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By W R. Adamson

"Optimisation of drill and blast design and engineering can deliver a significant positive impact on the profitability of any mining operation; however, true engineering of the blasting process is less common than might be thought. The paper that follows explores this gap and suggests a process control-based approach to the challenge.The concept of applying modifications to drill and blast designs in order to achieve efficiency improvements in downstream mining processes is far from new. However, the author suggests that the practical application has become less than rigorous in a number of different sectors of the mining industry in a wide range of countries.There is a common tendency for the design process to become simplified to the point where the objective is merely the communication of instructions to field implementers (drillers, explosive suppliers, blasters, etc). In effect ‘design’ often degrades to ‘cut and paste’ with consequences that vary from mild to critical, with respect to the profitability of the business.Engineering of the drill and blast process involves the design function, not on a one-off basis but rather as a component of a more complete cyclical process that includes a statement of objectives, a design based on a suggested hypothesis, field measurement of results, comparison with the target ‘set point’ and the application of control measures followed by new measurement, including interpretation of the results in financial terms.When applied in this fashion, engineering provides practitioners with the means to optimise the drill and blast impact on the full spectrum business result of the mining activity.These concepts are discussed with reference to a surface gold mining operation applying run-of-mine heap leach extraction. Engineering optimisation by adapting process control and measurement techniques is demonstrated to be a key component of the solution set applied to generate enhanced operations productivity and stakeholder value. It is shown that a combination of rigorous measurement, model calibration and hands-on quality assurance/quality control facilitates the creation of a road map to profitability, stressing the need to consider economic trade-offs between operational expense (investment) and measurement of enhanced value (return on investment).The process, however, does not cease at this point. Implementation of true design practices, incorporating innovation and discipline in implementation or execution can drive the process to deliver demonstrable, technically validated outcomes. Furthermore, these technical results can be related to financially quantifiable impacts. However, this accomplishment does not guarantee that these gains or savings will reach the bottom line of those mining, quarrying and construction companies that begin the process with such high hopes.CITATION:Adamson, W R, 2015. Application of engineering discipline and a full-process optimisation focus – productivity to profitability without profuse pruning, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 3–12 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 24, 2015

By R O. James

The usual focus of papers on fatty acid collector action in non-sulfide flotation is on the adsorption of the carboxylate and/or neutral molecule species at the mineral-solution interface. Little attention is paid as to whether or not the solution conditions correspond to true solutions, micellar and other self-assembly objects or precipitates. Our examination of the solution chemistry of the important fatty acid collector, oleic acid, has revealed that many, if not most investigators set their experimental conditions to be in micellar or precipitate domains while arguing, often by implication, that they have only solute species present. We have investigated the equilibrium solution domains usually encountered in studies of oleic acid flotation of such minerals as barite, calcite and fluorite. The alkaline earth-fatty acid and liquid oleic acid precipitate phases exert a strong influence on the solution chemistry, a fact not often appreciated in many studies.

