The purpose of this study was to use leaching test experiments to help explain the lithological controls on the groundwater geochemistry of different geologic formations in the Thunder Bay area.  A secondary goal of this project was to test the effectiveness of the 15 minute USGS Field Leach Test for this purpose relative to more conventional 30-day deionized water and acetic acid tests.

Samples were taken from different sedimentary units of the Gunflint and Rove as well as from the Sudbury Impact layer, diabase, and granite formations of the Thunder Bay area.  Some of the samples used in this study were collected from previously logged drill core from the MNDM library.  Each sample was crushed into a fine powder.  The fine powders were bottled and labeled, with half the bottles being shipped to the Geoscience Labs in Sudbury for whole rock geochemical analysis and the other half remaining in Thunder Bay to be used for leach test analysis.

Three types of leach tests were performed in this study.  These included the USGS Field Leach Test, a 30-day double deionized water leach test, and a 30-day leach test using a 5% acetic acid solution.  All three of the leach test types used a 20:1 leachate to sample ratio, using 2.5 grams of sample and 50 mL of leaching agent.  The USGS Field Leach Test is a relatively new method developed for testing the leaching potential of different geologic and environmental materials.  This testing method requires the use of the 20:1 sample to leachate ratio, and that the sample be added to deionized water, shaken for a period of five minutes, and then allowed to settle for ten minutes before being filtered and submitted for geochemical analysis.  The effectiveness of this method as a way of determining the leaching potential of rocks in groundwater basins was in question because it did not seem logical that such a short-term test could provide any accurate insight into the water rock reactions that occur over long-periods of time in groundwater basins.

Whole rock and leach test geochemical data were used to produce two types of graphs.  The first graph type showed a comparison of whole rock and leach attest concentrations for each element analyzed.  The second graph showed the percentage of whole rock elemental content that was leached into solution for each of the three leach tests.  Through analysis of each graph it was determined that calcium, magnesium, sodium, and potassium are the elements most readily leached into solution from the rock samples analyzed.

The second method used to analyze data in this study was Piper plots.  Piper plots are commonly used for analyzing groundwater geochemistry.  A Piper plot classifies water samples into four different types based on its concentration of major cations (Ca²⁺, Mg²⁺,Na²⁺, and K⁺) and major anions (HCO₃^-, CO₃^-, CI^-, SO₄^2-).  Through analysis of each Piper plot, it was determined that samples collected from the Rove Formation tend to produce sodium bicarbonate type groundwater, whereas samples collected from the Gunflint Formation produce a variety of groundwater types.

Lastly, this study was conducted to evaluate the effectiveness of the USGS Field Leach Test as a method for determining the leaching potential of elements in groundwater analysis.  Due to the difficulty of filtering the leach test solutions performed in the method specified by the USGS Field Leach Test protocols and the poor geochemical data provided by these leach test solutions, it was determined that this is not the best method that can be used for groundwater analysis.

The Gold Creek prospect is hosted in a brittle-ductile shear zone within the eastern margin of the Peewatai pluton, a dioritic to monzodioritic intrusion in supracrustal rocks of the Greenwater and Shebandowan assemblages, within the Shebandowan greenstone belt of the southern Superior province.  The deformed plutonic host rock, a quartz-feldspar gneiss, is cross-cut by discrete east-northeast-to east-trending dextral shear zones.  Gold mineralization occurs in approximately north-trending extensional veins, which are hosted entirely within quartz-feldspar gneiss along the contact of ductile shear zones.  The emplacement of the auriferous extensional veins is interpreted to have taken place contemporaneously during dextral shearing.

The Chipman Lake carbonatite is located NW of Marathon, Ontario, within the Wabigoon Subprovince of the Superior Province.  The dikes are generally less than one meter thick and outcrop along the glaciated shores of Chipman Lake.  The spatial localization of multiple alkaline and carbonatite complexes along the Thiel Fault supports a relationship to Midcontinent rift related events.  Recent exploration in the area has revealed some new outcropping thin dikes, which had not been previously identified.  The focus of this study was to classify these new occurrences of Chipman Lake carbonatite dikes, based on their mineralogy and petrology, and compare with other previously investigated carbonatites.  Minerals identified include dolomite, calcite, ferroan dolomite, phlogopite, biotite, fluoromagnesio- arfvedsonite, apatite, albite, K-feldspar, aegirine, pyrochlore, pyrite, synchysite, cerrusite and burbankite.  The Chipman Lake dikes were determined to represent carbonatites without associated silicate rocks and are interpreted to be the late stage fluids derived from a nearby or buried carbonatitic parent.  The presence of Ca-bearing niobium pyrochlore and the REE-fluorocarbonate synchysite are strong indications of a primary carbonatite parent.  Detailed analysis of pyrochlore indicated that these pyrochlore were calcium-bearing niobium pyrochlore with enrichment in U and Ce.

