indicator mineral and till geochemical signatures of the ... · indicator mineral and till...

Journal of Geochemical Exploration 172 (2017) 151–166

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Journal of Geochemical Exploration

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Indicator mineral and till geochemical signatures of the Mount PleasantW-Mo-Bi and Sn-Zn-In deposits, New Brunswick, Canada

M.B. McClenaghan a,⁎, M.A. Parkhill b, A.G. Pronk c, W.D. Sinclair a

a Geological Survey of Canada, 601 Booth St, Ottawa, ON K1A 0E8, Canadab New Brunswick Department of Energy and Resource Development, Geological Surveys Branch, P.O. Box 50, Bathurst, NB E2A 3Z1, Canadac New Brunswick Department of Energy and Resource Development, Geological Surveys Branch, P.O. Box 6000, Fredericton, NB E3B 5H1, Canada

⁎ Corresponding author.E-mail address: [email protected] (M.B. M

http://dx.doi.org/10.1016/j.gexplo.2016.10.0040375-6742/Crown Copyright © 2016 Published by Elsevie

a b s t r a c t
a r t i c l e i n f o
Article history:Received 22 March 2016Revised 22 August 2016Accepted 15 October 2016Available online 18 October 2016

A study of the till indicatormineral andmatrix geochemical signature of theMount PleasantW-Mo-Bi and Sn-Zn-In deposits inNewBrunswick, Canadawas undertakenusing commercially availablemethods. Indicatormineralsof the deposits include: cassiterite, wolframite, and molybdenite, as well as gangue minerals topaz, chalcopyrite,galena, sphalerite, arsenopyrite, pyrite, and loellingite and secondary Pb minerals beudantite, anglesite,plumboferrite, and plumbogummite in the 0.25–0.5 mmheavymineral (N3.2 specific gravity) fraction, and fluo-rite in the 0.25–0.5 mmmid-density (3.0–3.2 specific gravity) fraction. The presence of coarse (0.5–2.0 mm) in-dicator minerals in till close (b1 km) to the deposits marks the close proximity to mineralization. Indicatorelements in the b0.063 mm fraction of till overlying and down ice of the deposits include Sn, W, Mo, Bi, Zn,and In. Pathfinder elements in till include Ag, As, Cd, Cu, Pb, Re, Te, and Tl. This study reports In values of b0.02to 13 ppm in thematrix of till overlying the deposit; values N5 ppm are some of the highest ever reported for till.Crown Copyright © 2016 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Keywords:Indicator mineralsTill geochemistryCassiteriteIndiumMineral explorationGlaciated terrain

1. Introduction

Tin is a dense metal that has a low melting point, high malleability,resistance to corrosion, the ability to alloy with other metals, and easeof recycling, that make it optimal for a wide range of industrial applica-tions (USGS, 2016; Mineral Council of Australia, 2016). Placer depositsin southeast Asia currently supply approximately 35% of the world'sSn production (USGS, 2016). Currently, Canada has no Snmines in pro-duction, though Sn has been mined (e.g. East Kemptville, Boyle et al.(1991)) and limited tin exploration is ongoing (e.g. McCutcheon et al.,2013). The aim of this study was to document the type and abundanceof indicator minerals in till at varying distances down ice from a signif-icant Sn deposit as an aid to Sn exploration and discovery in the glaciat-ed terrain of Canada.

2. Mount Pleasant deposit

2.1. Location and exploration history

TheMount PleasantW-Mo-Bi and Sn-Zn-In deposits are in southernNew Brunswick (Fig. 1), in eastern Canada, at latitude 45°26′N and lon-gitude 66°49′W. The deposits are 60 km south of the city of Frederictonand are easily accessible by road.Mineralizationwas discovered in 1955as a result of stream sediment and soil sampling (Parrish and Tully,

cClenaghan).

r B.V. This is an open access article u

1978; McCutcheon et al., 2013). Subsequent soil sampling, geophysicalsurveys, bedrock stripping, and diamond drilling continued over thenext 30 years, until the deposit was mined for W between 1983 and1985. Exploration and delineation of the resources has been ongoinguntil the present.

2.2. Bedrock geology and mineralogy

The bedrock geology of the Mount Pleasant area is summarizedbelow from Hosking (1963), Kooiman et al. (1986), Sinclair (1994),Invemo and Hutchinson (2004), Sinclair et al. (2006), McCutcheon etal. (1997, 2010, 2013), Fyffe and Thorne (2010), and Thorne et al.(2013). The deposits are associated with subvolcanic intrusions in theLate Devonian Mount Pleasant Caldera Complex along the north flankof the Saint George Batholith (Figs. 1,2). The Mount Pleasant CalderaComplex includes the McDougall Brook Granitic Suite, which is relatedto the early stages of caldera development, and theMount Pleasant Gra-nitic Suite, which is related to the late stages of caldera development.The Mount Pleasant deposits are genetically related to highly evolvedgranitic rocks of the Mount Pleasant Granitic Suite that are enriched inthe incompatible elements F, Li, Rb, Cs, U, Th, and Nb. Large, low-grade, porphyry-type deposits of W-Mo-Bi are related to an earlystage of the Mount Pleasant Granitic Suite referred to as Granite I(Figs. 2,3). Smaller, but higher-grade vein, breccia, and replacement de-posits of Sn-Zn-In are related to a later stage of theMount Pleasant Gra-nitic Suite designated Granite II. A third stage of the Mount Pleasant

