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The Warraua and Mount Poole Inliers form part of a discontinuous series of basement complexes in the northwestern corner of New South Wales. The Inliers comprise mainly clastic sediments of low metamorphic grade (Wonominta Beds) and minor sills, dykes and intrusives, particularly within the Mount Poole lnJier. The Warratta rnlier has received attention due to the occurrence of auriferous quartz-veins where reef mining activities havetaken place.The deformational history of the Warratta and Mount Poole Inljers is characterised by a continuous subhorizontally WSW-ENE directed compression. Deformation was associated with the development of NNW-trending and steeply west-dipping major faults, which bound or biscct the inliers. Chevron folds and a penetrative axial planar cleavage characterise the deformational architecture and document crustal shorterung of at least 40 per cent. In zones adjacent to the major faults and within pelitic and semi-pelitic uruts, a multiple deformational evolution becomes apparent, comprising two events (D1 and D2). Deformational structures considered significant in this study were the result of D1. Tight, northeast-vergent fold patterns FI' and associated axjal plane cleavage SI' and reverse dip-slip movements at major faults indicate early northeast-directed thrusting during D1. This was followed by dextral strike-slip deformation displayed by tight, recumbent folds, en-echelon fold patterns (F2'), a northeast trending crenulation cleavage (52'), and two sets of second order faults, the latter showing high angular relationship to the major faults. A final stage of the deformational history (D2) is represented by WSW-ENE trending kink folds (F2).Auriferous quartz veins, predominantly occurring within pelitic and semi-pelitic units, were generated syntectorucally during the early deformational event (D1) in the course of commencing development of cleavage (S2'). Vein textures point towards vein formation by repeated hydrauJjc fracturing and fracture healing (crack-seal process), and by simple accretionary vein growth. Folded pelite-dominated horizons, considered as low permeability units, are suggested preferential sites where migrating metamorphic Ouids pooled and were trapped, causing high fluid pressure.Hydraulic fracturing and vein precipitation was controlled by lithology and structural constraints such as cleavage.K-Ar dates of approximately 440 Ma (Benambran Orogeny) marking the peak of metamorphism, and coinciding with the development of cleavage S1', also indicate the time of auriferous quartz-vein formation. A period of deformation of at least 30 Ma is proposed for the development of cleavage S1', as constrained by K-Ar dating and the intrusion of a syntectonic granitoid, the Tibooburra Granodiorite.

Jan 1, 1992

By M W. Chen, I Canbulat, S Saydam, C G. Zhang

The height of fracturing (HoF) measures the propagation distance of continuous fracturing from the mining horizon and is also termed the height of cracking (Hebblewhite, 2020; Khanal et al, 2019) or hydrologically the height of groundwater drainage (Tammetta, 2013). In longwall practice, HoF is an important predictive indicator for assessing the dewatering effect of panel extraction on the shallow aquifer and surface flows. The HoF determination is basically dependent on field measurement works, typically using surface extensometer, borehole televiewer imaging, piezometer monitoring, packer testing, borehole breakout logging, and isotopic tracer monitoring (Brown and Walsh, 2022; Corbett, 2022; Hebblewhite, 2020; Holla and Armstrong, 1986; Mills and O’Grady, 1998; Walsh et al, 2022a, 2022b). These methods or tools have been widely applied to observe rock fracturing and groundwater responses to longwalls at Australian coalmines, for example, Dendrobium Mine (Brown and Walsh, 2022; Walsh et al, 2022b), Appin Mine (Walsh et al, 2022a), and Springvale Mine (Corbett, 2022). In Chinese mines, borehole televiewer imaging and packer testing are more frequently used due to convenient instrumentation, quick testing, and not requiring long-term maintenance of the instrumentation boreholes. The HoF determination also involves further raw data interpretations, for which specialist software for data extraction and quantitative criteria for bounding the fracture transition and termination are necessary. By combining the measured fracture distribution and longwall parameters regarding panel geometry and geological settings, several HoF models have been developed for conceptualising the understanding of strata depressurisation and providing mine engineers fast calculation tools for HoF prediction. The Mackie model considered the height of fracturing as the upper bound of fractured zone and revealed that within the fractured zone there are highly connected fractures and accordingly porosity enhancement and groundwater depressurisation, where the fracture network can be less transmissive from the mining horizon up (Hebblewhite, 2020). The fractured zone shares similar fracturing regime but different heights in varying models: HoF is 30 to 58 times of the mining height (t) based on Australian, Soviet and UK experience (Kendorski, 1993, 2006), and 21 to 33 t according to the field measurements in NSW Central Coast, Australia (Galvin, 2016). Some Australian longwall mines adopt Ditton model (Ditton and Merrick, 2014) (Equations 1.1 and 1.2 in Table 1) sourcing from NSW coalfield experience for HoF prediction, while Liu model (Liu, 1981) (Equations 2.1 to 2.4 in Table 1) developed from 27 coalmines in China is frequently used by Chinese coalmines.

