson, Connell Wagner and Transfield to design andconstruct approximately 20 kilometres of tunnel, tunnel declines and shafts in just over three years. In order to achieve this tight timeframe construction of the NST has been undertaken simultaneously at seven construction sites located across the northern suburbs of Sydney. As with most tunnelling operations, tunnel boring machines (TBMÆs) and roadheaders dominated the excavation activities. Tunks Park and North Head STP are the major tunnelling sites. An access decline was excavated using roadheaders at both of these sites to facilitate tunnelling using TBMÆs. Three TBMÆs 3.8 m, 6.0 m and 6.3 m diameter) were launched from Tunks Park and one TBM (6.5 m diameter) was launched from North Head. At the overflow interception sites of Scotts Creek, Lane Cove River and Quakers Hat Bay two vertical shafts known as drop and access/ventilation shafts were constructed. These shafts would provide the linkage between the existing sewer and the tunnel. As their names suggest the drop shaft would convey the wet weather sewage overflows to the tunnel while the access/ventilation shaft would provide access during dry weather and ventilation during a filling event. The fourth overflow site of Tunks Park would use the tunnel decline as its link to the tunnel. Originally these shafts were to be excavated using the raise bore method. This technique however, is entirely dependent on the TBMÆs reaching the shaft locations at the specified time. This was not the case at two of the three shaft excavation locations and top down methods of excavation such as, a percussive cone fracturing (PCF), blind bore, mechanical excavation and drill and blast were investigated to ensure the project met its completion schedule. Traditionally project decisions are dominated by cost and schedule objectives. The contractual arrangement of the Alliance however, required that the objectives of safety, community and environment also be considered in any decision making process. Thus each of these top down methods of excavation were assessed against these five objectives. On considering all of these factors the use of explosives was considered to be the superior technique.

Jan 1, 2001

INDEX OF CONTENTSIntroduction.Systems of classification of coals.RankClassification of Australian coals.Defects of systems in use in other countries.Indexing by Fuel Ratio.Classification by Ultimate Carbon/Ultimate Hydrogen.Relationship between Fuel Ratio and ultimate composition.Suggested convention for classification.Origin and Evolution.Notes on directions of change of composition on Carbon Hydrogen chart.Summary and conclusion.Acknowledgments.Bibliography.Appendix.

Jan 1, 1948

The valuation of resources companies is open to a huge amount of subjectivity. Not only are valuations subject to fast changing assumptions, such as commodity prices, exchange rates, ore grades, etc., but there is also no common agreement on the methodology to be used. To borrow from Malcolm Fraser, life wasn't meant to be easy for the resource company valuer. I will demonstrate three recent examples of valuations carried out but where the market or actual transactions done show very different results.

Jan 1, 1989

By Wickham P

Digital computer based control systems are used to implement control and monitoring over most unit operations in Mount Isa Mines Limited lead-zinc concentrator and copper concentrator. Implementation has been gradually devel- oped and expanded since the first process computer installation in 1969. Operations currently using high level control logic include crushing, grinding, on-stream analysis of flotation products, flotation reagent additions, and tailings thickening. Details of gains in metallurgical efficiency for each system are considered.

Jan 1, 1978

The cost of constantly extending a decline tunnel that plays a part in the actual extractive process is a revenue cost. The characteristics of such a decline tunnel are that it is dug in a series of relatively small excavations. It follows the ore body and is dug as close to the ore body as practicable. In addition, the decline allows for the extraction of ore in the immediate vicinity, with the ore being extracted in a relatively short period of time.

Jan 1, 1990

Construction of Western Mining Corporation's nickel refinery at Kwinana, Western Australia, commenced in July, 1968. Production of 15,000 tons per annum of refined nickel metal will commence early in 1970, The plant will also produce approx- imately 150,000 tons of ammonium sulphate0 The ammonia leach process which was developed by Sherritt Gordon Mines Ltd., and has been in operation at their plant at Fort Saskatchewan, Alberta, Canada, for the past 15 years, will be used at Kwinana. The refinery will cost approximately 435 million, and will employ upwards of 250 people.

Jan 1, 1969

By Valenti M

A by-product of the lead smelting operations at BHAS is a copper-lead matte typically containing 35% copper, 38% lead and 12% sulphur. A hydrometallurgical treatment process has been developed for the treatment of this matte to recover copper as cathode and results in a lead-sulphur residue which is recycled to the lead smelter. A commercial plant with a nominal capacity of 4000 tpa utilising this process was commissioned during 1984. This plant has been shown to be capable of producing copper cathode at rates approaching 4000 tpa over short periods of time.

Jan 1, 1989

This work describes preliminary laboratory testwork to study the relative leaching response to cyanidation and thiourea leaching of an oxidised low grade gold ore. The potential of an alternative lixiviant like thiourea to commercial processing of mine dumps is discussed by specific reference to selected case histories. It would appear that on the basis of the available published information, there could well be a case advanced for the acid thiourea leaching of sulphide concentrate tailings being subjected

Jan 1, 1994