Seamus Magnus Honours thesis abstract

Thesis Title: 
An Investigation of the Assimilation Hypothesis in the Navilus Sill, Thunder Bay, Ontario
Seamus
Magnus
HBSc
2012

Pink granophyric features in some of theLogan sills, particularly in the Navilus sill, just west ofThunder Bay, were attributed by Blackadar (1956) to in-situ assimilation of granitic material.  Petrographic and geochemical studies have been performed on both the Navilus and Terry Fox sills, with a more modern approach, in order to re-evaluate Blackadar's hypothesis.

Two unique zones consistently appear around the xenoliths found in the Navilus sill: a zone of quartzo-feldspathic intergrowths, or "granophyre", directly adjacent to the xenoliths, followed by a zone of discreet pyroxene grains on the interface between normal diabase magma and the granophyric zone.  Similar granophyric formations are found interstitial to plagioclase and pyroxene grains, along with closely associated iron-oxides, both of which appear to have formed during the latest stage of crystallization due to the immiscibility of a silica-rich and an iron-rich liquid which exsolved from the magma.  The similarity between the granophyre observed around the xenoliths, and the late-stage "groundmass" granophyre indicates that the former was also formed due to liquid immiscibility.  Introduction of silicate-rich xenoliths to the already silica-saturated, quartz-tholeiitic magma has been proposed as the cause for the premature exsolution of silica and iron-rich liquids from the magma.

Spherules have been observed in close proximity to the xenoliths and granophyric zones, with carbonate nuclei and chlorite rims.  Due to the high melting temperature of carbonate minerals, it is unlikely that these were derived from a melt, and were more likely formed as carbonate xenoliths from the overlying Gunflint Formation recrystallized and interacted with the magma to produce spherical chlorite rims.

REE diagrams for both the Navilus and Terry Fox sills indicate that geochemical variations between the diabase with inclusions (such as xenoliths and spherules) and the normal diabase have been caused by late stage fractionation during crystallization.

Variable enrichment of LILs as seen in the Spider diagrams for both sills may indicate that in-situ assimilation has taken place, though variable depletion of HFSEs may indicate that these patterns also represent the effects of fractionation.

The basal contact of the Terry Fox sill with Rove shale (SM011) displays REE and Spider diagram patterns that differ from the normal diabase in that sill, which may indicate that in-situ assimilation has taken place, though a more detailed analysis is required to fully understand the role of assimilation in these sills.

Plotting the samples of normal diabase from both sillson Gd/Yb vs. La/Sm and TiO2 vs. Mg# discrimination diagrams has grouped the Navilus and Terry Fox sills with the Nipigon sills, contrary to their previous designation as Logan sills.

Jeff Myllyaho HBSc thesis abstract

Thesis Title: 
Mineralogical indicators of Ni-bearing zones within the Bird River Sill, Manitoba
Jeff
Myllyaho
HBSc
2007

The Bird River Sill is an approximately 600 metres thick, layered ultramafic and mafic intrusion that is intermittently exposed over a strike length of approximately 20 kilometres in southeastern Manitoba, Canada.  Continental arc and intra-arc, rift-related magmatism occurred from 2.75-2.73 Ga and resulted in the intrusion of the Bird River Sill into the Rice Lake Group of the Archean Bird River Greenstone Belt (Sanborn-Barrie et al., 2001).  Initial interest in the mineral potential of the Bird River Belt resulted from the discovery in 1917 of nickel and copper sulphides in ultramafic rocks within the northern limb of the sill.  Economic interest in the sill has continued to the present with the main objective of this study being to determine if there any minerlogical indicators for nickel-bearing sulphide within drill core provided by North American Palladium Ltd. in the summer of 2005.

Petrology, X-ray diffraction (XRD) and scanning electron microscopy (SEM) shows that regional metamorphism in the Bird River area induced weak to strong alteration within certain ultramafic rocks.  Major alteration products include uralitization of pyroxene and serpentinization of olivine within peridotite intervals.  Clinochlore also commonly replaces ferromagnesium pyroxene and olivine in ultramafic.  Mineralized intervals from North American Palladium's 2005 drill holes showed increased abundances of actinolite and clinochlore.  Along with this increased alteration, the minor amount of remnant olivine crystals present in mineralized samples display a slightly rounded habit.  This contrasts with unmineralized, less altered intervals within the Bird River Sill.  These unmineralized intervals show slightly elongated and more abundant remnant olivine crystals.  Alteration between mineralized and unmineralized intervals also shows differences in the modal abundance of actinolite and clinochlore where there is decrease inabundance of both phases unmineralized sections.

