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By J. Noll, A. Miller, J. Volkwein, C. Pritchard

Hecla Limited, Magee Scientific, and NIOSH have combined efforts to evaluate an in-situ air filtration system for use in an underground mine environment. The purpose of the collaboration was to determine the efficacy of such a technology for reducing the concentration of airborne diesel particulate matter (DPM), with the aim of improving air quality in underground hardrock mines. A secondary goal was to evaluate the use of an Aethalometer as a means of real-time measurement of black carbon as a surrogate for DPM. The evaluation included measuring the DPM-capture efficiency of the filter when it was pre-loaded with dust. Toward this end, rock dust was introduced at the filter inlet to create a dust layer on the filter surface, with the intent of providing improved capture of the much smaller DPM particles. The filtration efficiency for DPM was assessed by comparing measurements of DPM taken at the inlet and outlet of the system, using both real-time and time-weighted-average approaches. The real-time measurements were performed with the model AE33 Aethalometer® made by Magee Scientific. The results of the NIOSH 5040 method analysis were used to assess the effects of the system on time-weighted-average concentrations of total carbon. Results showed a reduction in DPM concentrations in the range of 82%-89%. While the calculated efficiencies based on the two different measurement methods were similar, the DPM levels reported by the Aethalometer were higher, possibly due to differences in the performance of the size-selectors used for the two methods (impactors versus cyclones). More research is required to develop a robust correlation between the two methods, to support the use of the Aethalometer for future mining applications. The advantage of the Aethalometer is that it can measure and record DPM levels for weeks at a time, and can be directly connected to a mine monitoring system, potentially at multiple locations. Ideally such data can be used to initiate the startup of the filtration system should DPM concentrations reach an action level. This work demonstrated that in-situ filtration systems, modified to collect DPM and coupled with real-time monitoring, show promise at reducing DPM concentrations in the mine environment.

Jan 1, 2016

By William G. Pariseau

The purpose of this paper is to present a design procedure for the quantitative estimation of support load requirements in underground mines. Emphasis is upon the basic features of support behavior common to a large variety of support systems-bolts, timber sets, stope fill, steel arches, concrete liners and so forth. A strong reliance is placed upon fundamental principles and modern computing techniques for their quantitative implementation. Example problems illustrate the approach. Where artificial support is required, the ground in the vicinity of the face usually stands unsupported long enough for the support to be installed. At the time of installation, the load transferred to the support from the adjacent rock is essentially zero, although in some cases there may be an initial set load, for example, from timber blocking. With the passage of time and advance of the face, ground motion loads the supports. If the support system is properly designed, then the additional loading poses no threat to the safety and productivity of operations. If not, then difficulties may arise including high maintenance costs, hazardous work conditions and reduced productivity. Of course, over-design can be equally wasteful. Quantitative estimation of support loads is therefore essential to overall efficiency in mining.