Jan 1, 2005

Current models for the origin of banded iron-formation (BIF) derived in situ iron ore deposits assume that the typical chert and iron oxide banded BIF is the primary rock from which enriched iron ore deposits arise by the selective leaching of quartz and the residual accumulation of the iron oxides. Weathering extends to the base of all the hematite deposits of the Hamersley Province, which lie within the saprolitic weathering zone, as shown by the preservation of the primary textures, and are overlain by a hydrated goethite zone representing the solum. Since groundwater typically contains dissolved silica, derived from the hydrolysis of silicate minerals, greatly in excess of the saturation solubility of quartz, it is incapable of removing quartz from below the watertable, and quartz is preserved in all saprolites derived from quartz bearing rocks. Quartz may be dissolved in the solum due to the influx of meteoric water having little or no dissolved silica, but soil-forming processes that dissolve quartz likewise alter the oxides by hydration and transposition with consequent destruction of primary textures, and there is no suggestion of soil-forming processes having produced the deposits, which typically extend to considerable depths below the water-table. A characteristic feature of the typical hematite orebodies is the unaltered nature of the iron oxides in the ore compared to those in the adjacent cherty BIF. Although the solubility of ferric iron at >10 ppb is much less than quartz, any process capable of dissolving the huge volume of quartz must also affect the iron oxides, but evidence of this is completely lacking in most ore deposits. Hydrothermal alteration at Koolyanobbing in the Southern Cross Province affects both cherty BIF and ore, and clearly shows equal mobilisation and recrystallisation of hematite within quartz/hematite veins and in the surrounding cherty BIF, which shows no evidence for the selective leaching of quartz. Similarly, any metamorphic process capable of removing all quartz from BIF would leave characteristic evidence in the remaining oxides. However, a hydrothermal process may account for at least portions of certain ore deposits, in which the chert bands have been replaced by carbonates at comparatively low temperatures, to produce a quartz-free magnetite/ carbonate rock that is readily upgraded to high-grade ore by supergene dissolution of the carbonates. This process is interpreted to have formed high grade ore at Mt Gibson, Koolyanobbing æAÆ Deposit and Mt Tom Price North Deposit. In addition to carbonate replaced cherty BIF at Mt Gibson in the Murchison Province, there are extensive sequences of magnetite BIF without chert bands, and this chert-free facies of BIF is interpreted as the precursor to the majority of in situ hematite ore deposits, through oxidation and weathering of magnetite and iron silicate and carbonate minerals. The world-class martite/microplaty-hematite deposits of the Hamersley Province are a special case of BIF-derived iron ore deposits that were initiated during the Proterozoic era. Evidence from overlying Wyloo Group conglomeratic horizons containing clasts of Hamersley Group BIF indicates that microplaty-hematite formed within the clasts before deposition, and that Proterozoic subaerial oxidation and weathering of uplifted Hamersley Group formations produced the microplaty-hematite in both chert-free and cherty BIF.

Jan 1, 2002

By J-P Franzidis

A technique for determining the recovery of attached particles across the froth phase in flotation that relies on measuring the rate at which bubble-particle aggregates enter the froth is used to investigate the selectivity of attached particles across the froth phase. Combining these measurements with those of other techniques for determining the froth recovery of attached particles provides an insight into the different subprocesses of particle rejection in the froth phase. The results of experiments conducted in a 3 m3 Outokumpu tank cell show that the detachment of particles from aggregates in the froth phase occurs largely at the pulp-froth interface. In particular it is shown that the pulp-froth interface selectively detaches particles from aggregates according to their physical attributes.

Jan 1, 2005

By D Michaelsen, S Miller

The Grasberg Mine is a copper and gold open pit mine operated by PT Freeport Indonesia (PTFI) and located in the high equatorial mountains of the Indonesian province of Papua. The climate is alpine/subalpine with little seasonal variation in temperature or rainfall. The daily average temperature ranges from about 2¦C to 14¦C and the annual rainfall in the vicinity of the mine and overburden stockpiles is about 4000 mm to 5000 mm. Mining of the Grasberg open pit will continue until 2014 at which time approximately 2750 Mt of overburden will have been produced. Current overburden production rates are 200 Mt per annum. The current mill rate is 230 000 t/day from the Grasberg pit (190 000 t/day) and the underground operations (40 000 t/day). The acid rock drainage (ARD) issues associated with overburden from the Grasberg operations were identified early in the mining operation. Almost all overburden placed to date has been Potentially Acid Forming (PAF). Laboratory testing has identified four main overburden types: limestone and non-acid forming (Green waste), PAF low capacity (Blue waste) and PAF high capacity (Red waste), and Heavy Sulfide Zone (HSZ), which contains greater than 20 per cent pyrite. Waste type block modelling indicates that at least 30 per cent of the overburden production from 2003 to the end of Grasberg pit operations will be limestone. Strategies are being developed to maximise the beneficial use of limestone through strategic blending and placement for ARD mitigation and control.

Jan 1, 2003

By M McCurd, M Lynch, B H. Yin, S Mendoza, C W. Bumby, Y Iwasaki, B Rumsey

Iron and steel production is responsible for approximately 6.3 per cent of global anthropogenic CO2 emissions. Direct reduction of iron with hydrogen is a potential route for decarbonising the iron and steel industry. Extensive small-scale laboratory experiments have been performed to test the feasibility of hydrogen-direct reduction of iron ores sourced from diverse geographical locations. However, test results from the batch reduction of small-sample do not necessarily translate to continuous commercial-scale processes. Establishing a small-scale continuous test reactor for H2- DRI process is challenging, requiring substantial resources and investment. The limited availability of small-scale reactors that enable testing under relevant conditions has become a major obstacle for H2-DRI development, leaving a big gap between laboratory success and proof of commercial feasibility. Here, we report on the recent commissioning of a continuous counter-flow vertical shaft reactor, which has a processing capacity of 6 kg/hr iron ore pellets at up to 100 NL/min H2 flow. We believe this to currently be the largest H2-DRI facility in the Southern Hemisphere. In this talk, we will discuss the design and construction journey for this reactor, starting from the initial system design to the initial demonstration of H2 reduction of titanomagnetite ironsand pellets. This reactor now enables a range of research capacities, including the validation of laboratory results on a larger scale with practical operational variables, feasibility assessment of hydrogen direct reduction of different iron ores on a commercial scale; identification of scalability, sticking, and other potential issues before building a full-scale plant; and a viable solution for producing small-quantity DRIs for downstream melting investigations. Overall, this new research facility offers significant benefits for assisting the transformation of iron and steel production to a more sustainable and green industry.

Sep 18, 2023

While specific definitions of the main categories of mineral reserves and mineral resources are becoming well established through the efforts of the Australasian Joint Ore Reserves Committee (JORC) and the Combined Reserves International Reporting Standards Committee (CRIRSCO), there has been perhaps less attention paid to the standardisation of language used in the definition and reporting of Mineral Exploration Results and a clear understanding of the transition to Inferred Mineral Resources. This is an area of significant importance to small and medium sized enterprises in the mineral exploration sector as it represents in many cases the only tangible information by which the reader or potential investor can evaluate the future potential of such enterprises. By its very nature information in the Mineral Exploration Results category is incomplete, and frequently complex, and it is open to a broad range of interpretation by readers of various competency levels and disciplines. Many will have a short-term speculative view rather than a long-term perspective, with others out deliberately to misrepresent the information, and as such it can have an enormous impact on investment decisions if the risks associated with this information being reported are not fully understood. Authors of reports on Mineral Exploration Results, who may be Competent Persons or company directors, have to put themselves in the shoes of the reader of the report, second-guessing if you like what the reader will understand by a report, which in many cases will be of a highly technical nature. This raises reporting dilemmas and questions that require to be understood and addressed. Looking at reports on Mineral Exploration Results from the other side, readers have a degree of responsibility as well, particularly if they engage in an advisory or communications role. The tendency of commentators, journalists, analysts, and bulletin board posters to over-exaggerate the significance of a particular exploration result is all too familiar. Questions arise here as well about whether there should be more regulatory supervision and control exercised over those who use this information, all of whom greatly influence investment decisions, and many of whom have no idea there is a Reporting Code, far less an understanding of it. Examples are given and questions raised to illustrate the dilemmas surrounding the reporting of Mineral Exploration Results. In order to retain credibility with markets it is incumbent on companies to be transparent, not to be selective and to report all material information. On the other hand, information has to be taken and read in its proper context in order to avoid fuelling dramatic and unjustified company share price escalation. Timing of course is another factor that can affect the market price of shares, which may be beyond the control of those making the reports. Emotive and imprecise language, however, when reporting Mineral Exploration Results, coupled by speculation, can trigger damaging short runs on shares and destroy credibility where formerly there was long-term promise. The paper will review how Mineral Exploration Results are dealt with in various jurisdictions, and conclude that there has to be a balance between prescription and the tempering of undue optimism on the one hand, and the entrepreneurial spirit, which the industry needs, on the other.

