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By Gruenewaldt von

Paper presented at the IAGOD international symposium on mineralization related to mafic and ultramafic rocks held in Orleans, France, 1-3 September 1993. The principles of shear-driven aggregation of particulate matter suspended in fluids, a common industrial method of concentration and separation, were applied to a convecting magma to estimate the time required to sparge or strip the PGE and Cr content and concentrate it into the boundary layers. It was calculated that an ore-grade (e.g. 6 ppm PGE) boundary layer about 1 m thick would require 100 000 years at most to form from a body of magma 500 m deep with a PGE content of 20 ppb. Since concentration would be most vigorous when the magma was warmest, at least half of this concentration would take place in the first 10 000 years. The effect of dispersive pressure in the boundary layer would generate a concentration high of refractories just below the top of each boundary layer and another just above the bottom. If the magma was a double-diffusive system, it might evolve by the downward cascade of enriched boundary-layer material into the hotter, lower magma layers, where depending on saturation levels chromites would equilibrate and sulphides undergo partial or total resorption, enriching PGE levels in any remaining sulphides. This cascade process would in time greatly enrich the lower regions in PGE-bearing sulphides and chromites

Apr 1, 1994

By R. Lahtinen, M. Tiainen, R. Salminen

The application of similarity analysis derived from regional geochemical mapping data to the location of Ni-bearing intrusions was tested in southwest Finland, where a well-known nickel belt is situated. Samples of till from the vicinity of the Vammala and Kylmakoski Ni-Cu deposits, which were collected independently of the Geological Survey of Finland's regional geochemical mapping programme, were used to provide geochemical modelling data. The data consist of the aqua regia-leachable concentrations of 20 elements from the less than 0.06-mm fraction of glacial till. The variables used in the similarity analysis were selected on the basis of a factor analysis in which the method of oblique rotation was used. A hierarchical clustering of the modelling samples produced two main groups. The first group was described as the "nickel deposit environment model" and the second as the "nickel deposit location model". The data for the standardised variables were compared sample by sample with the model data by similarity analysis using the Simana program with a cos theta measure of pattern similarity. The nickel deposit environment model delineated the known Ni belt and indicated an extension to the east. The nickel deposit location model identified target areas of reasonable size with the greatest potential for Ni ores within the nickel belt

Dec 1, 1991

By F. Tailoka, G. Zhao

Pb is an unwanted impurity in Al for which there is no established method of removal. As it interacts strongly with alkali metals, separation was achieved by adding Na or K to molten Al at 953-1 003 K. Direct Na addition led to considerable evaporative loss but in-situ addition by electrochemical titration from a eutectic NaCl-KCl or KCl-BaCl2 mixture was found far more effective, in some cases reducing Pb content below detection levels within 2 h of titration. K appeared more effective than Na at low Pb concentrations but the use of Na was preferred as it is less toxic and explosive. Na removal from Al-Na and Na-Pb alloys was also carried out electrochemically, the use of these two alloys rather than the eutectic salt as a source of Na avoiding liberation of Cl2 at the anode

Apr 1, 1995

By O. R. Eckstrand, M. Asif, P. L. Schwann, A. J. Naldrett, R. J. F. Scoates

Paper presented at the IAGOD international symposium on mineralisation related to mafic and ultramafic rocks, held in Orleans, France, 1-3 September 1993. PGE-bearing sulphide mineralisation is contained in the lower 600 m of the Upper Central Layered Zone of the intrusion. There are four regimes with distinctive crystallisation characteristics. PGE content is low, both in bulk rock and in terms of metal in 100% sulphides, in the sulphide-rich cumulates but increases sharply in the sulphide-poor cumulates at the base of regime 1. Increases in regime 2 have no such clear relationship with incoming cumulus sulphides. PGE contents are low throughout regime 3, but regime 4 has sulphides with high PGE content, decreasing rapidly upwards, at the base of many of its cyclic units. The observations are interpreted as indicating that sulphide saturation occurred in the middle of a cyclic unit in regime 1, after which fractional segregation of sulphide caused a systematic decrease in PGE content. The resulting contrast between 40 000 ppb PGE in sulphides below the mineralised zone and less than 1 000 ppb above is of practical importance in exploration for such zones. In regime 2 the magma chamber was open to fresh influxes and PGE content was not so sensitive to sulphide saturation. In many regime 4 units influxes of new magma caused immediate sulphide saturation and PGE depletion, so that PGE-rich cumulates do not underlie PGE-bearing sulphide zones. Theoretical analysis indicates that regime 1-type behaviour is likely to characterise intrusions below the level at which plagioclase has entered as a cumulus phase and regime 4-type behaviour above

Apr 1, 1994

By M. R. Smith, H. Kanli

The impact crusher is a popular device for producing crushed aggregates from non-abrasive rocks such as limestones, offering the advantages of high reduction ratios and relatively low installed costs. To extend the application of a process-flowsheet simulator to the quarrying industry, a mathematical model of an impact crusher was therefore developed using the general crusher models of Andersen and Whiten as a basis

Aug 1, 1995

By V. A. Melezhik, P. K. Skufin, L. P. Nilsson

these factors into account. Theoretical and

Aug 1, 1994

By R. Ciccu, P. P. Manca, A. Bortolussi, G. Massacci

Tool performance and the unit cost of cutting depend on a number of operational variables (peripheral velocity, pull-back force, water injection rate, angles of the sections of wire outside the rock) as well as on the geometric features of the cut itself (area and shape). Cutting rate and wire productivity are also influenced by the type and number of diamond beads per unit length of wire and by the characteristics of the rock (granite or marble). A computer program aimed at handling a problem of this complexity has been developed and tested with the use of available field and laboratory data and has been found acceptably reliable. Discrepancies between current industrial data and some of the results suggest future lines of research, while the simulation should also be extended to include different types of rock and tool and a variety of bench face geometries

Aug 1, 1994

By P. H. Williams, D. J. Morris

The co-disposal of coarse and fine coal wastes by combined pumping through a pipeline to subaerial deposition was pioneered in Australia in 1990 by Jeebropilly colliery in Queensland. Significant segregation of fines is found to occur in its co-disposal delta, leading to the formation of distinct mainly coarse upper and fine-dominated lower segments; the upper delta drains rapidly and is able to support traffic on its surface immediately after deposition. An existing theory of subaerial deposition, originally developed for mine tailings alone and later extended to trial co-disposal, is shown to apply also to the upper segment of the full-scale Jeebropilly delta

Jun 19, 1905

By G. X. Wang, R. E. Siemens, M. C. Fuerstenau, D. Chandra

Soda roasting of concentrates from Mouat, Montana, was performed in a temperature range of 450 to 650 degrees C and chromium was solubilised by water leaching at room temperature. It was found that high extraction yields of chromium were primarily dependent on the conversion of Cr3+ to Cr6+ during the roasting step, and this was enhanced significantly by simple attrition of chromite particles during this step. Gangue impurities (mainly Si) were more detrimental to Cr extraction than lattice impurities such as Al or Mg. It appears that oxidation proceeds into grains along a preferred crystallographic plane in the cubic lattice of the chromite. The effects of roasting time, temperature, soda to chromite ratio and particle size on the extraction of chromium are presented

Jun 18, 1905

By T. Lenarcic, R. Svrkota, J. M. McNeal, E. Prohic, S. Pirc

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). Surface drainage samples, the usual media employed in mapping national territories, cannot be used for the geochemical mapping of carbonate terrains because there is no regular surface-drainage pattern on karst. Suitable sampling media have been studied in Yugoslavia, one-third of which consists of karst terrain. Sampling designs for the work were based on analysis of variance techniques. During initial investigations of various sampling materials in NW Yugoslavia sediment and aquatic moss from karst springs, along with soil, were established as the most appropriate media. Modified sampling procedures were then carefully applied along the entire Yugoslav karst belt, which includes terrains of contrasting topography, climate, pedology and vegetation. The studies indicate that climate and relief do not systematically influence the geochemical composition of soil. Regional and local variability was assessed for 21 chemical elements and the feasibility of producing stable regional geochemical maps was determined for a number of elements on the basis of sampling aquatic moss and sediment from karst springs and soil

Jul 1, 1991

By Boorder De, B. S. Panov, A. B. Westerhof, V. A. Korcemagin

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. The Hg and Sb deposits of the Mediterranean and Circum-Pacific Belts are often found at elevated structural levels, suggesting that their preferential occurrence in young orogenic belts is not a fundamental metallogenic feature but merely reflects their chances of surviving post-orogenic peneplanation. In western Europe their emplacement appears often to be related to late orogenic extensional events accompanied by a notable increase in heat flow. Although Nikitovka and Almaden have quite different settings, both appear to be related to deep-reaching shears. Together with brittle fault zones at higher levels, these provided pathways for fluid phases that originated at least partially within the mantle. The Nikitovka deposits are located in the Donets segment of the 2 000 km Pripyat-Dniepr-Donets palaeorift in the East European Platform. Initiated in the mid-Devonian with a possible Precambrian precursor, its listric boundary faults displace the Moho from a depth of about 50 km north and south of the rift to 35 km along the axes of the Pripyat and Dniepr segments. The steep central anticline of the Donets segment, within which the main Hg-Sb district is located, is interpreted to be associated with a reactivated fault reaching into the upper mantle. The Almaden syncline, formed during the Variscan Orogeny, may be an older pull-apart basin or half-graben associated with the collapse of the Cadomian Orogenic Belt. It is situated on a major ENE-WSW-striking shear zone which may represent a Late Cadomian transfer zone reaching into the mantle

