The Precambrian Mafic Magmatism of the Northeastern Superior Province, Canada

The Precambrian mafic magmatism of the Northeastern Superior Province, Canada

CHARLES MAURICE

Department of Earth and Planetary Sciences

McGill University, Montréal

September 2009

A thesis submitted to

the Faculty of Graduate Studies and Research

in partial fulfilment of requirements of the degree of

Doctor of Philosophy

Major, trace and rare earth elements (REE), along with Nd isotopes and U-

Pb ages, were determined for Archean greenstone belts (2.88-2.72 Ga) and

Paleoproterozoic mafic dyke swarms (2.51-2.00 Ga) of the Northeastern Superior

Province (NESP) of Canada in order to gain insights on the nature of mafic magmas across the Precambrian. Geographically separate, but coeval (2.78 Ga), greenstone assemblages with distinctive Fe-tholeiites occur across a large surface area of the NESP. This geographic separation, along with the numerous inheritance ages of greenstone lithologies that replicate those of older volcanic- plutonic assemblages, are consistent with these belts being the remnants of an extensive autochthonous mafic volcanic cover sequence. An increase of Th/Nb ratios in light REE-enriched basalts reflects a change in the nature of coeval crustal contaminants, from tonalite-trondhjemite prior to 2.75 Ga, to granite- granodiorite afterwards. The isotopically-enriched character of these magmas after 2.75 Ga implies more extensive contamination by a felsic crust affected by regional partial melting, succeeding the amalgamation of the Hudson Bay (TDM

4.3-3.1 Ga) and Rivière Arnaud (TDM < 3.1 Ga) terranes.

Paleoproterozoic mafic dyke swarms follow the stabilization of the Archean crust. The magmas of most dykes are sourced in fertile lherzolite at ~1.5 GPa, but others are either sourced from deep (~5 GPa) lherzolite or pyroxenite, Fe-rich mantle, or harzburgite. The presence of all dyke types within the older Hudson

Bay Terrane reflects the heterogeneous nature of its lithospheric mantle. All contain a crustal component in the form of an increase in La/Yb with Zr/Nb ratios,

ii and negative εNd values. In contrast, voluminous 2.2 Ga dykes of the Rivière

Arnaud Terrane display an increase in La/Yb with a decrease in Zr/Nb ratios, and positive εNd values indicative of an alkaline mantle component similar to that of

Paleoproterozoic alkaline rocks recognized across the NESP. Despite their 2.0-

1.9 Ga ages, these alkaline rocks and coeval basaltic belts collectively display ca.

2.2 Ga Nd model ages that are identical to the numerous 2.2 Ga mafic dykes.

This time correlation suggests that the composition of the mantle was modified by a pervasive metasomatism associated with the emplacement of the 2.2 Ga dykes.

The secular variation of Archean and Paleoproterozoic mafic rocks of the NESP shows that their composition has been controlled by the nature of the crust and lithosphere they intruded.

iii Résumé

Les éléments majeurs, traces et du groupe des terres rares (ÉTR), ainsi que les isotopes du Nd et des âges U-Pb, ont été déterminés pour les ceintures de roches vertes archéennes (2.88-2.72 Ga) et pour les essaims de dykes mafiques paléoprotérozoïques (2.51-2.00 Ga) du nord-est de la Province du Supérieur

(NEPS) du Canada, afin de définir la nature des magmas mafiques au

Précambrien. Dans les ceintures de roches vertes archéennes, des assemblages géographiquement séparés, mais contemporains (2.78 Ga) et contenant des tholéiites ferrifères distinctives, sont reconnus sur une large portion du NEPS.

Cette séparation géographique, ainsi que les nombreux âges hérités qui répliquent ceux des assemblages volcano-plutoniques anciens, suggèrent que ces ceintures représentent les lambeaux d’une séquence volcanique mafique autochtone ayant couvert une grande surface. Une augmentation des rapports Th/Nb des basaltes enrichis en ÉTR légers reflète un changement de la nature de leurs contaminants crustaux, de tonalite-trondhjémite avant 2.75 Ga, à granite-granodiorite ensuite.

L’enrichissement isotopique de ces magmas après 2.75 Ga implique une contamination plus importante par une croûte felsique affectée par une fusion partielle régionale, résultant de la collision des terranes de la Baie d’Hudson (TDM

4.3-3.1 Ga) et de la Rivière Arnaud (TDM < 3.1 Ga).

Les essaims de dykes mafiques paléoprotérozoïques succèdent à la stabilisation de la croûte archéenne. Les magmas de la plupart de ces dykes prennent leur source dans un manteau lherzolitique à ~1.5 GPa, mais d’autres proviennent soit d’un manteau lherzolitique ou pyroxenitique plus profond (~5

iv GPa), d’un manteau riche en Fe, ou d’un manteau harzburgitique. La présence de tous ces dykes dans le Terrane de la Baie d’Hudson reflète la nature hétérogène du manteau lithosphérique. Tous contiennent un composant crustal sous la forme d’une augmentation des rapports La/Yb et Zr/Nb rapports, et de valeurs εNd négatives. À l’opposé, les volumineux dykes âgés de 2.2 Ga dans le Terrane de la

Rivière Arnaud montrent une augmentation des rapports La/Yb avec une diminution des rapports Zr/Nb, et des valeurs εNd positives qui indiquent un composant mantellique alcalin similaire à celui des roches alcalines paléoprotérozoïques retrouvées dans tout le NEPS. Malgré des âges de cristallisation de 2.0-1.9 Ga, ces roches alcalines et leurs ceintures basaltiques contemporaines, affichent collectivement des âges modèles du Nd de ca. 2.2 Ga identiques à ceux des nombreux dykes mafiques. Cette corrélation temporelle suggère que la composition du manteau a été modifiée par un évènement métasomatique associé à la mise en place des dykes âgés de 2.2 Ga. L’évolution temporelle des roches mafiques archéennes et paléoprotérozoïques du NEPS montre que leur composition a été contrôlée par la nature de la croûte et de la lithosphère dans laquelle elles se sont mises en place.

v Acknowledgements

The first obvious person to be acknowledged here is my supervisor Don

Francis, who always supported my (not always comprehensible) ideas in writing the three manuscripts of this thesis. His guidance, support, and editorial skills made available the thorough realization of the project of my life. I would like to thank Bill Minarik for his help at the ICP-MS for the calibration of the chromatographic columns that permitted efficient separations of Sm and Nd.

Mes patrons Robert Marquis et Sylvain Lacroix de Géologie Québec m’ont donné une grande latitude afin de travailler sur la rédaction de cette thèse et d’en présenter une partie à la conférence Goldschmidt 2007 à Cologne, Allemagne.

Cette conférence aura été profitable autant sur le plan professionnel que personnel. Merci beaucoup à Maman pour m’avoir demandé mensuellement :

« quand est-ce que tu termines ton doctorat? ». Cela m’aura permis de ne pas oublier pendant au moins 2 ans que je n’avais effectivement pas terminé. Je suis aussi reconnaissant à mon père pour avoir eu l’air de comprendre à quoi peuvent servir les isotopes du néodyme. Merci Annie pour m’avoir encouragé à me lancer dans cette aventure, et merci Olivier pour avoir été, du début à la fin de ma rédaction, mon fan le plus fidèle et le plus au courant de l’avancement de mes travaux. Merci beaucoup à Jean aussi, pour avoir pu rester sobre et attendre le dépôt de cette thèse pour enfin aller prendre une bière. Mes remerciements finaux sont les plus tendres, et volent directement de mon cœur vers les grands yeux de ma fée, pour avoir su comprendre comment la fin de ce projet a pu affecter mon

être et, surtout, pour s’être acquitté efficacement d’une grande portion des tâches ingrates de mise en page.

vi Table of Contents

Abstract ...…………………………………………………………………..……… ii Résumé ……………………………………………………….……………..……... iv Acknowledgements …………………………………………………………..……. vi Table of Contents ………………………….……………………………..………... vii List of Tables ………………………………..…………………….………………. ix List of Figures ………………………………..………………………………...... x List of Appendices …………..…………………………………………………..… xiii Preface …………………………………………………………………………..…. xiv Contributions of Authors …………………………………………………...... xvi b

CHAPTER 1: Introduction ……………………………………………...…….…… 1 b References …………………………………………………………..…...... 7

CHAPTER 2: Evidence for a widespread mafic cover sequence and its implications for continental growth in the Northeastern Superior Province 10

Abstract ………………………………………………….…..…………… 11 1. Introduction ……………………………………………………….…...... 13 2. Geological framework ………………………………………………...… 14 3. Geology and age of the greenstone belts ……………………………… 17 4. Geochemical results …………………………………………….…...... 23 5. Discussion ………………………………………………………….….... 28 6. Concluding remarks ……………………………………….………...... 40 Acknowledgements ……………………………………………………...… 42 References ………………………………………………………………..... 44 Figure Captions …………………………………………………………..... 51 Tables ………………………………………………………………….…... 56 Figures ………………………………...………………………………….... 69 b

CHAPTER 3: Les essaims de dykes mafiques du nord-est de la province du supérieur ………………………………………………………………………..… 80 b 1. Introduction ……………………………………………………………... 81 2. Les essaims de dykes mafiques ……………………………………..…... 82 3. Une nouvelle carte de compilation ….…….……….……………………. 84 4. Unités d’âge Protérozoïque ……………………………………………... 86 5. Conclusions …………………………………………………………..…. 93 Références …………………………………………………………….....… 95 b

vii CHAPTER 4: Enriched crustal and mantle components and the role of the lithosphere in generating Paleoproterozoic dyke swarms of the Ungava Peninsula, Canada 100

Abstract ……………………………………………………………………. 101 1. Introduction ……………………………………………………………... 103 2. Geological framework …………………………………………………... 104 3. Data ……………………………………………………………………... 107 4. Compositional groups …………………………………………….…….. 109 5. Discussion ……………..……………………………………………..…. 116 6. Conclusions …………..………………………………………………..... 127 Acknowledgements ……………………………………………………...… 128 References ……………………………………………………………...….. 129 Figure Captions ………...………………………………………………….. 136 Tables ……………………………………………………………..……….. 142 Figures ………………………………...…………………………..……….. 143 b

CHAPTER 5: Age and tectonic implications of Paleoproterozoic mafic dyke swarms for the origin of 2.2 Ga enriched lithosphere beneath the Ungava Peninsula, Canada………....…………………………………..…………………… 154

Abstract ……………………………………………………………………. 155 1. Introduction ……………………………………………………………... 157 2. Geological background………………………………………………….. 158 3. Isotopic data ………………………………………………………..…… 164 4. Geochemical systematics………………………………………….…….. 172 5. Discussion …..…………..………………………………………………. 176 6. Conclusions ...…………..……………………………………………….. 187 Acknowledgements ………………...……………………………………… 189 References ………………………...……………………………………….. 190 Table captions ………………...………………………………………….. 196 Figure captions ………………………..…………………………………… 197 Tables ……………………………...………………………..…………….. 203 Figure ……………………………...………………………..…………….. 208

CHAPTER 6: General Conclusions ………..……………………………………… 218

APPENDIX A ……………………………………………………………………... 224

APPENDIX B ……………………………………………………………………... 226

APPENDIX C ……………………………………………………………………... 255

viii List of Tables

Table Description 2-1 U-Pb crystallization and inheritance ages obtained in greenstone belts from the NESP …………………………………………………………. 56

2-2 Authors, laboratory, number of samples and methods used for the quantitative analysis of major and trace elements as well as Nd isotopes for the greenstone belts from the northern part of the NESP ………….. 58

2-3 Major (wt.%) and trace element (ppm) analysis for mafic rocks of the Pélican, Nantais, Duquet and Curotte belts ……………………………. 59

2-4 Nd isotopic data acquired on whole rock samples collected in greenstone belts and in surrounding granitoids from the NESP ……………………. 66

4-1 Synoptic table of geochemical groups, characteristics, symbols, possible components and sources for mafic dyke swarms of the Ungava Peninsula of northern Québec ………………………………………………………. 142

5-1 U-Pb isotope dilution - thermal ionization mass spectrometry (ID-TIMS) analytical data for Paleoproterozoic dykes of the Ungava Peninsula……. 203

5-2 Synoptic table of coordinates and physical characteristics of sample on which U-Pb data were acquired …………………………………………. 205

5-3 Nd isotopic data acquired on whole rock samples from Paleoproterozoic dykes of the Ungava Peninsula. …………………………………………. 206

ix List of Figures

Figure Description 2-1 Isotopic terranes (Boily et al., 2008) and domains of the Northeastern Superior Province (NESP; Leclair, 2005) ………………………..……. 69

2-2 Simplified geological map of the NESP (modified from Leclair, 2005) showing the distribution of Archean greenstone belts discussed in the text ……………………………………………………..………... 70

2-3 Synoptic table of crystallization and inheritance ages recorded in greenstone belts of the NESP ………………………………..……….... 71

2-4 Frequency of a) U-Pb crystallization ages and b) inheritance ages (in Ma) acquired on magmatic rocks of the NESP …….……..…………… 72

2-5 Schematic cross section and geochronological summary of the Duquet belt (Fig. 2-2) ………………………………………………….………. 73

2-6 a) TiO2 vs. MgO and b) Al2O3 vs. MgO in wt.% for the tholeiitic and LREE-enriched suites of the NESP …………………………….……... 74

2-7 MgO vs. Fe2O3 in wt.% for a) the tholeiitic and LREE-enriched suites of the NESP, b) recent mid-oceanic ridge basalts (MORB) and Miocene Columbia River continental flood basalts and c) Cretaceous basalts from the Kerguelen and Ontong Java plateaux. …………….…. 75

2-8 Nb/Th vs. La/Sm for tholeiitic and LREE-enriched suites of the NESP 76

2-9 Al2O3/TiO2 vs. Gd/Yb for tholeiitic suites of the NESP …………..…... 77

2-10 a) εNd(t) vs. age for the NESP divided according to MgO contents (mafic or felsic) and the isotopic terranes defined by Boily et al. (2008); b) εNd(t) vs. age for rocks of greenstone belts from the NESP and engulfing tonalites ……………………………………………...…. 78

2-11 Mg vs. Fe in cation units for the Mg-tholeiite and Fe-tholeiite suites … 79

4-1 Schematic distribution of mafic dyke swarms (modified from Buchan and Ernst, 2004; Maurice, 2008) and alkaline rocks of the Superior Province emplaced over a) ca. 2.51-2.44 Ga; b) ca. 2.23-2.17 and c) ca. 2.15-1.88 Ga. ………………………………………………………. 143

4-2 Distribution of the mafic dykes (adapted from Maurice, 2008) and mafic dyke samples of the Ungava Peninsula …………………………. 144

x 4-3 Crustal contamination indicators a) K/Ti, and b) La/Yb vs. dyke thicknesses for dykes of the Ungava Peninsula ………………..……… 145

4-4 a) Fe, b) Ti, c) Al and d) Ca/Al vs. Mg in cation units for the mafic dykes of the Ungava Peninsula ……………………………….………. 146

4-5 a) Na, b) Mg, c) Fe and d) Al vs. Si in cation units for the mafic dykes of the Ungava Peninsula …………………………………….………… 147

4-6 V vs. Ti in ppm for the mafic dykes and alkaline rocks……………….. 148

4-7 Ternary projection of CIPW (cation) normative minerals in Ol-Di-Hy, Hy-Di-Qz and Ol-Ne-Di planes ……………………………………..… 149

4-8 Multi-element diagram normalized over primitive mantle (Sun and McDonough, 1989) for representative mafic dyke samples with ~8 wt.% MgO of the five chemical groups and subgroups of the Ungava Peninsula ………………………………………………………………. 150

4-9 a) Nb, b) Th, c),Yb and d) La/Yb vs. Zr for mafic dykes of the Ungava Peninsula ………………………………………………..……………... 151

4-10 a) Th/Nb, b) K/Ti, c) Zr/Nb and d) εNd(2.0Ga) vs. La/Yb for mafic dykes, alkaline rocks and granitoids of the Ungava Peninsula…….…... 152

4-11 La-Yb-Nb ternary diagram for mafic dykes, alkaline rocks and granitoids of the Ungava Peninsula.…………………………..……….. 153

5-1 Schematic distribution of mafic dyke swarms and alkaline rocks of the Superior Province emplaced over a) ca. 2.51-2.44 Ga; b) ca. 2.23-2.17 and c) ca. 2.15-1.88 Ga. ……………………………………………….. 208

5-2 Map of Paleoproterozoic mafic dyke swarms, alkaline, and supracrustal rocks of the Ungava Peninsula. ……………………..…… 209

5-3 Schematic stratigraphic columns and available ages for the Circum- Ungava Paleoproterozoic volcano-sedimentary belts …………...…….. 210

5-4 Si vs. Fe in cation units for the ultramafic lamprophyres of the Ungava Peninsula ……………………………………………………………… 211

5-5 U-Pb concordia diagrams showing analyses of the mineral fractions reported in Table 1 …………………………………………………….. 212

5-6 143Nd/144Nd vs. 147Sm/144Nd for Paleoprotorezoic mafic dykes, circum- Ungava supracrustal rocks, alkaline dykes and lavas of the Ungava Peninsula and carbonatites of the western Superior Province. ….……. 213

5-7 εNd(t) vs. age for mafic and alkalic rocks of the Ungava Peninsula and carbonatites of the Southern Superior Province. ………………………. 214

5-8 Zr/Nb vs. La/Yb vs. for Archean granitoids, Paleoproterozoic alkaline rocks and mafic dykes of the Ungava Peninsula ………………………. 215

5-9 Zr/Nb vs. La/Yb vs. for mafic dykes of the Ungava Peninsula for which U-Pb ages are well known (a and b), and for mafic volcanic rocks and alkaline rocks from Circum-Ungava belts (c). ……………... 216

5-10 Schematic mantle sections showing the possible evolution of the Ungava Peninsula between 2.5 and 1.9 Ga ……………………………. 217

xii List of Appendices

Appendix

A Mafic dyke swarms of the Northeastern Superior Province ……………. 224

B Major (wt.%), trace element (ppm) and Nd isotopic analyses of mafic dykes of the Ungava Peninsula. …………………………………………. 226

C Major (wt.%), trace element (ppm) and Nd isotopic analyses of the Lac Aigneau alkaline lamprophyres ..…………………………………….….. 255

xiii Preface

The main body of this thesis consists of four chapters addressing the chemical and tectonic implications of the composition of mafic magmas between

2.9 and 1.9 billion years (Ga) in the Northeastern Superior Province of Canada

(NESP). Two chapters are already published, while the two others are to be submitted to scientific journals over the winter of 2009. Each of these paper is self-contained with an abstract, introduction, presentation of data, discussion and conclusions. References, tables and figures are located at the end of each chapter, and are in the format of the journal in which the work was, or will be, submitted.

Chapter I is an introduction that presents the rationale and objectives of the thesis. It also contains a review of the literature, and addresses the unresolved issues concerning the nature of the mantle source of Precambrian mafic rocks.

Chapter II reports new bulk rock geochemical and Nd isotopic data acquired on

2.9-2.7 Ga Archean greenstone belts of the NESP. It questions the applicability of plate tectonic models for the greenstone belts of this portion of the Superior

Province and proposes that a widespread basaltic sequence once covered a large portion of the craton. It also addresses the role of contamination by the numerous and voluminous coeval granitoid components in the petrogenesis of the basaltic magmas of greenstone belts. The three following chapters discuss the distribution and geochemical characteristics of Paleoproterozoic mafic dyke swarms of the

Ungava Peninsula aged between 2.5 and 2.0 Ga, and link their composition to the nature of the Archean lithosphere they intrude. Chapter III presents the methodology for the construction of a compilation map of mafic dyke swarms.

Chapter IV examines the implications of the major and trace element geochemical

xiv signature of the mafic dykes for their petrogenesis, and proposes that the relative involvements of enriched crustal and mantle components account for the variability of four distinct mantle sources. Chapter V focuses on the interpretation of new U-Pb ages acquired on these dykes, and links the 2.2-2.1 Ga Nd isotopic ages of the surrounding 2.0-1.9 Ga basaltic and alkaline magmas to a metasomatic enrichment triggered by the genesis of the many coeval northern ca. 2.2 dyke swarms. Finally, chapter VI ends the thesis with a summary of the results, presents a general discussion of their implications and suggestions for further possible work.

xv Contribution of authors

This study involves the interpretation of a large number of samples that were acquired by many geologists, including myself, over a period of more than 10 years. The whole rock major and trace element data come from a compilation of the results of different geochemical laboratories for which the number of samples and provenance of data are sourced within each chapter. Most samples from

Archean greenstone belts presented in Table 3 of Chapter 2 were acquired by myself. The Nd isotopic analyses acquired on Archean rocks and used in Chapter

2 were also produced by a large number of different authors (see compilation of

Maurice, 2007), but 90% of those acquired in the greenstone belts of the northern part of the NESP (n = 40) were acquired by myself at GEOTOP under the supervision of Jean David and Ross Stevenson. Nd isotopic analyses from

Paleoproterozoic mafic dykes (Chapter 5) were obtained by myself (n = 31), while those of the Lac Aigneau dykes were obtained by Jonathan O’Neil (n = 8). The unpublished U-Pb ages acquired on Archean rocks (Chapter 2) are the work of

Jean David, while those obtained on mafic dykes (Chapter 5) reflect a cooperative effort; I treated all dyke samples for heavy mineral recovery, and did approximately 40% of the lab and analytical work. Finally, the U-Pb dating on a

Lac Aigneau dyke is the sole work of Jean David.

I, Charles Maurice, am responsible for the preparation and writing of the three scientific manuscripts and acknowledge the critical reviews of co-authors

Don Francis (co-author on three papers) and Jean Bédard (co-author of one paper). Interpretations of the analytical data are the result of numerous discussions with the various co-authors.

xvi The current status of the papers and the map contained in this thesis is as follows:

Chapter 2 : PUBLISHED - Maurice, C., David, J., Bédard, J.H., Francis, D.

(2009) Evidence for a widespread mafic cover sequence and its implications for continental growth in the Northeastern Superior Province of Canada.

Precambrian Research 168; pages 45-65.

Chapter 3 : PUBLISHED - Maurice, C. (2008) Les essaims de dykes mafiques du

Nord-Est de la Province du Supérieur, In : Simard, M. (Coord.), Synthèse du

Nord-Est de la Province du Supérieur, Ministère des Ressources naturelles et de la Faune, Québec MM 2008-02, pp.137-141.

Chapter 4 : IN PRESS - Maurice, C., Francis, D. Enriched crustal and mantle components and the role of the lithosphere in generating Paleoproterozoic dyke swarms of the Ungava Peninsula, Canada. DOI: 10.1016/j.lithos.2009.08.002

Chapter 5 : IN PRESS - Maurice, C., David, J., O’Neil, J., Francis, D. Age and tectonic implications of Paleoproterozoic mafic dyke swarms for the origin of 2.2

Ga enriched lithosphere beneath the Ungava Peninsula, Canada. DOI:

10.1016/j.precamres.2009.07.007

Appendix A : PUBLISHED - Maurice, C. (2008) Les essaims et dykes mafiques du Nord-Est de la Province du Supérieur, In : M. Simard (Coord). Synthèse du

Nord-Est de la Province du Supérieur, Ministère des Ressources naturelles et de la Faune, Québec, map MM 2008-02C006.

xvii

CHAPTER 1

Introduction

1 The Precambrian comprises three eons that group more than 85% of the

Earth’s history: the Hadean (4560-4000 Ma), the Archean (4000-2500 Ma) and the Proterozoic (2500-544 Ma). Precambrian mafic (basaltic) magmas that now occur at the surface of the Earth’s crust are sourced in the mantle, and although they have experienced some degree of crystal fractionation, convey key information on the nature of their mantle source across geological time.

The oldest records of volcano-sedimentary basins range in age from 3800 to

2500 Ma and occur in Archean greenstone belts that occur in the Precambrian shields around the world. They are characterized by a variety of lithological assemblages emplaced in different depositional settings that reflect their modes of emplacement. Greenstone belts host important volumes of basaltic lavas, and hence provide the only direct insights of early mantle conditions. Many Archean greenstone belts can be subdivided into a lower, dominantly volcanic assemblage, and an upper sedimentary assemblage (Windley 1995). In most belts, the lower volcanic assemblage is commonly further divided into a lower, primarily mafic- ultramafic group exhibiting a tholeiitic affinity, and an upper volcanic group with calc-alkaline affinities. The volcanic rocks of the ancient Earth differed from modern analogues in being formed at higher temperatures, and having ubiquitous coeval and spatially-related plutonic felsic rocks (tonalite-trondhjemite- granodiorite – TTG) now forming granite-greenstone terranes. For instance, the

Fe-rich compositions of Archean basaltic rocks do not resemble any modern basalt, while Archean TTG have no modern counterparts. Although Archean granite-greenstone terranes are widely studied, the origin of the continental crust

2 and associated lithospheric mantle remains in dispute. There is little consensus about:

a) the rate at which the early continental crust formed (Campbell 2003;

McCulloch and Bennet 1993; Nelson and DePaolo 1985; Sylvester et al.

1997; Taylor and McLennan 1985);

b) the relationship between Archean volcanic belts and enclosing felsic

plutons (Lin 2005; Peschler et al. 2004);

c) the composition of the Archean mantle (Francis 2003; Griffin et al. 2003;

Herzberg 1993), and;

d) the mode of emplacement of Archean greenstone belts, and the dominant

tectonic regime in which they were emplaced.

This last topic is particularly debated and genetic models for the origin of granite-greenstone terranes have historically split between two different settings, plate tectonic and vertical tectonic models. Many genetic models call upon plate tectonic processes because of the systematic age-progression of volcano-plutonic belts (Card 1990; Stott 1997), the detection of dipping seismic reflectors interpreted to be relict subduction scars (Calvert et al. 1995), and the chemical similarities between Archean calc-alkaline rocks and those found at modern convergent boundaries. Plate tectonic models posit that the continents grew by the accretion of oceanic terranes (Dimroth et al. 1982; Kimura et al. 1993) and amalgamation of continental nuclei of distinct isotopic character (Tomlinson et al.

2004), occasionally coupled with interactions with mantle plumes (Abbott 1996;

Wyman and Hollings 1998).

3 The proposal that many greenstone assemblages are essentially autochthonous constructions (Ayer et al. 2002; Thurston 2002), however, brings into question the applicability of plate tectonic models for the internal growth of terranes, prior to their amalgamation to older continental nuclei. Granite- greenstone terranes have also been interpreted to reflect lithospheric-scale vertical processes because of: the synformal geometry of greenstone keels separating granitoid domes, the identification of ‘greenstone-down/pluton-up’ sense of shear indicators, the widespread occurrence of vertical lineations and rarity of lithologies representing accretionary mélanges, andesites, blueschists, as well as mass balance and thermal/viscosity constraints (Bédard 2006; Bédard et al. 2003;

Chardon et al. 1996; Collins et al. 1998; Mareschal and West 1980; Stern 2005;

Zegers and Van Keken 2001).

The emplacement of late anorogenic felsic granitoids ca. 2600 Ma marks the final stabilization of Archean cratons. These cratons are now underlain by lithospheric mantle roots (Jordan, 1988) that represent the depleted residue left after extensive partial melting of the mantle (Boyd 1989; Griffin et al. 2003;

Herzberg 1993), which may have been re-enriched by the infiltration of melts and fluids of various origins (Coltorti and Grégoire 2008). This subcontinental lithospheric mantle extends to depths greater than 200 km, and a low density explains its long-term stability and isolation from the convecting asthenosphere

(Jordan 1978; Pollack 1986). The lithospheric mantle is often considered to be refractory, anhydrous, and cold, such that it would be difficult to generate large volumes of magmas from it (McKenzie 1989). In the presence of water, however,

4 significant quantities of melt may be generated entirely within the lithospheric mantle (Gallagher and Hawkesworth 1992).

Mafic magmas emplaced later in the Paleoproterozoic era produced numerous mafic dyke swarms intruding Archean cratons that ultimately rifted, followed by the deposition of volcano-sedimentary belts. Some basaltic units of these belts, along with their accompanying mafic dykes, share the trace element- enriched characteristics of modern continental flood basalts (CFB). A long- standing debate concerning these basalts centers on whether their trace element enrichment reflects the involvement of continental crust or an enriched mantle component (Collerson and Sheraton 1986; Patchett et al. 1994). Two classes of models have emerged to explain the incompatible element and isotopic characteristics of CFB magmas. The first involves two distinct source regions, with asthenosphere derived magmas interacting with either the continental crust

(Arndt et al. 1993), or small degree partial melts from the subcontinental lithosphere (Cadman et al. 1995; Ellam and Cox 1991; McKenzie 1989). The second class of models holds that the chemical characteristics of CFB magmas are largely inherited from a lithospheric mantle that had previously been enriched while beneath continents (Hawkesworth et al. 1984; Hergt and Brauns 2001).

These examples illustrate the lack of consensus concerning the source of mafic dyke swarms and CFB, and highlight the need for better targeted chemical and isotopic studies to resolve the roles of lithospheric and asthenospheric mantle in their origin. Although the subcratonic mantle is directly sampled by mantle xenoliths (Menzies 1990), the scarcity of kimberlites and alkali basalts hosting them limits their use to provide significant regional insights. Contrastingly, the

5 numerous and widespread mafic dyke swarms of Archean cratons offer promising vehicles with which to investigate the nature of the subcratonic mantle.

The Northeastern Superior Province of Canada (NESP) is an excellent place to investigate the relative contributions of the Precambrian crust and mantle to the generation of mafic magmas. Regional geological mapping programs by governmental agencies between 1991 and 2003 has produced a large chemical and

Nd isotopic data set (Simard 2008 and references therein). The many U-Pb age determinations obtained across the NESP further provide an ideal framework with which to examine the secular chemical and isotopic evolution of the Precambrian crust and mantle over one billion years, between ca. 2900 and 1900 Ma. This thesis focuses on the investigation of the major, trace, and rare earth element compositions, and Nd isotope systematics, of Archean greenstone belts and

Paleoproterozoic mafic dyke swarms of the Ungava Craton. The chemical signatures of the Archean basalts are first examined for their implications for the tectonic regime in which they were emplaced. The significance of the composition of Paleoproterozoic dyke swarms is then examined with respect to the enriched crustal and mantle components they record. An appraisal of the distribution, possible tectonic environments, U-Pb ages and Nd isotopic compositions of these dykes supply genetic links to the syn- to late tectonic magmas of the surrounding Circum-Ungava mobile belts. The results presented in this thesis provide new insights into the secular evolution of Precambrian cratons, by constraining the roles of the lithosphere and crust in the mafic magmatic events recorded in Archean greenstone belts and Paleoproterozoic dyke swarms.

6 References: Abbott, D.H. 1996. Plumes and hotspots as sources of greenstone belts. Lithos, 37: 113-127. Arndt, N.T., Czamanske, G.K., Wooden, J.L., and Fedorenko, V.A. 1993. Mantle and crustal contributions to continental flood volcanism. Tectonophysics, 223(1-2): 39-52. Ayer, J., Amelin, Y., Corfu, F., Kamo, S., Ketchum, J., Kwok, K., and Trowell, N. 2002. Evolution of the southern Abitibi greenstone belt based on U-Pb geochronology; autochthonous volcanic construction followed by plutonism, regional deformation and sedimentation. In Evolution of the Archean Abitibi greenstone belt and adjacent terranes; insights from geochronology, geochemistry, structure and facies analysis. Elsevier, Amsterdam. pp. 63-95. Bédard, J.H. 2006. A catalytic delamination-driven model for coupled genesis of Archaean crust and sub-continental lithospheric mantle. Geochimica et Cosmochimica Acta, 70: 1188-1214. Bédard, J.H., Brouillette, P., Madore, L., and Berclaz, A. 2003. Archaean cratonization and deformation in the northern Superior Province, Canada; an evaluation of plate tectonic versus vertical tectonic models. Precambrian Research, 127: 61-87. Boyd, F.R. 1989. Compositional distinction between oceanic and cratonic lithosphere. Earth and Planetary Science Letters, 96: 15-26. Cadman, A.C., Tarney, J., and Baragar, W.R.A. 1995. Nature of mantle source contributions and the role of contamination and in situ crystallisation in the petrogenesis of Proterozoic mafic dykes and flood basalts Labrador. Contributions to Mineralogy and Petrology, 122(3): 213-229. Calvert, A.J., Sawyer, E.W., Davis, W.J., and Ludden, J.N. 1995. Archaean subduction inferred from seismic images of a mantle suture in the Superior Province. Nature, 375(6533): 670-674. Campbell, I.H. 2003. Constraints on continental growth models from Nb/U ratios in the 3.5 Ga Barberton and other Archaean basalt-komatiite suites. American Journal of Science, 303: 319-351. Card, K.D. 1990. A review of the Superior Province of the Canadian Shield, a product of Archean accretion. Precambrian Research, 48(1-2): 99-156. Chardon, D., Choukroune, P., and Jayananda, M. 1996. Strain patterns, decollement and incipient sagducted greenstone terrains in the Archean Dharwar craton (south India). Journal of Structural Geology, 18: 991- 1004. Collerson, K.D., and Sheraton, J.W. 1986. Age and geochemical characteristics of a mafic dyke swarm in the Archean Vestfold Block, Antarctica - Inferences about Proterozoic dyke emplacement in Gondwana. Journal of Petrology, 27(4): 853-886. Collins, W.J., Van Kranendonk, M.J., and Teyssier, C. 1998. Partial convective overturn of Archaean crust in the east Pilbara Craton, Western Australia: driving mechanisms and tectonic implications. Journal of Structural Geology, 20: 1405-1424.

7 Coltorti, M., and Grégoire, M. 2008. Metasomatism in oceanic and continental lithospheric mantle: introduction. In Metasomatism in oceanic and continental lithospheric mantle. Geological Society, London. pp. 1-9. Dimroth, E., Imreh, L., Rocheleau, M., and Goulet, N. 1982. Evolution of the south-central part of the Archean Abitibi Belt, Quebec; Part I, Stratigraphy and paleogeographic model. Canadian Journal of Earth Sciences, 19(9): 1729-1758. Ellam, R.M., and Cox, K.G. 1991. An interpretation of Karoo picrite basalts in terms of interaction between asthenospheric magmas and the mantle lithosphere. Earth and Planetary Science Letters, 105(1-3): 330-342. Francis, D. 2003. Cratonic Mantle roots, remnants of a more chondritic Archean Mantle? Lithos, 71: 135-152. Gallagher, K., and Hawkesworth, C. 1992. Dehydration melting and the generation of continental flood basalts. Nature, 358: 57-59. Griffin, W.L., O’Reilly, S.Y., Abe, N., Aulbach, S., Davies, R.M., Pearson, N.J., Doyle, B.J., and Kivi, K. 2003. The origin and evolution of Archean lithospheric mantle. Precambrian Research, 127: 19-41. Hawkesworth, C.J., Rogers, N.W., Vancalsteren, P.W.C., and Menzies, M.A. 1984. Mantle enrichment processes. Nature, 311(5984): 331-335. Hergt, J.M., and Brauns, C.M. 2001. On the origin of Tasmanian dolerites. Australian Journal of Earth Sciences, 48(4): 543-549. Herzberg, C.T. 1993. Lithosphere peridotites of the Kaapvaal craton. Earth and Planetary Science Letters, 120: 13-29. Jordan, T.H. 1978. Composition and development of the continental tectosphere. Nature, 274: 544-548. Kimura, G., Ludden, J.N., Desrochers, J.P., and Hori, R. 1993. A model of ocean- crust accretion for the Superior Province, Canada. In The evolving Earth. Elsevier, Amsterdam, International. pp. 337-355. Lin, S. 2005. Synchronous vertical and horizontal tectonism in the Neoarchean: Kinematic evidence from a synclinal keel in the northwestern Superior Craton, Manitoba. Precambrian Research, 139: 181-194. Mareschal, J.C., and West, G.F. 1980. A model for Archean tectonism; Part 2, Numerical models of vertical tectonism in greenstone belts. Canadian Journal of Earth Sciences, 17(1): 60-71. McCulloch, M.T., and Bennet, V.C. 1993. Evolution of the early Earth: Constraints from 143Nd-142Nd isotopic systematics. Lithos, 30: 237-255. McKenzie, D. 1989. Some remarks on the movement of small melt fractions in the mantle. Earth and Planetary Science Letters, 95(1-2): 53-72. Menzies, M.A. 1990. Archean, Proterozoic, and Phanerozoic lithospheres. In Continental mantle. Oxford University Press, Oxford. pp. 67-86. Nelson, B.K., and DePaolo, D.J. 1985. Rapid production of continental crust 1.7- 1.9 b.y. ago: Nd and Sr isotopic evidence from the basement of the North American midcontinent. Geological Society of America Bulletin, 96: 746- 754. Patchett, P.J., Lehnert, K., Rehkamper, M., and Sieber, G. 1994. Mantle and crustal effects on the geochemistry of proterozoic dikes and sills in sweden. Journal of Petrology, 35(4): 1095-1125.

8 Peschler, A.P., Benn, K., and Roest, W.R. 2004. Insights on Archean continental geodynamics from gravity modelling of granite-greenstone terranes. Journal of Geodynamics, 38: 185-207. Pollack, H.N. 1986. Cratonization and thermal evolution of the mantle. Earth and Planetary Science Letters, 80: 175-182. Simard, M. 2008. Synthèse du Nord-Est de la Province du Supérieur. Ministère des Ressources naturelles et de la Faune, Québec. Stern, R.J. 2005. Evidence from ophiolites, blueschists, and ultrahigh-pressure metamorphic terranes that the modern episode of subduction tectonics began in the Neoproterozoic time. Geology, 33: 557-560. Stott, G.M. 1997. The Superior Province, Canada. In Greenstone belts. Oxford University Press, London. pp. 480-507. Sylvester, P.J., Campbell, I.H., and Bowyer, D.A. 1997. Niobium/ uranium evidence for early formation of the continental crust. Science, 275: 521- 523. Taylor, S.R., and McLennan, S.M. 1985. The Continental Crust; Its composition and evolution; an examination of the geochemical record preserved in sedimentary rocks. Blackwell, Oxford. Thurston, P.C. 2002. Autochthonous development of Superior Province greenstone belts? In Evolution of the Archean Abitibi greenstone belt and adjacent terranes; insights from geochronology, geochemistry, structure and facies analysis. Elsevier, Amsterdam. pp. 11-36. Tomlinson, K.Y., Stott, G.M., Percival, J.A., and Stone, D. 2004. Basement terrane correlations and crustal recycling in the western Superior Province; Nd isotopic character of granitoid and felsic volcanic rocks in the Wabigoon Subprovince, N. Ontario, Canada. Precambrian Research, 132(3): 245-274. Windley, B.F. 1995. The evolving continents, 3rd edition. Wiley, New York. Wyman, D., and Hollings, P. 1998. Long-lived mantle-plume influence on an Archean protocontinent; geochemical evidence from the 3 Ga Lumby Lake greenstone belt, Ontario, Canada. Geology (Boulder), 26(8): 719- 722. Zegers, T.E., and Van Keken, P.E. 2001. Middle Archean continent formation by crustal delamination. Geology, 29: 1083-1086.

CHAPTER 2

Evidence for a widespread mafic cover sequence and its implications for

continental growth in the Northeastern Superior Province

Abstract

Archean greenstone belts of the Northeastern Superior Province (NESP) were emplaced over a 160 Ma period (2.88-2.72 Ga), spanning a major episode of crustal reworking in which early tonalite-trondhjemite plutonism evolved to dominant granite-granodiorite and pyroxene-bearing felsic plutonism. The numerous greenstone belts that crop up across the craton contain lavas belonging to three mafic volcanic suites:

1) Mg-tholeiites that have chemical compositions typical of many Archean

basalts, with 4-10 wt.% MgO, 9-15 wt.% Fe2O3t, 0.4-1.2 wt.% TiO2 and

La/Sm ratios between 1 and 3.

2) Fe-tholeiites that have similar MgO contents and La/Sm ratios, but

markedly higher Fe2O3t (11-20 wt.%), TiO2 (1.0-2.6 wt.%), and Gd/Yb

ratios that may reflect derivation from a distinct garnet-bearing mantle

source.

3) Light rare earth element (LREE)-enriched rocks that have the chemical

characteristics typical of ‘calc-alkaline’ mafic magmas, with higher SiO2,

Al2O3 and La/Sm ratios, but lower Fe2O3t and TiO2 than the tholeiitic

suites at a given MgO content.

The presence of unconformities within single greenstone belts, numerous inheritance ages in volcanic rocks replicating those of older volcanic-plutonic assemblages, and the recognition of widespread, geographically separate, yet coeval (2.78 Ga) extrusive assemblages containing the distinctive Fe-tholeiites, do not support a plate tectonic model for a large portion of the NESP. The correlations in composition and ages of greenstone belts are more consistent with

a model in which they represent the remnants of an extensive autochthonous mafic cover sequence. Nd isotopic evidence for the presence of evolved crust in some syn-volcanic felsic plutons and volcaniclastic rocks implies that this mafic cover sequence was erupted onto an older granitoid crust.

The amalgamation of two isotopically distinct terranes at ca. 2.76-2.74 Ga created a proto-cratonic mass that consisted of a composite tonalite-trondhjemite- greenstone crust. Underplating by mafic mantle melts and widespread insulation after 2.75 Ga increased temperatures sufficiently to produce extensive melting of this crust to generate pyroxene-bearing felsic rocks and granodiorite to granite partial melts. The isotopically-enriched character of mantle-derived magmas after

2.75 Ga may reflect more extensive contamination by a felsic crust affected by widespread partial melting. Furthermore, a decrease of Nb/Th ratios in the

LREE-enriched mafic rocks younger than 2.75 Ga reflects a change in the nature of the crustal contaminant, from tonalite-trondhjemite prior to 2.75 Ga, to granite- granodiorite afterwards.

Keywords: Archean, Northeastern Superior Province, greenstone belts, geochemistry, continental growth

1. Introduction

Archean greenstone belts provide insights into the temporal evolution of the

Earth’s cratonic nuclei. Although widely studied, the origin of the continental crust and associated lithospheric mantle remains in dispute, and the nature of the tectonic processes that fashioned them is debated (Hamilton, 1998; de Wit, 1998).

Archean greenstone belts are characterized by a variety of lithological assemblages emplaced in different depositional settings that mirror their modes of emplacement. Genetic models for the origin of granite-greenstone terranes have historically split between two fundamentally different scenarios, plate tectonic versus vertical tectonic models. Many crustal growth models for Archean cratons call upon plate tectonic processes because of the systematic age-progression of volcano-plutonic belts (e.g. Card, 1990; Stott, 1997), the detection of dipping seismic reflectors interpreted to be relict subduction scars (Calvert et al., 1995), and the chemical similarities between Archean calc-alkaline rocks and those found at modern convergent boundaries. Plate tectonic models posit that the continents grow by the accretion of oceanic terranes (Dimroth et al., 1982;

Kimura et al., 1993) and amalgamation of continental nuclei of distinct isotopic characters (Tomlinson et al., 2004), occasionally coupled with interactions with mantle plumes (Abbott, 1996; Wyman and Hollings, 1998). The proposal that many greenstone assemblages from the Superior Province are essentially autochthonous constructions (Stott and Corfu, 1991; Ayer et al., 2002; Thurston,

2002), however, brings into question the common applicability of plate tectonic models for the internal growth of terranes prior to their amalgamation to older continental nuclei. Granite-greenstone terranes have also been interpreted to

reflect lithospheric-scale vertical processes because of: the synformal geometry of greenstone keels separating granitoid domes, the identification of ‘greenstone- down/pluton-up’ sense of shear indicators, the widespread occurrence of vertical lineations and rarity of lithologies representing accretionary mélanges, andesites, blueschists, as well as mass balance and thermal/viscosity constraints (Mareschal and West, 1980; Chardon et al., 1996; Collins et al., 1998; Zegers and Van

Keken, 2001; Bédard et al., 2003; Stern, 2005; Bédard, 2006).

This paper presents chemical, isotopic, and age data on greenstone belts and enclosing plutonic felsic rocks across the entire NESP, spanning a period of more than 200 million years (ca. 2.88-2.67 Ga, excluding the Paleoarchean

Nuvvuagittuq belt; Figure 2). We argue that despite their geographic dispersion, the scattered greenstone belts of a large portion of the NESP once constituted a continuous mafic supracrustal sequence, rather than being pieces of distinct, laterally-accreted terranes. We suggest that the mafic magmas covering a maturing tonalite-trondhjemite-greenstone crust evolved through the assimilation of variable amounts of water and felsic crustal material, generating a compositional continuum between ‘tholeiitic’ and ‘calc-alkaline’ magma that does not require the involvement of magmatic arcs in their genesis.

2. Geological framework

The Northeastern Superior Province (NESP) was formerly described as being composed mostly of granulite-grade granitoids (Card and Ciesielski, 1986).

Recent work by the Geological Survey of Canada and the Ministère des

Ressources naturelles et de la Faune of Québec (Leclair, 2005 and references

therein), however, have shown that the NESP is dominated by Neoarchean plutonic suites that engulf and rework scattered volcano-sedimentary belts.

Mapping by J. Percival and coworkers led to the partitioning of the NESP (the

Minto Block) into lithotectonic domains (Percival et al., 1997b) that have been subsequently modified on the basis of more recent mapping (Fig. 1: Leclair,

2005). The NESP is now further divided into two distinct regional-scale terranes

(Fig. 1), the isotopically-juvenile Rivière Arnaud terrane to the northeast (TDM =

3.0-2.8 Ga) and the isotopically-enriched Hudson Bay terrane to the west and southwest (TDM = 3.9-2.9 Ga).

Greenstone belts occur as relatively thin keels (1-10 km) that can be traced along strike for distances of up to 150 km. Many are engulfed by syn- to late tonalite-trondhjemite (TT) intrusions characterized by negative magnetic anomalies, while a smaller proportion are engulfed by late granodiorite-granite and enderbite-opdalite-charnockite (hereafter referred as the pyroxene-bearing felsic plutons) intrusions characterized by positive magnetic anomalies. The magmatic and metamorphic evolution of the NESP spans nearly 2 billion years

(3.8 – 1.9 Ga, as determined by zircon ages acquired by provincial and federal governmental surveys) and can be summarized as follows :

(i) The oldest rocks outcrop in the 3.8 Ga Paleoarchean Nuvvuagittuq belt

(David et al., 2004, Cates and Mojzsis, 2007; O’Neil et al., 2007) of the

Hudson Bay terrane (Figs. 1 and 2). Within this terrane, rare Mesoarchean

rocks occur either as relict ‘rafts’ or more commonly as assimilated remnants

identified by inherited zircon cores and old Nd model ages in younger rocks.

(ii) Voluminous tonalite-trondhjemite bodies and greenstone belts dominated by

mafic volcanic rocks were emplaced between 2.90 and 2.75 Ga (Figs. 3 and

4).

(iii) The onset of significant potassic magmatism occurs in the form of granite-

granodiorite plutons between 2.74 and 2.72 Ga (Fig. 4). These magmas

reflect a major episode of intracrustal melting, coeval with voluminous high-

temperature pyroxene-bearing felsic plutons (810-1100 °C; Percival and

Mortensen, 2002; Bédard, 2003; 2007). This period also records increasing

proportions of ‘calc-alkaline’ mafic rocks, felsic volcanic and felsic

volcaniclastic rocks in greenstone belts.

(iv) The emplacement of monzonite, granite, granodiorite, pyroxene-bearing

felsic plutons, diatexite and pegmatite bodies between ca. 2.70 and 2.67 Ga

marks further recycling of older lithologies.

(v) Small alkaline and carbonatite intrusions were emplaced locally between ca.

2.70-2.64 Ga (Fig. 4), associated with the hydrothermal activity recorded by

monazite grains in greenstone belts (Percival and Skulski, 2000) and along

brittle faults.

(vi) The intrusion of numerous mafic dyke swarms marks the beginning of the

Proterozoic eon (Buchan et al., 1998; Maurice and David, 2008), while the

intrusion of mafic-ultramafic alkaline lamprophyres and carbonatites at 1.94

Ga are the last known magmatic events in the NESP.

3. Geology and age of the greenstone belts

The greenstone belts of the Northeastern Superior Province (NESP) are small and dismembered compared to those found in the Southern and Western

Superior provinces. They are meta-volcano-sedimentary belts whose protolith consisted largely of basalt, pelite, and greywacke, with minor ultramafic rocks, mafic to felsic volcaniclastic rocks, andesite, rhyodacite, conglomerate, marble and iron formation. All the greenstone belts discussed in this study have been deformed and recrystallized in the amphibolite facies, but others have reached granulite facies conditions. The degree of deformation is quite variable and although primary textures (e.g. pillows, pillow breccias, layering and phenocrysts) can be locally identified within fold hinges, or low strain zones, the state of preservation of primary structures is typically too poor for stratigraphic tops to be determined with confidence, and the field relationships amongst many rock assemblages remain uncertain.

With the exception of the Paleoarchean Nuvvuagittuq belt, the volcano- sedimentary rocks of the NESP were deposited between 2.88-2.72 Ga (ca. 160

Ma, Table 1 and Fig. 4a). This study focuses on the lithogeochemistry of five greenstone belts from the Rivière Arnaud terrane (Buet, Curotte, Pélican, Nantais and Duquet) and two from the Hudson Bay terrane (Vizien and Roulier belts; Fig.

2). These greenstone belts preserve evidence for crustal and mantle evolution over a 100 Ma period (ca. 2.82 to 2.72 Ga) that largely predates the volcanism of the Wawa-Abitibi (ca. 2.75-2.69 Ga; Ayer et al., 2002 and references therein) and

Western Wabigoon (ca. 2.74-2.71 Ga; Tomlinson et al., 2004 and references therein) terranes, but overlaps with ages obtained in the Marmion (ca. 3.01-2.73

Ga), Winnipeg River (ca. 3.06-2.70) and North Caribou (ca. 2.99-2.72 Ga) terranes (Percival et al., 2006 and references therein).

3.1 Buet belt (2.82 Ga)

The 5 by 20 kilometer Buet belt is located in the northeastern part of Rivière

Arnaud terrane (Fig. 2) and dominantly comprises basaltic rocks (Maurice et al.,

2003). It is engulfed in a tonalite complex that yielded ages between ca. 2.81 and

2.77 Ga (Percival et al., 2001; David et al., 2008). Zircon fragments, with crystal faces, were recovered from a pillow basalt and yielded an age of ca. 2.82 Ga

(Table 1; Figs 3 and 4). All zircons have similar Th/U ratios, which suggest they record the same magmatic event rather than being inherited from various lithologies. The juvenile Nd isotopic composition of this sample (εNd2.82Ga = 3.3) does not support the presence of an older evolved contaminant. This could suggest that the recovered zircons once belonged to a contemporaneous volcaniclastic horizon or a syn-volcanic pluton that was digested by mafic lava flows, and thus represent the age of the belt.

3.2 Curotte belt (2.78 Ga)

The 2 by 10 km Curotte belt is engulfed in the same tonalitic unit 150 km to the SSW of the Buet belt, caught between two large pyroxene-bearing felsic complexes (2.72-2.74 Ga, Fig. 2; Madore et al., 2000; David et al., 2008). The data reported in this study were compiled from samples within the belt, and from dissected greenstone fragments occurring ~15 km to the East and West of Lac

Curotte. The greenstones are dominated by basaltic rocks, with subordinate pelite, iron formation, and minor felsic tuffs. A syn-volcanic quartz-feldspar porphyry (QFP) sill, injected into felsic crystal tuffs in the northern part of the belt, yielded a crystallization age of ca. 2.78 Ga, coupled with an inheritance age of ca. 2.83 Ga (Table 1).

3.3 Vizien belt (2.78 and 2.72 Ga)

The Vizien belt outcrops in the Hudson Bay terrane, close to the limit with the Rivière Arnaud terrane (Fig. 2), and has been described in detail by Skulski and Percival (1996). The belt consists of mid-amphibolite facies volcanic and sedimentary rocks and is interpreted as a collage of tectonically juxtaposed panels. A ca. 2.78 Ga mafic-ultramafic sequence comprises ultramafic schists with gabbroic pods and minor variolitic komatiites that are overlain by gabbro, pillowed basaltic andesite, and fragmental mafic rocks. Two younger ca. 2.72 Ga sequences are composed of a wide spectrum of mafic through felsic volcanic rocks interpreted to be continental arc and continental rift deposits (Skulski and

Percival, 1996: Table 1, Figs. 3 and 4). The ca. 2.78 and 2.72 Ga assemblages are fault-delimited, the oldest being interpreted as an allochthonous package. The presence of an inheritance age of ca. 2.79 Ga (within error of the 2.78 Ga assemblage) in a 2.72 Ga rhyolite raises the possibility that the oldest assemblage may be parautochthonous (Table 1, Fig. 3).

3.4 Pelican belt (2.74 Ga)

The Pelican belt is located in the central part of the Rivière Arnaud terrane

(Fig. 2) and is dominated by psammitic to pelitic paragneisses, with subordinate basaltic and felsic volcaniclastic rocks, iron formation, and conglomerate

(Cadieux et al. 2004 and references therein). Two samples taken 700 m apart along strike in a felsic volcaniclastic unit yielded identical crystallization ages of ca. 2.74 Ga (Table 1 and Figs. 3 and 4). A sample of granitic mobilisate in the paragneiss yielded an age of migmatisation at ca. 2.73 Ga, contemporary with the surrounding granites and pyroxene-bearing felsic plutons (ca. 2.72-2.74 Ga;

David et al., 2008).

3.4 Nantais belt (2.78 Ga)

The N-S trending Nantais belt (Fig. 2) crops out over a strike length of 50 kilometers to the north of the Pélican belt (Madore et al., 2002 and references therein). Most of the basaltic samples in this study were collected on a peninsula along the south shore of Lac Nantais, where felsic volcaniclastic and sedimentary rocks constitute a minor proportion of the assemblage (Labbé and Lacoste, 2001;

Madore et al., 2002). A felsic tuff from the Nantais belt yielded a crystallization age of ca. 2.78 Ga, coupled with an age of ca. 2.82 Ga obtained on inherited zircons (Table 1, Figs 3 and 4). These age relationships are identical to those obtained for the Curotte belt to the southeast (Table 1). A tonalite ‘raft’ engulfed in the voluminous ca. 2.73-2.71 Ga granite-granodiorite and pyroxene-bearing felsic plutons ~40 km to the East of the Nantais belt yielded an age of ca. 2.78 Ga, similar to the felsic tuffs (Percival et al., 2001; David et al., 2008).

3.5 Duquet belt (2.82, 2.78 and <2.76 Ga)

The Duquet belt is located in the northwestern part of the Rivière Arnaud terrane (Fig. 2) and has four arms caught between ovoid tonalite bodies, a geometry similar to that observed in the Qalluviartuuq-Payne belt to the southeast

(Fig. 2; Berclaz et al., 2005 and references therein). Its geology has been described in detail (Madore et al., 2004 and references therein), but more recent work furthers our understanding. The Duquet belt comprises three distinct supracrustal assemblages bounded by unconformities:

- Assemblage 1 is composed of basalt, plagioclase-phyric basaltic andesite,

layered amphibolite and subordinate rhyolite (Fig. 5). The basaltic unit

includes a massive rhyolite dated at 2822 Ma, an age within error of a

rhyolite sampled in a dissected fragment of the belt to the southwest

(2828 Ma). These two ages are identical to the crystallization age

obtained for the Buet belt, and to the inheritance ages documented in

many younger belts across the NESP (Table 1 and Fig. 3).

- Assemblage 2 is composed of massive to pillowed basalt and gabbro

intruded by a 2775 Ma QFP (Table 1, Figs. 3, 4 and 5). It is separated

from basaltic andesites of assemblage 1 by an unconformity marked by a

silicate iron formation.

- The younger assemblage 3 is dominated by sedimentary rocks and rests

unconformably on the QFP and basalts of assemblage 2 in the north-

central portion of the belt (Fig. 5; the unconformity ‘A’ in Percival et al.,

1997b). Zircons recovered in deformed clasts from a lower

conglomeratic unit of the younger assemblage provide a deposition age

of less than 2764 Ma (Figs. 3 and 5).

The layered mafic to intermediate amphibolites at the eastern margin of the southwestern arm of the belt were first included within the youngest assemblage

(Percival et al., 1997b). They are however intruded by a 2800 Ma tonalite and are thus better grouped with rocks of the older assemblage 1 (Fig. 5). Two tonalitic plutons bordering the belt to the northeast and northwest have yielded ages of

2775 and 2789 Ma respectively. These ages suggest that the felsic intrusive rocks are younger than the volcanic rocks of assemblage 1 and that some are coeval with those of assemblage 2.

3.6 Roulier belt (2.76 Ga)

The Roulier belt occurs in the northwestern part of the Hudson Bay terrane

(Fig. 2) and is distinguished from the nearby greenstone belt remnants in being less recrystallized, migmatized, and metamorphosed (Maurice et al., 2005a). The belt is dominated by basaltic rocks with smaller proportions of sedimentary and volcaniclastic rocks that make up ~10% of the belt. Zircons recovered from a felsic tuff in the central portion of the belt yielded a crystallization age of ca. 2.76

Ga (Table 1, Figs. 3 and 4).

3.7 Age patterns in NESP greenstone belts

Viewed globally, the available age data for the volcanic rocks indicate the occurrence of eight volcanic pulses at 20-40 Ma intervals across the entire NESP, commonly associated with coeval plutonic rocks (Figs. 3 and 4). Many other

greenstone belts have been reported (Leclair, 2005), but their chemical signatures are not as well documented as those reported here. Several belts are nevertheless constrained in time by U-Pb crystallization ages and many of the younger assemblages exhibit inheritance ages identical within error to those obtained on older assemblages (Table 1, Figs 3 and 4). The Duquet, Qalluviartuuq and Vizien belts comprise at least two distinct volcano-sedimentary assemblages (Winsky et al., 1995; Skulski and Percival, 1996; Percival et al., 1997b; Berclaz et al., 2005).

Unconformities marked by iron formations and conglomerates separate rocks aged 2.82 Ga, 2.78 Ga and <2.76 Ga in the Duquet belt, while the older assemblage of the Qalluviartuuq belt (ca. 2.85 Ga) is unconformably overlain by a younger (<2.77 but >2.73 Ga) assemblage. This younger assemblage is approximately concurrent with dated assemblages from at least three other greenstone belts of the NESP (Kogaluk, Roulier and Pélican belts: Table 1; Figs.

2, 3 and 4).

4. Geochemical results

This study presents new major and trace element chemical data, as well as bulk rock Nd isotopic determinations, but also incorporates data previously acquired in a variety of studies (Table 2) or recovered from the SIGEOM

(Système d’Information Géographique et Minière) database. Such a compilation involves the reconciliation of data acquired in several laboratories, an especially difficult task for trace elements. When possible, we compared the trace element data analyzed via two different methods (XRF and ICP-MS) or two different laboratories. As a consequence of this comparison, the XRF yttrium and niobium

results for the Pélican belt reported by Labbé and Lacoste (2001), and the 1998-

2001 SIGEOM database samples were not used in this study.

The mafic rocks of the seven greenstone belts (Table 2) have basaltic to basaltic andesite compositions that can be divided into three distinct compositional suites; 1) Mg-tholeiite, 2) Fe-tholeiite, and 3) light rare earth element (LREE)-enriched suites. This subdivision is based on the chemical characteristics of the samples and is further constrained by the zircon dating available on possible coeval felsic units.

4.1 Mg-tholeiitic suite

The Mg-tholeiites have chemical compositions typical of many Archean basalts, with 4-10 wt.% MgO, 9-15 wt.% Fe2O3t and 0.4-1.2 wt.% TiO2 (Figs. 6 and 7; Table 3). These rocks display constant to slightly increasing Al2O3 with decreasing MgO (Fig. 6), and the most magnesian have Al, Ti and Fe concentrations similar to that of Archean komatiitic basalts (Fan and Kerrich,

1997). The Mg-tholeiites exhibit low incompatible trace element contents (15-85 ppm Zr), with Al2O3/TiO2 (>13) and Gd/Yb ratios (1.0-1.4) that are similar to those of Al-undepleted komatiites and komatiitic basalts of the Abitibi greenstone belt (AUK; Fig. 9). Although a few samples scatter towards the composition defined by Archean granitoids in trace element ratios plots (Fig. 8), most have

La/Sm and Nb/Th ratios that cluster around primitive mantle values.

The Mg-tholeiites are found in all volcanic assemblages other than those with an age of 2.78 and 2.72 Ga (Fig. 3), including the Duquet, Buet, Roulier and

Pélican belts (Figs. 2 and 3). Unpublished bulk rock data from the Qalluviartuuq

belt indicate that its older assemblage (2.85 Ga; Table 1) is also characterized by

Mg-tholeiites (Figs. 3 and 4 of Skulski et al., 1996).

4.2 Fe-tholeiitic suite

The Fe-tholeiite suite exhibits a similar range in Mg contents (4-10 wt.%

MgO) to the Mg-tholeiites, but is generally higher in Fe (11-20 wt% Fe2O3t) and

Ti (1.0-2.6 wt% TiO2) at any given Mg content (Figs. 6 and 7). The Fe-tholeiite suite also has higher incompatible trace element concentrations (50-155 ppm Zr), with lower Al2O3/TiO2 (<15) and higher Gd/Yb ratios (1.2-2.0), similar to those of Al-depleted komatiites and komatiitic basalts of the Barberton greenstone belt

(ADK; Fig. 9; Table 3). Aluminum, however, remains relatively constant with decreasing MgO in the Fe-tholeiite suite down to 5 wt.% MgO, and their lower

Al2O3/TiO2 ratios are thus caused by high Ti contents rather than low Al (Fig. 6).

The Fe-tholeiite suite has primitive mantle-like La/Sm and Nb/Th ratios that are similar to those of the Mg-tholeiites, although a few scatter towards the composition of Archean granitoids (Fig. 8).

The Fe-tholeiites are found exclusively in the 2.78 Ga volcanic assemblages of the Nantais, Duquet, and Curotte belts (Figs. 2, 3 and 5). The few samples having compositions that overlap with the Mg-tholeiites (Figs. 6 and 7) are attributed to the Fe-tholeiite suite solely on the basis of their age. There are too few available analyses (n=2) to unambiguously identify Fe-tholeiites in the 2.78

Ga assemblage of the Vizien belt (Skulski and Percival, 1996). Nonetheless, calculations and relic igneous olivine crystals both suggest that the parental liquid to the peridotite sills of this assemblage were in equilibrium with Fo87 olivine

crystals (Skulski and Percival, 1996), a composition close to that required by the modeled OL-fractionation trend to yield the most primitive Fe-tholeiite samples

(the grey star in Fig. 11).

4.3 LREE-enriched suite

Most rocks of the LREE-enriched suite have higher SiO2 and lower TiO2 concentrations than the rocks of either tholeiitic suite at any given MgO content

(Fig. 6a). They also generally have higher Al (Fig. 6b) and lower Fe contents

(Fig. 7a). However, many samples can only be distinguished from the tholeiites on the basis of their trace element signature. The LREE-enriched rocks exhibit systematically higher La/Sm (>3) and lower Nb/Th (<6) ratios than primitive mantle. The younger LREE-enriched rocks (<2.75 Ga) are the most compositionally extreme, with the highest La/Sm but lowest Nb/Th ratios (Fig. 8).

Mafic rocks of the LREE-enriched suite, along with associated felsic volcaniclastic and volcanic rocks, become volumetrically more important relative to the tholeiitic suites in the youngest greenstone assemblages (< 2.75 Ga). The

LREE-enriched suite nevertheless occurs in greenstone belts with a wide range in ages. Both layered amphibolites and massive flows of assemblage 1 (2.82 Ga) in the Duquet belt belong to this suite, as well as basalt to basaltic andesites of the

Pélican (2.74 Ga) and Vizien (2.72 Ga) belts. Whereas only LREE-enriched rocks are documented in the 2.72 Ga assemblages of the Vizien belts, some Mg- tholeiites are intercalated with the LREE-enriched rocks in the Pélican belt and in the 2.82 Ga assemblage of the Duquet belt. In addition to the greenstone belts of this study, LREE-enriched mafic rocks have been documented in the Vénus (2.88

Ga), Qalluviartuuq (2.85 Ga and <2.77 Ga), Vallerenne (2.78 Ga), Kogaluk (2.76

Ga) and Duvert (2.72 Ga) belts (Table 1, Fig. 8; Skulski et al., 1996 and Boily et al., 2002). The insufficient detail of mapping in these belts, however, does not permit their stratigraphic relationships with tholeiitic suites to be established.

4.4 Nd isotopic data

More than 330 Nd isotopic analyses have been compiled from the entire

NESP (Maurice, 2007) and are divided according to isotopic terranes (Fig. 10a).

Mafic to ultramafic (MgO > 4 wt.%) mantle-derived plutonic and volcanic rocks older than ca. 2.75 Ga straddle the Nd isotopic composition of the depleted mantle, regardless of the isotopic terrane in which they occur (XεNd = 2.5 ± 0.3, n

= 32 for the Rivière Arnaud terrane and XεNd = 1.9 ± 0.8, n = 20 for the Hudson

Bay terrane). Younger (<2.75 Ga) mafic to ultramafic rocks, however, have variably enriched isotopic signatures in both isotopic terranes (XεNd = 0.8 ± 0.3, n

= 31 for the Rivière Arnaud terrane and XεNd = -0.3 ± 0.7, n = 31 for the Hudson

Bay terrane). This secular shift in the Nd isotopic compositions of mantle-derived magmas at 2.75 Ga appears to correspond with the emergence of :

1. K-feldspar-rich and pyroxene-bearing felsic plutons throughout the NESP

(Fig. 4a).

2. Larger volumes of LREE-enriched mafic magmas and associated felsic

volcaniclastic and volcanic rocks in greenstone belts.

Most of the greenstone belts discussed in this study occur in the relatively isotopically-juvenile Rivière Arnaud terrane (Figs. 1 and 2), the exception being

the Roulier and Vizien belts, which occur in the isotopically-enriched Hudson

Bay terrane. Samples of the Mg- and Fe-tholeiitic suites, along with their coeval gabbros and ultramafic rocks have, however, positive εNd(t) values (+1 to +3.8;

Table 4), regardless of the isotopic terrane in which they occur (Fig. 10b). The

LREE-enriched mafic rocks from belts older than 2.75 Ga also have positive

εNd(t) values that straddle the depleted mantle array (+1.9 to +3.3), but those in the younger belts (Pélican and Vizien) have markedly lower values (-0.5 to +1.7;

Fig. 10b). The felsic volcanic, volcaniclastic, and plutonic rocks coeval with the

2.82-2.83 Ga assemblages have juvenile isotopic signatures with positive εNd(t) values (+1.3 to +3.0), but the younger felsic rocks have more heterogeneous isotopic signatures, with εNd(t) values ranging between -1.4 and +3.9. The plutonic rocks intruding the volcanic assemblages also have more enriched isotopic signatures (-13 to -0.1), with the gabbros and tonalites intruding the

Roulier belt being the most enriched (Fig. 10 and Table 4).

5. Discussion

5.1 Element mobility and alteration

The interpretation of the chemistry of Archean rocks is not straightforward because of the post-magmatic processes they are likely to have experienced. In this study, the alkalis (e.g.: Na, K, Rb), alkaline-earths (e.g.: Ca, Sr, Ba), U and Pb were not used in the interpretations because of their mobility during postmagmatic alteration or metamorphic processes. Furthermore, basaltic samples in the Duquet belt with anomalously low CaO (< 5 wt%), high LOI (> 2 wt%), or high Na2O (>

5 wt%) concentrations are interpreted to be heavily altered and were omitted from our compilation. For the suite of samples used, the other major elements (Al, Ti,

Mg, Fe) appear to define cohesive magmatic trends and the high field strength trace elements (Nb, Ta, Hf, Zr, Y), and the rare earth elements (REE) display smooth profiles in chondrite-normalized diagrams indicating that they have been relatively immobile.

5.2 Origin of Mg- and Fe-tholeiite suites

The most magnesian samples of both tholeiitic suites have ~10 wt.% MgO and are not likely to have experienced significant gabbroic fractionation. The two tholeiitic suites have markedly different Ti and Fe contents at equivalent MgO, however, which preclude the possibility of a simple crystal fractionation relationship (Figs. 6, 7 and 9). One possible explanation for their differences is derivation through melting at different depths. The iron content of the initial melt of the mantle increases with pressure (Langmuir and Hanson, 1980), and the Fe- tholeiites might then be derived from greater depths than the Mg-tholeiites. If the magmas of the most magnesian Mg and Fe tholeiite samples once coexisted with a similar olivine composition (arbitrarily taken as Fo85 on Fig. 11), the intersection of their calculated liquid lines of descent with the line describing the locus of liquids in equilibrium (with Fo85) would indicate a temperature difference of ~60°C between the two (Fig. 11). Assuming the P-T gradient of the dry pyrolitic solidus to be 10-12°C/kbar (Green and Liebermann, 1976) leads to a 15-

20 km (5-6 kbar) depth difference in their origin (Fig. 11). Because the minimum pressure for garnet stability on the mantle solidus is ~25 kbar (80 km), this

pressure difference could be consistent with the higher Gd/Yb ratios of the Fe- tholeiites compared to the Mg-tholeiites (Fig. 9), suggesting the presence of greater residual garnet in their source (Jahn et al., 1982).

The most magnesian samples of the Fe-tholeiite suite, however, have Al contents similar to those of the Mg-tholeiites (Fig. 6b), which suggests that neither tholeiite suite equilibrated with significant residual garnet (Tuff et al.,

2005). Furthermore, the Fe-tholeiites do not exhibit the lower HFSE/REE ratios

(e.g. Zr/Sm) that have been argued to signify greater depth of melting (Xie et al.,

1993). In addition, the distinct Ti contents of the Fe- and Mg-tholeiite suites can not be explained by different depths of melting and suggest that the Fe-tholeiites originated from the melting of a mantle domain that was richer in both Fe and Ti than that of the Mg-tholeiites. The ‘garnet signature’ of the Fe-tholeiites could reflect a higher garnet-pyroxenite component in their source, compared to that of the Mg-tholeiites (Hirschmann and Stolper, 1996).

The most primitive samples of both tholeiite suites have slightly higher iron contents than that of modern mid-oceanic ridge basalts (MORB), but similar to those of the Ontong Java plateau and Columbia River continental flood basalts

(Figs. 7b and 7c). Although most NESP tholeiite samples do not exhibit the enrichments typical of crustal contamination in trace element ratio plots (Fig. 8), many lie off the low pressure dry gabbroic cotectic and scatter towards the major element compositions of the evolved granitoids (Figs. 6 and 7a). The lower Fe and Ti contents of NESP tholeiites relative to the low pressure gabbroic cotectic, at any given Mg, may reflect fractionation under hydrous conditions (Figs. 6 and

7a). The effect of water is to reduce the proportion of plagioclase in the cumulate

assemblage, such that liquid lines of descent diverge from the dry low-pressure gabbroic cotectic towards lower Fe and Ti contents and higher Al contents. A comparison of the NESP tholeiites to experimental and modeled liquid lines of descent indicates that the observed data are best fit by fractionation with ~1 wt.%

H2O, at pressures on the order of 1 kb (Fig. 6 and 7a). Such a small amount of water could have been derived by melting of hydrous mantle or by the assimilation of crustal material (e.g. sedimentary rocks) during ascent and emplacement of the magma (Stone et al., 2005).

Many NESP tholeiites have trace element ratios similar to those of primitive mantle, but others scatter towards higher La/Sm and/or lower Nb/Th ratios (Fig.

8). Although oceanic plateaux are frequently used as modern analogues to some

Archean greenstone belts (Puchtel et al., 1998), the lower Nb/Th ratios of many

NESP tholeiites relative to that of the Ontong Java plateau, coupled with the spread of some samples towards higher La/Sm ratios (Fig. 8) raises the question as to whether the NESP tholeiites interacted with an evolved felsic crust, as has been proposed for the Kerguelen plateau (Frey et al., 2002).

5.3 ‘Calc-alkaline’ signatures do not imply arc magmatism

The term ‘calc-alkaline’ is employed by many geologists in ways that differ fundamentally from Peacock’s (1931) original definition (Arculus, 2003).

Archean specialists engaged in the study of mafic to intermediate volcanic rocks typically use this term to refer to rocks having higher SiO2 concentrations for a given FeO*/MgO ratio (Miyashiro, 1974), or more simply to rocks defining a

‘calc-alkaline’ trend in an AFM diagram (Irvine and Baragar, 1971). Archean

lavas with high La/Sm, but low Nb/Th ratios, are routinely interpreted as being of subduction origin. The most accepted interpretations of this calc-alkaline signature is that it reflects high pressure (12-20 kbar) processes occurring at convergent margins, involving melting of the mantle wedge above a subducted zone or within the downgoing slab itself (Pearce and Peate, 1995). Contamination by evolved felsic material, however, can yield essentially identical ‘calc-alkaline’ geochemical signatures (Pearce, 2007), and the identification of an Archean tectonic environment on the basis of chemical comparisons with modern geological settings remains hazardous. For instance, the generation of the negative Nb anomaly associated with tonalitic rocks can be explained if ~2% rutile is kept in the melting residues of an anatectic basalt (Bédard, 2006).

Some samples of the LREE-enriched mafic suite cannot be distinguished from the tholeiites in terms of major elements (Figs. 6 and 7), but only on the basis of their higher La/Sm ratios (Fig. 8). The LREE-enriched samples trend towards higher Al at lower Mg contents, a trend that could reflect both crustal contamination and crystal fractionation at higher water pressures (Fig. 6b). The

LREE-enriched samples with high Al and Mg could be derived from tholeiitic parental magmas slightly more magnesian than the observed tholeiites. The

LREE-enriched magmas of the NESP exhibit the characteristics frequently attributed to calc-alkaline arc magmas, but they can also be explained with the coupled fractionation and crustal contamination of tholeiitic mantle-derived magmas in shallow to mid-crustal magma chambers (3-15 km). Similarly, a small amount of contamination by felsic anatectic melts could produce the negative Nb anomalies observed in the LREE-enriched basalts.

The older LREE-enriched rocks scatter between those of the tholeiite suites and those of coeval tonalite-trondhjemite magmas in a plot of Nb/Th vs. La/Sm

(Fig. 8). In contrast, the younger LREE-enriched magmas fall in an array between the tholeiite suites and the younger granite-granodiorite magmas (Fig. 8).

The fact that they fall along similar chemical trends could suggest that they shared similar petrogenetic processes, perhaps controlled by magmatic arc processes.

This contrast could alternatively suggest that the older LREE-enriched magmas are mantle-derived tholeiitic magmas contaminated by coeval tonalites, whereas the younger LREE-enriched magmas represent tholeiitic magmas contaminated by coeval granitoids.

The appearance of granite-granodiorite and pyroxene-bearing felsic plutonism at ca. 2.75 Ga (Fig. 4) marks an important point in the evolution of the

NESP. Proposals for the production of the <2.75 Ga crustal melts include the amalgamation of island and Andean-type arcs at 2.75-2.70 Ga (Percival et al.,

1994b), the docking of the Hudson Bay and Rivière Arnaud terranes prior to 2.74

Ga (this study), or the final steps of a ‘self-cannibalizing’ crust triggered by the delamination of dense eclogitic restites from partial melting of the mafic crust

(Bédard, 2006). Although the isotopic signature of the NESP felsic rocks requires the involvement of an evolved crust as old as ca. 3.0-3.1 Ga in the Rivière Arnaud terrane and ca. 3.7-3.8 Ga in the Hudson Bay terrane (Boily et al., 2008), mantle- derived magmas emplaced prior to 2.75 Ga in both terranes display juvenile isotopic signatures (Fig. 10a). The emplacement of large volumes of coeval granite-granodiorite and pyroxene-bearing felsic plutons after 2.75 Ga likely reflects widespread melting in the crust, producing favorable conditions for

extensive contamination of mantle-derived magmas (Thompson et al., 2002). The trace element systematics and lower εNd values of the LREE-enriched mafic volcanic rocks (Fig. 10), their dominance over tholeiites in the youngest greenstone assemblages and their common intercalation with Mg-tholeiites all support a petrogenesis involving an increasing crustal input to mantle-derived tholeiitic magmas with time, reflecting the extensive partial melting of the crust.

5.4 A widespread mafic cover sequence

Thurston (2002) argued for the autochthonous nature of many Archean greenstone belts of the Superior Province. The most direct lines of evidence are the identification of inter-assemblage unconformities within individual belts, and the presence of inherited zircon populations (Thurston, 2002). Inherited zircons in lavas must reflect the entrainment of older material by younger magmas. A striking correlation exists in the NESP between three ca. 2.82 Ga inheritance ages in geographically distinct 2.78 Ga assemblages (Nantais, Dupire and Curotte belts) that replicate the ages obtained from the two unconformity-bounded assemblages of the Duquet belt (Figs. 3 and 5). Three other 2.78 Ga inherited ages obtained in assemblages <2.76 Ga are identical within error to the magmatic age of at least six greenstone belts and seven tonalite samples of the NESP (Table

1, Fig. 3). The identification of eight inheritance ages in the greenstone belts across the NESP, reproducing within error the ages of older volcanic pulses (Fig.

3), strongly supports their autochthonous development on an older crust over a large area.

The restriction of the Fe-tholeiites to 2.78 Ga assemblages in greenstone belts across the Rivière Arnaud terrane (Nantais, Duquet and Curotte belts; Figs. 1 and 2) suggests that these greenstone belts, which are now scattered over more than 250 km, were once part of the same mafic volcanic sequence. Despite this coherent geochronological and geochemical framework, old supracrustal rocks have yet to be observed sitting unconformably on older TT bodies in the NESP.

Typically, lithological contacts between older greenstones and granitoids are strongly sheared or obliterated by intrusion of younger or coeval plutons, suggesting that the older unconformable contacts may not be preserved. In contrast, clearer unconformable relationships are observed between the granitoid basements and the younger belts (<2.72 Ga, e.g. the Juet belt; Maurice et al.,

2005b).

Although most mafic-ultramafic magmas emplaced prior to 2.75 Ga in the

Rivière Arnaud terrane have depleted-mantle εNd values, a few have enriched values between +1 and 0, implying the incorporation of an evolved crustal component into some mantle-derived magmas (Fig. 10a). Also, two 2.79 and 2.80

Ga tonalite bodies intruding the older assemblage of the Duquet belt yielded 3.05 and 2.98 Ga Nd model ages (Fig. 10a). Similarly, felsic tuffs from the 2.78 Ga

Nantais and 2.76 Ga Kogaluk belts have 3.02 and 2.91 Ga Nd model ages respectively (Fig. 10b). The Nd isotopic evidence for an evolved crust as old as

2.9-3.1 Ga in the genesis of some felsic rocks coeval to the greenstone belts of the

Rivière Arnaud terrane (Fig. 10b), and the evidence of tonalite-trondhjemite contamination in the older (>2.75 Ga) LREE-enriched mafic rocks (Fig. 8),

indicate that the proposed mafic cover sequence was emplaced on a pre-existing tonalitic crust that once covered a large portion of the NESP, before the emplacement of the voluminous younger (<2.75 Ga) plutons that obliterated its architecture.

5.5 Plate tectonic and vertical tectonic continental growth

The first continental growth models in the NESP involved the lateral accretion of allochthonous oceanic plateaux, oceanic arcs, and continental arcs via subduction-obduction processes (Percival et al., 1994b; Skulski and Percival,

1996; Percival and Skulski, 2000; Percival et al., 2001; Percival and Mortensen,

2002). Relict zircon cores and enriched εNd signatures within 2.74-2.72 Ga plutonic rocks of the Utsalik and Tikkerutuk domains support an interaction with an older cratonic basement, which, coupled with the presence of mantle-derived components (gabbros, pyroxenites), was taken as evidence that the young plutonic domains represents the former root zones of Andean-type continental arcs

(Percival et al., 1992; Percival et al., 1994b; Stern et al., 1994). Percival et al.

(2001) later concluded, on the basis of U-Pb ages on the plutonic rocks, that the ca. 2.70-2.71 Ga Tikkerutuk domain was accreted to previous ca. 2.84, 2.77 and

2.73 Ga arcs from the Rivière Arnaud terrane. The wide exposure of the ca. 2.74-

2.72 Ga magmatic event across the NESP, however, contrasts with the 50-100 km arc width and long-term magmatic productivity of the Andean template (Percival et al., 2001). This was taken as evidence for the presence of paired subduction zones with opposite facing directions (Percival and Skulski, 2000).

The lithotectonic domains comprising the NESP were first identified on the basis of reconnaissance mapping, and their extent was later extrapolated with the support of aeromagnetic maps (Percival et al., 1992; 1997b). The expression

‘lithotectonic domain’ implicitly suggests that the domains reflect the juxtaposition of physically distinct terrains. However, tectonic contacts between these domains are nowhere observed. The younger granitoids are commonly more magnetic than the older TT-greenstone rocks, such that it is their relative abundance that actually defines the domains. Trapped between, or at the margin of two 2.74-2.72 Ga continental arcs (i.e. the Utsalik and Tikkerutuk plutonic domains), the composite TT-greenstone crust recorded the intrusion of coeval plutonic rocks (Madore et al., 2002; Cadieux et al., 2004), but to a lesser extent, which suggests they nonetheless shared identical histories (Figs. 1 and 2).

Kilometer-scale ‘rafts’ of older TT (2.78-2.77 Ga) and greenstones (Nantais belt;

2.78 Ga) are both engulfed in the granite-granodiorite and pyroxene-bearing felsic plutons of the Utsalik domain. These relationships suggest that the Utsalik domain represents a remobilized older TT-greenstone crust. Although this would be compatible with a continental arc setting, there is no evidence for a systematic temporal progression of plutonic rocks across the craton, as would be expected in the accretion of a migrating arc (Percival et al., 2001). The key observation that argues against a plate tectonic scenario for the Rivière Arnaud terrane is that coeval Fe-tholeiites (2.78 Ga) occur to the west, east, and within the Utsalik domain, in the Duquet, Curotte and Nantais greenstone belts respectively (Fig. 2).

The plate tectonic paradigm for this portion of the NESP would thus require the

fortuitous collage of distinct terranes that all shared coeval basaltic rocks with identical Fe-rich characters.

The changes in trace element and isotopic characters of felsic plutonic and mantle-derived rocks (Figs. 8 and 10) at 2.75 Ga could reflect a switch from an oceanic to a continental arc environment. The compilation of both crystallization and inheritance ages available across the NESP, however, indicates that felsic magmatism appears to have been nearly continuous over 200 Ma (Fig. 4a). The repeated 20-40 Ma magmatic periodicity recorded in greenstone belts and mafic intrusions of the NESP (Fig. 4a) may indicate that cyclic mantle upwellings contributed to the heating of a maturing crust over time. A temporal analysis of the Earth’s high-Mg magmatic rocks has revealed similar periodicities of 26 ± 3 and 35 ± 5 Ma for magmatism in Archean and Phanerozoic times (Isley and

Abbott, 2002), while the analysis of a worldwide database on large igneous provinces (LIP) has shown the existence of a ca. 27 Ma periodicity for both continental and oceanic events (Prokoph et al., 2004). The comparable timeframes of LIP events with the basaltic pulses of the NESP, the overall continuous felsic magmatism record, and the occurrence of coeval 2.78 Ga Fe- tholeiites over a large surface area all argue against a plate tectonic model for the assembly of the Rivière Arnaud terrane.

Although plate-tectonic models cannot easily explain the internal architecture of either the Rivière Arnaud and Hudson Bay terranes, there are unresolved issues in considering alternative vertical tectonic models for the

NESP:

1) the supracrustal belts of the Qalluviartuuq domain (Figs. 1 and 2),

exhibit an elevated length/width ratio that contrasts with that expected

for a tectonic regime dominated by diapiric movements;

2) vertical tectonics provides no explanation for the dominant NNW

structural fabric of the plutonic domains (Fig. 2) and

3) vertical tectonics provides no explanation for differences between the

two isotopically distinct terranes.

The boundary between the two isotopic terranes is marked by a migmatized sedimentary basin in the Minto domain (Figs. 1 and 2). Although the absolute age of the wacke-siltstone sedimentary protolith of the basin is unknown, granitic neosomes imply a deposition before 2.70 Ga (David et al., 2008), while crosscutting felsic plutons indicate that it is older than 2.73 Ga (Maurice et al.,

2005b). Two 2.76 Ga ages obtained on felsic volcanic rocks from the sedimentary-dominated Kogaluc belt (Skulski et al., 1996) of the Minto domain make an age of ca. 2.76 Ga plausible for the deposition of the sedimentary rocks.

This paleo-basin could represent the margin to one or another of the two terranes, but few Nd data are available for the sedimentary rocks, and a U-Pb study of detrital zircons would be necessary to disentangle the provenance of the sediments. The extensive pyroxene-bearing crustal diatexites of the Tikkerutuk domain, whose protolith consisted largely of older TT (Maurice et al., 2005a), could be an indication that crustal thickening occurred in the western part of the

NESP during the docking of the two isotopic terranes (as postulated by Percival and Skulski, 2000 and Percival et al., 2001). However, geobarometric data do not

indicate high pressures (Percival and Skulski, 2000), which would not support a hard-docking (i.e. orogeny) scenario.

A possible model for the growth of the NESP involves the amalgamation of two isotopically distinct proto-cratonic terranes, constituted by TT and greenstones, between 2.76 and 2.74 Ga. The newly amalgamated craton was then underplated by voluminous basaltic melts and eventually underwent large scale melting. Large degrees of melting of the older TT crust would have generated enderbitic melts (Bédard, 2007), while smaller degrees of partial melting would have generated K-rich granodiorite and granite melts (Bédard, 2006). In such a scenario, the enriched Nd isotopic compositions of mafic and ultramafic magmas after 2.75 Ga (Fig. 10b) would largely be due to more extensive interaction with hot and partially molten crust, without a need for calc-alkaline oceanic or continental arc magmas. The trace element distinction between the older and younger LREE-enriched mafic volcanic magmas could reflect differences in their crustal contaminants, tonalite-trondhjemite prior to 2.75 Ga and granodiorite- granite afterwards (Fig. 8).

6. Concluding remarks

Archean greenstone belts of the Northeastern Superior Province (NESP), formed between 2.88 and 2.72 Ga, contain three geochemically distinct suites of mafic volcanics. The emplacement of the Mg-tholeiite, Fe-tholeiite and LREE- enriched suites encompass a secular change in the nature of coeval felsic magmas, from tonalite-trondhjemite prior to 2.75 Ga, to dominantly granite-granodiorite and pyroxene-bearing felsic plutons after 2.75 Ga.

The recognition of unconformities between greenstone assemblages, and the presence of numerous zircons with U-Pb inheritance ages corresponding to those of older volcanic or plutonic units suggest an autochthonous emplacement of greenstone belts across a large surface of the NESP. Although Fe-tholeiites requiring the involvement of a distinct Fe-rich garnet-bearing mantle reservoir are restricted to 2.78 Ga assemblages, they are found in greenstone belts across the entire Rivière Arnaud terrane. This suggests that the greenstone belts now scattered over more than 250 km were once part of the same cover sequence, which is not reconcilable with models in which the Rivière Arnaud terrane was built by the sequential accretion of distinct magmatic arcs. Nd isotopic data and zircon ages from felsic plutonic rocks coeval with some greenstone belts of the

Rivière Arnaud terrane require the presence of an evolved felsic crust as old as

2.9-3.1 Ga, and it is likely that the disparate greenstone belts of this terrane were emplaced onto an older composite tonalite-trondhjemite-greenstone crust.

A decrease in the Nb/Th ratios of LREE-enriched mafic magmas at 2.75 Ga likely reflects a change in the nature of their contaminant, from tonalite- trondhjemite prior to 2.75 Ga, to granite-granodiorite afterwards. This coupled evolution of the LREE-enriched mafic suite with coeval felsic crustal melts is strongly supportive of a model in which their ‘calc-alkaline’ signature reflects the assimilation of the evolved crust by mantle-derived tholeiitic magmas, rather than subduction-related arc processes. Our model for the evolution of the NESP differs from that of J. Percival and co-workers by postulating a single docking event of two isotopically distinct TT-greenstone terranes at ca. 2.76-2.74 Ga, whose contact is now marked by the migmatized sedimentary basin of the Minto

domain. The amalgamated cratonic block was heated by periodically underplating mantle-derived tholeiitic magmas at time intervals similar to that observed in large igneous provinces. This repeated mantle activity produced partial melting of the craton, leading to the production of voluminous granite, granodiorite and pyroxene-bearing felsic rocks that induced pluton-driven thermal metamorphic events, rather than a single orogenic metamorphic event. The increasing proportion of the LREE-enriched mafic suite in younger greenstone belts, and the isotopically-enriched character of mafic-ultramafic rocks after 2.75

Ga, reflect the more extensive contamination of mantle-derived tholeiitic magmas by a crust affected by widespread partial melting.

Acknowledgements

This research has been supported by grants from the Fonds québecois de la recherche sur la nature et les technologies (FQRNT) to C. Maurice and by a

National Scientific and Engineering Research Council of Canada (NSERC) discovery grant (RGPIN7977-00) to D. Francis. L. Madore kindly supported field logistics and helped sampling in the summers of 1999 through 2001. M. Leduc is acknowledged for his efficient sample organization of the MRNF archival collection. K.N.M. Sharma and P. Lacoste are thanked for their help with thin section descriptions. A. Berclaz, M. Boily, A. Leclair, O. Rabeau, P. Roy, M.

Simard and numerous colleagues of the MRNF are acknowledged for constructive discussions. Many thanks to R. Stevenson, B. Ghaleb, R. Lapointe and J. O’Neil for teaching C. Maurice the basics of Sm-Nd separation and for their assistance on the mass spectrometer. Our understanding of the Duquet Belt would have been

limited without the collaboration of M. Savard (Virginia Mines) and Y. Bourassa

(SRK consulting). J. Jobidon helped by reviewing the clarity of the figures.

Comprehensive reviews by J. Percival, P. Hollings and G. Stott resulted in significant improvements of earlier versions of the manuscript. Ministère des

Ressources naturelles et de la Faune contribution #2007-8430-04, Geological

Survey of Canada contribution #20080319, and GEOTOP contribution #2008-

0026.

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Figure caption Figure 2-1: Isotopic terranes (Boily et al., 2008) and domains of the Northeastern Superior Province (NESP; Leclair, 2005). Rivière Arnaud terrane in light grey and Hudson Bay terrane in white. The thick dotted outline indicates the location of Figure 2. Figure 2-2: Simplified geological map of the of the NESP (modified from Leclair, 2005) showing the distribution of Archean greenstone belts discussed in the text. Figure 2-3: Synoptic table of crystallization and inheritance ages recorded in greenstone belts of the NESP (see data listed in Table 1). Ages reported in the literature without errors were attributed hypothetical errors of ±5 Ma. Symbol height is 4 Ma, such that small error bars are not shown. The arrows outline minimum or maximum ages obtained on conglomeratic units and crosscutting dykes respectively. The shaded boxes outline the volcanic pulses at ca. 2880, 2850, 2820, 2780, 2760, 2740 and 2720 Ma. The location of all greenstone belts is shown on Figure 2. Figure 2-4: Frequency of a) U-Pb crystallization ages, and b) inheritance ages (in Ma) acquired on magmatic rocks of the NESP, with the names of all greenstone belts on which U-Pb ages were acquired. Rare Meso- and Paleoarchean crystallization ages >2950 Ma are not shown. Data from Percival et al. (1993; n = 3), Percival and Card (1994a; n = 11), Percival et al. (1996; n = 4), Skulski et al. (1996; n = 5), Skulski et al. (1997; n = 2), Percival et al. (1997b; n = 2), Percival and Skulski (2000; n = 3, including unpublished data by T. Skulski reported therein), Percival et al. (2001; n = 19), Percival and Mortensen (2002; n = 4), David et al. (2008; n = 78) and unpublished data by J. David (n = 49). Figure 2-5: Schematic cross section and geochronological summary of the Duquet belt (Fig. 2). U-Pb data from Percival et al. (1996); Percival et al. (1997b); unpublished data by T. Skulski reported in Percival and Skulski (2000); Bourassa (2002) and unpublished data by J. David.

Figure 2-6: a) TiO2 vs. MgO and b) Al2O3 vs. MgO in wt.% for the tholeiitic and LREE-enriched suites of the NESP. ‘TT’ shows the average composition

of 2.83-2.76 Ga tonalite-trondhjemite (K2O < 3 wt.%, n = 53, the black crosses), while ‘GG’ shows the average composition of 2.74-2.70 Ga

granite-granodiorite (K2O > 3 wt.%, n = 177, the grey crosses). The average granitoid compositions are calculated with data recovered from Bourassa (2002), Percival and Mortensen (2002), the SIGEOM database, and unpublished data of J. Bédard. The field labeled AK contains the compositions of both Archean Al-undepleted komatiitic basalt (AUK) and Al-depleted komatiitic basalt (ADK). The field labeled BCF contains the compositions of the Boston Creek ferropicrites (Stone et al., 1995). The field labeled LEF represents the Lake Enemy ferropicrites (Francis et al., 1999). The arrows correspond to the liquid lines of descent (LLD) based on the fractionation models obtained from the MELTS program (Ghiorso and Sack, 1995). Runs were conducted at temperature intervals of 25°C at an oxygen fugacity close to the QFM buffer. Water contents were varied

from 0 to 2.5 wt.% H2O at pressures between 0.5 and 5 kbar. For clarity, only the Fe-tholeiites LLDs are shown in figure 6a, those for the Mg-

tholeiites are similar, but shifted to ~0.5 wt.% TiO2.

Figure 2-7: MgO vs. Fe2O3 in wt.% for a) the tholeiitic and LREE-enriched suites of the NESP, b) recent mid-oceanic ridge basalts (MORB) and Miocene Columbia River continental flood basalts and c) Cretaceous basalts from the Kerguelen and Ontong Java plateaux. MORB, continental flood, and oceanic plateau data are filtered between 4 and 12 wt.% MgO. The dashed arrow shows a model gabbroic fractionation path involving olivine (Ol), clinopyroxene (Cpx), and plagioclase (Plag) in proportions close to the low pressure gabbroic cotectic (20% Ol, 30% Cpx and 50% Pl). The initial Fe3+/Fe2+ was set to 0.10, a condition approaching the QFM buffer. The dotted arrows in a) are LLD’s in water-saturated melting experiments on basaltic rocks at 1 and 2 kbar (Spulber and Rutherford, 1983). Ontong Java Plateau data from Mahoney et al. (1993a); Mahoney et al. (1993b);

Michael (1999); Tejada et al. (1996; excluding their alkalic rocks); Tejada et al. (2002) and Ely and Neal (2003). Kerguelen Plateau data from Neal et al. (2002); Frey et al. (2002) and Ingle et al. (2003). MORB glass data from the petrological database of the ocean floor and Columbia River data from a compilation obtain from the GEOROC database. Figure 2-8: Nb/Th vs. La/Sm for tholeiitic and LREE-enriched suites of the NESP. The black circles represent the LREE-enriched basalt to basaltic andesites of the 2.88 Ga Vénus (Boily et al., 2002), 2.82 Ga Duquet (this study and Bourassa, 2002) and 2.78 Ga Vallerenne (Boily et al., 2002) belts. The grey circles represent the LREE-enriched mafic rocks of the 2.74 Ga Pélican (this study), 2.72 Ga Vizien (Skulski and Percival, 1996) and 2.71 Ga Duvert (Boily et al., 2002) belts. Other symbols are as in figure 6. ‘TT’ indicates the average composition of the 2.83-2.76 Ga

tonalite-trondhjemite (K2O < 3 wt.%, n = 53), while ‘GG’ indicates the

average composition of the 2.74-2.69 Ga granite-granodiorite (K2O < 3 wt.%, n = 177). Twenty granitoid samples have La/Sm ratios >20 and do not show up on the diagram. The error bars on the average granitoid compositions correspond to a 90% confidence interval. The granitoid compositions are from ICP-MS data recovered from Bourassa (2002), Percival and Mortensen (2002), the SIGEOM database, and unpublished data by J. Bédard. The dashed lines indicate the simple mixing of a tholeiitic basalt whose composition approaches that of primitive mantle (PM) with the average old tonalite-trondhjemite (TT) and the average young granite-granodiorite (GG). The solid arrow shows the trend produced by fractional crystallization. The solid lines show the trends for assimilation fractional crystallization (r = 0.05) of the same tholeiitic basalt with the average granitoid, assuming a crystallization assemblage identical to that described in Fig. 7. Partition coefficients for olivine, clinopyroxene and plagioclase are from http://earthref.org/ and the bulk

partition coefficients are as follows: DLa = 0.066, DSm = 0.235, DNb =

0.009, DTh = 0.015. Ticks on AFC and mixing lines are spaced at 0.2F and

20% respectively. Primitive mantle values from Sun and McDonough (1989). Data for the Ontong Java plateau basalts from Mahoney et al. (1993a; 1993b). Data for the Kerguelen plateau from Neal et al. (2002), Frey et al. (2002) and Ingle et al. (2003).

Figure 2-9: Al2O3/TiO2 vs. Gd/Yb for tholeiitic suites of the NESP. The boxes labeled ‘AUK’ and ‘ADK’ represents the average value for Archean Al- undepleted komatiites of the Abitibi greenstone belt (n = 109) and Al- depleted komatiites of the Barberton greenstone belt (n = 59) recovered from the GEOROC database. The width and height of the rectangles correspond to a 95% confidence interval. The dotted arrow represents 60% low pressure crystal fractionation using the same parameters discussed in Figure 7. Figure 2-10: a) εNd(t) vs. age for the NESP divided according to MgO contents (mafic or felsic) and the isotopic terranes defined by Boily et al. (2008). Some symbols have been offset (±5 Ma) for clarity because of the number of data calculated with ages of 2820, 2780 and 2720 Ma. b) εNd(t) vs. age for rocks of greenstone belts from the NESP and engulfing tonalites. The individual greenstone belts are identified as follows: Q, Qalluviartuuq; D, Duquet; B, Buet; V, Vizien; C, Curotte; N, Nantais; R, Roulier; K,

Kogaluk and P, Pélican. An εNd2.73Ga value of -13 obtained on a tonalite intruding the Roulier belt is not plotted (Table 4). The array for the depleted mantle is taken from Stern et al. (1994). Values for the evolution of the 3.0-3.1 Ga crust are taken from samples reported by Tomlinson et al. (2004). The data other then those reported in Table 4 are compiled along with original sources in Maurice (2007). Figure 2-11 : Mg vs. Fe in cation units for the Mg-tholeiite and Fe-tholeiite suites. The two arrows represent liquid lines of descent controlled by olivine fractionation from hypothetical ultramafic parents having ~18 wt.% MgO. Parent A coexists with an olivine composition of ~Fo92, while parent B has a higher bulk Fe content and coexists with an olivine composition of ~Fo90. The grey star is the model liquid in equilibrium with a peridotite

sill of the 2.78 Ga mafic-ultramafic sequence of the Vizien belt (Fig. 7 of Skulski and Percival, 1996). Lines radiating from the center are isopleths for the Mg# of olivine coexisting with liquids whose Fe and Mg contents are given on the abscissa and ordinate respectively. The isotherms have

slopes of Kd (Fe/Mg) ~ -0.3 and are calibrated using melting experiments on dry spinel lherzolite at 20 kbar (Hirose and Kushiro, 1993). Olivine fractionation was modeled with a computer program in which olivine compositions were calculated using the expressions of Beattie et al. (1991). .

Table 2-1: U-Pb crystallization and inheritance ages obtained in greenstone belts from the NESP. Source of data: 1- David et al., 2008; 2- Percival et al., 1993; 3- Skulski and Percival, 1996; 4- unpublished data by J. David; 5- Percival et al., 1997a; 6- Skulski et al., 1996; 7- Percival et al., 1996 and 8- Bourassa, 2002. U-Pb methods as follows: ID-TIMS, Isotope Dilution and Thermal Ionization Mass Spectrometry; LA-ICP-QMS, Laser Ablation Inductively Coupled Plasma Mass Spectrometry using a Quadrupole-based Mass Spectrometer and LA-MC-ICP-MS, Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry.

Crystallization Inheritance U-Pb method Dominant rock type in assemblage Ref. Belts age (Ma) age (Ma) Chavigny (felsic tuff) ID-TIMS 2722 ± 4 - Rhyolite, rhyolitic tuff, sedimentary rocks 1 Vizien (Serindac ID-TIMS up to 2793 Rhyolite 2 rhyolite) 2722 +15/-8 Vizien (Lintelle ID-TIMS 2724 ± 1 - Rhyolite-andesite-porphytitic andesite 3 rhyolite) Vizien (gabbro) ID-TIMS 2786 ± 1 - Basalt - komatiite 3 LA-MC-ICP-MS 2739 ± 2 - 1 Pélican (felsic tuff) Paragneiss, andesite, rhyodacite ID-TIMS 2742 ± 1 - 4 Roulier (felsic tuff) ID-TIMS 2759 ± 1 - Basalt 1 Kogaluk (QFP) ID-TIMS 2757 +6/-4 none Paragneiss - calc-alkaline basalt 5 Kogaluk (felsic tuff) ID-TIMS <2759 ± 1 ca. 2770-2780 Paragneiss - calc-alkaline basalt 5 Duquet (QFP) ID-TIMS ca. 2775 - Basalt 6 Duquet (rhyolite) ID-TIMS 2822 ± 2 - Basalt - basaltic andesite 7 Duquet west (rhyolite) ID-TIMS ca. 2828 - Basalt - basaltic andesite 6

ID-TIMS 2777 ± 4 ca. 2810-2830 Nantais (felsic tuff) Basalt 1 LA-MC-ICP-MS 2782 ± 2 2819 ± 5 ID-TIMS 2782 ± 7 - Curotte (QFP sill) Basalt 1 LA-ICP-QMS 2776 ± 10 2830 ± 16 ID-TIMS 2786 ± 3 ca. 2815 Dupire (felsic tuff) Basalt 1 LA-ICP-QMS 2785 ± 8 2807 ± 21 Dupire (felsic tuff) LA-ICP-QMS 2798 ± 11 up to 2950 Basalt 1 Buet (pillow basalt) ID-TIMS 2818 ± 5 - Basalt 1 Qalluviartuuq* ID-TIMS <2768 / >2729 2826-2836 Calc-alkaline basalt 5 Qalluviartuuq LA-MC-ICP-MS <2851 ± 4 - Basalt 1 (anorthosite) * this age is bracketed by a cobble in a conglomerate overlying the older sequence and a diorite dyke cross-cutting the former.

Table 2-2: Authors, laboratory, number of samples and methods used for the quantitative analysis of major and trace elements as well as Nd isotopes for the greenstone belts from the northern part of the NESP.

Number Belt Elements of Laboratory Reference samples majors+traces 25 McGill Maurice et al., 2003 REEs 12 Actlabs Buet majors+traces 8 COREM SIGEOM database Nd isotopes 6 GEOTOP This study Nd isotopes 1 PC Boily et al., this volume majors+traces 4 COREM SIGEOM database majors+traces 6 INRS This study Curotte REEs 6 INRS This study Nd isotopes 1 PC Boily et al., this volume Nd isotopes 2 GEOTOP majors+traces 24 McGill This study REEs 11 ACME This study Nantais majors+traces 8 COREM SIGEOM database Nd isotopes 9 GEOTOP This study Nd isotopes 1 PC Boily et al., this volume majors+traces 22 McGill REEs 17 ACME This study Nd isotopes 9 GEOTOP Duquet majors+traces 11 Actlabs REEs 11 Actlabs Bourassa, 2002 Nd isotopes 7 GEOTOP traces 3 McGill REEs 3 McGill This study Pélican Nd isotopes 5 GEOTOP majors 6 XRAL Labbé and Lacoste, 2001 majors+traces 1 COREM SIGEOM database majors+traces 12 Vizien REEs 12 GSC Skulski and Percival., 1996 Nd isotopes 12 majors+traces 7 ACME SIGEOM database Roulier REEs 7 ACME Nd isotopes 10 GEOTOP This study

Table 2-3: Major (wt.%) and trace element (ppm) analysis for mafic rocks of the Pélican, Nantais, Duquet and Curotte belts. All samples were selected with extreme care to avoid fractures, anatectic melts, alteration, and veins. Fifty samples from the Pélican, Nantais and Duquet belts were cut to remove alteration, ground to remove saw marks, then crushed in a steel jaw crusher, and finally ground in an alumina shatterbox. Major elements, Co, Cr, Ga, Ni, Rb, Sr, V and Zn were analyzed by X-ray fluorescence (XRF) at the McGill Geochemical Laboratories using a Philips PW1400 spectrometer, and yielded totals of 100 ± 1%. The major elements, Ba, V, Cr, Ni, and Co were analyzed on fused discs using a α-coefficient technique. The other XRF trace elements were analyzed on pressed powder pellets using a Rh Kb Compton scatter matrix correction. The detection limits are based on three times the background sigma values and the relative precision for these elements is estimated to be better than 5%. The rare earth elements (REE), Nb, Zr, Y, Hf and Th were determined for twenty eight samples on a Perkin Elmer Elan 6000 quadrupole ICP-MS at ACME Analytical Laboratories Ltd. (Vancouver, BC). In the case of the Pélican belt samples, major elements, Co, Cr, Ga, Rb, Sr and Zn are from Labbé and Lacoste, 2001. Rare earth elements on the later samples were acquired at the McGill Geochemical Laboratories (Montréal, QC) using a Perkin Elmer ELAN DRCplus ICP-MS, with a fusion sample decomposition. Major elements of Curotte belt samples were analyzed at INRS-Québec with the ICP-AES method. NAD83 UTM zone 18 coordinates.

Table 3 Sample AC1142A JY9014A1 JY9031A1 00-CM-027 00-CM-030 00-CM-031 00-CM-033 Easting 577550 581804 582289 573525 573635 573702 573791 Northing 6649640 6636234 6634062 6760162 6760168 6760172 6760173 Zone 18 18 18 18 18 18 18 LREE- LREE- LREE- Suite Fe-tholeiite Fe-tholeiite Fe-tholeiite Fe-tholeiite enriched enriched enriched Age (Ga) 2.74 2.74 2.74 2.78 2.78 2.78 2.78 Belt Pélican Pélican Pélican Nantais Nantais Nantais Nantais Major elements in wt%

SiO2 54.6 48.9 55.7 49.01 51.58 52.8 50.66

TiO2 0.83 1.069 0.773 1.51 1.29 1.34 1.6

Al2O3 17.6 15.5 16.4 16.11 15.86 15.66 14.91

Fe2O3 9.12 13.5 8.33 16.21 13.08 11.77 16.58 MnO 0.14 0.19 0.15 0.21 0.26 0.21 0.25 MgO 4.44 8.88 4.68 4.03 4.98 4.83 4.12 CaO 7.43 10.5 6.79 8.38 9.7 10.56 8.82

K2O 1.7 0.15 1.25 0.71 0.21 0.21 0.28

Na2O 3.76 0.93 4.39 3.95 3.33 3.02 2.42

P2O5 0.25 0.06 0.23 0.19 0.1 0.1 0.18 LOI 0.92 0.65 0.55 0.44 0.31 0.37 0.14 Total 100.79 100.329 99.243 100.75 100.7 100.87 99.96 Trace elements in ppm (XRF) Co 0 48 23 38 45 43 48 Cr 20 217 74 115 247 228 168 Ga 0 4.6 20.1 23 18.3 18.4 21.4 Ni - - - 33 76 83 202 Rb 61 1.4 132.1 25 3.1 2.9 4.4 Sr 788 16.9 677.9 212.7 151.9 127.2 113.4 V - - - 137 308 324 143 Zn 0 112 92 118 115 92 151 Trace elements in ppm (ICP-MS) Hf - - - 3.5 2.3 2.8 4 Nb - - - 5.9 3.2 3.3 6.7 Th - - - 1.3 0.6 0.7 1.2 Y - - - 40.5 28.5 27 44.2 Zr - - - 111.3 69.6 75.2 120.6 La 24.76 6.93 15.37 10.2 4 3.4 5.3 Ce 52.41 17.68 35.84 21.7 9 10 12.8 Pr 6.56 1.75 4.21 3.5 1.7 1.84 2.44 Nd 28.85 8.43 17.92 16.9 8.5 9 14.6 Sm 5.14 1.25 2.95 5 3.2 3 4.3 Eu 1.601 1.195 1.097 1.79 0.98 1.16 1.5 Gd 3.91 1.94 3.2 6.06 3.97 4.59 6.86 Tb 0.607 0.27 0.407 1.2 0.81 0.79 1.16 Dy 2.93 1.47 1.76 7.05 4.56 4.67 7.06 Ho 0.557 0.315 0.345 1.53 1.12 1.02 1.48 Er 1.583 0.955 0.977 4.51 3.01 3.02 4.87 Tm 0.227 0.14 0.137 0.64 0.45 0.48 0.66 Yb 1.4 0.97 0.94 4.37 2.84 2.78 4.65 Lu 0.21 0.155 0.132 0.64 0.42 0.4 0.69

Table 3 (continued) Sample 00-CM-037 00-CM-053 00-CM-076 00-CM-079 00-CM-081 00-CM-083 00-CM-086 Easting 573860 575496 574279 574473 574565 574676 567831 Northing 6760132 6764750 6758304 6758270 6758271 6758205 6745436 Zone 18 18 18 18 18 18 18 Suite Fe-tholeiite Fe-tholeiite Fe-tholeiite Fe-tholeiite Fe-tholeiite Fe-tholeiite Fe-tholeiite Age (Ga) 2.78 2.78 2.78 2.78 2.78 2.78 2.78 Belt Nantais Nantais Nantais Nantais Nantais Nantais Nantais Major elements in wt%

SiO2 50.66 47.54 50.36 52.37 48.63 51 50.1

TiO2 2.19 1.17 1.26 1.46 1.26 1.37 1.36

Al2O3 12.55 15.87 16.97 14.33 14.98 15.05 15.19

Fe2O3 19.13 14.33 12.63 14.07 14.88 14.27 14.45 MnO 0.29 0.19 0.17 0.18 0.26 0.19 0.19 MgO 4.56 7.56 4.56 6.21 6.19 7.15 7.37 CaO 8.63 10.63 11.75 9.53 11.9 9.15 8.58

K2O 0.31 0.09 0.27 0.15 0.17 0.13 0.15

Na2O 2.13 3.02 2.47 2.04 1.98 2.24 3.15

P2O5 0.21 0.09 0.11 0.14 0.1 0.12 0.12 LOI 0.17 0.4 0.33 0.31 0.25 0.14 0.16 Total 100.83 100.89 100.88 100.79 100.6 100.81 100.82 Trace elements in ppm (XRF) Co 61 61 48 49 43 48 45 Cr 0 349 355 154 219 198 204 Ga 20.6 17.8 18.2 17.9 17.8 19.1 19.3 Ni 38 149 167 53 139 66 67 Rb 6.5 3.1 4.6 3.6 2.6 3 3.7 Sr 119.8 78.9 178.5 112 93.7 116.7 111.3 V 244 289 304 329 313 302 333 Zn 166 95 64 80 104 113 95 Trace elements in ppm (ICP-MS) Hf 4.1 2 2.3 3.4 1.8 2.6 2.5 Nb 6.5 2.8 3.2 4.3 3 4.1 3.8 Th 1.8 0.8 0.8 0.9 1.1 0.2 0.3 Y 50.1 26.9 27.5 36.1 26.1 31.3 31.5 Zr 136.1 65.3 69.8 91.9 67.3 80.1 81.7 La 9.2 5.4 5.5 5.3 13.2 4.5 4.2 Ce 20.6 11.6 12.2 12.2 22.3 12.8 11.5 Pr 3.54 1.91 1.96 2.16 3.35 2 1.81 Nd 18.1 10.2 10.3 12 15.8 9.4 10 Sm 5.3 2.9 3.5 4.1 3.7 3.3 3.6 Eu 1.75 1.02 1.03 1.34 0.95 1.41 1.14 Gd 7.49 4.04 4.52 6 5.08 4.78 4.82 Tb 1.42 0.78 0.82 1.11 0.79 0.76 0.88 Dy 8.4 4.58 4.79 6.89 4.83 4.88 4.87 Ho 1.84 0.99 1.08 1.38 1 1.12 1.16 Er 5.12 3.02 2.96 4.17 3.17 3.2 3.27 Tm 0.82 0.43 0.47 0.67 0.5 0.46 0.53 Yb 5.11 2.59 2.74 4.06 2.96 3.05 3.42 Lu 0.75 0.39 0.42 0.58 0.43 0.54 0.56

Table 3 (continued) 02-CM- 02-CM- 02-CM- 02-CM- 01-LM- 01-LM- 01-LM- Sample 2500 2502 2504 2506 1128 1130 1131 Easting 476503 477005 477632 478396 474301 474896 475132 Northing 6693409 6693780 6693793 6693872 6677881 6677813 6677860 Zone 18 18 18 18 18 18 18 LREE- LREE- LREE- Suite Fe-tholeiite Fe-tholeiite Fe-tholeiite Fe-tholeiite enriched enriched enriched Age (Ga) 2.78 2.78 2.78 2.78 2.82 2.82 2.82 Belt Duquet Duquet Duquet Duquet Duquet Duquet Duquet Major elements in wt%

SiO2 49.55 50.04 49.08 45.57 56.69 53.44 50.72

TiO2 2.01 1.257 1.15 1.12 0.39 0.91 1.24

Al2O3 14.38 13.95 15.06 14.79 18.89 16.18 15.69

Fe2O3 16.77 15.46 14.70 15.49 6.50 10.66 14.19 MnO 0.187 0.2 0.22 0.22 0.09 0.17 0.22 MgO 5.67 6.1 6.44 8.68 5.79 4.66 4.91 CaO 8.63 9.16 9.95 10.69 6.87 9.13 9.96

