McGill University Thèses et mémoires publiés en 2004

Wind generation has become the most important alternate energy source and has experienced increased growth in Europe during the past decade while more recently, the same trends have been exhibited in North America. Although it has great potential as an alternative to less environmentally friendly energy sources, there are various technical challenges that cause wind to be regarded negatively by many utilities. Others are hesitant to accept its widespread implementation, particularly when the penetration of wind in a given area is high. This work presents the addition of an energy storage system to a wind turbine design. Various advantages are …  Lire la suite

A phantom-embedded extrapolation chamber (PEEC) made of Solid Water(TM) was used for studying the buildup region of megavoltage radiation beams. We investigated the polarity effect produced in the PEEC and found that radiation induced currents, called the Compton current, were the dominant cause of the polarity effect in the PEEC. In the dose build-up region of megavoltage photon beams, the collecting electrode is the primary Compton current source and the magnitude of the current depends on the measurement depth, field size, and photon beam quality. The connecting cable acts as a secondary Compton current source that produces a very small …  Lire la suite

This dissertation studies three aspects of airfoil flows: (i) second-order theoretical solutions of airfoils in steady flows; (ii) unsteady solutions for oscillating flexible airfoils; and (iii) numerical analysis of airfoil flows at low Reynolds numbers. The first part presents simple and efficient analytical solutions in closed form for the velocity and pressure distributions on airfoils of arbitrary shapes in steady flows, which are obtained using special singularities in the expression of the fluid velocity. A second-order accurate method is first developed for airfoils in inviscid incompressible flows to simultaneously solve the symmetric and anti-symmetric flow components defined by coupled boundary …  Lire la suite

This thesis analyzes some potential applications of kinetic energy (KE) storage systems in power systems operation. The goal was to take advantage of the KE stored in the existing rotating machines in a power system such as synchronous generators and motors by "borrowing" some of the stored KE when electricity prices are high and "returning" this energy to the rotating masses when the prices are down. As shown in this thesis, this operation can be performed from the control center by optimally scheduling the set points of the generators under automatic generation control (AGC) over a given time horizon. This …  Lire la suite

The National Policies of Education in India have recognized the need for teacher professional development. However, science teachers continue to look for innovative methods to improve teaching. Through collaborative action research with four science teachers at a girls' school in Hyderabad, India, the study explored conditions that enhance or inhibit the implementation of constructivist instructional methods. Data were collected through interviews, reflective memos, research journal, collages and found poetry. The study found that teacher background and experience, teachers' views on science education and the school environment played a role in teacher development. The use of constructivist instructional strategies affected teachers' …  Lire la suite

Soil properties and their spatial variability was measured to provide a strong database to assess the modification in soil properties associated with future changes in land use. Surface (0--10 cm) soil samples were collected from a 9 ha, 46-year-old pasture being converted to a native tree plantation and a neighboring control pasture near Sardinilla, Panama. A small-scale nested grid of surface soil samples was replicated in the future plantation and a primary forest in the region to evaluate the spatial variability of soil properties. Seven 1 m profiles were sampled in the future plantation and litter samples were collected at …  Lire la suite

Arab Canadians are a heterogeneous and frequently misunderstood group whose educational background and cultural heritage have received little attention in the scholarly literature. In multicultural Canada, educators, curriculum developers, textbook authors and policy makers rely on available literature to inform their decision-making processes. Mainstream media, as a source of information and insight, do not fill this need. In this inquiry, I examine the cross cultural and educational experiences of ten Arab undergraduate students in two English-language universities in Montreal. Participants were from Libya, Tunisia, Algeria, and Morocco and have been in Canada for three to seven years. Classic qualitative methodological …  Lire la suite

The development and growth of new communication services and emerging applications requires high-performance access networks capable of providing high-bandwidth interconnections to end-users. In recent years, optical code-division multiple access (OCDMA) has been proposed as a means for providing flexible access to high-bandwidth applications and offering different levels of quality of service. This thesis explores the impact of encoder/decoder mismatch on system performance for 2 dimensional wavelength-time (2D lambda-t) OCDMA and the implementation of a multi-user 2D lambda-t OCDMA direct detection demonstrator system. Our analysis and experimental demonstrations are based on depth-first search codes (DFSCs) which have previously been shown to …  Lire la suite

The construction of phylogenetic trees commonly uses molecular sequence data (DNA, RNA or amino acid sequences) for a single gene family over a set of n extant taxa. However, difficulties arise when the phylogenetic gene tree for one gene family disagrees with the phylogenetic gene tree for a different gene family. Several computational problems arise when trying to explain this disagreement (the two gene trees are not equal). Typically, one assumes a (simplified) model of evolution restricted to a small set of events which are assumed to cause the disagreement. Two such well-studied events are gene duplications and lateral gene …  Lire la suite

Motivation : l'anisotropie invariante d'échelle est mise en évidence dans des images de nuage. Même si ces images paraissent les mêmes dans toutes les directions, des structures anisotropes peuvent s'observer à différentes échelles. Méthode de mesure de l'anisotropie invariante d échelle : une méthode simple de visualisation et de mesure des exposants de base de l'anisotropie invariante d'échelle dans toutes les directions est proposée pour le cas d'anisotropie légère. Des images des satellites MODIS sont utilisées pour mesurer l'anisotropie invariante d'échelle sur des champs de nuages. Principaux résultats : une variation douce de l'exposant de la fonction de structure avec …  Lire la suite

This thesis explores new methods of representing the electromagnetic forces in any electromechanical or electromagnetic devices using "off-the-shelf" equipment. It also explores the usefulness of these methods in the design process of such devices and in the understanding of electromagnetic forces. Finally, the thesis concentrates on an investigation of haptics as a new method of allowing the user to 'feel' the electromagnetic forces. The thesis describes the design of a system that involves the software development of Graphical User Interface (GUI) to represent the design, with its electromagnetic flux lines, together with a choice of a commercial haptic device to …  Lire la suite

Computer simulations play an important role in the design and verification of space robotic operations since on-orbit tests are impossible to conduct before launch. Thus, accurate computer modelling and simulation of space robotic tasks is essential. Of particular difficulty are space manipulator operations, which involve constrained or contact tasks. Here, the contact dynamics capability in the modelling tools becomes critical for high fidelity simulation. This in turn implies a need for accurate determination of contact parameters, which are used as inputs to contact dynamics simulation. In this work, the identification of contact dynamics parameters based on sensor data obtained during …  Lire la suite

Exposure of males to drugs or environmental chemicals can alter reproductive health and affect progeny outcome. The quality of the male germ cell is determined in part by the presence and function of stress response mechanisms. During spermatogenesis, different germ cell types display differential susceptibility to toxicants, suggesting there is variation in the presence and function of stress response mechanisms. Exposure of male rats to cyclophosphamide, a commonly used anticancer and immunosuppressive drug, alters male fertility and progeny outcome in a male-germ cell phase specific manner. The hypothesis of this thesis is that stress response mechanisms are differentially expressed during …  Lire la suite

There is growing consensus that health-related quality of life (HRQL) outcomes are important for the allocation of scarce medical resources and for facilitating clinical decision-making. However, because most instruments of HRQL are self-report measures inappropriate conclusions may be drawn from studies that assess changes in HRQL over time or between groups. If the individuals evaluating themselves experience a response shift (defined as changes in their internalized standard of evaluating their level of functioning, in their values, or in their conceptualization of the target construct), then measures taken over time or between groups are no longer comparable. To date, response shift …  Lire la suite

The heating, or sheet reheat, phase in thermoforming is the focus of this work. The first objective is to develop a reliable state-space model of this process for simulation analysis. The second objective is to develop a simple linear real-time in-cycle controller for the sheet reheat phase. This controller will improve part quality, decrease energy expenditures and machine wear, and optimize heating time by assuring a desired sheet temperature distribution. The final result is a reduction in production cost per part for the thermoforming industry. A sheet model is developed from first principles, and improved through the addition of energy …  Lire la suite

The Cyclic Nucleotide Binding Domain (CNBD) is conserved in a number of ion channels that belong to three distinct families, the Ether-A-Go-go (EAG); the Cyclic Nucleotide Gated (CNG) and the Hyperpolarization activated Cyclic Nucleotide modulated (HCN) channel families. Extensive biophysical characterizations have established that the function of these channels is directly modulated by cyclic nucleotides in a manner independent of kinase activity and channel phosphorylation. However, the role for this domain in the EAG family is unclear. In addition, although the biophysical properties of CNBD-containing channels are well understood, little is known about the biogenesis of these channels. The original …  Lire la suite