Jan 1, 2002

By Buisman C. J N, Koch R. O

Soil and groundwater beneath the Budelco zinc production plant at Budel-Dorplein (The Netherlands) are contaminated with metals and sulphate. To avoid contamination of nearby drinking water aquifers in the very distant future, a geohydrological containment system (GCS) and a microbial treatment plant for extracted contaminated groundwater have been developed. As a first step in the design of the system groundwater data from over 150 wells and geological profiles were used to model geohydrological conditions beneath the site. Several configurations of water-extraction wells were deduced from the model. Data gathered during additional fieldwork were then used to improve the model. Finally results that were calculated for the various configurations were used to select an optimal groundwater containment system. Currently some 5000 m3/day groundwater are extracted from a combination of 12 shallow and deep wells. Heavy metals and sulphate have to be removed from the extracted water before it can be discharged into the river system or used as process water. Several water treatment methods have been studied and pilot-tested at the site. The preferred and selected process is based on the activity of sulphate reducing bacteria (SRB) and combines sulphate removal and heavy metal removal in one single step. The anaerobic bacteria reduce the sulphate to sulphide resulting in the precipitation of metal sulphides. A pilot plant gave promising results and a commercial-scale plant has been designed. The proposed design has been tested in a demonstration plant which included all main process units. Test results for all process units are presented. The collected information was then used to optimise the design of the commercial-scale plant. Special attention was paid to automation and safety items. Construction of the plant was finished in May 1992. Start-up, commissioning and operational experience are reported. The concentrations of metals and sulphate in the effluent of the SRB water treatment plant are well within the limits set by the authorities for discharge to public waters.

Jan 1, 1993

Nickel ores from three different mines, Digger Rocks, Cosmic Boy and Flying Fox, are treated at the Forrestania concentration plant. The ore types vary from oxidised supergene ores to primary pyrrhotite+pentlandite ores. Mineralogical investigations on the ore and process samples have been carried out in different stages of process development. One of the studies was done with the samples collected from the flotation circuit in 19 June 1994 when the Cosmic Boy ore was processed. The process products were screened, and the size fractions were analysed for the main elements by appropriate analytical methods. Mineralogy of the products was studied microscopically and composition of the sulphides was analysed with an electron microprobe. Liberation of the main sulphides in the flotation feed was determined with the point-counting method, and weight percentages of the minerals were calculated using chemical and mineralogical data. The typical sulphide assemblage of the Cosmic Boy ore is violarite, pentlandite, pyrite, pyrrhotite and chalcopyrite. Violarite dominates over pentlandite (ratio being 70 per cent to 30 per cent), and pyrrhotite is strongly replaced with pyrite and magnetite. One of the most common mineralogical features of this ore type is secondary magnetite, which occurs as narrow rims in porous violarite or in association with secondary pyrite. Serpentine, talc and chlorite are the main gangue minerals. In the milled feed (76 per cent -74 ¦m) locked particles between nickel and iron sulphides are common. About 41 per cent of total pentlandite occurs as pure liberated particles, and 33 per cent as locked grains with violarite. Liberation degree of violarite is 55 per cent, and the most common type of locked particles is violarite+magnetite, carrying about 20 per cent of total violarite. To achieve a recovery of 80 per cent for pentlandite, all the particles containing at least 50 vol-% pentlandite should be floated into the nickel concentrate. Correspondingly recovery of 80 per cent can be reached for violarite if all the particles containing at least 65 vol-% violarite are floated.

Jan 1, 1996

By J Moncrieff, P Bellairs

The Black Star Open Cut is located immediately adjacent to the township of Mt Isa and is situated in the middle of extensive pre-existing infrastructure including two concentrators, two smelters, a wet fill plant and two shafts. At any one time there are in excess of 500 people working on the surface within an industry-accepted 600 m exclusion zone from Black Star blasts. Apart from the surface operations there are also the underground operations including the lead mine (closed in December 2005) and the Enterprise and X-41 mines that must clear for all Black Star blasts. The application of industry standard blasting exclusion zones (600 m) was risk assessed as imposing operationally prohibitive constraints which could cause significant business interruption due to the logistical challenges required to ensure that all personnel from surface plants were evacuated for each blast and potential for lost production whilst these personnel were not operating the plant. In was therefore an imperative for the blast exclusion zone to be reduced. This was achieved by the: use of a QA/QC team to ensure that relevant drill and blast implementation is within an acceptable tolerance (KPIs) from design; use of high-quality stemming material called HMR, which is a by- product of the concentrating process and is generally sized at -14 mm with very little fines; implementation of appropriate training and support to Black StarÆs own blast crews, reinforcing the need to achieve the designed amount of stemming in every hole; and provision of appropriate support from Black StarÆs management for additional resources to ensure that every blast achieves design within the KPIs but especially in high-risk areas. The blast exclusion zone was successfully reduced after monitoring the flyrock results from more than 176 blasts. Black Star Open Cut now maintains a minimum blast exclusion of 200 m in critical areas; however, general blasting currently uses a 250 m exclusion as this provides additional risk management whilst still minimising the logistics associated with clearing and securing the slightly increased area.

