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By Raymond G. F

Geostatistics - a tool used by geologists and mine planning engineers to estimate grades and rapidly evaluate alternative mining strategies has reached an advanced stage of development for the silver-lead-zinc orebodies at Isa and Hilton Mines. Geostatistics has been used for over a decade in the massive copper orebodies but the stratiform lead-zinc orebodies are much more complex and provided a completely different set of challenges. Recent increases in computer processing speed and power provided by the Integrated Mine Planning System (IMPS) has aided the development of the geostatistics package. Also the formation of a project team and the subsequent in-house development which has drawn together the expertise of geologists, engineers and system analysts has contributed significantly to the success of the project.The most important feature of any approach to modelling the lead-zinc orebodies is that the kriging search must consider estimate and sample points according to their positions relative to bedding surfaces. By transforming co-ordinates as perpendicular offsets from a plane representing the local strike and dip, it is possible to elongate the ellipsoidal influence to parallel bedding. By interactively modelling surfaces using CAD facilities and then specifying these surfaces as 'hard' or 'soft' boundaries, the geologist has complete control over the kriging process.

Jan 1, 1993

By Espi J

The Nena high sulphidation deposit, located in the Sandaun Province, PNG, contains a measured and indicated resource of 51 Mt of copper ore grading 0.5% Cu and 0.6 g/t Au at a 0.5% Cu cut-off. The copper orebody is overlain by an 18Mt oxide gold resource grading 0.1 % Cu and 1.4 g/t Au at a 0.6 g/t Au cut-off. The deposit is hosted in advanced argillic altered pyroclastics interstratified with lavas, volcanoclastics, epiclastics and sediments of the Debom Volcanics within the Frieda River Intrusive Complex. Foraminiferal sediments indicate the Debom Volcanics to be Early-Middle Miocene in age. Alteration is elongated along, and concentric about a northwest trending structure (Nena Structural Corridor) which is about 7km in length. The inner two alteration types, residual and massive silica-alunite are strongly brecciated and host the bulk of later hypogene Cu-Au mineralisation. Weakly mineralised weak silica- alunite and barren peripherally zoned clay alteration surround the inner mineralised alterations. The hypogene sulphide deposition was polyphasal, episodic and is zoned from north to south from covellite-enargite ¦ chalcocite (5600N to 5200N) to a mixed enargite-luzonite (5200N to 4700N) to luzonite-stibioluzonite (4700N to 4400N) in the south within a 1200m long by 300m diameter sub horizontal pipe like body. Paragenesis studies indicate that pyrite ¦ marcasite were introduced early with barite and black native sulphur before deposition of banded pyrite (melnicovite) with barite during a period of brecciation. Continued brecciation allowed bladed covellite ¦ chalcocite followed by enargite-luzonite-stibioluzonite ¦ pyrite (brassy) and minor acicular covellite deposition. Yellow native sulphur and trace amounts of galena were deposited in remaining pores. Pre-acid alteration intrusives domed the mainly volcanic stratigraphy in the southwest and post-mineralisation porphyries in the northeast truncate mineralisation. Supergene processes and erosion have modified the top of the deposit, creating a 45m thick goethitic-scoroditic-haematitic gold cap above a 40m thick (on average) chalcocite rich supergene blanket. Lesser amounts of digenite, covellite native copper and rarely seen malachite occur in the supergene copper zone.

Jan 1, 1997

Mining projects frequently fail to meet their financial objectives. A significant area of poor performance lies in the areas of resource estimation, reserve definitions, selective mining and metal accounting. The processes leading to the exploi

Jan 1, 1998

By Grimstone LR, Leach JHJ

An analytical technique is described to identify areas of structural disturbance to coal and interseam strata in coal measures. It is based on exploration borehole data which records seam intersections and interseam lithologies. Computerised data bases have been developed to allow processing of large quantities of borehole records. The case study discussed is located in a tectonic setting dominated by thrust faulting. It provides a mechanism for the identification of low angle and bedding plane faults. In addition it allows the preparation of plans showing the areal distribution of the thrust sheets in the statigraphic section throughout the mine prospect. The technique requires the identification of normal undisturbed depositional thickness of coal seams and interseams to be determined. This is done for coal by the identification of coal ply distribution over the area. For interseam lithologies it is based on sedimentological modelling of lithology distributions, related back to the original depositional environments. Variations from the expected values are interpreted as structural Deformations.

Jan 1, 1986

By Black PM, Itaya T

Arc-type volcanic activity has been a major feature of the late Cenozoic geological evolution of the Pacific-Australian plate boundary in the northern New Zealand region. The timelspace distribution patterns of arc-type rocks reflect changes in the nature of the plate boundary as it has evolved. Inception of volcanism began in the north during earliest Miocene times (26 Ma) following ophiolite emplacement and during the next 10 Ma developed into a volcanic arc segment extending south to the present position of the central North Island. The northern part of the arc became extinct about 15 Ma ago, but activity continued in the central (Coromandel) part of the arc until about 5 Ma ago. In late Pliocene and Quaternary times volcanic activity has become concentrated in a northeast trending zone which is collinear with the Tonga-Kermadec Arc.

Jan 1, 1995

By P Wollants, B Blanpain, R Ding

Vacuum oxygen decarburisation (VOD) is the refining process used by ALZ (Genk, Belgium) for their production of stainless steels. The process consists of three stages: oxygen blowing at a pressure of 100 mbar, degassing, and reduction of the slag with ferrosilicon at 5 mbar. The magnesia-chromite bricks used in the slag zone of the ladles suffer from acute wear. In this paper results obtained from a program to improve the refractory life span are presented. The dominant wear phenomena were identified with an electron microscopy study of bricks taken from different locations in the ladle. Concurrently a dynamic model for the vacuum oxygen decarburisation (VOD) refining process was developed. The model calculates the elementsÆ oxidation rate during the blowing oxygen stage and allows the continuous calculation of the change of the metal, slag and gas composition throughout the VOD process. From these activities a general scheme of the refractory wear was worked out and measures to improve the refractory life were proposed and implemented.

Jan 1, 2000

By McCarthy PL

Widespread interest in reopening Victorian gold mines, regenerated by increased gold prices, has highlighted the technical problems prevailing. A combination of historical lease legislation, minimal recent mining activity, forms of mineralisation, high insurance rates and tortuous approval requirements for mining mean the potential investor assessing an old mine must address a wide range of technical problems. The requirements for establishment of ore reserves and attraction of capital for mine development are fundamental. Underground reef mining was historically generally on a small scale, and as mining on many fields ceased about the turn of the century, past geological and production records cannot be correlated to personal experience and comment. The impact of modern mining technology on future reef mining will be to reduce operating costs and significantly improve historic metallurgical recovery. Roth these are commensurate with increased capital costs. Workers compensation rates currently applicable in Victoria are many times higher than in other states, adding significantly to operating costs. Establishment of a pilot plant testing facility in central Victoria would provide an invaluable service in treating bulk samples essential for grade and recovery assessments of Victorian ores.

Jan 1, 1982

The nickel ores mined in New Caledonia for one century are mainly silicate ores. These ores are nickel enriched saprolites, formed by partial weathering of peridotites (predominantly harzburgites and some dunites), serpentinised to varying degrees. Saprolites constitute the lower horizon of lateritic soils, sometimes up to 100 metres thick, developed on peneplains now greatly modified by erosion. Saprolites are generally overlain by laterites, a more weathered horizon, where the main components are iron oxy-hydroxides with a low nickel grade. The structure of saprolites depends essentially on the serpentine content of peridotites and, on the other hand, serpentine minerals may have a high nickel content and, so, represent important nickel bearing minerals in silicate ores. Two types of serpentines can be found in nickel ores from New Caledonia: ò primary serpentines, formed by hydration of olivine at temperatures below 400¦C, during overthrusting of peridotites in late-Eocene (Paris, Andreieff and Coudray, 1979), are generally very abundant; ò secondary nickeliferous serpentines, associated with other sheet silicates in garnierites, are now relatively scarce but garnierites were selectively mined one century ago, because of their high nickel grade.

Jan 1, 1996

Since 1969, a substantial number of geophysical methods have been applied in the search for porphyry copper and mesothermal type -sulpha-de deposits. These have assisted with geological mapping as well as the definition of various sulphide depos-its. The application of these methods at the Frieda-Nena deposits, Papua New Guinea, can be used as a case study for exploration in other parts of New Guinea.In 1993, Highlands Gold Limited carried out an intensive geophysical program over the Nena deposit. The methods employed included, CSAMT (controlled-source audio magneto-tellurics), airborne and ground elect-romagnetics, IP/resistivity and ground magnetics. The magnetic method was used as a regional mapping tool as well as a way of mapping alteration zones over both the Nena and Frieda River copper deposits. Electromagnetics, in part-icular FLAIRTEM, is a rapid reconn-aissance tool as well as a detailed mapping tool for the location of Nena-style massive sulphide deposits. IP/ resistivity is an expensive but most useful tool for mapping out Frieda porphyry copper style disseminated sulphides as well as Nena style deposits. It can be used to define drill targets in areas of difficult Access.a

Jan 1, 1994

By A van As

This paper serves to outline the circumstances and causes of the air-blast that occurred at Northparkes Mines in November 1999. It describes the design of the mine, the geotechnical issues surrounding cave propagation and the cave monitoring systems that were in place prior to the event. A short description of the air-blast that followed a sudden collapse is given. Details of the risk assessment process that evolved during the rectification process are provided with their subsequent modification to form the core of a major hazard monitoring process. The system is in line with the recommendations given by the Coroner resulting from the inquest into the deaths of the four people who lost their lives during the air-blast.