Murray J. Watt HBSc thesis abstract

Thesis Title: 
A Biogeochemical Study of the Influence of Lithology and Topography on Foliar Nutrient Levels in Vegetation Growing on Two Contrasting Rock Types in Quetico Provincial Park, Ontario
Murray J.
Watt
HBSc
1990

The purpose of this study was to provide biogeochemical data for a remote sensing companion study.  Rock, soil, and foliar samples were collected from an area covering two contrasting rock types - metavolcanic rocks and metasedimentary rocks.  The study area was located in the south east portion of Quetico Provincial Park, Ontario.  The foliar samples collected were Abiesbalsamea (L.) Mill, Acer spicatum Lam., Betula papyrifera Marsh., and Thuja occidentialis L..  The whole rock composition of rocks and soils were determined using X-ray fluorescence.  Mineralogy of soils was determined using X-ray diffraction techniques.  Foliar nutrient compositions were determined using Inductively Coupled Plasma Spectrophotometry.  Levels of foliar nutrients appear to be controlled by an array of factors.  Trends are more evident for foliar nutrient levels growing on the relatively homogeneous metavolcanic rocks than on the more chemically complex metasedimentary rocks.  Possible effects of nutrient inhibition and pH inhibition appear on some trends.

Marc Gasparotto HBSc thesis abstract

Thesis Title: 
A Microstructural Study of the Geology of the Otjikoto Gold Deposit, Namibia
Marc
Gasparotto
HBSc
2012

The Otjikoto project in Namibia is an orogenic gold deposit situated in the province of Otjozondjupa, approximately 300 km north of the capital city of Windhoek.  Research for this thesis was carried out through the microstructural analysis of thin sections (obtained from Auryx Gold) that were collected from drill core.  The microstructures produced by deformation exhibited in the minerals of this deposit provide information about the relative timing of metamorphism, deformation, quartz veins and gold mineralization of the Otjikoto project.

The metapelitic Okonguarri Formation, host to the Otjikoto gold mineralization, contains evidence for peak metamorphism at the temperatures and pressures of the sillimanite zone of the amphibolite facies.  Grain-size reduction of feldspar indicates that mylonitization also occurred at amphibolite facies temperatures.  The formation also exhibits heterogeneous ductile deformation, specifically associated with the competent amphibole and garnet porphyroblasts, which occurred during synchronous metamorphism and ductile deformation.  The mineralized quartz veins are synorogenic as evidenced by both brittle and ductile deformation under at least greenschist facies metamorphism.  In particular, boudins of coarse-grained quartz (interpreted to be boundinaged quartz veins) indicate the mutual overprinting of brittle and ductile deformation which is characteristic of a shear-zone-hosted gold deposit.

Based on evidence for the synchronous metamorphism, brittle deformation and ductile deformation, and the synorogenic mineralized quartz veins, a shear-zone-hosted gold deposit model should be considered for the Otjikoto project.  

Gordon R. Yule HBSc thesis abstract

Thesis Title: 
Investigations of The Good Morning Lake Radioactive Fault Breccia: Innes Lake Area, Dorion Township Northwestern Ontario
Gordon R.
Yule
HBSc
1979

A genetic model for the localization of uranium mineralization related to the Proterozoic rocks of the Thunder Bay District was proposed by Franklin (1978).  This model was investigated in detailed examination of a breccia-type uranium occurrence referred to as the Innes Lake Radioactive Breccia.  The occurrence is situated in the Good Morning Lake fault which transects a late Archean quartz monzonite.

Observations are:

  1. STRUCTURAL - The Good Morning Lake Fault strikes 330°.  It is characteristic of the regional early Keweenawan faulting and fracture systems proposed by McIlwaine et al (1974).  Detailed structural analysis indicates that this fault zone pre-dates late Keweenawan fractures which strike 60°.  These tensional fractures host the lead-zine-barite veins which are also found within the district (Franklin and Mitchell, 1977).
  2. VEIN SYSTEM- The fault zone comprises fine to coarse grained, altered wallrock and siliceous vein fragments within a very fine-grained hematitic groundmass.  Fragments indicate multiple stages of vein formation including: injection of siliceous fluids, crystallization, and subsequent brecciation.  Common vein structures include comb-structure, and miarolitic cavities.  Tourmaline formed at an early stage in vein development along with milky quartz.  A cherty breccia and a hematitic breccia are late stage events which are post-dated by uranium-bearing fluorapatite mineralization.
  3. MINERALIZATION - Detailed ground radiometric surveys indicates high uranium: thorium ratios.  Autoradiographs have delineated radioactive concentrations within hematite-enriched fractures within the hematitic breccia.  These uranium-bearing fractures crosscut this breccia, thereby suggesting that uranium introduction was a late stage event.  Anomalously high P2O5 values (greater than 3%) and x-ray analysis of the mineralization suggest that the uranium mineralization is mineralogically associated with phosphate within the apatite species.
  4. ALTERATION - Alteration zones are pervasive in the quartz monzonite wallrock which envelopes the breccia and consist of sericitization, chloritization, and hematitization.  The alteration is associated with the early stage tourmaline mineralization.  Geochemical analyses for uranium in the wallrock suggest that the metal is not derived from the alteration zones.