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CARBONIFEROUS

LATE DEVONIAN

ORDOVICIAN

ORDOVICIAN AND SILURIAN

SILURIAN AND DEVONIAN

SILURIAN

PISKAHEGAN GROUP

Conglomerate, sandstone, shale

Shale, wacke, siltstone

Quartzose wacke, sandstone,siltstone, shale

Granite, granodiorite, diorite

Feldspathic sandstone, siltstone,shale, conglomerate

Red conglomerate, sandstone, shale

Felsic volcanic and subvolcanicgranitic rocks

Intercalated volcanic andsedimentary rocks

66°40’

45°45’

45°25’

67°00’

MountPleasant

SAINT GEORGEBATHOLITH

10 km

67°00’Fault

USA

AtlanticOcean

MountPleasant

Fig. 1. Location of the study area in eastern Canada (inset map) and bedrock geology of the Mount Pleasant area (modified fromMcLeod et al., 1994).

152 M.B. McClenaghan et al. / Journal of Geochemical Exploration 172 (2017) 151–166

Granitic Suite (Granite III) has no significant mineralization related to it(Figs. 2, 3).

The deposits occur within three mineralized zones, the North, Sad-dle, and Fire Tower zones (Figs. 2,3). The North and the Fire Towerzones both contain significant W-Mo-Bi deposits, although the latter islarger and better defined. According to McCutcheon et al. (2013), the

Fig. 2. Local bedrock geologymap of theMount Pleasant Sn-W-Mo-Bi-In deposits area and locatice (southeast) of the deposit (modified from Sinclair et al., 2006).

Fire Tower Zone contains an indicated resource of 13.489million tonnesat 0.33% WO3 and 0.21% MoS2, 0.57% As, and 0.06% Bi, as well as an in-ferred resource of 0.8417 million tonnes at 0.26% WO3, 0.20% MoS2,0.21% As, and 0.04% Bi. In the North Zone, Sn-Zn-In deposits collectivelyhave an indicated resource of 12.4 million tonnes averaging 0.38% Sn,0.86% Zn, and 64 ppm In, as well as an inferred resource of 2.8 million

ion of till samples (black dots) collected in 2012 up-ice (northwest), overlying, and down-

Image of Fig. 1

Image of Fig. 2

?

?

?

?

Bx

Bx

?

?

?

?

AB Fire Tower Zone

FIRE

TOW

ERFA

ULT

200 m

100

Sea level

-100

-200

-300

-400

-500

12500N 13500N13000N 14000N

North Zone

QFP

QFP

QFP

QFP

QFP

QFP

QFPW-Mo

GP GP

FGFG

FG

PGPG/GRIII

GRIII

GRIIB

GRIIBGRIIB

Bx+GRIIAFPFP

SBx

SBx

SBx

SBx

0 250 m

deposit

Saddle Zone

Fig. 3. Cross-section A–B (shown in Fig. 2) through the North Zone and Fire Tower Zone at Mount Pleasant, showing the ore subzones (grey polygons). Bedrock geology legend same as inFig. 2 (modified from Sinclair et al., 2006).

Fig. 4. Colour photographs of indicatormineral grains recovered from till from theMount Pleasant area: a) wolframite in the 0.25–0.5mm fraction of till sample 12-MPB-1004; b) fluoritein the 0.5–1.0mm fraction of till sample 12-MPB-1008; c) topaz in the 0.5–1.0mmfraction of till sample 12-MPB-1004; d)prismatic brown cassiterite grains in the 0.25–0.5mmfraction oftill sample 12-MPB-1020; e) fine grained cassiterite intergrown with topaz in the 0.25–0.5 mm fraction of till sample 12-MPB-1020. Grains were photographed by Michael BainbridgePhotography (modified from McClenaghan et al., 2015d).

153M.B. McClenaghan et al. / Journal of Geochemical Exploration 172 (2017) 151–166

Image of Fig. 3

Image of Fig. 4


tonnes averaging 0.30% Sn, 1.13% Zn, and 70 ppm In (McCutcheon et al.,2013). In the Saddle Zone, significant drill intersections of both W-Mo-Bi and Sn-Zn-Inmineralization have been encountered but no resourceshave been defined as yet.

