The Quetico Fault is a significant regional structure forming part of the Archean terrane in Northwestern Ontario.  The fault transects medium to high grade gneisses of variable origin for much of its strike length.  The absence of easily identifiable stratigraphic marker horizons makes it difficult to readily determine the net slip or the sense of motion or the fault.  Microscopic examination of samples taken from the fault zone show a number of  structures and fabrics which permit the determination of movement sense locally.  Based on the geometry of porphyroclast systems and shear banding a dextral sense of motion is indicated for the fault zone at this locality.

The Little Pig Vein, which is thought to be associated with the West Beaver Mine due to its proximity, occurs within the northeast trending Mainland Belt of silver mines.  These deposits are associated with a zone of steeply dipping normal faults within the Southern Province.  These veined faults cut Archean basement rocks, Aphebian metasedimentary and Keweenawan instrusive rocks.

Hand samples and structural data were obtained from the Little Pig Vein and surrounding outcrop.  The sampling was tied into a cut grid.  Investigative methods included hand sample study and petrographic microscopy.

The vein is located within a fault-breccia zone in the Rove argillite.  The vein has a strike of 75 degrees and a dip of 70 degrees to the south.  The argillite is flat-lying with a gentle southerly dip of three to five degrees.  The vein does not enter the diabase.

Within the Little Pig Vein, there appear to have been two pulses of mineralization.  In these open-space filled veins, variable amounts of gangue and sulphide minerals are seen to be present.  The sulphides which are noted in the Little Pig Vein are sphalerite, galena, pyrite and chalcopyrite, in their respective order of abundance.  The gangue minerals which constitute a major portion of the vein are calcite, quartz and fluorite.  No silver was viewed in the samples collected for study.

Migration of metals in the Rove argillite was initiated by cooling diabase dikes and sills.  Faulting formed structural traps for the mineral-bearing solution moving along bedding planes to areas of lower pressures.  Precipitation in the vein proceeded according to sequential deposition.

No silver mineralization was found in the Little Pig Vein.  The silver mineralization may be lacking due to the absence of the mineralization pulse containing the silver metals.  The structural data note the lack of the phase of faulting during which silver mineralization has been noted to occur.  No opening occurred, thus no mineralization was found.  This later stage pulse of silver mineralization has not occurred in the Little Pig Vein.

The Finmark metasedimentary belt is situated west of Thunder Bay, Ontario.  Metasedimentary rocks predominate and form part of the Shebandowan-Wawa greenstone belt where they overlie a Keewatin succession of metabasalts.  The metasediments form interlayered sandstone-siltstone-mudstone sequences which alternate with thick deposits of cross-stratified sandstones.  The interlayered sequences contain many of the primary sedimentary structures characteristic of tidal flat deposits.

The rocks in the area have undergone very low grade greenschist metamorphism and are structurally complicated.  Reversals of top directions and the presence of both easterly and westerly plunging minor folds, suggest that one or more episodes of folding have occurred.  The attitude of cleavage within the area does not vary considerably, indicating that it may have developed after one or more episodes of folding.  Numerous left lateral displacements and the intrusion of mafic dikes have contributed to the structural deformation in the area.  One continuous section of outcrops have remained stratigraphically upright and were used to determine the depositional environment of the metasediments.

The sedimentary rocks are composed of feldspar, rock fragments, quartz, and some mafic minerals.  Modal analysis has revealed that most of the sandstones in the area are arkosic arenites.  The rock fragments are felsic to intermediate and predominantly volcanic, with lesser amounts of igneous and sedimentary rock fragments.  The volcanic clasts have been derived from the Lake Shebandowan metavolcanics which are part of a calc-alkaline suite of rocks.  Therefore, the metasediments probably represent immature detritus from proximal volcanic centers.

This study examined metavolcanic and metasedimentary strata from the about 3.0 Ga Balmer assemblage of the Birch-Uchi greenstone belt, Western Superior province.  ICP-AES wholerock geochemical analyses coupled with field and petrographic observations were used to better define the tectonic setting in which these rocks developed.  The geochemistry of 21 of 34 samples was taken to be representative of geochemical variation amongst the volcanic rocks of the study area and showed them to be comprised of two distinct suites.  The first suite is characterized by mafic volcanic rocks of basaltic to andesitic composition and was found to be tholeiitic in character.  The second suite is characterized by intermediate to felsic volcanic rocks of andesitic to rhyolitic and rhyodacitic composition and is calc-alkaline in character.  The geochemistry of these samples seems consistent with an arc-like setting.  Sedimentary rocks crop out poorly in the study area but may represent a submarine volcaniclastic apron or submarine fan/ramp feeding into an arc-related basin. The geochemistry of 16 samples of sedimentary rocks were analyzed in order to study their provenance.  Results from these analyses suggest that the Balmer assemblage sedimentary rocks are derived from the Balmer assemblage volcanic rocks and primarily the intermediate to felsic calc-alkaline suite.  This is consistent with the Balmer assemblage sedimentary rocks being deposited in an arc-related basin.  Suggestions made here should be tested through geochronological study of detrital zircons in the sedimentary rocks and high precision geochemical techniques with a more complete suite of trace elements.  