This thesis shows that series capacitive compensation of transmission lines by a combination of Static Synchronous Series Compensator (SSSC) and dielectric capacitors lowers the cost of series compensation. The SSSC has two functions: (1) to provide some series capacitive reactance compensation; (2) to damp out incipient unstable Subsynchronous Resonance (SSR) modes. Digital simulation using HYPERSIM shows that for an overall capacitive depth of compensation of 0.7 pu, the SSSC component is only about 1/3 of the capacitive Mvar. Based on the transient stability limit, the transmissibility of the line is increased by a factor of 2.23 for a depth of …  Lire la suite

In recent years there has been considerable interest in the development of microwave-based food processing technologies. Microwave radiation is considered to have both thermal and non-thermal effects. The thermal effects are related to the heat generated by the absorption of microwave energy by water or by organic molecules, but very little is known about the mechanisms involved in the putative non-thermal effects. It has been postulated that the latter could involve a direct energy transfer from the electromagnetic field to the vibrational modes of macromolecules, altering their conformation. In the present study, the non-thermal effects induced upon irradiation of protein …  Lire la suite

One critical issue in chloride hydrometallurgy is the regeneration of the lixiviant HCl that is commonly achieved by pyrohydrolysis. It is the scope of this thesis to investigate a low temperature HCl regeneration process, which regenerates HCl and produces saleable gypsum. Experiments were performed to determine the optimum conditions of the chemical reaction that involved the reactive mixing of calcium chloride (CaCl2) solution with sulfuric acid (H2SO4) solution at low temperature and atmospheric pressure. The results showed that the crystallization chemistry of the CaCl 2-H2SO4 reaction can be controlled in such away that favors the production of well grown gypsum …  Lire la suite

Task uncertainty and noise---generically referred to as uncertainties in the thesis---in the design and operation of robotic mechanical systems pose a major challenge to the designer. The aim of this thesis is to contribute to the laying down of the foundations on which the design of robotic mechanical systems, in the presence of uncertainties, is to be based. Uncertainties are accounted for by means of robustness. To this end, a theoretical framework as well as a general methodology for model-based robust design are proposed. Within this framework, all quantities involved in a design task are classified into three sets: the …  Lire la suite

Material characterization is a very important tool needed to describe and enhance material mechanical properties and to develop optimum material chemistries and microstructures. The usual approach of achieving the above using extensive experimental methods has been shown to be expensive and time consuming. This led to the development of the micro mechanical modeling, which can be used to predict the material behavior without the need for the extensive experimental investigation and is based on microstructural characteristics of the material. In this work, a micro mechanical model is developed to predict the mechanical properties of dual phase steels consisting of martensite …  Lire la suite

A new methodology is proposed to solve the runner balancing problem. The proposed methodology avoids problems associated with the traditional approach. The issues associated with runner balancing and the effects of design variables and processing conditions are evaluated. A general methodology for the robust optimization of a practical industrial problem is also developed. The runner balancing problem is optimized employing deterministic and robust schemes and the results were compared and analyzed. This provided insight into robust runner system design. Finally, an existing constrained genetic algorithm, the superiority of feasible points method is modified to include infeasible solutions in the search, …  Lire la suite

Six full-scale reinforced concrete corbel specimens were tested to study the influence of steel and polypropylene fibres, headed bars, and horizontal loading on their responses. The experimentally determined capacities were compared with predictions using simplified and refined strut-and-tie models, with the refined models providing better predictions of the capacities. The experimental study demonstrated the beneficial use of fibres in reinforced concrete corbels, that is a reduction in the number and the width of cracks at service loads. Headed bars provided excellent anchorage of the main tension tie reinforcement and eliminated the need to weld bearing plates to the reinforcement, as …  Lire la suite

Dose predictions by Monte-Carlo (MC) techniques could alleviate the measurement load required in linac commissioning and clinical radiotherapy practice, where small or irregular electron fields are routinely encountered. In particular, this study focused on the MC calculation of cutout factors for clinical electron beams. A MC model for a Varian linac CL2300C/D was built and validated for all electron energies and applicators. A MC user code for simulation of irregular cutouts was then developed and validated. Supported by a home-developed graphical user interface, it determines in situ cutout factors and depth dose curves for arbitrarily shaped electron fields and collects …  Lire la suite

The notion of foreseeability is at the heart of contracts and is based on the notion of corrective justice with a normative content. The quantum of damages should represent the obligational content of the contract. The analysis of foreseeability shows the importance of reasonable expectations and implied obligations. The notion brings to light criteria which are congruent with the criteria of certainty and predictability underlying the rule of law.  Lire la suite

