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By J. D. Goodrich

Success of The Carter Mining Company's safety program can be primarily attributed to "total immersion" of all operating and staff personnel in program design and implementation. Currently, the Company operates two surface coal mines in Campbell County, Wyoming. Total employment is about 440 and current annual production is about 15 million tons. The safety program has evolved from one which was administered primarily by staff personnel (the Safety Department) to one which requires active participation by line management and operating personnel. Lost time accident frequencies have declined from a high of 1.86 per 200K hours worked in 1978 to zero in 1982. Reportable accident frequencies have declined from slightly over 5 to slightly over 2 during the same period. Analysis of program results indicates that the most important achievement by the company has been to gain strong commitment to safe operation by all employees. It is important that program format and content be frequently changed and modified so that: 1) The requirement for safe job performance is communicated well and often, 2) The safe job performance message is trans- mitted in new and interesting ways, and 3) Operating personnel participate in design and implementation of the program.

Jan 1, 1983

By Stephen E. Kesler

Carbonaceous sedimentary rocks are abundant in the upper part of the caldera or maar that hosts the Puebio Viejo Au-Ag district, and much of the Moore sulfide zone is in these rocks. These rocks are thinly layered and contain scattered plant remains and variable amounts of volcaniclastic debris and pyrite. The carbonaceous matter in the sediments yields no X-ray diffraction pattern and is not graphite. It has C/N ratios of 4 to 10, and &13C values of about -25 per mil, which indicate that it is dominantly of marine organic origin and partly degraded. Atomic S/C ratios in the unmineralized part of the carbonaceous rocks have a median of about 1.2, much higher than most similar unmineralized rocks, reflecting not only the abundance of pyrite in the sediments, but also the fact that the organic material contains several percent sulfur. Extracts from the organic material indicate that it is thermally mature and that it reacted with the hydrothermal solutions. Atomic S/C ratios in the mineralized carbonaceous rocks are generally higher than those in unmineralized carbonaceous rocks, ranging to values of 5 and more. These differences indicate that significant amounts of carbon were consumed by the reduction of sulfate and metal chloride complexes in the mineralizing fluids as they passed through the carbonaceous sediments. Direct reaction between organic material and ferrous chloride-bearing, acid-sulfate hydrothermal solutions probably caused continuous deposition of pyrite during this period. Intermittent deposition of gold from chloride complexes by the same reaction was probably facilitated by boiling or C02 effervescence.

Jan 1, 2013

By N. R. Sainath

This paper discusses the results of a laboratory investigation carried out to study the microscale flow characteristics of copper ores and the variation in flow behavior resulting from flow of leach solution. Fractures in 1.5 and 4 inch diameter cores were mapped by visual inspection. The cores were stressed in a triaxial stress field representative of in situ conditions. The permeability of the samples to water was then estimated. The samples were exposed to 20 g/l sulfuric acid and the experiment repeated. The Permeability of unleached samples ranges from 10-1 to 10-19 m2 and it increases as leaching progresses. The porosity variation and the rate of recovery of copper from the specimen during leaching were also studied.

Jan 1, 1991

By John F. M. Sims

Political issues and a glaring infrastructure deficiency have retarded the emergence of a strong mining component to the Alaskan economy in recent years. Barriers to orderly mineral development are slowly being removed attendant upon changing political circumstances. Infrastructure development, as an investment avenue as well as a responsibility of the State, is receiving much greater attention than in the past. Alaska of course has a rich and varied mining history going back to the 19th Century. This paper, however, focuses on the mining potential, not the mining heritage of the 49th State. The mining industry is emerging from a nadir in the economic cycle - times during which it was buffeted by unsympathetic administrations and confused and confounded by the protracted land status- conflicts prior to enactment; of the Alaska National Interest Lands Conservation Act (ANILCA) and other milestone legislation. Today Alaska's mining industry looks toward a bright and healthy future and, in the process, will become a very important and vital component of the State and national economy.

Jan 1, 1982

By S. K. Bhatt

This paper reviews major developments in continuous haulage technology for underground coal mines. Haulage systems, both in use and development, are investigated through a comprehensive literature search and visits to mines and manufacturers. The systems include flexible conveyor train, mobile conveyor, multiple-unit continuous haulage, extensible, and belt turning systems. Strengths and weaknesses of the systems are assessed in light of their operating under remote control and their application to the computer-assisted continuous mining machine being developed by the U.S. Bureau of mines. Through mining scenarios, candidate haulage systems are conceptualized to be consistent with the capabilities of the mining machine.

