The Dog Lake Granite Chain is composed of six ovoid magnetite-bearing granitic intrusions within the Quetico Basin, Northwestern Ontario. From east- to west the intrusions are the Penasen Lake, White Lily, Barnum Lake, Trout Lake, Silver Falls, and Shabaqua intrusions. The Dog Lake Granite Chain is characterized by a linear trend, which parallels the tectonic boundary between the Wawa-Abitibi terrane to the south, and the Quetico Basin to the north.    

Petrologic and geochemical data has been used to classify the granites as both I- and S-type. The I-type granites can be classified into three broad groups, a microcline-phyric monzonite/quartz-monzonite, syenite/quartz-syenite, and a monzodiorite. These granites are massive, silica poor, largely metaluminous, and characterized by a hornblende+ magnetite+ sphene +/-pyroxene assemblage. The microcline-phyric monzonite/quartz-monzonite and syenite/quartz-syenite groups are characterized by positive _ɛNd (+1.44 to +2.11) values. The I-type granites have been recognized within the Trout Lake, Barnum Lake, White Lily, and Penasen Lake intrusions.

The S-type granites are typical of the Quetico Basin, and have a largely peraluminous affinity, variable _ɛNd signatures (-1.44 to +1.09), and are characterized by a muscovite+ biotite+/- garnet assemblage. The S-type granites have been sampled within the Silver Falls, Trout Lake and White Lily intrusions.

The recognition of I-type granites within the Quetico Basin, which is predominantly composed of S-type granites, requires a different model for the formation of this relatively rare rock type. It is proposed that the formation of I-type granites within the Quetico Basin involves the partial melting of the mantle wedge beneath the Wawa-Abitibi island arc. The mafic melt would have underplated the Archean lithosphere, where they would have evolved into granitic melts through fractionation, thus giving rise to the I-type granites. Small volumes of these melts were then emplaced within the Quetico Basin, possibly along weaknesses associated with lithosphere scale structures at the boundary between the Wawa-Abitibi terrane and Quetico Basin. The majority of the underplated melts would likely have contributed to the production of large S-type granites, which are typical of the Quetico Basin. These S-type melts formed from the melting of sedimentary rocks, and may have interacted with the I-type granites, producing variations in isotopic and geochemical signatures as seen within the S-type granites of this study.

Although magnetite-bearing granitic intrusions within the Quetico Basin are not unique, the identification and classification of I-type granites has not been widely documented. The regional implication of I-type granites within the Quetico Basin is both profound and complex. It is suggested that other magnetite-bearing metaluminous granites within the Basin (e.g., the Vermillion complex, northern Minnesota) may have formed through a similar process as the Dog Lake Granite Chain.

A representative collection of minerals from two niobium deposits found within the Oka carbonatite complex:  theBondZonedeposit; and the NIOCAN deposit, were analysed using an electron microprobe, and compared with existing data from the St. Lawrence Columbium deposit.  These minerals are good indicators of the petrological evolution of alkaline rocks, and can be used to re-evaluate the paragenesis of niobium mineralization, and the relationships between Nb-bearing minerals.  In addition, this study has revealed the presence of zirconolite as an accessory mineral in calciocarbonatite.

At Oka , pyrochlore typically occurs as euhedra -to -subhedral crystals, rarely as aggregates and clusters.  Back-scattered images, coupled with microprobe analyses, reveal complex compositional zoning in pyrochlore, which undoubtedly reflects changes in the fluid composition during the growth of the mineral.  Large compositional variations were observed for the major oxides of the pyrochlores:  CaO (ranging from 4.1-34.8 wt. % oxide), TiO₂ (2.3-40.4 wt. %), Nb₂O₅ (20.1-58.1 wt. %), ThO₂ (0.3-18.2 wt. %), and UO₂ (0.1-28.0 wt. %).  Ceriopyrochlore, cerium pyrochlore, and uranpyrochlore exhibit the greatest A-site vacancies, ranging from 8.1-62.5 %.  Of the REEs, only Ce is present at high concentration levels (ranging from 2.1-15.8 wt. %).  Of note is the significant content of ZrO₂, which ranges from 0.9-16.3 wt. %.  An A-site substitution in the pyrochlore-group minerals has been identified between (REE+U+Th) and (Na+Ca), as well as a B-site substitution between (Nb+Ti) and Zr.

