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By Georges Croisé, Les-Lee Thompson, Adrien Debergé

Membrane filtration systems have regained focus in recent years as an effective means of liquid-liquid separation to increase the concentration of valuable elements, recover reagents or remove impurities. ORANO Mining (formerly AREVA) investigated this cost optimization process opportunity as early as 2011 for implementation at the Trekkopje project (Namibia). The key focus was to separate and recycle bicarbonate from the uranium bearing eluate solution. The performance targets were successfully achieved at lab- and pilot scale with an ultrafiltration and nano-filtration configuration system. Early 2015, ORANO Mining further launched an investigation into the use of membranes for acid recycling at the KATCO In Situ recovery mine in Kazakhstan based on the favorable results from the original bicarbonate application. KATCO is the world leader in ISR uranium mining with an eluate processing capacity of 80 000 m3/yr. This site consists of two processing plants namely, Muyumkum and Tortkuduk, located 40 kilometers apart, both operating under acidic conditions whereas precipitation and packaging are based in Tortkuduk only. This paper serves to present the results from the integration of a nano-filtration system at the Muyumkum satellite processing plant. The project consisted of screening laboratory bench studies conducted at ORANO-CIME followed by process validation at KATCO through further bench and pilot test work. The feasibility study assessments were successfully concluded which led to the implementation at an industrial scale in Muyumkum of a nano-filtration process to reduce eluate volumes being sent to the uranium precipitation section whilst achieving effective separation of uranium from sulfuric acid. Nano-filtration technology has drawn significant attention due to the efficiency and reproducibility of the process and its moderate capital cost relative to operational savings. The reliability of the previous results is a great opportunity to reduce operative expenditures within ORANO’s next ISR mining project in Mongolia.

Jan 1, 2020

The Discrete Element Method (DEM) is a powerful tool for analysing the flow of charge, the energy consumption and the pattern of energy utilisation of a SAG mill. With the development of laser scanning measurement, the detailed internal working surfaces of a SAG mill can now be included in DEM models. Using scanned results for new and worn shell liners for a 32? (9.75 m) SAG mill, it is shown that the feed and discharge lifters have significant effect on the flow of the charge introducing significant threedimensionality. The effects of the resolution accuracy of liner geometry and the lower cut-off of the rock size distribution are explored. Finally, using a matched new and end of life worn liner and operating conditions taken from site surveys, the effect of wear on charge motion, distribution and energy utilisation are evaluated.

Jan 1, 2012

By A. Pearson, Auld. F. A., S. O. Colbeck

"To minimise mine shaft maintenance over the long-term, some potash mine shaft sinking projects have required the provision of a continuous fully welded waterproof steel liner over a substantial depth to achieve zero water ingress. This brings many challenges, including the implementation of a bottom-up construction sequence incorporating extensive waterproof welding and how to ensure the integrity of the welded liner when subject to substantial temperature fluctuations that are likely to occur with a composite steel-concrete liner placed within an artificially frozen shaft excavation. This paper highlights the key challenges and discusses multiple mitigation measures including vertical shaft movement joints and a combined structural-thermal analysis approach. INTRODUCTION Whilst the application of combined steel and concrete shaft liners using a fully welded steel liner is not new and has been used in several previous projects, most notably at Lanigan (Storck, 1968 & Roesner, 1980), recently the need to provide a continuously welded steel waterproof liner for over 800 m length of shaft for a potash mine has been considered. The need for a fully continuous welded steel liner arises from the perceived benefits of providing a fully dry shaft environment to; increase the life expectancy of the shaft; reduce routine maintenance particularly combatting salt accretion and minimising wash down practices; and improve long-term ground stability by preventing salt dissolution. Whereas previous projects have employed discontinuous sections of steel liner, when a fully continuous liner is employed longitudinal shaft strains from thermal changes result in significant deformations that must be either explicitly accommodated or resisted. Note, these thermal vertical expansion forces are more than capable of lifting the shaft collar and head frame structures should they be fixed in place. Typically, shafts are designed to resist vertical forces (collar loads and self-weight) by creating mechanical interlock with the adjacent ground. In competent rock this occurs incrementally with the construction of the shaft liner, and occasional hitch/crib structures are constructed as intermediate foundations to guarantee the transfer of vertical forces at distinct horizons. Usually this means cribs are constructed at first rock head, above the station level, and at the sump, although sometimes additional cribs are formed when entering and exiting weak strata or when a change in shaft liner construction is required."

Jan 1, 2019

By M. A. Clayton, D. Kinakin

The Mitchell Creek Landslide is a large, structurally controlled, complex bedrock instability located in northwestern British Columbia. Characterization of the landslide using aerial photograph, exploration geology, and geotechnical investigation data has been completed allowing the development of a three dimensional conceptual model of the landslide domains and slope behaviour. Three domains have been identified in the landslide, from top to bottom: the Sliding domain, a relatively intact slab slowly sliding into the valley; the Transition domain, located in the mid slope of the landslide and showing evidence of significant extension and continuing to subside and displace into the valley; and a Toppling domain, at the toe of the landslide in an area of overturned foliation. Movement is greatest in the Toppling domain, with long term estimated rates of movement up to 4 times that of the Sliding domain; the Transition domain exhibits the greatest range of displacement rates, with average long term values approximately double the slower Sliding domain. This paper documents the results of numerical modelling of the Mitchell Creek Landslide with variation in geomechanical properties, basal rupture surface configuration, structural fabric, and pore water pressure conditions. The locations of internal shear surfaces within the landslide have been estimated from surface scarps, structural fabric orientation, and borehole monitoring data. The performance of each numerical model was evaluated against observed behaviour of the landslide. The configuration and properties of the basal rupture surface were identified as critical to model behaviour, as was spacing and location of internal structures.

Jan 1, 2015

By A. Consigny

New "clean technologies" to treat mining and metallurgical effluents containing dissolved metals have been successfully applied at mine sites in North America and Asia, treating water flows up to 24,000 m3/day. These clean technologies offer significant benefits compared to conventional alternatives and provide a sustainable solution that eliminates residual waste sludge, improves water conservation, generates revenues from wastewater, and delivers overall improvements to the environment. This paper will profile these technologies, and provide best practice case study examples of their application at mining operations, including data for water chemistry, flows, water quality, capital and operating costs, and life cycle costs of treatment.

Jan 1, 2011

By Boris Yacksic, R. W. Bruce

"The flotation of a cassiterite ore with oleic acid will recover primary or rougher concentrates assaying over 10 per cent Sn, with a recovery of 80 to 90 per cent. These rougher concentrates cannot be up-graded to a marketable grade by normal reflotation. Experiments were conducted on low-grade tin ores, and a process was developed for up-grading the rougher flotation concentrates by a reverse flotation technique. The process was tested on a number of samples of ore from the Catavi mine in Bolivia. The results of these tests showed that a concentrate assaying 40 to 60 per cent Sn could be readily produced, with a recovery of 60 to 75 per cent of the tin in the ore."

Jan 1, 1967

By F. Calizaya, S. Bhattacharyya

"This study presents the results of a set of sound level measurements carried out in three underground mines where auxiliary fans are used regularly. Sound levels as high as 100 dB(A) by the workings and 115 dB(A) by the fans were measured in these mines. These levels are quite high even for intermittent noise. Ventilation layouts and best practices used to overcome potential problems related to overexposure to fan noise in underground hard-rock mines are presented here. Factors such as fan type, rotational speed, and silencer-duct arrangements and their effects on noise attenuation are discussed. INTRODUCTION Auxiliary fans are used in hard-rock mines extensively. They are used to ventilate development headings, crusher rooms, conveyor transfer points, and underground shops. They are also used in developing long tunnels and ramps. Depending on the flow requirements and space restrictions, single or double stage axial fans with rigid or flexible ducts are used. Usually, they are high pressure (3.75 kPa) fans with flow rates ranging from 7.1 m3/s to 30 m3/s. The input power varies from 15 kW to 113 kW (Mutama, 2004; O’Connor, 2008). Typically, a 113 kW fan can produce sound levels as high a 113 dB(A) (Howes, 2005). Silencers are often omitted for cost reduction purposes or when used, they are not well maintained. Furthermore, silencers provide limited attenuation depending on their length and type. Typically, the sound attenuation ranges from 10 dB(A) for a 1 × D silencer to 14 dB(A) for a 2 × D silencer, where D is the fan diameter. In a mine, the silencer is subject to wear and tear, especially when the silencer is used in harsh environments. The interior lining can get clogged and the acoustic fill can get covered by dust and diesel soot, thus reducing the silencer performance. Periodic cleaning of the interior casing can increase the attenuation capacity of a silencer by 6 to 9 dB(A) (Dabson & Acuña, 2017). However, this requires a special silencer design in which the inner cartridge can be removed, the sound absorbing material replaced, the inner casing cleaned and the whole set retrofitted. A number of techniques can be used to reduce auxiliary fan noise in underground mines. These range from selecting the right fan for the job to installing adequate silencers. The choice depends on the air quantity requirement at the working place, cross-sectional area of the opening, duct diameter, fan type (axial or centrifugal) and local restrictions. Auxiliary ventilation layouts and best practices used to overcome potential problems related to overexposure to fan noise in underground hard rock mines are presented here. Factors such as fan type, rotational speed, duct diameter, and silencer-duct arrangements and their effects on noise attenuation are discussed."