Jan 1, 2007

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 Johnson N. W, Manlapig E. V, Alexander D. J, Franzidis J. P

The importance of the froth region on flotation performance is often emphasised in the literature. It is well-known that decreasing froth depth or increasing air flowrate results in increasing cell recovery at the cost of lower concentrate gra

Jan 1, 1997

By R Forster

Direct ship iron ore (DSO) operations at Extension Hill in Western Australia’s Midwest region have commenced, with fi rst product railed to the port of Geraldton in July 2011. Reserves are 14.8 million tonnes (Mt) of haematite-goethite ore overlying an Archaean BIF-hosted larger magnetite deposit which Mount Gibson Iron Limited (MGI) sold to other parties in 2006.Some unique geological aspects of the deposit shape DSO mining and processing operations. Owner-operator selective mining, blending, crushing and screening on site will produce three million tonnes per year (Mt/a) of Lump and Fines product to be trucked 86 km to Perenjori, railed 232 km to Geraldton, and loaded aboard Panamax-sized ships through the dedicated iron ore shiploader at the Geraldton Port Authority’s Berth 5 facility.The statutory approvals process for this project formally began in 2004, dominating delays in a predevelopment phase which extended over a longer period than the likely life of DSO operations. The lack of transparency, uncertainties and costs inherent in state government processes have influenced decisions made by MGI while assessing other development opportunities in Western Australia. Potential for additional Reserves exists at Extension Hill, however MGI’s ability to extend the mine life will hinge on statutory approval to explore for and evaluate other DSO resources on surrounding granted mining leases.The nature of the resource and use of existing infrastructure for product transport have enabled MGI to keep operating costs and capital intensity of this project relatively low. A tenacious development approach by MGI and robust project economics have fi nally enabled this site to take its place as a revenue earner beside the company’s other DSO operations at Tallering Peak and Koolan Island.

Jul 11, 2011

By S Nie, I Bergqvist, F Ouchterlony

In blasting, a few or many cracks are driven from the borehole into the rock. But what causes the cracks? The most common theory of breakage consists of two stages; first the shock wave causes radial cracks to form around the hole then the gases penetrate into the cracks, and widen them and make them longer. Another theory presented by Brinkmann suggests that the back damage is primarily controlled by shock and that the gas penetration is the mechanism controlling breakout of the burden. He did his experimental work using blasthole liners. Recent research at SveBeFo has examined this matter further. In a quarry a number of benching holes have been blasted simultaneously. In some of these holes tubular Swellex bolts were inflated and decoupled charges put inside the tubes without stemming. Other holes were identically charged but without the lining. Finally some holes were also stemmed. After blasting the cracks in the remaining rock were studied. There was no difference in crack lengths between holes charged normally (no stemming) and holes where the charges were inside the bolts. On the other hand when stemming was used, the crack lengths increased for some explosives but remained the same for an emulsion explosive. In another set up blasted granite blocks were charged in the same way as above. Then we could also measure the bore hole pressure. The pressure gauge consists of a small carbon resistor inside a steel cylinder. It is called LHM (Location-fixed Hydrodynamic Measuring Cup) and is placed at the bottom of the hole. A smaller exit hole from the bottom is drilled for the cables. The paper presents the technique and the results obtained from both the quarry blasting and the blasting of the blocks.

Jan 1, 2001

By G Kennewell

At 11 am Monday 8 September 1997, the successful detonation of the 5/9 Mass Blast at Pasminco - Elura was signified by the subsiding of æMt KevinÆ (a 15 m high earth fill mound). The blast was in response to earlier mine subsidence, which holed through to the surface affecting future stability of underground workings. The blast was a first for Elura which fires small tonnages regularly to avoid rapid oxidation of the ore. This paper discusses the strategy and the considerable planning that went into EluraÆs first blast of this magnitude in order to succeed first time round.

