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By Jaczkowski B. M, Cox T. J, Domfeh I. A, Stalker I

Mining and treatment of gold ore in the Ashanti region at Obuasi, Ghana has been continuous for more than 100 years. Earlier production from this world class deposit can be traced far into the history of West Africa's gold trade. As part of a general development and expansion program, Ashanti Goldfields Corporation (Ghana) recently undertook a program to heap leach oxidized near surface ore. Kappes, Cassiday & Associates was given a major role in the design, equipment supply, installation and start-up management of the 3000 tonne/day heap leach. Unusual conditions included a high annual rainfall and an ore which could be characterized as a soft, decomposed, water saturated schist. Production began in March 1990. Startup problems and their solutions are discussed.

Jan 1, 1991

By R A. Bearman

Recent demand pressures for iron ore should not distract from the longer term view that intense competition in the industry has demanded technological innovation of a high order. There is a long track record of successful innovation underpinned by a solid base of scientific research and knowledge. By comment on recent developments in trucks, comminution and direct smelting, this paper suggests that innovation is still a key attribute of the industry. The spending of the minerals industry on underlying science, however, is not particularly high. By looking at other industries we can ascertain that for step change technologies, it is particularly advantageous to have a solid base of science and technology underpinning developments.

Jan 1, 2005

By A Jurg, F Leclercq

The total drill and blast concept is widely known in the mining industry. On the contrary, the quarry industry rarely adopts such working methods. Based on the experience of the CBS quarry in the North of France, this paper shows how up-to-date blasting technology and simple control methods can significantly improve the overall Mine to Mill efficiency of a quarry. The CBS quarry, in partnership with the EPC group and Nitro- Bickford Company, adopted a new working process three years ago aimed at increasing blast performance and related productivity of the downstream process (loading, hauling and crushing). The pattern geometry of each blast is controlled and explosive charging is carried out following the æconstant specific energyÆ CSE concept. This method provides a homogeneous fragmentation distribution and reduces vibration peak-particle-velocities. The impact on downstream productivity is controlled by means of a simple information management system, which collects and measures key parameters of the production process such as; hauling cycles, crusher throughput, secondary breaking and vibration peak particle velocity. This information system has clearly proved over time that consistent blast quality could be achieved, leading to a 30 per cent improvement in quarry productivity. Improved energy control of blasting through optimisation with electronic detonators, allowed a significant reduction in vibration impact on the environment. Improvement in blasting security, reduction in the environmental impact and productivity enhancement are major benefits that quarries can obtain from these CSE optimisation blasting methods.

Jan 1, 2007

By Hinton A. T

Three, and possibly four, distinct types of quartz-vein associated gold mineralisation are recognised in New Zealand. They are: epithermal, schist-hosted, metagreywacke-hosted and metamorphic core complex associated types. Each has a unique geological environment and structural regime which has provided the gold source, scavenging mechanism, emplacing mechanism and geometry. Each has a characteristic suite of associated metals and trace elements. The first three types form economically important gold deposits while the fourth type have been historically worked for gold and base metals. Intense exploration is currently being focussed on all four types.The epithermal type is typified by the extensive vein systems of Martha Hill, Karangahake and Golden Cross and numerous smaller examples. The veins were deposited in a near surface active volcanic environment from deeply circulating hot water. Their structure is tensional, veins are vertical-to sub-vertical and have limited depth. Their geochemistry is identical to that in active felsic hydrothermal centres in the central North Island. Major minerals are gold, pyrite, arsenopyrite, galena, chalcopyrite, sphalerite and argentite.

Jan 1, 1990

By Standish N

The heterogeneous reactions of carbonaceous materials with oxidising gases are basic to all combustion phenomena and to many gasification processes. The carbon- carbon dioxide reaction at elevated temperatures (Reactivity) plays important roles in many metallurgical operations like iron blast furnace and ferro-alloys smeltings, zinc and lead smelting, alumina reduction, cupola operation and direct reduction processes. The stoichiometry but not the mechanism of the reaction between CO2 and carbon is represented by the equation (Boudouard reaction) CO2 + C 2CO (1) This reaction is more complex than that between carbon monoxide and metal oxides, which involves essentially a transfer of oxygen from the oxide to carbon monoxide to generate carbon dioxide without any change in gas volume, whereas the volume of the product gas of Equation (1) is twice that of the reactant gas. In the present paper an attempt has been made to review critically the reactivity measurements of various carbonaceous materials in carbon dioxide atmosphere. Steps in C-CO2 reactions, surface reaction mechanism, role of mass transfer on reaction kinetics, dynamic oxygen exchange reaction and rate equations and rate controlling steps are discussed. Various methods of reactivity measurements with their pros and cons are also presented. Effects of pertinent process variables on the reactivity of carbon are also described in detail.

