Open-pit Operations Research Articles

Social mobilisation and violence at the mining frontier: The case of Honduras

This paper documents opposition to mining in Honduras, a country at the verge of an attempted ‘mining boom’ since the ratification of a new mining law in April 2013. It analyses how a broad movement – involving NGOs, social movements and local communities – engages in opposition to the extractive industry, declared a national development priority by the Honduran government. The movement emerged in the first decade of the 21st century in response to the establishment of two industrial mines and builds on the negative impact of Goldcorp’s open-pit operation in Valle de Siria, where serious health problems have been reported. The anti-mining movement has devised a successful campaign about access to uncontaminated water. By contrast, the extractive industry and the central government have been far less successful in convincing local populations of the potential benefits of mining. As political opportunities for dialogue with the central government have been lacking since the 2009 coup d’état, the anti-mining movement increasingly turned to the local level, motivating communities to declare their municipality free of mining via public referendums. In turn, when legal means to obtain consent from communities for mining projects fail, the ‘extractive frontier’ is frequently extended through criminalisation of dissent and the threat of violence.

Numerical modeling of open pit (OP) to underground (UG) transition in coal mining

Abstract The primary objective of the present paper is an attempt at evaluating the influence of sub-level caving operations on the slope stability of a still-functioning open pit coal mine in Vietnam. Initially, various methods of predicting the impact of underground mining on surface stability are discussed. Those theoretical considerations were later utilized in the process of constructing a Flac-2D-software-based numerical model for calculating the influence of underground operation on the deformation and possible loss of stability of an open pit slope. The numerical analysis proved that the values of open pit slope displacements were affected mainly by underground exploitation depth, direction of operation (i.e., from one slope to the other) and the distance from the slope plane. Real geomechanical strata parameters from the Vietnamese coal basin of Cam Pha were used in the modeling process. The paper is, therefore, a critical review of the hitherto proposed methods of predicting the impact of underground operation (UG) on open pit mining (OP), illustrated with selected examples of case studies on OP-UG interaction, followed by an original experiment based on numerical modeling method. This is first such study for the genuine conditions of the coal mining in Vietnam. The obtained results, however, should not be generalized due to a highly specific character of the analyzed phenomenon of mining-induced surface deformation. The practical implications of the study may occur extremely useful in the case of an UG-OP transition. Such a transition is often necessary for both technical and economical reasons, as in some coal basins open pit operations at greater depths occur unfeasible, which calls for a proper selection of parameters for a planned underground operation.

Optimizing the open pit-to-underground mining transition

A large number of metal deposits are initially extracted via surface methods, but then transition underground without necessarily ceasing to operate above ground. Currently, most mine operators schedule the open pit and underground operations independently and then merge the two, creating a myopic solution. We present a methodology to maximize the NPV for an entire metal deposit by determining the spatial expanse and production quantities of both the open pit and underground mines while adhering to operational production and processing constraints. By taking advantage of a new linear programming solution algorithm and using an ad-hoc branch-and-bound scheme, we solve real-world scenarios of our transition model to near optimality in a few hours, where such scenarios were otherwise completely intractable. The decision of where and when to transition changes the net present value of the mine by hundreds of millions of dollars.

Globally optimising open-pit and underground mining operations under geological uncertainty

A mining complex may be comprised of multiple components, including open-pit and underground operations. Traditional approaches in mine planning do not account for the various components simultaneously leading to under-value solutions. Over the last decade, some methods have been developed to incorporate multiple components of the mining value chain during optimisation. Even though these new methods incorporate more decisions and flexibility to the optimisation of a mining complex, they may either ignore uncertainties associated with the mining project or consider decisions taken before optimisation. This paper presents a method that optimises mining complexes comprised of multiple open-pits, underground operations and processing destinations. Mining, blending, processing and transportation decision variables are simultaneously optimised while accounting for geological uncertainty. The method uses a simulated annealing algorithm at different decision levels in order to generate a stochastic-based extraction sequence and processing policies. A case study shows its ability to generate a higher NPV while facing a reduced amount of risk when compared to traditional optimisation methods.

Implications of collecting additional data for slope design in an open pit operation

Implications of collecting additional data for slope design in an open pit operation

Application of vibration analysis of mining shovels for diggability assessment in open-pit operations

Over the past decades, technological advances and mining requirements have led to larger, more complex and more costly equipment. This trend in mining equipment has resulted in changing maintenance strategies from unplanned and scheduled maintenance to a condition-based maintenance (CBM) strategy. However, condition monitoring techniques used in CBM programmes are more than a maintenance management tool; they can provide the means to improve machine performance, production capacity and overall mine production. Vibration monitoring is usually the dominant technique of CBM programmes for critical machines such as electric rope shovels. It has been demonstrated that abnormal machine behaviour can be diagnosed using vibration monitoring techniques. However, this article aims to show the applicability of vibration monitoring of electric rope shovels for post-blast assessment rather than maintenance management. As a result, an electric rope shovel’s vibrations experienced by its boom during different operating conditions are measured by a tri-axial accelerometer mounted inside an enclosure on the side of shovel’s boom. The results show that the amount of apparent energy experienced by the tri-axial accelerometer can be used as an indirect measure of muck-pile digging conditions. Additionally, instantaneous and/or averaged vibration can be used as part of a system to monitor operator performance which potentially leads towards a machine with higher reliability, availability and maintainability and with higher productivity.

Geotechnical investigation and design of leaching heap No. 2, Meydook copper mine, Iran

The main objective of this paper was to investigate the behavior of waste rock material as a foundation for the construction of leaching heaps. In mountainous open pit operations, selection of an appropriate location for dumping waste rock material or building leaching heaps is a major challenge. Meydook copper mine is one of the largest copper operations in Iran. The mine has operated about 2 decades. The current waste rock dump is located 4km from the operation site but a new proposed dump only 1km away will be built in a valley to the North of the pit. Construction of leaching heap No. 2 has been on the mine technical department agenda. The main objective of the project is to evaluate the potential for construction of heap No. 2 on a waste dump. Considering the project condition, a 3D analysis of heap major structures including; valley rock foundation, waste dump, and low grade ore was carried out. Five sets of analyses were conducted and the displacement and stress fields were computed. In all analyses conducted, the subsidence profile was determined for the valley base rock and heap foundation (waste dump). The analyses showed that the maximum settlement at the heap base would be only 4–5cm so the waste dump provides a safe and reliable base for the heap construction. A sensitivity analysis of heap mechanical parameters was also conducted. The results showed that if the friction angle of heap material was reduced below 25°, the heap walls became unstable and the heap geometry would need to be redesigned.

COMPLEMENTARY USE OF INFORMATION FROM SPACE-BASED DINSAR AND FIELD MEASURING SYSTEMS FOR OPERATIONAL MONITORING PURPOSES IN OPEN PIT IRON MINES OF CARAJÁS MINING COMPLEX (BRAZILIAN AMAZON REGION)

Abstract. Now spanning five simultaneous open-pit operations with exploration carried out through open pit benching, Carajás complex encompasses the world´s largest iron reserves. Open pit mining operations in the area can lead to slope instabilities with risks to personnel, equipment and production due to intense excavations in rock products of low geomechanical quality, blasting practices and heavy precipitation. Thus, an effective prediction and management of surface deformations should be a key concern for the mining operations. The ground displacement monitoring techniques in Carajás include surface measurement techniques at discrete points (total station/reflective prisms) and over area using SSR (Slope Stability Radar, a ground based radar). On the other hand, DInSAR techniques are receiving relevance in the mining industry for reasons such a synoptic and continuous coverage without the need for ground instrumentation and a point-to-point good accuracy of measuring displacements (millimeter to centimeter scale) over a dense grid. Using a stack of 33 StripMap TerraSAR-X images acquired over Carajás covering the time span from March 2012 to April 2013, a monitoring approach is discussed based on the complementary use of information provided by DInSAR (DInSAR Time-Series and Persistent Scatterer Interferometry) and surface measuring techniques (total station/prisms, ground-based radar).

