The rocks of the Shuswap terrane have been the subject of controversy for more than 65 years. Jones (1959) recently presented evidence that in the Vernon map-area the original rocks and the superimposed metamorphism are all pre-Permian in age and probably pre-Cambrian. Jones also described (1959, pp. 47-4-9 and pp. 28-29) five different localities where unconformities separate Shuswap rocks of the Monashee and Chapperon groups from rocks of the Cache Creek group of Permian age. The present writer mapped in detail three of these localities, near Lavington, at B.X. Creek and at Salmon River. Near Lavington the contact described by Jones as an unconformity is considered to be a fault. However, the relations between metamorphic and non-metamorphic rocks are compatible with the existence of an unconformity which, if it exists, is not exposed. At B.X. Creek, the arcuate path described by Jones as marking an unconformity was found to follow a nearly-straight line in a northerly direction and to coincide with two parallel, steeply-dipping and north-trending faults which truncate the non-metamorphic rocks. At Salmon River the evidence for an unconformity is strong. The rocks below the unconformity are chloritic and argillaceous schists of the Chapperon group and strike northeast with steep dips to the southeast and northwest. The rocks above the unconformity are calcarenites, feld-spathic volcanic wackes and tuffs grading upward into argillites, and have been described by Jones as part of the Cache Creek group; they strike north or slightly east of north and dip gently to the west or west-northwest. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The purpose of this study is to critically review earlier studies of the Sooke Formation, to present a previously unreported microflora and to assign an age to the formation on the basis of paleontological evidence. The methods used to arrive at the general conclusions consisted of field work and laboratory analyses, supplemented by reference to the literature and to authorities in the fields of palynology, Tertiary invertebrate paleontology and vertebrate paleontology. The Sooke Formation crops out along the south and southwest coast of Vancouver Island in a series of isolated areas. Each area appears to represent a sedimentary basin. The lithology consists of interbedded conglomerates, sandstones and shales in varying proportions. Sooke strata contain a well preserved fossil fauna and-flora. The fauna consists of one vertebrate and 132 marine invertebrates. The flora consists of a few cones, leaf and wood fragments and a well preserved microflora. The Sooke Formation is correlated with the upper Blakeley Formation of Washington and shows close faunal resenblance to the Astoria fauna of Washington and Oregon. It is correlated with the European Aquitanian stage, but may range as high as the Helvetian stage. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Hawkesbury Island is in the Skeena Mining Division of British Columbia. It is underlain by Coast Intrusions, younger lamprophyre dykes and older metamorphic rocks. The latter form part of the Ecstall septum or roof pendant. The metamorphic rocks are mainly amphibolites and quartz-feldspar gneisses. A few bands of quartzite, crystalline limestone, kyanite-staurolite-almandine mica schist and other rock types are present. These rocks have been formed by dynamothermal metamorphism of the regional type. They generally have assemblages indicative of the staurolite-quartz and kyanite-muscovite-quartz subfacies of the almandine amphibolite facies. Shear zones are strongly sericitized. Small percentages of sericite and chlorite are common throughout the metamorphic rocks. These minerals have been formed during retrogressive metamorphism. Apart from a few small metamorphosed igneous bodies, these rocks were originally a thick eugeosynclinal sequence consisting mainly of tuffaceous sediments and semi-pelitic or arkosic sediments. The metamorphic rocks have probably undergone at least two periods of deformation, so that their structure is complex. However, the foliation has a general trend of north 50° west to north 70° west in the northern part of the septum and of north 20° east to north 55° east in the southern part. The Coast Intrusions have reached their present positions by The Coast Intrusions have reached their present positions by intrusion. They have not been formed by granitization in situ. Some assimilation of the country rock has occurred but this is a marginal feature. The Coast Intrusions have had little affect on the grade of metamorphism of the metamorphic rocks. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Deer Horn property lies astride the contact of the Coast Range batholith and a group of siliceous and shaly sediments of Jurassic or Lower Cretaceous age. The contact strikes westerly and dips about 50° to the South. The southern three fifths of the property are underlain by granitic rocks, the remaining northern part consists of slightly metamorphosed sediments striking approximately west, dipping about 70° south and believed to form an overturned syncline. The rocks are cut by two albitite dykes and several minor trap dykes. The granitic rocks are divided into two main types, "porphyritic" granodiorite and hornblende granodiorite. The latter contains the main part of the mineral deposit, and is further subdivided into several varieties produced by tectonic movements and hydrothermal alteration. Alkali metasomatism has affected both the granitic rocks and - to a lesser extent - the sediments. Some metasomatic features are discussed in detail. Two veins or vein systems, the Main and the Contact, lie in the hornblende granodiorite and in the contact zone. They strike westerly, converge towards the west