K2O 0.14 0.18 0.16 0.20 0.25 0.63 0.56

Na2O 2.26 3.05 2.64 2.41 3.95 3.85 2.59

P2O5 0.241 0.106 0.10 0.09 0.12 0.22 0.22 LOI 0.19 0.33 0.30 0.60 0.60 0.73 0.26 Total 100.028 99.833 99.81 99.86 100.14 100.58 100.56 Trace elements in ppm (XRF) Co 45 54 41 54 35 31 41 Cr 62 75 175 191 237 64 0 Ga 22.1 20.6 20.1 20.4 16.7 16.1 21.6 Ni 41 88 80 140 152 30 33 Rb 6 5.8 6.1 6.5 9.8 43.6 7.9 Sr 147.9 201 149 197.4 208.3 266.6 182.5 V 308 266 274 239 97 203 255 Zn 25 25 33 4 9 33 76 Trace elements in ppm (ICP-MS) Hf 4.1 2.5 1.9 1.9 1.8 1.9 2.8 Nb 8.7 3.9 3.4 5.3 2.8 5.8 5.3 Th 2.3 0.4 0.4 0.5 1.4 0.9 1.1 Y 41.5 20.7 26.4 20.7 12.2 17.4 27.6 Zr 148.4 68.8 65.6 72.9 81.3 67.9 97.4 La 14.8 4.8 3.5 7.9 19.5 20 17 Ce 32.4 12.4 10.3 17.2 36.8 45.2 38.1 Pr 4.44 1.86 1.61 2.65 4.93 6.57 5.24 Nd 20.5 9.1 8.3 12.8 19 24.7 21.9 Sm 5.6 3.1 2.9 3.6 3.5 5 4.6 Eu 1.71 1.26 1.14 1.23 0.78 1.43 1.41 Gd 6.7 4 4.14 3.9 2.01 4.56 4.7 Tb 1.12 0.68 0.72 0.67 0.39 0.52 0.7 Dy 6.86 4.22 4.49 3.91 1.8 2.91 4.4 Ho 1.59 0.79 0.97 0.8 0.4 0.58 1.01 Er 4.33 2.25 2.8 1.98 1.07 1.63 2.84 Tm 0.65 0.34 0.46 0.3 0.18 0.25 0.43 Yb 3.97 2.16 2.74 1.81 1.07 1.7 2.77 Lu 0.62 0.32 0.4 0.26 0.15 0.25 0.43

Table 3 (continued) 01-LM- 01-LM- 01-LM- 01-LM- 01-LM- 01-LM- 02-CM- Sample 1132 1134 1137 1138 1139 1141 2507 Easting 475218 475640 455125 455263 455848 456019 478918 Northing 6677867 6677573 6660348 6660273 6660245 6660235 6693711 Zone 18 18 18 18 18 18 18 LREE- LREE- Mg- Mg- LREE- Mg- LREE- Suite enriched enriched tholeiite tholeiite enriched tholeiite enriched Age (Ga) 2.82 2.82 2.82 2.82 2.82 2.82 2.82 Belt Duquet Duquet Duquet Duquet Duquet Duquet Duquet Major elements in wt%

SiO2 49.87 53.70 47.58 46.30 56.80 53.27 51.49

TiO2 1.00 0.55 1.10 0.79 0.70 0.68 0.56

Al2O3 16.08 18.11 15.50 15.63 15.67 14.94 17.64

Fe2O3 13.43 7.49 15.27 13.53 7.94 9.44 8.42 MnO 0.21 0.11 0.23 0.26 0.20 0.21 0.12 MgO 4.56 5.65 7.16 7.83 6.10 6.99 8.46 CaO 9.89 10.84 10.05 12.73 11.28 11.92 7.68

K2O 0.67 0.30 0.16 0.12 0.14 0.34 0.09

Na2O 4.04 3.45 2.85 1.86 1.49 1.83 4.04

P2O5 0.31 0.10 0.09 0.07 0.08 0.08 0.20 LOI 0.36 0.34 0.49 0.89 0.44 0.53 1.42 Total 100.42 100.64 100.48 100.01 100.84 100.23 100.12 Trace elements in ppm (XRF) Co 41 37 49 63 47 41 35 Cr 0 171 86 79 276 273 354 Ga 21.5 15.6 23.1 18.8 14.6 13.7 18.3 Ni 10 155 93 257 69 67 195 Rb 11.1 6.3 6.7 5.3 6 8.5 5.4 Sr 216.8 125.9 148.2 160.1 120.4 122.4 388.1 V 229 113 285 199 219 214 125 Zn 76 30 72 60 0 6 20 Trace elements in ppm (ICP-MS) Hf 2.5 1.9 2.2 1.2 1.5 1.5 2 Nb 10.2 2.9 2.3 1.6 2.3 2 3.8 Th 2.1 0.7 0 0.2 1.3 1.3 1.6 Y 21.9 10.1 24.1 18.7 16.7 16.4 16.3 Zr 86.6 56.2 57.3 43.5 53.4 52.3 82.3 La 27 7.6 3 2.2 8 5.8 19.2 Ce 66 17.3 8.6 6.7 15.4 12.2 42.9 Pr 9.09 2.35 1.42 1.02 2.02 1.8 5.26 Nd 36.9 10 7.4 4.6 8.7 8.4 22 Sm 7.4 2.2 2.6 1.9 2.3 2.1 4 Eu 1.89 0.79 1.1 0.62 0.78 0.7 1.05 Gd 6.16 2.24 4.12 2.48 2.69 2.43 2.92 Tb 0.73 0.31 0.72 0.5 0.46 0.38 0.53 Dy 4.06 1.93 4.06 3 2.81 2.69 2.86 Ho 0.75 0.38 0.93 0.71 0.6 0.6 0.6 Er 2.12 1.02 2.76 1.83 1.94 1.88 1.53 Tm 0.31 0.19 0.37 0.28 0.27 0.29 0.27 Yb 2.06 1 2.34 1.75 1.83 1.58 1.51 Lu 0.31 0.16 0.41 0.25 0.27 0.29 0.23

Table 3 (continued) 02-CM- 02-CM- 02-CM- Sample 2508 2510 2512 3078B 3081A 3081B 3133A Easting 479015 479188 479814 376412 379348 379348 358277 Northing 6693697 6693495 6693545 6629287 6627507 6627507 6611739 Zone 18 18 18 18 18 18 18 LREE- LREE- LREE- Suite Fe-tholeiite Fe-tholeiite Fe-tholeiite Fe-tholeiite enriched enriched enriched Age (Ga) 2.82 2.82 2.82 2.78 2.78 2.78 2.78 Belt Duquet Duquet Duquet Curotte Curotte Curotte Curotte Major elements in wt%

SiO2 53.39 51.88 53.05 48.61 53.33 53.32 49.05

TiO2 0.52 0.50 0.61 1.09 1.00 1.44 0.81

Al2O3 17.56 17.41 17.81 14.35 15.14 16.28 13.54

Fe2O3 7.70 7.94 8.37 13.61 9.41 10.91 13.82 MnO 0.11 0.11 0.12 0.22 0.18 0.26 0.21 MgO 7.46 8.15 6.14 6.93 6.78 5.11 7.02 CaO 9.15 10.76 9.04 10.51 9.81 8.44 10.23

K2O 0.21 0.08 0.16 0.48 0.46 0.78 0.47

Na2O 2.99 1.62 3.88 1.86 1.79 2.34 2.11

P2O5 0.16 0.13 0.13 0.06 0.07 0.08 0.05 LOI 1.02 1.39 0.65 4.03 0.73 1.28 1.04 Total 100.28 99.97 99.96 101.97 99.10 100.55 98.57 Trace elements in ppm (XRF) Co 38 34 0 65.7 33.8 58.6 63.7 Cr 320 387 256 169.3 160.9 100.6 205.7 Ga 18.2 17.7 20 - - - - Ni 167 222 107 - 52 44 97.54 Rb 7.7 5.6 6.2 2.2 4.4 15.88 5.3 Sr 265.1 214.1 386.7 117.7 77.6 62.8 91.3 V 113 117 132 332 342.5 414.5 281.4 Zn 5 11 0 69.9 69.8 72.8 58 Trace elements in ppm (ICP-MS) Hf 2.4 2.1 2.4 1.85 1.95 2.66 1.38 Nb 3.6 3.3 3 2.44 2.59 4.06 2.64 Th 1.3 1.3 0.6 0.14 0.68 0.46 0.3 Y 15.3 12.2 14.5 20.13 17.88 25.68 16.92 Zr 84.2 66.4 74.4 60.3 63.8 86.06 44.58 La 15.3 10.7 9.4 4.01 5.1 4.97 3.28 Ce 34.4 34 21.1 11.26 12.8 13.25 8.32 Pr 4.3 3.13 2.77 1.73 1.82 2.03 1.26 Nd 16.4 12.9 12.2 8.53 8.36 10.02 6.25 Sm 3.4 2.5 2.3 2.69 2.39 3.23 1.98 Eu 1.01 0.92 0.85 0.96 0.95 1.14 0.73 Gd 3.36 2.12 2.23 3.67 3.32 4.42 2.63 Tb 0.48 0.37 0.39 0.67 0.6 0.78 0.49 Dy 2.75 2.22 2.43 4.38 3.86 5.12 3.21 Ho 0.53 0.4 0.52 0.96 0.82 1.11 0.72 Er 1.52 1.27 1.39 2.9 2.52 3.39 2.07 Tm 0.25 0.22 0.24 0.34 0.3 0.44 0.28 Yb 1.34 1.33 1.26 2.17 1.9 2.71 1.75 Lu 0.23 0.21 0.21 0.33 0.3 0.43 0.26

Table 3 (continued) Sample 4102A 7177B Easting 380052 367409 Northing 6631277 6620560 Zone 18 18 Suite Fe-tholeiite Fe-tholeiite Age (Ga) 2.78 2.78 Belt Curotte Curotte Major elements in wt%

SiO2 49.74 49.02

TiO2 1.21 0.88

Al2O3 14.32 14.37

Fe2O3 16.09 13.08 MnO 0.20 0.21 MgO 6.98 7.32 CaO 9.06 10.93

K2O 0.43 0.18

Na2O 3.05 2.61

P2O5 0.08 0.07 LOI 0.34 1.06 Total 101.65 99.91 Trace elements in ppm (XRF) Co 85.2 42.7 Cr 125.3 239.9 Ga - - Ni 78 99 Rb 2.8 1.6 Sr 95.7 150.6 V 387.1 269.9 Zn 61.6 95.4 Trace elements in ppm (ICP-MS) Hf 2.24 1.63 Nb 2.53 3.41 Th 0.21 0.42 Y 29.57 19.01 Zr 68.51 56.01 La 3.32 3.63 Ce 10.56 9.48 Pr 1.62 1.47 Nd 8.63 7.15 Sm 2.89 1.99 Eu 0.92 0.83 Gd 4.44 2.98 Tb 0.79 0.52 Dy 5.51 3.49 Ho 1.23 0.73 Er 3.88 2.15 Tm 0.52 0.29 Yb 3.49 1.92 Lu 0.56 0.3

Table 2-4: Nd isotopic data acquired on whole rock samples collected in greenstone belts and in surrounding granitoids from the NESP. Ground samples were dissolved in a HF-HNO3 mixture in high-pressure Teflon vessels, with a 150Nd-149Sm tracer added to determine Nd and Sm concentrations. After evaporation, the samples were reacted with HClO4 and re-dissolved in 6M HCl. The remainder of the chemical procedure was adapted from Pin et al. (1994; 1997). The samples were transferred in chromatographic columns packed with 2 ml AG1X8 resin to remove iron. The clear solutions were next evaporated and transferred into 1M HNO3. The light rare earth elements were concentrated using ~100 mg of Eichrom’s TRU specific resin in small disposable columns and were immediately eluted in silica glass columns containing ~600 mg of Eichrom’s LN specific resin. The Nd and Sm isotopic compositions were measured on a VG Sector 54 mass spectrometer (at GEOTOP-UQAM-McGill, Montréal) in dynamic and static modes, respectively. 143Nd/144Nd ratios were normalized to 146Nd/144Nd = 0.7219. Repeated measurements of the JNdi-1 standard (Tanaka et al., 2000) yielded an average value of 143Nd/144Nd = 0.512139 ± 3 (n = 28). All 143Nd/144Nd ratios have been bias corrected by -0.000024 to yield the published standard 143 144 Nd/ Nd value of 0.512115. Nd-depleted mantle ages (TDM) are calculated using the model of DePaolo (1988). CHUR values for the calculation of the εNd notation as follows: 143Nd/144Nd = 0,512638 and 147Sm/144Nd = 0,1967. Crystallization and model ages are in billion years (Ga). TDM with high 147Sm/144Nd ratios (> 0.14) are not shown. Nd isotopic data acquired on samples dated with the U-Pb method are labeled ‘d’, while the ages interpreted from geological relationships are labeled ‘i’.

UTM NAD83 Nd Sm Sample NTS Suite Zone Age 147Sm/144Nd 143Nd/144Nd eNd(t) Tdm Easting Northing (ppm) (ppm) Buet greenstone belt 99-CM-021 25D Tonalite 386247 6747125 19 2.78 I 22.76 3.38 0.0896 0.510829 ± 12 2.97 2.73 1999022705 25D Tonalite 384986 6742596 19 2.78 I 30.36 4.95 0.0985 0.510965 ± 8 2.46 2.76 1999022802 25D Felsic tuff 382138 6750707 19 2.82 I 4.20 0.86 0.1242 0.511379 ± 8 1.77 2.85 2002034706 25D Mg-tholeiite 385921 6746926 19 2.82 I 9.15 2.48 0.1638 0.512076 ± 8 0.99 - 2002034707 25D Mg-tholeiite 389130 6737980 19 2.82 I 6.89 2.34 0.2053 0.512894 ± 9 1.89 - 2002034708 25D Mg-tholeiite 384827 6744658 19 2.82 I 4.19 1.38 0.1994 0.512807 ± 11 2.33 - Duquet greenstone belt 2002034835 35B Fe-tholeiite 476503 6693409 18 2.78 I 21.61 5.78 0.1617 0.512154 ± 7 3.07 - 2002034836 35B Fe-tholeiite 478396 6693872 18 2.78 I 12.85 3.58 0.1683 0.512281 ± 8 3.20 - 2001038770 35B Tonalite 485960 6699182 18 2.78 D 14.78 2.15 0.0877 0.510773 ± 10 2.64 2.76 2002034705 35B Rhyolite coble 476681 6693734 18 2.78 I 29.58 4.36 0.0891 0.510863 ± 8 3.93 2.68 2001038727 35B Rhyolite 480286 6685177 18 2.82 D 24.03 6.64 0.1671 0.512243 ± 9 3.05 - 2002034740 35B LREE-enriched 474896 6677813 18 2.82 I 26.07 4.93 0.1144 0.511253 ± 9 2.89 2.77 2002034742 35B LREE-enriched 475218 6677867 18 2.82 I 38.78 7.36 0.1147 0.511269 ± 11 3.09 2.75 2002034757 35B LREE-enriched 479015 6693697 18 2.82 I 17.50 3.36 0.1159 0.511283 ± 10 2.91 2.76 2002034759 35B LREE-enriched 479814 6693545 18 2.82 I 11.21 2.50 0.1347 0.511578 ± 9 1.86 2.85 Nantais greenstone belt 2000024407 35A Tonalite 580389 6762274 18 2.78 I 3.36 0.41 0.0732 0.510545 ± 12 3.34 2.72 2000025301 35A Felsic tuff 574652 6760056 18 2.78 I 31.28 4.52 0.0873 0.510771 ± 8 2.69 2.75 - - Nd duplicate* - - - - - 31.25 - - 0.510784± 11 - - 2002034729 35A Gabbro sill 574071 6760139 18 2.78 I 4.38 1.47 0.2021 0.512886 ± 12 2.92 - 2002034722 35A Fe-tholeiite 573525 6760162 18 2.78 I 15.92 4.62 0.1754 0.512384 ± 8 2.68 - 2002034727 35A Fe-tholeiite 573860 6760132 18 2.78 I 17.63 5.43 0.1861 0.512565 ± 10 2.39 - 2002034732 35A Fe-tholeiite 575496 6764750 18 2.78 I 8.88 2.80 0.1905 0.512709 ± 11 3.61 - 2002034733 35A Fe-tholeiite 574279 6758304 18 2.78 I 10.24 3.13 0.1850 0.512583 ± 8 3.14 - 2002034735 35A Fe-tholeiite 574565 6758271 18 2.78 I 8.85 2.87 0.1958 0.512785 ± 8 3.20 -

2002034736 35A Fe-tholeiite 574676 6758205 18 2.78 I 10.46 3.43 0.1982 0.512812 ± 7 2.87 - Pélican greenstone belt 2001032360 34P Felsic tuff 662226 6623896 18 2.74 D 34.79 5.14 0.0892 0.510793 ± 8 1.92 2.77 00-JY-9019C2 34P Felsic tuff 582105 6636755 18 2.74 I 21.50 3.24 0.0910 0.510803 ± 10 1.49 2.79 2000030239 34P LREE-enriched 577550 6649640 18 2.74 I 30.37 5.72 0.1139 0.511203 ± 9 1.23 2.83 00-JY-9014A1 34P LREE-enriched 581804 6636234 18 2.74 I 9.52 1.90 0.1207 0.511286 ± 9 0.46 2.90 00-JY-9031A1 34P LREE-enriched 582289 6634062 18 2.74 I 19.61 3.57 0.1101 0.511116 ± 8 0.88 2.85 Roulier greenstone belt 2003031406 34N Tonalite 398642 6589523 18 2.73 I 17.21 2.68 0.0942 0.510766 ± 7 -0.50 2.91 2003031435 34N Tonalite 405516 6590197 18 2.73 I 24.06 3.45 0.0865 0.510381 ± 9 -5.34 3.19 2003031499 34N Tonalite 407561 6585298 18 2.73 I 6.02 1.04 0.1046 0.510309 ± 9 -13.17 3.80 - - duplicate * - - - - - 6.02 1.04 0.1040 0.510314 ± 10 -12.85 3.78 - - duplicate ** - - - - - 6.41 1.09 0.1030 0.510325 ± 9 -12.253.73 2003031417 34N Gabbro 399398 6589871 18 2.73 I 34.17 7.13 0.1261 0.511148 ± 6 -4.29 3.30 2003031418 34N Gabbro 404910 6587376 18 2.73 I 6.45 1.86 0.1739 0.512223 ± 14 -0.08 3.19 2003031432 34N Felsic tuff 407973 6579228 18 2.76 D 53.21 6.84 0.0777 0.510493 ± 16 0.45 2.86 - - duplicate * - - - - - 53.15 6.86 0.0780 0.510514 ± 7 0.77 2.85 2003031416 34N Mg-tholeiite 399398 6589871 18 2.76 I 6.67 2.11 0.1913 0.512626 ± 10 1.71 - 2003031441 34N Mg-tholeiite 405516 6590197 18 2.76 I 7.97 2.65 0.2007 0.512805 ± 8 1.84 - 2003031489 34N Mg-tholeiite 404958 6584275 18 2.76 I 5.16 1.75 0.2057 0.512932 ± 6 2.56 - 2003031498 34N Mg-tholeiite 407561 6585298 18 2.76 I 4.97 1.59 0.1932 0.512676 ± 8 2.00 - * Duplicate from the sample solution ** Duplicate from the sample powder

Figure 2-1

Figure 2-2

Figure 2-3

Figure 2-4

Figure 2-5

Figure 2-6

Figure 2-7

Figure 2-8

Figure 2-9

Figure 2-10

Figure 2-11

CHAPTER 3

Les essaims de dykes mafiques du nord-est de la Province du Supérieur

Chapter 2 has examined the significance of the chemical signature of mafic magmas encountered in Archean greenstone belts aged 2.9-2.7 Ga across the

Northeastern Superior Province. We now shift to the Paleoproterozoic era (<2.5

Ga) and examine the regional distribution of the next mantle outbursts in time, expressed by the many mafic dyke swarms.

80 1. Introduction

Les essaims de dykes mafiques sont liés à des événements magmatiques importants s’étant produits sur tous les boucliers d’âge archéen depuis

2,5 milliards d’années (Ernst et al., 1995). Ces essaims peuvent être très impressionnants pour ce qui est du nombre, de la largeur et de la longueur des dykes. Les essaims les plus importants atteignent plus de 1000 km en longueur

(Fahrig et West, 1986), et le volume de magma généré pour remplir un seul dyke se compare à environ 100 ans de production de magmas basaltiques aux dorsales mid-océaniques modernes (McHone et al., 2005). Même s’ils constituent des unités géologiques appréciables, la communauté scientifique a manifesté peu d’intérêt pour ces roches avant la première conférence internationale sur les essaims de dykes mafiques qui s’est tenue à Toronto, en 1986 (International

Conference on Mafic Dyke Swarms; Halls et Fahrig, 1987).

L’étude des essaims de dykes mafiques contribue à la compréhension de l’histoire géologique d’une région. Leur mise en place peut marquer les derniers stades de stabilisation de la croûte continentale ou l’initiation de l’activité tectonique reliée au développement des ceintures volcano-sédimentaires contemporaines (Weaver et Tarney, 1981). Puisqu’ils se sont mis en place rapidement sur de grandes étendues, ils constituent des marqueurs temporels idéals pour élucider les champs de déformation régionaux, trouver des indices sur les processus tectoniques et donner de l’information sur la nature géochimique des sources mantelliques à l’époque de leur mise en place. La compilation présentée dans ce chapitre (Annexe A) et sur la carte qui l’accompagne (hors-texte)

81 améliore notre connaissance de la distribution des essaims de dykes mafiques du

NEPS, en contribuant non seulement à offrir un outil de corrélation géographique entre les cratons archéens fragmentés (Bleeker et Ernst, 2006), mais aussi à reconnaître les réseaux de fractures profondes qui pourraient avoir constitué des zones favorables à la mise en place de kimberlites diamantifères.

2. Les essaims de dykes mafiques

2.1 Caractéristiques générales

Les essaims injectant les cratons archéens peuvent être constitués de dykes de tailles variées (quelques centimètres à 200 m d’épaisseur), les plus petits représentant vraisemblablement des apophyses reliées aux dykes de plus grandes tailles. L’essaim de Mackenzie, le plus grand répertorié sur Terre (Territoires du

Nord-Ouest, Nunavut et Ontario; Fahrig et West, 1986), couvre une superficie d’environ 2,7 millions de kilomètres carrés, pour une longueur maximale de

2500 km. Ce type d’essaim géant montre fréquemment des motifs radiaux

(jusqu’à 150° à partir d’un point focal) et n’existe que depuis 2,5 Ga (Halls,

1987). La composition des dykes varie de pyroxénitique (dykes de Molson,

Manitoba; Scoates et Mecek, 1978) à monzodioritique (portions du Great Abitibi

Dyke; Ernst et Bell, 1992), mais les compositions basaltiques normatives en quartz sont les plus abondantes.

Les études géochronologiques des dykes d’un même essaim indiquent qu’ils se mettent en place très rapidement sur une grande surface (1267 à 1272 Ma pour les dykes de Mackenzie; Heaman et LeCheminant, 1993). Toutefois, des dykes de

82 plusieurs âges mais ayant le même aspect visuel peuvent avoir une même orientation. Un important programme de datation est alors nécessaire pour les différencier (French et al., 2004; Jourdan et al. 2006). De plus, des essaims d’âges différents peuvent montrer des relations de recoupement, mais de telles relations ne sont pas observées dans les essaims majeurs. Par exemple, les dykes de

Mackenzie (environ 1,27 Ga) ne recoupent pas les dykes de Matachewan (environ

2,47 Ma), l’essaim le plus vieux ayant probablement influencé la croûte en compressant la roche hôte (Ernst et al., 1995).

2.2 Mise en place et contexte tectonique

La géométrie et la mise en place des essaims de dykes sont régies par l’état des contraintes tectoniques au moment de leur intrusion. La portée de leur intrusion varie fortement selon les modèles tectoniques qui supposent soit des plumes mantelliques, afin d’expliquer le motif radial de certains essaims

(LeCheminant et Heaman, 1989; Ernst et al., 1995; Ernst et Buchan, 2001), soit des aulacogènes (rifts avortés; Fahrig et al., 1986; Fahrig, 1987).

Deux modèles sont proposés pour expliquer les mécanismes d’alimentation des essaims de dykes (Halls, 1987). Ils peuvent être alimentés soit horizontalement, à partir d’une chambre magmatique localisée à un niveau crustal ou mantellique, soit verticalement, à partir d’une chambre magmatique subcrustale aussi étendue que l’essaim ou migrant pendant l’intrusion. La propagation des dykes dans la croûte a longtemps été considérée comme étant verticale, mais une étude séismique sur des dykes reliés à un centre volcanique en

83 Islande indique un épanchement latéral sur plus de 100 km (Sigurdsson, 1987).

Les études de fabriques magnétiques sur des essaims majeurs concluent aussi à une propagation horizontale des dykes (Ernst, 1989; Ernst et Baragar, 1992), même si certains facteurs peuvent avoir contribué à l’effacement de ces fabriques

(McHone et al., 2005). Peu importe le modèle considéré, les études géochimiques des essaims de dykes mafiques indiquent que les magmas parentaux ont subi un important degré de cristallisation fractionnée dans des chambres magmatiques à des pressions inférieures ou égales à celles retrouvées à la base de la croûte continentale (Baragar et al., 1996).

3. Une nouvelle carte de compilation

3.1 Méthodologie

La plus récente compilation des essaims de dykes mafiques couvrant le nord- est de la Province du Supérieur provient de Buchan et Ernst (2004). En raison de son échelle (1 : 5 000 000) et de sa publication avant l’achèvement du Programme

Grand Nord, cette carte dresse un portrait incomplet de la région. De plus, les granitoïdes tardifs d’âge archéen étant fortement magnétiques, les dykes mafiques du NEPS peuvent difficilement être définis et tracés à partir de cartes magnétiques, et les photographies aériennes ne sont utiles que pour suivre les dykes majeurs dans le nord-est de la région, dans un secteur où les essaims de dykes sont déjà bien connus (Fahrig and West, 1986).

La base de données du SIGÉOM a été utilisée afin de compiler plus de

1782 sites où des dykes protérozoïques ont été observés. Dans les cas ambigus, les

84 notes manuscrites des géologues, les lames minces et les échantillons disponibles ont été consultés. La base de données du SIGÉOM a par la suite été uniformisée, tous les sites où des dykes d’âge protérozoïque ont été observés étant désignées avec le code lithologique « I3B » (diabase). Même si, en principe, ce terme réfère plus à une texture qu’à un type de lithologie, il n’en demeure pas moins que son utilisation facilite la discrimination entre les dykes de composition gabbroïque d’âge archéen et ceux du Protérozoïque.

La compilation a été utilisée pour produire une carte thématique (hors-texte).

Cette carte contient une base de données dans laquelle sont répertoriées les stations d’observation, y compris l’orientation et l’épaisseur de chaque dyke.

Lorsque ces informations sont manquantes, le champ a été laissé vide. Par contre, si l’estimation de l’épaisseur est manquante, mais que des indices laissent croire qu’il s’agit d’un dyke important (notes manuscrites des géologues, proportion relative du dyke en fonction de la taille de l’affleurement, échantillon ou lame mince ayant une granulométrie moyenne à grossière), une valeur de 99 est alors attribuée, signifiant que le dyke constitue un volume appréciable de l’affleurement. Sur la carte thématique, les dykes ne s’attachant à aucune station d’observation ont été numérisés à partir des compilations existantes (Fahrig et

West, 1986; Buchan et Ernst, 2004) ou des cartes régionales publiées par la CGC.

La longueur des dykes d’une épaisseur ≥10 m, tracés à partir d’une seule station d’observation, a été arbitrairement fixée à 20 km, tandis que celle des dykes d’une

épaisseur de ≥5 m mais <10 m a été fixée à 10 km. Afin de brosser un portrait

85 régional, les dykes de moins de 5 m d’épaisseur n’ont pas été tracés sur la carte de compilation, mais sont conservés dans la base de données.

4. Unités d’âge protérozoïque

4.1 Les roches supracrustales (2,17 à 1,80 Ga)

Les roches archéennes du NEPS sont entourées par des roches protérozoïques (Annexe A) qui se sont mises en place lors de l’Orogène Trans- hudsonien (Lewry et Collerson, 1990; Circum-Ungava geosyncline; Dimroth et al., 1970). Ces roches appartiennent à la Fosse du Labrador (Orogène du

Nouveau-Québec) à l’est (Wardle et al., 2002 ; Clark et Wares, 2004) et à la

Ceinture de Cape Smith (Orogénèse de l’Ungava) au nord (Taylor, 1982 ; St-

Onge et Lucas, 1990; Lamothe, 1994). À l’ouest, les îles Belcher, Hopewell et

Nastapoka sont aussi constituées de roches protérozoïques (Lee, 1965 ; Chandler,

1988). Au sud d’Umiujaq, dans le secteur du lac Guillaume-Deslisle, les roches protérozoïques du Graben de Richmond Gulf sont bien exposées (Chandler,

1988). Finalement, les roches sédimentaires protérozoïques de la Formation de

Sakami reposent sur le craton archéen, dans les secteurs du lac Gayot, du lac

Bienville et du lac Maricourt.

Les roches supracrustales de la Fosse du Labrador, orientées NNO-SSE, se sont mises en place en trois cycles volcano-sédimentaires, entre environ 2,17 et

1,80 Ga (Clark et Wares, 2004 et références incluses). Les plus vieilles roches du cycle 1 sont âgées d’environ 2,17 Ga (Rohon et al., 1993), ce cycle ayant possiblement pris fin vers 2,06 Ga (voir discussion de Clark et Wares, 2004). Le

86 cycle 2 inclut une séquence de plate-forme dont la déposition est limitée entre

1,88 à 1,87 Ga, selon les âges U/Pb obtenus dans des sills gabbroïques, un dyke de carbonatite et des roches volcaniques felsiques (Chevé et Machado, 1988;

Findlay et al., 1995; Machado et al., 1997; Wodicka et al., 2002). Finalement, le troisième cycle a produit des molasses synorogéniques qui se seraient déposées vers 1,80 Ga (Hoffman, 1987; Clark et Wares, 2004).

Les roches supracrustales de la Ceinture de Cape Smith, orientées E-O, contiennent des roches volcano-sedimentaires mises en place après l’ouverture d’un bassin dans le nord de la Province du Supérieur (Hynes and Francis, 1982;

St-Onge and Lucas, 1993). Les plus vieilles roches ont été cartographiées dans le sud, dans le Groupe de Povungnituk. L’âge d’un sill gabbroïque compris dans les roches sédimentaires de la base de la séquence situe le début de la déposition avant 2,04 Ga (Machado et al., 1993). L’âge d’une rhyolite dans la portion supérieure du Groupe de Povungnituk indique que le volcanisme et la sédimentation se sont poursuivis jusqu’aux environs de 1,96 Ga (Parrish, 1989).

Le second épisode magmatique est dominé par les basaltes tholéiitiques à picritiques du Groupe de Chukotat, lesquels chevauchent les roches du Groupe de

Povungnituk. L’âge de ces roches est moins bien connu, mais est probablement contemporain au cycle 2 de la Fosse du Labrador. En effet, un sill gabbroïque âgé d’environ 1,88 Ga s’est mis en place dans la portion supérieure de la séquence

(St-Onge et al., 1990). Les roches silicoclastiques du Groupe de Spartan et les roches volcaniques intermédiaires à felsiques du Groupe de Parent (environ 1,86 à

1,87 Ga; Machado et al., 1993) chevauchent les roches du groupe de Chukotat.

87 Plus au nord, le Groupe de Watts (2,00 Ga; Parrish, 1989) est interprétée comme une suite océanique démembrée (l’ophiolite de Purtuniq; Scott et al., 1992) qui est obduite sur les unités volcano-sédimentaires du sud.

D’autres roches volcano-sédimentaires protérozoïques sont retrouvées dans l’ouest du NEPS, mais les relations temporelles absolues y sont moins bien définies. Dans la baie d’Hudson, les îles Belcher sont constituées de roches sédimentaires déformées dans lesquelles s’intercalent deux unités de basaltes continentaux (les formations inférieure d’Eskimo et supérieure de Flaherty;

Ricketts and Donaldson, 1981; Legault et al., 1994). Un diagramme isochrone Pb-

Pb d’un échantillon de basalte appartenant à la formation la plus jeune donne un

âge imprécis de 1,96 ±0,08 Ga (Todt et al., 1984). Sur la côte est de la baie d’Hudson, dans le secteur du lac à l’Eau Claire, se trouvent des roches volcano- sédimentaires protérozoïques similaires (les groupes inférieur de Richmond Gulf et supérieur de Nastapoka; Chandler, 1988), mais qui sont moins déformées et qui reposent en discordance sur les roches archéennes. Les analyses effectuées sur des grains d’apatite diagénétiques provenant d’une unité de grès à la base du Groupe de Richmond Gulf donnent un âge de 2,03 ±0,03 Ga (Chandler et Parrish, 1989).

4.2 Les essaims de dykes mafiques (2,51 à 2,00 Ga)

Les nombreux essaims de dykes recoupant les roches archéennes du NEPS sont un complément unique à l’histoire géologique des unités de roches volcano- sédimentaires protérozoïques. Les dykes tracés sur la carte de compilation ArcGIS

(hors-texte) sont regroupés en essaims de différentes couleurs selon leur

88 orientation et, lorsque possible, en tenant compte des données géochronologiques existantes. Il faut toutefois considérer qu’en l’absence d’un important programme de datation, des dykes d’âges différents ayant des compositions similaires peuvent avoir une même orientation (French et al., 2004; Jourdan et al. 2006). Les dix

âges U/Pb considérés dans cette section proviennent des travaux de Buchan et al.

(1998) ou des travaux effectués par David et Maurice au centre GÉOTOP-

UQÀM-McGill. Les résultats de ces derniers seront publiés au cours de l’année

2009.

Les dix dykes datés sont tous du Paléoprotérozoïque. Les deux plus vieux essaims de la région se sont mis en place à la transition entre les éons Archéen et

Protérozoïque. Dans l’est de la région, l’essaim de Ptarmigan (2,51 Ga; Annexe

A; Buchan et al., 1998) est composé de dykes orientés NE pouvant atteindre une

épaisseur de 45 m. Dans le nord-ouest de la région, l’essaim d’Irsuaq est composé de dykes épars d’orientation N à NNO qui peuvent atteindre jusqu’à 200 m d’épaisseur. Leur âge est identique à celui des dykes de Ptarmigan.

Près de 300 Ma séparent ces deux essaims des nombreux autres qui se sont mis en place entre 2,2 et 2,0 Ga. L’âge radiométrique des dykes de Maguire

(Annexe A), orientés O à NO, est mal défini (2,23 ±0,03 Ga; Buchan et al., 1998).

Ces dykes se situent dans le centre de la région et s’injectent dans une zone d’environ 28 000 km2 qui a vu l’intrusion de très peu de dykes. Étant donné l’incertitude concernant leur âge, ces dykes pourraient être contemporains aux nombreux dykes générés vers 2,21 Ga, lors de l’événement magmatique

89 responsable de l’emplacement de l’essaim majeur de Klotz (ONO; Buchan et al.,

1998) ainsi que des essaims de Anuc et Kogaluk Bay (NO et ENE; Annexe A).

L’essaim de Couture (Annexe A) est composé de quelques dykes orientés

OSO à O, parallèlement à la Ceinture de Cape Smith, dans le nord de la région.

Leur mise en place à 2,20 Ga pourrait être liée à l’ouverture du bassin d’extension qui a précédé l’emplacement des roches sédimentaires du Groupe de Povungnituk.

Quant à l’essaim de Payne (Annexe A), il est formé par une population dense de dykes d’orientation NNO, parallèlement aux roches de la Fosse du Labrador. Ces dykes ont un âge compris entre 2,16 et 2,17 Ga (communication personnelle de S.

Pehrsson citée dans Ernst et Buchan, 2004) et marquent vraisemblablement l’extension des roches archéennes contemporaine à la mise en place des basaltes du cycle 1 dans cette région (Clark et Wares, 2004). Les données pétrographiques acquises sur ces dykes, à l’est de la Fosse du Labrador, montrent qu’ils ont subi une recristallisation au faciès des amphibolites, indiquant une mise en place avant l’Orogène Trans-hudsonien (>1,8 Ga; Madore et Larbi, 2000). Toujours dans le nord-est de la région, l’essaim de Pointe Raudot (Annexe A) est constitué de dykes d’orientation NE. Même si aucun âge radiométrique n’y a été obtenu, la composition minéralogique d’un dyke plissé montre que, contrairement aux dykes de Payne, le faciès des amphibolites n’a pas été atteint. Ceci implique une mise en place synchrone à tardive relativement à l’Orogenèse Trans-hudsonien (≤1,8 Ga).

Les dykes de rivière du Gué (Annexe A) sont orientés ENE, parallèlement aux roches de la Formation de Sakami, lesquelles sont préservées dans des demi-

90 grabens sur le craton Archéen. Elles sont interprétées comme des vestiges de

« l’Aulacogène du Lac Cambrien » (Hoffman, 1988), même si l’hypothèse d’un rift avorté n’est pas supportée par les directions obtenues sur les paléo-courants mesurés dans ces roches (Clark, 1984; Clark et Wares, 2004). En considérant le modèle de Hoffman (1988), l’essaim de Rivière du Gué délimiterait tout de même l’étendue et l’âge minimum (2,15 Ga) d’un tel rift. Cet âge est similaire à celui obtenu dans une roche volcanique felsique du cycle 1 de la Fosse du Labrador

(2,14 Ga; communication personnelle de T. Krogh, citée dans Machado et al.,

1997). Plus au sud, l’essaim de Minto (Annexe A), orienté ONO à NO, possède un âge identique à celui du Groupe de Watts, situé dans le nord de la Ceinture de

Cape Smith (2,00 Ga; Buchan et al., 1998).

Dans la région du lac Montrochand, Roy et al. (2004) ont mentionné la possibilité que les dykes orientés N à NNO (Annexe A) puissent appartenir à l’essaim du Lac Esprit (2,07 Ga; Hamilton et al., 2001), dont la localité type est située à la baie James (Goutier et al., 1999). Localisé le long de la baie d’Hudson, l’essaim d’Inukjuak (Annexe A) compte plusieurs dykes orientés NO

(Budkewitsch et al., 1991; Legault et al., 1994), mais aucun âge radiométrique n’y a été déterminé. Plusieurs autres dykes pour lesquels aucun âge n’est connu ou qui ne constituent pas d’essaims importants ont aussi été reconnus dans le cadre de notre compilation. Ces dykes, représentés sur la carte de compilation, ont des orientations préférentielles similaires aux essaims décrits plus haut, mais sont soit trop peu nombreux pour définir de nouveaux essaims, soit jugés trop loin des localités types pour être regroupés aux essaims existants.

91 Finalement, les dykes les plus jeunes de la région sont orientés NO et coupent les roches de la Ceinture de Cape Smith (Annexe A). Ces dykes sont par conséquent plus jeunes que 1,8 Ga et ont été attribués à l’essaim néoprotérozoïque de Franklin (environ 723 Ma) par Buchan et Ernst (2004). Puisqu’aucune datation isotopique n’a été effectuée sur ces dykes, ils pourraient aussi toutefois appartenir

à l’essaim mésoprotérozoïque de Mackenzie (environ 1,27 Ga).

4.2.1 Pétrographie

Les dykes mafiques sont massifs et homogènes, gris foncé à gris verdâtre avec une couleur d’altération brunâtre caractéristique. Leur granulométrie varie de fine à grossière, en fonction de l’épaisseur de chaque dyke. Ils ont des bordures figées aphanitiques de quelques centimètres. Les textures ophitiques et subophitiques sont les plus abondantes, quoique des textures amygdalaires, porphyriques ou trachytiques aient été observées localement. La roche, généralement de composition gabbroïque, est constituée de clinopyroxène et de plagioclase. L’orthopyroxène et l’olivine sont plus rarement observés. La magnétite est toujours présente en proportion plus ou moins importante, ce qui explique la variation de susceptibilité magnétique associée à ces roches. Le quartz interstitiel est commun, soit en grains ou en intercroissance (texture symplectique). Les textures ignées sont toujours préservées, même lorsque les pyroxènes sont remplacés par de l’actinote ou de la hornblende, le plagioclase par de la séricite et l’olivine par du talc ou de la serpentine. Des traces de zircon et de baddeleyite complètent l’assemblage minéralogique. Hormis les essaims de

Ptarmigan et d’Irsuaq, dont les compositions sont gabbronoritiques (olivine +

92 clinopyroxène + orthopyroxène), la nature des travaux effectués ne permet pas de discriminer les essaims selon leur composition pétrographique.

4.2.2 Géochimie

La géochimie des dykes du NEPS fait présentement l’objet de travaux détaillés (Maurice et al., 2005, 2007). Ces travaux sont basés sur les analyses géochimiques contenues dans la base de données incluse avec la carte de compilation. Cette base de données contient les analyses des éléments majeurs et traces de 199 échantillons, en plus des analyses du Nd de 30 échantillons réalisés au centre GÉOTOP-UQÀM-McGill par Maurice. Le champ « code » contient les attributs « a » ou « f » signifiant que l’échantillon est interprété comme étant altéré ou frais. La grande majorité des échantillons altérés provient de dykes recoupant les roches archéennes du secteur du lac à l’Eau Claire.

5 Conclusions

L’apparition des essaims de dykes mafiques relativement tard dans l’histoire de la Terre suggère des changements importants dans la dynamique de la croûte et du manteau entre les éons Archéen et Protérozoïque, vers 2,5 Ga. Les dykes mafiques du NEPS, témoins de ces changements, se retrouvent sur l’ensemble du territoire.

Des études récentes montrent que plusieurs générations de dykes mafiques peuvent être répertoriées à l’intérieur d’un même essaim, suggérant que la mise en place des magmas s’effectue dans des faiblesses lithosphériques préexistantes

93 (Mège et Korme, 2004; Jourdan et al., 2004; French et al., 2004; Jourdan et al.

2006). Dans le même ordre d’idées, plusieurs champs de kimberlites montrent un alignement de leurs cheminées, suggérant que des structures profondes ont contribuées à leur distribution (Wilkinson et al., 2001). Les essaims de dykes mafiques de la Province des Esclaves étant beaucoup plus vieux (2,23 à 1,27 Ga) que les kimberlites diamantifères éocènes du lac de Gras, de tels anciens réseaux de fractures ont probablement constitué des zones favorables à leur mise en place

(Wilkinson et al., 2001). En plus de parfaire la géométrie et l’étendue des essaims de dykes mafiques déjà connus et d’en documenter de nouveaux, la compilation présentée ici pourra contribuer à l’élaboration future d’un modèle régional pour l’exploration des kimberlites diamantifères dans le NEPS.

94 Références

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CHAPTER 4

Enriched crustal and mantle components and the role of the lithosphere in

generating Paleoproterozoic dyke swarms of the Ungava Peninsula, Canada

We have appreciated in chapter 3 the abundance and distribution of

Paleoproterozoic mafic dyke swarms across the Northeastern Superior Province.

Chapter 4 aims to decipher their nature and provenance in the mantle at the regional scale.

100

Abstract

Paleoproterozoic mafic dyke swarms (2.5-2.0 Ga) of the Ungava Peninsula can be divided in three chemical groups. The main group has a wide range of Fe

(10-18 wt.% Fe2O3) and Ti (0.8-2.0 wt.% TiO2) contents, and the most magnesian samples have compositions consistent with melting of a fertile lherzolitic mantle at ~1.5 GPa. Dykes of a low-LREE (light rare earth element) subgroup (La/Yb

≤4) display decreasing Zr/Nb with increasing La/Yb ratios and positive εNd2.0Ga values (+3.9 to +0.2) that trend from primitive mantle towards the composition of

Paleoproterozoic alkaline rocks. In contrast, dykes of a high-LREE subgroup

(La/Yb ≥4) display increasing Zr/Nb ratios and negative εNd2.0Ga values (-2.3 to -

6.4) that trend towards the composition of Archean crust. A low Fe-Ti group has low Fe (<11 wt.% Fe2O3), Ti (<0.8 wt.% TiO2), high field strength elements

(HFSE; <6 ppm Nb) and heavy rare earth elements (HREE; <2 ppm Yb) contents, but are enriched in large ion lithophile elements (LILE; K/Ti = 0.7-3) and LREE

(La/Yb >4). These dykes are interpreted as melts of a depleted harzburgitic mantle that has experienced metasomatic enrichment. A positive correlation of

Zr/Nb ratio and La/Yb ratio, negative εNd2.0Ga values (-14 to -6), and the presence of inherited Archean zircons further suggest the incorporation of a crustal component. A high Fe-Ti group has high Fe (>14 wt.% Fe2O3) and Ti (>1.4 wt.% TiO2) contents, along with higher Na contents relative to the main group dykes. Dykes of a high-Al subgroup (>12 wt.% Al2O3) share Fe contents,

εNd2.0Ga values (-2.3 to -3.4), La/Yb and Th/Nb ratios with Archean ferropicrites, and may represent evolved ferropicrite melts. A low-Al subgroup (<12 wt.%

101

Al2O3) has relatively lower Yb contents (<2 ppm) and fractionated HREE patterns that indicate the presence of garnet in their melting residue. A comparison with

~5 GPa experimentally-derived melts suggests that these dykes may be derived from garnet-bearing pyroxenite or peridotite. The εNd2.0Ga values (-0.3 to -2.0) of these dykes lie between the compositions of Archean granitoids and

Paleoproterozoic alkaline rocks, signifying their petrogenesis involved both crustal and mantle components.

Paleoproterozoic dykes containing a crustal component occur within, or close to, an isotopically enriched Archean terrane (TDM 4.3-3.1 Ga), whereas dykes without this component occur in an isotopically juvenile terrane (TDM < 3.1

Ga). The lack of a crustal component and the positive εNd2.0Ga values of dykes intruding the latter suggest that the crust they intruded was either too cold to be assimilated, or that its lower crust and/or lithosphere were Paleoproterozoic in age. In contrast, the ubiquitous presence of a crustal component and the diversity of mantle sources for dykes intruding the enriched terrane (lherzolite, harzburgite, pyroxenite) suggest a warmer crust with underlying heterogeneous lithospheric mantle.

Keywords: Paleoproterozoic, mafic dyke swarms, continental lithosphere, alkaline component, crustal component, North American Craton

102

1. Introduction

Proterozoic mafic (dolerite) dyke swarms are common to all Archean cratons and provide probes of the chemical composition and evolution of the

Earth’s mantle. Their message is, however, complicated by uncertainties about the relative roles of asthenosphere and lithosphere in their origin, as well as the effects of crystal fractionation and the assimilation of enriched crustal and/or mantle components (Tarney, 1992; Patchett et al., 1994; Condie, 1997). The magmas of many Proterozoic dykes have trace element characteristics that are similar to those of continental flood basalts (CFB), with light rare earth element

(LREE) and large ion lithophile element (LILE) enrichments, and Nb-Ta depletions relative to primitive mantle values. Petrogenetic models for the generation of such trace element signature typically range between two end- members, i.e. contamination of asthenospheric magmas by crust, or enriched lithospheric mantle sources (Tarney, 1992 and references therein). It is difficult to distinguish between these end-members on the basis of chemistry alone because the trace element signature of the continental crust (enriched in LILE and

REE, but depleted in Nb-Ta) is similar to that of metasomatized mantle (Tarney and Weaver, 1987; Boily and Ludden, 1991; Seymour and Kumarapeli, 1995;

Condie, 1997). Furthermore, radiogenic isotope analyses have not clearly resolved the problem, as some studies have concluded that enriched and heterogeneous lithospheric mantle is the source for CFB (Hart, 1985), whereas others propose an important role for crustal contamination (Carlson et al., 1981;

Peng et al., 1994; Baker et al., 2000).

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This paper presents a synthesis of the chemical data acquired on

Paleoproterozoic dyke swarms emplaced between 2.5 and 2.0 Ga in the Ungava

Peninsula of Canada (Figs. 1 and 2). We show that the Nd signature of enriched mafic dykes is inherited from an Archean crustal component, but that trace element systematics require the existence of two enriched components, one representing the Archean crust and the other a metasomatized lithospheric component. We argue that these dyke swarms reflect the composition of the continental lithospheric mantle in the Paleoproterozoic and investigate their use in probing its evolution.

2. Geological framework

Our study focuses on the Ungava Peninsula, that comprises rocks of

Precambrian age. Its center includes rocks of the Archean Northeastern Superior

Province (NESP) that are intruded by numerous Paleoproterozoic mafic dykes.

The NESP is surrounded by Paleoproterozoic supracrustal belts emplaced during the Trans-Hudson Orogeny (Lewry and Collerson, 1990), ca. 1.8 Ga.

2.1. Northeastern Superior Province (NESP)

The NESP comprises dominantly Neoarchean plutonic suites in which small amphibolite to granulite-grade greenstone belts occur (Maurice et al., 2009 and references therein). It is separated into two isotopically distinct regional terranes

(Fig. 2) bordered by migmatized pelites to semi-pelites of the Archean Lake

Minto metasedimentary basin (Simard, 2008). To the Northeast, the Rivière

Arnaud Terrane groups Archean rocks having juvenile isotopic signatures (TDM <

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3.1 Ga), while to the West and South, the Hudson Bay Terrane preserves the remnants of a reworked Meso- to Paleoarchean craton, with Nd model ages up to

4.3 Ga (O’Neil et al., 2008; Boily et al., 2009).

2.2. Volcano-sedimentary Circum-Ungava belts

The Paleoproterozoic supracrustal belts surrounding the Archean rocks of the Ungava Peninsula range in age from 2.17 to 1.88 Ga (see the review in

Maurice et al., in press for a complete reference list of U-Pb ages). These supracrustal belts include the Labrador Trough to the East, the Cape Smith

Foldbelt to the North, and the Belcher and Ottawa Islands and associated coastal continental basalts (the Richmond Gulf and Nastapoka groups) to the West (Fig.

2).

The supracrustal belts host a variety of alkaline rocks that include alkaline basalts near Kenty Lake (Gaonac’h et al., 1992; Modeland et al., 2003), lamprophyres near Lac Leclair (Baragar et al., 2001) and Lac Castignon, and carbonatites near Lac Lemoyne (Wright et al., 1999). While the Lac Leclair lamprophyres must have ages >2.04 Ga, all the other alkaline occurrences were emplaced ca. 1.96-1.88 Ga, in the same time frame as the 1.94 Ga Lac Aigneau mafic to ultramafic lamprophyre dykes that intrude the Archean basement of the eastern Ungava Peninsula (Maurice et al., in press).

2.3. Mafic dyke swarms

Numerous mafic dyke swarms ranging in age between 2.51 and 2.00 Ga

(Buchan et al., 1998; Maurice et al., in press) intrude the Archean basement (Fig.

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1). The oldest ages were obtained on the small north trending Irsuaq (2508 ±6

Ma) and the NE trending Ptarmigan (2505 +2/-1 Ma; Fig. 1a) swarms.

These two early swarms are separated by 280 Ma from the many dykes emplaced 2.23-2.17 Ga in the northern Ungava Peninsula. The WNW trending

Klotz dykes (2209 ±1 Ma; Fig. 1b) represent a voluminous magmatic event that emplaced large individual dykes (up to 100m in thickness) that are traceable over strike lengths greater than 250 km. The slightly older NW trending Anuc dykes

(2220 ±3 Ma) appear to define a coherent swarm having a distinct trend that contrasts with the Klotz dykes. The few WSW trending Kogaluk Bay (2212 ±3

Ma; Fig. 1b) and Couture (2199 ±5 Ma) dykes also occur with the Klotz dykes, and are closer to them in age. Although not precisely dated, the WNW trending

Maguire dykes in the center of the Ungava Peninsula (2229 +35/-20 Ma) may be coeval with the Anuc, Kogaluk Bay and Klotz dykes. On the basis of U-Pb ages,

Buchan et al. (1998) suggested that the Maguire, Klotz, and Senneterre dykes

(Fig. 1b) defined a radiating dyke swarm whose magma spread laterally from a focus above a mantle plume south of Ungava Bay. This model has however been challenged on the basis of a compilation of more recent data on these dykes and geochemical differences between the swarms (Maurice et al., in press).

The Payne River dykes (ca. 2.17 Ga) in the northern portion of the Ungava

Peninsula comprise a dense population of NNW trending dykes (Fig. 2). The southern dykes of the Ungava Peninsula have relatively younger ages, with the

Rivière du Gué dykes (2149 ±3 Ma; Fig. 1c) being the oldest. Although no age data is available in the southwestern Ungava Peninsula, Roy et al. (2004) suggested that the N to NNW trending dykes therein could belong to the Lac

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Esprit swarm recognized further to the South (2069 ±1 Ma). Finally, the WNW trending Minto dykes (1998 ±1 Ma) have the youngest U-Pb age. The Inukjuak swarm is undated, but is believed to be 2.0-1.9 Ga (Buchan and Ernst, 2004).

Overall, the time and distribution of 2.2-1.9 Ga mafic dykes of the Ungava

Peninsula record an evolution from older dykes which occur mainly in the Rivière

Arnaud Terrane (2.23-2.17 Ga) to younger mafic and alkaline dykes that occur in the Hudson Bay Terrane (2.15-1.94 Ga).

Most Paleoproterozoic mafic dykes of the Ungava Peninsula are fine to coarse grained gabbros dominated by an assemblage of clinopyroxene and plagioclase. Gabbronoritic compositions are only documented in the oldest 2.5

Ga dykes (Irsuaq and Ptarmigan swarms, Buchan et al., 1998; Maurice et al., in press). Igneous textures and mineral assemblages are commonly well preserved, with pyroxenes being variously replaced by amphiboles, and plagioclase by sericite. Rare olivine crystals are commonly altered to talc, chlorite, iddingsite and serpentine. Small proportions of Fe-Ti oxides, titanite, zircon and baddeleyite complete the mineral assemblage.

3. Data

3.1. Source

Most of the data presented in this paper were obtained during a geological mapping program conducted between 1998 and 2003 by the Ministère des

Ressources naturelles et de la Faune of Québec (Simard, 2008 and references therein). Of the 209 bulk rock analyses discussed in this paper (see supplementary data set), 176 were obtained from the Système d’Information

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Géominière (SIGEOM) database, 25 were extracted from the geochemical database of the Geological Survey of Canada (project #TGI010004) and 8 were provided by J. Bédard (GSC-Québec). Although these data were analyzed in a number of different laboratories, all of SIGEOM analyses (85%) were performed at ACME Analytical Laboratories (Vancouver). Nd isotopic analyses were carried out on 31 of the mafic dykes and 8 Lac Aigneau lamprophyric dykes reported in Maurice et al. (in press).

3.2. Sampling rationale

Comparing the chemical composition of samples acquired by many geologists has a number of problems. The most obvious is the uneven distribution of dyke samples (Fig. 2). While the lack of geochemical data in the center of the

Peninsula is due to a lack of dykes (Maurice, 2008), the small number of analyses from the South and Southeast reflects the small number of samples collected, rather than low dyke abundance.

Another problem involves the nature of the samples collected within each dyke. While judicious sample selection by visual inspection (e.g. avoiding secondary alteration and heterogeneity) is always possible, our database contains no information on the location of samples with respect to their dyke margins. The position of a sample within a dyke can be important, as the relative compositions of dyke margins and interiors may in part reflect the emplacement process(es). In the Mackenzie dyke swarm of northern Canada for example, thin dykes commonly appear homogeneous, but dykes having widths greater than 30 meters are markedly zoned, with the centers typically being more evolved in composition

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than the margins (Gibson et al., 1987). In contrast, the Harp dykes of Labrador are characterized by centers that are substantially more magnesian than their margins (Cadman et al., 1994). Because both flow banding and hydrous alteration can be more prevalent in dyke interiors (Southwick and Day, 1983), some workers prefer to sample dyke margins (e.g. Southwick and Halls, 1987), a choice that can, however, lead to samples that have been contaminated by the host rock

(Dostal and Fratta, 1977; Gill and Bridgwater, 1979). More than 80% of the samples in our database have dyke widths that were visually estimated in the field. Despite a three orders magnitude range in dyke widths, there appears to be no correlation between width and chemical indicators of crustal contamination such as K2O/TiO2 and La/Yb (Fig. 3). This suggests that larger dykes have not assimilated more crust than smaller ones during their emplacement, and that comparisons can be made in spite of a lack of knowledge of the location of samples within individual dykes.

The interpretation of the chemistry of Precambrian rocks is never straightforward because of the post-magmatic processes they are likely to have experienced. Fifteen dyke samples with anomalously low CaO (<6 wt.%) and high LOI (>4 wt.%) were interpreted to be heavily altered and omitted from our dataset.

4. Compositional groups

Dykes with a wide spectrum of ages can be found within apparently single dyke swarms (French et al., 2004; Jourdan et al., 2004; Mège and Korme, 2004;

Jourdan et al., 2006), while in other cases dykes with distinct trends can belong to

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the same swarm (Buchan et al., 2007). The attribution of magmatic ages to undated samples on the basis of swarm affiliation is thus hazardous. Furthermore, although recent efforts have been made to acquire more U-Pb ages on dykes of the NESP (Buchan et al., 1998; Maurice et al., in press), only 15% of the samples contained in our database can be confidently attributed magmatic ages. Our approach consists of grouping dyke samples on the basis of their geochemical characteristics, in a manner unprejudiced by apparent dyke swarm affiliation. The dyke analyses are divided hereafter into three chemically distinct groups, a main group, a low Fe-Ti group, and a high Fe-Ti group (Table 1) on the basis of the relative concentrations of the major elements: Fe, Ti, Mg, Al, and Na.

4.1. Main group

The main group comprises 65% of the dyke analyses contained in the database and has a large range of Fe (10-18 wt.% Fe2O3) and Ti (0.8-2.0 wt.%

TiO2) contents (Fig. 4). Samples of the main group with low Mg overlap those of the high Fe-Ti group in terms of Fe and Ti, but can be distinguished on the basis of their lower Na (Fig. 5a), and/or higher V/Ti ratios (30-50; Fig. 6). The most magnesian samples of the main group have Mg, Si and Al contents similar to those of ~12 wt.% MgO experimental melts of fertile lherzolite (HK-66 and KLB-

1) melts at pressures ~1.5 GPa (Figs. 4c and 5d). The increase in Fe and Ti contents with decreasing Mg in the quartz-normative dykes of the main group is similar to the liquid lines of descent of experimental tholeiitic liquids undergoing crystal fractionation between 1 atm and 1 GPa (Figs. 4 and 7). The decrease in Al content with increasing Si in the main group dykes is, however, less than that

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produced by fractionation at 1 GPa, and best matches trends produced at pressures between 1 atm and 0.7 GPa (Figs. 4c and 5c).

