Journal of Geochemical Exploration€¦ · rocks with intermediate, maﬁc metavolcanic and intrusive rocks, and metasedimentary rocks (Fig. 1). The Point Lake Formation has been

Journal of Geochemical Exploration 150 (2015) 84–103

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Journal of Geochemical Exploration

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The surface texture and morphology of magnetite from the Izok Lakevolcanogenic massive sulfide deposit and local glacial sediments,Nunavut, Canada: Application to mineral exploration

Sheida Makvandi a, Georges Beaudoin a,⁎, Beth M. McClenaghan b, Daniel Layton-Matthews c

a Département de géologie et de génie géologique, Université Laval, Quebec, QC, G1V0A6, Canadab Geological Survey of Canada, Ottawa, ON, K1A0E8, Canadac Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, ON, K7L3N6, Canada

⁎ Corresponding author at: Département de géologie etLaval, Pavillon Adrien-Pouliot, 1065 avenue de laMedecinTel.: +1 4186563141.

E-mail addresses: [email protected] (S. [email protected] (G. Beaudoin), bmcclena@(B.M. McClenaghan), [email protected] (D. Layton

http://dx.doi.org/10.1016/j.gexplo.2014.12.0130375-6742/© 2014 Elsevier B.V. All rights reserved.

a b s t r a c t
a r t i c l e i n f o
Article history:Received 1 August 2014Accepted 20 December 2014Available online 26 December 2014

Keywords:MagnetiteVMS depositIzok LakeSurface textureGrain-size distributionShape

Magnetite is a common mineral found in a wide range of mineral deposits and in different geologicalenvironments. The study of surface textures andmorphology of magnetite can provide information that is usefulto 1) discriminate different types of magnetite such as that attributed tomagmatic, metamorphic and supergeneenvironments, 2) identify host bedrocks, 3) sediment provenance, and 4) recognize chemical and mechanicalprocesses affecting grains during erosion, transport, and after deposition in sedimentary environments. In thisstudy, magnetite grains from the Izok Lake volcanogenic massive sulfide deposit (Nunavut, Canada) and fromtill covering the area have been investigated using scanning electron microscopy, mineral liberation analysis,and optical microscopy to document their mineral associations, surface textures, grain shape and sizedistribution. Evidences such as 1) contact relations between magnetite and sphalerite, 2) sphalerite andchalcopyrite inclusions in magnetite, and 3) intergrowths of magnetite with actinolite and gahnite suggest thatin Izok Lake deposit and related gahnite-rich stringer zone, magnetite formed by replacement of sulfideminerals during regional, upper greenschist to amphibolite faciesmetamorphism.Magnetite from iron formationalso formed as a result of oxidation–dissolution of almandine, or breakdown of Fe-bearing minerals duringmetamorphism. Euhedral, fine-grained magmatic magnetite in association with ilmenite, plagioclase andhornblende was identified in bedrock gabbro. Magnetite overgrowths on the surface of existing magnetite andother metamorphic minerals fingerprinted the supergene processes affecting bedrocks and sediments aftermetamorphism.Magnetite in till around the Izok Lake deposit ismostly imprinted bymechanicalmicrotextures such as crescenticgouges, deep grooves, arc-shaped steps, and troughs that are diagnostic of transportation by thick continental icesheets. A small proportion of magnetite grains characterized by V-shaped percussion cracks also indicatetransportation by fluvial and/or glaciofluvial environments. Shape, grain-size distribution, and mineralassociation of magnetite in till suggest that in vicinity of the Izok Lake deposit, till has mainly been fed by thedeposit and related alteration zones, though, a high proportion of grains have been derived from iron formations,bedrock gabbro, and Mackenzie dikes.

© 2014 Elsevier B.V. All rights reserved.

1. Introduction

The surface texture and shape of detrital mineral grains can be usedto document their geological history from hypogene formation througherosion, transportation and deposition (e.g. McClenaghan, 2005;Townley et al., 2003). These eroded minerals may undergo mechanical

de génie géologique, Universitée, Québec, QC, G1V0A6, Canada.

di),nrcan.gc.ca-Matthews).

abrasion and chemical alteration during transport from bedrock todepositional environments. During transport, minerals crack and/orfracture because of grain-to-grain impact (Mahaney, 2002). Before,during, or after deposition detrital grains can bemodified by dissolutionof chemically unstable interlocked minerals (e.g. sulfides), and precipi-tation of supergene minerals.

Each chemical or mechanical process may impart specificmicrotextures on mineral surfaces (Mahaney, 2002). The study ofmicrotextures and shape of detrital grains may help to 1) distinguishchemical and/or mechanical processes responsible for the formationof these textures on mineral surfaces, 2) identify mode of transport(Kleesment, 2009), and 3) provide an estimation of transport distancefrom the source (e.g. DiLabio, 1991; Golubev, 1995; McClenaghan

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85S. Makvandi et al. / Journal of Geochemical Exploration 150 (2015) 84–103

et al., 1997; Pokhilenko et al., 2010). Golubev (1995) studied surfacetextures of kimberlite indicator minerals (e.g. pyrope and chromite) inglaciated terrains and showed that these features reflect the distanceand mode of glacial transport. However, Pokhilenko et al. (2010)concluded that these minerals are not useful indicators for short-termglacial transport, since their grain shape and surface textures were notchanged after a few tens of kilometers of ice transport. Dill (2007) sug-gested that physically resistant minerals, such as corundum, kyaniteand zircon, are reliable minerals for morphology-based environmentalanalysis in short-distance placer deposits, whereas Fe- and Ti-richminerals, such as ilmenite and Ti-bearingmagnetite, are goodmeasuresof long distance of transport.

The shape of gold particles has been used to estimate the distanceof transport from the source (e.g. Averill and Zimmerman, 1986;Fisher, 1945; Grant et al., 1991; Knight and McTaggart, 1986;Knight et al., 1999; Stendal and Theobald, 1994; Utter, 1979;Youngson and Craw, 1999). Some researchers have suggested thatthe morphological evolution of gold particles is a function of thetransport media as well as the distance of transport (e.g DiLabio,1991; Giusti, 1987; Hallbauer and Utter, 1977; Herail et al., 1989;Townley et al., 2003). DiLabio (1991) proposed a simple classifica-tion for characterization of the shape and surface textures of goldparticles in till. He stated that the proportion of “pristine”, “modi-fied” and “reshaped” gold grains along the down-ice path showsthe relative proximity to the ore zone. In vicinity of the ore zone,there are higher proportions of pristine gold particles. DiLabio(1991) concluded that the abundance of reshaped gold grains in atill sample indicates the remoteness to the source area.

Most previous textural studies of glacial sediments have primarilyfocused on quartz grains (e.g. Alekseeva, 2005; Mahaney, 1991;Mahaney and Andres, 1991; Mahaney and Kalm, 2000; Mahaney et al.,2001; Mathur et al., 2008; Narayana et al., 2010; Sweet and Soreghan,2010). These studies reveal that quartz grains in till display characteris-tic microtextures (e.g. deep directional grooves, arc-shaped steps) thatare specific to glacial dispersal trains. Evidence of these quartz textureshas not been reported from other sedimentary environments. Mahaneyand Andres (1991) and Mahaney (1995) used fractures and abrasionfeatures imprinted on quartz grains to identify local ice transport, over-lying ice thickness, and depositional environments. Crescentic gougesare typically formed on the surface of quartz grains that are transportedby continental glaciers with a thickness of N800m. These textures havenever been observed on grains transported by cirque glaciers withthicknesses of less than ~200 m.

In this study, we examine themicro-scale surface textures andmor-phological features ofmagnetite grains from the ferromagnetic fractionsof bedrock and till at the Izok Lake volcanogenic massive sulfide deposit(Nunavut, Canada) to evaluate if they may be useful for mineral explo-ration. Specifically, the objectives are to determine if the surfacetextures and morphological features in till can be used to 1) identifythe nature of host bedrock, 2) determine the transport mechanisms,3) estimate the distance of transport from the source, and 4) identifysupergeneprocesses that affected grains after deposition in sedimentarybasins. Surface textures and morphology of magnetite grains frommassive sulfides andhost rocks are compared to that ofmagnetite grainsin up- and down-ice till collected from various distances from the IzokLake deposit to document the textures formed during erosion, transportand/or deposition. Magnetite is the focus of this study because: 1) it is acommon iron oxidemineral found in different geological environments,2) it is easily separated from sediments/disaggregated samples becauseit has the highest magnetic susceptibility among all naturally occurringminerals, 3) its physical properties (e.g. hardness, lack of cleavage) andmechanical behavior (conchoidal fractures) are similar to quartz(Mandolla and Brook, 2010), and therefore surface textures ofmagnetitecan be studied as indicators of transport media as well as depositionalenvironments, and 4) its chemical composition allows discriminationof different types of mineral deposits (e.g. Beaudoin et al., 2007, 2009;

Dare et al., 2011, 2012; Dupuis and Beaudoin, 2011; Nadoll et al., 2012,2014; Sappin et al., 2014).

1.1. Geological setting

The Izok Lake deposit is an Archean bimodal-felsic Zn–Pb–Cu–Agvolcanogenic massive sulfide deposit located at 65° 38′ 00″ N, 112° 47′45″ W in the northern part of the Slave Structural Province, NunavutTerritory, Canada (Fig. 1; Morrison, 2004; Hicken, 2012; Paulen et al.,2013). The deposit is situated under Izok Lake, which is 20 km west ofItchen Lake and 30 kmnorth of Point Lake. The Slave Structural Provinceis located on the northwest margin of the Canadian Precambrian Shield,and consists of Archean granite, granodiorite and granite gneiss, andlesser supercrustal sedimentary and volcanic rocks of the YellowknifeSupergroup. The Izok Lake area is mainly underlain by Archean rocks,which are overlain in the northwest by Paleoprotozoic rocks of theInterior Plains in the northwest (Bostock, 1980; Thomas, 1978).

The Izok Lake deposit is hosted in 2.70–2.67 Ga metasedimentaryand metavolcanic rocks of the Point Lake Formation, a subdivision ofthe Yellowknife Supergroup (Bleeker and Hall, 2007; Morrison, 2004;Padgham and Fyson, 1992; Paulen et al., 2013). In the Izok Lakearea, the Point Lake Formation comprises mostly felsic volcanicrocks with intermediate, mafic metavolcanic and intrusive rocks, andmetasedimentary rocks (Fig. 1). The Point Lake Formation has beenintruded extensively by syn-volcanic to post-volcanic granitic plutonsbetween 2.58 and 2.68 Ga (Bleeker et al., 1999). The hanging wall stra-tigraphy of the Izok Lake deposit includes felsic volcaniclastic rocks,dacite, andesitic and basaltic flows, thin sulfide-rich iron formations,and turbiditic sedimentary rocks (Fig. 1). Irregular granitic pegmatite,and diabase dikes subsequently cut all these lithologies (Hicken, 2012;Morrison, 2004). The Izok Lake deposit consists of 5 massive sulfidelenses (Northwest, North, Central West, Central East, and Inukshuk)with total resources of 14.8 Mt grading 12.8% Zn, 2.5% Cu, 1.3% Pb, and71 g/t Ag (Costello et al., 2012). The ore is composed of 25% pyrite,24% sphalerite, 9% chalcopyrite, 8% pyrrhotite, 3% galena, and 3%magnetite (Morrison, 2004).

Several diabase dikes of the Mackenzie Swarm crosscut the PointLake Formation. These 1.2 Ga diabase dikes trend north to northwestand crosscut the Central, East and Inukshuk massive sulfide lenses ofthe Izok Lake deposit (Buchan and Ernst, 2004). The Mackenzie dikesare composed of plagioclase, pyroxenes, and 1–15% fine-grained Fe–Tioxides (Baragar et al., 1996). Magnetite is dominant in Mackenziedikes, whereas ilmenite is subordinate or rare.

In the Izok Lake area, the felsic and intermediate volcanic rocks are ex-tensively intruded by gabbroic sills and dikes. These intrusive bodies areconsidered to have been volcanic feeders of the overlying flows. The gab-broic complex is typically medium to coarse grained, with equigranulartexture, and is massive to weakly foliated (Morrison, 2004). To the eastand north of Izok Lake, dacite and basalt are overlain by carbonate andsulfide facies iron formations (Hicken et al., 2013; Thomas, 1978).Carbonate iron formation is well-bedded and comprises carbonate layersinterbeddedwith equal-thickness cherty beds. Southward, the carbonatefacies iron formation changes laterally into sulfide facies, which locallycontains pods of zinc-rich massive sulfides composed of sphalerite,pyrite, chalcopyrite, and pyrrhotite (Hicken et al., 2013).

East of Izok Lake, a series of dacitic flows overlay rhyolite, markingthe end of felsic volcanism (Morrison, 2004; Fig. 1). The felsic flowsare fine to medium grained, and massive to well-foliated. The footwallto the Izok Lake deposit is comprised of felsic rocks. These rocks showthe same geochemical signatures as those forming the immediate hang-ing wall. Hydrothermal alteration zones, which are regionally distribut-ed in the area, occur in both hanging wall and foot wall rocks to thedeposit (Morrison, 2004). The felsic and intermediate volcanic bedrocksare strongly altered by widespread and pervasive development ofsericite. In immediate footwall and hanging wall rocks to the Izok lakedeposit, the sericitization zone consists of sericite, biotite and sillimanite

Fig. 1. Simplified bedrock geologymap of the Izok Lake deposit showing lithologies andmassive sulfide lenses (modified fromMorrison, 2004), and Locationmap of the Izok Lake area inCanada.

86 S. Makvandi et al. / Journal of Geochemical Exploration 150 (2015) 84–103

that encloses a zone of chloritization containing chlorite, biotite andcordierite (Morrison, 2004). The hydrothermal alteration zones arealso locally characterzed by intense silicification and sodium depletion.

In the northern and central parts of the Izok Lake area, volcanic andsedimentary rocks are metamorphosed to the upper amphibolite–sillimanite facies, whereas in the southern part, metamorphism reachedthe greenschist facies (Bostock, 1980; Morrison and Balint, 1993, 1999;Thomas, 1978). The upper amphibolite–sillimanite facies metamor-phism formed a gahnite-rich zone at the margins of the massive sulfideand the underlying stringer zone. The gahnite-rich dacite hosting thestringer zone consists of gahnite, sillimanite, magnetite, illmenite,pyrite, pyrrhotite, chalcopyrite, sphalerite, quartz, biotite, plagioclase,and hornblende (Bostock, 1980; Hicken, 2012; Morrison, 2004;Morrison and Balint, 1993; Thomas, 1978).

The Izok Lake area is a glaciated terrain affected by four phases of iceflow (Dredge et al., 1996; Kerr et al., 1995; Stea et al., 2009). Fig. 2 showsthe ice flow patterns in the Izok Lake region. Paulen et al. (2013) dem-onstrated that the oldest ice flow was directed towards the southwest(210° to 254°) followed by a flow directed towards the northwest(300° to 325°). The third ice flow from east to west-northwest (279°to 296°) was the dominant phase that shaped the present-day land-scape of the area. Evidence of the youngest glacial flow directiontowards the northwest (296° to 318°) is faint and rare, and are onlyfoundon outcrops east of Iznogoudh Lake (Paulen et al., 2013). Undulat-ing topography, glacially streamlined bedrock hills surrounded bysurficial sediments and abundant lakes are characteristic of the area.Till cover in the Izok area is generally thin, varying between b 0.5 m to3 m (Dredge et al., 1996; Hicken et al, 2013).

2. Methodology

2.1. Sampling methods

A total of 22 bedrock samples and 85 till samples were collected byGeological Survey of Canada (GSC) in the Izok Lake region in 2009 and

2010 (Hicken et al., 2013; McClenaghan et al., 2012). Heavy mineralconcentrates (HMC) of GSC bedrock and till were prepared by the Over-burden Drilling Management Limited (ODM; Ottawa, Canada) usingmethods described in McClenaghan et al. (2012). Massive sulfide andhost rock samples were disaggregated using Electric Pulse Disaggrega-tion (EPD). Electric Pulse Disaggregation liberates minerals from rockby applying a high-voltage electric current, which breaks the rockalong grain boundaries. The resulting mineral morphologies afterEDP reflect the original shape and grain size (Cabri et al., 2008;Rudashevsky et al., 2002). A heavy mineral preconcentrate was thenproduced for each disaggregated rock and for till samples using a shak-ing table (McClenaghan, 2011). The table preconcentrate was refinedusing methylene iodide diluted to a specific gravity of 3.2. The heavymineral concentrate was then further separated into ferromagneticand non-ferromagnetic fractions using a hand magnet. The ferromag-netic fraction contains mainly mineral grains and aggregates in whichmagnetite and/or pyrrhotite are principle components (Hicken et al.,2013). The b 0.25 mm ferromagnetic fraction was archived, whereasthe 2 to 0.25 mm ferromagnetic fractions of selected GSC till and bed-rock samples were shipped to Université Laval (ULaval) for furtherpreparation and examination of grains.

Each ferromagnetic fraction was homogenized by hand shaking thecontainer. Each sample was poured onto a sheet of paper and dividedinto four sections, and oneof the four sectionswas selected as a subsam-ple, according to themethod described byGerlach andNocerino (2003).The minimum number of grains for a representative subsample, basedon previous microtexture investigations, has been determined to be25 (Baker, 1976; Krinsley and Doornkamp, 1973; Madhavaraju et al.,2009;Mahaney, 2002; Townley et al., 2003). Townley et al. (2003) indi-cated that examination of at least 25 grains is required to document therange in shape of gold grains in stream sediments. Krinsley andDoornkamp (1973), Baker (1976), and Mahaney (2002), also statedthat study of at least 25 quartz grains was sufficient to record variationsin surface textures and morphology of quartz in a sample. The splittingprocedure was repeated until the subsample contained between 25 and

Fig. 2. Locations of bedrock and till samples in the Izok Lake area (modified from Hicken, 2012). In the map, the prefix 09-MPB has been removed from the sample names, as sample09-MPB-R64 is shown as R64.


50 ferromagnetic particles. A ferromagnetic particle is a mineral aggre-gate inwhichmagnetitemay be a component. In this study, 150magne-tite grains from 6 bedrock samples, and 225magnetite grains identifiedin ferromagnetic fractions of 9 till samples were examined for their sur-face textures using Scanning Electron Microscopy (SEM). The 6 rocksamples include 1) sample 09-MPB-R60 frommassive sulfides, 2) sam-ple 09-MPB-R64 from massive sulfides adjacent to gahnite-rich zone,3) sample 09-MPB-R61 from gahnite-rich dacite within the depositstringer zone, 4) samples 09-MPB-R42 and 5) 09-MPB-R90 from ironformations located 6 km up ice to the east of the deposit, and 6) sample09-MPB-R92 from the bedrock gabbro. The location of till samples, anddirections of iceflows as identified by Paulen et al. (2013) are illustratedin Fig. 2. Other subsamples were also prepared from the bedrock andtill samples to determine modal mineralogy, mineral association, grainsize distribution, and angularity of magnetite grains using MineralLiberation Analysis (MLA).

2.2. Analytical methods

2.2.1. Scanning electron microscopy (SEM)The SEM was used to examine and document the surface micro-

textures, morphological features, and shape of magnetite grains in theferromagnetic fraction. Subsamples were cleaned using acetone in anultrasonic bath for 5 min. Longer immersion in ultrasonic baths mayalter existing surface textures and even create new microtextures(Porter, 1962; Vos et al., 2014). Grains were mounted on 3 mm thickcarbon discs taped to 12.5 mm aluminum stubs. Grains were coatedwith gold and palladium. A JEOL JSM-840A SEM at ULaval equippedwith Back-Scattered Electron (BSE) and Secondary Electron (SE)modeswere used to examinemagnetite grains. The accelerating voltagewas 15 keV and the beam current was 60 μA, at a working distance of20 mm. Magnetite grains in each subsample were identified duringScanning Electron Microscopy using Energy Dispersive X-ray.

2.2.2. Mineral liberation analysis (MLA)The subsamples for theMLAweremounted in epoxy, and the surface

of the mounts was polished. The analyses were performed using theMLA 650 Field Emission Gun Environmental SEM at Queen's University,using an accelerating voltage of 25 kV and beam currents of 10–15 nA.The MLA software collects BSE images over the sample frame to auto-matically discriminate mineral grain boundaries and map distribution.Each particle is subdivided into grains, and grain boundaries are distin-guished based the greyscale variations in the BSE images. Each grain isfurther analyzed by X-ray, and the collected spectra are compared tothe library of reference spectra for mineral identification (Fandrichet al., 2007; Sylvester, 2012). For each sample, MLA produces differentdata sets including modal mineralogy, mineral association, particleproperties, grain properties (including angularity, area, perimeter,weight proportion, length, breadth, angle length, aspect ratio, andform factor), particle size distribution, and grain size distribution(Fandrich et al., 2007). Quantitativemineralogical data (e.g. modalmin-eralogy, and grain properties and size distribution) generated by theMLAmeasurement software for each sample are presented byDataViewsoftware and can be exported by the operator (Fandrich et al., 2007).Table 1A and B summarize the modal mineralogy and weight propor-tion of minerals in the ferromagnetic fractions of the Izok Lake bedrockand till samples, respectively.

3. Results

3.1. Surface textures of magnetite in bedrock samples

Table 2A summarizes the proportion of different microtexturesfound on the surface of magnetite grains in bedrock samples. The pro-portion of a surface texture in bedrock samples indicates the percentageof grains that are characterized by the given texture. The occurrence ofeach surface texture has been assessed independently to that of other

Table1

A)Th

eIzok

Lake

stud

iedbe

drocksamples

description;

B)Th

eIzok

Lake

stud

iedtillsamples

description.

Weigh

tpropo

rtions

ofmineralsin

ferrom

agne

ticfraction

sof

each

samplearepresen

ted.

A.

Samples

Samplingde

pth(m

)UTM

East

UTM

North

Mag

Hem

SpPy

Gn

PoCc

pGnh

Grt

Ti-m

Qz

Amp

Mic

Fds

Ap

Zrn

Mnz

Ax

Sil

MS(0

9-MPB

-60)

49.80

417,29

17,27

9,94

416

0.50

58.06

10.92

0.02

4.75

5.34

00.72

00.00

3.67

0.01

0.00

90

0.00

0.00

0.00

0.00

MS(0

9-MPB

-R64

)11

1.00

417,31

47,27

9,93

423

2.20

3218

.00

0.70

0.00

7.74

0.6

0.9

00.00

11.80

30.06

00.00

0.00

0.00

0.00

Dacite(0

9-MPB

-R61

)52

.00

417,29

17,27

9,94

429

.88

3.08

0.48

0.07

0.00

3.32

0.03

120.85

116

.37

0.17

3.48

29.10

0.00

0.05

0.02

0.00

0.10

IF(0

9-MPB

-R42

)14

0.00

417,29

17,27

9,94

42.2

3.00

0.00

60.00

40.00

0.00

0.00

012

.50.02

17.00

52.00

130.1

0.06

0.09

0.02

0.00

0.00

IF(0

9-MPB

-R90

)14

1.00

418,03

27,28

1,31

22.6

7.69

00.00

0.00

0.03

0.00

025

0.02

3.00

39.59

160.00

20.01

0.05

0.01

6.00

0.00

Gab

bro(0

9-MPB

-R92

)11

.00

418,68

47,27

9,62

65.2

2.50

00.01

0.00

0.73

0.02

00.03

70.60

60.00

17.4

60.00

0.00

0.00

0.04

0.46

B. Samples

UTM

East

UTM

North

Mag

Hem

PoGnh

Grt

Ti-m

Qz

Amp

Mic

Fds

Ap

Zrn

Spl

StPx

Crn

Till(0

9-MPB

-060

)41

8,78

47,28

0,20

230

6.50

0.00

04

212.50

8.80

74

0.20

0.00

00.00

160.00

Till(0

9-MPB

-016

)41

6,52

57,28

0,18

315

6.00

0.00

00.8

1110

.00

8.40

9.5

50.50

0.10

0.00

0.20

33.5

0.00

Till(0

9-MPB

-066

)41

6,20

47,27

9,26

022

20.00

0.02

01.02

142.50

8.00

10.5

3.5

0.40

0.02

0.01

0.03

162.00

Till(0

9-MPB

-052

)41

5,54

77,28

0,63

512

5.29

0.00

0.01

616

3.00

12.00

5.5

20.20

0.00

0.00

0.00

380.00

Till(0

9-MPB

-075

)41

4,41

37,28

1,10

319

11.00

0.00

01

154.70

16.00

121.2

0.10

0.00

00.00

200.00

Till(0

9-MPB

-077

)41

4,88

77,28

0,81

212

13.00

0.00

0.5

311

2.40

13.00

55

2.00

0.00

0.1

0.00

330.00

Till(0

9-MPB

-020

)41

1,77

37,28

1,59

416

.08

11.00

0.00

0.00

51.5

15.6

5.00

17.00

94.2

0.20

0.02

1.80

0.09

180.50

Till(0

9-MPB

-032

)41

3,15

47,28

5,37

722

.525

.12

0.00

0.00

50.8

135.00

4.50

82.5

1.50

0.02

0.03

0.01

170.02

Till(0

9-MPB

-002

)41

0,54

77,28

2,10

723

7.00

0.00

04

171.50

18.00

101.84

0.65

0.01

0.00

0.00

170.00

Abb

reviations

.MS:

massive

sulfide

s.IF:ironform

ations

.Mag

:Mag

netite.H

em:H

ematite.Sp

:Sph

alerite.Py

:Pyrite.Gn:

Galen

a.Po

:Pyrrhotite.Cc

p:Ch

alco

pyrite.G

hn:G

ahnite.G

rt:G

arne

tgroup

mineralssuch

aspy

rope

,alm

andine

,spe

ssartine

,and

andrad

ite.Ti-m

:Ti-be

aringmineralssu

chas

ilmen

ite,titano

mag

netite,and

titanite.Q

z:Qua

rtz.Amp:

Amph

ibolegrou

pmineralssuch

asactino

lite,ho

rnblen

de,and

grun

erite.Mic:M

icagrou

pmineralssu

chas

biotitean

dmusco

vite.Fds:F

eldspa

regrou

pmineralssu

chas

albite,ano

rthite,and

orthoclase.A

p:Apa

tite.Z

rn:Z

ircon.

Mnz

:Mon

azite.Ax:

Axinite.Sil:

Silliman

ite.Sp

l:Sp

inel.St:Stau

rolite.Px

:Pyrox

ene.Crn:

Corund

um.

Table 2Proportion ofmicrotextures found on the surface ofmagnetite in A) bedrocks, and B) till atthe Izok Lake area.

A

Type Microtextures Massivesulfide(%)

Dacite(%)

Ironformation(%)

Gabbro(%)

C Precipitation 20 43 30 15C Dissolution 50 14 17 15M Parting planes 10 36 17 0C Crystallographic defects 0 21 0 14M Conchoidal fractures 3 14 4 7

B

Type Microtextures % Type Microtextures %

M Adhering particles 72 M Conchoidal fractures 19C Dissolution 70 M Sub-parallel linear fractures 17M Abrasion 62 M Linear steps 16M-C Overprinted surfaces 50 M Arc-shaped steps 14M-C Medium relief 47 M Parting planes 8C Precipitation 42 M Straigth grooves 8M Fracture faces 35 M V-shaped percussion cracks 8M-C Low relief 30 M Troughs 7M-C High Relief 22 M Crescentic gouges 5M Uneven fractures 21 M Curved grooves 2

Microtextures are listed based on their frequency of observation on magnetite in till.M: Mechanical texture; C: Chemical texture; M-C: Mechanical–Chemical texture.


microtextures, as even if one texture is overprinted by another bothtextures have been counted.

A variety of grain morphologies and surface microtextures wereobserved onmagnetite from the Izok Lakemassive sulfides (Fig. 3). Grainsfrom massive sulfide samples are dominated by mineral aggregatesin which magnetite is associated with sulfide and silicate minerals(Fig. 3A). Magnetite from massive sulfides (MS-Mag) is subhedral toanhedral, medium to coarse grained (0.05–0.8 mm), and commonlyhosts sphalerite and chalcopyrite inclusions (Fig. 3B). Pyrite, sphalerite,and chalcopyrite are the abundant sulfide minerals in association withMS-Mag. Pyrite is typically cubic shaped, whereas MS-Mag is intergrownwith sphalerite and contains inclusions of muscovite and sphalerite.Muscovite, biotite, and amphibole (actinolite with lesser amounts ofhornblende) are either associatedwith sulfides andMS-Mag, or are inclu-sions in theseminerals. Mineral aggregates from the central parts ofmas-sive sulfide lenses (sample 09-MPB-R60) tend to be coarse-grained,whereas samples from margins of the massive sulfides (sample09-MPB-R64) are characterized by fine-grained magnetite with sulfideinclusions (Fig. 3A & B). Fig. 3C shows irregular grains of magnetite insphalerite. Sphalerite contains inclusions of chalcopyrite,whereasmagne-tite contains inclusions of both sphalerite and chalcopyrite. Despite thecentral parts of massive sulfides where magnetite is intergrown withactinolite (Fig. 3B), towards the margins, near the contact between mas-sive sulfides and gahnite-rich host rocks, banded actinolite andmagnetiteare common (Fig. 3D). Inmassive sulfides, parting planes are a character-istic texture in 10% of magnetite grains (Fig. 3E). Parting planes form as aresult of external stress inminerals, without formation of cleavage planes(Chang et al., 1998). External stress breaks minerals along their planes ofstructural weakness. Parallel micro-intergrowths of fine layers of magne-tite in sphalerite can cause octahedral parting planes (Fig. 3E). Dissolutiontextures are the most widespread surface texture characterizing 50% ofMS-Mag (Fig. 3F). Dissolution textures are commonly overprinted byprecipitation textures. Porous magnetite (Mag2) is a precipitationproduct observed on the surface of 20% of the grains (Fig. 3G). InFig. 3H, the surface of an actinolite aggregate is covered by a thin layerof porous Mag2. Mag2 precipitated on the surface of early-formed grainslocally forms layers of non-porous crystals as shown in Fig. 3I.

Based on previous petrographic studies (Hicken, 2012), gahnite-richdacite contains higher contents of magnetite relative to other bedrocklithologies in the Izok Lake area. Fig. 4A illustrates a mineral aggregate

Fig. 3. Typical morphology and microtextures of magnetite from Izok Lake massive sulfide lenses. A) A mineral aggregate including euhedral crystals of pyrite (Py), and magnetite (Mag)intergrownwith sphalerite (Sp). B)Mineral aggregate derived frommassive sulfides close to gahnite-rich zone showing intergrowths of small crystals of magnetite and sphalerite. Actin-olite (Act) filled the inter-minerals fractures. C) Magnetite replacing sphalerite and chalcopyrite (Ccp). Inclusions of these minerals are seen in magnetite. D) An aggregate of banded ac-tinolite andmagnetite. E) Parting planes in an octahedral crystal of magnetite. F) Dissolution texture on the surface of magnetite. G) Rims of porousmagnetite (Mag2) precipitated on thesurface of metamorphic magnetite (Mag). The arrow shows a shrinkage crack. H) Porous Mag2 precipitated on the surface of actinolite. I) Precipitation of layers of non-porous crystals ofMag2 on the surface of metamorphic magnetite grains.


composed of magnetite, pyrrhotite and pyrite with quartz, gahnite, sil-limanite and sphalerite. In gahnite-rich dacite, magnetite grains aregenerally larger (0.1–1.3 mm) than MS-Mag (0.05–0.8 mm). Precipita-tion textures characterize the surface of 43% of magnetite fromgahnite-rich dacite (GRD-Mag). A few GRD-Mag are partially coveredby porous Mag2 (Fig. 4B). Typically, porous Mag2 forms complex,circular-shaped precipitation textures (Fig. 4C). Octahedral partingplanes characterize 36% of GRD-Mag, whereas 21% of grains show trian-gular crystallographic defects (Fig. 4D). These crystallographic defectsare triangular voids formed as a result of lattice irregularities, extrinsicsubstitutions or interstitial impurities introduced during or after miner-al growth (Miller et al., 2009).

The ferromagnetic fractions of iron formation samples containanhedral, very fine-grained (N0.1mm)magnetite in aggregateswith bi-otite, hornblende, almandine, hematite, and pyrite. Magnetite from ironformations (IF-Mag) is commonly intergrownwith almandine (Fig. 4E),and less commonly with biotite (Fig. 4F). Rims of porous Mag2 arefound on the surface of 30% of IF-Mag (Fig. 5F). Hematite has a platy tex-ture in association with magnetite (Fig. 4G). Octahedral parting planesare observed on the surface of 17% of IF-Mag. Crystallographic defectsand dissolution textures are not foundon IF-Mag.Magnetite froma bed-rock gabbro sample is euhedral to subhedral, and very fine grained(≥0.1 mm; Fig. 4H & I). In this sample, hornblende and plagioclase aremajor constituents, whereas magnetite and ilmenite are accessories

Fig. 4. Typical surface textures of magnetite from gahnite-rich dacite (A to D), iron formations (E to G), and gabbro (H & I). A) Mineral aggregate including magnetite, pyrite, pyrrhotite(Po), sillimanite (Sil), gahnite (Ghn), and quartz (Qz). B) Overgrowth rims of non-porous Mag2 on the surface of metamorphic magnetite. C) Rims of porous Mag2 on the surface ofmetamorphic magnetite. D) Triangular crystallographic defects (shown by arrows). E) Intergrowths of magnetite and almandine garnet (Alm). Enlargement shows rims of porousMag2 precipitated on the surface of almandine. F) Intergrowths of magnetite and biotite (Bt). G) Hematite in association with magnetite in iron formations. H) A mineral aggregatefrom gabbro sample including euhedral to subhedral magnetite grains in association with ilmenite (Ilm), hornblende (Hbl) and plagioclase (Pl). I) An euhedral fine-grained magnetite.The surface of magnetite is characterized with precipitation texture (arrows 1 & 2).


(Fig. 4H). Ilmenite hosts hornblende microinclusions, and magnetite ispartly replaced by hornblende-plagioclase intergrowths. Fifteen percentof magnetites from gabbro (G-Mag) are characterized by precipitationand dissolution textures (Fig. 4I). Fourteen percent of the grains alsoshow crystallographic defects.

3.2. Surface textures of magnetite in till

Magnetite in till in the Izok Lake area forms individual grains(Fig. 5A) sporadically with layered textures (Fig. 5B). It locally con-tains small inclusions of apatite (Fig. 5C), muscovite, and/or rarelyzircon. Magnetite also occurs as fine-grained anhedral to medium-

grained euhedral grains disseminated in mica, amphibole or pyrox-ene aggregates (Fig. 5D & E). In some detrital particles, magnetite isintergrown with quartz (Fig. 5F), or associated with Ti-bearing min-erals such as ilmenite, titanomagnetite, titanite, and/or associatedwith almandine garnet (Table 1B). In contrast to bedrock samples,sulfides and gahnite are found in trace amounts in the ferromagneticheavy mineral fractions of till samples (Table 1B). A variety ofmechanical and chemical microtextures has imprinted the surfaceof magnetite in till samples (Figs. 5 to 8). The proportions of thesurface textures are presented in Table 2B. Since magnetite grainsfrom different till samples were characterized by the same typesand distribution of surface textures, the proportions in Table 2

Fig. 5. Typicalmorphology of till magnetite. A) Individual tillmagnetite grainwith semi-rounded edges and dissolution textures. B) Platymagnetite. C) Apatite (Ap) inclusion inmagnetitecharacterizedwith dissolution texture. D) Small magnetite grains disseminated in amphibole (Amp). E) Euhedral magnetite with fractured edges in association with quartz. F)Magnetiteand quartz intergrowths.


indicate what percentage of magnetite grains in all till samples ischaracterized by each surface texture.

3.2.1. Mechanical microtexturesAbrasion is defined asmechanical scraping of grain surfaces by friction

between grains during transport, producing rubbed or worn downsurfaces (Mahaney, 1995, 2002; Mahaney and Andres, 1996; Mahaneyand Kalm, 2000; Mahaney et al., 2001; Strand et al., 2003). It is the mostcommonmechanical texture characterizing the surface of 62% of magne-tite grains in till samples. Fig. 6A shows anoctahedralmagnetite grain thathas been abraded into a subrounded shape. More intense abrasion mayerase primary microtextures and smooth sharp angular edges. Grainsmay be abraded in various modes of transport, such as glacial or fluvialtransport (Van Hoesen and Orndorff, 2004; Vos et al., 2014).

Fracture faces are large, features with smooth fresh surfaces, mostlyfound on grains transported by alpine glaciers (Mahaney and Andres,1991, 1996;Mahaney andKalm, 2000;Mahaney et al., 2001). These tex-tures are fragile and can be overprinted by other microtextures such assub-parallel linear fractures, conchoidal fracture, arc-shaped steps, and/or deep grooves (Mahaney and Andres, 1991; Singh et al., 2011). Thirtyfive percent ofmagnetite grains in till show fracture faces (Fig. 6B). Con-choidal fractures defined by Campbell and Thompson (1991), Mahaney(1991, 1995), Mahaney et al. (1988a, 1988b, 1996, 2001), Mahaney andKalm (2000), Mazzullo and Ritter (1991), and Strand et al. (2003) alsocharacterize the surface of 19% of magnetite grains in till samples(Fig. 6B).

Steps are divided into arc-shaped and linear steps such as those thathave been described by Campbell and Thompson (1991), Helland andDiffendal (1993), Helland et al. (1997), Mahaney and Andres (1996),Mahaney et al. (2001), Mahaney and Kalm (2000), Mahaney (1995),

Strand et al. (2003), Van Hoesen and Orndorff (2004), and Vos et al.(2014). Arc-shaped steps are deep accurate tears, similar to conchoidalfractures, but steps are deeper and more widely spaced (N5 μm). Arc-shaped steps are seen on the surface of 14% of magnetite grains in till(Fig. 6C), whereas, 16% of grains show linear steps that are caused byimpacts (Mahaney and Andres, 1996; Mahaney and Kalm, 2000;Mahaney et al., 2001). Seventeen percent of detrital magnetites displaysub-parallel linear fractures (Fig. 6D). Twenty one percent of magnetitegrains also show uneven fractures, which are characterized by a roughsurface with random irregularities. Fig. 6E shows a magnetite grainwith an uneven surface that was subsequently partly abraded.

Curved and straight grooves are shallowly indented tears on thesurface of till grains produced with grain-to-grain collisions duringtransport (Fig. 6F; Krinsley and Donahue, 1968; Campbell andThompson, 1991; Helland and Diffendal, 1993; Helland et al., 1997;Mahaney et al., 1988a, 1988b; Mahaney and Andres, 1996; Mahaneyet al., 2001, 2004; Mahaney, 1990b, 1995; Vos et al., 2014). These tex-tures are restricted to coarse grains (≥0.4 mm) with surfaces largeenough to be scratched by other grains during transport (Margolis andKrinsley, 1974). The low percentage of groove features in magnetitegrains in till at the Izok Lake area (Table 2B) is consistentwithmagnetitegrain size distribution in both bedrock and till samples (discussed laterin this text). Throughs (Fig. 6F) and crescentic gouges (Fig. 6G) charac-terize small proportions of detrital magnetite in Izok Lake till samples(Table 2B). Throughs are deeper andwider than grooves, and crescenticgouges are different from conchoidal fractures by their depth and cres-cent shapes (Campbell and Thompson, 1991;Mahaney, 1995;Mahaneyand Andres, 1996; Mahaney et al., 1988a,1988b, 2004; Watts, 1985).

Parting planes on the surface of magnetite in bedrock samplesare also observed on the surface of detrital grains (Table 2B; Fig. 6H).

Fig. 6.A selection ofmechanical textures on the surface of Izok Lake tillmagnetite. A) An octahedral magnetite with abraded edges. B)Magnetite with fracture faces (arrow 1), conchoidalfractures (arrows 2 & 3), and adhering particles in different sizes (arrows 4, 5 & 6). C) Arc-shaped steps on the surface of magnetite. D) Sub-parallel linear fractures shown by the arrow.E)Magnetite with a low relief, uneven surface subsequently affected by abrasion during transport. F)Magnetite with an accurate groove (arrow 1), a short and deep (arrow 2) and a longand shallow (arrow 3) troughs. G) Magnetite grain with overprinted surfaces including crescentic gouges (arrow 1), fracture faces (arrow 2), a shallow trough (arrow 3), and aabraded surface overprinted by adhering particles and sub-parallel linear fractures (arrow 4). H) Magnetite parting planes shown by arrow 1. The grain also has dissolution textures(arrow 2). I) V- shaped percussion cracks are shown by an arrow.


V-shaped percussion cracks are triangular-shaped fractures withvariable size and depth, formed by mechanical impacts between grainscollision (Krinsley and Donahue, 1968; Krinsley and Doornkamp, 1973;Krinsley and Marshall, 1987; Campbell and Thompson, 1991; Hellandand Diffendal, 1993; Helland et al., 1997; Mahaney, 1991; Mahaneyand Andres, 1996; Mahaney et al., 2001; Mahaney and Kalm, 2000;Mahaney et al., 2010;). A small proportion of magnetite grains inIzok Lake till samples are imprinted by V-shaped percussion cracks(Table 2B; Fig. 6I).

3.2.2. Chemical mixrotexturesDissolution features imprint the surface of 70% of detrital magnetite

grains (Fig. 7). Dissolution features form either linear shallow (Fig. 7A)

or irregular (Fig. 7B) channels on the surface of magnetite. Fig. 8Cshows small cavities on the surface of till magnetite produced by disso-lution of magnetite (arrow 1) or by dissolution of mineral inclusions(arrow 2). Numerous, small pits on the surface of fine-grained magne-tite in an amphibole aggregate (Fig. 7D), dissolved ilmenite lamellae(Fig. 7E), and also dissolved muscovite flakes leave tabular cavities(Fig. 7F) are other textures produced by dissolution on the surface ofmagnetite in Izok Lake till samples.

Precipitation textures characterize 42% of magnetite grains in till(Fig. 8). In Fig. 8A to C, dissolution features are partly covered by precip-itation of supergene magnetite (Mag2). Fig. 8D shows rims of Mag2crystals on the broken surface of magnetite grains in till. The surface ofsome grains is almost entirely covered by Mag2 masking the earlier

Fig. 7. Different forms of dissolution characterizing the surface of till magnetite grains: linear shallow channels (A), irregular channels (B), and small cavities (C). D) Dissolved surface offine- grained magnetite aggregate in amphibole. E) Dissolution ilmenite lamellae exsolved from magnetite. F) Tabular cavities remained after dissolution of flakes of muscovite (Ms)inclusions in magnetite.


mechanical microtextures (Fig. 8E). In rare occurrence, dissolution pitsare completely filled by precipitation of Mag2 (Fig. 8F).

3.2.3. Mechanical and chemical microtexturesSome microtextures form as a result of combination of mechanical

and chemical processes (Vos et al., 2014). Relief refers to a mechanicaland chemical texture that reflects the variation in elevation of an areaon the grain surface. Relief describes the roughness or smoothness of agrain surface, and can be classified into three different categories: low,medium, and high (Campbell and Thompson, 1991; Helland et al.,1997; VanHoesen and Orndorff, 2004; Vos et al., 2014). The large differ-ence between high and low points on the surface of a grain gives highrelief (Fig. 6B). Grains with low relief have smooth surfaces withouttopographic irregularity (Fig. 6E). The irregularities can be causedby grain-to-grain collision during transport, or chemical weathering(Vos et al., 2014). In the Izok Lake area, almost half of the magnetitegrains in till have medium relief (Table 2).

Adhering particles are those that are attached to the surface ofgrains; 72% of magnetite grains in till samples display this microtexture.Adhering particles have variable grain sizes and composition (Fig. 6B;Higgs, 1969; Vos et al., 2014). Vos et al. (2014) categorized adheringparticles as mechanical and chemical microtextures. These particlesare commonly remnants of source rocks or diagenetic environments(Mahaney, 2002). However, a low proportion of adhering particles areproduced during glacial grinding, and/or transport in eolian environ-ments (Krinsley and Doornkamp, 1973; Mahaney, 2002; Mahaneyand Kalm, 2000; Smalley, 1966). Adhering particles can be useful inprovenance studies (Mahaney, 2002; Vos et al., 2014).

Overprinted surfaces feature chemical and/or mechanical mi-crotextures overprinted by younger microtextures. Fifty percent of

magnetite grains in Izok Lake till samples show overprinted surfaces(Table 2B). Although overprinted surfaces mask or destroy othersurface textures, their frequency indicates the proportion of grainsthat have been affected by chemical and mechanical processes. Fig. 7Fillustrates overprinted surfaces where primary dissolution textures onthe surface of magnetite have been later partly erased by abrasion.Overprinted surfaces in Fig. 8F have also formed by filling the dissolu-tion pit by precipitation.

3.3. Magnetite grain shape

3.3.1. Grain shape in bedrock samplesEuhedral, subhedral, and anhedral are common terms used to de-

scribe the shape of minerals. Euhedral grains are well-formed, andbounded with their easily recognized crystal faces (Best, 2002). In con-trary, anhedral grains have irregular shapes with undeveloped crystalfaces. Grains with partially developed crystal faces are classified assubhedral. Fig. 9 displays proportions of euhedral, subhedral andanhedral crystals of magnetite in different Izok Lake bedrock samples.In the sample from gabbro, G-Mag occurs as euhedral to anhedralgrains. In this sample, 59% of magnetite grains are anhedral, and therest are either subhedral (29%) or euhedral (12%). Iron formation sam-ples contain only anhedral grains of magnetite (Fig. 9). In samples frommassive sulfides and gahnite-rich dacite, a high proportion ofmagnetitegrains are anhedral (65% and 71% respectively), and the rest aresubhedral.

3.3.2. Grain shape in till samplesIn sediments, shape is commonly described by roundness or angu-

larity that indicate the morphology of grain corners (Wadell, 1932;

Fig. 8. A to C) Precipitation texture overprinting dissolution texture (shown by arrows). Arrow 2 in 9A shows triangular crystallographic defects on the surface of till magnetite.D)Overgrowth rims ofMag2 precipitated on broken surfaces of tillmagnetite. E)Widespreadprecipitation ofMag2maskedmechanicalmicrotextures. F) A dissolutionpitfilled completelyby precipitation of Mag2.


Janoo, 1998). Grain roundness is a function of the history of transportand abrasion (Folk, 1978; Kasper-Zubillaga, 2009; Kasper-Zubillagaet al., 2005; Pettijohn et al., 1973; Sagga, 1993). Russell and Taylor(1937), Pettijohn (1957), and Powers (1953) developed a classificationto assess the roundness of grains. Fig. 10 illustrates established exam-ples of magnetite grains from the Izok Lake till samples for 5 of the 6classes of the roundness qualitative scale developed by Powers(1953). Very rounded grains were not identified. Very angular grainshave sharp and jagged corners, whereas angular grains have fewerangles and sharp corners, though there are no signs of abrasion on

Fig. 9. Histograms show the proportions of euhedral, subhedral, and anhe

these grains (Fig. 10). The subangular and subrounded classes showgrains with sharp and rounded edges. In subangular grains sharp cor-ners are dominant. Rounded edges are more common in subroundedgrains. Rounded grains have very few sharp edges and corners (Fig. 10).

Fig. 11 shows histograms illustrating the distribution of grain round-ness of magnetite from different till samples as a function of distancefrom the Izok Lake deposit. Only 14% of the up-ice sample (09-MPB-060) ismadeupof angular grains, and86% are subangular or subrounded.Down ice from the Izok Lake deposit, the highest proportions of till grainsare subangular, while the rest of grains are almost equally distributed

dral crystals of magnetite from different Izok Lake bedrock samples.

Fig. 10. Izok Lake till magnetite grains classified into 5 roundness classes of Powers' angularity chart.


between the angular and subrounded classes. The highest proportions ofsub-angular grains (56%) are documented in till samples 09-MPB-066and 09-MPB-002. In addition, the distribution of roundness of magnetitegrains from sample 09-MPB-016 is almost identical to that of sample 002(Fig. 11). These three samples are located down ice from outcroppingmineralization of the Izok Lake deposit and West Iznogoudh (WIZ)showing, respectively (Fig. 2).

3.3.3. Quantitative measurement of angularity of magnetite grainsThe quantitative angularity of magnetite grains in both bedrock and

till samples was measured using MLA on grain cross sections. Based onG. Figueroa (personal communication, July 17, 2012) angularity (A) inMLA is defined as:

A ¼ Σ Radius½ �− Radius Equivalent Ellipse½ �ð Þ= Radius Equivalent Ellipse½ �ð1Þ

with Radius being the distance to the particle boundary, and RadiusEquivalent Ellipse being the minor radius of a hypothetical equivalentellipse enclosed in the particle as it is exemplified in Fig. 12. Box-and-whisker plots in Fig. 13 display values of MLA angularity for magnetitegrains in bedrock and till samples. Among bedrock samples, IF-Magand GRD-Mag respectively have the widest and the narrowest rangeof angularity. GRD-Mag also contains the highest proportion of grainswith high values of angularity as its median angularity value is 144.The median angularity value of MS-Mag is similar to that of IF-Mag,thought, IF-Mag covers wider range of angularity values. G-Magcontains the smallest median angularity value among the Izok Lakebedrock samples.

In till samples, magnetite grains display a wide range of angularitywith small differences. The range of angularity of magnetite in till

Fig. 11. Distribution of magnetite grains from Izok Lak

samples is almost identical to that of IF-Mag, though, it covers theranges of angularity of G-Mag and MS-Mag. The median angularityvalues for G-Mag,MS-Mag, and IF-Mag are 41.5, 54 and 54.5 respectively.The median value ranges from 40 to 51 for magnetite in till samples.

3.4. Magnetite grain size distribution in bedrock and till samples

Magnetite grain size was measured using the MLA on grain crosssections exposed in epoxy grain mounts. Values for the maximumlength of magnetite grains and grain size distribution are computedfor classes based on physical sieve sizes (Sylvester, 2012). The grainsize distribution of a sample is characterized by D10, D50, and D97values where D10 and D97 determine the lower and upper limitsrespectively, for 10% and 97% of the cumulative grain size distribution.The D50 value is the median value of the particle size distribution.

3.4.1. Grain size distribution in bedrock samplesFig. 14A displays the grains size distribution of magnetite from

different bedrock samples. The grain size distribution of MS-Mag is sim-ilar to GRD-Mag,whereas IF-Mag andG-Maghave similar sigmoidal sizedistribution. The largest magnetite grains belong to GRD-Mag, with 50%of grains (D50) larger than 600 μm, whereas IF-Mag has the smallestgrain size distribution as the value of D97 is 150 μm (Fig. 14A). Thegrain size ranges determined by petrographic examination supportgrain size distributions by the MLA calculations. As previously men-tioned, the grain size of MS-Mag varies between 0.1 mm to 1.2 mm,whereas the grain size of If-Mag is ≥ 0.1 mm.

3.4.2. Grain size distribution in till samplesFig. 14B shows the cumulative grain size distribution ofmagnetite in

till samples. D50 for detrital magnetite from all till samples range from

e till samples among different roundness classes.

Fig. 12. Equivalent Ellipse enclosed in a particle to calculate the angularity by the MLA.


125 to 500 μm. The D10 values range from 27 to 180 μm, whereas theD97 values range from 355 to 710 μm. The smallest grain size distribu-tion is displayed in sample 09-MPB-075, located 2.5 km down icefrom the Izok Lake deposit (Fig. 2), in which D97 is 300 μm and D10 is27 μm. However, in sample 09-MPB-066, located about 500 m downice from the deposit, the average size of grains are 500 μm or larger.The grain size distribution of the other till samples in both up-ice anddown-ice to the deposit is almost identical (Fig. 14B).

4. Discussion

4.1. Magnetite in bedrock samples

In bedrock samples, the morphology and surface textures of a mag-netite grain is determined by the conditions under which it initiallyformed. At the Izok Lake deposit, the irregular grain boundaries be-tween sphalerite and MS-Mag formed by replacing hypogene sulfideminerals (Fig. 3C). Sulfide replacement by magnetite has been docu-mented in other VMS deposits including the Ansil deposit in theNoranda district (Abitibi, Quebec; Galley et al., 1995; Boucher et al.,2010; Doyle and Allen, 2003). Actinolite commonly replaces silicatesduring upper greenschist facies metamorphic conditions (Winter,2001). Magnetite intergrown with actinolite in Izok Lake massivesulfides (Fig. 3B, D, & H) suggests formation of MS-Mag duringmetamorphism.

In gahnite-rich dacite, GRD-Mag is associatedwith gahnite, a zincianspinel (Money and Heslop, 1976), which is an accessory mineral inmetamorphosed massive sulfide deposits (Averill, 2001; Heimann

Fig. 13. Box-and-whisker plots showing values of angularity of magnetit

et al., 2005; Morris et al., 1997; Spry, 1982, 1987a, 1987b; Spry andScott, 1986; Spry and Teale, 2009). Gahnite can formduring amphibolitefacies metamorphism as a result of one of 3 different reaction paths:1) sphalerite desulfidation, 2) decomposition of zincian biotite orZn-bearing silicates such as staurolite, and 3) reactions of zinc oxidephases (Heimann et al., 2005). Gahnite is stable over a wide range ofoxygen- and sulfur fugacities. At higher ƒO2, gahnite coexists with mag-netite, whereas it is associated with Fe-rich silicates and pyrrhotite atlower ƒO2 (Sandhaus and Craig, 1986). At the Izok Lake deposit, pyrrho-tite inclusions in chalcopyrite, and chalcopyrite replacement bymagne-tite indicate that GRD-Mag and pyrrhotite did not form simultaneously.The coexistence of magnetite and gahnite at the Izok Lake deposit isconsistent with the liberation of Fe from sphalerite and chalcopyriteand formation of GRD-Mag during metamorphism.

In samples of iron formation, fine-grained IF-Mag is mostly inter-grown with biotite, amphibole, and almandine (Fig. 4E & F). Duringregional metamorphism, an increase in oxygen fugacity of the fluidphase causes the breakdown of Fe-bearing minerals such as biotite, andsubsequent development of iron formations (Nesbitt, 1986). Brearelyand Champness (1986) studied three metamorphic almandine garnetswith numerous magnetite inclusions. They concluded that magnetitecan exsolve from almandine garnet during cooling. The content of Fe3+

of hostmineral and fugacity of oxygen are parameters controlling exsolu-tion of magnetite from almandine (Brearely and Champness, 1986).

In gabbro, textural relationships between G-Mag and ilmenite, andtheir associationwith rock formingminerals suggest their simultaneousformation during crystallization of gabbroic magma (Fig. 4H). Micro-inclusions of hornblende in ilmenite indicate that the Fe–Ti oxidesformed during the late stages of magmatic crystallization (Tarassovaet al., 2013). Plagioclase-hornblende intergrowths replacing G-Mag canbe evidence of alteration of magmatic magnetite during metamorphism(Taipale, 2013). As a result, the local gabbro includes twodifferent gener-ations of hornblende: primarymagmatic hornblende hosted by ilmenite,and metamorphic hornblende intergrown with plagioclase (Fig. 4H).

