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By A. J. Phillips, A. A. Smith, J. S. Smart

The preparation of a sufficient quantity of high-purity copper for extensive laboratory use in the study of impurity effects has been an integral part of a research program in progress at the Central Research Laboratory of the American Smelting and Refining Co. for the past several years. Initially the degree of purity desired was that necessary to meet two essential requirements for experimental accuracy: (I) no impurity was to be present in the copper in an amount capable of producing a detectable effect on the properties to be studied, (2) even the minor changes in propertties caused by the addition of extremely small amounts of individual elements were to be measured without significant interference from contaminants. In the course of the investigation, evidence has accumulated to justify the conclusion that this copper is of exceptional purity; in fact, no impurity can be detected by any chemical method or spectrographic technique known to the authors. The present paper describes the method of production of the copper and presents some of its properties. Preparation oF High-purity Copper The elimination of impurities from commercial electrolytic copper is accomplished by a three-step purification process. The first operation consists of an electrolysis through a purified CuSO4-H2SO4 electrolyte using bagged anodes, low current density (5 amp. per sq. ft.) and low tem- perature (25°C max.). The electrolyte is prepared from commercial Cu2SO4 and is purified by heating the solution and adding I gram Fe as Fe2(SO4)3 to each 100 grams dissolved copper; sufficient hydrated oxide of copper, prepared from Cu2SO4 and NaOH, is supplied to precipitate Fe(OH)3, which carries down arsenic, antimony, tin, selenium, tellurium and other minor constituents. Silver and remaining traces of lead are removed by addition of Na2S to the acidified filtrate, which is then reatered after standing hot overnight. The cold solution is made up to 30 grams per liter Cu and 150 grams per liter H2SO4 and introduced without addition agents into the electrolytic system, which consists of a double row of hard-rubber battery boxes with the inside webbing and partitions removed, arranged in seven steps of ascending height. Electrolyte is uniformly supplied to the two highest cells by glass siphons operating from a constant-level reservoir, and flows by gravity through the bank of seven cells, entering each at the bottom and leaving at the top. Glass air lifts continuously supply the returning liquid to the constant-level reservoir for recirculation. Each cell contains three 4 3/4 by 4 3/8 by 1-in anodes cast from high-quality electrolytic wirebar copper, various lots of which have been used with equal success. The anodes are pinned to sheet copper hangars shaped to prevent crawl of the electrolyte to the multiple-wired bus bars—which would result in fouling of the contacts—-and hang inside wool flannel bags stretched over open wood frames. The deposit

Jan 1, 1941

By M. G. Yalçin

Marbles commercially known as the Nigde- white crop out in the town of Gümü?ler, around the Çalkama Hill within the Gümü?ler Formation of the Nigde Masif of Paleozoic age. Marbles sporadically occur within the masif, however its prevalent occurrence is associated with the Gümü?ler Formation. Due mainly to its intense fractured nature, the Nigde-white marbles are used as dimension stones, crushed stones and most recently micronized calcite. Insignificant portion accounts for block use through a few quarries.

Jan 1, 2005

By Hubert Gamarra

El presente trabajo señala el proyecto de evaluación y recuperación del molibdeno en la mina Chabuca Sur, perteneciente a BHP Tintaya. El proyecto sigue la metodología de Excelencia operacional (EO) o metodología de mejora continua utilizada en BHP Tintaya S.A y se realiza a corto plazo, con la finalidad de incorporarla bajo un costo mínimo en el stock. Asimismo, se determina una asociación del S2Mo como un pulso tardío de mineralización sin cobre en la zona de alteración argílica de los diques monzoníticos y en el endoskarn.

Sep 13, 2001

By L. J. Murphy

The production of crude oil in the United States is exceeding consumption by one-quarter million barrels per day and, with the possibilities of West Texas, this condition of overproduction, unless controlled, is likely to continue for some time. The resulting low price of oil has caused the operator to observe closely his lease operating costs. The installation of more efficient and reliable machinery has followed and it can well be said that the art of producing oil is on the threshold of a new era. In this advancement electricity has played a leading part. This paper covers only the problem of electricity as applied to lease operation and does not consider other phases of the industry, such as drilling and pipe-line pumping, in which electric power has been utilized economically. In considering electrification of pumping wells, the first question the operator asks is whether or not his costs will be reduced and the second question is whether or not the production will be increased. The third question, although in effect it is closely allied to the first, is the cost of power. The last question can be answered only after a thorough analysis of operating conditions and a study of the power rates prevailing in the particular field under consideration. Within the past few years, the power companies have realized the desirability of a steady 24-hr, pumping load, have made their rates for oil-field service particularly attractive, and in general have shown splendid cooperation in assisting the oil companies in the satisfactory application of electric power to their leases. When everything is taken into consideration, the first cost is practically the same for electric drive as for gas engines when pumping on the beam with individual motors. This cost, at prevailing prices, should aver-age approximately $2200 to $2400 per installation when using 15 to 35-hp., two-speed pumping equipment, including motor and control, countershaft, motor house, belt, installation charges, and a prorated portion of the cost of transmission lines and transformers for serving a number of wells. Since there is practically no difference in the cost of the two installations, it is evident that electricity, to justify its consideration, must have a lower operating cost or produce more oil.

Jan 1, 1928

By Rizzi Homestake Mining Co.

Geophysical methods of discovering new mineral deposits have long been routine with both the petroleum and mining industries. Experience has shown that most subsurface structures and mineral deposits can be located, provided that detectable differences in physical properties exist. The main properties exhibited by the more common rocks and formations are: density, magnetism, electricity, electrical conductivity, and radioactivity. This entails five major geophysical methods: gravitational, magnetic, seismic, electrical, and radiation. Applications of radioactivity measurements in geophysical exploration are concerned with location of concentrations of radioactive rocks and materials, such as uranium. The search for uranium ores and minerals has been carried on for more than 50 years, ever since the first atomic breakdown from uranium to radium was discovered. However, the comprehensive search now being made throughout the world for radioactive materials is a direct result of the first atomic explosion and the subsequent development of new and more sensitive portable equipment to detect radiation.

Mar 1, 1956

By Kenji Morinaga, Hiromichi Takebe

"Ge-S binary glasses in the range 57 to 90 at %S at 0.5 to 3 at %S intervals were prepared by a conventional melting technique using fused quartz ampoules as melting containers. Impurities contaminated during preparation process are evaluated by IR spectroscopy. The causes of impurity contaminations are discussed. Density data in a systematic series of Ge-S glasses is demonstrated. IntroductionSulfide glasses are of particular interest for new laser and nonlinear optical materials in the near-infrared and infrared regions [1]. Sulfide glasses have the features of low-phonon-energy and high refractive index with moderate rare-earth ion solubility. The low-phonon-energy is favorable for the reduction of nonradiative rate for the emission of rare-earth ions. The high refractive index results in a high radiative-rate and in a high third-order nonlinearity. However, impurities may degrade the superior optical properties of sulfide glasses.In this work Ge-S glasses were prepared by a conventional melting technique. Impurities contaminated during the preparation process are evaluated and their causes are discussed for future improvements. The measured densities of Ge-S glass samples were compared with the results of previous studies [2], [3]. Ge-S glasses have some favorable properties for practical .applications including non-toxicity, good thermal and chemical stabilities."

Jan 1, 2000

By Anthony Edey, Leigh A. Readdy, Bruce A. Kennedy

Introduction Very little attention normally is given by the experts, or the public at large, to the fact that the majority of the oil that has been or will be discovered within the U.S. remains in the ground. The inherent limitations of oil production through surface wells, either by primary or secondary techniques, will result in a total of over 300 billion bbl of oil left in the ground after completing production by standard petroleum techniques in currently producing or producible fields. This reserve represents some two-thirds of the original quantity of oil discovered in place. Recent work by a number of groups has shown that there is strong economic justification for extracting this remaining oil by mining and processing techniques. Table 1, taken from 1977 API reports, demonstrates the oil left in place at the end of the conventional petroleum production cycle in then-known fields within th’e U.S. Possible targets for oil mining operations include (1) oil remaining in place in fields and pools that have reached economic depletion by current petroleum production methods and that are not amenable to economic recovery by conventional petroleum industry techniques; (2) oilor bitumen-saturated rocks not normally considered by the industry to constitute producible reservoirs, such as shales and diatomites; and (3) asphalt- and bitumen-impregnated rocks. Economically Depleted Fields A more detailed examination of the depleted fields shows that estimates of oil remaining in place after primary, secondary, and nondestructive tertiary recovery can vary widely. There is significant evidence, however, that more than half the estimated original oil in place (OOIP) remains in the reservoir after all petroleum extraction techniques have been applied. If one compares the sum of past oil production and estimated remaining producible reserves with the API estimate of total discovered OOIP as of 1975, it becomes apparent that for the U.S. as a whole, 67070of the 00IP will remain in place at the end of the

Jan 1, 1980

By John E. Riddell

This review is based on a questionnaire sent out in 1959 to 24 Canadian exploration companies, known to be active in the mineral exploration field, concerning their practice in the use of applied geo-chemical techniques in Precambrian terrains. Of the companies questioned, 21 returned completed questionnaires and of these, 15 companies stated that they had some experience in this type of work. Of the companies who stated that they had no experience in geochemical prospecting in glaciated Precambrian areas it is interesting to note that only three have reported that they do not use applied geochemistry at all. The others have reported that they make use of applied geochemistry in New Brunswick and in the Cordillera in areas of light glaciation. Their opinion is that it is a useful aid when accompanied by other techniques in evaluating mineralized areas. GEOCHEMICAL SURVEYS Table I reviews the type of geochemical surveys used by these companies, and the following points of interest should be noted.

Jan 11, 1960

By G. Gaidajis

Sea water samples collected from coastal waters in the vicinity of the Stratoni mining operations, in North-Aegean Sea were analysed for dissolved metals and elements. The maximum concentrations observed were one to three orders of magnitude lower than the environmental limit which coincides with the quality of sea waters suitable for swimming purposes. The quality of the coastal sea waters are affected by the natural mineralization of the area and the urban activities drained through local small rivers, the past mining activities present in the sea bottom sediments in the form of disposed tailings, and finally by the presence of the adjacent Mill-Flotation Plant. The relative importance of the treated final effluents discharged from the mining operations is considered to be insignificant.

Jan 1, 2006

By E. Poiate, P. R. Cabral, A. V. N. Santos, P. V. M. Costa, C. S. Amaral, A. M. Costa

This paper discusses the design of underground salt caverns, opened by solution mining, for the production of brine and storage of natural gas under high pressures. The caverns are located in the salt basin in Maceio City, Alagoas State, at the northeast region of Brazil. Special attention is given to the geomechanical structural design of the caverns using computer codes specially developed for the simulation of excavations in salt rock formations, considering validated constitutive creep laws under different initial stress states and temperatures. The behavior of sedimentary rocks intercalations presented in the salt layer is simulated using elastic-plastic models. The excavation of the caverns by solution mining is also simulated starting from a geostatic initial equilibrium state of stresses, with a unique formulation only implemented in these computer codes, without the need of the application of boundary stresses to the model in order to develop the initial state of stresses. These computer codes have being used in the design of several clusters of caverns for brine production used as raw material of Poly Vinyl Chloride (PVC) of the Chemical Industryin Brazil. These computer codes and methodology were also applied to the design of the underground conventional potash mine in the state of Sergipe, overlying tachyhydrite and carnallite with very high creep strain rate. They have also been used in the design of the pre-salt oil wells through thick layers of stratified salt rock in Santos Basin, for the exploration and production of the pre-salt reservoirs in Brazil. The constitutive creep equations implemented in the codes are based on a double mechanism creep law. The creep constants adopted in the simulation are taken from a previous investigation carried out on an experimental panel of the potash mine, considering the stratified geology with different salt rocks of the basin where the mine is located. These constants were also obtained by lab tests under different confined and differential stresses and temperatures.

Jan 1, 2015

By Thomas W. Thompson

The Zebulon manganese deposit has been known for a number of years. It is situated about 3 miles east of Zebulon, Wake County, N. C., on the Avon, Privett property (fig. 1). The deposit outcrops as a vein, or dike averaging-16 to 20 feet in width. Drilling by the Bureau of Mines has shown that this outcrop results from consolidation of a number of small stringers near the surface. The surface width and the Percentage of manganese oxides (resulting from. weathering) diminish with depth. Below 50 to 80 feet, the vein material is mainly quartz and spessartite garnet. The deposit was first examined by W. T. Benson, a Bureau of Mines engineer, in 1941. The Bureau conducted a diamond-drilling exploratory program an the property from November 7, 1944, to January 25, 1945. A. total of 2,508.5 feet was drilled in 14 holes along the strike of the deposit.

