The rocks of the Rainy Lakearea have been deformed during three distinctive episodes.  Minor structures provide the geometry which characterizes each episode.  The youngest structures include regional faults, a crenulation cleavage, kink bands and minor F₃ folds.  These D₃ structures are superimposed on structures of the D₂ episode.  These include dominant F₂ folds having axes lying in a penetrative cleavage which parallels the axial surfaces of the folds.  Some F₂ folds have a downward structural facing which is evidence that the stratigraphic succession at Rainy Lake is overturned at a regional scale.  It is proposed that this inversion took place during a D₁ deformation by the formation of large F₁ fold nappes.  Minor D₁ structures are difficult to document.

The rocks of the region were metamorphosed simultaneously with much of the deformation.  The distribution of index minerals defines the boundaries of the biotite, staurolite-cordierite and sillimanite-muscovite zones.  The non-parallel distribution of metamorphic minerals may be explained by the non-parallelism of isotherms and isobars during medium grade metamorphism.

These new data support the view that the Coutchiching biotite schists at Rainy Lake are stratigraphically younger than metavolcanic rocks of the Keewatin Group although they presently underlie theKeewatinstructurally.  This observation resolves a part of the historically important "Seine-Coutchiching problem".

A copy of the thesis can be downloaded here

The Hemlo East property is located approximately 50 kilometres east of the town of Marathon, Ontario and is situated within the Schreiber-Hemlo greenstone belt of the Wawa-Abitibi Terrane of the Archean Superior Province. Lithologies within the Hemlo East Property are broadly divided into mafic metavolcanic, felsic metavolcanic, metasedimentary, intrusive and metaintrusive rocks. Stratigraphic continuity within the study area is demonstrated by the large number of drill holes in the area. Rock staining indicates that the K-feldspar present in felsic metavolcanic rocks in the Gouda-Thor-Carroll area of the Hemlo East Property is a product of alteration likely associated with base metal and gold mineralization.

New major and trace element, Sm-Nd isotope, and geochronology data are presented for volcanic, plutonic, and metasedimentary rocks of the Hemlo East property to investigate their origins. Positive to negative ε_Nd (-1.14 to 2.15) for tholeiitic basalts indicate that they were derived from depleted to moderately contaminated sources. FI rhyolites with steep trace element patterns (La/Yb_n = 16 to 44) and fractionated HREE (Gd/Yb_n = 2.1 to 7.5) are interpreted to have been derived from a deep mantle source. Metasedimentary rocks are geochemically similar to felsic metavolcanic rocks and are interpreted to be derived wholly, or in part, from a felsic source.

New U-Pb age dates include 2704.8 ±1.1 Ma and 2705.6 ±1 Ma from the Gouda and Thor metarhyolites, respectively; 2694.5 ±1 Ma from the DC Lake metadacite; 2691.6 ±1.1 Ma from the Upper Anomalous Zone volcaniclastic unit; 2693.1 ± 1 Ma from the Moose Lake Porphyry at Hemlo; 2683.4 ± 1.7 Ma from the Cedar Lake Pluton granodiorite; 2686.5 ±1.3 Ma from the White River Pluton monzogranite; and a maximum age of ~2696 Ma from the Frank Lake felsic metasedimentary unit. Results from the new and compiled U-Pb geochronological data indicate that there are two associations of felsic volcanism and two associations of plutonism, with a new association of felsic volcanism at 2705 Ma. This 2705 Ma phase represents the oldest felsic volcanic unit dated in the greenstone belt. This data points toward a northward younging of stratigraphy in the Gouda-Thor-Carroll area implying that the stratigraphy is right way up.