Mag2 is commonly porous and precipitated as small irregular rimson the surface of metamorphic magnetites (MS-Mag, GRD-Mag, andIF-Mag), actinolite, and/or other components of the mineral aggregates(Figs. 3H & 4C). This textural evidence shows that the precipitation ofMag2 post-dated crystallization of metamorphic magnetites. Erosionof the Izok Lake deposit during successive phases of ice flow exposeddeeper parts of the bedrock to chemical weathering. Infiltration ofgroundwater into bedrock and/or unconsolidated sediments couldresult in successive dissolution-precipitation processes to form Mag2.Dissolution creates microporosity in the labile mineral grain andincreases its permeability, resulting in increased infiltration of fluids

e grains obtained from Eq. (1) in Izok Lake bedrock and till samples.

Fig. 14. Cumulative weight percent passing graphs showing grain size distribution of magnetite in A) bedrock samples and B) till samples.


into the mineral grain. Supersaturation of fluids from dissolved min-erals/materials results in precipitation of new mineral, which mayformporous circular overgrowth deposits. The porous texture facilitatesthe infiltration of fluids. Development of porosity in unstableminerals isa function of: 1) differences in molar volume between parent andproduct minerals, and 2) the relative solubility of the host mineral inaqueous fluids (Putnis, 2009; Putnis and John, 2010). The transforma-tion of minerals, such as hematite (a hexagonal structure) to magnetite(a spinel structure), is accompanied by volume loss, which can increaseporosity (e.g. Baguley et al., 1983; Deo et al., 1989; Matthews, 1976).Irregular cracks commonly found near porous textures are “shrink-age cracks”, likely the result of volume loss in mineral replacementreactions (Fig. 3G; Larson, 1983; Deo et al., 1989; Boucher et al.,2010).

4.2. Detrital magnetite

4.2.1. Mineral associationsAbundance of rock formingminerals (e.g. quartz, feldspar,mica, am-

phibole, pyroxene; Table 1B), and Ti-bearingminerals (most commonly

ilmenite), in association with magnetite in ferromagnetic fractions ofthe Izok Lake till samples indicate that a high proportion of detrital par-ticleswere derived from lithologies other thanmassive sulfides. In addi-tion to bedrock gabbro, Mackenzie dikes crosscutting the Point LakeFormation in the Izok Lake area (Hicken et al., 2013; Morrison, 2004)are composed of plagioclase, pyroxene, and Fe–Ti oxides includingmag-netite and ilmenite (Baragar et al., 1996). Buddington and Lindsley(1964), and Baragar et al. (1996) suggested that formation of individualmagnetite and ilmenite grains is the result of oxidation–exsolution ofspinel at intermediate temperatures, whereas they commonly form acomplete solid solution at high temperatures. In Mackenzie dikes,magnetite is characterized by pitted and mottled surfaces indicatingincipient alteration (Baragar et al., 1996). The presence of hematiteand almandine garnet in association with magnetite in detrital mineralaggregates (Table 1B) may discriminate the proportion of particles thathave been eroded and transported from iron formations. However,under post-magmatic conditions and in supergene environmentswhere lower temperatures and higher oxygen or H2O fugacity are prev-alent, hematite can replace magnetite and/or ilmenite (e.g. Cornwall,1951; Hu et al., 2014; René, 2008; Tarassova et al., 2013). Thus, post-


magmatic alteration and/or supergene processes may in part explainthe abundance of hematite in till samples.

4.2.2. Mechanical texturesResults show that magnetite from Izok Lake till samples have been

imprinted by a variety of mechanical microtextures (Table 2B).Mechanical textures are mainly diagnostic of the transport media.Mineral grains transported by glaciers are characterized by conchoidalfractures, subparallel linear fractures, grooves, troughs, steps, and cres-centic gouges (Krinsley and Doornkamp, 1973; Mahaney, 1995, 2002;Mahaney and Andres, 1996; Mahaney and Kalm, 2000; Mahaney et al.,2001; Van Hoesen and Orndorff, 2004). Among these features, crescen-tic gouges, deep grooves and arc-shaped steps are considered to be typ-ical for continental glaciers that are N 800m in thickness. These textureshave never been observed on grains transported by glaciers b 200 mthick (Mahaney, 1990a, 1991). The presence of these textures on tillmagnetite grains demonstrates that they have been transported by athick continental glacier, most likely themost recent glacier (LaurentideIce Sheet) during the Wisconsinan. The grains may also have beenglacially transported during earlier glaciation of the Izok Lake regionand then re-entrained by the younger Wisconsin ice flow.

Detrital grains transported by glaciers, especially at the base of thickice sheets, commonly show high relief because of severe fracturingduring glacial crushing (Mahaney, 2002). However, in Izok Lake tillsamples, magnetite grains with low and medium relief are dominant(Table 2B). During long-distance transport, reworking, and/or transportin mixed environments (e.g. glaciofluvial environments), abrasion isdominant compared to fracturing, thereby reducing the grains reliefby obliteration of angular edges (Mahaney, 2002). Chemical processessuch as dissolution of angular edges or filling the dissolution pits withprecipitation (Fig. 8F) can also reduce the grains relief.

Previous transportation by glacial meltwater must also be consid-ered for some of the magnetite grains recovered from till. Grains modi-fied by fluvial transport are characterized by grain surfaces that areabraded, have rounded edges, and display V-shaped percussion cracks(Krinsley and Doornkamp, 1973;Mahaney, 2002). V-shaped percussioncracks, present on a small proportion of magnetite in till samples

Fig. 15. The diagram shows comparison between frequency of occurrences of microte

(Table 2B), suggest that this proportion of the grains in different tillsamples (09-MPB-060, 09-MPB-016, 09-MPB-020, 09-MPB-002, 09-MPB-032) were previously affected by fluvial or glaciofluvial processes.High proportions of till grainswith overprinted surfaces in the Izok Lakearea suggest that these grains have likely experienced different cycles oferosion, transport, and deposition. The four different episodes of iceflow documented in the Izok Lake are likely the causes for reworkingof grains through time.

4.2.3. Chemical texturesDissolution, and precipitation textures (Mag2) characterize a high

proportion of magnetite in till samples (Table 2B). Dissolution and pre-cipitation microtextures can pre-date or postdate a glacial episode(Mahaney, 2002). Overgrowth rims ofMag2 on the surface ofmagnetitein till must be a post-depositional product because: 1) this delicatemicrotexture is not expected to survive during mechanical transport,and 2)Mag2 commonly overlies mechanical microtextures that formedduring fluvial and glacial transport (Fig. 8). During glacial transport, ifsome grains sojourn in the ice, they remain unscathed (Mahaney,2002). Thus, formation of Mag2 on the surface of magnetite in till caneven pre-date the last glacier affecting the area. Mag2 is most likely asupergene magnetite that formed during chemical weathering ofhypogene minerals in bedrock and till samples.

4.3. Comparison between Izok Lake detrital magnetite and previous studies

A comparison between the results of the study of surface textures ofmagnetite in the Izok Lake till samples with that from other shows thepotential of magnetite microtextures as environmental discriminators,and emphasize the significance of the textural and morphological stud-ies inmineral exploration usingmagnetite. Fig. 15 compares the surfacetextures of magnetite in Izok Lake till samples and detrital magnetite ofthe Wahianoa moraines (Ruapehu Mountains, New Zealand; Mandollaand Brook, 2010) with detrital quartz in Weichselian till in Estoniaand Latvia (Mahaney and Kalm, 2000). Among varieties of indicatorminerals, the morphology and shape of placer gold particles have beenwell studied so far (e.g. DiLabio, 1991; Grant et al., 1991; Hallbauer

xtures in Izok Lake till magnetite, Wahianoa magnetite, and Weichselian quartz.


and Utter, 1977; Townley et al., 2003). However, comparing the resultsof magnetite with gold is not useful to understand transport conditionsof magnetite, because these minerals differ noticeably in their physicalproperties. These differences can result in formation of different surfacetextures and morphology in response to mechanical and chemicalprocesses affecting grains during erosion, transport, and deposition.Thus, magnetite from Izok Lake was compared to detrital magnetite ofthe Wahianoa moraines derived from magmatic rocks (Mandolla andBrook, 2010), which is only other study documenting the surfacetextures of magnetite in glaciated terrains.

Unlike magnetite in Izok Lake till samples, Wahianoa magnetite isnot imprinted by various types of mechanical fractures. Microtexturessuch as uneven fractures, curved grooves, straight grooves, troughs,arc-shaped steps, parting planes, crescentic gouges, and V-shaped per-cussion cracks were not reported for Wahianoa magnetite (Fig. 15).The most common mechanical microtexture documented amongWahianoamagnetite grains is linear steps,which is observed on the sur-face of 33%of the grains Conchoidal fractures, fracture faces, sub-parallellinear fractures, and abrasion are other less common mechanicaltextures among Wahianoa magnetite grains. The low diversity andfrequency of mechanical microtextures along with lack of overprintedsurfaces suggest that Wahianoa magnetite has not experiencedreworking. These patterns for the Wahianoa magnetite are consistentwith the moraine's formation by small cirque glaciers (Mandolla andBrook, 2010). Adhering particles is the most common mechanical–chemical microtexture documented for Wahianoa magnetite, thoughits frequency is almost half of that for Izok Lakemagnetite from till sam-ples (Fig. 15). This difference may indicate that Wahianoa magnetiteshave not been affected by severe glacial grinding during transport(Krinsley and Doornkamp, 1973; Mahaney, 2002; Mahaney and Kalm,2000; Smalley, 1966). The absence of dissolution and precipitationfurther documents that Wahianoa magnetite was not affected by postdeposition chemical processes. As a result, Wahianoa magnetite hashad a less complex history than magnetite in till in the Izok Lake area.

The result of magnetite in Izok Lake till samples was also comparedto that of quartz because quartz has been extensively studied, and is astandard for comparison of grain shape and surface texture of otherminerals (Basu, 1985; Basu et al., 1975; Beal and Shepard, 1956;Griffiths, 1967; Kasper-Zubillaga, 2009; Kasper-Zubillaga et al., 2005;Mahaney, 2002;Mandolla and Brook, 2010; Pettijohn et al., 1973; Shep-ard, 1973; Shepard and Young, 1961). In addition,magnetite and quartzhave similar physical properties (e.g. hardness, conchoidal fracture),and both are ubiquitous minerals found in a variety of igneous, meta-morphic and sedimentary rocks. Comparison of magnetite in Izok Laketill samples with Weichselian quartz described by Mahaney and Kalm(2000) shows that the majority of the textures on the surface of quartzgrains are the same as those on magnetite in Izok Lake till samples(Fig. 15). The diversity of microtextures and their frequency in boththe Izok Lake magnetite and the Weichselian quartz support complextransport histories. Magnetite in Izok Lake till samples andWeichselianquartz, both have experienced transportation in basal layers of conti-nental ice sheets producing significant mechanical forces during grain-to-grain collision. The V-shaped percussion cracks, common to bothWeichselian quartz and Izok Lake magnetite indicate transport inglaciofluvial environments. This hypothesis is also supported by a highproportion of abrasion textures for both minerals. The dominance ofmechanical relative to chemical textures inWeichselian quartz suggeststhat the surface of this mineral was mainly damaged during transport,and less affected by chemical processes causing dissolution and/orprecipitation of SiO2.

4.4. Shape of magnetite grains in Izok Lake bedrock samples

The equilibrium form of a mineral is typically controlled by its crys-tallographic structure (Higgins, 2006). In equilibrium conditions,minerals tend to form euhedral, coarse crystals to minimize the total

energy. This process consequently increases the mineral stability(Best, 2002; Cornell and Schwertmann, 2006; Higgins, 2006).Magnetitemost commonly forms octahedral or rhombo-dodecahedra crystals, inbetween, rhombo-dodecahedra forms are produced in lower energysurfaces (Cornell and Schwertmann, 2006; Heider et al., 1987).Intergrown octahedra (twins), cubes, spheres, and bullets are less com-mon crystal habits formed by magnetite. In all Izok Lake bedrock sam-ples, the highest proportion of magnetite grains are characterized byanhedral crystals (Fig. 9). With the exception of G-Mag, abundance ofanhedral magnetite grains in Izok Lake bedrock samples is consistentwith formation of magnetite by replacing previous sulfide and/orsilicate minerals during metamorphism. Under metamorphic condi-tions, new minerals grow in the solid state and to form their crystalhabits where they compete with previous, unstable minerals for space(Best, 2002). Thus, the shape of minerals in metamorphic rocks iscontrolled to some extent by interfacial free energy between growingand neighbouring crystals (Buerger, 1947; DeVore, 1956, 1957; Kretz,1966). Despite tendency of metamorphic systems towards equilibriumstates, metastable minerals are common in metamorphic rocks becauseof 1) slow kinetic rates, and 2)modifications in parameters such as tem-perature, pressure and fluid activities over time that drive the systemout of equilibrium (Best, 2002). In Izok Lake bedrock gabbro, magmaticmagnetite is characterized by a range of euhedral to anhedral crystals(Fig. 9). Unlike crystallization under metamorphic conditions, duringfractional or equilibrium crystallization of a magma, mineral phases cannucleate in themelt, grow, and frequently form their characteristic crystalhabits without restriction from neighbouring minerals (Best, 2002).

The distribution of quantitative angularity of magnetite grains inIzok Lake bedrock samples (Fig. 13) is consistentwith the shape ofmag-netite and its qualitative angularity in these samples (Figs. 3 & 4).Euhedral crystals of magnetite form angular grains because of theirdeveloped crystal faces and consequently sharp corners (Fig. 4I), where-as subhedral crystals form both angular and sub-angular grains asshown in Fig. 3I & A respectively. Anhedral crystals of magnetite canform very angular (Fig. 3B), angular (3C & 4C), sub-angular (Fig. 4E &F), sub-rounded (3D, 3H & 4G), and rounded (3H) grains. As a result,although all magnetite grains from the iron formation samples areconsidered as anhedral, their distribution among different classes ofroundness of Powers (1953) explains their distribution over a widerange of quantitative angularity (Fig. 13).

4.5. Shape of magnetite grains in Izok Lake till samples

Results from Izok Lake till samples show that angularity ofmagnetitein sediments, similar to quartz grains (Costa et al., 2013; Goudie andWatson, 1981; Kleesment, 2009), is initially determined by the originalgrain shape in host rocks, and then is noticeably controlled by themodeof transport and distance. The majority of magnetite grains in Izok Laketill samples are angular and subangular (Fig. 11). Proportions of sub-angular grains in Izok Lake till samples may indicate the proximity tothe mineralization since there is an increase in proportion of sub-angular magnetite grains down ice towards the Izok Lake deposit, andimmediately after the WIZ showing (Fig. 11). MS-Mag and GRD-Magform subhedral to anhedral crystals (Fig. 9) with limited range of highangularity values (Fig. 13). In contrary to sub-angular grains, propor-tions of angular and sub-rounded grains decrease towards the IzokLake deposit (Fig. 11). High proportions of angular and sub-roundedgrains in till samples away from the mineralized zone likely fingerprintIF-Mag and G-Mag, and also indicate the impact of transport media.

The abundance of angular and sub-angularmagnetite grains, togeth-er with the absence of very rounded grains and the low frequency ofrounded grains in Izok Lake till samples are consistent with glacialtransport. In fluvial and/or marginal marine environments, intenseabrasive processes will round the grain edges and the sediments willbe dominated by rounded and very rounded grains (Madhavarajuet al., 2009; Mahaney, 2002; Moral Cardona et al., 1997). The glacial


crushing of bedrock, entrainment and transport of grains by four phasesof ice flow in the Izok Lake area could in part explain the abundance ofangular and subangular grains in the surface till. Angular grains can alsobe formed by short distance transport in highly energetic fluvial envi-ronments. However, in such environments, there is not sufficient timeto abrade the grain edges to form subangular grains (Helland andHolmes, 1997). The absence of very angular grains can be related to1) their scarcity in the source rock, and 2) abrasion of grain edges duringtransport. Dissolution and precipitation can also affect the shape of agrain. Dissolving grains edges and/or overgrowths on the surface ofgrains modifies their angularity.

4.6. Grain size distribution of magnetite in Izok Lake bedrock and tillsamples

In the Izok Lake massive sulfides and gahnite-rich dacite, the grainsize of magnetite is likely controlled by rates of dissolution of previousminerals (e.g. hypogene sphalerite) and precipitation rate of magnetite.The dissolution-precipitation reactions are affected by 1) the composi-tion of fluid phases, 2) solubility of parent and new mineral phases,3) temperature, 4) pressure, 5) Eh-pH stability fields of magnetite andits precursors, and 6) oxygen and sulfur fugacity (Putnis, 2002; Putnisand Putnis, 2007; Xia et al., 2009; Putnis and John, 2010; Pollok et al.,2011; Jonas et al., 2013; Borg et al., 2014). The grain size of mineralsin magmatic rocks such as the Izok Lake bedrock gabbro is mainly con-trolled by the nucleation and growth rates inmagma,which are, in turn,functions of the cooling rate of magma (Best, 2002; Frost and Frost,2014). The cooling rate of magma is also controlled by the temperatureof magma, and the temperature and depth of rocks enclosing magma(Frost and Frost, 2014). At slower cooling rates, fewer but larger grainsform since the nucleation rate is slower than the growth rate. The easeof nucleation can also determine the grain size distribution of magmaticminerals as nucleation of Fe–Ti oxides in magma results in formation ofsmall grain size populations (Best, 2002) similar to G-Mag.

The grain size distribution of magnetite is almost identical amongIzok Lake till samples, and is similar to that of MS-Mag and GRD-Mag(Fig. 13). Specifically in till sample 09-MPB-066, located close to the de-posit, magnetite grains have the average size of 500 μm that is betweenthe average sizes ofMS-Mag andGRD-Mag (425 μmand 600 μmrespec-tively). In contrast, the average sizes of IF-Mag and G-Mag (32 μm and75 μm, respectively) are significantly smaller than that of till samples(125 to 500 μm; Fig. 13). However, 6% of IF-Mag, and 19% of G-Magare larger than 125 μm. These data demonstrate that analyzing the0.25 mm to 2.0 mm HMC fraction size of Izok Lake till samples mayhave caused under-representation of magnetite from iron formationand gabbro due to their fine-grained nature. This also indicatesthat magnetite from other lithologies may not be represented in a0.25 mm to 2.0 mm particle-size HMC if it has a small grain-size and/or is interlocked with other minerals, if their aggregate size is verysmall. Brooker et al. (1987) and Koski (2012) showed that hypogeneminerals in un-metamorphosed massive sulfide deposits commonlydisplay a narrower range in grain size distribution than that of meta-morphosed deposits. Klein (2005) also realized that grain size distri-bution of magnetite formed during metamorphism is commonlycontrolled by the grade of metamorphism wherein higher grades ofmetamorphism are characterized by coarser magnetite. All of thesestudies as well as the present study suggest that precautions shouldbe taken in selection of a representative particle-size fraction formorphological investigations because of the grain size distribution ofmagnetite.

5. Conclusions

This study showed that mineral associations, surface textures,shape, and grain size ofmagnetite are applicable tools to 1) discriminatedifferent types of magnetite, 2) identify the nature of host bedrock, and

3) distinguish transport media. The investigation of magnetite from0.25mm to 2.0mmHMC fraction size of Izok Lake bedrock and samplesreveals that: 1) Subhedral to anhedral, medium-grainedmagnetite con-taining sulfide inclusions, and in association with gahnite signaturesmetamorphosed massive sulfide deposits and related alteration zones.2) Euhedral to subhedral, fine-grained magnetite in association with il-menite, hornblende and plagioclasefingerprints formation ofmagnetiteduring crystallization of a gabbroic magma. 3) Anhedral, fine-grainedmagnetite in association with/or as an inclusion in almandine, biotite,or hornblende is the fingerprint of iron formations. Hematite is also acommon association of IF-Mag. 4) Intergrowths of magnetite and actin-olite indicate themetamorphic formation of magnetite. 5) Overgrowthsdeposits of magnetite on existing magnetite and/or other componentsof mineral aggregates are typical of supergene environments.

The investigation of magnetite surface textures in Izok Lake tillsamples also shows that they are diagnostic of transport media, as:1) Mechanical textures such as conchoidal fractures, subparallel linearfractures, grooves, troughs, steps, and/or crescentic gouges documentedon magnetite in Izok Lake till samples indicate that magnetite has beentransported by glaciers. Crescentic gouges, deep grooves and arc-shapedsteps are also signatures of thick continental glaciers with N 800 mthickness. 2) Magnetite grains characterized by V-shaped percussioncracks indicate transportation by fluvial or glaciofluvial environments.3) Overprinted surfaces of magnetite grains in till indicates these grainshave likely experienced different cycles of erosion, transport, and depo-sition that is consistent with 4 phases of ice flow affecting the Izok Lakearea through time.

The angularity of magnetite in till samples indicates the origin shapeof the mineral, and mode of transport as: 1) Euhedral to subhedralmagnetite forms angular to sub-angular crystals, whereas anhedralmagnetite can form very angular to rounded grains. 2) Glacial transportincreases the angularity of magnetite by fracturing, whereas fluvialtransport reduces the angularity by abrasion and rounding the graincorners. In Izok Lake till samples, the abundance of angular and sub-angular magnetite grains, the absence of very rounded grains, and thelow frequency of rounded grains are consistent with glacial transport.The grain size distribution and angularity ofmagnetite grains in till sam-ple located about 500mdown ice from the deposit, suggest that in closeproximity to the deposit, magnetite grains in till are mainly derivedfrom the mineralization.

Acknowledgements

This research was funded by the Geological Survey of Canada underits Geo-mapping for Energy and Minerals (GEM-1) program (2008–2013), Natural Science and Engineering Research Council (NSERC) ofCanada, and industry partners OverburdenDrillingManagement Limited,MMGLimited, TeckResources Limited, andAREVAResources Canada.Wewould like to thank all who collaborated on this project: A. Hicken(Queen's University) for the bedrock and till sampling; A. Ferland andM. Choquette for providing technical assistance with the SEM andEPMA at U-Laval; E. Lalonde (U-Laval) for text editing; G. Figueroa(FEI Australia) for assisting with the MLA software; and M. Javidani(U-Laval) for his technical assistance. Karen Kelley and Thomas Angererare thanked for their insightful reviews of this manuscript in Journal ofGeochemical Exploration.

References

Alekseeva, V., 2005. Micromorphology of quartz grain surface as indicator of glacialsedimentation sonditions: evidence from the Protva River Basin. Lithol. Miner.Resour. 40 (5), 420–428.

Averill, S.A., 2001. The application of heavy indicator minerals in mineral exploration. In:McClenaghan, M.B., Bobrowsky, P.T., Hall, G.E.M., Cooks, S. (Eds.), Drift Exploration inGlaciated Terrain. Geological Society of London Special Publication 185, pp. 69–82.

Averill, S.A., Zimmerman, J.R., 1986. The Riddle resolved: the discovery of the Prtridgegold zone using sonic drilling in glacial overburden at Waddy lake, Saskatchewan.Can. Geol. J. CIM 1, 14–20.

http://refhub.elsevier.com/S0375-6742(14)00404-X/rf0005










Baguley, P., St, John D.H., Hayes, P.C., 1983. The conditions for the formation of lath andporous magnetite on reduction of hematite in H2/H2O gas mixtures. Metall. Mater.Trans. 14B, 513–514.

Baker, H.W., 1976. Environmental sensitivity of submicroscopic surface textures on quartzsand grains — a statistical evaluation. J. Sediment. Petrol. 46, 871–880.

Baragar, W.R.A., Ernst, R.E., Hulbert, T., Peterson, T., 1996. Longitudinal petrochemicalvariation in the Mackenzie dyke swarm, Northwestern Canadian Shield. J. Petrol. 37(2), 317–359.

Basu, A., Young, S.W., Suttner, L.J., James,W.C.,Mack, G.H., 1975. Reevaluation of the use ofundulatory extinction and polycrystallinity in detrital quartz for provenanceinterpretation. J. Sediment. Petrol. 45, 873–882.

Basu, A., 1985. Reading provenance from detrital quartz. In: Zuffa, G.G.I. (Ed.), Provenanceof Arenites. Nato Series C. 148, pp. 231–247.

Beal, M.A., Shepard, F.P., 1956. A use of roundness to determine depositional environments.J. Sediment. Petrol. 26, 49–60.

Beaudoin, G., Dupuis, C., Gosselin, P., Jebark, M., 2007. Mineral chemistry of iron oxides:application to mineral exploration. Proceedings of the 9th Biennial SGA Meeting,Dublin. , pp. 497–500.

Beaudoin, G., Dupuis, C., McClenaghan, B., 2009. Fingerprinting mineral deposit typesusing iron-oxide chemistry: application to till from Thompson, Manitoba, Canada.Proceedings of the 24th IAGS, Fredericton. , pp. 107–121.

Best, M.G., 2002. Igneous andMetamorphic Petrology. 2nd ed. Wiley-Blackwell (752 pp.).Bleeker, W., Hall, B., 2007. The Slave Craton: geological and metallogenic evolution.

Mineral Deposits of Canada: A Sythesis of Major Deposit-Types, District Metallogeny,the Evolution of Geological Provinces, and Exploration Methods; W.D. Goodfellow(Ed.), Geological Association of Canada, Mineral Deposits Division. Spec. Publ. 5,849–879.

Bleeker, W., Ketchum, J.W.F., Jackson, V.A., Villeneuve, M.E., 1999. The Central SlaveBasement Complex, Part I: its structural topology and autochthonous cover. Can.J. Earth Sci. 36, 1083–1109.

Borg, S., Liu, W., Pearce, M., Cleverley, J., MacRae, C., 2014. Complex mineral zoningpatterns caused by ultra-local equilibrium at reaction interfaces. Geology 42 (5),415–418.

Bostock, H.H., 1980. Geology of the Itchen Lake Area, District of Mackenzie. GeologicalSurvey of Canada, Memoir 391 (101 pp.).

Boucher, S.M., Hannington, M.D., Dube, B., 2010. Primary and secondary ore textures inthe West Ansil volcanic-hosted massive-sulphide deposit, Noranda mining camp,Rouyn-Noranda, Quebec. Current Research 2010-10. Geol. Surv. Can. (16 pp.).

Brearely, A.J., Champness, P.E., 1986. Magnetite exsolution in almandine garnet. Mineral.Mag. 50, 621–633.

Brooker, D.D., Craig, J.R., Rimstidt, J.D., 1987. Ore metamorphism and pyrite porphyroblastdevelopment at the Cherokee mine, Ducktown, Tennessee. Econ. Geol. 82, 72–86.

Buchan K.L., and Ernst R.E., 2004. Diabase dyke swarms and related units in Canada andadjacent regions. Geological Survey of Canada, Map 2022A, scale 1:5,000,000.

Buerger, M.J., 1947. The relative importance of the several faces of a crystal. Am. Mineral.32, 593–606.

Buddington, A.F., Lindsley, D.H., 1964. Iron-titanium oxide minerals and syntheticequivalents. J. Petrol. 5, 310–357.

Cabri, L.J., Rudashevsky, N.S., Rudashevsky, V.N., Oberthur, T., 2008. Electric-pulsedisaggregation (EPD), Hydroseparation (HS) and their use in combination for mineralprocessing 232 and advanced characterization of ores. Proceedings of the 40thAnnualCanadian Mineral Processors Conference, Ottawa 2008, pp. 221–235.

