Search Documents

By R. W. Fountain, J. F. Libsch

ONSIDERABLE time and effort have been ex- pended recently in research designed to provide a better understanding of the solid state transformations leading to the permanent magnet qualities of many commercial alloys. The knowledge derived from these investigations has resulted in the development of new magnetic materials as well as improvements in some of the older materials. The permanent magnet qualities of the newer alloys having high residual inductions and high coercive force values, have been attributed to the precipitation of a second phase or an order-disorder transformation in a solid solution. The ternary Co-Fe-V alloys provide an interesting group of magnetic materials having a wide range of magnetic properties. The low vanadium alloys' possess soft magnetic properties similar to the binary Co-Fe alloys, while at higher vanadium contents (about 10 pct) interesting permanent magnet properties are obtained.2,3 Previous work by Nesbitt' on the ternary Co-Fe-V permanent magnet materials, resulted in the conclusion that the precipitation of a second phase, ?, was responsible for the permanent magnet qualities of these alloys. However, unlike the conventional precipitation hardening alloys, the ? phase, which is stable at high temperatures, is precipitated in the low temperature a phase upon aging. Recent work by Geisler and Martin"." has established that the order-disorder reaction inherent in the binary Co-Fe alloys is also present in the ternary Co-Fe-V alloys. On the basis of their investigation, it was proposed that ordering of the a phase is also a possible explanation of the mechanical and magnetic hardening in these alloys. Thus, it appears that the Co-Fe-V alloys are rather unique in that two solid state transformations are taking place which may account for the properties of these alloys. In view of these facts, the present investigation was undertaken to study the mechanism of mechanical and magnetic hardening in the 10 pct V-Co-Fe alloy with particular reference to the role of the ? phase; and to correlate the results of this study with other magnetic properties. In addition, the influence of increasing vanadium contents on the transformation of Co-Fe alloys was also undertaken to supplement the main objective of the investigation. Experimental Procedure The Co-Fe-V alloys used for study consisted of: 1—a commercial lot of Vicalloy I, a 10 pct V alloy, and 2—alloys prepared by powder metallurgy and containing 52 pct Co and 0 to 14 pct V, balance iron. The commercial alloy was received in the cast and forged condition and was used primarily for the detailed study of hardness, electrical resistivity, and magnetic properties of the 10 pct V alloy. The powder metallurgy alloys were prepared from electrolytic iron, commercial cobalt, and ferro-vanadium powders. The processing cycle was as follows: 1—Elemental powders were weighed and mechanically mixed for 24 hr. 2—Mixed powders were pressed at 60,000 psi into the form of bars 5/8 x 5/8 x 5 in. 3—Bars were sintered in an atmosphere of purified dry hydrogen for 24 hr at temperatures ranging from 1380" to 1340°C, depending upon the vanadium content. The as-sintered bars were cut in half; and one half was machined to 7/16 in. diam for thermal analysis. The remainder of the bar was hot forged to approximately 0.050 in. for X-ray diffraction analysis. Additional details of sample preparation are presented subsequently according to the type of test performed. Thermal Analysis Measurements One of the simplest and most widely used tools for determining phase relations as they change with temperature and composition is to study the rate of change of temperature of a material as heat is supplied or extracted at a constant rate. The thermal analysis method used in this investigation is the inverse-rate method described by Smith.'

Jan 1, 1954

By Knasmillner

During blasting body wave interaction with geometrical surfaces induces Rayleigh-waves which propagate along free surfaces, e.g. crack faces or delaminated rock layers. These Rayleigh-waves carry most of their energy within a very shallow surface layer and propagate with very little attenuation in real rock materials. Upon interaction with a crack front a very strong mixed mode stress intensity factor may result and lead to fracture initiation. On the basis of experimental photomechanical results the history of dynamic stress intensity factors Kt and K2 will be studied in Detail.

Jan 1, 1990

By Frank W. Osterwald

Violent, spontaneous destruction of coal faces and ribs during, what are commonly called, bumps endangers and at times destroys life and property in mines of the Book Cliffs coalfield, Carbon County, Utah. Because these mines supply much of the coking coal for the West Coast steel industries, mining is necessary, although costs are high and operating conditions are very difficult at times. As operations continue, mining will go to greater depths, and the difficulties will increase. Whether or not mining can be continued successfully depends in part on whether or not incidence of bumps can be controlled successfully. For this reason, the U.S. Geological Survey, at the request of and in cooperation with the U.S. Bureau of Mines, undertook a study of the Sunnyside No. 1 mine to determine what geologic factors were related to the incidence of bumps. This report presents the preliminary results of that study and indicates that some observable geologic features in the mine may be related directly or indirectly to bumps, and that other features may be used to infer stress distribution around workings that will aid in design of roof support measures. Coal is mined in the Sunnyside No. 1 mine from depths as great as 2500 ft by room-and-pillar methods. The surface topography is rugged with many steep cliffs and deep canyons, hence the load on the coal varies greatly within short distances. Much of the Sunnyside coal is under high stress, and while being mined, it shatters continuously' and falls from the face. Continuous shattering (bumping) makes mining easy, but if the shattering is interrupted, greater stress is built up and violent bumps may result when the coal is mined.

Jan 4, 1962

By G. J. W. Kor, F. D. Richardson

The sulfide capacities a1 1500°C of slags in the systern CaO + CaF, +Al2O3 have been measured by bringing samples into equilibrium with gas mixtures made from CO + CO2 + SO, + N2. The capacities are negligzble both JOY CaF, and CaF, + Al2O3 melts but when lime is present even at 20 wt pct capacilies as high as 30 x lom3 can be obtained. The results have yielded information concerning the liquidus at 1500°C and fluoride-oxide melts in general. The slags used in electroslag refining contain substantial amounts of calcium fluoride. Robinson and Grainger' report that good results can be obtained by using slags of the approximate composition 70 wt pct CaF2 + 30 pct Al2O3. It has also been reported2 that a mixture of 50 pct CaF2 + 30 pct A12O3 + 20 pct CaO makes a good slag for general use. In view of the fact that very low sulfur contents are claimed for ingots produced by the electroslag process. studies have been made of the sulfide capacities [c, = wt pct S (PO2/Ps2)1/2 at 1500°C. of slags consisting of pure calcium fluoride, and of its mixtures with lime and/or alumina. These studies have also provided information on the phase diagrams. The slags were brought into equilibrium with gas mixtures prepared from NZ + CO + CO2 + SO2. Because CaFz is volatile and also easily hydrolyzed. measurements were made of its loss in weight in various flowing gas mixtures. EXPERIMENTAL Procedure. The apparatus and procedure were the same as described previously. Both platinum and iridium crucibles were used (height and inner diameter about 1 cm), but those made from iridium were stronger and able to withstand a greater number of experiments. In each experiment two crucibles were set in an alumina support and 1 g of slag mixture was divided between them. The materials from each crucible were analyzed separately after being brought to equilibrium with the gas, and then quenched in the water-cooled end of the reaction tube. Materials. Alumina and lime were prepared as de-scribed previously.4 Calcium fluoride was obtained by igniting Analar calcium fluoride in a platinum boat at about 800°C in a stream of pure dry nitrogen: the product was cooled in a desiccator. The slags were produced from mixtures of the powdered constituents, these being melted together in the course of each equilibrium experiment. The sulfur analyses and the X-ray diffraction meas- urements on the solidified slags were made as described previously.4 From the latter it appears that the CaF2 contained less than 0.5 mol pct CaO. RESULTS Values of (ps2/po2) for the Gas Mixtures. The re-sults have been represented in terms of (ps, /Po,)"? for the various gas mixtures used. The va1;es of this function at 1500°C are listed in Table I: they were calculated from the data cited previously for calculations at 1350°C 4 Weight Losses with CaF, and CaF, + CaO. The re-sults of the weight loss measurements* at 1500°C for