Jan 1, 1999

By V Salamakha, K Tang, G Si, J Oh, X Wu, Z Yu

The development of machine learning (ML) algorithms has led to promising advances in lithology classification from geophysical logs, which is indispensable in various underground engineering applications. Due to the resolution and availability of logging data, ML models can recognise lithology change in a definitive form at a fine scale (0.01 m). While the results from previous models indicated promising performance in the classification, the robust capability of generalising lithology prediction to unseen data may not be true for those models due to: (1) data bias caused by borehole selections, and (2) logging data mismatches among boreholes. To this end, this paper aims to investigate the generalisability of ML models and seek potential improvements. Four ML models were selected to be trained on single reference boreholes to test the other (as unseen) in the same region, which includes Support Vector Classifier (SVC), Random Forest (RF), eXtreme Gradient Boosting (XGBoost) and Residual Neural Network (ResNet10). The data set involves 11 boreholes from a coalmine in north-western Bowen Basin (Queensland, Australia): density, gamma ray, neutron, and sonic logs are selected as inputs. Additionally, a data adaptation method is applied for better generalisability. The results show that there is an accuracy trade-off between the same borehole and unseen boreholes across the models. It also indicates a 16–43 per cent reduction in model performance when generalising the predictions (in marco-F1 score), while the adapted data sets can contribute to a around 12 per cent improvement. This study provides a fundamental understanding of the model generalisability when using a single borehole, essential for further correlating boreholes for regional lithology classification; the adaptation method can improve the generalised accuracy, and reduces the labour to label lithology, which facilitates the identification of gas storage mechanisms, geological/geophysical modelling, and stratigraphic analysis.

Sep 1, 2024

Commercial explosives range from pure emulsions to pure ANFO, with blends of these providing interesting alternatives: energy is often adjusted through addition of aluminium, or the control of density. The energy rating of explosives is derived chiefly from detonation codes, which are used to derive expressions for the internal energy change of the detonation products as they do work under expansion. While all codes used for this purpose work on the basis of Ideal detonation, it is common knowledge that commercial explosives operate in the Non-Ideal domain, which affects the mode of energy delivery to the environment. However, since Ideality represents the foundation from which actual performance evolves, it is valuable to examine the intrinsic energy release of a formulation before attempting to understand the influence of Non-Ideality. In examining the Ideal pressure profile of fundamental formulations, remarkable correlation has been found with field performance, and this increases understanding of the influence of various formulation modifications, especially in regard to the stage at which energy is released, and the effect on rockbreaking. This work has emphasised the value of attempting to understand and define better the non-ideal detonation process.

Jan 1, 2001

By O V. Vasyukova

Formation of porphyry-style ore deposits starts with the metal extraction from magmas at so-called magmatic-hydrothermal transition (MHT). The processes and compositions at MHT are difficult to study as the record of them is poorly preserved. As the MHT is characterised by massive crystallisation of quartz, including quartz æeyesÆ and veins, their study can elucidate questions related to metal transport and deposition. Quartz grains from the porphyry deposits all over the world (Antapaccay, Peru; Batu Hijao, Indonesia; Climax, USA; Panguna, PNG; Far Southeast porphyry, Philippines; Rio Blanco, Chile; Omsukchan, Russia) were studied by optical, SEM-CL and BSE microscopy, electron microprobe and LA ICPMS. Quartz grains, even within each sample, have different shapes (rounded, egg-shaped, amoeboid or euhedral) and cathodoluminesence (CL) patterns (shape, number and width of bands in CL images). The outer layers of quartz are markedly different, which is unexpected if the grains had formed in the same conditions. Inflections and blurring of CL bands are often structurally associated with fractures that are commonly healed with secondary quartz and associated fluid inclusions. Our results show that quartz æeyesÆ could not crystallise from a silicate melt as normal phenocrysts. It is likely that in situ segregation of residual SiO2- and H2O-rich liquid and its solidification followed by coagulation (eg formation of silica-gel globules) took place in the magma (crystal mush) during MHT. Such globules could remain in a plastic state for a long time even at rather low temperatures. The solidification of globules occurred after bands of different composition had formed and led to fracturing of solidified and inflection of unconsolidated layers. All fluids (liquid and vapour) released from the original silicagel during solidification were trapped as inclusions (aqueous, salt-rich and sulfide). An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

