The Guichon Creek Batholith, located in south-central British Columbia, contains several large, low grade copper deposits of extreme economic importance. A three dimensional model for the batholith has been determined on the basis of a gravity survey conducted in 1971. In addition the gravity data has been compared with the filtered aeromagnetic maps of the batholith. A striking correlation between the spatial relationship of the mineral deposits and the core of the batholith has been discovered. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Four olivine gabbro plugs crop out on the basaltic plateau in the south Cariboo region of British Columbia. The plugs form elliptical knobs of unaltered gabbro which stand 100 to 200 feet above the plateau surface. They are 300 to 600 feet in greatest diameter, as seen in plan view. Two plugs, Mt. Begbie and Forestry Hill, are described in detail in this thesis. Alignment of tabular feldspar grains resulting from the upward flow of magma, has produced a foliation in both Mt. Begbie and Forestry Hill plugs. Foliation dips toward the centre at moderate to steep angles in both plugs. Small, scattered lenses of leucogabbro and picritic gabbro lie approximately in the plane of foliation. Marginal foliation is assumed to be roughly parallel to the walls of the plug. Foliation trends indicate that both plugs are funnel-shaped, increasing in diameter toward the surface. The essential minerals of the plugs are olivine, calcic-augite and plagioclase. They are strongly zoned indicating a disequilibrium environment of crystallization. From a consideration of mineralogical and chemical characteristics it is concluded that the original magma was an alkali basalt magma. Differentiation by fractional crystallization produced small volumes of marginal dolerite and pegmatitic gabbro in the outer portions of Mt. Begbie plug. The trend of differentiation leads to iron-enrichment in the marginal dolerite, and then to alkali-enrichment in the pegmatitic gabbro. The four plugs occupy former volcanic vents which, in late Tertiary time, fed lava to the surrounding plateau. The exposed portions of the plugs crystallized possibly within 50 to 150 feet of the surface. General geological relationship, petrological similarity, and the close comparison of fused whole-rock powders suggest a definite kinship of the plugs to the surrounding basaltic lava. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Rainbow Range is a Late Miocene shield volcano (30 km diameter, 370 km³) whose stratiform flanks surround a complex central vent zone. Over a time span of 1-2 m.y., extrusion of highly fluid comendites and comenditic trachytes, along with minor mugearites and hawaiites, built up the gently sloping flanks. The viscosity of the peralkaline lavas was so low that their eruption produced a shield volcano rather than a composite cone. Comenditic trachytes (65.5 percent S10₂) are the lowest flows exposed on the north flank of the Rainbow Range. Chemical traits include high Na20 + K/jO (11 percent), moderately high AI₂O₃ (15 percent), low total iron as Fe₂0₃ (5 percent), and high Ba (300-1000 ppm). Thin flows of mugearite (54.9 percent Si0₂) rest on the comenditic trachytes. Comendites (68.7 percent Si02) uncon-formably overlie the mugearites and account for at least 75 percent of the volume of flows within the flank zone. These lavas are distinguished by lower AI2O3 (13 percent), higher total iron as Fe203 (7 percent), and extremely depleted Sr (1-10 ppm) and Ba (10-100 ppm). The termination of flank volcanic activity is recorded by the eruption of capping flows and related feeder dikes of hawaiite (50.1 percent Si0₂). Comenditic trachytes contain phenocrysts of anorthoclase (Or₂₅_₂₇), heden-bergite, and iron-titanium oxides in a groundmass of alkali feldspar, quartz, acmite, iron-titanium oxides, aenigmatite, and arfvedsonite. Comendites bear the phenocryst assemblage sanidine (Or₃₄_₃₇) + hedenbergite + fayalite + arfvedsonite set in a pilotaxitic groundmass of alkali feldspar, quartz, acmite, iron-titanium oxides, aenigmatite, and arfvedsonite. Continuous variation in major and trace element trends and feldspar compositions suggests that the hawaiite-mugearite-comenditic trachyte-comendite suite was derived from an alkali basalt parent, tapped several times as it underwent prolonged fractional crystallization in an intracrustal magma chamber. A best-fit mathematical model for the origin of the suite involves step-wise derivation of the lavas.in the order hawaiite > mugearite ? comenditic trachyte > comendite, with the main phases precipitating out in the order olivine, clinopyroxene, plagioclase, iron-titanium oxide, and alkali feldspar. Strontium isotopic evidence indicates that the peralkaline lavas were erupted soon after differentiation. The Rainbow Range and other peralkaline and alkaline volcanic centers of the Anahim volcanic belt are coeval.with calc-alkaline volcanic centers of the Pemberton volcanic belt. Together these belts outline the orientation and extent of the subducted Juan de Fuca plate during Late Miocene time. Volcanic activity in the Anahim belt may be related to a) an "edge effect" of the subducted Juan de Fuca plate, b) movement of the North American plate over a mantle hot spot at a rate of 2-3 cm/year, or c) an east-west trending rift zone. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Ice River igneous complex, exposed in the southern part of Yoho National Park in the Field area, British Columbia, is an asymmetrical laccolith made up of several varieties of undersaturated alkaline igneous rooks. Nepheline- sodalite syenite and urtite, two of the major types, are described. Several theories on the origin of undersaturated alkaline igneous rocks are discussed and it is concluded that Daly’s limestone syntexis theory best explains the origin of the Ice River complex. In the vicinity of Garnet Mountain and Aquila Ridge, the north-west extension of the laccolith has contact metasomatised enclosing limestone and limestone inclusions. The mineralogy and petrology of several extensive skarn zones which carry pyrochlore and radioactive minerals are described. The concentration of certain elements in alkaline igneous rooks is considered and the, addition of Na, K, Cb, Zr and others to Ice River limestone is described. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Tuzo Creek Molybdenite Prospect is in southern British Columbia approximately twenty air-miles east-southeast of Penticton within the Nelson-Valhalla batholithic complex. A stock of porphyritic quartz monzonite, approximately 1½ miles in diameter, and younger sub-volcanic sills, dykes and masses of quartz-albite-sanidine porphyry were eraplaced into a basement of Nelson granodiorite of probable Jurassic Age. Mid (?) Tertiary alkaline basic dykes are the youngest intrusions present. Porphyries were emplaced successively at three different times along structures developed either by subsidence of the stock or by regional deformation. Differentiation, level of crystallization of phenocrysts, level of emplacement and regional correlation of acid intrusions are discussed. Two phases of hydrothermal activity are recognized, separated in time by intrusions of porphyry. In both cases, alteration was controlled by fractures and local shear and breccia zones. The first phase resulted in widespread wallrock alteration, quartz veining and mineralization throughout most of the stock and bodies of pre-mineral porphyry. Zoning of argillization, potash feldspathization and silicification and of oxide or sulphide fields of mineralization occurs on a large scale throughout the alteration halo. A large zone of low grade molybdenite mineralization occurs in a zone of more intense wallrock alteration containing stockworks of quartz veins and pyrite. The chemical and physical aspects of wallrock alteration and mineralization are considered in light of experimental studies done by others. The second phase of hydrothermal activity only occurred locally and involved development of secondary sericite and quartz with associated Zn, Pb, Cu, Pe and Mo sulphides and calcite and fluorite. All structures can be explained either by periods of subsidence of the stock or by genetic relationship to forces developed by periodic movements along a nearby regional fault zone following the West Kettle River valley. Source rocks of hydrothermal fluids, paragenesis, zoning and exploration potential for molybdenite are discussed. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Lower Cretaceous Gates and Moosebar Formations in the Northeast Coalfields of British Columbia comprise a 350-450 m thick interval of marine and non-marine, coal bearing clastic sediments. The Moosebar Formation and lowermost unit of the Gates Formation (the Torrens Member) consist of between 2 and 4 coarsening-upward marine cycles. In the northern part of the study area, non-marine sediments in the Gates Formation occur interbedded with 3 major marine tongues (the Sheriff member, Falher C and Babcock member) which pinch out towards the south. In the study area south of Duke Mountain, sediments in the Gates Formation above the Torrens Member are entirely non-marine. The coarsening-upward marine cycles in the Moosebar-lower Gates interval were deposited mainly during regressions when the shorelines prograded northwards. The cycles are comprised of up to 3 main facies interpreted as offshore, transition zone and shoreface-beach (and locally distributary channel) deposits. Thin transgressive deposits are present at the base of the Sheriff member. Lower Gates shorelines are interpreted as high energy and wave dominated. Shoreline trends for the Torrens, Sheriff and Babcock Members are approximately E-W, and approximately NW-SE for the Falher C. Non-marine deposits in the Gates Formation are interpreted as forming in lagoons, fluvial channels and overbank environments within a coastal plain setting. The channels are mainly braided river types with anastomosing or straight (non-braided) and meandering river channels also present. The rivers flowed towards the northwest, north, northeast and east with northeasterly directions most common. Up to three separate very coarse fluvial conglomerates, interpreted as proximal braided river-alluvial fan deposits are present in the south near Mount Belcourt. Overbank sediments were deposited in levee, crevasse splay, lacustrine and well to poorly drained swamp environments The upper Gates marine unit (Babcock member) contains both transgressive and regressive deposits. Three types of transgressive deposits are recognised: 1. Thick (maximum 40 m) estuary mouth |shoal retreat massif) sandstones and conglomerates preserved in linear belts approximately 0.4-2 km wide trending NW-SE and N-S. 2. A thin (maximum 90 cm) but laterally extensive marine lag. 3. Lagoon-intertidal deposits. Upper Gates regressive deposits include shelf to shallow marine sandstones overlain by estuarine subtidal channel and shoal deposits which in turn are overlain locally by tidal flat and coastal plain deposits with thin coal seams. Upper Gates shorelines appear to be strongly tidally influenced. Thick (maximum 10 m), laterally extensive coal seams occur in the lower part of the Gates Formation. Coal seams in the upper Gates are thin (generally <1.0 m). With the exception of few very thin seams, the Gates coals appear to be entirely autochthonous and to have accumulated as peat in swamps in a coastal plain depositional setting. Some of the coals in the lower Gates were deposited in swamps which extended inland for at least 75 km from the shoreline. The maximum coal development in the Gates Formation (28 m total coal and 6 seams >1.5 m thick) occurs in the Foothills south of Kinuseo Creek, near the boundary between transitional marine and non-marine facies belts. Cross-sections based on closely spaced borehole and outcrop sections illustrate the occurrence and distribution of coal seams in the Duke, Honeymoon, Babcock, Frame and McConkey Pits. Thinning and pinchout of coal seams occurs adjacent to fluvial channel and splay deposits and near the landward pinchout of the Sheriff member. Draping of coal seams over fluvial channel deposits causes rapid variations in interseam thickness which may lead to correlation problems in the early stages of exploration and affect the potential mineability of coal seams. The main detrital components in the Gates sandstones are quartz and chert with siliceous rock fragments, carbonate rock fragments, clastic sedimentary and metasedimentary rock fragments, igneous rock fragments and feldspar present in lesser amounts. Mesozoic to Cambrian sedimentary rocks of the Rocky Mountain Front and Main Ranges are interpreted as the principal source of the detrital components. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Upper Cretaceous (Campanian) Cedar District Formation of the Gulf Islands and adjacent areas is composed of shale and sandstone, which are present as thick sequences of shale, which may or may not be fossiliferous, and as alternating rhythmic sandstone-shale sequences of the flysch-type. Presence of graded bedding, ripple and convolute laminations, and sole marks in the latter suggest a turbidity current origin. The internal structures of the individual turbidite units correspond largely to the C-E divisions of Bouma (1962) and other authors, and indicate that their deposition took place largely within the lower flow regime. Convolute lamination in the sandstones was formed by oversteepening and deformation of pre-existing ripple lamination and by the deformation of pre-existing plane-parallel lamination by the drag of the