Mineralogy and Petrography of Rare Earth Element (REE) Mineralisation, Browns Ranges, W.A
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Mineralogy and Petrography of Rare Earth Element (REE) mineralisation, Browns Ranges, W.A.
Daniel O’Rielly
A1176590
Supervisor Nigel J. Cook
Co-supervisor Cristiana L. Ciobanu
Centre for Tectonics, Resources and Exploration Department of Geology and Geophysics School of Earth and Environmental sciences University of Adelaide, South Australia [email protected] P a g e | 2
ABSTRACT
Northern Minerals’ current Browns Range exploration project is situated within the Gordon Downs
Region, W.A. This area is remote and relatively unstudied, with only a few regional mapping studies and old exploration reports available. The area is currently being explored for REE mineralisation. Identified REE-prospects contain xenotime-dominant mineralisation hosted within
Lower Proterozoic Arkoses and Archean metasediments (Browns Range Metamorphics). Detailed ore mineralogical, petrographic and mineral-chemical investigation of samples from the six currently-known prospects within the exploration area give insights into the mineralogical distribution of REE and provide evidence for the genetic evolution of the Browns Range REE mineralisation via a succession of hydrothermal processes.
Two main REE-bearing minerals are identified: xenotime [(Y,REE)PO4], HREE selective; and florencite [(REEAl3(PO4)2(OH)6], LREE selective. Two distinct generations of xenotime are recognised. EPMA and LA-ICP-MS analysis provide a large chemical data set for both xenotime and florencite allowing comparison with other localities worldwide. Xenotime contains Dy (up to 6.5 wt%), Er (up to 4.35 wt%), Gd (up to 7.56 wt%), Yb (up to 4.65 wt%) and Y (up to 43.3 wt%).
Xenotime composition is shown to be consistent across all prospects and xenotime generations.
Florencite is commonly zoned and contains Ce (up to 11.54 wt%), Nd (up to 10.05 wt%) and La (up to 5.40 wt%) and is also notably enriched in Sr (up to 11.63 wt%) and Ca. Subordinate zircon is also enriched in REE (up to 13 wt% ΣREE) and is the principal host of Sc (up to 0.8 wt%).
Early xenotime occurs as coarse euhedral grains which underwent surface etching, fracturing, partial breakdown and replacement by florencite. Second generation xenotime occurs as abundant small blades commonly associated with needles of hematite. Florencite occurs as replacement of xenotime and as overgrowths on detrital feldspar in the arkose, giving a P a g e | 3 characteristic skeletal replacement texture. The preliminary genetic model involves percolation of a reduced, acidic, volatile-rich, granite-derived hydrothermal fluid through porous arkose units.
The presence of late hematite suggests that mixing with meteoric water and subsequent oxidation may have played a role in the later stages of deposit evolution. Field observations suggest that faults acted as fluid conduits and that brecciation, possibly associated with release of volatiles from the fluid, occurred along these faults.
As well as providing a characterisation of the Browns Range deposits, the data generated provided valuable data, largely unavailable elsewhere, on chemical compositional trends in hydrothermal xenotime and coexisting minerals. Given the current surge in REE exploration, this data will assist in the development of exploration models for comparable terranes.
Keywords: Xenotime; florencite; hydrothermal; Browns Range; replacement; REE geochemistry
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INTRODUCTION
Northern Mineral’s Rare Earth Element (REE) exploration project at Browns Ranges, Gordon
Downs Region, northeastern W.A., is one of a number of new projects generating attention due to a rapid upsurge in the search for exploitable REE resources in Australia. The present focus of
Northern Minerals Ltd. within their exploration licenses is the elevated Heavy Rare Earth Element
(HREE)/ Light Rare Earth Element (LREE) ratio at a number of previously-known and newly- discovered prospects. Such exceptional HREE/LREE enrichment is unusual and of major economic significance. RC drilling began on the license area in late June 2011. The geology of the area is poorly constrained and the style of mineralisation containing the REE concentrations is largely unknown at the present time. This situation is exacerbated by the lack of comparable hydrothermal xenotime-dominant deposits elsewhere which might serve as the basis for an exploration model.
REEs are used for many purposes (Long et al. 2010; Hoatson et al. 2011) but are critical for the sustained development of new technologies. The current green energy drive is part of the reason for the sudden increase in demand for REE’s due to their importance in the development of these green technologies. REE’s are also important in a wide range of commercial and scientific applications for which demand continues to increase. Demand for REE’s is expected to increase dramatically over the next 5-10 years (Hoatson et al. 2011), with no expected major increase in current REE reserves, thus highlighting the need for more REE deposits to be located.
At present China produces around 95% of global REE production and no less than 99.8% of
Global HREE’s (Gleason et al. 2000; Long et al. 2010; Hoatson et al. 2011). Recently China has begun reducing its export quota which has been causing some panic in the stock market as prices P a g e | 5 of all REE have risen dramatically due to supply shortages. Many governments around the world are beginning to realise that a supply interruption could occur if China were to cease trading or further reduce their REE export quota. This would expose our reliance on China as rest of world
(ROW) production would be almost zero and would take many years to even partially cover ROW demand. A developed country would struggle to manage without available REE’s. As Australia further pursues a Green energy future and further improvements to current technologies and cutting edge scientific research our demand for REE’s will increase, hence the desire for domestic production that will reduce our reliance on China.
The current Northern Minerals Ltd. tenements lie along the North Western area of the Browns
Ranges Dome. This consists of Lower Proterozoic Arkoses and Archean metasediments (Blake et al.
1979; Page et al. 1995; Hendrickx et al. 2000; Cross & Crispe 2007; Tunks & Cooke 2007).
Throughout the exploration area, these metamorphic units contain abundant quartz veining in areas with dominant 260o and 320o structures (PNC Exploration 1989). The quartz veining appears to be somewhat controlled by these structures with the REE mineralisation being found within and surrounding the quartz veins particularly where veins intersect. During 1987-1991 a Japanese exploration company (PNC Exploration) carried out detailed field work in the Browns Range area searching for unconformity-style uranium mineralisation. They carried out geophysical surveys, geological mapping, rock chip assays, petrological analysis and drilling identifying REE elevations within the area however relinquished the area after receiving “uninspiring results”. Their work is noted in a series of exploration reports (PNC 1987-1991, 1988).
The present project aims to characterise potential REE-ore from the 6 prospects defined in June
2011. This is done using a combination of field observations along with an array of microanalytical methods. The main goals to achieve were: P a g e | 6
Identification of all minerals species present within the samples, with particular
focus on the minerals hosting REE and other elements of economic interest.
Identify the paragenetic, chemical and textural characteristics of the REE deposit
and its relationship with host rocks.
Develop a basic genetic model to account for the observations at various scales.
The requirement for careful petrographic-mineralogical observations on these REE deposits is due to the current gap in knowledge with respect to the origin of hydrothermal REE deposits and the reasons for economic concentrations of REE-, and especially HREE-bearing minerals. REE- hosting phases such as xenotime, goyazite and florencite all have complex chemistries with marked partitioning of the different REE between them. Understanding the REE distribution between the component minerals has economic significance for the company and will assist with ore processing should sufficient reserves be identified to support profitable exploitation.
Characterisation of the Browns Ranges REE deposit is critical for development of a genetic, and implicitly an exploration model. Factors such as pressure, temperature, fluid chemistry, generations of fluid that passed through the system, age and source of REE can all be potentially constrained by mineralogical and petrological observation and associated microanalysis.
The region around the Browns Ranges is relatively unexplored, with limited outcrop at surface due to regolith cover and rather dense vegetation. The poor or absent tracks in the area make exploration difficult. A credible genetic model for the known REE deposits would give Northern
Minerals a competitive advantage when searching for exploration targets within the rest of the
Browns Range dome, the surrounding regions and indeed elsewhere in Australia. The project thus P a g e | 7 aims to identify key mineralogical and geochemical signatures that may hint at a hydrothermal REE deposit similar to that examined here.
GEOLOGICAL SETTING
Regional Setting
The Browns Range Dome is located within the Gordon Downs (WA) and Tanami (NT) Regions. The current tenements held by Northern Minerals are solely within the W.A. segment (Figure 1). The
Browns Range Dome is located approximately 150 km southeast of Halls Creek. The regional geology of the area is quite complex with multiple deformation events affecting the package of
Late Archean to Paleoproterozoic rocks.
The basement rocks of the area are rarely exposed but are composed of Archean gneisses and meta-sedimentary rocks that have undergone regional metamorphism at conditions up to amphibolite facies. The basement rocks outcropping around the Browns Range Dome are known as the Browns Range Metamorphics (Blake et al. 1979; Hendrickx et al. 2000) and have been dated at 2510-2500 Ma (Page et al. 1995). Tanami Group sedimentary sequences unconformably overlie the Archean rocks and are dated at 1880-1830 Ma (Cross & Crispe 2007). The lower unit within the
Tanami Group, the deepwater siltstone Dead Bullock Formation, is an important gold host within the area (Crispe et al. 2007). Overlying this is the Killi Killi Formation comprising turbiditic sedimentary rocks. Deposition was terminated by the Tanami event (D1-M1) which led to uplift in the area and greenschist to lower amphibolite facies metamorphism (Hendrickx et al. 2000; Crispe et al. 2007). The Ware Group unconformably overlies the Tanami Group and consists of siliciclastic sediments and felsic ignimbrites deposited between 1825-1810 Ma (Cross & Crispe 2007). The
Stafford deformation event (Arunta Region 1810-1800 Ma) led to SE-NW shortening (D2) followed P a g e | 8 by SE-NW shortening (D3) (Collins & Shaw 1995). Intrusion of I-type granitoids accompanied this shortening throughout the area. The intrusives have been divided into three suites (Birthday,
Frederick and Grimwade) using the geochemical criteria of White et al (2001). The Browns Range
Dome shows signatures of both the Frederick and Grimwade suites suggesting multiple injections of intrusives (Crispe et al. 2007), and an interpreted igneous crystallization age between 1,821±4 and 1,791±4 Ma (Smith 2001). A failed continental rift resulted in deposition of the basaltic and clastic sediments of the Mount Charles Formation (≈1800 Ma) (Blake et al. 1979). SSE-shortening
(D4) took place syn- to post-granitoid intrusion and was followed by E-W convergence (D5), possibly a result of re-mobilising of faults between the granitoid intrusions. D5 structures are important and control the most of the gold mineralisation within the Tanami region (Huston et al.
2007). The Birrindudu Group sediments (Blake et al. 1979) extensively cover the area with a maximum thickness of 6,000 metres and were deposited between ≈1735-1640 Ma (Crispe et al.
2007). This unit comprises 3 formations: the Gardiners Sandstone (unconformably surrounding the
Browns Range Dome); the calcareous Talbot Wells Formation and the Coomarie Sandstone.
Cainozoic sediments cover the majority of the area making outcrops rather scarce. Episodes of thrust, oblique slip and normal faulting have affected the area (D6+) since the deposition of the
Birrindudu Group. Detailed descriptions of regional geology are given by Blake et al. (1975),
Hendrickx et al. (2001) and Crispe et al. (2007).
Uranium and REE exploration in the area has been undertaken by multiple exploration companies and a number of different exploration models have been employed. New Consolidated
Gold Fields Australasia Pty Ltd. intersected uranium anomalies within the basal conglomerates of the Gardiner Sandstone and reported xenotime and possible florencite mineralisation (PNC 1987-
1991). In the 1970’s, a number of companies, including Esso Australia, Peachiney Australia, Alcoa,
Cultus Pacific Uranex JV and Denison, searched for vein-unconformity style uranium mineralisation P a g e | 9 within the Gardiner sandstone and identified some REE anomalies. Mineral Reserves Group
Canada explored for a Athabasca Basin-style uranium deposits and located the Don uranium prospect. Last but not least, PNC Exploration located significant REE mineralisation around the
Browns Range Dome during their 1987-1991 exploration campaigns. Hydrothermal quartz veins were described and were demonstrated to contain HREE-enriched xenotime.
Local Setting and REE mineralisation
The current prospects of Northern Minerals all lie within the Western Australia Browns Range tenements. The local geology within this area has been studied sparingly by only a few authors, and this is being supplemented by new information being acquired by Northern Minerals. The only sizable database of detailed information exists in the PNC exploration relinquishment and exploration reports from 1987-1991.
The current prospects are all located within the Archean-Early Proterozoic Browns Range metamorphics. These units consist of meta-arkoses and meta-sandstones, as well as granitic gneisses and muscovite schists (Hendrickx et al. 2000; Crispe et al. 2007). The Gardiner Sandstone unconformable overlies the arkoses to the west. The Browns Range Granitic core occurs to the east and has an emplacement ages of 1805-1780 Ma (Smith 2001). There is a suggestion from geophysical interpretation (Hoatson & Blake 2000) that there are ultramafic intrusions in the area which appear to have used some of the 260° structures as a conduit for intrusion towards the
South of the prospects.
REE-mineralisation in the area is located within the arkosic unit, mainly as veins accompanied by haloes of dissemination. The mineralisation found by PNC Exploration Pty Ltd. (1987-1991) P a g e | 10 occurs in two forms: large replacement (10 m long, 1 m wide) veins of xenotime; and dissemination haloes around the smaller mm-scale veins. The former type is of high-grade yet low tonnage whilst the former would be low-grade yet potentially greater tonnage (PNC Exploration
1991).
PNC Exploration ran a detailed geochemical survey using rock chip assays, Percussion drill samples and costean sampling all of which returned positive REE results. The best result came from a replacement-style vein which was composed of up to 90% xenotime; assay results giving
28% (Y+ΣREE). Other sampling methods found only small erratic “pods” of mineralisation and failed to detect any large continuous mineralisation or elevated REE concentrations. A relationship between U/Y and ground radiometrics was thought to exist as a result of the xenotime mineralisation. A detailed petrological study was also carried out by PNC with a total of 69 samples being analysed. The conclusion was that the arkoses are the only unit that contains xenotime mineralisation in the area. PNC then relinquished the land rights due to results suggesting that no economic mining operation could be established at that time.
APPROACH, SAMPLING & ANALYTICAL/EXPERIMENTAL METHODS
This paper aims to further define the REE mineralisation at a microscopic scale and subsequently relate this to field observations in order to gain further insight into the genesis of the mineralisation. Optical and Scanning Electron Microscopy (SEM) enabled mineral species, textures and relationships to be accurately documented. This was accompanied by mineral compositional data obtained from the electron microprobe (EPMA) and Laser-Ablation Inductively-Coupled Mass
Spectroscopy (LA-ICP-MS) in which variations in trace element concentration might point to P a g e | 11 geochemical trends in minerals from different prospects which may have further implications for understanding ore genesis or in regional exploration.
Approach
A total of 22 rock chip samples were collected from the 6 prospects at the Browns Ranges project area (Area 5, Area 5 North, Gambit, Wolverine, Mystic and Banshee). These were prepared as one- inch polished sections for mineralogical and petrographic analysis (Pontifex and Associates). The
28 polished sections were examined using reflected light and SEM to establish the main ore minerals, accessory minerals and gangue phases, along with their mutual textures and relationships. Particular attention was given to xenotime and other REE-bearing minerals in order to determine relationships/textures which could reveal information about genesis. Selected samples were then analysed by EPMA and LA-ICP-MS. In the latter work, attention was given to
REE partitioning between xenotime and coexisting florencite.
Sampling
The rock chip samples from the 6 currently known prospects were collected at surface using a rock hammer. The goal was to collect samples that were representative of mineralisation at each prospect. Since these were grab samples, however, and contain macroscopic xenotime, their ore grades can be expected to be significantly higher, and thus not representative, of the grade that random sample selection would return.
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Optical microscopy and SEM
A Nikon petrological microscope with magnification up to 50x was used in reflected light mode to identify the main REE-bearing minerals and associated gangue, their relative abundances and relationships between minerals. Each sample was photographed using a mounted digital camera.
SEM work was carried out using a Phillips XL30 SEM instrument at Adelaide Microscopy, equipped with energy dispersive X-ray spectrometer (EDAX) and back-scattered electron (BSE) detector. The SEM was operated at 20eV accelerating voltage and spot size 4. BSE imaging allowed for observations of REE-bearing and other minerals at the micro-scale, notably fine textures, mineral intergrowths, compositional zoning and inclusions.
Electron Microprobe Analysis (EPMA)
Quantitative compositional data for representative REE-bearing and other minerals from each prospect was obtained using a CAMECA SX-51 instrument with wavelength-dispersive spectrometers at Adelaide Microscopy. Work focussed on compositional variation in REE-bearing minerals such as xenotime and florencite, as well as accessory REE-bearing phases such as zircon, gangue minerals and silicates belonging to the alteration accompanying mineralisation. The instrument was operated at an accelerating voltage of 20 kV and beam current of 19.5 nA. The following elements were analysed using the X-ray lines and standards observed in Appendix 1.
Laser-Ablation Inductively-coupled Plasma Mass Spectrometry (LA-ICP-MS)
LA-ICP-MS analysis of xenotime and florencite was made using the Agilent HP-7500 Quadrupole
ICPMS instrument at Adelaide Microscopy. The instrument is equipped with a New Wave UP-213 P a g e | 13
Nd:YAG laser ablation system equipped with MeoLaser 213 software. Data reduction was performed using Glitter software (GEMOC 2005).
Samples with suitable grains of xenotime and florencite were ablated. These had been inspected by SEM to check for inclusions and other textures (e.g., fractures) that might affect the quality of the trace element data. Analyses were made with spot size diameter of 30μm. The laser system was operated at pulse rates of 5 Hz, and 75% power level; laser energy was typically 6-9
J/cm-2, giving an ablation rate of approx. 1.5 μm/sec. The following isotopes were monitored:
23Na, 24Mg, 27Al, 29Si,33 S,34 S, 39K, 43Ca, 48Sc, 47Ti, 51V, 52Cr,55Mn, 57Fe, 75As, 82Se, 88Sr, 89Y, 90Zr, 137Ba,
139La, 140Ce, 141Pr, 146Nd, 147Sm, 153Eu, 157Gd, 159Tb, 163Dy, 165Ho, 166Er, 172Yb, 175Lu, 178Hf, 184W, 193Ir,
208Pb, 232Th and 238U. The analysis time for each sample was 90 seconds (30 second measurement of background with the laser off, and a 60 second analysis with the laser on. Data reduction was undertaken using Y as the internal standard for xenotime and Ca for florencite.
Calibration was performed using the NIST610 trace element standard created by the National
Institute of Standards, Gainsburg USA (Pearce et al. 1997). The raw analytical data for each spot analysis is plotted as a line graph and the integration times for background and sample signal selected. The counts are then corrected for instrument drift (standards were run after each 10 unknown samples) and converted to concentration values using known values of Y and Ca for xenotime and florencite, respectively in the analysed mineral (from EPMA data). Based on the measured concentrations, detection limits were calculated for each element in each spot analysis.
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RESULTS
Field geology
AREA 5 NORTH (A5N) PROSPECT
Xenotime mineralisation within this prospect was found as disseminations within massive poorly- sorted arkose along with associations with quartz veining and hematitic alteration. The arkose in areas had a schistose fabric which is probably the result of small-scale shearing. Quartz pebbles within the arkose ranged in size from 1-8 cm (Fig. 2a). Quartz veining is widespread throughout the prospect, with areas of intense narrow veining (1-3 mm), as well as larger-scale veining (1-8 cm). The smaller veins were often associated with hematitic alteration spreading approximately 1-
4cm into the arkose (Fig. 2c). Xenotime mineralisation occurs as a 1-2mm-thick layer between the quartz vein and the hematite alteration zone. Xenotime mineralisation, although commonly seen with hematite alteration, can also be observed lining quartz veins without apparent hematite alteration (Fig. 2a). Xenotime mineralisation also appears to be associated with elevated uranium
(as measured using a portable XRF unit). The XRF unit also revealed the sporadic distribution of xenotime mineralisation with high readings suddenly dropping to just above background level over a distance of 3-5 metres from observed mineralisation.
Mineralisation appears to be strongly structurally controlled with prominent 260° crosscutting
320° structures (Fig. 2b). Mineralisation is commonly found at these intersections as a result of these structures acting as a trap. The structures are sub-vertical with mineralisation probably occurring at depths along these structures. The mineralisation occurs in disconnected pods with little continuity between these pods which may however only be the surface expression of the mineralisation which may be occurring at depth.
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AREA 5 (A5) PROSPECT
The geology of Area 5, located approximately 300-400m to SW, is similar to Area 5 North. A massive poorly-sorted arkose contains quartz clasts around 2-4 cm in size. Area 5 also shows the same controls on mineralisation as Area 5 North, with 260° and 320° structures observed with xenotime mineralisation nearby. Xenotime occurs as small veins of possible massive xenotime, surrounding quartz veins with or without hematite alteration and disseminations throughout the arkose.
GAMBIT PROSPECT
The Gambit prospect is dominated by a relatively large vein breccia system, spanning approx. 20 x
20 m. This breccia system showed signs of crackle, mosaic and rubble textures (Fig. 3b). Xenotime mineralisation occurs within the quartz breccia zone forming around the edges of quartz veins disseminating into the arkose clasts (Fig. 2d). Mineralisation trends in an E-W direction and appears to be structurally controlled by a 260° fault structure with a crosscutting with a 320° structure. There is a zone of xenotime mineralisation at the intersection of these structures and this is coupled with heavy brecciation of the arkose. In parts, the quartz veins are vuggy with 4-5 cm-sized voids (Fig. 2e). As at A5N, the surface expression of the mineralisation is quite limited and sporadic. However, since the faults are sub-vertical it could be expected that xenotime mineralisation could be followed further down and may be continuous at depth. There is minor hematite alteration in the area, but conspicuously, none is observed in the breccia zone itself.
WOLVERINE PROSPECT
Mineralisation occurs as a 15 m-long breccia zone located along a 280° fault structure. This fault structure seemed to control fluid flow in the area as large quartz veins (1-15 cm in size) can be traced along the fault (Figure 3c). There is little evidence of mineralisation up-strike of the fault; P a g e | 16 some small breccia zones are noted but XRF analysis did not reveal elevated REE’s. Down-strike, the fault is covered by soil hence could the structure could continue for a longer distance with more mineralisation present at depth.
The breccia system at Wolverine consists of angular arkosic clasts 1-20 cm in size. The matrix between clasts is filled with pink xenotime-mineralised quartz. The outcrop is heavily silicified, a feature not observed at other prospects (Fig. 3a). Macroscopic muscovite is also observed throughout the outcrop – again differing markedly from the other prospects. The outcrop at
Wolverine also appears to be considerably less weathered than at the other prospects. This is probably due to little to no hematite alteration and the heavy silicification. Other observations include quartz having varying orientations and cross cutting each other (Fig. 2f).
BANSHEE PROSPECT
The Banshee prospect has little available outcrop making observations difficult. There is, however, plenty of REE-enriched quartz and hematite lag as determined using a XRF gun. The prospect differs from the others above in that it forms within a valley with ridges on either side. Other prospects have been found along ridge tops. This mineralised lag may be transported from the surrounding ridges or could be the result of weathering of rocks below the current soil cover.
Some of the rock fragments show quartz veining within arkose with slight hematite alteration.
MYSTIC PROSPECT
The Mystic prospect consists of a more poorly-sorted conglomerate arkose that contains pervasive small-scale (1-2 cm) narrow quartz veining which splay from larger 3-5cm quartz veins (Fig. 3d and
3e). There is a dominant 260° fault structure which controls the mineralisation, since xenotime mineralisation appeared to exist as a disseminated halo surrounding this structure and associated P a g e | 17 quartz veins (Fig. 3f). The outcrop once again occurs within a valley with ridges running along each side that may host more xenotime mineralisation.
Petrology
AREA 5 NORTH
Xenotime within the A5N prospect occurs in 3 main varieties, all of which vary considerably in physical characteristics and their relationships with other minerals. Xenotime is present as euhedral overgrowths on 10-20 m-sized zircon. The xenotime is often fragmented, either into eqant or pyrimidial shaped grains approximately 5-40 m (Fig. 4c, f). The zircons themselves can be fragmented and show internal zoning which is quite chaotic (Fig. 4f). Xenotime also occurs as small subhedral-euhedral intergrowths with acicular hematite (Fig. 4a, b, d, e). The xenotime appears as blades approximately 5-25 m in size, commonly clustered into aggregates of >10 grains. Figure 4a shows a close-up of xenotime within hematite were the xenotime appears to be nucleating on hematite. Lastly, xenotime occurs as euhedral disseminations within the quartz host rock as well as ‘suspensions’ within the kaolinite/sericite matrix within fractures. The xenotime blades vary from 5-40 m in length and commonly form a small cluster of xenotime grains (Fig. 4d, g).
In A5N, florencite is a very minor phase and occurs as tabular euhedral grains <5 m in size (Fig.
4h). These grains occurred within a sericite matrix and fill fractures within host quartz.
Compositional zoning was observed - a narrow (1 m) rim appears lighter on the BSE images than the cores.
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At A5N goyazite SrAl3(PO4)2(OH)5·(H2O) is found as a cement that fills fractures in the quartz host rock, as well as filling gaps between xenotime and hematite grains (Fig. 4g). Grains are typically 50-100 µm in size. BSE images reveal what may either be exosolution of a second mineral within the goyazite or a slight zonation throughout the grains.
Quartz is the dominant mineral throughout the A5N samples (>50% of rock volume). Quartz contains inclusions of fluorapatite (<5 µm), as well as disseminations of xenotime. Hematite is also a dominant mineral and typically forms euhedral acicular needles 10-50 µm in length. In some areas of the samples, these needles appear to fuse forming a hematite ‘cement’ (Fig. 4e). Rutile is observed as elongate euhedral grains approximately 10-30 µm in size. Sericite/kaolinite is present within fractures between quartz grains (typically <5-10 µm in size).
AREA 5 PROSPECT
Xenotime is the dominant mineral apart than quartz. There are four distinct types of xenotime; differences are expressed in a variety of characteristics, textures and appearance. The first occurs as euhedral overgrowths (Fig. 5a) partially or completely surrounding 20-100 µm-sized grains of zircon. The xenotime grains are equant or pyramidal in shape with sizes varying between 10-1,000
µm. The zircons coexisting with xenotime display fracturing due to oriented strain and in some cases, the fractures are filled by xenotime. The second form of xenotime appears as clustered, subhedral clustered grains (10-100 µm in size) surrounding a core-like structure of acicular hematite (2-10 µm) ± fine-grained (<5µm) sericite (Fig. 5b, g). Xenotime forms an interconnecting series of grains forming an envelope around the hematite/sericite. The xenotime aggregate can be more than 5 mm in size and appears to be concentrated along the margins of fractured quartz.
Xenotime can also appear as massive euhedral grains (100-400 µm in size), characterised by a distinct porosity (surface pitting) and fracturing, as well as inclusions of florencite (50 µm) and P a g e | 19 minor hematite (Fig. 5d). Lastly, xenotime can form as euhedral disseminations (5-20 µm in size) within the quartz-dominant host rock (Fig. 5c, e and f). These grains often form in large populations with 10-50+ individual grains concentrated within a small area.
Florencite is a minor constituent of the samples from A5 and displays a variety of different textures. The mineral typically occurs as euhedral, equant grains 10-70 µm in size that have undergone skeletal replacement (Fig. 5c, e). This skeletal replacement has destroyed the cores of most florencite grains leaving an empty or sericite-filled core. Such florencite still displays a subtle compositional zoning (see below). The image in Figure 5c illustrates xenotime replacing or overgrowing florencite. Florencite 5-50µm in size is also observed as inclusions within xenotime.
This included florencite (Fig. 5d, h) does not display the skeletal replacement which is characteristic of ‘free’ florencite grains. Such florencite also appears to have no compositional zoning and includes inclusions/intergrowths with hematite (Fig. 5d).
Four gangue minerals are identified in the A5 samples. Quartz is dominant and makes up >50% of the samples. The quartz had been hydrothermally fractured, creating space for deposition of the other minerals. Hematite is second in abundance and typically occurs as acicular needles varying between 5 and 30 m in size. In sample A5c, hematite is the major gangue phase with quartz almost absent. Sericite and kaolinite are present in fractures between quartz grains, both are typically very fine-grained (often <5m).
GAMBIT PROSPECT
Xenotime within the Gambit Prospect (GP) occurs in two varieties. The first consists of equant euhedral grains 5-300 µm in size (Fig. 6e, g). These are often heavily pitted and fractured along their margins (Fig. 6a). They occur as disseminations throughout the host quartz (Fig. 6c) as well as P a g e | 20 within fractures in the quartz (Fig. 6d). Figure 6d also shows that equant florencite can occur as inclusions within xenotime. Figure 6h shows fractures within xenotime that are filled by sericite.
Xenotime also occurs as cement that completely fills fractures within quartz not exhibiting its usual euhedral shape. This cement completely encloses the quartz (Fig. 6f).
Florencite occurs as equant euhedral 10-80µm disseminations within quartz (Fig. 6b, c) and within the sericite matrix filling fractures (Fig. 6d). This florencite also exhibits some slight zonation however appears to be quite chaotic. Florencite also occurs as inclusions within xenotime (Fig. 6d) forming 10-30µm size equant grains.
Quartz is the dominant gangue mineral (>70 vo.%). Rutile was observed as euhedral 90-100 µm grains intergrown with xenotime (Fig. 6a). Sericite and kaolinite form a matrix which fills most of the fractures within quartz where REE-bearing phases were not present.