Distal air-fall ashes are widespread deposits that may record volcanism many hundreds of kilometres from their source. They are characteristically thin, fine-grained and have a low preservation potential usually being either eroded, or reworked and incorporated in overlying sediments following deposition. The most likely sites of accumulation are deep sea, lake and swamp environments where low energy conditions favour preservation. Post-depositional alteration of predominantly glassy volcanic ash is commonly extensive hampering identification of such layers in the geological record. As a result air-fall tuffs are poorly represented in the rock record and furthermore are commonly misinterpreted. Southeast Queensland during the late Triassic hosted active silicic volcanism and a number of fault-controlled basins in which coal-bearing sediments were accumulating. Silicic volcanics of late Triassic age are represented by the Brisbane Tuff in the Brisbane city area, the Chillingham Volcanics to the south of Brisbane and extending into New South Wales, the North Arm and Mount Byron Volcanics to the north of Brisbane, the Aranbanga Beds exposed around Gayndah and the Agnes Waters and Muncon Volcanics which occur northwest of Bundaberg. Stephens (1986) interprets these Volcanics as the remnants of a major silicic igneous 'province which he likens to modern continental orogenic margins. The Ipswich, Tarong and Callide Basins of southeast Queensland all contain coal measure sequences of late Triassic age that accumulated in alluvial plain environments. A Dicroidium flora is common to all and palynol.ogical evidence indicates a late Triassic (Carnian) age (de Jersey, 1975; Stevens, 1981). The coal seams of the three basins are characterised by their thickness (up to 25 m) and the presence of abundant thin, laterally persistent, kaolinite claystones (tonsteins) that show a marked similarity of morphology, texture and mineralogy. Detailed studies of the Ipswich Coal Measures (Falkner, 1986) suggest a volcanic air-fall origin for the tonsteins of the Ipswich Basin. Similar.tonsteins from the Tarong and Callide Basins provide evidence for widespread silicic volcanism during the late Triassic in southeast Queensland.

Jan 1, 1987

By A J. Morrison, M Yahyaei, J S. Siong, J Wang, K Runge

The flotation cells used to upgrade ultrafine metallurgical coal (-250 µm) are usually poorly controlled leading to unnecessary loss of combustibles from the flotation system. This is mainly because coal flotation cells are typically controlled for process stability rather than optimisation of flotation performance. This is especially true for a flotation device commonly used in coal applications in Australia – the Jameson Cell. This then provides an opportunity to improve the flotation performance by shifting from a stabilising control strategy to a proactive optimising control strategy. For an optimising control strategy, the control system will require a means of relating and then measuring in real-time, the effect of changing operating conditions on the coal flotation performance. Hence, the major aim of this work is to propose a possible model-informed process control strategy that could be used for real-time performance optimisation. In this study, industrial site work was conducted on an industrial-scaled Jameson Cell at a Coal Handling and Preparation Plant (CHPP) in Central Queensland, Australia where superficial gas velocity was controlled to six different levels. At the same time, other process variables such as froth depth and flotation feed properties were measured. The empirical models developed from this study suggested that combustible recovery is a function of superficial gas velocity, froth depth, feed solid content and feed ash content and that a peak in combustible recovery existed as a function of superficial gas velocity. This led to the development of a model-informed control strategy that aimed to maximise the combustible recovery by determining and then operating the cell at the superficial gas velocity at which the peak occurs. This peak superficial gas velocity was found to be only a function of feed solid content. Based on these findings it would seem possible to operate a Jameson cell at peak performance by online measurement of feed solid content, prediction of the optimum superficial gas velocity and stabilising control to maintain operation at that superficial gas velocity set point. The development of this modelinformed control strategy can serve as a basis for the development of a more sophisticated modelpredictive control (MPC) system. However, more work will need to be done to improve the predictivity of the combustible recovery model by measuring and modelling performance over a wider range of operating conditions.

Aug 24, 2022