and dip towards each other, forming a shallow troughlike structure. Both carry sulphides and minor tellurides with gold and silver. Scheelite occurs sparsely in the veins and in bands of epidotegarnet skarn in the sediments, being somewhat more concentrated in two areas of fine talus in the western part of the property. The Main vein is shown to be a replacement vein formed in a thrust fault. The shearing angle of the fault flattened in the more brittle contact zone, and the fault terminated in a series of complementary shears. The combination of these two factors produced the curving trough-like shape of the vein. The narrow Contact vein was formed in a later gravity fault. The zone of intersection of the two veins was highly sheared and thus rendered more permeable to the mineralizing fluids. This accounts for the numerous high-grade stringers present near the intersection. In view of the known and inferred limits of the two veins it is not expected that the ore will continue either laterally or in depth. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Ruth-Hope and Silversmith areas are mainly underlain by structurally-competent quartzites, sandy limestones, and thick argillites. Bedding attitudes are steep; several major and minor recumbent folds occur within the local section of bedding structures. The strong northeasterly-trending Standard-Silversmith lode system is represented locally by the Hope, New Ruth, and Silversmith lodes. The Old Ruth-Stewart section lies about one-half mile north, and in the footwall of the main belt. Lodes strike easterly to northeasterly across the trend of bedding structures; they dip to the southeast at moderate to high angles. The most important ore minerals are argentiferous galena, sphalerite, and grey copper. The major bedding structure of the Old Ruth-Stewart section is a recumbent anticline which is convex to the southwest. Bedding within the New Ruth-West Silversmith section dips moderately to steeply southwest. The pattern of lode and cross-fault displacements is reasonably consistent within the mines area. From evidence provided by minor structures, the relative displacements were such that lode hanging walls moved downward to the east and southeast; normal displacements occurred on all cross-faults. Within the productive part of the Old Ruth Mine, mineralization apparently followed a late normal displacement within a major strand of the lode. Lode movements, at least later ones, were, to some extent, transmitted by cross-faults which join the offset segments of the lodes. Also, to a minor extent, the cross-faults contain ore minerals which probably entered by way of fault-lode linking fractures. Apparently porphyry, alteration, and ore were emplaced consecutively, but concurrently with displacements on the lodes and cross-faults. The stronger mineralization of the northeasterly-trending fractures was probably due to a close timing of ore deposition with more intense late movements on this set of fractures. In addition, deeper "ore channels" could be expected within fractures which cross-cut, rather than parallel the bedding. That the West Silversmith porphyry "plug" was emplaced as a separate body, and is not a faulted block from the main Silversmith Stock was proved by the study of flow structures within the "plug". / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

A study of the Slocan Series of South Eastern British Columbia along the three related paths of Lithology, Biology and Tectonics is made. The Lithotopes studied are mainly microscopic, though some megascopic characters are used to determine bottom conditions. The microscopic work was done on slides made from specimens taken at random on a cross-section of these sediments from near Zincton B.C. along the valleys of Seaton and Carpenter Creeks, to New Denver, B.C. The specimens indicated an increase of grain size and feldspar content from the bottom of the section towards the top. This is correlated with an increase in sediment supply and rate of subsidence. The fossils found by Cairnes show that these sediments were laid down in marine waters. A study of lithologic assemblages and types leads to some hypotheses. These, taken with a study of the Windermere geosynclinal assemblage, and theoretical considerations based on the orogenic cycle, allow a history of the area to be made. This history indicates that the Slocan Series, while the result of a separate downwarp of the crust, is probably part of the complex Purcell-Windermere geosynclinal sequence. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The area near the Sullivan Mine, Kimberley B.C., is underlain by rocks of the Purcell series which consist of two sedimentary formations of late Pre-Cambrian age, the Aldridge and the Creston. Both are composed of argillite, siltstone, and quartzite. The Sullivan ore body is a replacement deposit in certain favourable horizons in the Aldridge formation. The only known igneous rocks near the mine are the Purcell intrusives of late Pre-Cambrian age. These intrusives occur as large sheets, or sills, at a small angle to the bedding of the Purcell series.They are chemically about the same as gabbro. The object of this research was to determine the changes induced in the sedimentary rocks of the Aldridge formation near the Sullivan Mine by the intrusion of the Purcell sills; to compare the alterations found with the alterations known to be present in the wall rocks of the Sullivan ore body; and from this comparison, determine whether there is any justification for relating the mineralization of the Sullivan ore body to the intrusion of the Purcell sills. In order to obtain the information required the writer made a petrographic examination of thirty-six thin sections of specimens of the core of the