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It is a pleasure and a privilege to be with you for the Annual Conference of The Australasian Institute of Mining and Metallurgy.The inaugural meeting of The Institute was held in Adelaide in April, 1893. Through the kindness of your President, who passed on to me several publications concerning The Institutute I have been able to glance back over the eighty years in which The Institute has served both the profession and Australia.In that record, many names of great distinction caught my eyes. When one reads the list of past presidents of the The Institute since 1893 and the list of those to whom The Institute Medal has been awarded, one reads the headings of a biographical dictionary of the Australian mineral industries. Many famous names are there-men from the great mining companies, engineers, scientists, metallurgists and geologists. Simply to read the names is to recall great enterprise and great achievement. Going over those names one hears the echoes of the inspiring story of the establishment of the Australian steel industry, the electrolytic zinc inq.ustry, all the major developments in the mining of coal, gold, copper, silver and lead, the treatment of difficult ores, the geological exploration of a cqntinent, the discovery of uranium, bauxite, petroleum, nickel, the establishment of the alumina industry and finally the mammoth earthmoving operations of today. The list of names is a chronicle of great men who did a mighty work. They stand like milestones in the progress of a nation.When one reads further and runs down the titles of some of the papers published in the Proceedings of The Institute even a layman like myself can appreciate the dramatic developments in mining and metallurgy that have transformed the whole practice of the mineral industries in our land. Australians have made some notable innovations and discoveries both in mining techniques and in the processing of ores. The history of mining is not only a story of the discovery of the mineral resources of this continent but of adventurous steps taken to perfect new ways of mining the ore and extracting the metal.I read with great admiration the presidential address given by Sir Maurice Mawby in 1968 and wa...

Jan 1, 1973

It has been proven theoretically and experimentally that the use of 10 - 30 per cent DRI in blast furnace along with iron ore or sinter results in lower coke rate and higher productivity. However, to-date this remains unpractised on a regular basis mainly because of economic reasons. The DRI produced by several methods are expensive and difficult to store/handle in large quantities because of its reactive nature and thus DRI in blast furnace remains unacceptable.

Jan 1, 1999

By B Powell

Coastal acid sulfate soils (ASS) are wetland soils and unconsolidated sediments that contain iron sulfides which, when exposed to atmospheric oxygen in the presence of water, form sulfuric acid. ASS form in protected low energy environments such as barrier estuaries and coastal lakes and commonly occur in low lying coastal lands as Holocene marine muds and sands. When disturbed, the iron sulfides in these soils can oxidise and produce large volumes of sulfuric acid (essentially similar chemistry to acid rock drainage with mines) resulting in the subsequent release of toxic levels of iron, aluminium, manganese and possibly heavy metals. This results in detrimental effects on aquatic biota, plants, animals and steel/concrete structures and on human health in the surrounding environment. There are an estimated 2.3 million ha of ASS located along 6500 km of the Queensland coastline. In contrast to many mineral sulfides encountered in the mining industry, the pyrite crystals in ASS can be as small as 2 mm and commonly occur as framboids with extremely large surface area per unit mass, substantially increasing their reactivity if exposed to air (oxidation). Highly reactive iron monosulfides can also occur, particularly in drains and shallow lakes. Many coastal areas, where some 80 per cent of the population of Queensland reside, are coming under pressure for agricultural and urban development. Construction of canal estates, marinas, housing/industrial estates, roads, golf courses, aquaculture ponds, sand/gravel extraction and drainage for sugar cane can disturb ASS and release sulfuric acid, which may then drain into adjacent waterways with heavy rain. As development continues to encroach on coastal lowlands, the identification, quantification and management of ASS must be addressed as part of a commitment to the principles of Ecologically Sustainable Development (ESD). ASS can be successfully managed by adopting best practices and following guidelines, but government, community and industry must collaborate to raise awareness, avoid æhot spotsÆ and develop more cost-effective solutions. Scientists led the education and public awareness program showing infrastructure and environmental damages arising from ASS in Queensland. Using results from mapping and research, they convinced policy makers, industry and polititians to accept the need for legislation founded on good science. The resulting æState Planning Policy 2/02: Planning and Managing Development Involving Acid Sulfate SoilsÆ identifies the StateÆs interest in acid sulfate soils. The Queensland Government considers that development involving acid sulfate soils in low-lying coastal areas should be planned and managed to avoid potential adverse effects on the natural and built environment (including infrastructure) and human health. SPP 2/02 states where the policy applies and when a development application will trigger the policy. It can also be used to assist local governments in preparing their planning schemes under the æIntegrated Planning Act 1997Æ. The SPP 2/02 comes with a æState Planning Policy 2/02 GuidelineÆ to provide advice and technical information on interpreting and implementing the SPP 2/02. This guideline has legal status in assisting in the interpretation of SPP 2/02. Those seeking more detailed technical information can now also access the æSoil Management GuidelinesÆ and ASS æSampling GuidelineÆ, available from the Department of Natural Resources and Mines website. These are some of a series of chapters being developed for the æQueensland Acid Sulfate Soil Technical ManualÆ.

