The world-class Hemlo gold deposit is representative of an atypical mesozonal shear-hosted lode-gold deposit that is comprised of numerous lithologies.   A contemporary classification scheme for the categorization of dyke lithologies that occur in the immediate Hemlo deposit is utilized by the mine geologists of Williams Operating Corporation at Barrick Gold’s Williams Mine.  Although the deposit area has been studied extensively by myriad researchers, the physical and chemical properties of an intermediate intrusive lithology, designated as unit (11) in accordance with the Hemlo Geology Legend, are not well described.  Nineteen samples representative of the (11) Intermediate Intrusive unit were obtained from varying localities throughout the Williams “C Zone” and “B Zone” sites, specific to the Hemlo deposit, within the Williams mine.  Petrographic and geochemical analysis of these samples suggests that they are representative of a calc-alkalic magma series that evolved via the process of fractional crystallization in an island arc setting.

The Badwater Gabbro south of Armstrong, Ontario is a Proterozoic mafic intrusion.  It is cut through by thin dikes of the Badwater Syenite and overlain by the Pillar Lake volcanics.  Through petrographic work, the intrusion was subdivided into six lithologies: altered mafic rocks, syenite, norite, gabbronorite, olivine gabbro/olivine gabbronorite, and gabbro.  The altered mafic rocks consist of metagabbro, metagabbronorite, serpentine-actinolite gneiss as well as talc-magnetite schist.  Much of the alteration is present in the form of hydrous alteration minerals.  This section is heavily altered and overprinted, likely the result of surficial weathering as well as hydrothermal alteration from extrusion of the Pillar Lake volcanics on top of the Badwater Gabbro.  The alteration minerals and textures seen throughout the intrusion could be the result of localized contact metamorphism caused by emplacement of the Nipigon sills at ~1.1 Ma.  Geochemically the Badwater Gabbro are similar to rocks derived from a mantel plume.  The Badwater Gabbro is characterized by high Gd/Yb ratios (2-7), indicating that the melt is sourced from within the garnet stability field.  The Badwater Gabbro was possibly emplaced along the lithospheric scale weakness of the Black Sturgeon fault zone.  The intrusion was likely affected by crustal contamination during emplacement; as suggested by the depletion of the HFSE on the trace element plots, indicating assimilation and enrichment of LREE relative to HFSE.

the Hemlo gold mine is located along the Hemlo shear zone within the Hemlo-Schreiber greenstone belt, within the Wawa subprovince of the Superior Province.  Geographically, the mine is located 350 km east of Thunder Bay, Ontario, Canada.  The C-zone has a mineralization style distinct from the well-studied B-zone.  Detailed mapping, oriented sampling, drill core observations, and a microstructural analysis were completed to determine the role brittle deformation plays in gold mineralization.  Ductile deformation of feldspar grains indicates amphibolite facies temperatures during deformation, consistent with historical work on metamorphism.  Annealed grains are evidence for lingering high temperatures.  The area is characterized by mutually overprinting brittle and ductile deformation within all lithological units.  The degree of deformation within each lithological unit indicates competency contrast during brittle-ductile deformation and the competency contrast plays a key role in the mineralization of gold in the C-zone at Hemlo.  Gold occurs within deformed quartz veins in more competent rock bodies.  Gold is also found along quartz veins within the less competent rock and within the more competent rock as fine-grained disseminated gold.

Located in the western area of the Uchi subprovince of Superior Province Mesoarchean carbonates and iron formation that extend from western Red Lake to Wallace Lake are the remnants of a large carbonate platform that formed at some time between 2940Ma and 2925Ma.  The platform is dominated by peritidal depositional structures overlain by basin transitional lithofacies which give the impression that the platform had a flat topped and relatively steep sided geometry.  The peritidal lithofacies assemblage consists of tidal flat to subtidal structures that are common in the Archean (i.e. laterally linked and unlinked domal stromatolites, crystal fans, and herring bone calcite), and has REE characteristics of carbonate precipitated from water with near neutral pH, high pCO₂, and an oceanic REE reservoir dominated by hydrothermal input.  The peritidal lithofacies assemblage has δ¹³C_PDB=0.42‰ +/- 0.53‰ which is consistent with other shallow water carbonates of the Meso- and Neoarchean.  The basin transitional lithofacies assemblage consists of slump structures and carbonate associated oxide facies iron formation (IF).  The REE characteristics and depositional structures are the result of down-welling water from a saline, semi-restricted, peritidal depositional environment and mixing with basin waters.  The carbon isotopes of the carbonate associated oxide facies IF show basin transitional values  δ¹³C_PDB  as low as -3.07‰ reflecting the mixing of shallow water with positive δ¹³C_PDB  values and basin water with more negative δ¹³C_PDB values.  More distal lithofacies consist of chert-oxide facies IF.  The chert-oxide facies IF shows positively sloping shale normalized FEE patterns and strong positive Eu anomalies characteristic of the precipitation of iron hydroxides from ocean waters with a pH~5 and REE characteristics that are strongly influence by hydrothermal alteration of oceanic crust.

Negative Ce anomalies in the peritidal carbonates occur consistently in the crystal fans and rarely in other facies suggesting precipitation from water that was relatively oxic.  The fans also contain consistently elevated basin derived elements such as P, Fe, Sr, and Ba.  Storm events and/or small scale transgressive-regressive cycles probably episodically added open ocean water to the semi-restricted platform providing nutrients for photosynthesising organisms.  Blooms of photosynthesising organisms would remove CO₂ from the platform water and cause an increase in pH resulting in the precipitation of fans.  The Red Lake-Wallace Lake carbonate platform is the oldest known carbonate platform in a series of geographically scattered platforms contributing to a gradual change in oceanic processes in the Mesoarchean and Neoarchean including the gradual oxidation of the atmosphere by the initial production of oxygen in these semi-restricted, shallow water settings.  The evidence for oxygenic photosynthesis presented here predates the Great Oxidation Event by 400 my.

The central Gulf of California coast region of the Baja Peninsula records the transition from arc to rift tectonics.  As a consequence of the changing tectonic regime, magmatic activity in the area changed from arc-related andesites to rift-related basalt-andesite-rhyolite pyroclastics.  Associated with rifting was the development of the Santa Rosalia basin, one of several proto-Gulf basins to develop, and the Boléo Cu-Co-Zn-Mn district.  The aim of this study was to utilize remote sensing techniques in order to see if it is possible to map the arc and rift lithologies of the Santa Rosalia basin and its border lands.  A key goal was to assess if remote sensing techniques could be used to differentiate between arc- and rift-related igneous units, that make up the central peninsular arch (Sierra Santa Lucia) and form the western boundary of the Santa Rosalia basin; as various studies over the past decade have shown that Sierra Santa Lucia is not comprised entirely of arc-related andesite.  An additional objective of the work is to assess the plausibility for the existence of a collapse caldera that lies along the west-south western margin of the Santa Rosalia basin.  Confirmation of a rift-related caldera would establish a key genetic link between early Gulf magmatism, incipient basin sedimentation and hydrothermal activity of the Boleo district.

To answer these questions, remote sensing techniques were utilized to analyze a 30m resolution Landsat 8 satellite imagery.  Based on the spectral bands of the Landsat 8 imagery and remote sensing techniques, such as band ratios and combinations, principal components analysis, and classification, some of the rock types present were separated based on their differing mineralogy and a geological map was created.  By taking advantage of specific spectral bands such as 2/4:6/7:4/6, 4/2, and 7/6, arc to rift volcanic rocks could be differentiated from unlithified alluvium and carbonates and sulphates.  However, it was not possible to separate arc volcanic rocks from rift volcanic rocks because their mineralogical differences were too subtle to produce different spectral responses.

Intensive forest management practices may differ from natural fire disturbances in its effects on soil properties, such as carbon (C) and nitrogen (N) storage, that may cause long-term changes in stand productivity.  This study compared soil properties of three black spruce (Picea mariana) stands in Northwestern Ontario, which included two disturbed stands and one recently undisturbed control stand.  Both disturbed stands are regenerating areas that had experienced disturbance 20 years prior to sampling; one represents conditions from a natural burn and the other represents conditions of a whole-tree havesting (WTH) with blading treatment.  Soil samples were collected in three established plots within each stand.  The organic layer of the forest floor and the mineral soil (0 - 50 cm) were sampled at three locations in each plot and bulk density samples in the mineral soil were determined.  Both the organic material and mineral soil were air analysed for organic C and N content.  The mineral soil was also analysed for its pH.  Significant differences were observed between the disturbed sties and the control site in these study areas, with disturbance effects being most significant within the WTH with blading treatment.  The burn site had forest floors with thicker organic layers, higher organic carbon masses, lower pH, higher concentrations of total C and N in the mineral soil, and higher C and N storage in the mineral soil compared to the WTH with blading site.  Although significant losses in total N stores within the burn site were observed, C stores did not appear to be affected by the burn.  This may be due, however, to the nature of the wildfire which was described as being a relatively low intensity burn with only a moderate depth of burn into the humus layer.  The WTH with blading site, as mentioned was the most significantly affected by disturbance and the forest floor at this site had significantly lower masses of organic material and significant losses of both C and N stores, with concentrations measuring approximately 45% and 60% less, respectively, than those of the control site.  The decreased organic material and subsequent diminished C content is a direct result of the great quantities of forest volumes taken away during harvesting activities and indicates that this type of harvesting is not a sustainable practice.  Also, this study suggested that WTH with blading can result in significant negative impacts to C  and N stores that are different from those produced by a naturally occurring wildfire.  A final notable finding of this study was that both C and N storage was significantly greater in the organic layer than the mineral soil for all treatments (by approximately 70%), indicating that a larger portion of the C and N content resides in the unprotected labile portion of the system which makes forest floors naturally vulnerable to disturance.  Further study is necessary to determine the stabilization mechanisms of the soil organic matter (SOM) to systematically characterize the physical protection mechanisms of the soil environment.

The North Caribou Greenstone Belt (NCGB), located within the North Caribou Terrane of the Archean Superior Province, is host to multiple ~3.0 Ga metavolcanic and metasedimentary assemblages.  The assemblages have been metamorphosed from greenschist to upper-amphibolite grade and are bounded by ~2.7-3.0 Ga granitoids and gneisses.  The study area is located approximately 5km south of Musselwhite Mine within what was previously thought to be the Opapimiskan-Markop metavolcanic assemblage. Three lithologies were identified within the study area (basaltic, komatiitic, and felsic volcanic flows) which have been subdivided into four separate volcanic suites: Volcanic Suite A, Volcanic Suite B, Volcanic Suite C, and the Felsic Volcanic Suite.

Volcanic Suite A is comprised of a succession of massive and pillowed basaltic flows that have been metamorphosed to amphibolites.  These flows exhibit a mineral assemblage of amphibole, chlorite, and plagioclase with minor quartz, muscovite, titanite and epidote.  Major element geochemistry reveals that this suite is compositionally similar to that of a high-Mg tholeiitic basalt.  Primitive mantle normalized plots for this volcanic suite are characterized by a flat rare earth element (REE) pattern comparable to tholeiites from the South Rim Unit (SRU), which have been interpreted to represent ocean plateau basalts formed from a mantle plume.  Volcanic Suite B is comprised of pillowed and massive basaltic flows that have been metamorphosed to amphibolites.  The main mineral assemblage observed in this suite was amphibole and chlorite with minor plagioclase, clinozoisite, quartz, titanite and dolomite.  Major element geochemistry indicates that this suite is comprised of high-Mg tholeiitic basalts, komatiitic basalts, and a komatiite.  Primitive mantle normalized plots display a relatively flat REE pattern but with a negative Nb anomaly. The similar trace element geochemistry of Volcanic Suites A and B suggests that they are both derived from a plume source, however, the negative Nb anomaly in Volcanic Suite B indicates that it has undergone crustal contamination during emplacement.  Volcanic Suite C is also comprised of massive and pillowed basaltic flows with a main mineral assemblage of amphibole and chlorite.  A single sample was taken from this suite and it was determined to be a high-Fe tholeiitic basalt based on major element geochemistry.  Primitive mantle plots of this suite are light rare earth element (LREE) enriched with a negative Nb anomaly and positive Zr and Hf anomalies.  A similar REE pattern was observed in the tholeiitic basalts from the Opapimiskan-Markop Unit (OMU).   The Felsic Volcanic Suite overlies the mafic volcanic suites and is comprised of rhyolitic flows.  This suite is LREE enriched with a relatively flat heavy rare earth element (HREE) pattern and negative Nb and Ti anomalies in conjunction with positive Zr and Hf anomalies. Similar REE patterns were observed in the SRU and were interpreted to be derived from a subduction tectonic setting. 

The results of this study are consistent with previous work in the region and suggest that the early history of the area preserved the interaction of a mantle plume with pre-existing continental crust. In addition this study has refined the boundaries of the various assemblages within the NCGB.

The Hele Member of the Outan Island Formation, Sibley Group, is dominantly composed of fine-grained sediments, most commonly mudstone/siltstone to fine-grained sandstone.  Sedimentary structures consist of parallel lamination, soft sediment deformation features, in the form of load structures, and cross-stratified sandstone featuring a distinct lack of desiccation cracks, vegetation and evaporite formation.
The frequency of small-form ripples and parallel laminations in fine-grained sediment were taken to be representative of a low-energy system with a high suspended load.  The abundant load structures are indicative of frequent, flashing addition of sediment to a wet substrate.  The lack of desiccation cracks and evaporites indicate a non-arid environment ranging into the sub-humid.  Ancient, sub-humid dryland fluvial systems are sparsely researched and comparisons were instead drawn to modern dryland systems and ancient dryland systems, omitting or compensating for factors such as aridity conditions (formation of caliche and evaporites) and bioturbation (ruining the preservation of depositional structures.)

The Hele Member is theorized to be representative of an inland, basinal, sub-aerial, low-gradient, ephemeal, semi-humid, ancient, fluvial floodplain dominated environment based on the outcome of this study and data from Rogala, 2003.

An outcrop present along Hwy 11/17 east of Thunder Bay contains a sequence of stacked clastic rocks with dike intrusions.  The clastic units are dominated by surge flows and ash fallout deposits, with less common debris flows and fluvial reworking.  The presence of surge deposits and pyroclastic falls in association with one another show the sequence was deposited proximal to the source.  The ash beds are on average 3 cm in thickness and grade from medium-grained sand to very fine-grained sandy tops.  These normal graded beds are likely ash fallout deposits, and are frequent throughout the study outcrop.  The thin, very explosive and wet surge deposits likely formed from a maar volcano landform.  Deposition of the clastic units likely took place in a subaerial environment with subaqueous areas, such as a flooded plain or swamp.

Hornblendite dikes cut through the sequence and also occur as veinlets and sill-like intrusions infiltrating into the clastic material.  The intrusions incorporate the clastic material and often there is a dissipative zoning of sediment in the hornblendite intrusions.  This shows the sediment at the time of intrusion was wet.

The outcrop was formed in a volcanic environment within the Shebandowan Greenstone Belt of the Wawa Subprovince.