There have been many studies investigating microbial mat colonies in carbonate environments, yet few have been completed for siliciclastic settings.  This thesis presents research of microbially induced sedimentary structures from the siliciclastic portion of the Paleoproterozoic Gunflint and Rove Formations, Animikie Group, northwestern Ontario.  Four outcrops were chosen for investigation in the Thunder Bay area based on their depositional environments.  The first of the 3 sites was in the Rove Formation, where the physical features resemble a submarine fan environment with turbidity current deposits.  The other two Rove Formation sites were comprised of fine, parallel laminated black shale near its base.  These 3 sites did not show evidence of microbial communities, while the fourth site in the Gunflint Formation at Current River did.  The outcrop is located north of the famous Gunflint stromatolites on the Eastern River bank of Current River.  Multiple microbially induced sedimentary structures (MISS) were located on the bedding surfaces and were recorded by photograph.  These include:  (a) bulges of mat growth due to repeated wetting of the area, (b) preserved mat chips, (c) Kinneyia wrinkle structures, (d) ripple patches, and (e) similar textures on multiple sand layers indicating extracellular polymeric substances (EPS).  Further inspection using a petrographic microscope revealed (f) wavy-crinkly biolamination and (g) redeposited roll-up structures from the rock samples.  None of these examples can be indisputably proven as microbially induced sedimentary structures, yet these features should be considered as indicators of microbial mats in the siliciclastic sediments of the Gunflint Formation.

Orangeites occur within a sub-parallel en-echelon dike system on several farms near Swartruggens, Transvaal.  Emplaced during the upper Jurassic in an approximately 1 km thick sequence of lavas of the Pretoria series, they are underlain by approximately 1.5 km of highly fractured shale/slate which overlies Transvaal dolomite.  The incompetent and fractured nature of the shale is believed to be responsible for the meandering, splitting, and intertwining nature of the dikes which may vary considerably in thickness over short distances or pinch out rapidly.  Composite dikes are common, with different levels and segments of individual dikes displaying petrographically different character and degrees of alteration.  Evidence exists for multiple intrusions with relatively slow magma-emplacement rates, as demonstrated by the preservation of delicate flow banding as dikes curve around irregular host rock protrusions.

This study of the Swartruggens orangeite was limited to the investigation by transmitted light and electron microscopy of samples from mining levels 3, 4, 6, and 7 of th Helam Mine.  Flow banding is evident in samples from levels 6 east and west and 7 east.  Levels 6 and 7 also contain the greatest diversity and abundance of accessory minerals which commonly include apatite, barite, and calcite.  Less common but important phases are perovskite, wadeite, and an unidentified Ca-Ti-Fe silicate.  Minor phases include strontianite, an unidentified Ca-REE phosphate, zircon, an unidentified Ca-Zr silicate, and diverse oxides and sulphides.  Strontium is a common component in apatite, barite, calcite, and perovskite, with barium present to a lesser extent in some of the apatite and calcite.  Both SrO and BaO contents within these minerals may vary considerably within samples from different levels.  REE-oxides are a minor component of some of the apatite and are present in perovskite in moderate amounts.

Compositionally distinct from archetypal kimberlites, Swartruggens orangeite bears closer similarities to lamproites, but differs sufficiently to preclude classification as such.  The accessory minerals apatite, barite, perovskite, and wadeite are common to both Swartruggens orangeite and lamproites.  Differences include the presence of calcite, a relatively rare mineral in lamproites, in Swartruggens orangeite.  An unidentified Ca-Ti-Fe silicate is unique to Swartruggens.  Common lamproitic phases such as leucite, sanidine, shcherbakovite, and K-Ti richterite are absent from Swartruggens.

Lamproite and orangeite magmas are believed to have similar origins in being the products of partial melting of metasomatized lithospheric mantle.  Unique differences resulting from long term evolutionary patterns of diverse lithospheric sources are believed to be responsible for the production of orangeite magmas within the Kaapvaal craton and lamproite magmas on other cratons, and could produce other types of potassic rocks elsewhere.  A proposal has been suggested to include all potassic magmas within a broad group termed the Metasomatized Mantle Magma (MMM) group reflecting similar petrogenetic processes in their origins.

