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By D. W. I. Griffiths, J. C. Bélanger

"La Division Matagami de Minéraux Noranda inc. a profité de la construction de sa nouvelle mine (Isle-Dieu) pour continuer sa modernisation.L'utilisation d'automates programmables (PLC) s'est intensifiée pour contrôler et automatiser de plus en plus d'équipement dans ses minessouterraines, au concentrateur, dans les atelierset bureaux.Tous les PLC comrnuniquent entre eux et les IBM PC sont utilisespour exterioriser l'information et faire Ie lien entre Ie personnel et les automates. Le système Central IBM 36 emmagasine les donnees traitees par lesPLC (a travers les PC). Ces donnees sont transmisesau programme d'entretien de chaque equipement et compile les heures, cycles, tonnes, etc., fait imprimer automatiquement les feuilles d'entretien préventif ', etc.Les principales realisations adate et en progrès pour la mine Isle-Dieu sont:• automation complète du système de remblayage du concentrateur ala mine Isle-Dieu situee a2 km de la mine principale;• automation du fonctionnnement des ventilateurs qui comprendra la position des portes de ventilation, Ie chauffage, Ie débit, etc.;• automation des pompes, surveillance des sous stat ions électriques, concentration des gas (CO, SO2) à chaque niveau en tout temps et du propane à l'entree d'air frais;• tonnage et cycles par Ie treuil; et• contrôle d'autres équipernents à differénts niveaux. D'autres travaux furent egalement effectues par les employes, tels que:• la conversion d'un Scooptram ST5A de diesel à électrique;• I'installation complete de systèmes de depoussierage a I'eau (scrubber) pour le concassage secondaire;• I'installation d'un marteau hydraulique avant les concasseurs coniques;• la rénovation des cellules de flottation ; et• l'installation d'un système de gardiennage par caméra. D'autres projets seront effectués ou étudiés:• automation d'un Scooptram"";• automation d'un marteau hydraulique;• récupération de Scooptrarn; téléguidé:• gestion de l'énergie, contrôle de la demande, surveillance et contrôle de l'équipernent de machines fixes(compresseurs, boulloires, pompes à vide, génératrices, débits et pression d'air, eau pour diagnostiquer les problémes, analyser les coûts;• concasseur portatif pour fabriquer de la pierre concassée pour utiliser dans les chemins sous-terre, et• utilisation de micro-ondes pour transmettre les images captées par camera."

Jan 1, 1990

By A. Lee Barrett

"THE COAL INDUSTRY of the United States• and Canada has made great progress in recent years. Coal mining in •the old days represented one of the most arduous tasks for labour and industry, but over the years great progress has been made in reducing the effort required from labour. Also, the tonnage produced per man, the cost of the coal per ton, and the overall safety of the operation, have been greatly improved.Looking back over the past fifty years:, the era can be divided into four principal parts: (a) hand-loading, (b) track mining methods, (c) off-track mining methods, and (d) continuous mining. For many years, all of the coal was won by hand-mining methods. The first forms of mechanization •resembled the move from the horse •and buggy to the automobile. Early track mechanical mining methods were usually adaptations of the direct methods involved in hand-mining, with each improvement directed toward some specific process. A revolutionary development came about with off-track mining methods. The first efforts in this direction were provided by off-track mechanical loading machines, which loaded the cars •on track and differed from conventional track mining methods only in that the loading machines themselves operated on the mine floor. With the advent -of the shuttle car about ten years ago, true off-track mining came into being, and real progress in this direction began to be made.At the present time we •are at the beginning of a new era -.the era of continuous mining. There will be a period of development with some time needed before the system is generally applied throughout the industry, but -already enough •has been done to indicate rather dearly what the future holds in this direction."

Jan 1, 1953

By N. R. Paterson

"More than a dozen AEM systems are currently being used in the routine exploration for massive sulphides. The systems differ from one another in minor respects, but fall into four main categories: rigid-coupled in-phase/quadrature systems; towed-bird, single-component systems; differential systems; and passive systems.Although field tests are important in demonstrating the performance characteristics of the AEM/airframe assembly (noise-levels, coupling effects, etc.), more meaningful evaluations can be made through physical or computer modelling. The latter approach has been used to compare the response of twelve AEM systems to both vertical and horizontal sheets, simulating a large orebody and a con-ductive overburden respectively. The effects of height changes are also studied.The results demonstrate that each AEM system has its own particular advantages and disadvantages. The relative importance of these is a matter for the geophysicist to judge, on the basis of specific geological and environ-mental information. Data currently available on AEM systems are adequate to permit an objective evaluation of the systems for a particular exploration program."

Jan 1, 1971

By John B. Phillips

The mine is entered by a central vertical shaft, strongly timbered, and containing two compartments-one for the passenger cage, the other for the large skips bringing the ore to the surface. A man-way, for emergencies, is also provided, parallel to the shaft. The cage is a single-deck steel box, carrying about thirty persons; by means of arrangements above and below, it can also hoist and lower materials needed in the workings. Levels are run at intervals of 100 feet. In special cases, where the ore conditions warrant, sub-levels are operated, such as those at 1,113 feet and 1,123 feet (Fig. 7), which are connected by winzes with the 11 th level. One of these was pushed for 40 feet, and then abandoned because it was unprofitable to take up ore of the grade encountered. The ore between levels is removed by stoping. The drifts follow the course of the veins as much as possible, with numerous cross-cuts. Winzes, raises, connections, etc., are blasted out where needed. The main drifts are at least 8 ft. high by about 9 ft. wide. All former narrow drifts had to be widened sorne time ago, by ruling of the Ontario Department of Mines, to lessen the danger of accidents with cars in the small passages. Accurate plans of the under-ground workings are kept in the office, and extensive surveying is always being done underground to keep the maps up to date, measure the cubical contents of stopes, and so forth. Timber is extensively used in the construction of supports and chutes, and in the sinking of the shaft. Steel and concrete are too expensive to compete with timber, which 1s abundant in such sections as have escaped forest tires.

Jan 1, 1926

By M. Nagamori, A. J. Plumpton

"A low-grade concentrate from the Crevier Township, Quebec, containing 1.8% Ta205 and 13.7% Nb205 was reduced with carbon at 1600°C, and niobium and tantalum were selectively absorbed in liquid iron. To slag off the zirconia-rich gangue, some silica and lime were added as flux. Metallic iron was added in such a way that the combined contents of TaC and NbC did not exceed 20% in the ferroalloy . Up to 95% of the niobium, and up to 80% of the tantalum contained in the concentrate were recovered in the metal. The ferroalloy was ground finely and dissolved in 2 wt % sulphuric acid to leach out iron and silicon preferentially. The insoluble residue consisted principally of NbC and TaC, the calcination of which yielded an enriched concentrate comprising 80% Nb2O5 and 8% Ta2O5. The insoluble residue could also be chlorinated to obtain an impure liquid of Nb2Cl5 and TaCl5. Process variables and their effects are discussed in terms of higher metal recoveries in the smelting.IntroductionPresently, about one-third of the world production of tantalum comes from the pyrometallurgical reprocessing of tin slag, a by-product of tin smelting, containing sometimes 2 to 10% Ta205 and about the same amount of Nb205. Upon heating tin slags with carbon at about 1600°C in an electric furnace, tantalum and niobium oxides are converted to TaC and NbC, which are absorbed by the coexisting phase of molten metallic iron(1,2). The Fe-Nb-Ta-C melts cannot be decarburized by oxidation because of the preferential formation of Nb and Ta oxides over CO gas(3). So, the ferroalloys containing tantalum and niobium carbides are commercially treated by acid-leaching and I or chlorination to eliminate iron and thus permitting the eventual recovery of purified tantalum and niobium oxides(2).Absorbing Ta and Nb carbides in molten iron was first proposed and demonstrated by Zimmerley and Back(4) in 1957 in order to recover selectively tantalum and niobium from lowgrade concentrates. The process was successfully applied to the electric furnace smelting of tin slags by Hunter and Fursmant(5) over a period preceding 1965."

Jan 1, 1985

By L. E. Djingheuzian

ANON-CATARACTING (N-C) ball mill is so operated that the balls are not thrown in-ward at the top of their paths. The result is to maintain, in the mill, a quiescent pool in which classification will occur at a limiting size corresponding to the pulp density. N-C operation is produced by effecting proper relationship among mill speed, ball diameter, volume of ball load, and pulp density. Such operation is typified by the primary ball-mill operation of the Tennessee Copper Company, Copper-hill, Tenn., and the Cleveland Cliff Iron Company, near Ishpeming, Mich.

