Perry Sarvas MSc thesis abstract

Thesis Title: 
The Structure and Magnetic Fabric of the Quetico Metasedimentary Rocks in the Calm Lake - Perch Lake Area, near Atikokan, Northwestern Ontario
Perry
Sarvas
MSc
1987

The Quetico metasedimentary rocks are the metamorphosed equivalents of a turbidite sequence, comprised of a repetitive interstratification of sandstones and mudstones.  The rocks are metamorphosed to lower greenschist facies, but metamorphic grade increases progressively from north to south.  Anchimetamorphosed phyllites and slates in the north part of the present study area grade progressively into biotite schists in the south part.

Interpretation of structural features in the study area, mainly bedding (S0) - cleavage (S1) relationships and structural facing directions, has led to the delineation of a number of major F1 folds.

These are tight to isoclinal, asymmetric sheath folds, with axial planes arranged en echelon and slightly oblique to the dominant east-west, vertically-dipping, structural trend.  The orientation, geometry and disposition of the F1 fold suggest the Quetico rocks of the present study area have experienced a regional dextral transpressional tectonic evolution, with components of north-south regional shortening and east-west regional dextral shear, with a possible component of vertical (south side up) displacement.

The Quetico metasedimentary rocks have a polyminerallic magnetic mineralogy comprised of significant proportions of a ferromagnetic (magnetite and pyrrhotite) and a paramagnetic (chlorite, biotite, muscovite) component.  The rocks possess a predominantly tectonic magnetic fabric, which consists of a deformational, and a metamorphic, magnetic fabric.  In some rocks (especially coarse-grained sandstones with wide-spaced cleavage planes) a depositional magnetic fabric is partially preserved.  The complexities involved in having component deformational, metamorphic and depositional magnetic fabrics indicate that the principal magnetic susceptibility directions of the rock's magnetic susceptibility anisotropy cannot be considered reliable indicators of principal finite strain directions in the Quetico metasedimentary rocks.  Great care must be taken in interpreting the significance of principal magnetic susceptibility directions.

A copy of the thesis can be downloaded here

Douglas Bruce McKay MSc thesis abstract

Thesis Title: 
Aspects of Gallium Geochemistry in Upper Mantle-Derived Lherzolite Xenoliths and Continental Alkaline Volcanic Rocks
Douglas Bruce
McKay
MSc
1987

Various aspects of the geochemistry of Ga in upper mantle-derived garnet lherzolite xenoliths (from the Bultfontein Floors mine dump in Kimberly, South Africa), spinel lherzolite xenoliths (from Mount Pordnon, Australia), and continental alkaline volcanic rocks (from the Freemans Cove, Balcones, Urach and Hegau suites of Canada, the U.S.A., and Germany, respectively) have been investigated.  Ga abundances were determined by RNAA.  The feasibility of using epithermal INAA to generate accurate Ga data was investigated.  Analysis of U.S.G.S. standard granite G-2 suggests that epithermal INAA utilizing 630.1 KeV72Ga data has the potential to produce geologically useful Ga data.

The abundance of Ga in the lherzolite xenoliths varies by a factor of approximately 10 from 0.52 ± 0.14 ppm to 5.23 ± 0.44 ppm.  The spinel lherzolite xenoliths contain appreciably more Ga (2.78 ± 0.26 ppm to 5.23 ± 0.44 ppm) than the garnet lherzolite xenoliths (0.52 ± 0.14 ppm to 1.44 ± 0.18 ppm).  The sequence of enrichment of Ga in the minerals comprising the lherzolites is, from lowest to highest Ga content, olivine (0.20 ± 0.04 ppm to 0.72 ± 0.11 ppm), clinopyroxene (1.31 ± 0.13 ppm to 4.92 ± 0.32 ppm), garnet, if present (3.17 ± 0.16 ppm to 6.03 ± 0.48 ppm) phlogopite, if present (7.65 ± 0.21 ppm), and spinel, if present (43.49 ± 0.91 ppm to 65.91 ± 2.10 ppm).  Ga mineral/mineral distribution coefficients have been calculated.  Preliminary results suggest the distribution of Ga between certain mineral pairs (e.g., DGaopx/pcx) is temperature dependent and might be profitably utilized as a geothermometer.