Jan 1, 1990

By S. M. Hsiung

This paper presents the results of an extensive study concerning a series of roof falls in a room-and-pillar coal mine located in West Virginia. Three dimensional finite element modeling was employed to identify the possible causes for the roof falls. The effectiveness of possible roof control measures for alleviating or eliminating the adverse roof conditions is analyzed, discussed, and compared. The best mining alternatives are recommended. It has been found that large overburden depth and typical roof geology are the major reasons for the roof falls. Angle bolting may not solve the problem encountered in the mine studied. Changing the mine layout currently used in the mine appears to be the best alternative. The recommended pillar size and entry width which will eliminate the problem completely are 90 ft. x 90 ft. and 14 it., respectively.

Jan 1, 1985

By G. Kris Kapoor

Each new period of public concern, whether rooted in things political, social, economical, or technological, brings with it new words or phrases which highlight that new interest. With people's awareness of our rapid depletion of readily available energy sources and the enormous increase in energy .costs came the new, and now often heard, terms "energy intensive", "energy sensitive", and "energy conservation". Since its birth in 1926, Fuller Company had been directly associated and involved with energy intensive products and processes. We are located in the heart of the Cement Industry. Many of our products and processes are geared to the needs of the portland cement manufacturer, and a look at the inferno within an operating cement or lime kiln will certainly convince anyone that here is an energy intensive process. Fuller Company, then, has always been energy sensitive. Process kilns, hard rock crushers, tube and roller mills, fluid bed thermal reactors, pneumatic compressors and conveyors, material coolers - all are Fuller Company products utilizing or transferring large amounts of energy. Consequently, much of our success in the marketplace depends on how wisely we design and plan for efficient use of power and for conservation of each unit of heat available.

Jan 1, 1975

By S. R. Dismukes

Mining is likely to be targeted by The United States Environmental Protection Agency (“EPA”) as one of its key enforcement targets for fiscal year 2002-2003. Identifying the mining industry as an enforcement target, coupled with an increase in enforcement activity in recent years, places each mining operation at increased risk of receiving enforcement attention. A properly developed and implemented Environmental Management System (“EMS”) tailored for your operation is invaluable in reducing the risk of incurring liability for non-compliance. At the heart of an effective EMS is an audit program that checks the company’s compliance with environmental requirements. In addition, audit privilege (in select states), voluntary self-disclosure, and the attorney-client privilege serve as very effective tools for managing those liabilities that may arise during auditing a well-developed program. Of course, these latter tools are effective only if the auditing program is properly structured and properly managed. EPA and some states also provide varying degrees of immunity for environmental violations that are voluntarily disclosed in writing by the company. However, self-disclosure laws and policies typically prescribe stringent requirements for parties seeking to take advantage of them. For example: U.S. EPA has recently extended the time period in which to provide full written self-disclosure to 21 days. However, U.S. EPA’s revised Self-Disclosure guidance also addresses when a company obtains knowledge of a violation for purposes of triggering the 21-day clock and specifically extends the knowledge requirement to include the company’s agents and consultants. This expansion increases the difficulty companies may have in clearly defining and managing when they obtained knowledge. This difficulty increases the importance of managing factual development and the strategic use of other

Jan 1, 2001

The 25th Peruvian Mining Convention (Convención de Ingeneieros de-Minas del Perú) was held Sept. 10-14, 2001, in Arequipa, Peru. The biennual meeting, sponsored by the Peruvian Institute of Mining Engineers (Instituto de Ingeneiros de Minas del Peru), is designed to showcase the Peruvian mining industry and to ?promote progress in the national mining sector.? The convention consisted of technical sessions, forums, field trips and social activities. The technical sessions featured 80 papers selected from more than 200 papers submitted. The well-organized 2001 meeting was held at the Tecsup Institute of Technology of Arequipa. The meeting was held in conjunction with Exposición Technologica Minera (Extemin), a mining trade exhibition. The2001 Extemin had representatives from more than 400 companies in attendance. In addition to the many Peruvian companies present, the trade exhibition featured pavilions representing the United States, Canada, Germany, Australia and Chile. Registration at the 2001 meeting was about 3,300, a conference record. The theme for the 2001 meeting was Mining: Society and Development. Mario Brescia was chairman of the organizing committee. He said in his opening remarks that ?this year?s meeting seeks to emphasize the commitment on the part of the [mining] companies to treat our natural resources responsibly, controlling any adverse impacts and giving priority to group benefits.? Consistent with this theme, many of the technical papers stressed environmental and social responsibility. Many successful examples of environ-mental and social responsibility on the part of the mining industry were presented in the technical sessions.