Dykes of the main group have a wide range of high field strength (HFSE;

25-300 ppm Zr, 2-30 ppm Nb) and heavy rare earth elements (HREE; 1-6 ppm

Yb), and can be further divided into two subgroups on the basis of their La/Yb and Zr/Nb ratios (Figs. 8 and 9). The low-LREE main group dykes have less fractionated REE profiles, and thus lower La/Yb ratios (≤4; Fig. 9d). They have

Zr/Nb, Th/Nb, and K/Ti ratios that overlap those of the high-LREE dykes, but do not extend to the higher values of the latter (Fig. 10). The least enriched samples of this subgroup have trace element ratios that plot near those of primitive mantle

(PM; Figs. 10 and 11), but their Zr/Nb ratios decrease with increasing La/Yb towards the compositions of Paleoproterozoic alkaline magmas of the Ungava

Peninsula. Eight of the low-LREE dykes yielded positive εNd2.0Ga values ranging between +3.9 and +0.2 (Fig. 10d). The low-LREE dykes occur largely in the northeastern portion of the Ungava Peninsula, in the Rivière Arnaud Terrane, as dykes of the Klotz (2.21 Ga), Couture (2.20 Ga) and Payne River (2.17 Ga) swarms, but are also found in few scattered localities elsewhere (Fig. 2).

The high-LREE main group dykes have similar HREE, but elevated La/Yb ratios (≥4) compared to the low-LREE main group dykes (Figs. 8 and 9). These enriched dykes have La/Yb ratios that are similar to those of the low Fe-Ti dyke group, but most have distinctly lower Zr/Nb, Th/Nb and K/Ti ratios (Fig. 10). In a La-Yb-Nb diagram, the high-LREE main group dykes scatter from a position close to that of primitive mantle towards the composition of the Archean

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granitoids of the Ungava Peninsula (Fig. 11). The five high-LREE dykes analyzed for Nd isotopes are isotopically enriched, with negative εNd2.0Ga values ranging between -2.3 and -6.4 (Fig. 10d). These dykes include a dated dyke from the Rivière du Gué swarm (2.15 Ga; Fig. 1), along with many other dykes of unknown age that occur mainly in the western and southern parts of the Ungava

Peninsula, in the Hudson Bay Terrane (Fig. 2).

4.2. Low Fe-Ti group

Dykes in our database having distinctly lower Fe (<11 wt.% Fe2O3) and Ti contents (<0.8 wt.% TiO2; Fig. 4) relative to the main group dykes are grouped into a low Fe-Ti group. They display a slight increase in Fe, Ti and Al with decreasing Mg, are characterized by systematically higher Mg at any Si content

(Fig. 5b), low Fe similar to harzburgite experimental melts (Figs. 4a and 5c), and low V and Ti contents (Fig. 6). The low Fe-Ti dykes are further characterized by low HFSE (25-125 ppm Zr; <5 ppm Nb) and HREE contents (<2 ppm Yb), but are relatively enriched in large ion lithophile elements (LILE; 1-5 ppm Th) contents at any Zr content (Fig. 9). They have pronounced negative Nb-Ta anomalies in primitive mantle-normalized diagrams (Fig. 8), and high ratios of incompatible trace elements (Th/Nb, K/Ti, Zr/Nb) that scatter with those of the high-LREE main group dykes towards those of Archean granitoids (Fig. 10).

Four dykes within this chemical group yielded strongly negative whole rock

εNd2.0Ga values (-6 to -14) that approach those of Archean granitoids (Fig. 10d).

The dated dykes of the Irsuaq (2.51 Ga) and Maguire (2.23 Ga) swarms (Fig. 1),

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that occur along the boundary of the two isotopic Archean terranes, belong to the low Fe-Ti group (Fig. 2), but this group also includes other dykes of unknown age found mainly in the Hudson Bay Terrane.

4.3. High Fe-Ti group

Samples of the high Fe-Ti group are characterized by high Fe (>14 wt.%

Fe2O3) and Ti (>1.4 wt.% TiO2) contents (Fig. 4) and have systematically higher

Na (Fig. 5a), and/or lower V/Ti ratios (12-30; Fig. 6) relative to the main group dykes. Most of these dykes are ol-normative basalts (Fig. 7), but are not alkaline sensu stricto (i.e. nepheline-normative). They have, however, high Na (Fig. 5a) and incompatible trace element contents (Figs. 8 and 9; Zr> 100 ppm), and low

V/Ti ratios which approach those of alkaline rocks of the Ungava Peninsula (Fig.

6). The high Fe-Ti group dykes can be divided into two subgroups on the basis of their Al contents.

The high-Al subgroup includes dykes with >12 wt.% Al2O3 whose Al contents decrease with Si (Fig. 5d). They display the lowest Si, but highest Fe contents, of all the Paleoproterozoic dykes of the Ungava Peninsula, and are similar to Archean ferropicrites of the Western Superior Province (FP; Figs. 4a and 5c). The most primitive samples of this subgroup have Al contents similar to experimental melts of fertile lherzolite and pyroxenite produced at ~2.0 GPa (Fig.

5d), but their relatively low Si contents at any Mg (Fig. 5b) more closely resemble pyroxenite experimental melts, whereas their high Fe contents resemble the ferropicrites (Fig. 4a). Most of the high-Al subgroup dykes are olivine-normative with low normative diopside contents, and scatter from the diopside-olivine join

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towards the diopside-hypersthene join (Fig. 7). The high-Al subgroup dykes have high HFSE (>100 ppm Zr; >7 ppm Nb) and HREE (≥2 ppm Yb) contents and

La/Yb ratios that are similar to the most enriched high-LREE main group dykes

(Fig. 9). They differ from the high-LREE main group dykes in having lower

Th/Nb and Zr/Nb ratios similar to those of Archean ferropicrites (Fig. 10). Four of these samples yielded negative εNd2.0Ga values that range between -2.3 and -

3.4, while a fifth sample has a positive value of 3.1 (Fig. 10d). The dated dyke of the Minto swarm (2.00 Ga; Fig. 1) belongs to the high-Al subgroup, along with many dykes of unknown age from the Hudson Bay Terrane (Fig. 2).

The low-Al subgroup dykes have <12 wt.% Al2O3 (Fig. 4c) and display increasing Al with increasing Si, but decreasing Mg content, in contrast to the high-Al subgroup (Figs. 4c and 5d). Two distinct liquid lines of descent appear to be defined by the variations in their Ca/Al ratios and Mg contents (Fig. 4d). The increase in Al content with Si in these trends diverge from olivine control lines and are better matched by fractionation trends involving clinopyroxene varying in proportions between 65% (trend 1) and 30% (trend 2). The low Al and high Fe contents of this subgroup distinguish them from all other dykes, and their most magnesian samples have low Al (Figs. 4c) and high Ca/Al ratios (Fig. 4d) that resemble experimental melts of garnet pyroxenite and/or fertile lherzolite produced at 5 GPa. Most of the low-Al dykes have olivine-normative compositions that are high in normative diopside, and appear to scatter from the high pressure experimental melts of garnet pyroxenite towards the diopside- hypersthene join (Fig. 7). The low-Al subgroup dykes typically display higher Th

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contents than the high-Al subgroup, which gives them higher Th/Nb ratios (>0.2;

Figs. 9 and 10). Although their Zr/Nb ratios overlap those of the high-Al dykes, many have higher La/Yb ratios (Fig. 10) because of their distinctly more fractionated HREE patterns (Fig. 8) and lower Yb contents (Yb ≤2 ppm; Fig. 9).

Six of the low-Al subgroup dykes yielded negative εNd2.0Ga values ranging between -0.3 and -2.0 and are displaced from the array of other dykes towards the

Kenty Lake alkaline basalts and Lac Aigneau lamprophyres (Fig. 10d). The dated dykes of the Anuc (2.22 Ga) and Kogaluk Bay (2.21 Ga) swarms belong to the low-Al subgroup (Fig. 1), together with many dykes of unknown age mainly from the western and southern portions of the Ungava Peninsula, in the Hudson Bay

Terrane (Fig. 2).

4.4. Geographical occurrence of mafic dykes and the nature of the Ungava

Peninsula

The mafic dykes intruding the Rivière Arnaud Terrane belong dominantly to the low-LREE main group. In distinct contrast, virtually all the other dyke groups occur within the older Hudson Bay Terrane, or along the contact between the two terranes. In addition to this terrane dependence, all dykes emplaced in the 2.23-

2.17 Ga period are spatially associated with a decrease in lithospheric thickness towards the North of the Ungava Peninsula (Fig. 2). Younger dykes emplaced in the 2.15-2.00 Ga period are underlain by a thicker lithosphere. Although few data exist for dykes in the crust overlying the thickest lithosphere to the Southeast

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(>200 km), most samples in this area are low-Al high Fe-Ti group dykes spatially associated with the lac Aigneau lamprophyre dykes.

5. Discussion

Mafic dykes are documented in a variety of geological settings, with parallel linear swarms commonly being associated with failed rifts or the breakup of continental margins (Fahrig, 1987; Ernst and Buchan, 2001). The tectonic significance of giant radiating swarms is, however, model dependent. The fanning that is characteristic of these swarms can be related to lithospheric stress regimes associated with plate tectonics (McHone et al., 2005) or to the rise of deep mantle plumes ( Ernst et al., 1995; Ernst and Buchan, 2001). The tendency of these swarms to radiate from a focal point may imply the lateral transport of magmas from a central plume source, but direct evidence for flow direction is disputed. Studies of the anisotropy of magnetic susceptibility (AMS) hold lateral flow in some dyke swarms (Ernst and Baragar, 1992; Ernst, 1994), but the original AMS fabrics of other swarms have been shown to be vertical, before being replaced by late horizontal fabrics (Cadman et al., 1992). Such constraints may imply that crustal fractures are initially filled vertically, but then magma propagates laterally (Tarney, 1992). The many rift zones surrounding the Ungava

Peninsula and the older ages of most mafic dykes relative to the supracrustal rocks

(Maurice et al., in press) suggest that a large number of dykes may be associated with the early breakup of the lithosphere. Although some dykes may belong to radiating swarms with magma sources located off the cratonic margins, we

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assume in the following discussion that dykes record the regional nature of the immediately underlying mantle.

Another debate concerning the origin of continental dyke swarms (and continental flood basalts) centers on whether their trace element enrichment reflects crustal contamination or an enriched mantle source (Collerson and

Sheraton, 1986; Patchett et al., 1994; Hergt and Brauns, 2001). Two broad models have emerged to explain the incompatible element and isotopic features.

The first involves two distinct source regions, with asthenosphere-derived magmas interacting with either the continental crust (Arndt et al., 1993), or small degree partial melts of the subcontinental lithosphere (McKenzie, 1989; Ellam and Cox, 1991; Cadman et al., 1995). The second class of model holds that these chemical characteristics are inherited from a lithospheric mantle that had previously been enriched while beneath continents (Hawkesworth et al., 1984;

Hergt and Brauns, 2001).

The differences between chemical groups of mafic dykes of the Ungava

Peninsula may reflect a number of different processes, including crystal fractionation, different degrees of partial melting, mixing between mantle reservoirs, melting of heterogeneous mantle sources, crustal contamination, metasomatic source enrichment, or a combination of these processes (Collerson and Sheraton, 1986; Tarney, 1992; Patchett et al., 1994; Seymour and

Kumarapeli, 1995; Condie, 1997). Because the compositional changes produced by low pressure crystallization obscure the primary magmatic composition of magmatic suites (Cox, 1980; Grove and Baker, 1984; Klein and Langmuir, 1987),

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and it is necessary to consider the effects of differentiation on the compositional arrays of dykes.

5.1. Main group

The low Mg contents (Fig. 4) and quartz-normative compositions (Fig. 7) of most main group dykes imply that their magmas have evolved since leaving the mantle. The increasing Fe and Ti with decreasing Mg contents of the low-LREE and high-LREE main group dykes (Fig. 4) is typical of tholeiitic magmatic suites.

Most dykes are consistent with experimental liquid lines of descent of tholeiitic basalts fractionating between 1.0 GPa and 1atm (Figs. 4, 5 and 7), but the lower

Al with decreasing Mg (Fig. 4a) and increasing Si (Fig. 5d) contents relative to

1.0 GPa experimental liquids suggests that most fractionated at intermediate to shallow crustal levels between 0.7 GPa and 1 atm. A gabbroic crystal fractionation model involving olivine (20%), clinopyroxene (30%), and plagioclase (50%) reproduces the trend defined by the 1 atm experimental liquids.

It indicates that the range of observed main group dyke compositions corresponds to ~65% fractionation of a parental magma with 9 wt.% MgO, whose cumulate assemblages may lie hidden in the crust. A fractionation model cannot, however, reproduce the increase in La/Yb ratios and Zr contents within each of the main group dyke subgroups (Fig. 9), much less the La/Yb differences between the two subgroups. Although a combined assimilation-fractional crystallization (AFC) process with a small proportion (r = 0.05) of a La/Yb enriched component can produce the increase in La/Yb ratios within each subgroup, no reasonable r factor

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can produce the high-LREE dykes from the low-LREE dykes, and these subgroups must therefore have distinct origins.

A comparison of the trends of olivine fractionation for fertile-mantle experimental melts to the few high magnesian samples of the main group dykes suggests parental magmas have either been derived from a mantle similar to KLB-

1 (Mg# = 90) at ~3 GPa, or a more Fe-rich mantle similar to HK-66 (Mg# = 85) at

~1.5 GPa (Fig 4a). However, these high magnesian samples exhibit the high Si contents expected for melting under pressures of ~1.5 GPa (Figs. 5c and 5d), and their relatively high Fe contents would rather be consistent with the main group dykes being sourced from a Fe-rich fertile lherzolite similar to HK-66. Because the minimum pressure for garnet stability in peridotites is >2.2 GPa (Kinzler,

1997; Walter, 1998; Longhi, 2002), the lack of HREE depletion of the main group dykes (Figs. 8 and 9) is further consistent with melting a Fe-rich lherzolite at ~1.5

GPa.

Partial melting of a peridotitic mantle source produces negative slopes in the

Zr/Nb vs. La/Yb, with garnet-bearing assemblages defining a flatter slope than a spinel-bearing one (Fig. 10c). Although dykes of the low-LREE subgroup, and to a lesser extent the high-LREE subgroup, respectively fall along the melting arrays predicted for spinel- and garnet-lherzolite having primitive mantle compositions, their similar range in Al (Figs. 4 and 5) and HREE (Yb; Fig. 9) contents makes it unlikely that the distinct La/Yb ratios reflect the presence or absence of garnet in their source. The rise in the La/Yb ratio with Zr of the low-LREE dykes (Fig. 9) along with their trend towards the Paleoproterozoic alkaline magmas of the

Ungava Peninsula (Figs. 10c and 11), rather suggest the possible involvement of

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an alkaline mantle component. In contrast, the high-LREE dykes appear to have incorporated Archean granitoids of the Ungava Peninsula, a feature consistent with their low εNd2.0Ga values (Fig. 10d).

5.2. Low Fe-Ti group

The low Fe, but high Mg and Si contents of the low Fe-Ti group dykes with respect to the other dyke groups of the Ungava Peninsula are most similar to experimental melts of depleted harzburgite (HZ; Figs. 4a, 5b and 5c). A depleted refractory source for the low Fe-Ti dykes is also consistent with their low HREE and HFSE contents (Fig. 9). Most of these dykes have high Mg contents and the limited increase in Fe and Ti is inconsistent with low pressure liquid lines of descent for magmas derived from a fertile source (Fig. 4). This feature is similar to trends defined by calc-alkaline volcanic suites that have fractionated under hydrous conditions, but contamination by evolved felsic material yields an essentially identical signature, and the distinction between these two petrogenetic processes is difficult.

The higher relative magmatic temperatures of many of the Mg-rich dykes in the low Fe-Ti group mean that they had a greater potential to assimilate contaminants. The displacement of the low Fe-Ti dykes towards the composition of the Archean Ungava crust (Figs. 10 and 11) is coupled with strongly enriched

Nd isotopic compositions approaching those of the Archean granitoids (Fig. 10d).

This, along with the presence of inherited Archean-age zircons in an Irsuaq dyke belonging to this group (Maurice et al., in press), suggests that the trace element

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enrichments of the low Fe-Ti dykes are best explained by the incorporation of an

Archean crustal component. The LILE enrichments of the low Fe-Ti dykes compared to the high-LREE main dykes (high Th/Nb and K/Ti ratios, Fig. 10) may also imply that the depleted harzburgite source for the low Fe-Ti dykes was metasomatically re-fertilized by fluids prior to or during melting. The geographical association of many low Fe-Ti dykes with the boundary of the two

Archean isotopic terranes (e.g. the Irsuaq and Maguire dykes; Fig. 2) may indicate that such a harzburgitic mantle wedge, depleted by melt extraction in the Archean, was sandwiched between the two terranes. The existence of low Fe-Ti dykes that are not associated with known tectonic boundaries, however, requires that depleted mantle domains also exist peppered beneath the Hudson Bay Terrane

(Fig. 2).

5.3. High Fe-Ti group

The parental magmas of the high Fe-Ti group dykes lie close to the olivine- diopside join and give insights on the conditions under which they fractionated.

Crystallization experiments on mildly alkaline basaltic liquids (3-5% normative nepheline) indicate that liquid lines of descent are a function of pressure (Mahood and Baker, 1986; Thy, 1991). During the initial stages of crystallization at 1 atm, experimental liquids remain near the thermal crest defined by the olivine- plagioclase-clinopyroxene plane, but with higher degrees of crystallization move away from the divide towards quartz-normative compositions. At pressures above

0.8 GPa, however, alkaline liquids are driven towards increasingly ne-normative compositions. These systematics indicate that mildly alkaline basaltic liquids

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lying close to the thermal divide would fractionate at low pressure to produce residual compositions similar to those of the most evolved high Fe-Ti group dykes

(Fig. 7).

The alkaline affinities of the high Fe-Ti group dykes may further imply a range of possible mantle sources. Small-degree partial melts of peridotite at high pressure can be alkaline (Takahashi and Kushiro, 1983), especially if generated in the presence of carbonate (Hirose, 1997). However, partial melting of lower crustal eclogite or pyroxenite plus peridotite mixtures (Kogiso et al., 1998; Yaxley and Green, 1998), or pyroxenite itself (Hirschmann et al., 2003; Kogiso et al.,

2004), also yield alkaline melts. Pyroxenite is a minor, but ubiquitous, component in the mantle (Hirschmann and Stolper, 1996). Because the range of pyroxenite compositions is rather large, a wide spectrum of compositions may modify the predominantly peridotitic mantle melts. Increasing the pressure of melting of peridotite increases the Fe content (Langmuir and Hanson, 1980), but decreases the Si content of initial melts (Green, 1973; Takahashi and Kushiro,

1983; Hirose and Kushiro, 1993), such that Si and Fe are negatively correlated with increasing pressure (Fig. 5c). In contrast, melting experiments of silica- deficient pyroxenite produces more Si-rich liquids with increasing pressure.

Furthermore, the expansion of the phase volume of garnet relative to clinopyroxene with increasing pressure yields liquids with higher Ca/Al, but lower MgO, compared with garnet peridotite-derived partial melts (Fig. 4d,

Kogiso et al., 2004).

Despite their similar alkaline affinities, the low-Al dykes of the high Fe-Ti group cannot simply be related to the high-Al dykes through crystal fractionation

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because of their distinctly lower Fe and higher Si contents (Figs. 4 and 5).

Melting a fertile lherzolite with a Fe content intermediate between HK-66 and

KLB-1 at ~5 GPa, followed by olivine-dominated crystal fractionation (Fig. 4a), would explain the higher Fe, and lower Al contents of the low-Al dykes relative to the main group dykes (Fig. 4c, 5b and 5d). These features are, however, also consistent with melting a garnet pyroxenite source at similar pressures ~5 GPa.

The trends of increasing Al with decreasing Mg (Fig. 4c) and increasing Si (Fig.

5d) contents defined by most low-Al dykes significantly diverges from olivine fractionation alone, and require the involvement of clinopyroxene. The existence of these distinct trends defined by the low-Al dykes in the Ca/Al vs. Mg space may signify that both pyroxenite and peridotite existed, with samples having the highest Ca/Al ratios at any Mg contents being derived from a pyroxenite source, and those with the lowest Ca/Al ratios being derived from a peridotite source.

These two trends appear to reflect the fractionation of two different proportions of olivine and clinopyroxene (35% olivine + 65% clinopyroxene for trend 1; 70% olivine + 30% clinopyroxene for trend 2; Fig. 4d). Regardless of the exact nature of the mantle source(s) for the low-Al subgroup dykes, their low Al and Yb contents (<2 ppm; Fig. 9) and fractionated HREE profiles (Gd/Yb >2; Fig. 8), indicate the presence of significant residual garnet in their source, suggesting higher pressure melting than that for the main group dykes. Furthermore, the spatial association of many low-Al dykes with the lac Aigneau lamprophyre dykes that may have a very deep mantle source (ca. 9 GPa, Francis and Patterson,

2009), along with their location over the thick lithospheric root of the southeastern

Ungava Peninsula, are both consistent with a deep-seated source.

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The relatively higher Yb contents of the high-Al dykes are inconsistent with a garnet-bearing source and indicate melting at relatively lower pressures.

Although the high Al and low Si contents of the high-Al dykes are similar to experimental liquids produced by melting fertile lherzolite at ~2 GPa (Fig. 5d), olivine fractionation of a fertile source cannot yield both low Mg and Si contents, a feature that may imply a more Si-poor source (Fig. 5b). The low Si contents of the high-Al subgroup dykes are similar to those of 2-2.5 GPa experimental melts of Si-undersaturated pyroxenite and to those of Archean ferropicrites of the

Western Superior Province (Figs. 4a and 5c). Their exceptional Fe-rich nature and alkaline affinities may suggest they represent evolved ferropicrite melts.

Although no experimental melts exist, Archean ferropicrites may also be considered as a possible source for the high-Al dykes because of their similarly enriched εNd(2.0Ga) values and La/Yb ratios, but depleted Th/Nb and Zr/Nb ratios

(Fig. 10). Melting an isotopically enriched Archean ferropicrite reservoir would be sustained by the high density estimated for these magmas (e.g. 3.33 g/cm3), which suggest they would have difficulties rising to the Earth’s surface and stagnate or sink within the mantle (Goldstein and Francis, 2008).

5.4. Nature of the mantle beneath the Ungava Peninsula

The two distinct arrays in a La-Yb-Nb ternary diagram, one defined by the high-LREE main group dykes and low Fe-Ti dykes that scatter from primitive mantle towards Archean granitoids, and a second by the low-LREE main group dykes towards the composition of the Paleoproterozoic alkaline magmas (Fig. 11),

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suggest the existence of two distinctly enriched components. The high Fe-Ti group dykes lie between the two arrays, which may imply contributions from both crustal and enriched lithospheric components. The mafic dykes exhibiting the crustal component are dominantly in the Hudson Bay Terrane (Fig. 2), but no chemical difference other than isotopic enrichment appears to exist between granitoid suites of the two isotopic terranes (Boily and Maurice, 2008), such that the geographical prevalence of the crustal component is difficult to explain by differences in the crust dykes intrude.

In some localities of Labrador and Greenland, only dyke margin samples have been documented to be locally contaminated by the country rock, which exchanged the alkalis, Ca, and the LILE with the dyke (Dostal and Fratta, 1977;

Gill and Bridgwater, 1979). In contrast, a more recent study has shown that wallrock contamination is uncommon (Baragar et al., 1996). Furthermore, country rocks intruded by mafic dykes rarely show evidence of melting, even when the magmas are high-temperature picrites (Tarney, 1992), and only actively convecting (kilometer-scale) magma chambers provide sufficient heat capacity to assimilate their host rocks (e.g. the Muskox intrusion, Francis, 1994). The lack of correlation between dyke composition and width in our dataset (Fig. 3) indicates that it is unlikely that local crustal contamination is responsible for the evidence of the Archean crustal component seen in the Hudson Bay Terrane. Although the two subgroups of the main group dykes exhibit identical major element systematics, a crustal component is only recorded in the high-LREE subgroup.

This may imply a higher flux of radioactive heat for the crust of the Hudson Bay

Terrane, in which case the assimilation of crustal material by mafic magmas

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would have been eased by smaller temperature contrasts (Thompson et al., 2002).

Alternatively, the distinct enrichments for dykes intruding both terranes may have occurred at greater depth than fractionation estimates, through the assimilation of chemically distinct lower crusts or lithospheres.

In order to explain the voluminous ca. 2.21 Ga low-LREE main group dykes occurring above the thinnest lithosphere of the Ungava Peninsula, Maurice et al.

(in press) suggested the magmas were produced by decompression melting of the asthenosphere, following the removal of the northern Archean lithospheric keel and/or lower crust. In such a scenario, the parental magmas of dykes emplaced coevally, and after the delamination event, recorded the deep crustal or lithosphere signature with which they coexisted. The lack of a crustal component and the presence of an isotopically-depleted alkaline component in the low-LREE main group dykes (Figs. 10 and 11) would be explained if their parental melts have reacted with the thinned nascent Paleoproterozoic lithosphere that may now underlie much of the Rivière Arnaud Terrane.

The nature of the alkaline component recorded in the high Fe-Ti dykes across the long-lived Hudson Bay Terrane is more enigmatic. The Archean lower crust and lithosphere of the Hudson Bay Terrane likely contain a heterogeneous assortment of mafic lithologies introduced periodically in the Archean (Maurice et al., 2009), which offer a compositionally diverse range of possible sources and mantle components (e.g. pyroxenite, eclogite, ferropicrite, hybrid peridotite). In the case of the high-Al high Fe-Ti dykes, their alkaline component may be similar to that in Archean ferropicrites with which they share identical enriched εNd2.0Ga

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values, La/Yb ratios and depleted Th/Nb ratios (Fig. 10). The slightly lower

εNd2.0Ga values at any La/Yb ratio of the low-Al high Fe-Ti dykes with respect to all other dyke groups (Fig. 10d) may be indicative of the incorporation of two isotopically distinct enriched components in their high pressure pyroxenite and/or peridotite parental melts. A dominant component likely reflects the assimilation of the Archean crust or melting of an Archean mafic lithology with negative

εNd2.0Ga values, while a minor component may reflect the assimilation of a mantle component similar to the Paleoproterozoic alkaline magmas with positive values.

Although Archean lithospheric roots are generally considered to be depleted residues left after extensive partial melting of the mantle (Boyd, 1989; Herzberg,

1993), the widespread main group dykes require a relatively fertile mantle source beneath the Ungava Peninsula in the Paleoproterozoic. The fertile source of the low-LREE main group dykes of the Rivière Arnaud Terrane may represent

Paleoproterozoic mantle upwelling to replace Archean lower crust and/or lithosphere. The occurrence of the high-LREE main group, low Fe-Ti group and high Fe-Ti group dykes within or along the border of the older Hudson Bay

Terrane implies a complex and heterogeneous lithosphere composed of a variety of mantle lithologies, including lherzolite, harzburgite and pyroxenite.

6. Conclusions

Our study has shown that the Ungava Peninsula hosts diverse groups of

Paleoproterozoic dykes swarms requiring a number of different mantle sources.

The most significant correlation is between dyke groups and the Archean terrane

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that they intruded. The low-LREE main group dykes intruding the juvenile

Rivière Arnaud Terrane are derived from a fertile and isotopically depleted mantle, and appear to contain an alkaline component. They lack evidence of any

Archean crustal component, either signifying the crust they intruded was too cold to be assimilated, or that the lower crust and lithosphere were Paleoproterozoic in age. At least 4 possible mantle sources are needed to explain the diverse groups of Paleoproterozoic dykes intruding the older Hudson Bay Terrane. The high-

LREE main group dykes of this terrane appear to be derived from fertile lherzolite, but have assimilated an Archean crustal component, suggesting that fertile mantle domains persisted below this terrane in Paleoproterozoic times despite a long history of melt extraction. Volumetrically less important, but ubiquitous, high Fe-Ti and high-Al dykes within the Hudson Bay Terrane may represent ferropicrite melts. High Fe-Ti but low-Al dykes appear to represent deep-seated (5+ GPa) melts that were sourced in garnet-bearing pyroxenite and fertile peridotite. Low Fe-Ti group dykes occur within the Hudson Bay Terrane, and along the boundary of the two terranes. These dykes may represent the melts of depleted harzburgite that may occur preferentially as a wedge sandwiched during terrane accretion in the Archean. In the absence of direct mantle samples, the composition of mafic dyke swarms yield an effective means of probing the nature and architecture of subcontinental mantle roots.

Acknowledgments

This research has been supported by a National Scientific and Engineering

Research Council of Canada (NSERC) discovery grant (RGPIN7977-00) to D.

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Francis. J.-Y. Labbé (MRNF) supervised the re-analysis of mafic dykes of the

Ungava Peninsula, J. Bédard (GSC-Québec) provided 8 unpublished analyses from Payne River and Klotz dyke swarms, and R. Ernst (Ernst Geosciences) provided analyses obtained during the TGI project #010004 (2001-2003). Many geologists of the MRNF are acknowledged for beneficial discussions.

Comprehensive reviews by D. Canil and R. Ernst, and competent handling by editor in-chief A. Kerr resulted in improvements of an earlier version of the manuscript. Ministère des Ressources naturelles et de la Faune contribution

#2009-2010-8439-02.

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135

Figure captions

Figure 4-1: Schematic distribution of mafic dyke swarms (modified from Buchan

et al., 2007; Maurice, 2008) and alkaline rocks of the Superior Province

emplaced over a) ca. 2.51-2.44 Ga (age for the Mistassini dykes from an

internal report by M.A. Hamilton, Jack Satterly Geochronology

Laboratory); b) ca. 2.23-2.17 Ga (the different dyke colors distinguish

distinct swarms) and c) ca. 2.15-1.88 Ga. Acronyms for alkaline rocks as

follows: KL, Kenty Lake; LA, Lac Aigneau; LC, Lac Castignon; LE, Lac

Lemoyne; LL, Lac Leclair; CG, Cargill; BO, Borden; SR, Spanish River.

The inset in a) shows the location of Fig. 2 and corresponds to the Ungava

Peninsula.

Figure 4-2: Distribution of the mafic dykes (adapted from Maurice, 2008) and

mafic dyke samples of the Ungava Peninsula. The initial dyke

compilation map included only dykes with widths >5 m, such that samples

that appear not to be linked with dykes on this figure were taken from

small dykes. The dashed line separates the isotopically juvenile Rivière

Arnaud Terrane (RAT) to the East from the Hudson Bay Terrane (HBT) to

the West and South (Boily et al., 2009). The white stars indicate the

location of Paleoproterozoic alkaline rocks: LA, Lac Aigneau

lamprophyres; LE, Lac Lemoyne carbonatite; LL, Lac Leclair

lamprophyres; KT, Kenty Lake alkaline basalts. Names of the dated

swarms are shown with a white shade close to each dated sample. The

background figure is constructed with the extrapolation of Nd isotopic

136

data acquired on over 300 Archean rocks of the Northeastern Superior

Province (see compilation by Maurice, 2007). Each sample was given a

value between 1 and 6 that reflects the extent to which an older evolved

crust was recycled. Samples with 147Sm/144Nd ratios >0.14 (mainly mafic

and ultramafic rocks) were classified with respect of the εNd(t) notation,

similarly to that reported in Tomlinson et al. (2004). Samples with

147Sm/144Nd ratios < 0.14 (mainly felsic rocks) were classified with respect

of their model ages (TDM). As a result of the interpolation, the darker

shades outline areas with lower εNd(t) or higher TDM values. Symbols are

as defined in Table 1.

Figure 4-3: Crustal contamination indicators a) K/Ti, and b) La/Yb vs. dyke

thicknesses for dykes of the Ungava Peninsula. Symbols as defined in

Table 1.

Figure 4-4: a) Fe, b) Ti, c) Al and d) Ca/Al vs. Mg in cation units for the mafic

dykes of the Ungava Peninsula. The dotted arrows show the vectors

produced by experimental liquids between 9 and 4 wt.% MgO. Crystal

fractionation experiments conducted at 0.7 and 1.0 GPa (Villiger et al.,

2004; 2007) used a starting material in equilibrium with a composition

identical to the 1.5 GPa KLB-1 lherzolitic residuum of sample #19 from

Hirose and Kushiro (1993). Experiments conducted at 1 atm (Thy et al.,

1998) used natural basalt #11R4 as a starting material. The positions of

137

the 0.7 and 1.0 GPa vectors are offset +1.5 cat. Fe and +0.5 cat. Ti owing

to the higher Fe and Ti contents of the Ungava Peninsula mafic dykes

relative to the starting materials used in the experiments. White numbers

are the pressures to which experimental melts from fertile lherzolites

KLB-1 and HK-66 (Hirose and Kushiro, 1993) were produced (1+, 1.0 and

1.5 GPa; 2+, 2.0 and 2.5 GPa; 3, 3GPa; 4+, 4.0 to 4.6 GPa; 5+, 5.0 to 7.0

GPa). Black numbers are the pressures to which experimental liquids (2+,

2.0 and 2.5 GPa; 5, 5 GPa) from melting garnet pyroxenite MIX1G

(Hirschmann et al., 2003; Kogiso et al., 2003) were produced. HZ are the

1.5 GPa experimental melts of a synthetic harzburgite (Falloon and

Danyushevsky, 2000). Trend 1 is produced by the low pressure

fractionation of 35% ol + 65% cpx, while trend 2 is produced by the

fractionation of 70% ol + 30% cpx. The data of Archean Western

Superior ferropicrites are from Goldstein and Francis (2008).

Figure 4-5: a) Na, b) Mg, c) Fe and c) Al vs. Si in cation units for the mafic dykes

of the Ungava Peninsula. Samples of the low Fe-Ti group are not plotted

for clarity in panel a). High Fe-Ti dykes overlapping with the Na contents

of main dykes have lower V/Ti ratios and higher Fe contents. Conversely,

dykes of the main group plotting at high Na have higher V/Ti ratios and

lower Fe contents. The dotted arrows in panel c) show the vectors

produced by experimental liquids between 9 and 4 wt.% MgO, as

explained in Fig. 4. The significance of black and white numbers and HZ

138

are as explained in Fig. 4. Other symbols as defined in Table 1, LH,

lherzolite; PX, pyroxenite.

Figure 4-6: V vs. Ti in ppm for the mafic dykes and alkaline rocks of the NESP.

Source of data for the alkaline rocks as follows: Kenty Lake; Gaonac’h et

al. (1992) and Modeland et al. (2003), Lac Leclair; Baragar et al. (2001),

Lac Aigneau (SIGEOM database), and Lac Castignon (unpublished data).

Mafic dyke symbols as defined in Table 1.

Figure 4-7: Ternary projection of CIPW (cation) normative minerals in Ol-Di-Hy,

Hy-Di-Qz and Ol-Ne-Di planes. The signification of arrows and squares

are as explained in Figs. 4 and 5, but MgO contents decrease from 13 to 4

wt.% MgO in the crystallization experiments. Symbols as defined in

Table 1.

Figure 4-8: Multi-element diagram normalized over primitive mantle (Sun and

McDonough, 1989) for representative mafic dyke samples with ~8 wt.%

MgO of the five chemical groups and subgroups of the Ungava Peninsula.

Symbols as defined in Table 1. Sample numbers as follows: low-LREE

main group, 1999022816; high-LREE main group, 2000025651; low Fe-

Ti group, 2001035385; low-Al high Fe-Ti group, 1999020157; high-Al

high Fe-Ti group 2001035397.

139

Figure 4-9: a) Nb, b) Th, c) Yb and d) La/Yb vs. Zr for mafic dykes of the Ungava

Peninsula. Symbols as defined in Table 1. The flat and the sloped arrows

in panel d) are the products of crystal fraction and assimilation fractional

crystallization, respectively. The bulk partition coefficients for Zr, La, and

Yb are quantified with a gabbroic crystal fractionation from a model

involving olivine (ol), clinopyroxene (cpx), and plagioclase (plag)

fractionating in proportions close to the low pressure gabbroic cotectic

(20% ol, 30% cpx and 50% plag). This model reproduces the Mg, Ti, and

Fe variations of much of the main group dykes. The ol and plag partition

cpx coefficients, along with KdZr, are from the experiments from a tholeiitic

cpx mafic magma reported in Fujimaki et al. (1984). KdLa (0.042) and

cpx KdYb (0.56) were calculated from a predictive model for REE

partitioning between clinopyroxene and anhydrous silicate melts (Wood

and Blundy, 1997) with sample 1999022816 (8 wt.% MgO, and 1 wt.%

TiO2). Bulk partition coefficients are as follows: DLa = 0.03, Dzr = 0.045

and DYb = 0.18. The assimilation factor (r) in the assimilation fractional

crystallization model (AFC) was set to 0.05 (r = dMa/dMfc, where dMa is

the assimilation rate of wallrock and dMfc is the crystallization rate at

which fractionating phases are removed). The enriched contaminant is an

average granite with La/Yb = 55 and Zr = 165 ppm. The position of the

dividing line between the low- and high-LREE main group dykes follows

a slope similar to that of the AFC model.

140

Figure 4-10: a) Th/Nb, b) K/Ti, c) Zr/Nb and d) εNd2.0Ga vs. La/Yb for

Paleoproterozoic mafic dykes and alkaline rocks and Archean granitoids

of the Ungava Peninsula. Mafic dyke symbols as defined in Table 1,

alkaline rocks as in Fig. 6. White diamonds are for Archean tonalites and

trondhjemites (TT is the average of 53 samples), while grey diamonds are

for granites and granodiorites (GG is the average of 177 samples). Data

for Archean granitoids are from Percival and Mortensen (2002), the

SIGEOM database, and unpublished data by J. Bédard. Panel c) shows

melting trajectories obtained using a nonmodal batch melting model by

Aldanmaz et al. (2006). Melting curves are for spinel-lherzolite and

garnet-lherzolite having bulk compositions similar to that of primitive

mantle. The Nd isotopic data of panel d) for mafic dykes and Lac Aigneau

alkaline lamprophyres are from Maurice et al. (in press) and data for

Kenty Lake from Gaonac’h et al. (1992). The source of data for Archean

granitoids is compiled in Maurice (2007).

Figure 4-11: La-Yb-Nb ternary diagram for mafic dykes, alkaline rocks and

Archean granitoids of the Ungava Peninsula. Symbols as defined in Table

1, Figs. 6 and 10 respectively.

141

Table 4-1: Synoptic table of symbols, characteristics, possible components and sources for geochemical groups of mafic dyke swarms of the Ungava Peninsula.

142

Figure 4-1

143

Figure 4-2:

144

Figure 4-3:

145

Figure 4-4:

146

Figure 4-5:

147

Figure 4-6:

148

Figure 4-7:

149

Figure 4-8:

150

Figure 4-9:

151

Figure 4-10:

152

Figure 4-11:

153

CHAPTER 5

Age and tectonic implications of Paleoproterozoic mafic dyke swarms for the

origin of 2.2 Ga enriched lithosphere beneath the Ungava Peninsula, Canada

Chapter 4 documented in details the significance of the diverse chemical signatures recorded in the Paleoproterozoic dyke swarms. Chapter 5 aims to attribute time constraints on the numerous mantle-derived magmatic events that intruded the Peninsula and contributed to its breakup.

154 Abstract

Mafic dyke swarms represent short-lived magmatic events that carry important temporal and chemical constraints for the evolution of the lithospheric mantle. Five baddeleyite U-Pb isotopic analyses of Paleoproterozoic mafic dyke swarms intruding the Ungava Peninsula yielded ages of 2508 ±6, 2220 ±1, 2212

±3, 2199 ±5 and 2149 ±3 Ma. These ages fall within the 2.5-2.0 Ga period previously defined by five other swarms, which together comprise a magmatic record of more than 500 Ma. The similar age, composition and surface area of two 2.51 Ga swarms, along with the lack of coeval supracrustal rocks, suggest they correspond to failed rifts. An important magmatic hiatus of 280 Ma follows, but ends with the intrusion of numerous dykes between 2.23 and 2.20 Ga in the thinnest lithosphere of the northern Ungava Peninsula. These dykes exhibit chemical signatures that vary from enriched older 2229-2212 Ma dykes (εNd(t)

<+0.4, La/Yb >4) to relatively-depleted 2209-2199 Ma voluminous younger dykes (εNd(t) >+1.4, La/Yb <4). The depleted character, great volume, and occurrence of these younger dykes in a thin lithosphere may represent decompression melting of the asthenosphere, following delamination of the

Archean lithospheric keel ca. 2.21-2.20 Ga. Later dykes emplaced ca. 2.17 Ga within a rejuvenated Paleoproterozoic lithosphere also have depleted chemical compositions, and map the extent of rifting coeval with the emplacement of early basalts in the Labrador Trough. Dykes emplaced in the 2.15-2.00 Ga period further to the South are proximal to coeval continental basalts, with which they share enriched isotopic compositions (εNd(t) = -1.5 to -7) and a positive

155 correlation between La/Yb and Zr/Nb (La/Yb = 4-10; Zr/Nb = 7-20) that suggest assimilation of an Archean crustal component. A progressive decrease in the

εNd(t) values of these magmas with decreasing age further implies increasing contamination, until the Archean lithosphere failed ca. 2.0 Ga and permitted the eruption of isotopically-depleted basalts.

The ca. 2.2 Ga depleted northern dykes and the 2.1-1.9 Ga Povungnituk basalts of the Cape Smith foldbelt share a negative correlation between Zr/Nb and

La/Yb that is expected for the incorporation of an enriched lithospheric component. This component is represented by the alkaline rocks comprised in the

Circum-Ungava supracrustal belts (carbonatites, lamprophyric lavas, alkaline basalts) and by the Lac Aigneau lamprophyric dykes (1941 ±3 Ma) intruding the

Ungava Peninsula. These alkaline magmas collectively have 2.2-2.1 Ga depleted- mantle Nd model ages (TDM) similar to a 2.15 Ga Sm-Nd isochron defined by the basaltic rocks of the supracrustal belts. Although these Nd TDM ages and isochron are 100-300 Ma older than magmatic ages, they are identical with the ca. 2.2 Ga mafic dykes of the Ungava Peninsula. This time correlation, along with the similar chemical signature of the northern dykes and younger Povungnituk basalts, suggest that the composition of younger lavas and alkaline magmas was influenced by an enriched component associated with the pervasive metasomatism of the lithosphere, coeval with the emplacement of the many ca. 2.2 Ga dykes.

Keywords: Mafic dyke swarms, alkaline magmas, U-Pb geochronology, Nd isotopes, continental lithosphere, Northeastern Superior Province

156 1. Introduction

Mafic dyke swarms can be traced back in time to the Archean-Proterozoic transition (ca. 2.5 Ga), and reflect magmatic events that are common to all

Archean Peninsulas. Genetic models for their origin have focused largely on their geographic patterns (Ernst et al., 1995; Fahrig, 1987), the loci of giant radiating swarms being interpreted by many as the sites of rising mantle plumes (Ernst and

Buchan, 2001a; LeCheminant and Heaman, 1989), whereas other workers interpret these patterns to reflect lithospheric stresses due to plate tectonic activity

(McHone et al., 2005). Because they appear to have been emplaced rapidly over large regions, mafic dyke swarms are also believed to be ideal markers with which to constrain regional stress fields and track the timing of supercontinent fragmentation (Bleeker and Ernst, 2006). Recent investigations, however, support an important role for pre-existing lithospheric weaknesses in controlling dyke emplacement (Jourdan et al., 2004; Mège and Korme, 2004), as a large range of magmatic ages are found within apparent individual dyke swarms (French et al.,

2004; Jourdan et al., 2006).

Over the past decades, studies of the Superior Province of Canada have produced many insights into the timing and extent of the numerous

Paleoproterozoic mafic dyke swarms intruding the Peninsula (Fig. 1, see compilation by Buchan and Ernst, 2004). Although some geochronological work

(Buchan et al., 1998) has been carried out on mafic dykes of the Northeastern

Superior Province, recent geological mapping of this area has increased our knowledge, and resulted in the recognition of a number of previously unknown dyke swarms. An appraisal of their distribution, age and chemical signatures

157 provide insights for the possible tectonic environments in which they were intruded. These mafic dykes also convey key information with which to constrain the chemical evolution of the lithospheric mantle between ca. 2.5 and 2.0 Ga, a period which saw the emplacement of both mafic dykes and mobile belts surrounding the Ungava Peninsula.

This paper presents six new U-Pb ages, and thirty nine neodymium isotopic determinations acquired on Paleoproterozoic mafic and lamprophyric dykes of the

Ungava Peninsula. The U-Pb results give new insights into the breakup of the

Superior Province, document an important Paleoproterozoic event that led to the emplacement of numerous dyke swarms with differing trends ca. 2.2 Ga, and have important implications for the secular evolution of its underlying mantle. We show that the Nd isotopic composition of the ca. 2.0-1.9 Ga volcanic and alkaline rocks of the Circum-Ungava mobile belts requires an enriched component whose age is coeval with the voluminous mafic dykes emplaced ca. 2.2 Ga. We propose that the remobilization of a metasomatized mantle, perhaps emplaced coevally with the delamination of the lithospheric mantle, controlled the composition of the more recent Paleoproterozoic magmas.

2. Geological background

2.1. Archean Northeastern Superior Province

Little knowledge about the interior of the Ungava Peninsula was gained after the pioneering work of Stevenson (1968), until regional mapping programs of the

Northeastern Superior Province by the Geological Survey of Canada (Percival et al., 1997 and references therein) and the Ministère des Ressources naturelles et de

158 la Faune of Québec (Simard, 2008 and references therein). Its magmatic and metamorphic evolution spans more than a billion years (3.8 – 2.6 Ga), as defined by over 200 U-Pb ages (see compilation in Simard, 2008), and it is comprised dominantly of Neoarchean plutonic suites, in which amphibolite- to granulite- grade greenstone belts occur as thin keels (1-10 km). The Northeastern Superior

Province is separated into two isotopically distinct regional terranes; to the East, the Rivière Arnaud Terrane (RAT) groups Archean rocks having juvenile isotopic signatures (depleted mantle model ages - TDM < 3.0 Ga), while to the West, the

Hudson Bay Terrane (HBT) is the remnant of a reworked Meso- to Paleoarchean

Peninsula, with Nd model ages as old as 3.8-4.3 Ga (Boily et al., 2009; O’Neil et al., 2008).

2.2. Paleoproterozoic volcano-sedimentary belts

Paleoproterozoic supracrustal belts emplaced during the Trans-Hudson

Orogeny (Lewry and Collerson, 1990) surround the Archean rocks of the

Northeastern Superior Province (the ‘Circum-Ungava geosyncline’ of Dimroth et al., 1970, Figs. 2 and 3). These belts include the Labrador Trough (New Québec

Orogen) to the East, the Cape Smith Foldbelt (Ungava Trough) to the North, and the Belcher Islands and associated coastal continental basalts (the Richmond Gulf and Nastapoka groups), to the West.

The supracrustal rocks of the Labrador Trough formed between ca. 2.17 and

1.80 Ga in three volcano-sedimentary depositional episodes (Clark and Wares,

2006, Fig. 3). The age of the first cycle is constrained by a ca. 2.17 Ga basal basalt unit (#1, Fig. 3), with deposition continuing to ca. 2.14 Ga (crosscutting

159 felsic granophyre, #2, Fig. 3), and possibly as recently as ca. 2.06 Ga (#3, Fig. 3,

Clark and Wares, 2006). The second depositional episode includes a platform sequence composed of sandstones, iron formation, turbidite and basalts lying uncomformably on both the Archean Peninsula and the first depositional cycle.

Its age is constrained by gabbroic sills (ca. 1.88 Ga), the Lac Lemoyne carbonatite

(<1.87 Ga), and the Lac Castignon lamprophyre (ca. 1.88 Ga #4, Fig. 3). The third depositional episode is interpreted to have occurred ca. 1.80 Ga and produced synorogenic foredeep sediments (Hoffman, 1987).

The E-W striking Cape Smith foldbelt is interpreted as the foreland thrust- belt of the Ungava Orogen, and contains volcano-sedimentary rocks deposited after the rifting of the Superior Peninsula (Hynes and Francis, 1982; Lamothe,

1994). An older depositional episode comprises the Povungnituk Group in the

South, which is divided into a sedimentary and a volcanic sequence (Fig. 3). The volcanics are dominated by flat to light REE-enriched tholeiitic basalts that lack the negative Nb-Ta anomalies typical of continental flood basalts (Modeland et al., 2003), and a small volume of alkaline basalt that occurs near Kenty Lake

(Gaonac’h et al., 1992). A gabbroic sill intruding the sedimentary rocks near the base of this group sets the beginning of the rifting event before 2.04 Ga (#5, Fig.

3), while the age of a rhyolite located within the upper part of the volcanic sequence indicates that deposition in the Povungnituk Group continued to ca. 1.96

Ga (#6, Fig. 3). The next magmatic episode is comprised of light REE-depleted picritic to tholeiitic basalts of the overlying Chukotat Group (Francis et al., 1983) that are coeval with the second depositional cycle of the Labrador Trough (Fig. 3).

The age of this group is constrained by comagmatic sills near the base (1.92 Ga)

160 and top (1.88 Ga) of the sequence (#7 and #8, Fig. 3). Further to the North, the

Watts Group comprises a dismembered suite of oceanic rocks including layered mafic to ultramafic rocks, basalts, and minor sedimentary rocks that has been dated at ca. 2.00 Ga (#9, Fig. 3).

Paleoproterozoic volcano-sedimentary rocks also outcrop in the western part of the Ungava Peninsula, on the Ottawa and Belcher islands, and along the eastern shore of Hudson Bay. The coastal basalts of the Richmond Gulf and Nastapoka groups lie uncomformably on the Archean basement (Chandler, 1988). Isotopic analyses made on diagenetic apatite grains in a sandstone unit at the base of the

Richmond Gulf Group yielded an age of 2.03 ±0.03 Ga (#10, Fig. 3). To the

West, the Belcher Islands expose continental and shallow water marine sedimentary sequences which contain two intercalated continental basalt units (the

Eskimo and Flaherty formations) whose ages are not well established (Legault et al., 1994; Ricketts and Donaldson, 1981). A Pb-Pb isochron from samples taken at the base of the Flaherty flows defines an imprecise age of 1.96 ±0.08 Ga (#11,

Fig. 3).

2.3. Alkaline rocks

The 2.04-1.88 Ga Circum-Ungava supracrustal belts host a wide variety of alkaline rocks (Fig. 2), including alkaline basalts near Kenty Lake (ca. 1.96 Ga,

Gaonac’h et al., 1992; Modeland et al., 2003), carbonatites near Lac Lemoyne

(<1.87 Ga, Wright et al., 1999), and ultramafic lamprophyres near Lac Castignon

(ca. 1.88 Ga, Chevé and Machado, 1988) and Lac Leclair (>2.04 Ga, Baragar et al., 2001). Other lamprophyres occur in the Lac Aigneau area, where more than

161 70 carbonated mafic to ultramafic alkaline dykes intrude the Archean basement

(Fig. 2, Berclaz et al., 2001; Lemieux et al., 2001). These dykes exhibit a wide range of compositions (18-42 wt.% SiO2; 10-18 wt.% Fe2O3t; 4-24 wt.% MgO; 3-

40 wt.% Ctot), and are highly enriched in incompatible trace elements (30-275 ppm La; 50-300 ppm Nb). The high Fe contents of the most magnesian samples are similar to those of Lac Leclair and Lac Castignon lamprophyres, and exhibit compositions ranging between aillikites and meimechites (Fig. 4).

2.4. Mafic dyke swarms

Numerous mafic dyke swarms intruded the Ungava Peninsula. The surface extents of swarms other than those found in the northeastern part of the region were poorly defined prior to the compilation of Maurice (2008). Fig. 2 presents a schematic summary of this compilation, which synthesizes preexisting data

(Buchan and Ernst, 2004; Fahrig and West, 1986) with recent ground observation stations compiled from the Système d’Information Géominière (SIGEOM) database. The dyke swarm nomenclature presented by Maurice (2008) is largely based on dyke trends, because of the small number of existing age dates and paleomagnetic data. This nomenclature should be used with some caution, because of the possibilities of dykes of different swarms being intermingled

(Jourdan et al., 2006), and dykes with different trends belonging to the same swarm (Buchan et al., 2007).

Previous U-Pb ages acquired on Ungava Peninsula mafic dykes range between 2.51 and 2.00 Ga (Buchan et al., 1998), a period that encompasses the new age data presented in the next section. The oldest age of 2505 +2/-1 Ma was

162 obtained on the NE trending Ptarmigan dykes in the eastern part of the Ungava

Peninsula. The next known dykes were intruded nearly 300 Ma later, in a voluminous magmatic event at 2209 ±1 Ma that emplaced the large WNW trending Klotz swarm. The WNW trending Maguire dykes in the center of the

Ungava Peninsula (Fig. 2) gave an age of 2229 +35/-20 Ma and could be coeval with the Klotz magmatic event. To the East, the Payne River swarm comprises a dense population of NNW dykes paralleling the supracrustal rocks of the northern

Labrador Trough. These dykes have an age of ca. 2.17-2.16 Ga (unpublished work by S. Pehrsson) and are probably coeval with the rifting event that emplaced the first cycle basalts of the Labrador Trough (Clark and Wares, 2006). To the

South, the WNW trending Minto dykes (Fig. 2) have the youngest U-Pb age obtained on mafic dykes of the Ungava Peninsula (1998 ±1 Ma, Buchan et al.,

1998), and are coeval with rocks of the Watts Group, in the northern part of the

Cape Smith foldbelt. Finally, although not dated, the NW trending dykes that cut the rocks of the Cape Smith foldbelt (Moorhead, 1996, fig. 2) are attributed to the

Franklin swarm (ca. 723 Ma, Buchan and Ernst, 2004).

Several other undated dyke swarms have been recognized prior to our study.

The north to NNW trending Irsuaq swarm in the northern Ungava Peninsula is composed of a few individual dykes that consist largely of gabbronorite, in contrast to the dominant gabbroic mineralogy of most mafic dykes in the Ungava

Peninsula. To the South, the Anuc dykes appear to define a coherent swarm having a NW trend that contrasts with the prevailing WNW trend of the Klotz dykes with which they occur, but parallels the Inukjuak dykes further to the West

(Budkewitsch et al., 1991; Legault et al., 1994). The few ENE to NE trending

163 Kogaluk Bay dykes in the western portion of the Ungava Peninsula parallel the

Couture swarm and the Cape Smith foldbelt to the Northeast. Few mafic dykes occur in the central portion of the Ungava Peninsula, but many are recognized in its southern portion (Fig. 2). The ENE trending Rivière du Gué dykes were initially defined in the compilation by Buchan and Ernst (2004) and later extended by Maurice (2008). These dykes roughly parallel the Paleoproterozoic sandstones of the Sakami formation, which outcrop as outliers in half-grabens in the Archean

Peninsula. The Rivière du Gué dykes, and rocks of the Sakami formation, collectively define an ENE corridor with a width of nearly 200 km that overlaps the Saindon-Cambrien structural corridor. Finally, although no age data is available in the southwestern Ungava Peninsula, Roy et al. (2004) suggested that the N to NNW dykes therein could belong to the Lac Esprit swarm recognized in the James bay area further to the South (2.07 Ga, Buchan et al., 2007).

3. Isotopic data

Most of the previous U-Pb isotopic data acquired on mafic dykes were collected along a reconnaissance geological transect (Percival and Card, 1994), such that aside from the northern Klotz and Payne River dyke swarms, only dykes of the central portion of the Ungava Peninsula had known ages (Fig. 2, Ptarmigan,

Maguire and Minto dykes, Buchan et al., 1998). The five new ages reported here for mafic dykes were chosen to fill in regional gaps in the existing data set.

Furthermore, no Nd isotopic data existed prior to this study.

164 3.1. U-Pb analytical protocol

Samples of an Irsuaq mafic dyke and a Lac Aigneau alkaline dyke collected during regional mapping projects were treated using traditional heavy mineral separation techniques (25-30 kg; Wilfley table, heavy liquids and Frantz magnetic separator), and respectively yielded zircon and perovskite grains. Twelve mafic dyke samples weighing 0.5-1.0 kg were also chosen from the MRNF archival collection and processed for baddeleyite recovery using a water-based separation technique (Söderlund and Johansson, 2002). Seven of these samples yielded baddeleyite grains (including the Irsuaq sample), and five were chosen for U-Pb analysis. The separated baddeleyite grains are generally transparent, light to medium metallic brown in color, and dominated by needle-shaped fragments.

The width of the baddeleyite grains is normally <30 μm, although rare grains reached 50 μm. Grains selected for isotopic analysis (Tables 1 and 2) were chosen optically at high magnification in order to obtain fractions containing between 5 and 25 crystals or fragments (<0.5 mg).

The fractions were washed in HNO3, H2O and acetone, and dissolved in

Teflon bombs using HF at 200ºC in the presence of a mixed 205Pb/233-235U spike.