Jan 1, 2003

By W B. Edgar, I M. Platten, C A. J Towsey, B W. Cuffley

The evaluation of historical goldfields has been common over the past 15 years, reflecting changing economic conditions, improvements in knowledge and technology and lack of greenfield sites. Many goldfields comprise narrow gold-quartz veins, which are structurally complex with an irregular distribution of gold, have variable geometry and architecture and display late deformational effects. The study of historical mine records can be an important tool during early and advanced project evaluation, since it contributes to understanding the orebody, exploration target size and setting expectations. Mine records include documents such as plans, sections, reports, news cuttings, production tabulations, etc. A major advantage for the modern explorer is the capability of computer modelling to display this data in 3D. Historical records can give the explorer substantial information on various deposit characteristics, not least grade and geological continuity, geometry and architecture, mineralogy, metallurgical properties, bulk density and ground conditions. From an evaluation perspective, historical records can be used to support a Mineral Resource estimate, though its application will depend upon the quality and quantity of the data and judgement of the Competent Person. Effectively used, historical records can reduce geological uncertainty and focus evaluation efforts û thus reducing project risk.

Jan 1, 2009

Population growth, social inequality, pollution, global warming, poverty, overexploitation of natural resources and biodiversity loss, are a few examples of the many challenges facing the world today. Sustainable development is about meeting these challenges and improving the standard of living for the benefit of the maximum number of people. These issues concern governments, communities, environmental and social action groups and individuals all over the world. Business too, has a fundamental role to play in delivering sustainable development. In particular, sustainable development is becoming increasingly recognised as a critical issue for the oil and gas industry to address and act upon. BP is committed to positively respond to the challenges posed by the objective of sustainable development.

Jan 1, 2002

By G R. Ballantyne, M S. Powell

A comprehensive Australia-wide survey of comminution energy consumption at copper and gold mines was presented by the authors at the 11th AusIMM Mill Operators’ Conference 2012. The database has been extended to include major overseas mines and used to benchmark comminution energy consumption across the industry. The mines included in this study now represent 15 and 24 per cent of the total global gold and copper production respectively, and almost all Australian production. The comminution energy intensity per unit of saleable metal has been presented in a graphical form similar to a cost curve used in economics. The graphical method has been developed to assess the competitive advantage that can be achieved by reducing comminution energy intensity.This benchmarking tool has been applied to three published case studies to assess its applicability. The first case study indicated that a large reduction in size-specific energy (kWh/t -75 µm) was achievable by converting standard semi-autogenous and ball mill circuits to include high pressure grinding roll and stirred mills. The second case study investigated the metal-specific energy reduction historically achieved by Bougainville with the addition of a preconcentration screening plant. The final case study was conducted by Barrick Gold Corporation and involved incremental efficiency upgrades at three of its gold mines: Cortez, Cowal and Mara North. The application of the benchmarking tool to each of these case studies successfully demonstrated the scale and competitive advantage that was achieved by reducing energy intensity.CITATION:Ballantyne, G R and Powell, M S, 2014. Benchmarking comminution energy consumption for improved efficiency, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 95–100 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

Two types of low-sulphidation epithermal mineralisation may be recognised in volcanic terranes. Chalcedonic Silica- Adularia-Illite type mineralisation is most common in rhyolitic terranes, whereas Crystalline Quartz-Illite-(Adularia- Kaolinite) type mineralisation is more typically formed in andesitic terranes. A third type of epithermal mineralisation, the high sulphidation or Vuggy Silica-Alunite- Kaolinite-Illite type, is also common in andesitic terranes. Episodic violent boiling, accompanying hydraulic fracturing and hydrothermal eruptions, characteristic of geothermal systems in rhyolitic terranes, is stressed for the formation of Chalcedonic Silica mineralisation. Such boiling of deeply circulating meteoric groundwater, with some magmatic fluid contribution, provides chalcedonic veining, episodic banding and brecciation textures, adularia stability, bladed calcite, and extreme loss of H2S from the fluid to cause major gold deposition. Crystalline Quartz mineralisation is probably caused by the mixing of shallow acidic groundwater with ascending deep geothermal fluids beneath andesitic strato- volcanoes. The cooling effect, oxidation, and increased acidity, overcomes the dilution effect, and results in quartz deposition, illite (and locally kaolinite) alteration, and precipitation of metals. Extensive formation of base-metal sulphides further enhances gold deposition. Violent boiling is restricted to local structural dilation sites, potentially producing high grade "bonanza" gold mineralisation.

