The Paleoproterozoic Rove Formation of Northwestern Ontario is part of the Animikie Group.  The Animikie basin derived clastic sediments from eruptive activities of the surrounding volcanoes.  These clastic sediments accumulated in the basin from at approximately 1880 to 1870 Ma.  This accumulation of clastic sediments became the Rove Formation.  The Rove Formation consists mainly of interbedded shale and sandstone layers.  Shale is the dominant rock type.  About 70% of the Rove Formation is made up of organic shale.  The organic content of the shale indicates that the basin, at one time, was petroliferous - the hydrocarbon contents are now degraded. 

Three main lithofacies were defined based on sediment types - sandstone lithofacies, shale lithofacies, and volcanic ash lithofacies.  The sandstone lithofacies is made up of massive sandstone, normal-graded sandstone, reverse-graded sandstone, parallel-stratified sandstone, and cross-stratified sandstone members.  Sediment sizes of the sandstone lithofacies vary from coarse to fine-grained sand, and average thickness of stratification is about 5 mm.  The shale lithofacies includes massive shale and parallel-stratified shale.  Some of the parallel-stratified shale layers were fissile.  The average thickness of stratification for the shale lithofacies is about 5 mm.  The volcanic ash lithofacies is made up of parallel-stratified ash (average thickness = 5 mm).  Volcanic ash is also dispersed and intermixed with sand and mud.

The depositional setting of the Rove Formation is a submarine ramp system.  The movement of coarse sediments into the deeper parts of the Animikie basin was mainly through the action of low and high-density turbidity currents, while fair-weather and storm-generated currents dominated depositional activity at the edge of the basin.  The basin accumulated mud and ash particles during tranquil periods.

The bedrock north of Thunder Bay, Ontario is mostly the greenschist facies metasedimentary and metavolcanic rocks of the Shebandowan Greenstone Belt and the high grade metamorphic rocks of the Quetico Gneiss Belt.  The boundary between the two is locally obscured in part by a zone of plutons extending west from Hwy 527 for over 45 km.  The Barnum Lake Pluton occupies a central position within this zone, and is hosted entirely by metasedimentary rocks, mostly biotite schists.  It has been classified compositionally as a porphyritic quartz monzonite, and is easily recognized on the regional aeromagnetic map as an elliptical positive anomaly.

A groundborne vertical component magnetic survey was performed over the area of the pluton and combined with the total field aeromagnetic data and pertinent structural measurements for interpretation.  Strike and dip data from the surrounding conformable bedding suggests a cylindrical body dripping very steeply towards the north northwest.  Preliminary modeling of the magnetic data shows good agreement between the aeromagnetic data and predicted profiles for a near vertical prism-shaped body of depth extent greater than 2 km.

Modern-day stromatolites primarily form in carbonate-dominated environments through binding particulate matter to the sticky extracellular polysaccharides secreted by the cyanobacteria. Evidence of the operation of this process in constructing stromatolites extends back into the Phanerozoic. However, Precambrian stromatolites do not contain abundant silt- to sand-sized particles characteristic of this process. Instead they are primarily composed of material that has precipitated from seawater. This is commonly a carbonate phase, though chert stromatolites are common in some Proterozoic and Archean sequences. In recent years controversy has developed in the literature as to whether the chert stromatolites in the Gunflint Formation and similar rock units represent silicification of carbonate or are primary silica precipitates (see: Knoll and Simonson, 1981; Simonson, 1985; Knoll, 1985; Siever,1992; Maliva et al., 2005). Some of this work utilized outcroppings of the Gunflint Formation that are highly diagenically altered, and thus ambiguous concerning primary mineralogy. Roadwork on Highway 590 near Kakabeka Falls exposed an excellent example of chert microbialites and stromatolites entombed in ankeritic grainstone with a sharp boundary between the two, providing an opportunity to add to the debate on the possible primary origin of the silica in chert stromatolites.