Jan 1, 1975

By J. Groppo, W. Zhang, R. Honaker

"Rare earth elements (REEs) found in coal are in the form of minerals, ion-substitution with clays and organically bound. Rare earth minerals (REMs) such as monazite exist in coal and have a grain size less than 5 microns. Froth flotation was successful in concentrating REMs existing in a thickener underflow material derived from Fire Clay seam coal which contained around 300 ppm of rare earth elements (REEs). Conditioning with fatty acid followed by processing using multiple stages of conventional flotation produced a final concentrate containing 2300 ppm REEs. Using a laboratory flotation column, a concentrate containing around 4700 ppm of total REEs was produced equating to an enrichment ratio of 10:1. INTRODUCTION Rare earth elements (REEs) are becoming increasingly important and have been widely used as raw materials for the production of phosphor, metal catalysts, magnets, and batteries [1, 2]. REE recovery from alternative sources such as coal and coal by-products has the potential to stabilize the economic viability of coal mining operations while providing a dependable supply of critical materials. The average REE content of the world coal is around 60-70 ppm [2]. There are many well-known coal beds with high contents of REEs such as those in the Far East coalfields in Russia (300-1000 ppm), the Fire Clay coal seam in eastern Kentucky (500 ppm), and the Sydney Basin in Nova Scotia, Canada (72-483 ppm) [3-6]. The occurrence of REEs in coal and coal by-products can be classified into three types, i.e., rare earth minerals such as monazite and xenotime, ion exchangeable REEs in clays, and REEs associated with organic matrix. The particle size of the rare earth (RE) minerals in coal and coal by-products is very small and normally in the micron and/or nanometer scales. The flotation technique, which is based on the surface chemistry difference, has been widely used to treat fine rare earth industrial minerals such as monazite, xenotime, and bastnaesite [7-11]. As such, flotation is a promising method for the concentration of REEs from coal and coal by-products. In the current study, rare earth flotation was conducted using the fine coal refuse generated at an operating coal preparation plant treating coal from the Fire Clay seam. REE concentration by flotation required an appropriate amount of grinding and control of the pH value while using typical collectors. Prior to RE concentration, release tests were conducted to evaluate the floatability of the recoverable coal and the REE distribution in the flotation fractions in the fine refuse. Mineralogy of the REE was studied using SEM-EDX."

Jan 1, 2017

By R. H. Parker, B. A. Wills, D. G. Binns

Introduction With the increasing need to mine lower grade ores, high energy-related costs in comminution are of major concern. Very fine grinding is needed to liberate the fine mineral particles in these ores. Not only is this expensive, but it leads to greater losses in slimes. Gravity concentration techniques become unacceptably inefficient for particle treatment below 25 to 50 µm, and even flotation fails in the ultra-fine range. Ore from the South Crofty mine near Redruth, Cornwall, was subjected to thermal pretreatment in the hope that differential thermal expansion of the minerals would lead to intergranular cracking, and thus enhanced liberation. South Crofty ore contains about 1% tin as cassiterite associated with a complex assemblage of quartz, chlorite, tourmaline, and hema¬tite in granite and slate. Recovery of cassiterite can be as low as 70%, as overgrinding occurs during stage reduction of the material to 1 mm (primary grinding) and 180 µm (regrinding). Cassiterite is present in grain sizes ranging from submicroscopic to + 10 mm, the bulk being predominantly in the range of 50 µm to 3 mm. Experimental Flat polished sections of the ore were photographed in reflected light using a Vickers M17 microscope. The sections were then heated in a Carbolite LMF4 muffle furnace. The heating rate and temperature were monitored by a thermocouple immersed in the bed of particles. Previous work by Sherring (1981) on the same material showed that a 55% reduction in grinding resistance occurred when the material was rapidly heated and cooled through the quartz inversion tem¬perature (573°C), where a volumetric expansion of 0.86% occurs. The samples were therefore heated to 650°C at 26°/min, and were then water-quenched to room temperature. The effect of heat treatment on the mineralogy and fracture network was assessed by examining the same area after treatment. Results Most of the sections examined showed that extensive transgranular cracking occurred as a result of heat treatment. Such cracking, although weakening the rock and hence reducing the work index, would in no way enhance the liberation of the cassiterite from the host minerals. Intergranular cracking, which would lead to enhanced liberation, was difficult to discern under reflected light, but there was evidence of such cracking in some of the sections examined. Figures 1 and 2 are examples of typical sections before and after heat treatment. Figures la and lb - show cassiterite in hematite, Fig. lb, in normal incident illumination, illustrating clearly that after heat treatment, transgranular fracture is evident in the cassiterite. If any intergranular cracking has occurred, it is not evident in this photograph. Figures 2a and 2b show cassiterite in quartz before and after treatment. Fracturing in both minerals after treatment can clearly be seen, and there is evidence of intergranular fracturing. However, protruding "arms" of cassiterite are severed by transgranular fracture. Subgrains of quartz have also been isolated by trans¬granular fracture. There is major transgranular cracking across the wider sections of cassiterite. Discussion The effect of rapidly heating South Crofty tin ore to 650°C, followed by water-quenching to room temperature, has been studied by observing the fracture networks in mineral grains. The choice of 650°C as the heating temperature was influenced by the work of Sherring (1981), who found considerable reduction in grinding resistance after thermal pretreatment of the same ore. Scheding et al. (1981), however, have shown, by means of a crude calculation, that heat treatment cannot be justified solely on the basis of reduced grinding costs. The cost of heat treatment far out-weighs that of grinding, resulting in the combined costs for heat treatment being over six times that for grinding unheated material. The most economically attractive aspect of heat treatment is the possibility of enhanced liberation of the valuable mineral due to increased intergranular rather than transgranular fracture. Grinding costs would be greatly reduced by improved liberation at coarser sizes, and the costs of ancillary processes, such as dewatering and tailings disposal, would be reduced. The most significant economic effect, however, would be in improved metallurgical efficiency. Improved liberation would increase concentrate grades, and recoveries would be higher, particularly in the case of ores where high slime losses are produced due to the excessively fine grinding required to produce adequate liberation. Manser (1983) has shown that only a 1% increase in tin recovery, at the same concentrate grade, would be sufficient to offset heat treatment costs on South Crofty ore. Heavy liquid analysis and shaking table separation have been used to evaluate the effect of thermal treatment on processing (Binns, 1984; Scheding, 1981; Sherring, 1981). However, treatment of unheated and heated samples of South Crofty ore, ground to the same product size, by such methods have shown little evidence of improved metallurgical efficiency after thermal pretreatment. The large amount of transgranular fracturing revealed by reflected light studies helps to explain this lack of improvement. Nevertheless, from the evidence of some of the fracture work, it is surprising that no improvements in metallurgical

