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By D. Lopez, D. L. Doerr, T. J. Drake

Automated scanning electron microscopy has been widely used in recent years for gold and other precious metals characterization. However, application of this technology is resource intensive and in most instances needs specialized technical personnel to process the samples and information. Newmont Metallurgical Services (NMS) has recently acquired an ASPEX SEM. The ASPEX SEM offers some significant benefits/improvements in sample preparation and sample processing time. NMS and ASPEX have been working together to develop an approach utilizing this technology for the minerals processing industry and specifically for gold characterization.

Jan 1, 2011

By Fatemeh Pourakbari, Mohammad Reza Yarahmadi, Abbas Sam

Pyrite is the most abundant sulfide gangue mineral in copper porphyry ores. In spite of addition of lime in large quantities to depress pyrite in flotation, considerable amount of this mineral is reported to concentrate, particularly in rougher and scavenger stages. With the Sarcheshmeh pit advancing to a greater depth and reaching to the hypogene zone, the amounts of pyrite and chalcopyrite in the feed are increased. Hence, a reduction in the copper grade and increase in the sulfur content of the concentrate are observed. In this study the effective factors on the pyrite floatability at the circuit flotation was considered at Sarcheshmeh Mine. Mineralization zones in the pit were firstly identified. Then, sampling points were located using GPS system. On the basis of mineralogical composition and morphology, the ore was categorized into five main classes. In this classification the amount of lead and zinc and also pyrite locking with other minerals were analyzed. The study of polished section indicated that inclusion in pyrite was very frequent in all classes, mostly composed of the floatability of pyrite. Flotation tests were performed on the samples of different classes at pH of 11.8 after conditioning time. It was shown that, pyrite floatability was decreased with a decrease in the lead content of the feed samples except for the second class, while for all classes an increase in zinc content contributed to a decrease in pyrite floatability and recovery. It was found that, the lowest pyrite recovery (1.89%) was corresponding to pyrite–molybdenite dominant mineralization with Zn of 0.33% and the highest recovery (86.89%) corresponding to pyrite vein dominant mineralization with Zn equals to 0.9%.

Jan 1, 2016

By E. P. Evoy, A. W. Jolliffe

"The Uranium deposit of Gunnar Mines, Limited, is on the south shore of Crackingstone peninsula in the Beaverlodge area of northern Saskatchewan.The ore consists of disseminated pitchblende and uranophane in brecciated syenite, and forms a tubular or pipelike body, outcropping at the surface and plunging southward at about 45 degrees for a known length of1,400 feet (see Figure I). The upper portion is being removed by open-pit mining to a depth of 300 feet below adjacent Lake Athabasca. The remainder will require underground mining methods (see Figure 2).The property was staked in July, I 952, and the orebody was subsequently defined by about 70,000 feet of diamond drilling. A 1,250-ton mill was completed in 1955, and production commenced in September of that year with ore from the open-pit operation. The mill is presently being increased to 1,650 tons capacity, and a three-compartment vertical shaft is being sunk to 1,250 feet in preparation for underground mining.GeologyThe mine property is underlain by an assemblage of Precambrian metasediments known locally as paragneiss, granite-gneiss, and syenite. These lie on the southeast limb of a southwest-plunging anticline, strike about north 75 degrees east, and dip southward at about 45 degrees. Para- gneiss outcrops in the northwestern half of the claim group, and again on the islands south of St. Mary's Channel. The granite-gneiss lies conform-ably within the paragneiss and makes up the southeastern part of the property. The syenite forms an irregular, triangular-shaped mass within, and near the footwall of, the granite-gneiss band. Small lenticular bodies of mafic rocks are also present, the former being most prevalent in the paragneiss.The granite-gneiss is coarse to medium-grained, pink to grey, well foliated, and composed of feldspar (65 per cent), quartz (20 per cent), chlorite, and minor mica. The general concordance of its contacts with paragneiss and the absence of intrusive relationships along these, the presence of uniformly oriented inclusions of obviously sedimentary origin within the granite-gneiss, and the variation in colour and texture across the strike all strongly suggest that this member represents a granitized sedimentary rock."