Jan 1, 2005

Mineral deposits in New Zealand whose origin can be ascribed to primary magmatic segregations are associated with mafic-ultra- mafic complexes related to two orogenic episodes which took place during Paleozoic and Mesozoic times. These mafic-ultramafic complexes are essentially of two types. One is ophiolitic and has podiform chromite mineralisation presumably formed below a spreading ridge. The other type occurs as intraplate layered intrusions in which Fe-Cu-Ni sulphides and Fe- Ti-V oxides have formed as a result of liquid immiscibility with the host magma, and have subsequently accumulated by gravity means. Generalised descriptions are given for some deposits in NW Nelson, Fiordland and Marlborough districts.

Jan 1, 1980

By Leach T

The Tolukuma Gold Deposit is hosted by metamorphic and volcanic rocks, and igneous intrusions. Dilatant structures for the main veining appear to be provided by post-metamorphic flexure/faulting; syn-mineralisation tectonics is recognised from the en-echelon patterns of much of the veining. A SSE trending structure containing high grade mineralisation has acted as a major dilational zone within or at the contacts of porphyry intrusions. An ESE trend has controlled numerous dilational structures splaying eastward from the SSE vein structure and containing medium grade mineralisation.Early hydrothermal activity (Stage I) is represented by unmineralised, pyrite-rich brecciation and fracturing. Associated chloritic veining is indicative of single phase neutral-chloride fluids upwelling in relatively low fracture controlled nenneahility

Jan 1, 1993

By Stump NW

Until a year ago all isotope on-stream analysis utilised flow cells similar to those designed for conventional X-ray on-stream analysis. These systems incorporated a fairly complex sampling system necessary to present a representa- tive air-free sample of the main process to the flow cell. Maintenance costs and capital costs associated with flow cells and sampling systems have been generally high. Costs can be greatly reduced and reliability greatly increased, by using isotopes incorporated in immersible on-stream analysis probes which actually dip into the main process stream eliminating the need for sampling. A bonus of other advantages associated with immersible probes includes temperature stability and ease of calibration. This paper discusses details and results of the probe systems, justifica- tion for installing on-stream analysis, comparison of conventional X-ray and isotope techniques, and a brief survey of methods of analysis using radio- isotopes in on-stream elemental determinations.

Jan 1, 1971

Small scale gold mining operations in Papua New Guinea (PNG) have been observed to use very low flow rates of water in sluice boxes. In a series of laboratory experiments carried out to determine whether this approach was unsatisfactory or not for their situation, indications were obtained that it had some advantages in the recovery of fine gold but at the cost of considerable throughput. The separation mechanisms operating in such a system are analysed.

Jan 1, 1986

By Weatherhead J, Grounds J

The Nabarlek Uranium Project located in Arnhem Land in the Northern Territory of Australia was a small high-grade deposit which was the first uranium mine brought into operation following the extensive Commissioner Fox Inquiries into uranium mining during the late 1970s. The operation is almost complete and decommissioning plans have been prepared. This paper reviews all phases of the water management and tailings disposal for the project and compares results with design predictions.

Jan 1, 1988

In Australia, current production of rare earth element (REE) minerals, monazite and xenotime, occurs as by-product from titanium-enriched placers and beach sands. Undeveloped REE resources are associated with carbonatites, alkaline igneous rocks, pegmatites, phosphorites, cemented fluvial sandstones, and uranium mineralisations. The REE are held within a range of minerals including silicates, phosphates, a1uminophosphates, carbonates, and oxides. The development of these REE resources may require new processing and extraction methods. The distribution of REE in the currently mined ore minerals, monazite and bastnaesite, does not match that requested by the market. Exploration for new REE resources should be focused on ores with more marketable REE distributions, particularly with heavy REE, neodymium, samarium, europium and yttrium enrichments. Such ores occur within alkaline igneous rocks, in laterites overlying carbonatites and alkaline igneous rocks, and in placers derived from low-grade regional and contact metamorphic sediments. Lateritic REE deposits may be easily and economically mined by shovel in open pits and are unlikely to require extensive crushing and milling. In addition, lateritic REE clay deposits may be processed by simple hydrometallurgicaltreatment mehtods.

