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By R. J. Gochin, G. D. Schena, R. Spencer

The impact of a mineral project in a developing country is evaluated in the broad context of its economy using input-output models. Minimum economic theory is used to develop simple numerical models. Sets of technical coefficients are exploited in the development of linear models of the productive element of an economy. The analysis allows assessment of the overall economic consequences of a mineral development in which issues broader in scope than financial objectives need to be incorporated in the evaluation. In part 1, the framework for the development of the input-output model is presented. The model is refined to incorporate country-specific behaviour. The increased flexibility of the enhanced semi-input-output model permits a more confident investigation of the economy-wide effects associated with a new project in the mineral sector of a developing country. The relevance of the models is illustrated using an example from Namibia

Sep 1, 1991

By N. Krauland, A. Nystrom, M. Board, S. Sandstrom

Several deep Swedish cut-and-fill mines experience severe ground control problems, including roof collapse and wall sloughing, as a result of variable rock quality and high in situ stresses. A project to examine the problem included two main areas. The first was prediction of mining conditions at depth and the adaptation of cut-and-fill mining to such conditions; the second was the assessment and improvement of support methods at present and future depths. Simple, elastic, mine-scale numerical models were used to optimise stope sequencing and more detailed, stope-scale models to simulate the failure processes around a stope and the interaction of rock mass and support. Kristineberg was chosen for testing and calibration of the predictive methods because of its long history of severe ground conditions and the large base of observational and monitoring data available for comparison. Horizontal cut and fill was found technically suitable to depths beyond 1 000 m and economically viable if ore value covers support costs. Stability can be achieved with the present support technology down to 1 000 m but the 7-strand 15.2 mm cables have poor deformation properties (5% failure strain) compared with rebar rock bolts (17%). Reducing the intervals between levels from 100 m to 50 m will cut support costs and improve production reliability and capacity. Simulation of sill-pillar mining indicated that conditions would be most severe when pillar height was reduced to 15-20 m; mining of a sill pillar has been carried out successfully to the last 3 m, whose extraction is planned for the near future

Dec 1, 1995

By C. McCall, J. T. Knight, J. R. Ridley

Gold mineralisation in the gabbro sills is mainly stratabound to quartz- and Fe-rich, granophyric-textured units and is sited in undeformed, brittle quartz vein sets, which form pipe-like orebodies. Hydrothermal wallrock alteration consists of hornblende-plagioclase-calcite-quartz with minor biotite, garnet and chlorite and with arsenopyrite and pyrrhotite as the dominant sulphides. Geothermobarometric data suggest that gold was deposited at around 520 degrees C at 2.8-3.8 bar. Mineralisation is thought to have occurred during amphibolite-facies metamorphism. Fluid inclusion and isotope data indicate that gold mineralisation was the result of deposition from a low-salinity H2O-CO2-CH4 fluid of either metamorphic or magmatic origin. Although the Three Mile Hill deposit differs from others in the area in its wallrock-alteration assemblages, peak-metamorphic timing of gold deposition and distinct geochemical associations it forms a brittle stratabound ore body which suggests structural and gold-depositional mechanisms in common with those of the other gabbro-hosted gold deposits

Jun 18, 1905

By G. Adachi, K. Machida, T. Ozaki, K. Murase

The chlorination rate with CCl4 was unexpectedly slower than carbochlorination using chlorine under the same reaction conditions. Chlorination with CCl4 was topochemical and the amount of monazite reacted after different periods suggested that the kinetic control step was the reaction between CCl4 and the monazite core at the interface. The kinetic order of the reaction was 0.5. The presence of a complex former, AlCl3, promoted the chemical vapour transport of rare-earth chlorides as complexes

Jun 18, 1905

By M. C. Ruiz, M. E. Godoy, J. B. Rivarola, M. W. Ojeda

The amount of Pd recovered from an exhausted olefin hydrogenation catalyst was found to depend on mixing technique, particle size, carbon percentage, chlorine flow, reaction time and temperature. Pd extraction was total when a sample in the 125-175 micrometre particle size range was chlorinated for 60 min at 723 K with 20 cm3 Cl2/min, for 60 min at 748 K with 30 cm3 Cl2/min and for 30 min at 773 K with 30 cm3 Cl2/min. No C addition was needed; the initial C content of the catalyst was sufficient for total recovery. Pd extraction was also affected by heat treatment in different atmospheres before chlorination. Treatment with O2, N2 and N2 with traces of O2 led to different degrees of oxidation of C and permitted the formation of oxidised Pd species. Thermal pretreatment in N2 with traces of O2 was most conducive to Pd extraction

Jun 21, 1905

By Dean S.

Further discussion at the North of England Institute of Mining and Mechanical Engineers' general meeting held in Newcastle-upon-Tyne, 12th February 1916, with Mr. T.Y. Greener, President, in the chair, of the paper published in Trans. I.Min.E. vol.L, 1915, p.179 and 388. Written contributions to discussion included Mr. Dean's reply to earlier discussion (p.35-44), further written contributions by Tate S. (p.44-54) and Brown E.O.F. (p.54-56), and oral comments by Hare S., Merivale J.H., Greener T.Y. and Tate S. Particularly debated were the causes of the difference in output between American and British coal miners

Dec 1, 1916

By A. H. G. Mitchell

Most, if not all, of the six recognised post-Cretaceous, predominantly andesitic mineralised belts in the region are now thought to be subduction-related magmatic arcs. The Inner Carpathian arc and the Eastern Bosnia or Drina-Rhodope arc host numerous vein and replacement deposits with epithermal features and Zn-Pb+/-Ag as the predominant economic minerals. In contrast, the south Apuseni Mountains have produced over 1 600 t Au from epithermal veins but very little Zn-Pb. Recent age determinations and geophysical data from the Baia Mare district of the Inner Carpathians suggest that mineralisation succeeded volcanism by 1-2 m.y. and accompanied crustal extension and the cooling of a large, mushroom-shaped pluton whose boundaries define the mineral district. In the south Apuseni district, mineralisation can be explained by mixing of meteoric with low-salinity metamorphic water expelled during intrusion of mafic rocks into the middle or lower crust. The more continental or cratonic crust in the Drina-Rhodope and Inner Carpathian arcs precluded the input of low-salinity, Au-bearing metamorphic water; the Zn-Pb deposits formed where convecting meteoric water mixed with saline water, possibly introduced through carbonate rocks in the basement

Aug 1, 1996

By M. T. Styles, E. Condliffe, R. C. Leake, R. J. Chapman, D. J. Bland

Paper presented at Mineralisation in the Caledonides, the Mike Gallagher memorial meeting held in Edinburgh, 27-28 June 1996. Quantitative point analysis and microchemical mapping identified 52 different types of mineral in inclusions, usually ranging in size from 5 to less than 1 micrometre, inherited from source bedrock. A combination of grain chemistry, heterogeneity and inclusions provides a grain signature reflecting the type and history of source mineralisation. Several grains from an alluvial site are needed, to allow for bedrock variation and the presence of inclusions in only 10-20% of grains. A total of 1 530 grains obtained from 30 localities in Scotland were of ten types, two of them minor variants. Two types in the Highlands may be related to centres of Caledonian igneous activity, but the most widespread is likely to have been of deep-seated origin and structurally controlled. Gold in the Ochil Hills is probably from a source associated with Devonian andesitic activity. In the Southern Uplands, grain types reflect two separate episodes of mesothermal lode gold mineralisation and relationships with Permian red beds/mafic volcanics and with Tertiary dykes

Jun 19, 1905

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 W. P. C. Duyvesteyn, B. J. Sabacky

Reprinted with revisions from Extractive metallurgy of copper, nickel and cobalt, volume I: Fundamental aspects. ed. Reddy R.G., Weizenbach R.N. Warrendale, Pennsylvania: The Minerals, Metals and Materials Society, 1993. Development work on the Escondida process, concluding with the successful operation of an integrated leach-SX-EW pilot plant and a pilot flotation plant for the upgrading of leach residues, demonstrated that all major process objectives could be achieved. Extraction of 40% of copper in concentrates containing monovalent copper was achieved with essentially no oxidation of sulphide sulphur. The Cu contents of leach residues from four different types of concentrate were successfully upgraded to the original feed grades, giving a product that has potential as a high-quality concentrate for the smelter market. A compact solvent extraction section effectively recovered the ammonia lixiviant for recycling to leaching and selectively transferred Cu into a conventional acid sulphate electrowinning system. High-quality "six-nines" copper cathode was produced on commercial-scale stainless steel blanks, demonstrating that the process will be able to compete effectively in the premium cathode market