Jan 1, 1949

By M. Massinaei

Recently constructed circuits have included multiple stages of columns in a variety of applications, from roughing to cleaning. The Miduk copper concentrator (in south-eastern Iran) is one of the unique mineral processing plants which use column flotation cells as rougher. As the bulk of final concentrate is produced by rougher columns, optimized metallurgical performance of these cells is crucial. This paper will present the study and optimization of, a froth washing system of columns. For this purpose, the cross-sectional area of orifices was increased and their orientation altered. Concentrate assay for copper and silica, in addition to bias rate were found to be the assessment criteria. Modification of the wash water system resulted in increasing the purity of rougher and final concentrate. Negative bias and short-circuiting of wash water into the concentrate launder were the main causes of improper froth zone washing in the former system.

Jan 1, 2007

By R. Clarkson

"Free gold particles occur in many base metal and precious metal mines throughout the world. Due to the high density and malleability of gold, large circulating loads of free gold particles can build up over time in grinding circuits. This gold is often deposited in unintended traps throughout the mineral processing system.These unidentified free gold deposits represent a serious security risk as well as an inaccessible inventory of gold. Deposits of free gold particles often remain undetected by mine management until they are accidentally discovered while repairing mill equipment.Nuclear tracers have been used to determine the free gold recovery efficiency of gravity recovery equipment, drills, and sampling equipment (Clarkson, 1994, 1995; Walsh and Rao, 1986; Walsh and Kelly, 1992). In November, 1993, the author inspected the grinding circuit at La Mine Doyon in Rouyn-Noranda, Quebec and made recommendations to recover coarse gold and to eliminate gold traps from the circuit. In 1995, the author salted mineral processing circuits with radioactive gold particles. The gamma and X-ray radiation from gold’s nuclear isotope (Au198) were detected through steel, in pipes, and in moving equipment using scintillometers. The radiotracers proved to be a safe, rapid and accurate method of identifying gold traps and improving security.Nuclear TracersWhen particles of gold are placed in a nuclear reactor, some of the gold atoms (Au197) absorb another neutron in their nucleus to form gold’s radioactive isotope (Au198). In the process of radioactive decay, this isotope emits high energy gamma rays and X-rays which are easily detected (even through steel) with scintillometers.Radioactive gold (Au198) has a very short halflife of 2.7 days. At the relatively low activity levels used for tracing, the particles remain detectable with a small hand-held scintillometer for about 10 to 14 days. After 14 days the irradiated gold is close to background levels and within two months it is essentially non-radioactive. The radiation has no effect on the recovery characteristics of the gold particles. The gold radiotracers are very safe due to their very low level of radiation, short half-life, and their inherent physical and chemical stability. However, the use and possession of even mildly irradiated gold is strictly licensed and regulated."

Jan 1, 1997

By H. Clare Horwood

"In the Red Lake area in northwestern Ontario the relationships between general structures and structures containing ore deposits are among the most unusual and most interesting of any in the Precambrian Shield. The more important orebodies, which are in the central-eastern part of the area, occur in a variety of rocks on the northeastern, eastern, or southeastern sides of a series of granite stocks. Other deposits in the western part of the camp also are structurally associated with granite masses .The relationships were determined in the course of general and detailed geological mapping by detailed analyses of the fracture patterns in the rocks adjacent to the orebodies. In every case it was found that the structures containing the ore were produced by compressive stresses from the direction of intrusion of the granite masses( 2).The Red Lake area lies in the Patricia part of the district of Kenora and is accessible by boat from Hudson or by airplane from Kenora, Sioux Lookout, or Winnipeg. A road from Vermilion lake, on highway No. 17, was opened in August, 1947.The first discoveries of mineralization in the area that proved to be of economic importance were made in 1925 by Lorne Howey and George McNeely for Haileybury interests and by Ray Howey and W. F. Morgan for Mcintyre-Porcupine Mines, Limited. Both prospecting ventures were organized because of information presented by Bruce(l) in his map and report for the Ontario Department of Mines. The discoveries, which were both along the same structure, a quartz porphyry dyke, later developed into the Howey and Hasaga gold mines. Other discoveries were made at intervals as a result of prospecting and development work on ground staked for its location."

Jan 1, 1954

By D. S. Campbell

THE chief factors influencing the decision to build the Big Missouri mill underground were the topography of the country and the climate. The location underground assured certain saving in the cost of operation, such as the hearing of the mill, shovelling snow, and handling ore, which, over a period of time, would offset the greater initial cost of the mill excavation and machinery installation underground, as compared with the cost of a like plant on the surface. At Gilman, Colorado, where conditions are somewhat similar, the Empire Zinc Company, at their Eagle mine, are treating their lead-zinc ore in a mill built entirely underground. Company officials made a study of this plant before proceeding with the mill at Big Missouri. LOCATION, CLIMATE, TOPOGRAPHY The Big Missouri mine is situated on the Upper Salmon river, 22 miles north of Stewart, B.C., which is at the head of Portland canal, a narrow natural channel which penetrates 100 miles inland from the coast into the Coast Range mountains. Stewart, the distributing centre for the district, is about 600 miles north of Vancouver. The Big Missouri claims lie on and down the sides of the Big Missouri ridge, which extends north and south between the Salmon River and Cascade Creek valleys. The ridge rises to an elevation of 3,600 feet, is about half a mile wide, and to the east slopes down to the Joker flats in Cascade Creek valley. The Big Missouri camp is located on the flats at elevation 2,800 (see Figure 1). Preliminary development of the property took place from this point with an adit driven under the ridge. The western side of the ridge slopes steeply down to the Salmon glacier at elevation 1,900. Ore found on the 2,850 level extended down, and, in order further to explore the ore-body, the 2,850 level was driven through to the west side of the ridge, a surface incline tramway was built, and a lower tunnel driven at elevation 2,350, five hundred feet below the original 2,850 level, from the west side of the ridge. This tunnel development avoided the necessity of sinking, which would have been costly, as the mine makes a great deal of water (see Figures 1 and 2).

Jan 1, 1938

By G. C. Bateman

Canada is a very large country with a small population which is growing very slowly. We have great natural resources, but with our limited population we are continually looking afield for new capital to develop these resources. Our mining areas are among the most important fields offering opportunities for new capital and because of the wide-spread appeal which mining makes this industry commands a great deal of attention. While we are glad to see new capital from any source, we welcome it particularly from Great Britain, for, although we offer equal opportunities to the nationals of any country we would be glad to see the development of our natural resources financed as far as possible within the Empire. However, when we invite ne capital we must accept certain responsibilities, and while we have opportunities to offer, we should ask ourselves how these opportunities are taken advantage of and what sort of treatment the foreign investor receives.

Jan 1, 1925

By J. A. H. Church

My paper entitled "Spontaneous Combustion of Coal in Mines;" read some time ago before this Branch, consisted chiefly of extracts from the British Blue Book dealing with the same subject. Fallowing my article, Mr. de Hart submitted a paper dealing with the application of existing methods of working in Alberta to the conditions obtaining in our bituminous mines. I must confess that the perusal of his paper did not enlighten me either as to what might be a method preferable to those in vogue or even to Mr. de Hart's ideas on the subject, nor did the ensuing discussion of Mr. de Hart's paper afford any great clarification of the problem. The outstanding idea, supplied by Mr. Dick, seemed to be that a retreating system could not be employed, as no operator would feel justified in risking the capital necessary to driving to the boundary when the whole might be jeopardized by a fire breaking out in the waste. That a fire would break out in the waste of any adit-level working seemed to be conceded by all, and with that I agree; that an ignited waste could not be safely sealed off by means of stoppings in a coal barrier-pillar appeared to be the contention of Mr. Dick, or perhaps he attributed this idea to the Mines Branch-anyhow, it seemed to loom over the discussion like a miasma. With this aspect I do not agree, as ? reliance is placed wholly on stoppings in the thick seams of South Staffordshire, even in fiery mines. In the thick coal at Exhall colliery, or elsewhere in Warwickshire (34 feet 4 inches) containing hard and soft coal in layers, a fire assuming serious proportions is sealed off. By the way, retreating long-wall methods are employed. In Fifeshire, sealing off fire in the Dysart mine has been accomplished successfully. The seam averages about 20 feet thick.

