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By Alexsander Orrico Marchesi

Este trabalho foi realizado com o objetivo de identificar os motivos das trocas prematuras dos segmentos da máquina de lingotamento contínuo 1 da ArcelorMittal Tubarão e indicar propostas de engenharia para aumentar a sua confiabilidade e disponibilidade operacional . A metodologia utilizada foi a estratificação dos dados históricos, coletados no sistema informatizado de manutenção da empresa (SIM), para identificar, classificar e analisar as causas das trocas prematuras realizadas. A partir disso, baseado em conceitos de engenharia de manutenção, foram utilizados métodos de análises de falhas, como Diagrama de Pareto, Brainstorming, Diagrama de Ishikawa e Matriz Esforço x Impacto para elaboração de propostas de plano de ação modelo 5W1H visando à eliminação dos problemas.

Aug 7, 2018

Sandsloot open pit is situated on the northern limb of the Bushveld Complex, 250 km north east of Johannesburg, South Africa. Sandsloot is currently the largest open pit platinum mine in the world and is one of six potential open pits in the area. The geotechnical strength properties of the Platreef have posed significant mining and processing challenges to the PPRust operation since inception in 1992. In order to optimize the whole business as opposed to isolated cost centres a mine to mill initiative was embarked upon in 1997. Initial work focused on ore characterization and an entire suite of data was collected for each rock type. This included mineralogy, geochemistry, geotechnical, blast ability indices, as well as metallurgical strength data. The second phase involved the clear definition of customer requirements, namely the optimum performance criteria for the plant and mining departments. This involved extensive field trials and data capture to measure the interaction and influence of the mine to mill value chain. Once the design targets were defined, a 3D geotechnical model was constructed to ensure that the targets were consistently achieved. The model is very similar to an ore reserve model; however, it is populated with geotechnical, metallurgical and blast index data. Through software queries the appropriate blast powder factor for each mining block can be obtained, thereby ensuring the correct fragmentation is blasted for the plant and mining operation. The initiative has delivered significant results showing improvements across the mine to mill value chain. These include increased loading rates, reduced electricity and crushing consumables, as well as higher plant throughput. Additionally, the initiative has benefited both brownfield and greenfield projects on the PPRust operation

Jan 1, 2006

By James L. Hendrix

The applicability of a rotating drum with an attached trommel as a flocculation dewatering device of Florida phosphatic claywastes was studied. Several experiments were conducted in order to determine the important fabrication and operating parameters. Results from the experiments indicated flint the dosage of polyethylene oxide required to form a satisfactory product cake could be reduced by using the rotary drum, which introduces less shear stress into the fluid than a constant stirred tank mixer. It was found that the length of the mixer was the most important parameter. Increased length increased the retention time the flocs stayed in the mixer without dewatering. Such increased time decreased the stability of the flocs. Through analysis of residence time distribution data it was found that the longer mixers approached plug flow characteristics. Other important parameters were trommel length and rotational speed. Mixers from 10 cm diameter to 35.6 cm diameter were tested with good results.

Jan 1, 1982

By Sachihiko Tokunaga, Hirofumi Taguchi, Kenji Maruyama, Hidenori Takahashi, Yoshiyuki Morikawa

"Abstract The present study proposed a new liquefaction countermeasure to improve sandy ground and conducted a trial execution. The new method is a floating-type and lattice-shaped cement treatment method, where cement-treated soil is not fixed to a non-liquefiable stratum. A fixed structure such as treated soil should be formed at the side of the floating-type treated soil to reduce its lateral displacement. In the study, one-dimensional dynamic response analyses were first conducted to confirm the mechanism of the new method. Then, a series of centrifuge model tests were performed to demonstrate the effect under a stress condition at the prototype scale. The analyses and model tests confirmed the effect of the liquefaction countermeasure. Finally, trial executions were carried out to confirm high-quality vertical execution.INTRODUCTIONLiquefaction induced by an earthquake generates sand boiling and ground settlement. Other problems have also been reported, including a decrease in bearing capacity and an increase in the horizontal earth pressure against retaining walls. To prevent these problems caused by liquefaction of the ground, various countermeasures have been proposed, such as cement deep mixing and high-pressure jet mixing methods. These methods have the big advantage of being applicable to ground that contains soil with a fine-grain fraction. Furthermore, the unnecessary displacement caused by the construction can be reduced. In Japan, a lattice-shaped cement-treatment method has frequently been used at many construction sites to prevent liquefaction, where cement-treated piles are intersected to form a lattice, as shown in Fig. 1. The lattice-shaped walls can reduce the shear stress generated by an earthquake, restricting the liquefaction at that location. However, the construction cost of the cement treatment is relatively high compared to other methods such as the sand compaction pile (SCP) method, and needs to be reduced. In particular, the cost of the high-pressure jet mixing method, which can be applied to the liquefiable ground under existing structures, is significantly high. Therefore, decreasing the total volume of the cement treatment is necessary to reduce the construction cost."