Dawson, Don (Supervisor)  Lire la suite

There is a need to enhance our understanding of the corrosion mechanisms and their effect on the level and loss of prestressing forces. This research program consisted of accelerated corrosion tests on eight prestressed concrete prisms, measuring 127 x 127 x 2,060 mm, with three different levels of prestress (0, 30, and 60% of the ultimate strength of prestressing strand). The aim of the investigation was to simulate and monitor the corrosion of prestressing strands in prestressed systems. The specimens were submerged in a saline solution and subjected to an impressed constant voltage, aimed at accelerating the corrosion of the …  Lire la suite

Solution methods for MDPs employing approximation allow for more acceptable computation time in domains with large state spaces. In this thesis we discuss the use of a metric based on the notion of bisimulation for solving MDPs described in a factored form. We propose an algorithm for performing state aggregation using this metric, and illustrate its performance on a standard benchmark domain.  Lire la suite

This study explores the relationships between the integration experiences of adolescent newcomers in one francophone secondary school in Montreal and the current policies and programs related to educational integration. The research draws on observations and participants' descriptions and insights to address three principal questions: How is integration experienced by adolescent newcomers in a francophone school in Montreal? How do these students' experiences inform our understanding of the relationships among host (second) language learning/teaching, integration, and identity construction? What are the implications of these newcomer students' integration experiences for educational theories, policies and programs/practices that target such newcomers? These questions emerge …  Lire la suite

In this thesis, I describe how interactive journal writing was used to improve the understanding of mathematics, and to foster communication with two groups of remedial grade ten students. Mathematics is a gatekeeper course in high school, and students who are not successful with this subject are at a distinct disadvantage, both in terms of their education and in their future careers. A persistent source of difficulty for these students is related to language; students often struggle both to understand what is being taught, and how to explain concepts or problem solutions in their own words. Interactive journal writing was …  Lire la suite

The accumulation of eosinophils at sites of inflammation is one of the hallmarks of asthma. The aim of the present study was to investigate the involvement of PGD2 and the DP1 and DP2 receptors in eosinophil recruitment in vivo. In this project, a group of Brown Norway rats were administered intratracheally with PGD2, which activates both DP1 and DP2 receptors, as well as selective agonists of DP1 (BW245C) and DP2 (15R-methyl-PGD 2 and 13,14-dihydro-15-oxo-PGD2) receptors. In addition, we have also tested the effect of 15-deoxy-Delta12,14-PGJ 2 which known to activate PPARgamma and NF-kappaB, and DP2 receptors. Negative control animals received …  Lire la suite

In brain mapping, the regions of the brain that are 'activated' by a task or external stimulus are detected by thresholding an image of test statistics. Often the experiment is repeated on several different subjects or for several different stimuli on the same subject, and the researcher is interested in the common points in the brain where 'activation' occurs in all test statistic images. The conjunction is thus defined as those points in the brain that show 'activation' in all images. We are interested in which parts of the conjunction are noise, and which show true activation in all test …  Lire la suite

Recent studies have demonstrated that applied hydrostatic pressure can affect the functional properties of whey protein isolate (WPI). In this work, the effects of applied hydrostatic pressure on the tertiary and secondary structure of whey proteins were investigated by spectroscopic and rheological techniques to elucidate the molecular basis of such pressure-induced changes in protein functionality. The individual protein components of WPI and various samples of WPI obtained from different sources were subjected to different single-cycle pressure treatments of up to 400 MPa in 100 MPa increments with 30-min holding time as well as to pressures ranging from 450 to 650 …  Lire la suite

The search for extraterrestrial life begins with understanding how life developed and evolved on our own planet. Earth's polar regions provide a unique setting conducive to developing the methodologies and techniques that will be needed to find new life forms either as living organisms or as some biological signal in a sedimentary record. The highest latitude perennial spring system in a region of thick, continuous permafrost resides in the Arctic archipelago of northern Canada. At Expedition Fiord on Axel Heiberg Island there are two sets of springs that provide useful analogs to liquid water habitats that may have existed on …  Lire la suite

This thesis presents a study of the validity of video portfolios as an assessment tool. For this study, first and second grade students were videotaped doing exercises four times in reading and four times in math over the course of a school year. After portfolios were collected, each set of four videos (either math or reading) was shown to teachers in random order. The teachers were asked to put the clips into the correct chronological and, therefore, developmental order. Interviews after the task investigated the criteria teachers used to order the clips, and found that they used task complexity, task …  Lire la suite

For some time now, Article 2061 of the French Civil Code had laid down the general principle that arbitration clauses were invalid. In 2001, an amendment to Article 2061 reversed the concept, so that the former principle became the exception and the law was made to favour arbitration. While the reform was a progressive step, it did leave some ambiguity especially concerning the consumer disputes. Arbitration is indeed a very convenient alternative dispute resolution method in this arena. The purpose of this thesis is to address some of the issues related to consumer disputes. It seeks to demonstrate that by …  Lire la suite

The extreme susceptibility to infection with Salmonella Typhimurium of wild-derived MOLF/Ei has been linked to one chromosomal region (Ity3). Toll-like receptor 5 (Tlr5) is located within the Ity3 interval and its candidacy as a Salmonella-susceptibility gene was evaluated in vitro and in vivo by comparing the Tlr5 C57BL/6J and MOLF/Ei alleles (85). In vitro studies using NF-kappaB-dependent reporter genes showed that sequence variants found within the coding region of MOLF/Ei Tlr5 did not affect the response of Tlr5 to flagellin compared to C57BL/6J. MOLF/Ei promoter had a slightly stronger basal activity than the C57BL/6J allele. In vivo study using Ity3 …  Lire la suite

Swine manure creates much public resentment in Quebec due to nutrient overloading, potential water pollution and odour. Anaerobic digestion is one of the solutions that allows to lessen the odour problem. Anaerobic bacteria in manure produce methane. The latter can be burnt to produce heat and electricity on farms. Moreover, there is a potential for receiving carbon emission reduction credits for the capturing of methane. Investment analysis was performed to assess the economic feasibility of a potential anaerobic digestion system on a grower-to-finisher hog operation. The study was conducted for a case farm, which had plans to expand from 2000 …  Lire la suite

Tumbling mills, which consume around 6% of world's electric power, though inefficient (use 1% of the supplied energy) have been used in mineral processing industry for over a century. Harsh internal mill environments have prevented the access to in-mill dynamics. This situation has led researchers to develop models based on the Discrete Element Method (DEM) to predict internal mill dynamics. But before DEM models can be used in the mineral processing industry, their rigorous validation is essential. In this thesis, we have carried out real time analysis of the DEM model to enable online availability of the mill parameters for …  Lire la suite

Previous research has shown that Japanese-speaking 20-month-old children associate novel words with objects over actions when the words are presented as a single word. This study investigated young Japanese children's ability to use verb morphosyntactic cues in input to form associations between novel words and actions using a habituation paradigm with a switch design. Sixteen 20-month-old Japanese children were habituated to novel words in a verb syntactic frame paired with movies that show novel objects engaging in unfamiliar actions. The children were then tested with three trials in which one of the original word, object, or action was switched. The …  Lire la suite

The purpose of this study was to examine what a national public science educator does when attempting to educate the general public. This investigation was conducted with the goal of expanding the literature on the treatment of science in multimedia to include descriptive work on whom the general public goes to learn science. The science educator's work in radio, television, and print were explored through interview and content analyses with themes and patterns emerging. The educator appeared to apply a loose formula of keeping a finger on the public's pulse, exhibiting scientific rigor, using variables and techniques such as props …  Lire la suite

The biocatalysis of a crude chlorophyllase extract, obtained from the biomass culture of Phaeodactylum tricornutum, in neat organic solvent media was investigated. The addition of selected excipients, including crown ether (enzyme:crown ether, 135:1--2.7:1, w/w), dextran (enzyme:dextran, 1:2--1:0.25, w/w), Span 40 and Span 60 (enzyme:Span, 1:2, w/w) and sodium bis (2-ethylhexyl) sulfosuccinate (enzyme:AOT, 1:12.6, w/w), to the crude solid enzyme preparation decreased the chlorophyllase activity. The effects of selected parameters, including solvent hydrophobicity (Log P, 2.40--4.45), initial water activity (aw, 0.44--0.97), agitation speed (0--200 rpm), reaction temperature (25--45°C) and enzyme concentration (1.67--5.3 mg solid enzyme/mL) on chlorophyllase activity, were investigated using …  Lire la suite