Hogarth Pit Lake was formed from the continual flooding of the open pit iron mine at Steep Rock Lake near Atikokan, Ontario, Canada.  In the past Hogarth Pit Lake has been toxic to aquatic species, although recent studies are beginning to show that toxicity is no longer a problem.  It was the purpose of this stuffy to relate the sources of the Hogarth Pit Lake waters to the surrounding geological units.  To further the study potential sulphate sources were investigated for any sulphides present in the rock units that may lead to high sulphate levels through oxidation.  Water-rock reactions such as carbonate buffering reactions were used to aid in determining potential sulphide sources producing high sulphate levels through oxidation.  Carbon and sulphur isotope abundances of surrounding rocks and water were another tool used to further aid in determining sulphate sources.  Tributaries from the hangingwall and footwall display a wide range in trace element and stable carbon and sulphur isotope composition.  δ³⁴S water values as low as -3.6€ indicate sulphide oxidation which matches δ³⁴S depleted rock values (>-7.2€).  Water samples show depletions up to -20.3€  δ¹³C while the lowest rock sample is only -4.0€  δ¹³C.  The investigations carried out isolated they pyritic rich Ore Zone as a sulphate source that leads to high sulphate waters by a groundwater source.

The Bol©o Cu-Co-Zn deposit is located on the eastern coast of the Baja Peninsula, Mexico and comprises an area of approximately 90 km². The Bol©o sub-basin is contained entirely within the Santa Rosalía basin and represents a sediment hosted, stratiform copper-cobalt-zinc deposit. Baja Mining Corporation currently holds the mining rights to the area with planned exploitation of the deposit commencing in 2009.

The overriding geological control for the area is the continental rifting that formed the Gulf of California. One of the resultants of this tectonism is that much of eastern Baja is underlain by volcanic rock. Consequently, the Bol©o Formation represents the initial rift fill sedimentary sequence in the Santa Rosalía basin and is approximately 250 to 350 meters thick. There is an initial basal sequence of limestone and gypsum followed by five separate instances of upward coarsening fan-delta cycles. Each cycle can be broadly defined as clay-siltstone-sandstone layer followed by a conglomerate followed by a mineralised layer.

The alteration in the conglomerates can be characterised in two broad patterns. As such, there are alteration trends that can be considered as diagenetic in origin, meaning during and/or as a result of the lithification process. The results of this initial alteration can be further categorised. On the one hand, widespread & pervasive hematisation with an increase in montmorillonite can be observed. On the other hand, calcite alteration can be seen in selected units that are associated with an interbedded gypsum layer. However, the former is not mutually exclusive to the latter.

Conversely, there is another alteration trend only seen specifically that can be considered hydrothermal. In this case, the rocks will have pronounced dolomite alteration combined with the possibility of additional montmorillonite. As a comparison, the tuffaceous claystone in tandem with the conglomerate can be used to define a signature of least alteration. 

For more details about this thesis contact Dr. Andrew Conly

The Canadian Shield is mostly composed of granite, and patches of rock outcrop cover about 30% of the Shield.  Soils on the outcrops are much shallower than forested areas and the vegetation communities that persist on the rock outcrops are not well known.  This thesis explores the control of the physical factors on the soils and vegetation communities that develop on the rock outcrops (barrens) in the Thunder Bay area.  In this thesis I investigate the relationship between parent material and soil chemistry characteristics, and the importance of physical factors in determining species assemblages.  The research area was located in Thunder Bay, Ontario, along the north shore of Lake Superior and included five sites with different parent materials.  The bedrock geology in the area is Archaean (granite) to Proterozoic (Gunflint Formation) in age.  Soil samples were collected in the field and analyzed in the laboratory for: bulk density, moisture content, organic matter content, available nutrients, cation exchange capacity, particle size distribution, water holding capacity, and pH.  Nonmetric multidimensional scaling was used to identify physical factors that control the variation in species assemblages and analysis of variance was used to test for differences in soil characteristics among the sites.  Distinct vegetation communities were present at each site and the physical factors controlling vegetation structure differed among the sites.  Generally the main controlling factors were exposure, pH, organic matter content and available nutrient concentrations.  Significant differences in soil chemistry among the sites were reported that indicates the important role of lithology in soil development.