Jan 1, 2014

Ten years ago, only 3% of Consol's underground coal production resulted from using the longwall mining method. Today, that figure has grown to 45% and has helped the Pittsburgh-based concern fuel an upswing in productivity. The company reported that productivity at its underground mines, excluding labor strike periods, increased 24% between 1978 and 1981. Last year, an additional 8% increase was achieved. Efforts such as improved safety, training, engineering, and maintenance programs as well as the closing of unproductive mines has contributed to these gains, according to Joseph M. Richards, Consol's executive vice president of operations. But, Richards adds, a great part of the credit goes to longwall mining. What is Longwall Mining? To fully appreciate the advantages of longwall, one needs an understanding of how mining is done by other methods. For instance, in both conventional and continuous mining, rooms or tunnels are dug in the coal seam. Pillars of coal are left standing to support the roof as mining moves forward in the seam. In conventional mining, a slot is cut in the base of the seam and holes for blasting are drilled. After blasting, the coal is loaded. A more efficient method - continuous mining - uses a machine that combines cutting and loading. Longwall mining, by contrast, works backwards from the end of a panel. Two parallel sets of tunnels (development panels) are cut into a seam with continuous mining machines, then connected with a set of crosscuts at the far end. Min¬ing then proceeds back toward the entrance. Longwall mining employs some very productive machines. Large drum shearers, for example, run on a track along the length of the coal face for some 150-180 m (500-600 ft). The shearers cut the coal which falls onto a conveyor system or pan that also runs the entire length of the face. The longwall crew works under a roof of heavy steel supports called shields. As the coal is removed, shearers, pans, and shields are moved forward by hydraulic rams. The roof is allowed to collapse behind the shields. In addition to increasing production, longwall mining is considered to be safer because the miners work under strong steel shields. New designs have made them more rugged and maintenance free, as well as more stable on soft mine floors. Early roof supports, called chocks, had gaps in the roof canopies. The new roof shields now cover the entire working area and are better able to prevent roof material from falling into the working area, thereby improving safety and productivity. Longwall mining also results in a cleaner product in many mines. If the first layer of rock over the coal seam is thin, it might have to be removed with the coal in a room-and-pillar operation so a

Jan 11, 1983

By D. Schleiss

Reduced access to knowledgeable workers is creating challenges for operations. We are doing more 4D Operations - dirty, dull, dangerous, and distant. Personnel costs in these environments are high, and it is not always possible to get the people where you need them. Integrated Operations is a strategy to integrate people, process, and technology for faster and better decision making. Adopting an integrated operations approach can help to relocate personnel, improve collaboration, and align objectives to deliver reduced costs and improved performance. In this paper, the authors will highlight the required infrastructure to enable an Integrated Operations platform. Key decision points for enabling this technology for both Greenfield projects and existing mines will be discussed. Furthermore, the benefits and improved return on investment that result from deployment of an Integrated Operations strategy will be presented.

Jan 1, 2014

By L. R. Herrmann

The most fundamental feature of fracture is that it involves separation. Such separation can arise by either separation of molecules, more or less along the line joining their centers (tension), or by d sliding separation roughly perpendicular to that line (shear). Theoretically, a perfect crystal could never be broken by the application of perfectly axial compressive stress (until some sub-molecular actions occur). In tension fields the calculated forces between molecules are extremely high. Consequently, calculations based on the forces known to exist in materials at the molecular and crystalline levels always lead to strengths which are two or three magnitudes higher than the strengths obtained in service or in the laboratory. It has been a major problem, therefore, to explain: (a) How fracture can occur in compressive stress states. (b) Why the observed strength of a material is always much lower than its calculated strength.

Jan 1, 2012

By R. G. Gifkins

Mean boundary migration depended linearly upon creep extension under various conditions. Prolonged annealing or air-casting increased the proportion of immobile boundaries at a given stage of tests. Grain growth during annealing followed a power law. The linking of migration and sliding in creep and models for migration are examined; activation energies are calculated from these models. Segregation of oxygen to boundaries appears to be a controlling factor. THE idea that boundary migration and boundary sliding during creep are linked has often been suggested,'-5 especially when evidence has been obtained for an alternation between the two processes. In simple bicrystals sliding can occur without any migration6 but in more complex bicrystals7 it is observed. McLean' and Couling and Roberts 5 made measurements of both sliding and migration; McLean concluded that there was no linking of the two processes whereas Couling and Roberts supported the idea. McLean' also developed a model for migration during creep and annealing. The present work was initiated as part of a study of the recrystallization of lead during creep9 but has been extended to examine some aspects of the mechanism of migration. MATERIALS AND METHODS Specially refined high-purity lead* was used; the total of impurities, excluding oxygen, was 0.0008 wt pct. Oxygen was removed as far as possible by melting in vacuo, treating at 550" to 600°C with hydrogen and then casting at 450°C under a vacuum of 10-2 mm Hg; the oxygen was then believed to be 0.00005 wt pct. Specimens were made from extruded strip and then annealed at the required temperature in an air oven, controlled to 5 lac. They were then polished in a mixture of acetic acid and hydrogen peroxide. At this stage some specimens were etched to give grain contrast and their grain sizes determined by the intercept method. Migration of boundaries during creep was measured on the surface of polished (not etched) specimens, directly loaded at room temperature (22°C) or 50°C (52"C) to initial stresses of 300 to 700 1b per sq in. Twenty six vacuum-cast hydrogen-reduced specimens were used and, in addition, two specimens were from material air cast after hydrogen reduction ("partial" air cast) and two from air-cast material not treated with hydrogen ("full" air cast). Duplicates were made in the majority of tests. At intervals through the creep tests, specimens were unloaded and the migration measured, normal to the direction of migration at the point of measurement, for each boundary along standard traverses. Usually between 110 to 180 boundaries were measured at each of some twelve stages of the tests. Migration was measured on the projected image (X100) using prism illumination. Fig. 1 illustrates the method of measurement and shows the kind of variation of migration found from boundary to boundary and along particular boundaries. Fig. 2 gives an example of more extensive migration. The mean value of distance migrated was generally reproducible to *10 pct but occasional points gave a scatter of *20 pct. The correctibn applied by McLean8 to allow for the contribution sliding makes to the apparent distance of migration could not be used, for the sliding at most boundaries was too small to measure with the equipment available. There were two reasons for supposing the correction unnecessary in the present work;

Jan 1, 1960

By Conny Postupack

To make money in mining coal you have to sell it for a lot more than it cost you to get it out of the ground. And yet, every year it cost us more and more to stay inbusiness, while the price we get for coal does not increase at the same rate.

Jan 1, 1990

By M. A. Trevits, J. E. Urosek, A. C. Smith, M. P. Valoski

The National Institute for Occupational Safety and Health (NIOSH), in partnership with the Mine Safety and Health Administration (MSHA), is conducting research to test, evaluate, improve or modify coal mine fire-fighting strategies and methodologies through large-scale tests. Since wood is the second most abundant fuel available during a coal mine fire, it was decided that series of large-scale wood crib fire tests were needed to measure the products of combustion and to observe the capability of commonly available direct application fire suppression equipment, namely, fire extinguishers, water and gas-enhanced foam. This paper discusses the wood crib fire tests, provides insight into the products of combustion and describes observations made during the application of the fire suppression agents.