Purification of U and Pb follows the procedure of Krogh (1973), modified by using small anion exchange columns. The samples were loaded on zone-refined

Re filaments with Si-gel and H3PO4 and measured on a VG Sector54 mass spectrometer by peak-jumping using the ion-counting Daly photomultiplier.

Corrections for mass fractionation (0.16% amu for < Pb, 0.14% amu for U) and dead time (11.5 ns) were determined by the repeated measurements of the

165 SRM981 and SRM982 Pb standard, U-500 U standard, as well as in-situ using the

233-235U ratio from the spike. The baddeleyite analyses were corrected for a Pb blank of 5 pg and 0.5 pg for U, but for some analyses, blanks have been higher, such that allowance was made during data reduction. The residual initial common

Pb was subtracted using compositions calculated with the Stacey and Kramers

(1975) model. Overall evaluation of the reproducibility was determined by the analysis of aliquots of separate fragments of zircon standard 91500 (Wiedenbeck et al., 1995). Results from sixteen analyses yield an age of 1066.2 ±0.6 Ma

(MSWD = 1.1). Age determinations and uncertainties were calculated using

Isoplot3 (Ludwig, 2003). Because the weight of baddeleyite fractions was estimated, U and Pb concentrations are approximate.

3.2. New U-Pb ages

The analyzed fractions are concordant to moderately discordant (-0.1 to

3.0%; Table 1; Fig. 5) and the results are interpreted to reflect magmatic crystallization. A regression of five baddeleyite fractions obtained from the

Irsuaq dyke yields an upper intercept of 2507.5 ±5.8 Ma (Fig. 5a), an age within error of that for the Ptarmigan dykes to the East (2505 +2/-1 Ma; Fig. 2) and the

Mistassini dykes further to the South (Fig. 1). Three zircon crystals yield Archean

207Pb/206Pb ages between 2.76 Ga and 2.70 Ga (Table 1; Fig. 5), that are significantly older than the dyke crystallization age and indicating they are xenocrysts. The regression of four baddeleyite fractions from an Anuc dyke yields an upper intercept defining an age of 2219.7 ±1.3 Ma (Fig. 5b), slightly older than that obtained for the Klotz dykes (2210 ±1 Ma) with which they occur

166 (Fig. 2), but similar to the Senneterre dykes of the southern Superior Province

(Fig. 1). The regression of five baddeleyite fractions from a Kogaluk Bay dyke yields an upper intercept defining an age of 2211.5 ±2.8 Ma (Fig. 5c), again similar to that obtained for Klotz dykes. Four baddeleyite fractions of a Couture dyke define a regression line with an upper intercept of 2199.4 ±5.1 Ma (Fig. 5d).

The Anuc, Kogaluk Bay, Klotz, Couture, and perhaps Maguire dykes, were collectively emplaced over a narrow time period of 20-30 Ma and cover a large portion of the Ungava Peninsula that is underlain by the thinnest lithospheric root

(Fig. 2). Finally, three baddeleyite fractions of a Rivière du Gué dyke are concordant, and a regression forced to 0 Ma yields an upper intercept with an age of 2149.4 ±3.0 Ma (Fig. 5e), an age close to that of a rhyolite dated in the first depositional cycle of the Labrador Trough (Fig. 3).

A Lac Aigneau alkaline dyke with relatively high Si content (36 wt.% SiO2;

00-GL-3178A4; Fig. 4) yielded four perovskite fractions whose linear regression has an upper intercept with an age of 1940.7 ±2.7 Ma (Fig. 5f). Perovskite grains from another Lac Aigneau dyke with lower Si content (26 wt.% SiO2; 00-GL-

3269A5) yielded a similar Pb-Pb age of 1932 ±14 Ma (Table 2; unpublished data) using the laser ablation inductively coupled plasma quadrupole mass spectrometry method (LA-ICP-QMS). In comparison, the nearby Lac LeMoyne carbonatite

(<1.87 Ga) and the Castignon lamprophyre (ca. 1.88 Ga) of the Labrador Trough

(Figs. 2 and 3) are more than 60 Ma younger than the Lac Aigneau dykes.

167 3.3. Sm-Nd analytical protocol

Whole rock ground samples were dissolved in a HF-HNO3 mixture in high- pressure Teflon vessels, with a 150Nd-149Sm tracer added to determine Nd and Sm concentrations. After evaporation, the samples reacted with HClO4 and were re- dissolved in 6M HCl. The remainder of the chemical procedure was adapted from

Pin et al. (1994) and Pin and Santos (1997). The samples were transferred to chromatographic columns packed with 2 ml AG1X8 resin to remove iron. The clear solutions were next evaporated and transferred into 1M HNO3. The light rare earth elements were concentrated using ~100 mg of Eichrom’s TRU specific resin in small disposable columns and were immediately eluted in silica glass columns containing ~600 mg of Eichrom’s LN specific resin. The Nd and Sm isotopic compositions were measured on a VG-Sector 54 mass spectrometer in dynamic and static modes, respectively. 143Nd/144Nd ratios were normalized to

146 144 Nd/ Nd = 0.7219. Repeated measurements of the JNdi-1 standard (Tanaka et al., 2000) yielded an average value of 143Nd/144Nd = 0.512139 ±8 (n = 7). All

143Nd/144Nd ratios have been bias corrected by -0.000027 to yield the published

143 144 standard Nd/ Nd value of 0.512115. Nd-depleted mantle ages (TDM) are calculated using the model of DePaolo (1988) and the CHUR values for the

143 144 calculation of the εNd(t) notation are as follows: Nd/ Nd = 0.512638 and

147Sm/144Nd = 0.1967.

168 3.4. Nd results

Nd isotopic analyses were obtained on 25 dykes for which age systematics are well constrained, and on 6 additional samples of other dykes across the

Ungava Peninsula (Table 3). All the analyzed samples were recovered from the

MRNF archival collection and their complete geochemical analyses are available in Maurice and Francis (in press). The mafic dykes of the Ungava Peninsula

143 144 display a large range of εNd(t) values between -10.5 and +4.8, with Nd/ Nd ratios ranging between 0.5112 and 0.5126 (Figs. 6 and 7). The four 2.51 Ga

Irsuaq dykes exhibit the most isotopically enriched compositions, with one sample having an anomalously high 147Sm/144Nd value that results in an extreme

εNd(2.51Ga) value of -10.5.

The Anuc, Kogaluk Bay, Klotz, Couture and Payne River dykes emplaced approximately 280 Ma later (2.22-2.17 Ga) have εNd(t) values ranging between -

0.3 and +4.1 (Fig. 7). The 2209-2199 Ma dykes (Klotz, Payne River and Couture) from the northernmost portion of the Ungava Peninsula within this timeframe exhibit values > +1.44, and occur exclusively in the juvenile Rivière Arnaud

Terrane, over the thinnest lithosphere of the Peninsula (Fig. 2). The analyzed samples of the slightly older 2220-2212 Ma swarms (Anuc and Kogaluk Bay) that also occur over a relatively thin lithosphere, contrastingly have εNd(t) values closer to 0 (Fig. 7), but occur within, or close to, the isotopically enriched Hudson

Bay Terrane (Fig. 2). The Rivière du Gué, Inukjuak, Lac Esprit and Minto dykes emplaced over the following 2.15-2.00 Ga period display negative εNd(t) values between -5.5 and +0.5 (Fig. 7), with the exception of one sample from the Rivière

169 du Gué swarm (εNd(2.15Ga) = +4.8). These dykes occur exclusively in the Hudson

Bay Terrane, over a thicker lithosphere than dykes emplaced in the 2.22-2.17 Ga period (Fig. 2). These enriched samples, together with the most enriched samples from older swarms, collectively define a mixing array corresponding to a ca. 2.85

Ga isochron that is significantly older than their Paleoproterozoic magmatic ages

(Fig. 6).

Hegner and Bevier (1991) have shown that Paleoproterozoic lavas and sills of the Cape Smith foldbelt (the Povungnituk Group, Chukotat Group and the

Purtuniq ophiolite) define a mixing array corresponding to a 2.21 ±0.03 Ga Nd whole rock isochron. Adding whole rock Nd data for basaltic and gabbroic samples from the Belcher Islands (Flaherty formation), the Ottawa islands, and the Labrador Trough (Hellancourt and Baby formations) produces an isotopic array with a similar age of 2.15 ±0.07 Ga. This age is statistically older than the magmatic age of these supracrustal rocks (2.04-1.88 Ga; Figs. 3 and 7), but similar to the age of the dykes of the Klotz, Payne River and Couture swarms that collectively scatter along the same isochron (Fig. 6). The 2.04-1.88 Ga supracrustal rocks of the Circum-Ungava belts have generally positive εNd(t) values close to that of the depleted mantle, with the exception of three spinifex basalts from the Ottawa Islands. In contrast, older 2.03 Ga samples from the

Belcher Islands (the Eskimo Formation) and from the Richmond Gulf (Persillon

Formation) have εNd(t) values between -6.8 and -4.3.

The Lac Aigneau alkaline dykes and Kenty lake alkaline lavas have positive

εNd(t) values (+3.6 and +0.5) that fall dominantly below the depleted mantle curve

170 (Fig. 7), and near the ca. 2.15 Ga isochron defined by the supracrustal rocks (Fig.

6). These isotopic characteristics are similar to those of Paleoproterozoic carbonatites of the southern Superior Province, with which they share 2.2-2.1 Ga depleted-mantle Nd model ages (TDM) that are significantly older than their 1.96-

1.84 Ga crystallization ages (Table 3). The ca. 2.15 Ga isochron obtained for the supracrustal rocks (Fig. 6), together with the 2.2-2.1 Ga model ages of alkaline rocks, are similar in age to the widespread emplacement of ca. 2.2 Ga mafic dyke swarms in the Ungava Peninsula (Fig. 2).

In summary, the few early dykes emplaced at ca. 2.5 Ga display strongly enriched isotopic signatures and were followed by an important hiatus of 300 Ma.

Widespread dykes at 2.22-2.20 Ga occur over the thinnest lithosphere of the

Ungava Peninsula and display contrasting isotopic signatures: those with the youngest 2209-2199 Ma ages emplaced in the Rivière Arnaud Terrane being the most primitive, while the oldest 2220-2212 Ma dykes emplaced close or within the Hudson Bay Terrane are the most enriched. The youngest and more isotopically enriched mafic dykes are recognized in the Hudson Bay Terrane, over a relatively thicker lithosphere, where dykes and continental basalts show progressively lower εNd(t) values with decreasing magmatic ages down to 2.0 Ga.

These isotopically enriched mafic magmas precede the ubiquitous emplacement of tholeiitic basalts with dominantly juvenile signatures in Circum-Ungava belts, and of alkaline magmas with εNd(t) values slightly lower than those of primitive mantle.

171 4. Geochemical systematics

Despite efforts to acquire U-Pb ages on mafic dykes of the Ungava Peninsula

(Buchan et al., 1998, this paper), only ~15% of the 209 samples for which geochemical data are available can be confidently attributed magmatic ages. This led Maurice and Francis (in press) to divide mafic dykes into chemically distinct groups in a manner unprejudiced by apparent dyke swarming. Their study identified four possible mantle sources, whose chemical systematics may be summarized as follows:

1- Main group dykes constitute ~65% of samples and have a large range of

Fe and Ti contents, with low Na contents and high V/Ti ratios. The main

group dykes can be separated into two subgroups on the basis of their

La/Yb and Zr/Nb ratios. Dykes of a low-LREE subgroup, which includes

dykes of the Klotz, Couture and Payne River swarms, have positive εNd(t)

values and display decreasing Zr/Nb with increasing La/Yb ratios towards

Paleoproterozoic alkaline magmas of the Ungava Peninsula (Fig. 8).

Dykes of a high-LREE subgroup, such as the Rivière du Gué swarm,

display contrastingly negative εNd(t) with increasing Zr/Nb ratios towards

Archean granitoids (Fig. 8). Dykes of the main group are interpreted as

magmas derived from fertile peridotite modified by enriched components

of distinct natures, the Archean crust in the case of the high-LREE

subgroup, and a Paleoproterozoic lithosphere in the case of the low-LREE

subgroup.

172 2- Low Fe-Ti group dykes have lower Fe, Ti, HFSE and HREE, and higher

Si contents compared to the main group dykes, and display relative

enrichments in LREE and LILE. These dykes are interpreted to reflect

melting of a refertilized refractory harzburgite mantle source. Dykes of

the low Fe-Ti group include the dated dykes of the Irsuaq and Maguire

swarms. The increasing Zr/Nb with La/Yb ratios (Fig. 8), along with

inherited Archean zircons in an Irsuaq dyke (Fig. 5a), both suggest that an

Archean crustal component is required in their petrogenesis.

3- High Fe-Ti group dykes have the highest Fe and Ti contents and exhibit

alkaline affinities in the form of high Na and low V/Ti ratios, but are not

alkaline sensu stricto (ne-normative). Al content separates this group into

a high-Al subgroup with low Si and high Yb contents that includes the

Minto swarm, and a low-Al subgroup with relatively higher Si but lower

Yb contents that includes the Anuc and Kogaluk Bay swarms (Fig. 8).

Dykes of the high-Al subgroup are interpreted has evolved ferropicrite

melts, while dykes of the low-Al subgroup are interpreted to reflect deep-

seated (5+ GPa) garnet-bearing pyroxenite and peridotite melts. The lower

Zr/Nb ratios of both subgroups relative to the high-LREE main group and

low Fe-Ti dykes, and higher La/Yb ratios relative to the low-LREE main

group dykes may reflect various proportions of both crustal and alkaline

lithospheric components in their petrogenesis (Fig. 8).

173 4.1. Comparison between dated dyke swarms

The oldest Irsuaq, Ptarmigan and Mistassini swarms (ca. 2.51 Ga) share similar La/Yb ratios (>10) that contrast from the lower values of the 2.47-2.45 Ga

Matachewan swarm of the Southern Superior Province (Fig. 1; Fig. 9a). Only the

Irsuaq dykes (low Fe-Ti group), however, have both high La/Yb and Zr/Nb ratios that approach those of evolved Archean crust (Fig. 9a), although a lack of data for the Ptarmigan dykes prevents a comprehensive comparison. The many swarms emplaced between 2.23 and 2.17 Ga exhibit a wide range of trace element compositions. The younger (2209-2170 Ma) Klotz, Payne River and Couture dykes (low-LREE main group) in the northern Ungava Peninsula (Fig. 2) have the least enriched La/Yb ratios (<4; Fig. 9b). The slightly older (2220-2212 Ma)

Anuc and Kogaluk Bay dykes (low-Al high Fe-Ti group) further to the southwest exhibit contrastingly higher La/Yb ratios (10-20) at similar Zr/Nb (~12), while the

Maguire and Senneterre swarms (low Fe-Ti group; 2230-2220 Ma) exhibit lower

La/Yb (4-6), but higher Zr/Nb (~20) ratios. Finally, the youngest Minto (high-Al high Fe-Ti group), Rivière du Gué (high-LREE main group), and the N-NNW subset of Lac Esprit dykes (2.15 to 2.00 Ga) have intermediate La/Yb values (4-

10), but similar Zr/Nb (10-15) values compared to the low-LREE main group dykes of the northern Ungava Peninsula. The regional distribution of the geochemical dyke groups of the Ungava Peninsula mirrors that of the Nd isotopic systematics, with dykes exhibiting evidence of a crustal component and having enriched isotopic compositions (high-LREE main, low Fe-Ti and high Fe-Ti groups) occurring within or close to the isotopically-enriched Hudson Bay

Terrane, while dykes without such a crustal component and having primitive

174 isotopic compositions (low-LREE main group) occurring in the Rivière Arnaud

Terrane (Maurice and Francis, in press).

4.2. Comparison with mafic volcanic and alkaline rocks

Few of the mafic dykes have the low La/Yb ratios of the basaltic rocks of the ca. 1.88 Ga Chukotat Group and cycle 2 of Labrador Trough (Fig. 9), an observation in agreement with the lack of mafic dykes with similar ages. The basaltic rocks of the Povungnituk Group (>2.04-1.96 Ga) contrastingly share an anti-correlation of La/Yb and Zr/Nb ratios with the more than 150 Ma older

Klotz, Couture and Payne River swarms, which are typical of the low-LREE main dyke group (Figs. 8 and 9). This feature is attributed to mixing with an enriched lithospheric component with high La/Yb but low Zr/Nb ratios (Modeland et al.,

2003), that is typified by the Lac Aigneau (1.94 Ga), Lac Leclair (>2.04 Ga), and

Lac Castignon (1.88 Ga) lamprophyres, along with the Kenty Lake basalts (ca.

1.96 Ga), which collectively exhibit increasingly La/Yb with decreasing Zr/Nb

(Fig. 9c).

Basalts of the lowermost Eskimo formation of the Belcher Islands are discriminated from the younger Flaherty formation on the basis of their higher trace element ratios that have been interpreted to reflect contamination by

Archean crust (Hegner and Bevier, 1991; Legault et al., 1994). Collectively, the continental basaltic rocks from the Belcher Islands and the Richmond Gulf

(Nastapoca Group, Hopewell and Long Island) of eastern Hudson Bay display a positive slope in a plot of Zr/Nb vs. La/Yb that trends towards the composition of

Archean crust, in distinct contrast to the array defined by the Povungnituk basalts

175 (Fig. 9c). The basaltic rocks of the Nastapoca Group (2.03 ±0.03 Ga) and the

Eskimo Formation have trace element characteristics that are similar to those of the Rivière du Gué (2.15 Ga), and roughly coeval Lac Esprit (2.07 Ga) and Minto

(2.00 Ga) swarms, with which they are all geographically associated (Fig. 2).

5. Discussion

The new U-Pb ages presented in this paper refine our constraints on the secular magmatic evolution of the Ungava Peninsula during the Paleoproterozoic era. While a few mafic dyke swarms with a limited areal distribution occurred at ca. 2.51 Ga (the Ptarmigan and Irsuaq swarms), voluminous dykes with many contrasting trends and a wide range of compositions, were emplaced later, between 2.23 and 1.94 Ga (Fig. 2).

5.1. Tectonic significance

Dykes are considered to propagate parallel to the highest compressive stress, their emplacement and distribution being controlled by the regional tectonic environment. Mafic dyke swarms are documented in a variety of geological settings, with parallel linear swarms commonly being associated with failed rifts, or the breakup of continental margins (Ernst and Buchan, 2001b; Fahrig, 1987).

The spatial and temporal association of mafic dyke swarms with rifting and continental break-ups is a significant help in paleogeographic reconstructions of now distant pieces of continental crust (Bleeker and Ernst, 2006). The tectonic significance of giant radiating swarms is, however, model dependent, with two end-members being proposed. The fanning that is characteristic of these swarms

176 can be related to lithospheric stress regimes associated with plate tectonics

(McHone et al., 2005) or to the rising of deep mantle plumes (Ernst and Buchan,

2001b; Ernst et al., 1995).

The tendency of some mafic dyke swarms to radiate from a focal point is taken to support the lateral transport of magmas from a central plume source

(Ernst and Buchan, 2001a), but direct evidence for flow direction is divisive.

Studies of the anisotropy of magnetic susceptibility (AMS) may support lateral flow in some dyke swarms (Ernst, 1989; 1994; Ernst and Baragar, 1992), but others do not produce consistent results (Phinney and Halls, 2001). Furthermore, the original AMS fabrics of dyke swarms from Labrador have been shown to have been vertical, before being replaced by later horizontal fabrics (Cadman et al.,

1992). Dykes can only propagate upward under conditions of positive buoyancy, and will propagate laterally as neutral buoyancy is approached (Lister, 1991;

Lister and Kerr, 1990). Such constraints may imply that crustal fractures are initially filled vertically, but then magma propagates laterally, unless there is a way to the surface, in which case vertical flow will dominate (Tarney, 1992).

5.1.1. Early 2.51 Ga dykes

The recognition of the Irsuaq swarm amongst the older mafic dykes of the

Superior Province expands the area of magmatic events at ca. 2.51 Ga. The comparable ages of the Irsuaq, Ptarmigan, and Mistassini dykes (2.51 Ga; Fig. 1), and their similar La/Yb ratios (Fig. 9), suggest they may be parts of a single giant radiating dyke swarm with a surface extent similar to the Matachewan swarm

(Fig.1). However, the gabbronorite mineralogy of the Irsuaq (Maurice et al.,

177 2005) and Ptarmigan dykes (Buchan et al., 1998) contrasts with the gabbro mineralogy of the Mistassini dykes (Fahrig et al., 1986). Furthermore, the Irsuaq and Ptarmigan swarms are composed of a few (5 to 7) individual dykes with restricted lateral extent (Fig. 2), whereas the Mistassini dykes are traceable over lengths >150 km and radiate from a common focal point (Fig. 1, Fahrig and West,

1986). These mineralogical and spatial differences may indicate that only the

Irsuaq and Ptarmigan dykes are comagmatic. An extension of their trends into the

Peninsula intersects in the Archean-aged Bienville plutonic sub-province to the

South, which seems an improbable locus for a radiating swarm.

The 2.51 Ga Irsuaq and Ptarmigan dyke swarms are markedly older than the volcanic rocks of Circum-Ungava belts (Fig. 3) and any other dyke swarms of the

Ungava Peninsula. Although no data is available for the Ptarmigan dykes, the

Irsuaq dykes display the most radiogenic isotopic ratios (Fig. 6), and have compositions that lie between those of the crustally contaminated basalts of eastern Hudson Bay and Archean granitoids (Fig. 9a). These characteristics, along with their negative εNd(t) values (Fig. 7), and the presence of Archean aged zircons (Fig. 5a) suggest that their petrogenesis involved extensive assimilation of evolved crustal components (Maurice and Francis, in press). The lack of coeval supracrustal belts preserved on the margins of the Ungava Peninsula further suggests that the early 2.51 Ga swarms may have been related to continental breakup to the North and Northeast, prior to the rifting events beginning at ca. 2.2

Ga that preceded the emplacement of the Circum-Ungava belts (Fig. 10).

178 5.1.2. Mantle plume or lithosphere delamination at 2.2 Ga?

Buchan et al. (1998) have proposed that the Maguire, Klotz, and Senneterre dykes (Fig. 1) collectively defined a ca. 2.21 Ga giant radiating dyke swarm, whose magma spread laterally from a focus above a mantle plume south of

Ungava Bay. Although a mantle plume scenario is plausible for the coeval Klotz and Senneterre dykes, the connection to the Maguire dykes remains tentative because of the uncertainty in their age (2229 +35/-20 Ma, Buchan et al., 1998).

Furthermore, the most recent compilation of the Ungava Peninsula dykes indicates that the Maguire dykes do not converge on the locus of the inferred plume, but rather parallel the Klotz dykes (Fig. 2). These discrepancies, along with the lower Zr/Nb and La/Yb ratios of Klotz dykes compared to that of the

Maguire and Senneterre dykes (Fig. 9), argue against the possibility that the three dyke sets were sourced from a common plume. A mantle plume model is also complicated by the identification of two new sets of nearly coeval dykes (2220-

2212 Ma; the Anuc and Kogaluk Bay dykes; Fig. 2). Their contrasting NW and

ENE trendings (Fig. 2), and distinctly more enriched isotopic (Fig. 7) and La/Yb ratios (Fig. 9b) make it unlikely they shared a common source.

The magmatic inactivity of the Ungava Peninsula after the emplacement of the Paleoproterozoic dyke swarms and Circum-Ungava belts implies that the present structure of its underlying mantle has not been affected by younger events.

Seismic tomography images indicate that the thickness of the lithosphere beneath the Ungava Peninsula changes dramatically from over 220 km in the center, to as little as ~140 km to the North (Fig. 2). The many dykes emplaced 2.23-2.20 Ga suggests that important perturbations occurred in the mantle underlying the

179 northern Ungava Peninsula in a relatively short time interval. The geographic correlation of these dyke swarms with the thinnest lithosphere may further implies that their magmas have been produced by decompression melting following the loss of the lower Archean crust and/or sub-continental lithosphere to the asthenosphere (Fig. 10). In this hypothesis, the relatively low La/Yb ratios and positive εNd(t) values of the voluminous 2209-2199 Ma mafic dykes (Klotz and

Couture) occurring in the Rivière Arnaud Terrane would reflect the composition of nascent asthenospheric melts. The high La/Yb (Fig. 9), but low εNd(t) values

(Fig. 7), of the slightly older 2229-2212 Ma mafic dykes (Maguire, Anuc and

Kogaluk Bay) would contrastingly reflect the chemical imprint of an Archean- aged lithosphere or lower crust prior to this event. Because these older dykes occur close to the boundary with the Hudson Bay Terrane (Fig. 2), it may further be postulated that the lithospheric stresses attributed to the purported delamination event were first initiated below the suture of the two terranes. In a model in which Klotz and Couture dykes represent the melting of asthenosphere following the loss of the lower crust and/or lithospheric mantle, the enriched La/Yb and

Zr/Nb ratios, negative εNd(t) values and inherited Archean zircons of the much older 2.51 Ga Irsuaq dykes (Figs. 5, 7 and 9) that also occur over a relatively thin lithosphere, would reflect the imprint of Archean material prior to the delamination event.

180 5.1.3. Rifting and failure of the lithosphere between 2.17 and 2.00 Ga

The supracrustal rocks of the Labrador Trough and Cape Smith belt respectively define the eastern and northern rifted margins of the Ungava

Peninsula (Fig. 2). The dense Payne River swarm (ca. 2.17 Ga), at the northeastern edge of the Ungava Peninsula, parallels the northern Labrador

Trough, and is interpreted to be the expression of early rifting (Fig. 2, Fahrig,

1987; Fahrig et al., 1986) coeval with cycle 1 basalts (Clark and Wares, 2006).

These dykes have depleted chemical compositions identical to those of the older

Klotz dykes (Fig. 9b), and the Archean lithosphere in this area may have been completely lost or sufficiently thinned to allow the passage of melts without the influence of Archean material.

Further to the South, the Rivière du Gué dykes (2.15 Ga) parallel the clastic sedimentary rocks of the Sakami formation (Fig. 2), which are interpreted as the expression of an aulacogen (Hoffman, 1988). Crosscutting mafic dyke relationships to the South, in the James Bay area, constrain the deposition of the

Sakami rocks to between 2.50 and 2.22 Ga (Buchan et al., 2007), an age bracket similar to that of the Huronian Supergroup of the Paleoproterozoic Southern

Province (Fig. 1). The Rivière du Gué dykes appear to fan 120º from a focus that corresponds to the NW to N bend in the Labrador Trough (at ~57ºN; Fig. 2), and could thus represent a fracture set associated with a failed rift in a thick Archean lithosphere. The >70 Ma age difference between the formation of the Sakami basins and the emplacement of Rivière du Gué dykes suggests that the dykes exploited pre-existing lithospheric structures. The occurrence of the Rivière du

Gué dykes (2.15 Ga) interspersed with Minto dykes (2.00 Ga), along with nearby

181 alkaline dykes and intrusions with ages of 1.94 and 1.88 Ga (Lac Aigneau, Lac

Lemoyne and Lac Castignon, Fig. 2), suggest that long-lived lithospheric structures controlled the emplacement of mantle-derived magmas over a period of at least 340 Ma in the southern Ungava Peninsula.

Continental dyke swarms are often interpreted as feeders to missing volcanic sequences assumed to have been lost to erosion. Many swarms are not, however, connected to volcanic sequences, with the spatial-temporal associations of the

MacKenzie dykes to the Muskox Intrusion and Coppermine continental basalts being the exception rather than the rule (Tarney, 1992). Our current knowledge on the timing of the emplacement of Circum-Ungava belts is limited by the few available U-Pb data (Fig. 3). Also, there is a body of Nd isotopic data for the

Circum-Ungava basaltic rocks (Fig. 7), but there are few precise Nb analyses aside from those compiled in Fig. 9c. This lack of data is especially acute for the

Labrador Trough, where numerous Nd isotopic data are available for the ca. 1.9

Ga volcanic cycle (Fig. 7), but nothing is available on the older 2.17-2.14 Ga cycle, for which coeval dyke swarms exist. Although this situation prevents a comprehensive comparison of the mafic dykes with volcanic rocks, straightforward correlations do exist.

The mafic volcanic rocks of the Eskimo and Persillon formations of eastern

Hudson Bay are not precisely dated (ca. 2.03 ±0.03 Ga), but share negative εNd(t) values (Fig. 7) and enriched trace element signatures (Fig. 9) of the youngest mafic dykes of the southern Ungava Peninsula (2.15-2.00 Ga; Minto, Lac Esprit,

Inukjuak, Rivière du Gué) with which they are spatially associated (Fig. 2). The

182 increasing Zr/Nb with La/Yb ratios and enriched isotopic signature of the Eskimo basalts of Belcher Islands are interpreted to reflect the assimilation of the Archean crust (Hegner and Bevier, 1991; Legault et al., 1994). The similarities between the basaltic rocks of eastern Hudson Bay and the mafic dykes of the Hudson Bay

Terrane suggest they shared a common petrogenesis, controlled by the assimilation of an Archean crustal component. The progressively decreasing

εNd(t) values of mafic dykes and coastal basalts of the Hudson Bay Terrane between 2.15 and 2.00 Ga (Fig. 7) further suggests that mantle-derived magmas became increasingly contaminated by the Archean crust or lithosphere, until the failure of the lithosphere at ca. 2.0 Ga, and subsequent eruption of the depleted basalts of the Flaherty Formation (Figs. 3, 7 and 9). The diachronic rifting of the western Hudson Bay Terrane crust relatively to the Rivière Arnaud crust has been hindered by a thicker lithosphere that produced increasingly isotopically enriched basaltic melts. The lack of mafic dykes with <2.0 Ga ages coeval with the majority of the Circum-Ungava basaltic rocks (Fig. 7) suggests that the latest mantle melting events were focused below rifted margins. Furthermore, the primitive mantle-like La/Yb ratios of the youngest ca. 1.9 Ga Chukotat Group and cycle 2 Labrador Trough lavas (Fig 9c) suggests that these late mantle-derived magmas erupted along the rifted margins of a completely failed lithosphere.

5.2. Imprint of the 2.2 Ga event on 2.0-1.9 Ga magmas

The different mantle sources (lherzolite, harzburgite, pyroxenite) and contrasting enriched contaminants (enriched mantle and crustal components)

183 recorded in dykes with negative εNd(t) values intruding the Hudson Bay Terrane lead Maurice and Francis (in press) to propose that their petrogenesis was controlled by a heterogeneous Archean lithosphere left after a long-lived history of melt extraction and enrichment. In contrast, the positive εNd(t) values and the negative correlation of the Zr/Nb and La/Yb ratios of dykes intruding the Rivière

Arnaud Terrane (Klotz, Couture and Payne River dykes; Fig. 7) are similar to those of the basaltic rocks of the Povungnituk basalts (Fig. 9). Although these

2.21-2.17 Ga dykes are >100 Ma older than the basalts, these common features are attributed to the involvement of an enriched lithospheric component

(Modeland et al., 2003). The lack of an Archean crustal component in dykes intruding the Rivière Arnaud Terrane, but a widespread occurrence of the enriched lithospheric component in both terranes (Maurice and Francis, in press) may suggest that much of the lithosphere underlying the Ungava Peninsula has been modified by metasomatic event(s).

The emplacement of the 2.0-1.9 Ga volcanic rocks of Circum-Ungava belts coincides with the production of Paleoproterozoic alkaline magmas within the belts and the Ungava Peninsula (carbonatites, ultramafic lamprophyres and alkaline basalts; Figs. 1 and 2). The frequent association of ultramafic lamprophyres having compositions ranging from aillikites to meimechites (Fig. 4) with zones of rifting, lithospheric weakness, and/or Peninsula peripheries is difficult to explain because they are too Fe-rich to have equilibrated with primitive mantle at shallow depths. Their Fe-rich character cannot be reconciled by special pleading for an Fe-rich lithospheric reservoir, and they likely originated

184 from depths approaching the intersection of the mantle 1350ºC adiabat with the

CO2 solidus at ca. 9 GPa (Francis and Patterson, 2009). The association of the

Lac Castignon, Lac Leclair and Lac Aigneau lamprophyres with zones of rifting that formed the present Ungava Peninsula (Fig. 2) would thus be consistent with a very deep seated source in the asthenosphere.

The ubiquitous 2.2-2.1 Ga depleted mantle model ages of 2.0-1.9 Ga alkaline magmas of the Superior Province (Table 3) indicate that they sampled a common isotopically enriched component. Their low Zr/Nb ratios (<7) limit the possible involvement of enriched Archean crust (~30; Fig. 8) in explaining their slightly enriched isotopic compositions. The striking correspondence between the model ages of alkaline magmas and the magmatic ages of the numerous ca. 2.2-2.1 Ga dyke swarms of the Ungava Peninsula suggests that their source region was influenced by the magmatic event responsible for the dyke swarms. Furthermore, the ca. 2.15 Ga Sm-Nd isotopic array defined by the 2.00-1.88 Ga volcanic rocks and syn-volcanic gabbroic sills of the Circum-Ungava belt (Fig. 6) would also be consistent with the magmas of the volcanic belts recording the influence of such an older ca. 2.2 Ga event. The decrease in Zr/Nb with increasing La/Yb ratio

(Fig. 9) towards alkaline magmas, but positive mantle-like εNd(t) values (Fig. 7) of the ca. 2.2 Ga depleted dykes, require that the metasomatic enrichment was pene-contemporaneous with the melting event.

An active debate surrounds the possibility of genetically relating metasomatic agents with coeval magmas through a single infiltration-reaction process. For instance, Bodinier et al. (2004) suggested that the emplacement of

185 amphibole-garnet pyroxenite dykes is associated with the infiltration of coeval silicate, hydrous, and carbonate melts responsible for the metasomatic aureoles in mantle harzburgites. In a similar fashion, a study of pyroxenite xenoliths hosted by lamprophyric dykes has identified three different trace element signatures in mafic minerals (LREE-enriched but HFSE depleted clinopyroxene; LILE-, HFSE- and REE-enriched clinopyroxene; and HFSE-and REE-depleted clinopyroxene), each of which is correlated with a distinct metasomatic agent (carbonatites, silicate magmas and hydrous fluids or melts, Orejana and Villaseca, 2008). Their study proposes that these agents are derived coevally from the progressive differentiation of a single CO2–H2O-rich alkaline agent associated with the lamprophyric melts. In the case of the Ungava Peninsula, the deep-seated source estimated for the lamprophyres that record ca. 2.2 Ga model ages requires either that these enrichments occurred in the asthenosphere, or while passing through the lithosphere.

The metasomatic alkaline agent associated with the 2.2 Ga magmatic event remains cryptic, as aside from the perhaps older Lac Leclair lamprophyres (>2.04

Ga), alkaline rocks with 2.2 Ga crystallization ages have yet to be found. The ubiquitous ca. 2.2 Ga Nd model ages for 2.0-1.9 Ga basaltic and alkaline magmas throughout the Ungava Peninsula nonetheless imply that their melts have incorporated an enriched component and retained the older Nd isotopic signature of a 2.2 Ga metasomatized mantle. These observations support former proposals that two mantle reservoirs are required to explain the Nd isotopic (Hegner and

Bevier, 1991) and trace element variations (Modeland et al., 2003) of Cape Smith belt lavas. By linking ca. 2.0-1.9 Ga magmatism to the numerous ca. 2.2 Ga

186 continental dyke swarms, our study extends these observations to the entire

Ungava Peninsula and identifies the two isotopic reservoirs as: 1) a volumetrically dominant asthenospheric source typified by the northernmost mafic dykes (εNd(t)

+5 to +3) of the Klotz event, and 2) a volumetrically subordinate, but widespread, enriched source typified by the alkaline magmas (εNd(t) +3 to +1). The recognition of 1.9-1.8 Ga carbonatites with 2.2-2.1 Ga Nd model ages geographically associated with voluminous ca. 2.2 Ga mafic dykes in the

Southern Superior Province (Fig. 1; Table 3) may further signify that the enrichment observed in the Ungava Peninsula is not unique, and that the whole

Superior Province may have been influenced by similar processes.

6. Conclusions

The numerous Paleoproterozoic mafic dyke swarms emplaced between 2.51 and 2.00 Ga carry important temporal information for the breakup in the Ungava

Peninsula, as well as chemical constraints for the secular evolution of its underlying mantle. Two small coeval dyke swarms ca. 2.51 Ga represent the first magmatic events that followed the stabilization of the Archean Peninsula and map the extent of early failed arms. The many swarms emplaced after a 280 Ma magmatic hiatus, between 2.23 and 2.20 Ga, record major lithospheric stresses that led the breakup of the Craton. These dykes now occur above the thinnest lithosphere of the northern Ungava Peninsula and exhibit chemical signatures that vary from enriched 2229-2212 Ma dykes to voluminous and relatively-depleted

2209-2199 Ma younger dykes. The depleted character of the latter may reflect the

187 dominant input of the asthenosphere after decompression melting associated with the lost of the Archean lithospheric keel. Dykes emplaced ca. 2.17 Ga in the northeastern Ungava Peninsula have identical depleted chemical signatures that reflect early rifting of a nascent Paleoproterozoic lithosphere. Progressively decreasing εNd(t) values of mafic dykes and coastal basalts of the western margin of the Ungava Peninsula between 2.15 and 2.00 Ga contrastingly suggests increasingly contaminated mantle-derived magmas by a preserved Archean lithosphere, until its failure at ca. 2.0 Ga, and subsequent eruption of depleted basalts. The lack of mafic dykes with <2.0 Ga ages coeval with the majority of the Circum-Ungava basaltic rocks, along with the primitive mantle-like compositions of the youngest lavas, suggest that the latest mantle melting events were focused below rifted margins.

The voluminous ca. 2.2 Ga depleted northern dykes record enriched lithospheric components in the form of increasing La/Yb with decreasing Zr/Nb ratios similar to those of the younger (>100 Ma) Povungnituk basalts. This relationship is likely due to the incorporation of an enriched lithospheric component similar to the younger (ca. 1.9 Ga) alkaline magmas (carbonatites, lamprophyres, and alkaline basalts) both seen in the supracrustal belts and

Archean basement. Although these alkaline magmas are 2.0-1.9 Ga in age, they have uniform 2.2-2.1 Ga depleted-mantle Nd model ages similar to a 2.15 Ga Sm-

Nd isochron defined by the basaltic rocks of Circum-Ungava belts. These Nd ages suggest that the isotopic composition of the younger magmas reflects an earlier metasomatic enrichment event associated with the emplacement of the

188 many ca. 2.2 Ga mafic dykes of the Ungava Peninsula, indicating that these mafic dyke swarms correspond to a major magmatic episode that modified much of the lithospheric mantle.

Acknowledgments

R. Stevenson, B. Ghaleb and R. Lapointe kindly helped C. Maurice with the basics of Sm-Nd separation and assisted with the mass spectrometer. Discussions with A. Berclaz, R. Ernst and J. Goutier helped to clarify the regional field observations related to mafic dykes and alkaline lamprophyres. S. Faure

(CONSOREM) kindly provided unpublished seismic tomography images of the

Ungava Peninsula. K.N.M. Sharma and P. Lacoste are thanked for contributing their thin section description database and M. Leduc and P. Drapeau are acknowledged for their efficient sample organization of the MRNF archival collection. Comprehensive reviews by O. Nebel and U. Söderlund, and competent handling by associate editor W. Mueller resulted in significant improvements of and earlier version of the manuscript. This research has been partly supported by a National Scientific and Engineering Research Council of

Canada (NSERC) discovery grant (RGPIN7977-00) to D. Francis. Ministère des

Ressources naturelles et de la Faune contribution #2009-2010-8439-01.

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195 Table captions

Table 5-1: U-Pb isotope dilution - thermal ionization mass spectrometry (ID-

TIMS) analytical data for five Paleoproterozoic dykes and one

lamprophyric dyke of the Ungava Peninsula. Abbreviations of mineral

as follows: bad, baddeleyite; prv, perovskite; zc, zircon.

Table 5-2: Synoptic table of coordinates and physical characteristics of sample on

which U-Pb data were acquired (see Table 1).

Table 5-3: Nd isotopic data acquired on whole rock samples from five

Paleoproterozoic dykes and a Lac Aigneau lamprophyric dyke of the

Ungava Peninsula, Kenty Lake alkaline basalts and carbonatite

intrusions of the Superior Province.

196 Figure captions

Figure 5-1: Schematic distribution of mafic dyke swarms (modified from Buchan

et al., 2007; Maurice, 2008) and alkaline rocks of the Superior Province

emplaced over a) ca. 2.51-2.44 Ga; b) ca. 2.23-2.17 and c) ca. 2.15-1.88

Ga. Acronyms for alkaline rocks as follows: KL, Kenty Lake; LA, Lac

Aigneau; LC, Lac Castignon; LE, Lac Lemoyne; LL, Lac Leclair; CG,

Cargill; BO, Borden; SR, Spanish River. The inset in a) shows the

location of the Ungava Peninsula and the location of Fig.2.

Figure 5-2: Map of Paleoproterozoic mafic dyke swarms, alkaline, and

supracrustal rocks of the Ungava Peninsula. Figure modified from

Maurice (2008). Acronyms as follows: SCSC, Saindon-Cambrien

structural corridor (Portella, 1980); KL, Kenty Lake; LA, Lac Aigneau;

LC, Lac Castignon; LE, Lac Lemoyne; LL, Lac Leclair. Isotopic data

apparently not corresponding with dykes are from dykes having

thicknesses < 10m. The contour lines indicate lithospheric thickness (in

km) and are a courtesy of S. Faure (CONSOREM), based on the data and

modeling by Godey et al. (2003). εNd(t) values as reported in Table 3.

Figure 5-3 : Schematic stratigraphic columns and available ages for the Circum-

Ungava Paleoproterozoic volcano-sedimentary belts (St-Onge et al.,

2000). U-Pb ages from (Chandler and Parrish, 1989; Chevé and Machado,

1988; Findlay et al., 1995; Machado et al., 1997; Machado et al., 1993;

197 Parrish, 1989; Rohon et al., 1993; St-Onge et al., 1992; Todt et al., 1984;

Wodicka et al., 2002).

Figure 5-4 : Si vs. Fe in cation units for ultramafic lamprophyres of the Ungava

Peninsula (MgO > 10 wt.% on a LOI free basis). CO2 is calculated as a

rock forming cation. Black triangles are for Lac Leclair, dark grey

symbols for Lac Aigneau dykes and light grey symbols for Lac Castignon

lamprophyres. The vertical solid line represents the composition of

olivine (Si = 33.33 cation units). The dashed lines are taken from a

comparative study of alkaline ultramafic dykes (Francis and Patterson,

2008). The dashed line on the left separates most aillikites from Group-I

kimberlites, while the dashed line on the right separates meimechites from

olivine lamproites.

Figure 5-5: U-Pb concordia diagrams showing analyses of the mineral fractions

reported in Table 1.

Figure 5-6: 143Nd/144Nd vs. 147Sm/144Nd for Paleoprotorezoic mafic dykes (n =

30), circum-Ungava supracrustal rocks (n = 50), alkaline dykes (n = 8) and

lavas (n = 4) of the Ungava Peninsula and carbonatites of the western

Superior Province. The 2.15 ±0.07 Ga isochron is calculated with the

mixing array defined by samples from 1.88-2.00 Ga supracrustal rocks of

the circum-Ungava belts, but excluding the isotopically enriched samples

from the Ottawa Islands, the Eskimo Formation and the Persillon

198 Formation. Acronyms for dyke swarms are as follow: Ir, Irsuaq; A, Anuc;

B, Kogaluk Bay; K, Klotz; C, Couture; P, Payne River; G, Rivière du Gué;

In, Inukjuak; ?, unknown swarm; E, Lac Esprit and M, Minto. Acronyms

for supracrustal rocks are as follow: Ef, Eskimo Formation; Pf, Persillon

Formation; Po, Purtuniq Ophiolite; Ff, Flaherty Formation; Pg,

Povungnituq Group; Cg, Chukotat Group; Oi, Ottawa Islands and Lt,

Labrador Trough. Acronyms for carbonatites of the southern Superior

Province are as follows: S, Spanish River; D, Borden and C, Cargill. All

data for mafic dykes and the datum for a Persillon Formation sill are from

this study (Table 3). Data for supracrustal rocks are from Chauvel et al.

(1987), Hegner and Bevier (1991), Rohon et al. (1993), and Skulski et al.

(1993). Data for the three western Superior carbonatites from Bell and

Blenkinsop (1987). Lac Aigneau Alkaline dykes are plotted at 1940 Ma

(data from Table 3), while alkaline lavas of the Povungnituq Group are

plotted at 1960 Ma (data from Gaonac’h et al., 1992).

Figure 5-7 : εNd(t) vs. age for mafic and alkaline rocks of the Ungava Peninsula

and carbonatites of the Southern Superior Province. The juvenile Archean

crust evolution field for the Ungava Peninsula is calculated with the

average of twenty three 2.78-2.70 Ga felsic rock samples having εNdt

values >+1.5 (data from the compilation by Maurice, 2007). The depleted

mantle field is calculated following the model of DePaolo (1981). Data

and symbols as reported in Fig. 6. Acronyms for mafic dykes as in Fig. 6.

199 Acronyms for supracrustal rocks not in the caption of Fig. 6 are as follow:

Po, Purtuniq Ophiolite; Ff, Flaherty Formation; Pg, Povungnituq Group

and Cg, Chukotat Group. Some overlapping symbols have been slightly

offset for clarity.

Figure 5-8 : Zr/Nb vs. La/Yb vs. for Archean granitoids (diamonds),

Paleoproterozoic alkaline rocks (triangles) and mafic dykes of the Ungava

Peninsula (see graphic legend) divided accordingly to the chemical groups

presented in Maurice and Francis (in press). Mafic dyke samples on

which U-Pb ages were acquired in the Ungava Peninsula (from Fig. 5 and

Buchan et al., 1998) are indicated with the same acronyms as in Fig. 6

(Maguire sample is labeled ‘Mg’). TT is the average of Archean tonalite-

trondhjemite samples of the Ungava Peninsula (light grey diamonds) and

GG is the average of granite-granodiorite samples (dark grey diamonds).

Data for Archean granitoids from Percival and Mortensen (2002), the

SIGEOM database, and unpublished data by J. Bédard. Mafic dyke data

from Maurice and Francis (in press), and from an unpublished compilation

by R. Ernst. Kenty Lake data from Modeland et al. (2003); Lac Leclair

data from Baragar et al. (2001); Lac Aigneau data from the SIGEOM

database; and Castignon lamprophyres are unpublished data of D. Francis.

Figure 5-9 : Zr/Nb vs. La/Yb vs. for mafic dykes of the eastern Superior Province

for which U-Pb ages are well known (a and b), and for mafic volcanic

rocks and alkaline rocks from Circum-Ungava belts (c). Archean

200 granitoids and alkaline rocks data as in Fig. 8. Povungnituk data from

Modeland et al. (2003); Chukotat data from the SIGEOM database; coastal

and island basalts from Legault et al. (1994) and unpublished data; cycle 2

Labrador Trough (Lt) from Skulski et al. (1993).

Figure 5-10 : Schematic mantle sections showing the possible evolution of the

Ungava Peninsula between 2.5 and 1.9 Ga. a) 2.51 Ga – the crust and

lithosphere are tectonically thickened after the collage of the two

Archean terranes and the production of late felsic melts. The basaltic

lower crust transforms into amphibolite and granulite/garnet

pyroxenite/eclogite assemblages. This period sees the formation of

failed rifts evidenced by the coeval Irsuaq and Ptarmigan swarms and

perhaps the Sakami basins. b) 2.23-2.20 Ga – the density increase in

the lower crust results in gravitational instabilities in the lithospheric

keel, which lead to detachment and foundering into the asthenosphere

(see a review of this process in Lustrino, 2005). Decompression

melting first triggers lithospheric melts in the vicinity of the Archean

terranes suture and produce the 2.23-2.21 Ga Maguire, Anuc and

Kogaluk Bay dykes with enriched trace element and isotopic

signatures inherited from the Archean lithosphere and crust. The

ongoing sinking of the lithosphere allows the impingement of hot

buoyant asthenosphere and the production of voluminous melts of the

2.21-2.20 Ga Klotz event with depleted trace element and isotopic

signatures. The asthenosphere accretes to the remaining lower crust

201 and is coevally modified into a newly metasomatically enriched lithosphere, perhaps through contemporaneous partial melting of the sinking lower crust (Lustrino, 2005). c) 2.0-1.9 Ga – a period that sees the emplacement of alkaline rocks and basalts recording ca. 2.2 Ga Nd ages inherited from their interaction with enriched metasomatic components (LA, Lac Aigneau lamprophyres; KL, Kenty Lake alkaline basalts). In the Cape Smith Foldbelt (CSF) to the North, the basalts of the Povungnituk Group display lithospheric components, while later lithospheric failure released asthenospheric melts of the

Chukutat Group. The lowermost supracrustal rocks of the Richmond

Gulf (RG) and Belcher Islands (BI) to the SW contrastingly display crustally contaminated signatures similar to those of coeval and geographically related mafic dykes, until the lithosphere failed and permitted the emplacement of the juvenile basalts of the Flaherty

Formation.

202 Table 5-1:

Mineral Pb U Isotopic ratios Age (Ma) com fct. Weight Disc. Th/U ±1 ±1 ±1 # (mg) (ppm) (pg) 206Pb/204Pb 206Pb/238U 207Pb/235U 207Pb/206Pb ±2 ±2 ±2 (%) σ σ σ 206Pb/238U 207Pb/235U 207Pb/206Pb σ σ σ (1) (2) (3) (4) (%) (4) (%) (4) (%) 02-OR-6200A – Irsuaq badd. 1 0.0100 26 16.1 0.041 503 0.4734 0.24 10.773 0.26 0.16505 0.11 2498.4 9.9 2503.7 4.9 2508.1 3.5 0.5 badd. 2 0.0020 49 4.8 0.037 633 0.4705 0.31 10.691 0.35 0.16481 0.13 2485.5 12.8 2496.6 6.4 2505.7 4.4 1.0 badd. 3 0.0020 248 9.6 0.034 1548 0.4662 0.18 10.565 0.19 0.16437 0.07 2466.8 7.3 2485.6 3.6 2501.1 2.5 1.6 badd. 4 0.0100 29 21.3 0.109 421 0.4609 0.28 10.478 0.32 0.16488 0.10 2443.4 11.4 2478.0 5.8 2506.4 3.5 3.0 badd. 5 0.0030 37 9.6 0.076 358 0.4612 0.32 10.479 0.37 0.16478 0.13 2445.0 13.1 2478.1 6.8 2505.3 4.4 2.9 zc. 6 0.0020 341 18.6 0.926 1224 0.5341 0.17 14.105 0.19 0.19155 0.07 2758.5 7.4 2756.8 3.6 2755.5 1.2 -0.1 zc. 7 0.0010 167 5.1 0.701 1362 0.5191 0.25 13.377 0.26 0.18691 0.07 2695.3 11.0 2706.7 5.0 2715.2 1.2 0.9 zc. 8 0.0008 245 2.0 0.429 4396 0.5235 0.30 13.389 0.31 0.18549 0.08 2714.1 13.1 2707.5 5.8 2702.5 1.3 -0.5 01-JD-8224A – Anuc badd. 1 0.0060 114 36.4 0.062 505 0.4115 0.16 7.913 0.19 0.13947 0.08 2221.8 6.2 2221.2 3.4 2220.6 2.7 -0.1 badd. 2 0.0080 51 7.0 0.046 1523 0.4082 0.15 7.834 0.16 0.13918 0.04 2206.8 5.5 2212.1 2.9 2217.0 1.5 0.5 badd. 3 0.0040 111 2.8 0.119 4016 0.4061 0.15 7.795 0.17 0.13922 0.05 2197.0 5.7 2207.7 3.0 2217.5 1.8 1.1 badd. 4 0.0030 384 3.9 0.043 7676 0.4062 0.18 7.796 0.22 0.13919 0.10 2197.6 6.9 2207.7 3.9 2217.1 3.5 1.0 03-SG-7060A - Kogaluk Bay badd. 1 0.0150 30 13.1 0.083 892 0.4064 0.18 7.747 0.24 0.13827 0.15 2198.3 6.9 2202.1 4.4 2205.6 5.2 0.4 badd. 2 0.0040 104 5.2 0.020 1999 0.4044 0.18 7.729 0.20 0.13863 0.08 2189.0 6.8 2199.9 3.5 2210.1 2.6 1.1 badd. 3 0.0150 55 3.4 0.093 6120 0.4034 0.17 7.695 0.18 0.13836 0.06 2184.5 6.2 2196.0 3.2 2206.8 1.9 1.2 badd. 4 0.0050 94 5.8 0.114 2089 0.4010 0.16 7.651 0.18 0.13837 0.06 2173.8 5.8 2190.9 3.1 2206.9 1.9 1.8 badd. 5 0.0050 105 5.0 0.130 2646 0.3983 0.15 7.590 0.16 0.13820 0.06 2161.2 5.4 2183.6 2.9 2204.8 2.0 2.3 01-ST-4156A – Couture badd. 1 0.0020 45 2.7 0.029 889 0.4038 0.34 7.659 0.35 0.13757 0.08 2186.4 12.5 2191.8 6.3 2196.9 2.9 0.6 badd. 2 0.0030 50 3.0 0.060 1275 0.4018 0.25 7.621 0.26 0.13754 0.09 2177.5 9.3 2187.3 4.6 2196.5 3.1 1.0 badd. 3 0.0050 29 2.9 0.127 1247 0.3996 0.24 7.558 0.25 0.13718 0.07 2167.1 8.7 2179.8 4.5 2191.9 2.3 1.3 badd. 4 0.0050 17 8.5 0.042 272 0.3926 0.42 7.412 0.48 0.13692 0.18 2135.1 15.1 2162.4 8.6 2188.6 6.4 2.9

203

Pb U Isotopic ratios Age (Ma) com fct. Weight Disc. Mineral Th/U 206 204 206 238 ±1 207 235 ±1 207 206 ±1 # (mg) (ppm) (pg) Pb/ Pb Pb/ U Pb/ U Pb/ Pb ±2 ±2 ±2 (%) σ σ σ 206Pb/238U 207Pb/235U 207Pb/206Pb σ σ σ (1) (2) (3) (4) (%) (4) (%) (4) (%) 02-RT-4058A - Rivière du Gué badd. 1 0.0040 17 5.9 0.126 374 0.3938 0.46 7.265 0.60 0.13383 0.31 2140.2 16.6 2144.6 10.6 2148.8 10.9 0.5 badd. 2 0.0100 25 5.7 0.082 1149 0.3958 0.22 7.306 0.24 0.13387 0.11 2149.7 8.0 2149.5 4.3 2149.3 3.7 0.0 badd. 3 0.0150 26 6.4 0.119 1554 0.3933 0.30 7.262 0.29 0.13392 0.19 2138.1 10.8 2144.1 5.2 2150.0 6.5 0.7 00-GL-3178A4 - Lac Aigneau Prv. 1 0.230 21 106.7 8.210 995 0.3499 0.16 5.740 0.21 0.11898 0.10 1934.1 5.5 1937.4 3.6 1941.0 3.6 0.4 Prv. 2 0.220 25 132.7 9.470 921 0.3490 0.17 5.726 0.20 0.11901 0.07 1929.6 5.5 1935.3 3.4 1941.5 2.6 0.7 Prv. 3 0.033 66 97.1 10.047 514 0.3476 0.20 5.700 0.21 0.11894 0.13 1923 6.6 1931.4 3.7 1940.4 4.7 1.0 Prv. 4 0.040 93 106.1 7.950 771 0.3398 0.30 5.582 0.33 0.11913 0.17 1885.8 9.9 1913.3 5.7 1943.2 6.2 3.4

(1) Concentrations are evaluated with a 10-20% precision (2) Total common lead (spike, contamination and mineral) (3) Ratios corrected for mass bias (4) Ratios corrected for mass bias, contamination (Pb = 5 pg, U = 0.5 pg), 205Pb-233U-235U spike and common initial Pb. Errors are presented at 1s. The common Pb isotopic composition is calculated following the two stages evolution model of Stacey and Kramers (1975).