Jan 1, 1970

The equity market is now very much within a global village environ- ment, with various exchanges acting as agencies for the big casino. In this predicament, mining companies, who provide the most extensive, but relevant risk assessment information, will be best placed for favoured treatment by potential international investors: But what risk assessment information in summary form can be provided to support a resource/reserve statement? Even more importantly, does "objective" data exist, whose trends will support a resource/reserve state- ment? A prime need of the informed mining investor is to determine whether or not the resource/reserve statement is believable? But more importantly will it be realised? While the implications within the text of the majority of reports on resource/reserves suggests that the estimates are conservative, the record indicates that very few estimates are. In fact, to date, reports claiming to be conservative in respect of the overall grade estimate at a specfic cutoff have not reflected the realised grade at the stated cutoff; it has been more common for the realised grade to be lower than implied by the resource/reserve statement. Further, it is not uncommon for penalty elements to be understated and these components are rarely incorporated within resource/reserve statements.

Jan 1, 1988

By Badal R

Rock Discontinuities ("joints") affect blasting results. An investigation was carried out to understand if blast parameter such as spacing needs to be altered with the change in joint direction. Small scale laboratory studies in jointed limestone blocks have been carried out. It is shown that optimum spacing is variable with the "joint" orientations. Evidence is presented from field studies in four limestone quarries supporting laboratory studies. Reasons for success and failure of widespacing technique is also provided. Only with suitable orientations of "joints: widespacing is successful.

Jan 1, 1990

By Ritchie IM

The Parker Centre was formally established by the Australian Government's Co-operative Research Centre (CRC) Program in 1992 and is one of over 60 such centres encompassing a wide-range of applied scientific and resource based disciplines. Government funding for the CRC Program is currently around $A140 million per annum and the Parker Centre receives $A1.8 million per annum to support its core research and education activities.

Jan 1, 1997

In the hard rocks of the Nordic countries of Norway, Sweden and Finland underground works have a long tradition. Today the subsurface has been taken into use for a wide variety of purposes. In this paper only the more uncon- ventional examples are described such as caverns for drinking water, sand bunkers, molasses silos, wine and liquor stores, cold stores, heat storage, waste disposal and state archives. The particular use of unlined high pressure tunnels and socalled air-cushions for hydropower schemes is discussed. The dual use of subsurface air-raid shelters for sports activities seems to be a special Nordic tradition. Some cost figures are given and the advantages of using the underground is Discussed.

Jan 1, 1987

By Shrivastava P, Humphreys M, Guibal D, Deraisme J

Customer requirements concerning the final products of iron mines are extremely stringent. Because of this, there is an ever-increasing need for mine operators to monitor and strictly control the quality of their product. This quality, as measured by the stockpile grade variability, is the result of a very complex process, where natural characteristics (the orebody and its geology) are transformed through the mining technique (open pit, shovel and truck fleet, blending into stockpile). The only way to reproduce and hence to control the variability of such a system, which is composed of several interactive sub-processes, is by simulation. A complete simulation of a Hamersley Iron Pty Ltd (HI) ore deposit has been undertaken to forecast the impact and cost of various mining methods, mining schedules and product stockpile sizes on variability of chemical and physical characteristics of the products. The mining simulation was made on a conditionally simulated orebody. On a range of criteria, the simulation was considered to fulfil the objectives set and was a valuable aid to analysis of product grade variability, operating and capital costs, selection of equipment, mine scheduling and setting of product grade targets.