Oreminerals in theW-Mo-Bi deposits mainly consist of fine grainedwolframite and molybdenite, with minor amounts of native Bi andbismuthinite (Bi2S3). Wolframite ((Fe,Mn)WO4) occurs as anhedral tosubhedral grains, euhedral crystals, and as clusters in gangue. In theFire Tower Zone, wolframite grains vary from 1 to 1000 μm in diameter,with an average size of 100 μm (Petruk, 1973a). In bedrock and tillheavymineral concentrates,wolframite is recognized by its black colour(Fig. 4a) combined with its moderate hardness and reddish-brownstreak. Scheelite (Ca(WO4)), the other W-bearing mineral, is rare atMount Pleasant. According to Parrish (1977), rare discrete grains are20–100 μm in size and usually occur with wolframite. Gangue mineralsin the W-Mo-Bi deposits consist mainly of loellingite (FeAs2), topaz,fluorite, and quartz. Fluorite occurs as veinlets along fractures and dis-seminated together with topaz in zones of pervasive alteration. Mostof the fluorite is various shades of purple (Fig. 4b), but some colourless,brown, light green, and purple-black fluorite has been also documented

Table 1Indicator minerals present in theMount Pleasant deposits (Petruk, 1973a, 1973b; Parrish, 1977bedrock heavy mineral concentrates (HMC), and till heavy mineral concentrates (HMC) in this

Mineral Formula Hardness SpecificGravity

Presence in Mt Pleasas reported by others

Cassiterite SnO2 6–7 6.8–7 Petruk (1973a)Stannite Cu2FeSnS4 3.5–4 4.3–4.5 Petruk (1973a)Kësterite Cu2(Zn,Fe)SnS4 4.5 4.5–4.6 Petruk (1973a)Ferrokësterite Cu2(Fe,Zn)SnS4 4.0 4.5 Parrish (1977)Stannoidite Cu8Fe3Sn2S12 4 4.3 Petruk (1973a)Mawsonite Cu6Fe2SnS8 3.5–4 4.7 Petruk (1973a)Scheelite CaWO4 4–5 5.9–6.1 Parrish (1977)Wolframite (Fe,Mn)WO4 4.5 7.1–7.5 Petruk (1973a)Molybdenite MoS2 1.0 5.5 Petruk (1973a)Pyrite FeS2 5.0 6.5 Petruk (1973a)Marcasite FeS2 6.0–6.5 4.9 Petruk (1973a)Sphalerite (Zn,Fe)S 3.5–4 3.9–4.2 Petruk (1973a)Pyrrhotite Fe(1-x)S (x=0-0.17) 3.5–4 4.6–4.7 Petruk (1973a)Arsenopyrite FeAsS 5 6.1 Petruk (1973a)Loellingite FeAs2 5.0 7.1–7.7 Petruk (1973a)Ferrimolybdite Fe2(MoO4)3•8(H2O) 2.5–3 4–4.5 Parrish (1977)Scorodite Fe(AsO4)•2(H2O) 3.5–4 3.1–3.3 Parrish (1977)Bismuthinite Bi2S3 2 6.8–7.2 Petruk (1973a)Native bismuth Bi 2–2.5 9.7–9.8 Petruk (1973a)Arsenobismite Bi2(AsO4)(OH)3 3 5.7 Parrish (1977)Zairite Bi(Fe,Al)3[(OH)6(PO4)2]) 4.5 4.4 NoEulytite Bi4(SiO4)3 4.5 6.6 NoRoquesite CuInS2 3.5–4 4.8 Petruk (1973a)Chalcopyrite CuFeS2 3.5 4.1–4.3 Petruk (1973a)Covellite CuS 1.5–2.0 4.6–4.8 Petruk (1973a)Tennantite (Cu,Fe)12As4S13 3.5–4 4.6–4.7 Petruk (1973a)Bornite Cu5FeS4 3.0 4.9–5.3 Petruk (1973a)Chalcocite Cu2S 2.5–3 5.5–5.8 Parrish (1977)Digenite Cu9S5 2.5–3 5.6 Parrish (1977)Famatinite Cu3SbS4 3–4 4.6 Parrish (1977)Galena PbS 2.5 7.2–7.6 Petruk (1973a)Wittichenite Cu3BiS3 2.5 6.3–6.7 Petruk, (1973b)Galenobismutite PbBi2S4 2.5–3 6.9–7.1 Petruk (1973a)Aikinite PbCuBiS3 2–2.5 6.1–6.8 Petruk (1973a)Cosalite Pb2Bi2S5 2.5–3 6.4–6.8 Petruk (1973a)Krupkaite PbCuBi3S6 4 7 Petruk (1973a)Beudantite PbFe3(AsO4)(SO4)(OH)6 4 4.1–4.3 NoAnglesite Pb(SO4) 2.5–3 6.3 NoPlumbogummite PbAl3(PO4)2(OH)5H2O 4–5 4–5 NoPlumboferrite Pb2(Fe,Mn,Mg)11O19 5 6 NoFreibergite (Ag,Cu,Fe)12(Sb,As)4S13 3.5–4 4.9–5 Petruk, (1973b)Pyrargyrite Ag3SbS3 2.5 5.9 Petruk, (1973b)Native silver Ag 2.5–3 10–11 Petruk (1973a)Gold Au 2.5–3 16–19.3 Parrish (1977)Topaz Al2SiO4(F,OH)2 8 3.5–3.6 Petruk (1973a)Fluorite CaF2 4 3.0–3.3 Petruk (1973a)Columbite (Fe,Mn)(Nb,Ta)2O6 6 5.3–7.3 Petruk (1973a)

(Petruk, 1973a; Parrish, 1977).Most grains are 150–200 μmindiameter.Topaz is by far themost abundant alterationmineral associatedwithW-Mo mineralization. It occurs in shades of white (Fig. 4c), grey, and yel-low (Petruk, 1973a). Parrish (1977) has estimated the Fire TowerZone W-Mo deposit contains 10% topaz and the topaz alteration, withsome associated W-Mo-Bi mineralization, extends to surface. The pres-ence of this hard mineral (H = 8) is one of the reasons why the FireTower area is a prominent topographic high.

Although the Fire Tower Zone contains some vein and replacementzones of Sn-Zn-In, the North Zone hosts the largest and best developedof these deposits, some of which occur at or near surface. Ore mineralsin the Sn-Zn-In zones consist mainly of cassiterite, sphalerite, and chal-copyrite, along with minor amounts of a variety of other sulphide min-erals listed in Table 1. Cassiterite grains vary from 10 to 250 μm indiameter, with an average size of 20 to 50 μm. They can be anhedral,euhedral (Fig. 4d), or irregular in shape. Some irregular grains areintergrown with sphalerite, rutile, chlorite, or topaz (Fig. 4e). It ismost commonly red-brown in colour (Petruk, 1973a; Parrish, 1977). In-dium occurs mainly in sphalerite, replacing Zn and Fe in a limited solidsolution between sphalerite and roquesite. Small amounts of In are also

; Kooiman et al., 1986; Sinclair et al., 2006) and those found in polished thin sections (PTS),study.

ant deposits Identified in bedrockPTS in this study

Identified in bedrockHMC in this study

identified in tillHMC in this study

No Yes YesNo No NoNo No NoNo No NoNo No NoNo No NoNo No YesNo No YesNo No YesYes Yes YesNo No NoYes Yes NoNo No NoNo Yes YesNo No YesNo No NoNo No NoNo No NoNo No NoNo No NoNo No YesNo No YesNo No NoNo Yes NoNo No NoNo No NoNo No NoNo No NoNo No NoNo No NoYes Yes YesNo No NoNo No NoNo No NoNo No NoNo No NoNo No YesNo No YesNo No YesNo No YesNo No NoNo No NoNo No NoNo No YesYes Yes YesYes Yes YesNo No No


present in chalcopyrite and stannite (Boorman and Abbott, 1967;Petruk, 1973a, 1973b; Sinclair et al., 2006). In places, the ore mineralsin the Sn-Zn-In zones are so fine-grained that they cannot be distin-guished in hand specimen (Petruk, 1973a). Gangue minerals includeloellingite, quartz, topaz, and fluorite.

Mineralization in the Saddle Zone is associated with a cupola ofGranite II that does not extend to surface. Although the main W-Mo-Biand Sn-Zn-In zones do not outcrop, Sn-and W-bearing base metalveins peripheral to these zones occur for up to 300m or more verticallyand laterally and some likely subcrop under glacial cover.

2.3. Surficial geology

The present-day landscape of the Mount Pleasant area is character-ized by relatively thin drift cover (b3m thick) and lack of deeplyweath-ered bedrock, and is assumed to be a product of the last glaciation, theLaurentide Ice Sheet (Szabo et al., 1975; Allard, 2011; Stea et al.,2011). Mount Pleasant itself is a striking topographic feature that risesapproximately 220 m above the surrounding landscape and is coveredby a till veneer b1 m thick. The surrounding lower lying areas are cov-ered by a till blanket 1 to 5 m thick. Till in the region was deposited bysoutheast to south-southeast-flowing ice during the Caledonia Phase(Early to Middle Wisconsin) of glaciation (Szabo et al., 1975; Allard,2011; Stea et al., 2011). Szabo et al. (1975) defined a glacial dispersaltrain extending N16 km southeast of the deposit using the Sn (Fig. 5),As, Cu, Pb, and Zn content of the 0.5–2.0 mm and the heavy mineral(specific gravity N2.95) fractions of till. Their survey was conductedprior to mining of the deposit.

3. Methods

Surface till samples were collected at 22 sites up-ice, overlying, andup to 2 km down-ice (southeast) of the Mount Pleasant deposits (Fig.6) to document the deposits' indicator mineral signature. One till sam-ple (12-MPB-1024), not shown in the figures, was collected 13 km upice of the deposits (McClenaghan et al., 2015a, 2015b, 2015c) to repre-sent background concentrations of trace elements and indicator

40

1000

Sn (ppm)Heavy Mineral Fraction 0.5-2.0 mm

< 10

10-100

>1000100-1000

Sn (ppm) 0.5-2.0 mm

< 10

10-20

>4020-40

Fire TowerZone

North Zone

Fire ToweZone

North Zone

a)

b)

