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By Terri Jordan, Gregory Hempen, Thomas Keevin

Water-borne blast pressures from confined blasts were recorded as part of a submerged blasting program in Florida for channel deepening. The blasting was confined within the rock floor by stemming. Shot patterns of stemmed borings were recorded, as were two open-water shots. One hole of one shot was not confined properly, which allowed comparison of confined and a poorly confined larger charge weights per delay. The pressure data were intended to gain information on typical pressure measures from the rock removal program relative to impacts on marine organisms. Water-borne pressures from actual confined, rock-removal shots validate the hypothesis of lessened impacts to aquatic and marine biota.

Jan 1, 2007

By William A. Beck

"In 1912 bauxite was discovered in the Andersonville district, which lies in the 28th and 29th land districts of Georgia and comprises parts of Sumter, Macon, and Schley Counties. Mining was begun in May 1914 by the Republic Mining & Manufacturing Co. Considerable ore has been produced in this region since that time by individual interests and by the American Cyanamid & Chemical Corp., which acquired the property formerly owned by the Republic Co.The area was examined in the fall of 1941 by representatives of the Bureau of Mines and the Geological Survey, after which a prospecting program was begun by the Bureau. Drilling was started on December 26, 1941, and continued until November 18, 1943. A total of 1,192 holes was drilled in the district, and 3,679 samples were taken and analyzed.Mineral exploration agreements were signed by 146 property owners covering 42,128 acres. Holes were drilled on 121 of these properties, which have a total area of 38,778 acres.Drilling under this project disclosed several new deposits, of which four have been completely delimited. Previous prospecting in this area by mining companies did not find bauxite, as it lies under heavy overburden. Work by the Bureau indicates 14,412,000 long tons of ore containing 30 percent or more alumina. The total tonnage is divided as follows:Georgia State Highway Routes 26 and 4-9 traverse the district. The Central of Georgia Railroad passes through the center of the entire district (see fig. 1).The project was initiated by J. R. Thoenen, supervising engineer, Non-metals Mining Section, Mining Division, Bureau of Mines. It was under his general supervision until July 1942, after which it was under the general supervision of E. J. Lintner and Rowe McCrae, district engineers for Georgia, South Carolina, and Flordia, respectively.John C. Feeley, Jr., was project engineer from December 1941 to April 1942. Other engineers who assisted in the work on the project are R. E. Babcock, T. M. Romslo, Don M. Coulter, and Walter T. Lewiecki.Acknowledgment is due the metallurgical staffs at College Park, Md., and Tuscaloosa, Ala., for analyses of samples and beneficiation tests.Acknowledgment is also expressed to Alfred D. Zapp, M. W. Harris, Elmer Kneedler,and Parke D. Snavely, of the United States Geological Survey, for their aid, data, and maps.Bauxite was discovered in the Andersonville district in 1912 on lot 187 of the 28th land district, in Sumter County. This lot is situated about 1.5 miles west of the Flint River, on the south slope of the valley of Sweetwater Creek. Mining was started in May 1914 by the Republic Mining & Manufacturing Co. This and adjacent properties were acquired in 1930 by the American Cyanamid & Chemical Corp., which has been operating there since."

Dec 1, 1949

By K. V. Raj

In the mining industry, computational fluid dynamics (CFD) modeling is used extensively to simulate air flow in underground mines. CFD modeling of pollutant transport in open-pit mines is relatively new. Modeling the actual pit geometry of an open-pit mine and the open domain is complex. The complexity is primarily due to the faceted geometry of an open-pit mine with its numerous associated sharp features. Important issues that are not considered carefully at the geometry level are generally propagated to the subsequent processes. Several challenges and pitfalls are encountered in modeling pollutant transport in open-pit mines. These challenges and pitfalls are related to the geometry, meshing, boundary conditions, and turbulence modeling parameterization. An appropriate mesh selection is critical. A detail discussion of the meshing of the domain of an open-pit mine is presented in this paper. The selection of an appropriate turbulence model, such as kappa-epsilon (?-e), large eddy simulation (LES), Reynolds stress model (RSM), etc., to obtain the best possible solution is equally significant. This paper discusses the various challenges in modeling the pollutant transport process in an open pit and some of the approaches adopted to address these challenges.

Feb 27, 2013

By D Will

RedrossThe Redross orebody averages 1 m wide, has a strike of 50 - 350 m, dips at 55° and has a basalt footwall and an ultramafic hanging wall. The most successful and innovative aspects of mining Redross were:•ore development innovations, 90 per cent of development was split fired with a shanty back profile to enable larger and more productive equipment to be used and resulted in higher development grades, improved project payback time and improved ore recovery;•hand held stoping using a multiple level, bottom up ‘V’ shaped hand held stoping method that allowed mining on multiple levels with hand held productivities between 50 and 90 tonnes per shift;•the use of 1 m cement pillars and 7 m high crown pillars were used to create multiple mining areas that enabled high overall production rates from hand held mining this orebody; and•the use of vertical cement pillars to enable hand held mining of adjacent stopes without leaving ore pillars.MarinersThe Mariners orebody averages 3 m wide, has a strike length of 50 - 250 m and dips at 50° with a basalt footwall and poor ultramafic hanging wall. The most successful innovative ideas of re-opening Mariners were:•Dewatering the existing mine workings utilising ‘oilfield’ technology by installing a long submersible pump in on existing pump rising main. This enabled the mine to be dewatered at rates up to 100l/ sec and helped overcome the 45 to 55 L/s inflows.•Overcoming the technical problems associated with Mining N07 ore blocks which had severely deteriorated from being underwater for five years by using reverse firing techniques to improve extraction rates and reduce dilution.•Mass firing a large mining block in the N08 with minimal void space because of deteriorating ground conditions.•Use of a longhole version of the Redross hand held mining method to achieve 100 per cent extraction of the N09 higher grade lenses.

Mar 21, 2011

By A. C. Stevenson

IN OUTLINING the various steps taken and the exigences met during the time of unwatering and rebuilding the burnt top equipment at the Hecla mine, the major portion of the detail is omitted and a general description of the experience only is given. All the electrical power lines were out of commission, as were the mine feeder cables. The first effort, there- fore, was to restore electrical connections. The Washington Water Power Co. immediately put a crew to work restoring the power line, it being necessary to rebuild about 4000 ft. of 66,000 volt transmission and about 2000 ft. of 2200 volt feeder. This work was rushed and power was again available at the mine sub- station about 26 hours after the fire. During the same time temporary lighting lines were strung and transformer equipment obtained, so that when electrical connection was resumed the lights were turned on and the dump well lighted that night.

Jan 1, 1924

By Young C. Kim

Introduction and Objective of This Paper Computerized open pit mine models* are more and more used today for feasi¬bility studies as well as for long range mine planning. In fact, using these models is becoming an enforced practice due to various reasons. One main reason is its capacity to evaluate several designs in a fraction of time required by manual effort. Another reason is the necessity to evaluate several. pit designs due to ever decreasing grade of the orebody and increasing financial risk due to smaller profitability margin. In spite of today's accepted use of computer models, very little guidelines are available which the average practitioner can follow either to choose or to build the type of model best suited for his need. Consequently, the objectives of this paper are: 1. To review the current state of the art in the computerized open pit mine models. 2. To provide some suggestions for model selection. 3. To share our experiences in developing a model for a highly irregular copper ore deposit (see Appendix).

Jan 1, 1977

By R. Dass

Paper written on project work carried out in partial fulfilment of B. Sc Eng (Extractive Metallurgy) degree Screening is an industrial process that splits material at a specific cut size into one fraction of particles larger than the cut size and another fraction of particles smaller than the cut size. Particles are vibrated to increase the probability of them being accurately classified and to move the oversize particles off the screen surface. In conventional screening, the screen mesh vibrates with a single frequency and the particles on the screen are all exposed to this same frequency. The Ultimate Screener (see Figure 1) is a new screen technology that imparts multi-frequency vibrations to the screen mesh so that different parts of the screen surface vibrate at different frequencies. The Ultimate Screener incorporates an additional deck that holds the multi frequency adapters as shown by Figure 2. These special adapters can transform single frequency vibrations into multi frequency vibrations. When the screen motors are switched on they begin to vibrate. This vibration is transmitted to the adapters via the body of the machine. The adapters then modify the vibration to have multiple frequencies, which are transmitted to the screen surface via resonating rings.