Jan 1, 1991

Autogenous-Carrier Effect and Gangue Influence in Fine Particle Flotation of Ilmenite/Titanaugite System

Sep 13, 2010

A quantitative chemical model of the rocks of the Broken Hill lode environment is presented to illustrate a stratiform orebody in a meaningful form to scientists interested in environmental control on the chemicalcomposition of sediments.Even though this study was restricted by the narrow range of rock analyses available it is obvious that significant chemical differences exist between the various rock units and also that some association of metallic sulphides with Ca, Mn, Fe, and P is indicated.Correlation of this evidence with that from other mining fields may point out more definite chemical relationships and elucidate the puzzle of the mode of formation of many stratiform orebodies.

Jan 1, 1968

Although small scale mining is regarded by many as of historical value only, this kind of mining activity is still much more widespread than is usually assumed. It has been estimated that it produces as much as ten per cent of the global mineral output. More significantly this figure is often much higher for many of the developing countries of Africa, Asia and South America, signifying the relatively greater contribution of small scale mining to the economies of those countries. It is also noted that small scale mining has always been a feature of mineral production in New Zealand and Australia. An attempt is made to define small scale mining, and the factors determining the suitability of small scale mining operations are discussed. The state of the art in small scale mining is reviewed and the author endeavours to rationalise the important parameters which contribute to successful small scale mining operations and discusses how these parameters may be optimised. The benefits of small scale mining to the mining industry as a whole and to the community at large are outlined. The paper concludes by emphasising the necessity to maintain small scale mining and 'explores' its future 'prospects'.

Jan 1, 1990

In March 1990, Heritage Mining conducted a 2000 line km high resolution aeromagnetic survey of all its prospects in the Coromandel Peninsula. One of the areas covered was the Onemana Peninsula, situated about 5 km north of Whangamata. Details of location and geology are given by Robson and Stevens (this volume).   The detailed helicopter-borne magnetic and radiometric survey over the Onemana area consisted of 163 line kmÆs of flying, and was carried out in order to assist in the definition of hydrothermal alteration and pre- or post- mineralisation structures. The line spacing chosen was 100 m, flown east-west, with a mean sensor terrain clearance of 80 m. Tie lines were flown north-south every kilometre for levelling purposes. The sensor was a Geoinstruments G-813 proton precession magnetometer in a towed bird, with data recorded using a Geoinstruments G-2000 acquisition system.   The Onemana alteration system is at the northern end of a major north-north east trending structural corridor defined by regional aeromagnetic surveys performed by AMOCO in 1980 (Rabone, 1991). T his structure hosts a number of other extinct hydrothermal systems including Karangahake and Golden Cross. In the Onemana contour plot the predominant north-northeast structures form the boundaries of a large area of subdued magnetism in the southern part of the surveyed area that is caused by intense hydrothermal alteration. This area is about 3.5 km long by 1 km or more wide and contains outcropping sinters and hydrothermal eruption breccias, as described in Robson and Stevens. A number of other structures transect this alteration zone, with strike directions ranging from northwest to north. A northwest feature notably truncates the zone to the south, while the northern end seems to be simi1arly bounded; however as data coverage ends at the coast, this feature is less conclusive.    Two distinctive types of strongly magnetic rock were discernible the contoured data. The strong negative magnetic anomalies the north and west are caused by fresh negatively magnetised rhyolites. This was confirmed by ground follow-up work that showed the rocks to be fresh biotite rhyolites with high magnetic susceptibilities.