By B. A. Day

The traditional view taken of commodity prices is that they are cyclical, with strong demand boosting prices and attracting new suppliers. The resulting increased supply pushes prices down with consequent exit of the higher cost producers. And so the process repeats itself. Little attention is given to shifts in underlying global issues and their effect on the traditional process which is seen as being controlled by ?amorphous? market forces with producers profiting from the good times and trying to survive in the bad.. The questions posed are: does this still apply and will it apply into the future? What new factors are affecting the cycles? Can we expect to find the traditional commodity cycles repeated in the 21stcentury? Are producers powerless within the forces of the cycles? Forces likely to affect future commodity prices will be suggested, using gold, zinc, copper, tin and coal as case studies. The long-term downward trend in the real price of commodities is identified.

Jan 1, 2000

By A. Nieto

A vehicle proximity warning–collision avoidance system is being developed using GPS and wireless local area networks to improve safety of off-highway trucks in open pit mines. After two-and a-half years of research, software development, and laboratory testing, field tests were carried out at operating limestone quarries and open pit mining operations to evaluate GPS accuracy and overall system effectiveness under rugged operating conditions. This article describes the progress made on this NIOSH-funded project and discusses the GPS accuracy tests and overall system tests that were carried out during the year 2001 at the Colorado School of Mines Survey Field and at the Morenci open pit copper mine in Arizona. Keywords: GPS, Advanced Mining, Virtual Reality, Wireless Networks, Proximity Warning

Jan 1, 2003

By Y Sha

During the last two decades, China has expanded its iron and steel industry very quickly, from less than 100 Mt/a steel production to over 700 Mt/a. It caused big increases in both domestic iron ore production and imported iron ore quantities year by year. The mode of iron ore supply has changed from almost all domestic supply to major tonnes of imported ore plus domestic ore supply. Over 200 blast furnaces with volumes larger than 1000 m3 each have been built and put into operation. Sinter machines have been enlarged quickly. There are now 135 sinter machines with =200 m2 sintering area each. Pellet production increased from 11.94 Mt in 1999 to 210 Mt in 2011, resulting from rapidly increasing domestic concentrate supply and rapid development of the grate-kiln process. The typical ferrous burden constitution is high basicity sinter plus pellets plus lump. The pellet proportion increased and the sinter proportion decreased gradually. A lot of technical improvements, like deep bed sintering, sintering with a high ratio of limonite, composite sintering, pellet process optimisation, a high ratio of hematite in pelletisation, blast furnace operation with low-grade ferrous burdens and hazardous element control, etc have been made to enhance iron burden quality and to reduce hot metal cost. Chinese iron and steel production is expected to increase slightly in the next few years. Its overcapacity should be controlled effectively. Given the variations of iron ore supply, pellet production will keep progressing in terms of production scale and pellet quality, the sintering process will be improved further by various measures to utilise different ores efficiently, and ferrous burden constitution will be optimised continuously to realise the lowest cost of hot metal production.CITATION:Sha, Y and Wang, Z, 2013. The Chinese iron and steel industry response to the challenges of iron ore supply, in Proceedings Iron Ore 2013 , pp 7-14 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By W. A. Krivsky, R. Schuhmann

Jan 1, 1962

By Tatsunori Matsumoto

In order to investigate the variation of the load-displacement relations of piles in a site, vertical load tests were carried out on 25 small diameter steel pipe piles. Out of 25 piles, 15 piles were close-ended pipe piles attached with a blade at the pile toe and 10 piles were open-ended pipe piles. To carry out these load tests in a short period, two types of rapid load test methods, Spring hammer load test and Falling mass load test, were employed. The load tests of all piles were completed in two days with 180 blows in total. In order to estimate a static load-displacement of a pile, non-linear damping method was used. It is shown from the test results that the performance of the pipe piles such as the ultimate pile resistance and the initial pile head stiffness is improved by re-driving.

Jan 1, 2006

By I Coombes, M Trim, Y Sun, M McRae, A Spiegl, H Lagger, A Amon, P Barraclough, M Villeneuve

The Brisbane Airport Link Project (AirportlinkM7) includes the design and construction of more than 12.5 km of tunnels, with the Kedron interchange including four ramp tunnels that intersect with mainline tunnels and result in caverns with spans of up to 26 m. These caverns are in highly variable ground conditions with less than 35 m of cover underlying residential neighbourhoods and commercial properties. The Kedron caverns were constructed using the sequential excavation method (SEM). Owing to complex geometry and excavation sequence, the caverns were designed based on numerical modelling methods, including both two- and three-dimensional models. These numerical methods were used to develop a suite of support types with excavation sequences for the expected range of ground conditions. A combination of methods that included in-tunnel monitoring (convergence monitoring and extensometers), probe holes, endoscope probes, face mapping and ground settlement measurements were used to verify performance of the tunnel support systems and to select and refine the appropriate support system for each section of the caverns. The construction monitoring data indicated that numerical modelling can provide a good basis for predicting the performance of large-span underground openings in highly variable ground conditions. This paper presents a comparison of the performance of the caverns predicted by state-of-the-art numerical models and the actual measured performance.CITATION:McRae, M, Villeneuve, M, Trim, M, Sun, Y, Barraclough, P, Spiegl, A, Amon, A, Lagger, H and Coombes, I, 2014. Brisbane Airport Link Project – design and construction of the 26 m span Kedron Caverns: comparing monitoring data with the design, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 295–306 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By T. F. Bower, M. C. Flemings

Results are reported of a study of surface dendrilic structure of an Al- Cu alloy solidified against a chill wall. Most primary and secondary "arms " in the surface dendritic structure are arranged orthogonally, giving the impression of strong preferred orientalion on the surface. However, no such preferred orientation exists and it is therefore evident the arms do not represent (100) directions. The primary arms are shown to be interseclions of a (100) plane wilh the chill plane, or, equally often. the projeclion of a (100) direction on the chill plane. Secondary dendrite arms are usually within a few degrees of 90 deg to the primary arm, independent of grain orientalion. Prirary, secondary, and higher-order surface dendrite arms almost always represenl intersections of (100) platzes with the chill surace, or pvojections of (100) direclions. Growlh of secondary arms is favored on the side of the primary arm where a (100) direclion points toward the chill surfAce a1 a Lou, angle. Surface dendrile arms are often observed to be bent. In these cases, the crystal lallice changes orientation; bending is concave to the chill surface. In a previous paper,' a technique was discussed whereby large grains can be obtained at a chill surface. The technique used involves quickly drawing superheated liquid A1-4.5 pct Cu alloy into a thin copper mold, so that the mold is full well before solidification begins. The chill surfaces employed are polished copper blocks coated with amorphous carbon. Shrinkage during solidification between dendrite arms and grains delineates both, without the need for polishing or etching of the cast surface. The grain structure of the chill surface was discussed in a previous paper;' in this paper, the dendrite arms within each grain are examined. Previous work on surface dendrites includes that of Edmunds, who studied the development of preferred orientation in zinc, cadmium, and magnesium.' In zinc and cadmium, he found that the surface region has a (0001) texture (parallel to the chill surface). Walton and Chalmers reasoned that, since the fast growth (1010) directions are in the basal plane, nuclei which have this plane parallel to the mold wall would produce larger grains than nuclei with other orientations. Hence, the texture observed is as expected.3 The same authors, in measurements on aluminum ingots, found no preferred orientation at the mold wall. However, the X-ray technique they used measured the preferred orientation in terms of grain numbers, not grain areas; larger grains were weighted equally with small ones. No preferred orientation is expected on this basis at the chill surface. In a later paper,' Edmunds stated that experiments show a random grain orientation at the surface in die cast aluminum; his technique, also used in his earlier paper, takes account of grain area. Little work has been published on the dendritic structure of metal chill grains. Recent work of Biloni and Chalmers on "predendritic growth" shows the change in morphology from spherical to dendritic during the initial stages of freezing, 5 but this work did not include detailed examination of the fully developed dendrites. Other pertinent work includes that of Lin-denmeyer, who investigated the growth of ice dendrites. 6 When growth was on a substrate, the dendrite axes were bent. The bend corresponded to a change in orientation of the crystal lattice and occurred in such a way as to align the basal plane to the substrate. DENDRITE STRUCTURE Fig. 1 shows the chill surface of a typical casting poured above the critical temperature necessary to produce coarse grains. A cursory examination of these grains shows that the surface dendrite arms within most of the grains are oriented roughly perpendicular to each other. One is tempted to assume that these are (100) directions and that, therefore, marked preferred orientation exists at the chill face. This, however, is not the case. Each of the grains in the casting of Fig. 1 was separately identified, Fig. 2, and its orientation determined by the Laue back-reflect ion method. Results are given in Fig. 3 and it is seen there that no preferred orientation exists. Even when grain area is accounted for, there is no significant preferred orientation. The relationship between surface grain structure and crystal orientation was then obtained by assigning X and Y axes to the casting surface, Fig. 1, and assigning the same axes to the stereographic projections of each grain. Thus, the visible surface structure could be compared readily with grain orientation. This was done for fifty-five of the grains of Fig. 1. Results of this study on three typical grains are described below, and some general observations given subsequently. Fig. 4 shows the structure and stereographic projection of a grain which lies near the (100) zone (with respect to the casting surface). The X and Y directions are marked on the projection, and the photomicrograph mounted with the same orientation. Poles of the stereographic projection represent crys-tallographic directions in the grain which point out of the casting, toward the chill. Two (100) directions are shown in Fig. 4. A line joining the center of the projection and a pole represents the projection of the pole onto the X-Y plane (chill surface). Two such lines are shown in Fig. 4 (solid lines). A line joining the intersection of a great circle with the circumference of the projection gives the trace of a crystallo-graphic plane in the chill surface; two such traces are shown (dashed lines).

