Thesis (M. Sc.)--University of Alberta, 2009. / Title from PDF file main screen (viewed on Sept. 4, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Earth and Atmospheric Science, University of Alberta." Includes bibliographical references.

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Porphyry copper and molybdenum deposits in west-central British Columbia are associated with plutons of Late Cretaceous and Tertiary age which intrude Mesozoic volcanic and sedimentary rocks of the Intermontane Tectonic Belt. The porphyry deposits are contained in an area bounded on the west by granitic rocks of the Coast Plutonic Complex, and on the east and southeast by a belt containing Mesozoic granitic stocks and an extensive area of Tertiary volcanic rocks. The porphyry intrusions take the form of small stocks, plugs , dykes, and dyke swarms generally not exceeding 1 square mile in surface area. The intrusions are commonly multiple and range in composition from quartz diorite to granite. Copper and molybdenum sulphides occur as fracture fillings and as veinlet stockworks within and adjacent to the intrusive bodies. Sulphide and alteration minerals exhibit concentric zoning patterns. Volcanic and sedimentary rocks marginal to the intrusions are thermally metamorphosed to biotite hornfels. Results of potassium-argon dating indicate four crudely parallel north to northwest-trending belts of porphyry intrusions, each being distinctive in age, rock composition, and contained metallic mineralization. From west to east these include: (1) Alice Arm intrusions - 50 m.y. molybdenum-bearing quartz monzonite and granite intrusions; (2) Bulkley intrusions - 70 to 84 m.y. copper-molybdenum and molybdenum-bearing porphyries of granodiorite to quartz monzonite composition; (3) Nanika intrusions - 50 m.y. copper-molybdenum and molybdenum-bearing intrusions of quartz monzonite composition; (4) Babine intrusions - 50 m.y. copper-bearing intrusions of quartz diorite and granodiorite composition. Potassium-argon analyses were carried out mainly on biotite separates from the mineralized porphyry phases within the deposits. Dating of inter-mineral and post-mineral porphyry phases, common at many of the deposits, yielded ages equivalent to, or 2 to 3 m.y. younger than, the mineralized phases, indicating that the age of mineralization is essentially synchronous with the age of intrusion. Limits of analytical errors in these potassium-argon analyses are within 3 per cent of the calculated ages. The distribution of potasslum-argon ages for porphyry deposits in west-central British Columbia does not fit the plate tectonic theories proposed for the origin of similar deposits elsehwere in the Cordillera of North and South America, in which deposits are progressively younger in a given direction. Here, four crudely parallel belts of porphyry intrusions display a reversal in age from 50 m.y. to 70 - 84 m.y. to 50 m.y. in an eastward direction. This distribution of ages may have been caused by periodic movement from Late Jurassic to Tertiary time along a subduction zone beneath the Coast Plutonic Complex which forms the west border of the area containing the porphyry deposits. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Molybdenum is a versatile alloying and refractory metal of strategic importance. In India almost all molybdenite is obtained currently as st byproduct from copper and uranium deposits. The present Indian production is only about 66 tonnes while the demand is over 1000 tomes. It thus becomes important to explore newer deposits of molybdenum and develop efficient beneficiation strategies to recover the metal. A potential source of primary rnolybdenite has been found in the Ham area of Dharmapuri district in Tamil Nadu. In the present investigation, taking into consideration the importance of the problem beneficiation studies have been undertaken on core - drill molybdenite ore samples from the Hanu area. Initially, detailed characterization of the molybdenite ore has been carried out with respect to its mineralogy and chemical composition. The X-ray diffkactogam of the ore has also been recorded These studies have indicated that quartz and sericite are the major minerals followed by carbonates and feldspar. Among the sulphide minerals, pyrite is dominant with trace amounts of galena, sphalerite, chalcopyrite and molybdenite. The molybdenum content in the ore sample has been determined to be about 0.1%. Liberation studies have revealed that molybdenum is more or less uniformly distributed in the different size fractions from 1.7 mm down below to 75 microns. However, mineralogical analysis of the different size fractions has indicated that about 85% of the molybdenite is liberated. from associated silicate and carbonates below 2 12 microns. The results of the flotation kinetic tests have shown that percentage recovery and grade of molybdenum foLZow an inverse relationship with time. Studies carried out to evaluate different reagent - combinations, reveal that optimum values of grade and recovery could be achieved using kerosene and M1IBC. Further, these studies have shown that flotation time of 4 minutes is adequate, as beyond this time the grade of molybdenum is found to deteriorate. Detailed mesh-of-grind studies have indicated that 20 minutes of grinding yields optimum values of molybdenum and lead in the float product and this time was fixed for all subsequent experiments. Preliminary experiments conducted to evaluate djfferent depressants for galena have shown that satisfactory results are obtained only with sodium