The 1.878+-1 Ga Gunflint Formation is a chemical sediment dominated shelf succession deposited on Archean basement. It records a number of transgressive-regressive cycles. Hofmann (1969) and Franklin et al. (1982) described stromatolites occurring at two different stratigraphic levels; at the base of the Gunflint growing on Archean units and the basal conglomerate and secondly, on a hard-ground in the middle of the Formation developed during regression. The basal biogenic sediment at Kakabeka Falls directly overlies Archean granodiorite and consists of a lower one meter thick, continuous chert microbialite. The millimeter-scale, crinkly layering is sub-horizontal, with organic carbon only giving the unit a dark colouration in limited places. A large stromatolitic head develops off the upper microbialite layers. It is the size of a beach ball, with a slightly narrower base. There appears to be a sharp contact between the microbialite-stromatolite and carbonate grainstone, which overlies the microbialite and abuts against the stromatolite. The layering in the stromatolite does not build on top of the lower grainstone laminae, indicating that the stromatolite was fully grown before the grainstone entered the environment.

Samples of all lithologies were investigated with a petrographic microscope, a field emission scanning electron microscope with an energy dispersive spectrometer, inductively coupled plasma atomic emission spectrometry and mass spectrometry.

The diagenetic history is more complex than it appears to the naked eye. The stromatolite contains abundant microquartz, megaquartz, chalcedony, and organic matter. The silica is rather clean and well developed with little to no carbonate inclusions or ghosts. Carbonate present in the stromatolite is seen replacing chalcedony fans. Distinct growth zones can be seen in the outer portions of the carbonate. Rarely, quartz crystals present in the stromatolite show carbonate overprinting, replacing them to varying degrees. Carbonate is visible replacing megaquartz grains and overprinting microquartz as very fine grained specular carbonate. Growth zoning is present in most of the carbonate grains. The carbonate grainstone unit overlying the stromatolite has been highly silicified. The quartz is texturally similar to the quartz in the stromatolite; microquartz and megaquartz are abundant with minor amounts of chalcedony. The megaquartz is seen in the intergranular spaces as space-filling cement. Higher magnification shows extinct carbonate grains that have been silicified with small amounts of carbonate remaining behind.

However, further from the contact with the stromatolite the carbonate grainstone unit is silicified to a much lower degree. Some of the carbonate grains have experienced some silicification, but the rock is mainly composed of carbonate with some organic material. Silica in the form of microquartz is forming within the carbonate grains. A closer observation reveals that the quartz developing in the carbonate grains is itself being over-printed by carbonate growth. The carbonate grains have growth zoning in their outer portions. Rare earth element plots for the ankerite and chert are generally similar, though this probably reflects both inheriting the seawater pattern. The most striking difference between the two lithologies is the Ba/Sr ratio. The stromatolitic cherts have one consistent ratio, whereas the carbonates and known replacement cherts from the area have a different consistent ratio. All of the above is consistent with the microbial and stromatolitic cherts being a primary precipitate, but it is not conclusive. If the silica is primary new models will need to be developed to explain how Precambrian cherty stromatolites form.

No abstract provided.

Cryptomelane was synthesized by refluxing KMnO₃ with Mn(NO₃)₂xH₂O and M(NO₃)₂xH₂O (M=Co, Cu, Ni, Zn, Pb) in various ratios in order to produce highly metalliferous cryptomelane.  Weight percents of 1.567%, 0.914%, 0.13%, 0.027% and 11.424% were obtained for Co, Cu, Ni, Zn, and Pb respectively.  With the exception of Pb (which substitutes for K), it is difficult to establish whether these metals are substituting for K or Mn, as the metals are in too small a concentration.  The metal content increases in order of Ni²⁺<Zn²⁺<Cu²⁺<Co²⁺<Pb²⁺.  Increasing the ratio of metals to potassium does not guarantee higher metal content.  It is apparent that most of the inputted metals are washed off during the filtration step, being less stable in the crystal structure than manganese or potassium.

The Rainy Lake - Bad Vermilion Lake anorthosite intrusion, is found in the Rainy Lake Wrench Zone (RLWZ) of the Quetico belt, in the Superior Province of the Canadian Shield.  It has a sigmoidal NE-SW to E-W orientation and dips steeply to the northwest.  The sigmoidal form cuts across the width of the RLWZ.

Anisotropy of magnetic susceptibility (AMS) fabric is controlled by paramagnetic chlorite and biotite, while anisotropy of anhysteretic remanence magnetism (AARM) fabric is controlled by ferromagnetic pyrrhotite and magnetite.  On the southern boundary of the RLWZ, AMS fabric is offset anticlockwise with respect to AARM fabric, consistent with dextral shearing.  In the interior, the AMS fabric is offset clockwise with respect to AARM fabric, suggesting the existence of conjugate faults with sinistral motion within the interior of the RLWZ.

Thermal demagnetization uncovered two meaningful components.  Principal component analysis (PCA) defined an A - component with a mean orientation of 318°/-29° and a B -component with a mean orientation of 004°/67°.  The orientations are consistent with a progressive northward tilting of the intrusion through time.  Coupled with smeared demagnetization curves, indicating syn-rotational magnetization, northward tilting is compatible with northward subduction.

The Lac de Gras Kimberlite field is located approximately 295 kilometers north of the town of Yellowknife, within the Slave structural province.  Since the discovery of the first kimberlite pipe in 1991, nearly two hundred kimberlite pipes have been identified in the Lac de Gras region, more than fifty of which are diamond-bearing.  The kimberlites studied thus far have been of two broad textural types, hypabyssal and volcaniclastic (pyroclastic).  Three kimberlites of each textural type were selected for study, and the spinel grains within each kimberlite studied.  Roughly eighty spinel grains were analyzed, producing approximately four hundred analyses.

From these analyses, it was found that the hypabyssal kimberlite spinels followed essentially two evolutionary trends.  The majority of the spinel grains analyzed followed the magnesian ulvöspinel magmatic trend, the characteristic magmatic trend observed in archetypal kimberlites.  This trend consisted of euhedral titanian magnesium aluminous chromite (TIMAC) cores mantled by magnesian ulvöspinel - ulvöspinel magnetite series (MUM) compositions.  When plotted on a reduced spinel prism, the trend begins near the MgCr₂O₄-FeCr₂O₄ join and heads towards the rear rectangular face and up towards the Mg₂TiO₄-Fe₂TiO₄ apex.  The secondary evolutionary trend observed was the pleonaste reaction trend.  This consisted of either: euhedral pleonaste cores mantled by TIMAC or MUM compositions, or more commonly, TIMAC cores, mantled by pleonaste compositions followed by an iron-rich rim.  In terms of morphology, the hypabyssal kimberlites were dominated by atoll grains rimmed by a thin magnetite layer.  In addition, the atoll grains appear to have preferentially nucleated about phlogopite phenocrysts.  In the pyroclastic kimberlites, the spinel grains displayed little or no spinel evolution in terms of core and mantle textures.  Rather, the magnesian ulvöspinel trend was preserved in two distinct grain populations, unlike the hypabyssal units, which exhibited core and mantle textures.  In terms of morphology, these units were dominated by corroded atoll grains of TIMAC compositions, with subeuhedral to euhedral groundmass spinel grains of MUM compositions forming the rest of the population.  

The Hadley Prospect is a massive Zn-Pb mineral occurrence situated in the Savant Lake area of northwestern Ontario.  This occurrence displays many of the characteristics typical of volcanogenic massive sulphide deposits found in the Canadian Shield.  The thesis area is found in a felsic volcanic pile of bedded tuffs intercalated with fine to medium grained flows and lapilli/tuff breccia units with localized metasedimentary and quartz porphoritic intrusive units.