Jan 1, 1988

By Marc Carriere

Bright-orange couplings adorning piping systems are a common sight in just about every underground mine in North America. Grooved mechanical piping, the pipe-joining system that utilizes these couplings, is the preferred method for joining underground and plant piping systems in the mining industry, due to the ease and speed of installation and maintenance. However, the applications for such systems have traditionally excluded high-pressure systems. Most grooved mechanical couplings have a moderate working-pressure limitation, so high-pressure systems have required the use of alternative joining methods, typically heavy-duty flanges. However, the introduction of high-pressure couplings (up to 4,000 psi) has made the grooved joining method viable, and even preferable, for backfill, deep-mine chilled water and dewatering lines and other high-pressure piping applications. As engineers explore the use of high-pressure couplings, questions will undoubtedly arise about the joining method?s capabilities. This article will address the capabilities and specifications of high-pressure couplings, and compare flanged and grooved mechanical pipe joining in traditional as well as high-pressure underground mining applications.

Jan 1, 2011

By Karl J. Ellefsen

A geophysical investigation can provide valuable geologic information needed to characterize sand-and- gravel deposits and can be an attractive complement to more common characterization methods such as drilling. Although such investigations have been conducted already, a comparison of the different geophysical methods used in these investigations apparently has never been done. For this reason, a study was initiated by the Mineral Resources Program of the U.S. Geological Survey to determine the advantages and the limitations of different geophysical methods when used to evaluate alluvial sand-and-gravel deposits. The study is focused on those geophysical methods that are commonly available, because these are most likely to be used by industry. Furthermore, the study is focused on surface geophysical methods. Heretofore, four different methods have been evaluated. Three of the four methods-time-domain electro-magnetic (TEM) soundings, frequency-domain electro-magnetic profiling, DC-resistivity soundings-are similar in that they all measure the electrical resistivity of the ground with depth. Ground-penetrating radar, however, maps changes in the dielectric permittivity and for the electrical resistivity with depth. For all, four methods, the objective is to relate the measured physical quantity to the stratigraphy of the alluvial sediments.