Jan 1, 1950

By J. Nell

Heavy mineral deposits often contain relatively high levels of radioactive elements (thorium and uranium in particular).It is difficult to obtain clean separation of ilmenite and monazite (the main impurity mineral containing radioactive elements), and physical intergrowths of the two minerals are, in fact, not uncommon. As a result, ilmenite concentrates obtained from such deposits often contain high levels of thorium and uranium. Because of the large negative free energies of formation of ThO2and U3O8boththorium and uranium report to the slag during smelting and if an ilmenite concentrate contaminated with monazite is used to make high titania slag, the concentrations of these elements in the slag end up about 40% higher than in the ilmenite feed. Previous work, patented by RGC Mineral Sands Limited, and subsequently confirmed by Mintek, showed that radioactivity may be reduced by roasting an ilmenite concentrate with borax at 1000°C to 1100°C and leaching it with hydrochloric acid1. It is evident that the cost of an ilmenite roast/leach process will be high and there may be economic benefits in removing the radioactive elements from the slag instead (the volume of slag to be treated is smaller than the volume of ilmenite feed). To remove radioactive elements from the slag it is necessary to know how these elements occur in the slag. Inother words, the distribution of uranium and thorium between the various oxide, silicate and metallic phases in high titania slag must be determined. Once the deportment of thorium and uranium between the various phases ha sbeen determined, an appropriate process for slag purification can be developed. Test samples High-titania slag was prepared in a pilot-scale DC furnace from ilmenite concentrates with different levels of uranium and thorium. Subsequently, ten slag samples representing a range of compositions were selected for bulk chemical analysis, scanning electron microscopy and micro-analysis. The samples were crushed to a maximum particle size of 1 mm and from each sample a 20-kg batch was riffled out for analysis. Bulk chemical composition Chemical compositions of the samples selected for test work are given in Table I. TiO2, Al2O3, SiO2, MgO, MnO, FeO and V2O5were analysed by ICP-OES, Na2O, CaO andCr2O3by atomic absorption spectroscopy and U and Th by XRF (the XRF detection limit for U and Th was around 4 ppm). The ?B? series has a higher silica content than the others as a result of small silica additions that were made during smelting. All samples have elevated alumina levels as a result of furnace refractory contamination during smelting. As expected, there is an inverse relationship between the concentrations of TiO2and FeO in the samples (Figure 1).The TiO2and FeO levels are similar to the levels found in industrial slags2. Extreme conditions of reduction under which reduction of more ?refractory? oxides (e.g., chromia, magnesia, silica, alumina and even urania and thoria) might take place were not explored in the study. Note that BB1and BBB1 contain more than 7% combined silica and alumina (SiO2as a flux addition during smelting, and Al2O3from refractory contamination) and they do not fall on the general trend defined by the other samples. The U and Th concentrations of sample E2 is noteworthy. In the preparation of slag E2, monazite concentrate was added to the ilmenite to increase the concentrations of radioactive elements in the slag. This was done primarily to facilitate the detection of Th and U during the phase chemical characterization of the slag. Radioactivity measurements Gamma ray emissions from the samples were measured [ ]

Jan 1, 2007

By C. A. Pierce

UNDERGROUND operations of the United States Potash Co. at its mine near Carlsbad, N.M., have been continuous since the property was opened about five years ago. Approximately one million tons of potash has been mined and two shafts have been sunk, each to a depth of about 1000 ft. Outstanding in the company's operations is the fact that not a single blasting accident has occurred during the aforesaid period. The purpose of this paper is to describe the blasting practice that has made possible the achievement of this accident-prevention record. The mining method employed in extracting the thick horizontal bed of potash may be described as a double-entry room-and-pillar system. Mine development is kept well in advance of extraction operations, and a three years' supply of ore, at least, is always available. Limits of the orebody have not been determined, and in the present system of mining headings are advanced by a "shortwall" method. This was the first potash ore bed developed in the United States. The nature of the deposit, therefore, was unknown, and it was deemed expedient to outline a conservative mining policy. Later, when more is known about the deposit and certain control ascertained, a "longwall" panel retreating method may be found advisable. The necessity for a domestic supply of potash became a national issue previous to and during the World War. The United States Govern-ment came to realize that this country should not be dependent upon foreign sources of potash, and began extensive explorations in many parts of the country, seeking an orebody that would meet the exacting require-ments of the domestic market. The Department of Interior, through the Geological Survey and Bureau of Mines, made every effort to determine the location of potash deposits and encouraged their exploitation by private capital. Through the combined efforts of the Department of Interior and private industry, the deposit now being worked by the United States Potash Co. was discovered and brought into production.