Jan 1, 1924

By R. A. Lunceford, K. C. Shaver

Acquired by Teck Corporation in 1990, the White Earth project, located in southwestern Colorado is the largest titanium resource in the U.S. Teck Corporation has conducted geologic, reserve, mineral processing, pre-marketing, and environmental baseline studies directed toward the economic feasibility of producing titanium pigment. The White Earth project is situated in a 31 km2 alkalic-carbonatite complex intruded into Precambrian granite and metamorphic rocks about 570 million years ago. Perovskite occurs in a 8 km by 1.2 km Acquired by Teck Corporation in 1990, the White Earth project, located in southwestern Colorado is the largest titanium resource in the U.S. Teck Corporation has conducted geologic, reserve, mineral processing, pre-marketing, and environmental baseline studies directed toward the economic feasibility of producing titanium pigment. The White Earth project is situated in a 31 km2 alkalic-carbonatite complex intruded into Precambrian granite and metamorphic rocks about 570 million years ago. Perovskite occurs in a 8 km by 1.2 km

Jan 1, 1998

By T. Richard Davies

This paper primarily deals with the application of wearfacing materials and their role within a well-established preventive maintenance welding program. Some examples are shown, as well as a synopsis of possible benefits and a compendium of methods and materials.

Jan 1, 1979

By M. Fairclough, B. Moldovan

Insights into uranium mining projects of the future can be gained by a careful statistical analysis of past and present deposits, as well as an examination of recent trends for uranium resource evaluation and primary uranium production. The International Atomic Energy Agency (IAEA) provides the necessary data and corresponding mechanisms as inputs for methodologies that enable strategic and scientific evaluations of long-term security of supply uranium required to sustain the demand for nuclear fuel. Sustainability of the uranium mining industry and subsequently new uranium mines of the future requires innovation and expertise to lower operating costs, maintain or improve uranium recovery while meeting the requirements of stakeholders in regard to protection of the environment and safety of the workers and general public.

Jan 1, 2020

By D. R. BUDINSKI

Clinton Creek Mine in west-central Yukon produced 0.94 million tonnes of fibre from 15 million tonnes of asbestos ore between 1968 and 1978. The mine closed in 1978. The deposit lies along the margin of a medium sized ultramafic pluton that intrudes schistose and gneissic rocks of the Yukon Metamorphic Complex. Country rocks are metamorphic equivalents of a mixed sedimentary and volcanic assemblage deposited during Precambrian or early Paleozaic time. Movement along the north west-trending Tintina Fault System probably caused the fairly high meromorphic grade that altered the original rocks to schists and gneisses. The ultramafic pluton hosting Clinton Creek Mine is one of several bodies that were emplaced along a deep seated imbricate fault system parallel to the Tintina Trench. Most of rhe intrusions were hydrothermally altered to serpentinite, bur apparently only the one at Clinton Creek contains commercial quantities of asbestos. The Clinton Creek pluton was probably injecred slowly at relatively low temperatures into the crustal rocks as a "mush" that cooled gradually, allowing sufficient time for serpentinization and chrysotile fibre crystallizarion.

Jan 1, 1984

By Patrick Rennkamp, Wolf-Dieter Trodel, Andy Fearn

"The Jansen shafts are completed using purely mechanical excavation. This paper summarises the geology, a description of the shafts, the method used for excavation and the results achieved along with the challenges encountered and the solutions developed during the project. This experience is now being applied in the next generation machines and shaft sinking processes. This pioneering approach is changing shaft sinking in soft and medium to hard rock. INTRODUCTION The Jansen Mining project located approximately 150 km east of the city Saskatoon is the location of the BHP owned potash mine with an expected mining output of eight million tonnes annually upon completion. Mining contractors DMC Mining Services have used two Herrenknecht Shaft Boring Roadheaders (SBRs) to excavate the two blind shafts with an approximate excavation diameter of ten metres (inner diameter approximately 8.3 m) to depths of -975 and -1005 metres, respectively. The SBRs excavate the rock by a partial-face cutting method, using a transverse cutting drum mounted on a telescopic boom. The excavated rock is then conveyed away from the bench by an innovative pneumatic system and transferred into muck buckets to be hoisted to the surface. No drilling and blasting was done to keep to the BHP philosophy of using only mechanical excavation for this reference project. BHP VISION – MECHANICAL EXCAVATION BHP focused on mechanical excavation at Jansen due to the following perceived benefits: 1.No workers in the excavation chamber (shaft bottom), minimizing the exposure to traditional shaftsinking hazards associated with working in the shaft bottom. 2. Minimal damage to the rock fabric reducing the need for ground support and avoiding potential impact damage to freeze tubes located around the shaft. 3. Accurate excavation diameters with no overbreak, reducing volumes of rock to be removed and replaced with concrete lining."