Throughout the Boreal Forest the bedrock of the Canadian Shield is seen on barren outcrops.  These areas are classified as alternating sequences of bare rock, lichen patches and treed islands.  On the rock barrens soils are typically shallow and the freeze-thaw and wet-dry cycles that characterize these systems result in a stressful environment for the plants and animals that inhabit these systems.  Despite the prominence of these systems on the landscape, particularly in Northwestern Ontario, we know very little about their structure and function.  This study examines soil properties and rates of net nitrogen mineralization and net nitrification of lichen patches and treed islands on three outcrops in Northwestern Ontario. The bedrock geology, slope and aspect of the three sites were similar among the studied sites. The plants and soils were characterized at each of the sites and soil samples were collected from lichen patches and treed islands.  Soil samples were analyzed in the laboratory for pH, carbon to nitrogen ratio, nitrogen concentrations, net nitrogen mineralization and net nitrification.  The lichen patches had thinner, more acidic soils with a lower carbon to nitrogen ratio when compared to the treed islands.  The results from the aerobic incubation showed that there was no difference in the rates of net nitrogen mineralization and net nitrification.  This could be due to immobilization from the microbial biomass.  Nitrogen is one of the limiting nutrients in plant growth as it controls net primary productivity, making it essential to further investigate nitrogen processes that occur on barren outcrops.

New expansion along Highway 11/17 east of Thunder Bay, Ontario exposes faults and damage zones that cut through and displace the Gunflint Formation of the Animikie Group, the underlying Archean basement rock, and the basal unconformity between them.  Observations and stereographic projections were used to characterize outcrop-scale deformation along a curved road-cut on a hill approximately 1km long and covering an increase in elevation from west to east (where the unconformity is exposed) of about 65m.  The Highway 11/17 road-cut exposes a fault zone network that has accommodated a minimum of 60m of vertical displacement and unknown horizontal displacement.  Two sets of well-preserved slickenlines record normal oblique sense movement on the fault zone.  A void-filling calcite vein system is exposed in conjunction with the fault systems and is associated with brecciation.

Calcite crystals reach up to 10cm in diameter where larger voids are filled.  At least two major fault zones with damage zones at least 1m wide are exposed at the study site and are seen at the far east and far west of the road-cut.  The Eastern Fault Zone (EFZ) has an average strike and dip of 071°/72° cutting through both Archean basement rock and Gunflint Formation.  The Western Fault Zone (WFZ) average strike and dip is 067°/65° and cuts through Gunflint Formation rocks.  Two relatively minor reverse faults strike 345° and dipping 48° to 58° cut through the Gunflint Formation about 80m southwest of where the WFZ first appears.  The relationship between EFZ and WFZ is obscured by an oblique fault cutting through Archean rock between them with an average strike and dip of 040° and 60°.

The site is a potentially important study location for understanding fault/fluid interactions and how extensional faulting can accommodate fluid transportation.  All major extensional features in the study area have a roughly northeast strike which aligns well with the orientation of the Mid-Continent Rift to the southeast suggesting that this fault zone is associated with extension ca.  1Ga. 

The Paint Lake Deformation Zone is an east-west trending lineament that extends approximately 40 km east of Lake Nipigon, in theWabigoonSubprovincein the Superior Province of Ontario.  Sage Gold Inc. owns thePaintLakeproperty, host to a shear zone hosted gold occurrence at a major lithological contact.  This lithological contact occurs between the Northern Sedimentary Unit (NSU) and Northern Volcanic Unit (NVU) of the Beardmore-Geraldton Greenstone Belt, from north to south respectively.  Mapping of the property, combined with transmitted light microscopy and geochemical analyses revealed the Northern Sedimentary Unit to be represented by polymictic metaconglomerate, and the Northern Volcanic unit to consists of steeply-dipping pillowed to massive tholeiitic basaltic flows and interleaved lenses of intrusive high-Fe tholeiites, with one occurrence of a calc-alkaline dacite tuff.  A total of four rock suites were identified on the property and later confirmed using geochemical data.  An arc/back-arc environment was characterized as the tectonic environment, within which the volcanic units were deposited.