Jan 1, 2019

By Z. D. Hora

Air hough diatomite is known in many parrs of British Columbia, deposirs of mineable size have only been found in the area between Kam/oops and Quesnel in the sourh-cenrral parr of rhe province. Ar Quesnel, commercial producrion has continued since 1950 from diatomite lenses up ro 35m rhick. OCCURRENCES of diatomite are reported from many parts of British Columbia, but deposits of mineable size are known only from the area between Kamloops and Quesnel. Only Quesnel deposits have yet reached the production stage. Commercial production dates back to 1950, and up until 1979 approximately 22,700 tonnes of diatomite had been produced. Most extracted diatomite was processed until 1980 by Crownite Industrial Minerals Limited in Quesnel to produce an oil absorbent and animal bedding. Smaller shipments are used to make insulating bricks on the lower mainland. Deposits near Quesnel extend 40 km along the western bank of the Fraser River from Quesnel to Alexandria; most production has come from Lots o. 6132 and 906. Di atomite is present as discontinuous lenses up to 35 m thick. Diatomite beds Industrial Minerals in Canada are of Upper Miocene age and are overlain by plateau basalts. Diatomite consists almost exclusively of Melosira granulara diatoms that are usually very small and mixed with variable amounts of clay, ilt and volcanic ash. In recent years, extensive beds of diatomite were identified near the confluence of the Chilcotin and Fraser rivers. Diatomite in this locale is a part o f the Upper Miocene to Pliocene Chilcotin Group of sedimentary rocks that are overlain by olivine basalt and related luffs. A deposit near Red Lake is situated 50 km northwest of Kamloops. Diatomite beds occur in the Tranquille Series of Eocene age and are similar in composition to those in the Quesnel area. The Red Lake deposit is abo ut 4 m thick but its areal extent is only a few tens of hectares.

Jan 1, 1984

By C. Harold Riches

This article is directed co a commentary on the patent system in its relation to the public interest. As man gained supremacy over his environment, he could devote progressively increasing portions o his time to improving his standards of living. In the history of the human race, we have advanced from the hollowed floating log to the modern steamship of the present age; from the sickle and flail to the reaper and combine; from the trumpet and drum as a means of communication co the telegraph, telephone, and radio; from the horse and ox cart to the automobile, truck, aeroplane, and train; and so on ad infinitum through the list of inventions on which are based the industrial and political economies and standards of living we enjoy today. It has also been a long road from the day of the alchemist and his closely guarded secrets to the era of the patent system and its storehouses of knowledge open to the world. The alchemist and the craft and merchant guilds closely guarded their secrets. In fact, they largely opposed innovations on the grounds that they might injure profits and restrict employment. In these days of unrest, with great clamour out of doors for radical changes in our political and industrial economies, it may not be untimely to examine one of the keystones which support the economic structure we know as the free enterprise system, the system which is predicated upon the right of the individual to own property. Many, through impractical idealism, ignorance, confused thinking, or blind political prejudice, advocate the substitution of ownership by the State ? for the right of ownership by the individual. As civilization has advanced to the high standards of living we enjoy today through the efforts of a comparatively few inventors, the patent system which has provided the incentive that created the inventions on which our industries and our employment are based is fully understood and appreciated by a comparatively small percentage of our people. As a result, the patent system, as a keystone in our free enterprise economy, is an apt target for destructive criticism, with the thought, possibly, that by eliminating or drastically restricting the several rights to individual ownership one by one, ownership by the State will progressively replace ownership by the individual.