204 Table 5-2:

(1) Swarm Coordinates (2) (3) (4) Petrographic description Trend Width (m) Age (Ma) eNd(t) sample# Easting Northing Zone Irsuaq 02-OR-6200A Cpx, Opx enclosed by Pl. Intersticial qtz. 427799 6720338 18 359º 100 2508 ±6 -1.00 (gabbronotite) Acicular Am partially replaces Cpx. Anuc 01-JD-8224A Twinned Cpx, Pl and Ol embedded in Cpx. 470566 6560798 18 315º 15 2220 ±1 0.44 (gabbro) Acicular Am partially replaces Cpx. Kogaluk Bay 03-SG-7060A Cpx, Pl. Acicular Am partially replaces Cpx. 372272 6557855 18 252º > 30 2212 ±3 -0.26 (gabbro) Couture 02-ST-4156A Cpx surrounding Pl. Am, Chl and Bt strongly 473310 6690066 18 265º > 30 2199 ±5 4.09 (gabbro) replace Cpx. Common intersticial qtz. Rivière du Gué 02-RT-4058A Cpx surrounding Pl. Common Cb and Ser 490277 6227128 18 260º 80 2149 ±3 -1.23 (gabbro) replace Plag. Aigneau 00-GL-3178A4 Ol, Cpx, Phl phenocrysts and Ap, Mag, Cb, Tlc 369334 6356976 19 345º 4 1941 ±3 1.92 (meimechite) in matrix. Granitoid and peridotite xenoliths. (5) Aigneau 00-GL-3169A5 Ol, Phl phenocrysts and Phl, Ap, Mag, Cb in 371654 6410890 19 315º 1 1932 ±14 - (aillikite ) matrix. Granitoid xenoliths. (5) (1) UTM NAD83; (2) All widths estimated visually; (3) Refers to data presented in Table 1 and Figure 5; (4) data from Table 3; (5) unpublished work by G. Lemieux

205 Table 5-3: Coordinates (1) Age I or D Nd Sm Tdm (4) Sample Zone Swarm 147Sm/144Nd 143Nd/144Nd e Easting Northing (Ga) (3) (ppm) (ppm) Nd(t) (Ga) Mafic dykes 2001032394 470586 6560995 18 Anuc 2.22 D 23.45 5.18 0.1336 0.511738 ± 8 0.44 2.68 2001038774 473310 6690066 18 Couture 2.20 D 12.60 3.44 0.1649 0.512386 ± 23 4.11 - 2001035381 353407 6541338 18 Inukjuak 2.10 I 40.77 8.44 0.1251 0.511366 ± 6 -5.51 3.05 2001035388 369698 6464132 18 Inukjuak 2.10 I 28.06 8.14 0.1755 0.512370 ± 6 0.51 - 2001035396 402741 6529304 18 Inukjuak 2.10 I 34.25 8.39 0.1480 0.511856 ± 9 -2.13 - 2002034803 431596 6685783 18 Irsuaq 2.51 I 12.27 2.41 0.1189 0.511288 ± 11 -1.23 2.98 2002034806 416866 6687557 18 Irsuaq 2.51 I 16.81 4.04 0.1451 0.511252 ± 7 -10.47 - 2002034858 423707 6713123 18 Irsuaq 2.51 I 16.35 3.17 0.1173 0.511263 ± 7 -1.21 2.97 2003031459 427799 6720338 18 Irsuaq 2.51 D 9.08 1.85 0.1230 0.511368 ± 8 -1.00 2.98 2000024427 646201 6674243 18 Klotz 2.21 D 31.70 9.35 0.1783 0.512581 ± 8 4.13 - 2000024430 642383 6663408 18 Klotz 2.21 I 37.38 9.47 0.1532 0.512078 ± 39 1.44 - 2000024433 580086 6679604 18 Klotz 2.21 I 15.46 4.17 0.1631 0.512357 ± 8 4.10 - 2003031577 372272 6557855 18 Kogaluk Bay 2.21 D 41.44 9.09 0.1326 0.511690 ± 14 -0.26 2.73 2006047179 376629 6559372 18 Kogaluk Bay 2.21 I 27.76 5.99 0.1304 0.511688 ± 11 0.32 2.66 2002037376 459131 6220448 18 Lac Esprit 2.07 I 19.90 4.70 0.1427 0.511798 ± 9 -2.05 - 2003039848 418526 6385537 18 Minto 2.00 I 28.45 6.14 0.1303 0.511633 ± 9 -2.59 2.76 2003039990 479576 6326424 18 Minto 2.00 D 17.24 3.96 0.1388 0.511761 ± 9 -2.28 2.82 1999022708 392735 6655192 19 Payne 2.17 I 37.27 11.49 0.1864 0.512701 ± 7 4.14 - 1999022736 418853 6714988 19 Payne 2.17 I 34.07 10.61 0.1883 0.512694 ± 10 3.46 - 1999022743 378217 6720846 19 Payne 2.17 I 45.80 12.69 0.1675 0.512435 ± 7 4.20 - 2002037331 436876 6230913 18 Sill Eskimo Fm. 2.03 I 7.55 1.89 0.1510 0.511806 ± 11 -4.34 - 2002037239 432796 6297603 18 R. du Gué 2.15 I 23.46 4.30 0.1109 0.511668 ± 9 4.80 2.19 2002037240 515268 6252605 18 R. du Gué 2.15 I 14.97 3.57 0.1441 0.511806 ± 8 -1.71 - 2002037339 490277 6227128 18 R. du Gué 2.15 D 15.73 3.72 0.1432 0.511817 ± 10 -1.23 - 2002037340 442291 6263812 18 R. du Gué 2.15 I 37.14 8.10 0.1319 0.511613 ± 18 -2.11 2.85

206 Coordinates (1) Age I or D Nd Sm Tdm (4) Sample Zone Swarm 147Sm/144Nd 143Nd/144Nd e Easting Northing (Ga) (3) (ppm) (ppm) Nd(t) (Ga) Mafic dykes 1999020157 361806 6337914 19 (2) 2.10 I 19.05 4.54 0.1439 0.511812 ± 10 -1.89 - 1999021063 400252 6337392 19 (2) 2.10 I 22.22 5.15 0.1399 0.511875 ± 8 0.42 2.63 2000030310 361445 6414090 19 (2) 2.10 I 15.23 3.35 0.1328 0.511699 ± 10 -1.09 2.72 2001035370 372604 6511107 18 (2) 2.10 I 20.91 4.82 0.1394 0.511852 ± 13 0.13 2.65 2006047178 412823 6773645 18 (2) 2.10 I 12.52 2.91 0.1405 0.511743 ± 6 -2.30 - Alkaline dykes 2000030303 361445 6414090 19 Lac Aigneau 1.94 I 41.70 7.35 0.1065 0.511575 ± 291 1.75 2.23 2000030306 361445 6414090 19 Lac Aigneau 1.94 I 132.92 21.27 0.0967 0.511511 ± 8 2.95 2.13 2000030319 400791 6359146 19 Lac Aigneau 1.94 I 46.85 8.10 0.1046 0.511589 ± 23 2.50 2.18 2000030321 378559 6357898 19 Lac Aigneau 1.94 I 1409 167.88 0.0720 0.511071 ± 8 0.51 2.23 2000030323 369334 6356976 19 Lac Aigneau 1.94 D 44.45 8.37 0.1139 0.511678 ± 25 1.92 2.24 2000030327 371654 6410890 19 Lac Aigneau 1.94 I 74.44 11.46 0.0930 0.511465 ± 14 2.98 2.12 2000030330 396533 6388429 19 Lac Aigneau 1.94 I 67.19 11.05 0.0994 0.511580 ± 15 3.63 2.09 2000030332 369061 6394764 19 Lac Aigneau 1.94 I 118.16 17.29 0.0885 0.511344 ± 8 1.73 2.19 Kenty Lake(5) 145- F - - - - 1.96 I 144.6 25.48 0.1066 0.511598 2.41 2.20 146-C - - - - 1.96 I 110.3 20.77 0.1139 0.511664 1.86 2.26 78-A - - - - 1.96I 96.32 14.84 0.0932 0.511425 2.40 2.18 81-D - - - - 1.96I 90.80 13.43 0.0895 0.511391 2.68 2.15 Carbonatite intrusions of the Superior Province (6) Spanish River - - - - 1.84 D 92.9 14.3 0.0929 0.51145 1.35 2.14 Borden - - - - 1.87 D 109.9 22.4 0.1230 0.51182 1.74 2.23 Cargill - - - - 1.91 D 283 49.2 0.1050 0.51158 1.82 2.20 (1) UTM NAD83; (2) Dyke for which swarm belonging is not determined. An hypothetical age of 2.1 Ga is attributed for the eNd calculation; (3) I = Dyke for which the age is interpreted; D = Dyke that has been dated (this study; Table 2 or Buchan et al., 1998); (4) Model ages of samples having high 147Sm/144Nd ratios (> 0.14) are not included; (5) Data from Gaonac'h et al. (1992); (6) Data from Bell and Blenkinsop (1987).

207 Figure 5-1:

208 Figure 5-2:

209 Figure 5-3:

210 Figure 5-4:

211 Figure 5-5:

212 Figure 5-6:

213 Figure 5-7:

214 Figure 5-8:

215 Figure 5-9:

216 Figure 5-10:

217

CHAPTER 6

General Conclusions

218 The secular study of geochemical data collected across the Northeastern

Superior Province (NESP) documents the composition of mantle-derived magmas emplaced over a period of 1 billion years (Ga), between 2.9 Ga and 1.9 Ga, and shows that their signature depends on the nature of the crust and lithosphere they intruded. The NESP comprises dominantly Neoarchean felsic plutonic suites in which greenstone belts aged 2.9-2.7 Ga were emplaced at 20-40 million years

(Ma) intervals. Both felsic plutonic suites and greenstones are sparsely peppered by volumetrically minor mafic-ultramafic plutonic bodies. On the regional scale, the Archean craton is divided into two isotopically distinct terranes that are separated by a migmatized sedimentary basin. The Rivière Arnaud Terrane in the

Northeast groups Archean rocks having dominantly juvenile Nd isotopic signatures (TDM 2.8-3.0 Ga), and the Hudson Bay Terrane in the West and South comprises the remnants of a reworked Meso- to Paleoarchean craton (TDM 3.0-4.3

Ga). The intrusion of a few mafic dyke swarms at 2.5 Ga marks the beginning of the Paleoproterozoic era and is followed by more voluminous swarms emplaced between 2.2 and 2.0 Ga. The intrusion of alkaline lamprophyres at 1.9 Ga is the last known magmatic event occurring in the NESP.

We recognized three geochemically distinct suites of mafic volcanics contained in the Archean greenstone belts: the Mg-tholeiite, Fe-tholeiite and

LREE-enriched suites, whose emplacement encompasses a secular change in the nature of coeval felsic magmas, from tonalite-trondhjemite prior to 2.75 Ga, to dominantly granite-granodiorite and pyroxene-bearing felsic rocks. The Fe- tholeiites are restricted to the 2.78 Ga assemblages, but are found in greenstone belts across the entire Rivière Arnaud Terrane. This geographical distribution,

219 along with numerous zircons recovered from greenstone belts having inheritance ages corresponding to those of older volcanic units, suggest the autochthonous emplacement of a mafic cover sequence across a large area of the NESP. Our model for the Archean evolution of the NESP questions the applicability of plate tectonic models for the assembly of terranes, and postulates a single docking event of two isotopically distinct TT-greenstone terranes at ca. 2.76-2.74 Ga. An increase in the Th/Nb ratios of LREE-enriched mafic magmas at 2.75 Ga likely reflects a change in the nature of their contaminant; from tonalite-trondhjemite prior to 2.75 Ga to granite-granodiorite afterwards. The increasing proportion of

LREE-enriched lavas in younger greenstone belts, and the isotopically-enriched character of mafic-ultramafic rocks after 2.75 Ga, reflect more extensive contamination of mantle-derived tholeiitic magmas by a felsic crust affected by regional partial melting. This study did not examine the volumetrically small, but widespread, 2.73-2.69 Ga mafic-ultramafic bodies ranging in composition from peridotite to hornblende websterite and gabbronorite that are encountered throughout the NESP. A comprehensive understanding of their petrogenesis would possibly clarify the role of mantle-derived magmas in the regional melting of the NESP crust, coevally to their emplacement.

The numerous mafic dyke swarms emplaced after the stabilization of the

Archean craton provide constraints for the evolution of the underlying mantle in the Paleoproterozoic, with their composition being dependent on the terrane they intruded. We have shown that an Archean crustal component, characterized by negative εNd values and high La/Yb, Th/Nb and Zr/Nb ratios, was assimilated by

220 a variety of primary mantle melts of dykes intruding the older Hudson Bay

Terrane;

1- Most of the dykes were formed by basaltic magmas derived from a

lherzolite source, suggesting that despite a long-lived history of Archean

melt extraction, fertile mantle domains persisted in Paleoproterozoic

times,

2- Volumetrically less important, but ubiquitous, Fe-rich and high-Al dykes

that may represent evolved ferropicrite magmas,

3- Fe-rich, but low-Al dykes, formed by deep-seated (5+ GPa) melts

sourced in garnet-bearing pyroxenite and lherzolite,

4- Fe-poor mafic dykes that occur dominantly along the boundary of the

two terranes may represent melts of depleted harzburgite from a

sandwiched mantle wedge.

The voluminous mafic dykes that intrude the juvenile Rivière Arnaud

Terrane at 2.2 Ga are derived from a fertile lherzolitic mantle and carry positive

εNd values. The lack of an Archean crustal component in these dykes may either signify that the underlying lower crust and lithosphere are Paleoproterozoic in age, or that the crust was too cold to be assimilated at the time of their emplacement. The mafic dykes of the Rivière Arnaud Terrane record an enriched mantle component in the form of increasing La/Yb with decreasing Zr/Nb ratios that is likely due to the incorporation of a component that was similar to the younger (ca. 1.9 Ga) alkaline rocks (carbonatites, lamprophyres, and alkaline basalts) seen in both the supracrustal belts and Archean basement. Although these

221 alkaline magmas are relatively young, they carry 2.2-2.1 Ga depleted-mantle Nd model ages similar to a 2.15 Ga Sm-Nd isochron defined by basaltic rocks of the

Circum-Ungava belts, suggesting that the isotopic composition of the younger magmas reflect an earlier metasomatic enrichment event associated with the emplacement of the 2.2 Ga mafic dykes. The few Nd isotopic data that exist for the 1.9 Ga alkaline rocks in the Southern Superior Province appear to record identical 2.2 Ga Nd model ages to those of the NESP and a more systematic investigation of their isotopic signature would perhaps lead to the recognition of a

2.2 Ga mantle-modifying event on the scale of the entire Superior Province.

The Paleoproterozoic mafic dyke swarms intruding the NESP also provide a temporal record of the breakup of the craton. The two oldest 2.51 Ga swarms represent the first mafic magmas after the stabilization of the Archean craton, and may map the extent of early failed rifts. The many swarms emplaced between

2.23 and 2.20 Ga, after a 280 Ma magmatic hiatus, record major lithospheric stresses prior to the breakup of the craton to the North and Northeast, and eruption of basalts of the Circum-Ungava belts. These dykes now occur above the thinnest lithosphere of the NESP and exhibit chemical signatures that vary from enriched

2229-2212 Ma dykes to voluminous relatively-depleted 2209-2199 Ma younger dykes. The depleted character and abundance of the latter may reflect the dominant input of asthenospheric melts after decompression melting associated with the loss of an Archean lithospheric keel. A progressive decrease in the εNd values of mafic dykes and coastal basalts in the western NESP between 2.15 and

2.00 Ga suggests increasing contamination of mantle-derived magmas by Archean

222 lithosphere, until its failure at 2.0 Ga led to the eruption of depleted basalts. The

Paleoproterozoic mafic dyke swarms of the NESP provide an ideal opportunity to study the evolution of sulfur isotopes of their magmatic sulphides over the 2.5-2.0

Ga time interval that spans the rise of oxygen in the Earth’s atmosphere. A systematic comparison of the sulfur isotopes of these mantle-derived dykes with those of coeval sedimentary rocks would provide new insights into the rise of oxygen in the Earth’s mantle.

223

APPENDIX A

224

APPENDIX B

226 Sample 1998018123 1998018131 1998018238 1998018239 1998018241 1998018242 1998018547 1998018548 Group Main Main Main Main Main Main Main Hi Fe-Ti Subgroup Lo-LREE Hi-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE Hi-Al Swarm Klotz - Klotz Klotz Klotz Klotz - - Age (Ma) 2209 0 2209 2209 2209 2209 0 0 Width (m) large20----12- Trend 125 7.7 110 110 295 110 94 170 Northing 6606333 6586084 6653108 6652395 6644163 6648633 6176067 6173590 Easting 392463 334562 354222 356211 404281 367649 340095 403811 Zone 19 19 19 19 19 19 19 19 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 47.94 46.46 50.03 49.12 50.04 49.83 49.15 45.69 TiO2 1.29 0.96 0.96 1.4 1.15 1.14 0.74 2.14 Al2O3 14.1 17.6 14.17 15.85 14.23 14.79 15.58 14.78 Fe2O3 13.82 11.12 12.58 14.17 13.34 13.95 10.01 17.19 MnO 0.21 0.14 0.19 0.2 0.2 0.21 0.17 0.22 MgO 6.95 7.24 7.5 4.86 6.9 5.8 7.59 5.54 CaO 9.21 12.41 11.81 10.89 11.32 11.39 10.68 9.52 Na2O 1.54 1.52 1.79 2.37 1.84 2.12 2.15 2.51 K2O 2.78 0.22 0.15 0.18 0.15 0.11 1.27 0.77 P2O5 0.08 0.1 0.06 0.1 0.07 0.09 0.02 0.22 LOI 1.8 2.1 0.7 0.3 0.8 0.5 2 1.1 Cr2O3 0.024 0.021 0.04 0.008 0.028 0.014 0.033 0.01 Ctot 0.03 0.09 0.06 0.01 0 0 0.04 0

As0.50000000 Au 1 0 0.7 8.3 0.7 2.7 0.6 0 Ba 450 120 58 60 26 40 270 377 Ce 15 21.6 9.1 12.9 9 11 12.7 40.7 Co 51.5 64.6 49.4 50.7 46.3 52.9 47.9 61.8 Cs 0.3 0.6 0 0.1 0 0.1 8.8 3.5 Cr 00000000 Cu 149.5 63.6 111.9 220.3 131.7 169.2 83.7 58.9 Dy 4.19 1.61 3.42 3.78 3.44 3.84 2.65 5.74 Er 2.34 1.05 1.99 2.21 2.26 2.37 1.67 3.4 Eu 1.13 1.01 0.73 0.96 0.84 1.07 0.84 1.73 Ga 17.3 22.9 15.8 18.9 17.5 17.3 14.1 23.5 Ge 3.62 2.64 2.84 3.77 3.4 3.86 2.06 5.96 Hf 2 0.8 1.4 2.1 1.6 1.8 1.6 3.5 Ho 0.94 0.36 0.63 0.8 0.72 0.76 0.55 1.23 La 5.5 9.5 3.7 5 3.4 4.2 5.2 17.4 Lu 0.31 0.1 0.22 0.33 0.26 0.33 0.23 0.47 Mo 0.1 0.1 0.1 0.2 0.1 0.1 0.2 0.4 Nb 4.4 0.9 3.4 5.5 3.6 4.5 2 9.7 Nd 11.2 13.3 7.6 8.2 7 7.7 8.3 22.8 Ni 63.9 45.3 31.1 16.9 13.2 11.9 67.2 42.1 Pb 1.9 2.5 0.3 0.6 0.3 0.3 4.7 2.8 Pd 3.3 0 2.3 41.1 0.7 18.3 3.5 0 Pr 1.9 2.88 1.43 1.91 1.43 1.79 1.94 5.13 Pt 4.3 0 1.9 48.7 0.9 25.7 3.4 0 Rb 69.4 6.2 3.8 7.5 4.9 4.1 95.2 24.2 Rh 0.25 0 0 1.9 0 2.93 0 0.14 S 0.14 0.39 0.11 0.07 0.06 0.05 0.07 0.13 Sc 44 33 42 35 40 40 35 35 Sm 2.9 2.7 2 2.4 2.4 2.3 2.5 5.4 Sr 287 696 106.3 155.9 105.3 118.9 278.6 280.7 Ta 0.3 0 0.2 0.3 0.3 0.3 0.2 0.6 Tb 0.75 0.38 0.49 0.6 0.54 0.52 0.48 0.92 Th 0.5 0.1 0.6 0.2 0.1 0.4 0.1 1.3 Tl0.4000000.10.1 Tm 0.38 0.13 0.28 0.31 0.37 0.27 0.25 0.43 U0.10000000.3 V 349 289 282 353 316 298 215 301 W 0.1 0.1 0.1 0.1 0 0.1 0.2 0.5 Y 25.5 9.7 17.6 22.8 21.2 22.6 15.6 35.7 Yb 2.34 1.04 1.9 2.43 2.23 2.52 1.79 3.54 Zn 78 30 20 33 13 29 59 56 Zr 68.2 18.4 50.1 69.8 55.8 61.8 40.8 115.2 Nd (TIMS) 00000000 Sm (TIMS) 00000000 147Sm/144Nd 00000000 143Nd/144Nd 00000000 Tdm (Ma) 00000000

227 Sample 1998018549 1998020065 1998020066 1998020069 1998028823 1999020157 1999021044 1999021063 Group Lo Fe-Ti Main Main Main Main Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Subgroup - Lo-LREE Lo-LREE Lo-LREE Lo-LREE Hi-Al Hi-Al Lo-Al Swarm - - - Klotz Klotz - - - Age (Ma) 0 0 0 2209 2209 2100? 0 2100? Width (m) 10 20 50 - large 10 large large Trend 210 100 100 105 110 305 295 280 Northing 6172277 6582000 6571995 6595914 6635584 6337914 6341397 6337392 Easting 415884 336863 349327 355953 384483 361806 376059 400252 Zone 19 19 19 19 19 19 19 19 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 54.79 49.82 48.86 50.39 47.95 44.94 45.83 49.75 TiO2 0.4 1.58 1.6 1.49 1.24 1.97 2.33 1.79 Al2O3 9.22 13.09 13.13 13.31 14.85 15.36 14.26 11.44 Fe2O3 9.65 16.47 16.7 16.35 14.62 17.11 16.71 15.43 MnO 0.15 0.23 0.24 0.23 0.21 0.21 0.21 0.24 MgO 15.66 5.38 5.73 5.29 5.35 6.59 5.82 6.19 CaO 6.31 9.88 10.34 10.18 11.45 9.64 8.58 7.72 Na2O 1.56 2.08 2.01 2.14 1.95 2.45 2.52 4.21 K2O 0.7 0.26 0.37 0.22 0.26 0.7 1.1 0.76 P2O5 0.05 0.16 0.13 0.14 0.09 0.18 0.39 0.1 LOI 0.6 0.6 0.9 0.2 1.7 1.2 1.4 2.4 Cr2O3 0.278 0.009 0.013 0.012 0.018 0.014 0.011 0.012 Ctot 0.01 0.02 0.02 0 0 0 0.04 0.29

As 00000.7001.3 Au 0 1 1.1 2 4.6 0 0 0.8 Ba 205 72 53 70 70 326 484 133 Ce 22 21.8 18.1 19.5 14.6 32.6 61.5 36.8 Co 64.7 56.9 58.3 55.3 47.1 66.8 58.3 53.6 Cs 0.9 0.4 0.2 0 0.2 2.3 3.7 0.3 Cr 00000000 Cu 43.8 177.9 146.6 191.8 215.6 47.3 47.4 143.4 Dy 1.63 4.61 4.69 4.6 3.47 4.97 6.41 4.15 Er 0.97 3.12 2.99 3.08 2.58 2.95 3.62 2.1 Eu 0.49 1.1 1.09 1.16 0.99 1.76 2.26 1.48 Ga 11.3 17.4 17.7 18.8 17.1 21.8 21.6 17.2 Ge 1.5 4.41 4.04 4.09 3.48 4.83 6.36 4.58 Hf 1.5 2.6 2.5 2.9 2 2.8 4.4 3.7 Ho 0.36 1.14 0.98 1.05 0.91 1.06 1.33 0.81 La 10 9.2 7 8.4 5.6 15.5 29.5 15.6 Lu 0.12 0.42 0.36 0.41 0.3 0.38 0.46 0.28 Mo 0.2 0.3 0.2 0.3 0.2 0.3 0.5 0.5 Nb 1.7 10.3 8.7 8.4 5.5 9.3 12.4 9.7 Nd 8.3 14.1 12.8 13.5 9.3 21.2 38.1 22.6 Ni 45.3 21.5 32.9 13 29.4 57.1 55.8 73.1 Pb 1.6 1.6 0.3 0.4 1.3 1.9 4.9 1.4 Pd 6.1 0.6 0.6 5.4 26.4 0 0.7 2.4 Pr 2.5 3.02 2.51 2.85 1.98 4.3 7.9 5.02 Pt 6.8 0 0 7.8 31.3 0 0 2.2 Rb 26.6 6 8.2 5.4 8.2 30.2 45.4 25.6 Rh 1.69 0.22 0 0.12 0.63 0 0 0.47 S 0.02 0.19 0.18 0.13 0.07 0.11 0.16 0.31 Sc 25 45 46 45 39 32 31 19 Sm 1.7 3.7 3.7 4 3 4.8 7.2 5.3 Sr 173.7 133.5 126.5 128.9 153.7 292.8 294 256.7 Ta 0 0.7 0.6 0.6 0.4 0.5 0.6 0.7 Tb 0.28 0.83 0.78 0.72 0.68 0.85 1.04 0.85 Th 1.5 0.9 0.6 0.9 0.4 0.5 1.3 3.7 Tl 0.1 0.1 0 0 0 0.1 0.2 0 Tm 0.13 0.42 0.36 0.44 0.38 0.46 0.47 0.28 U 0.5 0.2 0.1 0.2 0.1 0.2 0.3 0.9 V 139 363 380 354 271 276 255 220 W 0.1 0.2 0 0.1 0 0.1 0.2 0.4 Y 10.5 31.6 27.5 30.8 25 31.3 37.7 21.1 Yb 0.98 3.21 2.96 3.07 2.64 2.74 4.05 2.05 Zn 10 29 44 32 78 73 94 54 Zr 54.4 99.2 76.4 95 63.6 103.9 167.7 125.2 Nd (TIMS) 0000019.05 0 22.22 Sm (TIMS) 000004.54 0 5.15 147Sm/144Nd 000000.1439 0 0.1399 143Nd/144Nd 000000.511812 0 0.511875 Tdm (Ma) 00000002626

228 Sample 1999021069 1999021366 1999021382 1999022708 1999022712 1999022735 1999022736 1999022743 Group Hi Fe-Ti Hi Fe-Ti Lo Fe-Ti Main Main Main Main Main Subgroup Lo-Al Lo-Al - Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE Swarm ---Payne - Payne - - Age (Ma) 0 0 0 2170 0 2170 2170 2170 Width (m) 50 2 large large 30 large - large Trend 200 280 30 330 231 330 - 330 Northing 6406999 6333770 6328986 6655192 6679285 6756507 6714988 6720846 Easting 414218 417754 398208 392735 400933 374296 418853 378217 Zone 19 19 19 19 19 19 19 19 Laboratory ACME COREM ACME ACME ACME ACME ACME ACME SiO2 50.73 50.1 50.02 48.95 49.36 48 48.52 49.85 TiO2 1.59 1.62 0.48 1.76 1.34 1.37 1.04 2.04 Al2O3 12.08 11.1 13.55 14.54 13.92 13.99 16.3 15.51 Fe2O3 14.82 14.6 10.6 15.99 14.08 13.91 10.59 15.49 MnO 0.17 0.17 0.16 0.22 0.2 0.19 0.16 0.22 MgO 5.52 5.8 10 4.56 6.5 7.11 6.41 2.8 CaO 7.39 8.04 10.35 10.48 10.82 10.14 11.91 9.34 Na2O 4.86 4.7 2.01 2.33 1.97 1.38 1.91 2.76 K2O 0.54 1.21 0.8 0.19 0.2 0.62 0.64 0.32 P2O5 0.16 0.13 0.02 0.16 0.11 0.11 0.07 0.21 LOI 1.3 2.3 1.8 0.3 0.8 2.7 1.8 1.4 Cr2O3 0.016 0.02 0.069 0.01 0.016 0.027 0.028 0 Ctot 0.04 0 0.06 0.02 0.03 0.03 0.07 0.03

As 0.60.5000000 Au 0 2 1.6 2.2 0 0.5 0.5 0 Ba 120 130 135 41 34 133 259 86 Ce 51.8 28 17.5 16.2 11.7 21.6 9.4 32.1 Co 51.5 57 51.3 46.5 51.6 45.8 40.9 38.5 Cs 0 0.5 0.9 0.1 0.4 2 0.1 0.4 Cr 094000000 Cu 157 0 65.4 231.7 103.6 37.4 108.3 71.3 Dy 5.32 0 2.49 5.47 4.08 4.33 3.19 6.68 Er 2.75 0 1.89 3.67 2.75 2.75 2.17 4.41 Eu 1.57 0 0.55 1.54 1.15 1.1 1.03 2.05 Ga 18 16 13.6 20.9 17.4 19.6 18 23.6 Ge 5.42 0 2.32 4.77 3.79 4.11 3.33 6.72 Hf 4.9 3.9 1.8 3.5 2.3 2 2.1 4.7 Ho 1.03 0.8 0.61 1.21 0.97 0.92 0.71 1.6 La 22.5 0 8.3 6.6 4.5 8.2 3.8 12.6 Lu 0.41 0 0.27 0.54 0.44 0.41 0.29 0.66 Mo 0.2 1 0.1 0.3 0.1 0.1 0.2 0.5 Nb 15.1 0 3.9 7 4.9 5.7 3.8 14.7 Nd 27.9 8 8.2 14.1 10.1 13.1 8.6 22.9 Ni 79.7 100 88.8 19.3 26.2 57.2 50.2 9.7 Pb 0.9 0 2.4 0.9 0.2 0.6 0.5 0.7 Pd 2.7 0 16.3 9.1 1.4 0.8 3.6 0 Pr 6.37 0 2.18 2.46 1.89 2.67 1.43 4.43 Pt 2.9 0 15.7 9.8 1 0 1.5 0 Rb 16.9 47 36.2 6 10.9 36.2 17.5 10.1 Rh 1.07 0 2.2 00000.07 S 0.08 0 0.12 0.13 0.14 0.06 0.1 0.16 Sc 17 20 34 41 44 44 39 30 Sm 6 0 1.8 4.2 3.1 3.2 2.3 5.3 Sr 155.4 114 142.5 108.1 99.1 173 174.2 175.4 Ta 0.9 0 0.1 0.5 0.4 0.3 0.2 1 Tb 1.03 0.2 0.43 0.94 0.75 0.69 0.56 1.26 Th 5.5 4.1 2.8 0.4 0.3 0.6 0.4 1 Tl 000000.200 Tm 0.41 0 0.25 0.51 0.4 0.38 0.31 0.6 U 0.9 1 0.4 0.2 0.1 0 0 0.3 V 215 0 216 357 376 358 292 253 W 0.1 3 0.1 0 0.1 0 0.1 0.3 Y 29.8 22 16.7 33.8 26.7 26 19.7 43 Yb 2.76 0 1.9 3.54 2.7 2.87 1.98 4.08 Zn 350 262917503375 Zr 161.3 146 61.5 98.5 70.9 66.8 56.3 139.4 Nd (TIMS) 0 0 0 37.27 0 0 34.07 45.8 Sm (TIMS) 0 0 0 11.49 0 0 10.61 12.69 147Sm/144Nd 0 0 0 0.1864 0 0 0.1883 0.1675 143Nd/144Nd 0 0 0 0.512701 0 0 0.512694 0.512435 Tdm (Ma) 00000000

229 Sample 1999022786 1999022816 1999022822 1999022827 1999022828 1999022829 1999022830 1999022858 Group Main Main Main Main Main Main Main Main Subgroup Lo-LREE Lo-LREE Hi-LREE Hi-LREE Lo-LREE Lo-LREE Lo-LREE Hi-LREE Swarm Payne - - - Payne Payne Payne - Age (Ma) 2170 0 0 0 2170 2170 2170 0 Width (m) -1-202--5 Trend 170 291 - 231 313 330 330 110 Northing 6757939 6749963 6764200 6764405 6742874 6743042 6743319 6734741 Easting 344942 384840 350641 351562 380863 381237 381852 395515 Zone 19 19 19 19 19 19 19 19 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 48.06 48.74 49.55 49.74 49.37 49.07 48.88 49.44 TiO2 2.23 1.01 1.29 1.31 1.38 0.99 1 1.27 Al2O3 14.55 14.25 14.32 14.43 12.78 14.23 13.9 14.41 Fe2O3 16.06 11.57 10.97 10.9 15.12 12.9 12.93 10.67 MnO 0.2 0.19 0.16 0.16 0.22 0.19 0.2 0.18 MgO 4.4 7.64 8.12 8.2 6.41 7.04 7.41 8.41 CaO 8.7 11.5 12.37 11.83 9.92 10.82 10.4 11.59 Na2O 2.46 0.79 1.45 1.55 1.72 1.59 2.24 1.51 K2O 0.29 2.22 0.29 0.33 0.23 0.4 0.75 0.42 P2O5 0.23 0.1 0.12 0.11 0.13 0.08 0.1 0.14 LOI 2.3 2.1 1.5 1.2 2.6 2.5 2.1 1.8 Cr2O3 0.006 0.034 0.047 0.042 0.017 0.036 0.037 0.046 Ctot 0.08 0.04 0.17 0.03 0.03 0 0.01 0

As 0 0 0 0.5 0 0 1.1 0.8 Au 0.6 0 0 0 4.2 2 1.3 0 Ba 75 459 120 119 38 60 108 135 Ce 29.1 10.1 18.6 19.3 12.1 10.1 7.7 21.3 Co 44.1 49 47.6 48.3 54.3 48.5 48.8 47.7 Cs 0.3 2.6 0.6 0.4 0.6 0.8 1 1 Cr 00000000 Cu 101.8 113.3 53 65.4 358.2 155.8 135.6 61.8 Dy 6.84 3.26 3.19 2.77 4.4 3.12 3.4 3.21 Er 4.53 2.05 1.83 1.67 2.84 2.08 2.05 1.76 Eu 2.04 0.82 1.05 0.93 1.07 0.8 0.81 1.06 Ga 21.8 17.6 16.6 15.4 17.7 16.3 16.9 15.7 Ge 6.33 2.69 3.01 2.97 3.71 2.93 2.91 3.02 Hf 4 1.5 2.1 1.7 1.9 1.3 1.9 2 Ho 1.42 0.74 0.66 0.55 0.92 0.75 0.65 0.64 La 12.5 4.2 8.8 8.3 4.4 5.2 3 9 Lu 0.65 0.32 0.27 0.25 0.41 0.28 0.32 0.25 Mo 0.3 0.2 0.3 0.2 0.3 0.1 0.1 0.3 Nb 9.1 3.5 7 6.4 4.3 3.2 2.9 7.6 Nd 18.9 7.9 12.4 11.2 10.2 7.6 6.9 11.6 Ni 27.6 75.5 45.5 51 39.2 52.8 54.7 46.7 Pb 0.6 0.9 1.4 1.1 0.5 1 0.9 0.6 Pd 0.2 4.5 0.5 0.7 28.9 18.2 16.7 0.1 Pr 3.58 1.53 2.53 2.5 1.81 1.46 1.21 2.61 Pt 0 1.4 0.5 0 28.2 16.5 16.4 0 Rb 10.8 101.7 8.7 10.8 10.1 25.7 40.8 12.1 Rh 0.28 1.57 0.61 0.41 2.85 2.43 2.3 0.36 S 0.11 0.2 0.11 0.13 0.04 0.09 0.04 0.11 Sc 37 41 39 38 43 39 39 38 Sm 5.5 2.4 2.9 2.7 2.9 2.5 2.2 3 Sr 141.1 353.9 209.9 236.8 122.3 146.9 200.7 195 Ta 0.6 0.2 0.4 0.4 0.3 0.1 0.2 0.5 Tb 1.21 0.55 0.63 0.5 0.63 0.54 0.5 0.53 Th 0.9 0.5 1.4 2 0.7 0 0.4 0.8 Tl 0.1 0.2 0.1 0.1 0.1 0.1 0.2 0 Tm 0.61 0.3 0.27 0.22 0.44 0.3 0.31 0.25 U 0.1 0.1 0.3 0.2 0 0 0 0.3 V 374 305 302 289 352 294 288 278 W 0.4 0.8 0 0.3 0.3 0.2 0.1 0.3 Y 39.9 20.7 18.9 16.5 27.2 19.8 19.7 17.6 Yb 4.13 2.04 1.72 1.61 2.91 1.83 1.9 1.82 Zn 54 34 47 43 59 41 41 41 Zr 133.4 50.3 70.2 62.7 72 46.6 48 73.3 Nd (TIMS) 00000000 Sm (TIMS) 00000000 147Sm/144Nd 00000000 143Nd/144Nd 00000000 Tdm (Ma) 00000000

230 Sample 1999022866 1999022867 1999022928 1999027389 2000024422 2000024427 2000024430 2000024431 Group Main Main Lo Fe-Ti Main Main Main Main Main Subgroup Lo-LREE Lo-LREE - Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE Swarm ----Klotz Klotz - - Age (Ma) 00002209 2209 2210 0 Width (m) - 10- - 30104020 Trend 330 330 100 110 - 318 - 360 Northing 6684636 6685065 6773018 6510049 6665307 6674243 6663408 6656527 Easting 409319 411367 399069 357553 663072 646201 642383 557737 Zone 19 19 19 19 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 49.03 48.79 52.07 49.97 49.28 50.02 47.08 48.42 TiO2 1.22 1.07 0.61 1.24 1.42 1.24 3.35 1.32 Al2O3 14.22 15.99 13.65 14.44 15.06 15.24 12.82 14.67 Fe2O3 13.1 12.29 10.05 13.68 15.24 14.11 19.25 13.41 MnO 0.2 0.18 0.15 0.2 0.2 0.2 0.25 0.21 MgO 7.3 5.92 9.24 6.22 5.26 5.2 4.49 7.3 CaO 10.56 11.21 9.45 10.88 10.68 10.75 9.57 11.6 Na2O 2.46 1.75 1.83 2.2 2.35 2.44 2.19 1.81 K2O 0.48 0.4 0.71 0.22 0.16 0.17 0.56 0.76 P2O5 0.1 0.08 0.09 0.14 0.08 0.08 0.34 0.09 LOI 1.4 2.1 2.1 0.7 0.2 0.3 0.2 0.2 Cr2O3 0.037 0.024 0.075 0.009 0.011 0.013 0.013 0.029 Ctot 0 0.02 0.03 0.01 0.03 0.02 0.03 0.02

As 00000000 Au 0 0 1.1 0.8 1 0.7 8.2 1.6 Ba 56 65 236 60 36 40 169 146 Ce 12.1 10.2 20.5 14.2 13.1 13.8 55 14.5 Co 48.8 44.5 50.3 43.9 56.1 49 54.3 53.8 Cs 0 0.7 0.9 0.3 0.2 0.3 1 0.2 Cr 00000000 Cu 143.7 101.4 70.4 128.2 204 168.3 562.2 141.6 Dy 3.82 3.62 2.36 3.3 3.99 4.35 9.47 4.15 Er 2.56 2.5 1.57 2.03 2.36 2.62 5.53 2.31 Eu 1.01 0.91 0.79 1.02 1.02 1.02 2.15 1.08 Ga 17.6 16.7 14.4 16 20.2 19.6 25.5 20 Ge 3.22 3.23 2.55 3.12 3.74 4.02 9.28 3.86 Hf 1.8 1.9 1.8 1.9 1.9 2.1 6.4 1.6 Ho 0.89 0.83 0.51 0.71 0.8 0.84 1.93 0.78 La 5.8 3.8 10.2 6.4 5.1 5.6 23.2 5.6 Lu 0.39 0.33 0.25 0.36 0.37 0.37 0.79 0.28 Mo 0.2 0.2 0.2 0.2 0.2 0.2 0.7 0.2 Nb 3.4 3.5 2.5 5.9 6 6.2 19.8 6.7 Nd 8.5 7.2 11 10.8 10.2 9.9 34.3 10.8 Ni 54.2 46.4 92.5 29.9 17 12.9 17.8 68.4 Pb 2.3 0.3 1.4 0.8 0.5 0.7 1.1 2.4 Pd 2.9 3.1 10.7 0.4 4.8 4.8 14.4 8.5 Pr 1.78 1.6 2.52 2.06 1.77 2.07 7.15 2.12 Pt 2 1.4 8.5 0 4.9 6.9 60.2 10.2 Rb 10.5 23.7 24.9 6.8 4.1 4.2 22.6 48.3 Rh 0.3 0.24 1.48 0 0 0.22 1.36 0.15 S 0.12 0.14 0.06 0.15 0.11 0.11 0.09 0.15 Sc 43 40 31 41 40 40 39 39 Sm 2.6 2.6 2.2 2.9 2.6 2.8 8 2.9 Sr 94.7 145.1 240.2 140.1 135.9 132.8 172.6 212.2 Ta 0.3 0.3 0.1 0.4 0.3 0.3 1.2 0.3 Tb 0.67 0.59 0.37 0.52 0.61 0.6 1.5 0.58 Th 0 0 1.1 0.4 0.5 0.6 2.8 0.6 Tl 00.10.100000.1 Tm 0.35 0.31 0.23 0.28 0.32 0.35 0.8 0.29 U 0 0 0.2 0.2 0.1 0.2 0.7 0.2 V 350 308 207 286 423 313 378 334 W 0 0.1 0.2 0 0 0 0.1 0.1 Y 24.9 23.1 14.7 19.6 22.4 23.5 54.9 20.5 Yb 2.36 2.1 1.46 2.06 2.7 2.67 5.47 1.88 Zn 26 40 31 35 30 25 56 58 Zr 58.5 57.5 58.2 63.6 63.2 70.4 222.4 69.9 Nd (TIMS) 0000031.7 37.38 0 Sm (TIMS) 000009.35 9.47 0 147Sm/144Nd 000000.1783 0.1532 0 143Nd/144Nd 000000.512581 0.512078 0 Tdm (Ma) 00000000

231 Sample 2000024432 2000024433 2000024436 2000024477 2000025651 2000025718 2000030019 2000030037 Group Main Main Main Lo Fe-Ti Main Main Main Main Subgroup Lo-LREE Lo-LREE Lo-LREE - Hi-LREE Hi-LREE Lo-LREE Lo-LREE Swarm - Klotz Payne----Payne Age (Ma) 0 2209 2170 00002170 Width (m) 40 30 0.6 large 30 - 0.7 7 Trend 269 300 330 305 330 126 110 340 Northing 6743380 6679604 6719587 6736768 6403382 6442519 6580014 6644859 Easting 580797 580086 654165 611497 449656 494336 629604 651183 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 49.44 50.66 50.03 50.23 49.76 51.74 49.56 50.83 TiO2 1.33 1.73 1.18 0.46 1.11 0.73 1.76 1.84 Al2O3 13.18 12.94 14.21 11.7 15.09 17.99 12.09 12.55 Fe2O3 14.8 16.32 12.89 10.1 12.06 10.23 15.59 16.23 MnO 0.22 0.22 0.19 0.14 0.18 0.17 0.23 0.23 MgO 6.57 5.37 7.02 13.6 7.74 4.45 5.41 5.26 CaO 11.15 9.92 11.58 6.51 11.2 7.63 9.22 9.78 Na2O 1.95 2.23 1.69 2.07 1.97 4.16 2.49 2.11 K2O 0.33 0.27 0.23 0.91 0.32 1.34 0.22 0.25 P2O5 0.11 0.14 0.07 0.1 0.09 0.22 0.17 0.17 LOI 0.5 0.3 1 3.9 0.6 1.3 2.8 0.6 Cr2O3 0.02 0.013 0.024 0.223 0.042 0.003 0.011 0.007 Ctot 0.05 0.02 0.05 0.07 0 0.02 0 0.05

As 0000.50000 Au 2.9 0.7 0 0.8 0.8 0 1.1 1.2 Ba 48 69 47 228 121 463 103 66 Ce 13.6 24.4 11.4 26.6 18.1 35.4 23 23.8 Co 56.6 53.5 56.8 70 55.1 33.9 55.1 53.8 Cs 0.3 0.2 0.5 0.5 2.1 1.9 0.6 0 Cr 00000000 Cu 188.4 132.5 106.2 34.5 101.5 20.7 130.4 120.5 Dy 4.26 5.7 4.2 2.09 3.19 2.92 5.66 5.22 Er 2.66 3.24 2.32 1.09 2.05 1.63 3.13 3.14 Eu 1 1.44 1.04 0.67 1.06 1.14 1.53 1.58 Ga 20.8 20.5 20.1 17.3 17.5 21.3 18.2 20.5 Ge 4.17 6.03 3.79 2.53 2.82 3.5 4.99 5.06 Hf 2.4 3.1 2.1 2.1 2.1 1.5 3.4 3.9 Ho 0.86 1.12 0.8 0.37 0.73 0.59 1.08 1.11 La 5.4 10.4 4.8 13.1 8.5 18.3 10.5 10.2 Lu 0.4 0.51 0.32 0.17 0.28 0.24 0.45 0.43 Mo 0.2 0.3 0.2 0.1 0.1 0.2 0.4 0.3 Nb 5.8 11.5 5 2.7 4.8 2 10.3 11.1 Nd 11.1 18.4 9.9 14.5 11.4 20.3 15.8 17.4 Ni 17.2 28.4 34.3 287.9 58.4 7.2 36.8 20.9 Pb 0.3 1 0.4 0.7 1 1.5 1.4 0.4 Pd 21.5 0.7 0.4 11.1 0.4 0.2 0.7 1.3 Pr 1.99 3.39 1.83 3.03 2.42 4.37 3.33 3.38 Pt 26.5 0 0 8.5 0 0 0 1.2 Rb 17.9 9.3 11.7 37.5 12.9 75.2 15.8 5.4 Rh 0.83 0 0 1.72 0.36 0.15 0 0.14 S 0.07 0.17 0.11 0.04 0.08 0.04 0.15 0.16 Sc 43 45 43 28 37 25 44 44 Sm 2.8 4.3 2.7 2.2 2.7 3.8 4.6 4.2 Sr 121.8 161.6 130.4 131.2 231.2 567.8 239.7 157.7 Ta 0.4 0.6 0.3 0.1 0.3 0.1 0.7 0.7 Tb 0.7 0.83 0.59 0.33 0.54 0.48 0.83 0.81 Th 0.5 1.2 0.2 1.9 0.8 2.4 1.1 0.9 Tl 0.1 0 0 0.1 0 0.1 0.1 0 Tm 0.37 0.51 0.31 0.15 0.27 0.27 0.47 0.44 U 0.1 0.3 0.2 0.3 0.2 0.9 0.2 0.2 V 343 419 350 156 267 224 398 414 W 0.1 0.2 0.1 0.2 0.2 0.1 0.1 0.2 Y 24 32.1 22.2 11 19.9 17.8 31.5 34.1 Yb 2.68 3.43 2.32 1.17 2.06 1.77 2.98 3.18 Zn 28 39 35 38 35 50 81 43 Zr 71.4 113.2 64.5 61.7 55.1 45.1 107.3 111.3 Nd (TIMS) 0 15.46 000000 Sm (TIMS) 0 4.17 000000 147Sm/144Nd 0 0.1631 000000 143Nd/144Nd 0 0.512357 000000 Tdm (Ma) 00000000

232 Sample 2000030038 2000030215 2000030216 2000030224 2000030251 2000030258 2000030309 2000030310 Group Main Main Main Main Main Main Hi Fe-Ti Hi Fe-Ti Subgroup Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-Al Lo-Al Swarm ------Age (Ma) 00000002100? Width (m) 1 30 10 0.1 0.1 0.5 - - Trend 280 285 - 325 310 130 - - Northing 6643470 6583227 6610460 6639697 6609555 6612033 6414245 6414245 Easting 650099 641764 632126 588629 622700 621311 361592 361592 Zone 18 18 18 18 18 18 19 19 Laboratory ACME ACME ACME COREM COREM ACME Geolab Geolab SiO2 51.2 47.74 49.23 48 48.5 49.31 47.9 45.7 TiO2 1.82 1.73 0.9 1.25 1.2 0.89 1.33 0.94 Al2O3 12.73 14.42 13.62 14.3 13.7 13.58 6.95 5.02 Fe2O3 16.14 16.79 13.3 12.7 12.2 13.05 14 14.3 MnO 0.23 0.21 0.21 0.2 0.21 0.21 0.2 0.2 MgO 5.44 4.94 7.55 7.93 8.39 7.45 15.6 22 CaO 9.19 10.23 12.22 12.1 12.3 11.9 8.48 7.15 Na2O 1.31 2.21 1.85 1.46 1.66 1.83 2.24 1.58 K2O 0.51 0.13 0.47 0.54 0.52 0.43 0.8 0.56 P2O5 0.18 0.07 0.04 0.05 0.05 0.05 0.11 0.07 LOI 1.6 1.3 0.6 1.5 1.58 1 2.21 1.72 Cr2O3 0.012 0.002 0.02 0.04 0.05 0.02 0.21 0.28 Ctot 0.03 0.02 0.05 0 0 0.08 0 0

As 0 0 0 0.5 0.5 0 0 0 Au 0.9 0.8 1.9 7 2 2.3 0 0 Ba 188 40 46 54 69 56 273.6 197.95 Ce 24.7 13.4 7.3 0 0 8 35.82 25.28 Co 54.2 60.2 53.9 54 52 61.1 87 110 Cs 0 0 0.9 0.5 1.6 0.6 0.25 0.16 Cr 0 0 0 250 340 0 1400 1900 Cu 104.5 351.4 102 0 0 105.3 0 0 Dy 5.57 3.78 3.44 0 0 3.66 3.07 2.21 Er 3.21 2.09 2.13 0 0 2.25 1.45 1.06 Eu 1.44 1.01 0.79 0 0 0.82 1.27 0.94 Ga 19.6 18 15.1 19 18 19.6 13 10 Ge 5.59 3.05 2.84 0 0 2.82 0 0 Hf 3.6 1.6 1.2 0 0 1.9 2.83 2.04 Ho 1.13 0.67 0.66 0 0 0.82 0.56 0.41 La 11.9 6 3.1 0 0 3.3 15.53 10.99 Lu 0.42 0.29 0.24 0 0 0.32 0.176 0.121 Mo 0.3 0.2 0.1 1 1 0.1 0 0 Nb 11.4 5.6 2.3 7 5 2.6 8.08 5.8 Nd 17.9 9.2 6.9 0 0 6.9 20.53 14.7 Ni 40.8 24.6 16.8 130 140 27.1 720 1100 Pb 0.6 0.4 0.5 0 0 0.4 0 0 Pd 0.5 1 14.7 0 0 14.7 0 0 Pr 3.5 1.83 1.09 0 0 1.26 4.8 3.36 Pt 0 0.7 18.6 0 0 19.3 0 0 Rb 15.1 4.5 40.9 30 54 44.4 21.05 15.19 Rh 0 0 1.16 0 0 4.12 0 0 S 0.17 0.15 0.12 0 0 0.12 0 0 Sc 46 44 48 42 46 48 23 19 Sm 4.2 2.6 2.1 0 0 2.1 4.47 3.29 Sr 248.1 117.9 103.9 150 126 122.5 294 212 Ta 0.7 0.4 0.2 5 5 0.2 0.45 0.31 Tb 0.83 0.49 0.54 0 0 0.52 0.57 0.4 Th 0.9 0.6 0 0.4 0.3 0.6 1.95 1.33 Tl 0 0 0.2 0 0 0.2 0 0 Tm 0.45 0.32 0.31 0 0 0.36 0.2 0.14 U 0.2 0 0 0.5 0.5 0 0.27 0.18 V 409 614 300 0 0 322 0 0 W 0.20011000 Y 33.4 19.7 20.1 22 18 21.3 14.33 10.31 Yb 3.04 2.24 2.07 0 0 2.52 1.23 0.88 Zn 87 32 27 0 0 33 0 0 Zr 111 62.1 43.7 69 63 47 107.89 79.95 Nd (TIMS) 000000015.23 Sm (TIMS) 00000003.35 147Sm/144Nd 00000000.1328 143Nd/144Nd 00000000.511699 Tdm (Ma) 00000003

233 Sample 2001032332 2001032333 2001032343 2001032355 2001032394 2001032395 2001032397 2001032563 Group Main Main Main Main Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Subgroup Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-Al Lo-Al Lo-Al Lo-Al Swarm ----Anuc Anuc Anuc Anuc Age (Ma) 00002220 2220 2220 2220 Width (m) 30 30 40 20 15 15 20 25 Trend 300 300 290 292 315 315 315 147 Northing 6606208 6606208 6587270 6588971 6560995 6560995 6561401 6645054 Easting 474989 474989 537102 447183 470586 470586 469741 532935 Zone 18 18 18 18 18 18 18 18 Laboratory REM+GEOLA ACME ACME ACME REM+GEOLA ACME ACME ACME SiO2 49.5 51.49 56.27 49.71 49.3 49.41 49.93 40.86 TiO2 1.53 1.64 1.57 1.83 1.86 1.35 1.79 1.62 Al2O3 13.1 13.29 14.26 12.86 10.3 7.17 9.36 9.01 Fe2O3 15.2 15 13.97 16.26 13.7 13.87 14.78 23.46 MnO 0.22 0.22 0.19 0.23 0.16 0.19 0.18 0.19 MgO 5.62 4.11 2.26 5.53 9.66 13.29 10.1 9.93 CaO 10 8.81 5.94 9.91 8.37 10.83 8.63 10.56 Na2O 2.26 2.6 3.52 2.11 3.62 2.15 3.37 1.26 K2O 0.4 0.46 0.24 0.22 0.06 0.47 0.84 0.51 P2O5 0.1 0.24 0.39 0.17 0.11 0.12 0.17 1.06 LOI 1.74 2 1.1 0.9 2.4 0.4 0.2 1.7 Cr2O3 0.02 0.009 0.002 0.008 0.11 0.163 0.095 0.008 Ctot 0 0.03 0.02 0.03 0 0.05 0.03 0.04

As 0.5 0 0 0 0.99 1.3 0.7 0.6 Au 4 0.8 0 1.1 2 0.8 0.9 5 Ba 80.7 119 80 72 18.2 111 290 176 Ce 22.77 34.7 79.8 23.1 38.19 34.8 52.2 67.4 Co 49 44 31.2 55.1 67 90 66.5 102 Cs 0.12 0.2 0 0 0.18 1.4 1 0.2 Cr 96000780000 Cu 0 80.7 52.4 130.7 0 194.8 249.3 233 Dy 5.06 7.11 10.56 4.95 3.172 3.72 4.54 3.59 Er 3.062 4.16 5.96 3.17 1.449 1.64 1.9 1.64 Eu 1.41 2.1 3.19 1.51 1.372 1.33 1.83 1.63 Ga 18 20.5 25.4 20.4 16 12.7 17.6 24.2 Ge 0 5.93 10.31 4.43 0 4.42 5.5 5.17 Hf 2.547 4.1 8.3 2.9 2.951 2.9 4.8 1.6 Ho 1.048 1.56 2.22 1.1 0.562 0.6 0.68 0.58 La 9.17 13.7 33.2 9.3 16.57 15.3 22.8 30.9 Lu 0.401 0.63 0.89 0.41 0.163 0.19 0.23 0.22 Mo 1 0.4 0.5 0.2 1 0.3 0.4 0.2 Nb 8.64 15.1 26.3 9.8 9.81 8.7 12 2.1 Nd 15.59 24.6 46.8 15.9 20.57 21.6 29.1 36.1 Ni 100 19 7.8 26.9 330 302.5 228.7 72 Pb 0.4 0.9 0.4 0 18 3.7 2.6 Pd 0.6 0.8 1.3 0 4.6 3 0 Pr 3.27 4.82 9.67 3.18 4.8 4.64 6.79 8.47 Pt 0.5 0 0 0 4.1 2.6 0 Rb 9.7 14.7 6 6.2 1 25 33.1 12.7 Rh 0 0.16 0 0 0 0.18 0.62 0 S 0 0.15 0.1 0.08 0 0.21 0.03 0.72 Sc 45 37 25 45 23 26 19 47 Sm 4.14 6.3 10.4 4.2 4.52 4.6 5.6 7.1 Sr 145.7 216 215.1 150.5 315.4 193.1 405.7 281.1 Ta 0.704 1 1.9 0.6 0.721 0.5 0.7 0 Tb 0.757 1.09 1.68 0.86 0.557 0.64 0.75 0.64 Th 0.69 1.6 4.5 0.9 2.77 2.2 3 1.5 Tl 000000.10.10 Tm 0.43 0.65 0.97 0.51 0.188 0.26 0.26 0.22 U 0.16 0.3 0.7 0.2 0.51 0.5 0.9 0.4 V 0 321 155 462 0 212 253 670 W 2 0.1 0.3 0.1 1 0 0.3 0 Y 24.3 42.2 58.5 30.5 17.8 16.9 20.3 17.4 Yb 2.813 4.25 6.22 2.72 1.079 1.39 1.53 1.35 Zn 0 65 52 41 0 32 51 36 Zr 89.4 156.9 304.7 103.9 126.7 105.8 156.5 48.6 Nd (TIMS) 000023.45 0 0 0 Sm (TIMS) 00005.18 0 0 0 147Sm/144Nd 00000.1336 0 0 0 143Nd/144Nd 00000.511738 0 0 0 Tdm (Ma) 00002677 0 0 0

234 Sample 2001035365 2001035366 2001035367 2001035368 2001035369 2001035370 2001035371 2001035372 Group Main Lo Fe-Ti Main Lo Fe-Ti Main Hi Fe-Ti Main Main Subgroup Hi-LREE - Hi-LREE - Hi-LREE Lo-Al Hi-LREE Hi-LREE Swarm ------Age (Ma) 000002100? 0 0 Width (m) 1 0.3 30 6 4 2 0.3 - Trend 280 158 170 210 115 270 330 140 Northing 6508717 6491329 6472385 6513120 6527151 6511107 6493434 6490528 Easting 326222 330226 403084 390744 416736 372604 397155 354336 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 50.37 50.65 49.14 53.51 47.68 49.23 53.67 47.45 TiO2 1.09 0.64 0.85 0.45 1.32 1.35 1.37 0.98 Al2O3 13.4 15.2 15.61 10.35 14.15 9.46 12.83 15.61 Fe2O3 13.48 10.31 10.52 10.13 14.78 14.42 14.23 11.52 MnO 0.21 0.17 0.16 0.16 0.21 0.19 0.19 0.17 MgO 6.07 7.36 7.56 14.91 7.07 8.76 4.09 6.7 CaO 10.58 10.77 11.83 6.84 10.77 10.09 8.27 11.21 Na2O 2.11 2.07 1.93 1.67 1.78 3.28 2.58 2.34 K2O 0.35 0.68 0.45 0.59 0.14 0.25 0.99 0.41 P2O5 0.09 0.07 0.07 0.09 0.11 0.14 0.19 0.06 LOI 1.3 2.2 1.6 1.3 1.9 2.4 1.2 3.2 Cr2O3 0.016 0.033 0.046 0.229 0.02 0.06 0.004 0.02 Ctot 0.05 0.05 0.04 0.06 0.18 0.01 0.04 0.3

