Joshua J. Selagi HBSc thesis abstract

Thesis Title: 
Microstructural Analysis of Porcelaineous Syenite, Coldwell Complex, Ontario, Canada
Joshua J.
Selagi
HBSc
2012

The Coldwell Complex is a large Proterozoic alkaline igneous complex on the north shore of Lake Superior west of Marathon, Ontario.  From east to west across the complex, three distinct magmatic centres form an overlapping sequence; Center 2 is characterized by biotite-bearing alkaline gabbro and nepheline syenite (Mitchell and Platt, 1982).  Within Center 2, a fine-grained porcelaineous variety of nepheline syenite is recognized as being chemically eqivalent to the more typical coarse-grained nepheline syenite.  This porcelaineous nepheline syenite outcrops in a narrow arcuate zone along the western shore of Redsucker Cove.

Microstructural evidence for dislocation creep indicates that the porcelaineous syenite is a mylonite formed by localized solid-state deformation.  As the Coldwell Complex has not been subjected to regional metamorphism, the high temperature required for ductile solid-state deformation in the procelaineous syenite must be related to the magmatic activity.  Localized high-temperature ductile strain within this arcuate zone could have led to catastrophic brittle failure along ring faults culminating in caldera collapse.  This discovery may have implications for understanding the processes associated with caldera collapse in large alkaline igneous complexes.

Peter Gordon Harvey HBSc thesis abstract

Thesis Title: 
A Test of the Lateral Secretion Hypothesis at the Rabbit Mountain Mine, Mainland Belt Silver Region Thunder Bay District, Ontario
Peter Gordon
Harvey
HBSc
1985

The Rabbit Mountain Mine hosts silver-bearing quartz-carbonate veins that are representative of the veins encompassing the Mainland Belt Silver Region near Thunder Bay, Ontario.  These veins, which also contain base-metal sulphide mineralization, fill fractures within Rove Formation argillite and Logan diabase sills of the Proterozoic Southern Province of the Canadian Shield.

Silver and base-metals could have been derived from the diabase; however, a lack of differentiation within the sills and spatial relationships, which indicate that the veins occupy post-diabase faults, seem to preclude the diabase as the source of the metals.

The intruding diabase caused a contact metamorphic zone to be developed within the shale.  Metamorphic reactions released calcium, carbon, and water from the shales, and these products migrated to low pressure zones centered on faults to form the gangue minerals.

To determine if silver, base-metals and arsenic accompanied this lateral secretion of gangue constituents, an outcrop of altered argillite cut by a vein (located at the Rabbit Mountain Mine) was sampled on lines perpendicular to the vein.  The samples were analyzed by the Atomic Absorption method to determine the distribution pattern of silver, base-metals, arsenic and mercury in the argillite adjacent to the vein.  Copper, zinc, lead, silver and possibly nickel are all depleted below their background levels indicating they have been removed from the shale during the heating event instigate by the diabase, and, like the gangue minerals, were deposited as vein constituents.  Cobalt is elevated above background levels adjacent to the vein, indicating it was introduced to the argillite from the vein, ultimately being derived from the cooling diabase.  Arsenic shows a slight depletion towards the vein.  Mercury was above the lower detection limits only in samples taken immediately adjacent to the vein.

Daniel J. Bihari HBSc thesis abstract

Thesis Title: 
Alteration and PGE-AU Mineralization of the North Roby Zone, Lac des Iles Mine, Northwestern Ontario
Daniel J.
Bihari
HBSc
2001

The Lac des Iles Complex appears as a linear zone of mafic plutons that trend east to northeast and extends from Lake Nipigon to Atikokan in northwestern Ontario (Sutcliffe, 1986).  The complex is situated in Archean granitoids that consist of gneissic tonalites, medium-grained hornblende diorites and quartz diorites.  The Lac des Iles Complex occurs in a circular outcrop fashion that is approximately 30 km in diameter and is the largest of a series of mafic to ultramafic intrusions (Sutcliffe, 1986).  The Roby Zone was the initial site of mining at the Lac des Iles Mine.  The North Roby Zone is its narrow northward extension.

The North Roby Zone contains a narrow strip (<50 m) of anomalously high PGE and Au values associated with sparse sulfides called "Noseeum Ore".  Five stripped outcrops approximately 50 x 10 m were studied in the North Roby Zone.  Alteration of primary pyroxene to talc and pink coloration of recessively weathered plagioclase is strongly suggestive of hydrothermal alteration.

The five stripped outcrops reveal a northeasterly striking, steeply dipping sequence of leucogabbro, varitextured gabbro, pyroxenite and east gabbro.  A total of 32 hand samples were collected and studied in thin section.  From these 21 were selected for whole-rock and trace element analysis in order to compare chemistry of altered and unaltered samples.

Hydrothermal alteration appears to have affected the primary ortho-and clinopyroxenes of the host rocks, progressively converting them to talc.  Other petrographic indications are obscure, as regional metamorphism has overprinted the Lac des Iles Complex and its mineralized rocks.

The grade of metamorphism is the albite-epidote subfacies of greenschist facies as evidence by incipient breakdown of plagioclase to sericite and clinozoisite, chloritization of pyroxenes and formation of tremolite-actinolite, as well as minor metamorphic albite.  Chlorite coronas surround mafic minerals, and develops decussate assemblages of chlorite and tremolite-actinolite.  Minor penetrative deformation is evident in undulatory extinction in plagioclase and development of weak schistosity.

The development chlorite coronas and general overprinting of mafic minerals by chlorite and sericitization of plagioclase are significant in distinguishing hydrothermal alteration from subsequent regional metamorphism.

Analysis did not generally reveal striking compositional variations in the host rocks; however, more detailed analysis did show chemical effects of alteration.  Chondrite-normalized REE plots revealed that all REEs were depleted relative to unaltered rocks; however, in most altered leucogabbro and varitextured gabbro, minor to insignificant depletion of Eu relative to other REEs produced an apparent positive Eu anomaly in the plots.  Other chemical changes, because of their subtle expression and obscurity owing the problem of closure, were examined by use of Pearce Element Ratios.  Most notable was Na-depletion due to alteration, which can be distinguished from igneous fractionation effects in plagioclase.

Riku T. Metsaranta MSc thesis abstract

Thesis Title: 
Sedimentology and Geochemistry of the Mesoproterozoic Pass Lake and Rossport Formations, Sibley Group
Riku T.
Metsaranta
MSc
2006

The Sibley Group is an essentially unmetamorphosed, Mesoproterozoic sedimentary succession consisting of a mixture of siliciclastic and chemical sedimentary rocks.  This study examined the sedimentology and geochemistry of the Pass Lake and Rossport Formations, the lowermost lithostratigraphic units of the Sibley Group. 

Lithofacies analysis subdivided the sections studied into sixteen lithofacies associations corresponding to distinct allostratrigrahic units, roughly equivalent to previous lithostratigraphic subdivisions.  A lower clastic unit is comprised of the following lithofacies associations:  boulder conglomerate-sandstone-dolocrete (proximal ephemeral braided system), pebble to cobble conglomerate (ephemeral braided stream), massive cobble conglomerate (transgressive lag, reworking of braided stream deposits during transgression), trough cross-stratified sandstone (braided stream), green sandstone-siltstone (wave and storm influenced fluvial dominated delta), planar cross-stratified sandstone (nearshore migration of large sandwaves), and thinning-upward sandstone (beach and storm remobilized nearshore sandstone sheets).  The lower clastic unit is disconformably to conformably, depending on geographic location, overlain by a mixed siliciclastic-carbonate unit.  The mixed siliciclastic-carbonate unit is comprised of the red siltstone (non-saline lake), red siltstone-dolostone (perennial saline lake, distal from clastic source) and red siltstone-dolomitic sandstone (perennial saline lake, proximal to clastic source) lithofacies associations and is sharply overlain by an upper clastic unit.  The upper clastic unit consists of the sheet sandstone (ephemeral playa lake (?) or perennial lake with increased sand supply with respect to underlying units) and black chert-carbonate (microbial mats forming at restricted, shallow, subaqueous shoreline) lithofacies associations.   Subaerial exposure features are present at the top 0of the black-chert-carbonate lithofacies association and include the intraformational conglomerate lithofacies association (subaerial debris flows, intrusive and/or extrusive sedimentary breccias, terra rossa style soils, dissolution collapse breccias).  Subaerial exposure features at the top of the upper clastic unit are overlain by the massive dolostone (saline lake), red siltstone-sulfate (wet evaporate-rich mudflats around lake margins) and fine-grained sandstone (dry, evaporate-poor mud and sand flats around lake margins) lithofacies associations of the mixed siliciclastic-carbonate-evaporite unit.

During deposition of the lower clastic unit paleocurrents and detrital zircon geochronology suggest a south- to southeast-down paleoslope.  A lack of major thickness changes in stratigraphic units or laterally extensive coarse-grained clastic deposits is consistent with a broad intracratonic sag architecture during initial basin subsidence.  Paleocurrents from the upper clastic unit suggest a change to northward oriented paleoslope during its deposition.  This corresponds with an apparent thickening of the upper two units towards the north and Black Surgeon Fault, consistent with the development of half-graben structure and increased evidence of tectonic activity (e.g. intrusive sedimentary breccias, synsedimentary faulting and debris flows).

