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By S Durucan, A Korre

The application of simple methods of statistical analysis, coupled with geostatistical analysis and geographic information systems, can only summarise and give an outline of the spatial distribution of the parameters measured. Spatial analysis of the components or factors calculated, through principal component analysis or factor analysis, allows assessment of the geographical distribution of the dominant processes contributing to soil composition and/or contamination. Neither of these tools, however, distinguishes between the different sources of pollution. The application of canonical correlation to the data, driven by expert appraisal of the potential pollution sources, allows their quantitative and spatial assessment while GIS provides the environment in which to organise and present the results. The methodology is illustrated by its application to soil-contamination data from the Lavrio area in Greece, where silver-bearing orebodies have been mined for more than 25 centuries

Jun 21, 1905

By C. A. Jeffrey

The Dirtlow Rake vein deposit, which is up to 12 m thick, contains a range of paragenetically linked replacement mineralisation styles typical of many Mississippi Valley-type deposit environments. The main ore zone lies within the solution collapse breccia domes, the more southerly of which has recently been well exposed, allowing its relationship to the associated mineral-hosting structures to be studied. The domes were largely formed during early silicification, propagated by dissolution collapse and infilled by subsequent fluorite-barite mineralisation. The location of pipes and pervasive replacement was also controlled by early silicification. Structurally controlled bow tie shears were formed as a result of fluid access at fracture-bedding plane intersections. The nature and distribution of the mineralisation styles indicate that the degree of fluid access, residence time of solutions in contact with the wallrock and susceptibility of the limestone to silicification each played a major role in dictating mineralisation

Jun 19, 1905

By J. Konnerup-Madsen, T. Unlu, H. Stendal

Paper presented at the conference Economic geology in Europe and beyond II, models for mineral deposits in sedimentary basins, held in Keyworth, UK, 13-14 April 1994. The region includes the Deveci siderite/goethite deposit and the Hasancelebi, Karakuz and Kuluncak magnetite/goethite deposits; Deveci is the only mine in operation. The area consists of a serpentine-gabbro complex overlain by a volcano-sedimentary sequence hosting the iron ores. At least three generations of hydrothermal alteration have affected all rock types except the latest trachytic dykes. The Deveci deposits occur in a pyroclastic volcano-sedimentary sequence with shales and carbonates equivalent to the main mafic sequence, whereas the other three deposits formed contemporaneously with the intrusion of trachytic dykes. The deposits are of the volcanic-exhalative type, with syngenetic siderite in pillow lavas or stratiform layers the primary and main Fe-bearing mineral. In the west hydrothermal alteration has replaced siderite in pillow lavas with magnetite or has remobilised sideritic iron into magnetite veins

Apr 1, 1995

By P. E. J. Pitfield, S. D. G. Campbell

The regional shear zone runs along or near the southern margin of the Chinhoyi greenstone belt. It hosts four of the seven mines in the southern part of the belt with recorded production above 100 kg Au, including the top two current producers. Displacement occurred in the late Archaean, producing a shear zone with a trend ranging from northeast at Golden Kopje to east at Muriel. The orebodies at the two mines formed synchronously with the shearing and show strong but contrasting structural controls on mineralisation. The Golden Kopje orebodies plunge to the southwest, parallel to the intersection of curved foliation with discrete shear planes and sub-perpendicular to local stretching lineations. The Muriel orebodies plunge steeply west but parallel to local stretching lineations. The greatest fluid flow during mineralisation of the shear zone was along either the intersection of fabrics (Golden Kopje) or the extension direction (Muriel). There is no unique relation between the orebodies and the extension or shear direction. Where earlier mining has not established the directions of the oreshoots it is essential to understand the possible structurally controlled geometries of orebodies before planning a drilling programme to evaluate their potential

Apr 1, 1996

During the construction of storage caverns, and during their lifetime if the use to which they are put so requires, it is necessary to provide adequate ventilation to ensure the safety and comfort of the underground workforce. An analysis of likely contaminants during construction has indicated that where a large facility is situated in a rock mass of even moderate temperature climatic conditions are likely to be the limiting factor during most of the mining operation and atmospheric pollution when blasting is undertaken. Possible options for improvement are increased air flow, cooling of intake air and reduction of the heat source by altering the number and type of haulage units employed in the cavern. Local solutions are an alternative approach where heat problems are confined to a few specific locations