Jan 1, 1949

By Franz Simon

Conventional fine gold electrolytes for barrel applications working electrolytically actually permit significant precious metal savings by corresponding optimizations but the most gold is still deposited on areas of the components where it is not absolutely essential for the desired bonding and soldering applications, i.e. in high current density areas. Therefore an electrolyte working electrolessly has been developed which inevitably leads to a much more uniform thickness distribution since in an electroless process there are no areas favoured by metal deposition and current distribution. The new electrolyte will be presented and its performance will be compared with conventional electrolytes as regards thickness distribution. The potential gold savings will be discussed.

Oct 1, 2003

By Maxim Martel, Karolan Tremblay

Westwood Mine has experienced several episodes of increased seismic activity. While current geotechnical characterizations such as RMR, GSI, and Q' index can identify the general rock quality and zones at risk of convergence, they fail in identifying zones at risk of seismic activity. Previous research at Westwood Mine has shown a correlation between seismicity and areas with strong rheology contrasts. To characterize this contrast, 300 UCS tests were analyzed with their associated geochemical data, and statistical analysis and regression were performed using IOGAS software to establish a relationship between resistance and geochemistry. UCS-generated data with XRF results were transferred to Leapfrog Geo to create a block model of intact rock strength. This block model dataset was used to perform a competency contrast block model, and back-analysis of specific seismic sectors at Westwood Mine were conducted to validate the model. The purpose is to develop an established geomechanical tool capable in identifying areas with greater seismic risk associated to a change in the rock strength characteristics. By identifying those areas, mitigation measures can be implemented to minimize impact of seismicity on the operation.

Jan 1, 2023

By DAVID C. MILLER

Barite deposits occur worldwide and in a variety of geological environments. In recent years, several deposits of barite and barite-lead-zinc have been discovered in northern British Columbia, Yukon Territory and Alaska. Most are associated with Devonian-Mississippian age sediments, and many are syngenetic, bedded-type deposits. The Mel is a barite-lead-zinc deposit; it lies within Lower Cambrian strata and appears to be of epigenetic replacement origin. Figure I is an aerial view of the property from the south. Observations herein described are based largely upon field work, megascopic studies and two recent B.A.Sc. theses (Biasucci 1979, Rennie 1979).

Jan 1, 1984

By Lawrence Devon Smith

"This paper examines the impact of the various assumptions that go into an economic evaluation, and shows how these can be combined to show an exciting result that may not really exist. An example of an embellished case (the kind that one frequently sees when projects are being promoted) is developed and the cumulative impact is analysed to show the actual project underneath. The paper also points out some areas to watch for overly optimistic assumptions such as prices, inflation, and debt. The concept of a ""bare bones"" base case is proposed (constant metal prices, constant dollars, no inflation, no debt, no interest, on a project basis, after tax) as a common reference point.As well, the discount rate is examined as a fundamental means of reflecting risk in discounted cash flow evaluations. Current industry practice is discussed, and a methodology for the analysis of risk levels is proposed that assesses the constituent components of the discount rate: real interest, mineral project risks, and country risk.INTRODUCTIONOften, the first time that all of the technical and economic data for a mineral project comes together in one place is when the economic evaluation is developed. This typically happens when work on the project has progressed to a sufficient level of detail that the effort to produce a year-by-year cash flow is justified, usually at the pre-feasibility or feasibility study stage. The data involved will include:• production; tonnes waste and ore mined, ore grade, mining recovery, metallurgical recovery, metal sold• revenue; metal price, smelting & refining charges, marketing costs• operating Costs; mining, milling, administration, fees, royalties• capital Costs; exploration, development, construction, indirect costs (engineering, management), contingencies, start-up, inventories, working capital, replacement and sustaining capital, closure costs• taxes and royalties• exclusions; depreciation (this is not a cash item), sunk costs (only costs going forward)."

