The Morley Pyrite Occurrence is an Algoma Type sulfide-facies iron formation, located southeast of the town of Schreiber, in the Abitibi-Wawa Subprovince of the Superior Structural Province.  The iron formation consists of colloform pyritic structures, horizontally laminated pyrite, veins and massive pyrite in a chert/carbonaceous slate assemblage.  This is overlain by fine grained metasediments and mafic volcanics, and underlain by intermediate volcanics.

Colloform structures, up to 5.2 centimeters in diameter, are comprised of alternating, millimeter thick laminae consisting of pyrite or chert/carbonaceous slate.  The colloform structures have distinctive morphologies and display variable angular relationships with underlying strata.  Where several structures have developed adjacent to one another, the resulting structure appears stromatolitic.

Carbon, while present in pyritic laminae, was a major constituent in the siliceous bands, with magnetite, hematite, greenalite and stilpnomelane also being identified.  Magnetite and hematite, present at the upper chert and lower pyritic laminae contacts, indicate cyclical variations in Eh conditions during the formation of the laminae.  Stilpnomelane, indicative of greenschist metamorphism, is also associated with brecciated fragments of colloform structures.  Pyrite rims have developed on these fragments, which in turn are locally mantled by sphalerite.  Stilpnomelane is associated as rinds on the sphalerite.  Stilpnomelane is associated as rinds on the sphalerite, indicating post breccia development and possible association with higher temperature hydrothermal fluids.

The geochemistry of the occurrence, the fine grained nature of the sediment, the abundance of pyrite and the presence of tuffaceous material incorporated into the laminae, suggests a distal, anoxic basin in which reducing conditions dominated and episodic, low temperature hydrothermal input played a significant role.  The presence of carbon in the laminae and the regular morphology of the colloform structures suggests an at least partial biogenic origin in which Archean organic mats accumulated sulfidic and siliceous sediment.

The study area is located approximately 55 km west of the city of Thunder Bay, at the intersection of Highwasy 11 and 17.

Two outcrops were studied; one being a coarse lithic greywacke and the other a polymict conglomerate, both of Archean age.

R_f/φ analysis was used to determine the shape and orientation of five strain ellipsoids from oriented samples of greywacke, and one strain ellipsoid from the conglomerate.  An averaged strain ellipsoid was calculated using averaged strain components.

Analysis showed that original pebbles had cross-sections ranging from circular (R_o = 1.0) to elliptical (R_o = 6.0).  The strain ellipsoid is a flattened type ellipsoid with k = 0.19, and the X_tY_t plane lying parallel to the plane of bedding in the greywackes.

The close approximation of the averaged strain ellipsoid to a uniaxial pancake type ellipsoid allows discussion to be simplified to the X_tZ_t plane (ie. the maximum strain ellipse) of the strain ellipsoid.  The plane of the maximum strain ellipse lies perpendicular to the plane of bedding and defines a maximum shear strain of 4.5, a maximum angular shear of 77° with 80% shortening in the Z_t direction versus 83% lengthening in the X_t direction.

A simple model involving progressive deformation of an infinity long bed is proposed to explain the shape and orientation of the strain ellipsoid, as well as the closely spaced opposing facing directions which occur in the study area.

The area of investigation is located at the interface of the Quetico and Wabigoon Subprovince of the Superior Province of the Canadian Shield, in Northwestern Ontario, about 235 kilometers west of Thunder Bay.

The Quetico Subprovince comprises a monotonous series of thin- to medium-based, metamorphosed mudstones, wackes and sandstones that display many of the primary sedimentary features attributed to turbidites.  To the north, a highly sheared polymictic conglomerate grades conformably into a mafic to intermediate tuff.  This shear zone, believed to represent rocks of the Quetico Fault zone, accentuates the boundary of the Quetico and Wabigoon Subprovinces at this point.

Greenschist facies metamorphic grade increases from chlorite zone in the north to biotite zone in the south. 

A single, dominant deformation event resulted in the development of two isoclinal folds with ENE striking axial surfaces accompanied by a discrete, penetrative and, probably axial planar cleavage.  These folds are identified as an antiformal syncline closing to the west and a synformal anticline closing to the east.  The folds have moderate to steeply plunging, curved hinge lines.   The structural facing of the folds of the Quetico metasediments varies from vertically downward- facing to eastward- facing

The bedrock underlying Burnt Island and portions of the East Bay of Dog Lake is typical of the lithologies commonly associated with those of the Quetico Gneiss Belt.

Investigation of this area has revealed five distinct rock units, many of which are comprised of more than one rock type.  Two of these units represent metamorphic equivalents of pre-existing rocks of pelitic and basic compositions.  These units have undergone polyphase deformation and metamorphism.

The first deformational episode produced folding about east-west axial surfaces and was associated with amphibolite grade metamorphism.  Partial melting of the host rocks during this metamorphism gave rise to two distinctive rock units.  The last of the five rock units recognized is incorporated in crystallized partial melt products as exotic blocks.

A second deformational event affected the rocks producing folds with north-south striking axial surfaces.

All rocks in this area are variably affected by a later retrogressive metamorphic event.

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.