The abundance of Ga in the continental alkaline volcanic rocks varies by a factor of approximately 3.5 from 12:14 ± 0.32 ppm to 41.97 ± 1.20 ppm.  Ga behaved as an incompatible trace element during the genesis of these rocks.  Model-derived constraints for Ga bulk-solid/melt distribution coefficients vary from 0.16 (Balcones suite) to 0.28 (Hegau suite).  Intrasuite variations in the Ga/Al ratios of the mafic continental alkaline volcanic rocks range from approximately 14% (Hegau and Urach suites) to approximately 20% (Freemans Cove suite).  Ga/Al ratios of primary melts from the Freemans Cove and Balcones suites decrease slightly (from 2.86 ± 0.16 top 2.28 ± 0.13, and from 4.12 ± 0.24 to 3.35 ± 0.19 respectively) with increasing degrees of partial melting.

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Jonathan Ross Devaney MSc thesis abstract

Thesis Title: 
Sedimentology and Stratigraphy of the Northern and Central Metasedimentary Belts in the Beardmore-Geraldton Area of Northern Ontario
Jonathan Ross
Devaney
MSc
1987

The northern and central metasedimentary belts (NMB, CMB) are east-trending, regional (formation- to group-scale) lithostratigraphic units within the Beardmore-Geraldton Archean terrane of northern Ontario's Superior Province.

Gravelly braided rivers deposited the lithofacies assemblage of clast-supported polymict conglomerate and interbedded sandstone that comprises most of the NMB.  Felsic volcanic pebbles and cobbles are the most abundant clast lithology.

The CMB contains several east-trending lithofacies assemblages that together form a generally northward-coarsening sequence.  The southern CMB is composed of mudstone, iron formation and sandstone with common graded beds.  This fine-grained assemblage is paralleled to the north by a horizon of rhythmically bedded and cross-bedded sandstone units, and a heterogeneous, conglomerate-rich assemblage.  The northern CMB strata are mostly a conglomeratic assemblage similar in form (lithofacies) and composition (provenance) to the NMB.  Some fine-grained units (mudstone, iron formation, graded sandstone) of relatively minor regional extent are present near the north margin of the CMB.

The CMB's southern (lower) fine-grained subaqueous facies are apparently capped at different sites by:  1) rhythmic delta front couplets;  2) sandy braided river deposits with very rare associated intertidal strata;  and 3) a conglomerate submarine fan or fan-delta front resedimented assemblage.  The northern (upper) CMB is a gravelly braided river deposit, with minor aquabasinal facies.

The CMB is probably a 1 - 2 km thick structurally modified homoclinal sequence.  Relative positions of its depositional paleoenvironments, as deduced from lithofacies assemblages, suggest that the epiclastic portion of the CMB is the record of a dominantly coarsening-upward, subaqueous to subaerial trend that was produced by a prograding clastic system(s), likely a number of fan-deltas.

The extreme eastern part of the CMB is composed of generally oligomict, coarse (conglomerate) felsic pyroclastic and/or reworked volcaniclastic facies which are probably subaerial deposits.

Similar clast compositions and several sedimentological criteria, including average maximum deformed clast size, strongly suggest that highly proximal fluvial facies in the NMB and more distal fluvial and aquabasinal facies in the CMB were originally part of a continuous coarse clastic wedge or sheet.

A copy of the thesis can be downloaded here

Owen J. Steele MSc thesis abstract

Thesis Title: 
A Theoretical and Experimental Investigation of Pressure Solution
Owen J.
Steele
MSc
1988

Consideration of the existing thermodynamic theory of pressure solution (PS) shows that this theory is applicable to the development of PS structures as well as to local grain-scale diffusive transfer.  Local precipitation of pressure solved material ceases when pores are reduced to equilibrium size, if not before by kinetic considerations.  Longer range diffusion may then occur if a site of non-equilibrium porosity is available.  Such porosity may be generated by particulate flow or by hydraulic fracturing.  Long range diffusion may also depend on greater ease of diffusion, as may occur along stylolites.

Measurement of PS strain rates was attempted by stress relaxation tests (SRTs) at room temperature of both Carrara marble and compacted aggregates of calcite and quartz sands.  Neither material gave results indicative of PS although strain rates as low as 10-8.5s-1 were obtained.  Work hardening during loading resulted in alternating increase and decrease of strain rate concomitant with steadily declining differential stress during the SRTs.  The variation in strain rate, termed cycling, was interpreted to be the result of non-steady state flow during loading.  Thermal expansion and contraction were shown to be the cause of pressure fluctuation in a long term quantitative experiment on PS begun during this study.  Such expansion and contraction should be avoided in quantitative studies, particularly at low strain rates.