The Thunder Bay Amethyst Mine is composed of vein and breccia mineralization, containing amethyst, colourless quartz, prasiolite and citrine.  The mine occurs in a strike-slip fault situated within a Archean batholitic intrusion of granodiorite.

During the present study fluid inclusions in amethyst indicated temperatures on the order 60 to 90°C during vein deposition.  Eutectic temperatures in fluid inclusions suggest the solution composition consisted of a CaCl₂ + NaCl system.  Salinity of the solution decreases in the direction of vein growth from 22.9 to 15.3 equiv. wt.% NaCl.  The presents of Na in the system may assist in the production of hole and electron colour centers by allowing for a charge compensation in the substitution of Fe³⁺ for Si⁴⁺ in the crystal lattice of quartz.  Variations in salinity in the direction of growth may reflect changes in amethystine colour density.

 Eh-pH conditions, calculated on the basis of paragenetic sequence within Cu-sulfide inclusions, suggest a reducing thrend during deposition.

Sulfur isotopic composition of pyrite in amethyst (delta³⁴S = -0.6 to -0.4) was compared to the sulfur isotopic composition of lead-zinc-barite veins in the Dorion area (delta³⁴ S = -0.1).  The similarity in isotopic signature suggest that both types of deposit have similar origin.

The paleo-declination and inclination measurements of the natural remanent magnetism of oriented samples taken along cores of glacial and post-glacial lacustrine sediments represent the magnetic conditions prevalent at the time of deposition.  As such, graphs plotting the change in declination and inclination with depth are records of the secular variations in the earth's magnetic field.  Similarities in the oscillations of these values noted for cores within the Goderich basin, as well as the Great Lakes system, mark layers of comparable ages.  Other paleomagnetic parameters, such as magnetic intensity (J), magnetic susceptibility (K), and Q-ratio (J/K) are also useful for time-parallel correlation and as stratigraphic markers, albeit to a lesser extent.

Sixteen cores of Late Quaternary lacustrine sediments from Lake Superior were collecting during the summer of 1983.  Paleomagnetic ages for post-glacial to glacial-varve contacts were determined by correlating with the paleomagnetic 'type' logs of Creer and Tucholka, 1982.  This provided insight into the rate of glacial retreat and also the post-glacial sedimentologic history of Lake Superior.

The rate of glacial retreat appears to have been uneven over time but generally followed a northeast direction.  Glacial varve deposition ended about 8700 years BP in the southeastern part of the lake and about 8000 years BP in the Nipigon Bay region.  Rates of sedimentation varied greatly throughout the lake but generally were related to the various lake phases of Lake Superior during post-glacial time.

The Coldwell alkaline complex was intruded into rocks of the Schreiber-White River belt, during the Neohelikian Subera.  The complex was emplaced in three distinct magmatic episodes, magmatic centers were displaced to the west with time.  Block Faulting has disturbed the geometry of the major rock units in the western and central regions of the complex. 

Syenitic rocks in the vicinity of Craddock Cove were formed by albitization of a monzonitic parent.  A basaltic xenolith, several square kilometers in area, was block faulted into the syenite.  Fracturing of the xenolith during its emplacement allowed contact metasomatism of the basalt.

Lamprophyre dykes associated with Center II magmatism, intrude the syenite.  These dykes show evidence that they formed as a result of magma maxing at depth.  Intrusion of the syenite by these dykes and petrographic features of the syenite, indicate it to be a Center I rock type.

The geology of the Thunder Bay area exhibits a sequence of flat-lying Proterozoic Aphebian sedimentary rocks essentially free from tectonic deformation.  These unconformably overly the Archean metamorphic rocks.

Within the Proterozoic sequence lies a pronounced, thin, stratiform lapilli tuff.  The tuff comprises crystal fragments, pumice fragments as well as accretionary lapilli and lapilli of other origins.

There has been a strong post-depositional compaction.  This was recognized from shape (strain) analysis of the accretionary lapilli and from the shape and orientation of the magnetic susceptibility ellipsoid.  A preliminary paleomagnetic investigation indicates a paleolatitude of the time of sedimentation (or diagenesis) of about 66°.

Detailed study of the sequence has indicated that it is characterized by intimately interbanded pyroclastic and epiclastic facies rock units.  The predominantly felsic (rhyolitic) to intermediate compositions of most of the rock units within the sequence indicate that, assuming a single source of rock material, that rock material was derived from an active volcano.  Primary depositional structures indicate that the sequence was deposited in a subaqueous environment of the flank of that volcano.

The presence of planar laminated and bedded ash flow tuffs, a planar laminated base surge deposit and an adjacently overlying coarse, felsic volcanic breccia indicate that the sequence was deposited as a result of intermittent periods of volcanism which probably varied from effusive to explosive in nature.  The presence of interbedded turbidite sediments and a graded, probably channelized conglomerate unit supports the intermittent nature of the volcanic activity.  Considered collectively, these facies indicate that the depositional environment of the sequence was analogous to a submarine fan environment.

The pyroclastic facies within the sequence have been compared to other similar deposits.  The planar laminated base surge deposit and overlying volcanic breccia have been interpreted to have been deposited simultaneously as two distinct facies of a single pyroclastic flow.  This interpretation is supported by the physical characteristics of the two units and grain size and composition analyses which were done on representative samples from these and all other pyroclastic units within the sequence.