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By B. I. Whittington

This paper examines the effect of cation type (i.e. NH4+, Na+ and K+) and anion type (i.e. SO42- and C1-) on the extraction of nickel during the pressure acid leaching of a Western Australian laterite ore. The results are compared with testwork conducted with other Western Australian nickel laterite ores and the possible process implications of adding an additive to a plant autoclave are considered. Addition of either (NH4)2SO4, Na2SO4 or K2SO4 increased both the nickel extraction and the acid consumption, provided that the level of additive was not too great. For example, the nickel extraction of 93% increased to above 96% in the presence of additives, but decreased to 94% when, for example, NH4 levels increased from 7 kg/t ore to 21 kg/t ore. The relative stability of the jarosite species formed when additives were present influenced the amount of jarosite in the residue and, hence, both the final free acidity and overall nickel extraction. The use of Cl- versus SO42- salts as additives had little effect on overall nickel extraction or overall free acid values, although the presence of SO42- additives appeared to enhance nickel extraction kinetics over the first 60 minutes of the reaction. In contrast, manganese extraction was enhanced by the presence of Cl- additives.

Jan 1, 2004

By Cris Sideco

This paper describes the concentration processes of the Sullivan. Concentrator, including crushing , transportation, sink-float, grinding , flotation and dewatering. Handling of hot muck has had a deleterious effect on most of the processes, resulting in significant operating problems and poorer metallurgy. These problems are described -in detail. THE SULLIVAN CONCENTRATOR is situated in Kimberley, high up in the Purcell Range of the Selkirk Mountains, at an elevation of 3,600 feet, approximately 4 miles from the Sullivan Mine (see Fig. 1). The original plant went on stream on August 23, 1923 at a designed capacity of 2,500 tons per day. This has been increased in stages to its present rated capacity of 11,000 tons per day. The latest stage was in 1949, when several major projects, including the underground crushing plant, the sink-float plant and the installation of a rod mill, were completed. Some 112,800,000 tons of ore have been treated in this concentrator to November 1975. The plant started on a 48-hour/ week schedule, but was reduced to 44 hours/week in October 1946 and down to 40 hours/week by the end of 1949. Except for a 6-month period in 1952 when the mill operated continuously, the 40-hour/week, Monday to Friday schedule was in effect.

Jan 1, 1977

By Paul B. Batten

Shutdown is a generic term for what may be called an Outage, Turn Around (TAR) or Overhaul etc. Running a plant shutdown well has always been key to the financial contribution of a mine. However, something important has changed. The post pandemic reality is that it is harder to retain workers and many of those near retirement just didn’t come back to work. This is creating a shortage of experienced people and a workforce that changes employers easily. We are seeing the impact of this manifested in the erosion of established maintenance and supply chain processes that now struggle to yield the plant runtime that could once be taken for granted. The scope, cost and duration of a shutdown varies widely depending on the nature of the work and the equipment being renewed. The PM of an electric shovel might require a week of downtime and cost $100,000. A gold plant may need to go down for 3 days when its time to change mill liners and cost $500,000. A turnaround in a refinery can take more than a month and cost multi millions. Despite the huge differences.