Saddle Zone

Saddle Zone

Fig. 5.Distribution of Sn (ppm) in the: a) sand sized (0.5–2.0mm) heavymineral fraction (SG 2.Pleasant deposit reported by Szabo et al. (1975). Locations of till samples collected in this stud

minerals in local till. Sampling was focused within the first 2 km ofSzabo et al.'s (1975) well defined glacial dispersal train (Fig. 5) to max-imize the possibility of collecting metal-rich till for indicator mineralsstudies. The intent of this sampling was not to define an indicator min-eral dispersal train, but to collect till samples at different locationsaround and over the deposits that could be used to identify the usefulindicator minerals. At each site, an 8 to 15 kg till sample was collectedfor recovery of indicator minerals and a 3 kg sample was collected forgeochemical analysis of the till matrix and archiving. Striations weremeasured on outcropswhere possible (Fig. 6). Fivemineralized bedrocksamples were collected to recover and examine the ore and alterationminerals (Fig. 6).

Bedrock and till samples were processed at a commercial laboratoryusing a combination of shaking table, panning, and heavy liquidmethods to produce a 0.25 to 0.5 mm, 0.5 to 1.0 mm and 1.0 to2.0 mm non-ferromagnetic heavy mineral concentrate (HMC) (N3.2SG) andmid-density concentrate (3.0–3.2 specific gravity) of each sam-ple for examination and identification of potential indicator minerals ofSn-W-Mo-Bi-In mineralization. Detailed descriptions of sample pro-cessing andmineral identificationmethods, as well as sample weightand indicator mineral abundance data for bedrock and till samples,including field duplicates and blanks, are reported in McClenaghanet al. (2014, 2015a, 2015b). All indicator mineral abundancesreported here are normalized to a 10 kg mass of b2 mm material(table feed).

The b0.063mm fraction of each 3 kg till samplewas digested using amodified aqua regia leach (HCl:HNO3 in a 1:1 ratio) followed by an ICP-MS determination on a 0.5 g aliquot in order to determine element con-centrations in till held in sulphides, arsenides, selenides, tellurides, car-bonates, most sulphates, and oxyhydroxides (e.g., Fe, Mn), for whichaqua regia is considered total or near-total (Chao and Sanzolone,1992; Chao, 1984; Hall, 1999). A second analysis was conducted on aseparate 0.2 g aliquot using lithium metaborate/tetraborate fusionfollowed by a nitric acid digestion/ICP-ES, -MS to digest all mineralphases and determine the total element content. Geochemical data forall till samples, as well as field duplicates, blind duplicates, and silicasand blanks, have been reported in McClenaghan et al. (2015c).

ice flow

ice flow

McDougall Lake Inlet

McDougall Lake Inlet

N

mineralized source

N

mineralized source

r

3 km

95) and b) in the sand sized (0.5–2.0mm) fraction of surface till samples around theMounty are shown as black dots.

Image of Fig. 5

Fig. 6. Location of till and bedrock samples collected around theMount Pleasant deposit in 2012. Dashed line indicates location of the Saddle Zone at depth. Bedrock geology fromMcLeodet al. (2005).


4. Results

4.1. Indicator mineral species

Indicator mineral data for bedrock and till around the deposit are re-ported in McClenaghan et al. (2014, 2015a, 2015b). Table 2 lists the in-dicator mineral abundances for the 0.25–0.5 mm heavy and mid-density (fluorite and tourmaline) fractions of till samples listed by loca-tion relative to theMount Pleasant deposits: up ice, overlying, and up to2.2 km down ice. Table 3 lists the abundances of a subset of indicatorminerals aswell as trace elements in the b0.063mm fraction of till sam-ples from the deposit area. Both tables identify threshold values

between background and anomalous indicator mineral-bearing sam-ples established using values for up ice till sample 12-MPB-1024 to de-fine background.

Ore and other indicator minerals recovered from both bedrock andtill samples from the Mount Pleasant deposits include cassiterite (Fig.4d,e), wolframite (Fig. 4a), and molybdenite. Other indicator mineralsrecovered frommineralized bedrock and local glacial sediments includeloellingite (FeAs2) (Fig. 7a), chalcopyrite, galena, sphalerite, arsenopy-rite, pyrrhotite, and pyrite (Table 1), as well as fluorite (Fig. 4b) andtopaz (Fig. 4c). The most abundant indicator minerals in till down-iceof mineralization are cassiterite, wolframite, and topaz. Cassiterite con-tent of the 0.25 to 0.5mmHMC fraction till varies from zero grains in the

Image of Fig. 6

Table 2Abundance of indicator minerals in the 0.25–0.5 mm non-ferromagnetic heavy (N3.2 SG) mineral and mid-density (3.0–3.2 SG) fractions of till at varying distances up ice (indicated bynegative sign), overlying, and down ice of mineralization. Mineral abundances are normalized to a 10 kg mass of the b2 mm fraction (table feed) of each till sample (data fromMcClenaghan et al., 2014).

