The Yubileinaya kimberlite pipe, discovered in 1957, is located within the central part of the Alakit kimberlite field of the Yakutian diamondiferous Province.  The Yakutian Province is located within the East Siberia Platform.  Host rocks include Lower-Middle Ordovician and Lower Silurian terrigenous-carbonate sequences.  The pipe is overlain entirely by Permo-Carboniferous sediments and Lower Triassic tuffs.  The intrusion consists of at least two different kimberlite types.  An initial injection of volcaniclastic kimberlite breccia has been intruded by a macrocrystal hypabyssal kimberlite forming distinct central channel which flares rapidly outward in the upper portion of the kimberlite.

This study of the Yubileinaya intrusion was limited to the macroscopic and microscopic investigation of a single hand specimen by transmitted light and electron microscopy.  Associated rocks and geological relationships were not observed.

The hand specimen examined is typical of Group I or archetypal kimberlite, containing rounded macrocrysts of pseudomorphed olivine, common macrocrysts of mica and rare garnet together with groundmass serpentine, spinel, apatite, perovskite and carbonate.  Texturally, the hand specimen comprises crater facies kimberlite with a conspicuous alternation of two distinct units.  Clast-supported, volcaniclastic sandstone alternate with crypto-crystalline, pelitic carbonate mudstone.  The former represents pyroclastic airfall lapilli tuffs and coarse ash, composed primarily of juvenile lapilli which have undergone little or no reworking.  The latter unit can be termed a volcaniclastic kimberlitic mudstone, as its genesis is unclear.

Oriented samples collected from the Plateau Lake Quetico Intrusion (9 km E and 4.5 km S of Atikokan, Ontario) and the Stawson Lake Quetico Intrusion (19 km W and 9 km S of Atikokan) showed NRM vectors in accordance with previously-determined NRM vectors of posttectonic plutons of the Quetico Subprovince.  The strongly anisotropic AMS fabric of oriented samples form the Plateau Quetico Schist country rocks showed strong, east-west magnetic foliation, typical of the study area.  The AMS of the Western sub-area of the Plateau Intrusion revealed an east-west L-fabric resultant from igneous flow concordant with regional structure.  Magnetic fabrics from the Eastern sub-area of Plateau and Stawson are a result of dynamic flow of a 'fluid' magma from the SE (in the direction from their parent, the Quetico Batholithic Complex).

Characteristic remanent magnetism (ChRM) determined from principal component analysis (PCA) of the samples from Plateau East revealed a strong, southwest-directed component of remanence that passed the reversal test.  The ChRM from Plateau West showed little evidence of such geomagnetic reversals.  Despite this evidence, when the site-mean paleopoles from Plateau East and West were plotted on a tentative Precambrian Apparent Polar Wander Path, overlapping confidence ellipses failed to prove significant age differences.  The best age estimation from Plateau West was ~2600 Ma while that at Plateau East is 2550+/-25 Ma.  The limited sampling program at the Stawson Intrusion precluded meaningful age estimations.  In addition, secondary remanences from Plateau East and West were limited in their interpretation.

A first approximation suggests the Ni-,Cu-, and PGE-mineralized core of Plateau may be coeval and comagmatic with its mafic host.  The orientations of L-fabrics of untectonized igneous intrusions reflect the source-direction and may also relate to shape.  As the Stawson Intrusion also hosts economic concentrations of PGE's, it is certain that both concordant and discordant Quetico Intrusions are targets for PGE mineralization.

The area of investigation is located at the interface of the Quetico and Wabigoon Subprovince of the Canadian Superior Province in northwestern Ontario.

The Quetico metasedimentary belt comprises a monotonous sequence of thin to medium bedded turbidite deposits characteristic of a submarine fan environment, within the study region.  This metagreywacke-metapelite sequence gradually passes into biotite schist to the south.

The Wabigoon metavolcanic - granite belt consists of intermediate volcanic flows and felsic volcaniclastic deposits.  (Some metavolcanic rocks are, in part, conformable to the Quetico metasediments).

Greenschist facies metamorphism in the study area is chlorite zone in the north and biotite zone in the south.

One deformation event in the northern part of the Quetico Subprovince was accompanied by a smooth, penetrative, discrete planar cleavage in the Quetico metasediments.  An antiformal syncline and a synformal anticline are located in the northwest of the present study area with vertical, ENE striking axial planes.  The folds plunge moderately from the horizontal.  These overturned, folded structures may have evolved in response to differential strain within the axial planes.

The Rabbit Mountain Mine vein deposits occur in a fault controlled valley on the southern periphery of the northeast trending Mainland Belt of silver mines.  They were discovered about 12 miles southwest of Thunder Bay in 1882 and after 10 years of operation, mining operations closed.

A detailed surficial investigation was undertaken on the property through mapping and sampling.  Petrographic microscopy and x-ray diffraction was conducted on a number of rocks and minerals.

The hypogene deposits are dependent on the regional structures.  The deposits are confined to structural traps provided by post-diabase block faults which strike southwest, parallel to the Mainland Belt.  Post-diabase faulting was in response to sinking of the Lake Superior Basin.

The country rock is Precambrian Rove Argillite and semiconformable Logan diabase sills.  To the south of the Main Fault zone, the argillite dips southeast 5° and on the north side of 5° to the northwest.  Metamorphism of the argillite by the diabase is that of the albite-epidote hornfels facies.

Several types of veins occur:  simple veins, which are dominant in the diabase; and complex veins which are prevalent in the metasediments.  Emplacement of the veins occurred after a sufficient period of time for the diabase to cool to non-metamorphic temperature.  Heat from the cooling diabase sheets supplied the mobilizing forces to the metal rich complexes available in the argillite.

The metasedimentary derived deposits are largely gangue minerals; calcite, quartz and fluorite respectively.  Intermittent deposition, in order of abundance, of sphalerite, galena and pyrite, acanthite, native silver and chalcopyrite occurred in later stages.  Lattice parameter calculation of chalcopyrite crystals indicate the temperature of deposition to be at least below 600°C.  Throughout the veining history there was recurrent fault movement.

The Kenbridge deposit is a nickel-copper deposit hosted in a pyroxenite intrusion.  The country rock consists of pillowed mafic lavas, while the deposit consists of several gabbroic intrusions followed by a later pyroxenite intrusion, which hosts the mineralization.  The edges of the Kenbridge deposit have been altered to a talc schist.  This was originally believed to have been caused by a shear zone.  However, petrographic observations show that the transition between the pyroxenite to the talc schist is very gradual.  Therefore, it seems more likely the talc schist was created by metamorphic fluid and is an alteration product of the talc schist.  The idea of a metamorphic fluid is supported by the analysis of the variable nickel : copper ratio seen in the deposit.  The secondary ore minerals, which for the most part include chalcopyrite, showed a strong correlation with quartz.  The quartz is a secondary mineral which was brought into the system; therefore, it was concluded that the same method that brought the quartz into the system was also responsible for remobilizing the chalcopyrite.  The possibility that the system could have been altered by a metamorphic fluid is supported through SEM analysis and the creation of theoretical equilibrium reactions for the mineral assemblage using SupCRT92.  The SEM analysis was used to determine the chemical composition of the clinopyroxenes and amphiboles in the deposit.  It was established that metamorphic talc, tremolite and diopside were being created.  These minerals were used in the theoretical equilibrium reactions, and it was determined that first appearance of each of the three minerals represent its own pressure-temperature boundary.  More importantly, these reactions can occur at relatively low pressure and temperature ranges meaning that it is possible for thee reactions to have occurred in the Kenbridge deposit.

The Mackenzie Granite is a large granitic intrusion consisting of medium to coarse grained, pink to green granite composed primarily of oligoclase, microcline and quartz.  It is located within the Shebandowan-Wawa greenstone belt of the Superior Province where it is hosted by mafic to felsic volcanic country rocks and an amphibolite rock which may be contact metamorphic or later in origin.  The intrusion appears to be unconformably overlain to the south by Gunflint formation sediments.  The granite contains sparce xenolithic enclaves and is cut by a number of late stage dikes and later joints dikes and veins.

Detailed mapping and sampling of the granite, its immediate host rock, enclaves and dikes have been undertaken to ascertain the structure and internal fabric of the intrusion; the detailed petrology of granitic intrusive rocks, their enclaves and the possible source of such enclaves.

The instrusion contains felsci and mafic xenoliths which are representative of the contact metamorphic country rocks.  A single enclave sample of a chlorite litharenite containing oolitic fragments may represent a fragment of a Proterozoic paleosoil horizon.

The granite appears to have been intruded during the Archean Kenoran orogeny.  Structural data suggests that subsequent deformation and alteration of some areas of the granite, intrusion of later dikes and the origin of mineralized veins occurred during the Proterozoic.  Petrological evidence indicates that chloritic altearion of the granite may be genetically related to the formation of the mineralized veins.

This study investigates the environmental impact of pyritic waste dumps and associated catchment ponds at the southern portion of the Steep Rock mine site, an abandoned iron mine north of Atikokan, Ontario. The primary concern of these piles is the oxidation of pyrite and the production of acid rock drainage (ARD). In this study, only the top one meter of waste rock piles was sampled; thus the redox front was not transected and only materials within the oxidizing zone were studied.

The dominant mineral phases present in the waste rock piles are quartz, goethite and hematite. The presence of goethite and hematite stems partially from oxidation of pyrite to these iron oxides, although the majority of these minerals were present in the original mine wastes. The flow of contaminated groundwater produces precipitates in the waste rock materials and lake sediments. The primary product is gypsum; however, jarosite is also produced, although in lower abundances. Acid rock drainage contaminated water ultimately flows from the waste rock piles into adjacent catchment ponds via groundwater flow or surface runoff. These ponds consequently have serious water quality concerns, characterized by pH as low as 2.5, sulphate concentrations as high as 2000 mg/L and high concentrations of metals such as iron, calcium, magnesium, manganese, aluminum, nickel and zinc. In some areas, carbonate minerals are able to partially buffer the low pH.

The former mine pits at the Steep Rock site have flooded since mining operations ceased, and the lake levels continue to rise. The rising water level will ultimately flood the study area and result in the pit lakes merging, and this combined lake will eventually reach the former lake level. The presents a unique situation of a pit lake with a littoral zone, and in this case the littoral zone will consist of pyritic waste rock materials. This interaction of shallow, oxygenated water with the waste rock materials presents long term concerns about the potential for continued production of acid rock drainage, and the resultant water quality of the combined lake. 

For more details about this thesis contact Dr. Andrew Conly

The area of investigation is located in the Wabigoon subprovince of the Canadian Superior Province in Northwestern Ontario.

The rocks in the study area consist largely of graywackes of intermediate composition.

Turbiditic sedimentary features reflect a submarine fan environment.

The structure of the metasedimentary rocks is critically examined.

A well developed cleavage is present in the steeply dipping bedding planes of the sedimentary units.  The cleavage is shown to be axial planar to the dominant, sideways closing folds in the area.  Reversals in structural facing directions indicate that the cleavage developed in previously deformed rocks.  

A third deformation event produced locally occurring kink bands by shortening parallel to the bedding and the well developed cleavage in the rocks.

The Hamlin Lake area is located approximately 120km southwest of Thunder Bay, Ontario, in the Shebandowan Greenstone Belt of the Wawa Subprovince in the Superior Province.  The area has been explored for its copper and gold mineralization for more than 50 years, but has only recently been treated as an iron-oxide copper gold (IOCG) occurrence.  The aim of this study was to characterize the alteration at the occurrence through space and time, and to relate this paragenesis to the formation of mineralization.

Localized field mapping and re-logging of drill core established several relationships between styles of alteration.  Rocks were examined in hand specimen and thin section, and minerals were examined with scanning electron microscope (SEM) to identify mineral assemblages and associations.  Consistent variations in space could not be mapped, so textural relationships were used to relate the timing between six styles of alteration and the local brecciation that hosts the potential ore.  These are: (1) sodic, (2) early potassic, (3) calcic(-iron), (4) late potassic, (5) carbonate, and (6) silicic.

Sodic alteration is largely composed of albitisation, and is occasionally conserved in fragments of the breccia.  The early potassic stage of alteration consists of biotite and magnetite in the matrix of the breccia, which is cross-cut by epidote and sphene from the calcic(-iron) stage.  Sodium cobaltinitrite staining was used to identify potassium feldspar alteration associated with mineralization of the late potassic stage.  The mineralization in this stage is represented by the assemblage chalcopyrite + pyrite + magnetite.  This first stage of mineralization was succeeded by carbonate precipitation, and finally by a second stage of mineralization associated with a vuggy quartz breccia.

The two phases of mineralization are primarily different in that stage I mineralization is associated with potassic alteration and iron-oxide mineralization, whereas stage II mineralization is associated with quartz and has a general lack of massive iron-oxide.  The alteration leading up to the first stage of mineralization, and the stage I mineralization itself are consistent with the general alteration patterns observed in other magnetite-group IOCG deposits worldwide.  The onset of carbonate alteration, followed by vuggy quartz with moderate- to high-sulfidation assemblages of stage II mineralization, is more typical of an epithermal environment.

Thermodynamic parameters of the mineralizing fluids were ascertained by the use of fluid inclusions.  Fluid inclusions from the vuggy quartz associated with stage II mineralization were analyzed and suggest a low-salinity fluid with a temperature in the approximate range of 200° to 250°C responsible for mineralization.

Stable oxygen isotopes from chlorite, magnetite and sulphur isotopes from sulphides were measured to establish the source of the fluids responsible for the formation of the deposit.  Oxygen from the magnetite of early mineralizing assemblages has a narrow range of values for δ¹⁸O_water from +8.9€ to +10.9€.  These are indicative of a deep-seated metamorphic or magmatic source for early fluids.  Oxygen from chlorite associated with the later stages of mineralization have a wider range of δ¹⁸O_water values (+0.4€ to +5.9€), which may suggest that meteoric or other crustally derived fluids played a role in stage II mineralization.  δD values were measured on the chlorite as well; however, these may have been reset by later metasomatic events.  Sulphur isotope values from mineralization were measured (δ³⁴S -6.9€ to +1.8€), and indicated that an exotic sulphur source probably played a role in mineralization.  

The most common dyke rocks in the Coldwell Alkaline complex are lamprophyres associated with Centre 2 magmatic activity.  Samples of analcite tinguaites, sannaities and ocellar lamprophyres were analysed by Neutron Activation Analysis.

Distribution patterns of rare earth, incompatible and transition elements define a comagmatic series from parental mafic ocellar lamprophyres to evolved analcite tinguaites.  A proposed petrogenetic scheme involves 86 percent batch fractionation of mafic magma in deep seated "plumbing" systems to produce the felsic rocks.