The Geochemistry of the Marmoraton Fe Skarn and Associated Syenodiorite Intrusion, Grenville Province, S. Ontario

by

Shilika Mathur

A thesis submitted in conformity with the requirements for the degree of Master of Science

Department of Earth Sciences University of Toronto

© Copyright by Shilika Mathur 2015

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The Geochemistry of the Marmoraton Fe Skarn and Associated

Syenodiorite Intrusion, Grenville Province, S. Ontario

Shilika Mathur

Master of Science

Department of Earth Sciences University of Toronto

2015

Abstract

This research focuses on the major and trace element geochemistry of the Marmoraton Fe skarn

and associated intrusive material in the Grenville Province, southern Ontario. The analytical

methods used are NAA, XRF and LA-ICPMS. The plotted analytical data show clear trends and

clustering, representing accurate sample collection and classification. Co is enriched in sulphide-

rich samples to sub-ore grade. No consistent, significant enrichments in Au, Pd and Pt were

observed; however, one Cu and Co enriched sample contains sub-ore grade Pd (~1 g/t). The

intrusion geochemistry suggests that there is limited distal Au mineralization potential. The

intrusion geochemistry is consistent with Marmoraton being an Fe-only skarn based on the data

and plots of Meinert (1995). The REE values are not sufficiently significant to be considered of

economic potential. There is a ~15 km long crescent shaped magnetic anomaly containing

magnetite skarns that indicates a major sub-surface Fe (magnetite) resource. The syenodiorite

intrusion at Marmoraton should be dated to establish the timing of the intrusion and associated

mineralization.

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Acknowledgements

A special thanks to my supervisor, Ed Spooner, for all his guidance and support in this research

project. Big thanks to the MNDM and OGS team in Tweed (Pam Sangster, Peter LeBaron and

Scott Charbonneau) for providing me with continuous information related to the research area. I

would particularly like to thank Glenn Ferguson and the AECON team at Marmora for their

assistance with accessing the sampling site. Assistance provided by Lingeswaren Rama Moorthy

both in the field and in the lab was greatly appreciated. My deepest gratitude to Mike Gorton for

all the technical help and advice he provided and Colin Bray for his help with LA-ICPMS

analyses. Last but not least, I would like to thank my family and friends for all their support and

encouragement.

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Dedication

In memory of Rick Hutson (1957 – 2014) for all his guidance, encouragement and wisdom.

Do not go where the path may lead, go instead where there is no path and leave a trail.

– Ralph Waldo Emerson

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Table of Contents

ACKNOWLEDGEMENTS ................................................................................................................................ III

DEDICATION ........................................................................................................................................................IV

TABLE OF CONTENTS ....................................................................................................................................... V

LIST OF TABLES ............................................................................................................................................... VII

LIST OF PLATES .................................................................................................................................................. IX

LIST OF FIGURES ............................................................................................................................................. XII

LIST OF APPENDICES ..................................................................................................................................... XV

RESEARCH OBJECTIVES.......................................................................................................................... 1

BACKGROUND............................................................................................................................................... 2 2.1 LOCALITIES ................................................................................................................................................................. 2 2.2 GEOPHYSICS ............................................................................................................................................................... 3 2.3 MINING HISTORY ...................................................................................................................................................... 4 2.4 IRON SKARN FORMATION....................................................................................................................................... 5 2.5 GEOLOGICAL BACKGROUND ................................................................................................................................. 5

SAMPLING METHODOLOGY .................................................................................................................. 9 3.1 SAMPLE COLLECTION .............................................................................................................................................. 9 3.2 SAMPLE PREPARATION.......................................................................................................................................... 10

ANALYTICAL METHODOLOGY .......................................................................................................... 13 4.1 ORDINARY AND POLISHED THIN SECTIONS ................................................................................................... 14 4.2 X-RAY FLUORESCENCE (XRF) ANALYSIS ...................................................................................................... 14 4.3 NEUTRON ACTIVATION ANALYSIS (NAA) ..................................................................................................... 14 4.4 LASER ABLATION – INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY (LA-ICPMS)

ANALYSIS .............................................................................................................................................................................. 15

RESULTS ......................................................................................................................................................... 16 5.1 MAJOR ELEMENTS .................................................................................................................................................. 16 5.2 TRACE ELEMENTS ................................................................................................................................................... 17 5.3 RARE EARTH ELEMENTS (REES) ....................................................................................................................... 18

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DISCUSSION .................................................................................................................................................. 20 6.1 TAILINGS.................................................................................................................................................................... 25 6.2 ORE GEOCHEMISTRY (EXCLUDING REES) ...................................................................................................... 27 6.3 ORE GEOCHEMISTRY (REES) .............................................................................................................................. 35 6.4 INTRUSION GEOCHEMISTRY ................................................................................................................................ 39

PRINCIPAL CONCLUSIONS ................................................................................................................... 44

FUTURE WORK ........................................................................................................................................... 45

REFERENCES....................................................................................................................................................... 46

APPENDICES ........................................................................................................................................................ 51

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List of Tables

Table 1: Ages of plutons in the Belmont Domain (Easton et al., 2007). ........................................ 9

Table 2: Description of hand samples collected from Marmora (MARM) with sample number,

classification, field notes and hand sample description. Abbreviations for minerals are from

Whitney and Evans (2010). ................................................................................................... 11

Table 3: Description of drill core samples obtained from Marmora (MARM), Allan Mills (AM)

and Blairton (BL) with sample number, classification and description, end interval and

DDH box interval. Abbreviations for minerals are from Whitney and Evans (2010). ......... 12

Table 4: Analytical work on selected samples from Marmoraton, Allan Mills and Blairton. ...... 13

Table 5: Major element data for the Marmoraton (MARM), Allan Mills (AM) and Blairton (BL)

samples in percent. ................................................................................................................ 16

Table 6: Trace element data for the Marmoraton (MARM), Allan Mills (AM) and Blairton (BL)

samples in ppm; for Co 10% of W value was removed; Au in ppb. ..................................... 17

Table 7: Rare earth element data for the Marmoraton (MARM), Allan Mills (AM) and Blairton

(BL) samples, in ppm. ........................................................................................................... 18

Table 8: Rare earth element averages, REO, REE, TREO and TREE for each sample type.

Decimal places are for computational purpose only. ............................................................ 19

Table 9: Summary of major and trace element analyses of Fe skarns in Mississippian Madison

Limestone, Montana and Fe-Cu skarn in Cambrian Meagher Limestone, Montana

(Hammarstrom et al., 1995). The Fe2O3 is given as FeTO3, oxides in weight percent and Au

in ppb. ................................................................................................................................... 34

Table 10: Estimated upper crustal abundances for REEs, Y and Sc in increasing atomic number,

in parts per million (Long et al., 2010). ................................................................................ 36

Table 11: REE projects in Canada in decreasing order of total REE in %. These projects contain

at least 10% of the total REE as HREE (Natural Resources Canada, 2014). ....................... 38

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Table 12: Average crustal abundance and concentrations of REEs and Y in various REE

deposits. REEs listed in increasing atomic number (Long et al., 2010). .............................. 38

Table 13: Major and trace element composition of plutons related to Fe skarns, oxides in per cent

and trace elements in parts per million (Meinert, 1995). ...................................................... 42

Table 14: Table of the Marmoraton samples with their coordinates (latitude and longitude) and

elevation of sample site. ........................................................................................................ 51

Table 15: Table of sample numbers for the Marmaton site with corresponding photo ID. .......... 52

Table 16: Sample numbers with corresponding sample weights for neutron activation analysis. 63

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List of Plates

Plate 1: Metasomatism of Grenville marble into magnetite-bearing material. On the left Grenville

marble and on the right magnetite bearing rock (Mathur, 2014). ........................................... 8

Plate 2: MARM-14-01 .................................................................................................................. 53

Plate 3: MARM-14-02 .................................................................................................................. 53

Plate 4: MARM-14-03 .................................................................................................................. 53

Plate 5: MARM-14-04 .................................................................................................................. 53

Plate 6: MARM-14-05 .................................................................................................................. 53

Plate 7: MARM-14-06 .................................................................................................................. 53

Plate 8: MARM-14-07 ................................................................................................................ 54

Plate 9: MARM-14-08 .................................................................................................................. 54

Plate 10: MARM-14-09 ................................................................................................................ 54

Plate 11: MARM-14-10 ................................................................................................................ 54

Plate 12: MARM-14-11 ................................................................................................................ 54

Plate 13: MARM-14-12 ................................................................................................................ 54

Plate 14: MARM-14-13 ................................................................................................................ 55

Plate 15: MARM-14-14 ................................................................................................................ 55

Plate 16: MARM-14-15 ............................................................................................................... 55

Plate 17: MARM-14-16 ................................................................................................................ 55

Plate 18: MARM-14-17 ............................................................................................................... 55

Plate 19: MARM-14-18 ................................................................................................................ 55

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Plate 20: MARM-14-19 ................................................................................................................ 56

Plate 21: MARM-14-20 ................................................................................................................ 56

Plate 22: MARM-14-21 ................................................................................................................ 56

Plate 23: MARM-14-22 ................................................................................................................ 56

Plate 24: MARM-14-23 ................................................................................................................ 56

Plate 25: MARM-14-24 ................................................................................................................ 56

Plate 26: MARM-14-25 ................................................................................................................ 57

Plate 27: MARM-14-26 ................................................................................................................ 57

Plate 28: MARM-14-27 ................................................................................................................ 57

Plate 29: MARM-14-28 ................................................................................................................ 57

Plate 30: MARM-14-29 ................................................................................................................ 57

Plate 31: MARM-14-30 ................................................................................................................ 57

Plate 32: MARM-14-31 ................................................................................................................ 58

Plate 33: MARM-14-32 ................................................................................................................ 58

Plate 34: MARM-14-33 ................................................................................................................ 58

Plate 35: MARM-14-34 ................................................................................................................ 58

Plate 36: MARM-14-35 ................................................................................................................ 58

Plate 37: MARM-14-36 ................................................................................................................ 58

Plate 38: MARM-14-37 ................................................................................................................ 59

Plate 39: MARM-14-38 ................................................................................................................ 59

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Plate 40: MARM-14-39 ................................................................................................................ 59

Plate 41: MARM-14-40 ................................................................................................................ 59

Plate 42: MARM-14-41 ................................................................................................................ 59

Plate 43: MARM-14-42 ................................................................................................................ 59

Plate 44: MARM-14-43 ................................................................................................................ 60

Plate 45: MARM-14-44 ................................................................................................................ 60

Plate 46: MARM-14-45 ................................................................................................................ 60

Plate 47: MARM-14-46 ................................................................................................................ 60

Plate 48: AM-14-01 ...................................................................................................................... 60

Plate 49: AM-14-02 ...................................................................................................................... 60

Plate 50: AM-14-03 ...................................................................................................................... 61

Plate 51: BL-14-01 ........................................................................................................................ 61

Plate 52: BL-14-02 ........................................................................................................................ 61

Plate 53: BL-14-03 ........................................................................................................................ 61

Plate 54: BL-14-04 ........................................................................................................................ 61

Plate 55: MARM-14-54 ................................................................................................................ 61

Plate 56: MARM-14-56 ................................................................................................................ 62

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List of Figures

Figure 1: Physical and geological map of the Marmoraton open pit. The tailings due east of the

pit  were  sampled.  The  “tailings”  on  the  west  side  are  waste  dumps  (Bartlett  and Moore,

1985). For symbols, see next page. ......................................................................................... 2

Figure 2: Aeromagnetic map showing the Marmoraton anomaly (NE corner) together with a

crescent-like feature on the west side, which includes the locations of Allan Mills and

Blairton. Values are shown in gammas and the original scale is 1 inch to 1 mile (GSC,

1970). ...................................................................................................................................... 4

Figure 3: Surface plan and cross section of the Marmoraton iron skarn with the outline of the pit

boundary and locations of drill holes (Rose, 1958). Note: the Grenville limestone is marble.

................................................................................................................................................. 7

Figure 4: Cross section of the pit during production showing the different lithologies (Park,

1966). Note separation of outcrops of syenitic and dioritic material. The skarn is clearly

spatially related to the syenitic material. ................................................................................. 8

Figure 5: Scatter plot showing %SiO2 and %CaO in tailings and ore from Marmora, Allan Mills

and Blairton. .......................................................................................................................... 20

Figure 6: Scatter plot showing %SiO2 and %Al2O3 in tailings and ore from Marmora, Allan Mills

and Blairton. .......................................................................................................................... 20

Figure 7: Scatter plot showing %SiO2 and %MgO in tailings and ore from Marmora, Allan Mills

and Blairton. .......................................................................................................................... 21

Figure 8: Scatter plot showing %SiO2 and %FeS2 + Fe3O4 in tailings and ore from Marmora,

Allan Mills and Blairton. ...................................................................................................... 21

Figure 9: Scatter plot showing %SiO2, and %FeS2 and %Fe3O4, in tailings and ore from

Marmora, Allan Mills and Blairton. ..................................................................................... 22

Figure 10: Scatter plot showing %Fe3O4 and %FeS2 in tailings and ore from Marmora, Allan

Mills and Blairton based on classification of each sample. .................................................. 22

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Figure 11: Scatter plot showing %FeS2 and Co (ppm) in tailings and ore from Marmora, Allan

Mills and Blairton. ................................................................................................................ 23

Figure 12: Scatter plot showing %FeS2 and Ni (ppm) in tailings and ore from Marmora, Allan

Mills and Blairton. ................................................................................................................ 23

Figure 13: Scatter plot showing %FeS2 and Cu (ppm) in tailings and ore from Marmora and

Blairton. Data point with * is MARM-14-4. ......................................................................... 24

Figure 14: Scatter plot showing Ni (ppm) and Co (ppm) in tailings and ore from Marmora, Allan

Mills and Blairton. ................................................................................................................ 24

Figure 15: Scatter plot showing Cu (ppm) and Co (ppm) in tailings and ore from Marmora and

Blairton. ................................................................................................................................ 25

Figure 16: Cross section of the Nickel Plate deposit, Hedley, British Columbia (Dawson, 1996).

............................................................................................................................................... 32

Figure 17: Composition of the Marmoraton intrusion based on the scatter plot showing %SiO2

and (FeO + CaO + Na2O)/K2O. Sample MARM-14-46 is plotted in the red box and in Fig.

18. .......................................................................................................................................... 39

Figure 18: Average compositions of plutons related to various types of skarns and one

Marmoraton intrusion sample, which plots on this diagram (see Fig. 17). Modified from

Meinert (1993). ..................................................................................................................... 40

Figure 19: Trace element compositions of plutons based on a log scatter plot of Ni and V

(Meinert, 1995). .................................................................................................................... 43

Figure 20: Composition of MARM-14-28 and Fe skarn composition from Meinert (1995) based

on the log plot between Ni (ppm) and V (ppm). ................................................................... 43

Figure 21: REE in the periodic table separated into light and heavy rare earths (Canadian Rare

Earth Element Network, 2013). ............................................................................................ 64

Figure 22: Aeromagnetic map showing the Marmoraton anomaly (NE corner) together with a

crescent-like anomaly on the west side, which includes the locations of Allan Mills and

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Blairton. There are four suggested drill holes and a potential fault-like structure on the east

side of the crescent. Values are shown in gammas and the scale is 1 inch to 1 mile

(Modified from GSC, 1970). ................................................................................................ 65

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List of Appendices

Appendix 1: Additional documents for sampling methodology. .................................................. 51

Appendix 2: Additional document for analytical methodology. .................................................. 63

Appendix 3: Additional documents for discussion. ...................................................................... 64

Appendix 4: Additional documents for key conclusions and future work. .................................. 65

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Research  Objectives The principal objective of my research is to analyze the pyrometasomatic Fe skarn

deposit at Marmora, Hastings County, Ontario. Specifically the research develops an

integrated geophysical, geological and geochemical analysis of the Marmora Fe skarn,

related syenodiorite and tailings. In addition, Fe skarn samples have been analyzed from

Blairton (approximately 7.5 km west of Marmoraton) and Allan Mills (approximately 12

km south of Marmoraton).

The methodology of the project is as follows:

1) Analyze the major and trace element geochemistry of the skarn Fe mineralization with

special emphasis on both sulphide-rich and oxide-rich samples from Marmoraton, Allan

Mills and Blairton.

2) Analyze the tailings from the Marmoraton operation.

3) Analysis of the samples for the following elements:

a. Fe, Mn, S, As, Bi, P, Cu, Pb, Zn, Ni, Co, Cd, Ti, V, Cr, REE, Y, Sc, U, Zr, Nb, and Th

b. Precious metals: Au, Ag, Pt, Pd

4) Analyze the geochemistry of the Marmora syenodiorite stock.

Previous work has been done in the region, where the Marmora deposit was

mined as an open pit for Fe from 1955 to 1978 producing 28 Mt at 42.8% (Gross, 1996).

Based on other Fe-Au skarn deposits, indicator minerals that are important to look at are

pyrite, pyrrhotite and traces of chalcopyrite (up to 5% in some locations). Furthermore, a

study done by Meinert (1993) indicates that the typical compositions of igneous

intrusions associated with Fe and Au skarns contain approximately 62-63 % SiO2 and

(FeO + Fe2O3 + CaO + Na2O)/K2O values of 5-7. This information is important in

comparing the chemical concentration results from the field samples. The key goal of this

project is to analyze the Marmora deposit for the precious metals Au, Ag, Pt and Pd. The

project was designed such that the information obtained will help indicate if and where

Au, Ag, Pt and Pd are enriched. A complete sample set from the waste piles was

collected at the Marmoraton site, focusing on samples that were magnetite rich, sulphide

rich, mixed assemblages of magnetite and sulphides and felsic, intermediate and mafic

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syenodorite assemblages. Samples (n = 8) from the tailings were also taken for

comparative analysis. Additionally, located DDH core from the past producing iron mine

was obtained from the OGS, Tweed. Core from diamond drilling holes was sampled from

Marmoraton, Blairton and Allan Mills. Blairton and Allan Mills are part of a crescent-

shaped anomaly outlined by the aeromagnetic survey (see below). Both locations are a

resource for Fe, and were sampled and analyzed to compare with Marmoraton samples.

Background  

2.1 Localities

The open pit (Figure 1) is located 2 km east of Marmora, 210 km east of Toronto

(Lorenson and McChesney, 1985) in Marmora Township, Hastings County, Ontario. The

Marmoraton mine is located at latitude 44o28’N  and  longitude 77o40’W  (Park,  1996).

Figure 1: Physical and geological map of the Marmoraton open pit. The tailings due east

of  the  pit  were  sampled.  The  “tailings”  on  the west side are waste dumps (Bartlett and

Moore, 1985). For symbols, see next page.

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The symbols within the Marmoraton area represent the following: 8 – Carbonate

metasediment (8b – Calcitic marble, 8e – Tremolite marble, 8f – Skarn), 10 – Intrusive

contact (10b – Fine-grained gabbro), 11 – Intermediate to ultramafic intrusive rocks (11a

– Diorite), 13 – Felsic intrusive rocks (13g – Fine-grained leucogranite, 13h – Massive,

medium to coarse grained syenite to quartz syenite) and 14 – Ordovician; unsubdivided

(14c – Grey, chalky-weathering limestone) (Bartlett and Moore, 1985).

2.2 Geophysics

The discovery of the Marmoraton Fe skarn was a result of surveys carried out in

the   early   1800’s.  Due   to   the   intense  magnetization   of   the   rock,   deflections  were   noted  

when using the compass over the anomaly. Between 1948 and 1949, the Ontario

Department of Mines (later changed to the Ministry of Northern Development and

Mines) and the Geological Survey of Canada ran an aeromagnetic survey (Lorenson and

McChesney, 1958) that covered the area containing the magnetic anomaly. In 1950, a

ground geophysical survey and drilling of 40 holes, totaling approximately 11,000m,

were carried out by Bethlehem Mines Corporation (Lorenson and McChesney, 1958). A

map was published in 1970 showing the original Bethlehem  Mines’ data (Figure 2). The

ellipse shaped aeromagnetic anomaly measures 1.2 km wide by ~1.6 km long, trending

southeasterly. It has a high amplitude of approximately 7500-8500 gammas (Rose, 1958)

and a magnetic relief of 6800 gammas (Park, 1966). A high magnetic anomaly can occur

due to the following: 1) Oxidized plutons will have primary magnetite compared to

reduced plutons, which have more ilmenite than magnetite. 2) Significant magnetite

concentration in a skarn body (Meinert et al., 2005). The Marmoraton anomaly, labeled

on Figure 2, occurs on one end of an overall crescent shaped anomaly. Blairton and Allan

Mills are also found along the crescent shape, which measures ~9 km N.E./S.W. and ~6

km N.W./S.E. From Marmoraton to Allan Mills, it measures ~15 km along the crescent.

All three sites contain a high aeromagnetic anomaly, with Marmoraton being the highest,

followed by Allan Mills then Blairton. With all three anomalies being close in proximity

to each other, there is a potential for a significant Fe resource.

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Figure 2: Aeromagnetic map showing the Marmoraton anomaly (NE corner) together

with a crescent-like feature on the west side, which includes the locations of Allan Mills

and Blairton. Values are shown in gammas and the original scale is 1 inch to 1 mile

(GSC, 1970).

2.3 Mining  History

The open pit iron mine was operated by Bethlehem Mines Corporation (Rose,

1958) from 1955 to 1978 (Bartlett and Moore, 1985; Gross, 1996). Following the

geophysical surveys, Bethlehem Mines Corporation commenced the stripping of the

overburden and waste rock in 1952 (Rose, 1958). The mine production rate was 0.5 Mt of

iron pellets a year and the total production during the mine life was 28 Mt at an average

grade of 42.8% Fe (Gross, 1996). Sulphides, mainly pyrite and some chalcopyrite

comprise up to 5% of the ore (Gross, 1967). The final dimensions of the pit once all

production had ceased are ~220 m deep, 850 m long and 460 m wide (Carter, 1984). The

Marmoraton deposit was discovered by an aeromagnetic survey flown in 1949, one of the

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first airborne geophysical discoveries. Previous magnetite mining had taken place in

Hastings County. The first was the Blairton Mine (1820-1875), one of the earliest mining

operations in Ontario, which produced 300,000 tons of magnetite ore. The second was the

Belmont Mine (operated occasionally until 1914), which produced 200,000 tons of

magnetite (Park, 1966).

2.4 Iron  Skarn  Formation

Skarns can develop next to plutons, along faults and shear zones, in shallow

geothermal systems, and in metamorphic terranes at lower crustal depths (Meinert, 1993).

Orthomagmatic skarns are formed by reactions between carbonate wall rocks and fluids

derived from igneous intrusions, causing replacement of limestone/dolomite (Burt, 1977;

Park, 1966). Economic skarn deposits are related to metasomatic replacement and the

mineral assemblage is controlled by the fluid and wall rock compositions, and the

integrated fluid/rock ratio. Iron content is an important factor in skarn systems as iron-

rich skarns contain low silica content, and are associated with primitive plutons. The host

rock undergoes alteration and mineralization during late stage hydrothermal evolution of

the pluton/intrusive body. The common silicate minerals found in the majority of skarns

are garnet, pyroxene, amphibole and epidote (Meinert, 1993). Skarns are an aggregate of

Ca, Fe, and Mg silicates, with occasional Mn enrichments (Park, 1966). Iron skarns form

the largest skarn deposits compared to other skarn types (Meinert et al., 2005).

2.5 Geological  Background

The Marmora deposit is a stratiform, iron-rich skarn in a metamorphic terrane

(Gross, 1996). The deposit is unconformably overlain by 30-40 m of subhorizontal

Ordovician limestone (Rose, 1958; Park, 1965; Gross, 1996) and Pleistocene glacial till

(Park, 1966).

Stratiform skarns are thought to develop in one of two ways (Gross, 1996):

1) From a metasedimentary rock enriched in Fe;

2) By Fe transport in fluids derived from more mafic magmas

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The rock types found in the Marmoraton pit are marble, silicic metasediments,

syenite, diorite, skarn, dykes and Paleozoic cover (Figure 3). The initial rock for the ore

body is comprised of Precambrian Grenville marble (Park, 1966). The Grenville marble,

which was located adjacent to the diorite-syenite intrusive rocks, has been replaced by

magnetite (Plate 1), pyrrhotite, pyrite and Ca, Mg, Fe-silicates (Park, 1965).

The classification of the ore body is pyrometasomatic, meaning formed by high

temperature metasomatism of the carbonate rocks by fluids derived from the diorite-

syenite body (Park, 1965; Bartlett and Moore, 1985). Pyrometasomatic deposits form

hydrothermal ore deposits at high temperatures that often contain Fe, Cu, Zn, and W

along with other metals (Burt, 1977). The zone with the magnetite-bearing skarn is found

parallel to the marble-syenite contact (Figure 4). Research indicates that pyrometasomatic

replacement occurred at relatively high temperatures at Marmoraton, at ~500oC and

higher (Park, 1965). The ore body occurs as a replacement of the Precambrian marble

with banded or zoned magnetite (Plate 1), with a lens-like shape in horizontal section that

strikes southeasterly and dips southwesterly (Rose, 1958; Park, 1966; Figure 4). The ore

mineralization is controlled by the diorite-syenite contact and by the foliation of the host

marble. The interlayering of siliceous materials caused grade variability. The purest

carbonate rock will be replaced by the best magnetite. Alternating layers of magnetite and

silicates cause the planar fabric in the skarn. The silicic metasediments are subdivided

into different units; however, they show a conformable contact with the marble creating

one overall sequence. There is no record of a diorite-marble contact observed and diorite-

syenite contacts are uncommon (Park, 1966).

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Figure 3: Surface plan and cross section of the Marmoraton iron skarn with the outline of the pit boundary and locations of drill holes

(Rose, 1958). Note: the Grenville limestone is marble.

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Plate 1: Metasomatism of Grenville marble into magnetite-bearing material. On the left

Grenville marble and on the right magnetite bearing rock (Mathur, 2014).

Figure 4: Cross section of the pit during production showing the different lithologies

(Park, 1966). Note separation of outcrops of syenitic and dioritic material. The skarn is

clearly spatially related to the syenitic material.

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The exact age of the skarn within Grenville evolution has not yet been defined. However,

plutons in the surrounding area have been dated by Easton (2007), as listed in Table 1.

These plutons are part of the Belmont Domain within the Elzevir Terrane, within the

Central Metasedimentary Belt. The age of volcanism in the Belmont Domain is known to

be >1300 Ma and <1260 Ma. The age of the Elzevirian orogeny is approximately 1230 –

1180 Ma and of the Ottawan orogeny is approximately 1120 – 1050 Ma (Easton, 1992).

Based on the relative ages of the intrusive bodies listed in Table 1, the Dingman pluton is

related to the Elzevirian orogeny and Gawley Creek Syenite is related to the Ottawan

orogeny. The remaining plutons are pre-Elzevirian in age. The Marmoraton pluton has

not been age dated.

Table 1: Ages of plutons in the Belmont Domain (Easton et al., 2007).

Intrusive Body Age (Ma) Deloro Granite 1241 +/- 2 Malone Pluton 1241 +/- 2 Dingman Pluton 1218 +/- 5 Cordova Gabbro 1242 +/- 3 Gawley Creek Syenite ~1085

Sampling  Methodology  

3.1 Sample  Collection

The fieldwork was conducted over two separate visits to the Marmoraton Iron

Mine in Marmora, Ontario during the summer, 2014. The initial visit to the sampling site

was done to investigate the rock types that were present and potential areas for sampling.

Sample collection was carried out during the second visit in August 2014 from both the

mine and OGS Tweed office. The GPS coordinates for each sample were recorded using

a Garmin etrex 10 (see Table 14, in Appendix 1). A total of 56 samples were collected: 8

tailings, 16 magnetite rich, 6 sulphide rich, 11 magnetite and sulphide rich, 3 vein, 6

intrusive, 1 bag of iron pellets and 5 observational. All drill core samples from Marmora,

Blairton and Allan Mills were obtained from the OGS. Drill core samples taken from the

Marmoraton mine were determined by the drilled intervals in the pit using cross sections.

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3.2 Sample  Preparation

Once the samples were brought back to the University of Toronto, they were each

cleaned, labeled and catalogued. Each sample was assigned a category and accompanied

with a hand specimen description (Tables 2 & 3) and photographed (see Table 15 &

Plates 2-56, in Appendix 1). Samples for analytical work were prepared using the

following procedure. Each sample was cut in half to produce a reference sample using a

rock saw. Areas of interest for thin sections were removed from the samples and put aside

for further preparation. All samples were then moved into the Rocklab for crushing. The

work surface was first cleaned to prevent contamination from previous use along with the

tungsten carbide puck mill. A steel plate and rock hammer were used to break down each

sample to approximately 2 cm-sized chips. 2-3 spoons of mixed small fragments and

powder were placed in the puck mill to provide representative material. The puck mill

was then placed in the pulverizer and each sample was pulverized for 1.5-2 min, until no

grains could be felt when rubbed between the fingers. The powdered sample was then

placed on a clean sheet of paper, which was used to transfer the material into a labeled

new Ziploc bag. The puck mill and all tools used to handle the samples were cleaned

between each new sample with water and then ethanol.

11

11

Table 2: Description of hand samples collected from Marmora (MARM) with sample

number, classification, field notes and hand sample description. Abbreviations for

minerals are from Whitney and Evans (2010).

12

12

Table 3: Description of drill core samples obtained from Marmora (MARM), Allan Mills (AM) and Blairton (BL) with sample

number, classification and description, end interval and DDH box interval. Abbreviations for minerals are from Whitney and Evans

(2010).

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13

Analytical  Methodology

All analytical methods are summarized in Table 4. From the samples that were collected

in the field, the samples that were best for statistical representation were selected for

analytical work.

Table 4: Analytical work on selected samples from Marmoraton, Allan Mills and

Blairton.

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14

4.1 Ordinary  and  Polished  Thin  Sections

Samples for petrographic analysis were chosen from the hand samples collected

in the waste dumps. A total of 17 thin sections were made, of which three intrusion

samples were made into ordinary thin sections and the remaining into polished thin

sections. Samples were chosen from the following classifications: magnetite rich,

magnetite and sulphide, sulphide rich, vein and intrusion. The following procedure was

used to produce the thin sections. The selected samples were first cut in half using a rock

saw. The area of petrographic interest was marked and cut to the appropriate size. The cut

pieces were then labeled and shipped to Vancouver Petrographics for preparation. Thin

sections were observed using a Leitz transmitted and reflected light microscope.

4.2 X-Ray  Fluorescence  (XRF)  Analysis

XRF analysis was used to measure major, trace and rare earth elements in selected

samples using a Philips PW2404 X-Ray Spectrometer. A preset semi-quantitative

analytical method was used for each sample. The samples were made into powder pellets

using the following procedure. First, the counter top and all equipment were wiped down

to remove material from previous work. Approximately 3 g of the powdered sample were

measured out onto a Kimtech sheet. The measured sample was then placed in a die and

hand pressed in the pellet presser. A ring was placed in the capsule prior to the powder to

create a seal for the pellet. 1-2 spoonfuls of boric acid was/were then placed in the

capsule to form support for the pellet. A 30-ton press was used to harden the pellet by

compressing it to 5 tons of pressure. The completed pellet was carefully removed from

the capsule and labeled. One pellet was made per sample, with the exception of MARM-

14-10 which had a duplicate pellet prepared. Each sample was then placed in the X-ray

spectrometer, which had been calibrated for the preferred analytical method. Samples

were run one at a time for approximately 20 minutes using the analytical software.

4.3 Neutron  Activation  Analysis  (NAA)

Neutron activation analysis was used to measure the concentration of major, trace

and rare earth elements. The samples were measured 7 and 40 days after irradiation using

an APTEC/NRD Energy Dispersive Spectrometer. The samples were prepared for

15

15

radiation and analysis using the following procedure. The counter and weighing scales

were first wiped down to remove material from previous work. A small and a large bag

were made using the Decosonic vacuum bag sealer. The small bag was first weighed

empty, then filled with 0.180 – 0.220 g of sample and reweighed (see Table 16, in

Appendix 2). The final weight of the sample was recorded. The bag was then sealed and

labeled and placed inside the larger bag, which was also sealed. A double seal system

was used to prevent leakage of material during irradiation. The samples were then placed

in a vial with a standard (UTB2) and Fe wire. The samples were sent in three different

shipments to the McMaster Nuclear Reactor Center where they were irradiated for 1 hour

at a flux of 3 x 102 neutrons per second. The irradiated samples were set aside until they

were safe to handle and analyze. The 25% efficient high-purity germanium detector was

calibrated to the international rock standard and each sample was run for a minimum of 3

hours. The sample name and weight were entered into the software prior to the

measurements. Due to leakage from the first sample set, seven of the samples were

reanalyzed using a new batch of irradiated samples.

4.4 Laser  Ablation  –  Inductively  Coupled  Plasma  Mass  Spectrometry  (LA-ICPMS)  Analysis

The LA-ICPMS analytical method was used to measure the concentrations of Au,

Ag, Pd and Pt in 8 samples that showed the highest Au values from NAA results. The

following procedure was used to prepare the samples into pellets. The counter and

weighing scales were first wiped down to remove material from previous work.

Approximately 0.3g of sample was weighed out on Kimtech paper. The measured sample

was then placed in a die and hand pressed in the pellet presser to create a 4mm thick

pellet of approximately 1cm diameter. The sample was carefully removed from the die

and placed in a labeled container. The equipment used at the University of Toronto

contains two components: a New Wave UP-213 laser ablation microscope and a VG PQ

ExCell ICP-MS. The operating conditions for the Marmoraton samples were 45%

operating level at which coupling would occur, 10Hz laser pulse (10 pulses per second),

65μm  and  100  μm  (used  to  increase  the  sensitivity)  width  of  the  line,  20μm  per  second  

speed. The Indium 115 isotope was used to set the operating condition. ICP-MS was

16

16

tuned to give oxides of <2% using ThO+/Th (masses, 248 and 232) and by ensuring U/Th

(masses, 238 and 232) was close to 1.0. Calibration used sample NIST 610, with two

measurements taken before and after to account for drift in measurements and have a

more accurate data set.

Results Compiled geochemical analytical results for the samples listed in Table 4 are given in

Tables 5-8.

5.1 Major  Elements

Table 5: Major element data for the Marmoraton (MARM), Allan Mills (AM) and

Blairton (BL) samples in percent.

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17

5.2 Trace  Elements

Table 6: Trace element data for the Marmoraton (MARM), Allan Mills (AM) and

Blairton (BL) samples in ppm; for Co 10% of W value was removed; Au in ppb.

Pd, has two analytical values for the same sample because two different lines were

analyzed using LA-ICPMS.

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18

5.3 Rare  Earth  Elements  (REEs)

Table 7: Rare earth element data for the Marmoraton (MARM), Allan Mills (AM) and

Blairton (BL) samples, in ppm.

19

19

Table 8: Rare earth element averages, REO, REE, TREO and TREE for each sample

type. Decimal places are for computational purpose only.

20

20

Discussion The discussion part of this research has been divided into tailings, ore geochemistry

(excluding REEs), ore geochemistry (REEs) and intrusion geochemistry. Figures 5 to 15

will be discussed below in each of the subsections.

Figure 5: Scatter plot showing %SiO2 and %CaO in tailings and ore from Marmora,

Allan Mills and Blairton.

Figure 6: Scatter plot showing %SiO2 and %Al2O3 in tailings and ore from Marmora,

Allan Mills and Blairton.

0

5

10

15

20

25

-5 5 15 25 35 45

% C

aO

% SiO2

Tailings Ore (Marmora) Ore (Allan Mills) Ore (Blairton)

0

1

2

3

4

5

6

7

8

-5 5 15 25 35 45

% A

l2O

3

% SiO2

Tailings Ore (Marmora) Ore (Allan Mills) Ore (Blairton)

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21

Figure 7: Scatter plot showing %SiO2 and %MgO in tailings and ore from Marmora,

Allan Mills and Blairton.

Figure 8: Scatter plot showing %SiO2 and %FeS2 + Fe3O4 in tailings and ore from

Marmora, Allan Mills and Blairton.

0

5

10

15

20

25

30

35

40

45

0 5 10 15 20 25 30 35 40 45

% M

gO

% SiO2

Tailings Ore (Marmora) Ore (Allan Mills) Ore (Blairton)

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45

% F

eS2

+ Fe

3O4

% SiO2

Tailings Ore (Marmora) Ore (Allan Mills) Ore (Blairton)

22

22

Figure 9: Scatter plot showing %SiO2, and %FeS2 and %Fe3O4, in tailings and ore from

Marmora, Allan Mills and Blairton.

Figure 10: Scatter plot showing %Fe3O4 and %FeS2 in tailings and ore from Marmora,

Allan Mills and Blairton based on classification of each sample.

0

10

20

30

40

50

60

70

80

90

100

-5 5 15 25 35 45

% F

eS2

& %

Fe3

O4

%SiO2

Tailings (FeS2)

Tailings (Fe3O4)

Ore (Marmora - FeS2)

Ore (Allan Mills - FeS2)

Ore (Blairton - FeS2)

Ore (Marmora - Fe3O4)

Ore (Allan Mills - Fe3O4)

Ore (Blairton - Fe3O4)

0

10

20

30

40

50

60

0 20 40 60 80 100

% F

eS2

% Fe3O4

Tailings

Magnetite Rich (Marmora)

Magnetite Rich (Allan Mills)

Magnetite Rich (Blairton)

Magnetite + Sulphide(Marmora)Magnetite + Sulphide(Blairton)Sulphide Rich (Marmora)

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23

Figure 11: Scatter plot showing %FeS2 and Co (ppm) in tailings and ore from Marmora,

Allan Mills and Blairton.

Figure 12: Scatter plot showing %FeS2 and Ni (ppm) in tailings and ore from Marmora,

Allan Mills and Blairton.

0

100

200

300

400

500

600

700

800

900

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Co (p

pm)

% FeS2

Tailings Ore (Marmora) Ore (Allan Mills) Ore (Blairton)

0

100

200

300

400

500

600

700

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Ni (

ppm

)

% FeS2

Tailings Ore (Marmora) Ore (Allan Mills) Ore (Blairton)

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24

Figure 13: Scatter plot showing %FeS2 and Cu (ppm) in tailings and ore from Marmora

and Blairton. Data point with * is MARM-14-4.

Figure 14: Scatter plot showing Ni (ppm) and Co (ppm) in tailings and ore from

Marmora, Allan Mills and Blairton.

0

200

400

600

800

1000

1200

1400

1600

1800

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Cu (p

pm)

% FeS2

Tailings Ore (Marmora) Ore (Blairton)

*

0

100

200

300

400

500

600

700

800

900

0 100 200 300 400 500 600 700

Co (p

pm)

Ni (ppm)

Tailings Ore (Marmora) Ore (Allan Mills) Ore (Blairton)

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25

Figure 15: Scatter plot showing Cu (ppm) and Co (ppm) in tailings and ore from

Marmora and Blairton.

6.1 Tailings

In general the tailings samples are grouped together quite clearly on the bivariate

major element plots. When comparing the oxides with the silica contents, the sample

cluster is well defined with high silica values, and in decreasing order CaO, MgO and

Al2O3 values (Figures 5-7). There is half the amount of MgO in the tailings (Figure 7)

compared to CaO (Figure 5). The Al2O3 values (Figure 6) are slightly lower than the

MgO values. The high silica values of ~ 40-45% are due to magnetite removal and

enrichment in silicates.

Comparing the silica content with Fe, the tailings contain low Fe with high silica

(Figure 8 and 9) and follow closely with the trends shown by the Marmora skarn samples.

In Figure 9, the sulphide and oxide components of Fe are separated and two distinct

clusters are present in the tailings. Based on this plot, the tailings have a higher

percentage of Fe as oxide than as sulphides. This finding can also be seen in Figure 10,

where the tailings cluster is higher on the Fe3O4 axis than the FeS2.

0

100

200

300

400

500

600

700

800

900

-200 300 800 1300 1800

Co (p

pm)

Cu (ppm)

Tailings Ore (Marmora) Ore (Blairton)

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The tailings also show clustering in the trace element data, but with some scatter

and one anomaly. The tailings are well defined when plotting Co and Ni with FeS2

(Figure 11 and 12). Where FeS2 is low, Co values show a range that connects with skarn

samples. Ni values stay relatively the same with changing FeS2 values. When plotting Cu

against FeS2 (Figure 13), one anomaly is present for which the Cu value is significantly

greater compared to the other tailings samples, but with low FeS2. The same anomaly is

seen on plots of Co with Ni (Figure 14) and Cu (Figure 15). On both the bivariate plots

the tailings are clustered and fall in the same value range as the Marmora skarn samples.

Other trace elements of interest in the skarn were Pd and Pt. Of the eight samples

that were analyzed only one had high values of Pd of 0.95 ppm and 0.72 ppm (just less

than 1 g/tonne). The sample containing the values is one of the tailings samples. The

remaining samples were below the detection limits of 0.02 ppm for Pd and 0.002 ppm for

Pt. The samples chosen were those with the highest Au values. The Marmoraton Pd

values were compared with current industry cut off grades to evaluate their significance.

At the Lac des Iles mine operated by North American Palladium the near surface reserves

are 6.3 Mt at 1 g/t Pd. The near surface measured and indicated resources are 35.6 Mt at

1.28 g/t Pd (Keevil, 2015). The preliminary lowest underground cut off is 2.00 g/t (Peck

et al., 2015). Even though Pt values for the samples in this study were below detection

limit, it is still important to note the cut off grade. The New Waterberg Joint Venture by

Platinum Group Metals uses a combined cut off grade of 2.5 g/t (0.97 g/t Pt; 2.11 g/t Pd;

0.16   g/t   Au)   for   their   open   pit   operation   (Muller,   2015).   Additionally,   Ivanhoe’s  

operation in South Africa has an average grade of ~ 4 g/t 4PE (platinum, palladium, gold

and rhodium) for indicated resources. The cut-off grade for the resource is 2 g/t 4PE

(Saywell, 2015). With regards to accepted cut off grades for Pd, the value of Pd at

Marmoraton can be considered sub-ore grade to ore grade depending on the total average.

Further analytical work is needed on the samples to clarify. As for Pt, the detection limit

is significantly lower than accepted cut off grades; as such the Marmoraton samples

would not be considered economically viable.

The Pd-rich tailing sample, MARM-14-4 is one of the three orange (due to

oxidation) tailings samples that were analyzed. This sample is quite low in S relative to

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27

its Cu concentration (see Figure 13). This sample was taken at approximately 20 cm

depth from the surface of the tailings. Chemical weathering of the tailings has occurred

over ~45-55 years, and FeS2 has been oxidized, forming FeOOH, H+ and SO42-. Any Cu

present would have been left behind, as either a secondary Cu mineral or absorbed in Fe-

hydroxides. However, the S content would have been significantly reduced by removal of

soluble SO42-.

6.2 Ore  Geochemistry  (excluding  REEs)

When examining the bivariate plots of CaO and Al2O3 with SiO2 (Figures 5 and

6), a positive correlation can be noted for the Marmoraton and Blairton samples. The

Allan Mills samples do not show any trend and contain very low values of CaO. There is

a large spread in the silica contents of the Marmoraton samples, however the majority

contain less than 20% SiO2. The results and clustering of data points show there are no

particular rock types that contain more or less CaO, Al2O3 and MgO (Figure 7) based on

the amount of silica present. As such the Al2O3 values are not affected by the amounts of

CaO present. The bivariate plot of MgO and SiO2 does not show any trend for the

Marmoraton samples, but does show a positive correlation for the Allan Mills samples. In

general, Blairton values are similar to those of Marmoraton.

To understand the relationship between silica and iron content, bivariate plots

were used to compare SiO2 values with FeS2 and Fe3O4 (Figures 8-10). A clear trend can

be seen in Figure 8, when comparing SiO2 values against FeS2 + Fe3O4 where the amount

of Fe decreases as the amount of silica increases. The magnetite and sulphide bearing

samples, as expected, have higher Fe contents and lower silica values compared to the

intrusion and the tailings. The Fe values can be further divided into sulphide and oxide

content for each sample and compared with the amount of silica in the respective samples

(Figure 9). Both Blairton and Allan Mills have greater amounts of Fe present as oxide

than in sulphides; in fact both contain very low amounts of sulphides. Marmoraton also

contains more Fe in oxides than sulphides. The oxides show a decrease in Fe with

increasing silica with some variation in the values. The Fe in the sulphides on the other

hand, does not show any correlation with silica. To further differentiate how the Fe is

distributed amongst the samples, FeS2 is compared with Fe3O4 (Figure 10). No direct

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28

correlation can be identified on this plot between FeS2 and Fe3O4; however, the samples

were plotted based on their classification and each one plots within their respective

clusters with slight scattering. For example, the majority of the Marmoraton sulphide-rich

samples plot at high FeS2 and low Fe3O4. The reverse can be noted for the Marmoraton

magnetite-rich samples, the samples plot in an area of low FeS2 and high Fe3O4. Allan

Mills and Blairton samples contain low amounts of FeS2 and moderate to high amounts

of Fe3O4.

Bivariate plots of trace elements were chosen based on elements that were

enriched in the samples. Of the eleven trace elements measured, three (Co, Ni, Cu) were

plotted against FeS2 to understand how they varied with changing sulphur content

(Figures 11-13). The bivariate plot for Co and FeS2 (Figure 11) shows a positive linear

correlation for the Marmoraton samples, where samples with high FeS2 are enriched in

Co up to almost 900 ppm (~0.10%). The samples for Allan Mills and Blairton show a

tight cluster at low Co and FeS2, but they split into two smaller clusters that overlap with

Marmoraton samples. The bivariate plot for Ni and FeS2 (Figure 12) shows a similar

linear correlation to the Co- FeS2 plot, in which the samples with high FeS2 tend to

contain higher amounts of Ni up to ~650 ppm. Samples from Blairton contain higher

amounts of Ni than those from Allan Mills. The reason for the Co and Ni correlations

with FeS2 is probably selective substitution for Co and Ni in the sulphide lattices.

The bivariate plot for Cu and FeS2 (Figure 13) shows significant scatter for the

Marmoraton samples. The values with high Cu, up to ~0.18%, are from sulphur rich

samples, whereas the low Cu values are from magnetite rich samples with the exception

of one tailings sample. Since a strong linear correlation is not present between the Cu and

FeS2, it was hypothesized that the Cu could be present in a non-sulphide mineral perhaps

in silicates. However, no trend was present when comparing Cu values with SiO2 data.

Copper values were also compared with CaO data in case the Cu was present in

carbonate minerals, however much like silicates, no trend was present. Hence, the cause

of the Cu scatters is probably just independent variation in volume % relative to pyrite

and pyrrhotite.

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29

The trace elements were further examined by comparing Co with Ni and Cu

(Figures 14 and 15). The bivariate plot of Co and Ni (Figure 14) shows a relatively

confined cluster for the Marmoraton samples, with two outliers that have high values for

both Ni and Co. The Co values have a larger range (~10-650ppm) compared to the Ni

values (~100-370ppm). The Allan Mills samples have low Co and moderately low Ni.

The Blairton samples contain low Co and low Ni values. The bivariate plot of Co and Cu

(Figure 15) shows a slight positive correlation, but there is significant scatter. One cluster

of the Marmoraton samples can be noted, at low Co and Cu values, which is comprised of

mainly magnetite-rich samples. No Co values were detected for Allan Mills. Blairton on

the other hand, has low Co and Cu values.

Apart from the magnetite being the primary mineral produced from iron skarns,

trace amounts of Cu, Co, Ni and Au can also be found in such deposits (Meinert et al.,

2005). The values for Co, Ni and Cu can be considered enriched in this location relative

to average crustal abundances, which are as follows: 10 ppm, 20 ppm and 25 ppm

(Taylor and McClennan, 1985). The above average values for Co, Ni and Cu can be used

to understand the changes occurring in the magma and the behaviour of certain elements.

It is important to note that cobalt can easily replace transition metals such as iron and

nickel due to similarities in atomic properties. As such, cobalt is commonly produced as a

by- or co-product of processing nickel and copper sulphides. In order for Co to be

considered of economic value, the grade for a magmatic or hydrothermal deposit should

be at least 0.1% Co (British Geological Survey, 2009). A few of the Marmoraton

samples, mainly sulphide-rich, show sub-ore grade values (Table 6). The highest value,

of 0.18%, is ore grade and is found in one of the two vein samples (MARM-14-26). The

higher concentration of Co in the vein is a result of precipitation of Co from

hydrothermal fluids as they flowed through the host rock (British Geological Survey,

2009). Sulphides, which contain Co in place of other elements, are pyrrhotite and

chalcopyrite (British Geological Survey, 2009), both of which are present in the

mineralogy of the skarn.

The sulphide rich samples also contain high concentrations of Ni and Cu together

with Co. The Ni in the Marmoraton samples is considered not be of economic potential.

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30

The range in economic grade for sulphides is 0.15% to approximately 8% Ni (British

Geological Survey, 2008). The Ni concentrations in the samples from this study are

significantly lower than the accepted Ni cut off grade. Although the Ni is not of economic

value, the concentrations are elevated compared to average crustal abundance. This can

be due to Ni being enriched by hydrothermal fluids. It is likely that both Co and Ni were

introduced into the system at the same time and substituted for one another as the

magmatic processes changed and developed. Co can easily substitute for Fe and Ni as

they have similar properties (British Geological Survery, 2009). Together with the two

elements, Cu would also have been brought into the system. Copper appears to have two

peaks in values: one tailings and two magnetite and sulphide rich samples. The high Cu

values in the sulphide-rich samples of 0.17% and 0.13% are sub-ore grade. The minimum

grade at which a Cu deposit can be mined is 0.4% (British Geological Survey, 2007). The

enriched Cu values are associated with observed chalcopyrite (British Geological Survey,

2007).

As mentioned above, Fe skarns can have Au present with other trace elements.

For the Marmoraton samples, the Au values of 0.35 – 27.36 ppb are not of economic

significance, but several are above the average crustal abundance of 1.8 ppb (Taylor and

McClennan, 1985). In this deposit, if economically viable amounts of Au were present it

would be considered to be a by-product of the Fe. A study by Theodore et al. (1991),

calculated the median Au grade from 50 by-product Au deposits to be 3.7 g/t. For a

deposit to be classified as a Au skarn, however, the minimum average grade of the

deposit must be 1 g/t Au (= 1 ppm). In comparison to that concentration, the samples

from Marmoraton are significantly low in Au. A comparison can be made between the

Marmoraton skarn and the Nickel Plate gold deposit in Hedley, B.C. to understand the

possible location of Au enrichment. The Hedley formation is intruded by the Toronto

Stock (Figure 16) 1.5 kilometres northeast of Hedley. The Toronto Stock is of economic

importance as it is thought to be the main body of the diorite dike-sill swarm and skarn

development that contains the Nickel Plate gold deposit (Ray and Dawson, 1994). Sills

coming off the Toronto stock extend approximately 400m into the Hedley formation,

which develops into a skarn. The stock itself has a width of up to 500m and length of

about 2km. Geochemical analyses of the stock show that it is subalkalic and calcalkaline

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31

in composition. The stock is comprised of quartz diorite and quartz gabbro and lacks

magnetite. The gold-skarn mineralization forms near the Hedley sills (intrusions) and is

restricted to the exoskarn. The gold is commonly found with arsenopyrite- and pyrrhotite-

rich skarn, where the mineralization is controlled by fractures and replacement of ore by

sulphides (Ray and Dawson, 1994). Although the Marmoraton skarn has a similar

structure to Nickel Plate, the samples collected were very close to the emplacement of the

intrusion. In addition, Park (1966), found that metasomatism occurred at the high

temperature of greater or equal ~500 oC, which is not a favourable temperature for Au to

precipitate. It can be proposed that there is potential for the Marmoraton skarn to contain

associated Au, however, it would be located distally and outside the pit boundary. As the

intrusive magma made its way through the Grenville marble and fractures the fluid would

have cooled down allowing for minerals to precipitate. It is important to note that in this

type of system, there is a large volume of fluid present and that increases the potential for

various metals to precipitate at favourable conditions. Geochemical signatures can be

used to see zoned metal assemblages that change from proximal base metals to distal

precious metal zones (e.g. Theodore and Blake, 1975). The zones can be traced for over a

1000 m past the proximal skarn with the anomaly ranging from 10s to 100s of ppm for

each metal (Meinert et al., 2005).