Jan 1, 2003

By Ken McIntyre, Trodel Wolf-Dieter

"Sirius Minerals is a UK based fertilizer development company focused on advancing into operation its polyhalite project in North Yorkshire, England. The operation is known as the Woodsmith Mine which has an estimated 2.7 Billion Tonnes of reserves and is currently in the construction phase. DMC Mining Services was selected to carry out the construction of four shafts for the project, a production shaft of 6.75m diameter to a depth of 1594 m, a ventilation shaft of 6.75 m diameter to a depth of 1565 m, and two additional shafts to support the construction of the material transport system (the MTS and Lockwood Beck intermediate) to 360m in depth for servicing the underground conveyor network for transport of product from the mine site to the costal port facilities located at Teasside. This paper will review the status of the project to date and the innovative approaches that DMC is utilizing to ensure a safe and successful shaft sinking project. INTRODUCTION The Woodsmith Mine in North Yorkshire is a Sirius Minerals-owned deep potash and polyhalite mine located near to the hamlet of Sneatonthorpe, Whitby in North Yorkshire, England, approximately 75 km east of York. The area of interest is more than 700 km2. The £3.2 billion project is to develop the Woodsmith Mine to extract polyhalite, and a tunnel system to transport it to a materials handling facility and harbour at Teesside. The site is the world's largest and highest-grade deposit of polyhalite and is expected to produce 20 million tonnes of polyhalite, potash and POLY4 per annum, as well as create over 1,000 direct jobs and many more indirectly. It has the potential to generate over £2 billion of annual exports for the UK. As the project will require mining to be undertaken in the North York Moors National Park, many objections were raised about the mine. Sirius Minerals has gone to great lengths to ensure that the project is sensitive to the local landscape, including: mineshaft head frames that will be positioned below ground to reduce their visual impact; surface buildings will be kept to a minimum; and the entire site will be landscaped and screened by existing woodland to blend in with the surrounding area. The project will also abide by strict environmental limits which govern our activity during the construction phase."

Jan 1, 2019

By A. G. Roach

MILLING of Nova Scotia gold ores began in 1862 with arrastras and wooden stamps and has progressed to heavier stamps followed by tables and other forms of concentration for the recovery of the sulphides. Chlorination and cyanide leaching of the concentrates has been practised, and in 1936 the combined amalgamation and all-sliming cyanidation plant of Seal Harbor Gold Mines was built. It has since been found that it is not necessary to cyanide the full tonnage and now only the concentrates are being so treated. From his experience in this enterprise, the writer presents the accompanying flow-sheet and supporting comments. While he has not the temerity to maintain that it is the best or only flow-sheet for Nova Scotia gold ores, he feels that it warrants thoughtful consideration by members of the milling fraternity of the Province. THE ORE The gold in Nova Scotia ores occurs both free and intimately associated with sulphides-chiefly arsenopyrite. Much of the free gold is quite coarse and crystalline. This is especially true when it occurs in white quartz. When in the slate, it is usually in thin plates and scales, frequently coated and discoloured. The values bound up in the sulphides are not amenable to amalgamation and must be recovered by other methods-concentration, followed by smelting or fine grinding and cyanidation. While high freight and treatment charges apply on concentrates shipped from the Province to smelters, a considerable quantity has been so disposed of in the past. However, it is hoped that a customs cyanidation plant will soon become available to producers of these auriferous concentrates in Nova Scotia.

Jan 1, 1938

By B. A. Watters, G. A. Parslow, F. H. Mcdougall

Carbonate-rich rocks occur at several localities within the Flin Flon volcanic sequence of the eastern Amisk Lake area. The rocks occur in two areas: as a group of small occurrences on islands within Amisk Lake and as two much larger linear belts running parallel to the regional structure east of Amisk Lake. Mineralogically, the rocks consist of talc and Ca-poor ankerite with occasional graphite. Segregation of these minerals and colour variation impart a well-defined planar fabric to the rocks and where the units are fairly continuous (e.g. Mosher Lake), their trend and attitude suggests a concordant relationship to the volcanics. Major and trace analysis of22 samples confirms the presence of two types, with one type being represented in each of the two areas. Most of the elements studied can be used to characterize the two groups, but three elements in particular give a clear separation: Mg, AI and Ni. Recalculation of the major element analyses, on a water and carbonate-f ree basis, indicates that one group (large concordant bodies with high MgO, high Ni and low AI20.J is altered ultrabasic material of peridotitic or dunitic composition. Because no relict igneous material is observed, and the contacts are apparently very sharp, it is possible that the hydration-carbonization process occurred simultaneously with intrusion, .in a closed system. The other group (small occurrences with relatively low MgO, low Ni and high AI203J represents alteration of basaltic rocks. AIthough some analyses suggest the introduction of calcium, as carbonate, along with the volatiles, the major oxides have remained remarkably stable during the alteration process(es).