Jan 1, 1991

By D Craw, D Falconer

The Morning Star mine is one of numerous historically mined gold-quartz lodes in the Preservation Inlet goldfield of southwest Fiordland. The mine is hosted in Early Ordovician metasedimentary rocks that are composed predominantly of psammitic and pelitic lithologies. These rocks still contain their primary depositional features and are characterised by upper greenschist facies metamorphic grade.   The Morning Star mine lies on the eastern limb of a gently south plunging anticline. A bedding parallel fault-vein and an associated network of minor quartz veins hosts mineralisation. The main fault-vein structure strikes N-NW, dips steeply (~60¦) W, has a strike length of ~350 m, a vertical extent of ~170 m and is up to 2 m in thickness. The internal structure of the fault-vein consists of laminated quartz, massive and fibrous quartz, and silicified breccias/cataclasites. Gold is typically coarse grained (~1 - 2 mm) and associated with pyrite, arsenopyrite, chalcopyrite, tetrahedrite and galena. The geometry of the Morning Star mine is similar in form to that of a saddle reef. Gold-quartz lodes in the Preservation Inlet goldfield are comparable in geometry and host rock to their offset equivalents in the Golden Blocks field of NW Nelson.

Jan 1, 2005

The success of smooth blasting essentially depends on geological condition of rock. Also, in the perimeter hole, borehole pressures with light, well-distributed explosive loads are important to minimise overbreak. In order to simulate perimeter holes with scaled model test, the borehole pressure was considered as a factor of scale. Hydraulic oil pressure is applied as borehole pressure instead of using explosives and detonators in order to remove the undesirable effects of detonators in an experimental set-up of just two perimeter holes in a tunnel blast. The borehole pressure on a perimeter hole is nearly reproduced with hydraulic pressure which is generated by non-electric detonators in the hermetical cylinder.

Dec 6, 2010

The C.S.A. copper-lead-zinc mine, located 7 miles north of Cobar in central-western New South Wales, is the largest known mineral ocurrence in the Cobar mining field. The generally discordant orebodies occur within a strike width of 600 ft and an overall strike length of 1200 ft. They are enclosed by the steeply westdipping, west-facing sediments of the Cobar Group, and comprise lenticular steeply north-pitching and eastdipping zones of sulphide mineralization which range in composition from massive pyrite-sphalerite-pyrrhotitegalena to less massive pyrite-pyrrhotite-chalcopyrite varieties.The thinly bedded siltstones, shales, and greywackes enclosing the mineralization appear to have derived some of their constituents from volcanic sources. They have been metamorphosed to the greenschist facies of regional metamorphism. At least two stages of deformation and folding have occurred. The first stage folded the rocks on a south pitching fold axis into their present configuration, and superimposed a strong axial plane cleavage which subsequently guided the emplacement of the mineralization. The second stage of deformation is considered to have controlled the zonal distribution of the orebodies.

Jan 1, 1970

By M Pizey, M Kingsbury

Since 1950 Stockton Open Cast Mine has excavated over 60 million tonnes of Brunner Coal Measures overburden sandstones and mudstones. The current operator, Solid Energy New Zealand, recognises that acidic drainage from this overburden and from historic underground mines has led to depressed pH levels and elevated levels of metals in streams draining the Stockton Plateau. These streams report to the Ngakawau River. To quantify the effects of mine site acid drainage remediation/mitigation on the lower Ngakawau River water quality, a catchment hydrogeochemical model has been field calibrated and ecotoxicology tests have been undertaken. The hydrogeochemical model indicates that pre-mining and present pH values in the lower Ngakawau River are similar but present aluminium and iron concentrations are elevated. Ecotoxicology tests have semi-quantified the critical metal concentrations and interim water quality targets to achieve ecological recovery are presented. Analyses of long-term total suspended solids (TSS) and turbidity monitoring in the lower Ngakawau River and St Patrick's Stream indicate that TSS of 120 mg/L and turbidity of 20 NTU are exceeded for <20% per cent of the time. Hence, specific criteria to protect migratory native fish from turbid water are currently met in the Ngakawau River and St Patrick's Stream.