Jan 1, 1958

By G. J. Desroches, E. Ozberk, M. J. Collins, B. D. Krysa, I. M. Masters

The zinc refinery of Hudson Bay Mining and Smelting Co., Ltd. went through a major modernization in 1993, when the roaster and the calcine and fume leach circuits were replaced by a new Sherritt zinc pressure leach plant. The HBMS plant, in Flin Ron, Manitoba, represents the first commercial application of the Sherritt two-stage zinc pressure leach process, with /00% of the zinc concentrate feed processed in autoclaves. The process design of the new plant required definition of the deportments of elements such as antimony, arsenic, chlorine, cobalt, fluorine, germanium, magnesium, manganese, selenium, tellurium and thallium. This paper describes the deportment of these elements in the commercial zinc plant during the first nine months of pressure leach operation, and compares these results with operations prior to the introduction of pressure leaching, and with the results of tests carried out in the She"itt laboratory during the process development phase.

Jan 1, 1995

By T. H. Chuang, Y. Y. Shiue

"Rapid whisker growth was significantly alleviated in a Sn-58Bi alloy doped with 0.5 wt.% La. Experimental results showed that many thin, plate-form intermetallic phases appeared in the solder matrix. The absence of tin whiskers was correlated to the shape effect of RE-containing intermetallic plates. After reflowing, Cu6Sn5 intermetallic compounds appeared at the solder/pad interfaces of Sn-58Bi and Sn-58Bi- 0.5La packages with OSP pads, which grow linearly during the aging at 75 and 100? for various times ranging from 100 to 1000 h. In addition, the interfacial intermetallics layers in Sn-58Bi-0.5La solder joints were also observed thinner than those in undoped Sn-58Bi joints. However, RE-containing interfacial intermetallic compounds in Sn-58Bi-0.5La solder joints led to lower bonding strengths in both ball shear tests (0.4 mm/s) and high speed ball shear tests (2000 mm/s). All the reflowed and aged solder joints of both packages were ruptured through the solder balls indicating brittle characteristic INTRODUCTIONIt has been widely reported that solder alloys doped with rare earth (RE) elements reveal many beneficial effects, such as higher strength, lower melting point, improved wettability, and longer creep life (Wu et al., 2004; Ma et al., 2002; Chen et al., 2002). In addition, Dudek et al. reported that the alloying with 0.5 wt.% La in Sn-3.8Ag-0.7Cu solders resulted in an increase of rupture strain, up to 150% over undoped solders (Dudek et al., 2006). However, Chuang and Yen observed that a large amount of long, fiber-shaped tin whiskers were extruded out of the oxidized CeSn3 intermetallic clusters in the matrix of a Sn-3Ag-0.5Cu-0.5Ce solder air-stored at room temperature for several days (Chuang & Yen, 2006). Furthermore, many coarse hillocks appeared around the CeSn3 clusters in the RE-doped alloy after storage in an air furnace at 150? for several minutes. Chuang proposed a mechanism for the phenomenon of rapid whisker growth, which the predominate oxidation of CeSn3 intermetallics in Sn-3Ag-0.5Cu-0.5Ce solders induced compressive stress and extruded the tin atoms out of the specimen in the form of tin whiskers (Chuang, 2007). However, further investigation showed that Sn-9Zn-0.5Ce solders, after long term exposure at room temperature and 150?, were immune to the whisker growth; the immunity was attributed to the refining of the CeSn3 intermetallic phase in the alloy (Chuang & Lin, 2008). The inhibition of tin whiskers through the refining of rare earth containing intermetallics was further observed in Sn-3Ag- 0.5Cu-0.5Ce solders doped with 0.5 wt. Zn (Chuang & Lin, 2009). In addition to the size effect, the thin plate shape of intermetallic compounds was also shown in this study to inhibit the whisker growth on the surface of Sn-58Bi-0.5La solders."

Jan 1, 2012

By J. Kramer, T. Hartmann

In the Hydrometallurgical processes, the presence of the so-called “crud” is a constant challenge in solvent extraction. Crud is a stable emulsion which forms along the interface between the aqueous and organic phase. The spread is influenced by the following parameters: first, wind blows the dust and impurities into the open sedimentation tanks. Second, the undissolved solids such as sand transported in the PLS causing problems in conjunction with incorrect agitator design. The crud fraction can decisively impact the efficiency of the hydrometallurgical extraction because the phase interface can constitute a large fraction and the sedimentation tanks cannot react flexibly to it. In the downstream process of the seriesconnected sedimentation tanks, they are thus all contaminated with crud. At the same time, the necessary mass transport is significantly impeded at the phase boundary between organic phase and aqueous phase due to the crud formation. The transfer of the organic phase into the electrolysis cell can result in a “burnout” of the cathode. The carry-over of this electrolyte into the extraction can cause problems with the pH regulation. The carry-over of the organic components into the raffinate also leads to contamination of the leaching circuit. The continuous treatment of the crud with a 3-phase decanter centrifuge is extremely effective in combating this problem. This technology splits all three phases from each other and they are consequently continuously separated. All subsequent process steps exhibit a stable, uniform effectiveness. The main advantage for the customer is that fluctuations in the process are eliminated and the organic phase can be recirculated back to the extraction. The recycling of the solvent alone justifies the investment in less than 6 months as examples from South Africa and Chile show. To operate solvent recovery in daily operation fully automated online at the optimum limit, the decanter centrifuge is equipped with a concentration-dependent pond adjustment called DControl®. By this means, we can guarantee our customers the maximum possible solvent recovery and minimise the solvent costs in this process step. This system is presented in detail in this paper.