Jan 1, 1981

By M. R. Julien

"The geomechanical behavior of rocksalt shows very distinctive features. The response of this most ductile of all low porosity rocks is dominated by inelastic processes that are strongly time- and historydependent. These characteristics must be taken into account when analyzing underground openings. Different constitutive models have been proposed and used for this purpose, and this paper presents the general formulation and applications of one of these. The SUVIC model relies on a unified approach with internal state variables producing mixed hardening to represent the inelastic behavior, which lead to specific solutions for plasticity and creep. The model equations have been implemented into a finite element code to perform numerical analyses. Simulations results are presented to show that this model captures essential aspects of rocksalt behavior under simple and complex laboratory testing conditions. Simulations are also conducted to analyze the response of underground openings. INTRODUCTIONPredicting the response of man-made excavations in rocksalt can be quite a challenge as it requires a reliable constitutive model to represent the material behavior. This softest of all low porosity rocks shows a highly non-linear inelastic behavior, very sensitive to history and rate effects (e.g. Senseny et al., 1993; Cristescu & Hunsche, 1997; Julien, 1999; Wittdke, 2014). The many deformation (micro) mechanisms acting locally in rocksalt make the construction of appropriate constitutive equations quite complex. Nonetheless, there have been significant progresses made over the last two decades or so; many of these developments have been included in a series of specialized Conferences Proceedings (Ghoreychi et al., 1996; Aubertin & Hardy, 1998; Cristescu et al., 2002; Wallner et al., 2007; Bérest et al., 2012)."

Jan 1, 2015

"The Australasian Joint Ore Reserves Committee (JORC), which is sponsored by the Australian mining industry and its professional organisations, developed the JORC Code to provide minimum standards for public reporting. JORC was first published in 1989 and later incorporated into the Listing Rules of the Australian and New Zealand Stock Exchanges making compliance mandatory for listing public companies in Australia and New Zealand."

Jan 1, 2003

By J. Reinhardt, R. Uken, S. S. Chinnasamy

Au mineralization in the Kilpwal Gold Mine is confined to laminated quartz-carbonate lodes and associated alteration along the Klipwal Shear Zone (KSZ) in the upper Mozaan Group of the Mesoarchaean Pongola Supergroup. The brittle-ductile shear zone is characterized by inner and proximal hydrothermal alteration domains that are comprised of chlorite, epidote, sericite, pyrite, arsenopyrite and gold. Possible sources of gold are: (i) paleo-placer U-Au rich conglomerates from the lower Mozaan Group; (ii) the underlying mafic volcanics of the Nsuze Group; (iii) greenstone belts in the basement to the Pongola basin. Post-Pongola granites probably provided the heat to mobilize auriferous fluids into the KSZ.

Jan 1, 2011

By R. J. Labine, D. I. Brisbin, R. Roussain, P. R. Coad

"Abstract - The Owl Creek Mine is located near the west end of the Neo-archean Abitibi greenstone belt, 17 km northeast of Timmins, Ontario, and 4 km north of the Destor Porcupine fault. Gold occurs in epigenetic quartz veins and their pyritic wallrocks in two zones within a package of east striking, steeply north dipping, volcanic and sedimentary rocks. At the West Zone, 1 729 603 t of ore with a grade of 4.83 g/t Au (268 587 troy oz.) were produced from an open pit centered on a wedgeshaped unit of Tisdale Group basalt that occurs between two overturned, south facing units of Porcupine Group graywacke and argillite. Basalt/graywacke contacts are locally marked by graphiticcarbonaceous argillite, strike-parallel faults and massive quartz veins.Deformed quartz+/-ankerite veins occur along the graphitic sedimentary/volcanic contacts and in gently to moderately dipping fractures in basalts, and, to a lesser extent, in graywackes. Veins also occur sub-parallel to steeply dipping 070° foliation. Altered host basalts are composed of iron carbonate, sericite, quartz, carbon, chlorite and disseminated pyrite. Gold occurs as inclusions in pyrite, and less commonly as free gold in fractures and along graphite-quartz grain boundaries in quartz veins. Fractures preferentially developed in more competent basalts during pre- to syn-ore deformation are interpreted to have provided the permeability required for emplacement of mineralized quartz veins. Carbonaceous basalt/graywacke contacts further enhanced gold deposition by acting as chemical traps. The interaction of hydrothermal fluids with these carbonaceous sedimentary rocks led to the characteristic local darkening of host basalts due to carbon impregnation and chlorite development."

Jan 1, 1998