Jan 1, 1936

By E. W. Davis

I . OPERATING TESTS 1. CHARACTER OF ORE UNDER INVESTIGATION On the eastern end of the Mesabi Range, in Northern Minnesota, is a large formation of siliceous rock which contains bands and fine grains of magnetite . The magnetite comprises about 35 per cent. of the rock. Fig.. 1 show's graphically that the tonnage of minus 200-mesh material produced varies directly with the tonnage fed to the mill. There is undoubtedly some limit to this relation, but there seems to be no indication of it at 18 T. per hr. Some of the conclusions drawn from this test are that: (a) The ball-mill is naturally a machine of very large capacity; (b) if it is not possible to deliver a large tonnage of original feed to the mill, a closed circuit should be provided so that the mill may crush its own oversize.

Jan 2, 1919

By E. T. Dumble

The history of the several petroleum deposits of Texas and Mexico, or of the sediments in which they now occur, if the deposits are not indigenous to such sediments, is known in a general way only, but it nevertheless casts strong light on the conditions surrounding them and is of great importance in the search for and exploitation of them. The petroleum deposits of Texas are separable into two main divisions: 1. The deposits of northwestern Texas, which are directly connected with the Oklahoma fields to the north, and have no representatives at all in the Mexican area. 2. The deposits of the coastal area, which extend into Louisiana on the east and connect with those of the Mexican coast to the south. Early in the Pennsylvanian period a series of bituminous shales and limestones were laid down over a broad area in Texas, Arkansas, and Oklahoma. These are known as the Bend series in Texas, the Caney shales in Oklahoma, and the Fayetteville beds in Arltansas. Following their deposition an uplift occurred, forming the Lampasas geanticlinal, which runs northeastward from the old Paleozoic land area of the Llano region toward Red River. The Bend series is petroliferous in places and has furnished a few producing wells on each side of the Lampasas uplift. This uplift forms the barrier and dividing line between the two divisions of the Texas petroleum deposits. To the west of it, in waters which were the southcrn extension of the interior continental seas, in connection with the sedimcnts and coal beds of the Pennsylvanian and Permian, great quantities of petroleum were deposited either as oil or as "potential petroleum." These sediments have been subject to very slight disturbance, and only very gentle folds are found, with no signs of volcanic action in any part of the area. The conditions, therefore, indicate that the greater part, if not all, of the oil in this area is indigenous to the beds in which it is found. East of the anticlinal the oldest beds which appear in contact with the Bend are the Trinity Sands of the Lower Cretaceous. No evidence has

Jan 1, 1916

By P. G. Linder

The mechanical concentration of ores has not attained any considerable extent in Sweden, by reason of a scarcity of ores calling for this kind of treatment. Of rich iron-ores there is still an abundant supply; and magnetic concentration, which in the future undoubtedly will become of great importance, not being as yet demanded by necessity, has not advanced beyond a few experiments. At the copper-mines mechanical concentration has been superseded by chemical processes; the lead mines are worked out; and it is (with one exception) only the mines producing blende, or blende and galena intimately mixed, that have adopted mechanical methods for enriching their low-grade ores. While the concentrating-plants in Sweden are few and their output is comparatively insignificant, the methods employed, the general features of the work and the results obtained under extremely unfavorable conditions, may offer some points of interest to persons who are engaged in this branch of industry and have similar problems to deal with. Before going into a detailed description of the several plants, I will offer a few remarks that hold good for all of them and constitute a general review of Swedish concentration and its conditions. At all the works the ore to be treated is a mixture of blende and

Jan 1, 1895

Modify conventional mining practices to reduce significantly the amount of material brought to the surface from underground mines, or to ?re-mine? existing surface mine dumps by backfilling empty underground stopes.

Jan 1, 1994

By S. P. Kinney, C. E. Wood, T. L. Joseph

In connection with its investigations of the blast-furnace process, the Bureau of Mines, in cooperation with the Minnesota School of Mines Experiment Station, developed a 6-ton experimental furnace. Such a furnace was needed to determine the feasibility of producing ferroman-ganese from Minnesota manganiferous iron ores, a problem of national importance because of the present need for manganese in the steel industry and our small reserves of ferro-grade ores. Furnace operators are reluctant to use new or untried raw materials or to make decided innovations in practice on account of the financial hazard of experimenting with full-scale equipment. A small furnace which can be operated at a relatively low cost is particularly adapted for testing new raw materials and for determining the feasibility of decided innovations in practice. Laboratory experiments, plus whatever information may be available, are valuable but often do not indicate the net result of changes in an operation involving a large number of interrelated variables. From time to time the cooperation of the Bureau of Mines is solicited in connection with problems involving departures from normal procedure. Under these circumstances some sort of a practical demonstration is a desirable forerunner to full-scale operations which appear feasible after small-scale tests. The Aluminum Co. of America was interested in knowing the practicability of smelting a charge of bauxite, iron ore, and limestone, of proportions that would produce slag of the following composition: A1203, 47 to 48 per cent.; CaO, 41 to 42 per cent.; SiO2,4 to 5 per cent.; TiO2, 2 to 3 per cent.; FeO, 1 percent., and MgO, 1.8 percent. In addition to determining whether it was feasible to operate a blast furnace on slag approaching the composition given above, a quantity of slag was needed for a series of experiments that would show the relative ease and cost of extracting alumina from slag which could be made in the blast furnace, as compared to extracting it from raw bauxite. The value of the slag as a raw material

