The north side of Cowichan Lake, Vancouver Island B.C. is underlain by volcanic rocks, sediments, and intrusives of Mesozoic age. The oldest rocks, Jurassic or Triassic flows known as the Sicker andesites, are conformably overlain by about 3000 feet of cherty tuffs, coarser pyroclastics, and small lenses of limestone known as the Sicker sediments. Cherty tuffs form the lower members of the Sicker sediments, felspathic tuffs the central members, and coarser pyroclastics the upper members. About 2000 or 3000 feet of basaltic and andesitic flows conformably overly the Sicker sediments. The Sicker andesites and sediments and younger flows are intruded by large dyke-like bodies of granodiorite or quartz monzonite, known as the Saanich granodlorite and correlated with the Coast Range intrusives. Upper Cretaceous shales sandstones and conglomerate unconformably overlie the volcanics and Intrusives. The Sicker series and overlying flows are tightly folded into overturned and asymmetrical northwesterly trending synclines and anticlines. The Cretaceous rocks are gently folded and dip north along a narrow belt on the north side of a down-faulted block. Manganese deposits occur in the lower cherty beds of the Sicker sediments as lens shaped bodies parallel to the bedding of the sediments. They are commonly in chert free from felspatnic material, and are always associated with jasper or jaspery sediments. The main manganese minerals are rhodonite, spessartite, an unidentified yellow manganese silicate, and small amounts of rhoaochrosite. Residual manganese oxides coat the surfaces of the deposits. Several features of the deposits, such as the fact that rhodonite commonly cross cuts and replaces the chert suggest that the deposits are of replacement origin. Other features such as their bedded appearance and the fact that they occur, at about the same horizon In the Sicker sediments indicate a sedimentary origin. Theoretical considerations support the view that the deposits are sedimentary and suggest that the replacement features were formed by metamorphism. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Kamloops Group is a widespread assemblage of Eocene volcanic and sedimentary rocks in south-central British Columbia. Detailed mapping of the type area near Kamloops has resulted in its subdivision into two formations and thirteen formal and informal members. The Tranquille Formation, 0-450 metres thick, consists of lacustrine sediments which grade upward into pillowed flows, hyaloclastite breccia and aquagene tuff. The overlying Dewdrop Flats Formation, with nine members, consists of up to 1000 metres of basalt to andesite phreatic breccia, flow breccia and flat-lying flows. In one large and four minor volcanic cones, basal phreatic volcanic rocks pass upward into subaerial flows and breccia. A fault zone of inferred strike-slip displacement to the southwest, and a complex reverse-faulted zone to the south of the area, localized deposition of the Tranquille Formation. Later fault activity created the complex Tranquille Canyon graben, in part filled with Dewdrop Flats Formation volcanics. Reconnaissance of the Kamloops Group throughout the Thompson-Okanagan region, and detailed mapping at McAbee and Savona, have shown that most Kamloops Group sections consist of a lower sedimentary and volcanosedimentary unit, followed by thicker, dominantly basalt to andesite, flow and breccia units. Thick sedimentary accumulations were localized in zones of extension within a network of strike-slip faults. The Kamloops Group is a high-alkali calc-alkaline volcanic suite dominated by augite - pigeonite - labradorite andesite and basalt, with unusually high K, Sr and Ba. Initial strontium isotopic ratios distinguish a boundary between 'old' crust upper mantle to the east and 'young' or Rb-depleted materials to the west. Petrographic and chemical data are consistent with magma genesis by partial melting of alkali-enriched peridotite between 40 and 75 km depth, with subsequent deep- and shallow-level fractional crystallization producing the observed volcanic chemistry. Compilation of Paleogene geology and geochronometry in the Pacific Northwest shows the Kamloops Group to be part of a robust calc-alkaline volcanic arc extending from Wyoming to Alaska. Superimposed on this arc were dextral, strike-slip faults, sedimentary basins and reset metamorphic terranes. These elements formed a tectonic, network which accommodated 90 to 450 kilometres of right-lateral displacement between coastal British Columbia and North America. A tentative plate-tectonic reconstruction is based on the compilation. A northeast-dipping subduction zone, active along the entire coast of the Paleocene Pacific Northwest, ceased to be active after 53 Ma. The transform motion between Pacific and North American plates was distributed inland, driving the Eocene tectonic activity, while the remnant subducted slab gave rise to the Eocene magmatic arc. Transform motion later became localized along the continental margin, as the east-dipping subduction zone south of 49° latitude intiated the Cascade volcanic arc in the Late Eocene and Oligocene. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Guichon Creek batholith is exposed approximately 200 miles N.E. of Vancouver, B.C. and is a zoned 'granitic' pluton of Lower Jurassic age (198±8my). The batholith consists of seven major intrusive phases. The predominant rock typo is granodiorite with lessor amounts of quartz diorite and quartz monzonite. Study of rock and mineral compositions has revealed a gradual variation in the relative proportions of mineral phases as crystallisation of the batholith proceeded. The chemical compositions, however, of the individual mineral phases show very little change. The relative roles of assimilation and magma convection in producing compositional variations in the early phases of the batholith are discussed. Alkali feldspars are microperthitic with bulk compositions in the range 71-86 Wt% Or and the compositions of the porthitic components approach pure end members. The potassic phases of the perthites have structural states equivalent to that of orthoclase. The plagioclase feldspars are oligoclases with low to intermediate structural states. Plagioclase from the early phases of the batholith (Hybrid and Highland Valley phases) show normal zoning whereas those from the later phases (Bethlehem and Bethsaida) show oscillatory zoning. Biotites from the major phases of the batholith have progressively lower Fe/(Fe+Mg) ratios with progressively increasing silica content of the host rocks. Plagioclase crystallized early in the older phases of the batholith whereas quartz was the early mineral to crystallize from the younger major phases. Evidence suggests that magma convectod during crystallisation of the older phases of the batholith but that the younger phases crystallised from a stationary magma. Comparisons with experimental systems suggest that the early magma crystallised under conditions of relatively low total pressures in the order of 1 or 2 kb but that the later phases may have been subjected to total pressures in the order of 4 or 5 kb during crystallisation. This increase in total pressures was most probably due to increasing volatile pressures during crystallisation / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The rocks of the Upper Triassic Nicola Group represent the altered broken remnants of a volcanic island archipelago. About 23,000 feet of Upper Triassic sediments and volcanic rock are present in the thesis area. The group is the product of two cycles of deposition distinguishable on the basis of relative abundance of phenocrysts in the volcanic members. Rocks of the lower cycle (P), characterized by abundant feldspar phenocrysts, are separated into a lower, 6,000 foot thick assemblage of flows, breccias, and tuffs composed mainly of basaltic andesite; and an upper, heterogeneous, 8,000 foot thick assemblage composed of andesitic and rarer basaltic or dacitic agglomerates, breccias, tuffs, flows, and associated sediments as well as coral reef bodies. Rocks of the upper cycle (A), characterized by abundant augite phenocrysts, are separated into a lower assemblage about 7,500 feet thick composed of flows, breccias, tuff, and greywacke with rare limestone; and an upper assemblage about 1,600 feet thick composed of tuff, argillites, and cherts. During the Lower Jurassic, the group was gently folded, variably fractured, and intruded by a sequence of plutons culminating in the near-surface emplacement of huge batholiths. Metamorphism and metasomatism associated with batholiths altered the rocks so that they are now composed of low-grade metamorphic mineral assemblages. By mid-Mesozoic time, the plutons were exposed and a conglomerate laid down. Faulting along previous zones of weakness affected area during late Mesozoic time. Eocene deposits formed in an environment of hills and swamps. By late Miocene, after some jostling of faults blocks, the main topographic features of the Interior Plateau were fixed. Subsequent outpouring of Plateau and Valley basalts as well as glacial erosion and deposits have only mildly affected the main topographic features. The Nicola Group provides a chapter on the evolution of the Cordillera. The relationships provide certain limits to events that occurred outside the thesis area. Equally, relationships within the thesis area cannot all be answered without reference to larger areas. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Lorraine property area occupies the north eastern part of the Duckling Creek syenite located within the central part of the Hogem batholith in British Columbia. The rocks of the Lorraine property area consist of "metasomatic syenites" or "fenites" formed by the metasomatism of the fractured Hogem diorite. They are believed to have been derived from a hypothetical alkaline magma formed beneath the diorite. The residual magma differentiated from the alkaline magma, produced late dykes and hydrothermal fluid. A K-Ar date, 170±8 m. y.(Lower Jurassic) may correspond to both the minimum age of the fenites and the maximum age of the sulphide mineralization at the Lorraine property. Also, the age may mark the time point dividing the first division and the second division of the Hogem batholith. The characteristic minerals of the successive stages of alteration are 1. biotite, 2. albite, 3. orthoclase, if. quartz, 5. sericite, 6. chlorite, and 7. epidote. The altering fluid contained concentrations of soda, potash, silica, hydrogen sulphide, water, and a minor amount of lime. The primary sulphides are bornite, chalcopyrite, and pyrite. The Lorraine deposit posseses no noticeable gossan, but contains secondary copper minerals such as covellite, chalcocite, azurite and malachite. The deposit is divided in plan into three mineral zones on the basis of the primary sulphide assemblages. The dykes, mafic rocks, and fractures were the main controls of mineralization. The composition of the hydro thermal, fluid changed as sulphur reacted with iron of the host rock to form pyrite. The reduced sulphur ratio appears to have caused deposition of bornite and chalcopyrite. In the mineral zones pyrite was replaced progressively by chalcopyrite and bornite. The best classification for the Lorraine deposit is xenothermal. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Detailed investigation of the Boss Mountain molybdenite deposits, which are on the northeast slope of Takomkane Mountain approximately 35 miles north-northeast of 100 Mile House, British Columbia, was undertaken to determine the origin of the deposits, controls of mineralization, effects of mineralization on the host rock, origin of the breccia bodies, and the relationship of these features to the Boss Mountain Stock. The deposits occur in granodiorite and porphyritic biotite granodiorite phases of the composite Takomkane Batholith near an epizonal Cretaceous quartz monzonite porphyry body, the Boss Mountain Stock. Molybdenite occurs in economic concentrations in two classes of deposits: 1) Breccia Deposits, which include fracture zones, and 2) Vein Deposits, which include both single and multiple systems. The sequence of ore formation, which includes rhyolite porphyry and rhyolite dyke emplacement, breccia formation, fracture development, mineralization, and alteration, is directly related to the oscillatory emplacement of the Boss Mountain Stock. The Boss Breccias, including Phase I Breccia, Quartz Breccia, and Phase III Breccia, were formed by pulsating magmatic activity acting on an irregularity on the side of the magma chamber (Boss Mountain Stock). The rock above this irregularity was fractured by magmatic advances. Withdrawal of magmatic pressure permitted collapse of the overlying fractured rock forming breccia bodies. Rhyolite porphyry dykes, apophyses of the Boss Mountain Stock, preceded and accompanied Phase I Breccia formation. Non-porphyritic rhyolite dykes cut Phase I Breccia and have been engulfed by later breccia phases. Four stages of rock alteration genetically related to the deposits, including (in chronological order): Stage 1, garnet-hornblende Stage 2, biotite; Stage 3, microperthite-chlorite-sericite; and. Stage k, chlorite-talc, have been identified and delineated. Stage 1 formed in mylonite zones around the Boss Mountain Stock, Stages 2 and 3 around centres of mineralization and Stage H- occurs in and near shear zones. Five periods of fracture development, each of which contains quartz veins of unique mineralogy and characteristics, were interspersed with breccia formation, alteration and mineralization. Mineralization accompanied breccia formation and fracture development. Molybdenite was introduced, during three separate periods of mineralization, two of which were separated by a barren stage that produced a complex mineral assemblage. Pyrite accompanies all stages of mineralization. Pleistocene (?) alkali basalt dykes related to Takomkane Volcano, which forms the twin summits of Takomkane Mountain, cut all rocks and ore structures. The volcanic rocks of the volcano contain xenoliths of granodiorite, glassy black augit and peridotite. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

