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By P. Farsangi, A. Hara

"Kidd Creek Mines places approximately 10 000 tonnes of consolidated rockfill on a daily basis. Consolidated rockfill is comprised of sized aggregate mixed with different ratio and amounts of binders. Consolidated rockfill, with closely controlled specification, is employed for subsequent pillar recovery and improved passive active/ ground support. With the same amount of cementing agents consolidated rockfill mass yields a higher, compressive strength, modulus of elasticity, cohesion, and angle of friction compared to a typical cemented hydraulic fill mass.The consolidated rockfill at Kidd Creek Mines is designed to sustain not only the gravitational loading of the overlaying fill material, but also to some extent the dynamic loading applied during blasting of the adjacent stopes and/or pillars.The quality control of materials used in Kidd Creek's rockfill system could be effected in three stages of handling: (1) at the surface backfill plant; (2) during transportation; and (3) placement of the fill.The emphasis in this paper is placed on individual stope backfill design and quality control measures at Kidd Creek Mines to place fill in large-scale open stopes which eventually could be exposed on all four walls during pillar recoveries."

Jan 1, 1993

By Candido Bariáin

A new vapochromic material of formula [Au2Ag2(C6F5)4(bipy)2]n (bipy = 2,2´ bipyridine) has been developed and used for the detection of some volatile organic compounds as acetone either in vapour or in water solution. The material is presented in the form of powders which colour changes with acetone vapours turning from bright yellow in the absence of vapour to white in the presence of vapour. By using the sol-gel technique, the powder ? dispersed in tetraethyl orthosilicate- was easily deposited on optical fibres. In order to study experimentally the behaviour of this material for construction practical optical fibre sensors, a sol-gel material doped with the vapochromic material is deposited onto an extreme of a monomode fibre connected to a coupler. The behaviour of the material was studied for different wavelengths and concentrations of acetone vapours and acetone/water solutions. Changes up to 4dB in the reflected optical power were detected. Optical fibre sensors have many advantages over conventional ones, such as electromagnetic interference immunity, passivity behaviour, possibility of using multiplexation techniques, low weigh and little size, etc. Actually, there is an increasing interest in developing optical fibre sensor for vapour detection in the chemical industry and in fact many sensor had been developed [1]. Some are based on the deposition of a sol-gel-based material either over the core of an optical fibre [1] or onto the thinner zone of a biconically tapered optical fibre [2]. Others are based on Fabry-Perot interferometers [3]. Also there are sensors based on the reflection of the light on films, on the fluorescence of dye-doped polymer cladding in fibre, on colorimetric reagents in the core of a silica fibre or on surface plasmon [4]. The possible materials for the construction of such sensor should be colorimetric reagents able to change the colour or refractive index in the presence of same organic vapours. There are not many metallic complexes with these properties, although same interesting examples have been reported in the chemistry of palladium and platinum as [Pt(p-R-C6H4NC)4][Pd(CN)4] described by Nagel [5] and Mann [6], which reported the construction of some LEDs. We recently reported the preparation of a novel vapochromic material (Fig 1) [7] which can be used for the construction of optical fibre tapered environmental sensors [8,9] of vapour organic compounds (VOC´s). Also we reported other nickel and palladium derivatives which present this type of behaviour [10]

Oct 1, 2003

By Robert B. Parsons

"The February 18, 1987, Federal Budget contains a proposed amendment which would simplify somewhat the ""successor corporation"" rules in the Income Tax Act. Despite this amendment, though, the important successor rules will continue to be relatively complex.IntroductionThe February 18, 1987, Federal Budget papers propose an income tax amendment whereby the so-called ""successor corporation"" rules would be revised by removing the present provision which limits the application of these rules to a maximum of two ""successions"". The successor corporation rules represent one of the most complicated sets of rules in the Income Tax Act. This month, Tax Notes seeks to explain these rules and the proposed amendment in simplified terms.Basically, the successor rules provide a mechanism for transferring unused exploration and development expenses from one taxpayer to another , in specified circumstances. The aforementioned limitation of two successions refers to the rule which allows a maximum of two such transfers with respect to any particular pool of deductions."

Jan 1, 1987

By A. B. Szwilski

The paper outlines the factors taken into account for the selection of steel arch supports. The results are based on experience using the long wall system of coal mining where roadway closure can be extreme. Results of tests on scale-model steel arches and full-scale yield elements are also presented.

Jan 1, 1979

By G. W. Poling, J. R. Hoffert

"A common practice in preventing gravity-fed tailing pipeline from plugging due to sanding is to add lime at relatively high dosage rates. The lime affects the rheology of the slurry ""vehicle"" which transports the coarser particles in a heterogeneous flow-regime. This paper describes a study of the effect of lime on the critical deposition velocities and friction head losses of Highmont Mining Company's mill tailing. Testwork using an extrusion viscometer was related to the surface chemistry changes brought about by the high lime additions. Lime additions which typically increased the tailing pH from 8.4 to 11.5 reduced the critical deposition velocities from approximately 3.2 to 1.7 m/sec.IntroductionCommon practice, at least in base metal concentrators in British Columbia, is to use high lime additions in tailing slurries when the pipeline becomes partially plugged with sands. Some concentrators, such as the Highmont Mining Co. Ltd. plant, add lime on a continuous basis during low tonnage periods and during startup/shutdown transition s. Although such high lime additions often solve temporary plugging problems, the effect of lime on slurry rheology has not been well understood.Slurry pipelines are designed to transport solids in suspension with a minimum of wear and without particle deposition. These two objectives are in opposition because the velocities required to maintain solid suspension can sometimes cause high head losses in the pipeline, as well as wear problems. Thus, the optimum velocity for a long distance slurry pipeline is in the range that provides just enough turbulence to keep coarse particles in suspension."

Jan 1, 1985

By Brian Penney

"The Iron Ore Company of Canada (IOCC} has mined and processed an iron deposit in Western Labrador along the Labrador-Quebec border since the early 1960' s. Current capacity is approximately 19 million tonnes of concentrate, 70% of which is converted to pellets at these facilities.The ore deposits are located in hills rising 150 to 300 meters above the adjacent lakes, and most of them are covered by very little overburden. The iron minerals are mainly specular hematite and magnetite hosted in a quartz formation. Crude ore averages 40% Fe that is concentrated to 65.5% Fe. IOCC is an extensive operation extending from Labrador City NF to Sept-Iles Quebec. It consists of open pit mining, concentrating, pelletizing, railway, and dock loading facilities.The Concentrator liberates iron from the silica by crushing and grinding the ore to -14 mesh (-1190 microns}. Ground ore is concentrated in spirals and filtered for transportation. Spiral tailings are treated in a Magnetic Recovery Plant (Mag Plant} that recovers lost magnetite. Mag Plant tailings are treated in a Hematite Spiral Plant (Hem Plant} that scavenges fine iron remaining in this stream.This report deals with ongoing iron recovery initiatives within the ConcentratorIron Losses in the ConcentratorIron recovery at IOCC is approximately 70.5%. This compares with recoveries that range from 65% to 86% for other iron mines in our area. Other world large iron ore producers dig and ship concentrate quality ore directly out of the ground and have an effective recovery of 100%. With increasing costs for labour, equipment, and supplies an increase in iron recovery is required to keep the operation viable.More than 90% of our iron concentrate is produced by gravity separation using spirals. The physical characteristics of the iron minerals that most effect recovery are mineral grain size and degree of liberation. We divide ground ore into three size categories -coarse, intermediate, and fines. A brief description of each size fraction follows:"

Jan 1, 1996

By T. Newton, G. A. Bezuidenhout, P. J. Tauetsile, F. Trask

The technology to selectively leach gold, silver and base metals from ores, concentrates, and wastes, using an alkaline glycine solution, has initiated significant interest in using the new technology in various environments such as in-situ, in-place, dump, heap, and vat and agitated tank leaching. It has been shown that glycine acts synergistically with a number of other lixiviants to lower the net consumption of the other lixiviants while allowing low cost glycine solution recovery. Glycine is a non-toxic, stable, environmentally benign reagent that is available in bulk industrial quantities. It has the ability to dissolve most copper oxide and sulfide minerals, as well as native copper, whilst not interacting with acid consuming gangue nor dissolving iron and various or ubiquitous gangue elements. It acts synergistically with small amounts of cyanide to leach gold-copper ores at leach rates higher than either glycine or cyanide on their own, while significantly reducing cyanide consumption and eliminating detoxification requirements. The leaching behaviour of various glycine based systems will be reviewed, followed by the evaluation of the adsorption of gold onto activated carbon. Where the economics merit it, copper can be easily recovered using solvent extraction or sulfide precipitation.

Jan 1, 2017

By S. Zakaria

"Inco's Automated Haulage Truck System (AHT) is a revolutionary automatic guided vehicle that performs all load, haul and dump operations without human intervention. The high level of sophistication and the short period it has been in operation has only allowed a select few Inco personnel to become familiar with the ART operation and maintenance. As an aid to operations an expert system using the knowledge gained from the experienced specialists was implemented in the field.The AHT operating and maintenance assistance expert system will reason through the information given, arrive at conclusions and give advice to operations, technical and management personnel. It will provide comprehensive real-time troubleshooting assistance for the hydraulic, electrical and mechanical subsystems of the ART. The ART expert system has many benefits to Inco which include increased skill levels of ART operations and maintenance personnel, reduction in ART downtime, standardization of troubleshooting procedures and reduction in ART operating and maintenance costs. In the future, the expert system application will be linked to SCADA (Supervisory Control and Data Acquisition), maintenance and statistical software to display current and historical trends of variables from a centralized historical database. As well, a wide variety of features will be integrated into the system including AutoCad drawings, graphics, photographs, voice and video capabilities."

Jan 1, 1994

By D. Nikols, G. Caraghiaur, P. C. Roxburgh

"IntroductionThe Highvale Mine is located 70 km west of Edmonton , Alberta on the south side of Lake Wabamun. It has been developed by TransAlta Utilities Corporation as a captive mine to supply fuel to two genera ting power plant s. The mine is owned by TransAlta and operated under contract by Manalta Coal. Within the mine permit area, TransAlta own s the right to mine 80% of the recoverable surface mineable coal.The planning process starts with the annually produced 25-year energy forecast which is provided by the Electric Utility Planning Council (EUPC). A 1983 forecast predicts an average annual increase in energy requirements of 4% over the next 25 years. Put another way, the requirement will double before the end of the century. A lar ge part of the base load generation of the Province of Alberta is provided by th e plants fueled from Highvale Mine. The Highvale Mine is therefore expected to maintain a high output over a long period of time.Mine PlanningMine planning is an ongoing, interative process that draws from many sources. All levels of planning draw from the same sources but du e to the different processes and objectives of each planning class, the degree of influence may differ. The planner becomes then a coordinator bringing together data and excerpts from several disciplines in groups. Generally, there are four classes of mining plan s; these are all used at the Highvale Mine (Table I)."

Jan 1, 1986

By D. Lessard, S. Nantel

"Surface crown pillars are important Canadian,mining structures. Mines operating in the Canadian Shield usually have several, forming a first line of protection from surface elements.Detailed technical information from twenty-four Canadian hard rock mines show that the deposits dip steeply and are generally either single or multiple veins. Considerable overburden usually cap the deposits. The rock mass is often altered and intersected by important discontinuities.The designs for these types of pillars lack basic data and are based on experience rather than a scientific approach. Regardless of the competence of the rock mass, the surface crown-pillar thickness to width ratios (an unscientific design tool used by the industry) are usually less than five. Rock bolting is, in almost every case, used as a support measure. However, there are many openings neither backfilled nor monitored.The characteristics of openings with surface crown pillars are also examined."