Jan 1, 1994

By Edward Keller

About a dozen years ago the art of bessemerizing copper- * matte, brought to these shores from France, was first established at the smelter, in Butte, Montana, of the Parrot Silver and Copper Company, which had bought the process from Mr. Manhks, the inventor. Through the efforts of Mr. J. E. Gaylord, general manager, and Mr. A. J. Schumacher, snperintendent,, assisted by an able staff, the new method rapidly underwent, at the Parrot establishment, an evolution towards higher perfedion, and within a few years its success and its advantages were so marked that all the great works in the west followed in the footsteps of this pioneer. The converter-process has now practically superseded the reverberatory-process in this country. The latter will undoubtedly, in a not very distant future, be relegated to metallurgical history. The writer has availed himself of what was perhaps the last chance to make comparisons of the two methods, working practically on the same material on an extensive scale, the reverberatory process being that of the Baltimore Copper Smelting and Rolling Company,* while the converter-process is that of the Anaconda Copper Company—both using the matte from the latter company's works in Anaconda, Montana. For the greater portion of the material considered in this paper, the writer is indebted to the two companies. In order to understand the difference of behavior of the several elements, and the difference of the copper produced in the two processes, it is best to study and follow those elements

Jan 1, 1899

The New South Wales coal industry is a highly mechanised well organised industry which has developed from an annual production of slightly less than 13 million tons in 1950 to over 33 million tons in 1969. Although continuous miners were not introduced into the mines until 1950, by June 1969 the percentage of coal won by these units was 87.3. The paper describes mining conditions in the various coalfields of the State, their complexities and problems and how these have been dealt with. The introduction of fully mechanised longwall faces has presented a challenge which has been accepted and descriptions of systems in use are discussed. Major expansion of the industry is anticipated to meet the requirements of the growing Australian steel industry, for local power generation and to meet the increasing demands of overseas markets.

Jan 1, 1980

By Lawrence K. Nordell, Vinit Sethi

Published standards and specifications do not adequately cover engineered class pulleys for modern high strength steel cord belt conveyors. This paper discusses the Conveyor Dynamics, Inc. (CDI) design criteria and stress analysis techniques emphasizing the finite element method (FEM), fatigue failure criteria, design limits and manufacturing requirements to ensure successful and safe pulley installations.

Jan 1, 1993

By D. Robert Weir, M. J. H. Ruscoe, R. M. Berezowsky, M. A. Clegg

The metallurgical processing involved in the produc-tion of the new Canadian one dollar coin is reviewed starting with the hydrometallurgical production of pure nickel powder, followed by the powder metallurgy process for the production of nickel strip and coinage blanks, and concluding with the Aureate bronze electroplating and heat treatment procedure. Coinage requirements are then reviewed with regard to economic, public acceptance, and service requirements. Finally the properties of Aureate nickel coinage are presented in the light of the many and varied coinage requirements, and it is concluded that the new Canadian dollar coin exceeds the requirements admirably.

Jan 1, 1990

By Scales PJ

Fatigue is the primary cause of failure of structural and mechanical components subject to dynamic loading. Recognition of this basic fact and the development of appropriate techniques and details are important in the design and repair of off highway trucks (OHTs). The frames and appendages of OHTs and other mobile plant used in the Pilbara are subject to tough operating conditions. Any fatigue-prone details quickly show up and become a maintenance liability of considerable concern. Much of this equipment is approaching the limit of its fatigue life and maintenance managers face decisions on whether to repair or replace. Even new equipment often contains some poor details which suffer distress soon after commissioning. In those cases a repair is required which will reinstate the detail to its original intended design life. Repair details must be practical and cost effective. They must also be tailored to the capability and expertise available in the field or in local manufacturers' establishments. This is particularly important where original equipment was manufactured overseas and long delivery times are involved. Lessons are drawn from components which have failed, using the evidence constructively, to provide an upgraded part or an improved substitute. With the experience now available it is relatively easy to extrapolate to cover new problem areas. This paper describes specialised techniques of mechanical fastening and detailing for low fatigue susceptibility, built up over many years of experience with OHTs and other mining plant and equipment in the Pilbara.