The anomalous P2O5 values associated with the uranium mineralization stage suggest that local apatite-bearing uraniferous Archean pegmatites are the probable source rocks as proposed by Franklin (1978).  The role which the nearby Archean/Helikian unconformity at the base of the Sibley Group played with regard to this mineralized fracture is unclear but Franklin (1970) has suggested that other types of vein mineralization within the district are the result of precipitation from circulating groundwaters along the unconformity.

Gilbert Kahara HBSc thesis abstract

Thesis Title: 
The Behaviour of Isothermal Remanent Magnetization of Magnetite and Hematite in Non-coaxial Strain
Gilbert
Kahara
HBSc
1992

Gilbert J. Kahara - 1992

Recent studies have shown that remanent magnetization can be affected by tectonic deformation.  It can be reoriented by the effects of plastic strain.  Its magnitude may change also.  This project was undertaken to test the behaviour of remanence rotation and to determine whether it behaves as a passive line or a material line.  Two magnetic minerals, magnetite and hematite were suspended in silicone-putty.  The two rock analogues were individually given an isothermal remanent magnetization (IRM) and deformed by simple shear.  The results show that the IRM in each mineral rotates as a rigid line, although the IRM in hematite tends to behave as a passive line.  These results are perhaps explained by a microscopic examination of both magnetite and hematite, which showed that hematite was plate-like and magnetite was equidimensional.  IRM rotation was accompanied by a decrease in intensity due to grain-scale scattering of remanence directions.

Katharine Masun HBSc thesis abstract

Thesis Title: 
Crater Facies Kimberlites
Katharine
Masun
HBSc
1997

The Yubileinaya kimberlite pipe, discovered in 1957, is located within the central part of the Alakit kimberlite field of the Yakutian diamondiferous Province.  The Yakutian Province is located within the East Siberia Platform.  Host rocks include Lower-Middle Ordovician and Lower Silurian terrigenous-carbonate sequences.  The pipe is overlain entirely by Permo-Carboniferous sediments and Lower Triassic tuffs.  The intrusion consists of at least two different kimberlite types.  An initial injection of volcaniclastic kimberlite breccia has been intruded by a macrocrystal hypabyssal kimberlite forming distinct central channel which flares rapidly outward in the upper portion of the kimberlite.

This study of the Yubileinaya intrusion was limited to the macroscopic and microscopic investigation of a single hand specimen by transmitted light and electron microscopy.  Associated rocks and geological relationships were not observed.

The hand specimen examined is typical of Group I or archetypal kimberlite, containing rounded macrocrysts of pseudomorphed olivine, common macrocrysts of mica and rare garnet together with groundmass serpentine, spinel, apatite, perovskite and carbonate.  Texturally, the hand specimen comprises crater facies kimberlite with a conspicuous alternation of two distinct units.  Clast-supported, volcaniclastic sandstone alternate with crypto-crystalline, pelitic carbonate mudstone.  The former represents pyroclastic airfall lapilli tuffs and coarse ash, composed primarily of juvenile lapilli which have undergone little or no reworking.  The latter unit can be termed a volcaniclastic kimberlitic mudstone, as its genesis is unclear.

Jesse Halle HBSc thesis abstract

Thesis Title: 
Paleomagnetic Study of the Plateau and Stawson Intrusions of the Quetico Subprovince, Northwestern Ontario
Jesse
Halle
HBSc
2002

Oriented samples collected from the Plateau Lake Quetico Intrusion (9 km E and 4.5 km S of Atikokan, Ontario) and the Stawson Lake Quetico Intrusion (19 km W and 9 km S of Atikokan) showed NRM vectors in accordance with previously-determined NRM vectors of posttectonic plutons of the Quetico Subprovince.  The strongly anisotropic AMS fabric of oriented samples form the Plateau Quetico Schist country rocks showed strong, east-west magnetic foliation, typical of the study area.  The AMS of the Western sub-area of the Plateau Intrusion revealed an east-west L-fabric resultant from igneous flow concordant with regional structure.  Magnetic fabrics from the Eastern sub-area of Plateau and Stawson are a result of dynamic flow of a 'fluid' magma from the SE (in the direction from their parent, the Quetico Batholithic Complex).