Hydrogeochemistry and microbiology of mine drainage: An update

The extraction of mineral resources requires access through underground workings, or open pit operations, or through drillholes for solution mining. Additionally, mineral processing can generate large quantities of waste, including mill tailings, waste rock and refinery wastes, heap leach pads, and slag. Thus, through mining and mineral processing activities, large surface areas of sulfide minerals can be exposed to oxygen, water, and microbes, resulting in accelerated oxidation of sulfide and other minerals and the potential for the generation of low-quality drainage. The oxidation of sulfide minerals in mine wastes is accelerated by microbial catalysis of the oxidation of aqueous ferrous iron and sulfide. These reactions, particularly when combined with evaporation, can lead to extremely acidic drainage and very high concentrations of dissolved constituents. Although acid mine drainage is the most prevalent and damaging environmental concern associated with mining activities, generation of saline, basic and neutral drainage containing elevated concentrations of dissolved metals, non-metals, and metalloids has recently been recognized as a potential environmental concern. Acid neutralization reactions through the dissolution of carbonate, hydroxide, and silicate minerals and formation of secondary aluminum and ferric hydroxide phases can moderate the effects of acid generation and enhance the formation of secondary hydrated iron and aluminum minerals which may lessen the concentration of dissolved metals. Numerical models provide powerful tools for assessing impacts of these reactions on water quality.

The role of Carclaze tin mine in eighteenth and nineteenth century geotourism

Abstract Carclaze tin mine was an open pit operation which exploited a massive cassiterite-bearing greisen-bordered quartz-tourmaline vein stockwork, straddling the granite margin near St Austell. It became a ‘must-see’ location for visitors to Cornwall from all over Europe in the late eighteenth and early nineteenth centuries, particularly those interested in the then-fashionable pursuits of geology and mineralogy. Intellectually, the early scientific interest in Carclaze can be seen as part of the Enlightenment, but in the nineteenth century the influence of Romanticism can also be detected. Much of the attraction was due to the openness and accessibility of Carclaze pit, which allowed the geology to be easily appreciated. This resulted in the development of the mine being particularly well documented by a large number of contemporary accounts and illustrations, which has also enabled an early, partly underground, canal to be rediscovered. The earliest account was by the Frenchman M. Jars who visited the pit in 1765; this was followed by accounts by other French geotourists from the early to mid-nineteenth century. The Germans Von Oeynhausen and Von Dechen provided the first geological map and cross-section of the pit in 1829. Accounts by local Cornish authors emphasize that Carclaze was a significant ‘sight’ for visitors. The earliest account of the pit by an English geologist was by Adam Sedgwick in 1822 ; in later publications he speculated on the formation of parallel vein swarms and schorl rock, partly based on his observations in Carclaze Old Tin Pit. De la Beche provided a pen-and-ink sketch of the south face of the pit in 1839. There are also many accounts by non-scientific visitors throughout the nineteenth century and, together with published lithographs, these are particularly helpful in describing and showing the methods of mining. Tin extraction from the Old Tin Pit had practically ceased by the mid-nineteenth century as production switched to china clay from new pits to the north. The historic south face of the Old Tin Pit, as illustrated by De La Beche, has survived into the twenty-first century and has been designated a County Geology Site by the Cornwall Geoconservation Group, although it is now threatened by housing and industrial development proposals.