dichromate. Optimisation studies performed to arrive at the dosage of sodium dichromate have shown that the addition of 0.25kg/t of sodium dichromate gives optimum results with respect to overall recovery and grade of molybdenum, copper and lead in the float and tailing fractions. In a similar manner, the optimum dosage of kerosene (collector for molybdenite) has been arrived at to be 0.8kg/t taking a holistic view of the grades and recoveries of the different metal values of interest. Based on the studies carried out with respect to optimization of the mesh-of-grind, depressant and collector concentrations, it became apparent that a grade of about 0.8% Mo only could be achieved with over 80% recovery. The redeeming feature however was that over 90% of the feed could be rejected at the rougher flotation stage itself with a negligence loss of about 0.02% Mo in the tailings. It was thus considered logical to further upgrade the Mo content by regrinding. An extensive flotation campaign was therefore mounted, adopting the following strategies: (1) Ist stage regrinding and one cleaning (2) IInd stage regrinding and three cleanings (3) IIIrd stage regrinding and two cleanings Based on the first stage regrinding tests it was found that by regrinding to 100% passing 106 microns, the Mo assay could be enhanced to over 32% from a initial value of about 0.1% in the feed. The enrichment ratio at this stage corresponds to about 340.After the second stage regrinding followed by three stages of cleaning, close to 75% recovery of Mo with an assay value of about 52% could be achieved, further enhancing the enrichment ratio to about 540. A few experiments were conducted using sodium cyanide during second stage regrinding tests and it was found that copper assay could be brought down to 0.3% from about 0.8%, without affecting the grade of lead and molybdenum. The results of the third stage regrinding tests have highlighted that a final concentrate assaying about 55% molybdenum with over 70% recovery could be obtained. It is worthy to mention that the concentrate so produced meets the specification of metallurgical grade molybdenite. The overall enrichment ratio obtained, commencing from a feed assaying 0.1% Mo, corresponds to about 580. In order to explore the efficacy of organic depressants, which are more acceptable on environmental grounds, detailed flotation studies were carried out using dextrin with particular emphasis on galena depression. A series of experiments was carried out in an identical manner to those conducted using sodium dichromate. Here again, three stages of regrinding/cleanings test where carried out, akin to those performed using sodium dichromate. A dextrin concentration of 0.01 kg/t was found to be an optimum value from the point of grade, wt. % recovery and distribution of molybdenum, lead and copper in the cleaner concentrate. It is noteworthy that after second stage regrinding followed by four stages of cleaning, the molybdenum assay value has significantly improved from 16% to about 53% with over 70% recovery. Another notable feature is that copper content in the concentrate is only about 0.2% even without the addition of sodium cyanide. The results of the third stage regrinding/cleaning tests have shown marginal improvement in the molybdenum assay values without affecting the grade of copper and lead. On a comparative basis, it can be inferred that dextrin holds promise to be used as a potential substitute for the inorganic depressants such as sodium dichromate and sodium cyanide. On the basis of the extensive investigations carried out on the beneficiation of molybdenite ore, a comprehensive flowsheet has been developed.

In recent years our understanding of the genesis of porphyry copper systems has advanced to a sufficient level to be able to construct predictive models that enhance exploration for these deposits. Our understanding of primary and secondary geochemical dispersion around these deposits is not so advanced as variables such as climate and topography cause geochemical patterns to be distorted or masked at surface with the result of different deposits having quite different geochemical characteristics. In this study the geology and geochemistry of a porphyry copper-molybdenum from the Canadian Cordillera is examined with the aim of demonstrating how primary geochemical patterns are affected by the development of a supergene enrichment blanket and leached capping. Topographic controls on the extent of leaching and supergene enrichment are also explored. The Berg porphyry copper-molybdenum deposit is in the Tahtsa Mountain Ranges, approximately 84 km southwest of Houston, central British Columbia. Mineralized zones are centered on a circa 50 Ma composite quartz monzonite stock. Hydrothermal alteration zones are similar to those of the classic model by Lowell and Guilbert. Central zones are potassic (orthoclase and biotite) while peripheral zones are propylitic (chlorite, epidote, carbonate). Intense phyllic alteration (quartz, sericite, pyrite) occurs at the north and south margins of the stock. Hypogene mineralization (characterized by pyrite, chalcopyrite and molybdenite) is concentrated in an annular zone straddling the quartz monzonite contact. Best grades are localized in altered quartz diorite and altered and hornfelsed Telkwa Formation (Hazelton Group) volcanic rocks at the east side of the deposit. The nature of these altered hornfelsed rocks has been a subject for much debate in previous studies. One school of thought suggests that they are part of a hornfels aureole associated