Jan 1, 1986

By L Wsrell

During recent years the iron ore industry has experienced a continuous consolidation trend following increased merger and acquisition activities. Analysing and evaluating these mergers is important in order to establish potential effects. The purpose of this paper is to analyse the price effects caused by the merger between Rio Tinto and North Ltd in 2000. The merger was cleared by the European Commission, as well as the Australian Competition and Consumer Commission, shortly after its announcement. The analysis will be conducted using a simulation model based on a proportionality calibrated almost ideal demand system, which uses the premerger situation in order to estimate the post-merger outcome. The relevant market is defined using shipments data. This is followed by the simulation model applied to the defined relevant market. The results show that the concentration on the market, given by the HHI, increases approximately 15 per cent, and that the market share of the new companyÆs reaches almost 20 per cent. Compared to the CommissionÆs assessment the results indicate a more concentrated market and thus a higher concern for possible competitive effects. Furthermore, the results suggest that the predicted average market price increase from the merger is 1.6 per cent. However, the merged firm is able to increase their average price by 5.1 per cent.

Jan 1, 2005

An attempt was made to determine the lateral extent of analcite in the Newcastle Coal Measure sediments of the Sydney Basin. From an examination of the cores of eleven bores it was concluded that the mineral is concentrated in the western sector of the original Newcastle Basin and this presumably was the region of greatest sodium concentration and aridity. The distribution of the analcite is such that it appears to have little correlative value.

Jan 1, 1967

By G Partington

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

Jan 1, 2008

Tasker (1985) has detailed the accepted practices for constructing polygonal blocks of influerrce in the estimation of ore reserves. Further he suggests that users might fall into traps such as omission or overlap when determining the area of influence for each sample point.As an example of these types of errors Tasker (1985) describes under "Coverage ofthe Area" how 25 per cent of the exploration area will not be included in an equiangular triangular grid where hexagonal blocks of influence are used.The introductory suggestion of Tasker (1985) of "incorrect procedure" by Rudenno (1983) (and Armstrong (1983)) reiterated around the Figure 2a of Tasker (1985), is based on the brief description of the polygonal area of influence by Rudenno (1983). That description is not too different from that given by King, McMahon and Bujtor (1982).

Jan 1, 1985

By Kennerley P

A significant part of the reserves of the Southern Coalfield lie beneath major water storages and their impounding dam structures. One of the functions of the NSW Government's Dams Safety Committee is to specify the particular mine layouts which can be used beneath the stored waters according to certain guidelines. A study was made of examples of the two different methods of extraction used under the stored waters as proposed by the mining company according to the guidelines and approved by the Dams Safety Committee. Using both pillar monitoring and mathematical modelling approaches it was shown that the recovery of coal from these layouts could be improved while still ensuring the long term stability of both the underground support pillars and the body of the strata. The integrity of the water storages and their impounding structures would therefore not be Affected.

Jan 1, 1986

By Korsch RJ

Permian oroclines in eastern Australia must have formed by sliding on a detachment surface. It is identified as a westward- dipping Devonian and Carboniferous sub- duction zone. Major strike-slip faults probably sole out on the same surface. One major fault with an associated serpentinite belt was pulled away from the craton abd bent into loops. Basins formed in the loops.

Jan 1, 1987

By Parida K. M, Paramguru R. K

Laboratory-scale studies aimed at developing a process for solubilising manganese values from a low grade pyrolusite containing material using low grade pyrite, both available in India, are described. Leaching 21 parts by mole of pyrolusite with 6 and 26 parts by mole of pyrite and sulphuric acid respectively results in good manganese dissolution (98 per cent) at 100°C within one hour. The probable kinetics of the leaching process has also been given.