Iron Will: Cleveland-Cliffs and the Mining of Iron Ore, 1847–2006 by Terry S. Reynolds and Virginia P. Dawson (review)

Reviewed by: Iron Will: Cleveland-Cliffs and the Mining of Iron Ore, 1847–2006 by Terry S. Reynolds and Virginia P. Dawson Clayton Ruminski Iron Will: Cleveland-Cliffs and the Mining of Iron Ore, 1847–2006. By Terry S. Reynolds and Virginia P. Dawson. (Detroit: Wayne State Univ. Press, 2011. 351 pp. Cloth $44.95, ISBN 978-0-8143-3511-6.) Terry S. Reynolds and Virginia P. Dawson’s cowritten Iron Will is an excellent example of business and industrial history, a relatively narrow field of study. Sanctioned as a company history by the last remaining independent iron-mining company now known as Cliffs Natural Resources, the book chronicles “Cleveland Cliffs’ rise to prominence in the late nineteenth century, its struggle to survive the consolidation of the steel industry . . . , the shift from a labor intensive to a capital-intensive business . . . , and the company’s recent transition to a global iron merchant” (3). Despite the authors’ stringent focus upon the company itself, they also succeed in showing the importance the mining of iron ore in the Great Lakes region had on the Midwest and the subsequent development of the iron and steel industry in the late nineteenth and early twentieth centuries. As a professor of history at Michigan Technological University, Reynolds has published several essays on the mining of iron ore in the Great Lakes region and the Cleveland Iron Mining Company, while Dawson, president of History Enterprises, Inc., based in Cleveland, has authored several institutional histories. Included within the authors’ chronological narrative of Cleveland-Cliffs are a number of themes that embrace management, fear of mineral depletion, the cyclical nature of the iron and steel industry, and labor and technology (4). Throughout the book, these themes are well examined, particularly the company’s focus on iron-mining technology and its evolution, such as its transition to greater mechanized open-pit operations and underground mining in the 1860s and 1870s, which led to the depletion of high-grade ores, and the development of taconite pellets in the 1950s. In addition to the mining of iron ore, Dawson and Reynolds also focus on the company’s product diversification throughout various economic crises. Of particular interest is the company’s decision to go into the charcoal iron-smelting business during the depression years of the 1890s by utilizing Michigan’s vast woodlands for fuel for their blast furnaces and by exploiting its by-products, such as wood alcohol and acetone. By the turn of the twentieth century, Cleveland-Cliffs used partnerships to leverage capital resources, as well as investment in other companies, in order to ensure a market for their ore, one such example of the latter being the construction of a large blast furnace in Warren, Ohio, known as the Trumbull-Cliffs Furnace Co., a joint venture between Cleveland-Cliffs and the Trumbull Steel Co. Supplementing the authors’ extensive and detailed narrative is the use of a vast amount of primary sources, including internal reports and correspondence from the company, as well as daybooks and interviews with company personnel. Their sources, which include more than one hundred illustrations, provide a detailed exploration of the company’s history and deliver a unique glimpse [End Page 139] into one of the country’s most important raw-material providers. Despite its sanctioning by Cliffs Natural Resources, the authors successfully removed many of the downfalls that often accompany such a project, including discernible bias within the text and oversight of unscrupulous company labor relations and practice; however, removing all bias is a daunting task. Those interested in mining technology, iron and steel, business, economic, regional and industrial history will find Iron Will both an informative and important addition to the field. Both Dawson and Reynolds present a well-researched economic and industrial history of a company so essential to the Midwest’s industrial prowess throughout the twentieth century, yet with the expanding global economy, Cliffs Natural Resources is currently presented with similar challenges that had plagued them throughout the nineteenth and twentieth centuries. Clayton Ruminski Youngstown State University Copyright © 2014 The Kent State University Press

Integrating geological uncertainty into planning and modelling for modern and efficient dewatering concepts in large surface mines

The dewatering of subsurface unconsolidated rock strata is a critical prerequisite for many mining operations. The uncertainty in knowledge about the aquifer geometry is critical for both, the planning of directional dewatering drilling and the hydrological planning. This contribution focuses on investigating the influence of geological uncertainty on modern mining-related dewatering measures, namely horizontal directional dewatering wells. The traditional approach of drilling, planning and groundwater modelling on the basis of interpolated geological models is extended to integrate geological uncertainty. Using conditional simulation allows for more robust decisions in planning and subsequently increased efficiency. A case study in a large open pit operation demonstrates the benefit of using such methods. For a specified level of confidence, proposed methods provide a means of determining the number of samples required for the optimal placement of the filter section. The results also provide the means of quantifying uncertainty in predicting filter-well output.