Jan 1, 1988

By David R. Ray, Arthur J. Pyron, William F. Thomann

"Proterozoic plutonic and volcanic rocks in the Franklin Mountains, west Texas, exhibit similar values in average concentrations of equivalent uranium (eU), equivalent thorium (eTh) and equivalent potassium (eK) when compared to Proterozoic igneous rocks of the southwestern United States. Variations of radioelement concentrations for all Proterozoic igneous rocks of the Franklin Mountains range from 1.1 to 357.1 ppm U, 2.1to 259.1 ppm Th and 2.5 to 10.2% K.Recent geologic mapping of the Proterozoic rocks in the Franklin Mountains revealed several types of granites previously unrecognized, and these warrant further exploration for U and Th resources. Fluorite-bearing granites and riebeckite pegmatites are likely targets for further investigation, as these have the highest U and Th concentrations compared to all other granites.IntroductionThis is a summary of the paper presented at the CIM Geology Division Uranium Symposium held in Saskatoon, Saskatchewan, September 8-13, 1981. The purpose of this study was to evaluate the distribution of uranium (U), thorium (Th) and potassium (K) in Proterozoic igneous rocks in the Franklin Mountains, and compare radioelement concentrations to Proterozoic igneous rocks elsewhere in the southwestern United States.General GeologyThe Franklin Mountains are located in west Texas and southcentral New Mexico, within the southeastern part of the Basin and Range Province o f the southwestern United States. The Franklins are a complex fault-block range trending northsouth with strata dipping toward the west. Ages of the rocks range from Proterozoic to Cretaceous. Harbour (1972, 1960) provides the most recent account of the general geology of the Franklin Mountains. Most recent accounts of the detailed Pro Proterozoic geology o f the Franklins are provided by Hoffer (1976), Thomann (1980, 1981), Pyron (1980), Ray (1982) and McCutcheon (1982)."

Jan 1, 1983

By G. Grant Smith

In situ bulk density of coal is a variable applied to various aspects of coal resource evaluation, such as compositing ply analyses of coal attributes that are expressed on a weight per cent basis, and determining tonnages from volume estimates. Its value is a function of composition and porosity of the in situ material. When densities of ash-free coal, ash and water are fixed, in situ bulk density of a coaly mix can be expressed as a function of proportionate weight of ash in the mix. Correlations between in situ bulk densities and weight per cent ash contents of coaly mixes have been estimated for four general rank classes of coal (low medium volatile bituminous, high volatile bituminous, subbituminous, and lignitic).

Jan 1, 1991

By G. M. Humphrey

It is a great honour and privilege to be here in this distinguished company of the outstanding men in the mining industry and the political life of Canada. I fully recognize that I am so honoured as a symbol of the combination of American and Canadian leaders in industry who are partners in the sponsor-ship of the Quebec-Labrador iron-ore mining development which we are undertaking, and as such I want to express our great appreciation of the co-operation and assistance we have met on every hand in Canada, and the genuine friendliness and never-failing courtesy which we are always accorded. We are quite aware that it springs primarily from the very high regard in which our partner and sponsor, Jules Timmins, and our other Canadian associates are held. Their high standing among you is well known and we quite naturally fall heir to the benefits of the great esteem in which you hold them. Jules Timmins and his long-time associate, John Knox, were the original inspiration for our participation in this venture. It was their enthusiasm and vision which caught our interest and led to our joining with them in the years of exploration and search which have brought us to the threshold of this great development where we stand today. So much has been written of the details of our exploration and plans for future development that it would bore you for me to review them further here, but there is a phase of this development, and an extremely important phase of it, which I think has passed almost unnoticed and which it may be well worth while for me to bring to your attention this evening.