Jan 1, 2012

By J. Guha, R. Kanwar, G. Archambault, A. Tremblay

The Copper Rand Cu-Au deposit lies within a shear zone which strikes N50-60W and dips steeply southward (50°-55°) and extends over 1. 5 km with a thickness which varies form 350 to 425 metres. Mineralization, inside the shear zone, is structurally controlled by a dilation mechanism which can be explained by a fracture dilatancy model. The principle of this model involves the mechanics of overriding of irregular planes and surfaces of faults and schistosities, These structures are characteristic features of the Copper Rand shear zone. A structural analysis of the shear zone has been carried out to establish relations between the different structures within the shear zone and their evolution with the development of the shear zone. A geomechanical interpretation of the Copper Rand shear zone explains the formation of internal structures such as faults, schistosities and microstructure during the shearing. This interpretation confirms Ramsay's theoretical model on the geomechanical evolutuion of shear zone development, and the experimental work of Morgenstern-Tchalenko on the simulation of shear zones in clay models. The geomechanical interpretation of the shear zone demonstrates that at the onset, subsidiary fracture patterns are developed in second order faults in the following sequence. At peak strength Riedel shears ( R and R') are formed which propagate outside the strength, restraint (P) shears are developed in the thrust attitude within the shear zones. Principal displacement shears (D) develop toward residual strength in the direction of movement. Shear lenses are formed by the interaction of these shear discontinuities and these facilitate the formation of schis tosi ties with the continuation of the shear displacement within the main shear zone. While the main shear zone and the P and D shears within the main shear zone were in continual movement, the Rand R' structures, once formed, retained a simple fracture pattern and moved little outside the shear limits in comparison to the main shear zone. Parts of these structures inside the shear zone were reactivated by subsequent movements and deformed into folds to account for the present attitudes of the HW-1 and HW-2 and HW-3 structures. This geomechanical model for the shear zone with its subsidiary structures (R, R', P and D shears) is also applied on a larger scale to the Dore Lake shear belt and explains the different structures accompanying it. The initial development of the WNW shears (most are ore deposits) was followed by the subsidiary structures of the Dore Lake shear in a north-south stress field and is well defined by the movements characteristic of the different structures. It is concluded that the Dore Lake shear cannot be the prolongation of the McKenzie Narrows shear but it seems that this prolongation relates to the Henderson-Portage shear zone.

Jan 1, 1984

By G. F. Flaherty

THE property of Tashota Goldfields, Limited, in the Lake Nipigon area, Ontario, is located about 4 miles west of Onaman lake and 16 miles by winter road south-southeast of Tashota station on the transcontinental line of the Canadian National railways. The mine, formerly developed to a limited extent under the name of Tashota Gold mine, has, since late in 1933, been under the management of Minefinders Limited, who, in 1935, brought it into production on a 60-ton per day basis. During the winter of 1934-35, the writer was geologist at the property. The geological structure in the immediate vicinity of the mine workings lends itself well to analysis on the basis of the mechanical principles of folding. Since structure is of prime importance in the localization of the ore-shoots and of the host shear-zones at the property, the correlation of all structural details and their mechanical interpretation forms a working hypothesis of structural control for the direction of exploration and development work. It is believed that the structural relations here set forth may be found applicable in part, or at least suggestive, in working out the relations of ore-shoots to structure in the Sturgeon River area to the south, and in the Little Long Lac area to the southeast (Figure 1).