Jan 1, 1999

By Michael Fehler, Hidenshi Kaieda, Leigh House

Hydraulic fracturing has gained in popularity in recent years as a way to determine the orientations and magnitudes of tectonic stresses. By augmenting conventional hydraulic fracturing measurements with detection and mapping of the microearthquakes induced by fracturing, we can supplement and independent1 y confirm information obtained from conventional analysis. Important information obtained from seismic monitoring includes: the state of stress of the rock, orientation and spacing of the major joint sets, and measurements of rock elastic parameters at locations distant from the wellbore. While conventional we1l 1ogging operations can provide information about several of these parameters, the zone of interrogation is usually limited to the immediate proximity of the borehole. The seismic waveforms of the microearthquakes contain a wealth of information about the rock in regions that are otherwise inaccessible for study. By reliably locating the hypocenters of many microearthquakes, we have inferred the joint patterns in the rock. We observed that microearthquake locations do not define a simple, thin, planar distribution, that the fault plane solutions are consistent with shear slippage, and that spectral analysis indicates that the source dimensions and slip along the faults are small. Hence we be1 ieve that the microearthquakes result from slip along preexisting joints, and not from tensile extension at the tip of the fracture. Orientations of the principal stresses can be estimated by using fault plane solutions of the larger microearthquakes. By using a joint earthquake location scheme, and/or calibrations with downhole detonators, rock velocities and heterogeneities thereof can be investigated in rock volumes that are far enough from the borehole to be representative of intrinsic rock properties.

Jan 1, 1986

By M. T. Smith

In a 2,000 square mile area of Polk, Hillsborough, Hardee and Manatee Counties in Central Florida is located one of the richest known deposits of the life-giving mineral, phosphorus. Under layers of sand and clay are found millions of tons of phosphate rock, best source of this element which is necessary to all forms of life - plant, animal and human. Phosphorus is an irreplaceable ingredient in all complete plant foods, and more than 90% of Florida's vast production goes to enrich the croplands of the United States and many other areas of a hungry world. In addition to this, it has wide industrial use in the manufacture of many products - detergents, baking powder, carbonated beverages, steel, matches, munitions, glass, insecticides, dyes, water softeners and innumerable others. Not only does phosphorus make life possible for us - it also helps us to live longer and better.

Jan 1, 1962

By E. Bonates

Dispatching systems have attracted considerable attention in the last years due to substantial gains in productivity achieved through their implementation. These systems will be extensively used in the future by mine operators as a means of optimizing productivity. This paper describes a computer simulation model designed to study the feasibility of continuously dispatching trucks in open-pit mines based on different operating procedures. The system developed is semi-automated and performs an active role by suggesting to the dispatcher the best assignment according to each specific circumstance. It is modeled based on an advance-clock increment to reduce computing time and allows the insertion of heuristic dispatching policies and equipment real-locations when breakdowns occur. Dispatching procedures taking into account long-term production objectives are considered in system development.

Jan 1, 1988

By Ted DePooter, Mun Wei Leong, Chad Frederick

Downtown Bellevue Tunnel (DBT) is part of Sound Transit’s $3.7 billion, 14-mile light rail transit system from downtown Seattle, across Lake Washington, to the cities of Mercer Island, Bellevue, and Redmond. The tunnel was the first Sound Transit East Link project and posed significant construction risk. This paper discusses implementation of design changes to the soft ground tunneling method, implementation of several technologies such as the use macro-synthetic fiber initial shotcrete lining, use of spray-applied waterproofing, and use of shotcrete for the final tunnel lining. These efforts allowed for significant time and cost savings to the project.