Jan 1, 2019

By Frank D. Shepherd

THE Gunnar Gold Mines property is on the west shore of Beresford lake, in the Rice Lake mining division, southeastern Manitoba. Gold was first discovered in place in the Rice-Beresford Lakes area in 1911 on the Gabrielle claim, now included in the San Antonio Mines property at Rice lake. Following an eastward trend of favourable prospecting ground, promising showings were next staked in the vicinity of Long lake during the years 1915 and 1916. At that time, William Walton and associates, among them Gilbert LaBine, staked the Eldorado vein, north of Long lake, and Eldorado Gold Mines, Limited, was formed to develop the property a Company that, later, was to become widely known through successful operation of its radium-silver mine at Great Bear lake, Northwest Territories. Continuing eastward from Long lake, Walton and his partners, Gunnar Berg, Leo Seaberg, and Wm. Quesnel, staked claims during the years 1920-24 in the vicinity of Beresford lake which, later, were to become incorporated into the Gunnar Gold Mines property. The presence of gold-bearing quartz on these claims had been known from the time they were staked, but an opportunity to consolidate them into a group was not forth-coming until early in the year 1933. Although promising gold showings had been disclosed during the performance of assessment work on individual claims, no continuous mineralization having mine-making possibilities was discovered until after the consolidation of the entire group. From this stage onward, progress was rapid. Active exploration was begun on August 1st, 1933, and late in October James Houston reported favourably on the property. On October 27th, Gunnar Gold Mines, Limited, was incorporated in the Province of Ontario to develop and operate the property. The Company is also registered in Manitoba. The authorized capitalization is 3,000,000 shares of $1.00 par value. Gilbert LaBine was appointed president of the Company, with James Houston as mine manager. Following completion of a diamond-drilling programme, planned in 1933, it was decided to install a mine plant capable of carrying development to a depth of 1,000 feet. A transmission line, 5 miles in length, was built to the Great Falls-Central Manitoba line of the Manitoba Power Company, Limited.

Jan 1, 1939

By K. Barbetti, J. Avraamides

"The processing of gold ores with high silver contents can provide operational challenges, such as high cyanide consumption, retardation of gold leaching and competition during adsorption stages of carbon-in-pulp/leach/column (CIP/CIL/CIC) circuits. In particular, the silver, which is about 1.5% of the value of gold, competes with gold during carbon adsorption due to its higher concentration in many Ag-Au ores, potentially leading to gold solution losses. Fresh and partially fouled (barren and regenerated) activated carbons were evaluated at various Ag:Au ratios and total metal concentrations with regard to the adsorption kinetics and equilibrium loadings. Conventional Freundlich isotherms were found to be highly inaccurate for predicting equilibrium loadings in the competitive adsorption environment. An integrated model, which incorporates competitive adsorption kinetics with a modified competitive adsorption isotherm model has been developed and validated using plant and laboratory data. The model performance and some of its salient features will be discussed.INTRODUCTIONThe processing of gold ores with high silver contents can present a range of operational challenges, such as high cyanide consumption, retardation of gold leaching and competition in carbon adsorption circuits. Silver is often present at significantly higher concentrations than gold in many gold-silver ores and competes with gold in carbon adsorption circuits, limiting the gold loading rate and capacity, resulting in gold solution losses and reduced gold recovery.Curtin University’s Gold Technology Group has evaluated fresh and partially fouled (barren and regenerated) activated carbons at various Ag:Au ratios and total metal concentrations to determine the adsorption kinetics and equilibrium loadings for gold and silver. Conventional Freundlich isotherms were found to be highly inaccurate for predicting equilibrium loadings in the presence of both gold and silver.An integrated model, which incorporates competitive adsorption kinetics with a modified competitive adsorption isotherm model has been developed and validated using plant and laboratory data. This paper describes the model performance and some of its salient features."

Jan 1, 2016

By Yongfeng Jia, Shaofeng Wang, Danni Zhang

Arsenic in mineral processing solutions and effluents is commonly removed and immobilized via iron(III)-arsenatecoprecipitation. The effect of re-crystallization of 2-line ferrihydrite on the long-term stability of iron(III)-arsenate coprecipitate is still not fully understood. This work investigated the redistribution of arsenic and iron during 2-line ferrihydrite transformation at different pHs and temperatures over time. X-ray diffraction (XRD), transmission electron microscopy (TEM) and chemical extraction were employed to characterize the crystallinity of the iron oxyhydroxides. Results showed that the amount of arsenic released into solution during aging increased significantly with increasing media pH.