Latrappite and Nb-rich members of the perovskite-group are found occurring as euhedral - to -subhedral crystals.  Both oscillatory and patchy zonation in theOkaperovskites has been identified using back-scattered imaging.  Small compositional variations are observed in the major oxides of both the latrappite- and -perovskite end-members. Okaperovskites are slightly enriched in the LREE's, Ce being the dominant LREE (averaging 3.5 wt. % oxide).

This thesis is in two parts.  Part One compares Ion Exchange and Oxalate Precipitation as post irradiation techniques for isolation of Rare Earth Elements (REE) from geologic samples prior to analysis by gamma ray spectrometry.  Ion Exchange, although effective, was determined to be less applicable than Oxalate Precipitation.

Part Two concerns the distribution of REE in silica undersaturated rocks from Uvalde, Texas.  REE distributions suggest that phonolites in the region may be related to rephelinites in the region through processes of fractional crystallization involving kaersutite (amphibole).  Similarities between REE distribution patterns for melilite-olivine nephelinites from Texas and various European melilitites suggest that each may have resulted from similar degrees of partial melting of parental materials having similar initial REE abundances.

The structure of the Archean metasedimentary rocks of the Beardmore-Geraldton fold belt is investigated.  It has been suggested that two deformational episodes have affected the area near Geraldton.  The F₁ folds are recumbent and not seen in outcrop.  An early foliation (S₁) is observed in thin section that closely parallels bedding (S_o).  The dominant folds of the area, called F₂, have associated an axial-planar, penetrative cleavage (S₂).  This S₂ fabric element is subvertical and generally strikes east-west.

The structural facing direction of F₂ folds is either upward to the west or downward to the east.  Folds with consistent facing directions are separated by an east-west trending shear zone.

Modification of F₂ flexure folds by homogeneous compressive strain, has flattened folds so that they approach the geometry of similar fold styles.  Further modification of fold geometry has occurred due to shear displacements that are typical of the fold belt.  The zone of intense shearing shows how earlier fabric elements have been transposed into the S₂ foliation.

The horizontal compressive forces acting from the north and south have produced the east-west trending shear zone and folds of the area.  These crustal forces have affected the well-stratified metasedimentary rocks and are reflected by the structure, observed on all scales.

The study consisted of examining six porphyry copper deposits (Ingerbelle, Copper Mountain, Afton, Lornex, Bethlehem and Brenda Mine), four Precambrian volcanogenic massive sulphide deposits (Millenbach, Mattabi, Geco and Winston Lake), and a syn-sedimentary deposit (Sullivan Mine).  The examinations included a petrographic study to determine the titanium minerals and alteration present, an analysis of whole rocks of altered and unaltered equivalents, to determine if titania content fluctuates with alteration, and a microprobe analysis of biotites, a mineral that can contain significant amounts of titanium in its structure.

The porphyry copper deposits related to calc-alkaline intrusions contained rutile produced from the alteration of primary, magmatic biotite.  The highly metamorphosed volcanogenic massive sulphide deposits contained ilmenite present in the altered mafic, volcanic flows of related rocks.  The ilmenite is formed due to the metamorphism of rutile plus magnetite with the rutile originally forming due to the alteration of titanomagnetites.  At the Sullivan mine, the syn-sedimentary deposit studied, rutile of detrital origin is found in the hanging wall sediments.  Sphene is present in the albitized hanging wall sediments.  The titanium minerals that are present in the different deposit types formed under different conditions and are therefore unrelated genetically.

The area of this study occupies a transitional terrane between the Quetico and the Wabigoon subprovince, near Geraldton, Ontario.

Rocks in the study area have been grouped into four categories including metasedimentary rocks, conglomerates, iron formations, and intrusive rocks.  The vast majority of outcrops visited were metasedimentary rocks.  All rocks in the study area have been metamorphosed to the lower Greenschist facies.

Detailed structural mapping has led to the establishment of major fold structures.  Evidence suggests that the rocks have been subjected to at least two episodes of folding.  Dominant folds have a consistent shallow plunge to the west.  A shear zone has affected the rocks and trends from east to west, roughly through the center of the study area.  The shear zone divides the area into two domains:  north of the shear zone folds face upward to the west; folds south of the shear zone face downward to the east.

The Coldwell Complex, of Neo-Helikian age intrudes Archean metasedimentary and metavolcanic rocks during three intrusive episodes.  The major rock units of two episodes, Center I and Center III, were studied in petrographic detail.  In addition, exotic and cognote xenoliths were examined.  An overview of mafic and felsic dikes and structural features completed the study.

Field mapping and microscopic examination were used to detail changes in lithologies.  Several x-ray diffraction determinations were made on opaque minerals.