Jan 1, 2003

In most mines using presplitting the final excavated wall shows a zone of damage just below the crest and well defined presplit half barrels. The crest damage (surface dilation) zone varies and is added to by subsequent adjacent perimeter blasting operations. Keeping the preconditioning to a minimum is possible using the methods described in this paper, developed on several diverse and geographically distant mining operations to control crest dilation and preconditioning by presplitting in advance - not just laterally but vertically in advance. The first documented case (Delbridge, Marton and McSweeney, 2004) in the development of the concept was undertaken at AngloGold Australia Pty Ltd's Sunrise Dam Gold Mine (SDGM), located beside Lake Carey, some 730 km northeast of Perth, Western Australia. The mine had been developed in a series of cutbacks to a depth of over 300 m and began underground mining during the latter stages of open cut operations. This mine is fairly unique in that it utilised a single pass vertical presplit which initially extended over three bench heights and after the failure mechanisms were understood, over four benches. The presplit drilling for the three stacked benches started on the floor of the second bench so that any dilation was confined to the surface one bench above the crest and modified perimeter blasting was then developed to curtail damage from blasting adjacent to the new crest. The second case is based on a South African coal mine in the Witbank Coal Measures, 140 km northeast of Johannesburg, Republic of South Africa (RSA). It was important that blasting for optimal wall stability and minimal scaling was developed in advance. A dragline is scheduled to excavate the #2 seam midburden which is the lowest of the economically viable coal seams in the five seam Witbank Coal Measures. Mining of the overburden, coal and partings above the dragline midburden pass are by excavator and truck and each mining layer is individually blasted. The results of presplitting the midburden through the overlying coal seams and partings have provided a presplit with no surface dilation of the midburden crest and ensures any subsequent crest loss is solely due to blasting adjacent to the vertical presplit. Typical of all coal mines in South Africa only vertical presplits are used. Wall control is most commonly delivered by presplit blasting and one common sight after the dust clears is a ridge of broken blocks along the presplit row, usually with a main crack running between the presplit blastholes and often parallel cracks either side of the perimeter line. The surface rock strata or block structures have been dilated by the venting gases and shock waves. Decoupled, fully coupled, single or double deck charges are used depending on a variety of factors, anecdotal practices and perceived benefits. Preconditioning of the crest rock by blasting from above may not be visible to the naked eye (or non-existent in overburden in strip coal mines) but the high speed venting of explosives gases (and often the water in the presplits) preferentially follow existing cracks and structures because there is no developed presplit crack near the surface. This nearly always lifts, shifts and separates the surface structures and geological layers. Stopping the dilation by 'sacrificial' or 'in advance' presplitting has been shown to reduce the crest loss at both metal and coal mines. Drilling and presplit blasting through an upper level of bench or layer provides a degree of restraint to the target layer where the crest must be maintained and any damage caused by the venting gases will not cause concern as it is removed as planned, leaving a stable crest.

May 1, 2010

By Madgwick J. C

Four manganese dioxide leaching microorganisms, an Achromobacter spp, Aspergillus niger, Elllerobacter cloacae and Elllerobacter agglomerails were purified from sucrose enriched crude mixed cultures which contained at least sixteen, non-leaching, morphologically different, colony types. Fastest leaching rates were obtained from the original enrichment's mixed cultures (1.26 g Mn++ I/d) while best yields of Mn++ m terms of sugar use came from Achromobacter and A. niger being 0.84 and 0.89 g Mn++/g sucrose respectively. The peak efficiency in manganese reduced, per carbohydrate used, coincided with the exponential growth phase for Achromobacter. The two Elllerobacter species performed better in stationary or senescent growth phases.

Jan 1, 1985

To optimise the haulage of the large tonnages produced from stopes in this high production gold mine, an ore pass and feeder system was introduced. This ore pass was designed and developed in 2006 and the plate feeder installed and commissioned soon after. Cavity Monitoring Surveys (CMS) have been undertaken of the ore pass since it was commissioned. The original thickness that was surveyed of the pillar between the ore pass and decline in 2006 was approximated to be 19 m. Throughout its use large blocks of rock were reporting at the plate feeder. This was the first indication that the ore pass was failing somewhere between the tipping level of the 9410 level and the plate feeder at the 9330. Even so CMS surveys were not taken systematically to firstly identify the area of failure or for monitoring. In August 2008 after implementing management systems, large blocks were still reporting to the plate feeder. The decision was made to empty the pass enough to carry out a CMS survey of the area. Subsequently it was discovered that the area of failure was between the decline and ore pass and that since the first survey the pillar thickness had been reduced to approximately 9.7 m. Further management controls were put in place to slow movement of the material and to limit the use of the 9410 tipping level, but this did not alleviate the rate of failure entirely. The results of an initial inelastic numerical model indicated that most of the pillar was damaged and that failure into the decline likely if no changes were made. The numerical modelling predicted that even if material was no longer passing through the ore pass interaction between the voids was unavoidable and would most likely result in instability. The ore pass and plate feeder are an integral part of the haulage system for the remaining life-of-mnie. Two solutions were sought to firstly reinforce and stabilise the pillar between the ore pass and decline and secondly to rehabilitate the ore pass or find an alternate design that could still utilise the plate feeder. This paper summarises the analysis and resulting rehabilitation that was used to accomplish this.

