The Kama Hill Formation of the Sibley Group has been sampled in detail at Albert Lake, Kama Hill and Stewart Lake.  Depositional microtextures such as interbedding of reworked and undisturbed laminae, soft-sediment deformation and clay galls suggest tidal flat sedimentation.  However, crossbeds, flaser bedding and substantial current ripple marks are not observed - thus, convincing evidence of tidal activity in not documented.

Salt casts, authigenic microcline, thomsonite and mixed-layer clay minerals point to a warm, semi-arid climate and a high pH, saline depositional and post-depositional environment.  Such a climate is consistent with paleo-equatorial position of the Sibley depositional site as preposed by Robertson (1973).

The purpose of this study was to estimate the relative accumulation rates of different sediment types within the Lumby Lake and Finlayson Lake Greenstone Belts.  Platinum group element (PGE) geochemistry (specifically iridium values), major and trace element geochemistry, cosmic element abundances, and a constant influx of extraterrestrial material for the Earth were used in calculations to determine the sedimentation rate.  Sedimentation rates calculated represent minimum values due to a probable decrease in cosmic influx rates through time.  Ascertaining the relative sediment accumulation rates for various lithologies, especially of certain chemical sedimentary units not presently forming represents an important advance in our understanding of Mesoarchean depositional systems.

Different types of iron oxides occur in the oceanic rocks, found in the ophiolites of Cyprus, at different stages of alteration at varying depths and distances from the fossil spreading axes.  The distinct Curie temperatures and susceptibilities are identified by tests done on the Curie Balance and the susceptibility-temperature apparatus, respectively.

Cyprus provides a perfectly exposed ophiolite and various parts to study the ocean floor structure of part of the Cretaceous Neotethys Sea.  The ocean floor structure is generally as follows: a harzburgite and lherzolite mantle at its core, an overlying, discontinuous gabbroic complex, succeeded by a large sheeted dike complex topped by pillowed volcanics and a sedimentary succession.  The Troodos ophiolite is thought to have had three fossil spreading axes that were of intermediate spreading rate, around 50 to 150mm/year.

From Troodos there were six mantle sequence rocks and eight sheeted dike complex rocks used in the Curie balance.  Nine of the Troodos mantle rocks and ten from the sheeted dike complex were used for the low temperature (77K to 300K) susceptibility variations with temperature experiments.  The high temperature (300K to 900K) susceptibility variations with temperature experiments involved five Troodos mantle specimens and five sheeted dike complex specimens.  From Akamas eight samples were used in the Curie balance, ten in the low temperature susceptibility experiments and five used in the high temperature susceptibility variations with temperature tests.

It is concluded that the sheeted dike complex underwent more alteration than the mantle sequence rocks of Troodos and Akamas.  The Akamas ophiolite mantle sequence shows more oxides to indicate more alteration when compared to the Troodos mantle sequence rocks.  In the mantle sequence, magnetite is the most common with a Curie temperature of 582°C in the Curie balance and a range of 855K (582°C) to 885K (612°C) in the susceptibility versus temperature apparatus.  TM60 is found in both the Troodos and Akamas mantle sequence rocks, but more frequently in the Akamas specimens.

In the sheeted dikes, TM60 was found to be fairly constant in the high temperature susceptibility experiments.  The unblocking temperature for titanomagnetite, TM60 was established to be in the range of 410K to 440K.  The unblocking temperatures for magnetite were between 850K (577°C) and 890K (617°C).  The more often a specimen was heated, the more pronounced the presence of the magnetite became.  Specimens would start out with three to five transitions and after one or two more heating treatments all transitions were removed except the Tc for magnetite.  The Tc would also decrease in temperature by small increments after each heating.  Two samples from the sheeted dike complex in Troodos ophiolite was heated and one from the Akamas mantle sequence.

The Rossport Formation stratotype, located on Channel Island near Rossport, Ontario, may be subdivided into eight distinct lithostratigraphic units.  The lower six units, which belong to the Lower Member of the formation, consist primarily of dolomite, sandy dolomite, and arenite.  The Central Member is composed of cryptalgal and banded chert-carbonate, and the Upper Member consists of crudely banded dolomite.  The red colouring of the carbonates is due to a diagenetic hematization process.

The Rossport Formation, at Channel Island, appears to be representative of a Neohelikian shallow shelf sea environment which became shallower and more restricted as deposition progressed.

Mainland Belt silver deposits of the Thunder Bay District are hosted in steeply dipping normal faults that cut Aphebian Rove Shale and Neohelikian Logan diabase sills.  The Mainland Belt is located in the southern province of the Canadian Shield.