The study defined textural changes across both the Center I border gabbro and ferro-augite syenite.  This will aid in the formulation of an evolutionary model for the western contact and perhaps the intrusion in general. 

Three textural and mineralogical variations were noted in Center III quartz-syenite and a porphyritic and contaminated porphyritic-porphyroblastic quartz-syenite were defined. 

Structural relationships indicated a correlation between joint forming episodes and dike forming episodes.

Studies of mafic and felsic dikes and correlation with structural data indicated some dike forming episodes were closely related to some joint forming episodes.

The Quetico Belt is an Archean metasedimentary unit, possibly an accretionary prism, over 800 km long within the Superior Province of the Canadian Shield.  It is bounded by the Wabigoon metavolcanic belt to the north and the Shebandowan - Wawa volcanic - plutonic belt to the south.  The sediments within the Quetico belt are primarily greywacke and mudstone turbidities which, toward the centre of the belt, have been folded, progressively metamorphosed, migmatized, and undergone local anatexis with increasing metamorphic grades.

The metamorphic grades observed within the Quetico belt range from lower greenschist facies at the margins to upper amphibolite with concomitant anatexis.  In the study area, the lower grade rocks are characterized by the presence of sericite and chlorite, with increasing grades resulting in the development of biotite, hornblende, garnet, cordierite and staurolite, and increasing calcium content of plagioclase.

The regional metamorphic conditions across the belt have been estimated to range from low greenschist facies conditions near the north and south boundaries through areas at 500°C, 3 kb pressure to 700°C, 4 kb pressure, up to a maximum of 720°C and 4.2 kb pressure.  The metamorphic conditions in this study area probably range form the same lower boundary conditions up to approximately 600°C at 3.5 kb.

In this paper, heterogeneous simple shear model kinematic indicators are used to determine the presence of a shearing event in Gorham Township of Thunder Bay.  Field observations combined with microscopic analysis reveal that highly complex shearing occurred in this area possibly as a result of transpressional effects.  Four exposures were studied and data collected from these support the view that mylonites are a common occurrence in shear zones and act as a method by which deformation of this nature can occur.

The study area lies within the Beardmore-Geraldton Greenstone Belt, a portion of the Wabigoon Subprovince.  This belt hosts one of the most famous gold camps in the Canadian Shield where production was realized from eighteen mines.  Gold mines and occurrences within the belt have been subdivided on the basis of location and host rock lithology.  The three sub-belts include: the southern mafic volcanic dominated belt, the southern sedimentary dominated belt, and the northern felsic volcanic dominated belt.

This study is concerned with mineralization in the Maki prospect which lies within the southern mafic volcanic dominated belt.  It is underlain by massive, pillowed, and tuffaceous intermediate to mafic metavolcanics.  Oxide-silicate-carbonate iron formation of regional extent as well as quartz-carbonate veins occur within the mafic to intermediate metavolcanic assemblage.  Gold, although erratic, is associated with sulphides within iron formation and quartz-carbonate veins.

The petrology of two trenched gold showings on the Maki prospect was examined.  This study entailed extensive use of thin sections and X-Ray diffraction techniques to determine mineralogy as well as relative timing of metamorphism and hydrothermal alteration.

It was determined from mineral crosscutting relationships that the hydrothermal alteration responsible for gold deposition, pre-dated greenschist to epidote-amphibolite facies metamorphism.

Extensive carbonate alteration of host rocks suggests that the fluid responsible for gold deposition were rich in CO₂.  Such fluids could be produced from dehydration and decarbonation of a deeply buried mafic volcanic sequence during upper amphibolite to granulite facies metamorphism.  Fluid access to the above rocks was probably provided by fracture zones and other conduits.  Gold deposition within vein systems is thought to be a result of fluid-wallrock interaction at temperatures and pressures of greenschist to lower amphibolite facies metamorphism.  Since metamorphism post dated infiltration of hydrothermal fluids within the Maki prospect, it is believed that the required temperature range of the metamorphic front had not yet reached the study area at the time of hydrothermal flooding.  If this fluid once carried significant amounts of gold, then most of it was probably deposited at greater temperatures and depths.  It is possible that small amounts of gold which did not precipitate as the preferred temperatures may have continued upward, forming low grad auriferous deposits within the study area.

The iron formations lack suitable structurally prepared sites, (i.e. minor folding) and thus, even if temperature conditions had been favourable, it is debatable whether viable gold deposition would have occurred.