Jan 1, 2014

By C. Ayora

The Iberian Pyrite Belt (SW Spain and Portugal) contains one of the largest reserves of pyrite in the world with mining activities dating back to prehistoric times. About one hundred abandoned mine wastes and galleries release a huge acidity and metal load to the Tinto and Odiel rivers. Once the mining activity is over, polluting discharges can persists for decades or even centuries with no specific responsible entity. In-situ passive remediation technologies are especially suitable for these orphan sites. The concept is to insert a reactive porous material in the natural flow path of contaminated surface and ground waters, and it is implemented through infiltration ponds and reactive barriers, respectively. Calcium carbonate pea-size gravel is the common alkalinity supplier to neutralize acidity and precipitate metals. These remediation systems have been traditionally implemented in coal mines. However, the acid drainages from the Iberian Pyrite Belt contain metal concentrations one to two orders of magnitude higher than those from coal mines and require special designs to avoid quick clogging or passivation (coating) of the grains of reactive material. To overcome these problems, a Dispersed Alkaline Substrate (DAS) mixed from fine-grained limestone sand and a coarse inert matrix (e.g. wood chips) was developed. The small grains provide a large reactive surface and dissolve almost completely before the growing layer of precipitates passivates the substrate. The high porosity and the dispersion of nuclei for precipitation on the inert surfaces retard clogging. However, limestone dissolution only raises pH to values around 6.5, which is sufficient to precipitate the hydroxides of trivalent metals (Al, Fe), but it is not alkaline enough to remove divalent metals. Magnesium oxide, which hydrates to Mg hydroxide upon contact with water, buffers the solution pH between 8.5 and 10. A DAS system replacing limestone with caustic magnesium oxide has been tested to be very efficient to remove divalent metals (Zn, Cd, Mn, Cu, Co, Ni, Pb) from drainage previously treated with limestone.

Aug 1, 2013

By H. Al-Kazzaz

The effects of laser power and joint gap on the welding quality of 2-mm butt joints of ZE41A-T5 sand castings were investigated using a continuous wave 4 kW Nd:YAG laser system and 1.6-mm EZ33A-T5 filler wire at a welding speed of 6 m/min and surface defocusing. The smooth weld profiles with the minor welding defects were obtained at a laser power of 4 kW and joint gap of 0.3-0.4 mm. The hardness values in the fusion zone are similar to those of the base metal but there is a drop in the heat-affected zone after a natural aging of 18 months.

Jan 1, 2006

By A. A. Bakke

"The Fort Knox gold deposit is hosted within the Fort Knox Pluton, a Cretaceous multiphase granitic body that intrudes the Fairbanks schist. Gold occurs along the margins of stockwork veins and veinlets, quartz-filled shear zones, and along fractures within the granite. The mineralization is generally sulphide-poor and closely associated with trace amounts of bismuth, tellurium and to a lesser extent with molybdenum and tungsten. At present, proven/probable reserve estimates, based on a cutoff grade of 0.39 g/t Au, are 158.3 million tonnes grading 0.83 g/t Au.The Fairbanks schist comprises the bulk of the country rock. The dominant lithologies present include muscovite-quartz schist and micaceous quartzite. Immediately north and south of the main orebody, mixed metamorphic lithologies of the Cleary sequence, a subunit of the Fairbanks schist, have been mapped. Development of local zones of weakness, most likely due to a broad regional warping event, resulted in brittle-ductile deformation and activation of a northwest-southeast shear couple between contrasting lithologies.The Fort Knox Pluton consists of at least three phases based primarily on textural differences. Intrusion of a fine-grained granite was followed by a medium-grained porphyritic granite. The youngest intrusive phase is a coarse-grained, seriate porphyritic granite, the Vogt Stock. The Vogt Stock forms an elongate dome with the axis in the east-west direction. Structures displayed in the overlying units, believed to be the result of doming, include tension fiSSUres and longitudinal fractures.Premineralization fractures, the result of the magmatic doming, provided conduits for initial stockwork quartz vein development and quartz enrichment in shear zones. Weak development of vein-controlled phyl/ic, potassic, albitic, and argillic alteration styles are present. Evidence of a late thermal event resulting in a low-temperature alteration assemblage of calcite + zeolite (stilbite) + chalcedony + clay occupies breccia zones, joint surfaces, and fractures within the granite."

Jan 1, 1995