By S Meffre, S Golding, K Zaw, J McPhie, R James, S Suphananthi

The Chatree deposit is located in the central portion of Loei Fold Belt, which extends from Lao PDR in the north through centralThailand to Cambodia in the south. Epithermal gold-silver mineralisation at Chatree occurs as veins/veinlets and stockworks with minor breccia in volcaniclastic and volcano-sedimentary rocks of andesitic to basaltic andesite composition and Permo-Triassic age. This preliminary oxygen isotope study mainly focuses on vein quartz of Au-Ag bearing mineralization (Stage 2) and a few samples of late Stage 4 quartz ¦ calcite veins. Quartz from Au-Ag bearing mineralisation has oxygen isotope values ranging from 8.1 to 12.3ë with the lowest values generally occurring at the deeper level (140 m below the surface). The late barren quartz ¦ calcite veins (Stage 4) tend to have higher oxygen isotope values ranging from 11.9 to 12.0ë. The oxygen isotope composition of the Chatree ore fluids were calculated at 250¦C, 300¦C and 350¦C based on homogenisation temperatures of fluid inclusions. The calculated oxygen isotopic composition of the Chatree ore fluid ranges between -1 and 6ë that overlaps with both meteoric and magmatic compositions. This shift in oxygen isotope compositions may relate to processes such as water rock-interaction and/or mixing of meteoric and magmatic fluids. It is interesting to note that the lowest quartz oxygen isotope values are spatially more or less confined to the prominent structures in the centre of the major ore zones. These structures may have been acted as conduits for higher temperature magmatic fluids. The quartz oxygen isotope values increase outwards from the centre of the main ore zones to the margin of the pits possibly due to mixing of magmatic fluids with lower temperature meteoric water. Whole rock oxygen and hydrogen isotope studies are in progress to investigate isotopic trends in the wall rock away from the ore zone. The systematic variation of oxygen isotopes in quartz from the mineralised veins and adjacent wall rocks could potentially be used as a vector to ore. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By J L. Mauk

Gladstone Hill, a volcanic-hosted low-sulfidation epithermal prospect in the Coromandel Peninsula, is less than 1 km from the world-class Martha Hill Au-Ag deposit. Gold-silver-bearing quartz veins occur in Late Miocene andesitic volcanic rocks of the Waipupu Formation that are extensively altered. The occurrence, spatial distribution and temporal relationships of hydrothermal minerals have been determined along two cross sections that transect the Amaranth, Gladstone, Cowshed and Moonlight veins. Quartz and pyrite are ubiquitous along these sections. Adularia and chlorite are widespread, but both are scarce in wall rocks adjacent to the Moonlight and Cowshed veins. By contrast, rare hydrothermal albite and epidote are restricted to wall rocks surrounding the Amaranth vein. Illite, which replaces adularia, is widespread and grades laterally eastwards into a zone of interstratified illite-smectite that envelops the Moonlight and Cowshed veins. During late-stage hydrothermal activity, rare calcite formed at depth and uncommon kaolinite and alunite formed at shallow levels. The overall clay mineral zonation with illite grading eastward into interstratified illite-smectite reflects paleothermal gradients of >220¦C to -170¦C towards the margin. The alteration assemblage of quartz, adularia, chlorite, albite, epidote, illite, interstratified illite-smectite and pyrite reflects formation from a near-neutral to weakly alkaline pH chloride water that contained low concentrations of CO2, Late calcite formed from very local descending steam-heated CO2rich water, whereas the rare assemblage of kaolinite and alunite formed from shallow steam-heated acid-sulfate water. Analysis of the available data indicates that the Martha Hill deposit and the Gladstone Hill area formed within a single large geothermal system. We infer that the Martha Hill deposit formed in the main upflow zone, whereas the Gladstone Hill area may have formed adjacent to this upflow zone.

Jan 1, 2001