As 10.8 5.4 3.1 2.6 1.6 2.5 3.1 3.9 Au 21.7 4.1 9.7 13.7 3.6 4.9 6.8 5.3 Ba 103 293 128 216 58 59 423 224 Ce 15.1 16.6 14.8 19.1 17.2 35.4 54.5 14.2 Co 51.1 49.2 49.3 66.2 61.4 61.9 48.9 51.7 Cs 0.2 0 0.2 0.8 0.5 0.3 0.4 0 Cr 00000000 Cu 132.2 74.5 96.8 54.8 122.2 169.5 66.1 134.2 Dy 4.37 2.41 2.8 2.07 3.65 4.34 5.13 3.22 Er 2.7 1.54 1.6 1.14 2.23 2.21 2.97 1.83 Eu 1.16 0.86 0.92 0.67 1.11 1.57 1.82 1.01 Ga 18 15.4 17.5 12.8 17.5 15.6 19.5 17.9 Ge 4.2 2.42 2.73 2.08 3.88 5 5.8 3.08 Hf 1.9 1.5 1.4 1.5 1.7 3.8 3.8 1.4 Ho 1.1 0.55 0.61 0.41 0.82 0.92 1.16 0.71 La 9.1 9.3 7.8 9.8 9 16.1 26.7 6.7 Lu 0.48 0.23 0.26 0.21 0.32 0.31 0.37 0.27 Mo 0.3 1.1 0.3 1.2 0.3 1 0.3 1 Nb 3.6 2.7 2.8 1.5 4 9.8 6.6 2.8 Nd 12.5 10.7 11.3 11 12.5 24.9 30 9.9 Ni 22.9 65.8 58.1 52.8 61.6 139.8 18.7 124.6 Pb 4.3 5.9 6.6 2 1.7 3 4 3 Pd 13.7 9.3 0.4 8 0.5 3.2 0 2.4 Pr 2.55 2.51 2.18 2.5 2.66 5.01 6.73 1.96 Pt 14 5.6 0 8.5 0 4.5 0 1.6 Rb 16 35.5 13.5 19.4 6 8 33.3 15 Rh 0.39 0.13 0 1.34 0 0.89 0 0 S 0.09 0.1 0.09 0.05 0.18 0.15 0.16 0.06 Sc 47 37 35 25 41 25 37 37 Sm 3.4 2.3 2.5 2.3 3.2 5.2 5.8 2.6 Sr 162.3 273.3 242.9 196.8 169.8 119.5 264.5 264.6 Ta 0.2 0.2 0.2 0.1 0.3 0.6 0.4 0.3 Tb 0.64 0.37 0.43 0.35 0.57 0.72 0.79 0.49 Th 1 1 0.7 1.5 0.7 3.6 2.3 0.3 Tl 0.1 0.1 0 0.1 0 0 0.1 0 Tm 0.53 0.26 0.3 0.19 0.37 0.38 0.46 0.3 U 0.1 0.1 0.1 0.3 0 0.7 0.3 0.1 V 343 229 237 161 320 200 339 255 W 1.9 2.5 0.6 2 0.5 1.8 0.6 1.9 Y 29.5 16.1 17.3 12.5 24.3 26.1 31.4 20.1 Yb 2.92 1.49 1.65 1.13 2.14 2.33 3.06 1.91 Zn 58 66 52 9 53 69 64 59 Zr 65.5 46.2 45.9 51.2 57.4 119.4 132.1 43 Nd (TIMS) 0000020.91 0 0 Sm (TIMS) 000004.82 0 0 147Sm/144Nd 000000.1394 0 0 143Nd/144Nd 000000.511852 0 0 Tdm (Ma) 000002652 0 0

235 Sample 2001035373 2001035374 2001035376 2001035377 2001035378 2001035379 2001035380 2001035381 Group Main Main Lo Fe-Ti Lo Fe-Ti Hi Fe-Ti Main Main Main Subgroup Hi-LREE Hi-LREE - - Hi-Al Hi-LREE Hi-LREE Hi-LREE Swarm ------Age (Ma) 00000002100? Width (m) 0.527380.51020 Trend 130 150 160 125 10 30 310 330 Northing 6469742 6532156 6476932 6474945 6461660 6493149 6515955 6541338 Easting 390133 347330 403878 675183 349274 371288 420645 353407 Zone 18 18 18 17 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 50.78 49.57 49.68 50.63 45.04 50.66 50.8 53.01 TiO2 1.16 1.07 0.44 0.46 2.19 1.12 1.41 1.26 Al2O3 14.28 15.21 13.35 13.74 15.01 14.52 13.19 13.02 Fe2O3 12.38 11.5 9.47 9.37 15.93 12.18 14.85 13.94 MnO 0.19 0.17 0.14 0.13 0.18 0.19 0.21 0.19 MgO 5.57 6.84 9.86 10.14 6.3 5.98 5.66 4.38 CaO 10.14 10.82 10.01 8.96 8.08 10.41 9.76 8.88 Na2O 2.44 2.04 2.04 2.16 2.04 2.3 2.22 2.44 K2O 0.7 0.5 1.29 1.13 1.67 0.83 0.63 0.95 P2O5 0.09 0.09 0.05 0.06 0.31 0.09 0.15 0.19 LOI 1.8 1.8 3.1 2.7 3 1.3 0.5 0.9 Cr2O3 0.015 0.037 0.067 0.067 0.011 0.018 0.007 0.006 Ctot 0.06 0.29 0.02 0.08 0.17 0.08 0.03 0.05

As 1.6 2.2 1.6 3.1 1.1 1.8 1.8 1 Au 6.4 7.4 9.4 3.7 2.4 4.7 3.4 5.5 Ba 201 158 331 1157 519 215 228 461 Ce 37.6 28.8 16.2 16.6 47.6 28.2 29.3 46.5 Co 48.2 47.1 47.4 43.4 63.4 47.3 54.3 49 Cs 0.2 0.3 0.1 0.7 2.1 0.2 0.2 0.1 Cr 00000000 Cu 114.9 94 55.2 74.2 35.6 109.5 113.6 75.5 Dy 4.6 3.79 2.52 2.38 5.75 4.02 5.09 4.57 Er 2.74 2.49 1.61 1.69 3.27 2.39 2.67 2.5 Eu 1.65 1.36 0.71 0.68 2.04 1.23 1.45 1.57 Ga 19.9 18.9 14.4 14.2 24.7 18.7 17.9 19.5 Ge 4.24 4.39 2 2.13 6.35 4.37 4.73 5.16 Hf 2.6 2.7 1.5 1.5 3.8 2.6 2.7 3.3 Ho 1.26 0.98 0.6 0.61 1.26 0.87 1.01 0.94 La 25.5 15.6 8.6 9.1 22.5 13 14.2 23.2 Lu 0.52 0.38 0.26 0.29 0.48 0.37 0.42 0.37 Mo 0.4 1.4 0.2 0.5 0.6 1.2 0.2 1.7 Nb 7.5 6.8 2.2 2.6 15 7.5 5.3 5.7 Nd 21.1 17.7 9.1 9.2 30.8 16.7 18.6 25.3 Ni 19.4 40.8 124.4 136 80.6 20.2 20.8 19 Pb 3.2 3 1.6 19.1 7.3 2.5 2.3 3.5 Pd 3.7 0.3 12.8 13.1 0 4.4 0.3 0 Pr 4.75 3.74 2.09 2.2 6.35 3.66 3.99 5.81 Pt 2.3 0 12.7 13.1 0 2.9 0 0 Rb 28.2 19 46.9 48 57 32.6 20.1 20.2 Rh 0 0 2.12 1.32 0000 S 0.02 0.09 0.16 0.1 0.16 0.09 0.13 0.15 Sc 39 34 36 37 28 38 42 39 Sm 4.4 3.6 1.7 2.1 6.4 3.9 4.3 5.2 Sr 244.6 242.9 164.7 244.9 317 229 219.7 270.9 Ta 0.4 0.4 0.3 0.2 0.9 0.4 0.2 0.3 Tb 0.92 0.7 0.36 0.42 0.94 0.66 0.7 0.7 Th 2.4 2.3 2.6 2.2 1.2 2.1 1.8 2.7 Tl 0 0.1 0 0.1 0.2 0.1 0 0.1 Tm 0.57 0.38 0.29 0.29 0.56 0.46 0.4 0.39 U 0.3 0.3 0.4 0.5 0.2 0.2 0.2 0.2 V 293 247 200 207 252 283 346 314 W 0.6 2.1 0.3 1.1 0.4 1.8 0.2 2.2 Y 32.8 26.5 17.4 17.7 36.3 26.3 29.5 27.8 Yb 2.64 2.34 1.68 1.6 3.64 2.6 2.61 2.67 Zn 66 23 30 33 96 46 51 58 Zr 91.6 84.1 50 54.1 148.8 85.6 92.4 116.1 Nd (TIMS) 000000040.77 Sm (TIMS) 00000008.44 147Sm/144Nd 00000000.1251 143Nd/144Nd 00000000.511366 Tdm (Ma) 00000003051

236 Sample 2001035382 2001035383 2001035384 2001035385 2001035386 2001035387 2001035388 2001035389 Group Main Main Main Lo Fe-Ti Main Main Main Main Subgroup Hi-LREE Hi-LREE Hi-LREE - Hi-LREE Hi-LREE Lo-LREE Hi-LREE Swarm ------Age (Ma) 0000002100? 0 Width (m) 10 10 10 20 - 30 20 - Trend 305 350 315 115 170 130 135 360 Northing 6488946 6497073 6514448 6480116 6480540 6463850 6464132 6509138 Easting 373130 349242 349266 404936 326504 370598 369698 353876 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 50.95 47.7 50.84 50.27 52.44 48.22 47.28 51.08 TiO2 1.18 1.01 1.21 0.45 1.63 0.98 0.97 1.15 Al2O3 13.94 15.68 14.39 13.82 13.35 15.91 15.34 14.68 Fe2O3 13.05 13.07 12.66 9.51 13.37 12.26 13.19 12.5 MnO 0.19 0.19 0.19 0.13 0.18 0.19 0.19 0.18 MgO 5.91 6.92 5.42 8.72 4.65 7.1 7.54 5.58 CaO 10.42 10.77 9.95 10.66 9.06 11.06 10.91 10.37 Na2O 2.26 2.05 2.37 2.11 2.5 2.07 1.88 2.29 K2O 0.36 0.29 0.61 0.77 1.11 0.31 0.59 0.58 P2O5 0.1 0.07 0.11 0.08 0.28 0.08 0.08 0.11 LOI 1.3 1.8 1.6 2.7 1.1 1.3 1.7 0.9 Cr2O3 0.018 0.021 0.014 0.051 0.004 0.021 0.021 0.017 Ctot 0.13 0.04 0.01 0.05 0.07 0.08 0.06 0.04

As 2.9 1.3 2.3 1.3 1.5 0.5 0.5 0.6 Au 5.6 3.2 4 3.1 2.4 1.2 2.8 1.9 Ba 135 70 167 169 505 89 76 176 Ce 28.4 12.3 29 18 60.9 13.8 11 27.9 Co 47.4 56.3 48 50.8 43.1 59.4 58.1 43.1 Cs 0 0.2 0.2 0.1 0.2 0.2 0.2 0.1 Cr 00000000 Cu 126.4 131.2 108.7 55.3 42.9 125.2 122.8 104.7 Dy 3.96 3.25 4.35 2.58 5.76 3.46 2.95 4.53 Er 2.38 1.83 2.68 1.7 2.85 1.91 1.88 2.45 Eu 1.23 0.99 1.29 0.65 2.16 1.04 0.98 1.17 Ga 19.1 18.2 19.1 14.7 20.2 19.4 18.5 17.6 Ge 4.45 3 4.59 2.68 6.83 3.38 2.79 4.56 Hf 2.6 1.4 2.5 1.8 4.5 1.3 1.6 2.6 Ho 0.97 0.67 0.91 0.63 1.12 0.75 0.65 0.92 La 13.6 5.8 14 8.8 29.2 6.7 5.2 13.2 Lu 0.4 0.29 0.35 0.28 0.46 0.29 0.28 0.38 Mo 0.5 0.9 0.5 1 0.6 0.7 0.1 0.8 Nb 7.2 2.5 7.8 2.6 10 2.4 2.7 7.4 Nd 16.9 9.7 16.3 9.5 32.4 9.7 8.3 16.3 Ni 20.5 78.5 19.7 94.5 13.4 78.4 83.8 24.1 Pb 1.8 2.1 1.6 1.9 3.5 17.9 1.4 3.4 Pd 4.8 2.4 3.8 12 0.2 2.5 2.3 4.3 Pr 3.68 1.86 3.76 2.35 7.85 1.96 1.66 3.77 Pt 3 1.9 2.4 12.5 0 2.4 1.7 2.8 Rb 10.5 11.1 21.9 24.5 27 9.5 17.2 17.8 Rh 0000.20000 S 0.13 0.06 0.08 0.15 0.18 0.11 0.09 0.11 Sc 40 36 39 36 35 37 37 39 Sm 4 2.5 4.1 2.1 6.7 2.7 2.2 4.2 Sr 188.3 183.8 194.7 125.4 301.3 200 203.3 194.2 Ta 0.5 0 0.5 0.2 0.6 0.3 0.2 0.5 Tb 0.74 0.46 0.71 0.42 0.89 0.5 0.48 0.71 Th 2 0.3 2 2.9 2.8 0.3 0.3 1.7 Tl 00000.1000 Tm 0.41 0.27 0.39 0.26 0.45 0.31 0.26 0.4 U 0.3 0 0.3 0.4 0.4 0 0 0.3 V 289 256 288 206 330 265 254 252 W 0.4 1.3 0.3 1.2 0.4 1.4 0.1 1.4 Y 26.3 20.4 27.1 19.3 32.8 20.2 19.3 26.7 Yb 2.6 1.71 2.57 1.7 3.27 1.88 1.85 2.6 Zn 44 59 53 31 61 46 39 48 Zr 86.5 40.3 95.7 54.4 160.6 41.9 39.5 91.9 Nd (TIMS) 00000028.06 0 Sm (TIMS) 0000008.14 0 147Sm/144Nd 0000000.1755 0 143Nd/144Nd 0000000.51237 0 Tdm (Ma) 00000000

237 Sample 2001035390 2001035391 2001035392 2001035393 2001035394 2001035395 2001035396 2001035397 Group Main Main Main Lo Fe-Ti Hi Fe-Ti Main Main Hi Fe-Ti Subgroup Hi-LREE Hi-LREE Lo-LREE - Lo-Al Hi-LREE Hi-LREE Lo-Al Swarm ------Age (Ma) 0000002100? 0 Width (m) 4 30 10 4 0.4 - 15 - Trend 305 130 320 350 360 278 154 245 Northing 6513628 6531206 6506413 6541351 6541390 6524843 6529304 6507798 Easting 659496 649092 653683 667404 660549 646313 402741 350613 Zone 17 17 17 17 17 17 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 52.45 46.56 49.73 53.07 49.48 50.29 51.25 50.6 TiO2 1.74 0.91 2.06 0.44 1.4 0.64 1.41 1.4 Al2O3 12.75 15.62 12.92 9.98 9.76 15.65 13.45 9.92 Fe2O3 15.1 12.33 14.67 10.19 14.18 10.24 14.41 14.34 MnO 0.22 0.18 0.22 0.16 0.18 0.16 0.2 0.22 MgO 4.27 8.87 5.53 15.54 8.41 7.18 5.08 7.79 CaO 7.81 9.85 9.61 7.14 10.19 10.56 10.05 9.66 Na2O 2.7 2.29 2.18 1.58 3.73 2.71 2.22 3.37 K2O 1.06 0.32 0.7 0.5 0.06 0.91 0.48 0.57 P2O5 0.21 0.06 0.19 0.1 0.16 0.08 0.15 0.14 LOI 1.3 2.5 1.6 0.7 1.7 1.2 1.1 2.1 Cr2O3 0.003 0.016 0.011 0.252 0.058 0.032 0.011 0.053 Ctot 0.11 0.08 0.02 0.17 0.06 0 0.07 0.08

As 0.9 2.5 0.7 0.8 1.1 1.1 0 0 Au 0 1.6 1.8 2 4.6 3.5 0.6 3.7 Ba 467 99 195 184 36 293 158 112 Ce 51.1 11 37.4 18.6 36.6 16.3 29.3 32.8 Co 49.8 54.1 48.7 65.6 66.4 46.8 54.3 60.8 Cs 0 0.1 0.2 0.3 0.1 0 0 0.3 Cr 00000000 Cu 53.8 89.6 64.7 46.5 201.3 75.4 102.5 147 Dy 5.23 2.36 6.36 1.87 4.14 2.35 4.83 4.29 Er 2.76 1.26 3.25 1.09 2.21 1.44 2.46 2.06 Eu 1.89 0.94 1.99 0.67 1.66 0.81 1.37 1.61 Ga 20.3 16.8 20.6 11.8 14.8 14.2 18.4 14.9 Ge 6.28 2.23 6.8 1.87 4.82 2.45 4.19 4.78 Hf 4.2 1.1 3.6 1.3 3.3 1.4 3 3.5 Ho 1.12 0.53 1.31 0.39 0.82 0.46 1 0.84 La 24.1 5.9 16.1 9.2 15.7 8 14.9 15.4 Lu 0.42 0.2 0.53 0.15 0.32 0.21 0.43 0.33 Mo 0.7 0.7 0.5 1.1 0.8 0.9 0.3 0.5 Nb 9.2 2.8 12.5 1.6 9.5 2.2 5.4 9.5 Nd 27.1 7.7 24.6 10 23.3 9.7 17.1 20.8 Ni 12 74.1 27.8 32.9 132.3 51.3 24.9 116.2 Pb 3.6 0.6 0.7 1.3 6.9 0.8 4.6 2.1 Pd 0 0.2 0.1 6.7 3.2 9.2 0.3 3.6 Pr 6.87 1.72 5.5 2.43 5.13 2.52 3.73 4.53 Pt 0 0 0 7.3 4.1 6.7 0 5.1 Rb 31.8 9.6 19.5 13.4 2.9 26.6 10.8 12.9 Rh 0 0 0 1.08 0 0.16 0 0.55 S 0.2 0.04 0.15 0.03 0.25 0.1 0.16 0.12 Sc 38 32 41 25 25 37 40 23 Sm 5.7 2.2 6 2 5.3 2.3 4.1 5 Sr 263.1 226.7 216.1 168.7 85.8 260.8 219.6 144.6 Ta 0.6 0.2 0.7 0.1 0.8 0 0.3 0.6 Tb 0.95 0.4 1.02 0.31 0.88 0.44 0.72 0.75 Th 3.2 0.3 1.6 1.2 2.9 0.6 1.2 4.4 Tl 0.1000.10000 Tm 0.46 0.2 0.56 0.18 0.38 0.21 0.47 0.35 U 0.4 0 0.3 0.2 0.8 0 0.2 0.8 V 391 216 393 145 197 196 351 201 W 0.1 1.1 0.2 1.9 0.5 1.8 0.3 1 Y 31.9 15.1 36.7 12 24.6 14.9 26.1 21.6 Yb 2.96 1.26 3.34 1.04 1.87 1.24 2.97 2.15 Zn 73 60 56 12 69 29 56 73 Zr 141.1 32.2 132.5 47.3 119.4 42.9 88.1 116 Nd (TIMS) 00000034.25 0 Sm (TIMS) 0000008.39 0 147Sm/144Nd 0000000.148 0 143Nd/144Nd 0000000.511856 0 Tdm (Ma) 00000000

238 Sample 2001038445 2001038731 2001038733 2001038734 2001038774 2002034803 2002034806 2002034810 Group Hi Fe-Ti Main Main Main Main Lo Fe-Ti Lo Fe-Ti Main Subgroup Hi-Al Lo-LREE Lo-LREE Lo-LREE Lo-LREE - - Hi-LREE Swarm - - - Couture Couture Irsuaq Irsuaq - Age (Ma) 0 0 0 2199 2199 2508 2508 0 Width (m) 30 20 5 large large4050- Trend 350 20 330 85 85 210 0 320 Northing 6188228 6714663 6660878 6716403 6690066 6685783 6687557 6758162 Easting 607298 478514 505930 510336 473310 431596 416866 442684 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 48.36 48.38 49.84 49.43 48.97 52.55 53 50.35 TiO2 2.26 1.38 1.02 1.13 1.48 0.51 0.66 1.3 Al2O3 13.77 13.2 13.57 14.33 13.69 13.41 14.92 13.31 Fe2O3 13.99 14.1 13.27 14.5 15.94 9.78 9.56 14.29 MnO 0.27 0.21 0.2 0.21 0.23 0.14 0.13 0.2 MgO 5.57 7.27 6.72 6.32 5.35 9.81 6.44 6.33 CaO 6.06 12.17 9.91 11.37 10.65 8.42 7.49 10.45 Na2O 4.33 1.84 2.37 2.07 2.16 2.14 2.87 1.29 K2O 1.53 0.21 0.88 0.27 0.24 0.9 1.8 0.42 P2O5 0.5 0.12 0.08 0.09 0.11 0.11 0.12 0.12 LOI 2.8 0.8 2 0.1 0.9 1.6 2.8 1.8 Cr2O3 0.004 0.021 0.011 0.007 0.007 0.123 0.054 0.017 Ctot 0.16 0.03 0.06 0.02 0.02 0.09 0.15 0.03

As 0000002.21.4 Au 1.7 2.5 13.3 11 1.8 1.5 1 3.9 Ba 467 47 155 42 56 301 547 103 Ce 74 16 11.8 11.1 18.4 26.8 39 22.9 Co 29.7 54.1 51.4 52.4 52 54 45.9 56.1 Cs 0.2 1 0.4 0.4 0.6 0.9 0.2 0.2 Cr 00000000 Cu 2.5 119.7 119.1 170.3 165.6 59.5 82.2 125.9 Dy 4.43 4.21 3.6 3.69 4.25 2.03 2.99 3.91 Er 2.62 2.55 2.39 2.42 2.71 1.11 1.56 2.44 Eu 3.42 1.18 0.91 1.04 1.09 0.76 0.98 1.14 Ga 22.4 20.2 17.1 17.9 18.7 14.6 18.9 18.1 Ge 6.37 3.96 3.28 3.25 3.95 2.59 0 0 Hf 3.7 2.3 1.8 1.7 2.7 2.2 2.3 1.9 Ho 0.95 0.86 0.84 0.75 0.85 0.4 0.54 0.86 La 38.9 6.8 4.9 5 8.5 12.1 18.6 10.9 Lu 0.33 0.32 0.37 0.33 0.4 0.2 0.22 0.34 Mo 0.2 0.2 0.1 0.2 0.3 0.4 0.3 0.5 Nb 16.3 6.8 3.4 4.6 8.8 2.2 3.8 5.5 Nd 42.1 13.4 10.1 8.8 13.8 13 18.4 14.3 Ni 32 32.6 38 19.9 23.4 63.1 74.8 45.5 Pb 33 0.6 1.3 0.6 0.3 5.1 33.7 10.9 Pd 0 1.4 12.1 19.3 2 9.3 9.4 0.4 Pr 9.11 2.38 1.69 1.69 2.68 3.16 4.32 2.99 Pt 0 0.9 11.9 28.5 2.3 11 10.1 0 Rb 40.3 11.2 69.2 16.2 7.6 28.2 61.2 18 Rh 0 0 0.09 1.91 0 1.14 2.77 0 S 0.03 0.13 0.16 0.08 0.13 0.03 0.03 0.13 Sc 20 45 44 42 44 25 23 38 Sm 7.6 3.3 2.6 2.6 3.6 2.4 3.8 3.8 Sr 208.8 146 187.5 126.2 127.9 246.1 250 206.2 Ta 1.1 0.4 0.1 0.4 0.6 0.1 0.2 0.3 Tb 0.9 0.66 0.63 0.57 0.68 0.41 0.45 0.64 Th 2.9 0.5 0.4 0.4 0.8 2.2 4.1 0.9 Tl 0 0.1 0.2 0 0 0.1 0.1 0 Tm 0.39 0.37 0.38 0.39 0.41 0.19 0.23 0.35 U 0.6 0.3 0.1 0 0.2 0.4 0.7 0.3 V 169 361 295 323 394 162 171 342 W 0.6 0.3 0.1 0 0.1 1.1 0.5 0.4 Y 26.6 24.8 23.7 22.4 26.5 13.2 16.8 25.1 Yb 2.35 2.32 2.33 2.53 2.64 1.07 1.48 2.31 Zn 130 68 42 33 64 20 77 55 Zr 135.5 78.4 64.4 61 89.7 61.5 89.1 82 Nd (TIMS) 000012.6 12.27 16.81 0 Sm (TIMS) 00003.44 2.41 4.04 0 147Sm/144Nd 00000.1649 0.1189 0.1451 0 143Nd/144Nd 00000.512386 0.511288 0.511252 0 Tdm (Ma) 000002977 0 0

239 Sample 2002034827 2002034833 2002034834 2002034857 2002034858 2002034863 2002036242 2002036285 Group Lo Fe-Ti Main Main Lo Fe-Ti Lo Fe-Ti Lo Fe-Ti Main Lo Fe-Ti Subgroup - Hi-LREE Hi-LREE - - - Hi-LREE - Swarm - - - Irsuaq Irsuaq Irsuaq - - Age (Ma) 0 0 0 2508 2508 2508 0 0 Width (m) 50 20 30 40 200 100 25 3 Trend 20 20 315 340 355 359 2 90 Northing 6730879 6718932 6770041 6732826 6713123 6720338 6177138 6192684 Easting 375368 359244 424876 434652 423707 427799 466632 495135 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 53.87 50.83 49.06 53.28 54.19 54.61 48.08 54.71 TiO2 0.69 1.29 1.75 0.72 0.69 0.85 1.48 0.9 Al2O3 14.17 13.19 14.07 14.61 15.24 14.34 13.82 16.93 Fe2O3 10.62 12.5 13.27 10.38 10.47 11.03 13.87 8.66 MnO 0.14 0.17 0.18 0.13 0.14 0.14 0.2 0.11 MgO 5.98 7.73 6.55 6.88 5.59 5.74 8.01 4.01 CaO 8.58 9.51 10.58 8.82 9.09 8.28 8.9 6.15 Na2O 2.66 2.02 2.08 2.77 2.9 2.76 1.92 4.29 K2O 1.09 1.01 0.62 0.92 1.12 1.33 0.71 1.88 P2O5 0.13 0.13 0.18 0.13 0.15 0.15 0.21 0.47 LOI 1.9 1.4 1.5 1.2 0.3 0.6 2.4 1.6 Cr2O3 0.033 0.049 0.022 0.048 0.02 0.027 0.016 0.006 Ctot 0.01 0.01 0.02 0.24 0.05 0.03 0.02 0.03

As 5 1.7 1.2 0.8 0.9 0.9 1.6 0 Au 0.82.802001.10.7 Ba 336 185 140 369 395 467 241 379 Ce 38.1 30.8 24.4 39.6 37.3 42.5 37.8 91 Co 47.6 53 51.6 50.4 45 47 48.2 24.9 Cs 1 0.7 2.1 1.4 0.8 1.2 0.8 4 Cr 00000000 Cu 81.6 170.7 52.4 86.9 81.8 86.1 20.1 13.6 Dy 2.2 4.42 4.15 3.09 2.88 3.27 5.28 4.84 Er 1.79 2.52 2.18 1.71 1.55 1.89 3.38 2.16 Eu 1.03 1.25 1.39 0.97 0.94 0.99 1.82 1.9 Ga 17.3 19.3 20.5 19 19.7 19.2 22.6 22.9 Ge 00000007 Hf 3 3.1 2.7 2.8 2.4 3.2 4.2 3.3 Ho 0.65 0.88 0.86 0.54 0.53 0.67 1.05 0.81 La 19.8 16.6 12.5 20.4 19.6 22.1 18.7 41 Lu 0.25 0.32 0.31 0.25 0.24 0.3 0.49 0.28 Mo 0.9 2 0.9 1.4 1 1.7 0.6 0.7 Nb 3.6 6.9 8.6 5.6 4.3 4.3 8 7.7 Nd 17.8 16.7 15.2 20 18.6 22.5 24.6 47.3 Ni 59.2 54.1 28.9 69.2 32.4 44.2 29.5 11.1 Pb 4.1 4.6 1.8 3.1 2.9 2.9 3.1 3 Pd 12.4 18.5 0 11.9 0 0 0 1.4 Pr 4.28 3.81 3.26 4.52 4.3 4.94 5.09 11.31 Pt 10.3 9.4 0 9.4 0000 Rb 38.6 43.4 20.1 26.7 32 47.2 48.3 117.5 Rh 0000.10000 S 0.03 0.05 0.14 0.06 0.03 0.04 0.01 0.01 Sc 24 33 34 23 23 23 37 18 Sm 4 4.1 3.4 3.5 3.3 3.7 5.2 9.7 Sr 313.8 315.6 318 287.1 298.8 279.8 207.1 726.9 Ta 0.2 0.5 0.5 0.4 0.3 0.3 0.5 0.5 Tb 0.49 0.69 0.7 0.51 0.48 0.55 0.86 0.91 Th 3.4 2.9 1.2 3.5 3.1 4.6 1.5 5.1 Tl 0.2 0 0 0.1 0.1 0.2 0 0.3 Tm 0.23 0.32 0.33 0.25 0.25 0.26 0.49 0.34 U 0.8 0.5 0.3 0.7 0.9 0.5 0.4 0.8 V 172 344 328 180 171 182 355 166 W 1.7 5.9 3 4.5 3.4 5.4 0.8 4 Y 17.1 24.8 22.4 17.1 16.3 19.4 33.7 24.9 Yb 1.44 2.12 1.92 1.55 1.48 1.86 3.38 1.95 Zn 44 58 67 34 24 40 88 55 Zr 91.2 98.8 100.9 95 91.1 109.2 121.5 114.7 Nd (TIMS) 000016.35 0 0 0 Sm (TIMS) 00003.17 0 0 0 147Sm/144Nd 00000.1173 0 0 0 143Nd/144Nd 00000.511263 0 0 0 Tdm (Ma) 00002968 0 0 0

240 Sample 2002036288 2002036289 2002036295 2002036352 2002037232 2002037237 2002037238 2002037239 Group Hi Fe-Ti Main Main Main Main Main Main Hi Fe-Ti Subgroup Lo-Al Hi-LREE Hi-LREE Hi-LREE Hi-LREE Hi-LREE Hi-LREE Hi-Al Swarm ----R. du Gué--R. du Gué Age (Ma) 00002149 0 0 2149 Width (m) large 0.7 20 3 - large2020 Trend 210 100 277 90 70 280 - 255 Northing 6187120 6199043 6174079 6205181 6226187 6292832 6227113 6297603 Easting 489555 508122 443881 456678 478937 493621 474579 432796 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 51.1 49.51 0 48.28 50.51 48.46 50.11 47.19 TiO2 2.61 1.2 0 1.95 0.93 2.01 1.74 1.97 Al2O3 12.01 15.7 0 13.71 16.7 12.3 15.75 13.24 Fe2O3 15.97 11.3 0 15.44 9.7 16.15 12.13 15.2 MnO 0.24 0.15 0 0.22 0.14 0.21 0.14 0.19 MgO 3.5 6.03 0 6.39 5.46 5.22 4.58 6.03 CaO 6.74 8.01 0 8.72 9.58 9.91 7.63 7.59 Na2O 3.17 2.56 0 2.06 2.35 1.59 3.32 2.45 K2O 1.5 2.62 0 1.01 2.14 0.79 1.79 1.42 P2O5 0.83 0.14 0 0.26 0.1 0.28 0.23 0.26 LOI 2 2.5 0 1.7 2.2 2.9 2.4 4.2 Cr2O3 0.001 0.026 0 0.02 0.027 0.009 0.001 0.008 Ctot 0.04 0.12 0 0.01 0.05 0.12 0.02 0.24

As 00001.31.21.60.7 Au 0.6 0 0 0.7 1.5 0.8 5.2 0 Ba 895 471 390.3 274 319 359 343 965 Ce 103.5 29.8 55.5 36.7 17.7 54.4 41.2 41.7 Co 37.5 41.1 41.9 49.5 42.1 57.6 36.6 44.8 Cs 0.4 1.6 0 0.8 0 3.2 0.6 0.1 Cr 00000000 Cu 30 54.5 49.2 69.7 70.3 112 35.9 85.5 Dy 12.4 4.22 6.88 5.75 2.61 6.78 5.32 5.9 Er 6.42 2.23 4.26 3.5 1.71 3.85 3.21 3.57 Eu 3.3 1.15 1.84 1.63 0.96 2.04 1.88 1.9 Ga 24.1 18.7 19.4 21.7 21.6 20.4 22.6 20.2 Ge 12.65 4.19 0 5.72 0 6.86 5.49 0 Hf 7.2 2.7 4.9 3.3 2.4 4.6 3.8 3.6 Ho 2.33 0.77 1.46 1.24 0.62 1.37 1.1 1.25 La 46.6 14 25.4 17.9 9.4 25.5 19.7 21.8 Lu 0.96 0.32 0.56 0.51 0.22 0.55 0.47 0.54 Mo 1.6 0.4 0 0.7 1 1.2 0.9 0.7 Nb 19.4 6.1 10.9 7.8 3.8 18.5 10.4 8.2 Nd 57.8 16.9 30.3 22.8 13.1 30.2 24.7 26.6 Ni 15.3 41.7 17.5 43.5 37.5 34.5 14.1 44.5 Pb 10.7 3.9 3.8 6.2 2.7 2.9 6.8 10.5 Pd 1.6 2.6 0.5 1.9 0.5 0.3 0 0 Pr 13.19 3.94 6.64 4.7 2.83 6.46 5.44 5.35 Pt 0 0.7 0.1 1.7 0.9 0 0 0 Rb 55 174.8 50 39.6 106.5 59.9 61.2 39.1 Rh 0 0 0.05 0 0.07 0 0 0.1 S 0.17 0.09 0 0.11 0.11 0.13 0.11 0.05 Sc 29270 4025342335 Sm 11.9 4 6.9 5 2.8 6.5 5.8 6.1 Sr 238.1 231.1 261.6 210.3 344.4 244.1 450.9 347.7 Ta 1.3 0.5 0.8 0.5 0.3 1.1 0.7 0.6 Tb 1.96 0.66 1.19 0.92 0.49 1.07 0.88 0.9 Th 3.4 1 3.1 0.9 0.5 2.9 2.1 1.2 Tl 00000.10.200 Tm 1.02 0.37 0.6 0.5 0.28 0.61 0.46 0.55 U 0.9 0 0.2 0 0 0.3 0.3 0 V 231 231 318 354 242 356 278 356 W 1.9 0.6 3.6 2.3 0.1 1.9 1.7 0.7 Y 69.7 24.3 41.9 34.1 19 37.8 32.9 35.5 Yb 6.37 2.28 3.98 3.29 1.7 3.57 2.86 3.59 Zn 131 94 110 68 40 97 72 123 Zr 270.3 91.1 162.3 115.6 74.3 163.4 122.4 119.8 Nd (TIMS) 000000023.46 Sm (TIMS) 00000004.3 147Sm/144Nd 00000000.1109 143Nd/144Nd 00000000.511668 Tdm (Ma) 00000002192

241 Sample 2002037240 2002037241 2002037242 2002037243 2002037244 2002037245 2002037246 2002037247 Group Main Main Main Hi Fe-Ti Main Hi Fe-Ti Main Main Subgroup Hi-LREE Hi-LREE Lo-LREE Hi-Al Lo-LREE Hi-Al Lo-LREE Hi-LREE Swarm ------Age (Ma) 2100? 0000000 Width (m) 8 2 2 40 10 10 2 1 Trend 270 155 110 330 310 120 90 81 Northing 6252605 6209529 6259989 6228750 6235761 6287530 6256514 6276385 Easting 515268 480203 476383 490797 480728 427066 489285 480404 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 49.7 49.89 48.06 50.58 45.87 46.25 48.29 48.64 TiO2 1.27 1.47 1.16 2.36 1.04 2.13 1.22 2.18 Al2O3 13.98 14.39 13.95 15.65 15.89 12.84 14.26 13 Fe2O3 11.57 11.5 12.7 11.04 11.6 16.44 11.88 16.49 MnO 0.19 0.12 0.22 0.19 0.17 0.17 0.18 0.19 MgO 6.77 6.94 6.39 4.11 9.19 6.31 6.08 5.02 CaO 9.45 7.73 11.57 6.12 8.21 7.05 10.56 8.98 Na2O 2.67 2.55 1.72 3.75 1.89 3.22 1.82 2.1 K2O 1.11 2.02 0.47 2.03 0.91 1.52 0.63 1.12 P2O5 0.12 0.2 0.11 0.55 0.1 0.3 0.11 0.29 LOI 3 3 3.5 3.3 5 3.6 4.8 1.8 Cr2O3 0.015 0.011 0.02 0.004 0.023 0.013 0.016 0.007 Ctot 0.02 0.19 0.45 0.3 0.04 0.38 0.5 0.09

As 1 1.4 0.5 2.4 1.6 1.6 0 1.6 Au 0.8 0.7 1.8 0.5 0 1.1 0 1.1 Ba 273 463 175 1074 178 340 164 465 Ce 24.1 35.1 16.4 60.2 14.4 40.5 17.6 57.3 Co 47 48.1 49.3 40.9 65 47.6 49.1 54.7 Cs 0.2 1 0.3 0.5 0.2 0.5 0.3 1.5 Cr 00000000 Cu 85.4 38.1 97.8 19.7 54.3 52.2 98.5 64.5 Dy 3.59 4.1 3.99 4.3 3.35 6.18 3.94 6.91 Er 2.28 2.43 2.53 2.67 2.13 3.93 2.28 4.18 Eu 1.27 1.59 1.24 2.38 0.93 1.96 1.07 2.31 Ga 16.4 19.4 17.7 20.2 16.4 20 17.1 19.9 Ge 4.01 4.63 3.43 5.31 3.11 6.74 3.37 7.3 Hf 2.3 2.6 2 3 1.4 3.8 2.4 4.9 Ho 0.79 0.87 0.85 0.91 0.74 1.34 0.76 1.39 La 10.7 17.4 6.6 30 6.1 20.5 8.1 27.9 Lu 0.3 0.37 0.36 0.35 0.3 0.57 0.34 0.57 Mo 0.5 0.7 0.5 0.8 0.5 0.5 0.4 1.3 Nb 5.7 7.9 4.9 15.1 3.6 9.2 5.8 18.9 Nd 16.8 22.3 11.4 34.1 10.5 26.4 12.5 31.8 Ni 29.4 34.5 49.8 35.5 91.9 30 47.7 35.8 Pb 9 5 8.1 6.7 5.6 32.2 4.5 5.3 Pd 5.9 0.8 2.8 0.4 0.5 0 1.1 0 Pr 3.36 4.47 2.1 7.38 1.9 5.17 2.39 7.28 Pt 2.2 0 3.7 0.4 0.5 0 1.7 0 Rb 42.6 118.5 32.3 39.6 47 42.4 41.6 43.3 Rh 0.14 0.25 0.06 0 0 0.06 0 0 S 0.1 0.19 0.3 0.08 0.18 0.01 0.13 0.17 Sc 34 29 37 18 30 39 36 34 Sm 3.6 4.7 3.1 5.9 2.8 5.7 3.1 6.8 Sr 324.7 307.5 127.2 455.4 180.4 252.3 165.6 220.3 Ta 0.4 0.5 0.3 1 0.2 0.8 0.6 1.2 Tb 0.62 0.71 0.63 0.85 0.52 0.99 0.58 1.14 Th 1 1.1 0.6 1.8 0.4 1.3 0.5 2.9 Tl 0 0.1 0.1 0.1 0 0 0 0.2 Tm 0.34 0.34 0.39 0.33 0.33 0.55 0.35 0.57 U 0.2 0 0.1 0.3 0.2 0.1 0.3 0.4 V 274 283 324 199 248 359 320 376 W 0.5 0.6 0.4 1.1 0.3 1.3 1.1 1.7 Y 21.4 24.1 22.9 25.9 20 38.3 23.4 39.7 Yb 2.08 2.41 2.26 2.38 1.93 3.55 2.42 3.61 Zn 82 59 82 75 69 144 74 95 Zr 84.3 103.2 62.3 120.8 53.9 119.2 66.9 172.8 Nd (TIMS) 14.97 0000000 Sm (TIMS) 3.57 0000000 147Sm/144Nd 0.1441 0000000 143Nd/144Nd 0.511806 0000000 Tdm (Ma) 00000000

242 Sample 2002037249 2002037251 2002037252 2002037331 2002037336 2002037338 2002037339 2002037340 Group Main Main Hi Fe-Ti Sill Main Main Main Hi Fe-Ti Subgroup Hi-LREE Hi-LREE Hi-Al Richmond Gul Lo-LREE Hi-LREE Hi-LREE Hi-Al Swarm ------Age (Ma) 0 0 0 2030 0 0 2100? 2100? Width (m) 0.15 7 0.2 - 10 5 80 25 Trend 105 90 270 - 8 290 260 90 Northing 6274378 6256043 6270128 6230913 6220834 6224211 6227128 6263812 Easting 490227 496018 465271 436876 432812 441575 490277 442291 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 49.23 49.76 46.97 47.85 48.33 52.45 49.18 50.32 TiO2 2.11 0.77 2.33 0.62 2.47 1.54 1.41 2.38 Al2O3 12.94 15.75 13.49 17.83 12.19 13.22 14.92 13.42 Fe2O3 15.74 9.71 15.45 7.9 17.32 13.1 13.55 14.77 MnO 0.17 0.16 0.18 0.11 0.25 0.23 0.18 0.18 MgO 4.96 7.4 4.24 8.48 5.88 5.51 5.87 5.78 CaO 9.1 10.9 10 9.13 7.72 6.49 9.44 5.72 Na2O 2.22 2.08 2.19 2.61 1.6 2.28 2.35 3.06 K2O 0.72 0.99 0.47 1.45 0.13 1.45 1.08 1.25 P2O5 0.29 0.06 0.35 0.07 0.26 0.26 0.13 0.4 LOI 2.3 2.3 4.1 3.8 3.8 3.4 1.8 2.6 Cr2O3 0.008 0.034 0.007 0.033 0.005 0.015 0.008 0.005 Ctot 0.23 0.05 0.44 0.02 0.08 0.19 0.01 0.04

As 1 0.8 1 0.7 1 0.8 0 0 Au 1.201.300000 Ba 590 234 417 340 39 442 260 549 Ce 56.1 11.7 66.2 11.7 44.3 54.4 27.6 69.6 Co 52.8 45.4 59.9 42 49.9 46.4 57.9 44 Cs 0.6 0 0.1 0 0 0 0.1 0.6 Cr 00000000 Cu 61.4 87.7 43.5 27.7 79.2 58.5 63 16.8 Dy 6.7 2.52 6.8 1.95 8.58 7.99 4.06 8 Er 3.88 1.64 4.17 1.05 5.13 4.49 2.17 4.23 Eu 2.06 0.82 2.38 0.67 2.21 2.06 1.41 2.34 Ga 19.3 15.5 20.3 15 23 23.5 23.2 26.5 Ge 7.28 0 7.05 00000 Hf 5.1 1.4 5.2 1.5 4.9 4.3 1.6 4.8 Ho 1.36 0.54 1.45 0.39 1.74 1.55 0.77 1.66 La 26.6 5.3 35.7 5.2 19.8 24.4 12.7 31.1 Lu 0.55 0.23 0.64 0.18 0.7 0.65 0.31 0.59 Mo 1 0.4 1.2 0.6 1.1 1 1.2 0.7 Nb 18.7 2.1 25.9 2.1 21.4 12.6 6.7 25.8 Nd 29.9 8.3 35.4 7.7 27.2 31.9 15.6 36.5 Ni 32.8 55.7 50.9 142 41.3 43.2 39 25.5 Pb 6.6 1.9 9 7.9 2.4 17.9 3.7 5.5 Pd 03.1000000 Pr 6.79 1.61 7.98 1.53 5.57 6.78 3.4 8.31 Pt 03000000 Rb 23.7 53.4 19.5 21.2 1.7 26 21.8 23.2 Rh 00000000 S 0.15 0.1 0.13 0 0.24 0.13 0.19 0.1 Sc 33 30 29 18 39 29 30 32 Sm 6.4 2.1 7.5 1.9 7.6 7.5 4 8.4 Sr 238.6 233.4 309.1 394.1 201.3 251.8 392.6 234.8 Ta 1.2 0.1 1.7 0.2 1.3 0.7 0.5 1.4 Tb 1.1 0.45 1.18 0.31 1.33 1.1 0.63 1.19 Th 2.4 0.3 3.6 0 3.5 2 0.5 3.8 Tl 0.10.1000000.1 Tm 0.55 0.26 0.6 0.16 0.71 0.63 0.34 0.62 U 0.7 0.4 0.5 0 0.4 0 0 0.7 V 369 229 346 133 476 251 319 381 W 1.1 0.3 1 1.6 1.9 1.8 2.2 0.7 Y 39.3 16.1 40.1 10.3 50.3 44.3 22.5 45.6 Yb 3.61 1.44 4.17 0.99 4.37 4.26 2.16 4.24 Zn 94 39 114 47 100 110 77 43 Zr 167.7 41.1 170.6 38.8 180 170.2 85.4 222.1 Nd (TIMS) 0 0 0 7.55 0 0 15.73 37.14 Sm (TIMS) 0 0 0 1.89 0 0 3.72 8.1 147Sm/144Nd 0 0 0 0.151 0 0 0.1432 0.1319 143Nd/144Nd 0 0 0 0.511806 0 0 0.511817 0.511613 Tdm (Ma) 00000002851

243 Sample 2002037343 2002037346 2002037347 2002037351 2002037352 2002037353 2002037355 2002037376 Group Sill Hi Fe-Ti Main Main Sill Main Main Hi Fe-Ti Subgroup Richmond Gul Hi-Al Hi-LREE Hi-LREE Richmond Gul Hi-LREE Hi-LREE Hi-Al Swarm ------Age (Ma) 00000002100? Width (m) - 7 30 5 - 20 - 20 Trend 90 344 355 83 - 342 96 350 Northing 6239748 6254449 6225551 6237189 6223554 6263812 6235986 6220448 Easting 434993 445143 459339 448756 441261 442291 464064 459131 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 48.52 47.96 48.74 48.24 49.51 48.65 51.45 44.91 TiO2 0.78 1.93 1.59 1.62 0.83 1.84 1.8 1.83 Al2O3 16.19 13.21 13.69 14.1 16.68 13.91 13.16 14.44 Fe2O3 9.7 15.72 14.12 13.97 8.98 14.28 14.88 16.7 MnO 0.12 0.19 0.21 0.19 0.13 0.18 0.18 0.19 MgO 7.7 6.16 6.08 6.53 7.46 5.96 4.98 6.39 CaO 9.11 8.23 8.82 8.9 8.85 9.07 6.66 8.71 Na2O 2.56 3.09 2.51 1.94 2.4 1.99 2.49 2.88 K2O 1.41 0.55 1.19 1.23 1.48 0.9 2.52 0.7 P2O5 0.09 0.27 0.17 0.21 0.1 0.29 0.17 0.21 LOI 3.7 2.6 2.8 3 3.5 2.8 1.6 2.9 Cr2O3 0.044 0.018 0.01 0.013 0.03 0.01 0.004 0.012 Ctot 0.07 0.04 0.02 0.08 0.11 0.04 0.06 0.2

As 2.2 0 0 0.8 0.9 0.5 0 0.8 Au 00000000 Ba 393 187 341 336 326 366 581 227 Ce 14.7 39.3 35.9 35.5 16.3 48.9 35.4 35.2 Co 47 53.2 50.3 57.1 45.4 47.9 28.2 61 Cs 0.2 0.8 0.5 0.7 0.3 0.3 0.7 2 Cr 00000000 Cu 62.4 76.2 65.2 95 73 66.6 67.9 62.5 Dy 2.41 6.09 5.1 5.21 2.61 5.93 5.85 5.1 Er 1.4 3.67 3.04 3.26 1.5 3.41 3.4 3.17 Eu 0.86 1.83 1.58 1.65 0.98 1.87 1.67 1.63 Ga 18.2 23.3 21.4 20.6 17.7 20.9 19.8 21.3 Ge 00000000 Hf 1.4 3 2.7 2.6 1.3 2.7 3.5 3.3 Ho 0.51 1.28 1.11 1.13 0.55 1.23 1.18 1.08 La 6.2 18.1 17.5 16.8 7.8 22.5 15.7 16.3 Lu 0.16 0.53 0.43 0.42 0.21 0.5 0.48 0.43 Mo 1.1 0.8 1.5 0.7 0.8 0.8 0.6 0.8 Nb 2.1 8.6 7.7 7.2 3.1 9.7 8.5 8.5 Nd 8.9 26 20.8 20.9 11.2 26.6 19.8 19.9 Ni 101.8 43 33.1 58.3 91.9 43.2 21.4 72.8 Pb 2.4 3.3 4.2 2.6 47.6 3.6 4.5 2.2 Pd 00000000 Pr 1.92 4.88 4.52 4.62 2.28 5.75 4.48 4.57 Pt 00000000 Rb 19.2 12.8 47.1 80.6 25.5 18 121.2 35.1 Rh 00000000 S 0.09 0.12 0.15 0.03 0.07 0.08 0.02 0.17 Sc 24 38 36 32 22 33 40 28 Sm 2.2 5.6 4.9 4.8 2.8 5.5 5.3 5.1 Sr 370.8 211.7 354.9 278.6 285.2 446.6 193.9 207.8 Ta 0.2 0.6 0.5 0.5 0.2 0.7 0.5 0.6 Tb 0.37 0.91 0.72 0.76 0.42 0.8 0.88 0.86 Th 0.2 0.8 1.6 1 0.4 0.6 1.2 0.9 Tl 0 0 0 0.1 0 0 0.1 0.2 Tm 0.18 0.51 0.48 0.43 0.22 0.56 0.61 0.45 U 0 0.3 0 0.1 0 0.3 0.2 0.3 V 188 347 341 290 188 315 397 273 W 1.8 0.9 2 1.4 0.8 1.3 0.8 2 Y 13.6 35.4 31.9 30.4 16.1 35.4 35.1 30.3 Yb 1.36 3.37 3.34 3.21 1.53 3.55 3.59 3.02 Zn 48 79 89 84 75 81 79 91 Zr 52.1 112 118.9 104 56.4 124.1 117.9 108.9 Nd (TIMS) 000000019.9 Sm (TIMS) 00000004.7 147Sm/144Nd 00000000.1427 143Nd/144Nd 00000000.511798 Tdm (Ma) 00000000

244 Sample 2002037377 2002037378 2003031420 2003031422 2003031440 2003031459 2003031491 2003031494 Group Main Main Main Main Main Lo Fe-Ti Main Main Subgroup Lo-LREE Hi-LREE Hi-LREE Hi-LREE Hi-LREE - Lo-LREE Hi-LREE Swarm -----Irsuaq - - Age (Ma) 000002508 0 0 Width (m) 3 3 15 - 40 100 2 1 Trend 90 90 118 130 315 359 290 45 Northing 6229690 6229690 6589749 6590520 6568655 6720338 6583009 6587595 Easting 423781 423781 409808 340866 341064 427799 405695 368420 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 53.26 46.62 51.26 51.13 51.08 52.81 50.18 50.42 TiO2 2.85 2.85 1.06 1.31 0.85 0.38 1.18 1.27 Al2O3 13.56 13.63 13.96 13.68 14.34 14.11 13.34 12.98 Fe2O3 9.77 8.53 13 13.27 11.94 8.2 14.2 14.68 MnO 0.04 0.05 0.18 0.19 0.18 0.13 0.21 0.2 MgO 10.53 10.68 6.26 6.2 6.93 9.33 6.3 6.02 CaO 0.78 5.76 10.18 10.23 11.37 11.46 10.65 9.84 Na2O 0.97 1.29 2.14 2.19 1.96 2.25 2.06 1.94 K2O 1.03 0.95 0.58 0.48 0.34 0.61 0.4 0.7 P2O5 0.44 0.42 0.13 0.14 0.09 0.07 0.1 0.15 LOI 6.1 8.8 1 0.8 0.8 0.5 1.1 1.3 Cr2O3 0.005 0.005 0.01 0.01 0.01 0.15 0.01 0.01 Ctot 0.04 1.09 0.01 0.03 0.03 0.02 0.06 0.09

As 00.500000.60.5 Au 00000000 Ba 4747 2748 195 205 128 205 115 221 Ce 32.3 66.2 23.2 25.4 18.4 18.8 16.8 33.9 Co 32 34.8 49.5 48.4 50.1 52.5 53.2 51.1 Cs 0.2 0 0.7 0.7 0.2 0.6 1.5 0.2 Cr 00000000 Cu 15.5 2.5 88.5 64.4 108.9 38.7 107.9 113.7 Dy 7.39 7.97 3.25 3.65 3.1 1.9 4.01 4.15 Er 4.39 5.52 1.93 2.19 1.94 1.07 2.77 2.3 Eu 1.35 1.7 1.15 1.24 0.94 0.53 1.09 1.22 Ga 23.5 24.1 16.8 18.4 16.2 14.6 14.3 18.1 Ge 00000000 Hf 6.2 6.3 2 2.6 1.7 1.6 2.1 2.6 Ho 1.58 1.75 0.66 0.67 0.62 0.44 1.02 0.84 La 13.8 30.2 10.8 11.6 8.1 9.6 7.3 16.5 Lu 0.64 0.81 0.24 0.24 0.27 0.15 0.33 0.36 Mo 1.5 0.6 0.3 0.2 0.3 0.2 0.3 0.5 Nb 15 15.2 4 4.4 2.5 1.6 4 4.3 Nd 21.1 35.9 13.5 12.1 10.4 8.8 9.3 17.9 Ni 29.8 37.5 24.5 16.6 27.1 28.1 19.5 27.4 Pb 3.3 5.1 1.6 1.2 1.4 1.1 2.7 4.1 Pd 00000000 Pr 4.44 8.54 3.07 3.24 2.32 2.25 2.3 4.03 Pt 00000000 Rb 19.2 17.3 19.3 13.2 9.4 23.8 21.7 41.3 Rh 00000000 S 0.13 0.06 0.1 0.11 0.11 0.02 0.14 0.15 Sc 37 38 41 41 41 30 49 41 Sm 6 7.4 2.5 3.2 2.3 1.9 3.2 4.1 Sr 461.4 228.9 245.8 234.9 202.6 262.9 158.7 215.9 Ta 1 1 0.3 0.4 0.2 0 0.2 0.2 Tb 1.17 1.25 0.57 0.62 0.54 0.28 0.77 0.76 Th 2.8 2.5 0.6 0.7 1.1 1.1 0.5 1.8 Tl 0 0 0.1 0 0 0.1 0.1 0.2 Tm 0.7 0.82 0.22 0.25 0.27 0.18 0.41 0.37 U 0.4 0.6 0 0.1 0.1 0.4 0.1 0.2 V 458 471 266 289 253 167 326 305 W 3.6 2.1 0.2 0.4 0.1 0.2 0 0 Y 44.2 52 19.3 20.8 17.2 11 28.1 24.8 Yb 4.34 5.52 1.77 2.07 1.92 0.89 2.63 2.06 Zn 50 49 49 40 30 13 55 55 Zr 222.6 220.7 65.7 71.7 52.5 46 67.5 85.9 Nd (TIMS) 000009.08 0 0 Sm (TIMS) 000001.85 0 0 147Sm/144Nd 000000.123 0 0 143Nd/144Nd 000000.511368 0 0 Tdm (Ma) 000002979 0 0

245 Sample 2003031561 2003031564 2003031566 2003031567 2003031568 2003031577 2003039834 2003039835 Group Main Main Main Lo Fe-Ti Main Hi Fe-Ti Hi Fe-Ti Main Subgroup Hi-LREE Hi-LREE Lo-LREE - Hi-LREE Lo-Al Hi-Al Hi-LREE Swarm -----Kogaluk Bay -- Age (Ma) 000002210 0 0 Width (m) 40 - 30 2 0.2 30 5 3 Trend 305 285 310 195 330 252 90 90 Northing 6625651 6580213 6632492 6603081 6576202 6557855 6339769 6355588 Easting 372883 354141 400628 380951 365660 372272 435170 406094 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 53.18 51.88 49.73 53.32 51.92 48.75 44.74 47.76 TiO2 1.46 1.22 1.88 0.47 1.2 1.56 2.37 1.66 Al2O3 13.03 13.24 13.04 10.15 13.75 7.53 15.01 14.29 Fe2O3 14.5 14.12 16.94 10.78 13.79 15.12 16.97 14.85 MnO 0.19 0.2 0.23 0.15 0.18 0.19 0.21 0.2 MgO 4.31 5.75 5.04 14.75 5.4 12.03 5.4 6.12 CaO 8.4 9.82 9.78 7.31 9.87 10.17 8.49 9.58 Na2O 2.47 2.32 2.24 1.65 2.23 2.08 2.79 2.15 K2O 1.24 0.59 0.27 0.56 0.81 0.25 0.77 0.83 P2O5 0.24 0.15 0.16 0.09 0.13 0.18 0.29 0.21 LOI 0.5 0.4 0.6 0.2 0.8 2.1 2.7 2.2 Cr2O3 0 0 0.01 0.23 0 0.14 0.008 0.011 Ctot 0.08 0.02 0.01 0.07 0.07 0.02 0.1 0.03