This study examines the Creswel silver deposits which occur in and around a group of diabase sills 1.7 km west of Rabbit Mountain.  The term, Creswel silver deposits includes the following mines and prospects:  the Badger Mine, Porcupine Mine, Porcupine Jr. Mine, Keystone Veins, Eschweiller Veins, Animike Mines Vein 22 and the West Beaver Mining Property (Little Pig Vein and Vein No. 2).

The veins usually have a common mineralogy consisting of quartz, calcite, fluorite, and variable amounts of sphalerite, galena, pyrite, chalcopyrite, argentite and silver.  Silver bearing veins show evidence of secondary fracture, which crosscuts pre-existing vein development.  Silver bearing vein material is emplaced after secondary fracture and is richer in sulphides than pre-existing vein material.  Furthermore, calcite after secondary fracturing is coarser than calcite of the primary vein development.  Secondary pulses of vein material may also be more voluminous and calcite rich than the pre-existing vein.

Four controls may have been responsible for the development of silver bearing veins, these are:

1. A geochemical control, in that silver veins are commonly associated with lower argillite member of Rove Shale.
2. A structural control apparently exists such that secondary fracturing and a subsequent secondary pulse of vein material is necessary for the development of silver bearing veins.
3. Silver may be deposited at the intersection of vein systems.  This theory is somewhat tenuous and more work must be done to prove or refute this supposition.
4. A second sill is known to occur beneath some of the Creswel silver deposits.  The importance of the sill is, as yet, uncertain but it may have acted as a permeability barrier effectively trapping fluids between the two sills.  Furthermore, the added heat and concentrated circulation may have enhanced the "scavenging " ability of the fluids thus producing silver bearing veins.

At any rate, the common theory of genesis states that, heat from the intrusive diabase sills stimulated water circulation in the metal rich lower argillite unit of the Rove Shale.  Soon after diabase had crystallized a faulting event occurred and structural dilatent zones opened and vein material was deposited.

Adrian Simunovic - April 1985

The study area is located approximately 90 km north of Thunder Bay on Highway 527 which leads to Armstrong, Ontario.

Four outcrops of a polymict conglomerate were examined in detail.  The four exposures are all part of the same stratigraphic unit which forms a part of the Archean bedrock in this area.

R_f / ∅ analysis was used to determine an approximation of strain.  Granitic and volcanic clasts were treated separately.

Results show that due to competency contrasts the volcanic clasts reflect greater strain than the granite clasts. 

The harmonic mean of final pebble shape (R_f) was used as an approximation of R_s (strain ellipse shape) after Lisle (1977).

The averaged strain ellipsoid for the granite clasts and the volcanic clasts both, approximated a uniaxial pancake type ellipsoid (K = 0).

The Haughton impact structure is a 23 Ma old unaltered meteorite crater, located in the Paleozoic sediments of Devon Island in the Canadian Arctic Archepelago.  Fluid inclusions found within shock metamorphosed sandstone fragments were microthermometrically investigated.  The Onaping Formation of the 1850 Ma old Sudbury Structure is breccia zone that is of controversial origin.  The fluid inclusions found within these rocks were also analyzed and compared to the Haughton study and other previous studies.

Fluid inclusions found in shocked Haughton sandstones exhibit a wide range of eutectic and homogenization temperatures.  Eutectic temperatures are found to be extremely variable, suggesting the presence of complex, low- to high-salinity, aqueous solutions.  CO₂ was positively identified to be present in only one relict inclusion.

Fluid inclusions found within the rocks of the Onaping Formation also have variable eutectic and homogenization temperatures.  Many of the inclusions from the Onaping Formation decrepitated prior to homogenization.  The inclusions found within the matrix of the Onaping Formation are generally of low salinity and are found to contain some metastable ice phases.  Fluid inclusions found within the xenoliths are of highly variable compositions and often contain CO₂ phases and saturated salt solutions.

The presence of low salinity inclusions and metastable ice from the matrix of the Onaping Formation, is alalogous to the fluid inclusions studied in the melted rocks of the Haughton Structure.  The wide range of homogenization and eutectic temperatures, recorded from inclusions in shocked xenoliths of the Sudbury Structure, is also consistent with the measurements on shocked, unmelted rocks from Haughton and other meteorite impact sites.  This study supports an impact origin of the Onaping Formation rocks and thus the Sudbury Structure.

A paleoclimatic study of the laminated dolomite and shale sequence in the Rossport Formation of the Sibley Group in Northwestern Ontario was executed to determine the environment of deposition and the controlling climatic conditions.  The seventeen metre thick sequence was logged using a petrographic microscope and the colours of the layers were recorded on a scale of one to seven based on the fact that the higher the dolomite content, the lighter the sediment will appear.  Colour index numbers seven to two represents the laminae with the least and most dolomite respectively according to carbon-hydrogen-nitrogen (CHN) analyses.  The laminae do not alternate from pure shale to pure carbonate, but rather though a whole spectrum of compositions with shale and carbonate as the end members.  It is assumed that one cycle represents on year of deposition.  One cycle is defined in this study as one period on a sinusoidal-like line plot of the colour index data, not as two adjacent laminae.