with the quartz diorite. Others suggest that it is an alteration zone associated with the quartz monzonite stock. Thirteen diamond drill holes on a north south cross section of the deposit were logged (GEOLOG) and sampled. Outcrop samples were collected where possible close to each drill hole. Major elements were determined by XRF, trace metals by flame AAS and fluorine by specific ion electrode. A sequential extraction was used to study the distribution of copper between different host minerals. The origin of the hornfelsed rocks is solved by field mapping and geochemistry. In the field cross cutting relationships show that the quartz diorite predates the stock and that the hornfels zone is spacially related to it. Major element binary and ternary plots demonstrate that significant amounts of potassium have been added to these rocks in the mineralized zone. This implies that biotite alteration was superimposed onto an earlier hornfels. Trace metal data was partitioned into anomalous and background populations with probability graphs. In the hypogene zone Cu, Mo and Ag occur in an annular zone corresponding with the mineralogically defined potential ore zones. Fluorine is anomalous over the area of the potassic alteration zone. Lead and zinc are anomalous in peripheral haloes around the potential orebodies. These zones can be traced to surface through an extensive supergene enrichment blanket and leached capping. Three zones of supergene mineralization are recognized: supergene sulphide (covellite, digenite, chalcocite), supergene oxide (malachite/azurite, cuprite, tenorite, native Cu) and leached capping. Sulphides are the dominant host for Cu throughout most of the deposit but locally on steep slopes where supergene oxide is developed Cu is hosted in carbonate and oxide minerals. Enrichment or depletion of elements in the supergene is demonstrated with interelement ratios. Enrichment factors can be derived in two ways: a) by ratioing supergene values to hypogene values, or, b) by ratioing to a constant (e.g. TiO₂ ) for each zone and then ratioing this value between zones. Enrichment factors of <1 therefore imply depletion and >1, enrichment (1=hypogene grade). Results show that all elements (studied) are enriched in the supergene sulphide and oxide zones. In the leached cap Cu, Mn and Zn are depleted while Mo, Pb and Ag are significantly enriched. These elements are incorporated into immobile limonite mineral's (ferrimolybdite, jarosite, goethite etc.). / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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The Mineral Park mine is a porphyry copper-molybdenum deposit developed within and adjacent to a Laramide quartz monzonite porphyry stock which intrudes Precambrian rocks in northwestern Arizona. The Precambrain sequence consists of older, broadly folded metasedimentary and metavolcanic rocks which were intruded by a 1700-1800 m.y. old granite gneiss batholith. The contact between the two Precambrian terranes is a major structural element in the district and appears to have been important in localizing the Laramide intrusions and mineralization. Alteration is defined by early pervasive biotitization of hornblende in the Precambrain rocks and by recrystallization of rock biotite in the quartz monzonite porphyry. Pervasively biotitized rocks are crosscut first by biotite and then by K-feldspar veinlets. Fracture-controlled, economic sulfide mineralization then began with quartz-molybdenite-K-feldspar-anhydrite and was followed by quartz-chalcopyrite-K-feldspar-anhydrite. This potassic alteration and accompanying mineralization occur throughout the deposit and are crosscut by later quartz-pyrite-sericite veinlets. Orientations of mineralized fractures evolved through time from EW during molybdenum mineralization to NW during quartz-pyrite-sericite mineralization. Fracture densities during molybdenum mineralization averaged 0.05 cm⁻¹ and increased to 0.14 cm⁻¹ during quartz-pyrite-sericite mineralization. Sulfides were deposited from low salinity fluids (0.5 - 2.0 molal) in the temperature range 330°-360°C. High salinity fluids occurred only with quartz that was earlier than sulfide deposition. No homogenization temperatures greater than 440°C were observed. Molybdenum mineralization cuts all rock types and defines a vertical cylinder with a distinct low-grade core. Ore grade molybdenum mineralization is equally distributed between Laramide and Precambrian rocks, and overall grade decreases with depth. Hypogene copper mineralization has a greater lateral distribution than molybdenum mineralization, and surrounds a low grade core coincident with the low grade molybdenum core. The distribution of alteration and mineralization assemblages and the fact that both of these features crosscut all exposed rock types suggest that copper-molybdenum mineralization was not temporally related to the quartz monzonite porphyry exposed in the mine area. The narrow range of homogenization temperatures observed and the lack of high homogenization temperatures compared with the results of computer modelled systems indicate formation of mineralization 2 to 3 km above a source intrusion. Because no evidence for boiling was observed, only minimum pressures of formation can be determined. Minimum pressures during sulfide deposition varied from 180 to 80 bars. These pressures correspond to minimum depths of formation of 2 to 3 km which is in good agreement with an inferred depth of burial of approximately 3 km based on stratigraphy restored from the adjacent Colorado Plateau.