Optimising combined open pit and underground strategic plan

This paper examines the case of a large open pit that is being planned at the site of an existing underground mine. Strategic planning work is undertaken to investigate the project value associated with an expansion of underground operations in conjunction with the proposed pit. Previous analysis by mine planners has determined that any depletion of the available open pit resource that changes the optimum pushback sequence will have a significant negative impact on overall project value. As a result, the main objective of this case study is to determine a strategic plan capable of yielding the optimum economic value for a combined underground–open pit operation.To investigate the viability of an underground expansion, a system to identify the stope resource that would add value to a combined operation if mined ahead of the pit is required. The main solution to this problem is the use of a resource model variable that defines the blocks which have greater discounted value if mined by stoping rather than by the open pit. From this potential underground resource, a series of mineable stope shells are generated at various cut-offs. This stope reserve data formed the input to an optimisation process used to optimise the underground mining plan, at a conceptual level, for various project configurations. Then, a dynamic programming mathematical program is used to evaluate the optimum value of a combined open pit and underground operation. The results generated in the case study presented herein provide a clear focus and direction for the next level of detailed mine design and planning.

Lead isotope evidence for metal dispersal at the Callahan Cu–Zn–Pb mine: Goose Pond tidal estuary, Maine, USA

The abandoned massive sulfide Callahan mine, coastal Maine, is unique because the open pit operation was sited in a drained marine estuary. About 5million tons of sulfide-bearing waste and unprocessed ore remain on-site bordering ponds and tidal flats that comprise the estuary proper (US-EPA Superfund site). The prominence and position of the waste relative to the tidal estuary constitute key features representing point sources of heavily contaminated debris. The massive sulfides are hosted by bimodal volcanic rocks of the Cambrian Castine Volcanics (basalt and rhyolite). Sulfide minerals include pyrite, sphalerite, chalcopyrite, and minor galena.A total of 275 analyses of Pb isotopes were done to fully characterize barren volcanic and hydrothermally-altered and mineralized rocks, massive sulfides and disseminated sulfides, waste rock (and tailings) and pond sediments from drill cores, pit water, seeps, and aquatic biota (lobsters, crabs, and bivalves). Lead isotope compositions show a wide range in 206Pb/204Pb (17.972–20.239), 207Pb/204Pb (15.525–15.664), and 208Pb/204Pb (37.591–40.000) and extend from relatively unradiogenic massive sulfides to more radiogenic country rocks and sediments. Tailings, waste rocks, and pond sediments plot in a triangular area in standard Pb isotope diagrams, limited by the trend for the relatively unradiogenic massive sulfides (nearly constant and low 206Pb/204Pb ratios and somewhat variable but low 207Pb/204Pb) and a poorly defined but relatively more radiogenic component (high 206Pb/204Pb and 207Pb/204Pb). Estuary sediments adjacent to the tailings pile and waste rocks have high metal abundances and exhibit the closest resemblance to the massive sulfide isotopic compositions. Bivalve shells obtained from estuary core sediments have growth zones with contents of Pb (5–76ppm), Zn (6–443ppm), and Cu (0–262ppm) that do not vary systematically from zone to zone, and that display no correlation to geographic distribution. The bivalves incorporated lead and other metals by ingesting suspended fine sulfide and silicate particles in addition to dissolved metals in the contaminated waters of the estuary.Water from the open pit and from seeps draining the tailings pile (206Pb/204Pb=17.972–18.504, 207Pb/204Pb=15.501–15.590) overlaps the massive sulfide ore. The pit water maintains its isotopic resemblance to the massive sulfides partly by the influx of seeps draining the rock waste and tailings piles. Galena and other sulfides weather as acidic meteoric water filters through the waste piles. Fractures provide avenues for in-situ oxidation, redistribution of Pb++ and SO4−−, and precipitation of fine-grained anglesite and/or cerussite (depending on the activities of H+, HCO3− and sulfate) in veinlets. A rise in pH above 4.5 and reaction of fluid with calcite in the tailings results in removal of more than 65% of Pb (including anglesite precipitate) by sorption to iron-oxyhydroxide precipitates. Pb transport in the Callahan system is thus likely to occur dominantly within solid phases (galena→anglesite+Fe-oxide→cerussite/carbonate+Fe-oxide) rather than dissolved in solution. Mass wasting of such fine Pb-bearing solid particulates from the waste and tailing piles likely accounts for the largest fraction of the Pb load in the estuary.Lead-bearing water from the Callahan mine is transferred out of the site and available to lobsters and crabs; the aquatic biota thus partly reflect compositions (206Pb/204Pb=18.021–18.539, 207Pb/204Pb=15.497–15.627) within the range of the ores and tailings. The contaminating effects radiating from the mine are intense adjoining the tailings piles and waste rock and adjacent to the site. These effects are significantly attenuated and essentially undistinguishable from natural background in a short distance (~1km).