A copy of the thesis can be downloaded here

Craig Steven Alford MSc thesis abstract

Thesis Title: 
"Tectonic" Magnetic Fabrics in Pure and Simple Shear: Experimental Investigations
Craig Steven
Alford
MSc
1988

Triaxial compression tests were preformed such that changes in the magnetic susceptibility anisotropy with strain would be represented by experimental approximations of simple shear and pure shear.  Both types of tests were performed on artificial materials of high magnetic susceptibility at room temperature and atmospheric pore fluid pressure.  Experimental displacement-rates and strain-rates were computer controlled during testing.

Two different shear zone materials were employed for the "simple shear" testing, a sand-cement mixture and a calcite-cement mixture.   Three series of simple shear tests were conducted on the sand-cement material at various confining pressures; Series A, at 0.689 kbars, Series B at 1.0 kbar and Series C at 1.5 kbars.  Two series of simple shear tests were conducted on the calcite-cement material, Series 1, at 1.0 kbar confining pressure and Series 2 at 1.5 kbars Pc.  For both materials a constant axial displacement-rate of 5.0 x 10-6 inches.  s-1 (corresponding to a slip displacement-rate on the shear zone walls of 8.7 x 10-6 inches. s-1) was employed.  Final shear strain values ranged from 0.025(to 0.378(. 

One series of pure shear deformation was conducted on the calcite-cement material at 1.5 kbars confining pressure employing a constant natural strain-rate of 5.0 x 10-6s-1.  Final axial strain values ranged from 4.42% to 18.3% shortening.

The development of simulated "tectonic" magnetic fabrics in both pure and simple shear has been achieved.  Principal directions of susceptibility rotate sometimes in complex patterns toward 'tectonically' significant stable orientations.  Magnitudes of susceptibility show progressive changes consonant with the intensity of strain such that there appears to exist a consistent relation between the change in the degree of anisotropy of susceptibility ()P') and the bulk strain ratio (In X/Z) for both the pure and simple shear experiments.

A copy of the thesis can be downloaded here

John Peter Burton MSc thesis abstract

Thesis Title: 
Constraints on the Formation of Depositional Placer Accumulations in Coarse Alluvial Braided River Systems
John Peter
Burton
MSc
1989

Placer accumulations are formed by the preferential sedimentation of heavy minerals from the general population of detritus being transported by a fluid.  The depth, velocity, and grain size conditions under which placers form on beaches, sand-dominated meandering, and braided fluvial systems is at present only partially understood.  Our knowledge of the controls on alluvial placer formation in gravel-dominated longitudinal bars of braided rivers is even more poorly developed despite their obvious economic importance.

The accumulation of heavy minerals in coarse-grained longitudinal gravel bars was studied by examining and sampling surficial and matrix sediments from modern, naturally occurring bars, and by simulating these bars under a variety of controlled flow conditions in a sediment-water recirculating flume.

Two processes dominated the deposition of sediments in both the natural and artificial systems studied:  1) suspension rain out; and 2) avalanche face progradation.  Sediments which were deposited as a result of avalanche face progradation were found to contain significantly higher concentrations of heavy minerals in both the naturally occurring and experimental longitudinal gravel bars.  Data also indicate that the difference in heavy mineral content amongst sediments deposited as a result of these two processes will increase substantially with increasing density of the detrital minerals present.  This suggests that denser heavy minerals are more likely to be deposited amongst less dense surficial sediments whereas less dense heavy minerals are more likely to be vertically distributed throughout the bar sequence.

In the natural systems studied, heavy mineral content was found to be much higher in poorly sorted, coarse-grained sediments deposited amongst pebble sized clasts.  Flume tank experimentation similarly revealed that detrital lead content was highest amongst pebble sized clasts during the fastest velocity runs.  In addition, an increase in clast size resulted in a decrease in the amount of heavy minerals accumulating in surficial sediments.