Jan 1, 1936

By R. A. Nemchek

ABSTRACT Concentrator plant design has evolved from large numbers of small grinding mills to small numbers of large mills. Consequently, plant performance often hinges on the productivity of a single large semi-autogenous grinding mill. Industry attempts to address the grinding mills’ critical nature frequently result in specifications that can be made simpler, more economical, and better focused on the project’s goals. This paper surveys current specification writing practices and proposes an improved approach recognizing that product design, procurement, manufacturing, and quality are interrelated in a successful project. The lessons learned here can apply to all types of machinery specifications.

Jan 1, 2014

By H. Wilhelm, W. I. van Drunick

The Anglogold Ashanti (AGA) Navachab single stage SAG mill has provided an excellent setting for incremental optimization. Over the past decades, several interventions have resulted in marked improvements in specific performance; including steel ball scat removal, re-design of the mill lifters, replacement the pebble crusher and cyclone cluster, as well as the use of a vibrating screen in place of a discharge trommel. Recent initiatives now include an operating fine DMS circuit, studies on pre-crushing of the ROM feed and also fine-screening as an alternative to hydrocyclone classification. The current optimized state of the Navachab mill allows it to operate at approximately 20% higher efficiency when compared to mills of similar shell dimensions in gold mining, treating similar ore. This paper describes the systematic improvement of the SAG circuit to its current state.

Jan 1, 2012

By Takahiko Okura, Chiharu Tokoro, Shunta Shibuya

Copper concentrates bearing arsenic as enargite (Cu3AsS4) or tennantite (Cu12As4S13) have disadvantage on copper smelting environmentally and economically, so those concentrates should be treated decently. In this paper, some experiments of arsenic removal from several kinds of copper concentrates by heat treatment in an inert atmosphere were discussed. In this study, several samples in which arsenic contents varied 0.18 to 8.3 wt % were heated to the temperature range of 400 °C to 700 °C under argon gas flow during 1 hour. The heat residues and volatilized materials (V.M.) were analyzed by XRD, XRF, ICP-AES, XAFS and MLA to analyze residual concentration of arsenic and residual mineral composition. Experimental results showed that arsenic removal from copper concentrates advanced in 2 steps; at the temperature range of 500 ° C to 550 °C and of 550 °C to 650 °C, respectively. MLA analysis showed that a few of arsenic in enargite was removed by 550 °C heating and a majority of it was still combined with copper and sulfur as tennantite. On the other hand, arsenic in tennantite was removed almost completely by 650 °C heating. Furthermore, a particular type of arsenic mineral, such as Cobaltite (CoAsS) still remained after heating at 700 °C.

Jan 1, 2014

By N. Plint, D. Philips, J. Sweet, B. Durant

A pilot scale AG milling campaign was conducted at the AngloAmerican Platinum pilot plant in South Africa. Different blends of hard: soft (silicate: chromite) and coarse: fine particles in the AG mill fresh feed were tested. The effects of multi-component feed on the pilot scale autogenous grinding are presented in this paper, and can be used as a guideline for multi-component feed blends for AG mil

Jan 1, 2012

By J. U. MacEwan

Introduction The equilibrium between copper, zinc, and chlorine may be considered as the simultaneous equilibrium of the two separate chemical reactions of formation of the stable chlorides of copper and zinc at the temperature of the reaction i.e., l440°K. (1,167°C., 2,133°?F.)§ [Zn(g) +Ciz(g) ZnCl2z(g). ... (1) ] [2Cu(l)+Cbi'g) Cu2Cl2(l 1 ....... (21 ] Subtracting, [Zn(g) +Cu2(Clz(l i ZnClz(g) +2Cu!l) ... . (3) ] If this reaction is carried out with a copper-zinc alloy at some constant temperature above the melting point of brass, and at a total pressure of one atmosphere, the equilibrium concentrations obtained will depend on the free energy decrease .of the reaction as written in (3) and on the activities of the various components in. the reaction mixture. If the equilibrium is examined from the point of view of the phase rule, it is a three-component system, and if it exists in two phases (liquid and gas) it will have three degrees of freedom. If the restrictions of constant temperature and pressure are imposed, the degrees of freedom are reduced to one. This means that, in a two-phase system under these conditions, each different alloy phase will be associated with a gas phase of constant composition.

Jan 1, 1951

By W. J. Kuit

"Complex facilities which provide for the collection, management and treatment of effluents emanating from the Sullivan mine and concentrator tailings were made operational in October, 1979. Key features of the system are the use of upgraded tailings ponds for the storage of up to 800 million litres of metals-contaminated effluents, a treatment plant employing lime in a high density sludge process and a sludge-impoundment facility designed for maximum long-term environmental safety. The completed works are cap1ble of satisfying a difficult range of operating requirements imposed by highly variable weather conditions, drainage flows and soluble metals loadi11gs. Final capital expenditures for the project will approach $10 million and annual operating costs are estimated at $0.8 million.This paper discusses the Kimberley effluents treatment project and the major considerations in its development. The treatment process, major plant equipment and initial operating experience are also described."