As 0.6000.60000 Au 00000020 Ba 614 272 75 215 298 176 507 347 Ce 67.2 34 24.5 21.3 36 42.5 48.2 32.9 Co 47.8 55 56.4 66.8 57 74.4 64.2 58.3 Cs 0.5 0.5 0.1 0.4 0.2 0.4 0.4 1.1 Cr 00000000 Cu 86.7 86.2 133.2 41.4 74.9 156.5 64.4 60.5 Dy 5.7 4.36 5.51 1.83 3.64 3.5 6.79 5.02 Er 2.81 2.41 3.01 0.97 2.08 2 3.55 3.07 Eu 1.78 1.44 1.46 0.62 1.22 1.45 2.17 1.59 Ga 19.4 17.4 19.2 14.2 17.6 13.1 23.7 22.3 Ge 00000000 Hf 4.6 3.2 3.2 1.7 2.9 3.8 3.3 2.5 Ho 1.09 0.89 1.12 0.39 0.83 0.76 1.28 1.03 La 33.8 16.2 9.6 9.7 17.3 18.9 22.2 15.5 Lu 0.49 0.38 0.44 0.19 0.3 0.2 0.49 0.43 Mo 0.6 0.6 0.6 0.8 0.5 0.6 0.9 0.4 Nb 8.1 5.9 10.8 1.7 5.8 9.4 13.9 7.2 Nd 33.4 18.7 14.2 9.2 18.7 21.2 30.5 22.2 Ni 20.7 20.9 25.1 52.4 23.5 273.7 63.7 57.3 Pb 4 3.2 1.3 1.6 2.2 2.4 5.1 2.4 Pd 00000000 Pr 7.93 4.03 3.15 2.4 4.22 5.5 6.06 4.35 Pt 00000000 Rb 30.5 15.5 7.4 16.4 18.8 8.4 30.5 37.6 Rh 00000000 S 0.15 0.14 0.2 0.02 0.08 0.1 0.2 0.07 Sc 36 41 43 26 36 22 30 37 Sm 5.8 4.2 4.2 1.8 4.3 4.9 6.2 4.5 Sr 284.8 259.4 145.8 174.9 262.7 127.6 324.6 245 Ta 0.5 0.3 0.7 0 0.2 0.6 0.8 0.4 Tb 1.01 0.78 1.08 0.37 0.62 0.79 1.18 0.88 Th 3.6 0.9 0.8 1.6 2.1 3.2 1.6 1.2 Tl 0.1 0.1 0 0 0.1 0 0 0 Tm 0.47 0.39 0.5 0.17 0.33 0.26 0.47 0.4 U 0.4 0.3 0.3 0.2 0.2 0.6 0.1 0 V 313 307 420 154 309 209 256 279 W 0.2 0.1 0.2 0.1 0.1 0 0.7 0.7 Y 31.4 26.7 31.2 11.5 21.3 17.6 37.4 30.1 Yb 3.14 2.66 2.89 1.03 2.06 1.35 3.66 2.96 Zn 95 50 59 25 41 50 114 79 Zr 146 92.1 108 54.9 96.5 110.1 133.6 91.9 Nd (TIMS) 0000041.44 0 0 Sm (TIMS) 000009.09 0 0 147Sm/144Nd 000000.1326 0 0 143Nd/144Nd 000000.51169 0 0 Tdm (Ma) 000002732 0 0

246 Sample 2003039836 2003039837 2003039838 2003039839 2003039840 2003039841 2003039842 2003039843 Group Hi Fe-Ti Main Main Main Hi Fe-Ti Lo Fe-Ti Main Main Subgroup Hi-Al Lo-LREE Hi-LREE Hi-LREE Hi-Al - Hi-LREE Hi-LREE Swarm ------Age (Ma) 00000000 Width (m) 5 - - - 0.2 - 0.6 0.3 Trend 265 115 265 310 284 300 146 150 Northing 6375588 6327059 6340303 6343152 6387574 6327655 6363518 6363088 Easting 536335 557902 403867 409128 554616 424575 421771 420882 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 45.79 47.98 47.95 50.62 45.7 51.59 51.37 50.93 TiO2 1.9 0.77 0.85 0.8 1.9 0.36 1.15 1.19 Al2O3 15.37 16.25 17.11 14.99 15.26 6.2 13.49 13.33 Fe2O3 16.45 11.85 10.35 11.74 16.55 11.45 13.75 14.07 MnO 0.21 0.17 0.14 0.17 0.21 0.19 0.2 0.2 MgO 6.16 7.62 4.51 6.6 6.16 16.05 6.14 5.99 CaO 9.53 11.22 11.95 9.66 8.92 11.94 10.48 9.53 Na2O 2.55 1.97 2.36 2.26 1.99 0.94 1.98 2.32 K2O 0.54 0.51 0.75 1.19 0.94 0.43 0.52 0.84 P2O5 0.22 0.07 0.14 0.09 0.21 0.05 0.11 0.11 LOI 0.9 1.5 3.4 1.6 2 0.8 0.6 1.1 Cr2O3 0.011 0.023 0.008 0.014 0.008 0.075 0.008 0.01 Ctot 0.01 0.05 0.27 0.01 0.07 0.13 0.1 0.02

As 01.21.20.50000 Au 0 3.7 1.9 1 0 0 0.8 1.5 Ba 346 76 335 329 350 100 186 282 Ce 34 8.1 26.2 21.5 34.1 10.1 20.4 21.3 Co 67.7 59.2 32.2 56.4 68.6 70.8 52.8 56.9 Cs 0.3 0.2 0.1 0.4 1.3 0.6 0.3 0.5 Cr 00000000 Cu 54.6 94.3 47.9 80.6 45.4 87.1 107.1 106.7 Dy 4.8 2.31 2.85 2.63 5.22 1.61 3.91 4 Er 3.02 1.56 1.64 1.58 3.06 0.94 2.05 2.34 Eu 1.75 0.73 1.1 0.85 1.73 0.59 1.02 1.18 Ga 23.2 17.9 25.5 18.5 25 9.9 18.9 18.6 Ge 00000000 Hf 3.2 1 1.8 1.6 2.9 0.8 2.2 2.3 Ho 1.1 0.54 0.58 0.56 1.08 0.3 0.75 0.82 La 15.1 3.5 13.1 10 15.4 4.4 9.3 10 Lu 0.43 0.22 0.24 0.27 0.43 0.11 0.31 0.35 Mo 1.2 0.3 0.9 0.4 0.5 0.5 0.5 0.8 Nb 9.5 2.3 3.3 3.3 9.2 0.6 4.1 4.5 Nd 21.8 6.7 14.2 14.1 22.1 7.8 13.8 14 Ni 72.6 83.2 66.7 55.3 81.9 60.4 19.3 24.4 Pb 6 1 4.4 1.7 3 0.7 2.4 2.3 Pd 00000000 Pr 4.44 1.13 3.08 2.63 4.48 1.35 2.6 2.75 Pt 00000000 Rb 14 21.8 20.4 34.7 65.9 25.4 22.1 51 Rh 00000000 S 0.11 0.06 0.01 0.11 0.15 0.08 0.08 0.1 Sc 32 37 26 36 31 71 44 45 Sm 4.8 1.6 2.7 2.6 4.7 1.5 3.2 3.1 Sr 287 181 549.5 290.5 240.1 94.9 189.3 227.4 Ta 0.5 0.1 0.2 0.1 0.6 0 0.2 0.3 Tb 0.88 0.4 0.51 0.47 0.91 0.31 0.61 0.7 Th 1.4 0.3 1.5 0.8 1 0.8 0.7 0.7 Tl 00000000 Tm 0.48 0.2 0.24 0.25 0.46 0.12 0.3 0.34 U 00000.10.100 V 277 226 185 244 269 219 317 308 W 0.7 0.4 0.7 0.6 0.4 0.4 0.3 0.6 Y 30.8 14.5 17.5 16.2 30.7 9.4 21.9 22.6 Yb 3.1 1.67 1.59 1.67 2.86 0.88 2.14 2.28 Zn 76 43 71 45 103 8 60 66 Zr 101.5 30.1 60.5 61.5 102.2 21.7 66.3 70.9 Nd (TIMS) 00000000 Sm (TIMS) 00000000 147Sm/144Nd 00000000 143Nd/144Nd 00000000 Tdm (Ma) 00000000

247 Sample 2003039845 2003039846 2003039847 2003039848 2003039989 2003039990 2003039991 2003039992 Group Main Main Main Hi Fe-Ti Main Hi Fe-Ti Main Hi Fe-Ti Subgroup Hi-LREE Hi-LREE Hi-LREE Hi-Al Lo-LREE Hi-Al Hi-LREE Hi-Al Swarm -----Minto - - Age (Ma) 0 0 0 2100? 0 2000 0 0 Width (m) 5 1 15 6 large- 3 25 Trend 360 310 360 293 115 95 140 95 Northing 6371479 6377077 6364416 6385537 6337827 6326424 6343833 6383083 Easting 415054 407848 434413 418526 526502 479576 454678 452281 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 50.96 50.63 51.52 47.65 47.34 43.17 51.71 45.67 TiO2 1.24 1.21 1.54 2.48 0.93 2.21 1.52 1.99 Al2O3 13.09 13.12 12.82 14.25 15.57 15.5 12.66 14.12 Fe2O3 14.27 13.65 14.79 13.58 12.84 17.01 14.58 15.25 MnO 0.21 0.2 0.2 0.16 0.17 0.22 0.19 0.18 MgO 6.08 6.26 4.91 5.29 7.64 7.72 5.06 6.45 CaO 9.49 9.48 7.52 8.87 10.83 7.26 8.16 10.69 Na2O 2.3 2.22 3.18 2.96 1.94 2.19 3.11 2.16 K2O 1.05 0.99 1.64 1.27 0.25 1.22 1.01 0.67 P2O5 0.12 0.14 0.2 0.32 0.08 0.19 0.21 0.23 LOI 1 1.8 1.3 3.1 2 2.9 1.7 2.1 Cr2O3 0.007 0.009 0 0.01 0.018 0.017 0.006 0.011 Ctot 0.03 0.19 0 0.13 0.03 0.03 0.03 0.01

As 0 0 0.7 0.6 3.9 0 0 0 Au 1.7 3.1 2.6 3 1.5 0 1.2 0 Ba 250 267 418 541 92 743 367 364 Ce 23.6 21.9 47.6 52.5 11.5 29 44.2 43.7 Co 59.1 57.6 52.5 47 55.8 72.9 51.8 55.9 Cs 0.5 0.2 1 0.2 0.2 0.7 0.4 0.2 Cr 00000000 Cu 125.2 101.3 44.6 31.3 92.1 61.6 48.7 14.3 Dy 4.01 3.79 4.8 5.07 2.45 3.81 4.65 5.64 Er 2.36 2.28 2.64 2.39 1.9 2.84 2.83 3.61 Eu 1.27 1.12 1.62 2.37 0.76 1.78 1.43 1.91 Ga 19.8 18.9 20.6 25.2 17.6 20.6 16.1 23.9 Ge 00000000 Hf 2.1 2.3 3.4 3.7 1.1 3.2 3.3 2.8 Ho 0.88 0.81 0.95 0.94 0.66 0.91 0.99 1.21 La 10.8 10.2 22.6 23.3 5.4 14.9 21.5 19.6 Lu 0.34 0.32 0.39 0.31 0.25 0.35 0.38 0.49 Mo 0.8 0.3 1 0.6 0.1 0.3 0.5 0.2 Nb 4.7 4.5 8.1 12.5 2.7 7.7 7.4 8.9 Nd 15.9 14.6 24.2 33.5 7.8 18.1 24.8 26.8 Ni 20 16.2 15 46.6 108.8 70.1 17.4 43.9 Pb 1.7 2.5 3.5 3 3 1.4 2.4 1 Pd 00000000 Pr 3 2.76 5.32 6.4 1.67 3.46 5.21 5.21 Pt 00000000 Rb 65.5 51.3 115.8 40 13.6 46.9 35.6 22.7 Rh 00000000 S 0.11 0.1 0.19 0.18 0.06 0.1 0.14 0.01 Sc 43 44 38 25 35 30 37 32 Sm 3.5 3.3 5.3 6.2 2.2 4 5.3 5.7 Sr 240.1 208.9 281 515.5 194 236.4 246.5 331.5 Ta 0.4 0.2 0.5 0.8 0.1 0.5 0.5 0.5 Tb 0.75 0.71 0.89 0.99 0.47 0.8 0.79 1.12 Th 1 1.1 2 1.3 0.3 0.8 1.7 1 Tl 00000000 Tm 0.35 0.33 0.4 0.34 0.28 0.37 0.37 0.48 U 0 0.1 0.2 0.2 0 0.4 0.4 0.1 V 322 314 322 328 231 314 322 261 W 0.7 0.3 0.2 0.2 0 0.3 0.1 0 Y 24.5 24.2 29 25.8 17 23.3 26.2 30.8 Yb 2.54 2.13 2.76 2.01 1.85 2.05 2.49 3.12 Zn 58 64 93 117 49 93 92 54 Zr 75.5 74.7 123.6 125.7 41.4 93 117 99.5 Nd (TIMS) 0 0 0 28.45 0 17.24 0 0 Sm (TIMS) 0 0 0 6.14 0 3.96 0 0 147Sm/144Nd 0 0 0 0.1303 0 0.1388 0 0 143Nd/144Nd 0 0 0 0.511633 0 0.511761 0 0 Tdm (Ma) 0 0 0 2761 0 2817 0 0

248 Sample 2003039993 2003039994 2003039995 2003039996 2003039997 2003039998 2003039999 2003040201 Group Hi Fe-Ti Main Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Main Subgroup Hi-Al Hi-LREE Hi-Al Hi-Al Lo-Al Lo-Al Hi-Al Lo-LREE Swarm ------Age (Ma) 0 0 0 2100? 0000 Width (m) 0.5 50 0.2 10 0.4 2 0.2 10 Trend 265 330 55 220 120 70 85 330 Northing 6385277 6425368 6414867 6410778 6404915 6346690 6414867 6366414 Easting 390033 437132 419039 409135 401858 485932 419039 516603 Zone 18 18 18 18 18 18 18 18 Laboratory ACME ACME ACME ACME ACME ACME ACME ACME SiO2 47.21 48.76 45.17 45.89 50.17 49.75 42.88 46.92 TiO2 2.35 1.04 2.51 2.36 1.49 1.51 2.46 0.87 Al2O3 14.4 15.2 14.8 15.78 10.87 10.83 14.42 15.87 Fe2O3 13.32 12.31 16.53 14.99 14.69 14.67 16.39 12.35 MnO 0.15 0.17 0.2 0.18 0.19 0.18 0.19 0.17 MgO 5.65 7.64 5.77 5.18 6.97 6.39 5.09 7.81 CaO 9.09 10.93 8.67 8.21 8.89 8.83 10.86 10.92 Na2O 2.98 2.1 2.86 3.09 4 4.02 2.52 1.97 K2O 0.77 0.3 0.57 1.22 0.12 0.35 0.31 0.4 P2O5 0.3 0.08 0.42 0.38 0.17 0.17 0.39 0.05 LOI 3.5 0.9 2.2 2.2 2 2.9 4.2 2.1 Cr2O3 0.011 0.037 0.01 0.007 0.028 0.028 0.013 0.018 Ctot 0.34 0 0.19 0 0.09 0.52 0.52 0.04

As 00000000 Au 0.9 0 0.5 0 0.9 1.7 0 0.7 Ba 641 123 323 541 65 118 236 128 Ce 50.2 18.3 73.8 64.7 45.7 44.1 59.1 0 Co 46.7 48.5 62.7 40 55.3 58.1 51 60.8 Cs 0.5 0.3 0.8 0.2 0.3 2 0.4 0 Cr 00000000 Cu 21.6 94.7 37.6 41.2 222.9 157.2 33.8 114 Dy 4.29 2.91 5.95 5.92 4.96 4.99 5.44 2.77 Er 2.3 1.98 4.09 3.54 2.58 2.67 3.36 1.78 Eu 2.13 1.06 2.47 2.24 1.55 1.57 2.14 0.9 Ga 22.7 15.6 22.1 20.4 17.3 20.6 21.7 17.7 Ge 00000000 Hf 3.3 1.8 5.9 4.2 3.6 4.5 4.8 1.5 Ho 0.91 0.66 1.36 1.16 0.93 0.9 1.15 0.61 La 21.8 8.3 32 27.5 20.6 20.1 28.4 4.9 Lu 0.29 0.3 0.57 0.46 0.33 0.35 0.48 0.22 Mo 0.5 0.2 0.5 0.5 0.6 0.3 0.7 0.2 Nb 11.4 3.4 20 15.6 11.3 10.7 17.8 3 Nd 26.8 11.2 37 33.1 26.1 30.5 32.3 7.6 Ni 56.7 56.5 63.1 53.8 74.4 80.7 60.1 94.7 Pb 4.2 1 5.6 2.6 5.2 1.4 2.1 3 Pd 00000000 Pr 6.09 2.23 8.53 7.18 5.24 5.63 6.79 1.38 Pt 00000000 Rb 12.3 11.5 23.3 60.3 5.1 26.8 7.3 13.7 Rh 00000000 S 0.18 0.08 0.23 0.09 0.05 0.05 0.18 0.09 Sc 24 34 26 26 20 21 25 33 Sm 6 2.9 7.4 7.1 5.6 5.3 6.4 2 Sr 380.7 210.6 333.8 366.6 140 183 498.1 187.9 Ta 0.7 0.3 1.1 1 0.9 0.8 1 0.1 Tb 0.89 0.56 1.45 1.09 0.91 0.96 1.03 0.5 Th 0.6 0.8 1.5 1.7 4.6 4 1.7 0.4 Tl 00000000 Tm 0.32 0.27 0.61 0.48 0.37 0.38 0.51 0.31 U 0.3 0.1 0.4 0.4 1.4 1 0.3 0 V 315 208 224 195 192 206 237 223 W 0.3 0.1 0.3 0.5 0.1 0.1 0.5 0 Y 24.4 17.9 36.7 32.4 26.1 26.9 32 0 Yb 1.79 1.67 3.76 3.11 2.28 2.35 3.17 1.69 Zn 102 26 89 101 81 56 104 38 Zr 110.6 50.9 191 159.1 139.7 147 162.9 39.1 Nd (TIMS) 0 0 0 33.94 0000 Sm (TIMS) 0 0 0 7.03 0000 147Sm/144Nd 0 0 0 0.1251 0000 143Nd/144Nd 0 0 0 0.51152 0000 Tdm (Ma) 0 0 0 2792 0000

249 Sample 2003040202 CGQ-1068D 2006047178 2006047179 BXA91-6001 BXA91-6201 BXA91-6302 BXA91-6305 Group Main Main Main Hi Fe-Ti Lo Fe-Ti Lo Fe-Ti Lo Fe-Ti Lo Fe-Ti Subgroup Lo-LREE Lo-LREE Hi-LREE Lo-Al ---- Swarm ---Kogaluk Bay -Maguire Maguire Maguire Age (Ma) 0 0 2100? 2210 0 2230 2230 2230 Width (m) - 5 - large---- Trend 135--252---- Northing 6359596 6598173 6773645 6559372 6447244 6443243 6440994 6440994 Easting 487101 338915 412823 376629 620655 664426 663929 663929 Zone 18 19 18 18 18 18 18 18 Laboratory ACME CGQ ACME ACME GSC GSC GSC GSC SiO2 48.02 52.06 51.61 48.66 50.7 49.9 50.7 51.2 TiO2 0.92 0.93 1.02 1.64 0.49 0.62 0.6 0.57 Al2O3 15.64 14.86 15.89 9.63 14.7 13.4 13.9 15.4 Fe2O3 12.99 10.38 11.42 14.45 9.8 9.3 9.4 8.8 MnO 0.18 0.19 0.17 0.19 0.2 0.12 0.16 0.15 MgO 7.78 6.65 4.69 10.67 11.5 10.03 9.23 7.22 CaO 10.95 11.27 9.54 8.65 4.2 10.29 11.23 11.22 Na2O 2.06 1.94 3.31 3.31 4.16 2.1 2.1 2.2 K2O 0.45 0.14 0.69 0.65 0.61 0.7 0.65 0.89 P2O5 0.07 0.05 0.1 0.19 0.05 0.05 0.05 0.05 LOI 1 0.7 1.5 1.6 3.6 2.1 1 1.6 Cr2O3 0.019 0 0.05 0.131 0000 Ctot 0 0 0.03 0.13 0000

As 000.700000 Au 1.2 0 1 30.6 8 5 10 4 Ba 100 22 0 0 83 130 170 140 Ce 0 9.2 23.7 48.1 12 16 17 17 Co 58.7 54.7 40.8 65.9 66 58 58 51 Cs 0 0 0.6 0.3 1.7 0.16 0.46 0.42 Cr 0 98.5 0 0 381 515 430 137 Cu 108.9 157.0 55.4 158.5 32 74 70 69 Dy 2.72 0 3.24 4.06 1.6 2.4 2.5 2.4 Er 1.73 0 1.88 1.79 1.2 1.5 1.6 1.5 Eu 0.89 0.70 1 1.54 0.35 0.51 0.55 0.52 Ga 19.8 0 18.5 15.8 13 13 13 14 Ge 00000000 Hf 1.6 1.2 1.9 3.7 1.5 1.6 2 1.7 Ho 0.54 0.52 0.64 0.67 0.39 0.53 0.55 0.51 La 4.6 3.3 12.3 18.6 5.1 7.1 8 8.3 Lu 0.27 0.21 0.26 0.21 0.24 0.25 0.26 0.25 Mo 0.1 0 19.9 10.4 0.3 0.3 1 0.6 Nb 2.6 3.7 4.3 10.7 2.7 3 3.2 3.2 Nd 6.8 6.4 12.8 28.5 5.5 7.6 7.6 7.9 Ni 71.8 104.7 28.1 193 151 189 155 82 Pb 1 0 1.3 3.1 -1 2 3 6 Pd 0 0 10.9 3.6 16.3 13.9 14.3 14.6 Pr 1.29 0 3.11 6.55 1.4 1.9 2 2 Pt 0 0 8.6 3.8 16.3 14.9 14 14.9 Rb 17.4 1.9 30.5 25 19 33 21 35 Rh 00000.18 0 0.67 0.32 S 0.09 0 0.03 0.12 0.32 0.16 0.17 0.15 Sc 36 44 0 0 36 34 34 31 Sm 2 1.7 3.1 5.7 1.3 1.8 1.9 1.9 Sr 209.6 110.9 287.6 252 48 123 105 145 Ta 0.2 0.2 0.3 0.6 0.63 0.69 0.99 0.97 Tb 0.42 0.38 0.54 0.86 0.25 0.36 0.38 0.38 Th 0.4 0.3 0.8 3.3 2 2.4 2.5 2.8 Tl 0 0 0.2 0.1 0.05 0.14 0.08 0.17 Tm 0.25 0 0.26 0.22 0.21 0.24 0.24 0.23 U 0 0 0.2 0.7 0.41 0.45 0.47 0.52 V 237 0 260 225 184 191 190 183 W 0.100.50.40000 Y 0 14.8 16.3 16.8 12 16 16 16 Yb 1.83 1.43 1.64 1.41 1.4 1.6 1.6 1.6 Zn 36 0 39 57 102 53 78 72 Zr 41.1 46.1 70.9 134.9 55 60 75 66 Nd (TIMS) 0 0 12.52 27.76 0000 Sm (TIMS) 0 0 2.91 5.99 0000 147Sm/144Nd 0 0 0.1405 0.1304 0000 143Nd/144Nd 0 0 0.511743 0.511688 0000 Tdm (Ma) 0 0 0 2664 0000

250 Sample BXA91-6701 BXA91-6704 BXA91-7101 BXA91-7105 BXA91-7201 BXA91-7302 BXA91-7403 BXA91-7503 Group Main Main Lo Fe-Ti Lo Fe-Ti Main Main Main Main Subgroup Lo-LREE Lo-LREE - - Lo-LREE Lo-LREE Lo-LREE Lo-LREE Swarm --Maguire Maguire - Klotz Klotz Klotz Age (Ma) 0 0 2230 2230 0 2209 2209 2209 Width (m) ------Trend ------Northing 6482007 6482007 6441374 6441374 6646742 6716521 6707668 6712393 Easting 372229 372229 645024 645024 581554 560824 564270 577906 Zone 19 19 18 18 18 18 18 18 Laboratory GSC GSC GSC GSC GSC GSC GSC GSC SiO2 49.7 49.4 50.4 50.9 48.6 49.4 48.8 49 TiO2 1.1 1.23 0.56 0.52 1.55 1.64 1.36 1.42 Al2O3 14.1 16.7 13.5 14.8 12.8 13.3 13.1 13.9 Fe2O3 11.5 11 9.5 8.1 16.6 15.2 14 14.9 MnO 0.18 0.16 0.15 0.14 0.24 0.23 0.23 0.25 MgO 8.02 5.88 10.19 8.04 6.02 6.07 6.86 5.96 CaO 12.04 11.7 11.07 11.53 8.72 10.96 11.29 9.17 Na2O 1.7 2.1 2.2 2 2.3 2.3 2.1 3.1 K2O 0.33 0.28 0.56 1.21 0.63 0.2 0.19 0.44 P2O5 0.07 0.08 0.05 0.04 0.09 0.13 0.09 0.11 LOI 0.6 0.4 1.2 2 1.5 0.3 1.3 1.3 Cr2O3 00000000 Ctot 00000000

As 00000000 Au 1555102965 Ba 70 46 130 170 150 63 37 85 Ce 9.6 9.2 15 15 20 17 12 15 Co 61 56 61 49 65 68 60 63 Cs 0.44 0.28 0.57 0.52 2.5 0.14 0.09 0.4 Cr 286 134 551 320 89 101 145 89 Cu 141 82 64 56 248 269 202 188 Dy 3.5 3.4 2.4 2.2 3.6 5.4 4.1 4.5 Er 2 2 1.5 1.3 2.1 3.2 2.3 2.6 Eu 0.84 0.88 0.5 0.47 1 1.2 1 1.1 Ga 16 18 13 13 18 19 17 18 Ge 00000000 Hf 1.6 1.6 2.2 1.5 1.9 2.6 1.9 2.1 Ho 0.76 0.71 0.54 0.47 0.77 1.2 0.87 0.98 La 3.8 3.6 7.2 7.4 8.8 6.6 4.8 6.1 Lu 0.33 0.32 0.25 0.24 0.35 0.52 0.37 0.42 Mo 0.6 0.5 0.4 0.3 0.5 0.6 0.4 0.4 Nb 4 4 3 2.6 6.7 7.6 5.7 6.7 Nd 7.2 6.7 7.2 6.9 11 12 8.7 11 Ni 140 75 202 100 58 69 85 65 Pb -12223-146 Pd 3.2 1 13.7 12 9.7 40.4 26.1 5.5 Pr 1.4 1.4 1.8 1.8 2.6 2.4 1.8 2.2 Pt 7.3 1.4 14.2 10.7 7.5 25.5 20 5.3 Rb 17 9 21 55 33 5.3 4.5 19 Rh 0000.10000 S 0.1 0.03 0.16 0.12 0.14 0.06 0.03 0.09 Sc 42 35 35 34 44 45 42 42 Sm 2.4 2.3 1.8 1.7 3 3.7 2.8 3.4 Sr 92 115 101 129 228 102 133 242 Ta 1.2 1.1 0.85 0.74 0.88 1.4 0.93 0.99 Tb 0.56 0.53 0.37 0.32 0.58 0.84 0.65 0.73 Th 0.39 0.42 2.3 2.3 0.86 0.62 0.38 0.47 Tl 0.12 0.05 0.1 0.21 0.18 0.03 0 0.08 Tm 0.32 0.3 0.24 0.21 0.33 0.5 0.38 0.41 U 0.1 0.12 0.43 0.42 0.25 0.15 0.11 0.12 V 291 299 192 161 339 363 304 319 W 00000000 Y 22 20 16 14 22 34 25 28 Yb 2.1 2 1.6 1.5 2.2 3.3 2.4 2.7 Zn 87 91 72 67 160 114 97 121 Zr 60 60 86 57 68 97 70 78 Nd (TIMS) 00000000 Sm (TIMS) 00000000 147Sm/144Nd 00000000 143Nd/144Nd 00000000 Tdm (Ma) 00000000

251 Sample BXA91-7605 BXA91-7802 BXA91-7904 BXA91-8003 BXA91-8103 BXA91-8106 BXA91-8203 BXA91-8404 Group Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Hi Fe-Ti Main Subgroup Lo-Al Lo-Al Hi-Al Hi-Al Hi-Al Hi-Al Hi-Al Hi-LREE Swarm - - Minto Minto Minto Minto - - Age (Ma) 0 0 2000 2000 2000 2000 0 0 Width (m) ------Trend ------Northing 6341876 6341876 6327479 6327479 6328624 6328624 6327515 6340763 Easting 498188 498188 475154 475154 470314 470314 469700 502416 Zone 18 18 18 18 18 18 18 18 Laboratory GSC GSC GSC GSC GSC GSC GSC GSC SiO2 48.6 48.9 44.6 45.1 45.4 46.3 44.1 47.8 TiO2 2.02 1.97 2.69 2.41 2.39 2.95 1.74 1.64 Al2O3 10.5 10.3 14.4 14.3 14.4 13.1 14.8 14.8 Fe2O3 15 14.9 17.8 17.3 16.8 16.9 17.2 14.1 MnO 0.17 0.21 0.23 0.27 0.22 0.22 0.23 0.2 MgO 6.45 6.79 5.19 6.03 5.9 4.2 10.16 6.26 CaO 10.34 10.04 8.94 7.34 8.56 10.04 2.35 9.65 Na2O 3.6 3.8 2.7 3.3 2.6 3 2.1 2.2 K2O 0.43 0.36 1.17 0.78 1.01 1.03 1.49 0.9 P2O5 0.15 0.15 0.34 0.3 0.29 0.37 0.22 0.19 LOI 1.4 1 1.1 2.1 1.5 1.4 5.3 1.3 Cr2O3 00000000 Ctot 00000000

As 00000000 Au 541734040 Ba 96 74 420 680 360 460 240 370 Ce 37 34 52 48 57 60 57 36 Co 65 69 66 65 66 53 56 63 Cs 0.47 0.14 1.5 0.33 1.6 0.91 3.3 1.6 Cr 104 119 87 82 82 11 29 92 Cu 241 199 77 82 66 65 12 57 Dy 5.2 5 7.2 6.4 6.8 8.6 5.4 5.4 Er 2.4 2.4 3.9 3.5 3.7 4.6 2.9 3.1 Eu 1.7 1.7 2.3 2.1 2.2 2.7 1.7 1.7 Ga 19 19 24 22 23 25 22 20 Ge 00000000 Hf 4 3.9 4.4 3.9 4.3 5.1 3.6 3.3 Ho 0.96 0.95 1.5 1.3 1.4 1.7 1.1 1.1 La 15 14 24 22 27 27 26 17 Lu 0.32 0.32 0.6 0.55 0.58 0.72 0.42 0.49 Mo 0.8 0.6 0.9 1 0.9 1 0.4 0.5 Nb 11 11 17 15 16 19 9.7 8.6 Nd 23 21 29 26 30 33 28 20 Ni 105 110 53 72 68 15 31 72 Pb 225196654 Pd 8.16.6000000 Pr 5 4.7 6.8 6.1 7.1 7.7 7.1 4.6 Pt 10.1 7.1 00000.40.3 Rb 12 12 65 36 57 27 130 44 Rh 0 0.09 000000 S 0.22 0.24 0.21 0.15 0.19 0.11 0.15 0.12 Sc 24 26 33 30 29 53 44 33 Sm 6.1 6 7.3 6.6 7.2 8.5 6.3 5 Sr 95 150 233 284 236 229 98 243 Ta 1.2 1.2 1.2 1.1 1.4 1.5 0.63 0.92 Tb 0.93 0.93 1.2 1.1 1.1 1.4 0.93 0.91 Th 3.4 3.2 1.4 1.3 2.4 1.6 2.1 1 Tl 0.07 0.06 0.48 0.16 0.43 0.32 0.65 0.29 Tm 0.35 0.34 0.59 0.54 0.56 0.7 0.43 0.47 U 0.74 0.61 0.27 0.25 0.38 0.31 0.37 0.18 V 293 293 274 242 241 299 368 245 W 00000000 Y 27 26 42 38 39 50 31 32 Yb 2.1 2.1 3.8 3.5 3.7 4.5 2.7 3 Zn 70 77 168 246 157 128 265 123 Zr 140 130 160 150 160 190 140 120 Nd (TIMS) 00000000 Sm (TIMS) 00000000 147Sm/144Nd 00000000 143Nd/144Nd 00000000 Tdm (Ma) 00000000

252 Sample BXA91-8406 CGQ-3069B1CGQ-3069B2 CGQ-4066B CGQ-4257A CGQ-5062C CGQ-6058D CGQ-8045B Group Main Main Main Main Main Main Main Main Subgroup Hi-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE Swarm ------Age (Ma) 00000000 Width (m) - 25 25 large - 0.4 1 - Trend - 145 145 110 - 130 - - Northing 6340763 6641571 6641571 6642189 6552457 6600800 6606497 6599772 Easting 502416 337056 337056 375489 329494 335421 372830 399469 Zone 18 19 19 19 19 19 19 19 Laboratory GSC CGQ CGQ CGQ CGQ CGQ CGQ CGQ SiO2 47.8 49.27 47.26 51.32 51.95 50.94 51.47 51.12 TiO2 1.72 3.14 4.26 1.10 1.47 1.14 1.73 1.90 Al2O3 14.4 11.75 10.88 14.61 13.03 13.32 12.51 12.67 Fe2O3 15 16.36 18.10 11.52 12.30 12.25 13.27 14.52 MnO 0.22 0.26 0.27 0.21 0.22 0.22 0.23 0.21 MgO 6.34 5.47 5.41 6.58 6.31 6.75 5.78 5.89 CaO 9.8 9.39 9.13 10.99 10.05 10.70 9.51 9.04 Na2O 2.3 2.04 2.06 2.24 2.27 1.98 2.24 2.19 K2O 0.72 0.70 0.53 0.18 0.32 0.51 0.26 0.33 P2O5 0.2 0.36 0.31 0.07 0.12 0.08 0.14 0.15 LOI 1.1 1.0 1.1 0.0 0.9 1.7 1.8 0.4 Cr2O3 00000000 Ctot 00000000

As 00000000 Au 00000000 Ba 240 148 127 29 57 46 55 31 Ce 35 56.2 49.7 10.7 20.3 11.8 22.1 24.2 Co 68 68.6 85.1 58.1 52.4 92.6 75.1 74.6 Cs 3.70000000 Cr 100 133.5 63.2 58.8 104.1 106.6 74.4 109.2 Cu 61 476.4 622.6 158.1 143.9 167.8 137.2 77.0 Dy 5.50000000 Er 3.10000000 Eu 1.7 2.31 2.12 0.88 1.21 0.91 1.35 1.49 Ga 200000000 Ge 00000000 Hf 3.1 6.2 5.8 1.7 2.9 1.7 2.8 3.9 Ho 1.2 2.07 1.83 0.76 0.96 0.78 1.04 1.58 La 17 22.4 19.7 4.0 8.2 4.6 8.5 10.1 Lu 0.49 0.73 0.68 0.29 0.38 0.29 0.39 0.65 Mo 0.60000000 Nb 8.3 24.9 28.2 5.6 11.8 5.9 11.3 8.3 Nd 19 33.4 29.6 7.8 13.9 8.5 14.6 16.0 Ni 69 42.5 42.6 72.7 72.7 93.9 65.2 51.1 Pb 40000000 Pd 00000000 Pr 4.50000000 Pt 00000000 Rb 64 11.8 9.0 2.3 8.0 20.4 4.4 4.3 Rh 00000000 S 0.17 0000000 Sc 35 39 41 42 47 46 48 44 Sm 5.1 8.4 7.6 2.3 3.7 2.5 3.7 4.6 Sr 202 153.3 148.1 119.1 143.9 99.8 129.0 118.4 Ta 0.96 1.3 1.4 0.3 0.6 0.3 0.6 0.5 Tb 0.91 1.59 1.45 0.54 0.73 0.56 0.75 1.15 Th 0.95 2.8 2.4 0.3 0.8 0.4 0.9 2.3 Tl 0.59 0000000 Tm 0.47 0000000 U 0.16 0000000 V 2640000000 W 00000000 Y 32 49.3 43.9 17.8 25.4 20.2 26.8 41.2 Yb 3.1 4.91 4.58 1.89 2.41 1.91 2.57 4.19 Zn 1250000000 Zr 120 235.8 210.7 61.0 102.4 65.1 104.5 134.0 Nd (TIMS) 00000000 Sm (TIMS) 00000000 147Sm/144Nd 00000000 143Nd/144Nd 00000000 Tdm (Ma) 00000000

253 Sample FA65-068-07 FA65-068-08 FA65-068-09 FA65-073-04 MCGILL PBAB90-23BPBAH91-101A Group Main Main Main Main Main Lo Fe-Ti Lo Fe-Ti Subgroup Lo-LREE Lo-LREE Lo-LREE Lo-LREE Lo-LREE - - Swarm Payne Payne Payne Payne Payne Maguire Maguire Age (Ma) 2170 2170 2170 2170 2170 2230 2230 Width (m) ----30-- Trend ----335-- Northing 6682824 6682824 6682824 6730146 6746874 6444071 6441800 Easting 389356 389356 389356 361661 386253 639213 647200 Zone 19 19 19 19 19 18 18 Laboratory GSC GSC GSC GSC MCGILL GSC GSC SiO2 49.7 49.5 49.2 50.9 49.18 50.3 53.3 TiO2 1.18 1.17 1.5 1.18 0.93 0.55 0.49 Al2O3 15.9 14.2 14.9 14.3 14.8 13.7 12.1 Fe2O3 12.4 12.2 13.2 12.6 10.18 9.5 9.5 MnO 0.18 0.19 0.19 0.19 0.17 0.15 0.18 MgO 6.83 7.61 5.98 7.4 9.37 9.54 9 CaO 11.4 11.32 10.82 10.7 11.08 11 12.69 Na2O 1.96 1.9 2 1.98 1.54 2 0.1 K2O 0.13 0.58 0.2 0.27 0.79 0.76 0.04 P2O5 0.09 0.09 0.12 0.04 0.07 0.05 0.05 LOI 0.2 0.6 0.3 0.7 2.5 1.6 2.6 Cr2O3 0000000 Ctot 0000000

As 0000000 Au 0310053 Ba 38 85 41 144 0 160 28 Ce 12 12 15 12 0 17 16 Co 44 49 50 43 0 55 48 Cs 0.3 0.48 0.62 0.13 0 0.77 0.11 Cr 173 244 142 208 623.0 505 486 Cu 134 119 112 115 157.0 74 27 Dy 3.6 3.7 4.7 3.9 0 2.4 2.5 Er 2.1 2.2 2.7 2.2 0 1.5 1.5 Eu 0.98 0.95 1.2 1 0 0.52 0.54 Ga 18 16 19 17 15.4 13 13 Ge 0000000 Hf 1.8 1.6 2.2 1.8 0 1.7 1.6 Ho 0.76 0.78 1 0.8 0 0.54 0.55 La 4.4 4.7 5.7 4.5 0 8 7.5 Lu 0.33 0.35 0.44 0.36 0 0.25 0.26 Mo 0.9 1.2 0.9 1.2 0 0.2 0.4 Nb 4.9 5 6.5 5.2 6 3 2.9 Nd 9.1 8.4 11 8.7 0 7.7 7.8 Ni 110 131 93 114 219 181 146 Pb -1823026 Pd 2.7 1.3 1 0 14.5 15.5 Pr 1.8 1.7 2.2 1.8 0 2 2 Pt 2.7 0.7 0.6 0 14.6 14.7 Rb 4 13 7.7 8.1 47.7 27 0.71 Rh 00000.17 0 S 0.11 0.1 0.12 0.11 0 0.16 0.02 Sc 40 42 41 38 0 35 36 Sm 2.6 2.8 3.7 2.9 0 1.8 1.9 Sr 115 132 121 92 135 145 670 Ta 0.35 0.33 0.43 0.32 0 0.61 0.65 Tb 0.57 0.59 0.76 0.61 0 0.39 0.38 Th 0.33 0.31 0.44 0.34 0.2 2.4 2.5 Tl 0.03 0.16 0.06 0.06 0 0.11 0 Tm 0.31 0.34 0.43 0.35 0 0.24 0.24 U 0.09 0.09 0.12 0.09 0 0.45 0.46 V 307 294 327 272 246 192 169 W 0000000 Y 21 22 27 23 18.3 16 17 Yb 2.1 2.2 2.8 2.2 0 1.6 1.7 Zn 108 97 111 90 58 73 108 Zr 66 61 85 66 43.8 64 61 Nd (TIMS) 0000000 Sm (TIMS) 0000000 147Sm/144Nd 0000000 143Nd/144Nd 0000000 Tdm (Ma) 0000000

254

APPENDIX C

255 Sample 1999021074 1999021358 1999021379 1999021384 2000030301 2000030302 2000030303 2000030304 Northing 6356976 6357898 6321196 6382598 6414245 6414245 6414245 6414245 Easting 369334 378559 420336 388021 361592 361592 361592 361592 Zone 19 19 19 19 19 19 19 19 Laboratory Corem Corem Corem Corem Geolab Geolab Geolab Geolab SiO2 36.3 31 31.9 26.7 43.1 45.4 44.9 24.1 TiO2 3.34 1.47 2.89 1.78 2.13 2.14 2.06 3.16 Al2O3 3.98 8.76 6.12 4.01 13.8 14 12.4 4.5 Fe2O3 15.2 9.92 16.7 13.9 13.8 13.6 12.7 14.7 MnO 0.21 0.31 0.28 0.27 0.23 0.2 0.27 0.26 MgO 23.8 5.04 13.6 12.8 3.62 3.56 8.73 11.2 CaO 7.18 14.2 11.7 14.7 7.39 5.71 9.45 17.4 Na2O 1.06 0.19 0.42 1.96 2.08 4 2.39 1.82 K2O 1.06 7.48 2.51 1.06 6.83 4.87 1.42 2.55 P2O5 0.43 0.16 0.55 0.43 0.73 0.74 0.4 0.57 LOI 6.63 20.8 12 21.6 4.58 3.9 4.94 18.7 Cr2O3 0.22 0.02 0.07 0.08 0.01 0.01 0.06 0.05 Ctot 2.19 20.86 8.73 20.64 3.45 2.66 3.3 18.41

Ba 370 830 990 740 6896.78 6220.58 517.26 1679.59 Ce 105.4 508.3 181.6 195.7 472.41 446.06 77.9 380.08 Co 110 21 73 79 23 20 49 56 Cs 1.4 0.1 2.1 0.5 2.37 2.05 1.09 2.26 Cr 1500 110 460 560 90 77 430 340 Dy 4.96 29.98 6.5 7.55 13.35 12.58 3.81 8.38 Er 1.74 17.66 2.37 3.87 5.57 5.79 1.65 2.8 Eu 3.17 12.33 3.9 3.98 7.59 7.52 2.12 6.52 Ga 12.2 13.4 14.3 10.7 31 27 19 12 Gd 7.88 33.37 9.98 9.85 20.48 20.18 5.56 16.45 Hf 7.6 11.6 6 3.6 19.3 19.1 4.23 3.32 Ho00002.16 2.2 0.66 1.28 La 45.3 274 94.3 97.8 232.75 230.25 32.77 186.16 Lu 0.18 2.65 0.22 0.43 0.596 0.598 0.188 0.211 Mo10.11.40.80000 Nb 58.9 902.4 125.3 89 248.35 248.73 66.33 172.44 Nd 56.3 223.2 77.6 87.7 187.34 196.1 42.3 164.59 Ni 1032.6 41.1 230.7 417.3 100 100 100 100 Pr 14.11 63.87 21.8 23.99 51.63 51.89 10.3 44.75 Pt 45 133 224 44 251.27 181.77 61.08 108.47 Sc000012112215 Sm 10.18 35.91 13.35 13.38 28.42 29.18 7.3 24.86 Sr 490 556 607 1000 1400 1400 670 1200 Ta 3.3 27.4 7.2 4.1 12.74 12.52 5.52 9.41 Tb 1.07 5.37 1.34 1.37 2.45 2.46 0.74 1.85 Th 4 98.5 13.9 16 20.13 18.75 1.54 27.56 Tl0.201.20.20000 Tm 0.24 2.98 0.31 0.61 0.72 0.71 0.21 0.31 U 0.9 3.9 2.5 1.2 4.33 3.71 2.01 3.24 V2401852812070000 W 1.1 23.3 2.4 15.5 0000 Y 20.7 175.3 26 42 59.5 60.24 16.92 30.29 Yb 1.25 17.28 1.74 3.14 4.2 4.18 1.26 1.53 Zn2811365540000 Zr 269.4 839.1 234.7 203.2 1046.1 1029.43 169.41 148.62 Nd (TIMS) 00000041.7 0 Sm (TIMS) 0000007.35 0 147Sm/144Nd 0000000.1065 0 143Nd/144Nd 0000000.511575 0 Tdm (Ma) 0000002.23 0

256 Sample 2000030305 2000030306 2000030312 2000030313 2000030314 2000030315 2000030316 2000030318 Northing 6414245 6414245 6391241 6388649 6399023 6365047 6365047 6365047 Easting 361592 361592 360627 367517 384832 392395 392395 392395 Zone 19 19 19 19 19 19 19 19 Laboratory Geolab Geolab Geolab Geolab Geolab Geolab Geolab Geolab SiO2 32.1 24.2 27 26.1 26 40.9 43.4 18.7 TiO2 4.11 3.13 2.42 4.68 1.66 2.68 1.17 3.48 Al2O3 9.11 4.18 3.24 4.04 3.92 2.42 13.8 2.83 Fe2O3 11.2 14.8 12.4 16.2 13.4 6.57 11.4 11.2 MnO 0.2 0.32 0.25 0.35 0.23 0.22 0.11 0.23 MgO 6.06 10.3 14.7 14.9 14.3 6.74 5.15 9.84 CaO 10.9 18.4 12.4 13.5 11.7 16 6.93 20.8 Na2O 5.45 1.74 2.99 0.72 3.05 0.1 0.24 0.1 K2O 0.12 2.33 1.3 2.2 1.03 0.58 3.69 0.66 P2O5 0.2 0.84 0.73 0.34 0.03 1.13 0.3 0.64 LOI 20.3 18.4 21.8 15.8 23.6 22.4 14.6 30.4 Cr2O3 0.03 0.05 0.1 0.17 0.12 0.03 0.02 0.04 Ctot 21.16 18.85 20.68 14.34 12.25 22.66 11.7 31.53

Ba 39.48 1487.31 501.6 976.67 343.07 93.27 942.57 1428.37 Ce 70.02 309.36 222.15 451.61 190.18 184.28 62.43 215.33 Co 40 61 72 71 68 19 37 45 Cs 0.02 1.21 0.06 1.36 0.4 0.11 0.42 0.31 Cr 230 370 690 1200 760 220 120 310 Dy 6.48 10.3 11.83 10.57 3.96 7.18 3.67 6.12 Er 3.67 4.81 6.7 4.16 1.68 2.85 2.04 1.98 Eu 1.84 5.72 4.74 10.43 2.58 5.87 1.61 5.04 Ga 22 12 9 13 10 4 18 12 Gd 5.44 15.06 12.43 26.45 6.53 12.36 5.14 11.52 Hf 9.88 5.44 5.48 8.13 4.22 7.84 2.31 8.48 Ho 1.3 1.85 2.34 1.66 0.67 1.16 0.73 0.94 La 29.39 161.49 100.96 193.63 106.28 96.06 28.32 106.11 Lu 0.423 0.369 0.677 0.386 0.156 0.251 0.265 0.136 Mo 00000000 Nb 211.83 181.48 94.81 140.2 113.08 144.62 7.12 160.41 Nd 35.69 132.4 109.47 239.82 71.31 87.34 32.39 100.94 Ni 100 100 420 280 260 100 100 240 Pr 9 35.77 27.81 59.13 20.25 21.88 7.87 26.05 Pt 2.37 98.19 33.32 114.83 57.83 12.18 110.97 21.51 Sc 17 23 18 0 20 15 21 15 Sm 6.4 20.88 17.89 41.39 9.9 15.05 6.4 16.64 Sr 621 1300 1100 711 1000 748 107 888 Ta 5.38 8.41 5.14 8 4.39 6.6 0.33 9.36 Tb 0.92 1.95 1.93 2.58 0.8 1.47 0.7 1.35 Th 19.39 24.78 9.82 21.2 12.07 7.05 1.42 10.6 Tl 00000000 Tm 0.51 0.55 0.92 0.55 0.21 0.33 0.28 0.22 U 5.29 2.05 1.1 2.36 0.76 3.04 0.22 1.41 V 00000000 W 00000000 Y 37.92 48.31 67.32 41.58 17.07 33.58 19.89 23.84 Yb 3.11 2.86 5.26 3.12 1.2 1.84 1.85 1.13 Zn 00000000 Zr 499.88 246.79 315.26 306.72 219.75 337.93 76.46 381.72 Nd (TIMS) 0 132.92 000000 Sm (TIMS) 0 21.27 000000 147Sm/144Nd 0 0.0967 000000 143Nd/144Nd 0 0.511511 000000 Tdm (Ma) 0 2.13 000000

257 Sample 2000030319 2000030320 2000030321 2000030323 2000030324 2000030326 2000030327 2000030328 Northing 6358957 6358428 6358428 6356954 6356954 6361154 6410890 6410890 Easting 401606 378158 378158 368710 368710 356887 371654 371654 Zone 19 19 19 19 19 19 19 19 Laboratory Geolab Geolab Geolab Geolab Geolab Geolab Geolab Geolab SiO2 39.3 17.9 7.56 36.3 40.9 24.6 26.1 25.5 TiO2 2.51 0.01 0.03 3.18 2.13 3.1 1.52 1.2 Al2O3 5.81 0.69 1.59 3.26 13.9 3.54 3.2 2.18 Fe2O3 15.7 11.7 16.2 14.7 12.6 15.2 14.2 13.8 MnO 0.19 0.65 1.78 0.21 0.24 0.33 0.22 0.28 MgO 14 9.7 8.2 23.9 6.16 10.6 15 15.7 CaO 11.6 23.5 24.4 7.87 9.79 22.6 14 14.4 Na2O 1.07 0.1 0.12 0.64 3.14 0.28 2.01 2.09 K2O 3 0.24 1.28 0.87 3.66 0.46 1.29 1.56 P2O5 0.45 0.84 0.01 0.29 1.43 2.67 0.35 0.48 LOI 5.96 33.9 36.6 7.64 5.08 15.2 21.9 22 Cr2O3 0.09 0.01 0.01 0.2 0.01 0.1 0.08 0.1 Ctot 3.52 35.6 39.42 2.94 3.31 13.42 20.86 20.5

Ba 742.54 45.87 183.08 271.11 2453.72 446.45 742.15 405.2 Ce 109.47 80.24 0 81.08 362.55 396.77 180.47 77.23 Co 73 22 25 100 32 65 74 87 Cs 1.72 0.14 0.06 1.62 1.67 0.54 1.46 2.67 Cr 580 98 150 1400 98 670 530 680 Dy 4.21 78.67 34.96 3.82 7.52 14.76 4.61 3.09 Er 1.82 33.63 7.95 1.47 3.18 5.05 1.7 1.56 Eu 2.37 15.26 46.38 2.33 5.63 9.88 3.18 1.22 Ga 14 2 3 10 19 14 9 10 Gd 6.34 65.76 106.65 6.17 13.33 26.83 7.85 3.63 Hf 3.24 4.04 3.18 5.15 6.63 7.44 2.64 1.19 Ho 0.72 13.79 4.09 0.64 1.27 2.3 0.75 0.58 La 60.95 33.27 N.D. 35.37 187.51 172.46 93.91 44.33 Lu 0.16 2.917 0.884 0.136 0.359 0.371 0.144 0.127 Mo 00000000 Nb 73.72 8 141.97 49.37 248.96 136.69 84.84 49.74 Nd 47.14 56 1354.4 43.43 151.9 213.79 74.37 28.62 Ni 410 100 100 1100 100 400 480 600 Pr 12.3 11.61 395.23 10.42 42.21 51.88 20.46 8.1 Pt 182.63 6.53 23.02 38.23 156.96 26.88 63.26 95.7 Sc 21 23 23 24 15 19 17 12 Sm 8.02 26.93 168.19 8.17 20.6 37.91 11.49 4.16 Sr 393 541 1000 418 1400 1000 1100 997 Ta 4.14 0 2.85 2.93 12.64 9.6 4.3 2.12 Tb 0.79 13.39 9.79 0.78 1.56 3.18 0.95 0.54 Th 6.62 88.4 273.9 3.02 8.35 12.7 11.81 7.68 Tl 00000000 Tm 0.22 4.03 1.01 0.17 0.4 0.57 0.2 0.2 U 1.41 2.35 10.86 0.63 2.39 2.93 1.8 1.5 V 00000000 W 00000000 Y 18.5 355.07 98.48 15.36 34.43 56.71 18.57 16.28 Yb 1.26 22.19 6.15 1 2.53 2.97 1.15 1.14 Zn 00000000 Zr 130.1 321.64 152.24 216.74 368.95 451.67 137.31 71.59 Nd (TIMS) 46.85 0 1409 44.45 0 0 74.44 0 Sm (TIMS) 8.1 0 167.88 8.37 0 0 11.46 0 147Sm/144Nd 0.1046 0 0.072 0.1139 0 0 0.093 0 143Nd/144Nd 0.511589 0 0.511071 0.511678 0 0 0.511465 0 Tdm (Ma) 2.18 0 2.23 2.24 0 0 2.12 0

258 Sample 2000030329 2000030330 2000030331 2000030332 2000030333 Northing 6410890 6388573 6395060 6395060 6388573 Easting 371654 396331 369128 369128 396331 Zone 19 19 19 19 19 Laboratory Geolab Geolab Geolab Geolab Geolab SiO2 25.4 29.7 25 26.1 41.5 TiO2 1.41 3.01 3.1 3.32 3.3 Al2O3 3.2 5.86 5.83 3.03 11.6 Fe2O3 13.5 14.2 7.33 16.1 11 MnO 0.27 0.24 0.36 0.27 0.19 MgO 13.6 13.6 9.6 14.3 9.43 CaO 15.6 12.2 18.1 13.3 9.64 Na2O 1.11 0.39 0.1 2.08 0.88 K2O 1.4 3.43 1.81 1.59 5.38 P2O5 0.34 0.72 0.56 1.24 1.06 LOI 22.3 16 27.8 16.8 4.38 Cr2O3 0.07 0.07 0.1 0.1 0.05 Ctot 21.96 27.46 16.32 1.97 15.07

Ba 1900.45 124.14 563.7 3550.03 1444.15 Ce 156.54 153.6 168.6 243.87 174.88 Co 79 72 38 80 34 Cs 0.98 0.66 1.22 1.54 2.12 Cr 540 540 700 720 430 Dy 4.49 4.79 9.57 5.61 5.72 Er 1.83 1.91 4.24 2.21 2.1 Eu 2.69 2.83 4.9 4.42 3.54 Ga 10 12 15 14 18 Gd 7.36 7.56 13.65 10.48 9.37 Hf 6.26 5.63 6.44 15.37 5.4 Ho 0.74 0.83 1.7 0.89 0.9 La 86.47 79.68 78.04 115.44 88.37 Lu 0.157 0.203 0.282 0.242 0.196 Mo 00000 Nb 128.3 154.21 103.21 298.48 120.51 Nd 62.78 62.49 89.12 114.13 75.42 Ni 430 360 170 460 160 Pr 17.3 17.69 21.69 30.35 20.42 Pt 58.82 90.35 83.7 163.53 177.27 Sc 19 27 27 20 23 Sm 10.17 10.13 17.42 16.85 12.71 Sr 1100 1100 702 1300 1400 Ta 3.6 6.79 5.63 17.23 5.82 Tb 0.91 0.94 1.77 1.15 1.2 Th 8.23 11.77 10.1 6.01 10.38 Tl 00000 Tm 0.22 0.23 0.49 0.28 0.25 U 1.67 1.82 2.27 1.14 1.94 V 00000 W 00000 Y 19.46 20.27 44.43 24.66 22.09 Yb 1.28 1.44 2.44 1.71 1.4 Zn 00000 Zr 212.88 227.82 323.08 608.48 215.16 Nd (TIMS) 0 67.19 0 118.16 0 Sm (TIMS) 0 11.05 0 17.29 0 147Sm/144Nd 0 0.0994 0 0.0885 0 143Nd/144Nd 0 0.51158 0 0.511344 0 Tdm (Ma) 0 2.09 0 2.19 0

259