In the summer of 1967, dipole arrays were used to make deep resistivity soundings in the Fraser Valley of British Columbia. The large dipole moment of the input dipole (270 amp x 37 km) allowed input-to-measuring dipole spacings as great as 100 km. Calculations show that Georgia Strait, which is spanned by the input dipole, should have little effect on layered earth potentials for the dipole to dipole spacings used in this survey. A three-layer model with a resistive second layer (transverse resistance approximately 3000 times that of the upper layer) agrees well with the data. A more complicated four-layer model can be devised by using data from deep wells in the area. Interpretation of well and sounding data indicates that 500 m of conductive ocean and ocean sediments overlie 4-5 km of Tertiary and Cretaceous sedimentary rocks and 2 km of granitic rock. A conducting layer underlying the granitic rock may be the result of water saturation of the rocks at these depths. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Empire mine is located on north-central Vancouver Island about two miles south of Benson Lake; Orebodies are typical of the many contact metasomatic iron deposits of the West Coast of British Columbia. They occur in Bonanza volcanic rocks and Quatsino limestone of Upper Triassic age near the margins of a small granitic stock of intermediate composition. Structural controls at Empire mine are in part the configuration of the intrusion contact and in part the intersection of steep northeasterly faults with (a) folded and fractured volcanic rocks at the Merry Widow deposit and (b) with swarms of northwesterly striking greenstone dykes in the Kingfisher deposits. The Kingfisher fault transects both the Merry Widow and Kingfisher orebodies as well as the West Pipe and is considered one of the main channels for mineralizing solutions. Relatively intense folding occurs near margins of the Coast Copper stock. In the Merry Widow area, plot of poles to bedding on Schmidt equal area net indicate a north-northwesterly plunging major fold. Superimposed on this are minor drag and disharmonic folds. Fold axes all strike northerly sub-parallel to the intrusion contact and folding is considered a direct response to emplacement of the Coast Copper stock. Relation between intrusive greenstone and local folding would suggest that final stages of Bonanza volcanism, regional folding and emplacement of the stock with local folding and mineralization may be nearly contemporaneous. / 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

Bowie Seamount, a submerged volcano situated off the west coast of Canada at 53° 18; N, 135° 39' W, has a relief of 10,000 ft. and comes to within 100 ft. of the ocean surface. It is made up of a series of intersecting ridges which together give the mountain an overall northeast - southwest elongation. It appears to be a combination central and fissure type volcano which has been built up over a system of intersecting fractures in the oceanic crust. Two terraces form the flattened summit of the volcano at approximate depths of 45 and 130 fathoms. These are thought to be the remains of platforms produced by combined wave erosion and shallow-water vulcanism during late Quaternary time when sea level was lower than it is today. The last phase of volcanic activity on the summit occurred after the formation of the upper terrace no more than 18,000 years ago. Samples dredged from the upper half of the volcano include: pillow fragments, fragments of non-pillowed flows, pillow breccias, bombs, tuffs, ash, and unsorted tephra. The rocks are mainly alkali olivine basalts, accompanied by rare andesites which, presumably, were derived by differentiation of the basaltic magma. Feldspathic and gabbroic inclusions, many of which appear to be cumulates, are common in the basalt. Ice-rafted rocks are rare on the summit of Bowie Seampunt but are common on its nearest neighbour - Hodgkins Seamount. A ferro-manganese deposit, apparently over 1 million years old, that exists on the summit of Hodgkins Seamount, suggests that this peak is relatively much older than the summit area of Bowie Seamount. Palagonite appears to form as the initial phase of weathering of glassy basalts in the area of study but the products of more advanced weathering are montraorillonite and zeolites. Rock fragments that have been rounded by chemical weathering are common. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate