The 2.8 Ga Archean Steep Rock Group of north-western Ontario, Canada, contains one of the oldest well-preserved carbonate ramps in the world.  The Mosher Carbonate is host to a number of unique ancient depositional textures.  The purpose of this thesis is to perform a thorough analysis of the depositional textures of carbonate precipitates in the Steep Rock group’s Mosher carbonate.  These textures include: columnar stromatolites, microbial mat and fenestrate microbialites, sheet cracks, and crystal fans.  Columnar stromatolites are found in walled and unwalled varieties.  Microbial mat, microbial supports, and carbonate-filled void spaces in differing ratios make up fenestrate microbialites.  The most common form of fenestrate microbialites at Steep Rock are tented microbialites and “net-like” microbialites.  These are a result of a lesser influence from microbial supports and void spaces and domination by horizontal filmy laminae.  Sheet crack structures are common and have shown up to 4 stages of successive growth in some samples.  Crystal fans at Steep Rock form distinctive giant domes, alternating in deposition with fenestrate microbialites.  Fans grow in all directions, though downwards is uncommon and lateral growth is blocked early on by other fans.  Crystals grow preferentially from the tops of microbial supports, and in some cases from a darkened surface that may represent dissolution.

The Lyon Lake – Claw Lake sulphide bearing graphitic shale is contained within a predominantly sedimentary sequence of coarse to fine clastics with minor carbonate and mafic volcanic rock.

Sulphide mineralogy consists mainly of pyrite and pyrrhotite occurring as nodules, lensoid pods and narrow bands conformable with bedding. Traces of chalcopyrite, sphalerite and arsenopyrite are present as well.

Cu, Zn, Ni, Co, Mn and As were analysed in sulphides, graphitic shale and wall rock. Results suggest: (1) Sulphides contain higher contents of Cu, Zn, Co, Ni, and As than graphitic shale or wall rock and (2) Mn, Zn, Co and Ni content decreases eastward along the formation in graphitic shale.

Analyses of a vertical section through the formation suggests: (1) Cu, Zn, and Mn are enriched in the footwall rocks as opposed to the hanging wall rocks, (2) Zn and As are concentrated in graphitic shale in comparison with hanging wall rocks and (3) Co and Ni content is relatively uniform throughout the section.

Element ratios have been used to investigate the depositional environment of sulphides and host rock. Results show: (1) Co:Ni ratios in sulphides and graphitic shale are consistent with other worker's data for a sedimentary origin and (2) Mn:Fe ratios are suggestive of volcanic contribution to the western margin of the formation.

Carbon content in the graphitic shale varies from 1.60% - 12.06%. X-Ray studies indicate carbon is either present in an amorphous form or below the detection limit of this technique.

X-Ray studies indicate the pyrrohtite present in monoclinic possibly derived by metamorphism from pyrite.

Evidence suggests that the graphitic shale is derived in a sedimentary basin in which there was volcanic activity at the western margin. This was followed by large scale mafic volcanism. Sulphides derived by sedimentary or diagenetic processes is likely, since there is no evidence for a direct volcanic exhalative source.

The 1878 ± 1Ma Gunflint Formation is a chemical-sedimentary unit deposited in the Animike Basin; it shows a sequence of transgressive-regressive cycles.  Wolff (1917) and Broderick (1923) divided the Gunflint into several individual members; lower cherty, lower slaty, upper cherty and upper slaty.  These members were then grouped into two different sequences; the upper and lower sequences.  The first and most extensive transgressive-regressive cycle is made up of the lower cherty member, while overlying transgressive-regressive cycles are made up of the lower slaty member, the lower cherty member and the upper slaty member.

Two separate outcrops found near Mink Mountain UTM: 329,520 E/5,338,163N and off the Magnetic Rock Trail in Minnesota662034E/5329885N were examined and sampled.  These two outcrops show a complete section through the peak lower regressive-transgressive sequence.  Detailed stratigraphic columns were constructed from the logs takes through these sequences, which were divided into three main units; 1) a grainstone unit forms the bottom unit and lies directly below 2) stromatolites which are capped off by a 3) oncolithic unit.  At the outcrop behind Mink Mountain the grainstone directly below the stromatolites is brecciated and shows injection of jasper and hematite throughout.  Microscopically the grainstone unit is composed of angular to rounded grains of chert.  The cement is predominantly chert with some blocky quartz found forming at grain boundaries.  The stromatolite unit is present above the pre-lithified grainstone unit and contains distinct stratiform and columnar stromatolites.  The top unit is an oncolith-rich grainstone.  The grains have a nucleus composed of either microquartz-rich chert or blocky quartz.  The cement of the unit is composed of a combination of a chalcedony-rich chert and blocky quartz.  Samples were crushed and digested for ICP-AES analysis for major oxides and trace elements.  Several samples were collected up through this section and sent to the OGS lab in Sudbury for ICP-MS analysis of rare earth elements.  The results were normalized to Taylor and McLennan (1985) Post Archean Australian Shale values and plotted.  All the samples taken from the grainstone layer and three samples taken from the stromatolites show a characteristic europium anomaly and a distinct positive cerium anomaly.  The Ce anomaly is indicative of an oxidized environment where Ce (IV) was being precipitated and scavenged by the sediments.  This requires oxygen production in the near-shore, and precipitation of Ce from sea-water that had not been previously exposed to significant oxygen.

The ~3 Ga North Caribou greenstone belt in the North Caribou Terrane, Superior Province, comprises greenschist- to upper amphibolite-facies, ultramafic to felsic metavolcanic and metasedimentary rocks, intruded by 3000 to 2700 Ma felsic plutonic rocks. The study area was centered on a narrow (~100m wide), north-trending, felsic metavolcanic unit on the western side of Opapimiskan Lake, 5 km northwest of Musselwhite Mine, in the South Rim Volcanic Unit (SRV).  The felsic metavolcanic unit was mapped in detail over a distance of 2 km. Samples of the felsic rocks, as well as the associated metabasalts, metasedimentary, and intrusive units were collected and classified according to their petrography and whole rock geochemistry.

The metarhyolitic units are defined by mineral assemblage of quartz + plagioclase + K-feldspar with accessory muscovite + biotite + chlorite ± titanite ± clinozoisite ± zircon. Field observations identified some flows, tuffaceous and pyroclastic units as well as felsic dykes related to regional plutonism. The calculated anhydrous SiO₂ values for the felsic metavolcanic rocks in the SRV range from 75 – 81 wt%. These high-silica, calc-alkaline metarhyolites are classified as FII-type rhyolites. The unaltered felsic metavolcanic rocks are LREE-enriched with ε_Nd values of -2.79 and -0.89.

The tholeiitic metabasaltic and komatiitic-basalt units have been metamorphosed to amphibolites composed almost entirely of plagioclase and hornblende with accessory titanite + chlorite + opaques ± rutile ± biotite ± zircon. The komatiitic-basalt has a MgO value of 14 wt% (compared to 3 to 8 wt% MgO for the metabasalts) and has greater Ni and Cr (ppm) contents. The basalts can be subdivided into two classes based on their REE contents, those with flat REE and those that are LREE-enriched with negative Nb and Al anomalies. The ε_Nd values are +0.78 and +0.58 for the flat REE basalts and -1.58, -3.35, and -1.61 for the LREE-enriched basalts.

Metasedimentary rocks in the study area have been metamorphosed into schists and a quartzite. The protolith of the schists were probably pelitic sedimentary rocks. The mineral assemblage consists of strongly foliated quartz + biotite + muscovite + chlorite ± garnet ± zircon ± clinozoisite. These schists are associated with the felsic metavolcanic rocks. The quartzite is similar to the felsic metavolcanic units but does not contain feldspars. Its mineral assemblage comprises quartz + muscovite + biotite + garnet.

The metarhyolites plot as calc-alkaline rocks with consistent LREE enrichment with Nb and Ti depletions. This trend (including the LREE-enriched metabasalts and komatiitic-basalt) suggests a bimodal volcanic arc tectonic environment. The relative enrichment of LREEs occurs as the LILE enriched fluids are driven off the downgoing slab and modify the overlying mantle wedge. The negative Nb anomalies and negative ε_Nd value suggests that the melt interacted with and assimilated older continental crust. The tholeiitic metabasalts with flat REE patterns suggest an oceanic island plateau environment generated by a mantle plume. The positive ε_Nd values of these rocks suggest that the melts were derived from a depleted mantle source possibly a mix of upper depleted mantle and plume material. These geochemical signatures are seen in both the South Rim and Opapimiskan-Markop metavolcanic units. The interpretation of a plume-sourced oceanic island plateau arriving at a continental arc subduction zone validates the models of early proto-continental crust development of plume-sourced crustal material being accreted through subduction processes in the Superior Province.

The Gunflint and Biwabik Formations form the middle unit of the sedimentary- metasedimentary Animikie group. In an attempt to further understanding of the history of the Gunflint Formation a series of samples for chemical analysis were taken from five drill-holes (MC-1-89, ON-06, MGS-02, MGS-08, and 18279) throughout the formation. Special attention was given to the siliciclastic–volcaniclastic material that mixes with the chemical sediment at some horizons in the formation. Two areas of siliciclastics were defined through graphing Al₂O₃ vs depth, TiO₂ vs Depth and Na₂O/TiO₂ vs Depth.

The first, middle, area rich in volcaniclastics–siliciclastics was observed in drill-hole MC-1-89 at 103.2 meters from the top of the formation, ON-06 at 103.6 meters from the top of the formation, MGS-02 at 95.7 meters from the top of the formation, and MGS-08 at 64.1 meters from the top of the formation. The relationship between Zr/TiO₂ was analyzed through the use of a scatter point graph. It revealed a slope with an average of 166. The relationship between zirconium and titanium oxide was compared to possible volcanics to define a source. The most likely source, the Gunflint volcanics analyzed at Mink Mountain, revealed no correlation with the volcaniclastics - siliciclastics. However, the slope revealed the Zr/TiO₂ ratio of the siliciclastics – volcaniclastics had some similarities with the dacitic volcanic flows from the Emperor volcanics. A similar study of the relationship between V/TiO₂ revealed similar results in comparison with the Gunflint volcanics from Mink Mountain, However, it could not be compared successfully to the Emperor volcanics.

The top unit containing volcaniclastics - siliciclastics was observed in drill-hole MC-1-89 at 22.7 meters from the top of the formation, ON-06 at 26.7 meters from the top of the formation, and MGS-02 at 24.6 meters from the top of the formation. The volcaniclastics – siliciclastics do not appear in drill-hole MGS-08. The material continues to the top of the formation. The material was isolated and the relationship between Zr/TiO₂ was analyzed through the use of scatter point graphs. They revealed a slope with an average of 317.8. This slope differed from the ratio of the middle siliciclastics – volcaniclastics. The relationship between zirconium and titanium oxide was compared to possible volcanics for a source. It was found the most likely source for the siliciclastics is eroded average continental crust.

Lapilli tuffs were also analyzed and a comparison of Zr/TiO₂ and V/TiO₂ to the Gunflint volcanics indicated that it is likely that the Mink Mountain Gunflint volcanics were deposited in the area surrounding the flows as reworked Lapilli tuffs. These are interlayered with the middle siliciclastic-rich unit.

Two periods of alteration were observed in the vertical bar graphs of K₂O/Na₂O vs depth and vertical bar graphs of Al₂O₃/Fe₂O₃ vs Depth. In drill-hole MC-1-89 there is an area of alteration from 95.1 to 86.6 meters from the top of the formation and in ON-06 it occurs at 91.5 meters to 87.2 meters from the top of the formation. This period of alteration ended there in the north. This probably indicates a regression and drop in sealevel not exposing sediment in the offshore to the south. A second area of alteration was observed in MC-1-89 from 4.6 to 2.5 meters from the top of the formation, in ON-06 at 19.5 meters to 4.5 meters from the top of the formation, in MGS-02 there is only one noticeable region of alteration at 7.4 meters to 2.2 meters from the top of the formation, and in MGS-08 the upper area of alteration is at 3.4 meters to the top of the formation. Using Al₂O₃/Fe₂O₃ vs depth of depletion in iron is only seen in this top region of alteration. This depletion might exist because of dissolution and hydrolysis caused by infiltrating of rain water, probable due to a period of subaerial exposure.

The Gunflint and Biwabik Formations form the middle unit of the sedimentary-metasedimentary Animikie group.  In an attempt to further understanding of the history of the Gunflint Formation a series of samples for chemical analysis were taken from five drill-holes (MC-1-89, ON-06, MGS-02, MGS-08, and 18279) throughout the formation.  Special attention was given to the siliciclastic-volcaniclastic material that mixes with the chemical sediment at some horizons in the formation.  Two areas of siliciclastics were defined through graphing Al₂O₃ vs depth, TiO₂ vs Depth and Na₂O/TiO₂ vs Depth.

The first, middle, area rich in volcaniclastics-siliciclastics was observed in drill-hole MC-1-89 at 103.2 meters from the top of the formation, ON-06 at 103.6 meters from the top of the formation, MGS-02 at 95.7 meters from the top of the formation, and MGS-08 at 64.1 meters from the top of the formation.  The relationship between Zr/TiO₂ was analyzed through the use of a scatter point graph.  It revealed a slope with an average of 166.  The relationship between zirconium and titanium oxide was compared to possible volcanics to define a source.  The most likely source, the Gunflint volcanics analyzed at Mink Mountain, revealed no correlation with the volcaniclastics – siliciclastics.  However, the slope revealed the Zr/TiO₂ ratio of the siliciclastics – volcaniclastics had some similarities with the dacitic volcanic flows from the Emperor volcanics.  A similar study of the relationship between V/TiO₂ revealed similar results in comparison with the Gunflint volcanics from Mink Mountain.  However, it could not be compared successfully to the Emperor volcanics.

The top unit containing volcaniclastics – siliclastics was observed in drill-hole MC-1-89 at 22.7 meters from the top of the formation, ON-06 at 26.7 meters from the top of the formation, and MGS-02 at 24.6 meters from the top of the formation.  The volcaniclastics – siliciclastics do not appear in drill-hole MGS-08.  The material continues to the top of the formation.  The material was isolated and the relationship between Zr/TiO₂ was analyzed through the use of scatter point graphs.  They revealed a slope with an average of 317.8.  This slope differed from the ratio of the middle siliciclastics – volcaniclastics.  The relationship between zirconium and titanium oxide was compared to possible volcanics for a source.  It was found the most likely source for the siliciclastics is eroded average continental crust.

Lapilli tuffs were also analyzed and a comparison of Zr/TiO₂ and V/TiO₂ to the Gunflint volcanics indicated that it is likely that the Mink Mountain Gunflint volcanics were deposited in the area surrounding the flows as reworked Lapilli tuffs.  These are interlayered with the middle siliciclastic-rich units.

Two periods of alteration were observed in the vertical bar graphs of K₂O/Na₂O vs depth and vertical bar graphs of Al₂O₃/Fe₂O₃ vs Depth.  In drill-hole MC-1-89 there is an area of alteration from 95.1 to 86.6 meters from the top of the formation and in ON-06 it occurs at 91.5 meters to 87.2 meters from the top of the formation.  This period of alteration ended there in the north.  This probably indicates a regression and drop in sealevel not exposing sediment in the offshore to the south.  A second area of alteration was observed in MC-1-89 from 4.6 to 2.5 meters from the top of the formation, in ON-06 at 19.5 meters to 4.5 meters from the top of the formation, in MGS-02 there is only one noticeable region of alteration at 7.4 meters to 2.2 meters from the top of the formation, and in MGS-08 the upper area of alteration is at 3.4 meters to the top of the formation.  Using Al₂O₃/Fe₂O₃ vs depth of depletion in iron is only seen in this top region of alteration.  This depletion might exist because of dissolution and hydrolysis caused by infiltrating of rain water, probable due to a period of subaerial exposure.

Three granitic dike swarms of peraluminous composition within the southern North Caribou Terrane display both compositional and textural zoning.  Two distinct mineralogical phases can be recognized within each swarm: a granodiorite and tonalite phase at 6k Ridge and Lake 282 drill core, and a monzogranite and granodiorite phase at Cigar Lake.  In addition to mineralogical zoning, textual zoning is also present within the dikes at each of the locations.  A fine-grained border zone next to the contact with the host rock consists predominantly of albite and quartz.  Secondly a medium-grained wall zone with albite, quartz, microcline ± tourmaline that extends inward from the border zone and into the dike.  Finally, a coarse-grained quartz, albite, microcline, muscovite ± biotite ± garnet zone extends inward from the wall zone into the core of the dikes.  Structures such as internal foliation parallel to the adjacent host rock, as well as pinch and swell structures, suggest that the dikes and host rocks were still ductile when they were emplaced and that timing of emplacement was syn-orogenic.  Trace element geochemistry shows significant alteration within the dikes, as well minor assimilation of the adjacent host rock.  ɛNd values of -0.9 to -6.0 suggest enrichment of the magma from a crustal source through partial melting prior to emplacement.

The Steepledge Intrusion is an irregularly shaped mafic to ultramafic layered intrusion located north of Thunder Bay, Ontario.  It is recognized as part of the early intrusive phase of the 1.1 Ga Midcontinent Rift.  Light rare earth element enrichment and fractionation of the heavy rare earth elements is consistent with other early Midcontinent Rift-related intrusions and is interpreted to indicate a primitive mantle source.

The stratigraphy of the Steepledge Intrusion can be divided into seven zones on the basis of internal variations in petrology and geochemistry.  The Hybrid Zone is a quartz leucogabbro containing quartz rich inclusions assimilated from the Quetico Basin country rocks.  The Upper Layered Zone is a weakly layered sequence comprised of cm-scale layers of alternating troctolite and olivine gabbro.  A gradational contact exists between the Upper Layered Zone and the underlying Upper Gabbroic Zone.  The Upper Gabbroic Zone comprises a sequence of unlayered olivine gabbro containing oikocrystic clinopyroxene which poikilitically encloses fine-grained cumulate olivine.  The Middle and Lower Layered Zones comprise a 70m thick unit of olivine gabbro to olivine melagabbro with increasing olivine content at depth.  Centimetre-scale layering within the Middle and Lower Layered Zones are composed of alternating bands of olivine-cumulate peridotite and pyroxene-cumulate-pyroxenites. A transition from fine-grained olivine melagabbro to coarse-grained lherzolite marks the upper contact of the Coarse Peridotite Zone.  The Coarse Peridotite Zone is characterized by coarse-grained cumulate olivine, intercumulate plagioclase and megacrystic orthopyroxene that enclose the cumulate olivine.  The Basal Peridotite Zone is an approximately 130m thick zone of monotonous, very-fine grained to fine-grained peridotite.  Geochemical analysis has identified the presence of cryptic layering throughout the entirety of the intrusion and is interpreted to be the resulted of multiple pulses of more primitive magma causing cyclic variations in the magma composition within the intrusion.

Sulphur isotope values for the Steepledge Intrusion range from -3.0 to -0.8 and are consistent with a mantle-derived magma with no external input of sulphur.  Localized contamination by the host Quetico metasiltstones is concentrated in the Hybrid Zone, however, the overall negative Nb anomaly observed may represent an earlier, more pervasive contamination of the parent magma at depth.

The Nipigon Embayment encompasses ~10,000 km³ of magmatism in an area of 200,000 km² that stretches from Lake Nipigon to the southwestern side of Thunder Bay. The majority of the intrusive units within the embayment have been classified as Nipigon Sills. Diabase sills at Hele, Tease Lake and two at Thread Lake exhibit textures typical of Nipigon sills. All four sills contained three distinct textures throughout; a chill zone at contacts, a medium-grained to coarse-grained subophitic zone, and a coarse-grained ophitic texture, with Hele and Tease Lake also displaying of a fourth type of texture in the form of a megacrystic ophitic zone. The crude layering that is seen throughout the sills is evidence of a multiple pulse system. All sills maintained consistent mineral modal abundances down hole; Hele averaged 55% plagioclase and 45% pyroxene; Thread Lake 60% plagioclase and 40% pyroxene; and Tease Lake 55% plagioclase and 45% pyroxene.

Plots of Th/Yb_pm versus Nb/Th_pm subdivide the sills into distinct subclasses. Hele, Thread Lake 2 and Tease Lake all plot within the Nipigon 1 suite whereas Thread Lake 1 represents a Nipigon 2 Suite. This classification is based on the emplacement and contamination history of the sills. Hele, Thread Lake 2, and Tease Lake represent a more primitive magma, whereas Thread Lake 1 is derived from a less primitive magma. Thus giving evidence of differing contamination histories.

The occurrence of red granite and quartz diabase along the Jarvis Bay Road, in the Jarvis District of Thunder Bay, Ontario was found to be a tholeiitic Logan intrusion, formed primarily by the processes of fractional crystallization and associated assimilation. This is observed in the identification of fractionated plagioclase clusters, possessing a relative Sr, and Eu enrichment, as well as plagioclase compositions  and other mafic phases in disequilibrium  relative to the surrounding rock  (more An-rich, allowing greater substitution of Sr²⁺ for Ca²⁺).  Assimilation of upper crustal rocks in conjunction with fractionation processes can be shown on a primitive mantle normalized multi element diagram, where a relative Nb trough, and a consistent enrichment in LREE is found in all samples of the red granite and quartz diabase.

The mechanism that produced the granophyric intergrowths is observed to involve the interaction of a late stage volatile phase. This is shown through the pervasive iron oxide alteration, forming irregular patches, staining feldspar phenocrysts (in the red granite most notably), as well as replacing and rimming anhydrous mafic phases. The presence of abundant volatile phases such as hornblende, and biotite in all samples collected also support this interpretation.