This sequence was deposited in a playa and lacustrine complex.  The carbonate minerals formed as a chemical precipitate within the alkaline and saline ephemeral lake.  Periodic rain events washed the clastic sediment off of the subaerially exposed playa into the lake.  The fresh water would transport the coarse-grained quartz and feldspar fragments, lower the lake water salinity and supply calcium ions, and renew the nutrient supply in the water column producing an algal bloom.  Thus, carbonate mineral deposition could be the result of a combination of eutrophication-triggered precipitation and the mixing waters with different compositions that formed the cycles seen in the rock record today.

The climatic cycles represented by the sediment are arranged in at least a four-order hierarchical structure.  Annual deposition is transposed onto El Niño events.   El Niño events are identified within the eleven-year sunspot hemicycle.  The twenty-two year sunspot cycle is host to variations caused by annual, El Niño and the eleven-year sunspot hemicycle.  The first three cyclic events are also transposed onto a thirty-year cycle of unknown origin.  Additionally equinox cycles are documented.  Alternations between long hot summers and short cold winters to short warm summers and long mild winters are represented in the plotted data as areas with extreme variation in colour index (or dolomite content) and areas with slight variations in carbonate content respectively.

The Ash Bay Gneiss Dome is located in the most northern part of Rainy Lake.  The Quetico Fault and the Seine River-Rainy Lake Faults are located to the south of the dome.  Rainy Lake is wedged between the Wabigoon Subprovince to the north and the Quetico Subprovince to the south, all being apart of the Superior Province.  The mineralogy indicates that the rocks of the dome underwent amphibolite facies metamorphism at approximately 500°C and was emplaced during solid-state metamorphic flow by a diapiric inflation.  The indicating minerals found in samples RL-01 - Rl-29 are mostly quartz and oligoclase, but sillimanite, epidote, and hornblende are also found within the samples in smaller amounts.  There were no kinematic indicators located in the field, so a closer examination of the microstructures was necessary to understand the extent of the deformation of the crystals and their deformation mechanisms.  In all, 29 oriented samples were studied that were taken from the eastern side of the Ash Bay dome by G. Borradaile and D. Gauthier.  These samples were thin sectioned and quartz c-axis petrofabric studies were performed on them by the use of the universal stage.  The petrofabric reveals a northeast-southwest orientation of the quartz crystals c-axes maximum compressive direction of the stress on the rocks, which is interpreted to be in a northwest-southeast direction.  Anisotropy of magnetic susceptibility was also performed on the 29 oriented samples and was later compared with the petrofabrics.  It was found that the quartz c-axis petrofabrics were strongly clustered and dipping at higher angles than the magnetic fabrics.  This showed that the quartz fabrics were aligned before the magnetic fabrics and therefore record a longer period of shear.  The magnetic fabrics could not have formed until the later stages of the domes inflation to result in nearly horizontal magnetic fabrics.

Amy is currently working as an exploration geologist
 
For more details about this thesis contact Dr. Graham Borradaile

The Big Duck Lake metavolcanic belt is an east - west trending, steeply north-dipping sequence of mafic and felsic intrusive and extrusive rocks.  Field mapping has revealed two distinct porphyritic felsic rock types.  They are pyroclastic porphyritic tuffaceous rocks and quartz feldspar porphyritic intrusive rocks.  The intrusive felsic rocks in the Big Duck Lake area occur as sill-like bodies and are generally massive except for foliated contact zones.  The extrusive units are comprised of laterally extensive fragment and crystal-rich beds, which have been selectively altered by hydrothermal solutions.  Field relationships, petrography and chemistry were used to compare the two felsic porphyries.  These studies indicate that the extrusive and intrusive phases are distinct.  On the microscopic scale the intrusive rocks exhibit primary crystallization textures displayed by gradational quartz and feldspar phenocryst reduction into the fine-grained groundmass.  The extrusive rocks display distinctive bimodal phenocryst and groundmass phases and are dominated by secondary metamorphic textures.  Whole rock and trace element analysis indicate that the intrusive rocks have more Sr and Al and less Zr than the extrusive rocks.  Zinc is preferentially concentrated in the tuffaceous rocks while higher values of Cu and Au are associated with the main intrusive sill.

However, similar concentrations of Pb, Ni, Co, Cr, Ti and P imply that both units are derived from the same parent magma.  A model based on intracontinental rifting is presented to show a possible origin for the bimodal volcanic activity.  This model also proposes that the synvolcanic intrusives are feeders for the extrusive felsic crystal tuffs.