Sullivan Diamond Drill Hole 249 located just east of the mine. The hole was drilled vertically through a sixty foot sill, and on into the underlying sediments of the Aldridge formation. The results obtained from this examination indicate that the sediments adjacent to the sill have been subjected to low grade thermal metamorphism, which has resulted in the development of a pronounced biotite spotted contact zone. Late magmatic emanations, either from the partially consolidated sill, or from the parent magma chamber caused metasomatism in the sedimentary rocks of the contact zone, and the effects of the metasomatic action are super imposed upon the effects of the thermal metamorphism. Tourmaline, albite, pyrrhotite, sphalerite, sphene and rutile are the main minerals produced by the hydrothermal action. A comparison of the alterations found in these sedimentary rocks examined, with the alteration present in the Sullivan ore body and its wall rocks, reveals a distinct similarity. This similarity, plus the fact that the drill hole is within one half mile of the mine suggests a common origin for the magmatic solutions. Therefore, the solutions which produced the Sullivan Mine ore body may have been genetically related to the Purcell intrusives. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The northern Cascadia subduction zone has been the site of numerous geophysical studies during the past two decades. However, little is known of the deep structure (> 40 km) or S-velocities throughout this region. In this study, locally generated P-to-S conversions (Ps) contained in ~100 teleseismic P-wave coda have been analysed to determine the S-velocity structure to upper mantle depths. Prior to the analysis, the applications and limitations of this technique as applied to a dipping layer environment have been examined. It is concluded that strict stacking bounds (≤ 10° in ∆ and BAZ) should be applied. It is demonstrated that dipping boundaries which could not be detected using this technique (e.g. ∆Vs = 0.08 km/s), may significantly alter the amplitude and arrival time of reverberations from deeper interfaces. Therefore, such phases should not be quantitatively modelled. As reverberations are an important constituent of receiver functions, formal inversion of these waveforms is not justified in this environment. Only arrivals which exhibit the amplitude and arrival time characteristics of primary P-to-S conversions are considered in this study. Finally, most studies have normalised receiver functions to unit amplitude prior to modelling. However, synthetic data demonstrate that undetected dipping boundaries may alter Ps/P ratios and lead to inaccurate earth models. A recent modification to this technique (Ammon, 1991) which provides 'absolute' amplitudes is examined. In addition to providing information on the near-surface velocity structure and on dipping layers, this modification provides for a more accurate image of the earth structure. Three 3-component broadband event triggered seismic stations were deployed in a 90 km long linear array oriented perpendicular to the continental margin of southwestern British Columbia. Between December 1987 and October 1989 approximately 100 teleseisms covering a wide azimuthal and distance range were recorded and analysed. The two largest phases observed in data from the westernmost station ALB-B reveal a prominent low-velocity zone extending from 37-41 km depth beneath central Vancouver Island. This feature correlates well with the reflective 'E' zone, a region which also exhibits high electrical conductivity. Combining the S-velocity estimates with refraction P-velocities yields a high Poisson's ratio for this layer. The low P- and S-velocities and high Poisson's ratio and electrical conductivity are supportive of the recent interpretation of this feature as a fluid-saturated shear zone above the subducting Juan de Fuca (JdF) plate. Analysis of data at the mid-array and easternmost sites, LAS and EGM respectively, permits this zone to be mapped northeastward to a depth of 54 km beneath the British Columbia mainland, approximately 250 km from the locus of subduction. The subducting oceanic crust is imaged at 47-53 km depth dipping 15°±5° in the direction N30°E±20° beneath central Vancouver Island. The dip angle increases to 22° ±5° at a depth of 60-65 km beneath the Strait of Georgia. The results of this analysis provide the first definitive evidence for the location of the subducting plate in this region and indicates that the seismicity at depth occurs within the oceanic crust. Further, the dip direction of N30°E supports the theory (Rogers, 1983) that the JdF plate is arched upwards as it subducts in this region. Finally, the continental Moho is imaged at 36 km depth beneath LAS, and there is evidence at both this site and EGM for a low-velocity zone in the lower crust. A similar feature is imaged beneath Vancouver Island and coincides with the reflective ‘C’ zone. The depth estimated to the top of this layer denotes the lower limit of shallow seismicity suggesting a significant structural or compositional change at a depth of 20-26 km. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Nephrite is a compact, microfibrous variety of actinolite-tremolite in which bundles or tufts of minute fibers of the amphibole are twisted and thoroughly felted or interwoven with one another, producing a characteristic "nephritic" microstructure. In British Columbia, nephrite deposits, both in place and placer, are closely associated with a belt of alpine ultramafic rocks that extends for 1000 miles from the Hope area, east of Vancouver, northwestward to the Yukon border. The three major nephrite producing regions are the Bridge River - lower Fraser River area, the Takla Lake area and the Dease Lake area. The nephrite from British Columbia contains, in addition to essential tremolite, small amounts of chlorite, uvarovite, chrome spinel, diopside, talc, carbonate, sphene, phlogopite and pyrite. Grains of chrome spinel and uvarovite are usually visible in hand specimen. The colour of the majority of the specimens is yellowish green; this colouration is caused by the presence of iron in both the divalent and trivalent states. Polished surfaces of the nephrite have an average Vickers hardness of 950 Kg/mm² and an average Mohs hardness of 7. The average specific gravity is 3.00. The unit cell parameters of tremolite from British Columbia nephrite specimens are similar to those of nephritic tremolite from Siberia. X-ray diffraction data for the tremolite from these specimens are also in good agreement with those for nephritic tremolite from other localities. The nephrite specimens contain an average of 3.05 percent iron; small amounts of cobalt, nickel, manganese, copper, lead, zinc, chromium, titanium and vanadium are also present. Significant regional variations in the averages for iron, cobalt, manganese, copper, lead, zinc and vanadium are not observed when the specimens are grouped according to the area of origin; slight variations are observed in the average contents of nickel, chromium and titanium. The general similarity of the regional average values for these elements suggests that the nephrites have been formed in similar environments. At the O’Ne-ell Creek deposit in central British Columbia, nephrite occurs in a zone of tremolite-chlorite rock developed in serpentinite at the contact with metasomatically altered sediments. The nephrite has resulted from the metasomatic alteration, by addition of calcium and silica, of the serpentinite during the process of serpentinization. The calcium was derived from the pyroxenes contained in the original ultramafic rock; the source of the silica was the enclosing sediments. High concentrations of calcium and magnesium and relatively lower concentrations of sodium, iron, aluminum and silicon characterized the environment in which the nephrite formed. Calcium and sodium were perfectly mobile while the other elements were relatively inert. These conditions of mobility and concentration account for the fine fibrous nature of the nephritic tremolite. A temperature range of approximately 300°C to 500°C and a pressure in excess of 4 kilobars are suggested for the formation of the nephrite. / Arts, Faculty of / Geography, Department of / Graduate

Detailed structural mapping near Mt. Perseus, British Columbia, provides an overview of the nature of deformation across a portion of the Quesnellia-Omineca terrance boundary. Rocks within the Omineca Belt are comprised of the Hadrym'an to mid-Paleozoic Snowshoe Group. These rocks are structurally overlain by and act as basement to accreted rocks of the Intermontane Belt (Quesnellia): the Upper Paleozoic Slide Mountain Group (Antler Formation), Upper Triassic Black Phyllite (unnamed), and Jurassic volcanic rocks of Takla Group equivalence. Within the Snowshoe Group, four phases of regionally significant deformation have been established. Both basement and cover have common phases of deformation wherein the first phase of deformation present within the cover sequence is equivalent to the second phase within the basement. In general, deformation within the cover is less well developed with respect to the basement. Earliest structures, only observed within the Snowshoe Group are east-verging rootless isoclinal folds accompanied by a transposed foliation of a regional nature. Associated with this event is the intrusion of a large tabular granitic body, later metamorphosed into the Mt. Perseus Gneiss. Second phase structures are easterly verging and comprise large recumbent nappe structures. Third phase westerly verging folds dip moderately to the northeast. It is these large scale structures which control the present regional map pattern and local configuration of the Omineca-Quesnellia boundary, which in this study, is manifest in the Mt. Perseus antiformal culmination. Small scale crenulations and easterly verging buckle folds comprise the fourth deformational phase and do not appreciably affect earlier geometries. Second phase deformation marks the obduction of the easterly converging Quesnellia accretionary package onto the Omineca terrane. This tectonic contact is flanked by narrow longitudinal ductile shear zones containing mylonites, which in Snowshoe rocks are often associated with isolated fault bounded slivers of oceanic cover rock (ophiolite). These tectonic slivers are thought to be related to geometry resulting from the eastward subduction of oceanic Quesnellia rocks beneath the Omineca craton during the third deformational phase. The development of the late crenulation cleavage is likely a consequence of late eastward thrusting of early Jurassic volcanics during the later deformation stages of the underlying phyllites. Mineral assemblages describe a Barrovian metamorphic sequence which ranges from the middle to upper greenschist facies in cover rocks to the lower amphibolite in the Snowshoe basement. The earliest recorded metamorphism is associated with phase 1 deformation but details regarding this event remain ambiguous as most textures have been destroyed by successive metamorphism. Microscopic textures indicate that the peak of metamorphism is synchronous with phase 2 deformation followed by a reduction to the middle greenschist facies during the third deformational phase. Both obduction and subduction processes and their associated deformation and metamorphism were most likely the result of mid Mesozoic tectonics related to the Columbian Orogeny. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate