When dealing with acid mine drainage (AMD), the common accepted practice is to develop a predictive model using methodologies such as acid-base accounting (ABA).  These models are used to evaluate the neutralization potential (NP) and evaluate acid potential (AP) of geological materials that comprise mine waste and tailings; however, creating accurate predictive models for rocks of low neutralizing and low acid producing potentials is difficult.  Through modeling a series of synthesized alkalic igneous rock compositions, static acid-base accounting (ABA) testing methods were conducted.  These rock compositions were designed over a range in feldspar compositions: quartz syenite (Or > Ab); quartz monzonite (Or = Ab); albite-bearing quartz monzodiorite (Or < Ab); and labradorite-bearing quartz monzodiorite (Or < Lab).  By means of ABA testing, the experiments demonstrated that with minimal change in sulphide content (increasing from 0.1% to 0.5%) the neutralization potential of the rock can be overcome. 

In addition to ABA testing, static water-rock reaction experiments were conducted; in which the synthesized rocks were reacted at a 1:50 ratio with sulphuric acid solutions with varying pH values (2.0, 4.0, and 6.0) for a 4 week and 8 week period.  The intent of each solution was to simulate a different AMD scenario: pH 2.0 to be an analogue of highly acid waters; pH 4.0 to be weakly acid and natural waters mixture; and pH 6.0 to be more representative of natural waters.    The low to near neutral waters (pH 4.0 and pH 6.0) showed that feldspar composition has little to no effect in changing the buffering capacity, as the pH condition for initial pH 4.0 and 6.0 waters were neutralized to a pH in the range of 8.58 to 9.44.  For pH 2.0 waters, the pH of the sulphuric acid solution were moderately buffered by the rock compositions to varying degrees; however, did not fully neutralize the waters (final pH ranged from 2.69 to 4.04).  Feldspar composition in this situation is important in controlling the extent of buffering achieved. The largest buffering capacity was from the albite-bearing quartz monzodiorite, followed by labradorite-bearing quartz monzodiorite, and with the least amount by buffered by the quartz syenite.

The Coldwell Complex of the Superior Province is known to host multiple lamprophyric dykes varying from ultramafic to alkaline affinities. The Ney’s Lookout dyke is located within the Center II portion of the Coldwell Complex, crosscutting assimilated syenites. This area of Center II is highly brecciated and assimilated, which is interpreted to be representative as evidence of the cauldron collapse. The lamprophyre is devoid of diamonds, and has not been thoroughly analyzed other than brief field assessments. The objective of this research was to classify the lamprophyre according to the IUGS classifications of lamprophyre-clan rocks.

The main minerals that comprise the lamprophyre are euhedral zoned pyroxene phenocrysts and flow-aligned anorthoclase laths in a fine-grained groundmass composed of biotite, pyroxene, amphibole and feldspars. The pyroxene phenocrysts are poikilitic with inclusions of biotite, amphibole and relic olivine similar to the groundmass. Relic chloritized olivine phenocrysts are present in the groundmass and as inclusions in pyroxenes. The pyroxenes present in the sample are classified as diopside with minor augite. Mineralogical compositions of the Ney’s Lookout amphibole classify as Ferroan Paragasitic Hornblende. When compared to other lamprophyres within the Coldwell Complex, there were mineralogical and textural similarities between Ney’s Lookout Lamprophyre and local sannaites, such as porphyritic texture and mantling of amphiboles on pyroxene. Aside from minor variances in modal mineralogy, the lamprophyre best resembles a sannaite under the alkaline lamprophyre classification.

The chill margin along the dyke is a fine-grained rim with no contact metamorphism present, interpreted as representing a moderate emplacement temperature. Laths of anorthoclase are directionally aligned in the lamprophyre and are interpreted as flow textures. Zonation in the pyroxene is distinct in the phenocrysts, representing increasing Cr and Ti outward toward the rim with increased Fe in the core and decreasing amounts in the rim. Uralitization is the altertion of pyroxene phenocrysts to amphibole around the outer rim. The zonation and uralitization often occur from magma mixing events.

The Archean atmosphere is known only as bits and fragments – that often are at odds with each other, and certainly do not ultimately contribute to a “big-picture” composition of this atmosphere on the whole.  That said, there is still far more literature available for the Archean atmosphere than there is for Archean-aged offshore sedimentary deposits; there is virtually nothing out there that attempts to connect the two aspects together.

Because there is such controversy over the most probable composition of the Archean atmosphere, at a glance this makes it very difficult to try to narrow down the individual components to their most likely concentrations.  Comparing the Archean atmosphere to the present Martian one proved to be quite useful for this investigation – the only differences were for methane and water vapour, and being due to the presence of methanogens in the Archean Earth and to the simple size-difference between Earth and Mars (Earth’s larger size meant larger atmosphere which means more vapour), respectively.

Using data from the literature that has been produced concerning Archean-aged storm-related deposits, in particular of ripple formation, beaches (or lack thereof), and of hummocky cross-stratification, helped in constraining the average Archean surface temperature.  From there, it was only a matter of plugging the now-constrained (relatively-speaking) atmospheric values into known and novel methods for determining the specifics of the dynamics of sediments of certain grain-sizes – in particular, using the Shields method.

After all was said and done, the final task was to try to make physical sense of the sedimentary dynamics results.  The results themselves were consistent with each other, and helped to explain in particular, with some logic, why known hummocky bedding in Archean units appears so thin compared to present-day examples.  The results predict that any eolian ripples and dunes found in the Archean should be noticeably smaller in size than more modern examples, and also predict that in general winds and storms should have been noticeably weaker during the Archean when compared to today.

Diamond-bearing macrocrystic, and xenolithic rocks have been identified as occurring within the Rabbit Foot dyke within claim blocks held by Rio Tinto Diamonds Exploration Inc., 15km west of the town of White River, Northwestern Ontario.  Initial assessment of these rocks has led to their being classified “melnoite”, a term used to describe potentially diamondiferous ultramafic lamprophyres.

Olivine occurs in at least two distinct phases within the rocks of the Rabbit Foot dyke; macrocrystal olivine and groundmass olivine.  Macrocrystal olivine ranges in Mg/(Mg+Fe) from Fo₉₁ to Fo₉₃, while phenocrystal and groundmass olivine ranges from Fo₈₅ to Fo₈₇.  Phlogopite compositions range from Ba-phlogopite to tetraferriphlogopite. Spinel-group minerals commonly have chromite cores with titanomagnetite rims.  Spinel compositions follow the “Magmatic trend 2”, the titanomagnetite trend. Spinel-group minerals can be observed displaying atoll textures.  Spinel and perovskite are commonly spatially related, and can be observed surrounding larger macrocrysts such as olivine in a necklace texture.  Perovskite compositions are relatively pure CaTiO₃, lacking any REE concentrations.  In at least one outcrop of xenolithic rock, spherical magma clasts up to 10cm in diameter, which contain cores of olivine macrocrysts, can be observed.

The rocks of the Rabbit Foot dyke are in many ways analogous to kimberlite in texture and mineralogy, however, significant petrogenetic overlap with melnoites, or ultramafic lamprophyres, is evident.  The diamondiferous macrocrystic and xenolithic rocks of the Rabbit Foot Dyke can therefore be considered as kimberlite with melnoitic (ultramafic lamprophyre) affinity.

Kaminak’s Coffee Gold Project located south of Dawson City, Yukon is a structurally controlled gold deposit.  The Coffee Gold Project is hosted within the Yukon –Tanana Terrane, bounded between the Tintina and Denali Faults and along the strike of the Teslin Fault.  Microstructural analysis was completed on three zones within the project, the Kona, Latte and Supremo, to assess controls on mineralization, as well as to classify the protoliths at each zone.  Microstructures indicate significant deformation in the Latte and Supremo zones, and the least deformation in the Kona zone.  The Kona zone is a weakly deformed granite, composed of approximately 2mm euhedral grains of feldspar, quartz, and biotite. Microstructures in the quartz include subgrains, serrated grain boundaries, and undulose extinction, indicating deformation by dislocation creep.  The Supremo and Latte zones show more deformation; in these zones, feldspar has deformation twins and forms rigid porphyroclasts.  A well-developed foliation is defined by the parallel alignment of muscovite.  Each of the three zones contains porphyroclasts of feldspar that give evidence for the protolith being coarse-grained and felsic, likely a felsic plutonic rock.  The Latte zone is mapped as a biotite schist; however, biotite is present in only small amounts. Additionally, the mineralogy in the Latte zone consists dominantly of quartz and feldspar, consistent with an igneous origin.  A relationship between deformation and mineralization is observed; as deformation increases, the gold mineralization increases.  Gold mineralization, based on published assay values from Kaminak, were lowest in the Kona zone and higher in the Latte and Supremo zones. The protolith of all three zones is likely a deformed felsic plutonic rock with varying degrees of metamorphism and deformation.

The two breccia pipes that comprise the Albany graphite deposit, located near Hearst, Ontario are examples of fluid-derived, igneous-hosted graphite. Both the East and West pipes have been have been subjected to post-emplacement alteration at levels near the unconformity with the overlying Paleozoic carbonate rocks of the Gravel River Basin, and as a result have undergone various types of alteration. Carbonate and hematite alteration affect the supergene zone, while sericite alteration affects the known vertical extent of the deposit. Post-emplacement intrusions at depth within both pipes result in additional carbonate and hematite alteration zones within the graphite breccia.

The transitional trend in limestones/dolostones from continuous veins to isolated anhedral masses which underlain Paleozoic carbonate rock is attributed marine transgression of the Ordovician oceans. Sericitization is present in both pipes for the entire sampling depth and is controlled by the potassium feldspars. The degree of sericite alteration decrease with depth from the supergene zone into the breccia. Hematite alteration of the feldspars within the supergene zone correlates nicely with sericite alteration.

A combination of core logging, optical microscopy, x-ray diffraction, and whole-rock geochemistry have been used to document and determine the origin of this shallow level alteration of the Albany graphite deposit.  The alteration styles are similar for both pipes but there are key in differences for each. The spatial relationship among the three style is complex. At least two of the three alteration types noted above, are present at depth of within the deposit, often with all three overlapping.

The presence of each alteration type will have an impact on metallurgical beneficiation of the ore based on extent and degree of alteration. By delineating the zones and distinguishing between supergene alteration and alteration occurring at depth within the breccias, processing techniques can be varied as each complicating zone is encountered. 

Geological and mineralogical surveillance of metallurgical test work was conducted on reject from the Samapleu Deposit under exploration by Sama Resources Inc., in Cote D’Ivoire.  The grade of the rejects are 2810 ppm Ni and 2520 ppm Cu. Metallurgical testing yielded recoveries of 91% Copper and 71% Nickel, and respective grades of 18200 ppm and 16400 ppm for the rougher concentrate of a one stage flotation after milling to a P20 of 27 µm, a P50 of 59 µm and a P80 of 87 µm.  The milled reject was subject to testing on a Wifley shaking table and yielded 28% recovery at a grade of 9160 ppm for nickel and 18% recovery at 5100 ppm for copper concentrates.  Geological testwork involved conducting optical microscopy on metallurgical samples as well as characterizing the wall rocks. X ray diffraction and electron microscopy were used as to enhance knowledge of minerals.  The reject was websteritic with an approximate grade of 40% enstatite with minor blue green clinoamphiboles of either pargasitic, edenitic or magnesiohastingsitic composition and deep green clinoenstatite.  Mineralization was determined to be in discrete grains or along cleavage faces.  Assemblage was predominantly pyrrhotite with minor pentlandite and fine-grained flaky chalcopyrite, some fine-grained magnetite was present.  Tabling brought a form of sorting of minerals in specific size ranges and floatation favored the fine over milled chalcopyrite.  Results of experimentation suggested that flotation is a suitable beneficiation treatment for this ore.  Gravity based tabling yielded poor results in both grade concentration and recovery and is not a recommended concentration method for this ore.

Diamondiferous intrusive lamprophyric dykes have been identified North of Lake Superior, near Marathon, Ontario. The Madonna Dyke is a diamondiferous occurrence that lies within the Superior Province within a region host to multiple alkalic and carbonatitic complexes, many of which are linked to the intrusive activity resulting from the Midcontinent rifting event at 1.1 Ga.The Madonna Dyke is a hypabyssal rock with medium- to fine-grained phenocrysts of pseudomorphed olivine, spinel, pyroxene, and amphibole set in a dark green to black altered groundmass of mainly calcite after melilite, REE-poor apatite, phlogopite and spinel. Pseudomorphed olivine occurs as microphenocrysts, phenocrysts and rare macrocrysts replaced by serpentine, magnetite and calcite. A few fresh olivine macrocrysts show mantle compositions ranging from Fo₉₁ to Fo₉₂. Clinopyroxenes are aluminous diopside with Al₂O₃ ranging from 3.11 to 14.47 wt.%. Groundmass mica show kinoshitalite – phlogopite compositions with up to 4 wt.% BaO and 20.9 wt.% Al₂O₃. Spinel-group mineral compositions follow Magnetic Trend #2 – the Titanomagnetite Trend, where spinels range in composition from aluminous magnesian chromites to titanian magnesian chromites to titanian chromites to members of the ulvöspinel-magnetite series. Spinel-group minerals occur as red chromium spinel phenocrysts to macrocrysts with magnesium-rich cores and iron-rich rims, often associated with olivine phenocrysts and macrocrysts. They also occur as fine-grained opaque groundmass titanomagnetites with altered cores, and as reaction products forming a necklace texture around olivine. Atoll spinels are present. Although the Madonna Dyke shows some textural and petrogenetic features of kimberlites, the mineralogy, including the presence of calcite after melilite and amphibole, are analogous with an ultramafic lamprophyre of Alnöitic affinity.

The lithologic unit known as the “porphyry” at Geraldton, Ontario is host to widespread gold mineralization, and yet its origin is poorly understood.  The porphyry occurs within the Beardmore-Geraldton greenstone belt in the Superior Province of the Canadian Shield.  Samples from the porphyry contain approximately 1mm porphyroclasts of plagioclase within a groundmass composed of approximately 0.1mm quartz, plagioclase, and muscovite grains.  The plagioclase porphyroclasts commonly have asymmetrical tails, and muscovite crystals tend to bend around the porphyroclasts.  Undulose extinction and subgrain boundaries indicate dislocation creep in quartz. Plagioclase commonly contains deformation twins.  The porphyry also has a well-developed foliation defined by parallel alignment of muscovite.  The microstructures are typical of a mylonite.  The porphyroclasts give a minimum original grainsize of approximately 1mm for the protolith.  Based on microstructural analysis, it appears that the most likely protolith for the porphyry is a felsic plutonic rock.  Approximately 30km east of Geraldton, near Longlac, Ontario, is a 150 km² elliptical, granitic intrusion, the Croll Lake stock. This intrusion is the nearest felsic and plutonic rock to the porphyry at Geraldton.  The Croll Lake stock is also deformed. Deformational features in quartz include undulose extinction, subgrains and serrated grain boundaries.  Plagioclase commonly contains deformation twins.  Evidence for deformation of the stock increases towards the west where it resembles the porphyry. Microstructural analysis of the porphyry and the Croll Lake stock suggest that the “porphyry” is a mylonitized fragment of the Croll Lake stock. 

NASA’s Opportunity rover landed on Meridiani Planum in the summer of 2004 with the intention of studying a rich concentration of hematite in much finer detail than what the preliminary images from the orbiting Mars Global Surveyor could possibly allow. Small, diagenetic, 4mm spherules composed primarily of hematite were discovered embedded in sand blasted bedrock, arming the scientific community with further evidence for a past presence of water on Mars (NASA, 2012). This thesis is an attempt at providing a terrestrial analogue for the formation of Martian spherules by using hematite-rich concretions observed in the minimally metamorphosed, 1.8Ga Gunflint formation as a proxy.

Approximately 60km eastbound of Thunder Bay at intersections with Mirror Lake (ML) and West Loon (WL) road lie two recently exposed, iron-oxidized grainstone outcrops standing ~2-3m vertically. Original deposition occurred in the Paleoproterozoic at 1,878Ma in a storm-dominated shallow shelf. The grainstone has a typical grey-green ankeritic to white chert colour with spherical to rhombic hematite-rich concretions averaging <2mm to 2cm in diameter present in thin layers oriented parallel to the shallowly dipping, lensy bedding or randomly distributed within lenses as independent concretions or hematitic masses. Three fundamental questions occur in response to these outcroppings: Why are these rocks so iron stained when compared with the upper cherty and shaley Gunflint at outcrops of nearby Pass Lake (PL) road?; How do these concretions form?; Is the mechanism responsible for the formation of these concretions a reasonable analogue for those observed on Mars? A scaling down approach to these queries consisted of site mapping and stratigraphic sectioning, qualitative and quantitative petrographic and SEM analysis, and quantitative geochemical analysis using data acquired from ICP-MS, ICP-AES and XRD techniques.    

It is well known that the Gunflint is high in iron that precipitated out of seawater solution as an insoluble chemical precipitate. In the studied upper cherty member, individual grainstone grains have fine, iron-rich laminae that had precipitated onto the grain surface itself or were accumulated by rolling over an Fe-rich substrate. An implicit, unconformable upper contact with the Sibley group, present at one time above the Gunflint outcrop at large would have allowed for iron-rich and potentially oxidative fluid migration into the underlying Gunflint. Large, centimeter scale, iron-rich fracture sets as well as very fine, micrometer scale capillary networks provide evidence for fluid migration. Variability in the red colouration, from blood red to maroon, can be differentiated on concentric layers of individual concretions, as well as overprinting masses, and is suggestive of multiple phases of redox fluid front migrations. It is by some combination of intrinsic and extrinsic iron combined with oxidation that gave these rocks their ultimate red colouration.

Hematite concentrations within the ML and WL outcrops are always associated with carbonates that are at varying stages of decay. These hematite-bearing carbonates have been identified through geochemical, XRD and SEM analysis to be of ferroan dolomite to ankerite in composition. They are often found nucleating on or within siliceous and hematite altered grains as rhombs, and commonly mimic the entire grain. Spherical concretions occur when several altered carbonate grains are enclosed by the growth of successive poikilitic carbonate and rarely display a distinguishable nuclei: the appearance of framboidal pyrite central to a select group of concretions and scattered within the groundmass strongly suggests the influence of bacterial sulfate reduction (BSR) on carbonate growth. The variation in size, morphology and distribution of iron-bearing carbonates within individual grainstone lenses as concretionary spheres or masses, as well as the presence of framboidal pyrites, suggests that primary, hematite-poor carbonate concretions formed in a shallow phreatic, anaerobic environment at some time after cementation.

Gunflint hematite concretions differ in several ways to those observed on Mars. Negative weathering, original iron-carbonate composition, the promotion of growth by BSR and a lesser random to common bedding parallel stratigraphic distribution define the concretions observed at the terrestrial site whereas positive weathering, jarosite-hematite-alunite composition, spherulitic growth by supersaturation of Fe-rich fluids, and non-conformable growth over all stratigraphic units define the concretions at the Martian sites (Morris et al, 2010). Concretions preserve fluid chemistry and are blueprints for flow regimes and are as such important to the evolution of water on Mars and early Earth.