Carbon, oxygen and sulfur stable isotope analyses, Sr isotope analyses and trace element analyses (in some cases analyses include rare earth elements) were preformed on a variety of distinct carbonate and sulfate lithologies.  Sulfur isotope compositions, strontium isotope compositions and rare earth element/yttrium ratios support a non-marine depositional setting.  Low *18O values appear to be a good indicator of diagenetically altered samples.  *13C values have typical marine values consistent with lacustrine carbonate precipitated in equilibrium with atmospheric CO2.  Stratigraphic changes in C and O isotope compositions in the red siltstone-dolostone lithofacies association were likely driven by evaporations and residence time effects.  Stratigraphic variations in sulfur isotope compositions may reflect changes in the composition of sulfides weathering to supply sulfate to the basin.  Overall, both the interpretation of physical sedimentologic and various type of geochemical data strongly support a non-marine lacustrine setting for the deposition of the Pass Lake and Rossport Formations.

Riku is currently working for the Ontario Geological Survey

Brandon Gaspar HBSc thesis abstract

Thesis Title: 
The Black Line Faults of the Red Lake Gold Mine
Brandon
Gaspar
HBSc
2012

Black line faults tend to cut and displace various lithologies, dykes, and gold-bearing veins and are a common feature found in the Red Lake gold mines. They are characterized by their distinct black color and may have anomalous traces of gold but are usually barren. Black line faults along the Red Lake mine trend may vary in size, geometry, and significance, but they all share the same general composition of mostly tourmaline, chlorite, and interstitial quartz. They have previously been described as faults associated with brittle late stage deformation; however, some are overprinted by ductile deformation. Black line faults are significant in that they represent a time of brittle-ductile deformation and the presence of complex hydrothermal fluids, typically related to orogenic gold mineralization.

Greg F. Paju HBSc thesis abstract

Thesis Title: 
Nature of alteration associated with Co mineralization in the Bol©o Cu-Co-Zn-Mn deposit
Greg F.
Paju
HBSc
2012

Bol©o is a low-grade, sediment-hosted stratiform Cu-Co-Zn-Mn deposit located midway along the eastern side of the Baja Peninsula. The deposit consists of multiple conformable, laterally extensive horizons of disseminated sulphide and oxide mineralization, which extends over 90 square kilometres.

All four mantos studied display similar mineralogy, but manto 3 contains a greater proportion of both Mn- and Fe-oxides.  Both the breccia and parallel laminated claystone lithofacies have nearly identical mineralogy, but are texturally different, while the massive claystone lithofacies is dominantly composed of chrysocolla and Mn-oxide altered smectite-group clays. The gangue mineralogy of the three alteration facies, sulphide, oxide and mixed sulphide/oxide, are largely similar, except that the oxide facies contains higher, albeit variable, abundances of Mn-and Fe-oxides.

There is no direct correlation between Co concentrations of the lithofacies and mantos, all of which display localized high and low cobalt concentrations. Based on the concentration of Co within the various alteration facies, the higher Co concentrations are associated the sulphide facies, which implies that Co is occurring as a sulphide. Locally, high cobalt grades appear to be associated with high copper grades. As no discernable Co-bearing minerals were identified by optical microscopy and XRD analysis, additional study using SEM-EDS and/or EMP analysis is required to determine the host mineral(s) for Co within the mantos.

Ben Kuzmich HBSc thesis abstract

Thesis Title: 
Geochemistry and Petrology of the Dog Lake Granite Chain, Quetico Basin, Northwestern Ontario
Ben
Kuzmich
HBSc
2012

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.

Shannon Hay MSc thesis abstract

Thesis Title: 
The Nb-mineralization of the Oka Carbonatite Complex , Quebec
Shannon
Hay
MSc
2003

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).

Zirconolite is commonly found as lath-shaped discrete crystals or intergrown with perovskite and pyrochlore-group minerals.  Oka zirconolites have a large range of Nb2O5, ranging from 11.5-25.8 wt. %.  Compositional zoning has been identified using back-scattered imaging, correlating with an increase in LREE toward the rim of the crystals.  The zirconolite compositions are similar to other calciocarbonatite-hosted zirconolites, with the exception of their higher Nb contents.
 
The crystallization history of the NIOCAN and Bond Zone deposits cannot be deduced from the obsserved mineral assemblage.  The calciocarbonatite does not represent a liquid composition, as it has a bulk composition which is determined by mixing materials derived from several batches of magma.  The magmus with gave rise to the NIOCAN and Bond Zone seem more evolved than those forming the pyrochlore-group minerals in the St. Lawrence Columbium deposits, as the pyrochlores from St. Lawrence Columbium are "less-evolved" in relation to the NIOCAN and Bond Zone pyrochlores.  The major conclusion of this work is that the calciocarbonatites at NIOCAN and Bond Zone are hybrid rocks.  Enrichment of specific mineralized zones is probably dependent upon rheological factors rather than compositional controls. 

Douglas B. McKay HBSc thesis abstract

Thesis Title: 
Application of Ion Exchange to Neutron Activation Analysis of REE in Geologic Samples
Douglas B.
McKay
HBSc
1984

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.

Peter Kevin Holmes HBSc thesis abstract

Thesis Title: 
The Structure of Archean Metasedimentary Rocks Near Mosher Lake, Geraldton, Ontario
Peter Kevin
Holmes
HBSc
1987

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 (So).  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.

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