Nov 25, 2010

By N Hungerford, A Coote, S Doyle, D Henderson, F Della-Pasqua

A systematic, detailed airborne geophysical programme carried out in the Taupo Volcanic Region (TVR) in 2005 by Glass Earth NZ Ltd culminated in the identification of 21 epithermal gold targets. In this paper we present the follow up ground-truthing results from the first target drilled, Tahunaatara (TAH).   The Tahunaatara target was identified by means of a multi-disciplinary integrated approach (ôdata interventionö) that defined and ranked the target as being highly prospective for epithermal gold mineralisation. A follow-up ground resistivity survey over the target area revealed the presence of a ôresistorö buried beneath an extensive cover of recent volcaniclastic material. Geochemical soil sampling carried out in conjunction with the resistivity survey yielded anomalous gold values.   The host unit at TAH consists primarily of flow banded rhyolitic lavas, volcaniclastic deposits and tuffs of the Ohakuri Ignimbrite with small outcrops of silicified bedded breccias forming local topographic highs. Results from the first orientation drill hole show wide zones of intense silicification, clay alteration and mineralisation. Sulphide mineralisation is disseminated throughout the core in association with hydrothermal replacement and also occurs in association with quartz veins and infill in fractures (sulphide-only veinlets as opposed to quartz + sulphide veinlets). Textural evidence from drill core indicates that hydrothermal fluid flow was multi-staged with potential for multi-stage gold, and other elements. The presence of polymictic hydrothermal eruptive breccias indicates a hydrothermal vent system.   Alteration varies from argillic to silicic, with pervasive adularia and vuggy silicification also present. Chlorite is minor and associated with quartz, illitic clay and adularia. Assay results currently available confirm the presence of anomalous gold values in association with zones of vuggy silica deposition and intense silicification.

Jan 1, 2006

By P Illig, R Newberry

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Recent exploration efforts in Eastern Interior, Alaska have discovered significant ca 72 Ma Au-Cu-Ag sulfide-amphibole skarn mineralisation within metamorphic rocks of the Yukon Tanana Terrane, 20 km SE of Tok, Alaska. Contango ORE, Inc’s 1.1 Moz Au-equivalent Peak deposit skarn discovery is hosted by an argillaceous marble layer in quartzite and micaceous quartz schist. This skarn mineralisation is both younger and much more Cu-rich than the typical ca 90 Ma Au intrusive-related gold deposits in the Tintina Gold Belt (eg Ft Knox and Pogo). Silicates at the Peak skarn are predominantly high Cl-, randomly oriented, Fe-rich amphibole, lesser chlorite and minor (<1 per cent) residual clinopyroxene (Hd80–90). Amphibole is ferroedenite to hastingsite and contains up to 4.2 wt per cent Cl-. Pb-Zn-Sb veins are most distal and cut schist wall rocks and amphibole skarn. The predominant sulfide mineral is pyrrhotite, with subordinate arsenopyrite and lesser chalcopyrite, native gold, minor pyrargyrite (Ag3SbS3), trace Jonassonite (AuBi5S4) and maldonite (Au2Bi). Native bismuth, galena, hedlyite (Bi7Te3) and Joseite-A (Bi4TeS2) are also present.Unmineralised garnet (Ad38–43) + pyroxene (Hd60–63) and pyroxene-rich (Hd76–80) skarn occurs in different fault blocks from the Peak skarn and represent proximal skarn related to different intrusive centres. Amphibolites in the region are true metabasites, display metamorphic fabrics and lack the high Fe-Cl compositions of the amphiboles in mineralised skarn. Residual clinopyroxene in the Peak skarn is rare, and most of the hornblende is coarse radial splays that shows no evidence for replacement of pyroxene. Consequently, we propose that the sulfides and hornblende were mostly direct replacements of argillaceous marble and not formed by retrograde alteration of pyroxene-rich skarn. The high-Cl amphiboles indicate that the fluids were Cl-rich and presumably carried Cu via Cl complexing, unlike the Cl-poor fluids associated with ca 90 Ma Cu-poor deposits of the region.CITATION:Illig, P and Newberry, R, 2015. Amphibole Au-Cu skarn and massive sulfide replacement at the Peak deposit, Eastern Interior, Alaska, Peru , in Proceedings PACRIM 2015 Congress, pp 415–422 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015