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By R. A. D. Pattrick, R. A. F. Ixer

Paper presented at Mineralisation in the Caledonides, the Mike Gallagher memorial meeting held in Edinburgh, 27-28 June 1996. At Calliachar Burn, 14 steeply dipping quartz-sulphide veins, with and without gold, infill master joints that crosscut gently dipping metasediments and metabasics of the Pitlochry Schist Formation. The wallrock is extremely bleached and enriched in sericite, chlorite and carbonate. Gold grades vary from high with quartz-galena-pyrite to low with galena-chalcopyrite; the gold forms electrum inclusions smaller than 20 micrometres in pyrite or, rarely, arsenopyrite. At Urlar Burn, gold is present in small amounts in 4 quartz-galena-chalcopyrite veins. Although much of the mineralogy is similar to that at Calliachar, there are significant differences in Sb-, Te-, Bi- and Hg-bearing phases. Fluid inclusion data suggest mineralisation occurred over the range 320-140 degrees C, from fluids with significant CO2 and 2-13 wt% equiv. NaCl. Mantle-derived fluids appear to have been generated during the late Caledonian and focused by the Urlar Burn fault

Jun 19, 1905

By D. J. Esdale, D. F. Pridmore, F. W. Lindman, J. H. Coggon

Almost all the presently viable nickel reserves in the Yilgarn Block contain nickel in a sulphide phase. Both volcanic peridotite- associated (VPA) deposits and intrusive dunite-associated (IDA) deposits are characterized by massive, matrix and disseminated sulphides (typically, pyrrhotite, pentlandite, pyrite, chalcopyrite, magnetite and other spinels), though in the IDA deposits the volume of disseminated sulphides is far greater than that in the VPA deposits. Potentially all geophysical techniques have application in the direct detection of these deposits'gravity for the detection of the dense massive and matrix ore; magnetics for the detection of magnetite and pyrrhotite in the ores; electromagnetics for the detection of the massive and matrix ore; and induced polarization for the detection of disseminated and to some extent matrix and massive ore. In practice the application of geophysical techniques is limited to a varying extent by (1) the relatively small size of an economic accumulation of sulphides, particularly the VPA deposits, (2) the extreme depth of weathering and lack of outcrop on the Yilgarn Block and (3) the abundance of geological noise or anomalous responses caused by sources other than economic mineralization.

Jan 1, 1984

By A. D. Fowler, M. T. Anderson

A phenomenological model is presented that relates Pb-Zn mineralisation to proximal geopressure zones. Typically, geopressure zones (GPZ) consist of masses of undercompacted sediment encapsulated within impermeable shales and are characterised by high formation fluid pressures. Heat flow is perturbed in some GPZ on account of their insulating properties. Geothermal gradients as high as 150 degrees C/km have been observed over short distances in the sediments of the US coast of the Gulf of Mexico. Some modern geopressure zones are known to reach temperatures of 120-150 degrees C at depths of 2.5-3.5 km. It is demonstrated that the zones may act as proximal sources of hydrothermal fluids, thus explaining the high temperatures of mineralisation observed in the deposits, which are hosted in basins characterised by thick, rapidly deposited, shale-rich clastic sequences

Jan 1, 1991

During a programme to determine the suitability of the UK site for deep disposal of radioactive wastes, geostatistical methods were used to characterise rock heterogeneity on the basis of seismic and wireline acoustic-impedance data. The data were analysed to yield semi-variogram models that quantified the three-dimensional spatial heterogeneity of acoustic impedance. These models were reconciled with geological interpretations of the area and used to generate simulations of acoustic impedance, with wireline acoustic impedance as conditioning data. The three-dimensional simulated images were compared with actual seismic acoustic impedance. The variography confirmed a vertical zoning effect in the Borrowdale Volcanics, showing that it is caused by preferential clusters of high acoustic impedance values corresponding to regions of relatively low porosity. The method provided realistic three-dimensional models from sparse, one-dimensional wireline data

Jun 19, 1905

By G. Richards

Application of the Internet of Things (IoT) technologies - the interconnection of uniquely identifiable embedded computing devices within the existing internet infrastructure - to the mining industry is discussed. IoT technologies are aimed at making projects safer, better optimised and more economic and are applicable to current or new underground or open-pit mines, regardless of size. Two examples are presented of successful implementation of IoT technologies, the Chelopech gold, copper and silver mine in Bulgaria, where production has increased from 500 000 to 2 000 000 tonnes/y and communication costs have been reduced by US $2 500 000 over 2 y, and the Pilbara project in Western Australia, where remotely controlled wirelessly connected autonomous trucks have covered ca. 3 000 000 miles and hauled almost 250 000 000 t of ore since 2008

Apr 1, 2015

By R. Poulin, C. F. Gleeson

The Birimian rocks of the region are gold-bearing and show many similarities to those of Burkina Faso. All three greenstone belts (Goroual, Tera and Sirba) host gold-bearing quartz veins. It appears that, contrary to previous misconceptions, lateritic terrain is not an unfavourable environment for exploration geochemistry. This is demonstrated by the results for the Koma Bangou area, where soil and termite-mound geochemistry have been successfully used in the search for gold. Soil provides an effective sampling medium where it is shallower than about 2 m; there is evidence that some soil anomalies are enhanced by the presence of secondary (botryoidal) gold. In areas of thicker, allochthonous soil cover, termite-mound sampling is more effective. At Koma Bangou an identified resource of some 11 100 000 tonnes with an average gold grade of 2.44 g/t has been reported. The gold mineralisation occurs in quartz veins and stockworks aand in the wallrocks of shear and fault zones that trend N, NW and NE. The host rocks are a granodiorite-syenite porphyry and intermediate metavolcanic rocks and tuffs

Apr 1, 1996

By K. M. Kinealy, A. R. Ramsden, D. H. French

A negative correlation exists between sphalerite composition and gold content when gold is transported as Au(HS)2(-); however, there are spatial and temporal differences within a single deposit. A previous model for the formation of volcanogenic massive-sulphide deposits within thermally intensifying and waning hydrothermal sytems in much the same way as is observed around modern sea-floor vents is supported. The results also emphasise that recognition of the mechanisms of gold transport in ancient deposits depends critically on an understanding of their mineralogy and stratigraphy

Jan 1, 1991

By R. P. Foster, ed.

The short selection of papers in the special issue provides an insight into the level of exploration activity in Africa and the science and technology that are underpinning it. A country-by-country survey is followed by discussion of geochemical exploration in tropical soils, the Liptako region of Niger, structural styles of deposits in Zimbabwe's Bulawayo-Bubi greenstone belt, structural controls in Zimbabwe's Eldorado shear zone, the regional framework for deposits in the Odzi-Mutare-Manica greenstone belt of Zimbabwe and Mozambique, and the Iperindo deposit in Nigeria's Ilesha schist belt

Apr 1, 1996

By A. Sutton-Pratt

The African continent has been the most prolific producer of gold since mining began. Although most of this gold has come from South Africa, other countries have also been important contributors in the past. There is currently little production outside South Africa, Ghana and Zimbabwe, but the gradual globalisation of the industry over the past decade has resulted in growing interest in the region which bodes well for its future development. An outline is given of prospects and activity (or lack of it) in South Africa, Lesotho, Swaziland, Zimbabwe, Mozambique, Madagascar, Botswana, Namibia, Zaire, Tanzania, Kenya, Uganda, Rwanda, Burundi, Zambia, Malawi, Angola, Congo, Central African Republic, Gabon, Equatorial Guinea, Ethiopia, Eritrea, Djibouti, Somalia, Sudan, Chad, Libya, Tunisia, Egypt, Algeria, Morocco, Ghana, Ivory Coast, Liberia, Sierra Leone, Guinea, Senegal, Guinea-Bissau, Gambia, Mauritania, Mali, Burkina Faso, Togo, Benin, Niger, Nigeria and Cameroun

Apr 1, 1996

By P. J. O'Connor, V. Gallagher

examined analytically in relation to the ratio of the

Dec 1, 1994

By P. J. O'Connor, V. Gallagher

The addendum, to the paper published in Trans. IMM B, vol.103, 1994, p.B175-B187, acknowledges data from Celtic Gold plc at Navan and apologises for the omission

Jun 18, 1905

By A. M. R. Neiva

The WNW-ESE-trending hydrothermal veins cut alternating mica schists and quartzites of mainly Ordovician age and, to the west, a Hercynian muscovite-biotite granite. They have been prospected and developed to a depth of 300 m and reserves of 20 t Au estimated. The paragenetic sequence and chemical compositions of the ore minerals are generally similar to those at Jales to the south. Gold, electrum and aurian silver form inclusions in arsenopyrite, pyrite, galena, sphalerite, pyrrhotite and quartz and also occur in veinlets that cut these minerals. Silver has been found in gold, electrum, aurian silver, tetrahedrite, freibergite and the Ag-Pb-Sb sulphide owyheeite. Early arsenopyrite crystallised at an estimated 480 degrees C and the more common, later arsenopyrite in which Au and Ag are generally included at 430-300 degrees C. Sphalerite crystallised at 307-100 degrees C. Monoclinic pyrrhotite may have been formed by the inversion of hexagonal pyrrhotite at 248 degrees C

Jun 16, 1905

By D. J. Spottiswood, R. K. Tuteja

Axial grade profiles were analysed for a pilot column operating in reverse flotation mode to float talc from a gold-bearing sulphide ore. It was found that concentration gradients in the pulp are very low. Most of the cleaning action, both upgrading of valuable minerals and rejection of gangue, occurs in the froth zone

Jun 17, 1905

By C. C. Harris

The two best known graphical methods for presenting and comparing comminution data are obtained by linearising the Gates-Gaudin-Schuhmann and the Rosin-Rammler size distribution equations. It is shown that the Gates-Gaudin-Schuhmann equation can cause excessive congestion in the 50 per cent oversize range and that, overall, the Rosin-Rammler is a better procedure. Examples are given