Campbell, S., Thompson, I.C., 1991. Palaeoenvironmental history of Late Pleistocenedeposits at Moel Tryfan, North Wales: evidence from scanning electron microscopy.Proc. Geol. Assoc. 102, 123–134.

Chang, L.L.Y., Deer, W.A., Howie, R.A., Zussman, J., 1998. Rock-forming minerals. Non-silicates: sulphates, carbonates, phosphates, halides. Geol. Soc. Lond. 5B (383 pp.).

Cornell, R.M., Schwertmann, U., 2006. The Iron Oxides: Structure, Properties, Reactions,Occurrences and Uses. John Wiley & Sons (664 pp.).

Cornwall, H.R., 1951. Ilmenite, magnetite, hematite, and copper in lavas of KeweenawanSeries. Econ. Geol. 46, 51–57.

Costa, P.J.M., Andrade, C., Mahaney, W.C., Marques da Silva, F., Freire, P., Freitas, M.C.,Janardo, C., Oliviera, M.A., Silva, T., Lopes, V., 2013. Aeolian microtextures in silicaspheres induced in a wind tunnel experiment: comparison with aeolian quartz.Geomorphology 180–181, 120–129.

Costello, K., Senkow, M., Bigio, A., Budkewitsch, P., Ham, L., Mate, D., 2012. NunavutMineral Exploration, Mining and Geoscience Overview 2011. Aboriginal Affairs andNorthern Development Canada (71 pp.).

Dare, S.A.S., Barnes, S.J., Beaudoin, G., 2011. Evolution of trace element concentrations inmagnetite from a fractionating magmatic sulphide liquid: an example from theSudbury (Canada) Ni–Cu–PGE deposits. 11th Biennial SGA meeting: Let's Talk OreDeposits. The Society for Geology Applied to Mineral Deposits (SGA), Antofagasta,Chile, pp. 621–623.

Dare, S.A.S., Barnes, S.J., Beaudoin, G., 2012. Variation in trace element content of magnetitecrystallized from a fractionating sulfide liquid, Sudbury, Canada: Implications forprovenance discrimination. Geochim. Cosmochim. Acta 88, 27–50.

Deo, B., Dube, R.K., Chatterji, S., 1989. Formation of porous magnetite in the initial stage ofsolid state reduction of hematite by metallic iron. ISIJ Int. 29, 345–347.

DeVore, G.W., 1956. Surface chemistry as a chemical control on mineral association.J. Geol. 64, 31–55.

DeVore, G.W., 1957. The association of strongly polarizing cations with weakly polarizingcations as a major influence on element distribution, mineral composition, andcrystal growth. J. Geol. 65, 78–195.

DiLabio, R.N.W., 1991. Classification and interpretation of the shapes and surface tex-tures of gold grains from till. Geological Survey of Canada, contribution N°32391, pp. 297–313.

Dill, H.G., 2007. Grain morphology of heavy minerals from marine and continental placerdeposits, with special reference to Fe–Ti oxides. Sediment. Geol. 198, 1–27.

Doyle, M.G., Allen, R.L., 2003. Subsea-floor replacement in volcanic-hostedmassive sulfidedeposits. Ore Geol. Rev. 23 (3–4), 183–222.

Dredge L.A., Kerr D.E., Ward B.C., 1996. Surficial geology, Point Lake, District of Mackenzie,Northwest Territories. Geological Survey of Canada, Map 1890A, scale 1:125 000.

Dupuis, C., Beaudoin, G., 2011. Discriminant diagrams for iron oxide trace elementfingerprinting of mineral deposit types. Mineral. Deposita 46 (4), 319–335.

Fandrich, R., Gu, Y., Burrows, D., Moeller, K., 2007. Modern SEM-based mineral liberationanalysis. Int. J. Miner. Process. 84, 310–320.

Fisher, N.H., 1945. The fineness of gold, with special reference to the Morobe Goldfield,New Guinea. Soc. Econ. Geol. 40, 449–495.

Folk, R.L., 1978. Petrology of Sedimentary Rocks. Hemphill Publishing Co, Austin, Texas(182 pp.).

Frost, B.R., Frost, C.D., 2014. Essentials of Igneous and Metamorphic Petrology. Cambridgeuniversity press, United States of America (297 pp.).

Galley, A.G., Watkinson, D.H., Jonasson, I.R., Riverin, G., 1995. The subsea-floor formationof volcanic-hosted massive sulfide: evidence from the Ansil deposit, Rouyn Noranda,Canada. Econ. Geol. 90, 2006–2017.

Gerlach, R.W., Nocerino, J.M., 2003. Guidance for obtaining representative laboratoryanalytical subsamples from particulate laboratory samples. Environmental ProtectionAgency: the United States, Report N° EPA/600/R-03/027 (156 pp.).

Giusti, L., 1987. The morphology, mineralogy, and behavior of “fine-grained” gold fromplacer deposits of Alberta: sampling and implications for mineral exploration:Reply. Can. J. Earth Sci. 24, 1503.

Golubev, Yu.K., 1995. Diamond exploration in glaciated terrain: a Russian perspective.J. Geochem. Explor. 53 (1–3), 265–275.

Goudie, A.S., Watson, A., 1981. The shape of desert sand dune grains. J. Arid Environ. 4,185–190.

Grant, A.H., Lavin, O.P., Nichol, I., 1991. The morphology and chemistry of transportedgold grains as an exploration tool. J. Geochem. Explor. 40 (1–3), 73–94.

Griffiths, J.C., 1967. The Scientific Method in the Analysis of Sediments. McCraw-Hill, NewYork (508 pp.).

Hallbauer, D.K., Utter, T., 1977. Geochemical and morphological characteristics of goldparticles from recent river deposits and the fossil placers of the Witwatersrand.Mineral. Deposita 12 (3), 293–306.

Heider, F., Dunlop, D.J., Sugiura, N., 1987. Magnetic properties of hydrothermallyrecrystallized magnetite crystals. Science 236, 1287–1290.

Heimann, A., Spry, P.G., Teale, G.S., 2005. Zincian spinel associated with metamorphosedProterozoic base-metal sulfide occurrences, Colorado: a re-evaluation of gahnitecomposition as a guide in exploration. Can. Mineral. 43, 601–622.

Helland, P.E., Diffendal Jr., R.F., 1993. Probably glacial climate conditions in source areasduring deposition of parts of the AshHollow Formation, Ogallala Group (Late Tertiary)of western Nebraska. Am. J. Sci. 293, 744–757.

Helland, P.E., Holmes, M.A., 1997. Surface textural analysis of quartz sand grains from ODPSite 918 off the southeast coast of Greenland suggests glaciation in southernGreenland at 11 Ma. Palaeogeogr. Palaeoclimatol. Palaeoecol. 135, 109–121.

Helland, P.E., Huang, P.H., Diffendal, R.F., 1997. SEM analysis of quartz sand grain surfacetextures indicates alluvial/colluvial origin of the Quaternary “glacial” boulder clays atHuangshan (Yellow Mountain), East-Central China. Quat. Res. 48, 177–186.

Herail, G., Fornari, M., Rouhier, M., 1989. Geomorphological control of gold distributionand gold particle evolution in glacial and fluvioglacial placers of the Ancocala–Ananeabasin-Southeastern Andes of Peru. Geomorphology 2, 369–384.

Hicken, A.K., 2012. Glacial dispersal of indicator minerals from the Izok Lake Zn–Pb–Ag VMS deposit, Nunavut, Canada. (MSc. thesis), Department of GeologicalSciences and Geological Engineering. Queen's University, Kingston, Ontario,Canada (666 pp.).

Hicken, A.K., McClenaghan, M.B., Layton-Matthews, D., Paulen, R.C., Averill, S.A., Crabtree,D., 2013. Indicator mineral signatures of the Izok Lake Zn–Cu–Pb-Agvolcanogenicmassive sulphide deposit, Nunavut: Part 1 bedrock samples. Geological Survey ofCanada, Open file 7173.

Higgins, M.D., 2006. Quantitative Textural Measurements in Igneous and MetamorphicPetrology. Cambridge University Press, Cambridge, UK (276 pp.).

Higgs, R., 1969. Quartz grain surface features of Mesozoic-Cenozoic sands from theLabrador andwestern Greenland continental margins. J. Sediment. Petrol. 39, 599–610.

Hu, H., Li, J.W., Lentz, D., Ren, Z., Zhao, X.F., Deng, X.D., Hall, D., 2014. Dissolution-reprecipitation process of magnetite from the Chengchao iron deposit: insights intoore genesis and implication for in-situ chemical analysis of magnetite. Ore Geol.Rev. 57, 393–405.

Janoo, V., 1998. Quantification of shape, angularity and surface texture of base coarse ma-terials. US army corps of engineers cold region research. Special report 98–1.

Jonas, L., John, T., Putnis, A., 2013. Influence of temperature and Cl on the hydrothermalreplacement of calcite by apatite and the development of porous microstructures.Am. Mineral. 98, 1516–1525.

Kasper-Zubillaga, J.J., 2009. Roundness in quartz grains from island and coastal dunesands, Altar Desert, Sonora, Mexico. Bol. Soc. Geol. Mex. 61 (1), 1–12.

Kasper-Zubillaga, J.J., Dickinson, W.W., Carranza-Edwards, A., Hornelas-Orozco, Y., 2005.Petrography of quartz grains in beach and dune sands of Northland, North Island,New Zealand. J. Geol. Geophys. 48, 649–660.

Kerr, D.E., Dredge, L.A., Ward, B.C., Gebert, J.S., 1995. Quaternary geology and implicationsfor drift prospecting in the Napaktulik Lake, Point Lake, and Contwoyto Lake mapareas, northwest Slave Province, Northwest Territories. Current Research, Part E;Geological Survey of Canada, Paper 1995-E, pp. 201–209.

Kleesment, A., 2009. Roundness and surface textures of quartz grains in Middle Devoniandeposits of East Baltic and their palaeogeographic implications. Estonian J. Earth Sci.58 (1), 71–84.







































































































































































Klein, C., 2005. Some Precambrian banded iron-formations (BIFs) from around the world:Their age, geologic setting, mineralogy, metamorphism, geochemistry, and origin.Am. Mineral. 90, 1473–1499.

Knight, J.B., McTaggart, K.C., 1986. The composition of placer and lode gold from theFraser River drainage area, southwestern British Columbia. Can. J. CIM 1, 21–30.

Knight, J.B., Morison, S.R., Mortensen, J.K., 1999. The relationship between placer goldparticle shape, rimming, and distance of fluvial transport as exemplified by goldfrom the Klondike District, Yukon Territory, Canada. Econ. Geol. 94, 635–648.

Koski, R.A., 2012. Hypogene ore characteristics in volcanogenic massive sulfideoccurrence model. 2012, U.S. Geol. Surv. Chap 8, 135–146.

Kretz, R., 1966. Interpretation of the shape of mineral grains in metamorphic rocks.J. Petrol. 7 (1), 68–94.

Krinsley, D.H., Doornkamp, J.C., 1973. Atlas of quartz sand and surface textures. Cam-bridge University Press, Cambridge, UK (102 pp.).

Krinsley, D.H., Donahue, J., 1968. Environmental interpretation of sand grain surfacetextures by electron microscopy. Geol. Soc. Am. Bull. 79, 743–748.

Krinsley, D.H., Marshall, J.R., 1987. Sand grain textural analysis: an assessment. In:Marshall, John R. (Ed.), Clastic Particles: Scanning Electron Microscopy and ShapeAnalysis of Sedimentary and Volcanic Clasts. Van Nostand Reinhold Company, NewYork, New York.

Larson, J.E., 1983. Geology, geochemistry and wall-rock alteration at the Magusi andNew Insco massive sulfide deposits, Hebecourt Township, northwestern Quebec.(M.Sc., thesis), University of Western Ontario, London, Ontario (173 pp.).

Madhavaraju, J., Barragán, J.C.G., Hussain, S.M., Mohan, S.P., 2009.Microtextures on quartzgrains in the beach sediments of Puerto Peñasco and Bahia Kino, Gulf of California,Sonora, Mexico. Rev. Mex. Cien. Geol. 26, 367–379.

Mahaney,W.C., 1990a. Ice on the Equator.W. Caxton Press, Ellison Bay,Wisconsin (386 pp.).Mahaney, W.C., 1990b. Macrofabrics and quartz microstructures confirm glacial origin of

Sunnybrook drift in the Lake Ontario basin. Geology 18, 145–148.Mahaney, W.C., 1991. Microtextures on quartz and gold grains transported by glaciers.

Gisements alluviaux d'or, La Pazpp. 315–323.Mahaney, W.C., 1995. Pleistocene and Holocene glacier thicknesses, transport histories

and dynamics inferred from SEM microtextures on quartz particles. Boreas 24 (4),293–304.

Mahaney, W.C., Andres, W., 1991. Glacially crushed quartz grains in loess as indicators oflong distance transport from major European ice centers during the Pleistocene.Boreas 20, 231–240.

Mahaney, W.C., Andres, W., 1996. Scanning electron microscopy of quartz sand from theNorth-Central Saharan desert of Algeria. Z. Geomorphol. 103, 179–192.

Mahaney, W.C., Kalm, V., 2000. Comparative scanning electron microscopy study oforiented till blocks, glacial grains and Devonian sands in Estonia and Latvia. Boreas29, 35–51.

Mahaney, W.C., 2002. Atlas of Sand Grain Surface Textures and Applications. OxfordUniversity Press (256 pp.).

Mahaney, W.C., Dirszowsky, R.W., Milner, M.W., Menzies, J., Stewart, A., Kalm, V.,Bezada, M., 2004. Quartz microtextures and microstructures owing to deformationof glaciolacustrine sediments in the northern Venezuelan Andes. J. Quat. Sci. 19,23–33.

Mahaney, W.C., Dohm, J.M., Costa, P., Krinsley, D.H., 2010. Tsunamis on Mars: Earthanalogues of projected Martian sediment. Planet. Space Sci. 58, 1823–1831.