Jan 1, 1968

By Ulrich Paschedag

The WESTFALIA group of companies developer and manufactures underground mining machinery for complete high-performance longwalls. WESTFALIA uses a state of the art electrohydraulic system as the most important component for the realisation of today's fully automated plow or shearer longwall. The shield control unit (SCU) allows maximum custom designed software flexiblity as well as maximum hardware reliability. The master control unit (MCU) monitors shield support data as well as the plow/shearer position. By using an industry standard PC in an explosion-proof box with an intransically safe keyboard nearly unlimited software capabilities can be obtained with inexpensive hardware. Among various other modes of operation this MCU allows the monitoring and recording of data which can be transmitted to a surface computer. Production and operational adjustments can be made by the mine management based on the MCU information. Statistical analysis of the distribution of roof pressure under various conditions is also possible. The WESTFALIA automation system PM-4 gives the operator maximum flexibility and helps the mine management to run their longwall more efficiently and safely.

Jan 1, 1994

By N M. Caira

The North Arm of Sulawesi hosts numerous gold and base metal occurrences. Compilation and analysis of geological, tectonic, geochemical and isotopic age date data collected over the past six years on the central part of this region have resulted in the definition of 184 prospects and mineral occurrences of various styles occurring in diverse geological settings representing varying tectonic environments and erosional levels. Mineralisation of the following styles have been recognised: porphyry Cu-Au; porphyry-related gold and base metal veins; high-sulphidation Cu-Au-As; low-sulphidation epithermal Au; hydrothermal breccias; and sediment-hosted Au mineralisation. Clusters of occurrences/prospects form mineralised districts representative of magmatic systems with characteristics determined by the tectonic environment prevailing during formation and the subsequent level of exposure by erosion. Distinctly different Miocene and Pliocene porphyry systems are now recognised whilst most of the remaining epithermal mineralisation is thought to be Pliocene or later. The central North Arm of Sulawesi is composed of a Miocene magmatic island arc that is built on an Early Tertiary basement of predominantly oceanic basaltic rocks and overprinted by a Pliocene magmatic arc. A structural fabric dominated by SSE arc-normal and ESE arc-parallel faults was established during the Miocene under a dextral wrench regime and intersections of these major fault sets are favoured sites for Miocene porphyry Cu-Au mineralisation. Strong dextral tension caused by the collision of the Sula Platform, at the close of the Miocene, led to arc-parallel rifting. Sinistral reactivation of the major Miocene structures in the Pliocene led to further rifting, and ENE-dilation. Pliocene intrusions and related mineralisation exploit these dilatant settings. Miocene porphyry Cu-Au mineralisation occurs where late-Miocene quartz diorite stocks have intruded the margins of earlier Miocene plutons of intermediate composition. Porphyry centres have associated peripheral base metal veins, and skarns. Overprinting of porphyry vein sets by epithermal veins is common. Sediment-hosted gold mineralisation occurs in calcareous sediments associated with the Miocene arc. Remnants of the Pliocene volcanic arc, comprised of dacite volcanics, intrusions and voluminous pyroclastics, dominate the south coast and host porphyry Cu-Au, high sulphidation Cu-Au-As deposits, low-sulphidation epithermal Au veins and disseminated gold mineralisation. In some prospects, mineralised sinters are preserved adjacent to vein systems and deeper mineralised stockworks. Diatremes are common and large caldera structures have been identified. Pliocene stocks and porphyry dyke swarms penetrate the main central and northern parts of the Miocene- arc introducing additional porphyry Cu-Au, base metal hydrothermal breccias and low-sulphidation gold veins. Rapid uplift and erosion has resulted in a highly variable preservation of styles of mineralisation adding further diversity within the mineralised districts and telescoping within deposits.