Nov 29, 2022

By Henley R, Harris L

High resolution airborne magnetic and radiometric data have been shown to optimize exploration for epithermal gold deposits in the vicinity of Charters Towers, northeastern Queensland. The radiometric data allow extrapolation of poorly outcropping geology to provide a cost-effective mapping technique, even at exploration scales (eg. 1:25,000). At a regional scale (eg. 1:100,000) the magnetic data reflect the regional tectonics and divide the area into domains for the application of different genetic models. For example: 1. the Ravenswood Batholith is characterized by multiple intrusions dating from Ordovician to Permian age. The polarity of the magnetic anomalies implies an age for the intrusions and indicates a deposit style for exploration. 2. extensional and wrench tectonics along the northern margin of the Drummond Basin are interpreted from the magnetic data and indicate favourable blocks for detailed exploration. Genetic exploration models may be tested in favourable environments by the recognition of geophysical signatures. These signatures reflect structural, lithological and alteration patterns arising from controls on ore deposits and can be applied at regional or detailed scales.

Jan 1, 1989

By Borsaru M, Wylie AW

A neutron irradiation technique has been developed which is suitable for the determinat- ion of the iron and aluminium content of iron ore fines (-6 mm particle size) on a moving rubber conveyor belt. The determination of iron entails measure- ment with a NaI(Tl) gamma ray detector of the characteristic prompt gamma rays (7.64 MeV) due to thermal neutron capture in iron, while the determination of aluminium is based on thermal neutron activation analysis. For the latter a second detector must be placed down- stream to monitor the 1.78 MeV gamma radiation emitted after activation of aluminium. Although conveyor speed has no effect on the Fe measurement, it has an adverse influence on the aluminium signal, and the belt speed should not exceed 0.1 m/s if good accuracy is required. Static trials on a 460 mm rubber conveyor belt with constant ore geometry indicate that for iron an accuracy of ¦ 1.2% Fe (2a) can be achieved for crushed run-of-mine ore at

Jan 1, 1978

By Martins V, Dunne R

A re-evaluation of the Hampton Boulder prospect in the early eighties resulted in a decision to proceed with mine development in December 1985. A 500 000 tpa gold treatment plant was commissioned in December 1986. The treatment facility was expanded to 1 600 000 tpa in July 1988. A tailings treatment plant to improve recoveries from harder gold bearing sulphide ores was built in December 1990. The development of an underground mine in 1991 meant that a source of sand for backfill was required. A sands plant to fulfil this requirement was commissioned during November 1991.As of June 1992 a total of 7 710 487 tonnes of ore have been treated through the New Celebration gold plant. Total gold production from inception of the new mine until June 1992 is 545 470 ounces obtained at an average recovery of 90.1 per cent from an average gold head grade of 2.4 g/t. The combined quoted ore reserves at the end of December 1991 was 14Mt grading 1.8 g/t gold

Jan 1, 1992

During October 1947 an Authority to Prospect was granted by the Minister of Mines to lVIount Isa Mines Limited over an area of approximately 75 sq. miles to the north of Mount Isa.Application for the Authority to Prospect had been made after Zinc Corporation Limited had been granted prospecting rights over two areas, one of 1,265 acres immediately to the north of the Mount Isa Mines leases and the other of 1,960 acres adjoining the south end of Mount Isa Mines leases.METHODSAs a means of providing a cheap map of sufficient accuracy on which to plot geological features, both Mount Isa Mines Limited and Zinc Corporation Limited agreed upon aerial photographs and the two companies shared the cost of an aerial photographic survey by Adastra Airways of 130 sq. miles which covered the prospecting areas held by both companies.The photographs were on a scale of 800 ft. to I in. with 60% overlap on the north-south runs and 25% overlap east-west. A set of alternate prints enlarged to 400 ft. to 1 \in. were obtained for field work. The 400 ft. to 1 in. scale unglossed photographs (size 18 in. x 18 in.) were taken On to the field and rock outcrops, and uncorrelated structures were plotted directly on to them in red crayon pencil. The geological observations were then transferred in the office to a tracing on which accuracy of azimuth and scale was controlled by use of a photo mosaic and ground surveys.

Jan 1, 1953

By Williams DJ

Preliminary calculations suggest that spoil piles in the Bowen Basin will undergo approximately 4 m settlement as the ground water table recovers after mining is abandoned. Approximately 1 m of differential settlement is possible. Superimposed on this will be a long term creep settlement of 1-3 m/log cycle of time. Depending on the nature of the spoil material, partially submerged spoil piles could be sufficiently stable although to ensure stability during long term creep it may be necessary to flatten the final spoil pile face to approximately 25¦.

Jan 1, 1987

By D L. Richardson, B Tiedt, C D. Morgan

Following residentsÆ concerns that the ongoing operations of Collinsville Coal (CCP) mine may be resulting in the release of contaminants, including products of acid mine drainage (AMD), into downstream environments, the Queensland Environmental Protection Agency (QEPA) issued CCP with a Notice to Conduct or Commission an Environmental Evaluation at Three Mile Creek. A key objective of the Environmental Evaluation was to assess the extent and magnitude of impacts to aquatic communities and their habitats. A multidisciplinary investigation examined a suite of physical, chemical and biological indicators to meet this objective. The study also aimed to identify contaminants of concern and the location of potential pollutant sources. Potential indicators of AMD, including elevated dissolved solids concentrations and low pH, were evident within the mine lease. However, significant differences in concentration of these indicators upstream and downstream of the confluence with Three Mile Creek were not observed. Although only proxy indicators of AMD contamination, these results suggest that the extent of impacts downstream is minimal. For the purpose of this study, physio-chemical indicators were selected on the basis of those best likely to provide an understanding of the likelihood of contamination, within the constraints of readily available long-term monitoring data. Ecosystem health indicators were adopted to supplement the existing data set and provide a more æroundedÆ perspective of water quality attributes within the system, generally unattainable by standard physio-chemical assessments. In contrast to AMD products, sediments were considered more likely to have a widespread impact on aquatic ecosystems. Waterways throughout the study region, including those unaffected by mining, have been affected by broad-scale sedimentation and were typically highly turbid. Due to the many diffuse sources of sediment potentially liberated within the catchment, the contribution of the mine compared to other land uses on total sediment loads entering streams is difficult to determine. This is clearly a major management issue for mines throughout the Bowen Basin. Streams of the central Queensland region display enormous variability in water flows and physio-chemical characteristics over a range of spatial and temporal scales. This variability presents major difficulties in distinguishing anthropogenic impacts from natural variability (noise). Despite this variability, impact monitoring by mines in the central Queensland district has tended to focus almost entirely upon physio-chemical indicators. The results of the present study indicate that a multiple indicator approach to environmental assessment is more useful for separating mine related impacts from natural ænoiseÆ and impacts from other land uses. In the absence of such information, by adopting the precautionary principle of Ecologically Sustainable Development (ESD), there is potential for an environmental impact to be incorrectly attributed to mining when other activities in the catchment may be contributing to changes in stream æhealthÆ.

Jan 1, 2003

By P J. Colbert, P D. Munro

OZ Minerals' Prominent Hill copper-gold concentrator in South Australia was built in 2008 with commercial production commencing in early 2009. In addition to recovery of valuable minerals, the flow sheet for this iron oxide-hosted copper-gold deposit has to address the issue of producing a good quality saleable copper concentrate by high selectivity against non-sulfide gangue. Detailed mineralogical studies integrated with the metallurgical test work highlighted that liberation of fluorine-bearing minerals and subsequent very efficient rejection in cleaner flotation was necessary to produce a commercial quality copper-gold concentrate. Bench scale laboratory metallurgical tests and mineralogical studies identified the need to regrind rougher concentrate to a P80 of 20 -25 microns or finer for adequate liberation of the fluorine-bearing minerals. Satisfactory separation of the fluorine-rich gangue material from the valuable copper sulfides requires highly efficient cleaner flotation. This is done by a combination of washed froth cleaning and conventional dilution cleaning. Proven equipment developed to meet similar taxing liberation and separation duties for the treatment of the refractory zinc-lead-silver ores of the Carpentaria-Mount Isa Mineral Province have been selected. The combination of Xstrata Technology's IsaMillÖ and Jameson Cell technologies addressed both the liberation and separation issues in the Prominent Hill concentrator. The energy efficient IsaMillÖ technology both regrinds the rougher concentrate while its inert grinding environment prevents contamination of mineral surfaces with 'debris' ensuring subsequent optimum flotation performance. Heading up the cleaner circuit with a 'scalping' Jameson Cell followed by conventional flotation equipment allows this section to take advantage of the Jameson Cell's high intensity flotation environment and froth washing capability to achieve maximum concentrate grade (at minimum fluorine levels) while maximising recovery through the use of conventional flotation machines. This paper looks at the development of the Prominent Hill flow sheet from the initial mineralogical and laboratory test work to the design, scale-up and early operation of the Prominent Hill regrind and cleaner flotation circuits. The mineralogically-based approach of domaining metallurgical ore types combined with the axiom of size-by-size mineral particle behaviour by liberation class gave a clear understanding of the liberation and separation issues involved in the processing of Prominent Hill ore. Technologies developed to meet much more onerous liberation and separation duties for the treatment of the refractory zinc-lead-silver ores of the Carpentaria-Mount Isa Mineral Province were successfully used to improve concentrate quality by rejecting non-sulfide gangue containing impurities. An IsaMillÖ and a Jameson Cell are included in the circuit for fine grinding and for additional concentrate cleaning. Plant performance since commissioning has justified the approach for metallurgical test work and equipment choices for the flotation circuit.

Jan 1, 2009

By Smith CB, Boxer GL

The Argyle diamond deposits in the East Kimberley were found as a result of a long term exploration programme, begun in 1972 by the Kalumburu Joint Venture (KJV), to search for diamonds on the Kimberley craton. When CRA Exploration Pty. Limited joined the KJV in 1976, it was re-named the Ashton Joint Venture (AJV). The Kimberley craton was considered prospective by analogy with structural settings of diamondiferous kimberlites in Africa. Diamonds were found during regional drainage sampling in Smoke Creek in late 1979, which led directly to the discovery of the rich Argyle lamproite diatreme (AK1) and associated alluvial deposits of Smoke and Limestone Creeks. The diatreme intruded into quartzites, sandstones and shales of Adelaidean age, and consists predominantly of lapilli ash tuff, with minor coarse and fine ash tuffs, 'non-sandy tuff' and olivine lamproite dykes. Erosion of the diatreme has produced the alluvial deposits of Smoke Creek and Limestone Creek to the north and east. Argyle diamonds are of predominately industrial quality, and the typical diamond is a brown, irregularly shaped, frosted, heavily resorbed form with abundant graphite inclusions, well developed etch channels and prominent hexagonal surface depressions. The pre-feasibility evaluation of AK1 comprised diamond drilling, surface and underground sampling, metallurgical sampling, marketing studies and ore reserve estimation. The proven AK1 ore reserve is 61Mtonne at 6.8ct/tonne. Evaluation of the alluvial deposits gave results of Upper Smoke Creek, 580 000 tonne at 4.6ct/tonne and Limestone Creek, 1.7Mtonne at 3.5ct/tonne. Commercial production from the two alluvial deposits began in 1983 with production for the year reaching 6.2 Mct. Mining of the alluvial deposits at three to five Mct/year is proposed to continue until the start of mining of the AK1 deposit in late 1985 or early 1986 at which time a new processing plant and associated infra- structure will have been constructed adjacent to the AKl deposit in the Limestone Creek area. Production is planned at three Mtonne/year, producing 25Mct/year, which will make Western Australia the largest producer of natural diamond (by weight) in the world.

Jan 1, 1984

By E Ferrow, R Herbert, M E. Malmstr, M Fuchs

The study of microbial sulfide oxidation and oxidation rates of tailings requires the use of sterile control samples in laboratory experiments for comparison purposes. The need for sterile tailings sand is also apparent in the study of microbial communities and processes. This study compares six different methods with regard to sterilisation efficiency and investigates chemical and mineralogical changes in the samples as the result of sample treatment. In addition, the effect of sterilisation on mineral weathering rates is also studied. The efficiency of the different methods with regard to sterility is estimated by most probable numbers (MPN) of both sulfur and iron oxidising bacteria. The sterilisation methods that were compared are: washing with sterile water, washing with ethanol, applying antibiotics, repeated heating to 70¦C, autoclaving, and γ-irradiation. There are several possible drawbacks with the different methods, including the risk of an applied chemical acting as a substrate for micro-organisms in the system, and the risk of altering the tailings. The results show a substantial difference in sterilisation efficiency between the treatments. For example, autoclaving, repeated heating, ethanol and irradiation efficiently kill micro-organisms, rendering an undetectable amount of bacteria after one month of incubation, whilst washing with water exhibits virtually no microbiological effect, with a bacterial content comparable to the control. The use of antibiotics for sterilisation ranks intermediate: the lag-phase was twice as long in the antibiotics treatment compared with the controls. X-ray diffraction, optical and electron microscopy, M÷ssbauer spectroscopy, and mineral magnetism indicate no significant change in the bulk mineralogical composition. However, X-ray photoelectron spectroscopy analyses show that with some of the treatments, sulfides are partially oxidised, as indicated by the formation of sulfate and partially û oxidised sulfur species at the tailings surfaces. Aerated batch weathering experiments performed on sterilised tailings samples and untreated controls indicated that while the initial rates of element (S, Fe, Cu, Zn, Mg, Na, K, Ca) release may differ between the samples, over the course of ~100 days of experiment at pH 2 and room temperature, the rates declined toward a similar value for all samples. To conclude, there does not appear to be one perfect method for tailings sterilisation. Autoclaving and heating damage the mineral grain structure and oxidise the sulfide surfaces. Ethanol, antibiotics and rinsing greatly alter the pore water chemistry through the washing procedure. In addition, ethanol and denatured antibiotics might serve as a substrate and also, in the case of antibiotics, adhere to mineral surfaces thus obstructing chemical reactions. Irradiation seems to be the preferable method on an overall basis, although the formation of surface Fe3+ was suggested by M÷ssbauer spectroscopy.

Jan 1, 2003

By Ushakov S

New geological and geophysical in vestigation including our detailed field observation in different regions of the Koryak upland testify that Nor- theastern Eurasia margin eastward of the Ochotsk-Chukotka belt is composed of a collage of allochtonous terranes arcs and sedimentary filling of back- arc basins, which bordered North East Siberia and Chukotka (1)1). Ancient island are assemblages are the most tipical for this region (2-4; shown by heavy line). They are marked by long (500-1000 km) volcanic belts which become younger towards the Pacific up the Latest Jurassic-Neocomi- an (2) to Late Cretaceous (3) and Pale- Gene (4).

Jan 1, 1987

By Kelly GD

Prior to 1986, users of satellite based remotely sensed data were almost exclusively reliant on the United States Landsat series of satellites to monitor our Earth's resources. This situation changed when France, Belgium and Sweden launched SPOT-1 in 1986. The year of 1988 saw the Japanese also enter into the earth resource satellite business. The Japanese launched an earth resource monitoring satellite with an emphasis on marine resources, hence the name MOS-1 (Marine Observation Satellite). Many more remote sensing instruments are planned for launch by these nations and others in the next 10 years.

Jan 1, 1990

By West Coast Staff

Attention to the design of facilities for drainage, of both surface water and seepage, made it possible to attain, for a qam impounding residues from a concentrating mill, a more stable sand wall which can eventually be carried to a greater height.EXPERIENCE WITH No. 1 DAMResidue from the lead zinc concentrating mill, which treats the ore from the Rosebery and Hercules Mines, was pumped 3,600 ft. through a 5-in. diameter woodstave pipeline to the site of the dam. It was formerly delivered through a 4-in. steel pipeline.State laws prevent the residue being discharged to waste into the Stitt River. Furthermore, as a pyritic residue it is a potential source of sulphur.Between 1936 and 1956 more than 1,000,000 tons. of residue was paddocked. The run-of-mill product was roughly classified at the dam in a 6-ft. diameter cone classifier and the sand fraction was pumped by a 3-in. pump to the front wall of the dam across a shallow valley. The overflow gravitated to the rear of the dam (Fig. 1). Typical sizings were:

Jan 1, 1958

Coal production from Coal & Allied's Hunter Valley No 1 open cut is presently hauled 10 km by road to washing and train loading facilities at Liddell. This road haul, using bottom dump trucks on a bitumen sealed road, presents some unique earthmover tyre problems. Sound tyre management has controlled one potentially serious problem, that of heat damage, implicit with such a long haul. Tread abrasion or wear is therefore the limiting tyre performance factor. Study of abrasion mechanisms and interpretation of abrasion patterns has facilitated an understanding of the wear processes involved. This understand- ing has highlighted the importance of front tyre wheel alignment. The development of irregular wear is shown to be related to the mildness of the abrasion and methods of remving irregular wear are presented. In conclusion haulage by large off highway trucks on long sealed haul roads has been eooncoically and technically successful at Hunter Valley No 1. INTRODUCTION Hunter Valley No 1 (HVl) is a major open cut coal mine, owned and operated by Coal & Allied Operations Ltd, and located in the Hunter Valley of New South Wales. Present

Jan 1, 1982

By J Vann, S Dunham, M Job

Two-dimensional (2D) estimation approaches have significant advantages over three-dimensional (3D) approaches when dealing with a narrow vein- or layer-like geometry. The main motivation for 2D estimation is that bias due to non-additivity of grade is avoided. The various aspects of 2D estimation are illustrated by use of a case study from the 1A Shoot Nickel deposit at Leinster, Western Australia. The width of the 1A mineralisation is variable, and so are the angles of drilling intersection. Consequently, the variable of interest (in this case nickel grade) is not suitable for direct kriging because it is defined on non-uniform support. However, grade can also be defined as the ratio of two variables that are suitable for direct kriging: thickness and accumulation. In the 2D approach, tonnage equates to thickness and metal equates to the product of grade and thickness, also called æaccumulationÆ. In the simplest approach we can independently krige accumulation and thickness and derive the grade by the ratio of the two resultant estimates. The thickness and accumulation variables must be in a consistent projection orientation, for example a horizontal projection in the case of steeply inclined mineralisation like 1A. Because the density is not constant across the 1A (and most other) deposits, the issue of density weighting is also discussed. The impact of the correlation between grade and length, or grade and density are important issues in implementation of 2D estimation. The circumstances under which these correlations need to be taken into account (by co-kriging) are reviewed. Finally some comments are made on the final use of the resultant 2D estimate for mine planning purposes.

Jan 1, 2003

A description of:1. Air-lock at No. 14 Upcast shaft.2. Pit-top gates at Dudley winding shaft.3. Safety rider employed in sinking No. 18 shaft.1. AIR-LOCK AT No. 14 SHAFT.Some time ago it became desirable to raise and lower the McBride tunnel men to save them walking the inclined tunnel, about a mile in length, with a dip of nearly 600 ft., and a maximum gradient of 1 in 4. The main Upcast shaft, No. 14, was, therefore, equipped for winding the men. As this shaft was the main ventilating shaft for the McBride tunnel mine, it was necessary to take the greatest precautions against leakage of air. The writer therefore devised the concrete structure shown in Plate 1.The structure, as shown, surrounds the shaft inside the poppet legs. As the men are wound on double-decked cages (twelve men to each deck) provision is made at both top and bottom for the two decks to be loaded and emptied simultaneously. The doorsover the sky shaft, shown in the drawing, have been cut out and the sky shaft has been close-timbered with a double layer of T. and G. flooring boards, with building paper between, nearly up to the thimble frame, a small hole only being left for the winding rope topass through. The space between the ramps is glazed with plate glass to allow the winding-engine driver a good view of the pit top.The men are wound from two levels, 302 ft. and 611 ft.2. PIT-TOP GATES AT DUDLEY WINDING SHAFTTo minimise the shock to cage, couplings and rope when winding quickly, the writer devised the apparatus and arrangement shown in Plate n.