Geochemical sampling was implemented in an attempt to locate an alteration zone in the footwall rocks.  A total of 16 samples were taken for analysis by atomic absorption techniques for the elements Na, Ca, Mg, K, total Fe, Co, Cr, Cu, Zn, Mn, and Ni.  The survey failed to intersect an alteration zone and showed the hanging wall and footwall units to be essentially the same.

Textural analysis of samples taken from the thesis area revealed a distinct systematic sequence of metamorphic and cataclastic events.  Recrystallization, cataclastic, and replacement textures indicate a major metamorphic event accompanied by a shearing event with a possible later minor thermal event have acted on the occurrence since deposition.  The shearing event is believed to be responsible for the tectonic transport of the alteration zone to the western extension of the occurrence thus removing it from the vicinity of the geochemical sampling.  The alteration zone is contained in a pyroxene-amphibole-olivine breccia unit at the western extremity of the occurrence.

The major metamorphic period is a skarn-forming type metamorphism which has produced a contact areole over the regional metamorphism produced during the Kenoran Orogeny.

A comparison of the occurrence to the model of Sangster (1972) for fumaroltic volcanogenic massive sulphides revealed an excellent correlation and indicated a similar origin for the Hadley Prospect.

Forty eight rock powder samples from Freemans Cove volcanic suite were analysed for cesium using neutron activation analysis.  The samples analysed vary in composition and may fit into the following three series:

    i)  A sodic nephelinite-basanite (phonolite) series

    ii) A mildly potassic nepheline-basanite (phonolite) series

   iii) A mildy alkakine (sodic transitional) basalt suite.

The cesium was radio-chemically separated using an inorganic cation exchanger, Ammonium 12 moybdophosphate.  The gamma ray spectrometry was carried out using a Norland 5400 Ino Tech Multichannel Analyser.

The cesium concentration ranged from a low of 0.03 ppm, in a basalt to a high of 5.87 ppm, in a basanite or nephelinite.  The K/Cs ratio ranged from 3900 for a basalt to 702500 for a Ne bearing trachytoid of phonolitoid.  The majority of the samples have K/Cs ratios between 14,500 and 40,000.  The Rb/Cs ratio ranges between 8.6 for a basalt to 3747 for a Ne bearing trachytoid or phonolitoid.  The majority of points lye between Rb/Cs ratios of 25 to 100.

Graphs of Rb vs Cs and K vs Cs show trends that are very similar.  These trends show a loss of cesium without the loss of either rubidium or potassium.  These trends may indicate a degassing of cesium due to it's volatile nature, but these trends are found only in two rock groups, basalts and Ne bearing trachytoids and phonolitoids.

The graph of K vs Rb shows a linear trend indicating not only comagmatism, but also a coherence of potassium and rubidium through magma evolution.

AMS (anisotropy of magnetic susceptibility) is a useful tool for identifying petrofabrics, especially when the petrofabrics may be cryptic as in the case of the limestones of the present study.  Although a conventional penetrative tectonic fabric did not overprint the sedimentary fabric in the Polis limestones, the sedimentary fabrics were modified by the stress fields of fault block rotations.  The principal extension directions are recognized from the imposed alignments of certain paramagnetic minerals (micas and clay) and by ferromagnetic magnetite.  By comparing AMS data with structural evidence and seismic data (in the form of Centroid-Moment Tensors) it is possible to compare paleotectonics with neotectonic to prognosticate surface expression of the current tectonic regime.  The paleotectonic regime was expressed as ENE-WSW extension as indicated by AMS and fault orientations and movements; but the current tectonics exhibit ENE-WSW compression as inferred from fault-plane solutions.  This neotectonic regime has expressed itself surficially as a dextral strike-slip motion along one of the major extension faults of the former regime.  The data is also useful to compare with models of development of the tectonic regime of western Cyprus, which displays non-coaxial progressive strain history as a result of the Eratosthenes Seamount interfering with subduction rates of the Cyprus Trench.