A long lived oceanic subduction zone produced the arc rhyolites and granitic intrusive rocks seen in the Hemlo East Property. There is no indication from this study as to what comprised the crust that the pre-tectonic plutons were intruded into. High La/Yb_n ratios for the rhyolites suggest that their source magmas were derived at depth from the melting of the subducting slab. Island arc tholeiites (metabasalts) erupted from a primitive back-arc behind the island arc. The area between the arc and back-arc would have allowed for island arc tholeiites to be deposited alongside rhyolites in conjunction with sediments coming off of the volcanic arc to produce the stratigraphic associations seen in the Gouda-Thor-Carroll area. These supracrustal units were later intruded by TTG plutons.

A copy of the thesis can be downloaded here

The Coldwell Complex, northwestern Ontario, is a multiphase alkaline intrusion that is host to rare earth element, actinide and other high field strength element mineralization. Preliminary studies have shown that these minerals are concentrated in pegmatites associated with Center One ferrorichterite-ferroaugite syenites and Center Three syenites. The Center One syenites differentiate to pegmatitic residua and are characterized by cumulus perthitic-to-cryptoperthitic alkali feldspar, hedenbergite-aegirine pyroxenes, and intercumulous quartz, calcite, and calcic-to-sodic-calcic-to-sodic amphiboles. Center Three residua are similar, except that amphiboles are limited to calcic varieties (hastingsite) and precipitate before feldspar (as opposed to after). All pegmatitic residua are of the niobium-yttrium-fluorine (NYF) type. Back-scattered electron petrography has been used to characterize the mineral paragenesis. Pegmatitic syenitic residua emplaced in, but not derived from the border gabbro (Border Gabbro pegmatite), and residua within ferroaugite syenite units (Railway pegmatites) contain a wide range of rare element minerals which include britholite, chevkinite, fergusonite, monazite, allanite, kainosite, xenotime, REE fluorocarbonates bastnaesite, synchysite and parisite. Other rare element enriched minerals include apatite, thorite, zircon, zirconolite, niobium rutile and U-Th-Si-pyrochlore. Early-formed rare element minerals such as allanite, britholite, chevkinite, kainosite, and pyrochlore are commonly replaced by complex aggregates of later-forming phases such as REE-fluorocarbonates. Other riebeckite-quartz (Upper Marathon Shore pegmatites), richterite-quartz (Black pegmatites) and hastingsite-quartz (Center Three pegmatites) bearing pegmatitic residua contain a more restricted  range of rare element minerals, which include zircon, xenotime, monazite and fluorocarbonates together with REE-bearing apatite, thorite and pyrochlore. The differences in rock forming and accessory mineralization suggest that most, if not all, residua are derived from different batches of ferroaugite syenite and syenite magma.

Intensive parameters have been estimated using the habit of perthites, the coexistence of zircon and baddeleyite, Fe-Ti-oxide compositions, amphibole mineralogy, and fluorocarbonate stability. These parameters indicate all pegmatitic units are similar, with initial silica activities of 10-0.75, alkali-feldspar precipitation at approximately 750°C, magnetite-ilmenite subsolidus equilibration temperatures of 531 to 633°C and oxygen fugacities of 10-16.5 to 10-22.9 bars, subsolidus quenching of magnetite occurs at approximately 450°C, and subsequent 200°C hydro- and carbothermal induced recrystallization of rare earth mineral and REE-bearing minerals.

A copy of the thesis can be downloaded here

The Lower Steel River - Little Steel Lake area is located about 25 km east of Terrace Bay , Ontario .  Seventeen iron-formations were investigated within this metamorphosed Archean volcanic and sedimentary terrain, which represents a portion of the Abitibi - Wawa Subprovince of the Superior Structural Province .

Sulphide-facies iron-formations are the dominant chemical sedimentary rocks in the Schreiber - Terrace Bay area, and represent deposition during quiescent periods of clastic accumulation and in volcanic activity.  The iron-formations commonly mark contacts between the volcanic and sedimentary rocks.  They are interbedded with carbonaceous slates at the base of sedimentary successions and overlain by DE turbidites.  This suggests chemical sedimentation on a subaqueous basinal plain slightly distal to an outer fan.

Sulphide-facies iron-formations consist of a mixture of chemical and clastic components, and while highly variable, the iron-formation in the study area contain three commonly recognizable units:  1) pyretic-carbonaceous slate;  2) disseminated, massive, laminated and nodular pyrite; and  3) chert of siliceous sedimentary rock.  Sedimentary textures and structures combined with trace element abundances and geochemical components, and a hydrothermal source for the iron.  Exhalative discharge probably occurred episodically as moderate- to low-temperature solutions percolated through near-surface pillowed volcanics and, once vented, deposited a blanket of chemical sediment.  Vent-proximal deposits include massive and layered pyrite; the domal and colloform varieties support the existence of organic mats.  The presence of carbon is interpreted as a relic of the organic activity.  Pyritic-carbonaceous slates consisting of alternating chemical and clastic components represent vent-distal deposits.  Radial structures within pyrite nodules provide evidence of diagenetic transformation and tectonic deformation.

Structural evidence suggests that the study area was affected by a complex folding event related to one deformational episode, probably preceded by syn-sedimentary slumping in some areas.  The competency differences between sedimentary and volcanic rocks, combined with the fine-grained nature of the sedimentary rocks (DE turbidites and iron-formation) at major volcanic-sedimentary contacts, focused deformation and dike emplacement in the contact areas.

A copy of the thesis can be downloaded here

The Kitto intrusion is a Mesoproterozoic 1117.7 ±1.8 Ma peridotitic to gabbroic intrusion, that formed as a result of plume magmatism and was emplaced along Mesoproterozoic and Archean faults in the East Nipigon Embayment of northern Ontario.  The plume signature for the Kitto intrusion is suggested by five samples with OIB (ocean island basalt)-like primitive mantle normalized multielement patterns in the lherzolite-olivine websterites.

In the southern part of the intrusion, the sequence of lithologies from top to bottom is lherzolite, olivine websterite, vari-textured pyroxenite, pyroxenite and melanogabbro.  The basement is banded iron formation and mafic metavolcanic rocks.  Lithologies on surface are dominantly lherzolite, with olivine websterite present in the area of the Phoenix mineralized occurrence.  The Kitto intrusion is dominated by lherzolite that exhibits cumulate to pyroxene-poikilitic textures dominated by olivine with lesser clinopyroxene and poikilitic orthopyroxene.  The lithologies crop out as a 15 to 30 cm thick layer cake bed dipping from 0 to 30° to the SE and SW.  The olivine websterite displays similar cumulate to pyroxene-poikilitic textures, but contains more abundant clinopyroxene.  The pyroxenite exhibits orthocumulate textures consisting of cumulate clinopyroxene and intergranular plagioclase.  The melanogabbro comprises poikilitic plagioclase and minor cumulate clinopyroxene.  In the central part of the intrusion, lithologies from east to west are lherzolite, olivine websterite, pyroxene-porphyritic melanogabbro and granophyric gabbro.  Lherzolite and olivine websterites in the central part of the intrusion are more fractionated than at the southern part of the intrusion, and are characterized by the presence of secondary pyroxene and minor plagioclase.  The pyroxene-porphyritic melanogabbro also contains secondary pyroxene and, along with cumulate clinopyroxene, there is enrichment in intercumulus plagioclase component.

The lithologies of the Kitto intrusion have geochemical signatures consistent with crustal contamination of a primitive magma.  The lherzolite-olivine websterites are characterized by primitive mantle normalized multielement patterns with negative Nb and Ti anomalies, consistent with assimilation of Archean continental crust.  All the lithologies have εNd contents of -5.54 to -6.53 consistent with contamination by an older crustal source.  Trace element modeling of assimilation-fractional crystallization suggests the lithologies probably assimilated metasedimentary rock of the QST (Quetico Sedimentary Terrane) and mafic metavolcanic rock of the BGB (Beardmore-Geraldton Greenstone Belt) at depth. Emplacement at shallower depths was accompanied by assimilation of mafic metavolcanic rock and banded iron formation.  In the central part of the intrusion, pyroxene-porphyritic melanogabbros have more pronounced negative Nb anomalies indicative of greater assimilation of continental crust.

Emplacement of the Kitto intrusion occurred with an initial pulse of pyroxenite-melanogabbro followed by a pulse of lherzolite-olivine websterite magma in the southern part of the intrusion.  The initial pyroxenite-melanogabbro pulse is suggested by a trend of increasing forsterite and enstatite contents, and decreasing ferrosilite in olivine and pyroxene minerals from the melanogabbro to the higher pyroxenite.  A second pulse is suggested by a trend of replenishment to higher forsterite, enstatite, and ferrosilite contents, but lower wollastonite content in olivine and pyroxene minerals in the lherzolite-olivine websterite.  Towards the top of the intrusion trends of decreasing forsterite, enstatite and ferrosilite contents, but increasing wollastonite content, in olivine and pyroxene are consistent with fractionation of the magma. 

The Kitto intrusion was probably emplaced along north-south Proterozoic and east-west Archean faults in the East Nipigon Embayment.  Possible north-south orientated faults include the Nipigon River and Pijitawabik Faults.  As the magmas came in contact with the east-west orientated Blackwater, Empire, Princess Lake, Standingstone and Sandy Creek Faults of the BGB, they were displaced east or west along the faults, creating the ring-shaped form of the intrusion.

Mineralization of the Kitto intrusion is represented by interstitial Ni-Cu-PGE sulphides in one zone at the bottom of the lherzolite-olivine websterite, two zones in the underlying pyroxenite, and one zone at the contact of the melanogabbro and the basement iron formation.  On the surface outcrops, high Ni contents in the lherzolites and trends of increasing Ni with MgO in all the lithologies, show that Ni partitioned into olivine as the magma evolved.  On the surface outcrops in the central part of the intrusion, lower Ni contents are associated with higher Cu contents in the pyroxene-porphyritic melanogabbros, suggesting the lithologies did not contain sufficient olivine that would partition the Ni.  Generally, anomalous PGE contents occur with anomalous Ni and Cu contents in the lithologies.  Se and S data suggest that externally derived sulphur resulted in sulphur saturation and the precipitation of Ni-Cu-PGE sulphides.  High Se contents are detected in the main mineralized zone at the bottom of the lherzolite-olivine websterite, and in the zones of the underlying pyroxenite.  High Se contents have also been detected in basement iron formation and SVU (Southern Volcanic Unit) mafic metavolcanic rocks consistent with these lithologies being sulphur sources for contamination and mineralization.

A copy of the thesis can be downloaded here

Jordan is currently working on his PhD at the University of Western Ontario

Historic drill core form the Shuniah Mine and more recent drill core from the Keystone and Porcupine Mines have provided the basis for a study of these past silver-producing veins as a function of depth.  Precipitation was initiated from a boiling fluid at temperatures in excess of 370EC.  Cooling of the fluid and precipitation of calcite and sulfides followed generally at 100EC.  Several episodes of deposition separated by fracturing events are evidenced.  From fluid boiling temperatures the depth of emplacement for the veins is 1 km with the pressure regime alternating between hydrostatic and lithostatic.  The ore-depositing solutions appear, therefore, to have arisen from depth and deposited their ores in proximity to diabase sills, which cap the various vein systems, in response to hydrologic factors.

This study is focused on the geology and geochemistry of Midcontinent Rift-related intrusive and extrusive rocks present in northern Ontario, Canada. The study focuses on three sections in order to elucidate the geochemical characteristics of Midcontinent Rift-related rocks and investigate geochemical evolutionary signatures through time. The Coubran Lake basalts, the rocks of the Logan Basin and the intrusive rocks of the Nipigon Embayment were all included in this study to provide a sound spatial representation of Midcontinent Rift (MCR) intrusive and extrusive rocks present within Canada.

The Coubran Lake basalts within the Coldwell Complex, have provided new representation of Midcontinent Rift-related volcanism along the northeast shore of Lake Superior. Physical features, including proximity to surrounding syenites, as well as alteration features, suggest that the Coubran Lake basalts represent a pre-existing sequence into which the Coldwell Complex intruded. Geochemical evidence has linked the Coubran Lake basalt to the Two Duck Lake gabbro (TDLG) suggesting the basalts may represent the volcanic expression of the TDLG. Trace element and Nd isotope data suggest the Coubran Lake basalts are akin to the basalt type I composition, linking the unit to the Lower Siemens Creek volcanics, the basal units in the Ely's Peak and Grand Portage areas of the North Shore Volcanics, and to the lower suite of the Osler Group. The geochemical data presented here is consistent with the available paleomagnetic data suggesting the basalts were erupted early in the history of the Midcontinent Rift.

A re-evaluation of 2397 spatially referenced samples with associated whole-rock geochemistry has yielded previously unrecognized variation within the Midcontinent Rift-related Nipigon sills of the Nipigon Embayment. The whole rock major and trace element geochemistry of 796 Nipigon sill samples was re-examined to investigate the origin of the sills. This investigation revealed three distinct Nipigon sill types based on Th/Yb_pm ratios and ?_Nd1100 values: 395 Nipigon type I sill samples (Th/Yb_pm = 1.97 to 3.4; ε_Nd(t=1100Ma) = -0.5 to -1.5), 171 Nipigon type II sill samples (Th/Yb_pm = 3.4 to 5.0; ε_Nd(t=1100Ma) =  -1.5 to -3.0), and 55 Nipigon type III sill samples (Th/Yb_pm = 5.0 to 6.5; ε_Nd(t=1100Ma) = -5.0 to -7.0). Spatially, the distribution of the more contaminated Nipigon sill types II and III suggest centres which are inferred to represent zones of more contamination.

Field work in the Logan Basin has delineated the following timing requence between the various units present in the Logan Basin: the Riverdale sill, the Devon Volcanics, the Logan sills, the Pigeon River dykes, the Cloud River dykes, the Mount Mollie dyke and the Crystal Lake gabbro. Geochemical source characteristics support this timing relationship as the Riverdale sill, the Devon volcanic and the Logan sills are geochemically similar to the ultramafic intrusions of the Nipigon Embayment which were emplaced early in MCR history. The three dyke sets of the Logan Basin have been determined to be emplaced in the following order: Pigeon River dykes, the Cloud River dykes and the Mount Mollie dyke. All three dyke sets display similar source characteristics yet show stronger crustal contamination signatures (i.e., higher Th/Yb_pm and more negative ε_Nd(t=1100Ma) ) through time consistent with each dyke set having spent more time in the magma chamber through the duration of the emplacement sequence.

Based on the plots of Th/Yb_pm versus Nb/Th_pm and Th/Yb_pm versus Nb/Yb_pm, previously unrecognized relationships between units have allowed for inferences into the timing and geochemical evolution of the Midcontinent Rift. The progression of magmatism for both the Logan Basin and the Nipigon Embayment suggests that source characteristics became more depleted through time. Evidence of a link between the magmatism of the Logan Basin and the Nipigon Embayment is also indicated by the relationship between the Riverdale sill, the Devon Volcanics and the Logan sills with the mafic and ultramafic units of the Nipigon Embayment (excluding the Nipigon sills). Furthermore, the spatial link between the two magmatically endowed areas is bridged as the dykes of Sibley Peninsula showing evidence to be potential feeders to Nipigon sills.

For more details about this thesis contact Dr. Peter Hollings

A copy of the thesis can be downloaded here

The Thunder Bay Silver District is composed of two curvilinear groups of veins, the Mainland and Island Belts.  The veins can be mineralogically divided into the barren, silver-bearing, and 5-element association veins.

During the present study, fluid inclusion, sphalerite composition, and sulfur isotopic composition were investigated, as well as some aspects of the mineralogy of the veins.  Fluid inclusions in quartz, calcite, and fluorite indicate temperatures ranging from 70E-450EC during vein deposition could be found in veins of both geographical and all mineralogical groups.  Fluid inclusions in sphalerite indicate ore minerals were deposited between 80E-120EC at all locations, 1-30 equiv. wt. % NaCl.  The dominant salt in solution was CaCl₂.

Fe content in sphalerite indicates a log a₈₂ of -18 to -25 during ore deposition at all deposits except Spar Island .  At Spar Island copper sulfide mineralogy suggests log a₈₂ of -14 to -18.  Sphalerite often contained trace quantities of Cd.

Sulfur isotopic composition of sulfides and barite ranged from -9.7 to +12.2%, with two anomalous values (near +30%) from supergene samples.  Paired data indicated isotopic non-equilibrium during deposition sulfides.

The consistency of fluid inclusion, sulfur activity, and sulfur isotopic data suggest both depositional environment and hydrothermal fluid source were similar for all veins in the Thunder Bay district.  Heterogeneity of the deposits, particularly the presence or absence of Ag, Ni, Co and As may be due to the evolution of the fluids between their inception and entry into the depositional environment.

The source of the fluids is unknown, although their original sulfur isotopic composition is inferred to be fairly low (+4.7%), suggesting a magmatic source of sulfur is possible. 

A copy of the thesis can be found here

The Beardmore-Geraldton greenstone belt is located along the boundary between the Wabigoon and Quetico subprovinces in the Superior province of the Canadian Shield.  Historical gold mines and current gold exploration camps are located throughout the Beardmore-Geraldton greenstone belt and adjacent Wabigoon subprovince in moderately to steeply dipping ductile to brittle-ductile shear zones in many types of lithologies, with various metamorphic grades and alteration styles.  The shear zones typically strike east-west along the boundary of the Beardmore-Geraldton greenstone belt with the Wabigoon subprovince to the north as well as along the boundary with the Quetico subprovince to the south.

Field mapping and petrography, including microstructural analysis, were used to characterize the gold mineralization and investigate the control on gold mineralization in the Elmhirst, Castlewood, Pagwachuan, and Milestone properties in Greenstone, Ontario.  Two property-scale and seven trench-scale maps were produced from field mapping and one hundred twenty-three transmitted and reflected light thin sections were prepared from samples collected from these properties.  Lithology, structure, microstructure, metamorphic grade, alteration, and subprovince were considered as possible controlling factors on gold mineralization.

In the study area gold mineralization is hosted in relatively competent lithologies including schistose to mylonitic metamorphosed granodiorite, syenite, and pegmatite; chlorite-albite schist, schistose amphibolite, and garnet-hornblende-biotite schist.  The regional-scale structures that host gold mineralization are ductile to brittle-ductile shear zones that have a penetrative, schistose foliation and rarely a mylonitic fabric.  The property-scale structures that host gold mineralization are folded, mylonitized, and boudinaged quartz veins; shear-related early, late, and complex folds; folded fault breccia, and pressure shadows of rigid minerals within schistose to mylonitic fabric.  Gold mineralization is located in areas of micro-folds, micro-boudins, micro-fault breccia, undulatory extinction, and grain size reduction along irregular grain boundaries, subgrain boundaries, folded healed fractures, and in pressure shadows within areas of strain heterogeneity.  Gold mineralization is located in both areas of greenschist facies and amphibolite facies metamorphism in the study area.  The styles of alteration also vary within the study area with sericite, hematite, ankerite, calcite, and unaltered samples all hosting gold mineralization.  Both the Wabigoon and Quetico subprovinces host gold mineralization in similar structures and microstructures as the Beardmore-Geraldton greenstone belt although it is within different lithologies, metamorphic grades, and alteration styles.    

Similar structure and microstructure are always present in areas of gold mineralization in the study area while lithology, alteration, metamorphic grade, and subprovince vary.  Gold mineralization within stable prograde and retrograde metamorphic minerals indicates that gold mineralization was synchronous with ductile to brittle-ductile deformation and metamorphism.  Further gold exploration in the study area should focus on structure and microstructure as indicators for gold mineralization.

A copy of the thesis can be downloaded here

The Shakespeare intrusion, which hosts the Shakespeare Ni-Cu-PGE sulfide deposit, is part of the 2.2 Ga Nipissing Gabbro magmatic event, a large mafic-ultramafic suite located in the southern Superior and Southern Province. The Shakespeare intrusion intrudes the 2.2-2.45 Ga Huronian Supergroup and is located in the northern part of the Southern Province, only a few km from the Archean- Proterozoic unconformity which separates the Superior Province from the Southern Province and is adjacent to the ~ 2450 Ma East Bull Lake and Agnew Lake intrusions.

The Shakespeare deposit is the largest Ni-Cu-PGE deposit in the Nipissing Large Igneous Province (LIP). Field mapping and drilling have provided a detailed stratigraphic understanding of the deposit and provide the framework for geochemical models of sulfide segregation related to assimilation. The U-enriched rocks that interacted with the intrusion during ascent through the crust provide an excellent opportunity to gauge the role of assimilation during the formation of the Shakespeare deposit while providing further evidence that crustal sulfur is necessary in order to generate economic concentrations of magmatic sulfides.

A detailed study of three drill holes representing poor, average, and above average intercepts of Ni-Cu-PGE sulfides was performed  in order to establish the mechanism by which an immiscible sulfide liquid was produced and also to establish the contamination history of the Shakespeare deposit. Various geochemical techniques were employed, including SEM-EDS, ICP-MS, ICP-AES, total sulfur, sulfur isotope, and XRF analysis. During the course of the SEM­-EDS study primary magmatic textures within hollingworthite-irarsite-platarsite were observed, suggesting limited remobilization during metamorphism. Rheniite, cerium-rich allanite, and various tellurides and selenides were also observed.

δ³⁴S analysis yielded values between 0.01‰ and 2.38‰, averaging 1.14‰.  These values are indicative of an unfractionated sulfur source, suggesting that the source of sulfur in the Shakespeare deposit was either derived from the mantle or an unfractionated crustal source, such as the quartz pebble conglomerates of the Matinenda Formation. Sulfur: selenium ratios yielded values between 1245 to 3271, averaging  1810. The average value is significantly lower than accepted mantle values (2850-4000) and may point to an assimilant rich in selenium.

Spider diagrams of mantle normalized data from the Shakespeare intrusion indicate that all of the rocks of the Shakespeare intrusion display a geochemical profile which is characteristic of magmas that have undergone significant degrees of crustal contamination. Negative Nb and Ti anomalies, enrichment in HFSE relative to MREE, and enrichment in LREE  relative to HREE indicate that ascending  Shakespeare magmas assimilated significant quantities of upper crustal material.

The results of the study show that the Shakespeare intrusion is highly enriched in U, Th, and LREE, relative to other Nipissing intrusions. The most likely explanation for the enrichment is that the Shakespeare intrusion interacted with the pyritic quartz pebble conglomerates of the Matinenda Formation, possibly near the past producing Agnew Lake uranium mine. Geochemical and textural evidence suggests that magma mixing was the dominant mechanism responsible for the precipitation of an immiscible sulfide liquid. R factor calculations and sulfide metal concentrations suggest a second immiscible sulfide liquid precipitated from later mixing with the PGE- and base metal-poor biotite quartz diorite magmas which ponded in the roof zone of the intrusion.

The results of this study have major implications for Ni-Cu-PGE exploration in the Nipissing LIP and indicate that any economically significant concentrations of magmatic sulfides will be found in gabbroic rocks which have assimilated significant amounts of U- and Th-rich crustal material from the Matinenda Formation, resulting in discernable differences in the U-contents of potential host intrusions versus intrusions that are not likely to host a Ni-Cu­ PGE deposit.

A copy of the thesis can be downloaded here