Dec 1, 1971

By S. K. Chaulya, R. S. Singh, B. B. Dhar

Two prominent local species, Dendrocalmus strictus (bamboo) and Saccharum spontaneum (kashi), and two exotic species, Cymbopogon citratus (lemon grass) and Vetiveria zizanoides (vetiver), were selected for growth trials on dumps at Mandaman, Chora, Mudidih, South Balanda and Ghugus. The climate at these sites is dry tropical and the surface soil layer a slightly acid to neutral sandy to clayey loam 10-11 cm thick, impoverished in major plant nutrients. After two years bamboo had grown the most, up to 325 cm in height, and contributed the greatest biomass, 638 g/m2 of plant. The local kashi species had a very good regenerative capacity, which was lacking in the lemon grass and vetiver. The grasses had very good soil-binding capacity and could also provide income if used as cash crops

Jun 21, 1905

By R. Winand, P. Harlet

he cathodes produced are of electrorefined grade; metallographic structure and surface roughness are controlled to a depth of 1.3 cm (single-side deposits); silver levels in the cathode are regulated by the presence in solution of Cl- and Br- ions; organics must be used at very low concentrations (around 0.1 mg/l with a consumption of about 0.01 mg/l/hr). The required concentrations of additives were established according to a well-defined strategy based on the consumption of organics at the cathode by a mass transfer limited-process.

Jan 4, 1992

By Walshe J. M.

The slow-speed compressor is giving place to the high-speed type, with its greater economy of material and space; and, where very large units are required, the turbo-compressor is supplying the need. In the very large air-supply stations on the Rand, turbocompressor units of a capacity of 20,000 and even 50,000 cubic feet, requiring 4,000 to 13,000 horsepower, are quite a commercial proposition, and have proved a practical success. Air-compressors of this size are, however, very exceptional, and the high-speed reciprocating compressor is quite capable of dealing with the highest outputs so far required in this country and, in the hands of manufacturers experienced in the design of high-speed steam-engines, a very high standard of reliability and efficiency in operation is obtained. The so-called “high-speed” or more correctly quick-revolution type of compressor is now extensively used in mines and collieries; for the air-pressures required for power purposes in mining work, two-stage compression, with an intercooler between stages, is the design usually adopted in best practice. It is not the writer’s intention to describe a variety of high-speed air-compressors but to select as an example of this type of compressor the one with which he is most familiar, and which is probably more largely used than any other, namely, the double-acting two-cylinder two-crank type with automatic light-plate air-valves, and with the working parts lubricated on the forced-lubrication principle. Sectional drawings, efficiency curves, air-cylinder diagrams and other data accompany the descriptions and photographs of compressor design, components and mine applications

Dec 1, 1916

By P. Mousset-Jones, G. Danko

Variations of the temperature and steam/moisture content of the air with distance and time are modelled for a single airway. The input for the simulation is an air temperature that varies with time, together with the moisture/steam content that results, for example, from a fire with a given distribution of heat and of fume concentrations at the beginning of the airway. The transport of heat and moisture to the surface of the wallrock is assumed to be simultaneous. Such multiphase convection may result in evaporation from the moist wall close to the fire and recondensation downstream. The modelling of this non-linear effect is a unique feature of the new simulation. A new analytical solution is used to calculate the conduction of transient heat within the rock mantle, which, in the event of a fire, is typically a short-term process. This allows for an arbitrary variation of surface temperature with time - unlike that permitted by the age function solution, which is limited to stepped temperature changes. An iterative numerical scheme that has recently been developed to simulate mine climate is used to calculate the coupled transient heat conduction and multiphase surface heat transport in successive length increments along the airway. To demonstrate the simulation procedure a numerical example is presented in which a fire with a given distribution of heat and fume concentrations with time is located at the beginning of an airway

May 1, 1991

To maximise recovery by highwall mining, pillars must be designed which are long, slender and of relatively low width-to-height ratios. The strength of pillars with width/height less than 2 depends primarily on the mechanical response of the coal, due to the reduced influence of frictional restraint between roof and floor. A suitable pillar design approach therefore requires a method of estimating coal-seam properties. Experimental studies were carried out to determine ways of reliably predicting the large-scale mechanical properties of coal seams from small-scale test data. The studies led to a method of practical, systematic assessment of coal-seam properties based on measurement of coal rank and seam brightness profiles. The criterion employs the parameters sigma(c), m and s of the generalised Hoek-Brown empirical strength criterion for rock masses. A novel design approach combines the flexibility of modern numerical modelling programs with simple hand calculation for rapid assessment

Jun 21, 1905

By P. P. Jenkins, T. G. Ball

Paper presented at the Drillex '90 conference held in London, 5 April 1990. Two drilling techniques are employed - guided longhole drilling and reverse circulation coring - for underground longhole exploration of the coal reserves and the fault structures that affect them. These are complementary to, or replacements for, surface boreholes, underground development drivages and seismic techniques. The developments of the drilling techniques and some case histories are presented in detail.

Jan 1, 1991