THE PLATREEF OF THE BUSHVELD COMPLEX, SOUTH AFRICA: A NEW HYPOTHESIS OF MULTIPLE, NON-SEQUENTIAL MAGMA REPLENISHMENT BASED ON OBSERVATIONS AT THE AKANANI PROJECT, NORTH-WEST OF MOKOPANE

Detailed logging of relatively deep drill-core from the Akanani Project, in the northern limb of the Bushveld Complex, South Africa, has afforded new perspectives on the Platreef and its origins. In line with most recent studies, we believe the mineralization to be entirely orthomagmatic, rather than contamination-related. The primary orebody at Akanani is what we describe as the Main Mineralized Reef (MMR), which is situated within the Platreef Unit. Whereas the entire Platreef Unit may be as much as 250 m thick, the MMR is typically 4 to 30 m in thickness. In most previous descriptions of the Platreef, pyroxenite has been listed as an important constituent, but our investigations lead us to emphasize the importance of harzburgite (a lithology not previously described as a major component of the Platreef) as a critical component at Akanani. The MMR, despite being more complex than the seemingly layer-cake sequences associated with the Merensky Reef, is more or less laterally continuous (particularly in the southern or proximal facies at Akanani), and thus potentially more predictable than previously believed. Lithological relationships are significantly clearer than in the adjacent open pit operations, such as Sandsloot, where the sequence is disrupted by higher concentrations of dolomitic xenoliths and mineralization is located much closer to and even partially within the floor rocks to the intrusion. The principal component of the Platreef Unit at Akanani (sub-unit PU1) is a pervasive suite of complexly-layered medium to fine-grained gabbronorite-websterite lithologies, with minor feldspathic orthopyroxenite. These rocks are intercalated with numerous ultramafic layers (sub-unit PU2) that are dominated by harzburgite with minor chromitite. Coarse-grained (pegmatoidal) lithologies, including pyroxenite and gabbronorite, locally with minor olivine, constitute a third group (sub-unit PU3), typically associated spatially with the harzburgite. The MMR is a composite sequence of layers dominated by mineralized harzburgite. Pegmatoidal lithologies juxtaposed with the harzburgite are equally well mineralized, but rocks of the PU1 sub-unit incorporated within the reef-zone generally contain sparse PGE. We find that the three sub-units of the Platreef were emplaced subsequent to the lower few hundred meters of the overlying Main Zone. This is well illustrated in the northern (distal) part of Akanani where the poorly-mineralized PU1 component of the Platreef Unit and the most important of the harzburgite layers (part of the MMR) are intercalated with the Main Zone, into which they are interpreted to have intruded. The PU1 sub-unit crystallized from repeated additions of gabbroic magma and in situ differentiation prior to development of the ultramafic and pegmatoidal components of the Platreef Unit. The PU2 sub-unit formed from injections of ultramafic magma into the partially crystalline substrate, the latter being comprised of the PU1 sub-unit and the lowermost part of the Main Zone. The PU3 sub-unit developed from partial melting and recrystallization of the PU1 or Main Zone lithologies in response to intrusion of the ultramafic magmas. The latter are repeated at various depths in many drill-hole intersections, and the stratigraphic sequence of the PU1 and PU2/PU3 sub-units thus does not constitute a simple upward-younging sequence. This conflicts with the widely held view that the Platreef Unit is made up of three “reefs” emplaced more-or-less in stratigraphic sequence. Our categorization of the Platreef Unit into three sub-units is probably overly simplistic (and coincidental as regards the older A, B, C terminology) but has enabled us to cut to the chase and