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By Frank E. Chase

Geologic structures have been responsible for numerous underground accidents and fatalities, and are a constant-source of down time. During - longwall mining, ground control problems associated with geologic anomalies are aggravated by the abutment pressures which develop as the panel is retreated. Therefore, it is imperative that these structures be recognized and properly supported in head- and tailgates. Fractures, faults, clay veins, igneous dikes, and ancient stream channels (paleochannels) disrupt the lateral continuity of the mine roof and can cause falls in gateroads. Horsebacks and kettle bottoms are also hazardous because abutment pressures tend to "pop out' these structures into the gateroads. This Bureau of Mines investigation describes the physical characteristics associated with hazardous geologic structures, identifies the coal fields where-they have been observed, and, where possible, suggests support strategies and other mine plan modifications to help minimize their effect.

Jan 1, 1990

Detailed mapping in the Permian-Triassic clastic sediments of the Southern Alps delineates a number of strike-slip faults, both dextral and sinistral, associated with the major Alpine Fault to the west and displacing a tight array of fault blocks. Concurrent steeply plunging folds are deforming early major folds of probable Cretaceous age, and generating schist locally. To the east a major collapse zone has developed along the crest of a Cretaceous anticline, located over an ancient Permian submarine scarp, with a number of small normal faults. Further east, extensive Carboniferous to Triassic rocks of much the same appearance are exposed as horsts and grabens in a large possible extension zone through central and east Canterbury. This may have crept incrementally from Cretaceous from the offshore Bounty Trough to reach the eastern margins of the Southern Alps in the Pleistocene.

Jan 1, 1990

By C. W. Whitten

Iron ore deposits in south-central Missouri have emerged as a possible resource for the rare-earth elements. The Pea Ridge Iron Mine is one such deposit. Rare-earth minerals at the Pea Ridge Iron Mine are contained in breccia pipes consisting primarily of silicon oxides and feldspars. These pipes extend up through the magnetite ore body and appear to be alterations and replacement of earlier hematite. The mineralogy of these pipes is very complex and varied, which could complicate the concentration and extraction of the rare-earth minerals. This U.S. Bureau of Mines !eport represents a study by characterization of the mineral phases to assess the amenability and development of concentration and extraction techniques. Previous characterization of rare-earth minerals has been mainly by transmitted light microscopy. This method along with reflected light microscopy, scanning electron microscopy, and X-ray diffraction was used to identify and characterize the rare-earth and associated minerals. The minerals identified were the major ore minerals, magnetite and hematite; the rare-earth phosphates, monazite and xenotime; the rare-earth silicate, allanite; the minor associated minerals, cassiterite, pyrite, and apatite; and the gangue minerals, feldspar, quartz, and actinolite.

Jan 1, 1990

By Yves Gagnon, Nicole Gauthier, Daniel Kelly, Michel Rocheleau

"The Larder Lake-Cadillac Tectonic Zone in Rouyn-Beauchastel area (a 20 km long segment) contains distinct lithotectonic units bounded by artastomosing or sub-parallel shear zones. The gold deposits in the area are located within highly strained portions of E-W striking shear zones. The ore-zones are structurally controlled disseminated and vein-type lodes. They are spatially related either to megascopic z-shaped folds which refold E-W shears, or to areas of intersection between E-W shear zones and late NE-striking faults. Several ore bodies are enclosed within ultramafic rock units or at their contacts with adjacent units. All the lenses are elongated down dip and distributed, both loterally and vertically, ""en echelon"" . The ore zones tend to decrease in size and number away from the hinge zone of the megascopic z-shaped folds.Two main styles of mineralization are recognized at the Astoria deposit and at for most of the deposits in the Rouyn-Beauchastel segments a discontinuous ""Carbonate Ore"" and a more continuous, albitic sulphide-bearing ""Flow Ore"" (terminology used at the Kerr Addison mine).The typical ""Carbonate Ore"" zones are found within strongly arbonatized blocks bounded by conjugate late NE or NNW-striking fralls. The carbonatized blocks display features characteristic of llrittle to brittle-ductile deformation developed in shear zone system. Vein systems in the ""Carbonate Ore"" occur within shear fractures(D R)tension fractures (T), or within brecciated rocks adjacent to NS llrilcing faults. The ""Carbonate Ore"" zones are displaced by numer IU lole E-W, NNE, NW and N-S faults.The ""Flow Ore"" zones are found within predominantly ductile portions of E-W shear zones. The sulphide mineralization is finely disseminated and regularly distributed within mylonitic foliation or associated with veins and veinlets sub-parallel or oblique to the mylonitic foliation, in which case the mineralization is coarser grained. The gold mineralization is a late Archean event postdating the formation of the penetrative fabric, and synchronous with the end of the dextral oblique-slip motion."

Jan 1, 1990

By William C. Burkle

In this paper, the author has cited essential areas in which the explosives engineer can assist the mine manager in his planning of an entirely new operation or in a major expansion of an existing facility.

Jan 1, 1990

By I. Chatterjee

The application of microwaves has a demonstrated potential for the ultimate removal of water from fine coal. The principle of microwave drying of fine coal is based on the selective absorption of microwaves by water. Coal is a poor absorber of microwaves. As a result, water can be removed from fine coal by selectively heating water molecules. One of the difficult problems drilling microwave heating is the exact determination of temperature in the core of the materials. The electromagnetic energy absorption in coal/water mixtures during microwave drying is controlled by several factors including the dielectric properties of the constituents. In this paper the dielectric properties of various ranks of coal are presented as a function of frequency and moisture content. The measured dielectric data are incorporated into electromagnetic and thermal models of coal which predict the energy absorption and temperature distribution during microwave heating.

Jan 1, 1990

By Patrick J. Hannigan

The pile foundation designer typically performs a subsurface exploration program and static pile capacity calculations before selecting a pile foundation type, length, and capacity. During construction, a pile installation criterion must be established to meet these design requirements. This installation criterion usually consists of a minimum penetration resistance or blow count to confirm pile capacity and may also include a minimum embedment requirement. This text will focus on use of wave equation analysis and dynamic measurements to meet design requirements. BEFORE THE WAVE EQUATION Since the mid-1800s, over 450 dynamic formulas for pile driving control have proliferated. In their simplest form, these formulas relate hammer energy to the work of soil resistance, or simply: W ? h = R ? s (1) Where W = ram weight h = ram drop height or stroke R = pile capacity s = pile penetration per blow

Jan 1, 1990

The consideration of environmental constraints and issues is a fundamental component of all stages of planning, development, operation and decommissioning mining and quarrying projects. Provision needs to be made at all stages for the cost of environmental components since it is of fundamental importance that they be recognised as an integral component of any project. This paper presents an approach to environmental costing, suggested levels for budgeting, and the cost benefits.

Jan 1, 1990

By Large RR

Underlying the 15 million tonne, high grade Hellyer volcanogenic massive sulphide deposit of western Tasmania is an extensive, well developed, and well preserved stringer system. Pervasive alteration of the footwall mafic volcanics occurred as the hydrothermal system initiated. Mineralogical zoning exists within the footwall alteration pipe, with a central siliceous core giving way to zones of chlorite, chlorite-carbonate, sericite-chlorite, and finally sericite-quartz on the margins (stringer envelope zone). However, the alteration morphology and zonation is not symmetrical around the central siliceous core; eastward the alteration zones are steeply dipping and terminate abruptly under the massive sulphide, while westward they extend out under the ore body in a blanket fashion. Geologic evidence indicates that the pervasive alteration started with the development of sericite-quartz which was subsequently overprinted by chlorite and finally quartz-sericite as the hydrothermal system became focused towards the centre of the stringer system.