Jan 1, 2001

By C. William Parisi

Since the introduction of mechanical mining, some 35 years ago, a great deal of effort has been expended by the coal industry to solve the coal dust problem. The original concern was the possibility of a dust explosion or the propagation of a gas ignition; however, in recent years it has come to be recognized as a possible 'health hazard as well. In the middle thirties, the Pittsburgh Coal Company began an intensive study of the dust problem to determine the dust levels created by the various cycles of operation in mechanical mining and to make a comparison with those of hand loading operations. Numerous dust samples were collected with a midget impinger and it was found that dust counts varied from 38 to 268 million particles per cubic foot during hand loading and from 96 to 227 million particles per cubic foot during mechanical loading. The study indicated that the source of underground dust in coal mining could be classified as primary or secondary. A primary source is one associated with appreciable degradation of size, that is, where most of the fines capable of becoming air-borne are produced. A secondary source is one in which most of the fines have been produced at some previous operation and are in such condition that they can become air-borne. Cutting, drilling and blasting are the operations which produce the primary dust. Secondary dust is formed by operations which include; loading, transportation and discharge at transfer points. The study showed clearly that the coal cutting operation was responsible for the greatest amount of dust and that the amount of dust produced varied directly with the speed of cutting; type and dullness of cutting bits; and the distance the cuttings had to fall to the floor. The information obtained from the study enabled our company to decide on a course of action and the direction to follow. With the cooperation of mining machine manufacturers, water tanks with a 200 gallon capacity were built into the machine trucks and were provided with a pump driven by a small motor. A length of 1/2" water hose carried the water from the pump to the two water spray nozzles located at the front of the machine. Water was delivered to the machine tanks by water cars which were filled on the surface or from an underground water supply. It was during these early days that wetting agents were introduced into the water system. Our studies revealed that wetting agents did little better than plain water in the abatement of the dust problem. It was found that when using a wetting agent less water was required to obtain the same results but we could not take advantage of this fact because it was almost impossible to keep the smaller nozzles open to reduce the amount of water being used.

Jan 1, 1967

By E. J. Harvey

The Ozarks has been called "a diamond in the rough". In this region streams have steep gradients, sparkling clear flows of cold water fed by many springs, and a wildness that is almost unique in the central part of the United States today. The Current River and its tributary, Jacks Fork, have been set aside for preservation by the National Park Service as a "Wild River" in the first park of its kind in the country. It is called the Ozark National Scenic Riverway. Similarly, responsibility for the preservation of the Eleven Point River has been assigned to the U. S. Forest Service. Protection of other streams in the Ozarks has been considered by State agencies. The hydrologic system of the Ozarks is a complex network of gaining and losing streams, caves, conduits, and large springs. Increased sewage loads derived from the growing towns and expanding tourist trade are a potential hazard; effluents may flow underground for long distances, polluting springs and wells. To add another dimension to the hydrologic picture a new lead industry is also flourishing in the Ozarks. Although the history of lead mining in the area goes back to 1701 (U. S. G. S., p. 43), the area has not seen a revitalization like the one that has been developing in the last 10 years; and the economic growth promises to continue indefinitely. Although this brings capital expenditures and wages into the area, it also brings potential hydrologic problems. Chemicals, wastes and other substances either stored on the surface or transported across it are subject to accidental spillage. In an area where these substances remain on the surface their effects are subject to surveillance. In the Ozarks, however, this may not be possible.

Jan 1, 1970

By Charles F. Stack

The A. P. Green Refractories Co. operates clay mines in ten states. Eight of these states have reclamation laws with which we have to comply and indications are that the U. S. Congress will pass a federal surface mining reclamation act in the near future. These regulations, in addition to the value of land in most areas, dictate that mining and reclamation be considered as a single operation. In many instances the land may be more valuable after properly planned mining and reclamation than before. Refractory clay, commonly called "fire clay" is defined as a siliceous clay rich in hydrous aluminum silicates, capable of withstanding high temperatures. It is deficient in iron, calcium, and alkalies and approaches kaolin on composition. Refractory clay is much more limited in occurrence and usage than common clay or shale. During 1971, common clays and shales were mined in 47 states with a total production of 45 million tons. Fire clay production was reported in 22 states with a total production of only slightly over 3 million tons.(1) Many of these producing areas are extremely limited in extent and production. Several are contained within a one or two county area. This reflects the unique geological conditions required for the formation or development of fire clay. The major fire clay producing areas in the United States are shown in Figure 1.

Jan 1, 1974

By Ronald R. Hartman

I can recall a time 10 or 12 years ago when I spent a pleasant Sunday afternoon driving to Jim Thorpe, Pennsylvania to see a carnotite deposit that had recently been discovered. The announcement of the discovery stated that it was in the Pottsville conglomerate in a road cut along the highway. To my surprise, the highway was lined with cars and every weekend prospector for 100 miles had come to see the ?big uranium deposit of the east?. I literally had to stand in line to make a measurement with the scintillation counter I had with me. The thought at first occurred to me that this is evidence of how thoroughly the surface of the United States must have been prospected, more likely, perhaps it points out quite the opposite. A lot of time and energy was being spent in tracing the footsteps of others and a lot of time was spent looking for the obvious occurrences. The point is, that in the early days a tremendous amount of uranium exploration was carried out but few systematic surveys were made. Thorium anomalies were usually discounted after cursory surface field checks. Conversely, in airborne surveys - anomalies due to elevation changes or thin over- burden on hilltops were often investigated more thoroughly than smaller indications on hillsides and valleys. An adequate supply of uranium was nevertheless found due to the ingenuity and persistence of the geological profession and the public in general. This ?adequate? supply, like so many estimates for raw materials turned out to be far too low.

Jan 1, 1967

By M. A. Bouchat

The Kipushi deposit, where the Prince Leopold Mine has been installed, belongs to Union Miniere du Haut-Katanga and is located in the Belgian Congo, 20 miles SW of Elisabethville, at the vicinity of the Northern Rodhesian Border. The deposit is of the hydrothermal metasomatic vein-type; mineralisation took place, through the limestone of the, lower Kundelungu. This is a special fea¬ture of the deposit, compared to the other copper deposits of the neighbourhood, both in the. Belgian Congo and in Rhodesia. Actually, the primary mineralisation of these other deposits; is directly related to the stratigraphic systems: schistous dolomitic in the Belgian Congo and Roan in Rhodesia. Both facies are older than the Kundelungu and separated from this formation by a tectonic cataclysm. The valuable elements occuring at Kipushi are principally copper; and zinc. The deposit also contains smaller quantities of lead, precious metals and other elements including germanium.

Jan 1, 1960

By R. H. Busch, S. M. Loscutoff, F. T. Cross, R. E. Filipy, P. J. Mihalko, R. F. Palmer

INTRODUCTION During the last decade, several studies in France (e.g., Perraud et al. , 1970; Chameaud et al., 1974, 1979 and 1980) and the United States (e.g., Stuart et al., 1978; Cross et al., 1978, 1980 and 1981) have demonstrated the systematic production of emphysema, fibrosis and tumors in the lungs of animals exposed to radon daughters alone or to mixtures of uranium-mine air contaminants. The studies in beagle dogs have been particularly interesting because of the uncertain etiology of the disease and the (apparently) diverse results of the studies at the University of Rochester and the Pacific Northwest Laboratory (PNL). In the Rochester studies, reported by Morken (1973), beagle dogs were exposed to "normal" room air dust loads and radon daughters from 200 to 10,000 WLM*, delivered in 1 to 50 days (rate of delivery, about 200 WLM per day of exposure). Histological examination of tissues was conducted at 1, 2 and 3 years after exposure for all exposure levels. No cancers were noted in these dogs that received estimated alveolar doses of 34 to 1700 rad (0.34 to 17 Gy). Pathologic changes were found only in the alveolar and bronchiolar regions of the lung. These changes were small, subtle, variable, and widely separated, involving only a very small fraction of lung tissue. Lesions appeared as focal thickening of alveolar septa, with some metaplasia of alveolar cells and some hyperplasia of bronchial epithelium. In the PNL experiments reported by Cross et al. (1978), beagle dogs were exposed in lifespan studies to mixtures of radon daughters (rate of delivery, about 14 WLM per day of exposure), uranium ore dust and cigarette smoke. One group of dogs was exposed to cigarette smoke alone. Except in control and smoke-only groups, the dogs died within 4' years of the first radon daughter exposure, or were killed when death appeared imminent because of pulmonary insufficiency (characterized by rapid, shallow breathing). Control and smoke-only animals were killed at periods corresponding to highmortality periods in the groups exposed to radon daughters and mixtures of uranium ore dust and cigarette smoke. Emphysema and fibrosis were much more prevalent and severe in the lungs of dogs exposed to the mixtures. These dogs also had adenomatous lesions, which progressed to squamous metaplasia of alveolar epithelium, epidermoid carcinoma and bronchioloalveolar carcinoma. Pathologic changes in the upper airways of these dogs were most prominent in the nasal mucosa, and included a few squamous carcinomas in the nasal cavity. Respiratory tract neoplasia was noted after ~4 years exposure and at cumulative exposures exceeding approximately 12,000 WLM. Apart from differences in associated carrier aerosol (room air dust vs. uranium ore dust) and radon-daughter exposure rate (200 WLM/day, shortduration exposure vs. 14 WLM/day, long-duration exposure), the most obvious difference in the Rochester and PNL studies was the observation time following exposure (3 years maximum vs. >4 years). Although neoplasia may not have been observed in the Rochester animals because of the earlier termination of the experiments, it is surprising that other lesions, such as prominent fibrosis and emphysema, were not reported. A follow-up study (reported here) is currently in progress at PNL to determine the pathogenic role of uranium ore dust alone and, in particular, to clarify the role of the ore dust in the production of the massive pulmonary fibrosis observed in the earlier study. Pulmonary function testing (a recently acquired capability) was included in the follow-up study as an indicator of progressive change in lung tissue. MATERIALS AND METHODS Chronic (4 hr/day, 5 days/week) exposures began when the dogs were about 2 1/2 years old. Two identical exposure chambers provided space for simultaneous, head-only exposure of 24 dogs to ~l5 mg/m3 carnotite uranium ore dust. An aerosol diffusion system was incorporated in each chamber in order to channel fresh aerosol past each dog's head; uranium ore dust was added to the inlet room air with Wright Dust Feed Mechanisms* (WDFM). Uranium ore dust and condensation nuclei concentrations were measured daily; chamber aerosols were monitored occasionally for particle-size distributions as described for previous hamster experiments (Cross et al., 1981). The carnotite ore used in these experiments, from the Mitten mine in Utah, was furnished in 1970 through the Grand Junction, CO Office of the (then) U.S. Atomic Energy Commission (now the Department

Jan 1, 1981

The most common method used for cleaning the fine fraction in today's coal preparation plants is froth flotation. Past research and practice has found that froth flotation achieves excellent separation efficiencies for fine coals having only a small fraction of middling particles. However, its efficiency decreases sharply as the concentration of middling particles increases due to the flotation of high-ash particles having a small amount of hydrophobic coal present at the coal surface. Since gravity-based processes are much more efficient at treating middlings, the application of centrifugal washing for fine coal cleaning has been studied with an emphasis on the primary cleaning of fine circuit feed. Results will be shown from a parametric study using a Falcon centrifugal concentrator which reveals that the separation performance is a function of particle size, bowl geometry, feed solids content, and feed rate.

Jan 1, 1994

By Ross W. Smith

Many studies have been made of the microflotation of quartz (1,2,3,4,5,6) and alumina (3,5,6, 7,8) using various anionic and cationic hetero- polar hydrocarbon surfactants as collectors. A few studies have been made on these minerals using amphoteric hydrocarbon collectors ( 9,10, 11,12) and only a few studies have been made on the use of fluorocarbon surfactants as flotation collectors (13,14). The present investigation compares microflotation response of the two minerals in hydocarbon and fluorocarbon collector systems of the anionic, cationic and amphoteric types. An attempt is made to relate flotation response of the minerals to their electrokinetic behavior and the pKa values of the collectors.

Jan 1, 1979

By W. M. Ma, Daniel W. H. Su, K. Centofanti, Yi Luo, W. L. Zhong, Syd S. Peng

7.1 INTRODUCTION Subsidence measurements include surveys of surface and sub- surface movements and measurements and monitoring of surface structural damages. In this chapter the most commonly employed methods are discussed. 7.2 MEASUREMENT OF SURFACE MOVEMENT Surface movements involve two basic components, subsidence and displacement. The other five components (i.e., slope, curvature, strain, twisting, and shearing) are derived from the two basic components. Since all measurements are geometrical, they can be measured by common surveying techniques. 7.2.1 MONUMENTS The first step is to select the types of monuments or surveying stations. Various types of monuments have been employed. The simplest one is a paint mark on the pavement or concrete slab, although this should be discouraged because it is easily affected by artificial or environmental factors. Others use steel or wooden rods, 2 to 3 in. in diameter or square by 2 to 5 ft long, driven all the way down, flush with the ground. Both types of-monuments have no provision for frozen ground heave and both are tampered with easily. A more elaborate type is shown in Fig. 7.1 (O'Rourke et al., 1982). A rebar or iron pipe, 2 in. in diameter by 6 ft long is driven down to nearly flush with ground surface. The top 4-ft section of the hole around the pipe is enlarged to 1 ft in diameter and grouted with concrete. The most sophisticated type of monument is shown in Fig. 7.2 (Conroy and Gyannaty, 1983a). It consists of two hollow steel pipes. The inner I-in. pipe, 10 ft. long is enclosed by a 2-in. pipe at the upper 5-ft. interval. The gap between pipes is filled with foam to isolate the inner pipe from external environmental effects. The bottom of the inner pipe can either remain open or be sealed with a cap, depending on whether the ground is dry or wet. 7.2.2 MONUMENT ARRANGEMENT AND SURVEY LINES The monuments are installed strategically to form survey lines. Three basic types of monument arrangements are shown in Fig. 7.3. Figs. 7.3a and 7.3b are for single and multiple panels respectively; Fig. 7.3~ is mainly for research purposes with multiple survey lines both in longitudinal and transverse directions. This is extremely useful for defining the distributions of ground deformation, as shown in Figs. 2.10 and 2.11. Basically there are two types of survey lines: the whole basin survey line which extends across the panel width or length (e.g., lines R, R, in Fig. 7.3 a&b), and the half basin survey line which covers approximately half of the panel width or length (e.g., lines R, F in Fig. 7.3 &b). Survey lines are generally straight and linear. They should be located on the major crosssections of the subsidence basin. Survey lines must extend beyond the edge of the opening for a sufficient distance so that the edges of the subsidence basin can be determined accurately. The minimum distance from the edge of the opening must be [ ] where h = mining depth, [ ] = angle of draw, and [ ] = 5 to 7 times monument spacing for whole basin surveys, or 8 to 10 times the monument spacing for half basin surveys. There must be at least two controlling monuments at each end of each survey line. Controlling monuments must be located beyond the influence of underground mining. The spacing of the monuments ranges from 15 to 200 ft. The UK National Coal Board (NCB, 1975) recommended a spacing equivalent to 0.20 of the mining depth. Peng and Geng (1982) recommended that the maximum monument spacing be dependent on mining depths as follows:

Jan 1, 1992

By Harold E. Rowen

The listed title of my talk to-day is "MODERN ON STRAND SINTER COOLING". Perhaps it should he ve been "COMPLETION OF SINTERING ON THE STRAND" as the two are synonymous. By the very nature of the DWIGHT-LLOYD SINTERING PROCESS partial cooling on the strand is always present, but not completion of sintering and cooling on the strand. I have mentioned the Dwight-Lloyd process just to be certain the type of sintering under discussion is fully identified because some of the basic mechanisms of sintering occur in various pyro-processing of fines lying in close quiescent contact, such as powdered metals practices, some types of pellet induration, firing of briquets, or other compacts, where the entire bed is brought to, and held at, the high reaction temperatures of sintering. Figure 1, The continuous sintering process as originally conceived consisted of intimately mixing carefully proportioned burdens, placing them in a comparatively thin, draft permeable layer, on a moving grate and igniting the surface while drawing sir through the bedded burden. The moving grate was advanced slowly as the line of burning fuel travelled from the surface to the bottom of the bed and no more fire zone could be seen.

Jan 1, 1973

By Denys B. Smith

Electric logs and cuttings records from Zechstein 3 and 4 strata in boreholes in the British Sector of have been interpreted in the light of numerous cored boreholes through this sequence in north-east England. This interpretation shows that potash salts in the two cycles are thickest and most consistent in a belt 20 to 40 km wide parallel with and a few kilometres from the present basin margin, and are here generally similar in grade to those known onshore. The potash ores in both cycles are mainly of sylvinite in onshore areas, the layered Upper the Southern North Sea Potash of the fourth cycle being rather less variable but generally of appreciably lower average grade than the Boulby Potash of the third cycle. Potash salts in both cycles are highly variable in thickness and grade in basin centre areas where they have been grossly affected by diapirism of the thick second cycle salts.

Jan 1, 1978