Number Locationrelative tomineralization

Distance up ice(−) or down icerelative tomineralization(km)

SampleDepth(m)

Cassiterite0.25–0.5 mm


Cassiterite1.0–2 mm

Wolframite0.25–0.5 mm



Topaz0.25–0.5 mm

Topaz0.5–1.0 mm

12-MPB-1024 Background −13 NW ofNorth Zone

0.7 0 0 0 0 0 1 1 1

12-MPB-1013 Up ice −0.6 NW ofNorth Zone

0.7 2 0 0 0 0 0 40 2


0.5 630 24 2 3 1 0 787 31


0.6 7 3 0 0 0 0 14 2


0.5 2 0 0 0 0 0 1 0

12-MPB-1012 Up ice −0.2 W of NorthZone

0.8 89 36 0 14 1 0 268 15

12-MPB-1007 Overlying 0.0 from NorthZone

1.2 8 1 0 2 0 0 500 42


0.8 6 3 0 0 0 0 72 4


0.6 10 0 0 0 0 0 1266 14


0.6 37 3 0 8 2 0 2222 74

12-MPB-1015 Down ice 0.1 SE of NorthZone

0.6 44 11 1 11 4 1 5556 222

12-MPB-1006 Overlying 0.0 from SaddleZone

0.5 53 10 0 35 19 2 4425 88


0.3 63 10 1 32 6 3 1190 40

12-MPB-1018 Overlying 0.0 from FireTower Zone

0.9 1 0 0 0 0 0 44 9


0.1 5 0 0 2 2 0 317 32


0.5 2 0 0 0 0 0 870 43


0.3 12 0 0 32 13 0 31,746 952


0.6 9 0 0 9 0 0 214 15


0.8 0 0 0 0 0 0 0 0

12-MPB-1016 Down ice 0.3 SW of FireTower Zone

0.7 0 0 0 0 0 0 0 0

12-MPB-1022 Down ice 0.7 SSE of FireTower Zone

0.7 0 0 0 0 0 0 661 25

12-MPB-1023 Down ice 2.2 SE of FireTower Zone

0.8 0 0 0 0 0 0 561 37


background sample to a maximum of 89 grains (Fig. 8) overlying theSaddle Zone. The highest count of 630 grains (Fig. 8) is in sample 12-MPB-1020, 500 m to the northeast of the North Zone. Cassiterite occursboth as coarse crystals (Fig. 4d) and fine-grained aggregates intergrownwith topaz (Fig. 4e) in the till.

Wolframite content in till varies from zero grains in the 0.25 to0.5 mm HMC fraction of the background sample to a maximum of 35grains immediately down-ice of the mineralized zones (Fig. 9). Thegrains are angular and black (Fig. 4a). Topaz content ranges from 1grain in the 0.25 to 0.5 mm HMC fraction of the background sample to~32,000 grains in one of the samples overlying a mineralized zone.Grains recovered from till are white and translucent (Fig. 4c).

Background content offluorite in themid-densitymineral fraction oftill is zero grains. Between 4 and 106 fluorite grains were recoveredfrom five till samples that overlie mineralized zones. Grains recoveredfrom till are colourless to pale purple and angular (Fig. 4b). Backgroundabundance of tourmaline in the mid-density mineral fraction of till, asmeasured in a sample collected up ice, is 51 grains. Values in till overly-ing mineralization range from 5 to 83, and down ice of mineralizationvary from 30 to 75 grains (Table 2).

Sulphide and arsenide minerals (e.g. molybdenite, pyrite, arsenopy-rite, loellingite (Fig. 7a)) are present in the0.25–0.5mmHMC fraction oftill samples proximal to mineralization but only in low concentrations(one to tens of grains). Chalcopyrite and sphalerite were notrecovered from till samples (Table 2). Two Bi-bearing minerals wererecovered from till overlying mineralization: one grain of zairite(Bi(Fe,Al)3[(OH)6(PO4)2]) (Fig. 7b) and two grains of eulytite(Bi4(SiO4)3) (Fig. 7c). Pale white to yellow grains of anglesite (Fig. 7d)and orange grains of beudantite (PbFe3(OH)6SO4AsO4) (Fig. 7e) arepresent in till overlying the Fire Tower Zone, the Saddle Zone, and500 m of northeast of the North Zone. One till sample (12-MPB-1002)contains an exceptional number of beudantite grains (1587) and onesample (12-MPB-1004) contains an exceptional number of anglesitegrains (11905), as compared to the other samples (Table 2). Two grainsof plumboferrite (Pb2(Fe,Mn,Mg)11O19) were recovered from tillsample 12-MPB-1020, 500 m northwest of the North Zone, and onegrain of plumbogummite ((PbAl3(PO4)2(OH)5·(H2O)) was recov-ered from till sample 11-MPB-1022, 1.5 km southwest of the FireTower Zone. Till samples 500 m to the northwest of the North Zonealso contain some of the highest contents of cassiterite, fluorite,