The Coldwell Alkali Complex is a Proterozoic intrusion emplaced within the Archean Schreiber-Hemlo Greenstone belt in northern Ontario.  The rocks that comprise the greenstone belt include metavolcanic and metasedimentary rocks, as well as granitic intrusions.  Along the northwestern contact of the complex, the Archean host rocks have been altered in a manner not normally seen throughout the complex.  This study analyzed sandstones, felsic pyroclastic rocks, iron formation, lamprophyres and a gabbroic intrusion in order to characterize the mode of occurrence of alteration present and determine a potential origin.  The alteration types include silicification, sericitization, tourmaline alteration and hematite alteration.

Trenches were created in order to produce exposure of the units that host the alteration.  Hematite alteration has created a distinct reddening of the felsic pyroclastic units present, and displays great variability in its mode of occurrence and alteration intensity.  Although hematite alteration is most intense in the felsic units within the trench area, the alteration occurs throughout the area and affects all intrusive units present.  Distal sandstone samples taken as control units did not exhibit pervasive alteration.  The mode of occurrence of the hematite is consistently pervasive into the crystalline lattice of quartz and feldspar grains, and it is concentrated along quartz veins, within fractures, and forms as replacement of Fe-sulphides.  There is a weak correlation to iron concentration corresponding to areas of more intense hematite alteration.

The dominant lithology is a felsic tuff unit consisting of a quartz and feldspar dominated groundmass with varying intensity of pervasive hematite alteration.  There is a high incorporation of volcanic ash within the iron formation unit, and thus it has acquired the geochemical signature of the felsic tuff unit.  This felsic tuff is defined by U-Pb zircon geochronology that represents a Neoarchean zircon population that indicates an age of roughly 2708 ± 23Ma.

The Plateau Property in central-eastern Yukon hosts extensive high grade gold mineralization within the Tintina Gold Province.  The property lies roughly 130 kilometers east of Mayo, Yukon within the Selwyn Basin on the western edge of ancestral North America.  The purpose of this study is to identify the microstructural controls on gold mineralization at the Plateau Property.

The Goldstack and Gold Dome zones of the Goldstrike Resources’ Plateau Property shows microstructural evidence of brittle-ductile deformation.  Microstructures indicate moderate temperatures during ductile deformation throughout the two zones.  Feldspars with undulose extinction, serrated grain boundaries, and subgrains indicate ductile deformation accommodated by dislocation creep.  Deformed quartz stockwork veining is evidence of continuous brittle-ductile deformation.  Quartz veins filling fractures are evidence for brittle deformation.  Crosscutting relationships of older and younger quartz veins all exhibit evidence for dislocation creep.  Other microstructures include kink banding and deformation twinning in feldspars.  Relict devitrified pseudotachylyte in multiple areas of drill core is evidence for brittle deformation associated with seismicity and is also subsequently ductilely deformed.  Abundant evidence for brittle-ductile deformation microstructures is strongly associated with increased gold mineralization at this property.

The strong dependence of gold mineralization on brittle-ductile deformation at the Plateau Property in the Yukon, has been observed by others in multiple other gold occurrences elsewhere.  Pseudotachylyte might also be found at other gold properties associated with brittle-ductile deformation.  Pseudotachylyte is characteristic of the brittle-ductile transition and can be used as a macroscopic indicator when looking for these structurally controlled gold zones.

The Albany deposit is an igneous-hosted, magmatic-hydrothermal, breccia graphite deposit located near Hearst, Ontario.  The deposit is contained within two intrusive vertical pipe structures known as the east and west pipes.  The deposit is estimated to contain 24 million tonnes of ore with an average grade of 3.98% graphite.  The east and west breccia pipes are texturally distinct and contain different graphite grades (5.60% and 2.85%, respectively).  Higher grades in the east pipe are attributed to intragranular mineralization.   Such mineralization is much less abundant in the west pipe, which dominantly contains the intergranular matrix-hosted mineralization that typifies both pipes.

A quantitative assessment of the morphology of graphite hosting breccia within the deposit is conducted by semi-automated digital image analysis using the program Image-J.  Image J is used to manipulate digital images of breccia drill core segments and produce quantitative date based on morphological attributes of the clasts.  Measured properties include: area% of fragments versus matrix; fragment orientations; fractal roughness dimension; shape descriptors; and, sorting.  Results from this analysis are used to assess the key textural differences between the east and west pipes.  The data is also compared to an existing model for breccia classification in order to hypothesize the genetic origin of the Albany breccia pipes.

Key morphological differences between the east and west pipes indicated by the analysis are shown by data regarding fragment shape and area% fragments versus matrix.  Fragments within west pipe breccia samples exhibit a higher degree of roundness and isotropy on average than those from the east pipe.  Impact erosional processes responsible for this roundness can be attributed to a higher number of fluid pulses and or higher energy brecciation during the formation of the west pipe.  These attributes are characteristic of volume expansion brecciation and fluid assisted brecciation processes.  The relatively angular nature of fragments within the east pipe suggest that it was more strongly influenced by fluid-assisted brecciation during its formation.

The most significant morphological similarities determined by analysis are sorting and orientation.  Samples from both suites exhibited very poor sorting, which is indicative of a very high degree of energy during formation associated with volume expansion brecciation.  Fragment orientation is inconsistent within east pipe breccia and absent in west pipe breccia.  Orientation in hydrothermal breccia results from veining and fragment imbrication.  The inconsistent fragment orientation within the east pipe is likely caused by increased influence of fluid-assisted brecciation processes.

The current genetic model for the Albany deposit suggests that the breccia pipes were emplaced violently within a hypabyssal environment by magmatic-hydrothermal activity and in response to a large scale depressurization event.  The hypothesized classification of the breccia derived from the data suggests that both pipes are volume expansion breccia, with characteristics of fluid assisted and corrosive wear breccia.  Volume expansion breccia is what should be expected given the parameters of the current genetic model, therefore, the evidence from this study supports the existing theory of emplacement for the Albany deposit.

The Northwestern Ontario Healthy Soils Project (NOHSP) was funded by the Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA) in 2014 and 2015 to increase the uptake of soil testing by farmers in Northwestern Ontario. In the Fall of 2014 and Spring/Summer of 2015 farmers’ fields were sampled on a volunteer basis to assess physical and chemical soil quality parameters to assist farmers in managing their soils. These attributes included loss on ignition (LOI), pH, cation exchange capacity (CEC), texture, and available phosphorous, magnesium, copper, zinc, and iron concentrations. This thesis compiles the data of the NOHSP to identify trends in soil health attributes among the Dryden, Thunder Bay and Rainy River regions. 

The Dryden soils were identified by the farmers as a major concern due to low regional crop yields and lack of fertilizer response. The soils sampled were slightly acidic with an average pH of 5.68, however both the available phosphorous concentration and the CEC were ideal for crop growth. The organic matter content is low for this region, particularly in relation to the clay content of the soil. The potassium concentrations were in excess of OMAFRA recommendations in the region. There was no relationship between CEC and the clay content (R2=0.06), despite the expectation. 

Thunder Bay region reportedly experienced fewer problems with crop yield. The regional average pH value is 5.97; just above an ideal value for crop growth. The average available phosphorous concentration, 27.48 mg/kg, for Thunder Bay was more than ideal for crop growth. The Thunder Bay soil organic matter content is also above the requirement for the average soil type at 7.03 % organic matter. 

Rainy River analyses indicated that the sampled agricultural soils were overall healthy. The pH value is within the ideal range at 6.53, and the organic matter content averages 6.11%. The Rainy River area does show a significant relationship between CEC and clay content. 

Based on the synthesis of the data, I propose that farmers in Dryden increase the organic matter content of their soils. This will prevent the current heavy clay soil from binding together further trapping nutrients and moisture, and making them unavailable to plants.

The Good Hope Carbonatite Occurrence is a recently discovered high grade niobium and phosphate occurrence located adjacent to the Prairie Lake Carbonatite Complex, approximately 45 kilometres northwest of Marathon and about 28km North of Highway 17 (49˚ 02’ N, 86˚ 43’ W).  This study focuses on the paragenesis and classification of the pyrochlore-group minerals of the Good Hope occurrence. Minerals identified include calcite (CaCO₃); ferrodolomite (CaFe(CO₃)₂); siderite (FeCO₃); apatite (Ca₅(PO₄)₃(OH,F,Cl);  ferrocolumbite (FeNb₂O₆); fersmite (Ca,Ce,Na)(Nb,Ta,Ti)₂(O,OH,F); and pyrochlore(A16-xB16O48(O,OH,F)8-y·zH20). Less common minerals include: ankerite (Ca(Mg,Fe)(CO₃)₂); synchysite (CaCe(CO₃)₂F); bastnaesite (Ce(CO₃)F); parisite (CaCe₂(CO₃)₃F₂); quartz; rutile; pyrite; magnetite; and barite. Two paragenetic varieties of carbonatite were recognized on the basis of mineral abundances and the textures. These are referred to as the pyrochlore-rich and pyrochlore-poor phases.  The difference between the two phases is interpreted to suggest that the pyrochlore-poor phase represents a later stage of crystallization. The pyrochlore in the pyrochlore-rich phase are intimately intergrown with coarse-grained apatite and are interpreted as clasts derived from early-forming cumulate. The niobium mineralization is dominated by pyrochlore, which exhibits complex replacement textures involving both fersmite and ferrocolumbite. On the basis of textural evidence a definitive crystallization order or relationship between pyrochlore, fersmite and ferrocolumbite could not be established. The pyrochlore is dominated by Na-Ca pyrochlore with minor amounts of Sr-pyrochlore present only in drill core samples. The compositions of pyrochlore show a transition from magmatic to an alteration trend with drill core samples being more altered than surface samples. The latter are considered to be dominantly of a magmatic origin, whereas the drill core pyrochlore are considered to have been affected by hydrothermal processes. Our data indicate easy ore beneficiation due to the presence of only one significant niobium-bearing phase with limited compositional variations. The pyrochlore also does not contain significant amounts of U or Th, which increases its economic potential as these elements can cause environmental concerns involving radioactive refinery residues.

The mineralogy of the Good Hope carbonatite occurrence is different to that of carbonatites occurring in the western and southern margins of the Prairie Lake Carbonatite Complex. The latter are dominated by olivine, calcite, fluoroapatite, Ti-magnetite and phlogopite-tetraferriphlogpite, with niobium mineralization dominated by include Na-Ca pyrochlore, latrappite, loparite, U-pyrochlore, Ce-pyrochlore and Pb-pyrochlore. These differences, coupled with different magnetic signature, carbonatite texture, weathering profile and distinct topography, indicate that the Good Hope carbonatite occurrence is perhaps not directly related to the Prairie Lake carbonatite rock; however, the actual genetic relationship remains unknown.

The Roby Zone of the Lac des Iles Pd-Pt-Ni-Cu-Au mine, located 90 km north-northwest of Thunder Bay, Ontario, was the initial locus of mining activity in the deposit.  A striking aspect of the deposit in the early stages of mining was the coincidence of the ore zone with hydrothermal alteration.  Based on this an investigation of fluid inclusions was undertaken to determine if any correlation existed between the Roby Zone mineralization and hydrothermal activity existed.

From a suite of samples collected during pre-and early-mining stages at the Roby Zone hand specimen were selected.  Hand specimen were selected based on the presence and abundance of transparent minerals.  The selected samples were used in the resulting fluid inclusion work.  Four distinct types of fluid inclusions were observed in the study:  Type I - single-phase liquid inclusions,Type II - two-phase inclusions (liquid + vapour), Type III - polyphase inclusions (liquid + vapour + one or more solid phases) and Type IV - CO₂ rich polyphase inclusions.

The study shows that fluids with temperatures occurring between 350°C and 480°C, and with a composition of NaCl-CaCl₂-H₂O and/or NaCl-H₂O and salinities of 11 to 20 equivalent wt% NaCl are associated with the ore zone of the Roby Zone.  It is believed that the distribution of ore is the result of hydrothermal activity from these fluids remobilizing and concentrating the base and precious metals.

Musselwhite Mine is a fly-in underground gold mine 500km north of Thunder Bay, Ontario, Canada with a main ore zone of metamorphosed and deformed banded iron formation.  Adjacent to the main ore zone metapelites and amphibolites were sampled to study the metamorphic zones and facies using stable metamorphic mineral assemblages.  The metapelite samples included garnet-biotite schist, staurolite-garnet-biotite schist, and previously undocumented, sillimanite-staurolite-garnet-biotite schist.  The amphibolite samples, grunerite schist and biotite-grunerite schist, are unusual, as typical amphibolites have stable metamorphic mineral assemblages of plagioclase-hornblende, not biotite-grunerite-plagioclase.  As metamorphism, deformation, and gold mineralization were synchronous the presence of staurolite and sillimanite provide both metamorphic and gold mineralization conditions. The metamorphic zones at Musselwhite Mine are staurolite or first sillimanite and the metamorphic facies is amphibolite.  The presence of staurolite and sillimanite, in the form of fibrolite, constrain the temperatures of metamorphism, deformation, and gold mineralization to 500-690ºC. 

For more details about this thesis contact Dr. Mary Louise Hill