Jan 1, 1982

By C. F. Smart

SINCE their comparatively recent development, the alloys of cadmium with silver and copper or nickel, and of cadmium with nickel alone, have been used somewhat extensively as liners for connecting rod bearings and main bearings of internal-combustion engines. In applications where, owing to high hearing loads and elevated operating temperatures, the life of hearings made from tin-hale or lead-base alloys has been undesirably short, cadmium alloys have demonstrated considerable advantage. In applications where, because of deflection of the crankshaft or bearing supports, copper-lead bearing metals have resulted in scored shafts, cadmium alloys have been operated successfully. The somewhat serious drawback to these alloys in hearing service has been that they, in common with copper-lead and certain lead alloys, are susceptible to corrosion in the presence of lubricants containing organic acids. These acids may be fatty acids (such as oleic acid) derived from animal or vegetable oils that sometimes have been compounded with engine lubricants, or they may be compounds of an acid nature developed by the oxidation of some petroleum oils under operating conditions. The result of such acid attack on hearings is illustrated by the photograph, Fig. 1. The petroleum oils that are most readily oxidized to a corrosive condition, and the operating conditions under which such oxidation most readily occurs, are now rather well known among the technical organizations of both the petroleum and automotive industries. While means have been developed for inhibiting petroleum oils against such acid formation, the knowledge that this condition may be encountered has been a factor in restricting the wider use of cadmium alloys as engine bearings. It has appeared, therefore, that their value and use would be enhanced if they could be made corrosion-resistant to a degree compatible with the most severe operating requirements. Investigation, undertaken with this in view, indicated that the addition of fractional percentages of the metal indium to the cadmium bearing

Jan 1, 1938

By M. Isac, R. I. L. Guthrie, S. Ge

The Al-Mg-Sc-Zr alloys have shown exceptional potential as structural materials for transportation applications. These alloys have proved to be good candidates to be processed as thin strips via the Horizontal Single Belt Casting (HSBC) process. The HSBC process is a near-net-shape casting technology, which involves casting molten metal directly into thin strips, close to the final product thickness, at high cooling rates. It offers an efficient, economical and environmentally-friendly approach to the production of metal strips. Fluid mechanics and associated heat transfer are important aspects of any casting process, and the novel HSBC process is no exception. Three dimensional Computational Fluid Dynamics (CFD) simulations using ANSYS FLUENT 14.5 were performed, in order to assess the importance and effects of the various operational conditions of the HSBC process. This enabled process parameter optimization. Numerical predictions were validated against experimental casting results.

Jan 1, 2014

By S. D. Rosenthal

"This paper will share my ‘shift in career direction’ journey from corporate mine engineer, with 31 years of mining various commodities with a wide range of responsibilities in a variety of countries, to the world of academia. There are times in one’s career that a change is required, albeit perhaps not as drastic of a change as moving to teaching. This paper will share how the transition arose, the decision to make the change, the challenges of the first year in academia, and the journey within academia going into the second year. INTRODUCTION As a graduate of the Montana College of Mineral Science and Technology (Montana Tech) with a B.S. Mining Engineering degree in May of 1982, my first job with Utah International in the Farmington area took me back to my home state of New Mexico. Some of you will remember that the early 1980’s was not a period of prolific opportunities for mining engineers; given low commodity prices, especially for copper (for example, Anaconda Company had been taken over by Arco and was in the midst of closing down its Butte operations). Coal was good and the learning opportunities abounded with Utah (which became BHP and then BHP Billiton). Gold was taking off in the mid to late 1980’s thanks to use of cyanide and heap leaching technology improvements, coupled with deregulation of the gold price, so I ventured off to work in the gold industry with a (then) junior Canadian company called Barrick at a new acquisition of theirs known as Goldstrike. That same gold surge was causing a shortage of iron ore mining engineers in Australia so after a few years in Nevada, I uprooted the family and left for a little town in the Pilbara of West Australia, known as Newman, to work in the iron ore industry with BHP Iron Ore. An initial short overseas posting turned into six plus years before transferring to BHP’s Indonesian steam coal mines in Kalimantan on the island of Borneo. BHP was going through a rough period following some ill-fated projects (Magma copper purchase, Beanup and HBI) and was reviewing assets and staffing so internal opportunities became scarce. Employees were encouraged to ‘leave the company and find work elsewhere.’ So, off I go to Argentina to try copper mining in the Andes with Minera Alumbrera. This short stint in South America was followed by a move to another mining town, Morenci, Arizona, and a posting with Phelps Dodge (now Freeport McMoran). After 12+ years without living close to snow we moved to the Denver area in a new position with Newmont Mining Corporation. Along the way I became a Professional Engineer (Nevada) and completed a Masters in Project Engineering and Management. After 11 years with Newmont, I moved to Butte, Montana where I accepted a position as Assistant Professor of Mining Engineering."

Jan 1, 2015

By S. D. Rosenthal

"This article will share my ‘shift in career direction’ journey from corporate mine engineer, with 31 years of mining various commodities with a wide range of responsibilities in a variety of countries, to the world of academia. There are times in one’s career that a change is required, albeit perhaps not as drastic of a change as moving to teaching. This paper will share how the transition arose, the decision to make the change, the challenges of the first year in academia and the journey within academia going into the second year.As a graduate of the Montana College of Mineral Science and Technology (Montana Tech) with a B.S. mining engineering degree in May of 1982, my first job with Utah International in the Farmington, NM area took me back to my home state of New Mexico. Some of you will remember that the early 1980s was not a period of prolific opportunities for mining engineers, given low commodity prices, especially for copper (for example, Anaconda Co. had been taken over by Arco and was in the midst of closing down its Butte operations). Coal was good and the learning opportunities abounded with Utah (which became BHP and then BHP Billiton).Gold was taking off in the mid to late 1980s thanks to use of cyanide and heap leaching technology improvements, coupled with deregulation of the gold price, so I ventured off to work in the gold industry with a (then) junior Canadian company called Barrick at a new acquisition of theirs known as Goldstrike. That same gold surge was causing a shortage of iron ore mining engineers in Australia. So after a few years in Nevada, I uprooted the family and left for a little town in the Pilbara of West Australia, known as Newman, to work in the iron ore industry with BHP Iron Ore. An initial short overseas posting turned into six plus years before transferring to BHP’s Indonesian steam coal mines in Kalimantan on the island of Borneo. BHP was going through a rough period following some ill-fated projects (Magma Copper purchase, Beanup and HBI) and was reviewing assets and staffing, so internal opportunities became scarce. Employees were encouraged to “leave the company and find work elsewhere.” So, off I went to Argentina to try copper mining in the Andes with Minera Alumbrera. This short stint in South America was followed by a move to another mining town, Morenci, AZ, and a posting with Phelps Dodge (now Freeport- McMoRan). After 12-plus years without living close to snow, we moved to the Denver, CO area in a new position with Newmont Mining Corp. Along the way I became a professional engineer (Nevada) and completed a masters in project engineering and management. After 11 years with Newmont, I moved to Butte, MT where I accepted a position as assistant professor of mining engineering."

Jan 1, 2015

To develop a magnetic levitation transport system that can reduce the cost and improve safety in transporting coal from the face of underground coal mines to the surface. Background Many conventional mining operations use conveyor belts to transport coal from an underground face to the surface of the mine. The Mag-Lev Transport System design replaces conveyor belts with magnetically levitated coal haulage containers moving through a dedicated pipe¬line. Cost estimates, based on current design data, show the Mag-Lev Transport System would have operating and capital costs that are less than or equal to those of an equivalent-capacity conveyor belt system. The safety hazards associated with conveyor belt systems include exposure to moving parts and pinch points, potential fire hazards due to mechanical friction, and the exposure of miners to respirable dust. These hazards would be eliminated or significantly reduced by this novel technology. Approach The Mag-Lev Transport System uses magnetic levitation technology that allows noncontact, frictionless conveyance of a levitated body within a dedicated transit corridor. The mag-lev technology utilizes two types of permanent magnets coupled with an electronic position control system to achieve noncontact levitation. Levitation is provided by neodymium-iron boron (NdFeB) magnets mounted in the base of the haulage containers and inexpensive ceramic-5 magnets located in the bed of the transit corridor. An electronic position control system is used to overcome the inherent instability of the repelling permanent magnets. Proximity sensors, a signal processing circuit, electromagnetic actuators, and fixed ferrous side rails are the major components of the positioning system.