Table 2 continued

Number Topaz1.0–2.0 mm

Molybdenite0.25–0.5 mm

Beudantite0.25–0.5 mm

Anglesite0.25–0.5 mm

Pyrite0.25–0.5 mm

Fluorite0.25–0.5 mm SG3.0–3.2

Tourmaline0.25–0.5 mm SG 3.0–3.2

Scheelite0.25–0.5 mm

Arsenopyrite0.25–0.5 mm

12-MPB-1024 0 0 0 0 0 0 51 1 012-MPB-1013 0 0 1 0 12 0 4 0 5912-MPB-1020 8 0 0 1181 0 0 31 0 012-MPB-1019 0 0 1 1 0 0 68 0 012-MPB-1014 0 0 0 0 0 13 35 1 012-MPB-1012 0 0 0 0 45 0 45 0 012-MPB-1007 4 0 0 1 0 4 83 0 012-MPB-1008 0 0 0 0 4 72 11 0 012-MPB-1009 0 0 0 0 0 0 6 0 012-MPB-1010 4 0 0 0 0 0 30 0 012-MPB-1015 12 0 0 0 0 0 20 0 012-MPB-1006 1 0 2 18 0 106 35 0 012-MPB-1001 0 0 0 3 1 0 32 0 012-MPB-1018 0 0 0 0 1 0 10 0 012-MPB-1002 2 0 1587 2 0 0 5 0 012-MPB-1003 0 0 0 0 0 0 54 0 012-MPB-1004 0 1 0 11,905 0 12 32 0 012-MPB-1005 0 0 0 43 0 0 36 0 012-MPB-1017 0 0 0 0 0 0 43 1 012-MPB-1016 0 0 0 0 0 0 38 0 012-MPB-1022 0 0 0 0 0 0 41 0 012-MPB-1023 0 0 0 0 0 0 37 0 0


pyrite, beudantite, anglesite and the only recovered arsenopyritegrains.

Of the three size fractions examined, indicator minerals are mostabundant in the finest (0.25 to 0.5 mm) fraction. Coarser (0.5 to2.0 mm) grains of cassiterite, wolframite, topaz, and anglesite were re-covered from till samples overlying and immediately down-ice (up to1 kmsoutheast) ofmineralization, indicating that the presence of coarsegrained indicator minerals in till can be a guide to proximalmineralization.

4.2. Till geochemistry

The term ‘indicator element’ is used here to refer to an element thatis a potentially economically valuable component of the ore beingsought andmay be used to detect an orebody (Rose et al., 1979). Indica-tor elements in till at Mount Pleasant include: Sn, W, Mo, Bi, Zn, and In(Table 3). The term ‘pathfinder element’ is used here to refer to non-oreelements associated with the orebody that may be used to detect theorebody (Rose et al., 1979). Pathfinder elements in till at the MountPleasant deposit include Ag, As, Cd, Cu, Pb, Re, Te, and Tl. (Table 3).

Tin values in till range from 2 ppm in background samples to a max-imumof 349 ppmoverlying the Fire Tower Zone (Fig. 10).Molybdenumvalues in till range from a background value of 0.7 ppm to the highestvalues of 305 to 386ppm in till overlying the Fire Tower Zone. Overlyingall three zones, the till contains between 2.8 and 13.1 ppm In (Fig. 11).Tungsten values in till range from 2 ppm in background to the highestvalues of 22 to 35 ppm in the three till samples that overlie the FireTower Zone. The highest values of Cu (479 ppm), Bi (208 ppm), As(2392 ppm), and Pb (2479 ppm) overlie the Fire Tower Zone. Thehighest values of Zn (2213 ppm) and Cd (2.94 ppm) in till overlie theNorth Zone.

5. Discussion

5.1. Indicator minerals

The list of indicator minerals recovered from bedrock and till sam-ples in this study is more extensive than the list of minerals (fluorite,topaz, tourmaline, pyrite) identified by Szabo et al. (1975) in theirstudy of till in theMount Pleasant area. It is similar but alsomore exten-sive than the list of minerals (cassiterite, scheelite topaz, fluorite, chal-copyrite, pyrite) noted by Matilla and Peuraniemi (1980) and

Peuraniemi and Heinänen (1985) in Sn-rich till samples overlying theAhvenisto Massif in southern Finland. The few other studies of Sn-richtill reported only the presence of cassiterite, and rarely wolframite, inthe till (Brundin and Bergström, 1977; Ryan et al., 1988; Turner andStea, 1990).

Beudantite is a secondary mineral formed from the oxidation andweathering of polymetallic Pb- and As-bearing sulphide minerals (e.g.Nieto et al., 2003; Boyle, 2003). Anglesite forms as a result of the oxida-tion of Pb minerals such as galena (e.g. Boyle, 2003; Lara et al., 2011;Paradis et al., 2016). Their presence in till proximal to a sulphide-bear-ing deposit can indicate: (1) preglaciallyweathered sulphideswere gla-cially eroded and incorporated into the local till (e.g. Budulan et al.,2013); (2) fresh Pb-bearing (and As-bearing in the case of beudantite)sulphide minerals in the till were weathered in situ postglacially duringsoil formation (e.g. Brundin and Bergström, 1977; Kelley and Hudson,2007; Lara et al., 2011; Oviatt et al., 2013); or (3) base metals migratedin solution from the mineralized zone and reprecipitated proximally ordistally within the till. Regardless of how these minerals formed andcame to be in the till, their presence can be useful indicators of the pres-ence of nearby Pb-bearing sulphide minerals.