Aug 1, 1994

Carbon anode cells were studied by two-dimensional computer simulation to evaluate their suitability for alumina electrolysis at high superficial current densities. The most efficient anode arrangement was needed to overcome the electrochemical disadvantages of alumina's low solubility in chlorides. Cells with packed-bed anodes might provide practical superficial current densities greater than 0.67 A/cm2 when the granule size was less than 1 cm, but in the process of electrolysis the granules within the active zone would be consumed and become smaller, affecting alumina concentration transport. For zones of very small granules a concentration-dependent model should be considered; for more complete consideration a time-dependent model can be introduced to describe the variation of granule size and its influence on mass transfer and polarisation

Jun 19, 1905

By W. E. Stephens, A. J. Boyce, D. Lowry

Paper presented at Mineralisation in the Caledonides, the Mike Gallagher memorial meeting held in Edinburgh, 27-28 June 1996. An integration of S isotopic, fluid and mineralogical data for granitoid-related mineralisation showed that the porphyry systems had a predominantly subcrustal magma source, but the inner magma pulse of two-mica granite in the Fleet pluton was derived mainly from reduced sediments. The porphyry-style mineralisation formed from boiling fluids at high crustal levels, with a moderately saline fluid percolating down to the upper veins as they cooled but not penetrating the deeper Talnotry deposit. Veins in peripheral greywackes have a significant magmatic component but also incorporated CO2-rich components and metals released by dewatering of host sediments in response to granitoid intrusion. The low grade of regional metamorphism resulted in the significant fluid input from country rocks which led to the more exotic mineral compositions, especially where argillaceous sediments were involved

Jun 19, 1905

By R. A. Ixer, R. A. Lord, H. M. Prichard, A. J. Boyce, P. McConville, C. T. Pillinger, I. P. Wright, J. Maynard

Analysis of 62 samples show that the sulphides throughout the igneous stratigraphy have a magmatic signature, with the exception of the uppermost gabbros and the lowermost basal thrust talc-carbonate lithologies. Mean delta-34S values for whole-rock samples from harzburgites, dunite pods in harzburgite, crustal dunites and wehrlites, the main and high-level pyroxenites and gabbros suggest that the primary sulphides derived their sulphur from a magmatic source enriched in 34S. This finding is compatible with the proposed origin of the ophiolite above a subduction zone. Values for pyrite mineralisation in the uppermost part of the gabbros are thought to result from precipitation from a seawater-derived fluid, while isotopically light sulphur in the basal thrust could have been introduced from underlying metasediments. The replacement of pentlandite by heazlewoodite has not led to sulphur fractionation

Jun 19, 1905

By J. H. Morris, G. M. Steed

Paper presented at Mineralisation in the Caledonides, the Mike Gallagher memorial meeting held in Edinburgh, 27-28 June 1996. Oxygen isotope analysis indicates that quartz, carbonates and muscovite could all have formed in near-isotopic equilibrium with the mildly saline H2O-CO2 ore fluid at 330 degrees C. Calculated values for O, C and S in the ore fluids imply derivation from a deep, homogeneous source region and are consistent with formation either as a direct or an indirect result of igneous processes. Values for delta-O18 plot a little outside the accepted magmatic range, but have almost certainly been modified by exchange reactions with wall rocks. These reactions were also the most likely cause of deposition of the ore constituents. The chemical and isotopic character of the fluid was similar to that in many Archaean and later mesothermal auriferous vein systems, especially the Mother Lode region of California. If the Southern Uplands-Longford Down accretionary complex conceals an Ordovician arc, the tectonic setting was also broadly comparable

Jun 19, 1905

By P. H. Carr, G. G. Marino, K. A. Patel

Extensions to a correctional institution at Wabash Valley, Indiana, required development over abandoned coal-mine workings, at 90 m depth, where subsidence was possible at surface. Backfilling of the flooded mine in critical areas was determined to be the most cost-effective method of limiting the risk of damage to the buildings. Containment grout was first placed in selected entries and cross-cuts of each mine area; the remaining volume was then filled with a readily flowing infill grout. Where a high proportion of an area was taken up by rubble, calcium lignosulphonate was used as a retarder and plasticiser to increase penetration. Grout movement was monitored from adjacent boreholes with an electrical resistivity probe during grouting, while after the work was finished core samples were obtained from verification holes drilled in the backfilled areas

Jun 19, 1905

By A. Ersoy, M. D. Waller

The principal factors which require consideration in predicting drilling rates are the bit-type, the bit operating parameters and the characteristics of the penetrated rock. A single index is not a sufficient basis for predicting performance. A variety of rock types were drilled in the laboratory with polycrystalline diamond compact (PDC) and impregnated diamond core bits using a fully instrumented drilling rig at different rotational speeds and with a range of weights on the bit. Quantitative determinations of a wide range of textural, mechanical and intact rock properties were also made. Multi-variable linear regression analysis was then used to develop predictive models of rates of penetration from the operating and rock property data. The models have been verified by statistical tests. The analysis indicated that the models for the pin and hybrid PDC bits have potential for practical application. However, although the model for the impregnated diamond bit appears to be reasonable from a purely statistical point of view, it may not be satisfactory for drilling uses as it is based on two measures of rock hardness alone. The application of multiple regression analysis to PDC drilling performance is novel and the technique shows promise for the prediction of rock drillability with PDC bits. The ability of the technique to provide a mathematical characterisation of the performance of new drill bits in specific rocks may prove to be of value to drill manufacturers and users

Aug 1, 1995

By D. R. Wardrop, G. Walton

Paper presented at the UK minerals industry conference held in Leeds, UK, 3-5 April 1995. A description is given of the approach that has been taken to the design of the 550 000 000 t superquarry with a planned life of 60 years that is proposed for development. The quarry has been designed to replicate a corrie and a sea loch and will include excavated slopes more than 570 m high. The main geological and physical controls on the layout and the choice of development method are outlined. The operation phasing is presented and the geotechnical constraints on slope design and the feasibility of alternative quarry limits are discussed. Environmental considerations have been dominant in planning and the quarry has been specifically designed for closure

Jul 1, 1996

By M. A. Leosson, S. H. Bottrell, R. J. Newton

Sylvite at Boulby is mined 1 140 m beneath the sea and the mine suffers from the influx of water. This is of two kinds: persistent flows originating in the Sherwood Sandstone aquifer and entering the evaporite sequence through fractures in the intervening mudstone, and impersistent flows which are transient in nature and of uncertain origin. Water from the overlying sandstone has become enriched with NaCl and large amounts of KCl and some Mg and Br have been added by interaction with the evaporites. Waters from the transient flows are isotopically distinct from those in the Sherwood Sandstone, being enriched in H and O. They are also saturated with respect to halite and sylvite, but have higher K/Na than the persistent flows and are much more enriched in Mg and Br

Jun 18, 1905

By S. Al-Hassan

The deposit has been exploited for Mn oxide and carbonate since 1916. Known reserves of MnO, however, are almost depleted and the survival of the mine will depend on the exploitation of the carbonate. Kriging, inverse distance weighting (IDW) and cross-sectional methods have been applied to the evaluation of the carbonate resources and reconciliation of the estimates obtained shows that kriging and IDW give almost identical block values. A comparison using conditional probability indicates that there is virtually no difference between the global reserve estimates derived from the cross-sectional and kriging methods. The physical causes of these similarities are highlighted and the problems of dealing with multimodal distributions are discussed together with the difficulties of semi-variogram modelling

Jun 19, 1905

By H. S. Sichel, W. J. Kleingeld, C. E. Dohm

A model of ore value distributions is presented that is the culmination of a statistical approach rather than simply a model that has been successfully applied to the evaluation of ore reserves. Detailed geological and physical observations based on large sampling data sets have been used to support the statistical modelling. Fundamental to the modelling process is the concept that the occurrence of a given grade value in space is a function not only of the presence of the mineral but also of the fact that it is associated with a specific trapping mechanism. The concepts have been specifically applied to gold mineralisation

Aug 1, 1995

By Qing Wang

In this method the state of an open-pit mine is represented by the number of benches that are mined in each predesigned mining phase (or pushback). Consequently, a specific mining schedule can be represented by a sequence of states which starts with the topography of the mine site and ends with the ultimate pit. For a given set of mining phases all feasible states are first generated and sequences of states are then evaluated for technical and economical feasibility. The best sequence, which gives the maximum net present value (NPV), is found by applying a dynamic programming optimisation algorithm. The algorithm also optimises the cut-off grade which satisfies the mill feed requirement for each planning period. It was found that the algorithm can be used not only for scheduling but also as an effective tool for analysing the effects of mining and milling capacities and cut-off constraints on the mining schedule and the total NPV. The algorithm, which was programmed in C, was successfully applied to a large Au-Cu deposit

Jul 1, 1996

By E Oktay, I Yusufoglu, C Kahruman

Powder and spherical pellets of MoO2 were oxidised under controlled conditions in the temperature range 674-791 K at oxygen partial pressures of 8.1-30.4 kPa. Weight increase during the reaction was determined by thermogravimetric analysis. It was concluded that the reaction is 0.6th order with respect to oxygen concentation and that the activation energy is 148 kJ/mole. In experiments conducted with powder, fast transfer of reaction heat to the gas phase created isothermal conditions, but the temperature of pellets rose by a maximum of 54 K at 674 K and 105 K at 791 K. The rise in temperature caused structural changes such as sintering and crack formation, which had a considerable effect on the reaction rate. The findings should be taken into account in the design of equipment and choice of operating conditions for roasting MoS2

Jun 21, 1905

By J. K. Whyatt, W. P. Blake, T. J. Williams

A study at the Idaho mine revealed that, despite the apparent randomness of seismic events, common characteristics defined five recurring types. These characteristics included the geological structure that slipped, the first-motion pattern and the location and intensity of damage. Many large events caused little or no damage, and where it did occur it was concentrated at intersections between slipping structures and mine openings. Of 39 events between 1989 and 1994 with local magnitudes of 2.5 or more, 10 were caused by slip on bedding planes in the southern limb of the mine, 6 occurred near the vein along a set of near-vertical faults that form the central shear zone, 8 were strike-slip events on the Southern Control Fault, 4 were by slip on the vein itself and 10 involved strike-slip and/or dip-slip movement along the North Control Fault. Strategies for control of mining-induced seismicity need to consider all five types of event, lest a strategy to reduce one type increases others

Jun 19, 1905

By B. R. Reddy, Y. V. Swamy, B. V. R. Murthy, H. S. Ray

The Ni oxide was reduced with a CO-CO2-N2 gas mixture and the effects were observed of process variables such as roasting temperature, time and CO partial pressure. Extraction of over 90% of Ni was achieved by ammoniacal leaching of ore that had been reduced for 1 h at 760 degrees C under a gas mixture with a volumetric CO/(CO+CO2) ratio of 0.57. The kinetic data were found to conform to the Ginstling-Brounstein equation. The applicability of this model was confirmed by evaluating the apparent activation energy with the use of independently constructed differential and integral plots, which showed an excellent match

Dec 1, 1995

By P. H. Morris

The profile of a delta formed by fine-grained mineral processing wastes, disposed of as aqueous slurries by subaerial deposition from a pipeline, has a significant bearing on the volume that is available for waste and water storage in a given containment structure. Earlier field data and laboratory experiments suggested that mine waste delta profiles could be predicted with high levels of accuracy using data from small-scale laboratory deposition tests. The relationships between the profiles of full-size and laboratory-model deltas were analysed using the principles of kinematic similarity and a recent theory of delta formation based on engineering hydraulics. Measured profiles of full-size and model coal-mine tailings deltas are compared and the prediction of full-size profiles discussed. It is shown that the data-derived laboratory-model deltas are insufficient to allow accurate prediction of full-size delta profiles. Initial slope data or other, equivalent data for the full-size delta are also required

Apr 1, 1996