Jan 1, 1995

Thirty six different commodities were recorded from 3708 mineral occurrences in the Atherton 1:250 000 Sheet area, mapped by personnel of the Queensland Department of Resource Industries. Tin, occurring in 56% of all mineral occurrences, is the most common, followed by copper, tungsten, silver, lead, gold, fluorite molybdenum, zinc and antimony. The densest area of mineral occurrences is the Herberton Mineral Field, one of the most intensively mined areas in the state.The majority of occurrences in the sheet area are fracture, fault or shear related vein or lenticular deposits, with subordinate types being pipe, skarn, endogreisen, disseminated and porphyry copper deposits. However the larger mines in the area are commonly of the subordinate types including the Red Dome gold-copper skarn, the Wolfram Camp and Bamford Hill tungsten- m olydbenum endogreisens, and the Vulcan pipe tin deposit. Significant gold prospects occur in quartz-antimony veins, breccia pipes and skarn deposits associated with rhyolitic porphyry dykes. A fluorite-gold association has been noted in several areas on the western side of the sheet.Mineralised fractures are predominantly oriented in a NNW direction which is the major trend in the Hodgkinson Province. Secondary N and NE directions are also present.

Jan 1, 1990

The Mesozoic intrusive rocks in southeastern coastal China can be divided into three intrusive suites, and they can be brought into corresponding with four cycles of volcanic activity. This paper describes their time-space relation with volcanic rocks, and their geochemical characteristics. Data from the Mesozoic volcanic-intrusive. complex rocks in Eastern Zheijiang, Eastern Fujiang and Eastern Guangdong show distinct regional differences, both within and tectonomagmatic activity regions. The southeastern coast of China involves four tectonomagmatic activity regions. They have many differences on the nature of magma source regions, activity patterns of magma, time-space distribution, petrography and petrographic facies association of volcanic and intrusive rock and mineralization.

Jan 1, 1990

By S C. Dominy

A high nugget effect and the presence of coarse gold characterises many vein-gold deposits. The effective sampling of these deposits is often difficult because of the relatively low concentrations involved and erratic nature of the gold. Geological complexity often compounds this effect. Underground development, in-fill drilling and bulk sampling/trial mining are often required to delineate Ore Reserves. Winzing is an historical technique that was used to gather geological and sampling data during underground exploration. It permits access to the mineralised structure below the current datum to help determine viability. Winzing has always been considered an arduous and dangerous task. Modern technology has led to the development of the Mobile Supersucker, essentially a giant vacuum cleaner. This system permits safe and efficient winzing activities, and allows the collection of bulk samples for grade estimation. Bulk samples from horizontal development have long been collected to help define mineable grade. However, when defining blocks below current development, there has been over-reliance on ineffective æsmall sampleÆ drill data. The Mobile Supersucker permits safe and cost-effective development of winzes and off-winze sublevels.

Jan 1, 2003

By M Fallon

The full history of exploration successes, failures and related costs from initial greenfield exploration in 1987 to the current brownfield stages was analysed for the Plutonic Marymia Gold Belt of Western Australia. This belt, which had escaped the attention of turn-of-the-century prospectors and had not produced any gold until 1990, is an ideal area for a collectively exhaustive, progressive value and risk case study of expected return on gold exploration. The study analyses the progressive screening of over 200 greenfield and near mine prospects, through various stages of exploration to the establishment of 38 mining sites, ranging from a few large mines to small satellite operations. It provides empirical estimates of the historical Bayesian probability of projects advancing to successive stages of exploration, eg from reconnaissance, to systematic drill testing, resource delineation, feasibility and mine development, given a successful outcome in any exploration phase. The ratio between the estimated value of the gold discovered and the corresponding historical exploration expenditure in each year and cumulatively, ie the average cost of discovery per ounce of gold, are then computed as measures of historical return on the exploration investment in this belt. These, together with an estimate of the æresidualÆ gold endowment, ie of the number and size of possible as yet undiscovered deposits, generated through the use of rank statistics (ie ZipfÆs law), provide a basis for future strategic consideration in exploration targeting in this and similar geological terranes.