Jan 1, 1990

By T. R. C. Aston

Extensive undersea coal reserves, identified in the offshore portion of the Sydney coalfield, Nova Scotia, have resulted in the implementation of a multi-year research program to develop site specific guidelines for the undersea longwall mining operations. At present, uncertainty exists regarding the applicability of the current undersea mining guidelines. Preliminary studies have revealed four potential schemes for monitoring seafloor longwall subsidence profiles: seasurface, subsea, geophysics, and direct monitoring. However, further work has indicated that the use of marine geophysical techniques may be the most effective method of identifying and evaluating seafloor subsidence profiles by comparing pre- and post-mining seafloor topographies.

Jan 1, 1990

By David W. Cannon, Russell V. Mann

In a dispersion of particles in liquid a net charge will develop at the particle-liquid interface. This surface charge is usually due to the adsorption of charged material from solution. The existence of this surface charge gives rise to the formation of the electric double layer of counter-ions which surrond the charged particle. The particle surface charge and the electrostatic repulsion which exists between similarly charged particles is the primary stabilization mechanism for lyophobic colloids (1). The separation of charge which occurs at the particle-liquid interface gives rise to several dynamic phenomena associated with colloidal systems or with solid-liquid interfaces in general. These phenomena are known as electrokinetic phenomena and the four classic electrokinetic phenomena are; electrophoresis, electroosmosis, streaming potential, and sedimentation or Dorn potential. The actual driving force for electrokinetic phenomena is not the surface charge per se, but the charge at the interface between the liquid which is hydrodynamically bound to the particle surface and the bulk fluid. This interface is known as the slipping plane or the plane of shear and the potential at this interface is the zeta potential (2). The factors linking the electrokinetic phenomena is that they involve a relative motion between the liquid and the charged particle or solid surface and the driving force is the zeta potential of the solid. In addition to the four classic electrokinetic phenomena there are two additional electrokinetic effects in disperse systems; the electro-acoustic effects. When an alternating electric field is applied to a cooloidal dispersion the particles will move in the field due to their net zeta potential. If there is a density difference between the particles and the fluid this motion will result in the development of an acoustic wave. The effect was discovered at Matec and has been termed the Electrokinetic Sonic Amplitude or ESA (3). ESA is the pressure amplitude generated by the colloid per unit applied electric field strength and has SI units of pascals per volt per meter. When an alternating pressure field (acoustic wave) is applied to a colloidal dispersion the inverse of the ESA effects occurs. A density difference between the disperse phase and the continuous phase leads to a relative motion between the particles and the surrounding liquid. This means that there will be a periodic displacement between the charged particle and the oppositely charged counter-ions in the electric double year. This displacement results in the development of an alternating dipole moment at the frequency of the applied field. This effect is termed the Ultrasonic Vibration Potential or UVP and was first predicted for electrolyte solutions by Debye in 1933 (4). UVP is measured in units of volts per unit velocity amplitude of the applied acoustic field or volts per meter per second. In 1938, Rutgers (5) and Hermans (6) pointed out that the effect would also be present in colloidal dispersions. A detailed theory for UVP effects in colloids, also called CVP, was first presented by Enderby in 1951 (7). Extensive studies of the UVP in electrolytes have been carried out by Yeager et al (8). Recently, O'Brien (9) has developed a general theoretical treatment of electro- acoustic effects in colloids and has derived a reciprocal relation linking ESA and CVP effects. The most commonly studied electrokinetic phenomena is electrophoresis. Electrophoresis is the movement of charges particles in an applied electric field. The velocity of the particle divided by the applied electric field strength is the electrophoretic mobility of the particle. The zeta potential can be calculated from this mobility (2). The magnitude of both the ESA and CVP effects are directly proportional to the electrophoretic mobility of the particles. The mobility determined by the two electro-acoustic effects is the dynamic or AC mobility of the particles.

Jan 1, 1990

By R. Kent Comann

The sixth survey on the mining industry by Comann Associates provided data for entry-level and midlevel engineers as well as executive officers. Average 1989 compensation - base salary and anticipated bonus - for chief mining executive officers or chief mining operating officers: $237,943. This is an increase of 20% over the results of the last survey, on 1985 compensation. The latest survey also showed that bonuses for chief mining executive officers averaged 33% of base salary. Average 1989 compensation for chief executive or chief operating officers at mining operations with under $50 million in gross sales, $148,638; at mining operation with more than $50 million in gross sales, $275,141. The survey showed that these officers averaged 14 years employment with their present company, had five years in their present position, and had an average age of 54.

Jan 1, 1990

Two independent sets of observations from rifted con-tinental margins suggest a way to reach a quantitative under-standing of how the topography of rifted margins erodes. First, a prominent erosional escarpment, which demarcates an elevated, inland region of low relief from rugged, deeply-incised terrain on the seaward side, is the main feature of the geomorphology of many rifted continental margins. Second, apatite fission track ages from the southeast Australian and southwest Saudi Arabian margins scatter about constant Paleozoic ages over the higher elevations inland from the escarpment, but decrease systematically seaward of the escarpment to near-rifting ages approaching the coastlines. We have developed erosion models based on conservation of mass principles to explain these observations. These models seek to explain the "rejuvenation" of erosion at the time of rifting, initiation of the observed erosional escarpment, and its migration inland with time at a rate on the order of 1 km/10 yr. We find from the modeling that erosion at rift flanks and passive margins is fundamentally a non-linear pro-cess. The erosional development of passive margin topogra-phy has much is common with travelling wave solutions to non-linear diffusion-type problems, and to self-similar sto-chastic processes, such as diffusion-limited aggregation. We suggest that the fission track data record the thermal effects of erosional unroofing at rift flanks and passive continental margins. Models intended to explain the erosional develop-ment of continental margins must explain both the geomor-phology and the fission track observations as well.

Jan 1, 1990

By W. C. Hirt

Deposits of ferromanganese crust containing cobalt and nickel occur on the seafloor in the Pacific Ocean near the Hawaiian Islands and Johnston Atoll. This paper describes developmental flotation metallurgy to separate crust from its associated substrate gangue. Important variables in ferromanganese crust flotation include reagent type, aeration rate, conditioning time and agitation intensity, pH, temperature, water type, and feed size distribution. Flotation in seawater of minus 600 ~m (-28 mesh) material assaying 6.2% Mn, 0.2% Co, and 0.13% Ni with diesel fuel-crude tall oil-sulfonate collectors produces concentrates assaying 15% Mn, 0.6% Co, and 0.3% Ni with recoveries of 89-95% while removing 62% of the feed weight.

Jan 1, 1990

Analysis of the topography associated with large vertical strains measured in the upper crust in the Basin and Range and elsewhere in the US Cordillera shows that it varies systematically with upper crustal strain such that it decreases where tectonism has resulted in relative thinning. The magnitude of topographic deflection suggests that the amount of thickening or thinning of the upper crust cannot also be reflected in vertical motions of the Moho discontinuity, nor can the vertical strain be isostatically accommodated by inflow or outflow of asthenosphere, mantle lithosphere or mafic lower crust. Simple isostatic calculations show that the compensating medium had a density probably within 100-200 kg/m of average upper continental crust, thus indicating that the compensating medium lies within the crust and is probably in large part quartzose. This conclusion is in accord with laboratory experiments on the strengths of rocks, and with reflection seismograms in deformed regions which suggest that the Moho is generally flat beneath regions of extreme gradients in upper crustal vertical strain. The upper crust floats on a quartzose layer in the mid-crust which, under orogenic conditions, is apparently so weak that it behaves as a relatively inviscid fluid at geologic timescales (> 10,000 a) and subcontinental lengthscales (100-1000 km).

Jan 1, 1990

By H. Knorre, A. Griffiths, J. Loroesch

Introduction Hydrogen peroxide is known to the mining industry as a powerful oxidant. able to attack and to destroy cyanide, the most important leaching reagent (Knorre and Griffiths, 1984; Griffiths, 1988; Griffiths, 1988). [ ] The most recent development, however, is the use of H2O2 as an oxidant in the cyanidation of precious metals. This application may appear to be a contradiction to the above mentioned detoxification process. This can, indeed, be the case if certain conditions are not considered carefully. Degussa has developed a new process to enable the application of H2O, in this field without having any detrimental effect on the cyanide. The incentive to seek an oxygen supplier like H2O2 instead of air was the fact that one of the most important conditions for the fast dissolution of gold is the presence of physically dissolved oxygen in the pulp (Kydryk and Kellog, 1954; Warstell, 1987). [ ] Complete gold recovery within a reasonable leaching time may only be achieved if the pulp is saturated with dissolved oxygen. Gold losses in leach operations mainly occur due to the following reasons: In some cases, the saturation of oxygen in the pulp cannot be achieved by aeration due to the difficulty to transfer oxygen from the gaseous into the liquid phase. This happens, for example, in pulps with a high viscosity. In such cases, even violent aeration only results in a low concentration of dissolved oxygen in the pulp. In any case, the starting phase of leaching requires the highest amount of oxygen. Therefore, it is especially important to raise the dissolved oxygen level to saturation in the starting phase. Peroxide assisted leach process (PAL) The intention of the process is to introduce oxygen in a liquid form. As a result of intensive research work, it could be shown that hydrogen peroxide can be used as a source of oxygen in the leaching of gold ores. To avoid side reactions, the following conditions must be applied: Hydrogen peroxide must be diluted before it is added to the pulp. The dosage of H2O, must be properly regulated based on the oxygen level of the pulp. An important part of the continuous O, control is a special oxygen electrode, which resists the extremely abrasive action of the pulp.

Jan 1, 1990

By Miskelly N

The Joint Committee of The Australasian Institute of Mining and Metallurgy (AusIMM) and the Australian Mining Industry Council (AMIC) have published a Code for the Reporting of Identified Mineral Resources and Ore Reserves. The Code is the result of an initiative begunin 1971 to achieve industry self regulation of Resources and Ore Reserves reporting which resulted first in guidelines for reporting standards but which have now been incorporated in ASX Listing Rules as a Code withsignificant sanctions ensuring compliance. This paper describes the background to the Code, its key provisions, and comments on practical aspects of1 working with the Code and compliance issues.

Jan 1, 1990

By Neil Hillhouse

The Porgera gold district, like many other large gold deposits, has a long history of awareness, but only in the last five years has a geologic understanding of the district permitted the discovery of economically attractive gold reserves. The following sequence of events highlights the various significant steps in the evolution of the discovery process. The history of the district goes back about 50 years, and for several decades it was known only for its placer gold. Gradually, as gold became a more interesting metal, more and more attention was centered on the district. The sequence of events does not overstate the problems caused by isolation and climate, but the reader can imagine the difficulties inherent in such an area.

Jan 1, 1990

Gold-rich porphyry copper deposits areimportant sources of gold in the circum-Pacific region: 26 major deposits contain >7000 tonnes of gold. The deposits occur in a variety of subduction-related settings, and may be underlain by crust that is undergoing either extension or compression and that is either oceanic or cratonic in character. The deposits are associated intimately with composite porphyry stocks, which commonly were emplaced into coeval andesitic volcanic piles. The stocks range in composition from low-K calc-alkaline through high-K calc-alkaline to potassic alkaline. Much of the copper and gold were introduced as components of K-silicate alteration, which may undergo partial overprinting by intermediate argillic assemblages. Advanced argillic alteration is widespread in the shallow parts of the systems whereas sericitic alteration at deeper levels tends to be restricted. Gold distribution generally follows that of copper, which is present mainly as chalcopyrite with or without bornite. The gold is in the native state and occluded by cr in close proximity to the copper-iron and/or iron sulphides. The magmas and metals necessary for the generation of gold-rich porphyry deposits were derived mainly from subcrustal sources, with the subducted slab believed to play a pivotal role.

Jan 1, 1990

The Southwest Pacific is a region of active volcanism and geothermal systems. Only in New Zealand have the geothermal systems been exploited for electricity generation and industrial processing. At present, approximately 280 MWe of geothermal electricity is generated in New Zealand. A considerable amount of further exploration work is required before the total geothermal potential of the region can be assessed and before the significance of these resources can be judged against other local energy sources.

Jan 1, 1990