Characteristic remanent magnetism (ChRM) determined from principal component analysis (PCA) of the samples from Plateau East revealed a strong, southwest-directed component of remanence that passed the reversal test.  The ChRM from Plateau West showed little evidence of such geomagnetic reversals.  Despite this evidence, when the site-mean paleopoles from Plateau East and West were plotted on a tentative Precambrian Apparent Polar Wander Path, overlapping confidence ellipses failed to prove significant age differences.  The best age estimation from Plateau West was ~2600 Ma while that at Plateau East is 2550+/-25 Ma.  The limited sampling program at the Stawson Intrusion precluded meaningful age estimations.  In addition, secondary remanences from Plateau East and West were limited in their interpretation.

A first approximation suggests the Ni-,Cu-, and PGE-mineralized core of Plateau may be coeval and comagmatic with its mafic host.  The orientations of L-fabrics of untectonized igneous intrusions reflect the source-direction and may also relate to shape.  As the Stawson Intrusion also hosts economic concentrations of PGE's, it is certain that both concordant and discordant Quetico Intrusions are targets for PGE mineralization.

Michael P. Stubley HBSc thesis abstract

Thesis Title: 
The Structure and Lithology of the Quetico Metasediments in the Banning Lake - Seine River Area
Michael P.
Stubley
HBSc
1983

The area of investigation is located at the interface of the Quetico and Wabigoon Subprovince of the Canadian Superior Province in northwestern Ontario.

The Quetico metasedimentary belt comprises a monotonous sequence of thin to medium bedded turbidite deposits characteristic of a submarine fan environment, within the study region.  This metagreywacke-metapelite sequence gradually passes into biotite schist to the south.

The Wabigoon metavolcanic - granite belt consists of intermediate volcanic flows and felsic volcaniclastic deposits.  (Some metavolcanic rocks are, in part, conformable to the Quetico metasediments).

Greenschist facies metamorphism in the study area is chlorite zone in the north and biotite zone in the south.

One deformation event in the northern part of the Quetico Subprovince was accompanied by a smooth, penetrative, discrete planar cleavage in the Quetico metasediments.  An antiformal syncline and a synformal anticline are located in the northwest of the present study area with vertical, ENE striking axial planes.  The folds plunge moderately from the horizontal.  These overturned, folded structures may have evolved in response to differential strain within the axial planes.

 

Eric Bruce Mosley HBSc thesis abstract

Thesis Title: 
Geology and Mineralogy of the Rabbit Mountain Mine Mainland Belt Silver Region Thunder Bay District
Eric Bruce
Mosley
HBSc
1977

The Rabbit Mountain Mine vein deposits occur in a fault controlled valley on the southern periphery of the northeast trending Mainland Belt of silver mines.  They were discovered about 12 miles southwest of Thunder Bay in 1882 and after 10 years of operation, mining operations closed.

A detailed surficial investigation was undertaken on the property through mapping and sampling.  Petrographic microscopy and x-ray diffraction was conducted on a number of rocks and minerals.

The hypogene deposits are dependent on the regional structures.  The deposits are confined to structural traps provided by post-diabase block faults which strike southwest, parallel to the Mainland Belt.  Post-diabase faulting was in response to sinking of the Lake Superior Basin.

The country rock is Precambrian Rove Argillite and semiconformable Logan diabase sills.  To the south of the Main Fault zone, the argillite dips southeast 5° and on the north side of 5° to the northwest.  Metamorphism of the argillite by the diabase is that of the albite-epidote hornfels facies.

Several types of veins occur:  simple veins, which are dominant in the diabase; and complex veins which are prevalent in the metasediments.  Emplacement of the veins occurred after a sufficient period of time for the diabase to cool to non-metamorphic temperature.  Heat from the cooling diabase sheets supplied the mobilizing forces to the metal rich complexes available in the argillite.

The metasedimentary derived deposits are largely gangue minerals; calcite, quartz and fluorite respectively.  Intermittent deposition, in order of abundance, of sphalerite, galena and pyrite, acanthite, native silver and chalcopyrite occurred in later stages.  Lattice parameter calculation of chalcopyrite crystals indicate the temperature of deposition to be at least below 600°C.  Throughout the veining history there was recurrent fault movement.

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