Jan 1, 1980

By Don Lemmen

Impacts, Adaptation and Vulnerability ? regional climate changes (temperature and extreme events) have already affected many physical and biological systems ? natural systems are vulnerable to climate change, some will be irreversibly damaged ? many human systems are sensitive to climate change ? Projected changes in climate extremes could have major consequences

Nov 1, 2002

By C. S. Touchard, F. Bourgeois, L. Cassayre, Julcour-Lebigue C.

Developing a hydrometallurgical process that can overcome the refractory nature of chalcopyrite (CuFeS2) to leaching still eludes the minerals industry, despite major research efforts spanning decades. The several leaching experiments of this ore in sulfuric acid tend toward the same conclusion that the precipitation of elemental sulfur or iron containing species are the main dissolution inhibitors. Describing both the electrolyte composition and the various solid phases in equilibrium for the Fe-H2SO4-H2O system is essential to overcome this issue and to find an operating window. According to the thermodynamic models and to the thermodynamic data, we demonstrate, in this study, the need to use the Specific ion Interactive Theory (SIT) model to describe complex electrolytic systems through a limited number of parameters. Hence, the binary interactions for our case study have to be defined and estimated. This work develops a methodology to determine these parameters of the SIT model up to 90°C and an acid concentration of 1 mol/kg from published data for H2SO4-H2O and Fe(II)-H2SO4-H2O sub-systems or from new experimental data for the Fe(III)-H2SO4-H2O one. This method will eventually be applied to copper systems to lead to a thermodynamic description of the complete CuFeS2-H2SO4-H2O system. INTRODUCTION A leaching process consists in the dissolution of a solid phase into an aqueous medium in order to extract compounds of interest. It is a key step in the hydrometallurgical processes used in the primary production and recycling of metal components. One of the main leaching issues is the formation of passivating layers on the surface of solid particles, whose consequence is a partial or total hindrance of the dissolution. The leaching of chalcopyrite (CuFeS2) in sulfuric acid is a prime example. No industrial solution for the atmospheric pressure leaching of this ore has been developed to date because of passivation phenomena caused by the formation of elemental sulfur or iron-containing precipitates on the surface of the particles (Li, Kawashima, Li, Chandra, & Gerson, 2013). In the 1970s, the Pourbaix diagrams established for the Cu-Fe-S-H2O system at 25°C for low concentrated solutions (Garrels & Christ, 1965; Peters, 1976) agreed that copper and iron are fully dissolved at high potential and in acidic medium (pH < 4). However, they neglected the many stable solid phases that can form in these conditions. In addition, the Pourbaix diagrams of chalcopyrite in water, calculated with two recent databases (FactPS and Thermoddem 2017) associated to FactSage and PhreeqC softwares respectively, show large discrepancies at 75°C (Figure 1). Indeed, at high potential, FactSage predicts the formation of goethite FeOOH at a pH value of 1, while PhreeqC predicts the formation of jarosite (H3O)[Fe3(SO4)2(OH)6] for pH greater than 2.5.

Jan 1, 2019

By D. M. Baird

ABSTRACT A revised stratigraphic section of Carboniferous rocks which occupy about 700 square miles in southwestern Newfoundland is presented. Gypsum, which outcrops at thirty-five different localities, is found to belong to four principal zones in the section. The newly mapped structure of the region makes the otherwise random occurrences of gypsum appear as systematic outcroppings of the four zones which follow the regional structure. Details of several occurrences are given and those most advantageous for exploitation are pointed out. INTRODUCTION ROCKS of Carboniferous age occupy an area of about 700 square miles in southwestern Newfoundland. They occur in a belt, from 5 to 15 miles wide, which extends from the head of St. Georges bay southwestward for 65 miles to the mouth of Little Codroy river (see Figure 1). Several hundred feet of Pennsylvanian rocks overlie rocks of Mississippian age, which are at least 12,000 feet thick. The rocks of the Carboniferous section of Newfoundland are very similar to those of Nova Scotia and represent a northeastward continuation of the same palaeophysiographic conditions. Mississippian measures of Windsor equivalence include thick gypsum deposits which outcrop at many places and which extend under large areas as indicated by sink-holes and by structural considerations.

Jan 1, 1951