Jan 1, 2009

By D Deb, R Pramanik

This paper presents a generalised methodology in smoothed particle hydrodynamics (SPH) framework to analyse dynamic failure process of rock mass having natural joint under blast-induced stress wave and expansion, and penetration of high pressure gaseous product. The necessary interactions of gas-rock are incorporated in the model which describes features of coupling between damage and plasticity in tension and compression respectively. A Drucker-Prager formulation of plasticity is used to model the behaviour of aggregate field and the Grady-Kipp damage model is employed for tensile strain. These two material behaviours are then brought together within the framework of interacting continua. The model relies on the Drucker-Prager plasticity surface to predict the dilatancy aspect of the material response and to account change of strength according to the strain rate effect. Three numerical examples are presented with rock joint and multiple blastholes.CITATION:Deb, D and Pramanik, R, 2015. Smoothed particle hydrodynamics modelling of blast-induced fracture processes in naturally jointed rock medium, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 65–70 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

High-sulphidation (HS) gold, silver and/or copper deposits are generated in both the epithermal and the upper parts of the underlying porphyry environments over vertical intervals of up to 2 km. The HS deposits are generated in advanced argillic lithocaps, which are products of the absorption of acidic magmatic volatiles by voluminous groundwater systems. Mineralisation styles in HS systems reflect depth of formation as well as the interplay between structural, lithological and hydrothermal parameters. The deep parts of HS systems, at depths of >1000 m, are typified by disseminated copper¦gold mineralisation comprising digenite, chalcocite and covellite in pervasive advanced argillic as well as underlying sericitic alteration. In highly telescoped systems, such mineralisation may overprint porphyry stocks and associated quartz-veinlet stockworks. Intermediate levels of HS systems commonly contain fault-controlled copper-gold mineralisation, typically as enargite in bodies of vuggy residual quartz, silicification and/or massive pyritic sulphide. The shallow parts of HS systems, at depths of The exploration focus is on four principal HS mineralisation styles:copper (eg Chuquicamata, Monywa) or copper-gold (Wafi) in the deep porphyry-hosted parts of systems preferably, in the case of the latter, where supergene oxidation is limited and, hence, flotation may be used for metal recovery; copper¦gold-bearing replacement mantos and pipes hosted by carbonate wallrocks in the deep parts of systems (eg Bisbee); high-grade gold in late-stage veins or hydrothermal breccias that overprint the intermediate to shallow levels of systems (eg El Indio, Goldfield); and large, bulk-mineable gold deposits in the shallow parts of systems that were subjected to supergene oxidation, thereby permitting heap-leach treatment (eg Yanacocha, Pierina). To these preferred HS styles may be added the low-sulphidation vein or disseminated gold¦silver mineralisation that is commonplace alongside many HS systems (eg Victoria at Lepanto).

Jan 1, 1999

By Eggleton R. A, Taylor G

As the search for major orebodies continues, the regolith dominated areas of the Broken Hill region remain one of the major exploration frontiers. The past exploration philosophies emphasising bedrock related characteristics have been limited in their ability to effectively explore in the regolith dominated areas, that are a feature of most of the Broken Hill region (Figure 1). If mineral exploration is to be more effective across all of the Broken Hill region, particularly in the regolith dominated areas, an appreciation and increased understanding of the regolith and landscape features are a necessity. Ironically, there have been very few studies of the regional regolith and landscape features of this region. Owing to the previous lack of an established regolith-landform framework, this study initially concentrated on the general characterisation and variation in regolith types corresponding to the area of the Broken Hill Block, within NSW (Willis, 1989; Stevens, 1986). The approach has been to produce a regional regolith-landform map at 1:100 000 scale and conduct a complimentary program of regolith sampling and site descriptions. This was a basis to identify areas for more detailed regolith-landform mapping (1:25 000 scale) and for producing a regional stratigraphic framework and models for landscape and regolith evolution. This information can then be used to provide a basis for regional mineral exploration models and strategies. This paper highlights some of the regionally significant regolith-landform features and their general significance to mineral exploration. More detailed information on specific regolith-landform features and study sites may be found in Hill et al (1994; 1996; in press) and Hill (in prep).

Jan 1, 1997

Operations at two open cut mines have so far commenced on two out of the five potentially mineable seams in the Fair Hill - German Creek Coal Measures. Due to seam splitting, up to seven mining units are present in the Dysart Seam interval at Peak Downs giving a total of 12 mining units in the section. The coal is low to medium volatile type and produces strong coke. Rank increases and fluidity decreases in the southern part of the area.

Jan 1, 1974