Jun 13, 2021

By E Marambio, R Brändle, G Fischer, G von Rickenbach, L Burgos, R Luis Fonseca

Ground support systems must provide safe and effective designs for underground excavations under high stress conditions. These systems must be capable to resist dynamic impacts and yielding during the loading process. In this context dynamic testing of the reinforcement and retaining elements that compose the ground support system are required to study and improve the behaviour of these elements under dynamic load events. During the last years, Geobrugg has been working on the improvement of retaining products by testing them in a large-scale impact test facility located at Walenstadt, Switzerland. The test facility is composed of a double level platform with a square-shaped pyramidal trunk geometry, in the upper level housing a loading mass that drop from a height up to 5m. The loading mass is guided by one central steel pipe, and the impact occurs in the sample to be tested located at the lower level in a slab with an area of 3.6m × 3.6m where the ground support system is installed. During the last years, this innovative facility has been used to test several configurations of ground support systems. The results of these tests have enabled to improve the understating of the behaviour of ground support systems under dynamic loads. In this manuscript, the arrangement, measurement, results, and the preliminary analysis of a single impact dynamic test performed during 2021 of a ground support system with a high-tensile steel wire mesh MINAX 80-4.6 is presented.

Apr 26, 2022

By P. T. Bissert, J. P. Ducarme, J. L. Carr, A. K. Smith

The continuous mining machine is a key piece of equipment used in underground coal mining operations. Over the past several decades these machines have been involved in a number of mine worker fatalities. Proximity detection systems have been developed to avert hazards associated with operating continuous mining machines. Incorporating intelligent design into proximity detection systems allows workers greater freedom to position themselves to see visual cues or avoid other hazards such as haulage equipment or unsupported roof or ribs. However, intelligent systems must be as safe as conventional proximity detection systems. An evaluation of the 39 fatal accidents for which the Mine Safety and Health Administration has published fatality investigation reports was conducted to determine whether the accident may have been prevented by conventional or intelligent proximity. Multiple zone configurations for the intelligent systems were studied to determine how system performance might be affected by the zone configuration. Researchers found that 32 of the 39 fatalities, or 82 percent, may have been prevented by both conventional and intelligent proximity systems. These results indicate that, by properly configuring the zones of an intelligent proximity detection system, equivalent protection to a conventional system is possible.

Jan 1, 2016

By P. T. Bissert, T. J. Lutz, J. A. Yonkey, G. T. Homce

"The National Institute for Occupational Safety and Health (NIOSH) has been researching refuge alternatives (RAs) since 2007. Refuge alternatives typically have built-in pressure relief valves (PRVs) to prevent the unit from reaching unsafe pressures. The Mine Safety and Health Administration (MSHA) requires that the PRVs vent the chamber at a maximum pressure of 1.25 kPa (0.18 psi, 5.0 in. H2O), or as specified by the manufacturer. To facilitate PRV testing, an instrumented benchtop test fixture was developed using an off-the-shelf centrifugal blower and ductwork. Relief pressures and flow characteristics were measured for three units: a modified PVC check valve, an off-the-shelf brass/cast iron butterfly check valve, and a commercially available valve that was designed specifically for one manufacturer’s steel pre-fabricated RA and has been adapted for use in built-in-place (BIP) RAs located at one mine. PRVs used in tent style RAs were not investigated. The units were tested with different modifications and configurations in order to check compliance with 30 CFR regulations. BACKGROUND The Mine Improvement and New Emergency Response Act of 2006 (Miner Act) (1) was enacted in the wake of three mine explosions/fires that claimed 19 lives that year. Intended to help improve underground coal mine accident preparedness, the MINER Act includes provisions that target mine safety issues in areas such as emergency response planning, adoption of new technology, training and education, and mine safety standards enforcement. Section 13 of the MINER Act specifically directed the National Institute for Occupational Safety and Health (NIOSH) to provide for research into the effectiveness and viability of refuge alternatives (RAs) for underground coal mines, and the Department of Labor to act on the results of such research as appropriate. These mandates culminated in the 2009 adoption of changes to 30 CFR mining health and safety regulations, requiring underground coal mines to provide mine emergency RAs and associated components, to provide a life-sustaining environment for persons trapped underground. Such RAs can be either self-contained mobile units or built-in-place (BIP) facilities. The regulatory changes also include provisions establishing requirements for the Mine Safety and Health Administration (MSHA) approval of RAs and their components, and among these provisions are numerous criteria for providing a safe breathable atmosphere under positive pressure within the RAs. One specific criterion for maintaining a safe RA atmosphere requires the inclusion of an air pressure relief valve that will activate at a maximum of 1.25 kPa (specified as 0.18 psi, or approximately 5.0 in H2O), or at a pressure as specified by the RA manufacturer, above mine atmospheric pressure in the RA (2)."