overpassing currents. Flute and groove casts and frondescent marks were only found in beds thicker than a foot and a half. Calcareous concretions, most abundant in the shales and occasionally phosphatic, are crossed by organic borings and burrows which are filled with sediments of the surrounding beds. Host rocks of the calcareous concretions tend to thicken around them. The concretions show deformation when present in beds involved in soft-sediment deformation. All these observations suggest their formation in the early stage of diagenesis, probably shortly after, burial. Sandstones of the Cedar District Formation show a gradation from arenites that lack matrix and have a cal-cite cement, to wackes rich in fine-grained matrix. The majority of the wackes and the arenites are feldspathic and arkosic, using the classification of Gilbert (1954). Their composition indicates that the major source was acidic to intermediate igneous and/or low to medium grade metamorphic rock , sedimentary and volcanic rocks were a secondary source. The major source area was possibly a region of high relief that had undergone rapid uplift and erosion, and experienced mainly mechanical weathering. Paleocurrents and lithologic lateral variation indicate that the major source area for the coarse elastics was situated to the east and southeast of the study area. The pre-Jurassic low grade metamorphic rocks of the Cascade Mountains to the east, and the pre-Carboniferous- crystalline rocks of the San Juan Islands to the southeast served as possible source areas for the coarse elastics. Deposition of shaley, fossilif erous parts, of the formation in the southeastern part, of the study area, took place in littoral to upper neritic depths. Turbidite (flysch-type) sequences were deposited in deeper water, below the wave base. The unfossiliferous shale of the central and northern parts of the study area was deposited either at about the same depths as the turbidites, or in deeper water, since thin, delicate, horizontal and-cross laminations are preserved in these rocks. Paleontologic evidence suggests that deposition took place in a somewhat restricted basin having a narrow connection with the open ocean to the west. Paleontologic and mineralogic data suggest that the bottom conditions of the central and northern parts of the basin of deposition were stagnant and reducing. Facies relationships suggest that the basin of deposition had its longest dimension trending SE-NW. Its eastern, southeastern, and southern boundaries were situated between the mainland of British Columbia-Washington and the Gulf-San Juan Islands. Its northern and northwestern boundaries were possibly near the city of Nanaimo and Gabriola Island. To the west, it was connected at least partially to the open ocean. In the southeastern part of the study area, alternation of thick, fossiliferous shale sequences, and sequences which are predominantly turbidites suggests fluctuations in the depth of the basin floor, either due to changes in sea level or to tectonic movements. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Serb Creek molybdenite property is 26 miles west-northwest of Smithers, B. C. on the northeast flank of the Howson Range of the Coast Range physiographic province. The property lies within an upper mesozonal to lower epizonal batholithic offshoot of the Coast Range Intrusive Complex. Small irregular plutons and a series of northwesterly-striking dykes intrude the batholith. The rocks are quartz monzonitic and, in texture range from coarse-grained granitic to porphyritic. Plots of optic angle against composition show that feldspars are of intermediate structural type indicating an increasingly rapid rate of cooling from the oldest to the youngest intrusive body. This increase in the rate of cooling is ascribed to smaller size of intrusive body with decreasing age. Plots of normative Q:AbOr ratios suggest that, if one believes the magma to have formed by anatexis, high pressures of volatiles, HC1, or of both were present during crystallization. Two general attitudes—N20° W to N^5°w and N75° E--control the emplacement of intrusive bodies, hydrothermal alteration, and, to a large extent, molybdenite mineralization. Hydrothermal alteration and molybdenite mineralization appear to be related to igneous activity because they are closely associated in time and space. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Pioneer Ultramafite, south of Bralorne, British Columbia, is a fault-bounded lens of alpine-type peridotite enclosed in lower greenschist facies sediments and volcanics of the middle Triassic Fergusson Group and late Triassic Noel, Pioneer and Hurley Formations. The body consists of a core of well layered harzburgite, dunite and orthopyroxenite, rimmed by serpentinite and talc-carbonate alteration zones containing tectonic inclusions of sediments, volcanics and rodingite. Foliated harzburgite forms approximately 80 per cent of the ultramafite; dunite, as dikes, sills and irregular pods in harzburgite, comprises about 17 per cent; and orthopyroxenite as layers (1 to 15 cm thick), parallel to the foliation, in harzburgite, constitutes the remaining 3 per cent. Electron microprobe analyses of the primary minerals indicate olivine composition ranges from Fo 90.2 to 92.5, orthopyroxene from En 89.2 to 90.2 and clinopyroxene averages Ca₄₆․₉Mg₄₉․₇Fe₃․₄. Compositions of coexisting primary minerals indicate a temperature of equilibration of about 950°C at an unknown pressure. Alteration assemblages in the serpentinized contact zone indicate migration of 0, H₂O, C0₂, CaO, MgO and S10₂ resulting in metasomatism of the ultramafite and country rocks, producing rodingite, nephrite (jade) and talc-carbonate. Serpentinization apparently occurred during emplacement of the ultramafite into the surrounding country rocks. Plastic deformation and recrystallization of the peridotite produced the pervasive planar foliation or layering, which has been disrupted by several later episodes of folding and fracturing. Country rocks show evidence of two phases of deformation prior to emplacement of the ultramafite, A strong foliation of serpentinite and country rocks, near the contact, was produced during emplacement. The ultramafite and country rocks are interpreted as a partial, dismembered ophiolite which was emplaced in the late Triassic or early Jurassic by obduction of oceanic crust onto the continental margin. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Five major units were mapped in shoreline exposures of the Coast Plutonic Complex adjacent to Douglas, Sue and Loretta Channels: 1) paragneiss and migmatite of the Central Gneiss Complex, 2) quartz-biotite schist, amphibolite, quartzite,and marble of the Metasedimentary Rocks, 3) quartz diorite and quartz monzonite of the Kitkiata pluton, 4) granodiorite of the Quottoon pluton and 5) Agmatite, composed of early xenoliths of banded metamorphic rock, middle stage intrusions of granitic rock, and late pegmatite, aplite and lamprophyre dikes. Pressure estimates of 7 ± 1 kb for this part of the Coast Mountains are arrived at from the stable assemblages in a kyanite-staurolite schist, and by comparison with pressures published for areas along strike to the north. Amphibolites provide a low temperature estimate o f 550°C. Calcsilicate assemblages place the high temperature limit of metamorphism between 560 and 660°C at 5 kb. Elevated pressures would increase temperature somewhat. The area is structurally characterized by a well developed, steeply dipping foliation that strikes northwest, widespread isoclinal folds with axial plane foliation parallel to regional foliation, and a moderate to steeply plunging fold axis lineation. Interference structures show that the abundant isoclinal folds deform earlier approximately northeast-trending folds. Later tight to isoclinal folds deform the regional foliation. Metamorphic recrystallization outlasted deformation. The Kitkiata pluton has an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.7042 to 0.7043, depending on its age. One radiogenic Sr-rich sample gives a model date of 165 ± 11 Ma, but the possibility of anomalous initial ⁸⁷Sr/⁸⁶Sr ratio makes this result highly uncertain. The Quottoon pluton gives a whole-rock isochron of 51 ± 2 Ma with 0.7045 ± 1 initial ratio. The low initial ratios indicate a preponderance of mantle-derived magma of Mesozoic or early Cenozoic age in the plutons studied. Sr isotopic composition of the Central Gneiss Complex is compatible with late Paleozoic-early Mesozoic ages for precursor detrital and volcanic strata and local presence of marine carbonate with moderately enriched ⁸⁷Sr/⁸⁶Sr. The generally low radiogenic Sr content of these core gneisses rules out an origin by remobilization of greatly older rocks. Plutons of the Coast Plutonic Complex may have been generated by partial melting of the Central Gneiss Complex, and emplaced not far from their source of origin during regional metamorphism, as the surrounding rocks cooled from maximum temperature and pressure of metamorphism. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate