Petrogenesis of Carbonatites in the Alnö Complex, Central Sweden Sherissa Roopnarain

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Petrogenesis of Carbonatites in the Examensarbete i Hållbar Utveckling 176 Alnö Complex, Central Sweden Master thesis in Sustainable Development

Sherissa Roopnarain

Uppsala University, Department of Earth Sciences Master Thesis E, in Sustainable Development, 30 credits Printed at Department of Earth Sciences, Master’s Thesis Geotryckeriet, Uppsala University, Uppsala, 2014. E, 30 credits Examensarbete i Hållbar Utveckling 176 Master thesis in Sustainable Development

Petrogenesis of Carbonatites in the Alnö Complex, Central Sweden

Sherissa Roopnarain

Supervisor: Valentin R. Troll Evaluator: Abigail Barker Master thesis in

Sustainable Development

Uppsala University

Department of

Earth Sciences

Petrogenesis of Carbonatites in the Alnö Complex, Central Sweden

SHERISSA ROOPNARAIN

Roopnarain, S., 2013: Petrogenesis of Carbonatites in the Alnö Complex, Central Sweden. Master Thesis in Sustainable Development at Uppsala University No. 176, 100 pp., 30 ECTS/ hp.

Abstract:

The Alnö Complex is a Late Precambrian alkaline and carbonatite intrusion (c. 30km2) into Early Proterozoic country rock that extends from the north east, to the north western shoulder of Alnö Island. Carbonatites are rare among volcanic provinces, with Oldoinyo Lengai of northern Tanzania being the only active carbonatite volcano in the world today. The high carbonate mineral volumes and rare earth element (REE) concentrations of carbonatites, in combination with the intrusive-extrusive nature of their suites contribute to the rarity of these rocks. Carbonatites, through their peculiar petrological and geochemical compositions, provide vital insights to the composition and condition of the Earth’s mantle. The genesis of the Alnö carbonatites and their relation to other lithological units at the complex is however, only partially understood. This stems from the epistemological division of carbonatites as having either a ‘magmatic’ or ‘reactive’ origin. This study focuses on sampled carbonatites from the Alnö Complex, employing an oxygen and carbon isotope approach on their native calcite, complemented with petrological and mineralogical methods in order to constrain petrogenesis. As a reference, oxygen and carbon isotope data of calcite from an earlier Alnö investigation as well as from an array of data from comparative alkaline complexes elsewhere are also discussed. The combined data and the derived findings support a scenario that is consistent with the ‘magmatic’ model wherein carbonatites have a primary mantle-derived origin, and prospectively stem from a parent magma akin to that of Oldoinyo Lengai, but have experienced a degree of silicate and sedimentary assimilation. The extraction of the Alnö carbonatites for their rare earth metals is a looming possibility due to the current volatility in the rare earth market. The risks and opportunities involved in this kind of natural resource extraction provide a context wherein sustainable development paradigms can be applied. The capacity of the Alnö environment to withstand the impact of development in the mining sector is discussed through a perspective of establishing a quarry, and quarry-related methods for rare earth extraction.

Keywords: Petrogenesis, Carbonatite, Alnö Complex, Stable Isotope, Rare Earth Element (REE), Kimberlite, Sustainable Development, Resource Mining, Rural Landscape, Natural Heritage.

Sherissa Roopnarain, Department of Earth Sciences, Uppsala University, Villavägen 16, SE-752 36 Uppsala, Sweden.

Petrogenesis of Carbonatites in the Alnö Complex, Central Sweden

SHERISSA ROOPNARAIN

Roopnarain, S., 2013: Petrogenesis of Carbonatites in the Alnö Complex, Central Sweden. Master Thesis in Sustainable Development at Uppsala University, No. 176, 100 pp., 30 ECTS/ hp.

Popular Summary:

In the Gulf of Bothnia, there is an island known as Alnö. The island was formed in a volcanic eruption that occurred almost six hundred million years ago. The release of ash and lava from the eruption has carved an alkaline volcanic landscape, and when the magma solidified, igneous rocks were formed. Such rocks, borne out of complex volcanic processes are typically composed of essential elements and minerals. The Alnö igneous rocks are particularly captivating because they are rich in rare elements and minerals. This study analyses an array of these rocks that are known as carbonatites. Carbonatites are a most unusual breed of igneous rock, as intricate in texture as they are in composition. They are particularly enriched with carbonate minerals, the analysis of which is able to construct deeper insights on their origin, composition, structure and alteration. Such a task is encompassed by the term ‘petrogenesis’. Constraining petrogenesis involves deciphering between a ‘magmatic’ (i.e. of the mantle) or ‘reactive’ (i.e. non-mantle) origin. The carbonate mineral, calcite is encoded with signals (isotopes) that are able to indicate magmatic or reactive sources and influences. Hence, oxygen and carbon isotopes from calcite are analysed along with the textural and mineralogical properties of the carbonatite specimens. A distinction between the two types of origin remains controversial for carbonatites, derived in part from the overlap of mantle and reactive signals that sometimes occurs, and that invariably represents the lithological connection between carbonatites and other alkaline rocks that are accumulated in a particular site (e.g. the Alnö Complex). Comparative analysis, with earlier investigations on Alnö alkaline rocks as well as carbonatites from international alkaline volcanic provinces, similar to Alnö, buffers the retrieved data from elusive petrogenetic distinctions, and hence forms an integral part of the study. The research findings support a scenario that is consistent with a ‘magmatic’ model wherein carbonatites have a mantle-derived origin, and prospectively stem from a magma similar to that of Oldoinyo Lengai in Tanzania, which is currently the only known active carbonatite volcano in the world. The findings discuss that the Alnö carbonatite-forming magma had likely incorporated silicates as well as sedimentary material and gas on its journey through the mantle and even up to the point of intrusion at the crust. The extraction of the Alnö carbonatites for their rare earth metals is a looming possibility due to the current volatility in the rare earth market. The risks and opportunities involved in this kind of natural resource extraction provide a context wherein sustainable development paradigms can be applied. The capacity of the Alnö environment to withstand the impact of development in the mining sector is discussed through a perspective of establishing a quarry, and quarry-related methods for rare earth extraction.

Keywords: Petrogenesis, Carbonatite, Alnö Complex, Stable Isotope, Rare Earth Element (REE), Kimberlite, Sustainable Development, Resource Mining, Rural Landscape, Natural Heritage. Sherissa Roopnarain, Department of Earth Sciences, Uppsala University, Villavägen 16, SE-752 36 Uppsala, Sweden.

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‘Earth, water, air and fire. The question of whether they are endowed with an intellect, enabling them to comprehend, cannot be solved without deep research. Each of the four occupies a certain position of its own, assigned to it by nature. They are forced to move and to change their respective positions, so that fire and air are driven into the water, and again these three elements enter the depths of the earth. The elements will come together, to react upon each other and combine. When they return to their respective places, parts of the earth will sail together with the water. And parts will sail with the air, and with the fire. For the elements have the property of navigating back to their origin in a straight line, but they have no properties which would cause them to remain where they are, or to move otherwise than in a straight line. These rectilinear motions of the four elements, on their return voyage, are of two kinds: either centrifugal — the motion of the air and the fire, or centripetal — the motion of the earth and the water. And when the elements have reached their origins, they remain at rest.’

Moshe ben Maimon (1135-1204)

Table of Contents

1. Introduction ...... 1

1.1 Research Objectives ...... 3

2. Geological Background ...... 4

2.1 Alnö Island Volcanism ...... 4

2.2 The Age of the Complex ...... 5

2.3 The Carbonatite and Alkaline Intrusions of the Alnö Complex ...... 5

2.4 Complex Carbonatites — In Review of Literature on the Alnö Complex ...... 8

2.4.1 Composition ...... 8

2.4.2 Origin ...... 10

2.4.3 Research Hypothesis ...... 11

3. Archival Sampling and Observations ...... 13

3.1 The Archives ...... 13

3.2 Sample Size and Texture ...... 13

4. Analytical Methods ...... 19

4.1 Mineralogy and Textures with Optical Light Microscopy ...... 19

4.2 Electron Microprobe Analyser for Major Elements and Textures (FE-EMPA) ...... 19

4.3 Stable Isotopes, Mass Spectrometry and the Carbonate Line...... 20

4.3.1 Sample Preparation and Mineral Separation ...... 20

4.3.2 Oxygen and Carbon Isotopes ...... 22

4.4 Research Limitations ...... 22

5. Stable Isotope Systematics: A Petrogenetic Code ...... 23

6. Results ...... 24

6.1 Thin Section Petrography: Colour, Mineralogy and Occurrence of Calcite ...... 24

6.2 Electron Microprobe Analysis (FE-EMPA) ...... 28

6.3 Stable Isotope Results ...... 40

7. Discussion ...... 43

7.1 Petrogenesis of Carbonatites in the Alnö Complex ...... 43

7.1.1 The Petrographic Approach ...... 43

7.1.2 The Mineral Composition Approach ...... 44

7.1.3 The Migmatite Country Rock ...... 45

7.1.4 Unravelling Petrogenesis: The Stable Isotope Approach ...... 45

7.1.5 Resolving the Finer Details ...... 49

7.1.6 Alnö Relative to Other Carbonatite Complexes ...... 53

7.1.7 Conclusions ...... 55

7.2 Sustainable Development and the Alnö Complex ...... 56

7.2.1 Nature Reserves, Alnö Island and a Developmental Philosophy...... 56

7.2.2 Natural Resources of the Alnö Complex: The Petrogenetic Connection...... 58

7.2.3 The Rare Earth Market ...... 60

7.2.4 Sustain the Risk, to Develop the Opportunity ...... 63

7.2.5 Conclusion ...... 68

8. Summary and Conclusions ...... 69

9. Acknowledgements ...... 70

10. Bibliography ...... 72

11. Appendix ...... 85

11.1 Appendix A ...... 86

11.2 Appendix B ...... 87

1. Introduction

An igneous ‘complex’ is geological nomenclature for a collection of igneous rocks that intruded the Earth’s crust and are genetically related to a common geological event. The component rocks that make up an ‘igneous centre’ are therefore extrusively or intrusively created. A rock within a complex has its own traits which give rise to a distinctive character; however, it is also connected to the surrounding rocks within the complex. In the field, these connections are visible through observations on a rock’s colour, shape, size and texture. Later on, with observations in the laboratory, their compositional characteristics, over time, provide detailed insights into these genetic interconnections. These shared lithological relations are pivotal in the understanding of the origin, as well as the evolution of an igneous complex, which is part of the aim of the current dissertation.

The Alnö Complex, (~ 62º 24’19.59”N; 17º 27’40.71”E) is a Late Precambrian igneous intrusion on the east coast of central Sweden. The exposure of the complex extends within and along the northeastern part of Alnö Island, and into the Gulf of Bothnia (Figure 1.1), near the coastal town of Sundsvall (Figure 1.2). The heart of the island was formed in a large volcanic event that occurred approximately six hundred million years ago (von Eckermann, 1948). The release of ash and lava from the eruptions has produced a complex network of conduits, feeders and fissures that were subsequently carved into an alkaline magmatic landscape by erosion and glacial activity. These rocks, which are originally borne out of intricate magmatic processes, are naturally composed of essential earth elements and minerals. The Alnö igneous rocks are particularly captivating because of their high rare earth element (REE) concentrations and carbonatitic mineral compositions. Pyroxenites, ijolites, fenites, carbonatites, nepheline-syenites and urtites characterise the major breed of rocks originating within the complex, which are very rare in global occurrence (Kresten, 1990). Alongside these rocks, on its north-western shoulder, the complex is seen to intrude Early Proterozoic to Early Cambrian host rocks of gneiss and migmatite (Haslinger et al., 2007). Lamprophyres also characterise the complex and their discovery ignited a universal descriptive classification of their type being referred to as ‘alnöites’. Lamprophyres could be considered as a rebellious cluster of rock, for they exhibit geochemical, mineralogical and petrological1 properties that are in stark contrast to the more traditional igneous rock types. The alnöites of the complex are particularly rich in the carbonate and melilite mineral clusters, and could potentially be diamond-bearing (Woodard, 2010). A rock which is also abundantly rich in the carbonate minerals is the aforementioned carbonatite. Carbonatites are often placed alongside or underneath lamprophyritic classifications, and the Alnö Complex, in essence, is therefore considered to be an ‘alkaline’ or ‘carbonatite intrusion’ (Hode Vuorinen, 2005). Carbonatites, through their peculiar petrological and geochemical compositions, are an insight into the

1 Greek etymology derived from the word ‘petrology’ with petra being ‘rock’ and logos being ‘study’.

Figure 1.1: Physical map of Sweden. The place-mark on the map indicates the location of Alnö Island, in central Sweden. Google Earth (2013).

Figure 1.2: Geographical map of Alnö Island. The place-marks on the map indicate the location of Alnö Island in proximity to Sundsvall, in central Sweden. Google Earth (2013).

2 deep inner-workings of the Earth’s mantle – its condition over time in relation to the upsurges of magma on its journey from the mantle all the way up through the Earth’s crust (Andersen, 1988). A handful of these carbonatite rocks from Alnö, in both their structure and composition, will be analysed throughout this dissertation. A multi-disciplinary methodology, that spans petrological, mineralogical and geochemical approaches, will harness the research findings of the analysis. Geologically, the knowledge framework of ‘petrogenesis’ is rooted in uncovering the origin of a rock and such insights are a fundamental part of the considerations herein. Carbonatite petrogenesis is echoed by investigating the structure, composition and alteration of the carbonatite, therefore, these three tenets form the cornerstones of the research. There is a unique methodology that is required to shift from observing carbonatite petrography to ultimately understanding carbonatite petrogenesis and the writing of this dissertation aims to follow from one to the other, grounded by an analytic methodology chapter. The key carbonate mineral (calcite) is analysed through a stable isotope approach in order to construct deeper insights onto the origin, structure, composition and alteration of the Alnö carbonatites. Interwoven with these petrological and mineralogical methods is a discussion chapter which allows the ties between the research findings and epistemic indicators from sustainable development theory, to surface. The considerations within it embrace a sustainable approach to the Alnö Complex and its reserve of rare earth elements hosted by the carbonatites. Specifically, these are the tensions between preserving or utilising the carbonatites (and the complex); alongside what their inherent worth is considered to be at present, and what it could be in years to come.

1.1 Research Objectives

The objectives of this research are to:

(1) Microscopically analyse the petrographical and mineralogical characteristics of the Alnö Complex carbonatite rock suite.

(2) Compositionally probe the structural characteristics of the Alnö Complex carbonatites.

(3) Investigate single-crystal and stable isotope geochemical data through carbonatite sampling, mineral preparation and analytical geochemistry.

(4) Integrate the petrological, mineralogical and geochemical data and translate the findings into a petrogenetic assertion regarding the Alnö carbonatites.

(5) Apply the findings to a rudimentary philosophy on sustainable development in relation to essential rare earth elements.

(6) Connect the narrative on sustainable development to a renewed discussion on the significance of considering carbonatite origins, within the context of interactions between Earth’s mantle and Earth’s crust. Developmental conditions pertaining to resource extraction, versus resource preservation will also be explored.

2. Geological Background

2.1 Alnö Island Volcanism

Magma from within the Earth’s mantle is usually generated when the composite interplay between temperature, pressure and geothermal gradients permit mantle melting, during either the subduction or divergence of lithospheric plates or through isolated plumes (Lutgens et al., 2011). Around six hundred million years ago, volcanic magma surged upwards underneath what is now the Gulf of Bothnia, rupturing through the Earth’s surface (von Eckermann, 1948). The magma probably rose from a plume within Earth’s asthenosphere, creating an isolated magmatic centre (Figure 2.1). The swirls of this molten rock, in combination with steam and volcanic vapours, created the Alnö volcano when parts of the rising magma crystallised in the crust before reaching the surface (Schmincke, 2004). The phenomenon of magma crystallisation beneath the crust is known as an ‘igneous intrusion’ or ‘pluton’. Over time, magma and vapour ruptured through fissure vents and into the pluton’s roof to create the ring-type rock arrangement which is visible on the surface, to this day (Kresten, 1979; Andersson et al., 2013). The Sälskär vent, which is to the north of the island, is a site where the ancient volcanic release is documented. This way in which the magma formed has shaped the terrain of the Alnö complex as well as the unusual composition of the carbonatite rocks found within it.

Figure 2.1: Types of terrestrial volcanism. Alnö likely formed from a ‘hot spot’ or ‘plume’. Illustration from Lutgens et al. (2011).

2.2 The Age of the Complex

The Alnö Complex was emplaced during the Late Precambrian era (Kresten, 1979). The complex is embedded in a bedrock of gneiss and migmatite, which is of the Svecofennian (ca. 1.8-1.9 Ga2) orogeny (Kresten, 1990; Nironen, 1997). The age of the complex was estimated to be 562 Ma3 by von Eckermann and Wickman (1956), through their observations of the uranium and lead (U-Pb) concentrations on alkaline rocks. Twenty years later, investigation of the potassium and argon (K-Ar) age of carbonatites and ultramafic4 alnöites revealed an emplacement of 537 ± 16 Ma (Kresten et al., 1977). When observed through the rubidium and strontium (Rb-Sr) method, carbonatite and alkaline- silicate rocks yield an age of emplacement of 553 ± 6 Ma (Brueckner & Rex, 1980). The time during which the complex formed was most recently estimated to be 584 ± 13 Ma according to the strontium, neodymium and lead (Sr-Nd-Pb) isotopic method (Andersen, 1996). Radiometric observations thus allow for a window of activity of eighty million years, that is, 610 Ma to 530 Ma (Kresten, 1976; 1990). Palaeomagnetic observations in more recent years estimate that the intrusion solidified at around ± 590 Ma, which is consistent with the age of 584 ± 13 Ma provided by Andersen (1996) and indicates a considerably shorter lifespan for the Alnö volcanic complex (Walderhaug et al., 2003).

2.3 The Carbonatite and Alkaline Intrusions of the Alnö Complex

The Alnö Complex, as a whole, is an igneous intrusion which consists of a suite of separate sub- intrusions. The Smedsgården intrusion is the cardinal intrusion in the complex and it is surrounded by the Båräng, Hörningsholm, Långarsholmen and the Stornäset intrusions (Figures 2.2 and 2.3). The complex comprises the smaller Sälskär, Söråker, Stolpås and Åssjön intrusions. The carbonatite intrusions occur as cone-sheet5 dykes within the complex, whereas the alnöites intrude according to a radial dyke pattern (von Eckermann, 1958; Kresten, 1980). Calcium-carbonatite dykes intrude as the larger and more dominant sheets, compared to the smaller and less abundant magnesium-carbonatite dykes. The cardinal intrusion on the island is divided further according to northern and southern ring dyke formations. The southern ring is dominated by dykes composed of calcium-carbonatite, pyroxenite, nepheline and nepheline syenite. Alongside these are melteigite, ijolite and urtite dykes, which are collectively known as the ijolite-series of the Alnö rocks (Kresten, 1979). Dykes bearing alnöites and phonolites are also prominent in the southern ring (Kresten, 1990). The northern ring, which is characterised by the Hörningsholm and Långarsholmen intrusions, bears all the dykes described in the southern ring. Surrounding the intrusion is an aureole of fenite, which is a silica (Si)

2 Ga (abbreviation): ‘billion years’ 3 Ma (abbreviation): ‘million years’ 4 Ultramafic: Igneous rocks with a high mafic mineral composition. Mafic mineral: A dark mineral usually composed of iron and magnesium (ferromagnesian character). Classic mafic minerals are amphibole, biotite, olivine and pyroxene. 5 Cone-sheet pattern: Tabular segment of the igneous rock intrusion (the ‘sheet’), shaped in the form of a downward-pointing cone. 5

Figure 2.2: Simplified geological map of the Alnö Complex showing representative sheet intrusions. After Meert et al. (2007) and Kresten (1979; 1990).

6 depleted reaction product from interactions between carbon dioxide (CO2) rich fluids and carbonatite liquids with the gneisses of the surrounding country-rock during emplacement and subsequent metasomatic interaction (von Eckermann, 1950a; Morogan & Woolley, 1988). The Båräng intrusion is composed of calcium carbonatite and alkaline dykes respectively (von Eckermann, 1948; Kresten, 1979; 1990). Calcium carbonatite and melilite dykes intrude the Söråker region of the complex. The Söråker intrusion is absent from the detailed geological map in Figure 2.3 because of its limited exposure (Morogan & Lindblom, 1995; Hode Vuorinen, 2005). The northern ring is surrounded by an array of smaller islands (Figure 2.3), which feature carbonatitic breccia vents in the bay that surrounds Alnö Island (Kresten, 1979). At Alnö, rocks have evolved in a chronological sequence where the earliest intrusions in the complex are pyroxenite and ijolite-series rocks, followed by nepheline syenites and eventually abundant carbonatites (Kresten, 1979; 1980; 1990). Throughout the complex, the carbonatites bear the youngest intrusive age except within the cardinal intrusion, where alnöite intrusions have been found to postdate the carbonatite ones (Kresten, 1990).

Figure 2.3: Geological sketch map of the Alnö Complex. After Morogan & Lindblom (1995).

2.4 Complex Carbonatites — In Review of Literature on the Alnö Complex

2.4.1 Composition

Alkaline rocks with a dominant carbonate composition were initially discovered in the Lower Narmada Valley of Western India between the villages of Nimáwar and Káwant (Bose, 1884). In 1895, rocks of this nature were unearthed at the Alnö and the Fen Complex, in Sweden and present day Norway. The idea of ‘carbonatite’ magma was largely derived from these two Scandinavian complexes, where carbonate rocks occur as a breed of igneous rock that is characteristically rich in carbonate and silicate minerals (Högbohm, 1895; Holmquist, 1896; Brøgger, 1921).

The carbonate minerals abundant in carbonatites are calcite and dolomite, whereas manganese-, iron- and potassium-bearing carbonate minerals have been observed in small quantities. A number of these carbonate minerals comprise high rare earth element (REE) concentrations, including strontianite, calkinsite, synchisite, ancylite, lanthanite, bastnaesite, sahamalite and burbankite (Pecora, 1956; von Eckermann, 1974). Associated silicate minerals are aegirine, augite, nepheline, wollastonite, orthoclase, plagioclase, albite, sphene, aegirite, vermiculite, diopside, chondrodite, forsterite, biotite, phlogopite, melanite, cerite, clinopyroxene, titanite, quartz, olivine and melilite (Pecora, 1956; von Eckermann, 1974). Phosphate minerals such as monazite, isokite and fluorapatite, along with oxides such as pyrochlore, baddeleyite, anatase, magnetite, rutile, hematite, and ilmenite also characterise the mineral composition of carbonatite rocks at Alnö (Pecora, 1956). Barite is the dominant sulphate mineral in the Alnö alkaline rocks, however, sulphide minerals such as galena, bornite, pyrite, chalcocite, chalcopyrite, tetrahedrite, pyrrhotite, molybdenite and valleriite have also been observed (von Eckermann, 1952; 1974). Occurrences of fluorite, sellaite, zircon and perovskite have also been reported (Pecora, 1956).

Following the Indian and Scandinavian carbonatite discoveries in the late nineteenth century, there has been a gradual divide in literature regarding the geochemical definition of a carbonatite. Traditionally, carbonate mineral volumes in surplus of 50% are required in order to define a carbonatite. If the carbonate percentage is between 50% and 70%, then it is referred to as a silico-carbonatite; whereas if the carbonate volume exceeds 70%, then it is referred to as ‘carbonatite proper’ (Le Maitre, 2002). However, it was later argued that a rock with a 30% carbonate and 70% silicate volume is as much of a carbonatite as one with  50% carbonate present, as the mere existence of carbonate minerals in igneous rocks is the fundamental issue (Mitchell, 2005). Today, a ‘carbonatite’ rock (sensu lato) should indicate a magmatic carbonate volume of  30% (Mitchell, 1979; 1986). This latter compositional definition is acknowledged, as it encapsulates the disparities associated with defining carbonatites according to their constituent minerals and recognises the fact that a carbonatite-forming magma could, through differentiation of character and composition, create an array of rocks that are genetically related to each other (Mitchell, 2005). There has also been considerable emphasis placed

8 on the importance of classifying carbonatites according to their specific dominating minerals, especially if these are silicate minerals. The name of the carbonatite, according to such a classification, should bear the minerals in ascending order of their abundance in the rock, for example, ‘perovskite- calcite-carbonatite’, ‘magnetite-calcite-carbonatite’,‘calcite-pyroxenite-carbonatite’, and so on (Gittins et al., 2005). Where iron is chemically prevalent in the carbonate and silicate volumes, ‘ferrocarbonatite’ or ‘siderite-carbonatite’ should be used (Gittins & Harmer, 1997). However, these methods of classification are difficult to uphold and a more comprehensive method of distinction, that aims to capture the composition and texture of the rock specimens, is necessary. Exploration on the Alnö alkaline intrusions, have been pioneered in the twentieth century by von Eckermann (1948) who used the localities in and around Alnö in order to distinguish the rocks, and suggested the following compositional nomenclature for carbonatites native to Alnö:

(a) ‘Calciocarbonatite’ is used for a rock where the dominant mineral is calcite (≥ 70%). A coarse- grained calciocarbonatite is a sövite and a fine-grained one, an alvikite (Figure 2.2; von Eckermann, 1948).

(b) ‘Magnesiocarbonatite’ or ‘dolomite-carbonatite’ is used for a rock where the dominant mineral is dolomite (≥ 70%). This kind of carbonatite has historically been known as beforsite (Figure 2.2; von Eckermann, 1948).

Therefore, the compositional definitions of von Eckermann have been applied to the carbonatite descriptions throughout this study. In recent times, the Alnö carbonatites have been associated with carbonatites from the Fen Complex (Norway), Shombole (Kenya), Spitzkop Complex (South Africa), Tamazert Eocene Alkaline Complex (Morocco), Khibina Alkaline Complexes of the Kola- Kandalaksha Peninsula (Russia), Tororo and Napak Ring Complexes (Uganda) as well as at Loolmurwak, which is a hypabyssal6carbonatite intrusion situated in a valley east of the Tanzanian volcano, Oldoinyo Lengai. Calciocarbonatites, magnesiocarbonatites, siderite-carbonatites and ankerite-carbonatites have been observed in these sites, and akin to the Alnö carbonatites, they have all characteristically intruded alongside nepheline-syenite, ijolite, melteigite and urtite. The findings from these complexes have hypothesised a connection between carbonatites and other alkaline-silicate rocks originating from the same complex. The connection is attributed to the relative position of the rocks to each other, their chronological development as well as the geochemical concentration of elements present within the carbonatite (Strauss & Truter, 1950; Rankin, 1977; Kjarsgaard & Peterson, 1991; Kjarsgaard et al., 1995; Zaitsev & Bell, 1995; Zaitsev et al., 1998; Harmer, 1999; Hode Vuorinen & Skelton, 2004).

6 A magmatic intrusion with a shallow depth within the Earth’s crust. Characterised by dykes and sills, the Loolmurwak intrusion is connected to natrocarbonatite lava from the Oldoinyo Lengai volcano. 9

2.4.2 Origin

The origin of carbonatite magmas has been a matter of debate for many decades. The unusual characteristics of carbonatites allude to the complexities surrounding their origin. Two major hypotheses are available to help interpret the way in which a carbonatite is formed. The first is from the ‘magmatic’ school of thought that advocates either a direct origin from mantle melting of likely modified mantle peridotite (Strauss & Truter, 1950; Wyllie & Watkinson, 1970; Wyllie, 1974; Rankin, 1977; Nelson et al., 1988; Gittins, 1989; Bailey, 1993; Harmer & Gittins, 1997; Wyllie & Lee, 1998; Harmer, 1999; Mitchell, 2005; Dasgupta & Walker, 2008; Martin et al., 2012; Russell et al., 2012; Dasgupta et al., 2013) or due to magmatic differentiation processes in the volcano-plumbing system, such as liquid immiscibility and fractional crystallisation (Kresten & Morogan 1986; Andersen, 1987; Wyllie, 1987; 1988; Kjarsgaard & Hamilton, 1989; Le Bas, 1989; Kjarsgaard & Peterson, 1991; MacDonald et al., 1993; Lee & Wyllie, 1994; Kjarsgaard et al., 1995; Lee et al., 2000; Bühn et al., 2002; Fischer et al., 2009; Cooper et al., 2011). The second hypothesis considers widespread evidence that exists for non-magmatic carbonate components in many volcanic systems (Chadwick et al., 2007; Freda et al., 2008; Iacono-Marziano et al., 2009; Deegan et al., 2010), and hence the notion that carbonatites can also represent recycled basement carbonate or contact-metasomatic reaction products is still very attractive (Daly, 1910; Shand, 1947; Schuiling, 1961; Lentz, 1999; Demény et al., 2008).

Following the initial descriptions by Högbohm (1895) and Holmquist (1896), work on Alnö was pioneered by von Eckermann (1948; 1966) who believed that the alkaline rocks and carbonatites from the Alnö Complex had a metasomatic origin and that magmatic processes had catalysed the fenitisation of migmatite. A similar observation has been made in the Khibina Alkaline Complexes, where rare earth element (REE) bearing carbonatites are thought to have been derived from metasomatic fluid interactions (Zaitsev et al., 1998). von Eckermann (1966) asserts that the cardinal intrusion was created in a series of rapid and explosive episodes, however, tectonic and magnetometric observations have revealed otherwise. At the helm of these alternate observations is Kresten (1976), who believes that the tectonic setting of a carbonatite is vital to the interpretation of its genesis. The tectonic setting of the Alnö Complex, according to Kresten (1976; 1979; 1980), is a relatively ‘quiet’ one, with the cardinal intrusion having occurred gradually over time. The occurrence of migmatite fenitisation is upheld by Kresten (1979; 1980), however, he furthers von Eckermann’s observations by suggesting that the process was directly influenced by the intrusion of the ijolite-series of rocks.

Interpreting the origin of the carbonatites and the way in which they have formed, von Eckermann (1950b) asserted that the “gradual development of dolomitic and calcitic carbonates, as well as that of the alkaline rocks, results from a metasomatic interchange of substances between the wall-rock (country rock) and a highly-tensioned dolomitic, magmatic liquid, rich in fluorine and potash”. Evidently, von Eckermann strays from the idea that carbonatites are purely magmatic in origin, and

10 favours the idea of reactive formation, instead. The Alnö Complex is currently understood as dominantly magmatic in origin, however, the origin of that “carbonate liquid” is still not fully resolved and carbonatite genesis at Alnö remains enigmatic (Kresten, 1979; 1990; Hode Vuorinen & Skelton, 2004; Andersson et al., 2013). The pioneering work of von Eckermann, regarding Alnö is thus pivotal to the research hypothesis, and moreover, we use research samples that originate from fieldwork conducted at the Alnö Complex by H. von Eckermann and B. Collini (Uppsala University) in the late 1940’s.

2.4.3 Research Hypothesis

A distinction between the two types of carbonatite provenance is not always straightforward (Demény et al., 1998; 2008; Viladkar et al., 2005; Bouabdellah et al., 2010; Rosatelli et al., 2010; Cooper et al., 2011; Chazot & Mergoil-Daniel, 2012), and this dissertation aims to elucidate the origin of the carbonatite phase at the Alnö Complex (Figure 2.4).

Carbonatite Genesis

MAGMATIC Origin REACTIVE Origin (Primary) (Secondary) Mantle Melting Crustal Recycling Fractional Crystallisation Metasomatic Interactions Liquid Immiscibility Fenitisation

Figure 2.4: The research hypothesis. Uncovering the origin of an Alnö carbonatite involves considering the combination of its elements and minerals, and distinguishing between primary or secondary phase processes.

In an attempt to broadly constrain magma genesis the data obtained in this research will therefore be interpreted according to either mantle or crustal influences and the interactions which might have taken place between mantle derived components and the local Alnö bedrock (Andersen, 1987; Hode Vuorinen, 2005). The analysis will also consider whether the carbonatite magma has been exposed to varying degrees of hydrothermal7 alteration (Hode Vuorinen, 2005; Skelton et al., 2007). After having addressed the origin of the Alnö geochemical anomaly, it is vital to explore a sustainable perspective on Alnö’s reserve of rare earth elements (REEs). In review of literature on the Alnö Complex, issues such as mineral extraction or preservation are visibly absent from the research narratives. The consideration of Sweden’s REE import-export indices and the country’s role in the global REE market is on the other hand, a very recent development. The constituent findings in this aspect of the thesis are hence dominated by socio-economic models and perspectives, rather than geological ones. A holistic, sustainable perspective on Alnö’s reserve of REEs will be offered.

7 Hydrothermal activity involves hot water, usually between 50C and 400C, although neither end of this range is absolute. Hydrothermal reactions dissolve, alter and deposit minerals (and rocks), and is a vital part of ore formation and geothermal energy.

3. Archival Sampling and Observations

3.1 The Archives

The rock storage room in the basement of the Solid Earth Geology section at Uppsala University (UU) is home to an extensive archival rock collection which dates back to the eighteenth century. In particular, an assortment of more than one hundred and twenty rock specimens from the Alnö Complex is part of the collection. Fourteen rock samples with a carbonate component, which were collected during fieldwork expeditions in the summers of 1945 and 1946, have been selected for the research experiments and interpretations herein. The rocks from the Alnö Complex encompass the personal collections of Prof. B. Collini and Prof. H. von Eckermann, both at Uppsala University at that time. The original archival descriptions for each rock specimen along with a note on the archives and collectors are provided in the Appendix.

3.2 Sample Size and Texture

The samples from the Alnö Complex investigated here are plutonic (i.e. intrusive) rocks, and specimens of between ten to over twenty five centimetres across, were available in the Uppsala University collection. Texture reveals a rock’s crystallisation history and serves to tighten the nomenclature and classification of the broad genetic categories associated with this rock group. The fourteen selected carbonatite samples have a holocrystalline8 texture, but range from a very coarse- grained (>50mm grain size) to coarse-grained (>5mm to <50mm) mineral size with the exception of Sample A14, which has a combination of medium to fine-grained (>0.1mm to <5mm) features. Samples A1 to A13, therefore, have a phanerocrystalline9 granularity and grade into a pegmatitic texture in the coarsest samples. Sample A14 has a microcrystalline texture, where the individual crystals are not clearly visible without a microscope. The majority of the samples have a subhedral10 grain shape and the grain sizes of the crystals are approximately equal to each other. Samples A4, A7, A12 and A13, however, have euhedral11 crystals with a relatively equal grain size. Sample A6 has a traditional porphyritic texture where relatively large crystals are embedded in a finer-grained groundmass. The following tabulated sample list (Table 3.1), includes the principal hand-specimen observations on the selected carbonatite rocks. More detailed mineralogical descriptions of the samples are provided in the thin section petrography of the Results chapter (part 6.1).

8 Holocrystalline: Entirely crystalline, with relative quantities of volcanic glass being absent or substantially lower than the quantities of crystal in the rock. 9 Phanerocrystalline: Crystals of the abundant minerals are, for the most part, distinguished without a microscope and are seen comfortably with the naked eye. 10 Subhedral: Crystals are partly bound by their own faces. 11 Euhedral: Crystals are bound by their own faces. 13

Table 3.1: Archival research samples from the Alnö Complex.

Rock Photograph Observation on the Hand Specimens

Laboratory Sample Number A1 Original Rock Name Pyrochlore-sövite Archival Year in UU Collection 1945

. Coarse-grained intrusive rock . Light-grey rock-mass of calcite, pyrochlore, pyroxene, amphibole and biotite . The translucent and white calcite crystals are finer than the pyrochlore, pyroxene, amphibole and biotite crystals . Pyrochlore occurs as octahedral crystals with a green-gold resinous lustre, and pyroxene occurs as fine, needle-like crystals . Pseudohexagonal crystals of biotite, and dark-grey rectangular bands of muscovite have a metallic lustre . Orange-brown veins around the crystals indicate exposure to mild weathering or the presence of iron

Laboratory Sample Number A2 Original Rock Name Aegirine-sövite Archival Year in UU Collection 1945

. Coarse-grained intrusive rock . Light-grey rock-mass of calcite and aegirine . Calcite crystals occur in clusters and are either translucent, white or silver-grey . Aegirine occurs prominently as green-black, prismatic crystals sprayed throughout the rock-mass, with orange- brown veins and patches around these crystals . Medium to small sized pseudohexagonal crystals of biotite are interspersed with small, rectangular bands of muscovite and light-grey, prismatic crystals of nepheline

Laboratory Sample Number A3 Original Rock Name Nepheline-syenite Archival Year in UU Collection 1945

. Very coarse-grained intrusive rock . Medium-grey rock-mass of nepheline, potassium-feldspar (K-feldspar), calcite and biotite . Large, dark-grey crystals of nepheline and K-feldspar are dominant, the latter visible as orange-brown crystals . The white calcite crystals are dispersed across the rock- mass in thin layers, and only appear as thick clusters when surrounded with nepheline and K-feldspar crystals . Biotite crystals are large and pseudohexagonal, and small, rectangular bands of muscovite and needle-like aegirine crystals are also interspersed throughout the rock-mass

Laboratory Sample Number A4 Original Rock Name Sövite-pegmatite Archival Year in UU Collection 1945

. Very coarse-grained intrusive rock . Combination of a medium-grey and silver-white rock- mass of biotite, amphibole and calcite . Large, pseudohexagonal crystals of biotite bearing a flaked texture are prominent alongside crystal prisms of amphibole and small, rectangular bands of muscovite . Calcite crystals occur in clusters and are either translucent, white or silver-grey . The mafic crystals (biotite and amphibole) have a metallic lustre . Orange-brown veins stain the silver-white parts of the rock-mass locally indicating the exposure to some weathering

Laboratory Sample Number A5 Original Rock Name Ijolite Archival Year in UU Collection 1945

. Very coarse-grained intrusive rock . Dark-grey and orange-brown rock-mass of nepheline, augite, calcite and K-feldspar . Large, dark-grey crystals of nepheline and acicular augite crystals are dominant . Translucent to pure white and light-grey calcite crystals occur as clusters and elongated pods, whereas sparse dispersions of finer calcite crystals are light-pink in colour . Medium sized, orange-brown K-feldspar crystals are intergrown . Small, pseudohexagonal crystals of biotite and crystal prisms of amphibole are sparsely distributed in the rock- mass

Laboratory Sample Number A6 Original Rock Name Biotite-sövite Archival Year in UU Collection 1945

. Coarse-grained intrusive rock . Beige, white and silver-grey rock- mass of calcite, biotite and pyrochlore . Calcite crystals are fine-grained, translucent and silver-grey

. Large to medium sized pseudohexagonal biotite crystals are prominent, with flaked shards of muscovite and thin, rectangular needles of pyroxene interspersed throughout the rock-mass . The octahedral pyrochlore crystals have a resinous lustre . Giant mica is approximately eight centimetres across

Laboratory Sample Number A7 Original Rock Name Nepheline-pegmatite Archival Year in UU Collection 1945

. Very coarse-grained intrusive rock . Light-grey rock-mass of nepheline, calcite and pyroxene . Nepheline occurs as light-grey, prismatic crystals . Calcite crystals occur in clusters and are either translucent, white or silver-grey . Pyroxene crystals occur prominently as grain shards and needles dispersed throughout the rock-mass . Pink-orange K-feldspar crystals occur prominently as intergrown clusters, and deepen in colour towards the edges of the specimen . Small, pseudohexagonal crystals of biotite, muscovite and small, crystal prisms of amphibole are interspersed throughout the rock-mass

Laboratory Sample Number A8 Original Rock Name Nepheline-syenite Archival Year in UU Collection 1945

. Medium coarse-grained intrusive rock . Dark-grey rock-mass of K-feldspar, nepheline, pyroxene and calcite . Euhedral K-feldspar crystals are large and range from pink-orange to orange-brown in colour . Nepheline occurs as grey prismatic crystals . Pseudohexagonal crystals of biotite occurs prominently with muscovite; and small, crystal prisms of amphibole and thin, needle-like pyroxene crystals are interspersed throughout the rock-mass . Pure white to silver-white calcite crystals are encompassed by pyroxene, biotite and amphibole

Laboratory Sample Number A9 Original Rock Name Sövite-pegmatite Archival Year in UU Collection 1945

. Coarse-grained intrusive rock . Purple-brown and light-grey rock-mass of calcite, biotite and pyrochlore . Granular calcite crystals are translucent, light-pink or silver-grey in colour . Medium to large sized, pseudohexagonal biotite crystals have a metallic lustre . K-feldspar crystals are fine-grained, varying in colour intensity of pink-orange whereas the small, octahedral pyrochlore crystals have a green-gold resinous lustre . Needle-like crystals of pyroxene are sparsely distributed . Orange-brown veins around crystals indicate exposure to mild weathering or the presence of iron

Laboratory Sample Number A10 Original Rock Name Pyroxene-nepheline-sövite Archival Year in UU Collection 1945

. Coarse-grained intrusive rock . Dark-grey and light-brown rock-mass of nepheline, K- feldspar, calcite and pyroxene . Nepheline occurs as dark-grey prismatic crystals . K-feldspar crystals are orange-brown, of medium size and are enclosed by the rock-mass . Pure white, light-pink to silver-grey clusters of calcite are fine-grained in some regions and coarser in others . Needle-like crystals of pyroxene and pseudohexagonal biotite crystals are interspersed throughout the rock-mass . Orange-brown and green-brown veins are locally present, particularly around the prismatic amphibole crystals and rectangular shards of muscovite

Laboratory Sample Number A11 Original Rock Name Sövite-pegmatite Archival Year in UU Collection 1945

. Very coarse-grained intrusive rock . Dark-grey rock-mass of biotite, calcite, olivine, pyroxene and amphibole . Calcite occurs as vitreous, granular veins and clusters of pure white to silver-grey crystals that contour the deep grooves of the specimen . Large, pseudohexagonal crystals of biotite, bearing a very coarse, flaked texture and deep, metallic lustre are prominent alongside small, rectangular bands of muscovite and needle-like crystals of pyroxene . Light-grey to grey-pink patches of fine-grained K-feldspar crystals are enclosed in a light-brown rock-mass . Crystal prisms of amphibole and octahedral pyrochlore crystals with a dark, green-gold resinous lustre are sparsely distributed throughout the rock-mass

Laboratory Sample Number A12 Original Rock Name Sövite-pegmatite Archival Year in UU Collection 1945

. Very coarse-grained intrusive rock . Dark-grey rock-mass of pyroxene, calcite and K-feldspar . Abundant needle-like pyroxene crystals are interspersed in the rock-mass alongside small, pseudohexagonal crystals of biotite and crystal prisms of amphibole . Calcite occurs as either granular, pure white to silver-grey clusters or fine-grained elongated pods . K-feldspar is characterised through granular, intergrown pink-orange and red-brown clusters, wherein the crystals are euhedral

Laboratory Sample Number A13 Original Rock Name Titanite-sövite Archival Year in UU Collection 1945

. Coarse-grained intrusive rock . Dark-grey rock-mass of titanite, calcite and pyroxene . Titanite occurs as either dark-grey or red-brown granular crystals, being rectangular in some regions of the specimen, and more prismatic in others . White and light-brown pods, veins and clusters of calcite surround the intersecting titanite and pyroxene crystals, whereas light-grey plagioclase crystals contour the shallow grooves of the specimen . Needle-like pyroxene crystals are interspersed throughout the rock-mass . Pseudohexagonal biotite crystals occur as small sized crystals in the fine-grained rock-mass . Orange-brown patches, particularly around the titanite, pyroxene and biotite crystals indicate mild weathering

Laboratory Sample Number A14 Original Rock Name Migmatite12 (country rock) Archival Year in UU Collection 1946

. Medium to fine-grained metamorphic rock . Dark-grey and grey-brown rock-mass rich in biotite, calcite and amphibole that bears a combination texture between country rock and carbonatite-type rock . Calcite occurs as light-grey, powdery white pods and veins in the dark-grey rock-mass, and as translucent to shiny white and light-pink crystal grain clusters in the grey-brown rock-mass . Pseudohexagonal biotite crystals with a metallic lustre speckle the dark-grey rock-mass . Small, crystal prisms of amphibole, small, needle-like pyroxene crystals and small, light-brown patches of fine- grained K-feldspar crystals are also visible in the rock- mass

12 Migmatite: A hybrid species that is between a metamorphic and igneous rock in the sense that it shows partially melted domains.

4. Analytical Methods

The analytical methods described in this chapter were all conducted in the laboratories of the Centre for Experimental Mineralogy, Petrology and Geochemistry (CEMPEG) at the Department of Earth Sciences (Solid Earth Geology), at Uppsala University. The stable isotope analysis was carried out at the Department of Earth Sciences (Geology), University of Cape Town, South Africa.

4.1 Mineralogy and Textures with Optical Light Microscopy

The archival, whole-rock samples were cut to blocks of four by four centimetres using a diamond- infused circular blade. Weight measurements were recorded and the samples were then sent to Thin Section Preparation Laboratories at the AGH University of Science and Technology in Kraków, Poland. In Poland, these whole-rock wedges were sliced further to a length and corresponding width of two centimetres. This slice of whole-rock was then trimmed and mounted onto a glass microscope- slide with a transparent and ultra-adhesive epoxy resin. The rock-slide was then fixed onto a slide holder after which the sample was ground to a thickness of about thirty microns (30μm) and was finished by a high-quality hand-polish.

The returned thin sections were mounted on a Nikon NIS-Elements F2.20 Optical Microscope which reveals the internal microstructure and mineral association within the sample suite. In particular, structural patterns of calcite are observed and set in context to other minerals within the sample. The patterns are captured with an internal micro-photographic lens. The beam conditions of reflection from the light within the microscope were set to cross-polarisation (CPL) as well as plane-polarisation (PPL) alternatively, with a scale ranging from one thousand microns (1000μm) to five hundred microns (500μm). The micro-photographs were captured with pixel resolutions of between 1280 x 960 and 2560 x 1920. A 1000μm micro-photograph had an exposure value (EV) of 1.3, whereas a 500μm micro-photograph had an EV of 1.6.

4.2 Electron Microprobe Analyser for Major Elements and Textures (FE-EMPA)

Following microscopic analysis, the carbonatite thin sections were scanned in order to differentiate distinct parts of calcite from other minerals within the sample, prior to extensive microprobe analysis. Thereafter, three thin sections at a time were carbon coated in a four hour process that provided a protective layer for the thin sections against the microprobe’s powerful back-scatter electron beam. In addition, the carbon coating reduces the fluctuation of charged particles throughout the experiment. The microprobe instrument is a JEOL JXA-8530F Hyper-Probe which inspects the chemical

19 composition and mineral chemistry of the carbonatites. An electron beam penetrates a point on the surface of the mounted thin section, which produces characteristic x-rays of the elemental composition of that particular sample point. The x-rays are collected and counted as they are passed under a series of internal detectors. These detectors electronically separate the energy and wavelength patterns within the x-rays whilst calibrating their elemental concentrations. The chemical composition is ultimately determined and visualised on the microprobe’s digital screen as either a composition map, line scan or as a sequence of spectra.

The elemental composition of calcite was initially configured according to an Energy Dispersive Spectrometry (EDS) technique. Thereafter, the precise chemical composition was calibrated for elements within the calcite according to a Wavelength Dispersive Spectrometry (WDS) technique which utilised an elemental set of calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P) for its analysis. These four elements were the major set, while elements such as iron (Fe), manganese (Mn) and aluminium (Al) were the sub-set elements for the analysis. The WDS method is precise and allows for a quantitative determination of the elemental composition of minerals as opposed to the semi-quantitative EDS method. In Microprobe Back Scatter Electron (BSE) imaging of minerals, the lighter a mineral appears, the heavier it actually is in atomic weight. The microprobe tests for the presence of these elements and translates this presence into compositional weight percentages or images. The beam conditions for the EDS and WDS measurements were 15kV13 that accelerated on a 15nA14 current. The WDS measurements, in particular were calibrated according to each element. The analytical error for normalised weight percentages of the major and sub-set elements is estimated to be ± 0.1% (1σ).

4.3 Stable Isotopes, Mass Spectrometry and the Carbonate Line

4.3.1 Sample Preparation and Mineral Separation

The whole-rock samples were each cut to a length of eight centimetres and a corresponding width of five centimetres with a diamond saw. These sample aliquots were crushed in a steel jaw crusher and the yield was then separated into different grain sizes. The jaw crusher was thoroughly cleaned with acetone and an air gun between each sample in order to prevent contamination. The size populations were then individually sieved, removing their surplus ground mass and impurities. Thereafter, calcite crystals were extracted with hand-held tweezers from the samples using a Nikon SMZ-U Stereo Microscope. Eighty to one hundred milligrams (80mg -100mg) of calcite were extracted from each sample for isotope analysis. The crystals were hand-ground in an agate mortar to a fine powder. The pestle and mortar were thoroughly cleaned with acetone between each sample in order to prevent

13 kV: kilovolt 14 nA: nanoampere 20 contamination. Weight measurements of the powders were recorded and the samples were then sent to the Stable Isotope Laboratory at the Department of Geology, University of Cape Town, South Africa for analysis, in prime collaboration with Prof. C. Harris.

Figure 4.1 Apparatus for the extraction of oxygen and carbon from the samples at the Stable Isotope Laboratory, University of Cape Town, South Africa.

4.3.2 Oxygen and Carbon Isotopes

The oxygen-isotope (δ18O) and carbon-isotope (δ13C) ratios were analysed with a Thermo Delta-XP mass spectrometer. Oxygen and carbon were separated on the carbonate extraction line15, where ten milligrams (10mg) from the separate samples (n=14) reacted with ten millilitres (10ml) of pure phosphoric acid (H3PO4) at 25°C overnight, in order to release the carbon dioxide (CO2). The analyses for the δ18O and δ13C ratios were undertaken on aliquots of the liberated gas samples, which in this case is the CO2. One millilitre (1ml) of the gas was then injected into a capillary gas chromatograph.

The separated CO2 was ultimately transferred by a carrier gas via an open split directly into the ion source of the mass spectrometer. The CO2 extracted was analysed for both oxygen and carbon and the data were corrected with a fractionation factor of 1.01025. The stable isotope ratios are reported in the 18 16 13 12 standard delta (δ) notation where δ = (Rsample/Rstandard – 1) x 1000, and R= O/ O or C/ C while the standard is either SMOW (Standard Mean Ocean Water) or V-PDB (Vienna Pee Dee Belemnite), respectively. The accuracy in determining δ18O ratios was determined by calibration to the NBS-18 standard, whereas the δ13C ratios were calibrated against the NBS-20 standard. The analytical error for δ18O is estimated at ± 0.1‰ (1σ), based on a long-term duplication of the NBS-18. The analytical error for δ13C is estimated at ± 0.05‰ (1σ), based on a long-term duplication of the NBS-20. The extraction and conversion methods for oxygen and carbon, and further details on the carbonate extraction line are provided in Vennemann & Smith (1990), Harris & Erlank (1992), and Fagereng et al. (2008).

4.4 Research Limitations

Analytical uncertainties originate from the methods and processes undertaken in the laboratories. The contamination of samples during crushing and grinding, or the exposure to impurities during gas extraction and conversion which occurs throughout its experimental transfer, are all factors which affect the quality of the data. Although strict measures were adhered to in order to prevent sample contamination, the research herein acknowledges such features as natural limitations.

15 Carbonate extraction line: A 35-part technical process within a Stable Isotope Laboratory which analyses carbonate minerals (such as calcite and dolomite) for stable isotope ratios. Ratios are measured on gas and extracted by the carbonate line. 22

5. Stable Isotope Systematics: A Petrogenetic Code

In the very same way that our genes are encoded with nucleic acids which speak of our origin as well as inherent physical and behavioural traits, so too are igneous rock minerals encoded with isotopes, which bear the traits of their chemical origin. Variations in isotope values therefore indicate genetic traits, particularly the geochemical reservoirs involved in rock formation (e.g. Chacko et al., 1991; Hoefs, 1997; Bindeman, 2008). The δ18O and δ13C values for calcite from the Alnö Complex samples are therefore interpreted in a context of derivation from the Earth’s mantle versus derivation from the Earth’s crust (Taylor & Bucher-Nurminen, 1986; Morogan & Lindblom, 1995).

Stable isotopes are an essential tool in geochemistry, as it considers the way in which isotopic compositions fluctuate according to physicochemical processes and reactions (Hoefs, 2009). The ratio of two isotopes can be used to unravel the origin of a rock or mineral and therefore provides a robust framework within which to interpret the presented data (Hoefs, 1997). The stable isotopes of oxygen and carbon — the systematic pair of the research herein — are defined according to the widely used “δ-notation” (Equations 1 and 2). The relative abundance of the heavier isotope in a sample is then put relative to a known standard and expressed as the δ-value (in parts per mil, ‰). The δ-value for oxygen, with the pair 18O/16O is calculated according to Standard Mean Ocean Water (SMOW) whereas the δ-value for carbon is realised through the 13C/12C pair according to the Vienna Pee Dee Belemnite (V-PDB).

( ) — ( ) 18 Eq. (1) δ O (‰) = [ ] ( )

( ) — ( ) 13 Eq. (2) δ C (‰) = [ ] ( )

When using stable isotope ratios as indicators of mantle processes or crustal assimilation the need arises to define the stable isotopic composition of an ‘uncontaminated’ context (that is, the pure mantle). Although the mantle is not homogenous (e.g. Hofmann, 1997), as it may be contaminated through subduction and an array of internal reactive processes; rocks from the mantle usually bear an δ18O of 5.7 ± 0.3 and a δ13C of -6.5 ± 2.5 (e.g. Hoefs, 1997; Parente et al., 2007). On differentiation of a magma stable isotopes fractionate, contrasting radiogenic isotopes that are not affected by changes in pressure, temperature and pure fractional crystallisation processes (e.g. Wilson, 1989; Hoefs, 2009). At high temperatures this fractionation is relatively small; however, it should follow a Raleigh-type system — meaning that differentiated igneous rocks may reach values of up to 8 or 9‰, which defines igneous rock magmas of between ± 5.5 and 9‰ (e.g. Rollinson, 1993).

6. Results

Geological findings are anchored by the description and interpretation of data. The aim of this chapter is to present the acquired petrological and geochemical data in an objective framework in order to kindle a series of in-depth observations for the discussion in Chapter 7. The chapter is written in three parts, according to the research methodology, wherein the petrographic and geochemical data serve to contextualise the stable isotope data.

6.1 Thin Section Petrography: Colour, Mineralogy and Occurrence of Calcite

Colour, mineralogy and crystal matrices in rocks are deeply connected to each other. The colour of calcite for example, is kaleidoscopic under the polarising microscope, where it has the potential to appear colourless or as translucent white, light-pink, light-blue, light-green, light-brown and even light-grey hexagonal and rhombohedral crystals. Table 6.1 reports the thin section petrography in which colour and mineralogy are described according to the appearance and presence of the calcite mineral within each of the investigated rock specimens. The photomicrographs are all provided with a scale of 1000µm, and are given in cross-polarised light (CPL).

Table 6.1: Thin Section Petrography of Alnö Samples.

Photomicrograph Thin Section Petrography

Sample Number A1 Rock Name Pyrochlore-sövite

The minerals observed are calcite, pyrochlore, pyroxene, amphibole, biotite, muscovite and apatite. Calcite is the dominant mineral and the matrix comprises  70% of the rock-mass. The equigranular texture is observed through the dominant subhedral sequence of calcite crystals (hypidiomorphic), exhibiting a perfect rhombohedral cleavage with high order colours, and thus a high relief that changes with rotation of the thin section. Simple twinning is dominant among the calcite crystals, with lamellar twins visible on some crystal faces. The presence of thin, mafic veins around the calcite indicates weathering and the redistribution of iron.

Sample Number A2 Rock Name Aegirine-sövite

The minerals observed are calcite, aegirine, biotite, muscovite, nepheline, plagioclase and apatite. Calcite is the dominant mineral and the matrix comprises  90% of the rock-mass. The equigranular texture is observed through the occurrence of calcite in a combination of medium sized, euhedral crystals (idiomorphic) and finer, granular crystal layers that are strikingly homogeneous. The rhombohedral calcite crystals have a high birefringence and there is a relatively even occurrence between simple and lamellar twinning. Aegirine, biotite and nepheline occur in foliated layers within the calcite matrix.

Sample Number A3 Rock Name Nepheline-syenite

The minerals observed are nepheline, K-feldspar, calcite, biotite, muscovite, aegirine and apatite. Nepheline and K-feldspar are the dominant minerals and the calcite matrix comprises  15% of the rock-mass. A poikilitic texture is observed through the heterogeneous occurrence of calcite crystals that are either intergrown or embedded in the nepheline, biotite and K-feldspar crystals. The rhombohedral calcite crystals exhibit mostly simple twinning. The high birefringence and relief is distinct and the crystals change colour upon rotation under the polarising microscope.

Sample Number A4 Rock Name Sövite-pegmatite

The minerals observed are biotite, amphibole, calcite, apatite, muscovite and chlorite. There are trace quantities of quartz and opaque crystals dispersed between the dominant chloritised biotite and amphibole crystals. The calcite matrix comprises  25% of the rock-mass. The equigranular texture is observed through the subhedral sequence of medium sized calcite crystals in some layers, and an anhedral sequence in others (allotriomorphic). The layers of calcite are thus heterogeneous, and crystals have high order colours and a high relief that changes with rotation. Simple twinning is dominant among the calcite crystals.

Sample Number A5 Rock Name Ijolite

The minerals observed are nepheline, augite, calcite, K-feldspar, biotite, amphibole and apatite. Nepheline, augite, K-feldspar and biotite are dominant and the calcite matrix comprises  15% of the rock-mass. The equigranular texture is observed through the occurrence of calcite in a combination of small to medium sized, euhedral crystals (idiomorphic) in heterogeneous layers that have inclusions particularly from augite, K-feldspar, biotite and pyroxene. The calcite crystals have a rhombohedral cleavage, although a tabular cleavage is visible amidst some of the mineral layers. The characteristic high birefringence of the calcite crystals, with distinct simple twinning is visible.

Sample Number A6 Rock Name Biotite-sövite

The minerals observed are calcite, biotite, pyrochlore, muscovite, pyroxene, apatite and traces of iron-rich opaque minerals. The rock is dominated by calcite that forms between 50 to 70% of the rock- mass. Overall the rock-mass has a poikilitic texture and displays strong layering. In some parts, there are layers of only calcite and in other parts, heterogeneous layers of muscovite, biotite and pyroxene are seen. Calcite has an equigranular texture in the layers that it dominates, observed through either small or medium sized subhedral crystals (hypidiomorphic) that are brecciated within the heterogeneous mineral layers. Calcite crystals exhibit a high birefringence and simple twinning. Biotite is chloritised and appears to be particularly brittle, compared with calcite, which is more dispersed and wraps around the mineral layers.

Sample Number A7 Rock Name Nepheline-pegmatite

The minerals observed are nepheline, calcite, pyroxene, K-feldspar, biotite, muscovite, amphibole and apatite. Calcite is the dominant mineral and the matrix comprises  50% of the rock-mass. The equigranular texture is observed through the occurrence of calcite in a combination of medium to large sized subhedral crystals (hypidiomorphic) that form in clusters of heterogeneous layers. The rhombohedral calcite crystals have a high birefringence and there is a relatively even occurrence between simple and lamellar twinning. A garnet has also been identified in the rock-mass.

Sample Number A8 Rock Name Nepheline-syenite The minerals observed are K-feldspar, nepheline, pyroxene, calcite, biotite, muscovite and amphibole. K-feldspar and nepheline are the dominant minerals and the calcite matrix comprises  15% of the rock-mass. The rock-mass has a dominantly porphyritic texture wherein grains occur in fine layers with a combination of large crystal clots. The larger mafic crystals (biotite, pyroxene and amphibole) have inclusions of calcite. In layers where calcite is more pronounced, the texture is equigranular, observed through the subhedral sequence of small to medium sized calcite crystals in some layers, and an anhedral sequence in others (allotriomorphic); that range between having a prismatic or rhombohedral cleavage, with high order colours and high relief that changes with rotation. Simple twinning is dominant among the crystals. Sample Number A9 Rock Name Sövite-pegmatite

The minerals observed are calcite, biotite, pyrochlore, K-feldspar and pyroxene. Plagioclase is also visible, but only in trace quantities. Calcite is the dominant mineral and the matrix comprises  80% of the rock-mass. The equigranular texture is observed through the occurrence of calcite in a combination of medium to large sized, subhedral crystals (hypidiomorphic) that are homogenous. The rhombohedral calcite crystals have a high birefringence and there is a relatively even occurrence between simple and contact twinning. The presence of thin, mafic veins around the calcite indicates weathering and the redistribution of iron.

Sample Number A10 Rock Name Pyroxene-nepheline-sövite

The minerals observed are nepheline, K-feldspar, calcite, pyroxene, biotite and apatite. Plagioclase is observed in trace quantities. The rock-mass is comprised of  50% of calcite. The equigranular texture is observed through the occurrence of calcite in a combination of small to medium sized subhedral crystals (hypidiomorphic) that are heterogeneously layered. The rhombohedral calcite crystals have a high birefringence and there is a relatively even occurrence between simple and contact twinning, however lamellar twins are visible on some crystal faces. There are heterogeneous layers of mafic minerals which are coarser-grained in some parts of the rock and finer-grained in others. These are a combination between chloritised-biotite, amphibole and muscovite.

Sample Number A11 Rock Name Sövite-pegmatite

The minerals observed are biotite, calcite, olivine, pyroxene, amphibole, muscovite, pyrochlore, K-feldspar and apatite. The rock- mass is comprised of  50% of calcite. The rock-mass has a dominantly equigranular texture of well-defined heterogeneous layers with large crystal clots. The larger mafic crystals (biotite, pyroxene and amphibole) have inclusions of calcite. In layers where calcite is more pronounced, the texture is equigranular, observed through the subhedral sequence of small to medium sized calcite crystals in some layers, and an anhedral sequence in others (allotriomorphic). The crystals have a rhombohedral cleavage, with a high birefringence. Simple twinning is dominant among the calcite crystals, although lamellar twins are distinct on some crystal faces. Sample Number A12 Rock Name Sövite-pegmatite

The minerals observed are pyroxene, calcite, K-feldspar, biotite, amphibole and apatite. Trace quantities of opaque minerals are seen. Calcite is one of the dominant minerals and the matrix comprises between 50 to 70% of the rock-mass. A poikilitic texture is observed through the heterogeneous occurrence of large calcite crystals that are intergrown particularly with the K-feldspar, biotite and amphibole crystals. Notably, the calcite crystals appear to formatively continue with the same orientation. These rhombohedral crystals exhibit mostly simple and contact twinning. The high birefringence and relief is distinct and the crystals change colour upon rotation under the polarising microscope.

Sample Number A13 Rock Name Titanite-sövite

The minerals observed are titanite, calcite, pyroxene, biotite, plagioclase, and trace quantities of dolomite. Heterogeneous, foliated layers of pyroxene, titanite and biotite dominate the rock-mass, of which  50% is comprised of calcite. Some of the heterogeneous layers contain  80% of calcite, and in other layers calcite is barely visible. The equigranular texture is observed through the occurrence of calcite in a combination of small to medium sized, subhedral crystals (hypidiomorphic) that are heterogeneously layered. The rhombohedral and some prismatic calcite crystals in this specimen have a high birefringence, and there is a relatively even occurrence between simple and lamellar twinning.

Sample Number A14 Rock Name Migmatite (country rock)

This rock is dominated by fine-grained layers of partly-rounded lithic fragments, biotite, calcite, amphibole, pyroxene with traces of dolomite and K-feldspar. The rock-mass has a brecciated appearance, with rhombohedral, prismatic and acicular calcite crystals that comprise  15% of the rock-mass. Calcite, together with amphibole, pyroxene and K-feldspar occur as heterogeneous, small to medium-sized crystals. The fine calcite crystals that range between prismatic to acicular shapes, combined with the partially ophitic texture of the rock-mass in some of the mineral layers indicate that the rock is of a shallow intrusion. Partially melted crystals, across all the observed minerals, are distinct.

6.2 Electron Microprobe Analysis (FE-EMPA)

The electron microprobe results of one representative calcite crystal from each of the Alnö carbonatite samples are reported in Table 6.2, as a weight percentage (wt.%). Three EMPA spot analyses were initially conducted on three different calcite crystals for each sample. The selection of one spot analysis, per sample renders fourteen representative readings of relatively ‘pure’ calcite. Note, the stable isotope approach requires the calcite to be low in magnesium oxide (MgO), which has been ascertained. The composition for calcium carbonate (CaCO3) has been calculated based on the 2+ - stoichiometric formula equation for ideal calcite: CaCO3 → Ca + CO3 , wherein calcite can be calculated from the mass wt.% (and molecular formula) of its constituents. Hence, the formula for the - real calcite observed in the rock specimens is CaCO3 → (Ca(0.99…) + Fe(wt.%) + Mg(wt.%) + …) CO3 . The individual wt.% of each element (oxide) has been normalised according to the proportion of cations - - per CO3 in the formula, where CO3 is assumed to be 1 (see Appendix B). Microprobe Back Scatter Electron (BSE) images and elemental composition maps of the analysed calcite crystal are provided in Figures 6.2 (A) to (K). These images capture the textural interactions between calcite and other minerals in the rock specimen.

Table 6.2: Representative electron microprobe results of Alnö calcites.

Mineral: Calcite

Sample A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14

Al2O3 0.00 0.02 0.03 0.05 0.00 0.04 0.01 0.00 0.02 0.00 0.06 0.00 0.03 0.00

SiO2 0.00 0.02 0.05 0.43 0.38 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Na2O 0.01 0.09 0.32 0.10 0.24 0.05 0.14 0.14 0.04 0.00 0.05 0.00 0.19 0.00

MgO 0.38 0.44 0.17 0.14 0.02 0.19 0.00 0.05 0.26 0.11 0.00 0.02 0.07 0.03

MnO 0.55 0.10 0.02 0.07 0.00 0.25 0.17 0.14 0.15 0.31 0.00 0.31 0.05 0.28

K2O 0.00 0.06 0.10 0.04 0.01 0.00 0.03 0.01 0.00 0.01 0.00 0.00 0.00 0.03

CaO 99.06 99.12 99.14 99.14 99.27 99.33 99.68 99.64 99.41 99.44 99.89 99.65 99.57 99.54

TiO2 0.00 0.00 0.10 0.00 0.06 0.00 0.00 0.00 0.01 0.00 0.02 0.00 0.00 0.00

Cr2O3 0.01 0.02 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.01 0.02 0.00 0.00 0.00

FeO 0.09 0.22 0.16 0.14 0.12 0.22 0.08 0.13 0.23 0.21 0.06 0.11 0.19 0.21 Total 100.1 100.1 100.1 100.1 100.1 100.1 100.1 100.1 100.1 100.1 100.1 100.1 100.1 100.1 (CaCO3)

Figure 6.2 (A): Representative calcite crystal from Sample A1; left, light-grey region in the BSE image. The ‘yellow-box’ reflects the area of the elemental maps that comprise calcium (Ca), manganese (Mn), iron (Fe) and magnesium (Mg).

Figure 6.2 (B): Representative calcite crystal from Sample A2; left, light-grey region in the BSE image. The ‘yellow-box’ reflects the area of the elemental maps that comprise calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P).

Figure 6.2 (C): Representative calcite crystal from Sample A3; light-grey region beneath the yellow-box in the BSE image. The ‘yellow-box’ reflects the area of the elemental maps that comprise calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P).

Figure 6.2 (D): Large calcite crystal from Sample A4; dark-grey region in the BSE image. The ‘yellow-box’ reflects the area of the elemental maps, comprising calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P). The needle-like crystals on the left margin of the large calcite crystal are magnesium and potassium rich chlorite.

Figure 6.2 (E): Calcite crystals from Sample A6; medium-grey colour in the BSE image. The ‘yellow-box’ reflects the area of the elemental maps, comprising calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P). The light-grey mineral in the BSE image is apatite, whereas the chloritised biotite exhibits a medium-grey appearance. The whitest region is indicative of a heavy mineral that is rich in iron, and reaction of the mineral with the calcite is observed, towards the left of the yellow-box.

Figure 6.2 (F): Representative calcite crystal from Sample A7; light-grey region in the BSE image. The dark-grey mineral in the BSE image is nepheline, while the almost white mineral is apatite. The ‘yellow-box’ reflects the area of the elemental maps that comprise calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P). Nepheline is marked by K, while apatite is apparent through P. Calcite appears to have filled porous parts of the rock during post- nepheline crystallisation.

Figure 6.2 (G): Calcite crystals from Sample A10; medium-grey region in the BSE image. The ‘yellow-box’ reflects the area of the elemental maps, comprising calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P). Chloritised biotite (white to light-grey in colour) is magnesium rich.

Figure 6.2 (H): Large calcite crystal from Sample A11; medium-grey mineral towards the right side of the BSE image. The ‘yellow-box’ reflects the area of the elemental maps that comprise calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P). Apatite is indicated as small inclusions in calcite.

Figure 6.2 (I): Large single calcite crystal from Sample A12; medium-grey mineral in the centre of the BSE image. The ‘yellow-box’ reflects the area of the elemental maps, comprising calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P). The lighter-grey to white regions within the BSE image indicate the presence of heavy minerals. When observing the elemental map on calcium (Ca) in relation to the yellow-box in the BSE image, notice the way in which the calcite reacts with the opaque mineral phase and is observed diagonally across the yellow-box region.

Figure 6.2 (J): A calcite crystal from Sample A13; medium-grey in the centre of the BSE image. Elemental maps, comprising calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P) indicate that the mineral around the rhombohedral calcite is magnesium rich, bearing trace quantities of potassium as well. Likely several generations of vein and fracture-fill episodes are represented.

Figure 6.2 (K): Large calcite crystal in Sample A14, with marginal reactive breakdown due to a magnesium rich infiltration. The ‘yellow-box’ reflects the area of the elemental maps, comprising calcium (Ca), magnesium (Mg), potassium (K) and phosphorus (P). The texture of calcite is particularly fascinating in the BSE image, visibly indicating disintegration and recrystallisation to dolomite (or rhodochrosite) from interaction with an Mg-rich matrix.

6.3 Stable Isotope Results

The oxygen (δ18O) and carbon (δ13C) compositions of calcites from Alnö are reported in Table 6.3 and plotted in Figures 6.3 (A) and 6.3 (B). The obtained oxygen isotope ratios are reported relative to V-PDB (Vienna Pee Dee Belemnite) and then converted to SMOW (Standard Mean Ocean Water) ratios, employing the following equation:

δ18O ‰ (SMOW) = 1.03091 x [δ18O ‰ (V-PDB)] + 30.91

Table 6.3: Oxygen and carbon isotope compositions of Alnö calcite samples.

Sample Rock Name δ18O ‰ (±0.1) δ18O ‰ (±0.1) δ13C ‰ (±0.05) (V-PDB) (SMOW) (V-PDB) A1 Pyrochlore-sövite -22.6 7.6 -4.83 A2 Aegirine-sövite -22.6 7.6 -4.69 A3 Nepheline-syenite -22.2 8.0 -5.98 A4 Sövite-pegmatite -22.6 7.6 -4.46 A5 Ijolite -21.9 8.3 -5.74 A6 Biotite-sövite -22.7 7.5 -5.24 A7 Nepheline-pegmatite -22.2 8.1 -6.01 A8 Nepheline-syenite -22.1 8.1 -5.88 A9 Sövite-pegmatite -22.6 7.7 -6.41 A10 Pyroxene-nepheline-sövite -22.2 8.0 -5.72 A11 Sövite-pegmatite -22.4 7.8 -4.52 A12 Sövite-pegmatite -22.5 7.8 -6.37 A13 Titanite-sövite -22.2 8.0 -5.92 A14 Vein in Migmatite -12.9 17.6 0.70

The δ18O values of calcite from the carbonatite samples range from 7.5 to 17.6‰ (± 0.1‰, relative to SMOW; Figure 6.3 (A)). These are considerably higher than the δ18O value of known mantle-derived rocks and primitive carbonatites, which range between 5.5 and 6‰ (Ito et al., 1987; Harmon & Hoefs, 1995; Eiler et al., 1996). However, the Alnö values derived are consistent with previous δ18O values reported for calcite from carbonatites in the Fen Complex of Norway, on Fuerteventura (one of the Canary Islands), in the Kola Superdeep Drillhole of Russia, as well as in the Tamazert Eocene Complex of Morocco (Andersen, 1987; Demény et al., 1998; Melezhik et al., 2003; Bouabdellah et al., 2010).

The δ13C values of calcite range from -6.4 to 0.7‰ (± 0.05‰; Figure 6.3 (B)). The majority of these values align with the δ13C value of known mantle-derived rocks and primitive carbonatites, which is

40 considered to lie between approximately -7 and -4‰ (Exley, 1986; Hoefs, 1997; Parente et al., 2007). The δ18O and δ13C ratios for the Alnö Complex are plotted in relation to comparative δ18O and δ13C ratios in Figures 6.3 (A) and (B). Mid-Ocean Ridge Basalt (MORB) is a universal reference field which reflects the value of the upper mantle that feeds mid-oceanic ridge systems. The ‘primary carbonatite’ reference field of Taylor et al. (1967) reflects the value of ‘unaltered’ carbonatites which are considered to originate from primary magmatic sources. The number of samples number in each group is denoted by ‘n’-notation.

Figure 6.3 (A): The δ18O values of the Alnö calcite samples in comparison with mantle values (MORB), primary carbonatite values (red bar) and δ18O carbonatite values from comparative alkaline complexes (Taylor et al., 1967; Andersen, 1987; Ito et al., 1987; Keller & Hoefs, 1995; Eiler et al., 1996; Hoefs, 1997; Demény et al., 1998; Melezhik et al., 2003; Parente et al., 2007; Bouabdellah et al., 2010).

A ‘primary carbonatite’, in this context is defined as being “unaffected by secondary phase reactions, and does not necessarily denote an unmodified partial mantle melt” (Hoefs, 1987; 1997; Keller & Hoefs, 1995).

Figure 6.3 (B): The δ13C values of the Alnö calcite samples in comparison with mantle values (MORB), primary carbonatite values (red bar) and δ13C carbonatite values from comparative alkaline complexes (Taylor et al., 1967; Andersen, 1987; Ito et al., 1987; Keller & Hoefs, 1995; Eiler et al., 1996; Hoefs, 1997; Demény et al., 1998; Melezhik et al., 2003; Parente et al., 2007; Bouabdellah et al., 2010).

In the oxygen isotope histogram, it is evident that not all of the δ18O ratios from Alnö plot within the MORB field. The majority of the δ18O ratios for the Alnö Complex, however, fall within the primary carbonatite field. The vein sample bears a considerably higher δ18O ratio in contrast to the other samples from Alnö. According to this plot, the primary δ18O ratios for the Alnö carbonatites are relatively homogenous.

In the carbon isotope histogram, the majority of the δ13C ratios for the Alnö Complex fall within both the MORB-type mantle field and the primary carbonatite field. The vein sample, which carries a highly positive δ13C ratio, contrasts the negative ratios of the plutonic calcite samples from Alnö. According to this assessment, the δ13C ratios for the Alnö carbonatites are also relatively homogenous.

7. Discussion

This chapter is written in two parts. The first part summarises and consolidates the scientific experiments and data collected throughout the research project. The second part, in turn, seeks to interpret and connect the research findings to a sustainable perspective on the Alnö Complex. The framework of issues discussed builds upon the literature review and hypothesis formulated in Chapter Two.

7.1 Petrogenesis of Carbonatites in the Alnö Complex

7.1.1 The Petrographic Approach

The optical inspection of mineralogical properties (of carbonatite samples in this case) is called petrography. It is a tool which can help to unearth the petrogenesis of a rock (Hibbard, 1995). In addition, the aim of both the petrographic and geochemical approaches is to reconstruct the history of the Alnö carbonatite magma within an oxygen isotope (δ18O) and carbon isotope (δ13C) investigation. The context within which the isotope data are to be used is that of Earth’s isotopic reservoirs, such as the mantle and the crust (e.g. Hoefs, 1997; Bindeman, 2008). Methods that investigated the texture and mineralogy of the carbonatite samples are therefore used as a window into where the Alnö carbonatites originated.

There are three main observations that can be derived from the petrographic results of the Alnö rock specimens:

(1) The petrographic results reveal that the sövites and sövite-pegmatites are indeed calciocarbonates, with calcite being the dominant mineral (≥ 50%) in the rock-mass.

(2) Both the hand-specimen petrography and the thin section petrography suggest that the thirteen samples (A1-A13) are intrusive, bearing a granularity that ranges from very coarse-grained to medium coarse-grained, with distinctive crystalline textures. The textures of the samples are characterised by medium to large crystals that are often surrounded by a finer-grained matrix (porphyritic texture) which implies an igneous origin. The heterogeneous layers and irregular nature of the largest crystals imply that several generations of crystallisation have taken place (Hibbard, 1995).

(3) The migmatite country rock sample (A14), in contrast, has a medium to fine-grained texture and is cut by a calcite vein. It is representative of the older country rocks at the complex. The occurrence of the vein indicates that some measure of hydrothermal activity and associated rock alteration has taken place (cf. Hibbard, 1995; Holland et al., 2013).

Hode Vuorinen (2005) makes a striking observation in respect to the mineralogy of the Alnö rocks and expressed that calciocarbonatites, in particular,

“…contain a variety of silicate minerals, some of which are obviously not crystallised within the carbonatite magma (potassium-feldspar) and some of which the origin is more difficult to determine (the pyroxenes)”.

Thin section microscopy reveals that calcite is associated with aegirine, amphibole, biotite, muscovite, nepheline, olivine, potassium-feldspar, augite and titanite in variable proportions. Titanite (from the titanite-sövite) contains substantial amounts of Niobium (Nb), Zirconium (Zr) and light rare earth elements (LREEs) which are important to unravel carbonatite petrogenesis (Bühn et al., 2002; Hode Vuorinen & Hålenius, 2005). Microscopy also revealed that the titanite-sövite contains traces of dolomite. If larger quantities of dolomite were found, the characteristic texture and composition of the titanite-sövite would be entirely different and the specimen would be classified as a magnesiocarbonatite or titanite-beforsite (von Eckermann, 1948; Shearman et al., 1961). Traces of dolomite were also discovered in the migmatite; however, the particles were extremely fine and had a very cracked, almost broken texture (i.e. they could be secondary). The presence and texture of dolomite in the migmatite ought to be remembered, as it is a precursor to forthcoming insights on the stable isotope values of calcite in the migmatite, and the kinds of processes that these values are synonymous with.

7.1.2 The Mineral Composition Approach

Following on from the findings of the thin section petrography, that reveals a shared carbonate and silicate mineralogy across the range of Alnö rock specimens, the principal findings of the major element analyses reveal that there are only slight differences in the elemental concentrations between the calcites in these rocks. The main observation that can be derived from the major element results of the Alnö rock specimens and their corresponding calcites is that the Back Scatter Electron (BSE) images from the electron microprobe results indicate that calcite is not an inert mineral across the entire range of specimens within the sample set. The BSE images reveal the way in which calcite forms around other minerals and that calcite crystallised and disintegrated in a ‘fluid’ manner in relation to the silicate minerals. It has a strong textural relationship with magnesium, potassium, phosphorus and iron-rich minerals. Regarding the sample set, the calciocarbonatites are likely related to the nepheline-syenite and the ijolite-series rocks through a shared carbonate component (Hode Vuorinen, 2005; Skelton et al., 2007).

7.1.3 The Migmatite Country Rock

The morphology and composition of an intrusion is usually transformed through chemical reactions with its surrounds (e.g. Van Cappellen & Gaillard, 1996). A simultaneous comparison of the petrographic and geochemical approaches thus far revealed that the migmatite country rock sample records fluid-rock interaction in the form of calcite within a crosscutting vein. The calcite vein in the migmatite (gneissic) country rock is thus an indication that metasomatic processes may have been at play and are likely relevant for the local alteration of the ijolite-series rocks and for the process of fenitisation (von Eckermann, 1948; 1966; Kresten, 1979; 1980).

Continuous geophysical and magnetometric research according to the ‘Kresten model’ of dyke emplacement and fenitisation concur that magma emplacement had been associated with intense fenitisation of the migmatitic country rock and was associated with intrusions of ijolite, nepheline- syenite and pyroxenite (Kresten, 1976; Morogan & Woolley, 1988; Walderhaug et al., 2003; Meert et al., 2007, Skelton et al., 2007; Andersson et al., 2013). Fenitisation increased the levels of calcium oxide (CaO), the sodium oxide (Na2O), magnesium oxide (MgO), iron oxide (FeO) and potassium oxide (K2O) in the migmatite (Morogan & Woolley, 1988), but reduced the level of silicon dioxide

(SiO2) (Hode Vuorinen & Skelton, 2004; Skelton et al., 2007). The ijolite, nepheline-syenites and the veins in migmatite are thus linked in space and time, and all of the samples here therefore appear to relate to the magmatic phase at Alnö (Kresten & Morogan, 1986; Andersson et al., 2013).

7.1.4 Unravelling Petrogenesis: The Stable Isotope Approach

Contemporary investigations are vital in preserving and refining the knowledge and status of the Alnö complex. The Alnö Complex is special among carbonatite ring-complexes worldwide due to the sheer magnitude of its alkaline-carbonatite and carbonatite intrusions and the preserved intrusive- extrusive16 character of the carbonatite intrusions (von Eckermann, 1948; 1958; 1961; 1974; Kresten, 1976; 1980; Morogan & Woolley, 1988; Morogan & Lindblom, 1995; Walderhaug et al., 2003; Meert et al., 2007; Andersson et al., 2013). The core of the research investigation herein aims to investigate a hypothesis which is curious about (a) the origin and nature of the carbonatite magmas at Alnö and (b) the type(s) of processes that the magma had been susceptible to, prior to and during emplacement. Below, a contextual interpretation of the stable isotope data is presented, and it is this data which leads the discussion on the petrogenesis of carbonatites from the Alnö Complex later in this thesis. One of the most critical goals for the interpretation of the stable isotope data is to constrain the ultimate origin of the Alnö carbonatite magmas and what processes were influential during petrogenesis (cf. Taylor & Bucher-Nurminen, 1986; Chacko et al., 1991; Keller & Hoefs, 1995; Hoefs, 1997; Lentz, 1999;

16 Intrusive: Magma crystallises beneath the Earth’s crust and yields a rock which usually has a coarse-grained, crystalline texture. When extrusive, magma crystallises at the Earth’s surface and yields a rock which usually has a fine-grained texture. 45

Skelton et al., 2007; Bindeman, 2008; Rosatelli et al., 2010; Casillas et al., 2011; Downes et al., 2012). The evaluation of isotope data firstly considers whether or not a sample is primary and unmodified from the outset (Taylor et al., 1967; Keller & Hoefs, 1995; Skelton et al., 2007; Bouabdellah et al., 2010; Demény et al., 2010; Martin et al., 2012; Russell et al., 2012; Dasgupta et al., 2013) or whether it has been changed by differentiation processes or affected by low-temperature weathering and alteration (e.g. MacDonald et al., 1993; Lentz, 1999; Cooper et al., 2011). In addition, the isotope configuration can determine whether the magma has been influenced by crustal additions (e.g. Schuiling, 1961; Chadwick et al., 2007; Freda et al., 2008; Iacono-Marziano et al., 2009; Deegan et al., 2010; Cooper et al., 2011).

The distinction between primary (e.g. mantle-related), differentiation- and secondary-processes is crucial for an understanding of petrogenesis (Bouabdellah et al., 2010; Chazot & Mergoil-Daniel, 2012; Martin et al., 2012). The petrogenetic processes responsible will leave an imprint on the co- variations in δ18O and δ13C values and thus, they will reflect the various mantle or crustal influences (e.g. Deines, 1989; Demény et al., 1998; Mollo et al., 2009; Dasgupta & Hirschmann, 2010; Casillas et al., 2011; Cooper et al., 2011). To explain the δ18O and δ13C variation observed at Alnö is, therefore, the prime scope of this discussion and we shift now towards an integrated model for the δ18O and δ13C values from the Alnö Complex (Figure 7.1).

Figure 7.1 illustrates the primary carbonatite field, the surrounding influences and processes, the expected associated isotopic changes, and reveals a comprehensive picture of the origin and evolution of magmas through the stable isotope variations seen in carbonatite and alkaline intrusions worldwide. Chapter Six plotted the values for δ18O and δ13C separately. A fusion of the separate systems, further on in the discussion (Figures 7.2 and 7.3) in combination with Figure 7.1, will now provide a process- orientated interpretation for the investigated carbonatite specimens from Alnö. The ‘primary carbonatite’ field in Figure 7.1 refers to unaltered carbonatites that stem from a mantle-derived magma but may have experienced magmatic differentiation processes (e.g. fractional crystallisation or minor country-rock assimilation). The δ18O values of unaltered primary carbonatites range from ~ 6 to 10‰, and for δ13C from -8 to -4‰ (Taylor et al, 1967). The natrocarbonatites from Oldoinyo Lengai in Tanzania carved their own reference field within the ‘primary carbonatite’ domain and show a range of 5.8 to 6.7‰ for δ18O and -7.1 to -6.3‰ for δ13C (Keller & Hoefs, 1995). Variations between isotope compositions in both these ‘primary’ fields can then be attributed, as in mantle heterogeneity, magmatic fractionation, assimilation of crust, or hydrothermal alteration and fluid overprint (e.g. Deines & Gold, 1973; Zaitsev & Bell, 1995; Demény et al., 1998; Russell et al., 2012; Dasgupta et al., 2013). The ‘primary carbonatite’ and ‘Oldoinyo Lengai primary carbonatite’ fields, as in Figure 7.1, are further subdivided in order to constrain petrogenesis; the Mid-Ocean Ridge Basalt (MORB) and

the Ocean Island Basalt (OIB) fields are shown too. MORB17 is realised through 5.7 ± 0.3‰ for δ18O and a range between -7 to -4‰ for δ13C (Taylor et al., 1967; Exley et al., 1986; Ito et al., 1987; Hoefs, 1997), whereas a range of 4.8 to 8‰ for δ18O and -7 to -5‰ for δ13C, articulates an isotopic source that is characteristic of an OIB18 (Kyser 1986; Deines, 1989; Keller & Hoefs, 1995).

Sedimentary -1 Contamination or High Temperature -2 Seawater Influence Fractionation

-3

C C

13 -4

δ High Temperature -5 Interaction with Meteoric Water Mantle Heterogeneity and -6 Differentiation Processes 'Primary' Oldoinyo -7 Lengai, (Keller & Hoefs, 1995) Low Temperature Meteoric 'Primary' Carbonatite Field (Taylor et al., 1967) Alteration or -8 Water Silicate Influence Contamination -9 4 5 6 7 8 9 10 11 12 δ18O

Figure 7.1: Influences involved in isotopic variations of carbonatites. The oxygen (x-axis) and carbon (y-axis) scales encapsulate mantle and crustal reservoirs and processes. Reference fields after Taylor et al. (1967), Savin and Epstein (1970), Andersen (1987), Deines (1989), Keller and Hoefs (1995), Hoefs (1997), Demény et al. (1998), Melezhik et al. (2003), Skelton et al. (2007), Bouabdellah et al. (2010) and Casillas et al. (2011).

17 Mid-ocean ridges develop as magma emerges onto the ocean floor and into the crust. The crystallised magma forms a new crust of basalt. 18 Ocean island basalt is a rock type found on volcanic islands. Islands hosting ocean island basalts occur above the oceanic crust. 47

The cause for heterogeneities in original δ18O and δ13C are at times, difficult to determine as they may be affected by a range of processes such as partial melting, crystallisation, recrystallisation, deformation, and metasomatism that are all governed by variable temperature dependent fractionations (e.g. Hoefs, 2009). Specifically, low-temperature exchange between magma and external fluids rich in water (H2O) from, for example carbonate or marine sedimentary rocks will render high, positive isotope values for δ18O (Figure 7.1; O’Neil et al., 1969; Hoefs, 2009). This is because fractionation at low-temperatures is very intense for most mineral-fluid pairs and if substantial quantities of H2O or a high δ18O component are involved in such a process, the δ18O values of the magma will become more positive (Chacko et al., 1991; Bühn et al., 2002). Considering the carbonate specimens from the Alnö Complex in relation to Figure 7.1, the majority of the samples fall within the primary carbonatite field arising from the isotope plots in Chapter Six; whereas ‘crustal carbonatites’ are expected to fall within, or slightly below the marine sediment field. Below, the focus will first be on oxygen and then on carbon isotope variations.

All thirteen of the carbonatite rock specimens (A1-A13) fall within a ‘primary carbonatite’ classification for δ18O (Taylor et al., 1967), with a single outlier being the calcite vein from the migmatite (A14). Alnö igneous samples also do not overlap with sedimentary δ13C and values (that range between -3.8 to 3.8‰; Savin & Epstein, 1970; Keller & Hoefs, 1995), but rather record mantle like values. Notably, the Alnö samples do not follow high-temperature and low-temperature alteration trends either (Figure 7.2) and therefore, an essentially ‘primary’ origin for the carbonatites is indicated, in the sense that the original Alnö magma was mantle-derived. However, there are several other observations that can be derived from the reported isotope data of the Alnö calcite separates. The consistently high δ18O values of calcite from the Alnö calciocarbonatites, nepheline-syenites, ijolite and migmatite vein exceeds the average δ18O value of “pure mantle” (Taylor et al., 1967; Deines, 1989; Keller & Hoefs, 1995; Hoefs, 1997). The calcite from the biotite-sövite bears the lowest δ18O value (7.5‰), likely the closest reflection to the pristine mantle composition that fed Alnö. The migmatite vein, in contrast, bears a value that is far removed from the mantle field (17.6‰), implying that a sedimentary component was involved.

The majority of δ18O values for the Alnö Complex are compatible with reported δ18O values of calcite separates from other carbonatites for example, from the Fen Complex in Norway, Fuerteventura in the Canary Islands and the Tamazert Complex in Morocco (Andersen, 1987; Demény et al., 1998; Bouabdellah et al., 2010). The outlying calcite value from the migmatite vein is compatible with similar readings recorded from, for example, carbonatites from the Kola Peninsula in Russia and the Tamazert Complex (Melezhik et al., 2003; Bouabdellah et al., 2010).

The consistently mantle-like δ13C of calcite from the Alnö calciocarbonatites, the nepheline-syenites and ijolite also align with the average δ13C value of the mantle (Taylor et al., 1967; Deines, 1989;

Keller & Hoefs, 1995; Hoefs, 1997). A sövite-pegmatite bears the lowest δ13C value (-6.4‰) whereas the high δ13C value of the migmatite vein is far removed from the mantle field (0.7‰). Thirteen of the carbonate rock specimens (A1-A13) fall within a ‘primary carbonatite’ classification for δ13C (Taylor et al., 1967) with a single outlier, being the calcite vein from the migmatite (A14).

The accumulation of these observations within the framework of mantle and crustal influences, articulated in Figure 7.1, thus reveals magmatic δ18O and δ13C for all igneous carbonate specimens from the Alnö Complex. (Figure 7.2 A, B).

7.1.5 Resolving the Finer Details

The petrographic, geochemical and isotopic observations thus far, have now revealed that the carbonatite-forming magma is indeed, mantle-derived. Therefore, a major component of the initial hypothesis that was developed for the Alnö Complex, and the research experiments herein (Chapter Two) has been resolved. However, deductions pertaining to the primary nature of the magma are never straightforward, and it is a risk to directly infer that the samples are uncompromised just because their stable isotope compositions align within the ‘primary carbonatite’ field (Lentz, 1999; Bühn et al., 2002; Mitchell, 2005; Viladkar et al., 2005; Mollo et al., 2009). A reflection on the kind of minerals which are native to calciocarbonatites and the complexities surrounding whether they crystallised in the magma or not, prevents such a simplistic inference (Schuiling, 1961; von Eckermann, 1966; 1974; Kresten, 1979; Vennemann & Smith, 1990; Lee & Wyllie, 1994; Lee et al., 2000; Hode Vuorinen & Skelton, 2004; Rosatelli et al., 2010; Chazot & Mergoil-Daniel, 2012; Dasgupta et al., 2013). What else could have affected the mantle-derived magma?

The discussion therefore needs to consider whether the carbonatites arise from a magma that directly relates to the mantle (i.e. a pure, primary magma), or if the parental magma experienced ‘internal’ or ‘external’ processes as it traversed from the mantle to the point of its intrusion in the crust (i.e. daughter magma). In Figure 7.2 A, δ18O and δ13C values for calcite from the current research sample set (Alnö 2013; green triangles) are then compared to δ18O and δ13C values for calcite from an earlier investigation conducted at the complex. The values from the earlier sample set (Alnö 2007; yellow and purple squares) are further divided into (I) a pristine19 calcite suite, and (II) a metasomatised20 calcite suite (Skelton et al., 2007). Here, the combination of pristine and metasomatised calcite suites from the comparative data (calcite I and II; Figure 7.2 A) can help unearth the nature of the carbonatite forming magma at Alnö.

19 Pristine: The calcite has remained in its original, pure state and bears little or no impurities and evidence of decay. This pure state is a condition that typically relates to the earliest time of calcite formation or crystallisation. 20 Metasomatised: Metasomatic processes change the composition of a rock through either the introduction or removal of chemical constituents by a fluid. 49

Figure 7.2 A: Stable isotope (O, C) plot for calcite separates from the Alnö carbonatites. Green triangles symbolise the current isotopic data (2013); yellow and purple squares symbolise that of an earlier study (Skelton et al. 2007). B: Stable isotope (O, C) plot for calcite separates from the Alnö carbonatites with a prospective projection towards the ultimate Alnö parental magma. Reference fields for (a) and (b) after Taylor et al. (1967), Savin and Epstein (1970), Andersen (1987), Deines (1989), Keller and Hoefs (1995), Hoefs (1997), Demény et al. (1998), Melezhik et al. (2003), Skelton et al. (2007), Bouabdellah et al. (2010) and Casillas et al. (2011).

Evidently, the majority of the primary isotope values on the plot (this study) align more closely with the primary calcite (I) of Skelton et al. (2007) and less so with the calcite (II) samples that are considered metasomatised by these authors or rather, representative of metasomatism that occurred during emplacement in the crust (‘contact-metasomatism’, Skelton et al., 2007). Notably, all of the older calcite ratios (I and II) also plot in the mantle field, yet the δ18O and δ13C variations of the spread of data is ascribed in part to crustal processes (Skelton et al., 2007). This realisation is a vivid reminder of the difficulty in constraining the pristine origin of a carbonatite, wherein its constituent stable isotopes can reflect the influence of both primary and subsequent magmatic processes.

The attempt to “remove” the fluid-rock interaction (contact-metasomatism) in the Skelton et al. (2007) data (calcite II in Figure 7.2), appears to amplify the primary magmatic trends, although a small number of the present samples seem to overlap with the calcite II suite of Skelton et al. (2007). What is important to recognise, however, is the close alignment of our data with the primary calcite (I) suite of Skelton et al., (2007), which emphasises the sharply defined trends in our data. The partial alignment of our lower data trend with the metasomatised calcite (II) suite is, in turn, a useful indication that primary magma was likely modified in this fashion also. The two distinct evolutionary magmatic trends defined by our data can thus be interpreted to represent, on the one side, a trajectory for assimilation of sedimentary carbon or marine sediments (including their fluids), whereas the second trend follows an expected trajectory for a combined sediment and silicate assimilation (as low- temperature alteration is not prominent on textural grounds).

Modification of primary magma according to the first trend is plausible in that the migmatite in the Alnö Complex is believed to originate from greywacke marine sediments (von Eckermann, 1948; Kresten, 1979). Arising from its sedimentary origin, the migmatite (paragneiss) will not have the same source as the primary carbonatites. The outlying isotope ratio from the migmatite vein (A14) that is lodged in the marine sediment field, reflects this sedimentary signal, and also indicates that high δ18O and δ13C values are indeed, characteristic of magma-crust interaction phenomena (von Eckermann, 1948; 1966; Kresten, 1979; Dasgupta & Walker, 2008; Demény et al., 2010; Troll et al., 2013). At the Alnö Complex, as magma and magmatic fluids intruded the crust, fluid-rock interactions would have created an amalgamation of processes in its surrounds between host-rock and the magma-derived fluids, as observed in our migmatite sample. This metamorphosed sediment was likely intersected by a crack, and carbonate formed when magmatic and sedimentary fluids came into contact with each other (Mollo et al., 2009; Holland et al., 2013; Bhattacharya et al., 2013). In relation to these increased temperatures, Lentz (1999) argues that in shallow regions of the crust, the intensity of fluid-rock interaction and alteration is raised significantly when a highly peralkaline liquid or fluid, from a silicate-rich parental magma, comes into contact with country rock (such as limestone xenoliths) and creates ‘sodic fenites’ as opposed to a yield of minor carbonatite and silicic skarns as expected from a weaker peralkaline silicate parent magma.

The second trend in turn, is also plausible in that it aligns with evidence that carbonatite liquids are able to assimilate crustal material on the way from the mantle to the point of intrusion at the crust (e.g. Hode Vuorinen & Skelton, 2004; Russell et al., 2012). A well-mixed, oxygen-buffered reservoir in the volcano plumbing system, translates into carbonatites that have a common, but characteristic lithology (Javoy et al., 1986; Demény et al., 2004). This is a compelling concept, since the primary Alnö ratios from this study show pristine magmatic traits. The second trend on the plot could therefore placate Hode Vuorinen’s (2005) sensitivity towards assimilation of silicate minerals by the originally mantle- derived carbonatites at Alnö. Affirming the involvement of shallow-crust in the petrogenesis of the Alnö carbonatites, the stable isotope data presented, strengthen the existing evidence that a degree of silicate material was taken up by Alnö magmas through, for example, wall rock assimilation or due to the corrosive impacts of reactive metasomatism with the surrounding country rock during emplacement (e.g. Hode Vuorinen & Skelton, 2004; Skelton et al., 2007).

Therefore, the two trends on the plot (Figure 7.2 B) indicate that magma genesis in the Alnö carbonatite system involved both mantle and crustal components, and that the mantle-derived carbonatites are likely to have assimilated sedimentary components and/or silicate minerals en route to their final emplacement. Not only can our data see through the disturbed (or scattered) trend observed in the metasomatised (calcite II) suite (Skelton et al. 2007), the two trends from this study are furthermore able to infer a prospective common parental carbonatite magma for the Alnö Complex. The common parent is indicated through a back-projection from the two trends in Figure 7.2 B. The back-projection yields a coordinate that falls just below the reference field for carbonatites from Oldoinyo Lengai, towards the lower mid-right in the OIB field and, the primary carbonatite field of Taylor et al. (1967). Ocean island basalts are derived from hot spots, and the majority of the Alnö isotope values are located within or close to the OIB field, while plotting away from the MORB reservoir.

The magmatic origin of the Alnö Complex carbonatites was thus likely connected to a hot spot or plume event (Nelson et al., 1988; Eiler et al., 1996; Dasgupta & Walker, 2008; Andersson et al., 2013). Moreover, the location of the potential common parent magma of the Alnö carbonatites bears similar traits to the magma(s) of the Oldoinyo Lengai volcano, in Tanzania and from Lanzarote, Canary Islands. Recent experiments indicate that the origin of Oldoinyo Lengai natrocarbonatites involves carbonatite and nephelinite magmas that are rift-related and have likely been separated in the mantle by liquid immiscibility from a sub-continental mantle source (Fischer et al., 2009), while the Fuerteventura carbonatites are plume-related and probably represent low-degree partial melts from OIB-type and ambient upper mantle components (Demény et al., 1998, 2004; de Ignacio et al., 2006).

7.1.6 Alnö Relative to Other Carbonatite Complexes

Aside from the natrocarbonatites from Oldoinyo Lengai, the Alnö carbonatites also share petrogenetic traits with carbonatites from several alkaline complexes and so, the δ18O and δ13C isotope compositions from the current Alnö Complex sample set are plotted once more in Figure 7.3. Comparative carbonatites from the isotope histograms in Chapter Six, and previously used reference fields have also been included in the plot.

Figure 7.3: Comparative, stable isotope (O, C) plot for calcite separates from the Alnö carbonatites. Isotope values for calcite from the comparative carbonatites along with mantle and crustal domains are indicated according to Andersen (1987), Demény et al. (1998), Melezhik et al. (2003), Bouabdellah et al. (2010) and Casillas et al. (2011). Reference fields after Taylor et al. (1967), Savin and Epstein (1970), Deines (1989), Keller and Hoefs (1995) and Hoefs (1997).

In Figure 7.3, Alnö’s primary isotope ratios overlap with carbonatite ratios from the Fen Complex.

These Norwegian isotope ratios belong to sövites, and their high silicate content is attributed to CO2 enriched interactions between carbonatite magma and a mafic, silicate-rich magma in the middle to upper regions of the mantle (Kresten & Morogan, 1986; Andersen, 1988). The Fen magma is believed to have formed through the partial melting of carbonated lherzolite (Andersen, 1987), where pre- melting metasomatic reactions would have ignited the release of high quantities of calcium oxide

(CaO) and CO2, which ultimately seeped into the magma (cf. Dasgupta & Hirschmann, 2010). The Alnö carbonatites also correspond strongly with primary carbonatites from Fuerteventura in the Canary Islands, as briefly noted above (Figure 7.3). In Fuerteventura, carbonatite petrogenesis has been attributed to interactions between ancient subduction-related plume components and ambient upper mantle. The Fuerteventura carbonatites are believed to originate from a melt that was derived from a mantle peridotite that was metasomatised through such a subducted crustal component (Hoernle & Tilton, 1991). It is believed that the Fuerteventura carbonatite and syenitic magmas were stored separately in shallow-level21 magmatic chambers where they variably interacted with local crust, including sedimentary limestone (Hoernle et al., 1991; Demény et al., 1998; Casillas et al., 2011).

Calcite from the Kola Peninsula and from alkaline and silicate rocks from the Tamazert Complex in Morocco as well as metacarbonatites22 in Fuerteventura, fall, in part, into the marine sediment region (Figure 7.3), indicative of interaction with, or the assimilation of, sedimentary carbonate or marine sedimentary components (Demény et al., 1998; Melezhik et al., 2003; Bouabdellah et al., 2010; Casillas et al., 2011). Primitive isotope ratios from the Tamazert carbonatites are in close proximity to the Alnö ratios on the plot (Figure 7.3), reflecting a carbonatite magma that likely separated from a parental magma (or melt) through closed-system, low-temperature mantle processes such as liquid immiscibility or fractional crystallisation (cf. Wyllie, 1987; Bouabdli et al., 1988; Kjarsgaard & Hamilton, 1989; Kchit, 1990; Lee & Wyllie, 1994; Mourtada et al., 1997; Woolley, 2003). This theory corresponds to the petrogenetic framework also suggested for the Fen Complex (Andersen, 1987; 1988).

Furthermore, the Tamazert carbonatites, alkaline and silicate rocks are believed to have emerged as individual melts from a “heterogeneously carbonated amphibole-lherzolite mantle source” (Marks et al., 2008). A plume in the Canary Islands is believed to have released magmatic material that travelled through the sub-lithosphere, from beneath the Canary Islands all the way to north-west Africa (Bouabdellah et al., 2010). Arising from this, the origin of the Tamazert carbonatites has been intertwined with the magmatic model from Fuerteventura. In this context, the origin of the Alnö carbonatite parental magma can be explained by a parental magma that originated in a rift setting,

21 This is the uppermost region of the mantle; considered to be closer to the crust than any other region. Contamination of magma in this region is another form of crustal contamination. 22 Sedimentary carbonate that has experienced severe metamorphism and metasomatism. 54 tapping previously enriched sub-continental mantle or alternatively and perhaps more likely, from a plume finger fed by an OIB-type mantle source.

7.1.7 Conclusions

The key conclusions derived from the stable isotope study of carbonate from the Alnö Complex are:

(1) The δ18O and δ13C compositions of calcite from calciocarbonatite, nepheline-syenite, and ijolite rock specimens indicate a magmatic, mantle-derived origin. Moreover, both δ18O and δ13C compositions for these specimens fall within the ocean-island basalt (OIB) and ‘primary carbonatite’ fields. Isotope variations within and beyond the sample suite may be attributed to mantle heterogeneity, however, existing data from contact-metasomatic carbonatites at Alnö span the range of our data, implying that the observed variations are not mantle heterogeneities. Corresponding with isotope ratios from comparative complexes, the origin of the Alnö carbonatites involved a carbonate- rich parent magma that derives from partial melting of a carbonated peridotite in the mantle. These carbonatite-type magmas are then exposed to an uptake of silicate minerals (e.g. Hode Vuorinen & Skelton, 2004; Russell et al., 2012), and interaction with crustal fluids from fenitisation processes (von Eckermann, 1948; 1966; Kresten, 1979; 1980), thus explaining the two evolutionary trends seen in our data. Extrapolation of the two trends yields a ‘parental carbonatite magma’ similar to that of Oldoinyo Lengai in Tanzania today, but likely with a more OIB-type mantle-source.

(2) The δ18O and δ13C compositions of the calcite in the migmatite vein reveal that the fluids that passed through this vein had been affected by crustal processes. Dolomitisation could have occurred, but dolomite is not a key mineral in the vein. The derivation of the calcite in the migmatite vein is therefore the result of mobilisation processes of crustal fluids during fenitisation and fluid-country rock interaction stipulated by high-temperature magmatic fluid input.

7.2 Sustainable Development and the Alnö Complex

The Alnö Complex is only partially visible within emerging discussions on the divergent practices of rare earth element (REE) extraction and natural resource conservation. Whereas the first part of the discussion considered the geological processes that define the genesis of carbonatite rocks from the Alnö Complex, the current discussion will embrace the evolution of the complex, epistemologically. Conflicts are likely to arise in decision making processes that involve whether this Swedish rural landscape and heritage site should be preserved, or if it should be exploited for its resources. The ideas and observations raised are, therefore, an attempt to ripen a conversation which places the Alnö Complex and its reserve of REEs, at the heart of a sustainable development narrative.

7.2.1 Nature Reserves, Alnö Island and a Developmental Philosophy

Nature reserves were informally established in Sweden in the 1700’s, and arose out of a concern for pollution and the preservation of the environment. Symptoms of damage that were directly related to problems of noxious gas release and acid drainage from mining, particularly in the central and northern parts of the country, had become increasingly visible in the surrounding vulnerable forests and lake ecosystems (Mander & Jongman, 1998). In the years between 1910 and 1970, Sweden began to formally demarcate its nature reserves according to Swedish jurisdiction that simultaneously abided by international environmental treaties (Dahlström et al., 2006). The nature reserves were to be collectively managed, and balanced against the economic and social goals of the surrounding farms, towns or cities. Therefore, nature reserves are protected areas that are used for the common benefit of locals, with strict measures in place in order to prevent the collapse of biodiversity and protect the natural environment (Dasmann, 1972; Shafer, 1990).

A large part of the territory that constitutes Alnö Island, and wherein the Alnö Complex is situated, subsequently became a nature reserve in the 1940’s following such negotiations (Swedish Heritage Archives, 2012). The Stornäset Nature Reserve on the island is among the most well-known nature reserves throughout Sweden. A timber trade, as well as agricultural and fishing livelihoods on the island have all been cultivated within and around this nature reserve. Alnö Island has been divided into zones according to three main areas:

(1) Nature reserve that is absent of human settlements, tourism, and man-made structures. This is a low-use-zone area with options for walking and hiking along ungraded tracks.

(2) Nature reserve with a blend of wilderness and human settlements. These are medium-use-zones of the island where the natural environment is surrounded by the activity of local trades and livelihoods. The areas are linked to the developed roads of the high-use-zones.

(3) Natural environment of medium to high-use-zone area that is developed with settlements, roads and ferried waterways for local livelihoods, and the functioning of the tourism trade.

Alnö Island, encompassed by these nature reserve zones, is considered to be a heritage site that symbolises ‘rural’ Sweden. The island is not a biodiversity hotspot where numbers of endemic species are high or under threat, however, the outcome of increasing development on the island would result in an increase in fragmented habitats that could potentially cause a loss in biodiversity. The timber trade, agricultural and fishing livelihoods provided much needed employment and capital to the island and surrounding districts in the early to late 1800’s and into the early 1900’s, when unemployment in the region became remarkably high (Swedish Heritage Archives, 2012). Currently, there are three distinct types of employment that exist on Alnö: direct employment from the timber, agricultural, fishing and everyday small-market trades; indirect employment where a wide range of businesses thrive with tourism (e.g. excursions and crafts) and lastly, induced employment where local residents spend the money earned from tourism (Swedish Heritage Archives, 2012). The reserves are evidently managed through integrating a sense of wilderness and nature conservation with the local livelihoods and trades. The concept of ‘wilderness’ here does not denote ‘free of humans’, rather it seems to symbolise a ‘Hegelian ethic’23 ethic towards nature, where the human footprint is relatively negligible and in balance with the terrestrial biomes that are existent on the island.

The demarcation of the island into its nature reserve zones, however, came at a contested time as renewed commercial interest in the region was on the rise following the geological discoveries of alnöite in the northern, north-western and central parts of the Alnö Complex, respectively highlighting the possibility of diamond occurrences (von Eckermann, 1958; Brueckner & Rex, 1980; Kresten, 1980; Walderhaug et al., 2003; Meert et al., 2007). What is the root of such contestation? Deep geological exploration has a long history of conflict, despite whether the exploration has actually been for scientific research or industrial purposes (Gooch, 1995; Evans, 1997). For industry, in particular, the politics of REE mining is a relatively recent addition to the core of emerging debates that involve resource extraction, conservation activity, biodiversity concerns and environmental law (Bin, 2011). Understanding the causes and impacts of REE mining is, therefore, an urgent task. So too, is improving the knowledge of how to develop effective responses to the emerging discussions (Barrow, 1995; Angelstam et al., 2011). Approaches and concepts that focus on sustainability can contribute substantially to such an understanding (Bossel, 1998). At the same time, REE mining issues pose

23 A complex branch of philosophy that considers the impact and intricacy of the interaction between nature and humans according to a hermeneutic method (past-present and future-present time scales) that sees nature as always dominant, powerful and absolute. 57 significant challenges as well as opportunities for sustainability. At this point in the discussion, prior to allowing a handful of these issues to surface, REE mining in the context of ‘sustainable development’ needs to be defined.

The United Nations established a World Commission on Environment and Development, chaired by the then Prime Minister of Norway, Gro Harlem Brundtland, to propose ways to develop the environment. The 1987 Brundtland Commission created a developmental philosophy that argued for priority to be given to achieving sustainable development (Lafferty, 1996). Therefore, REE mining, in the context of sustainability, is concerned with REE extraction and purification that aims to meet the growing demands of modern society and encourages a vibrant economy whilst still safeguarding the environment (Sneddon et al., 2006). The Commission’s report and treaties since then have asserted that sustainable development is particularly vital within the sphere of natural resource initiatives, as commercial development for and within mining industries are inevitable in some respects (Stenmark, 2007; Jabareen, 2008). Initiatives should therefore focus on finding strategies to promote economic and social development in ways that avoid environmental degradation, over-exploitation, or pollution as well as side-line less productive debates about whether to prioritise development or the environment (Lélé, 1991; McCarthy & Prudham, 2004). Regarding the Alnö Complex, it is not only about considering present patterns of industrial and economic demand and supply indices, rather it is also about considering the site of the natural resources environmentally, and according to the site’s carrying capacity (Hopwood et al., 2005). Therefore, the fluctuation of boundaries between the private and public realm, global and local technology, demographic and development capital, the rural and urban individual — all colour the negotiations between natural resource conservation and natural resource mining for the modern landscape. When natural resources are concentrated in a particular region of a country, impacts that are both desired and difficult for that particular region begin to surface.

7.2.2 Natural Resources of the Alnö Complex: The Petrogenetic Connection

The turbulent undercurrents involved in the demarcation of the Alnö reserve, demonstrate the vulnerability of open access natural resources to over-exploitation. Traditionally, the approach to these resources has been to exploit and move on, as in agricultural communities in the tropical rainforests of South America, cattle herdsmen in North America, timber companies in central and northern Europe as well as mining companies in Africa and north-eastern Asia (Wagner & Wellmer, 2010). Increasingly, however, this is no longer an option. The environment cannot recover or is given insufficient time and space to do so, and there are fewer places to move on to. The nature reserve on Alnö Island has been established in order to preserve, or more succinctly, protect an integral part of the environment there. The carbonatites, in particular, are the natural resources within the Alnö Complex that are vulnerable to over-exploitation. Calciocarbonatites (sövites) from the Alnö Complex are

58 enriched with exceptionally high REE and light rare earth element (LREE) concentrations (Kresten, 1979). These carbonatites were previously exploited as fertiliser24 in the 1950’s and 1960’s; however the effort was terminated due to high radioactive element concentrations (e.g. uranium) that began to aggravate the incidence of agricultural ecotoxins (Rosén, 1994). The concentrations for heavy rare earth elements (HREEs) are less pronounced than those of the LREEs, however, all REEs reveal enriched concentrations, relative to sövites from an array of alkaline complexes throughout the world (Hode Vuorinen & Hålenius, 2005). The minerals that bear these remarkably high concentrations in the sövites are calcite, apatite, magnetite, titanite, pyrochlore, phlogopite, amphibole, melilite and olivine (Loubet et al., 1972; Hogarth, 1989). The Alnö Complex is also particularly rich in direct REE minerals, such as bastnäsite, monazite and zircon (Morogan & Lindblom, 1995). These are regarded as ‘economic minerals’ and are highly sought after in volcanic alkaline provinces (Evans, 1993). The high concentrations are generally attributed to the REE enriched nature of carbonatite and kimberlite magmas and to the intricate petrogenetic relationship shared between the sövites, melilite-rich silicate and nepheline carbonate rocks of the Alnö Complex (Kresten, 1980; von Maravic & Morteani, 1980; Andersen, 1987; Eriksson, 1989; Schleicher et al., 1990; Lupini et al., 1992; Mitchell, 2005). The REE and HREE distribution patterns for calcite from the sövites at the Alnö Complex are heterogeneous and are attributed to the sequence in which the calcite phases crystallise from the carbonatite-forming magma, however overall, the sövites have similar REE distribution patterns when compared with the other carbonate rocks from the complex (Möller et al., 1980). When calciocarbonatites and alkaline- silicate rocks share REE distribution patterns, as observed in the Alnö Complex, they are likely to share a common magmatic source and mode of formation (Kresten, 1986; Viladkar & Pawaskar, 1989; Lottermoser, 1990):

(a) The parental melt of the carbonatites and alkaline rocks is either (1) a carbonate liquid melt enriched with silicate minerals or (2) an alkali silicate liquid melt enriched with carbonate minerals (Möller et al., 1980). Carbonate would be present in both magmas due to the abundance of carbon within deep interiors of the mantle (Dasgupta & Hirschmann, 2010).

(b) One of the melts separated through liquid immiscibility and the REEs were then distributed between the two magmas (Hornig-Kjarsgaard, 1998). Although the REE distribution is in fact shared, the carbonatite liquid would hold a higher REE enrichment capacity, than the silicate liquid, resulting in the carbonatites having slightly higher REE concentrations, overall, than the associated alkaline and silicate rocks (Balashov & Pozharitskaya, 1968; Chakhmouradian & Zaitsev, 2012).

The magma in the above sequence is taken to be primarily mantle-derived, and is consistent with the stable isotope results presented in this study. This sequence provides evidence to the theory that when carbonatite melts evolve from an alkali-rich, carbonate silicate magma of mantle provenance that

24 Calcium carbonate (CaCO3) is an effective source for agricultural lime. 59 involves liquid immiscibility; there are definite implications for the origin of REE mineralisation (Möller et al., 1980; Lee & Wyllie, 1998; Moore et al., 2009). Moreover, the sequence validates that a working-knowledge of the kind of carbonatite-forming magma is vital for an assessment of minerals that could be economically relevant. Kimberlite magmas usually originate deep in the mantle too, and are the carriers of peridotitic xenoliths and xenocrystals such as garnets and diamonds (Wyllie & Huang, 1975; Sparks et al., 2007; Mitchell, 2008). These magmas bear remarkably high densities and in order to ascend from the mantle to the crust, volatile reactions between carbon dioxide (CO2) and water (H2O) need to occur to promote ascent (Sobolev & Chaussidon, 1996; Patterson et al., 2009).

Carbonatite magmas have a capacity to withhold substantial quantities of H2O without reducing their

CO2 concentration (Michael, 1988; Keppler, 2003; Dasgupta et al., 2007). When this distinctive capacity is complemented with the carbonatite magma being mantle-derived and primary they can mix with silicate mantle rocks to make kimberlite magma, which in turn has a remarkably high potential to ascend at relatively high speed from depth (Russell et al., 2012). von Eckermann (1961) asserts that the carbonatites intruded at the Alnö Complex, are associated with “olivine-melilititic and kimberlitic” magmas intruded into fissures. The carbonatites and kimberlites from the complex (the latter also known as ‘alnöite’) therefore, share a natural association with each other. We know that carbonatites bear a late intrusive age at the Alnö Complex, and from von Eckermann’s observation, the alnöites share this intrusive trait. The late occurrence of the carbonatites at the complex, together with a shallow magma chamber strengthens the inference of liquid immiscibility of kimberlite-type magmas to produce the Alnö carbonatites we see now at the surface (cf. Kresten, 1990; Andersson et al., 2013).

7.2.3 The Rare Earth Market

Seventeen metallic elements constitute the ‘rare earth elements (REEs)’ and they are an essential commodity for production in the mechanical, electronic, information technology, high-technology, green energy, medical and aerospace industries. The fifteen lanthanides along with scandium and yttrium are relatively abundant in the Earth’s crust; however they are often inaccessible (Rudnick & Gao, 2003). The highly specialised extraction and refinement techniques required, are what make these elements so ‘scarce’ (Gupta & Krishnamurthy, 2005). The rare earth metals are used among other things, in the development of electronic equipment and media, industrial and automotive engines and as an alloy substance in the steel industry (Wall, 2013). Furthermore, the nuclear properties of certain REEs are essential in harnessing the process of fission (Denschlag, 2011). Rare earth oxides (REOs) are important catalysts in petroleum refinement processes, such as crude oil conversion, and are vital components in the production of magnetic materials that tolerate high temperatures with resistant magnetic fields, such as those channelled through hard disk drives and electric motors (Chakhmouradian & Wall, 2012; Hatch, 2012a). Another noteworthy application area is in the

60 development of greener technologies for the future, where REOs have become an integral part of processes that engineer and develop, inter alia, wind and water turbines, automotive catalytic converters as well as hybrid and electric cars (Eliseeva & Bünzli, 2011; Alonso et al., 2012). This translates into providing and preserving renewable energy sources as alternatives to fossil fuels, which should be reduced globally and throughout Sweden (Jonsson et al., 2012). Moreover, the continuous development of technology is what ultimately drives the demand for REEs. For instance, the vibration unit in an iPhone consists of 0.25 grams of dysprosium (Hart, 2013). Multiplying this quantity several hundred thousand times over, would only begin to sketch the global demand curve for dysprosium as part of mobile phones. Furthermore, this is only one product, emerging from one industry. In the future, when your phone starts to ring, it will not have become impossible that a small piece of earth from Alnö will be vibrating in your pocket.

Arising from this increasing global demand, import and export trends have emerged as major foci of industrial activities throughout Sweden. The rare earth market relates to natural resource conservation as virtually all industrial and conservation issues are intimately linked to the dynamics of globalised and political economic processes (Naumov, 2008). Therefore, the fluctuations of REE import and export patterns carve the distinction between domestic and international spheres of activity. Many REEs were actually discovered in Sweden in the early nineteenth century; however Sweden has never sourced its own REEs on a large scale (Chakhmouradian & Wall, 2012). China has dominated the market with the leading REE mine in the world, Baiyun Obo, of Mongolia. Currently, China is experimenting with localising its REE distribution and has withdrawn, to a degree, from international REE provision in an approach that is connected to conforming to a more isolated political regime (WTO, 2012). The regime type is not dangerous; rather, it focuses on solving internal, narrow problems within China’s own borders. Conversely, China has developed a complex network of relationships with the international community and with Sweden in particular, regarding the interlinking of REE export-import and supply-demand indices (Chen, 2011).

More than 77% of the world’s rare earth production stems from Baiyun Obo whereas another 20% arises from other smaller mines in China, raising supply to 97% overall with a rising net worth that is currently in the region of four trillion pounds (Jones, 2010). The outlying 3% in supply originates from mines in Russia, Malaysia, India and Brazil (Lifton, 2013). Brazil currently indicates the highest potential for REEs among existent supplier countries at ±37% of supply, compared with China at ±19%, whose potential for the rare earth market has rapidly diminished as a result of excessive, and unsustainable mining practices (Topf, 2013a). China’s output quota for the mechanical, electronic and aerospace industries in 2013 is 46, 900 tonnes of REEs, whereas between 2011 and 2012 the quota had been approximately 93, 800 tonnes (Yuan, 2013). Therefore, rare earth mines are being opened in various parts of the world, following China’s export restrictions that are expected to remain steep for an upcoming seventy years (Ng, 2012). The vast mines of Mountain Pass in the United States, Mount

Weld and the Dubbo Alkaline Complex in Australia are expected to be at the helm of large scale rare earth mining production. Smaller reserves in Vietnam, Indonesia, Thailand, Mauritania, Burundi, Namibia, South Africa, Canada, Kyrgyzstan and Kazakhstan are also expected to raise their REE supply (Negishi, 2012; Topf, 2013b). However, these mines would still not be able to equal the Baiyun Obo Mine in terms of the rate of supply and efficiency costs involved in REE extraction, separation and refinement processes (Hatch, 2012b). Even if China did not impose quota restrictions, there would still be an imbalance in supply-demand indices, globally, with the demand for REEs significantly outweighing its supply (Bourzac, 2011).

Therefore, there is volatility developing in the rare earth market and the risk of converting the Alnö Complex into a resource reserve would be imminent in this regard. In order to reduce the fiscal burden that comes with outsourcing, Japan, more than any other country, has invested in stockpiling rare earth compounds, and in recycling REOs, believing that the approach could mitigate a forthcoming crisis for Japanese supply (Tabuchi, 2010). Closer to Swedish shores, industries are also considering REE mining projects in Greenland and in the expanse of seabed beneath the Arctic Ocean (Topf, 2013c). Geological explorations reveal a substantial number of rare earth reserves in this region, which could satisfy one quarter of global market demands for the next fifty years (Komnenic, 2013). However, the prospects for Greenland and the Arctic seabed are still in the process of reassuring environmental uncertainties. Similar concerns were raised regarding rare earths being dredged from the enriched seabed beneath the Pacific Ocean, whose potential supply is estimated at ±52% (Kato et al., 2011; Currie, 2013). Remarkably, the combined potential of the Greenland, Arctic and Pacific region’s reserves could fiercely topple China’s monopoly in the rare earth market (Komnenic, 2013). Such changes, however, will take time to fully review all the environmental, technical, financial and regulatory stages needed to establish these new mines.

Currently, as China withdraws from being the principal provider of raw-material bundles of REEs, alloys and REE-based compounds to Sweden by increasing tariffs and reducing supply quotas; and as the European Union (EU) emphasises internal sourcing of REEs in Europe through a directive on raw materials, political and economic pressures threaten to dilute barriers to entry, and raise market competition (EC, 2010; Moss et al., 2011; Jonsson et al., 2012). This, in turn, will ultimately shape the activities and expectations within Sweden, as well as all relevant actors in the international community that are concerned with their own rare earth production and consumption rates. It is vital that Sweden considers a similar approach to efforts already underway in Japan or concentrates its rare earth import investments, elsewhere. In addition, localising Swedish rare earth extraction and supply initiatives could prove to be a viable alternative, albeit one that would simultaneously place the Alnö Complex at a crossroads with its identity as a nature reserve and rural heritage site.

7.2.4 Sustain the Risk, to Develop the Opportunity

The kind of development we want, and how relationships between landscape, industry, privilege and power mature and shift in order to realise it, is a familiar narrative the world over. The Alnö Complex is a site that contextualises this narrative, and thus becomes a milieu within which sustainable development paradigms can be tested. Arising from the philosophical framework provided earlier, it is important to recognise that when environmental integrity functions as a critique of development, and does not banish it, we create a sphere, and moreover, a landscape where sustainability thrives (Jabareen, 2008; McPhail, 2010). This approach, that considers the development of verdant land as inevitable, also demands that sustainability should not become enmeshed in the actual environment and development that it critiques (Beddoe et al., 2009). Moreover, this breed of sustainability is created when environment and development have equal priority (Hopwood et al., 2005).

Historically, land that has been abundant in natural resources has, more often than not, been exposed to varying levels and types of development (Crowson, 2010). Therefore, there are dangers in isolating ‘the environment’ and ‘development’ from each other in the context of a diminishing supply, and an escalating demand for rare earths (McLellan et al., 2013). Separating ‘the environment’ from its ‘development’ would separate the Alnö nature reserve, comprised in part by the Alnö Complex, from the existent livelihoods of the Alnö locals. The vital issue here is that land and livelihood, are dependent upon each other for their survival. The Alnö nature reserve is in itself a symbol of bureaucratic development, and is a protected region only in so far, and up until it is deemed otherwise through the jurisdiction of environmental, commercial and civil laws of the state (Waye et al., 2010). Also, the privatisation and industrial acquisition of the land is considered to be a ruthless threat to the paper-thin veneer that protects the Alnö Complex (Swedish Heritage Archives, 2012). The defining attributes of the nature reserve that in turn, defends it as a rural heritage site are also dependent on the attitude and behaviour of the locals, who are compelled by law, to conserve their land.

Thus, there is a forthcoming risk that environmentally conscious behaviour will flounder if the Swedish government dissolves the heritage or ‘nature reserve’ designation of the island, arising from the Alnö Complex becoming a prosperous stronghold of rare earth supply in Sweden. Furthermore, the fishing and timber trades that are the existent local livelihoods on the island could take more advantage of the land and natural resources, if more of it were made available. As livelihoods contend with each other for more land, the land has to contend with the impacts of these existent livelihoods together with the prospect of REE mining becoming a future livelihood on the island. Therefore, the idea of ‘development of the Alnö Complex’ is incumbent, and it fulfils placing an equal emphasis on nourishing both land and livelihood for all stakeholders. In the following section, the development of the Alnö Complex is mapped according to methods that relate to REE mining. Analysing these

63 methods according to sustainability indicators is a tool that configures, and moreover, narrows potential scenarios for the Alnö environment (Wagner & Wellmer, 2010). The extent, to which sustainable development can take place in each scenario, is expected to surface. The indicators ultimately create an impression of a fragile, temperate or resilient environment for the scenarios that follow. Herein, a measure of resilience is created when the sustainability indicators are able to resolve each other (Bengtsson et al., 2003). The focus here is on the environmental aspects of mining — the kind of risks and recovery involved — and the relationship between these and other socio-economic considerations. The set of indicators chosen for the Alnö case study are:

(a) The risk to the surrounding Alnö environment and existent livelihoods, and

(b) The opportunity for the surrounding Alnö environment and existent livelihoods.

In the first scenario, the development of a rare earth mine at the Alnö Complex accommodates all the critical stages in the life-cycle of an REE. The stages range from exploration through to production, and exclude trade and consumption. The mine would have an open-cast structure that involves the drilling, blasting and hauling of the carbonatites. Within an on-site refinement plant, mineral concentrates are separated from ancillary rock material, and REE ore is retrieved. Some minerals require concentration through froth flotation, whereas others, depending on whether they are light or heavy minerals, require concentration through gravity separation with high-intensity magnetic and electrostatic techniques (Liu & Bongaerts, 2013). The rare earth ore is extracted from the mineral concentrate in multi-layered chemical processes that involve mineral roasting, leaching and the solution of solvents, dependent on the kind of mineral and the quantity of the mineral concentrate (Peiró & Méndez, 2013). The rare earth ore is further isolated or refined in supplementary chemical processes that remove impurities, generating individual REEs or REOs that are then prepared and packaged for industrial trade (Peiró & Méndez, 2013).

The extraction and processing of the carbonatites would require vast amounts of energy, and if the energy is derived from fossil fuels, there will be an increase of gas emissions into the Alnö environment. However, if the timber plantations remain on the island, their natural capture and storage capacities will buffer the risk of increased emissions. Yet, the timber trade, as a livelihood on the island will suffer if this counter-measure is implemented. Remediation for the loss of this livelihood will depend on the mining corporation at the helm of development in the Alnö Complex. An investment into the preservation of the timber plantations, and the provision of income security through the absorption and employment of timber trade workers, will prove to be the critical opportunities. It is important to note that the impact of potential REE mining could be relative or even negligible compared with the current activities and impacts of the forestry trade, such as the noise pollution from the felling and transportation stages of the logs, and all threats tied to deforestation (Parsons, 2011). There will come a time when REE mining comes to a halt, and the timber trade could

64 resume within this time. In this way, the timber trade will not completely collapse and a fluctuation between livelihoods at different intervals will allow for environmental recovery, in and around the Alnö Complex.

Rare earth ores are also very different to each other, despite originating from the same complex (Wall et al., 1997). Strikingly, this is tied to the immiscibility that occurs in a carbonatite magma that fractionates HREEs and LREEs from each other, thus enriching each mineral with a custom made blend (Chakhmouradian & Zaitsev, 2012). Naturally, ores will be extensively tested in order for extraction, processing and refinement to occur at an optimal level; however, chemical refinement processes will still vary according to the extracted ore, raising the intensity at which chemicals, water and energy is consumed and pollutants are released (Ayres & Peiró, 2013). These extensive processes could affect the water table in the Alnö Complex, and a diminished water supply for the local communities is a definite risk. Furthermore, agricultural livelihoods are often as dependent, and just as demanding of natural resources (air, land and water) as mining initiatives (Parsons, 2011). Currently the timber, agricultural and fishing industries on the island and in surrounding districts have divided the use of water in a way that each industry bears the full costs of any unsustainable practices, and each have the ability to control how the water is managed (Swedish Heritage Archives, 2012). The opportunity, here, is for the mining establishment to enter the ring, create allegiance with the existent livelihoods by contributing its share of the costs and where possible, avoid depending on the region’s ground-water or natural aquifers for rare earth processing and refinement. Improving water supply for the Alnö Complex from alternate and secondary sources, such as the surrounding lakes and rivers could safeguard the current water consumption of the Alnö locals, and their livelihoods.

However, in the refinement stage, when minerals are roasted or ‘cracked’ with either acid or alkali, and chemical precipitation or evaporation occurs with hot solutions, there is an accumulation of residue that is cleaned with water (Liu & Bongaerts, 2013). Uranium (U) and thorium (Th) in REE- bearing minerals are radioactive and this is imparted to water during refinement (Padmanabhan, 2002). Water from these processes is ultimately released as outflow from the treatment chambers, rendering water in the surrounding lake and river environments to the Alnö Complex as vulnerable to this chemical contamination. This is where environmental regulation comes into place, and as such, water recycling projects will become the responsibility of industries involved in Alnö’s development (Hudson-Edwards et al., 2011). Introducing advanced water reclamation technologies, such as separating the noxious chemicals from water through saponification; retaining water used in leaching through impoundment dams; recording the quality of ground-water through monitoring wells or storing radioactive waste through contained paste-tails, is an opportunity to strengthen refinement processes and alleviate contamination (Lottermoser, 2010; Feng et al., 2012; Gautam et al., 2012). However, the threat to water environments persists as a double-edged risk to the livelihood of local fisherman and farmers. As radioactive waste leaks into the water and affects water quality and the

65 occurrence of fish; the purification methods required to reclaim the water will also disrupt any attempts at fishing or land irrigation.

In the second scenario, the development of the REE mine accommodates only the exploration and extraction stage. The mine would have an open-cast, quarry structure that involves the drilling, blasting and hauling of the carbonatites that are transported away from the complex to a refinery plant. Unfortunately, the extraction stage in any open-cast mine utilises heavy industrial methods that come attached to high levels of noise and air pollution. Yet, with established trades in agriculture and forestry, the Alnö environment is not a tranquil one, in absolute terms. The mining corporation could mitigate noise pollution through planting a thicket of trees around the site to absorb the din, and air pollution through lightweight clusters of natural fibre or ‘suction shells’ that would be strategically placed around the Alnö Complex, in line with recent practices in Brazil, the UAE and Russia (Csavina et al., 2012).

Notably, the quality of water within and around the Alnö Complex will be well preserved in the absence of processing and refinement. In the event that ground-water is at risk during the extraction phase, mine workers are likely to seal the contact point between the quarry pit and the ground-water with waterproof clay, synthetic liners or barriers (Anandan et al., 2010). Still, any remaining fragments of rock that are typically affected by natural erosion are alkaline, and will therefore, not threaten any surrounding water environments. In contrast, the upheaval of land through extraction is a risk to the natural ground-water and surface-water flow, in and around the Alnö Complex. With this in mind, there is an opportunity for quarry plans to include the sampling of surface water and the construction of meters for monitoring wells in the ground, before the extraction phase occurs (Huang et al., 2010). As carbonatites will need to be transported to refineries, there will be an increase in heavy-vehicle traffic through lorries, to and from the Alnö Complex. Nonetheless, risking the durability of roads and bridges comes hand-in-hand with the opportunity to strengthen current infrastructure. Also, replacing the lorries with a cargo train-line will simultaneously mitigate pollution from exhaust fumes and reduce traffic altogether. Locals that oppose this train-line to Alnö could be appeased with the construction of a second train-line that caters solely to their needs. Also, the construction of a harbour from which the carbonatites would be transported as sea cargo, is another alternative that has the potential to expand trade and industry on the island.

The emergence of a quarry will raise concerns for the potential loss of ecological units that are rooted in the Alnö Complex. Employing an ecologist and fieldworkers to relocate the fragile habitats and species before creating the open-cast structure of the quarry, will allow the mining establishment to remain sensitive to issues of ecosystem loss. Over time, the threatened ecological unit builds an adaptive capacity that creates an adaptive and resilient surrounding environment (Folke et al., 2002). Moreover, once extraction in the quarry has been completed, the Alnö Complex will naturally recover

66 and restore its land, over time. Creating a ‘lake pit’ by landscaping and filling the hollow quarry with water is a way to strengthen this recovery because it replenishes the scarified land, improves the visual topography and kindles the growth of plant and animal life (Schultze et al., 2010; McCullough & van Etten, 2011). Development at the Alnö Complex is likely to adhere to such a recovery practice, as it will encourage and safeguard future REE deposits. Contemporary scholars recommend the practice of in-situ25 leaching of carbonatites with solvents, followed by the application of bacterial and microbiological methods (bio-leaching) in order for the rare earth ions to surface from the host mineral and ancillary rock material (Ibrahim & El-Sheikh, 2011). The retrieval of copper (Cu), gold (Au), zinc (Zn) and uranium (U) has become increasingly dependent on bio-leaching methods in recent times, and this has provoked experimentation with REE ores. Although there is a high recovery rate of rare earth ions (~ 92%), and bio-leaching would alleviate the deep scars on the Alnö Complex caused by quarrying and deep excavation — long periods of time are needed for ion recovery to occur, rendering the process as inefficient in the aspect of scarcities within highly-skilled and rapid supply quotas (Nakamura & Sato, 2011; Dodson et al., 2012). Furthermore, research is still articulating purification methods that correlate with bio-leaching, particularly because of the radioactive elements in carbonatites. Ensuring that indigenous bacteria is introduced, so as not to harm the surrounding environment will remain an important challenge if this method is considered for the Alnö Complex (Ibrahim & El-Sheikh, 2011).

It is difficult to gauge if the tourism trade on the island will survive in the context of development, according to the individual scenarios. The volcanic story of Alnö seems to be a drawcard for tourists, apparent in the local brochures from the rural museum and guest cottages (Swedish Heritage Archives, 2012). Any developmental model for the Alnö Complex will ignite infrastructural and economic development, with businesses, restaurants, centres for recreation, homes and hotels built to accommodate the increase in population and activity. The Alnö Complex could also become a site for excursion opportunities that teaches school learners, and deepens their insight into mining in the natural environment. Internship or apprenticeship opportunities for university students and graduates with the mining establishment, could also contribute to stabilising the tourism trade on the island. However, there could also be an exodus of locals from Alnö, in the wake of such upheaval and transformation. The risk, here is that the bonds of community, culture and tradition will be weakened. A way of negotiating the loss of culture and heritage is to remain critical of the idea that we often buy support through promising material advantage to a local population. It should never be assumed that objectives and priorities held within the mining industry are shared by all on a grassroots level. Alnö’s rural heritage or culture is something that is tangible, and it is inherent and embedded in the livelihoods and identities of people who live on the island. It is true, that people will take their trades

25 In-situ leaching or recovery describes the mining technique of injecting solvents underground (at the original site) to dissolve an ore and bring the REE-saturated liquid to the surface for extraction. 67 and culture with them, wherever they go, however, landscapes and waterscapes can also come to symbolise and reflect the culture and heritage of the people that are a part of it (Mels, 1999). The extent to which REE mining alters the Alnö environment is the extent to which bonds of heritage and culture will be destroyed. Sustainable development at the Alnö Complex, that grasps the applied indicators, and involves an ethical extraction and refinement of carbonatites (Scenario 1), is likely to create a temperate environment that is neither completely fragile, nor completely resilient. This is in view of water reclamation issues that still remain uncertain for the dependent agricultural and fishing livelihoods at Alnö. Quarrying (Scenario 2), with its limited impacts on the Alnö locals and livelihoods, is likely to cultivate resilience and is therefore, the preferred approach in the context of this discussion. In each scenario, however, the degree of sustainability has the dual capacity to become weaker if the mining establishment overlooks the indicators, and stronger if the indicators are used to navigate a plateau where environmental vulnerability is protected by developmental foresight. The critical moment for the Alnö Complex is closer than we think, and in its horizon — the idea that there can be a positive result within a wisely handled risk — is on the rise.

7.2.5 Conclusion

The idyllic vision for this rural landscape in years to come is that its environmental and cultural heritage will still be there and would have survived the pressures that continuously threaten to dissolve it. Yet, idealism is not going to sate the increasing demands for iDevices and high-technology appliances, nor will it galvanise breakthroughs in green energy or nuclear medicine. Rare earths are scarce in the sense that there are no known substitutes for them in their current functional uses. The search for hidden ore deposits with a growing trend of recycling for recovery, symbolise the growing volatility in the rare earth market. Although quarrying is the preferred development model for the Alnö Complex, it covers only one-third of a REE’s life-cycle. Herein, the heritage of locals, livelihoods and the Alnö environment will be preserved at the expense of outsourcing refinement, and dissolving a parallel heritage, elsewhere.

International refineries are a viable opportunity for any country that needs to invest outside of its borders to maintain stability, whilst still growing at home. Whether or not, the refinement of rare earth ores occurs beyond Swedish borders, a commitment to better refinement practices that protects both industry and the environment, should remain a priority. Typically, there will be considerable uncertainty about the problems, impacts and effective responses to REE mining in the Alnö Complex, up until the time that it actually occurs. With each risk involved, comes the opportunity to pioneer mining in a way that re-invigorates industry, labour and the environment. And, Sweden has more than just natural resources at the Alnö Complex, it has expertise.

8. Summary and Conclusions

In a petrogenetic narrative on carbonatites, changes in the mantle ultimately determined the rate of production of the carbonatite-forming magma at Alnö, but were modified by fluids, silicate minerals, and sedimentary country rock. The research findings resolve that the calciocarbonatites, nepheline- syenites and ijolites at the Alnö Complex were formed dominantly by magmatic processes, which includes the prospect that they stem from a carbonate-silicate parent magma that bears similarity with the natrocarbonatite magma of Oldoinyo Lengai, in Tanzania. In particular, stable isotope systematics (δ18O and δ13C) have been able to distinguish the mantle-derived carbonatites, and variations in the data are attributed to mainly silicate and sedimentary assimilation. The obtained results and interpretations, therefore, lend support to the ‘magmatic school of thought’ regarding the origin of carbonatites. Moreover, the vein in an Alnö paragneiss (country rock) reveals the possible interaction between high-temperature carbonate enriched magmatic fluids and crustal fluids that were mobilised, likely during magmatic emplacement. The similarity of the Alnö data with data from comparative alkaline volcanic provinces further strengthens the inference of a magmatic origin for the Alnö carbonatites, and hints at liquid immiscibility being an overarching process involved in carbonatite formation. Furthermore, the presented data relate the alkaline silicate rocks and carbonatites in the Alnö Complex to each other, which explains the variety of carbonatite type rocks that was ultimately formed.

Arising from its unique petrology and mineralogy, the Alnö Complex is a site where some of the most pressing challenges to sustainable development will be concentrated. The enriched rare earth element (REE) concentrations in the native carbonatites, along with the likelihood of shared connections between the carbonatite and kimberlite magmas raise the possibility of resource extraction and refinement taking place at the complex. However, this rural landscape is also a site where natural resource related opportunities can thrive. There are numerous instruments that test sustainable development, and the interpretations in this study are rooted in applying sustainability indicators in a tailored, context-specific way. Leveraging the incumbent risks with socio-economic opportunities requires placing equal emphasis on the environment and on development. The establishment of a quarry at the Alnö Complex is proposed as a multitrack approach that could balance the demands across economic, industrial, social and environmental spheres. The approach relates to the idea that the combined use of foresight and flexibility will better connect a prospective mining establishment to the Alnö locals and the existent livelihoods on the island. Notably, the approach asserts that a smart method, founded on technical expertise and sustainable, integrated thinking paves the way for a breed of development that responds effectively to the capacity of its surrounding environment.

9. Acknowledgements

The application for a Master’s Degree in Earth Science at Uppsala University had been inspired by a dream to cultivate experience, withstand independence, glow with wellbeing and strengthen the intellect. A scholarship was the only way I could reach this dream and it has been a vital element of a journey that has emboldened me to create, invigorate and reimagine the parameters of my work in science.

I know that knowledge is transformative. The experiences in the past three years at Uppsala University have been the landmark years in my young life. I am therefore humbled at the opportunity to acknowledge those who have shaped and coloured my world throughout this time. I firstly acknowledge the Faculty of Science and Technology and Department of Earth Sciences. It has been a privilege to uphold the 2011-2013 scholarship, and I am grateful, beyond measure, for the provision of academic resources and research instruments. I am honoured to have become a part of the deep tapestry that characterises your knowledge, research, academic traditions and vibrant student culture. I am particularly grateful to Cecilia Marklund of the Student Affairs and Academic Registry Division for her direction, and for coordinating all of the paper trails relating to my studies and scholarship.

I am deeply grateful to Professor Valentin Troll, whose collaborative strengths have propelled me to the helm of this research project. Sir, I humbly acknowledge your provision of this project as a whole: the samples, equipment, instruments, archival papers, current literature, and networks to other research or researchers, detailed insights and for the exposure to your in-depth knowledge, hands-on approach, pioneering ideas and brave-heart philosophies. I appreciate your detailed approach to every layer of the research, your constant consideration for my scientific understanding, and for persevering with me when I often lost my way throughout the writing phase, particularly in the final chapters. I take strength from the courage and wisdom that you radiate. Reflecting on the journey of the past one and a half years, I hope that the discoveries and thoughts expressed in this work will become a memoir of what has truly been an organic and inspirational time.

I humbly acknowledge Assistant Professor Abigail Barker, for the provision of her time and for the knowledge and skill imparted throughout the EMPA analysis. I appreciate your review of my dissertation, for your ability to trouble-shoot the difficult issues with me, and your thorough explanations that harnessed clarity in my observations.

Some of the CEMPEG researchers whose friendship and contributions to this work, whether through light-hearted conversation or otherwise, is appreciated. I am deeply grateful to Ester Muñoz Jolis for her reassurance and vibrant, detailed explanations throughout the methodology chapters. Peter Dahlin, I am grateful for all that you have taught me with the CEMPEG microscopes; for strengthening an

70 extinct mineral vocabulary, and for the enlightening conversations on the history of Alnö. I am also deeply grateful to Börje Dahrén, Iwona Klonowska and Franz Weis. I wish to acknowledge Elisabeth Almgren, Marzena Kohut, Leif Nilsson, Frances Deegan, Steffi Burchardt, Fredrik Sahlström, Michael Krumbholz, Kirsten Pedroza, Professor Hans Annersten, Karin Högdahl, the Swedish Heritage Archives and the Alnö Rural Museum.

Professor Erik Haëlhalsson, and all the elders of The European Science Foundation (ESF), the League of European Research Universities (LERU), the Golden Wreath Fellowship of the University of Bonn and the Ehli Pærs Medal Committee. Thank you for your recognition of the pilot projects I completed in the early parts of my Master’s year. Remarkably, it had been in the Earth and Life Sciences Library of the University of Bonn that I had the initial exposure to some of the research of Professor Troll. I am grateful to my coursework lecturer, Professor Veijo Pohjola for his wisdom and for safeguarding my precarious transition into solid earth geology. I also acknowledge Agnes Soto for her guidance and reassurance, and Carmen Vega Riquelme for mapping an approach (and understanding) of isotopes that are not embedded in water. I am grateful to you both, for your belief in me. I am also grateful to Malte Junge, who without urging me to take on the internship at CEMPEG, I can’t be sure of what would have happened to me. With hindsight, I can’t imagine not breaking the rules, not having the project that I had, and to not be surrounded by the people I’ve grown to know and respect. I wish to acknowledge Stella Karavazaki for reviewing my dissertation and for her recommendations. At the University of Cape Town, I wish to acknowledge those who have been an integral part of my academic growth. At the Department of Geology, Professor Chris Harris, and at the Department of Environmental & Geographical Science, Professor(s) Maano Ramutsindela, Sophie Oldfield and Michael Meadows. And, Professor Bernhard Weiss of the Department of Philosophy, who cultivated my awakening to science and mathematics as epistemology, and who was able to unite my majors in philosophy, poetry and earth science. I hope that I will continue to honour all that you have instilled in me.

I am grateful to my close friends both old and new, for their warmth and for the side splitting times that I will always treasure. I humbly acknowledge my grandparents, and the legacy of hard work and humility that they leave behind. Thank you Nani, Nana, Aaji and Aaja for being my inspiration. I am grateful to uTata Madiba and his contemporaries for bringing freedom to light in my country, who through their unconquerable vision and courage, I will continue to rise. I am deeply grateful to my Mother, for raising me to become the woman I am; for her sacrifice, resilience and unparalleled love. Thank you, Mama, with a deep pocketful of love from my heart, for being the backbone of my accomplishments thus far. Even though I had been far away, the long and turbulent journey that we had survived, gave me the strength to reach higher, and higher. I am grateful to Avania, who renders me the privilege of sisterhood and who infuses my world with her happy spirit and silent strength. With love, I thank you for your beautiful heart and sacrifices so that I could chase my dreams.

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11. Appendix

11.1 Appendix A Archival Sample List of Carbonatites from the Alnö Complex (Chapter 3) Alnö Fieldwork 1945-1946 / Professor(s) H. von Eckermann; B. Collini (Uppsala University)

*Laboratory Archival Rock Type Swedish English Locality Comment Number Sample Number 200 m WSW 6-30/9/1945, A1 - Pyrochlore in Sövite Pyroklor i Sövit Pyrochlore in Sövite Stavsätt Exk. Magmatic Limestone / 6-30/9/1945, A2 I:26 Magmatic Limestone / Aegirine Ägririnringit - Aegirine Exk. Fluidal Agirinringit i nefelinsyenit / Fluidic Aegirine in Nepheline 6-30/9/1945, A3 I:36 - - Kalksteen fluidal Syenite / Lime Stone fluidic Exk. 6-30/9/1945, A4 9/II - - - - Exk. 6-30/9/1945, A5 Sk-10 Ijolite Ijolit Ijolite - Exk. 6-30/9/1945, A6 I: 35 Biotite in Sövite Biotit i Sovit Biotite in Sövite - Exk. Nepheline Pegmatite/ = Nepheline Pegmatite/ = Hallalite Nefelinpegmatit/ = Hallalitpegmatit 6-30/9/1945, A7 I:30 Hallalite Pegmatite next to - Pegmatite next to Lime Stone gräns met Kalksten Exk. Lime Stone 6-30/9/1945, A8 Sy 28 Nepheline Syenite Eleolitsyenit Nefelinsyenit Nepheline Syenite - Exk. Lime Pegmatite / = Sövite Lime Pegmatite / = Sövite 6-30/9/1945, A9 I:29 Kalkpegmatit / = Sövitpegmatit - Pegmatite Pegmatite Exk. Pyroxene-Nepheline- 6-30/9/1945, A10 I:25 Pyroxene-Nepheline-Limestone Uritkäsenit Pyroxen-Nefelin- Kalksten - Limestone Exk. Olivine-Mica-Knopite Pegmatitic Olivin,Glimmer,Knopitmn; Pegmatitsk Olivine, Mica, Pegmatitic 6-30/9/1945, A11 I:32 - Limestone Kalksten, -Knopitkåsenit Limestone Exk. Pegmatite (Nephenline-Syenitic Ringitpegmatit (Nefelinsyenitsk Pegmatite (Nepheline-Syenitic 6-30/9/1945, A12 Sk.8 I:28 - Limestone Pegmatite) Kalkstenspegmatit) Limestone Pegmatite) Exk. 6-30/9/1945, A13 I:38 Titanite in Limestone Titanit i Kalksten Titanite in Limestone - Exk. A14 - Stavre Migmatiten Block 2 - Migmatite - 1946, Exk. *The laboratory number is a collation from the Department of Earth Sciences, Solid Earth Geology (CEMPEG), Uppsala University 2012-2013 (Prof. Troll)

Molecular Weights

Ca 40.1 11.2 Appendix B O 16 C 12

Electron Microprobe Raw and Normalised Data for Carbonatites from the Alnö Complex (Chapter 6.2) CaO 56.1 CaCO3 100.1 Sample A1 CO2 44 - CO3 60 Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0.0012 102 0.000 2 2.35294E-05 0.00002218 0.00

SiO2 0 60 0.000 1 0 0.00000000 0.00

Na2O 0.0037 62 0.000 2 0.000119355 0.00011249 0.01

MgO 0.1606 40 0.004 1 0.004015 0.00378406 0.38

MnO 0.4135 71 0.006 1 0.005823944 0.00548895 0.55

K2O 0 94 0.000 2 0 0.00000000 0.00

CaO 58.8 56 1.050 1 1.05 0.98960362 99.06

TiO2 0 80 0.000 1 0 0.00000000 0.00

Cr2O3 0.007 152 0.000 2 9.21053E-05 0.00008681 0.01

FeO 0.0689 72 0.001 1 0.000956944 0.00090190 0.09

Total 59.4549 - 1.061 - 1.061030878 1.00E+00 100.1

Sample A2

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0.01 102 0.000 2 0.000196078 0.00018342 0.02

SiO2 0.015 60 0.000 1 0.00025 0.00023386 0.02

Na2O 0.031 62 0.001 2 0.001 0.00093544 0.09

MgO 0.189 40 0.005 1 0.004725 0.00441997 0.44

MnO 0.077 71 0.001 1 0.001084507 0.00101450 0.10

K2O 0.032 94 0.000 2 0.000680851 0.00063690 0.06

CaO 59.28 56 1.059 1 1.058571429 0.99023388 99.12

TiO2 0 80 0.000 1 0 0.00000000 0.00

Cr2O3 0.014 152 0.000 2 0.000184211 0.00017232 0.02

FeO 0.167 72 0.002 1 0.002319444 0.00216971 0.22

Total 59.815 - 1.068 - 1.06901152 1.00E+00 100.1

Sample A3

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0.015 102 0.000 2 0.000294118 0.00028796 0.03

SiO2 0.031 60 0.001 1 0.000516667 0.00050585 0.05

Na2O 0.102 62 0.002 2 0.003290323 0.00322143 0.32

MgO 0.07 40 0.002 1 0.00175 0.00171336 0.17

MnO 0.0129 71 0.000 1 0.00018169 0.00017789 0.02

K2O 0.05 94 0.001 2 0.00106383 0.00104156 0.10

CaO 56.65 56 1.012 1 1.011607143 0.99042752 99.14

TiO2 0.08 80 0.001 1 0.001 0.00097906 0.10

Cr2O3 0 152 0.000 2 0 0.00000000 0.00

FeO 0.121 72 0.002 1 0.001680556 0.00164537 0.16

Total 57.1319 - 1.019 - 1.021384325 1.00E+00 100.1

Sample A4

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0.024 102 0.000 2 0.000470588 0.00053374 0.05

SiO2 0.225 60 0.004 1 0.00375 0.00425322 0.43

Na2O 0.026 62 0.000 2 0.00083871 0.00095126 0.10

MgO 0.048 40 0.001 1 0.0012 0.00136103 0.14

MnO 0.045 71 0.001 1 0.000633803 0.00071885 0.07

K2O 0.016 94 0.000 2 0.000340426 0.00038611 0.04

CaO 48.9 56 0.873 1 0.873214286 0.99039379 99.14

TiO2 0 80 0.000 1 0 0.00000000 0.00

Cr2O3 0 152 0.000 2 0 0.00000000 0.00

FeO 0.089 72 0.001 1 0.001236111 0.00140199 0.14

Total 49.374 - 0.881 - 0.881683923 1.00E+00 100.1

Sample A5

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0 102 0.000 2 0 0.00000000 0.00

SiO2 0.2226 60 0.004 1 0.00371 0.00378589 0.38

Na2O 0.0727 62 0.001 2 0.002345161 0.00239313 0.24

MgO 0.0082 40 0.000 1 0.000205 0.00020919 0.02

MnO 0 71 0.000 1 0 0.00000000 0.00

K2O 0.0066 94 0.000 2 0.000140426 0.00014330 0.01

CaO 54.42 56 0.972 1 0.971785714 0.99166440 99.27

TiO2 0.0491 80 0.001 1 0.00061375 0.00062630 0.06

Cr2O3 0 152 0.000 2 0 0.00000000 0.00

FeO 0.0831 72 0.001 1 0.001154167 0.00117778 0.12

Total 54.8623 - 0.979 - 0.979954218 1.00E+00 100.1

Sample A6

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0.02 102 0.000 2 0.000392157 0.00036943 0.04

SiO2 0 60 0.000 1 0 0.00000000 0.00

Na2O 0.0169 62 0.000 2 0.000545161 0.00051357 0.05

MgO 0.0815 40 0.002 1 0.0020375 0.00191942 0.19

MnO 0.1894 71 0.003 1 0.002667606 0.00251301 0.25

K2O 0.0008 94 0.000 2 1.70213E-05 0.00001603 0.00

CaO 58.99 56 1.053 1 1.053392857 0.99234613 99.33

TiO2 0 80 0.000 1 0 0.00000000 0.00

Cr2O3 0.0076 152 0.000 2 0.0001 0.00009420 0.01

FeO 0.1703 72 0.002 1 0.002365278 0.00222820 0.22

Total 59.4765 - 1.061 - 1.06151758 1.00E+00 100.1

Sample A7

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0.005 102 0.000 2 9.80392E-05 0.00008915 0.01

SiO2 0 60 0.000 1 0 0.00000000 0.00

Na2O 0.0479 62 0.001 2 0.001545161 0.00140501 0.14

MgO 0 40 0.000 1 0 0.00000000 0.00

MnO 0.1289 71 0.002 1 0.001815493 0.00165082 0.17

K2O 0.013 94 0.000 2 0.000276596 0.00025151 0.03

CaO 61.33 56 1.095 1 1.095178571 0.99583946 99.68

TiO2 0 80 0.000 1 0 0.00000000 0.00

Cr2O3 0 152 0.000 2 0 0.00000000 0.00

FeO 0.0605 72 0.001 1 0.000840278 0.00076406 0.08

Total 61.5853 - 1.099 - 1.099754138 1.00E+00 100.1

Sample A8

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0 102 0.000 2 0 0.00000000 0.00

SiO2 0 60 0.000 1 0 0.00000000 0.00

Na2O 0.0443 62 0.001 2 0.001429032 0.00136217 0.14

MgO 0.0196 40 0.000 1 0.00049 0.00046707 0.05

MnO 0.1018 71 0.001 1 0.001433803 0.00136671 0.14

K2O 0.004 94 0.000 2 8.51064E-05 0.00008112 0.01

CaO 58.48 56 1.044 1 1.044285714 0.99542285 99.64

TiO2 0 80 0.000 1 0 0.00000000 0.00

Cr2O3 0 152 0.000 2 0 0.00000000 0.00

FeO 0.0982 72 0.001 1 0.001363889 0.00130007 0.13

Total 58.7479 - 1.048 - 1.049087545 1.00E+00 100.1

Sample A9

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0.0093 102 0.000 2 0.000182353 0.00017930 0.02

SiO2 0 60 0.000 1 0 0.00000000 0.00

Na2O 0.0111 62 0.000 2 0.000358065 0.00035206 0.04

MgO 0.1044 40 0.003 1 0.00261 0.00256624 0.26

MnO 0.1049 71 0.001 1 0.001477465 0.00145269 0.15

K2O 0 94 0.000 2 0 0.00000000 0.00

CaO 56.56 56 1.010 1 1.01 0.99306497 99.41

TiO2 0.0097 80 0.000 1 0.00012125 0.00011922 0.01

Cr2O3 0 152 0.000 2 0 0.00000000 0.00

FeO 0.1659 72 0.002 1 0.002304167 0.00226553 0.23

Total 56.9653 - 1.017 - 1.017053299 1.00E+00 100.1

Sample A10

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0 102 0.000 2 0 0.00000000 0.00

SiO2 0 60 0.000 1 0 0.00000000 0.00

Na2O 0 62 0.000 2 0 0.00000000 0.00

MgO 0.0447 40 0.001 1 0.0011175 0.00109820 0.11

MnO 0.2257 71 0.003 1 0.003178873 0.00312398 0.31

K2O 0.0044 94 0.000 2 9.3617E-05 0.00009200 0.01

CaO 56.61 56 1.011 1 1.010892857 0.99343603 99.44

TiO2 0.003 80 0.000 1 0.0000375 0.00003685 0.00

Cr2O3 0.007 152 0.000 2 9.21053E-05 0.00009051 0.01

FeO 0.1555 72 0.002 1 0.002159722 0.00212243 0.21

Total 57.0503 - 1.017 - 1.017572175 1.00E+00 100.1

Sample A11

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0.0273 102 0.000 2 0.000535294 0.00055963 0.06

SiO2 0.0004 60 0.000 1 6.66667E-06 0.00000697 0.00

Na2O 0.016 62 0.000 2 0.000516129 0.00053959 0.05

MgO 0 40 0.000 1 0 0.00000000 0.00

MnO 0 71 0.000 1 0 0.00000000 0.00

K2O 0 94 0.000 2 0 0.00000000 0.00

CaO 53.45 56 0.954 1 0.954464286 0.99785461 99.89

TiO2 0.0161 80 0.000 1 0.00020125 0.00021040 0.02

Cr2O3 0.0137 152 0.000 2 0.000180263 0.00018846 0.02

FeO 0.0441 72 0.001 1 0.0006125 0.00064034 0.06

Total 53.5676 - 0.956 - 0.956516389 1.00E+00 100.1

Sample A12

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0 102 0.000 2 0 0.00000000 0.00

SiO2 0 60 0.000 1 0 0.00000000 0.00

Na2O 0 62 0.000 2 0 0.00000000 0.00

MgO 0.0097 40 0.000 1 0.0002425 0.00023603 0.02

MnO 0.2292 71 0.003 1 0.003228169 0.00314198 0.31

K2O 0 94 0.000 2 0 0.00000000 0.00

CaO 57.28 56 1.023 1 1.022857143 0.99554866 99.65

TiO2 0 80 0.000 1 0 0.00000000 0.00

Cr2O3 0 152 0.000 2 0 0.00000000 0.00

FeO 0.0794 72 0.001 1 0.001102778 0.00107334 0.11

Total 57.5983 - 1.027 - 1.02743059 1.00E+00 100.1

Sample A13

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0.0165 102 0.000 2 0.000323529 0.00030669 0.03

SiO2 0 60 0.000 1 0 0.00000000 0.00

Na2O 0.0631 62 0.001 2 0.002035484 0.00192953 0.19

MgO 0.0287 40 0.001 1 0.0007175 0.00068015 0.07

MnO 0.0378 71 0.001 1 0.000532394 0.00050468 0.05

K2O 0.001 94 0.000 2 2.12766E-05 0.00002017 0.00

CaO 58.76 56 1.049 1 1.049285714 0.99466815 99.57

TiO2 0 80 0.000 1 0 0.00000000 0.00

Cr2O3 0 152 0.000 2 0 0.00000000 0.00

FeO 0.1436 72 0.002 1 0.001994444 0.00189063 0.19

Total 59.0507 - 1.054 - 1.054910343 1.00E+00 100.1

Sample A14

Element EMPA Retrieved Mass % GFW (Molecular Weight) Mol. Units Cations Proportion of Cations Normalised Normalised (Decimal)

Al2O3 0 102 0.000 2 0 0.00000000 0.00

SiO2 0.0023 60 0.000 1 3.83333E-05 0.00003518 0.00

Na2O 0 62 0.000 2 0 0.00000000 0.00

MgO 0.0134 40 0.000 1 0.000335 0.00030745 0.03

MnO 0.2151 71 0.003 1 0.003029577 0.00278041 0.28

K2O 0.0161 94 0.000 2 0.000342553 0.00031438 0.03

CaO 60.68 56 1.084 1 1.083571429 0.99445175 99.54

TiO2 0 80 0.000 1 0 0.00000000 0.00

Cr2O3 0 152 0.000 2 0 0.00000000 0.00

FeO 0.1656 72 0.002 1 0.0023 0.00211083 0.21

Total 61.0925 - 1.089 - 1.089616893 1.00E+00 100.1

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