Jan 1, 2016

By M. Moats, J. Young

Short term laboratory cell electrorefining experiments were performed to examine the impact of electrolyte composition, current density and temperature on deposit structure, roughness, and adhesion to 2B mill finished 316L stainless steel. Copper electrodeposits were produced using synthetic electrolytes with thiourea and the continuous addition of glue. Deposit structures were evaluated using X-ray diffractometry. Surface roughness was measured using profilometry and analyzed using scaling analysis. Finally, an internally developed method was used to measure the force required to remove the electrodeposited copper from stainless steel to determine adhesion strength.

Mar 2, 2022

By Todd Kilduff, Ryan O’Connell

Pipe canopies continue to gain momentum as a reliable methodology for construction of excavations below critical facilities with minimal surface settlement tolerances, such as railroads or roadways. Two tunnel projects designed by Kilduff Underground Engineering in the Salt Lake City, UT area, each at varying stages of completion, had project design criteria for selection of a tunneling methodology to minimize surface settlement. Both projects consist of a pedestrian tunnel, one crossing beneath a major roadway in downtown Salt Lake City and the second beneath UPRR tracks. Both projects were in difficult, coarse alluvium/fan ground conditions with project criteria that resulted in minimal cover above the tunnel. For each project, a pre-support pipe canopy was designed, requiring the placement of steel, canopy pipes driven the extent of the tunnel length. The pipe canopy is installed using a trenchless technology and then excavated with SEM tunneling and shoring provided by traditional support of excavation methods. The pipe canopy pre-support method offers a low-impact method to install an underpass beneath critical structures by adding significant stiffness to the subgrade to mitigate surface settlement during the main tunnel excavation sequence. These case studies seek to communicate the challenges associated with pipe canopy installation in site-specific ground conditions and explains how these challenges were overcome. This paper aims to define the project risks and describes the pipe canopy methodology as a viable solution to mitigate surface settlement in low cover tunneling scenarios.

Jun 13, 2023

By P. T. Bissert, J. P. Ducarme, J. L. Carr, A. K. Smith

"The continuous mining machine is a key piece of equipment used in underground coal mining operations. Over the past several decades these machines have been involved in a number of mine worker fatalities. Proximity detection systems have been developed to avert hazards associated with operating continuous mining machines. Incorporating intelligent design into proximity detection systems allows workers greater freedom to position themselves to see visual cues or avoid other hazards such as haulage equipment or unsupported roof or ribs. However, intelligent systems must be as safe as conventional proximity detection systems. An evaluation of the 39 fatal accidents for which the Mine Safety and Health Administration has published fatality investigation reports was conducted to determine whether the accident may have been prevented by conventional or intelligent proximity. Multiple zone configurations for the intelligent systems were studied to determine how system performance might be affected by the zone configuration. Researchers found that 32 of the 39 fatalities (82%) may have been prevented by both conventional and intelligent proximity systems. These results indicate that, by properly configuring the zones of an intelligent proximity detection system, equivalent protection to a conventional system is possible. INTRODUCTION Underground coal miners are exposed to a variety of hazards on a daily basis. Among coal and rock dust exposure, high noise levels, roof and rib falls, and the potential for fires and explosions, operating and working with heavy machinery poses a significant risk to miner safety. One of the most hazardous jobs is operating or working nearby a continuous mining machine (CMM). According to Mine Safety and Health Administration (MSHA) statistics, 39 miners have been fatally struck or pinned by a CMM since 1984. In an effort to prevent future striking and pinning fatalities from occurring, proximity detection systems have been developed and are now required on all operating CMMs in underground coal mines with the exception of full-face CMMs [1]. Commercially available proximity detection (cPD) systems are based on the principle of magnetic flux density (B-field). Typically, four magnetic field generators are positioned on a CMM, and personal alarm devices (PADs) are worn by the miners that detect magnetic flux density difference. As a miner wearing a PAD gets closer to the machine, the flux density increases. Zones can be constructed around the machine so that an alarm will trigger on the PAD based on the flux density."