Dec 1, 1995

By S. L. R. Lenharo, H. Kahn, H. Born

Different ore types result from the irregular spatial distribution of the associated alkaline/carbonatite rocks and the zoned alteration profile within which apatite may have undergone reprecipitation. Different flotation responses are caused by their mineralogy, iron oxide impregnation and grain-size characteristics. Samples from seven deposits were crushed, screened and separated before being studied by chemical analysis, optical microscopy, X-ray diffraction, FTIR spectroscopy, cathodoluminescence and scanning electron microscopy. Two main apatite varieties with peculiar crystal morphology were identified: hydroxy-fluorapatite as the primary phase and carbonate-fluorapatite as the reprecipitated phase. The former occurs as prismatic or ovoid grains and the latter as polycrystalline aggregates or crusts on the primary grains; both are associated with iron oxide coatings (primary) or intergrowths (secondary). Microflotation tests showed variations in flotability for particular apatite associations as well as intensity of iron oxide coatings. The differences in flotation behaviour can be related to morphological properties and chemical substitution in the apatite structure

Aug 1, 1996

By J Hadijigeorgiou, R. W. Lawrence, R Pouling

The layered co-mingling method involves the disposal of waste rock with the addition, at predefined construction stages, of layers of dewatered mine tailings. The resulting waste structure displays bulk properties that are more favourable to acid rock drainage (ARD) control than the constituent materials alone. A laboratory test programme was conducted to examine the potential of this method. Columns containing different configurations of waste rock and tailings were percolation leached for 40 weeks and the leachates examined for various parameters. In the short term the chemical reactions that result from the introduction of dewatered tailings into rock waste can significantly improve the quality of the drainage. Columns with co-mingled material produced leachate with pH levels of 8, whereas leachate from the control column containing waste rock alone had a pH of 4. Larger-scale field tests are planned to determine the effect of the disposal method over the longer term

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

By T Grenne, R. B. Larsen

Paper presented at the conference on Economic geology in Europe and beyond II, models for mineral deposits in sedimentary basins, held in Keyworth, UK, 13-14 April 1994. Paper originally entitled: Processes in a newly discovered sulphide-PGE mineralisation in Norway. The Stormyrplutten mineralisation is hosted by a minor tholeiitic metagabbro of low-Ti composition intruded at a high level in the volcanic lithology. It is thought to be the subvolcanic counterpart of submarine basalts generated during an extensional episode of ensimatic arc evolution. The sulphide-PGE mineralisation occurs as stratabound pyrite, pyrrhotite and chalcopyrite disseminations with average grades of 376 ppb Pd, 313 ppb Pt, 40 ppb Au, 0.5% Cu and 0.08% Ni in a deposit 15-25 m thick. Locally the PGE content peaks at 2 ppm over 1 m. Microprobe analysis isolated 14 different platinum-group minerals, dominated by sperrylite, temagamite and borovskite and occurring as 1-20 micron compounds embedded in the main sulphide minerals or along the sulphide/silicate grain boundaries. Mantle-normalised plots reveal strong depletion in Os, Ir and Ru and enrichment in Pt, Pd, Cu and Au. The general decrease in Pd and Pt and increase in S up through the stratigraphy is similar to PGE distribution in the Darwendale subchamber of the Great Dyke in Zimbabwe, and may reflect strong fractionation of Pd and Pt in favour of the first droplets of sulphide melt; two reversals of the trend at the 4 and 12 metre levels represent replenishment with fresh magma and repetition of the cycle. In contrast to the Darwendale system, Cu and Ni also show peak concentrations in the first-formed liquids and Pt appears to have fractionated more strongly into the sulphide melt than Pd

Aug 1, 1995

By S. L. Gay

The conventional mass-balance equations used as constraints can lead to flow estimate values of zero even though the flow estimates should be some positive number. This is because many of the constraint equations are satisfied if the flow rates are zero. The way to overcome the problem is to use a slightly different form of the equations. For example, rather than use the conservation of flow of solids as a constraint it is better to use the constraint that the percentage of solids going into a unit equals the percentage of solids coming out of the unit. Examples are given using mineral processing data sets from Mount Isa, Queensland, and Red Dog, Alaska