The contrast between competent and incompetent rock units, and their associations with ductile and brittle structures is integral to the presence of alteration and mineralization.  Gold associated with pyrite occurred most often at or adjacent to lithological contacts between rocks differing competencies.  This idea can be examined on various scales, from the regional scale of thePaintLakedeformation zone and its relation to the contact between the NSU and NVU, to the outcrop scale in which mineralized quartz veins occur within contacts of differing lithons of rock.  Significant contrasts between the rock units are important, otherwise there might not be enough opportunity for considerable gold mineralization to occur.

Microstructural analysis provides evidence of significant ductile deformation concentrated along the Main Break, in Kirkland Lake, ON.  The Main Break is an east-west striking mineralized fault system that has sustained multiple gold mines since its discovery in 1911.  It is found in the southern Abitibi gold belt on Kirkland Lake Gold Inc.’s Lakeshore Mine property, which is a structurally controlled orogenic gold deposit.

Oriented samples for microstructural analysis were collected from two new 1-meter long channels across the Main Break spaced eight meters apart.  Samples were examined in transmitted and reflected light microscopy.  Evidence of ductile deformation by dislocation creep to produce mylonite, inclues porphyroclasts of potassium feldspar in an extremely fine-grained matrix, mineral alignment, and undulatory extinction and subgrains in potassium feldspar; as well as lenticular aggregates of feldspar and muscovite showing dextral shear sense.  Dislocation creep occurs in feldspar during ductile deformation at temperatures in the amphibolite facies of metamorphism or higher, which puts deformation of the Main Break at temperatures above 400°C.

Sericite aggregates replacing potassium feldspar likely enhanced grain softening during this ductile deformation process.  Sericite as well as evidence of pressure solution along grain boundaries indicate the presence of a hydrous fluid during deformation.

Ductile deformation will produce porphyroclasts with penetrative foliations wrapping around them.  Such porphyroclasts would normally be explained by a difference in rheology, however, even in monomineralic rocks it is possible to have adjacent grains deforming by different mechanisms.  These different responses could be controlled by variations in crystallographic orientation of the grains where the slip planes are favorably oriented for slip in one grain but in a hard orientation for surrounding grains or simply different sized grains of the same mineral accommodating deformation by different mechanisms.  The most significant evidence of simultaneous brittle-ductile deformation is a potassium feldspar porphyroclast with strong undulatory extinction and subgrains in one half of the grain and microfractures in the other half.

It is concluded that the Main Break is a narrow ductile shear zone with minor brittle deformation.

The McKenzie granite is an approximately 18 km igneous intrusion within the Quetico Subprovince, located 20 km northeast of Thunder Bay, Ontario. Petrologic and geochemical data has been used to classify the McKenzie granite as dominantly S-type. The intrusion is classified as a quartz monzonite with assemblages characterized by muscovite+biotite±sphene±hornblende. The McKenzie granite contains a peraluminous geochemistry with SiO₂ contents ranging from 63.8-68.2% along with enrichment in light rare earth elements, fractionated heavy rare earth elements, decreasing trends of major oxides, transition metals and high field strength elements and scattered large ion lithophile elements due to remobilization during chlorite, sericite, and carbonate alteration. Formation of the McKenzie granite was likely similar to the model proposed for the later stages of the genesis of the Dog Lake Granite Chain, which involved partial melting of the mantle wedge beneath the Wawa-Abitibi island arc. The mafic melt produced from the subducting oceanic lithosphere would underplate the Quetico Subprovince leading to formation of granitic I-type melts via fractionation. These melts would then rise through structural conduits at the Quetico-Abitibi border. The majority of the underplated melt would contribute to the production of the S-type granites that are normally seen in Quetico Subprovince. These S-type melts formed from the partial melting of the overlying metamorphosed sedimentary rock and may have been allowed to interact with I-type melts. This would allow for variations in geochemical and petrological data that is not common for standard S-type granites.