WOLVERINE PROSPECT
The Wolverine prospect appears to be the richest with respect to xenotime mineralisation. Three different varieties of xenotime were identified. Figures 7a, e and 8a show equant euhedral xenotime grains approximately 30-600 µm in size. These grains are heavily pitted or fractured possibly resulting from growth under a stress regime. Figure 7e show some slight compositional zonation within xenotime; note the narrow rim of on the BSE image. These equant grains appear as disseminations throughout the quartz host rock and often have small 2-10 µm grains surrounding them. Xenotime also occurs as heavily fractured euhedral grains (Figure 7d, 8b).
These have been completely destroyed and the fractures filled by quartz. This xenotime variety typically forms fragments <5-100 µm in size. Finally xenotime forms intricate intergrowths with florencite. Xenotime can appear as inclusions within florencite (Figure 8c, d). This variety of P a g e | 21 xenotime is quite small (<2-20 µm) and appears as irregular grains. The texture possibly suggests that replacement of xenotime has taken place or that florencite is nucleated on earlier xenotime.
Figures 7c, 8c and 7f show more complex intergrowths between xenotime and florencite. The distribution of the two minerals become chaotic with various sizes (5-90 µm) and irregular shapes of both minerals where they are interlocked with one other. This texture could represent contemporary formation of the two minerals or some sort of replacement.
Figure 8f shows an equant euhedral 50-100 µm florencite grain of the type commonly observed throughout the Wolverine samples. These grains showed distinct chemical zoning with the rim lighter than the core in the BSE images. This florencite could also possibly exhibit skeletal replacement as seen at other prospects as there are several largish pits beginning to develop central to the grain (Fig. 8f). These florencite grains are located within the sericite matrix between fractured quartz. As noted above, florencite also occurs in complex intergrowths with xenotime.
Florencite can be seen incorporating xenotime as inclusions (Fig. 8d) or included within xenotime
(Fig. 7c). Florencite may also replace xenotime or act as a cement interstitial to xenotime grains.
The typical size of this florencite is 5-70 µm.
Quartz is the dominant gangue mineral and contains disseminated REE minerals. The quartz is markedly more fractured where REE mineralisation has taken place. Late quartz also infills the fractured REE-bearing minerals. A sericite/kaolinite matrix is also observed within the fractures in quartz: again this is typically very fine grained (<5 µm). Two other phosphate minerals were identified (Fig. 7e), intergrown with one another. They have compositions that approximate to an undefined Ba-phosphate (without Al) and a Fe-phosphate, respectively.
BANSHEE PROSPECT P a g e | 22
Xenotime occurs in 3 different morphologies. Most commonly, xenotime is present as inclusions and/or intergrowths with florencite (Fig. 9b, c, e, f, h). This assortment of xenotime comes in a variety of shapes: irregular, bladed and equant and is typically 10-200 µm in size. The co-existing florencite appears to cement or replace the pre-existing xenotime. Xenotime also occurs as a nucleation/overgrowth of xenotime (e.g. Fig. 9g). Euhedral, pyramidal/tabular 2-30 µm-sized xenotime partially surrounds zoned zircons. Xenotime also occurs as large (up to 800 µm) euhedral grains or a cement filling available space in the fractured quartz (Fig. 9d).
Florencite forms euhedral equant grains, as well as more anhedral irregular shaped 140-200
µm-sized grains (Fig. 9h). A skeletal replacement texture is seen in which florencite of a certain chemical composition is selectively removed. This in turn suggests that there had initially been a chemical zonation within such florencite grains. Florencite also forms intergrowths with xenotime
(see above) in which it forms a cement or possible replacement texture with xenotime fully surrounding it (Fig. 9b, e, f). These Florencite aggregates are typically 20-400 µm in size and exhibit slight zoning. Florencite is also found as small inclusions within xenotime (Fig. 9d). Finally
Florencite forms equant euhedral gains 40-70 µm in size within the sericite matrix (Fig. 9a).
Quartz is the dominant mineral and has been fractured, allowing deposition of REE minerals and for disseminations of minerals into the quartz. A sericite/kaolinite matrix is observed that fills fractures within quartz where REE mineralisation doesn’t occur.
MYSTIC PROSPECT P a g e | 23
Xenotime at Mystic Prospect (MP) occurs in three varieties which differ considerably in size and texture. Xenotime occurs as euhedral 10-50µm pyramidal overgrowths around zircon. The xenotime is normally fractured along with the contained zoned zircon (Fig. 10a, h). Xenotime also occurs as small anhedral grains (2-6 µm) which form a feather-like texture when aggregated (Fig.
10h). Xenotime also occurs as clusters of small (<4µm) euhedral blades (Fig. 10b, g) disseminated throughout the quartz host or scattered within fractures (Fig. 10e). Finally xenotime occurs as large (50-300 µm) subhedral grains filling fractures within quartz (Fig. 10g); these grains can contain small florencite inclusions.
Florencite occurs as euhedral equant 30-80 µm-sized grains exhibiting skeletal replacement with the cores completely destroyed (Fig. 10d). Some of these cores have been later filled with sericite. Florencite also occurs as euhedral equant 5-40 µm-sized disseminations within quartz often surrounded by small bladed quartz (Fig. 10g). In addition, florencite occurs as equant euhedral 10-40 µm-sized intergrowths and/or inclusions within xenotime (Fig. 10c, g).
As in the other prospects, quartz is the dominant gangue mineral. A kaolinite/sericite matrix fills fractures where REE mineralisation is absent. Small (<1-2 µm) needles of hematite were observed yet in much lesser abundance than at A5 or A5N.
Mineral Compositional data -Microprobe
XENOTIME
EPMA data for xenotime from all prospects (summarised in Table 1a and 1b; full dataset given in
Appendix 2) shows the marked enrichment in HREE relative to LREE. HREE concentrations were as follows: Gd ranging from to 5.02 to 6.88 wt%, Tb ranging from 5.88 to 6.52 wt%, Ho was below the minimum detection limit in all samples, Er ranging from 3.32 P a g e | 24 to 4.58 wt% Yb ranging from 2.09 to 4.65 wt% and Lu ranging from 0.36 to 0.83 wt%. LREE are heavily depleted in xenotime, yet measurable concentrations (fractions of wt%) were obtained for most LREEs: La As expected, Y was a main constituent of xenotime with concentrations between 39.06 and 43.39 wt%. Phosphorus, the other main component of xenotime ranges from 30.98 wt% to 34.31 wt%. Scandium was consistently detected, although values were low (0.02 to 0.12 wt%). Uranium values were typically below 0.8 wt% and Th concentrations were below Surprisingly the chemistry of xenotime throughout each prospect, from grain to grain, across different grain morphologies and within different areas of an individual grain was very similar. Calculated standard deviations are often well below 1 wt%, demonstrating the compositional homogeneity of xenotime. It is observed that Fe appears to vary significantly between prospects. Xenotime from prospects A5 and A5N had values of Fe up to 1.02 wt% and 3.72 wt% respectively. Whilst xenotime incorporates some Fe in its crystal lattice (Masau et al. 2000; Wang et al. 2003; Ondrejka et al. 2007) it is often in the order of <0.8 wt%. The high Fe values observed in some xenotime samples from Browns Range possibly reflects micro-inclusions of hematite. The lack of detectable As and V in xenotime is a point to note, since the xenotime series contains both chernovite [(Y,REE)AsO4] and wakefieldite [(Y,REE)VO4] end-members. FLORENCITE EPMA data for florencite from all 6 prospects (Table 2a, 2b, Appendix 3) revealed a characteristic strong enrichment in LREE’s. Particular enrichment was observed for La (up to 4.3 wt%), Ce (up to 11.53 wt%) and Nd (up to 10.5 wt%). Enrichment was also observed in both Sr (concentrations up to 4.78 wt%) and Ca (up to 1.9 wt%). Whilst La, Ce and Nd are the dominant REEs partitioning into florencite other REE’s are present at lesser concentrations: Pr ranges from 0.87 to 1.64 wt%, Sm P a g e | 25 ranges between 0.45 to 1.05 wt%, Gd ranges between 0.57 wt%. Interestingly, these other REE are detectable only in florencite from the Gambit and Wolverine prospects; other prospects had The florencite mineral group contains three named minerals (end-members in the series): florencite-(La-), -(Ce) and –(Nd). In the Browns Range samples, florencite-(Nd-), florencite-(La-) and florencite-(Ce) are present based on the end member calculations (Table 3). The chemistry of florencite is quite variable from grain to grain as well as varying slightly between prospects. Variation in wt% and atom% values for La, Nd, Ce, Sr, Ca, Si, Al and P is markedly greater than in xenotime. This variance can in part be explained by the compositional zonation observed in the BSE images (Fig. 6b for example). The brighter zones appear to be enriched in Nd (by as much as 3- 9 wt%) and relatively depleted in Ca and Sr (by 1-2 wt%) if compared with the darker areas. Uranium and Th are only very minor components of florencite. Most analyses are (within the OH site); concentrations range between 0.27 to 1.28 wt% and 0.03 and 0.09 wt%, respectively. ZIRCON EPMA data was collected on zircon from all 6 prospects in order to identify whether zircon is a significant host for REE, and if so, which REE were partitioned into zircon. The dataset (Table 3, Appendix 4) shows a modest enrichment in REE’s with HREE’s being enriched relative to LREE as follows: Gd (up to 0.69 wt%), Dy (up to 0.93 wt%), Er (up to 1.6 wt%), Ce (up to 0.84 wt%), Nd (up to 0.25 wt%, Sm (up to 0.26 wt%, Yb (up to 1,7 wt%), Lu (up to 0.25 wt%) as well as stronger P a g e | 26 enrichment in Y (up to 7.43 wt%). The EPMA data also shows enrichment in P in zircon (up to 6.04 wt%). The analysed zircons from Browns Range appear to contain significant concentrations of other elements of interest. These include Sc (up to 0.79 wt%), Hf (Up to 1.64 wt%) and Sr (up to 0.17 wt%). Among other components, Al and Fe concentrations were up to 1.47 wt% and 2.43 wt%, respectively. Uranium and Th are enriched within zircon when compared to other minerals with concentrations of U are up to 1.07 wt% and Th up to 3.46 wt%. Fluorine was also identified at measurable concentrations in zircon (up to 0.84 wt%). There appears to be no major differences in zircon chemistry between prospects or from grain to grain within the same sample. BSE imaging did, however, reveal some compositional zoning within some zircons. EDAX spectra suggested that there was variation with respect to Ca and P from core to rim. The fine-scale zonation accompanied by the small size of the zircon grains made accurate quantitative microprobe analysis of individual zones impossible. GANGUE SILICATES EPMA data was collected for sericite, illite and kaolinite. Analyses of all minerals are close to ideal stoichiometry. Results are summarised in Tables 4-6, Appendices 5-7. Data collected for sericite was as would be expected with K (up to 9.73 wt%), Al (up to 37.07 wt%) and Si (up to 55.97 wt%). Mg and Fe (up to 4.84 wt%) are also found to be in sericite, giving calculated % phengite components typically between 14 and 20%. The Fe/(Fe+Mg) ratio is fairly constant throughout all the prospects. Fluorine and Cl are also present within the sampled sericites (replacing OH in the structure), with values up to 0.38 wt% and 0.08 wt%, respectively. Elevated F contents in white mica are often considered as indicative of hydrothermal fluids containing a high volatile component. P a g e | 27 Data collected for Illite were as expected with K (up to 9.35 wt%), Al (up to 33.68 wt%) and Si (up to 49.68 wt%). Mg and Fe were incorporated into illite structure at up to 1.74 wt% and 6.71 wt% respectively, giving a % phengite component ranging from 6.24 to 26.13 wt%. The Fe/(Fe+Mg) ratio showed little variance between prospects with a maximum variance of 0.3%. Chlorine and F were also included within the illite with values up to 0.08 wt% and 0.41 wt%, respectively. Microprobe analysis of kaolinite also gave close-to-stoichiometric compositions: Si reaching 55.16 wt% and Al reaching 43.68 wt%. Fe is present in only trace amounts (maximum 0.58 wt%). Mineral Compositional data LA-ICP-MS LA-ICP-MS analysis was carried out on both xenotime and florencite in order to further constrain concentrations of trace elements within these minerals along with identifying elements which may have been below the minimum detection limit of the Microprobe. XENOTIME LA-ICP-MS analysis was performed 86 times on xenotime grains from 5 samples WPb, A5c, GPa, MPa and A5a. The trace element results for xenotime were quite surprising with 36 elements detected across all the dataset. It appears that xenotime is able to accommodate a large amount of elements within its structure or that some elements could possibly occur as inclusions within xenotime. (Results in Table 7 and Appendix 8) The HREE data collected for xenotime using the laser shows that there appears to be a bit of variation between prospects as when the means were calculated there is significant differences in some HREE’s at different prospects such as sample A5c returning 61335 ppm whilst other P a g e | 28 prospects returned a mean below 42000 ppm. A variance with all HREE’s can be observed to some extent (Table 7). The reason for this variance is the limitations of LA-ICP-MS study on xenotime. Since LA-ICP-MS is sparingly used for xenotime analysis hence a accurate and suitable standard hasn’t been developed. Whilst this variance is occurring the laser data agrees with the microprobe data in that Dy is heavily enriched up to 62817 ppm (Sample A5c). This is followed by Yb (Up to 67597 ppm), Gd (up to 36886 ppm), Er (up to 47995 ppm), Ho (up to 15362 ppm), Tb (up to 8703 ppm) and Lu (up to 7830 ppm). Interestingly all LREE’s were detected within the sampled xenotime in trace amounts. La was found highest in sample A5a with a mean of 52 ppm, Ce was found highest in sample WPb with a mean of 536 ppm, Pr was found highest in WPb with a mean of 423 ppm, Nd was found highest in sample GPa with a mean of 7405 ppm, Sm was found highest in sample MPa with a mean of 18031 ppm and Eu was found highest in sample MPa with a mean of 3176 ppm. This further shows that HREE’s are preferentially partitioned into xenotime however LREE’s can be incorporated into xenotime at small concentrations. Pb, U and Th were all detected within the sampled xenotime with Pb occurring in very minute amounts the largest mean being 20 ppm in sample A5a, U peaked in sample A5c with a mean of 2855 ppm and Th was found highest in sample A5a with a mean of 267 ppm. Silicon, V and As were observed in the laser data and are known to all substitute for P in the standard xenotime formula (YPO4) forming various other minerals (Ni et al. 1995; Kanazawa & Kamitani 2006). Si was the most prominent of these and showed large variation throughout the prospects with the lowest mean occurring in sample GPa where it was MPa with a mean of 37983 ppm. As occurred as a trace element and peaked in sample GPa with 263 ppm with other prospects generally falling 100 ppm less than this. Finally V was highest in sample A5c with 101 ppm. P a g e | 29 Other elements of interest include Ca (up to 3362 ppm), Sc (up to 425 ppm), Ti (up to 160 ppm), Sr (up to 319 ppm), Zr (up to 347 ppm) and Ba (up to 12 ppm). All of which are able to substitute with Y and the REE’s in xenotime due to similar ionic radii. Fe is also of interest as values of up to 41997 ppm were observed in the A5c sample. This high Fe value could correspond to uptake into the structure but is likely due to the abundance of hematite in some samples micro inclusions within xenotime. FLORENCITE LA-ICP-MS analysis was carried out on 12 florencite grains from two samples MPb and BPb. 36 elements were assayed for and all were found within these grains of florencite in a variety of ppm’s. This highly variable chemistry from the analyses could signify the structure of florencite can substitute for a wide variety of elements or that certain elements may include themselves within florencite. (Results in Table 7 and Appendix 9) Like the xenotime data set florencite seems to have variance with REE concentrations between prospects. The LREE’s were once again proven to be preferentially enriched over the HREE’s within florencite with La having a maximum mean of 29599 ppm in sample MPb, Ce having a maximum mean of 86422 ppm in sample BPb, Pr having a maximum mean of 13132 in sample BPb, Nd having a maximum mean of 63866 ppm in sample BPb and Sm having a maximum mean of 9408 ppm in sample BPb. Whilst the laser showed LREE enrichment it also detected that small concentrations of HREE’s reside within florencite with sample BPb being more enriched than sample MPb in all HREE’s. Gd had a maximum mean of 2756 ppm, Tb had maximum mean of 414 ppm, Dy with a maximum mean of 2220 ppm, Ho had a maximum mean of 423 ppm, Er had a P a g e | 30 maximum mean of 786 ppm, Yb had a maximum mean of 473 ppm and Lu had a maximum mean of 80 ppm. Lead, U and Th are also found within florencite with Pb having a maximum mean of 901 ppm in sample MPb, Th having a maximum mean of 1965 ppm and U having a maximum mean of 128 ppm. Other elements of interest are Si (up to 95677 ppm), Ca (up to 24287 ppm), Sc (up to 53.39 ppm), Ti (up to 420 ppm), V (up to 95 ppm), Fe (up to 105853 ppm), As (up to 2791 ppm) and Ba (up to 3756 ppm). These elements appear to be in substitution with the LREE’s. Particular interest was given to Sr which was found in florencite in concentrations up to 35180 ppm. Strontium appears to be replacing LREE’s within florencite or could be evidence of intergrowths/inclusions or precipitations/exsolution of goyazite (SrAl3(PO4)2(OH)5·(H2O)) within florencite. DISCUSSION Mineralogy and mineral chemistry XENOTIME GEOCHEMISTRY The EPMA data for various samples (Table 1a, 1b) shows the composition of xenotime is very consistent across all samples and prospects despite the different morphologies and possible generations observed. There is little variation between major constituent elements (Y, P and HREE). HREE are enriched, with all analysed samples plotting similarly on the chondrite-normalised (Figure 11). Enrichment of Sm and Gd-Lu can be observed showing the preference of xenotime for P a g e | 31 partitioning HREEs into its crystal structure. The chondrite-normalised plot also shows a prominent Eu anomaly. This Eu could possibly resemble the formation of xenotime in a reduced environment (Michael J 1975). Since Eu has both a 2+ and 3+ state, under reduced conditions Eu2+ becomes dominant and will not be as readily substituted into the REE3+/Y3+ site within xenotime, hence creating an anomaly through decreased uptake of Eu into xenotime. Among the HREE, there appear to be only two elements which display some significant variance. Ytterbium in xenotime varies from as low as 1.46 wt% in the Banshee prospect to as much as 4.01 wt% at Wolverine. The Fe content of xenotime also appears to vary between prospects. In most cases, Fe concentrations are <0.8wt% but at Area 5 and Area 5 North, Fe concentrations attain maxima of 1.02 wt% and 3.12 wt%, respectively. This enrichment coincides with the observation of macroscopic hematite in the rock chip samples and confirmation of the presence of fine-grained hematite during petrographic examination and could allude to the presence of hematite inclusions. The LREE-Y-HREE ternary diagram (Figure 12) shows, as expected, the enrichment in Y+HREE and corresponding depletion in LREE. This is controlled by the tetragonal crystal structure of xenotime (Andrehs & Heinrich 1998; Boatner 2002; Spear & Pyle 2002; Kolitsch & Holtstam 2004). 3+ This tetragonal crystal structure has the ideal formula of ATO4 where A=Y and T=P, a tetrahedrally co-ordinated phosphorous atom (Kolitsch & Holtstam 2004; Hetherington et al. 2008). Due to the similar ionic radii of Y (104 pm) and REE (100.1-117.2 pm) simple isostructural exchange is favourable. HREE’s are partitioned more favourable into xenotime due to their smaller ionic radii which suits the tetragonal structure ‘A’ site within xenotime. It is however possible for the slightly larger LREE’s to enter the ‘A’ site in xenotime. This inclusion of LREE can theoretically be maintained in xenotime as long as the ‘A’ site is occupied <50% by LREE’s (Boatner 2002; Kolitsch & Holtstam 2004). The ‘A’ site can also be substituted via complex isomorphic substitutions involving Ca2+, Fe and Mn (Förster 2006; Ondrejka et al. 2007). Although these P a g e | 32 cations are similar in size to Y they are crystallographically less likely to fill the ‘A’ site in large concentrations (<10%) (Ondrejka et al. 2007; Hetherington et al. 2008). FLORENCITE GEOCHEMISTRY In the Browns Range samples, LREE are present within a number of different mineral phases, the most important of which is florencite. Figure 13 shows the chondrite-normalised plot for florencite in each prospect. The LREE (La-Nd) enrichment and depletion in the MREE and HREE can be clearly seen. The preferential partitioning of LREE into florencite over HREE’s can also be observed in the LREE:HREE:(Sr+Ca) ternary diagram (Figure 14). Florencite, (LREE)Al3(PO4)2OH6, is actually a group of three named minerals, Florencite-(Ce), Florencite-(Nd) and Florencite-(La). Browns Range florencite contains a mixture of all three end-members that can be observed in the ternary Diagram of La:Nd:Ce (Figure 15). Florencite-(Ce) is generally the larger component (up to 11 wt%) but Nd was dominant in two samples GPa and WP2 (up to 10 wt% Nd, otherwise typically only 5-7 wt%). Florencite-(La) is generally the lesser among the three components. The Pr-dominant analogue is not a named end-member (mineral); EPMA data indicate the presence of up to 1.8 wt% Pr. Strontium also appears to be readily substituted into the LREE site in florencite (up to 4.5 wt%). Strontium substitution in florencite is reported from other florencite occurrences, yet generally at lower wt% values of 0.67 wt% (Nagy et al. 2002) or 1.82 wt% (Rasmussen & Muhling 2009). The higher Sr concentration in the Browns Ranges florencite probably reflects a different source rock geochemistry allowing for greater availability of Sr which then gets incorporate into florencite. An inverse relationship between REE and (Sr+Ca+Th) is noted within florencite (Figure 16) and was also suggested by Nagy et al. (2002). This inverse relationship raises the possibility of the coupled substitution 2REE3+ ↔ Th4+ + (Ca,Sr)2+, thus maintaining charge balance. P a g e | 33 It is realistic to assume partitioning of LREE into florencite simultaneously with xenotime crystallisation and evidence for this was observed using the SEM. Despite this, florencite generally occurs as replacement of xenotime as, for example, in Figure 7b. This replacement process affects the first generation of xenotime which underwent surface etching and breakdown via interaction with mineralising fluid. Second-generation xenotime can occur as inclusions within florencite or completely overprint the earlier xenotime. As shown above in the results section, florencite can display chaotic zonation (Fig. 6b), concentric organised zonation (Fig. 8f), skeletal replacement textures (Fig. 10d) and grains which exhibit no zoning (Fig. 9a). Florencite which exhibits both chaotic and more concentric organised zoning have lighter and dark zones in the BSE images. EPMA analysis confirmed that this zoning pattern is chemical with the ‘light’ zones enriched in Nd by 3-9 wt% and depleted in Ca and Sr by 1-2 wt% when compared to the ‘dark’ zones. This chemical difference could explain the observed skeletal replacement as certain chemistries appear more susceptible to alteration than others. The cause of the zonation is unclear; it is possibly a primary growth feature, but may also relate to an overprinting or remobilising event. Florencite which exhibits no visible zoning in the BSE images did reveal a subtle chemical zoning by EPMA with a noticeable difference between core chemistry and rim chemistry (Fig. 17). The major differences are that the core is enriched in P, F, Th and REE’s whilst being depleted in Ca, Sr and Fe when compared to the rim (Table 8). This chemical pattern from core to rim appears to be a growth feature where the hydrothermal fluid became deficient over time in available REE’s and P due to the growth of florencite leaving Sr, Fe and Ca to be taken up into the florencite structure towards the rim. Nagy et al. (2002) noticed zoning within florencite and arrived to a similar conclusion, i.e. that compositional zonation in florencite is controlled by variance in Ca, Sr, REE’s and Th concentrations. The REE- and P-enriched core of P a g e | 34 florencite is further evidence for replacement of xenotime by florencite as P and REE reflect primary xenotime chemistry. Finally, and most importantly, florencite exhibiting a skeletal replacement like texture still preserved some zoning and is probably a growth feature. The cores of these florencites are composed of a sericite and kaolinite matrix which suggests the breakdown of hydrolysed feldspar. The florencite appears to have overgrown the feldspar grain prior to breakdown to sericite and kaolinite. REE-ENRICHMENT IN ZIRCON Zircon is a subordinate but abundant mineral in the Browns Range samples. EPMA and LA-ICP-MS analysis has confirmed that zircon is also a REE host mineral. Significant amounts of REE can be incorporated within the zircon structure (Belousova et al. 2002). Figure 18 shows a chondrite- normalised plot for zircon, showing a marked enrichment in Gd, Dy and Er-Lu. EPMA data indicate that the (Y+HREE) content of zircon varies between 5.2 and 12.4 wt%. Of note is the relatively high concentration of Dy in zircon (0.5-1.24 wt%). This may have economic implications if zircon is abundant. There exists a solid solution series between zircon and xenotime (Hetherington et al. 3+ 3+ 5+ 4+ 4+ 2008), in which substitution takes place via the coupled ([REE ][Y ])-1[P ]-1 [Zr ][Si ] exchange (Hanchar et al. 2001; Geisler et al. 2007). REE enrichment is supported by the lower than expected values of Si which appears to be substituted out in favour of P when REE are incorporated observed in figure 18 (Bea 1996; Bea & Montero 1999). Zircon also appears to be the primary host for the highly valuable, potential by-product element Sc in the Browns Range samples. Although the measured concentrations are still relatively low in zircon (up to ~0.8 wt%), they are nevertheless an order of magnitude or so higher than in xenotime (<0.1 wt%) or florencite ( COMPARISON WITH OTHER OCCURRENCES Xenotime at Browns Ranges appears to be slightly more enriched in total REE than other xenotime occurrences around the world. Table 9 gives a comparison of the chemistries from representative samples of xenotime from various geological settings and global locations all analysed by microprobe techniques. This table shows that the Browns Range xenotime is most comparable to another hydrothermal occurrence from the Witwatersrand Basin, South Africa (Kositcin et al. 2003) in terms of total REE’s, yet the abundance of individual REE’s appears to vary significantly. The REE’s between these two hydrothermal samples have significant differences in Yb, Er, Dy, Sm and Lu concentrations. Such variance is likely controlled by the initial abundance of certain REE’s from the source magmatic-hydrothermal fluid or from interaction with wallrock during flow to the site of deposition. One xenotime from within a granite (Forster 1998) returned a total REE content of 35 wt%, which is significantly higher than the samples from Browns Range. Besides hydrothermal- and granite-related xenotime, the Browns Range xenotime in general has approximately 3-7 wt% more REE’s than other samples of xenotime with significant differences in the proportions of Yb, Dy and Gd. Table 9 also shows that U and Th concentrations appear to be significantly lower in hydrothermal xenotime, with other types of xenotime returning extremely high U (4.22 wt%) and Th (3.50 wt%) concentrations. Calcium and Fe also appear to be minor constituents of xenotime, in agreement with observations at Browns Ranges. Iron, however, appears to be slightly more enriched in some the Browns Range xenotime. The LREE pattern of xenotime is very similar across all xenotime reported in the literature, with the larger (ionic radius) LREE’s (La-Pr) often being below minimum detection or below 0.01 wt%, whilst the smaller LREE’s (Nd-Eu) occur more prominently with values between 0.5-2 wt%. P a g e | 36 PROCESSING IMPLICATIONS Xenotime has a complex geochemistry with a large number of elements readily substituted into different sites in the crystal structure (Hetherington et al. 2008). These elements include U, As and to a lesser extent Th. Uranium can occur in concentrations ranging from low-ppm level up to several wt%. Xenotime forms a solid solution with coffinite (USiO4), via [Y]-1[PO4]-1 ↔ *U+*SiO4] substitution (Förster 2006; Hetherington et al. 2008). Xenotime also forms a solid solution with thorite (ThSiO4) via [Y]-1[PO4]-1 ↔ *Th+*SiO4] substitution (Förster 2006; Hetherington et al. 2008). It is therefore critical to consider the U and Th concentrations in xenotime if a heavy mineral concentrate is to be produced. The EPMA and LA-ICP-MS data for xenotime show that U and Th concentrations are relatively low (<0.62wt% and <0.92 wt%, respectively) but nevertheless significant. Coexisting florencite and zircon contain lower U; both minerals contain some Th. The study has not revealed significant amounts of other U- and Th-bearing minerals, suggesting that most, if not all U and Th is present within the REE-bearing phases. The As concentrations in the analysed minerals from Browns Ranges is extremely low. This is significant because the As concentration in xenotime can, in some cases, can be particularly high (Ondrejka et al. 2007). Arsenic contamination is unlikely to be an issue if the prospects are exploited. GENESIS OF THE BROWNS RANGE REE MINERALISATION: A comprehensive genetic model for the Browns Range REE mineralisation has not yet been developed and comparable styles of mineralisation appear to be either non-existent or negligibly studied (Hoatson et al. 2011). It is therefore hard to compare the findings from this study with other hydrothermal REE deposits in similar geological settings. Although a sizeable volume of data has been collected, encompassing petrography, mineralogy and geochemistry, only the following preliminary genetic model can be put forward at this point in time. This model does, however, aim to account for observations at scales from that of the prospect down to individual mineral grains. P a g e | 37 As discussed earlier, the Browns Range area has been subjected to multiple granite intrusions (Frederick and Grimwade suites). It is proposed that, in the final stages of crystallization, these granite intrusions exsolve an acidic aqueous fluid phase (Bottrell & Yardley 1988). In the Browns Range case, this fluid would be rich in volatiles, notably P (as evidenced by the abundance of phosphates), F (fluorapatite and elevated F concentrations in sericite), Cl, and possibly other volatiles. Granites are well-known sources of REE and REE are readily released from a granitic magma into a hydrothermal fluid (Alderton et al. 1980; Lottermoser 1992; Monecke et al. 2003; Migdisov et al. 2009). It is reasonable to assume that these granites were the source of REE in the mineralisation. It can also be reasonably assumed that the fluid was acidic and volatile-rich, and also relatively reduced. The prominent negative Eu anomaly observed in xenotime (see above) suggests the presence of Eu2+ rather than Eu3+ which is preferentially partitioned into xenotime along with the other trivalent REE’s (Michael 1991). This initial hydrothermal fluid infiltrated the Browns Range metamorphics that surround the granite intrusions, forming the first generation of xenotime mineralisation. The focus for mineralisation would have been the arkose units on account of their high porosity. Early xenotime appears as large euhedral grains (e.g. Fig. 6e) and would have been responsible for removal of Y+HREE from the hydrothermal fluid. Petrographic evidence indicates that the subsequent stage must have involved brecciation of the host rock and possible boiling of the hydrothermal fluids which in turn increased fluid salinity and acidity (Burt 1981), contributing to the etch pits and fragmentation of the coarse euhedral grains of xenotime. Xenotime has been shown to be somewhat unstable when subjected to highly acidic fluids at high temperatures (Hetherington et al. 2010). As a result, replacement of xenotime by florencite occurs. The latter has become stable since HREE’s have been incorporated into xenotime leaving a LREE-enriched P a g e | 38 fluid. Florencite replacement of xenotime (e.g. Fig. 7f) leads to the reintroduction of HREE into the fluid whereas LREE are consumed. Florencite thus grew as overgrowths surrounding hydrolysed feldspars within the host arkose. These feldspars would have then been obliterated by the acidic fluids leaving the skeletal kaolinite-illite replacement textures observed. Loss of feldspar from the host rock is likely to have further stabilised florencite at the expense of, for example, monazite, due to the availability of Al in the fluid. Over time, flow of magmatic-hydrothermal fluid would subside and influx of meteoric water would be able to influence the hydrothermal system. Fluid mixing would cool and oxidise the system leading to the stability of hematite which is observed throughout most prospects. Stabilisation of hematite leads to the crystallisation of small hematite needles and nucleation of a second generation of xenotime to take place. This late generation of xenotime appears as small blades which do not display etch pits but which are commonly associated with hematite (e.g. Fig. 4b). This nucleation event meant that HREE’s were once again removed from the fluid. The absence of larger grains of second-generation xenotime is notable, and is possibly due to the rapid formation of abundant small blades of xenotime as the cooling fluids became saturated in HREE. Further evidence for the role of Fe in this late-stage crystallisation event can be seen in the composition of the rims of florencite grains which would have been still growing. The rims show significant enrichment of Fe up to approx. 8 wt% (Table 8). Eventually the system would have consumed all available REE’s leading to quartz-only precipitation within the latest-stage veins. Such a model can also account for the elevated Sr within florencite and coexistence of minor goyazite, in that there are two possible sources of Sr that could contribute to the higher than expected concentrations. These sources are the source granite and the breakdown of pre-existing feldspars (which can carry significant amounts of Sr). The conspicuous absence of monazite, the P a g e | 39 most common LREE bearing mineral, in the Browns Range mineralization, is also explained by this model. As well as the availability of Al to stabilise florencite, the aluminophosphate is also suggested to be more selective for LREE’s than monazite (Nagy et al. 2002). Monazite crystallisation might also have been hampered by the relative lack of Th in the hydrothermal fluids. Thorium is a major constituent of monazite and may be an essential requirement for its stabilisation. When the initial xenotime generation was precipitated it left a fluid enriched in LREE’s but depleted in Th. Together with the release of Al from feldspar breakdown, all pre- requisites for florencite stability were satisfied and monazite could not form. CONCLUSION The Browns Ranges area contains significant REE mineralisation with skewness towards HREE’s. This mineralisation is a very real prospect for the development of an economically successful mining operation if sufficient ore reserves can be confirmed. REEs are hosted within 2 main phosphate minerals, xenotime and florencite. Xenotime is very selective towards HREE’s and Y. EPMA and LA-ICP-MS data revealed that HREE’s such as Dy (up to 6.5 wt. %), Er (up to 4.35 wt. %), Gd (up to 7.56 wt. %), Yb (up to 4.65 wt. %) and Y (up to 43.3 wt. %) can contribute up to 65 wt.% of xenotime and that the xenotime composition is consistent across all prospects and xenotime generations. Xenotime at Browns Ranges appears to be more enriched in ΣREE than other occurrences from around the world but is nevertheless comparable with xenotime from other hydrothermal settings. Florencite is very selective towards LREE’s. Cerium (up to 11.54 wt.%), Nd (up to 10.05 wt.%) and La (up to 5.40 wt.%) are the main REE present. Florencite is also notably enriched in Sr (up to 11.63 wt.%) and Ca (up to 1.93 wt.%). REE are also found in elevated concentrations within zircon, a subordinate mineral within the mineralisation. ΣREE concentrations within zircon are up to 13 wt.%, among the highest values reported in the P a g e | 40 literature. Zircon would also appear to concentrate Sc in the deposits. Concentrations of U and Th in xenotime and florencite are moderate to low and As concentrations are negligible. Petrological observations coupled with microanalytical data allow development of a preliminary genetic model. Evidence such as the marked overprinting of florencite by xenotime along with two distinct xenotime generations suggests that the hydrothermal fluid underwent evolution with respect to the REE budget and LREE/HREE ratios. The negative Eu anomaly in xenotime, elevated fluorine levels in sericite and abundant granites in the area lead to a model involving a reduced, acidic, volatile-rich fluid that percolated through porous arkose units. The observation of late hematite suggests that mixing with meteoric water and subsequent oxidation of the fluids may have played a role in the later stages of mineralisation. This in turn stabilised hematite and allowed for deposition of a second generation of xenotime. Field observations suggest that faults in the area acted as fluid conduits and that brecciation, possibly associated with release of volatiles from the fluid, occurred along these faults. RECOMMENDATIONS Further study of the Browns Range area is recommended to further constrain ore genesis and expand the exploration model. Particular attention should be paid to the possibility of using xenotime for geochronology, as proposed by Andrehs & Heinrich (1998), Rasmussen (2005), Rasmussen et al. (2007), Birger (2005) and Hetherington et al. (2008). Identification of a suitable geothermometer/geobarometer to constrain temperature and pressure conditions of ore mineralisation would also aid in constraining the genetic model. In particular the observation of rutile within hydrothermal quartz at some prospects is a promising target as a geothermometer as suggested by Rusk et al.(2008) using the TitaniQ geothermometer (Wark & Watson 2006). P a g e | 41 Structural mapping, especially from drill core, will help map structures at depth and confirm if the fault- and breccia-hosted mineralisation described here is more than a surface expression. Finally, since this study was limited by access to surface rock chip samples only, mineralised samples from deeper in the system could aid in identifying any systematic difference in the mineralisation with depth. ACKNOWLEDGMENTS Thanks go to Robin Wilson and Northern Minerals for the opportunity to carry out this project and supply financial and logistical support. Particular mention goes to Kevin Das and Claudio Sheriff for their help when on site. I appreciatively would like to thank my Supervisors Nigel Cook and Cristiana Ciobanu of Adelaide University for their expertise, tireless help and direction throughout the year. Finally I would like to thank Adelaide Microscopy for the use of their facilities with particular thanks to Angus Netting, Ben Wade and Aoife McFadden for their expertise and guidance in micro-analytical techniques. P a g e | 42 REFERENCES ALDERTON D. H. M., PEARCE J. A. & POTTS P. J. 1980. 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Granite suites and supersuites of eastern Australia. . Aust J Earth Sci 48:515–530. Table 1a. Electron probe microanalyses of xenotime. *La, Al, Nb, Mg, Ho, Zr, Hf, Sr and Pr were all analysed for but returned results consistently #K was not analysed due to the limitation with number of elements being analysed at the same time. Table 1b. Electron probe microanalyses of xenotime. * La, Al, Nb, Mg, Ho, Zr, Hf, Sr and Pr were all analysed for but returned results consistently #K was not analysed due to the limitation with number of elements being analysed at the same time. Table 2a. Electron probe microanalyses of florencite. *Tb, Ho, Er, Yb, Lu, Zr and Nb were all analysed for but returned results consistently #K was not analysed due to the limitation with number of elements being analysed at the same time. Table 2b. Electron probe microanalyses of florencite. * Tb, Ho, Er, Yb, Lu, Zr and Nb were all analysed for but returned results consistently #K was not analysed due to the limitation with number of elements being analysed at the same time. Table 3. Electron probe microanalyses of zircon *La, Nb, Tb, Pr, and Mg were all analysed for but returned results consistently #K was not analysed due to the limitation with number of elements being analysed at the same time. P a g e | 46 Table 4a/b. Electron probe microanalyses of sericite. Table 5a/b. Electron probe microanalyses of illite. Table 6. Electron probe microanalyses of kaolinite. Table 7. LA-ICP-MS analysis of xenotime and florencite Table 8. Partial EPMA data collected from a single florencite grain from Banshee Prospect. The data shows that the core is enriched in P, F, Th and REE’s whilst being depleted in Ca, Sr and Fe when compared to the rim. Table 9. Representative compositions of xenotime from Browns Range and other global xenotime occurrences *Columns: 1 - Ondrejka et al.( 2007), analysis number 165 from a rhyolite; 2: - Hetherington et al. (2008), average of 7 analyses from pegmatite-associated xenotime; 3 -(Bowins & Crocket 2011), sample N1b from Archean Banded iron formation; 4-7 - Kositcin et al. (2003), sample KP12BR (igneous detrital), MB347 (diagenetic), EVRK20-2 (hydrothermal) and XTC (igneous), respectively; 8 - Wang et al. (2003), analysis G-b4 from a granite; 9 - Masau et al. (2000), analysis 1 from a pegmatite; 10 -(Demartin et al. 1991), sample 6 from Alpine veins; 11 (Franz et al. 1996), sample 17329.1 from metasediments; 12 - Förster (1998), sample 1141-FS from a granite; 13-15 - Browns Ranges, this study samples A5a, WP2 and GPa, respectively. - Means below detection limit n/a means element not included in assay Figure Captions P a g e | 47 Figure 1. Location of the current tenements held by Northern Minerals. The location of each prospect is also shown as red stars. Figure 2 - A) 6 mm-sized quartz vein surrounded by pink xenotime mineralisation within the host arkose with visible 2-4 cm-sized quartz clasts (A5N). B) Crosscutting 260°-320° structures with surrounding hematite xenotime enrichment (A5N). C) 3 mm-thick quartz vein within the host arkose. On either side of the vein there is a 2-3 cm-wide zone of hematite and xenotime enrichment. (A5N) D) Brecciated arkose with quartz veins enriched in REE mineralisation (GP). E) Vuggy quartz vein within a breciated arkose (GP). F) Series of 1-3 cm-wide quartz veins in varying orientations with some clearly crosscutting others (GP). Figure 3 - A) Heavily silicified breccia system with visible pink xenotime mineralisation (WP). B) Heavily brecciated arkose with thick quartz veining which contains xenotime mineralisation (WP). C) 4-10 cm-thick quartz vein within the host arkose (WP). D) Quartz veins within arkose with clear pink xenotime mineralisation occurring along the boundary between the quartz vein and arkose. E) Heavily breciated arkose with quartz veins of varying size. F) Quartz vein with xenotime mineralisation occurring at the contact between arkose and the quartz vein. Figure 4 - Area 5 North Prospect Back-scatter electron images. A) Euhedral bladed xenotime (10-15 µm) overgrowing acicular hematite (70µm). B) A large population of euhedral bladed xenotime (10 µm) intergrown with acicular hematite (55 µm) filling a fracture within quartz. C) Euhedral overgrowths of xenotime (60 µm) surrounding a zoned zircon (10 µm). D) Euhedral bladed xenotime intergrown with acicular hematite (120 µm) and disseminated within quartz filling a fracture within quartz. E) Clusters of euhedral bladed xenotime (10 µm) intergrown with acicular hematite (110 µm) filling a fracture within quartz. F) Pyramidal overgrowth of xenotime (15 µm) surrounding a fractured and zoned zircon (70 µm) suspended in a kaolinite/sericite matrix. G) Euhedral bladed xenotime (15 µm) intergrown with acicular hematite (50 µm) with a cement of P a g e | 48 goyazite (75 µm). H) Euhedral tabular zoned florencite (5 µm) suspended within a matrix of kaolinite. (Xen=xenotime, Hem=hematite, Fl=florencite, Zr=zircon, Goy=goyazite, Qtz=quartz and Ser=sericite). Figure 5 - Area 5 Prospect Back-scatter electron images. A) Complete euhedral overgrowth of xenotime (120 µm) surrounding a zircon (30 µm). B) Bladed xenotime (20 µm) lining a fracture within quartz with a hematite core consisting of acicular needles (10 µm) suggesting late stage Fe grwoth. C) Bladed xenotime (20 µm) within fractured quartz and as disseminations (25 µm) within quartz with slight replacement of florencite (25 µm) by xenotime. D) Massive euhedral xenotime (250 µm) with inclusions of florencite (50 µm), as well as an inclusion of a aciclular hematite/florencite intergrowth (75 µm). E) Euhedral tabular zoned florencite (50 µm) exhibiting skeletal replacement forming a sericite core caused by the breakdown of feldspar. Note also bladed xenotime (15 µm) forming within fractured quartz. F) Bladed xenotime (20 µm) within fractured quartz and also as disseminations within quartz. G) Euhedral bladed xenotime (150 µm) surrounded by acicular hematite (30 µm) crosscut by a 150 µm wide quartz vein. H) Massive euhedral xenotime (600 µm) with inclusions of florencite (35 µm). (Xen=xenotime, Hem=hematite, Fl=florencite, Zr=zircon, Qtz=quartz and Ser=sericite). Figure 6 - Gambit Prospect Back-scatter electron images. A) Euhedral xenotime (120 µm) heavily fractured along the edges with etch pits due to fluid interactions intergrown with rutile (90 µm). B) Euhedral chaotically zoned florencite (100 µm) within quartz. C) Small disseminations of both xenotime (50 µm) and florencite (5 µm) within quartz. D) Euhedral massive xenotime (90 µm) with etch pits along with florencite occurring as inclusions within xenotime (8 µm), as dissemination in quartz (25 µm) and suspended in a sericite/kaolinite matrix (20 µm). E) Euhedral massive xenotime (350 µm) exhibiting surface etch pitting disseminated within quartz F) Remnants of a massive xenotime grain within quartz. G) Euhedral massive xenotime (150 µm) disseminated within quartz P a g e | 49 with surface pitting and undergoing breakdown. H) Fractured massive xenotime grain (400 µm) with fractures infilled by sericite along with surface etch pitting. (Xen=xenotime, Hem=hematite, Fl=florencite, Qtz=quartz and Ser=sericite). Figure 7 – Wolverine Prospect Back-scatter electron images. A) Euhedral tabular xenotime (220 µm) with surface etch pitting and fractures disseminated within quartz. B) Heavily fractured massive xenotime grain (300 µm) undergoing replacement by florencite (200 µm). C) Intergrowth of florencite (30 µm) and xenotime (20 µm) with possible replacement of xenotime by florencite. D) Heavily fractured massive xenotime grain (600 µm) disseminated throughout quartz. E) Large euhedral massive xenotime grain (700 µm) showing surface etch pitting with smaller disseminations of xenotime (20 µm) within quartz. F) Replacement of massive xenotime (60 µm) with florencite (50 µm). (Xen=xenotime, Fl=florencite, Qtz=quartz and Ser=sericite). Figure 8 - Wolverine Prospect Back-scatter electron images. A) Massive euhedral xenotime grain (120 µm) exhibiting surface etch pitting surrounded by smaller dissemination of xenotime (30 µm) within quartz. B) Heavily fractured massive xenotime grain (350 µm) with smaller disseminations of xenotime (30 µm) within quartz. C) Replacement texture of a massive xenotime grain (70 µm) being replaced by florencite (30 µm). D) Euhedral florencite grain (70 µm) with inclusions of xenotime (20 µm) also with some slight Fe rich compositional zoning around the rim. E) Intergrowth between Ba/Al- and Fe-rich phosphates (100 µm). F) Zoned florencite (70 µm) with euhedral bladed xenotime (40 µm) suspended within a kaolinite matrix. (Xen=xenotime, Fl=florencite, Qtz=quartz and Ba- Un-named Ba,Al phosphate + Fe=Fe rich phosphate). Figure 9 - Banshee Prospect Back-scatter electron images. A) Euhedral grain of florencite (60 µm) within quartz. B) Euhedral florencite (80 µm) with inclusions of xenotime (20 µm) suggesting an overprinting texture. C) Bladed xenotime (40 µm) surrounded by a florencite cement (50 µm). D) P a g e | 50 Xenotime (400 µm) filling a fracture within quartz with small florencite inclusions (7 µm). E) Replacement of massive xenotime (60 µm) by florencite (30 µm) F) Replacement of massive xenotime (70 µm) by florencite (120 µm) G) Small xenotime overgrowths (10 µm) of zoned zircons (30 µm) suspended within a sericite matrix. H) Florencite replacement (300 µm) of a tabular feldspar grain and xenotime (50 µm). (Xen=xenotime, Fl=florencite, Zr=zircon, Qtz=quartz and Ser=sericite). Figure 10 - Mystic Prospect Back-scatter electron images. A) Pyramidal overgrowths of xenotime (50 µm) surrounding a fractured zircon (100 µm). B) Cluster of euhedral bladed xenotime grains (15 µm) within a sericite matrix. A small inclusion of apatite is disseminated within quartz. C) Massive euhedral xenotime grain (70 µm) with a sericite core containing small inclusions of florencite. D) Tabular florencite (60 µm) exhibiting a skeletal replacement texture with sericite filling some of the cores due to breakdown of feldspar. E) Central large euhedral grain of xenotime (120 µm) with florencite replacement (10 µm) surrounded by small blades of xenotime (10 µm) within a quartz fracture possibly caused from remobilisation of REE’s. F) Replacement of euhedral xenotime (100 µm) by florencite (40 µm) suspended within a sericite matrix within fractured quartz. G) Euhedral tabular florencite (60 µm) surrounded by small blades of xenotime (5 µm). H) Overgrowth of xenotime (60 µm) with a feathery texture possibly due to breakdown of xenotime around a zircon (10 µm). (Xen=xenotime, Fl=florencite, Zr=zircon, Ap=apatite Qtz=quartz and Ser=sericite). Figure 11 - Chondrite-normalised REE patterns for xenotime from Browns Range (LA-ICP-MS data). Showing enrichment of Sm and HREE’s within xenotime due to crystal structure controlling portioning of REE’s. A prominent Eu anomaly is also observed suggesting a reduced environment. P a g e | 51 Figure 12 - Ternary Y-LREE-HREE diagram showing the composition of all analysed xenotime crystals (EPMA data). Showing that xenotime is Y+HREE dominant mineral with only minor LREE partitioning occurring into xenotime. Figure 13 - Chondrite-normalised REE patterns for florencite from Browns Range (LA-ICP-MS data). Showing strong enrichment in Ce, Pr, La and Nd. There is a slight Eu anomaly that can also be observed. Figure 14 - Ternary LREE-HREE-(Ca+Sr) diagram showing the composition of all analysed florencite crystals, includes zoned grains (EPMA data). Showing that florencite is LREE selective yet similar ionic radii elements such as Sr and Ca can be incorporated into the crystal structure. Figure 15 - Ternary La-Ce-Nd diagram showing variation in composition of florencite from Browns Ranges with respect to the three end-members minerals, florencite-(La), florencite-(Ce) and florencite-(Nd) (EPMA data). Showing that each florencite grain is a mixture of the 3 end members with an inclination to be Ce+Nd rich. Figure 16 - Incorporation of minor elements in florencite, expressed in ionic numbers (a.p.f.u) of Ca+Sr+Th vs. ΣREE. The black best fit line suggests that there is a inverse relationship between Ca+Sr+Th incorporation and ΣREE. The red points correlate to the Wolverine prospects do not share the same trend as the other data points, for as-yet unexplained reasons. Figure 17 - The single grain of florencite from Banshee Prospect, showing points from which the data in Table 8 was collected. Figure 18 - Chondrite-normalised REE patterns for zircon from Browns Range (EPMA data). Showing enrichment of Gd, Dy, Er, Yb and Lu within zircons. This reflects the observations of zircon being markedly enriched in REE’s compared to other zircon populations P a g e | 52 Figure 19 - Substitution of (Zr+Si) by (REE+Y+P) reveals the extent of solid solution between xenotime and isostructural zircon. Points are collected from zircons with xenotime overgrowths which have elevated REE content when compared to other zircon samples. P a g e | 53 Xenotime (Y,HREE)PO4 Prospect Area 5 Prospect Area 5 North Prospect Gambit Prospect Sample A5a A5b A5nb A5Na GP1 Gpa Number of Spots 12 7 5 16 12 8 (Wt.%) Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD CaO Ce2O3 0.05 Nd2 O3 0.47 0.17 0.37 0.37 0.40 0.12 0.14 0.09 0.83 0.48 1.14 0.82 Sm2O3 1.12 0.24 1.04 0.09 1.19 0.15 1.36 0.30 1.43 0.34 1.63 0.45 Gd2O3 5.61 0.46 5.02 0.42 5.66 0.31 6.00 0.33 6.14 0.53 6.53 0.68 Tb2O3 0.38 0.25 0.39 0.25 Dy2O3 6.50 0.17 6.27 0.14 6.05 0.23 6.04 0.18 6.48 0.32 6.52 0.23 Er2O3 4.35 0.52 4.04 0.16 3.58 0.09 3.35 0.18 3.45 0.46 3.32 0.21 Yb2O3 4.24 0.86 3.60 0.16 2.64 0.18 2.46 0.31 2.19 0.65 2.09 0.42 Lu2O3 0.75 0.12 0.61 0.05 0.56 0.05 0.48 0.05 0.44 0.10 0.47 0.08 Sc2O3 0.03 ThO2 0.02 0.03 0.11 0.08 P2O5 34.08 0.59 32.13 0.43 33.43 1.01 32.37 0.48 33.67 0.55 33.81 0.64 F (wt.%) P a g e | 54 Xenotime (Y,HREE)PO4 Prospect Wolverine Prospect Mystic Prospect Banshee Sample WP2 WP1 Wpa WPb MPb Mpa BPb Number of Spots 11 19 7 17 8 7 10 (Wt.%) Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD CaO 0.25 0.10 0.27 0.20 0.16 0.07 0.26 0.05 0.42 0.11 0.43 0.11 0.19 0.06 Y2O3 39.73 0.82 39.06 1.74 42.50 0.47 41.83 0.96 41.56 1.16 40.86 1.18 43.34 0.70 Ce2O3 0.08 0.06 0.06 0.05 0.05 0.03 0.14 0.06 0.05 0.10 0.12 0.03 0.10 0.06 Nd2 O3 0.74 0.42 0.76 0.41 0.44 0.25 0.80 0.36 0.24 0.10 0.25 0.08 0.77 0.40 Sm2O3 1.15 0.33 1.39 0.34 1.11 0.46 1.50 0.23 0.69 0.21 0.68 0.12 1.97 0.52 Gd2O3 5.53 0.90 5.57 0.74 6.88 0.79 5.51 0.84 4.97 0.28 4.54 0.45 7.56 0.40 Tb2O3 0.55 0.36 0.42 0.41 0.87 0.19 0.73 0.16 Er2O3 4.18 0.26 3.83 0.34 4.12 0.25 3.64 0.32 4.58 0.37 4.16 0.11 2.83 0.14 Yb2O3 3.81 0.48 3.02 0.47 3.48 0.49 3.05 0.62 4.65 0.56 4.03 0.26 1.46 0.17 Lu2O3 0.66 0.09 0.55 0.12 0.72 0.06 0.54 0.09 0.83 0.07 0.64 0.07 0.36 0.04 Sc2O3 0.06 0.03 0.04 0.02 0.04 0.03 0.05 0.02 0.12 0.03 0.09 0.02 UO2 0.36 0.15 0.41 0.20 0.38 0.24 0.28 0.16 0.62 0.15 0.61 0.18 0.43 0.14 FeO 0.53 0.70 1.72 2.41 0.00 0.00 0.03 0.08 0.82 0.74 0.66 0.51 0.71 0.40 TiO2 0.01 0.02 0.01 0.01 P2O5 33.00 0.77 32.93 1.07 34.31 0.33 32.31 0.74 32.80 0.59 30.98 1.59 33.98 0.38 F (wt.%) 0.13 0.04 0.22 0.44 P a g e | 55 Florencite (LREE)Al3(PO4)2(OH)6 Prospect Area 5 North Area 5 Prospect Wolverine Prospect Sample A5Na A5a A5b WP2 Wpa WPb WPc Number of spots 1 3 12 11 6 6 3 (Wt.%) Mean Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD CaO 1.57 0.78 0.95 1.41 0.69 1.04 0.09 1.23 0.19 1.16 0.07 1.93 0.12 Y2O3 Pr2O3 0.87 1.64 0.28 1.31 0.33 1.55 0.33 1.23 0.35 1.22 0.20 0.91 0.11 Sm2O3 0.75 0.65 0.21 0.50 0.33 1.01 0.09 1.05 0.24 1.03 0.07 0.51 0.12 Gd2O3 K2O 0.09 0.05 ThO2 UO2 TiO2 SiO2 0.20 0.49 0.21 0.32 0.19 0.55 0.35 0.45 0.22 2.05 1.63 1.05 0.51 Al2O3 34.04 32.87 0.75 31.70 0.88 30.49 0.83 33.68 2.27 30.88 0.98 30.96 1.73 P2O5 26.62 29.89 0.49 28.57 0.93 25.99 1.48 26.99 2.82 27.56 0.83 24.27 0.23 F (wt.%) 0.32 0.76 0.23 0.48 0.13 0.27 0.05 0.94 0.14 0.58 0.13 1.28 0.14 Cl (wt.%) 0.03 0.03 0.01 0.03 0.02 0.05 0.03 0.04 0.01 0.03 0.01 0.09 0.00 total 87.34 93.74 88.94 80.42 88.82 87.23 84.47 Formula (a.p.f.u) 14 14 14 14 14 14 14 (Wt.%) Mean Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Ca 0.10 0.07 0.08 0.12 0.06 0.10 0.01 0.11 0.02 0.10 0.01 0.18 0.02 Y 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.02 0.03 0.00 0.00 La 0.04 0.16 0.02 0.16 0.03 0.06 0.01 0.09 0.02 0.09 0.01 0.12 0.01 Ce 0.14 0.33 0.05 0.32 0.02 0.21 0.02 0.24 0.04 0.25 0.02 0.31 0.00 Nd 0.14 0.19 0.04 0.16 0.06 0.32 0.03 0.22 0.04 0.20 0.02 0.11 0.01 Pr 0.03 0.05 0.01 0.04 0.01 0.05 0.01 0.04 0.01 0.04 0.01 0.03 0.00 Sm 0.02 0.02 0.01 0.01 0.01 0.03 0.00 0.03 0.01 0.03 0.00 0.02 0.00 Gd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 Dy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe 0.02 0.09 0.10 0.03 0.03 0.05 0.03 0.07 0.05 0.01 0.00 0.09 0.01 Na 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 K 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Th 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.03 0.01 U 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Sr 0.56 0.08 0.02 0.13 0.04 0.00 0.00 0.16 0.04 0.20 0.02 0.22 0.01 Total 1.07 0.99 0.99 0.85 0.99 0.95 1.13 Al 3.34 3.05 3.08 3.21 3.27 3.02 3.22 P 1.88 1.99 0.03 1.99 0.04 1.96 0.07 1.88 0.15 1.94 0.08 1.81 0.06 Si 0.02 0.04 0.02 0.03 0.02 0.05 0.03 0.04 0.02 0.17 0.13 0.09 0.04 Total 1.89 2.03 2.02 2.01 1.92 2.11 1.90 F 0.08 0.19 0.06 0.12 0.03 0.08 0.01 0.24 0.04 0.15 0.04 0.36 0.03 Cl 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.01 0.00 0.00 0.00 0.01 0.00 OH (by difference) 5.91 5.81 0.06 5.87 0.04 5.92 0.02 5.75 0.04 5.84 0.04 5.63 0.03 Total 6.00 6.00 6.00 6.00 6.00 6.00 6.00 mol.% Florencite-(La) 4.05 15.96 2.47 16.58 2.73 7.66 1.20 9.47 1.41 9.78 1.03 11.00 0.09 mol.% Florencite-(Ce) 13.49 33.99 6.86 32.66 2.72 24.38 0.98 24.42 1.77 26.18 1.27 27.45 0.84 mol.% Florencite-(Nd) 13.44 19.95 5.48 16.52 6.64 37.78 2.73 22.54 3.55 21.11 1.37 10.12 1.07 P a g e | 56 Florencite (LREE)Al3(PO4)2(OH)6 Prospect Mystic Prospect Banshee Prospect Gambit Prospect Sample MPb Mpa BPb Bpa GP1 Gpa Number of spots 6 3 5 11 2 4 (Wt.%) Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD CaO 1.66 0.16 1.91 0.15 1.34 0.72 1.66 0.15 1.69 0.01 1.76 0.77 Y2O3 0.11 0.17 Nd2O3 4.01 1.01 3.92 1.86 7.15 0.64 7.24 0.95 5.02 1.38 9.12 6.79 Pr2O3 0.89 0.26 0.99 0.24 1.55 0.09 1.55 0.19 0.93 0.22 1.50 0.45 Sm2O3 0.45 0.28 0.55 0.25 1.09 0.25 0.84 0.15 0.53 0.13 0.75 0.34 Gd2O3 Dy2O3 Al2O3 32.32 3.18 30.41 2.92 32.58 1.52 30.97 0.85 30.82 1.76 35.80 2.07 P2O5 26.42 2.64 26.20 0.61 28.72 1.94 26.44 1.34 22.84 3.13 27.73 3.13 F (wt.%) 0.96 0.19 1.02 0.19 0.70 0.23 0.65 0.19 0.44 0.00 0.85 0.15 Cl (wt.%) 0.06 0.02 0.06 0.01 0.03 0.01 0.05 0.03 0.03 0.00 0.04 0.02 total 88.26 84.75 91.96 88.85 79.42 92.96 Formula (a.p.f.u) 14 14 14 14 14 14 (wt.%) Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Ca 0.15 0.01 0.18 0.02 0.11 0.06 0.15 0.01 0.16 0.00 0.15 0.07 Y 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.02 La 0.12 0.03 0.13 0.01 0.09 0.02 0.09 0.02 0.09 0.01 0.08 0.06 Ce 0.28 0.04 0.27 0.01 0.29 0.01 0.31 0.03 0.23 0.00 0.23 0.10 Nd 0.12 0.03 0.12 0.06 0.20 0.02 0.22 0.03 0.16 0.05 0.25 0.17 Pr 0.03 0.01 0.03 0.01 0.05 0.00 0.05 0.01 0.03 0.01 0.04 0.01 Sm 0.01 0.01 0.02 0.01 0.03 0.01 0.02 0.00 0.02 0.00 0.02 0.01 Gd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 Dy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.00 0.00 Fe 0.26 0.31 0.06 0.02 0.20 0.19 0.20 0.17 0.09 0.05 0.07 0.10 Na 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 K 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Th 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 U 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Sr 0.18 0.06 0.24 0.03 0.12 0.01 0.14 0.02 0.00 0.00 0.12 0.03 Total 1.16 1.07 1.11 1.19 0.81 1.00 Al 3.16 3.08 3.08 3.07 3.19 3.32 P 1.85 0.15 1.91 0.12 1.95 0.08 1.88 0.07 1.70 0.28 1.84 0.13 Si 0.09 0.08 0.11 0.06 0.03 0.02 0.07 0.05 0.43 0.58 0.05 0.05 Total 1.95 2.02 1.98 1.95 2.13 1.89 F 0.25 0.05 0.28 0.06 0.18 0.05 0.17 0.05 0.12 0.00 0.21 0.03 Cl 0.01 0.00 0.01 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 OH (by difference) 5.74 0.05 5.71 0.06 5.82 0.05 5.82 0.06 5.87 0.00 5.79 0.03 Total 6.00 6.00 6.00 6.00 6.00 6.00 mol.% Florencite-(La) 11.17 3.56 12.49 1.36 8.77 2.50 8.04 1.88 11.60 1.06 7.50 5.57 mol.% Florencite-(Ce) 24.78 6.65 25.62 0.65 26.71 4.63 26.09 3.95 28.37 0.24 22.75 8.79 mol.% Florencite-(Nd) 10.82 4.03 11.17 4.99 18.94 3.87 18.56 3.45 19.33 5.46 25.52 18.51 P a g e | 57 Zircon (Zr,REE,Sc)PO4 Prospect Area 5 North Banshee Prospect Mystic Prospect Wolverine Prospect Area 5 Prospect Sample A5Na BPb Bpa Mpa WPc A5b Number of spots 4 1 1 2 9 2 (Wt.%) Mean SD Mean Mean Mean SD Mean SD Mean SD CaO 0.61 0.22 0.87 0.81 0.50 0.01 0.44 0.17 0.39 0.04 Y2O3 3.79 3.52 4.71 2.85 7.43 1.33 3.17 2.57 6.12 0.84 Ce2O3 0.20 0.12 0.33 0.59 0.84 0.09 0.25 0.15 0.56 0.01 Nd2O3 0.13 0.16 Ho2O3 Sc2O3 0.33 0.18 0.51 0.58 0.33 0.01 0.31 0.17 0.79 0.31 ZrO2 53.49 5.93 47.17 53.17 46.87 0.69 53.77 5.45 46.60 0.08 HfO2 1.61 0.10 1.64 1.27 1.64 0.14 1.56 0.24 1.02 0.15 ThO2 0.22 0.22 0.51 3.46 1.50 0.62 1.03 0.83 2.15 0.66 UO2 0.40 0.06 0.87 1.07 0.93 0.08 0.38 0.21 0.52 0.20 SrO 0.15 0.00 0.15 0.17 0.15 0.00 0.15 0.04 0.11 0.02 FeO 2.43 1.38 2.42 1.33 1.26 0.04 1.85 1.10 1.08 0.14 TiO2 0.04 0.04 0.03 0.07 0.07 0.01 0.09 0.06 0.10 0.02 SiO2 24.26 2.29 28.11 24.31 22.06 0.07 24.59 3.97 21.28 0.70 Al2O3 0.81 0.24 1.24 1.15 1.14 0.01 1.47 1.10 1.35 0.10 P2O5 4.00 2.76 5.00 3.93 6.04 0.05 3.92 3.02 4.94 1.42 F (wt.%) 0.47 0.12 0.24 0.67 0.81 0.12 0.50 0.18 0.84 0.16 Cl (wt.%) 0.03 0.01 0.02 0.02 0.02 0.02 0.03 0.03 0.05 0.03 total 94.32 96.42 97.61 96.47 94.85 91.45 Formula (a.p.f.u.) 6 6 6 6 6 6 (Wt.%) Mean SD Mean Mean Mean SD Mean SD Mean SD Ca 0.02 0.00 0.03 0.02 0.01 0.00 0.01 0.00 0.01 0.00 Y 0.06 0.06 0.08 0.05 0.13 0.02 0.05 0.04 0.11 0.00 Ce 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 Nd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Sm 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Gd 0.05 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Dy 0.08 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.01 0.00 Ho 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Er 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.01 0.00 Yb 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.01 0.00 Lu 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Sc 0.01 0.00 0.01 0.01 0.01 0.00 0.00 0.00 0.02 0.00 Zr 0.87 0.09 0.73 0.86 0.77 0.01 0.87 0.08 0.81 0.04 Hf 0.00 0.00 0.01 0.01 0.01 0.00 0.01 0.00 0.01 0.00 Mg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe 0.06 0.03 0.06 0.03 0.03 0.00 0.05 0.03 0.03 0.00 K 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Th 0.00 0.00 0.00 0.02 0.01 0.00 0.00 0.00 0.01 0.00 U 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Sr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total 1.09 0.98 0.98 1.08 1.05 1.08 sum (Y+REE) 0.10 0.08 0.11 0.08 0.20 0.02 0.08 0.06 0.16 0.02 P 0.11 0.07 0.13 0.11 0.17 0.00 0.11 0.08 0.14 0.03 Si 0.81 0.05 0.89 0.80 0.74 0.00 0.81 0.11 0.75 0.02 Total 0.92 1.03 0.91 0.92 0.92 0.90 F 0.04 0.01 0.02 0.07 0.08 0.01 0.05 0.02 0.09 0.02 Cl 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total 0.05 0.02 0.07 0.08 0.05 0.09 P a g e | 58 Muscovite KAl2(Si3Al)O10(OH,F)2 Prospect Area 5 Prospect Area 5 North Prospect Wolverine Prospect Sample A5a A5b A5Na A5Nb WPa WPb WPc Number of spots 9 8 1 2 2 1 2 (Wt.%) Mean SD Mean SD Mean Mean SD Mean SD Mean Mean SD CaO 0.07 0.14 0.04 0.04 0.03 0.23 0.17 0.07 0.02 0.08 0.02 0.03 Na2O 0.02 0.01 0.09 0.05 0.00 0.07 0.05 0.01 0.02 0.24 0.10 0.09 K2O 9.61 0.94 6.87 0.88 6.99 7.25 1.41 8.72 0.22 6.35 6.83 0.57 FeO 1.63 0.80 1.57 0.68 1.40 4.84 5.41 4.14 2.69 2.95 2.17 0.49 TiO2 0.15 0.10 0.18 0.14 0.03 0.01 0.01 0.02 0.01 0.01 0.12 0.15 MgO 3.12 0.72 2.92 1.02 0.67 1.49 0.29 1.59 0.24 1.08 2.70 1.81 SiO2 53.09 1.40 51.54 0.87 52.01 50.31 2.42 51.79 2.42 50.72 50.37 1.94 MnO 0.03 0.02 0.02 0.02 0.13 0.17 0.20 0.01 0.01 0.01 0.02 0.03 Cr2O3 0.00 0.01 0.01 0.01 0.00 0.00 0.00 0.01 0.00 0.00 0.01 0.01 Al2O3 34.52 1.65 31.21 1.36 37.07 30.95 3.72 31.61 1.19 31.72 31.53 0.02 F (wt.%) 0.05 0.07 0.12 0.11 0.38 0.26 0.10 0.09 0.08 0.26 0.14 0.13 Cl (wt.%) 0.02 0.02 0.01 0.01 0.08 0.05 0.02 0.05 0.02 0.09 0.02 0.02 Total 102.31 94.55 98.78 95.63 98.10 93.51 94.03 Formula (a.p.f.u) 19 19 19 19 19 19 19 Na 0.00 0.00 0.01 0.01 0.00 0.01 0.01 0.00 0.00 0.03 0.01 0.01 K 0.75 0.08 0.57 0.07 0.56 0.61 0.14 0.72 0.05 0.54 0.57 0.05 Total 0.75 0.58 0.56 0.62 0.72 5 0.57 0.59 Total Al 2.49 0.11 2.40 0.08 2.72 2.40 0.21 2.40 0.03 2.48 2.45 0.00 Si 3.25 0.08 3.36 0.06 3.24 3.32 0.05 3.33 0.01 3.36 3.32 0.13 Al (iv) 0.75 0.08 0.64 0.06 0.76 0.68 0.05 0.67 0.01 0.64 0.68 0.13 Total 4.00 4.00 4.00 4.00 4.00 4.00 4.00 Al (iv) 1.74 0.04 1.76 0.05 1.97 1.72 0.26 1.73 0.05 1.84 1.77 0.12 Cr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.28 0.06 0.28 0.10 0.06 0.15 0.03 0.15 0.03 0.11 0.26 0.18 Fe 0.08 0.04 0.09 0.04 0.07 0.27 0.31 0.22 0.13 0.16 0.12 0.03 Mn 0.00 0.00 0.00 0.00 0.01 0.01 0.01 0.00 0.00 0.00 0.00 0.00 Ca 0.00 0.01 0.00 0.00 0.00 0.02 0.01 0.00 0.00 0.01 0.00 0.00 Ti 0.01 0.00 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 Total 2.12 0.05 2.14 0.04 2.11 2.17 0.08 2.11 0.06 2.12 2.16 0.09 TOTAL 6.87 6.72 6.67 6.79 6.83 6.68 6.75 F 0.01 0.01 0.03 0.02 0.08 0.06 0.02 0.02 0.01 0.05 0.03 0.03 Cl 0.00 0.00 0.00 0.00 0.01 0.01 0.00 0.01 0.00 0.01 0.00 0.00 OH 1.99 0.01 1.97 0.02 1.92 1.94 0.03 1.98 0.01 1.94 1.97 0.03 Total 2.00 2.00 2.00 2.00 2.00 2.00 2.00 phengite component % 17.92 2.12 17.74 3.27 6.87 20.23 15.06 17.92 4.43 13.07 18.04 8.95 Fe/(Fe+Mg) 0.23 0.12 0.25 0.14 0.54 0.52 0.31 0.56 0.20 0.61 0.34 0.11 % F-end-member 0.53 0.65 1.28 1.17 3.75 2.77 1.13 0.87 0.74 2.74 1.50 1.37 % Cl-end-member 0.08 0.10 0.06 0.08 0.40 0.26 0.13 0.26 0.12 0.49 0.11 0.12 % OH-end-member 99.40 98.70 95.80 97.00 98.90 96.80 98.40 P a g e | 59 Muscovite KAl2(Si3Al)O10(OH,F)2 Prospect Mystic Prospect Banshee Prospect Gambit Prospect Sample MPb BPb Bpa GP1 Gpa Number of spots 2 6 2 5 5 (Wt.%) Mean SD Mean SD Mean SD Mean SD Mean SD CaO 0.15 0.04 1.11 1.09 0.24 0.28 0.06 0.02 0.27 0.46 Na2O 0.02 0.02 0.01 0.01 0.02 0.01 0.04 0.02 0.01 0.01 K2O 6.81 0.32 8.81 0.45 4.11 0.97 9.73 0.38 9.27 1.08 FeO 3.36 2.83 3.16 0.68 2.64 0.95 1.24 0.07 1.48 0.19 TiO2 0.02 0.00 0.02 0.02 0.02 0.01 0.01 0.01 0.03 0.06 MgO 2.42 1.43 2.20 0.13 1.67 0.10 2.12 0.23 2.57 0.62 SiO2 55.97 7.99 54.53 2.24 52.23 1.28 53.36 1.14 54.13 2.39 MnO 0.01 0.02 0.08 0.02 0.03 0.04 0.01 0.01 0.01 0.01 Cr2O3 0.34 0.44 0.01 0.01 0.01 0.00 0.01 0.00 0.00 0.01 Al2O3 29.73 1.07 31.51 1.04 32.03 1.73 30.74 0.77 30.95 1.57 F (wt.%) 0.23 0.03 0.17 0.12 0.30 0.07 0.23 0.05 0.23 0.08 Cl (wt.%) 0.01 0.00 0.07 0.06 0.02 0.01 0.02 0.01 0.04 0.02 Total 99.06 101.69 93.34 97.57 98.98 Formula (a.p.f.u) 19 19 19 19 19 Na 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 K 0.54 0.02 0.70 0.04 0.34 0.09 0.80 0.03 0.75 0.09 Total 0.55 0.70 0.35 0.80 0.75 Total Al 2.20 0.25 2.30 0.03 2.46 0.08 2.32 0.05 2.30 0.09 Si 3.49 0.23 3.38 0.04 3.40 0.01 3.42 0.03 3.42 0.09 Al (iv) 0.51 0.23 0.62 0.04 0.60 0.01 0.58 0.03 0.58 0.09 Total 4.00 4.00 4.00 4.00 4.00 Al (iv) 1.69 0.01 1.68 0.06 1.86 0.09 1.74 0.02 1.72 0.04 Cr 0.02 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.22 0.12 0.20 0.01 0.16 0.01 0.20 0.02 0.24 0.05 Fe 0.18 0.16 0.16 0.04 0.14 0.05 0.07 0.00 0.08 0.01 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ca 0.01 0.00 0.07 0.07 0.02 0.02 0.00 0.00 0.02 0.03 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total 2.13 0.09 2.12 0.05 2.19 0.00 2.02 0.01 2.06 0.04 TOTAL 6.67 6.82 6.54 6.82 6.80 F 0.05 0.01 0.03 0.02 0.06 0.01 0.05 0.01 0.04 0.02 Cl 0.00 0.00 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0.00 OH 1.95 0.01 1.96 0.02 1.94 0.01 1.95 0.01 1.95 0.02 Total 2.00 2.00 2.00 2.00 2.00 phengite component % 19.47 1.58 20.95 4.46 14.93 4.10 13.60 0.82 16.44 2.24 Fe/(Fe+Mg) 0.43 0.35 0.44 0.06 0.46 0.08 0.25 0.03 0.25 0.03 % F-end-member 2.29 0.48 1.69 1.16 3.06 0.67 2.32 0.57 2.24 0.82 % Cl-end-member 0.03 0.01 0.39 0.32 0.10 0.05 0.11 0.05 0.23 0.12 % OH-end-member 97.70 97.90 96.80 97.60 97.50 P a g e | 60 Illite K1-1.5Al4(Si7Al)8O20(OH)4 Prospect Area 5 North Prospect Area 5 Wolverine Prospect Prospect Sample A5Nb A5Na A5b Wpa Wpb WPc Number of spots 2 1 1 3 2 5 (Wt.%) Mean SD Mean Mean Mean SD Mean SD Mean SD CaO 0.01 0.00 0.02 0.07 0.07 0.06 0.10 0.03 0.09 0.04 Na2O 0.01 0.01 0.05 0.02 0.01 0.01 0.17 0.01 0.03 0.00 K2O 9.35 0.63 3.53 5.50 6.24 1.08 2.15 0.46 7.54 0.93 FeO 1.63 0.68 1.52 1.84 6.27 3.55 2.84 1.11 3.63 1.69 TiO2 0.01 0.01 0.01 0.04 0.03 0.03 0.01 0.01 0.00 0.00 MgO 1.09 0.71 0.44 1.42 0.92 0.36 0.51 0.07 1.39 0.12 SiO2 46.08 4.40 45.61 49.68 39.11 11.30 49.01 3.30 47.61 3.51 MnO 0.01 0.01 0.00 0.01 0.01 0.01 0.01 0.02 0.03 0.02 Cr2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.00 Al2O3 30.30 1.89 33.68 24.22 24.56 2.87 32.61 0.90 27.73 2.30 P2O5 0.03 0.04 0.01 0.00 8.90 7.92 0.06 0.02 0.38 0.16 F (wt.%) 0.05 0.04 0.13 0.30 0.32 0.30 0.18 0.04 0.41 0.08 Cl (wt.%) 0.07 0.03 0.06 0.07 0.12 0.09 0.08 0.01 0.03 0.01 Total 88.66 85.06 83.18 86.56 87.74 88.88 Formula (a.p.f.u) Na 0.00 0.00 0.01 0.00 0.00 0.00 0.05 0.00 0.01 0.00 K 1.70 0.19 0.64 1.03 1.35 0.30 0.38 0.06 1.37 0.18 Total 1.70 0.65 1.04 1.35 0.42 1.38 Total Al 5.09 0.54 5.63 4.20 4.86 0.44 5.27 0.10 4.67 0.46 Si 6.54 0.34 6.47 7.31 6.41 0.74 6.72 0.14 6.78 0.35 Al (iv) 1.46 0.34 1.53 0.69 1.59 0.74 1.28 0.14 1.22 0.35 Total 8.00 8.00 8.00 8.00 8.00 8.00 Al (iv) 3.63 0.20 4.11 3.51 3.27 0.33 3.99 0.03 3.45 0.19 Cr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.23 0.14 0.09 0.31 0.22 0.06 0.10 0.01 0.30 0.03 Fe 0.19 0.07 0.18 0.23 0.97 0.75 0.33 0.14 0.43 0.20 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Ca 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total 4.06 4.38 4.07 4.48 4.44 4.19 TOTAL 13.76 13.04 13.10 13.83 12.86 13.57 F 0.02 0.02 0.06 0.14 0.20 0.22 0.08 0.01 0.18 0.03 Cl 0.02 0.01 0.01 0.02 0.03 0.02 0.02 0.00 0.01 0.00 OH 3.96 0.02 3.93 3.84 3.77 0.20 3.90 0.01 3.81 0.03 Total 4.00 4.00 4.00 4.00 4.00 4.00 phengite' component % 10.45 5.20 6.34 13.62 26.13 13.38 10.13 2.95 17.77 4.63 Fe/(Fe+Mg) 0.47 0.07 0.66 0.42 0.76 0.13 0.74 0.10 0.57 0.14 P a g e | 61 Illite K1-1.5Al4(Si7Al)8O20(OH)4 Prospect Gambit Prospect Mystic Prospect Banshee Prospect Sample Gpa MPb Mpa Bpa Number of spots 1 2 4 5 (Wt.%) Mean Mean SD Mean SD Mean SD CaO 0.04 0.17 0.08 0.09 0.05 0.19 0.16 Na2O 0.00 0.01 0.01 0.05 0.01 0.02 0.01 K2O 7.37 2.99 0.34 3.78 0.71 4.49 1.39 FeO 1.31 21.85 28.47 1.97 1.08 2.43 0.68 TiO2 0.02 0.02 0.01 0.02 0.01 0.01 0.01 MgO 1.74 0.69 0.11 0.86 0.24 1.71 0.66 SiO2 47.00 40.85 15.17 48.95 1.39 49.49 2.96 MnO 0.00 0.01 0.01 0.01 0.01 0.05 0.03 Cr2O3 0.00 0.20 0.05 0.02 0.01 0.01 0.01 Al2O3 27.10 21.90 11.24 31.62 3.40 29.11 1.73 P2O5 0.00 0.27 0.39 0.02 0.02 0.02 0.02 F (wt.%) 0.09 0.12 0.11 0.26 0.09 0.27 0.08 Cl (wt.%) 0.08 0.05 0.04 0.04 0.01 0.05 0.05 Total 84.75 89.13 87.68 87.85 Formula (a.p.f.u) Na 0.00 0.00 0.00 0.01 0.00 0.01 0.00 K 1.38 0.59 0.05 0.67 0.13 0.79 0.24 Total 1.38 0.60 0.68 0.80 Total Al 4.67 3.87 1.32 5.14 0.48 4.78 0.32 Si 6.88 6.21 1.18 6.76 0.29 6.88 0.16 Al (iv) 1.12 1.79 1.18 1.24 0.29 1.12 0.16 Total 8.00 8.00 8.00 0 8.00 Al (iv) 3.55 2.09 2.50 3.90 0.18 3.66 0.18 Cr 0.00 0.02 0.00 0.00 0.00 0.00 0.00 Mg 0.38 0.16 0.00 0.18 0.05 0.35 0.13 Fe 0.16 3.23 4.29 0.23 0.13 0.28 0.08 Mn 0.00 0.00 0.00 0.00 0.00 0.01 0.00 Ca 0.01 0.03 0.02 0.01 0.01 0.03 0.02 Ti 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total 4.10 5.54 4.32 4.33 TOTAL 13.47 14.13 13.00 13.13 F 0.04 0.07 0.07 0.11 0.04 0.12 0.03 Cl 0.02 0.01 0.01 0.01 0.00 0.01 0.01 OH 3.94 3.92 0.06 3.88 0.04 3.87 0.03 Total 4.00 4.00 4.00 4.00 phengite' component 13.35 51.86 60.97 9.77 3.13 15.49 2.41 % Fe/(Fe+Mg) 0.30 0.77 0.29 0.54 0.15 0.46 0.18 P a g e | 62 Kaolinite Al4Si4O10(OH)8 Area 5 North Prospect Area 5 Prospect A5Nb A5Na A5a A5b Number of spots 4 1 1 1 (Wt.%) Mean SD Mean Mean Mean CaO 0.01 0.01 0.03 0.02 0.01 Na2O 0.00 0.00 0.01 0.00 0.00 K2O 0.02 0.02 0.80 0.04 0.07 FeO 0.58 0.30 0.33 0.24 0.14 TiO2 0.00 0.00 0.01 0.00 0.00 MgO 0.00 0.01 0.09 0.04 0.02 SiO2 53.18 1.59 51.47 55.17 50.37 MnO 0.00 0.00 0.01 0.00 0.00 Cr2O3 0.00 0.00 0.01 0.00 0.00 Al2O3 42.64 0.82 40.41 43.69 40.66 P2O5 0.04 0.02 0.02 0.01 0.02 F (wt.%) 0.04 0.04 0.01 0.09 0.12 Cl (wt.%) 0.04 0.03 0.02 0.01 0.00 Total 96.56 93.22 99.30 91.42 Formula (a.p.f.u) 26 26 26 26 Na 0.00 0.00 0.00 0.00 0.00 K 0.00 0.00 0.08 0.00 0.01 Total 0.00 0.08 0.00 0.01 Total Al 3.86 0.03 3.80 3.84 3.88 Si 4.08 0.03 4.11 4.11 4.08 Total 4.08 4.11 4.11 4.08 Al (iv) 3.86 0.03 3.80 3.84 3.88 Cr 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.00 0.01 0.00 0.00 Fe 0.04 0.02 0.02 0.02 0.01 Mn 0.00 0.00 0.00 0.00 0.00 Ca 0.00 0.00 0.00 0.00 0.00 Ti 0.00 0.00 0.00 0.00 0.00 Total 3.90 3.84 3.86 3.90 TOTAL 7.99 8.03 7.97 7.98 F 0.01 0.01 0.00 0.02 0.03 Cl 0.00 0.00 0.00 0.00 0.00 OH 3.99 0.01 3.99 3.98 3.97 Total 4.00 4.00 4.00 4.00 phengite' component % 1.01 0.52 0.94 0.55 0.33 Fe/(Fe+Mg) 0.99 0.01 0.68 0.77 0.77 P a g e | 63 Xenotime Florencite WPb A5c Gpa Mpa A5a MPb BPb n samples 6 16 11 19 34 2 10 Element Mean Stdev Mean Stdev Mean Stdev Mean Stdev Mean Stdev Mean Stdev Mean Stdev Na 43.1 14.4 29.0 12.7 42.8 15.7 30.2 10.9 25.1 4.9 654 35 93 34 Mg 118.2 61.6 54.7 54.7 92.0 51.5 109.2 196.2 103.9 90.4 1147 329 227 84 Al 502 486 768 850 221 222 647 885 899 1241 166714 0.01 170948 0.01 Si 5878 2381 3874 1648 Sample 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 P2O5 20.74 32.25 38.10 35.09 35.90 35.09 34.48 34.45 36.73 32.60 33.57 32.90 33.57 34.03 34.38 As2O5 16.23 0.41 n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a SiO2 1.84 2.02 0.38 0.00 0.14 0.05 0.95 0.00 0.12 1.00 0.27 0.26 0.06 0.00 0.00 ThO2 0.32 3.50 n/a 0.14 0.16 0.03 1.30 0.14 0.00 0.10 0.00 0.00 0.00 0.00 0.01 UO 0.00 4.22 n/a 0.56 0.66 0.08 1.76 0.87 0.27 0.20 0.32 0.32 0.65 0.38 0.57 2 Y O 40.97 40.70 46.32 43.20 42.60 39.53 40.99 41.44 48.93 42.90 38.97 30.40 41.19 42.59 43.49 2 3 La2O3 0.02 0.03 0.02 0.00 0.00 0.00 0.14 0.09 0.00 - 0.02 - 0.00 0.00 0.00 Ce2O3 0.00 0.07 - 0.00 0.00 0.00 0.10 0.07 0.00 - 0.00 0.00 0.07 0.08 0.03 Pr2O3 0.00 0.05 0.02 0.04 0.01 0.00 0.08 n/a - - 0.00 0.03 0.09 0.00 0.00 Nd2O3 0.35 0.58 0.22 0.31 0.06 0.13 0.36 0.17 0.07 0.50 0.07 0.19 0.54 0.56 0.42 Sm2O3 0.54 0.92 0.21 0.49 0.36 1.36 0.68 1.09 0.00 1.20 1.03 0.22 0.81 0.95 0.98 EuO 0.78 0.03 1.21 0.10 0.21 0.82 0.07 n/a - 0.10 - - n/a n/a n/a Gd2O3 2.96 2.40 2.49 2.00 3.49 6.96 2.22 4.65 2.29 3.50 8.60 5.43 5.02 7.10 7.49 Tb2O3 0.83 0.60 n/a 0.56 1.12 1.29 0.58 0.66 1.16 0.90 0.90 1.05 0.25 1.01 0.86 Dy2O3 6.36 3.91 n/a 5.06 8.40 8.45 5.05 5.61 6.90 6.90 7.20 8.61 6.78 7.18 6.80 Ho O 1.11 0.70 n/a 1.23 1.61 1.39 1.07 0.61 0.60 1.20 1.20 2.00 0.00 0.07 0.26 2 3 Er O 4.06 2.27 n/a 4.14 3.34 3.05 3.99 3.85 1.42 3.80 4.00 7.23 5.11 3.81 3.14 2 3 Tm2O3 0.67 0.55 n/a 0.59 0.41 0.27 0.70 0.53 0.21 - - 1.13 n/a n/a n/a Yb2O3 2.65 3.46 5.80 5.22 2.62 1.75 3.89 4.35 1.07 3.00 2.20 7.82 5.72 3.12 1.91 Lu2O3 0.04 - n/a 0.66 0.15 0.00 0.52 0.35 0.01 0.30 0.20 1.30 0.94 0.68 0.43 FeO 0.51 ZrO2 n/a n/a n/a 0.22 0.00 0.00 0.90 n/a 0.00 ------ΣREE (La-Lu) 20.37 15.55 9.97 20.40 21.78 25.47 19.45 22.03 13.73 21.40 25.42 35.01 25.33 24.56 22.32 65 Daniel O’Rielly Honours Thesis Core Rim Rim Rim Rim Label 1 2 3 4 5 Ox%(F ) 0.62 0.56 0.51 0.47 0.37 Ox%(Al) 31.11 29.93 30.11 28.93 31.89 Ox%(P ) 28.97 25.76 27.56 23.84 24.84 Ox%(Ca) 1.49 1.59 1.78 1.71 1.68 Ox%(Fe) 1.12 8.98 1.54 9.36 5.52 Ox%(Sr) 2.22 3.23 2.72 3.09 3.12 Ox%(La) 2.99 2.36 2.44 2.26 2.63 Ox%(Ce) 10.41 8.32 9.62 7.72 9.28 Ox%(Pr) 1.92 1.31 1.76 1.43 1.61 Ox%(Nd) 8.91 7.11 7.84 6.09 7.03 Ox%(Sm) 1.17 0.93 0.86 0.78 0.66 Ox%(Dy) 0.04 0.06 0.00 0.02 0.00 Ox%(Th) 0.29 0.01 0.04 0.20 0.04