Jun 21, 1905

By M. Feely, W. G. O'Keefe, C. O'Reilly, M. P. Holdstock

A petrographic and microthermometric study of fluid inclusions in the Kentstown Granite, crosscutting quartz (VI) and calcite+quartz (V 2) veins in the granite and calcite+quartz (V 2) veins in the overlying sediments was performed on samples taken from the borehole. Comparisons of the type 1, type 2 and type 3 fluid inclusion populations recorded in the present study with those from other Irish Caledonian granites strongly suggest a similar fluid evolutionary history. Furthermore, the low-temperature CaC12-rich brines (type 5) of this study, which must be syn- to post-Lower Carboniferous in age, have correlatives both in Irish Caledonian granites and in the Lower Carboniferous base-metal deposits of the Irish midlands

Jun 19, 1905

By G. M. Steed, A. O. Oyinloye

The deposit lies in amphibolite-facies biotite granite-gneisses of Proterozoic age, 4 km east of a major crustal break known as the Ifewara-Zungeru fault. Gold mineralisation is contained in a zone of quartz-carbonate (mainly calcite) veins and hydrothermally altered gneisses with associated small-scale intrusions along a steeply dipping second-order fault zone that roughly parallels the main fault. Gold is present mainly at grain boundaries between quartz and carbonate as discrete particles up to 100 micrometres in size, in general association with sparse, scattered pyrite, pyrrhotite and some base metal sulphides. Adjacent to the gold-bearing zone the granite-gneisses have been hydrothermally altered with minor volume increase, most notable enrichment being in K2O, S, Pb and Cu (and Au). High concentrations of Th, Y, Ce and Zr in the granite-gneisses imply derivation from S-type granites. It is likely that their high heat production capacity maintained the high temperatures needed to transport gold in the hydrothermal systems. It is most probable that the mineralisation dates from the Pan-African orogeny (650-450 Ma)

Apr 1, 1996

By M. V. Swain, N. Bristow, R. D. Dukino

During mining, crushing and handling the size of iron ore lumps decreases. Key factors in determining the amount and size of fines that are produced are the mechanical properties of the ore. In a continuation of earlier work on the same ores the mechanical properties of three Australian iron ores from Yandi, Koolan and Mt. Whaleback were determined. In particular, fracture toughness was investigated in greater detail by examining its relationship to crack length using the compact tension test. The elastic modulus and strength of the ores were also determined in flexure and compression. The results were interpreted using Weibull statistics, enabling the ores to be ranked according to strength and elastic modulus. These results, together with data on the mechanical response of the ores to stress and observations concerning the effect of mineralogy on cracking, provide a coherent understanding of the mechanisms involved when the ores fracture

Jun 18, 1905

By J. A. Hudson, X. D. Pan

A rock mass responds to excavation according to the properties of the intact rock, the network of contained discontinuities and the susceptibility of the rock mass to weathering. Large deformation often occurs when one of these components causes the rock mass to have a low strength relative to the stress conditions. Analysis of such large deformations forms a significant feature of current numerical modelling in rock mechanics. A practical large deformation problem of roadways in a coal mine is described, demonstrating the requirements for improving numerical techniques. The development of a numerical model is then summarised with particular attention to several concepts pertinent to large deformation analysis in geomechanics. A numerical case study is presented in which the developed finite-element model is used and the results are compared with the in-situ measurements. Conclusions are drawn for rock engineering that are also relevant to both civil engineering and mining engineering projects

Sep 1, 1991

By Seong-Taek Yun, Chil-Sup So, Seung-Jun Youm

The greisen-bordered quartz veins are spatially, temporally and genetically associated with a late Cretaceous granite intruding an early Palaeozoic, limestone-rich formation. Paragenetic data indicate three stages of hydrothermal mineralisation, the first typically in or within 500 m of the granite stock and showing vertical zoning between deeper Mo and higher W, the other two more abundant in the upper and outer parts of the mineralised area. Fluid inclusion and stable isotope data indicate that hydrothermal veins formed over a temperature range of 120-395 degrees C from low-salinity fluids. Early wolframite and molybdenite deposition in stage I occurred at temperatures of 300-395 degrees C from magma-derived, low-salinity, CO2-rich fluid, mainly as a result of fluid boiling and associated CO2 effervescence. Progressively larger volumes of local meteoric water entering the system led to the successive deposition of scheelite in stage I vugs, stage II base-metal sulphides and stage III fluorite-carbonates. Remobilisation of W and its later deposition of scheelite in the outer and shallower portions of the system occurred at 215-275 degrees C and stage II and III mineralisation from lower-temperature fluids that became progressively lighter in stable isotopes. It is concluded that the influx of meteoric water increased with distance from the cooling pluton

Jun 18, 1905