Jan 1, 1999

By H Susanto, N Belluz, D Flint, A Edw

The Deep Ore Zone (DOZ) is a block cave mining operation exploiting a diluted reserve of 131 million tonnes grading 1.06 per cent copper and 0.81 g/t gold in the lower portion of the Ertsberg East Skarn System (EESS). The EESS is a calcium-magnesium silicate skarn containing in excess of 250 million tonnes of copper-gold ore, located in the Ertsberg Mining District on the crest of the Jawawijaya mountain range in the highlands of Irian Jaya, Indonesia. The EESS was discovered in 1968 where it cropped out at an elevation of 4050 metres above sea level. The Ertsberg Mining District is underlain by siliclastic carbonate and siltstone formations of Jurassic to Tertiary age. The sediments have been folded and are cut by major bedding subparallel and crosscutting structures. Intrusion of a series of igneous bodies post-dates folding and faulting. These I-type intrusions are the source for the copper-gold mineralisation found in the Ertsberg Mining District. The EESS is hosted by carbonates of the Tertiary Waripi and Faumai Formations that have been altered to calcium-magnesium silicate skarn and is situated on the southern limb of a northwest-trending syncline. The EESS is an essentially vertical tabular body with a vertical extent of at least 1200 metres and a lateral extent of up to 1000 metres. The width of the EESS averages 200 metres and locally is in excess of 300 metres. The northeast (hangingwall) contact of the EESS is a skarn reaction front in sudden contact with barren marbles. This contact coincides with a zone of localised faulting and brecciation. The EESS is bounded to the southwest (footwall) by the Ertsberg Diorite, a 3.25 Ma old intrusive. The DOZ block cave operation extends from 3040 metres above sea level to a maximum of 3388 metres above sea level, has a length of 860 metres and a maximum width of 350 metres. The DOZ is a high temperature skarn with a prograde forsterite/diopside mineralogy whose protolith is the dolomitic Tertiary Waripi Formation. The principal retrograde alteration minerals include tremolite, actinolite, serpentine, talc and chlorite. Grade is highest where bornite occurs in large dense complex intergrowths with magnetite and anhydrite. Grade has been locally enhanced in the DOZ by a late-stage pyrite-chalcopyrite hydrothermal alteration event with associated brecciation. Ertsberg Diorite along the footwall of the skarn is also included in the reserve where it is mineralised endoskarn or has been mineralised by porphyrytic or late stage hydrothermal alteration. Formation of the EESS was initiated by contact metamorphism during the intrusion of the Ertsberg Diorite with later metasomatic alteration during both prograde and retrograde phases. The bulk of sulphide mineralisation formed late in the retrograde phase. The EESS is open along strike to the northwest and down-dip with on-going exploration of these areas. Current exploration is targeting both endoskarn and porphyry style alteration and mineralisation of the Ertsberg Diorite.

Jan 1, 1999