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32

Figure 16: Cross section of the Nickel Plate deposit, Hedley, British Columbia (Dawson,

1996).

In addition to the ore samples from Marmora, the geochemistry of two vein

samples was also analyzed. It is hypothesized that the two veins represent lower

temperature fluid from below because they are high in carbonate. High carbonate levels

in veins surrounding the skarn would be expected since the acid rich fluids would

dissolve the carbonate material as it moves through replacing it with magnetite. As the

fluid cools in the vein structures, the dissolved carbonate would be precipitated. One of

the vein samples is also enriched in Co at 0.18%. Neither of the vein samples are

enriched in Au, which is supporting evidence for lack of potential for distal hydrothermal

Au mineralization.

Lastly, the ore geochemistry of the Marmoraton Fe skarn can be compared to

other Fe skarns in the literature. A study by Hammarstrom et al. (1995) summarized Fe

skarn analyses of both major and trace element data (Table 9). The analyses were carried

out on two sites in Montana: Mississippian Madison Limestone and Cambrian Meagher

Limestone. When comparing the two data sets, there are differences in the values since

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33

Hammarstrom et al., used both magnesian and calcic Fe skarn data and the number of

samples for each analysis varied. In general, the two datasets are similar for the major

oxides, with some concentrations for Marmoraton being higher and lower. This is

reflected in the regional geology of the area, which would differ for each data set. In

terms of trace element data, the values for As and Au are much higher in the two

Montana sites than those found at Marmoraton. The proximity of sampling of each

Montana skarn to the intrusion in unknown, which might account for the difference in As

and Au values. Chromium values in Marmoraton (ranging from 1-33 ppm) are similar to

the average Cr value of 32 ppm in Table 9. On the other hand, Co, Cu and Ni are higher

at Marmoraton. The concentrations of Mn and Zn are close to those of the averaged

deposits. Overall, the data from Marmoraton and Montana show variations in values, but

are mutually consistent.

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34

Table 9: Summary of major and trace element analyses of Fe skarns in Mississippian

Madison Limestone, Montana and Fe-Cu skarn in Cambrian Meagher Limestone,

Montana (Hammarstrom et al., 1995). The Fe2O3 is given as FeTO3, oxides in weight

percent and Au in ppb.

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35

6.3 Ore  Geochemistry  (REEs)

The rare earth elements (REEs) are comprised of 17 chemically alike metallic

elements (Figure 21, in Appendix 3), ranging from lanthanum (La 57) to lutetium (Lu

71), scandium (Sc 21) and yttrium (Y 39). Both Sc and Y are grouped together with the

REE due to similar chemical and physical properties (British Geological Survey, 2011).

All REE, Sc and Y are principally trivalent, affecting how they behave in magmatic melts

(M. Gorton, personal communication, April 9, 2015). They can be separated into two

categories: light REE (LREE) and heavy REE (HREE). The light REEs (atomic numbers

57 – 63) comprise lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd),

promethium (Pm), samarium (Sm) and europium (Eu); and scandium (Sc). The heavy

REEs (atomic numbers 64 – 71) comprise gadolinium (Gd), terbium (Tb), dysprosium

(Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu); and

yttrium (Y) (Canadian Rare Earth Element Network, 2013).

The REEs do not occur naturally as individual metallic elements, but in various

mineral types such as halides, carbonates, oxides, phosphates and silicates. The average

crustal abundance of individual REE is 9.2 ppm. The upper crustal abundances for each

REE are listed in Table 10. Cerium is the most abundant and thulium is the least

abundant (British Geological Survey, 2011). However, the two least abundant REE

elements (thulium and lutetium) are 200 times more common than gold in average

continental crust (Haxel et al., 2005). Despite the relatively high abundance of REEs,

they are less likely to get concentrated in the crust compared to gold due to their

compatibility in silicate magmas (British Geological Survey, 2011). The relative

abundance of each element is dependent on atomic number. The even atomic number

REE elements have a higher abundance compared to the odd atomic numbered, which is

referred to as the Oddo-Harkins effect (Haxel et al., 2005; British Geological Survey,

2011). The light REEs are more incompatible because they have larger ionic radii,

causing them to behave like elements that have a 2+ valence resulting in these REEs

favouring melts. On the other hand, the heavy REEs are more compatible in minerals and

are less likely to travel with the melt due to smaller ionic radii causing them to behave

like elements with a 4+ valence. As a result, light REEs are more enriched in the

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36

continental crust as opposed to heavy REEs (Haxel et al., 2005). Despite the abundance

of REEs in the crust, it is difficult to find high concentrations that are of economic value

(Canadian Rare Earth Element Network, 2013). Due to chemical similarity in ionic radii

and oxidation states, REEs can substitute for one another in crystal structures allowing

more than one REE to be present in an individual mineral (British Geological Survey,

2011)

Table 10: Estimated upper crustal abundances for REEs, Y and Sc in increasing atomic

number, in parts per million (Long et al., 2010).

Industrial use of REEs is low; however, they are important in development and

growth of specific high-technology applications (Long et al., 2010). This demand enables

exploration for REE deposits to be sustained. REE-bearing minerals in economic

concentrations can be found in carbonates, alkaline rocks, skarns and carbonate-

replacement deposits that are related to alkaline intrusions (Long et al., 2010). Skarns can

be enriched in REEs in addition to the metal content. The REEs are found in particular

mineral phases, for example, garnet, vesuvianite, epidote and allanite (Meinert et al.,

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37

2005). In this study, the concentrations of individual REEs were measured in each sample

(Table 7). These analytical values were first compared to the average crustal abundances

to detect any anomalies or enrichments. The Marmoraton REE values were compared

with the McGill (1997) values in Table 10. The values for La, Ce and Nd were above

average crustal abundance in some of the samples. Samples that were magnetite rich and

magnetite and sulphide mixed were often very low in La, Ce and Nd. Sm values were

significantly low in the ore compared to the average crustal abundance. Terbium, Yb and

Lu had low concentrations in the ore but were within the average crustal abundance range

in the intrusion. Two of the samples showed enrichment of LREEs: MARM-14-04

(tailings) and MARM-14-22 (sulphide rich). The two samples contained higher than

average crustal abundances of La, Ce and Nd. The higher value of Sc was analyzed in an

intrusion sample, whereas the remaining intrusion and ore samples were below or close to

average crustal abundance.

The individual REE values were further examined to evaluate economic potential.

Averages for each element based on category (tailings, ore, vein, intrusion and Fe pellet)

were calculated along with the rare earth oxide (REO), the total rare earth oxide (TREO)

and total rare earth element (TREE) values. These calculated values (Table 8) were

compared with current Canadian projects that may go into production in the next 2 years

(Table 11). The highest REE, 0.017 %, are found in the intrusion samples, which is

significantly low. The Eco Ridge project contains the lowest REE, 0.16 %, but has at

least 11% HREE which would allow it to  be  economically  viable.  In  Marmoraton’s  case,  

the overall REE concentration is low and most importantly there is a lack of HREE

without significant LREE enrichment. Additionally, the values are not high enough to be

considered economic for by-product mining if a primary economic commodity were

present. In order for a prospect to be considered economically viable it would need to

contain at least 1% TREO (P. LeBaron, personal communication, May 25, 2015). Table

12 shows the concentration of REEs in various REE deposits. In each of these deposits

the TREO would be considerably higher than 1% and each deposit is enriched in one or

more LREE. Overall, the Marmoraton samples have low REE values and do not show

economic potential.

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Table 11: REE projects in Canada in decreasing order of total REE in %. These projects

contain at least 10% of the total REE as HREE (Natural Resources Canada, 2014).

Table 12: Average crustal abundance and concentrations of REEs and Y in various REE

deposits. REEs listed in increasing atomic number (Long et al., 2010).

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6.4 Intrusion  Geochemistry

The geochemistry of the “Marmoraton intrusion” was compared to data in

Meinert’s  (1993) paper, in which the average compositions of plutons were plotted based

on different skarn types. The compositions of the plutons are calculated based on the ratio

(FeO + CaO + Na2O)/K2O and anhydrous SiO2. The intrusion samples from Marmoraton

(Figure 17) have (FeO + CaO + Na2O)/K2O values that are much higher than those found

on  Meinert’s  plot  (Figure 18). Of the four intrusion samples, one of the compositions can

be placed in the Fe skarn classification (Figure 18).   Based   on   Meinert’s   plot,   the  

Marmoraton intrusion can be classified as linked to Fe skarn since the values plot within

or above the given ranges of (FeO + CaO + Na2O/K2O) values.

Figure 17: Composition of the Marmoraton intrusion based on the scatter plot showing

%SiO2 and (FeO + CaO + Na2O)/K2O. Sample MARM-14-46 is plotted in the red box

and in Fig. 18.

0

20

40

60

80

100

120

140

160

180

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

FeO

+ C

aO +

Na2

O /

K2O

% SiO2

40

40

Figure 18: Average compositions of plutons related to various types of skarns and one

Marmoraton intrusion sample, which plots on this diagram (see Fig. 17). Modified from

Meinert (1993).

The major and trace element chemistry can be use to classify and understand the

Marmoraton intrusion samples. Ninety-five percent of igneous rocks are made up of the

following eight oxides: SiO2, Al2O3, FeO, Fe2O3, MgO, CaO, K2O and Na2O (Meinert,

1995), all of which are present in the intrusion samples. The silica content is highest in

the intrusion samples compared to the ore, in addition to Na2O and Al2O3. MgO in

general is much lower in the intrusion than in the ore. Fe bearing skarn plutons are

considered to be more primitive in terms of their geochemistry compared to Sn skarns,

which are for example, more evolved (Meinert et al., 2005). Similarities and differences

between the intrusion samples from Marmoraton and other Fe skarns can be compared to

the average pluton geochemistry of Fe skarn (Table 13) compiled by Meinert (1995). In

terms of major element composition, the Marmoraton intrusion samples fall within the

oxide ranges, with the exception of MnO and P2O5, which are a slightly lower in

concentration. Values for MnO were separately calculated for comparison. For the trace

elements, there are only a small number that were analyzed in the intrusion. Of those, Ni

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41

and Cu are within the range, Cr and Zn are lower than the range and V is higher than the

range.

Overall, the Marmoraton intrusion samples can be classified as linked to Fe

skarns based on the concentration of the major element oxides. The trace element

concentrations of the intrusion can also be used to evaluate the skarn association. Of the

trace elements, Meinert (1995) plotted V vs. Ni for the different pluton samples (Figure

19). Using the mean Fe skarn values from Table 13 and the Ni and V values from

Marmoraton, a similar plot can be created for comparison (Figure 20). The intrusion plots

within the Ni range of the pluton value, but the V is slightly higher than the average that

Meinert reported. Based on the Ni-V plot, it is evident that the intrusion also classifies as

linked to Fe skarns. Vanadium and Ni can be used to show the separation between

different skarn types because V will replace Fe3+ in oxide phases (i.e. magnetite). Both V

and Ni will decrease as magma undergoes crystallization and differentiation (Meinert,

1995). Since V and Ni values plot higher on the diagram and within the Fe skarn region,

the igneous rocks for Marmora are less differentiated.

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42

Table 13: Major and trace element composition of plutons related to Fe skarns, oxides in

per cent and trace elements in parts per million (Meinert, 1995).

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43

Figure 19: Trace element compositions of plutons based on a log scatter plot of Ni and V

(Meinert, 1995).

Figure 20: Composition of MARM-14-28 and Fe skarn composition from Meinert (1995)

based on the log plot between Ni (ppm) and V (ppm).

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Principal  conclusions

1. This research is one of the most detailed examinations of the major and trace element

geochemistry of an Fe (magnetite) skarn carried out.

2. Bivariate plots of the geochemistry of the skarn show clear trends and clustering of data,

indicating that sampling, classification of sample types and analytical work were done

effectively.

3. Cobalt is enriched to sub-economic concentrations of ~0.1%.

4. Analytical work shows that significant Au, Pd, and Pt enrichments do not occur in the

skarn. However, a single tailings sample contains 0.8 ppm Pd (~1 g/t; sub-ore grade)

associated with high Cu and Co.

5. The geochemistry of the intrusion is consistent with Marmoraton being an Fe-only skarn

based on (FeO + CaO + Na2O)/K2O vs. SiO2. In addition, V and Ni values plot in the Fe-

only skarn field. When comparing the intrusion geochemistry to that of other Fe skarn

plutons, both datasets showed similarities in the oxide values with slight variations in the

trace element compositions.

6. The above finding suggests that there is not significant potential for distal Au

mineralization as at Nickel Plate, B.C.

7. This inference is supported by low Au concentrations in cross-cutting hydrothermal

veins.

8. Based on the analytical results, Marmoraton, Allan Mills and Blairton contain low

concentrations of REEs. The TREO are not sufficient to be considered economically

significant; a minimum of 1% TREO is needed for economic potential.

9. The crescent shaped magnetic anomaly extending ~15 km from Marmoraton through

Blairton to Allan Mills, all of which contain proven magnetite skarns, indicates a major

subsurface Fe (magnetite) resource.

10. An hypothesis is that this crescent delineates the outer margin of a zoned alkaline

intrusive complex truncated to the S.E. by a N.E./S.W. structure (see Figure 22, in

Appendix 4). An inner crescentic magnetic anomaly is contained within the outer

crescent, supporting this suggestion.

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Future  Work

1. One of the key tasks that should be done is to name the “Marmoraton intrusion” in

accordance with OGS policies. Currently no formal name exists and the pluton is simply

referred to informally as   the   “Marmoraton   intrusion”.   Naming   of   the   pluton   will   help  

keep consistency in the literature. Dr. R.M. Easton at the OGS has been informed.

2. The correct petrographic names for the components of the intrusion should also be

determined from their normative compositions and Streckeisen (1974).

3. The Marmoraton intrusion can be dated using U-Pb dating on zircons from the syenitic

rocks. The age can be used to examine the timing of emplacement relative to the

surrounding plutons and to determine if any correlation exists between them. The age of

the intrusion can also be used to determine the age of skarn formation.

4. An integrated fluid inclusion microthermometic and analytical study could be carried out

on the skarn in order to constrain the temperature, compositions and transport properties

of the fluids using silicates such as pyroxenes, garnets and epidote. Quartz is not

abundant.

5. Additional work on the Pd and Pt concentrations should be done on the mineralization

emphasizing Cu, Co and Ni enriched samples. Analytical work should also be applied to

the tailings.

6. It can be suggested that the central part of the crescent-shaped magnetic anomaly should

be drilled at approximately three locations to test if it is a zoned intrusive body (see

Figure 22, in Appendix 4). Enough material should be recovered from each hole for U-Pb

zircon dating. It is also suggested that a fourth hole be drilled to the S.E. of the truncating

N.E./S.W. structure to test depth to Grenville basement and the type of lithology present.

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Appendices

Appendix 1: Additional documents for sampling methodology.

Table 14: Table of the Marmoraton samples with their coordinates (latitude and

longitude) and elevation of sample site.

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Table 15: Table of sample numbers for the Marmaton site with corresponding photo ID.

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Plate 2: MARM-14-01

Plate 3: MARM-14-02

Plate 4: MARM-14-03

Plate 5: MARM-14-04

Plate 6: MARM-14-05

Plate 7: MARM-14-06

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Plate 8: MARM-14-07

Plate 9: MARM-14-08

Plate 10: MARM-14-09

Plate 11: MARM-14-10

Plate 12: MARM-14-11

Plate 13: MARM-14-12

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Plate 14: MARM-14-13

Plate 15: MARM-14-14

Plate 16: MARM-14-15

Plate 17: MARM-14-16

Plate 18: MARM-14-17

Plate 19: MARM-14-18

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Plate 20: MARM-14-19

Plate 21: MARM-14-20

Plate 22: MARM-14-21

Plate 23: MARM-14-22

Plate 24: MARM-14-23

Plate 25: MARM-14-24

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Plate 26: MARM-14-25

Plate 27: MARM-14-26

Plate 28: MARM-14-27

Plate 29: MARM-14-28

Plate 30: MARM-14-29

Plate 31: MARM-14-30

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Plate 32: MARM-14-31

Plate 33: MARM-14-32

Plate 34: MARM-14-33

Plate 35: MARM-14-34

Plate 36: MARM-14-35

Plate 37: MARM-14-36

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Plate 38: MARM-14-37

Plate 39: MARM-14-38

Plate 40: MARM-14-39

Plate 41: MARM-14-40

Plate 42: MARM-14-41

Plate 43: MARM-14-42

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Plate 44: MARM-14-43

Plate 45: MARM-14-44

Plate 46: MARM-14-45

Plate 47: MARM-14-46

Plate 48: AM-14-01

Plate 49: AM-14-02

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Plate 50: AM-14-03

Plate 51: BL-14-01

Plate 52: BL-14-02

Plate 53: BL-14-03

Plate 54: BL-14-04

Plate 55: MARM-14-54

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Plate 56: MARM-14-56

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Appendix 2: Additional document for analytical methodology.

Table 16: Sample numbers with corresponding sample weights for neutron activation

analysis.

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Appendix 3: Additional documents for discussion.

Figure 21: REE in the periodic table separated into light and heavy rare earths (Canadian Rare Earth Element Network, 2013).

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Appendix 4: Additional documents for key conclusions and future work.

Figure 22: Aeromagnetic map showing the Marmoraton anomaly (NE corner) together with a crescent-like anomaly on the west side, which includes the locations of Allan Mills and Blairton. There are four suggested drill holes and a potential fault-like structure on the east side of the crescent. Values are shown in gammas and the scale is 1 inch to 1 mile (Modified from GSC, 1970).