Jan 1, 1951

By O. Garg

This paper summarizes the computer applications in open-pit mine planning at the Iron Ore Company of Canada (IOC). A brief history of the use of computers at IOC is given, and a description of the existing facilities is outlined. The following systems are discussed: storage and retrieval of geological data; geotechnical data analysis; long-term grade and tonnage forecasting; ore grading; and open-pit mine design. Justification for using computers in open-pit mine planning is given, and possible future areas of application are considered.

Jan 1, 1979

By Libao Zhu, David J. Williams, Nazife Erarslan

"Statistics show that the drawbell in underground mines is usually subjected to significant damage by impact loading due to falling ore. Drawbell damage causes a large quantity of residual ore to remain on the drawbell, thus leading to a huge waste of ore resources. In this study, the Cavity Monitoring System (CMS) and Surpac software were employed to visualize the 3-D damage. Also, the Discrete Element Method (DEM) was employed to perform simulations of the falling ore to investigate the damage evolution of drawbells under repeated ore impact and obtain the dynamic damage accumulation mechanism. The reason of drawbell damage was found due to the micro-shear cracks. The numerical simulations of a drawbell damage process under repeated impact loading showed the main failure type was shear failure and this type damage was found increasing with more ore falling. INTRODUCTIONDrawbells are an important part of underground mines and play a significant role in ore recovery in terms of safety, economy and efficiency (Brunton et al., 2010; Hustrulid & Bullock, 2001; Trueman et al., 2002). In most cases, blasted ore is gravitated along the drawbell and finally arrives at the footwall of the drawpoint. However, some of the blasted oversize ore blocks clog the drawbell road and those ore pieces are called hang ups (Penswick, 1997). However, any damage on a drawbell is believed to be the reason for these hang-ups. In the literature, researchers have reported that the stability of the draw-point is influenced by the stress distribution above and near the drawbell (Butcher, 1999; Neverov & Neverov, 2013). Much research in the literature has been done on draw-points in underground mines. In fact, rockfalls cause very serious damage on a small impact area in a very short time (Volkwein et al., 2011). Hoek (2000) pointed out that the blasted ore causes progressive ravelling and even collapse of the drawpoint, thus the ore in the stope is abandoned. In this paper, the Cavity Monitoring System (CMS) was employed to obtain the damage profile of a drawbell due to the impact of rockfalls and to confirm the residual blocking ore on the damaged drawbell. Then, the drawbell damage evolution due to repeated falling ore was simulated by the Discrete Element Method (DEM)."

Jan 1, 2015

By M. Cai

"It is well known that Peak Particle Velocity (PPV) plays a critical role in triggering rockburst damage in burst-prone underground mines. To estimate the PPV distribution around excavations, advanced numerical modeling can be used. In wave propagation numerical modeling, velocity field is often assumed to be uniform around an excavation. However, it is observed that wave velocities near mine openings are not constant, but rather non-uniform. Wave velocity in a rock mass depends on many factors such as rock quality and confinement. In particular, confinement has a large influence on wave velocity. The confinement around an excavation is low at the wall boundary and increases gradually and reaches a constant value far away from the excavation boundary. Hence, stress redistribution due to excavation will have a profound influence on wave propagation in underground mines. A better understanding of the influence of excavation effect on wave propagation helps to interpret the field observation of rockburst damage and improve mine safety. For this purpose, a non-uniform velocity model need to be constructed and the influence excavation effect should be taken into account in numerical wave propagation modeling.In the present study, a non-linear velocity model is developed firstly by considering the influence of confinement on wave velocity. This model links wave velocity to confinement explicitly. A coupled numerical method is then developed and used to study the seismic wave pattern around excavations in underground mines. Two codes, FLAC and SPECFEM2D, are coupled in the analysis. The motivation of developing the FLAC/SPECFEM2D coupled approach is to take merit of each code, such as the stress analysis capability in FLAC and the powerful wave propagation analysis capability in SPECFEM2D. The coupling process is realized through three steps: (1) static stress redistribution around an excavation is analyzed in FLAC; (2) data for coupling analysis, such as non-uniform velocity field (based on the new developed velocity model), mesh, absorbing boundaries, etc., are generated by FISH functions in FLAC and passed to SPECFEM2D; and (3) wave propagation modeling is performed in the SPECFEM2D considering a fault-slip seismic source. Because stress redistribution around the excavation is considered, non-uniform velocity field for the SPECFEM2D model can be obtained and this is a notable feature of this study. Very large difference in the S-wave response in these two modeling approaches with uniform and non-uniform velocity fields can be seen from the modeling results.Using the FLAC/SPECFEM2D coupled modeling approach, accurate velocity models can be constructed and this in turn will help to produce accurate PPV distribution around the excavations. Accurate PPV contours can be used to identify high rockburst risk zones for improved dynamic ground support strategy."

Jan 1, 2015

By D. F. Scott

"DEFINITION OF THE REGION AND ITS BOUNDARIESTHE REGION of Western Canada covered by this re-port lies between the Precambrian rocks of the Canadian Shield and the structurally deformed rocks of the eastern Cordillera, extending northward from the international border to the 60th parallel. It is some 487,000 square miles in area, with a total sedimentary fill of about 535,000 cubic miles0>. It includes parts of the prairie provinces of Manitoba, Saskatchewan and Alberta and the northeast corner of British Columbia and forms part of the geological region known as the Interior Platform, commonly referred to as the Western Canada Sedimentary Basin. The bedrock comprises carbonates and evaporites of Paleozoic age that lie on Precambrian crystalline rocks and are over-lain by a relatively thick blanket of Mesozoic and Tertiary elastic rocks. The nearly flat-lying bedrock, covered by a thick mantle of glacial drift, forms the Interior Plains physiographic province."

Jan 1, 1970

"In the present study, the reduction behavior of composite pellets comprising of iron oxide, synthetic graphite and slags were investigated in a laboratory-scale horizontal tube furnace. Two different types of slags indicating silicate base and aluminate base slags were chosen to examine the effect of slag chemistry on the reduction behavior of pellets. Slag composition of binding materials has influences on the reactions occurring in composite pellets during direct reduction. In-situ high temperature visualization approach was used to observe the slag / iron / carbon interactions at 1773K (1500°C). The off-gases were measured by means of infrared analyzer to determine the reaction rates of the pellets. Different physical appearances during the in situ reaction inferred a strong correlation between the slag composition and internal reactions. In addition, compression tests were conducted to examine physical strength of the pellets. This investigation was carried out to establish feasibility of physical property control of pellets by selecting optimum slag compositions of binding materials INTRODUCTIONCurrently, most of the iron ore mines have facilities that make an ore more usable for the blast furnace operation by improving its physical properties (e.g. pelletizing and sintering). However, during the process, a large amount of fuel is supplied to indurate materials which consequently deteriorate energy efficiency and produce more CO2 emission. Along with increased interests, direct reduced iron (DRI) making process; simply without coke oven or sintering process, has opened the era of clean and environmental friendly iron making process. While some of the established DRI technologies such as Midrex and HYL were restricted to certain locations where natural gas is abundant, coal based technologies using Rotary Hearth Furnace (RHF) such as FASMET and ITmk3 have been developed with regardless of expensive fuel deposit. In addition to the direct use of pulverized non coking coal and fine iron ore, RHF process also has advantages of utilizing waste materials such as EAF dust, biomass and recycled plastics. Nevertheless, there are still many challenges in the coal utilizing technologies as the unprocessed coal and the waste materials contain huge volatiles and ashes. Although recent investigations on volatiles in a RHF process (Sohn and Fruehan, 2005, 2006) have indicated the benefits of coal in terms of iron oxide reduction and have shown feasibility of multi-layer process, carbon composite pellets still have disadvantages because of its weak mechanical bonding strength. As the mixed system with carbon and oxides generates intermediate gases (e.g. CO and CO2) between solid particles, it is difficult to keep its physical state without the help of binding materials. In this reason, industries have been tried to use various binding materials such as bentonite, kaolinite and Portland cement. However, they are still struggling to find out new materials that provide not only sufficient mechanical strength but also metallurgical properties, such as porosity, reducibility and swelling throughout the reduction reaction. Recently, Canadian researchers (Aota et al, 2006) observed enhanced mechanical strength of pellets by using high alumina cement as a binder and concluded that the method could be used to recycle EAF dust as well, but in depth mechanism of reinforced strength has not been concerned. Most of the ashes coming from binders formulate certain type of slag during the reduction process due to its incombustibility. Thus, observation and regulation of slag property is an essential for the control of carbon composite pellet. Yet, only a little thermodynamic consideration from the perspective of slag chemistry has been adapted in the iron and steel making industries as ash has been easily ignored for its tiny proportion. In this study, effect of CaO-SiO2- Al2O3 slag system on the reduction of iron oxide was investigated in terms of"

Jan 1, 2012

By Yves C. Lizotte, Malcolm J. Scobie

Blast fragmentation is affected by the physical and mechanical characteristics of the rockmass as determined by geology as well as the explosive energy, the partition of this energy, the actual amount of energy transmitted to the rockmass, the blast geometry and the detonation sequence. This paper reviews studies of the influence of geology on blast fragmentation, particularly structure, i.e. the in situ or inherent fragmentation arising from rock discontinuities. Prior structural studies have mainly been limited to comparing equivalent diameters of the in situ blocks with the size distributions of the blasted material. No criteria exist to integrate structure into blast design. This paper reviews on-going studies of the blasted fragment shape and size observed in different rockmasses aimed at analyzing geological control over blasting. Digital photoanalysis was applied {o measure size and shape distributions, to correlate results with block size distributions and shape parameters of the inherent fragmentation. An integrated and comprehensive fragmentation assessment procedure which accounts for geological control is proposed. The potential of this research is to provide a greater understanding of the true contribution of explosives to fragmentation, the effects of fragment shape on system productivity and the reduction of blast-induced damage.

Jan 1, 1994

By I. G. L. Sinclair

"ABSTRACTTill geochemistry was the principal exploration tool employed by Selco in the investigation of a zinc prospect in Lanark Township, Ontario. The geochemical studies were undertaken after the discovery at surface of marble boulders containing bands of sphalerite and lesser amounts of galena.The source of these mineralized boulders was sought by means of B-horizon soil geochemistry, followed, where appropriate, by back-hoe trenching and till sampling. The thickness of the tiff in this part of Ontario seldom exceeds 3 m or 4 m and it was generally possible to sample complete profiles of the till and thus to obtain detailed information concerning the dispersion of zinc. Drilling and trenching at the up-ice extremity of the zinc dispersion trains showed the source of the float to be sub-economic bands of sphalerite in the Grenville marble. IntroductionTill geochemistry was used extensively by Selco during the period 1975 through 1980. It was the principal exploration technique employed in a program seeking carbonate-hosted lead-zinc deposits of the Balmat-Edwards type in the Grenville rocks of southeastern Ontario. This paper describes the use of the method to locate the bedrock source of a group of sphalerite boulders found at the surface near the village of Hopetown in Lanark Township (Fig. I) . Geochemical investigations at this locality were the subject of a previous publication by the author (Sinclair, 1979).All of the analytical work related to this project was done by Bondar-Clegg & Co. Ltd. in their Ottawa laboratory. In all cases the -80 mesh fraction of the till was analyzed. The total zinc content was determined by atomic ab sorption spectrometry after hot aqua regia digestion; readily extractable zinc was determined by atomic absorption after samples had been cold-leached for 18 hours in an ammonium citrate hydroxylamine hydrochloride solution, the pH of which was adjusted to 8.5"

Jan 1, 1986