propose a new hypothesis directed at assisting the mining industry. Changes along strike are of fundamental significance, and in the northern part of Akanani, as well as the Drenthe property further north, the PU1 and PU2/PU3 sub-units increasingly bifurcate as they were intruded, lit-par-lit , into an increasingly greater thickness of Main Zone. The PGE at Akanani preferentially occur in association with the ultramafic lithologies. The gabbronorite-websterite lithologies are typically poorly mineralized, except where they are spatially associated with ultramafic lithologies. The location of the richest and most consistently mineralized ultramafic layers (i.e. the MMR) near the top of the Platreef Unit at Akanani is possibly significant, in that it mirrors the location of the Merensky Reef near the top of the Upper Critical Zone elsewhere in the Bushveld Complex. A key factor in the development of all mineralized reefs in the Bushveld Complex is, we believe, the non-sequential intrusion of discrete lineages of tholeiitic/gabbroic and ultramafic magmas (Mitchell and Scoon, 2007). Thus we suggest that both the Merensky Reef and the Platreef can be explained within our overarching hypothesis of lateral mixing, whereby thin sheets of PGE-rich ultramafic magma were intruded into a pre-existing sequence of mafic cumulates.

Modification of a Palaeoproterozoic porphyry-like system: Integration of structural, geochemical, petrographic, and fluid inclusion data from the Aitik Cu–Au–Ag deposit, northern Sweden

The Aitik Cu–Au–Ag deposit in the Gällivare area in northern Sweden is Sweden's largest sulphide mine with an annual production of 35Mt of ore, and the biggest open pit operation in northern Europe. It is proposed in the present study that the Aitik deposit represents a Palaeoproterozoic, strongly metamorphosed porphyry copper deposit that was affected ca. 100Ma later by a regional IOCG-type hydrothermal event. Consequently, the Aitik deposit might represent a mixed ore system where an early copper mineralisation of porphyry type has been overprinted by later regional IOCG mineralisation.Several attempts have previously been made to genetically classify the Aitik Cu–Au–Ag deposit as a distinct ore type. New geochemical, petrographic, structural, and fluid inclusion results combined with published data have provided the opportunity to present new ideas on the genesis and evolution of the Aitik Cu–Au–Ag deposit. The emplacement of a ca. 1.9Ga quartz monzodiorite that host the ore at Aitik was related to subduction processes and volcanic arc formation, and synchronous with quartz vein stockwork formation and porphyry copper mineralisation. Highly saline aqueous (38wt.% NaCl) fluid inclusions in the stockwork veins suggest entrapment at 300°C and a pressure of nearly 3kbar, a high pressure for a typical porphyry copper ore, but consistent with conditions at associated deep root zones of intrusion-related magmatic–hydrothermal systems. The highly saline fluid formed disseminated and vein-type ore of mainly chalcopyrite and pyrite within comagmatic volcaniclastic rocks, and caused potassic alteration (biotite, microcline) of the host rocks. The early porphyry copper mineralising event was followed, and largely overprinted, by CO2 and aqueous medium- to high-salinity (16–57wt.% salts) fluids related to a ca. 1.8Ga tectonic and metamorphic event (peak conditions 500–600°C and 4–5kbar). Extensive deformation of rocks and redistribution of metals occurred. Magnetite enrichment locally found within late veins, and late amphibole–scapolite and K feldspar alterations within the deposit, are some of the features at Aitik implying that aqueous fluids responsible for IOCG-mineralisation (200–500°C and ~1kbar) and extensive Na–Ca alteration in the region during the 1.8Ga tectonic event also affected the Aitik rocks, possibly leading to addition of copper±gold.