Jan 1, 1994

By Erwin L. Zodrow

A geological model of the modes of formation of magnetite and its distribution in the Smallwood iron-ore mine, Labrador, Newfoundland, is given, based on observation and geological mapping. This is called the conceptual model. If mathematical expressions plus probabilistic uncertainty are used to represent the conceptual model, then this is termed a mathematical model. The purpose of this paper is to test if there exists a correspondence between the conceptual model and two related mathematical models (called factor analysis). Details of the statistical technique are given. The results of factor analyses in relation to the magnetite formations in the Smallwood mine are discussed. Several practical mine applications are presented. The difficulty of maintaining quality control over ore mined from any deposit naturally depends on geological conditions; these are usually imperfectly known to concerned mining geologists. One geological condition that would greatly facilitate ore predictions is if a relationship between the observed ore particle distribution* and its mode of origin could be demonstrated. Such a casual interrelationship is normally sought through the application of well-defined geochemical principles of primary mineralization in given geological environments. However, the application of conventional tools of geological research, including geochemistry, to areas that have undergone repeated periods of geological deformation and metamorphism subsequent to primary mineralization becomes rather difficult. More important, the interpretation of such research results are nearly impossible on an objective basis. Mineral assemblages may have been reworked and changed due to tectonic influences to the extent that the present-day observable mineralogy and ore-particle distribution can effectively obscure the mode of origin of the ore. Quantitative measurements, based on petrological investigation of mineral assemblages, reflect the sum-total of all geological influences. Which of several influences had the most effect on existing ore particle distribution is difficult to assess, for these influences can neither be measured directly nor quantified by petro-logical logical or geochemical means. The present study is concerned with the magnetite distribution and its modes of origin within the Small- wood mine,' located in the southern extension of the Labrador geosyncline; see Fig. 1. This geosyncline is thought to have undergone at least two periods of geo-tonic tectonic deformation, separated in time, since the fer-rugenous rugenous sediments were deposited." Detailed geological observations and mappings (1 in. to 40 ft) have highlighted subtle, distinctive features of the magnetite distribution in the Smallwood mine: (1) The magnetite is generally concentrated in bands or layers within this ore body; these bands alternate with specularite-rich bands and quartz bands. The banded or layered nature is common in Precambrian iron-ore deposits, and this has been interpreted as a result of changes in depositional environments. (2) The grain size of the magnetite varies; near the contacts between the iron and quartz-carbonate formations, the magnetite occurs as well-crystallized octa-hedra. In areas of intense folding, magnetite is extremely fine grained and concentrated in bands and occurs in association with earthy manganese minerals. (3) Magnetite tends to be more highly concentrated near the geological contacts of the iron and quartz-carbonate formation in the northeast part of this mine, Figs. 2, 3, and 4. (4) Magnetite is also fine grained and tends to higher concentration near and parallel to fold axes; however, in this case, the ore is much softer than given in item 2. (5) Magnetite mineralization decreases along strike and away from the areas of intense folding, i.e., towards the approximate center of the mine, Fig. 3. How can these variations of magnetite be explained on a geological basis? We can postulate a conceptual model that the distribution of magnetite appears to be related to three basic geological influences: (1) geo-tectonics, i.e., concentrations of magnetite near geological contacts of the iron and quartz-carbonate formations, the fine-grained nature of magnetite and its higher concentrations near fold axes, and decrease of magnetite towards the approximate center of the mine; (2) secondary alterations, i.e., variation of grain size of magnetite near the iron and quartz-carbonate contacts, and in areas of intense folding where magnetite occurs together with earthy manganese minerals: (3) original

Jan 1, 1971