Mahaney,W.C., Vortisch, W., Fecher, K., 1988a. Sedimentary petrographic study of tephra,glacial and aeolian grains in a Quaternary paleosol sequence on Mount Kenya, EastAfrica. Géog. Phys. Quatern. 42, 137–146.

Mahaney, W.C., Vortisch, W., Julig, P., 1988b. Relative differences between glaciallycrushed quartz transported by mountain and continental ice — some examplesfrom North America and East Africa. Am. J. Sci. 288, 810–826.

Mahaney, W.C., Stewart, A., Kalm, V., 2001. Quantification of SEM micortextures useful insedimentary environmental discrimination. Boreas 30 (2), 165–171.

Mandolla, S., Brook, M.S., 2010. A preliminary Scanning Electron Microscope (SEM) studyof magnetite surface microtextures from the Wahianoa moraines, Mt Ruapehu, NewZealand, in Geoscience. Working paper series in physical geography. PhysicalGeography Research Forum. Massey University, New Zealand, pp. 1–12.

Margolis, S.V., Krinsley, D.H., 1974. Processes of formation and environmental occurrenceof microfeatures on detrital quartz grains. Am. J. Sci. 274, 449–464.

Mathur, A.K., Mishra, V.P., Singh, J., 2008. Study of quartz grain surface texture by electronmicroscopy — a tool in evaluating palaeoglacial sediments in Uttarakhand. Curr. Sci.96 (10), 1377–1382.

Matthews, A., 1976. Magnetite formation by the reduction of hematite with iron underhydrothermal conditions. Am. Mineral. 61, 927–932.

Mazzullo, J., Ritter, C., 1991. Influence of sediment source on the shapes and surfacetextures of glacial quartz sand grains. Geology 19, 384–388.

McClenaghan, M.B., 2005. Indicator mineral methods in mineral exploration. Geochem.Explor. Environ. Anal. 5, 233–245.

McClenaghan, M.B., 2011. Overview of common processing methods for recovery ofindicator minerals from sediment and bedrock. Geochem. Explor. Environ. Anal. 11,265–278.

McClenaghan, M.B., Thorleifson, L.H., DiLabio, R.N.W., 1997. Till geochemical and indicatormineral methods in mineral exploration. Proceedings of Exploration 97: FourthDecennial International Conference on Mineral Exploration. In: Gubins, A.G. (Ed.),,pp. 233–248.

McClenaghan, M.B., Hicken, A.K., Averill, S.A., Paulen, R.C., Layton-Matthews, D., 2012.Indicator mineral abundance data for bedrock and till samples from the Izok LakeZn-Cu-Pb-Ag Volcanogenic Massive Sulphide Deposit, Nunavut. Geological Surveyof Canada, Open File 7075.

Miller, F.P., Vandome, A.F., McBrewter, J., 2009. Crystallographic Defects in Diamond. VDMPublishing (106 pp.).

Money, P.L., Heslop, J.B., 1976. Geology of the Izok Lake massive sulphide deposit. Can.Min. J. 97, 24–28.

Moral Cardona, J.P., Gutiérrez Mas, J.M., Sánchez, B.A., López-Aguayo, F., Caballero, M.A.,1997. Provenance of multicycle quartz arenites of Pliocene age at Arcos, southwest-ern Spain. Sediment. Geol. 112, 251–261.

Morris, T.F., Breaks, F.W., Averill, S.A., Crabtree, D.C., McDonald, A., 1997. Gahnitecomposition: implications for base metal and rare-element exploration. Explor.Min. Geol. 6, 253–260.

Morrison, I.R., 2004. Geology of the Izok Lake massive sulfide deposit, Nunavut Territory,Canada. Explor. Min. Geol. 13, 25–36.

Morrison, I.R., Balint, F., 1993. Geology of the Izok Lake massive sulphide deposits,Northwest Territories, Canada. Proceedings of theWorld Zinc'93 Symposium, Hobart,Australia, pp. 161–170.

Morrison, I.R., Balint, F., 1999. Geology of the Izok massive sulfide deposit, NorthwestTerritories, Canada. Can. J. Earth Sci. 36, 1227–1238.

Nadoll, P., Angerer, T., Mauk, J.L., French, D.,Walshe, J., 2014. The chemistry of hydrothermalmagnetite: a review. Ore Geol. Rev. 61, 1–32.

Nadoll, P., Mauk, J.L., Hayes, T.S., Koenig, A.E., Box, S.E., 2012. Geochemistry of magnetitefrom hydrothermal ore deposits and host rocks of the Mesoproterozoic BeltSupergroup, United States. Econ. Geol. 107, 1275–1292.

Narayana, A.C., Mohan, R., Mishra, R., 2010. Morphology and surface textures of quartzgrains from freshwater lakes of McLeod Island, Larsemann Hills, East Antarctica.Curr. Sci. 99 (10), 1420–1424.

Nesbitt, B.E., 1986. Oxide-sulfide-silicate equilibria associated with metamorphosed oredeposits. Part I: Theoretical considerations. Econ. Geol. 81, 831–840.

Padgham, W.A., Fyson, W.K., 1992. The Slave Province: a distinct Archean craton. Can.J. Earth Sci. 29, 2072–2086.

Paulen, R.C., McClenaghan, B., Hicken, A., 2013. Regional and local ice-flow history in thevicinity of the Izok Lake Zn–Cu–Pb–Ag deposit, Nunavut. Can. J. Earth Sci. 50,1209–1222.

Pettijohn, F.J., 1957. Sedimentary Rocks. 2nd ed. Harper & Row (718 pp.).Pettijohn, F.J., Potter, P.E., Siever, R., 1973. Sand and Sandstone. Springer, Verlag (618 pp.).Pokhilenko, N.P., Afanas'ev, V.P., Vavilov, M.A., 2010. Behavior of kimberlite indicator

minerals during the formation of mechanical dispersion halos in glacial settings.Lithol. Miner. Resour. 45 (4), 324–329.

Pollok, K., Putnis, C.V., Putnis, A., 2011. Mineral replacement reactions in solid solution-aqueous solution systems: volume changes, reactions paths and end-points usingthe example of model salt systems. Am. J. Sci. 311, 211–236.

Porter, J.J., 1962. Electron microscopy of sand surface texture. J. Sediment. Petrol. 32 (1),124–135.

Powers, M.C., 1953. A new roundness scale for sedimentary particles. J. Sediment. Petrol.23 (2), 117–119.

Putnis, A., 2002. Mineral replacement reactions: frommacroscopic observations to micro-scopic mechanisms. Mineral. Mag. 66 (5), 689–708.

Putnis, A., 2009. Mineral replacement reactions. Revi. Mineral. Geochem. 70, 87–124.Putnis, A., John, T., 2010. Replacement processes in the Earth's crust. Elem. 6, 159–164.Putnis, A., Putnis, C.V., 2007. The mechanism of re-equilibration of solids in the presence

of a fluid phase. J. Solid State Chem. 180, 1783–1786.René, M., 2008. Titanite-ilmenite-magnetite phase relations in amphibolites of the

Chynov area (Bohemian massif, Czech Republic). Acta Geodyn. Geomater. 5 (3),239–246.

Rudashevsky, N.S., Garuti, G., Anderson, J.C.O., Krester, Y.L., Rydashevsky, V.N., Zaccarini, F.,2002. Separation of accessory minerals from rocks and ores by hydroseparation (HS)technology: method and application to CHR-2 chromitite, Niquelandia intrusion,Brazil. Applied Earth Science: Mineral Process and Extractive Metallurgy Transactionssection B. 111 pp. 87–94.

Russell, R.D., Taylor, R.E., 1937. Roundness and shape of Mississippi river sands. Am.J. Geol. 45, 225–267.

Sagga, A.M.S., 1993. Roundness of sand grains of longitudinal dunes in Saudi Arabia.Sediment. Geol. 87, 63–68.

Sandhaus, D.J., Craig, J.R., 1986. Gahnite in the metamorphosed stratiformmassive sulfidedeposits of the Mineral District, Virginia, U.S.A. Mineral. Petrol. 35, 77–98.

Sappin, A.A., Dupuis, C., Beaudoin, G., McMartin, I., McClenaghan, M.B., 2014. Optimalferromagnetic fraction in till samples along ice-flow paths: Case studies from theSue-Dianne and Thompson deposits, Canada. Geochem. Explor. Environ. Anal.http://dx.doi.org/10.1144/geochem2013-212.

Shepard, F.P., 1973. Submarine Geology. Harper and Row, New York (517 pp.).Shepard, F.P., Young, R., 1961. Distinguishing between beach and dune sands. J. Sediment.

Petrol. 31, 196–214.Singh, V.P., Singh, P., Haritashya, U.K. (Eds.), 2011. Encyclopaedia of Snow, Ice and

Glaciers. XLVI. Springer (1253 pp. 659 illus., 428 illus. in color).Smalley, I.J., 1966. The properties of glacial loess and the formation of loess deposits.

J. Sediment. Res. 36 (3), 669–676.Spry, P.G., 1982. An unusual gahnite-forming reaction, Geco base metal deposit,

Manitouwadge, Ontario. Can. Mineral. 20, 549–553.Spry, P.G., 1987a. Compositional zoning in zincian spinel. Can. Mineral. 25, 97–104.Spry, P.G., 1987b. The chemistry and origin of zincian spinel associated with the

Aggeneys Cu–Pb–Zn–Ag deposits, Namaqualand, South Africa. Mineral. Deposita 22,262–268.

Spry, P.G., Scott, S.D., 1986. The stability of zincian spinels in sulfide systems and theirpotential as exploration guides for metamorphosed massive sulphide deposits.Econ. Geol. 81, 1446–1463.

Spry P.G., and Teale S., 2009. Gahnite composition as a guide in the search formetamorphosed massive sulphide deposit. International Applied GeochemistrySymposium Indicator Mineral Methods in Mineral Exploration, Fredericton,New Brunswick, Canada, 2009, unpublished notes Workshop B, 27-34.


















































































































































http://dx.doi.org/10.1144/geochem2013-212


















Stea, R.R., Johnson, M., Hanchar, D., 2009. The geometry of kimberlite indicator mineraldispersal fans in Nunavut, Canada; in Application of Till and Stream SedimentHeavy Mineral and Geochemical Methods to Mineral Exploration in Western andNorthern Canada. In: Paulen, R.C., McMartin, I. (Eds.), Geological Association ofCanada, GAC Short Course Notes. 18, pp. 1–13.

Stendal, H., Theobald, P.K., 1994. Heavy-mineral concentrates in geochemical exploration.Drain. Geochem. 6, 185–225.

Strand, K., Passchier, S., Nasi, J., 2003. Implications of quartz grain microtextures for onsetEocene/Oligocene glaciation in Prydz Bay, ODP Site 1166, Antarctica. Palaeogeogr.Palaeoclimatol. Palaeoecol. 198, 101–111.

Sweet, D.E., Soreghan, G.S., 2010. Application of quartz sand microtextural analysis toinfer cold-climate weathering for the Equatorial Fountain Formation (Pennsylvanian–Permian, Colorado, U.S.A.). J. Sediment. Res. 80, 666–677.

Sylvester, P.J., 2012. Chapter 1: Use of the Mineral Liberation Analyzer (MLA) formineralogical studies of sediments and sedimentary rocks. Mineralogical Associationof Canada, St. John's, NL. pp. 1–16.

Taipale, A., 2013. Composition of magnetite in gabbros of the Mustavaara Fe–Ti–VDeposit. (M.Sc. thesis), Department of Geosciences, University of Oulu, Oulu,Finland (65 pp.).

Tarassova, M., Tarassova, E., Tacheva, E., Peytcheva, I., Nedialkov, R., 2013. Contrastingresponse of accessory ilmenite and magnetite to magma mixing and postmagmaticalteration in Petrohan Pluton, Western Balkan, Bulgaria. C. R. Acad. Bulg. Sci. 66 (8),1151–1158.

Thomas, A., 1978. Volcanic stratigraphy of the Izok Lake Greenstone Belt, District ofMackenzie, N.W.T. University of Western Ontario (110 pp.).

Townley, B.K., Hérail, G., Maksaev, V., Palacios, C., Parseval, P., Sepulveda, F., Orellana, R.,Rivas, P., Ulloa, C., 2003. Gold grain morphology and composition as an explorationtool: application to gold exploration in covered areas. Geochem. Explor. Environ.Anal. 3, 29–38.

Utter, T., 1979. The morphology and silver content of gold from the upper Witwatersrandand Ventersdorp systems of the Klerkdrop Gold Field, South Africa. Econ. Geol. 74,27–44.

Van Hoesen, J.G., Orndorff, R.L., 2004. A comparative SEM study on the micromorphologyof glacial and nonglacial clasts with varying age and lithology. Can. J. Earth Sci. 41,1123–1139.

Vos, K., Vandenberghe, N., Elsen, J., 2014. Surface textural analysis of quartz grains byscanning electron microscopy (SEM): From sample preparation to environmentalinterpretation. Earth-Sci. Rev. 128, 93–104.

Wadell, H., 1932. Volume, shape and roundness of rock particles. J. Geol. 40, 443–451.Watts, S.H., 1985. A scanning electron microscope study of bedrock microfractures in

granites under high arctic conditions. Earth Surf. Process. Landf. 10, 161–172.Winter, J.D., 2001. An Introduction to Igneous and Metamorphic Petrology. Prentice Hall

(695 pp.).Xia, F., Brugger, J., Chen, G., Ngothai, Y., O'Neill, B., Putnis, A., Pring, A., 2009. Mechanism

and kinetics of pseudomorphic mineral replacement reactions: a case study of thereplacement of pentlandite by violarite. Geochim. Cosmochim. Acta 73, 1945–1969.

Youngson, J.H., Craw, D., 1999. Variation in placer style, gold morphology, and goldparticle behavior down gravel bed-load rivers: an example from the Shotover/Arrow–Kawarau–Clutha River system, Otago, New Zealand. Econ. Geol. 94, 615–634.

















































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