Effect of highwall parameters on the open pit operation and limits

The article addresses the open pit mining of lightly pitching coal below different surface topography. Based on the analysis of the effect exerted by highwall angle on the current stripping ratio, suggestions are made on possible improvement in the open pit mine performance and extension of its life by changing the slope angle of the open pit highwall.

Environmental effects of stone pits in Hatay (Turkey)

Open pit operation type is generally preferred in mining operations due to its applicability on all operable exposed rock grounds, its minimum production loss and high production rate. Especially materials like marble, travertine, limestone, dolomite, calcite and granite are mainly mined by open pit mining. Mined materials are put through breaking, crushing and sifting processes in pit area or facilities established close by. Number of this type of open pit mines in our country has increased in recent years. Open stone pits in Hatay area in the scope of Group 1st, 2nd and 4th as defined in law and environmental problems arising in relation to these are covered in this study. At the first step, stone pit operations in the province were identified by using geology and topography maps, satellite images and field studies. Then, operation potentials and environmental problems arising in relation to these were determined by field studies and surveys and suggestions on solutions were introduced. In the abovementioned studies it is determined that there are up to 90 stone pit operations and businesses in the province area. Swift increase in the number of pits and businesses in last 15 years is noteworthy. Environmental Impact Assessment reports were issued for only 11 of the operations that applied for permits in this time period. Swift increase in the numbers of these pits and lack of concern for environment in their establishment have led to environmental problems caused by these pits; problems like dust, tremors and disruption of natural landscape. Detailed Environmental Impact Assessment reports have to be prepared and operations have to be inspected and carried out in accord with findings of these reports to decrease these problems.

Algorithm Development of Production Scheduling for Open Pit Operations Using 4-D Network Relaxation

Algorithm Development of Production Scheduling for Open Pit Operations Using 4-D Network Relaxation

Developing rehabilitation design for the abandoned mine excavations in Central Sardinia, Italy

In central Sardinia, several talc–chlorite–feldspar bodies have long been mined by open-pit operations. The mining activity has deeply modified the original landscape of the Lasasai-Bonucoro area in the district of Orani. Thus, the rehabilitation of this area, in particular the open-pit works that are now occupied by pools filled with ground water from aquifers, should be considered as an overall project of landscape restoration. Particular conditions, such as the constant outflow of good-quality water and the scenic nature of the surrounding countryside, are favourable to the accomplishment of the recovery plan. On the basis of the naturalistic and geographical contexts of the mining area and its surroundings, a few proposals concerning the re-utilisation of these excavations are presented in this article. The preparatory work included the characterisation of the study area with a topographic survey, the establishment of a geodetic control network with global positioning system to describe the morphologic features of the landscape and the representation of the study area using three dimensional analysis and geoprocessing by commercial geographical information system GIS/CAD software. The final step involved the use of a digital scenery generator, capable of integrating graphical data layers with geological and morphological maps, to create virtual 3D environments thereby giving a rendering of a present, past and future landscape development.