This study has also highlighted two processes which results in the formation of alluvial depositional placer accumulations in coarse-grained braided river systems.  The first process occurs as a result of heavy minerals in channel bottom sediments becoming progressively enriched through the winnowing of less dense sediments, resulting in the formation of an erosional placer deposit.  Flume experimentation revealed that when high concentrations of heavy minerals armouring the stream-bed were reached, this often resulted in the initiation of their movement downstream.  This process can also be triggered by catastrophic events such as large floods of regional tectonic uplift.  A sudden increase in energy typically associated with such events results in the flushing of erosional placers and their eventual deposition in areas of higher preservation potential.  Therefore, a catastrophic adjustment helps to flush out erosional placer deposits into the basin to form a depositional placer accumulation.  The second process of depositional placer formation results from heavy minerals travelling in bed load transport, while less dense sediments are kept mostly in suspension.  With a decrease in velocity, heavy minerals are sedimented with hydraulically equivalent sized, less dense sediments in open framework gravels.

A copy of the thesis can be downloaded here

Robert Nicholas Spark MSc thesis abstract

Thesis Title: 
Magnetic Fabrics and Boundary Structure at the Quetico/Shebandowan Subprovince Boundary, near Kashabowie, NW Ontario
Robert Nicholas
Spark
MSc
1990

The Quetico metasedimentary subprovince and the volcanic-plutonic Shebandowan belt to the south meet along an east-west steeply dipping boundary that is believed to have been affected by dextral transpressional deformation.   It is also parallel to a steep metamorphic gradient from greenschist facies rocks to the north.

Macroscopic petrofabrics are difficult to observe along the belt to the west of Thunder Bay but magnetic susceptibility fabrics (low-field) are quite consistent.  These define a gently plunging extensional fabric parallel to the belt boundary.  Within the Kashabowie area, general field observations of subhorizontal stretching (and intersection) lineations, and cleavage directions are in agreement with magnetic susceptibility axis directions.  Mineral separation reveals that all samples have multiple sources of magnetic susceptibility, dominated by metamorphic phyllosilicates.  Consequently it is not possible to simply quantitatively relate the magnetic fabrics to strain magnitudes although the magnetic fabrics accurately monitor significant kinematic directions.  Analyses of strain of low-grade detrital quartz grains, magnetic fabrics and general field observations recognize flattened oblate fabrics.  Moreover oblique, subhorizontal lineations favour a transpressive kinematic model with compression normal to the belt boundary.  The obliquity between mineral and magnetic lineations seem to indicate dextral transpressive deformation.

A copy of the thesis can be downloaded here

Scott J. Mooney MSc thesis abstract

Thesis Title: 
Stratigraphy of Two Late Paleozoic Basins: Implications for the Timing of Final Emplacement of the Meguma Terrane
Scott J.
Mooney
MSc
1990

Paleomagnetic studies indicate the Meguma terrane's final emplacement occurred between the Mid-Devonian and Early Permian.  Lithostratigraphic units near the boundary of the terrane were investigated in order to provide constraints on the timing of this compressional event.

North of the Cobequid-Chedabucto Fault (Guysborough Basin), volcanic flows, pyroclastics and related sediments are overlain by gravelly to sandy braided fluvial and lacustrine lithofacies.  East-southeast paleocurrents and variable (non-Meguma) clast lithologies are typical of these units.  South of the Cobequid-Chedabucto Fault (St. Mary's Basin), coarse cobble - rich to sandy braided fluvial lithofacies are dominant.  Paleocurrents indicate flow to the north and clast lithologies are representative of the Meguma terrane.

Post Acadian (Late Devonian) basement fragmentation and associated volcanism modified the area noth of the Cobequid-Chedabucto Fault.  Basement block rotation, east end down, initiated Latest Devonian through Mid-Carboniferous sedimentation in a transtensile tectonic environment.  There is no lithostratigraphic evidence to suggest the presence of the Meguma terrane immediately south of the Guysborough Basin during this time interval.  However, the Meguma terrane was supplying sediment to the St. Mary's Basin by the Early Carboniferous.  Collison and wrench faulting probably initiated formation of this basin in a transtensile tectonic environment.  Subsequent dextral displacement along the Cobequid-Chedabucto Fault and transpressive tectonic conditions resulted in the removal of slices of both the St. Mary's and Guysborough Basins as these two distinct assemblages were juxtaposed.

A copy of the thesis can be downloaded here

Richard Morison McLaughlin MSc thesis abstract

Thesis Title: 
Accessory Rare Metal Mineralization in the Coldwell Alkaline Complex, Northwest Ontario
Richard Morison
McLaughlin
MSc
1990

Accessory rare mineralization has been investigated in seven lithologies in intrusive Centres I and III of the Coldwell alkaline complex.  All units contain minerals that are enriched in a suite of granitophile elements, which typically include Nb, REE, Y, Th, U and Zr.  Mineral abundances, composition, and mode of occurrence differ between units.