Jan 1, 2023

By Baochun Wang, Hongli Jia, Zhaolian Wang, Fengliang Liu

"Promote and apply a new beneficiation technology and equipment effectively processing the refractory and medium-fine grained weak-magnetic minerals. HUATE® Forced-oil Cooling Vertical Ring WHIMS adopts the transformer oil cooling technology to cool excitation coils, solving the easily generated scaling problem resulting from water cooling, thereby to eliminate the demineralized water system. With <25 temperature ?raise, its magnetic field is stable. Wrapped by outer magnetic armor, it can generate a background intensity 1360kA/m. It effects very well in 1) wet preseparating the weak-magnetic coarse grains, like hematite, manganese ore, ilmenite, and purifying the concentrate; 2) removing the ferrous impurities and purifying the non-metallic minerals, like quartz, feldspar, kaolin; 3) enriching and recovering tailings from non-ferrous metals, like copper, lead, cobalt, molybdenum, thereby to greatly improve the mine resource utilization. It has applied 14 relative patents in China, and the invention patent in 56 countries, like Russia, USA, Australia, via PCT international organization. HUATE® WHIMS has been applied and accepted in more than 100 mines in and out of China. Compared with water cooling vertical ring WHIMS, it’s energy-saving and water-saving, and avoiding generating the scale. While compared with JONES WHIMS under the same separation indexes, it’s featured of more space-effective, lighter, lower costs, higher gradient, higher efficiency, larger processing capacity and wider grain application scope. Greatly promoting development of mineral processing technologies, HUATE® WHIMS is the equipment to reduce costs and improve efficiency urgently needed by the mine enterprises now.INTRODUCTIONAt present, influenced by the price and production factors, the international market demand for the grade of iron ores is increasing continuously. Restricted by the ore occurrence state, the beneficiation technology level and product economic value, every year the stope strips the stockpiling and discards hundreds of millions of tons of waste rocks containing iron, especially the weak magnetic hematite and limonite with <20% Fe%. The utilization technological bottleneck of these waste rocks makes their concentration ratio as high as 5-6, which leads to the huge wastes of energy, materials and beneficiation reagents and the increase of production costs. The effective solution is to improve the selected Fe% of the waste rocks like hematite. With the successful application of HPGR technologies in Chinese large iron mines, the mill feeding size has been reduced to 6-0 mm or 3-0 mm from the original 15-0 mm in the crushing system with 3 stages of crushing and 1 stage of closed circuit. This creates the conditions for the wet separation and recovery. While for the medium-fine grained weak-magnetic minerals, it lacks of the effective separation and recovery equipment in the world, which’s badly in need of R&D of the medium-fine grained high gradient wet strong magnetic preseparation equipment."

Jan 1, 2016

By Shuo Zhang, Wenying Liu

"In dump leaching, the efficiency of metal extraction from ores is strongly influenced by the mechanisms of fluid flow. Particle size distribution acts as a fundamental parameter in the determination of fluid flow properties in packed ore beds. In this study, we investigated the particle size distribution in dump leaching by using image analysis technique. The results showed that the particles in the dump varied from smaller than 2 cm to larger than 200 cm in diameter. P80 was calculated to be 200 cm, which was significantly higher than the historical data used by the operation. P25, P50 and P80 were found to increase non-linearly with increasing depth towards the toe of the dump, suggesting the segregation of fine and coarse particles. The image analysis results were verified by applying the rock fragmentation models. The model with the Swebrec function was found to be in better agreement with the image analysis results. Future research will investigate the effect of particle size distribution on the behaviour of fluid flow.INTRODUCTION Fluid flow plays an essential role in the extraction of valuable metals using heap/dump leaching (Amos et al., 2009). The rates of the chemical leaching reactions and microbial activities determine metal concentrations in the leachates and therefore the efficiency of the metal extraction. The reaction rates are influenced by two fundamental processes: transport phenomenon and reaction kinetics (Bouffard & Dixon, 2001). The transport phenomenon refers to the percolation of fluids through channels and pores in a packed ore bed, which carries lixiviants and reaction products to/from ore surfaces by convection and diffusion. The percolation rate of the leaching solution is determined by the hydraulic conductivity of the packed ore bed, which is a function of the permeability and the degree of saturation (Guzman et al., 2008). Permeability, an intrinsic property of a packed ore bed, is strongly influenced by the particle size distribution of the ore grains (Bouffard & Dixon, 2001). Hence, the objective of this study was to investigate the particle size distribution in dump leaching."

Jan 1, 2017

By N. W. Hendry

ABSTRACT Exploration by geophysical methods and diamond drilling of an occurrence of chrysotile asbestos, located ten miles east of Matheson, Ontario, was commenced on March 25th, 1949, by the Canadian Johns-Manville Company, Limited. The asbestos is associated with a narrow sill-like body of basic and ultrabasic rocks which strikes northwesterly across portions of Munro and Beatty townships. To date, asbestos zones of commercial interest, many hundreds of feet in length, width, and depth, have been outlined by diamond drilling along a 2-mile length of serpentine. The fractures occupied by the asbestos veins are closely associated with the regional faulting in the area. The mining of the first occurrence, or A orebody, will be by open-pit methods. Milling will commence at a rate of 50 tons an hour. INTRODUCTION OCCURRENCES of chrysotile asbestos in Munro township have been known at least since 1914 and references to them appear in reports published by the Ontario Department of Mines in 1915 (1) and 1919 (2). J. G. Ross (3) in his excellent publication on Chrysotile Asbestos in Canada, mentions an occurrence in Munro township. The area was first mapped in detail by J. Satterly, of the Ontario Department of Mines, in 1944, and brief mention is made of chrysotile asbestos in Satterly&apos;s preliminary report (4), which was published the following year.

Jan 1, 1951

By Jan Butra

In copper ore mines located in the Pre-Sudeten Monocline the deposit mining using room and pillar systems has been carried out for more than forty years. When implementing mining systems in deep copper ore mines it appeared to be necessary to adapt them to variable geological conditions and natural hazards. In the initial period of exploitation there were mainly caving and rockburst hazards. The adaptation of room and pillar system was connected with a state of knowledge in the scope of identifying, forecasting and controlling rock mass hazards. The new solutions allowed the safe and efficient exploitation of a blanket deposit of variable thickness from about 2 to 15m, seated on progressively increasing depth. They included exploitation in constrained conditions, such as in protective pillars. In the exploitation period, technical and organisational activities aimed at rockburst hazard control were introduced including active methods for controlling rockburst hazard and procedures for conducting mining works in the rockburst hazard conditions. When mining at a depth exceeding 1,200 m, the exploitation method and technique are additionally affected by thermal hazard and by gas and rock breakout hazard. New solutions of the room and pillar system and a longwall system with mechanical mining have been developed for exploitation in the associated hazard conditions. The require application of many innovative solutions in the scope of mining process and ore haulage mechanisation, excavation support and forecasting and control of existing hazards. The main purpose of these solutions is to conduct the safe and economically effective exploitation of the deposit.

Aug 1, 2013

By Ross G. Bertinshaw

"The Line Creek Mine of Crows Nest Resources started mining coal in the fall of 1981. There are seven mineable seams with thicknesses ranging from 1.5 to 13 metres and with dips varying from 0 degrees to 60 degrees. This, together with internal partings and the very friable nature of the coal, creates a number of mining problems.The coal is divided into zones depending on the dip of the seam. Each zone requires a different mining technique to ensure optimum recovery and low dilution while still keeping fines to a minimum.Line Creek employs a combination of hydraulic front shovels and backhoes to mine its coal without blasting or use of dozers. This has been very successful in reducing the proportion of fine coal hauled to the plant, thus improving quality control and reducing costs in coal processing.There have been a number of other benefits from the use of excavators instead of more conventional methods. These include better selectivity, good cleanup, reduction in traffic at the face and lower cost.IntroductionThe Line Creek Mine is situated approximately 25 km north of Sparwood in southeastern British Columbia (Fig. I). Preproduction stripping began in J98J with the first coal shipments made in 1982. In 1983 the mine produced 2.1 million tonnes of raw coal.Similar to other East Kootenay coals, the seams at Line Creek are characterized by their friability, producing a large proportion of fine coal during mining. In an attempt to reduce these fines Crows Nest Resources has instituted the use of hydraulic excavators to mine and load the coal.Hydraulic excavators offer other substantial advantages over front-end loaders and dozers, which has been the conventional system in other mines in the area."

Jan 1, 1985

By Garston Blackwell

Abstract - During geostatistical estimation of block grades, the kriging process produces a measure of error, the kriging variance or the kriging standard deviation. Estimation of the block error depends on the semi-variogram model for a deposit, which reflects fundamental characteristics of a deposit such as (1) nugget effect, (2) range of influence of grades, (3) different local spreads of data as a function of average grade (proportional effect), (4) nested structures, and (5) underlying anisotropies in the data; this model may be affected by sampling or assaying limitations, however. Because the kriging error incorporates so many features of both the deposit and data to be used for estimation, it may offer a substantial improvement on block classification over traditional procedures such as data density. Practice indicates that the relative kriging standard deviation (RKSD) is particularly useful for block classification in measured, indicated and inferred categories. Plots of RKSD in plan and section also can be used to demonstrate where extra drilling and sampling would be most advantageous for upgrading the class of some blocks. Moreover, the use of grade and RKSD filters can show where material near cut-off grade is poorly defined, indicating sampling target areas to improve block classification in the vicinity of the ore-waste boundary.

Jan 1, 1998

By A. J. R. Smith

"CANADA'S ECONOMY TODAY is about two-fifths larger than it was six years ago, as measured by the total volume of production of goods and services. Such an achievement has been a rare phenomenon in Canada's first one hundred years. Excluding the forced-draft expansions which took place under war-time conditions, perhaps only the first decade of this century recorded a performance of greater dimensions, when, with massive immigration, the opening up of the West and a powerful array of well-de-signed development policies, the country was looking forward confidently to a great future of nation-building in the twentieth century.What makes Canada's over-all economic advance since 1961 all the more remarkable is that six years ago there was virtually no one in this country who anticipated an expansion of such dimensions. Back in the buoyant conditions of 1956-57, perhaps such an achievement would not have seemed beyond our grasp. After 1957, however, Canada stumbled through an extended period of slow economic growth, high unemployment and substantial and widespread under-utilization of its productive capacity. By the early 1960's, conditioned by the emergence of substantial, persistent and pervasive slack in the economy, t h e r e were few Canadians bold enough to anticipate that their economy was about to embark on a Great Expansion. However, this •is, in fact, what occurred. Beginning early in 1961, Canada moved forward into a sweeping advance which grew into the longest and largest peacetime business expansion in Canada's first century as a nation -a truly great expansion by any standard of measurement. This strong thrust has moved Canada into the front ranks of over-all economic expansion among the industrially advanced nations in the 1960's."

Jan 1, 1970

By Leonard Kellogg

Introduction The Mine Manager or Superintendent is a man faced with a difficult problem. He must direct the activities of his mine in such a manner that, over a period of time, the greatest possible profit will be realized. In this respect, a mine is no different from any other business organized for profit. What makes the mine manager&apos;s task so difficult then? The profit of a mine is determined by -among other things -the grade of ore, the market price of the metal or metals produced, and the cost to operate the mine. The mine manager cannot do much about the first two of these, but he has considerable control over the operating cost. This cost will depend in large measure on the nature of the programme on which he plans to operate his mine. This operating plan may be broad or specific, on a long-range basis or on a month to month basis. The development of the plan, however, is made very difficult by the existence of so many factors which must be considered. These may be (1) factors requiring decisions based on the best judgment and interpretation of engineering and geological information available, or (2) items which must be considered but which are largely non-controllable. To be more specific, examples of such items would be: (1).-(a) The amount and type of development work to be done in relation to amount of ore to be mined. (b) Mining methods to be followed and type of equipment to be used. © Amount of exploration diamond drilling to be done if the orebody is not clearly defined. (2).-(a) Rock type and degree of hardness. (b) Width, depth, and pitch of veins. © Amount of work requiring timbering. (d) Faults encountered. (e) Water and gas conditions met with.

Jan 1, 1952

By K. Mirkhani, P. Gebski, W. Ying

The campaign life of an industrial metallurgical vessels strongly relies on the quality and quantity of the refractory lining. An operating furnace or converter refractory lining can be assessed either by thermal modeling or by acousto ultrasonic-echo (AU-E) technique or a combination. AU-E is a Non-Destructive Testing (NDT) stress wave propagation technique that has been utilized on a wide variety of smelting vessels for over 12 years with good success. AU-E can determine the thickness of remaining refractory lining, estimate the thickness of build-up or accretion, detect and locate metal penetration and impregnation into the lining, and identify hydrated or cracked areas of refractory. This paper details the AU-E principles, equipment and recent improvements to the data analysis to further improve speed and accuracy. In addition, the paper discusses the AU-E accuracy and limitations through a diverse and vast array of practical examples including a comparison with thermal modeling and physical measurements.

Jan 1, 2011

By M. C. Ethier, A. L. Laramie

"The Granisle and Bell Copper mines were officially put into production in 1966 and 1972, respectively. The Granisle Mine was purchased in late 1979by Noranda and the two operations were amalgamated as one division. Both mines were closed in 1982after sustaining heavy financial losses during a period of low copper prices beginning in 1981.This paper describes the resumption of operations at the Bell Mine in 1985 after its shutdown period of three years and the dramatic and sustained improvements in productivity and efficiency realized as a result of a commitment by employees and management to the application of Participative Management and Employee Involvement principles. After a general description of the effects of such a philosophy on the operation as a whole, and a comparison to the operation&apos;s last full year as a producer, it deals with the practice of this philosophy in the maintenance department at the Bell Mine and the superb results realized.IntroductionThe Bell Copper deposit was discovered in 1963 and came onstream as a 10000 ton s per day open pit mine in the fall of 1972. Identified reserves at that time were 46 million tons of ore containing 0.50% copper. The mine shared facilities of the townsite of Granisle with the nearby Zapata-Granby mine which had established the community six years earlier.Because of easy grinding ore and improvements to milling circuits, Bell&apos;s throughput rate was increased to 17 000 tons per day by the late 1970s. In the open pit, improvements resulted in mining of additional reserves with higher stripping ratios. At startup, a half ton o f waste was mined for every ton of ore processed.By the end of 1982, with 48.2 million tons already mined, the Bell Mine had identified additional mineable reserves of 39.4 million tons containing 0.52% Cu.In November 1979 the Granisle Mine was purchased from Zapata-Granby. The two mines, with a total of 700 employees, were operated under common management as the Babine Division until 1982 when low copper price s forced the closure of both for an indefinite period.The outlook for copper prices remained bleak and only 50 people were retained on the payroll to maintain the two plants, most of them working on a part-time schedule.The population of the Village of Granisle dwindled from over 1500 inhabitants to under 500, as people moved away to seek other employment.Prior to the shutdown, the Bell Mine employed 370 people and pit extraction averaged nearly 50000 tons per day of which 16000 tons was mill feed, and the remainder waste. Total cost to produce a pound of copper was C$1.36 in 1982."

Jan 1, 1990

By Ivor da Cunha

Ontario Mining Association (OMA) represents 57 members that are engaged in exploring, producing & processing mineral resources in an environmentally responsible manner. Conservation Bureau at the Ontario Power Authority (OPA) develops, coordinates and stimulates commitment to electricity conservation and demand management programs ? OMA selected compressed air optimization for high impact cost savings and energy efficiency potential ? Ontario Power Authority (OPA) provided $218k funding for $532k project ? Commenced summer 2006, Final Report June 2007 ? Three representative sites participating: ? Williams, CVRD Inco & FNX McCreedy ? Different levels of energy management ? Small, medium and large mining operations ? Different corporate practices and culture

May 1, 2007

By R. B. Fermor

"AbstractAttention is drawn to the ventilation problems arising from the use of diesel vehicles underground, especially in view of the fact that diesel fumes in combination with other pollutants may be more harmful than diesel fumes alone or the other pollutants alone.Means for minimizing the harmful effects of using diesels underground are listed, and the quantities of air' required in mines in which diesel-powered vehicles are used are discussed. Mines are classified in three categories on the basis of severity of ventilation problems, and statistics are given for these categories.Details of the various components contributing to total ventilation needs are given, and the ventilation needs of individual mines in the three categories are listed. A description is given of the principles according to which main ventilation coursing is planned and the selection and siting of main fans is discussed.General Considerations in the Use of Diesel-Engined Vehicles UndergroundIN ORDER to reduce physiological hazards, present and latent, to workers in mines in which extensive use is made of diesel equipment underground, it is important that mine ventilation systems reduce the concentrations of rock dust, diesel fumes and particulate matter as rapidly as possible to an acceptable level in all parts of the mine.There is some evidence that the long-term effects of a combination of the above pollutants are greater than those of anyone of them alone, which makes the problem even more pressing."

Jan 1, 1977

By SANDVIK WHITE

The mining industry produces approximately 4-7% of global greenhouse gas (GHG) emissions. It is fundamental for mining operations to take immediate sustainable action to actively contribute to an emissions-free future for the next generations. The mining industry has traditionally relied heavily on diesel technology and transitioning to more sustainable solutions requires change management to drive cultural acceptance and new product development. Sandvik was interested to find out the lifetime emissions of a single drill rig and to compare similar application diesel and BEV drill rigs with same use profile to each other. That led the calculation and pondering towards comparing different countries and mine sites as well

Jan 1, 2023

By D. Nower

"The supply of copper is expected to be at a large deficit in 2012. To recover from these deficits mining companies are required to maximize production and there is no better way to accomplish this than to optimize the use of their mobile mining equipment fleets. To optimize these fleets, each equipment type has to be monitored in its own unique way. Automation would not only improve production, but also minimize the safety risks and eliminate planning errors. The automated vibration monitoring of multiple systems on the shovel can determine the machine’s condition at all times. This reduces unplanned downtime and keeps critical shovels in production. This paper will discuss the details of how shovels can be successfully monitored, continuously. INTRODUCTIONP&H Mining, part of Joy Global, is the world’s largest manufacturer of above-ground mining equipment. Its electric rope shovels, such as Figure 1, with capacities up to 115 tons (104.3 metric tons), are used for high production loading in surface mines; its draglines, such as Figure 2, have bucket capacities to 160 cubic yards (122 cubic meters). P&H also produces blasthole drills, mobile mining crushers and other essential mining equipment. Headquartered in Milwaukee, WI, the company does business on every continent, except Antarctica. ECONOMIC FACTORSDue to the global demands for metals and power, mines are required to operate at full capacity. Mine operations cannot afford any critical assets to shutdown unexpectedly; depending on the ore type and quality, downtime for a single shovel can be as much as $300,000 per hour.Electric rope shovels are one of the most critical assets in open pit mining. They are very large, complex machines with DC or AC motors, multiple reduction gearboxes (some of them complex planetary) and multiple large rolling element bearings. This complexity, combined with the tough 24/7 service, results in too much unplanned shovel downtime, which can affect the entire downstream process."