Jan 1, 2004

By N. H. Darton

In mining coal in the anthracite region of Pennsylvania the general custom has been to leave a large percentage of the coal in place as pillars to support the roof. Evidently any practice that involves partial waste of an important mineral resource is bound to be discarded. It is well recognized that one method of obviating probable waste is to fill the workings with cheap or worthless materials, a process extensively employed in the anthracite and some European mines. At present many of the collieries in the anthracite region of Pennsylvania are utilizing refuse from the old culm banks, which formerly were prominent features in the landscape, and are flushing the fine waste underground so that pillars may be reduced in size or removed. As a result the banks are now disappearing and soon will be gone. The fine culm from the breakers and rock from the mines will continue to be available, but the volume of these materials is insufficient to replace any considerable proportion of the coal removed. The next stage of progress suggested is the use of sand. Fortunately there are available large deposits of this material, much of which can be handled by dredges and pumps. This report is issued by the Bureau of Mines in the interest of safer and more efficient mining methods. I ts purpose is to describe the sand deposits in the northern anthracite coal field in Luzerne and Lackawanna Counties, Pa, Much of the information available is presented in the map, Plate I. Field studies, mostly preliminary, were made in the summer of 1911 to determine the distribution, amount, and character of the larger deposits. It was not thought desirable to make a detailed examination of the region because when the coal companies decide to utilize the sand their engineers will make precise surveys and drill test holes. In preparing the map the various coal companies were consulted; they contributed a large number of facts, especially as to the deposits in the buried valley of the Susquehanna between Pittston and Nan- ticoke, where nearly 1,000 test holes have been bored. The results of these borings were placed at the author's disposal, and have been utilized in drawing the boundaries given in the wide valley area and its extensions up Lackawanna River and NewportCreek. Wyoming Valley contains deposits of sand that are 100 feet thick over a wide area, 200 feet thick in places, and over 300 feet thick in the deep old channel south of Plymouth.

Jan 1, 1913

By Joseph M. Pugliese

This work was done by the Bureau of Mines to provide quarry operators with an uncomplicated, first-approximation method for designing blast patterns, considering geologic structure, and to show the valid use of the technique by comparing drill and blast pattern dimensions used in the quarry with those determined by the presented method. The author visited 12 limestone and dolomite quarries in Ohio (Adam, Crawford, and Highland Counties), Wisconsin (Milwaukee, Racine, and Waukesha Counties), and Minnesota (Fillmore, Olmsted, and Wabasha Counties); observed the blasting practices; studied the major geologic features; and after discussion with the quarry managers, foremen, and blasters, compared the quarry blasting patterns with those as calculated by the empirical formulas (after R. L. Ash), with geologic structural considerations. When geologic structure such as bedding, jointing, folding, and caves, as well as explosive properties and field performance characteristics are accounted for in a manner suggested by the research, the presented empirical formulas may be used as a good first approximation. The included steps in planning a blast design and generalized blast patterns should be of help to the quarry operator. Design changes are recommended for those quarries where problems are occurring.

Jan 1, 1972

By H. F. Feldmann

This work was done to provide thermodynamic, electrical, physical, and compositional data on the seeded combustion plasmas of seven coals for the design of MHD generators. The systems were assumed to be at equilibrium, and the design data were generated by solving for the composition of both gas and liquid phases with a digital computer. The coals reported in this study include a western subbituminous, a Pennsylvania anthracite, and five representative bituminous coals. The data include dewpoint temperatures of both slag and seed. A Mollier diagram for each coal is given to allow graphical generator calculations.

Jan 1, 1970

By K. Mallikarjuna Rao

There are several methods available to estimate deflection and ultimate Capacity of laterally loaded piles. In this investigation an attempt has been made to verify the existing methods for prediction of ultimate lateral resistance and deflection with the laboratory and field test results reported in the literature. A 75 pile loading test data obtained from the literature was used to evaluate two methods designed to predict the ultimate lateral resistance of rigid piles and three methods designed to predict the lateral deflections of rigid piles and four methods designed to predict the lateral deflection of flexible piles subjected to lateral loads. The accuracy and precision of each method is quantified statistically. The statistical results of the overall analysis indicate that the mean values of the ratios of predicted to measured lateral capacities vary from 0.62 to 1.14 with an average of 0.88. However, the settlement predictions were much more widely scattered than the ultimate load predictions and in general all the methods have a tendency to under predict the deflections. A new method is proposed by modifying the Broms's method to estimate the lateral deflections of free headed rigid and flexible piles separately. The proposed modified methods were found to be reasonably good in comparison to existing methods and to overestimate deflections.