Jan 1, 2016

By Hooman Askari-Nasab, AHLAM MAREMI, EUGENE BEN-AWUAH

In oil sands mining, tailings are voluminous unwanted byproducts generated from extracting the desired mineral from the mined ore. Dyke construction and backfilling activities require well-managed techniques to facilitate progressive reclamation at the earliest opportunity. This directly affects the sustainability and profitability of the mining operation. This research introduces a goal programming framework that simultaneously optimizes the (1) production schedule with limited duration stockpiling and directional mining, (2) dyke construction schedule, (3) size, shape and location of tailing cells and (4) mining and processing production targets. The results show that in creating in-pit tailing-cell designs, decreasing the mining-cell volume and increasing the number of mining cells improves the net present value (NPV) of the operation due to increased operational flexibility.

By Kevin Lundberg, Philip Sander, Daniel Weinberger, John Reilly

Since the early days of risk management, developments in technology and guidelines (ITA, ITIG, OGG, UCA) have advanced risk management and probable cost estimating, which are now widely recognized. WSDOT’s CEVP risk-based cost validation process is now established after 20 years. This paper traces these developments, summarizes advanced techniques, and presents examples of US and international projects with results. A particular case of using advanced risk evaluation to allow enhanced-capability TBMs to be considered in a competitive bid process is presented. Further advances, including the use of digital twin risk-based representation of complex projects, are described.

Jun 13, 2023

By JURGEN KRETSCHMANN

The European climate and energy framework for 2030 is highlighting the reduction of man-made CO2 by increasing the use of renewable energy. In this spirit, Germany has decided to erase coal use as an energy source by 2038 completely. This strategy premises a feasible, responsible and sustainable post-mining management. The Research Institute for Post-Mining (FZN) at the TH Georg Agricola University in Bochum, Germany, has developed a holistic approach to meet post-mining challenges. In all efforts, the FZN aims to achieve the fundamental goals of the United Nations to deal with the resources of our planet responsibly and sustainably.

By S. W. Nicholson, L. G. Woodruff, K. J. Schulz, W. E. Cannon

The 1.1 Ga Midcontinent rift of North America has many similarities to the geology of the Voisey's Bay region in Labrador and the geology of the Noril'sk region in Siberia. These similarities include the hosting of large volumes of sulfur- undersaturated and trace-element-enriched basalt, having igneous centers characterized by crustal contamination, being characterized by metal depletions in some mafic units (an indication of prior sulfide segregation) and having known occurrences of Ni-Cu sulfide mineralization. These similarities along with new geophysical data and refined models for Ni-Cu sulfide deposits suggest that the Midcontinent rift probably contains undiscovered Cu-Ni [±] PGE sulfide deposits, some of which could be the size and grade of a Voisey's Bay or Noril'sk deposit. In particular, intrusions and related feeder systems that occur in northern Michigan and Wisconsin, as well as to the southwest along the rift margin, deserve serious examination.

Jan 1, 1999