Jan 1, 2012

By Corby G. Anderson, Caelen D. Anderson, Patrick R. Taylor

"The United States contains a variety of domestic rare earth element mineral sources containing such as ancylite, bastnasite, monazite, and xenotime. Research has been performed to investigate the fundamental surface chemistry involved in the froth flotation of these minerals, and apply the knowledge gained to substantiate the results through experimental testwork on a domestically sourced rare earth ore. This paper will outline the fundamentals and literature of rare earth mineral flotation, review its industrial applications and provide some recent research updates.THE RARE EARTH ELEMENTSRare earth elements (REE’s) are a unique family of elements with nearly identical physical and chemical properties. They account for approximately 1/6th of all naturally occurring elements, but the entire group occupies only one position on the periodic table. These 15 elements make up the lanthanide series (atomic numbers 57–71), and all but one (promethium) occur naturally. In addition to these 15 elements, yttrium and scandium are also considered rare earths since they tend to occur in the same deposits as the rare earths and share similar physical and chemical properties as seen in Figure 1. In particular Figure 2 denotes, a cartoon of the subtle differences in each caused by the 4f atomic sub shell (Gschneidner Jr., 1964). These subtle differences result in very difficult challenges in the selective concentration and final separation of each rare earth. (Anderson, 2015, Kronholm, Anderson, Taylor, 2013)Rare earths are separated into two different subsections; the “lights” or LREE’s (lanthanum57 through europium63) and the “heavies” or HREE’s (gadolinium64 through lutetium71). Yttrium is generally considered a heavy rare earth since its ionic radius is close to that of the HREE’s, while scandium is not considered either a light or a heavy."

Jan 1, 2016

By P. Nelson, B. Salt, J. A. Scott, H. Shang

ABSTRACT In a nickel smelting process, large amounts of off-gas emissions are generated, which can cause serious environmental and plant hygiene problems if not properly treated. With increasingly stringent environmental regulations, an enhanced understanding of well-controlled, off-gas cleaning systems is vital. In this paper, dynamic models for an industrial smelter, off-gas system tackling hazardous sulphur dioxide, carbon monoxide, and carbon dioxide are developed using mass continuity, momentum, and energy conservation laws. The effect of air in-leakage is explored under different operating conditions. The developed models provide an enhanced process understanding and a necessary basis for highperformance control analysis of smelter off-gas systems.

Jan 1, 2011

By J. S. DeLury

Introduction The problems of metallogenesis are largely related to those concerning the origin of igneous rocks, which, in turn, are involved with the question of crustal mechanics. Many ore-bodies are genetically related to associated intrusive and there is an equally close association apparent between igneous intrusion and crustal deformation. The problem of ore-deposition is concerned, therefore, with the fundamental problems of geology. For a long time speculations regarding crustal movements rested largely on the contraction theory and its associated conceptions. Vertical movements were considered to be all important and horizontal movements secondary to them. Magmas were pictured as rising more or less vertically in the crust and were believed to form in vertically disposed magma-chambers or reservoirs. The principle of magmatic differentiation seemed to offer the best explanation of the origin and association of diverse rock types and it seemed also to require the existence of quiescent magma-chambers for the admittedly slow process of differentiation. Accumulating evidence of the importance of horizontal movement in the crust, has, along with other considerations, discredited the contraction hypothesis and many of the inferences that go with it. The same evidence may require some change in the prevailing conception of the origin of the various types of igneous rock and of the mechanics of intrusion. Geologists are now at sea concerning some of the vital and fundamental problems of the crust, and the field is open for speculation. The writer is developing a hypothesis which seems to permit an explanation and? a correlation of earth structures and phenomena. If it rests on a firm foundation, the hypothesis, because it is fundamental, is certain to have a profound bearing on the problems of economic geology. It is for this reason that an outline of the hypothesis is offered at this time. Only a few of its economic bearings are foreseen at this time and these will be indicated.

Jan 1, 1932