Jan 1, 1996

The Estonia Mine, operated by Eesti Energia Kaevandused AS (EEK), the mining division of the Estonian Government's energy company, Eesti Energia AS, is a large room and pillar mine located in Eastern Estonia. It supplied approximately 4.9 Mt/a of oil shale in financial year ending 2010, which is used for electricity and shale oil generation. Due to the Estonian climate and the power station's need for a dry product, Estonia Mine has developed a planning system where short-term demands of the power stations dictate the schedule. Such an arrangement requires maximising flexibility and consequently the mine only operated for 199 days in 2010.The footprint plays a key role in achieving mass mining rates as the 12 km + 12 km lease area allows the mine to split into mining districts that act independently of each other and maximise the number of work areas available. Coupled with this, the geology of the mine is relatively homogenous over the mining lease, simplifying the mine design and production methods.During the last five years, EEK has commissioned a comprehensive conveyor network. Consequently, material handling only requires loaders to dump oil shale direct from the production face onto a chain conveyor that feeds the conveyor network that ultimately supplies the enrichment plant. Dewatering is also of critical importance, with 90 Mm3 of water discharged annually. EEK uses large trenches up to 3.5 m deep and 1.2 m wide to channel groundwater. Track mounted mechanical saws are used to cut slots in the floor, to control overbreak in blasting these trenches.EEK has introduced Salzgitter Machinenbau GB 280S auger drills that drill three 280 mm diameter holes simultaneously. This has improved void hole drilling times and reduced the drilling required for each face, reducing the overall production cycle time. Blasting activities have also been decoupled from other mining activities negating the need for firing times through the use of small independent firings, required to control vibrations.

Dec 6, 2010

By Robert Jakiel

The following paper is being presented to provide a basic understanding of the equipment and procedures used in multi-auger deep soil mixing as part of the program for the Deep Foundations Institute (DFI) Deep Soil Mix Seminar. The paper is written as a summary of the author's experience using multi-auger deep soil mixing equipment while working with SMW Seiko, Inc. on several east coast projects in the United States, particularly the soil-cement mixing for the soil stabilization of the Fort Point Channel area in Boston, Massachusetts, one of the largest and most difficult soil mixing projects completed thus far in the United States. The summary provides a brief summary and insight into some of the operational aspects of the equipment and procedures, and some of the important considerations when using multi-auger deep soil mixing. This paper is intended for use by both the contractor and the designer involved in selecting appropriate soil mixing equipment and procedures for various types of soils, depths or applications, or for a better understanding of the operational aspects, potential benefits, and impacts that the performance criteria may have on the operational capabilities of the soil mix equipment, when specifying multi-auger soil mixing for a particular project. Prior to reading this article it is important to become more familiar with the various acronyms and terminology used in soil mixing technology. A Definitions section has been provided at the end of the paper that will help the reader become more familiar with some of the terms used throughout this paper.

Jan 1, 2001

By J. N. Van der Merwe

The current state of the South African mining industry is briefly reviewed from the point of view of an engineer not schooled in the finer details of predictive economics. Based on the assumption that current world exploration targets are indicative of which commodities the world will want in the future, it is concluded that the South African mining industry will continue to be viable and growing well into the future. South Africa holds the minerals the world wants and needs, and as long as the world has people, the demand for those, including gold, will continue to grow. There still is a growing demand for vanity commodities' and even the demand for platinum as a jewellery material displays significant growth. Mine safety still needs to improve, but significant improvement has already been made although the industry is not always acknowledged for the effort in this field. The safety target set for 2013 is within reach but will require sustained effort. The physical mining conditions for the main revenue earners, coal, platinum, and gold, will change substantially in the near future. Research in mining has declined alarmingly and it is urgently necessary for that to be revitalized to generate the knowledge that will be required. In order to streamline the transfer of knowledge to the mining engineers of the future, research needs to be conducted with the full involvement of the universities. It will also be necessary for the universities to continually review curricula to incorporate the latest knowledge and to embark on a campaign of knowledge transfer to the older generation of mining engineers. The mining industry is well supported by the universities, who have done their duty with regard to societal transformation, and the universities are in turn supported by the industry through vehicles like the METE Industry is also strongly supported by a number of professional and vocational societies. The SAIMM will continue to play its vital role as the meeting point of the mining technical sciences, and will continue to disseminate knowledge via the journal, schools, and conferences. In the future, it will review its modus operandi to support the needs of growing membership in the remote branches. It will enter the research arena in an appropriate manner and give effect to the developing integration of mining and society. The most important threat to the future of the mining industry is the recurrent mention of nationalization. While interaction between the mining industry and political and economic development of South Africa has always been characteristic, the current debate is emotional more than rational, and engineers are not well equipped to participate. This matter needs to be finalized before it becomes a popular force that politicians cannot control.

Jan 1, 2011

By Matthew N. Rubin

This report summarizes the work performed under USBM Contract No. H0155155, "Demonstrating the Noise Control of a Coal Preparation Plant." A Consolidation Coal Company coal preparation plant (the Georgetown Plant) was selected for demonstration of various noise control techniques and materials in a commercially operating plant. At the start of the project, the 1650 tons per hour (tph) plant was surveyed to document the existing sound levels and worker noise exposures. On the basis of the survey, individual noise sources were characterized and assigned priorities for treatment. Four categories of noise control treatments were installed in this plant: ? Resilient impact pads ? Curtains ? Chute liners ? Resilient screen decks. Currently (1977) available resilient impact pads and curtains were found to be suit-able for general use in coal preparation plants; in the Georgetown Plant, they provided significant noise reduction [6 to 10 dB(A)]. The overall performance of the chute liners which also provided useful noise reduction, was strongly dependent on the specific installation. Although the resilient screen decks have the potential for 7 to 9 dB(A) of coal/screen impact noise reduction, blinding and delamination (in composite decks) en-countered at the Georgetown Plant represented major design problems for these products. This program achieved noise reductions of up to 10 dB in various areas of the Georgetown Plant (within the restrictions imposed by the plant's operation) resulting in significant reduction in worker noise exposures.

Jan 1, 1977

By Gennaro Gerald Marino

Vast improvement in methods of design and analysis of the long- term stability of overburden above room and pillar mines is needed. Improved methods are vital for planning and land development and for prediction above existing, presently stable, room and pillar mines. As shown on the flow chart in [Figure 1], the assessment of the long-term stability is an integral part of the site investigation process regarding mitigation of surface damage effects. In Illinois, flat farmlands with subjacent coal reserves cover vast areas. In some of these areas high extraction of the underlying coal layer(s) may not be possible since the resulting surf ace subsidence combined with a pre-existing shallow water table would make the land too wet. Thus recovery of this coal might only be accomplished by room and pillar mining where the ground surface does not subside and the hydraulics of the overburden are not significantly affected.

Jan 1, 1986

By M. C. Villeneuve

A numerical modelling approach was developed to explicitly simulate geomechanical characteristics of intact rock: mineralogy, grain size and fabric. The approach involved creating a representative constitutive model for each of three common rock-forming minerals: mica, quartz and feldspar. The constitutive models developed are valid within the low confinement realm of excavation boundaries, where tensile fracture processes dominate. The mineral types were assigned to numerical elements, which were associated with each other through an algorithm created in a finite difference model, FLAC 2D (Itasca 2007a), to simulate real crystal geometries and orientations. The numerical models were used in a parametric investigation of the geomechanical characteristics and compared with published observations of the rock yielding process in laboratory testing. This approach has allowed the explicit grain-scale investigation of the impact of geomechanical characteristics on rock yielding at low confinement, leading to an improved mechanistic understanding of excavation-scale rock yielding processes at excavation boundaries.

May 1, 2009

By George Filz, Morales, Carlos, Bertero, Filippo Maria, Alessandro, Leoni

"The Deep Mixing Method (DMM) represents a viable solution to improve adverse geotechnical properties of foundation soils for many practical applications. A pre-construction soil investigation campaign is necessary to assess soil properties and to retrieve samples of different soil layers for a laboratory Bench Scale Testing program (BST). The BST has to be designed using various binder types, binder contents, and water/cement ratios in each of the soil types. Following the laboratory program, a full scale Field Test (FT) is typically necessary to verify the results of the BST. This paper will highlight the differences and the importance of performing both pre-construction laboratory tests and field tests to ascertain the proper mixing parameters in the different soil layers. Comparative analyses and interpretations between the lab and field stages, along with accumulated information about soil properties and quality control (QC) results, allow fine-tuning the production parameters throughout a project. Three Deep Mixing Method projects, where both laboratory and field tests were executed, are illustrated: (1) The LPV 111 Project (New Orleans, LA, USA): DMM was used for ground improvement/foundation strengthening to stabilize and support the burden of a new levee raise; (2) The Rio Puerto Nuevo Project (San Juan, PR, USA): DMM was applied to improve the soils adjacent to a 90"" forced sewer main relocation and to improve the soils for the base of a new drainage channel; and (3) State Road 83 (US 331) over Choctawhatchee Bay project (Walton County, FL, USA): DMM was applied to stabilize the causeway sections of the bridge enhancement project. Data recorded during laboratory and field tests for these projects were analyzed and interpreted to select the most appropriate construction parameters to provide a final high-quality product.INTRODUCTIONThe Deep Mixing Method (DMM) represents a viable solution to improve adverse geotechnical properties of foundation soils in many situations. The effectiveness of working parameters depends largely on the physical and mechanical properties of the soil to be treated. Therefore, well designed laboratory and field test programs, aimed to disclose the interaction between the site-specific soils and the mixing parameters, are essential to achieve the desired end product.Generally a pre-construction soil investigation campaign has to be performed to assess soil properties and to retrieve samples of different soil layers for the laboratory Bench Scale Testing programme (BST). The BST has to be designed using various binder types, binder contents (or cement factors - CF), and grout water/cement ratios (W/C) in each of the soil types; the selection of the different combinations and dosages for the BST is based on past extensive experiences on similar materials. Following the laboratory programme results, a full scale Field Test (FT) has to be designed and executed, installing several DMM elements to verify the results of the BST and fine tune the construction parameters, with the appropriate binder type and dosage and the most effective equipment and tool configuration."

Jan 1, 2015

By Shintaro Takamiya, Kazunari Yoshida

"Recently, small sized micro-needles for medical are required more frequently by patients. The biggest reason is that it presents great burden on the patients, due to the size of the needle injection. People need to use a very small needle to lower the pain, but the downfall is that it makes them more expensive due to their complicated manufacturing method. Therefore, we need to fabricate a needle by wire-drawing to decrease its price. Tube-drawing is beneficial for its production value; however, in conventional tube-drawing it is difficult of control the wall thickness of the tube and makes it 1mmor lower in diameter. That is why, we propose fluid-mandrel drawing for new tube drawing. This method allows fabrication of a fine tube by using the pressure of the fluid in the tube. In this research, the goal is the fabrication of a fine tube by fluid-mandrel drawing and its evaluation. Finally, the fabrication of a fine tube by fluid-mandrel drawing was conducted and in result a tube with a diameter of 0.2mm, high strength and thin wall and fine inner surface was drawn, which can be used as a lesser pain micro-needle.INTRODUCTIONThe main manufacturing method of the current medical needles is roll forming. With this method, it is difficult to make a tube with a diameter lower than 1mm. Deep drawing has been proposed and used as method to further reduce the diameter, but this method is costly and the injection needle obtained by this method is several times more expensive.Therefore, we need to obtain a fine medical needle by drawing process that can be mass-produced and inexpensively manufactured. However, with the conventional drawing process, it is not possible to obtain a syringe needle with a reduced diameter easily, that is why, a fluid-mandrel drawing has been proposed which can reduce the diameter without damaging the inner surface. The methodology of the method is, a fluid is filled in the sealed tube and the pressure inside the tube during drawing is responsible for the good inner surface and wall thickness. It is also expected that the fluid can be easily discarded and that the tube can be manufactured on a long scale."

Jan 1, 2017

By E. O. Afreh, R. J. Bowell, E. Hanssen, D. Pohl, S. Abe, R. K. Yao, N. d'A. Laffoley

In the largely preserved laterite profiles at Syama mine, in the savanna region of southern Mali, element geochemistry in the mottled-clay horizon and below can be related directly back to the protolith, but above this, in the ferricrete and cuirasse horizons, the hypogene signature is much modified by pedogenic processes. In tropical rainforest terrains extensive remobilisation can result in wide but weak geochemical targets for gold and pathfinder elements. At the Hire concession in central Ivory Coast, intense recent alteration of the largely intact laterite sequences has modified soil-geochemical dispersion patterns extensively, producing Fe-rich nodular stone lines and obliterating previous patterns and features. Where the upper horizons of the laterite profile have been removed or reworked, as at the Senoufo concession in northern Ivory Coast (savanna) or the Kubi prospect in Ghana (rainforest), all soil horizons can be related directly to hypogene geochemistry. In these truncated profiles, gold and base metal anomalies are essentially those of the lower weathering profile and form narrow but strong dispersion haloes. A good understanding of the geochemical processes active in deeply weathered profiles is required if targets are to be recognised effectively

Apr 1, 1996