Centre III is characterized by crystallization of subhedral-to-euhedral chevkinite, pyrochlore and monazite from late-stage melts or residual pore fluids in the more-evolved quartz and ferro-edenite syenites.  These minerals are invariably altered to fluorocarbonate or recrystallized by later F- and CO32- - bearing deuteric fluids.  The Centre I, ferroaugite syenite minerals exhibit similar morphological and replacement of plagioclase and amphibole by K-feldspar, zircon, fluorocarbonate, Nb-rutile (?), allanite, and rare chevkinite.  Fe-rich fluids under oxidizing conditions are believed to have precipitated Fe3+ - bearing fluorocarbonate in which one third of the (REE.)F layers are replaced by Fe3+ layers. 

Most Centre I rare earth minerals are enriched in the HREE relative to those from centre III, in particular pyrochlore, fluorocarbonate, allanite in the eastern contact pegmatites and the quartz syenite dykes.  Compositional data for adjacent syntaxial intergrown domains of bastnaesite, synchysite, and parasite indicate that HREE-enrichment may, in part, be influenced by the Ca content of the species. 

The highest contents of Ce (4193 ppm), Zr (1613 ppm), Y (650 ppm), Th (223 ppm) and U (428 ppm) were found in the quartz syenite dykes intruding the Craddock Cove syenite and Port Munroe megaxenolith.  The emplacement of the quartz syenite dykes and the introduction of the metasomatizing fluids of the Craddock Cove syenite may be temporally related to the differentiation of residual fluids in the apical zone of the Centre I magma chamber.  Complexing of F- and CO32- with rare metals may have permitted their concentration, transportation and precipitation in structurally favourable settings.  The megaxenoliths have been susceptible to brittle fracturing and should be considered primary targets for further exploration.  The Craddock Cove syenites, although intruded by the dykes, may have been hot during dyke emplacement and therefore not as prone to brittle fracturing.

A copy of the thesis can be downloaded here

John Robert McArthur MSc thesis abstract

Thesis Title: 
Dimensional and Crystallographic Fabric Development in Experimentally Deformed Synthetic Aggregate and Natural Rocks
John Robert
McArthur
MSc
1990

Calcite Portland-cement aggregate samples were deformed triaxially at 25E with confining pressures of 200 Mpa.  The samples were deformed under experimental approximations of pure shear (dry and wet experimental conditions), transpressional shear and simple shear.   The pore fluid pressure during the wet pure shear test was less than 195 MPa.  Extensive grain rotation accompanied by twinning of the calcite grains occurred.

Optical analyses of calcite crystallographic fabrics have been used to infer the orientation of the maximum principal compressive stress (F1).  Stress orientations in the deformed specimens agree well with the externally imposed stresses.  A new method has been successfully used to determine the F1 orientation.  The method used contouring of the lamellae index associated with the compression direction determined from Turner's Dynamic analysis method.

In pure shear, preferred dimensional orientation (PDO) of the calcite grains are produced more efficiently in the presence of a pore fluid pressure.  In dry specimens, transpressional shear is more effective in producing a PDO in the calcite grain than either pure shear or simple shear.  Grain shape fabrics do not conform to the symmetry of the bulk deformation when extensive rotation of calcite grains is involved.  Mean grain alignment is perpendicular to the shortening in pure shear, initially inclined and later parallel to the shear zone wall in transpressional shear, and inclined to the shear zone wall in simple shear.  The mean orientation of the grain-alignment fabrics is, therefore, a reliable kinematic indicator under the conditions investigated.  Transpressional shear and dry pure shear exhibit higher lamellae indices than either wet pure shear or simple shear. 

Strain analysis of calcite grains by Robin's method (1977), the linearization method (Yu and Zheng, 1984) and Harmonic mean method (Lisle, 1977) yields overestimates of the experimental bulk strain in wet pure shear.  These methods fail to take into account interparticle motions that occur in the presence of a high pore fluid pressure.

The triaxial deformation of the Ancaster oolitic limestone was performed with a confining pressure of 200 Mpa, a natural strain rate of 10-5/s and at a temperature of 135EC.  The samples were deformed under dry and wet experimental conditions.  The pore fluid pressure, during the wet test, was less than 60% of the confining pressure.   

A copy of the thesis can be downloaded here

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