Apr 1, 1995

By A. G. Pasamehmetoglu, N. Bolukbasi, O. Koncagul

A study has been undertaken to establish the relationships between the O&K wedge test cutting resistances and the geotechnical parameters of rock materials in the context of bucket-wheel excavator operation. Prediction equations were formed to estimate the cutting resistance from the geotechnical parameters by multiple regression analysis. The cone indentor index, uniaxial compressive strength and Shore hardness parameters have been found to be the most significant predictors

Sep 1, 1991

By K. Nielsen, J. Kristiansen

A series of laboratory blasting and grinding tests on three types of hard and competent rock (coarse-grained monzonite, fine-grained granite and very fine-grained gabbro) showed that a higher level of applied explosive energy enhanced grindability and produced a larger amount of fine (-0.106 mm) material. This confirmed reported industrial experience and the results of previous investigations. However, the results did not provide any information on the quantitative relationship between the energy applied in primary blasting and that required in subsequent comminution. Only about 1% of energy consumed in conventional grinding is used to create new surfaces, while power efficencies in cone crushers have been estimated at 70-80%. In blasting, up to 20% of explosive energy may be transmitted to the surrounding rock as elastic strain energy, leading to both primary rock breakage and the generation of microcracks

Dec 1, 1995

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 I. L. Bell

The ironmasters of America had asked the Iron and Steel Institute to visit the USA. The Council decided it was not possible to accept, but Mr. Bell visited; this is an account of his trip. Topics covered include transport, charcoal, coal measures, coal, anthracite, bituminous coal, flux, magnetic iron ore, specular iron ore, limonite, red hematite, clay ironstone, black band ironstone, smelting works, blast furnaces of Pennsylvania, Lake Champlain furnaces, Lake Superior furnaces, Cleveland furnaces, Pittsburg furnaces, Missouri furnaces, and those of the southern states. He goes on to describe Catalan hearths, malleable iron works, Bessemer works, the Blair steel process, and labour.

Jan 12, 1875

By G. D. Schena, C Chiaruttini

The feasibility is demonstrated of reconstructing the volumetric distribution of liberated particles and middlings by use of a damped, weighted least-square regularisation method. This allows a precise mass balance to be obtained around a separation/concentration unit, permitting evaluation of the partition curve (Tromp curve) of the separator. Areal grade measurements are made on polished sections of feed, concentrate and tailings and a kernel-based inversion technique is then used to obtain the volumetric grade distribution of the three assemblages. A plain kernel (number of occurrences) and a weighted kernel (each occurrence counted with its area) are used for the solution. Testing of the method on computer-generated synthetic areal grade measurements indicates that it offers a valid alternative to the tedious conventional procedure of conducting experiments with heavy liquids

Jun 21, 1905

By M. Gallego, R. Oyarzun, L. Ortega

Evidence of metallogenic activity in an area dominated by Upper Precambrian and Palaeozoic metasediments was partially explained in the 1980s when drilling and a geophysical survey detected hidden intrusions, but questions remained to be answered about the nature of the fluids. Sb mineralisation at El Juncalon vein-type deposit was selected for geological, geochemical and fluid inclusion studies as a model with a relatively simple quartz-stibnite-pyrite paragenesis. Many of the characteristics were those of Chinese-type vein Sb deposits, which can be regarded as atypical of the epithermal type as they are hosted by clastic rocks

Aug 1, 1995

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

The regional structure of shear and deformation zones in the belt, which is recognisable in plan view on Landsat TM images, is interpreted in terms of a conjugate-shear model. Gold mineralisation is related to this framework at a variety of scales. The principal recurrent structural geometries hosting deposits at mines such as Motapa, Durban, Charliesona, Cecil, Sunace, Turk group, Queens district, How, Peter Pat, Matabele Sheba, Goodenough, Old Nic and Bushtick are associated with shear zones and folds and include conjugate systems (shears, shear intersections, kink sets), side-step systems (en echelon segmentation, duplexes, monoclinal inflections, antiform-synform couplets) and interactions of the two. Linear sections of shear zones are generally poorly mineralised. The same geometries are identifiable on all scales from local to regional, so sections of regional structural lineaments or areas within mines should be prioritised for further investigation or development on the basis of the gold-bearing geometries observed to be dominant locally

Apr 1, 1996

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 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