Jan 1, 1991

By Gallet M, Watsford R. M S

The 1989 feasibility study of the chessy, france, copper, zinc, pyrite and barite orebody was based upon a classical flowsheet. The flowsheet included, three stages of crushing, conventional rod and ball mill grinding in series, and sequential flotation of four products utilising conventional mechanical flotation cells. To improve the profitability of the project the partners commenced a search for ways to reduce the projected capital and operating costs of the proposed development. This paper presents the improvements in the projected capital and operating costs as a result of design and concept changes. The major changes included: ò the simplification of the crushing section with the adoption of semi autogenous grinding (SAG) milling of primary crushed ore. ò the deferral of pyrite and barite flotation circuits until market conditions were positive. ò the simplification of the flotation circuit by the use of column flotation cells for combined rougher/cleaner duty. ò the purchase of second hand equipment. The result of these changes was to reduce the capital cost estimate of the plant from US$ 21 million to US$ 11 million and operating cost estimates from US$ 18.90 to US$ 13.60 per tonne of ore for a decrease of approximately ten per cent in potential revenues.

Jan 1, 1991

By K Rozlapa, P Waters, H Middlemis

A major challenge for closure planning at mining operations below the water table is evaporation from final void pit lakes and concentration of salts, which can impact on downstream groundwater (and surface water) flows and quality. Where such impacts are deemed unacceptable, the closure approach that is often adopted is to infill the final voids with waste rock to above the pre-mining water table to prevent the development of a pit lake and subsequent evaporative losses. BHP Billiton Iron OreÆs Marillana Creek (Yandi) mining operations face these issues. The orebody is a channel iron deposit that forms the major aquifer in the region, which will be completely mined as a series of elongated open pits over tens of kilometres. The major constraint on mine closure planning was the stripping ratio of less than one, which means that there is insufficient waste rock to infill all areas to the pre-mining water table. Hydrogeological investigations and groundwater modelling indicated that standard mine closure approaches would result in pit void lakes becoming saline sinks unless the residual void geometry was optimised to minimise evaporation and maximise throughflow. The solution developed is a cost-effective long-term mine plan that meets all mine closure objectives, and involved:the selective infilling of all pits, largely using run-of-mine waste dumping with limited re-handling; the diversion of the major part of up-catchment creek flows around the mining operations to allow mining of the resource under Marillana Creek crossings, which in turn restricted overall aquifer recharge and reduced the elevation of the long-term water table; the diversion of some minor creek tributary flows into specific locations within the mine path to induce hydraulic gradients to maintain groundwater throughflow and water quality; and close integration of mine plan optimisation (mining and waste dumping schedules) with groundwater modelling scenarios to achieve acceptable environmental outcomes. This approach is designed to result in no reduction in downstream surface water flows or quality, maintenance of adequate downstream groundwater throughflow to support groundwater dependent ecosystems, and no reduction in the beneficial use status of the downstream groundwater resource.

Jan 1, 2006

By J Zhao, Q B. Zhang

The shock behaviour of a material represents its response to very high strain rate loading at pressures associated with those generated by explosive and blasting loadings. Three sets of shock wave experiments have been conducted to determine shock Hugoniot behaviour, spall tensile strength and shear strength using a plate impact facility. Embedded manganin stress gauges (ie longitudinal and lateral gauges) and high-speed velocimetry using heterodyne techniques were used for the measurements of stresses, shock velocity and free surface velocity. The gabbro exhibited classic linear Hugoniot equations of state in the US-up (ie shock velocity-particle velocity) plane; while for marble a polymer-like non-linear response was observed. The detailed experimental procedures used to make these measurements are to a great extent standard methods when determining mechanical properties and deformation fields at high strain rate.CITATION:Zhang, Q B and Zhao, J, 2015. The response of rock materials to one-dimensional shock loading, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 665–672 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

A number of small copper deposits occur in the Pernatty Lagoon-Mt. Gunson area. Textural and mineralogical differences distinguished the lagoon sulphide deposits, which occur in a water filled basin of permeable bedrock immediately under the lagoon floor, from the largely oxidized deposits which occur in the low hills adjacent to the lagoon deposits.Groundwaters are carrying copper, and to a lesser extent zinc, downstream to the lagoon. Several species of sulphate-reducing bacteria are widespread in the groundwaters and lagoon muds.It is suggested that copper sulphides were first deposited at the same time as, or soon after, the host Proterozoic sediments, and that during the present cycle of erosion the lagoon deposits may have been enriched, or largely formed, by bacterial precipitation of copper sulphides from laterally migrating cupriferous groundwaters.

Jan 1, 1971