The superior mechanical properties of carbon nanotubes would make them excellent candidates for the next generation of composite materials. Researchers have tried to demonstrate the potential of that novel material with various degree of success. In order to complement the experimental efforts in this new field, the modeling of these new material systems is required. One challenge when modeling nanotube composites is the large scale span between the nanotube itself and the final component. The present study focuses on the creation of a framework and methodology to span three orders of magnitude in scale with interconnected models that relate performance …  Lire la suite

String theory is to date the best candidate for the "theory of everything" which would describe all four fundamental interactions, including gravity, on the same footing. The general description of black holes and other spacetimes with horizons remains a key aspect of quantum gravity that must be addressed by a consistent theory, such as string theory. Also, the resolution of singularities is a fundamental problem in a quantum theory of gravity. At the same time, the recent revolution in observational cosmology creates a pressing need to accommodate fundamental issues such as cosmic acceleration and cosmological horizons within the framework of …  Lire la suite

The study explores trainee teachers' perceptions and experiences of sexual harassment in Teacher Training Institutions in Ghana. Guided by the research literature on sexual harassment and a feminist framework, the study seeks to understand how sexual harassment and its subtleties are experienced by trainee teachers in Ghana. It particularly throws light on the coping strategies of these trainee teachers in different sexual harassment scenarios. The study also seeks to increase awareness of sexual harassment in the Teacher Training Institutions and the population at large. This study is also a contribution to the scanty literature in the area of sexual harassment …  Lire la suite

This qualitative research project explores the multicultural awareness development of white counsellors. Participants for this study consisted of 16 multiculturally competent counsellors. The data was analyzed using grounded theory methodology. Early personal experiences with differences in which they were sensitized to social injustices were the most important contributor to their multicultural awareness development. This factor appeared to lay the foundation for an ongoing personal initiative to develop multicultural awareness in which they maximized what they could learn from their culturally diverse clients, work environments, coursework, supervision, and mentoring opportunities. Their personal initiative also inspired them to persevere despite the difficult …  Lire la suite

Integrals of products of unitary matrix elements over the unitary group will be discussed. A group theoretical formula is available to convert them into multiple sums, but unfortunately the latter are often tedious to compute. In this thesis, we develop an alternative method in which these sums are avoided, and group theory is rendered unnecessary. Only unitarity and the invariance of the Haar measure are required for the computation. Then, we return to the more traditional group theoretical approach, and compare its strengths and weaknesses with those of our invariant method. As a result, we are able to introduce another …  Lire la suite

This thesis examines the character of the unhappy bride in three French novels of the 19th century: Le Lys dans la vallee (1836) by Honore de Balzac, Madame Bovary (1857) by Gustave Flaubert and L'Assommoir (1877) by Emile Zola. It compares the heroines' tragic destinies based on the following points: childhood; education; marriage; the philosophy of love and psychology; and escapism and death. We are shown that it is education that leads to the philosophy of love, which is filled with ideas of platonic love, and that unhappy marriages involve compensation. Research by psychoanalyst Karen Horney is applied to the …  Lire la suite

The Finite Element and Finite Difference methods are both widely used in estimating magnetic field solutions. Both methods are based on refining an initial estimate oft a solution using an iterative process; unfortunately, this rarely contains knowledge of the most likely correct solution, which has the potential of reducing the iteration time. Feed-forward neural networks may provide the bridge to provide the initial estimate. This thesis reviews the basic framework of feed-forward neural networks, specifically Multi-Layered Perceptron (MLP) networks and Basis Function networks, which are, in turn, subdivided into Radial Basis Function (RBF) networks and Wavelet Basis Function (WBF) networks. …  Lire la suite

The El Mochito mine, located in west-central Honduras, exploits a distal Zn-Pb-Ag skarn-hosted deposit. The bulk of economic mineralization, occurring either as steeply dipping pipes or flat-lying manto bodies, is hosted by Cretaceous Atima Formation limestone. Skarn mineralogy consists of early grossularitic garnet followed by andraditic garnet and hedenbergitic pyroxene, with pyroxene skarn the principal host to sphalerite mineralization. Ore minerals, which post-dated silicate precipitation, comprise sphalerite of variable Fe content, galena, magnetite, pyrrhotite, chalcopyrite, pyrite and trace amounts of arsenopyrite. The distribution of ore metals in the orebodies is zoned from Zn-Fe-rich cores to adjacent Pb- and Ag-rich zones …  Lire la suite