Jan 1, 1928

Mt Muro was a gold and silver mine in Central Kalimantan on the Island of Borneo, Indonesia. Aurora Gold through its Indonesian subsidiary Indo Muro Kencana owned the project. Processing commenced in November 1994, and ceased in June 2002. Mining, including prestripping, commenced in March 1994, and ceased in May 2002. Nominal throughput was 1.5 Mtpa, at average grades of 3.80 g/t Au and 99 g/t Ag. From the start of prestripping until the end of 1996, Drill Blast sampling was the main grade control method. After several studies into the viability of Reverse Circulation, including an assessment of costs and benefits, the switch from Drill Blast to Reverse Circulation was made in late-1996. From 1997 until the end of the project Reverse Circulation was the main grade control method. The mine-to-mill call factors û the reconciliation between predicted and actual tonnes and grades delivered to the mill û for the period from commencement of processing to December 1996 were 1.069 for tonnes, 0.949 for gold, and 0.969 for silver. The mine-to-mill call factors between January 1997 and June 2002 (excluding a period of significant illegal mining) are 1.086 for tonnes, 0.977 for gold and 1.025 for silver. At face value this indicates a 2.8 per cent absolute improvement for gold, and 5.6 per cent for silver. Using average grades for the project, an additional 5112 oz of gold, and 267 173 oz of silver were delivered annually to the mill using Reverse Circulation sampling instead of Drill Blast sampling. The additional recovered metal value is estimated at $US 2.87 M annually, significantly exceeding the cost of Reverse Circulation drilling. This paper discusses a number of issues that may affect the estimated benefits.

Jan 1, 2003

The Ranger Project Area covers 78.6sq km and is approximately six km east-west by 14km north-south (Fig. 1). The area is known to con- tain two uranium orebodies, Ranger No. 1 and No. 3, two uranium occurrences, Anomalies 4 and 5 and three significant radon anomalies, Ranger 18, 19 and 48. The Ranger No. 1 and No. 3 Orebodies con- tain approximately 120 000 tonnes of U308 in highly chloritised metasediments of the Lower Proterozoic Cahill Formation. The orebodies occur as suboutcrop and exhibit significant radiometric anomalies. These occur within approximately 400m vertically of the projected unconformity with the sandstone of the Middle Proterozoic Kombolgie Formation. Oxidised and reduced uranium minerals occur in quartz-rich schists containing variable muscovite, chlorite and sericite and in the chloritic matrix of chert breccia. Secondary uranium minerals namely saleeite, metatorbernite and gummite associated with earthy iron oxides occur from the surface to 50m depth in No. 1 Orebody and up to 80m depth in No. 3 Orebody. Below the oxidised zone, uranium occurs as pitchblende finely disseminated throughout sequences of quartz muscovite chlorite schist up to 150m thick and as open space fillings in zones of structural deformation. The uranium-bearing schists directly overlie up to 300m of dolomite and magnesite containing minor interbedded schist units and are themselves overlain by approximately 2 000m of more micaceous schists of the upper part of the Cahill Formation. Regional metamorphism has occurred to at least amphibolite facies and has been followed by retrograde metamorphism to a greenschist facies equivalent. The metasediments are intruded by granitic pegmatites and dolerites. Uranium is associated strongly with chlorite of which there are at least five textural varieties. Not all of the various generations of chlorite have associated uranium. Graphitic schist horizons occur which are often less than one metre thick and discontinuous. These are best developed at the base of the quartz chlorite schist sequence where uranium grades up to 1 000ppm U may extend for several hundred metres beyond the main ore zone. Uran- ium is not common in the carbonate sequences and only occurs in chlorite segregations in disrupted zones. The unoxidised ore contains sulphides, mostly pyrite, which are low in abundance (

Jan 1, 1984

By R M. Briggs, I E. Smith, P M. Black, A B, R L. Brathwaite, J L. Mauk

The Hauraki Volcanic Region of the North Island developed between 18 and 1.9 Ma. Initial andesitic volcanism from 18 to 12 Ma was followed by 12 to 1.9 Ma volcanic activity that included rhyolitic, dacitic, andesitic, and basaltic compositions, with a gradual migration of activity to the SSE. Early andesitic volcanism evolved over the course of 8 m.y. to more silicic compositions; this trend was reset and repeated by post-10 Ma andesitic volcanism. Early and later andesites are otherwise remarkably similar in trace element composition. Rhyolites have the most diverse compositions, suggesting a major role for crustal input in their formation.

Jan 1, 2007