The unusually large number of beudantite grains in sample 12-MPB-1002 and anglesite grains in till sample 12-MPB-1004, both of whichoverlie the Fire Tower Zone, may be the result of postglacial weatheringof till that contained significant numbers of Pb- and As-bearing sulphideminerals. The fact that the till at these two sites was collected at a muchshallower depth (b0.3 m) than at other sites (0.5 to 1.2 m) and washighly oxidized, supports this conclusion.

The recovery of the Bi minerals eulytite and zairite from till in thisstudy is the first ever report of their presence in a till sample, hencetheir photos (Fig. 7b,c) have been included here. The presence of Bimin-erals in till here is not unexpected as theW-Mo zones atMount Pleasantare noted for their elevated Bi (up to 0.06%) content.

The presence of pyrite and arsenopyrite in till sample 11-MPB-1013may indicate that a less oxidized till was sampled or that the till at thissite was contaminated with metal-rich debris during exploration activ-ities on the property.

Brown tourmaline is widespread in background and local till sam-ples around the deposit. However, tourmaline in theMount Pleasant de-posits is rare and occurs primarily as very fine-grained pale greenneedles in tin-basemetal lodes (Parrish, 1977). The distribution of tour-maline grains in till in this study does not display a pattern that is relat-ed to the presence of mineralization. The bedrock source of the brown

Table 3Comparison of the normalized (10 kg) abundance of selected indicator minerals in the 0.25–0.5 mm non-ferromagnetic heavy (N3.2 SG) heavy mineral fraction and trace elements in the b0.063 mm fraction of till samples from the Mount Pleasantdeposits (data fromMcClenaghan et al., 2014). Distance up ice indicated by a negative sign. Sn andW values were determined by borate fusion-ICP-MS, and all other elements were determined by aqua regia-ICP-MS. Mineral abundances are nor-malized to a 10 kg mass of the b2 mm fraction (table feed) of each till sample (data from McClenaghan et al., 2014).

Sample Locationrelative tomineralization

Distance up ice(−) or down icerelative tomineralization(km)



Topaz0.25–0.5 mm

Fluorite0.25–0.5 mmSG 3.0–3.2

Beudantite0.25–0.5 mm

Anglesite0.25–0.5 mm

Snppm

Wppm

Moppm

Cuppm

Pbppm

Znppm

Agppb

Asppm

Cdppm

Sbppm

Bippm

Tlppm

Teppm

Inppm

Reppb

12-MPB-1024 Background −13 NW of NorthZone

0 0 1 0 0 0 2 2 1 25 15 53 54 13 0.1 0.4 1 0.1 0.04 0.0 b1

12-MPB-1013 Up ice −0.6 NW of NorthZone

2 0 40 0 1 0 5 2 1 38 27 2989 21 166 1.6 0.7 1 0.2 b0.02 0.1 b1


630 3 787 0 0 1181 166 3 9 110 292 1149 228 384 0.7 0.6 10 0.3 0.03 2.8 b1


7 0 14 0 1 1 59 4 8 144 254 1241 877 302 1.1 0.4 12 0.3 0.03 2.2 b1


2 0 1 13 0 0 5 2 11 125 17 2214 17 145 2.9 0.8 2 0.1 0.06 0.3 b1

12-MPB-1012 Up ice −0.2 W of NorthZone

89 14 268 0 0 0 52 5 13 123 59 1487 36 541 2.2 0.8 9 0.1 0.05 2.2 2


8 2 500 4 0 1 85 6 9 103 327 986 124 426 1.6 1.3 14 0.2 0.12 4.7 b1


6 0 72 72 0 0 10 2 15 165 168 2060 42 312 2.6 1.3 4 0.3 0.07 1.1 b1


10 0 1266 0 0 0 70 11 14 44 273 563 640 198 0.7 0.3 46 1.6 0.28 1.5 2


37 8 2222 0 0 0 59 8 4 82 41 397 47 195 1.9 0.7 8 0.1 0.07 1.3 b1

12-MPB-1015 Down ice 0.1 SE of NorthZone

44 11 5556 0 0 0 143 8 45 115 214 671 94 520 0.7 1.1 69 0.5 0.34 2.7 b1


53 35 4425 106 2 18 142 25 18 165 270 462 503 937 0.5 1.8 41 0.4 0.18 4.1 b1


63 32 1190 0 0 3 75 19 16 167 179 455 66 477 0.3 1.5 43 0.6 0.36 2.3 b1


1 0 44 0 0 0 6 4 1 41 40 882 28 44 2.9 0.6 2 0.1 b0.02 0.1 1


5 2 317 0 1587 2 263 35 386 82 1799 440 165 800 0.5 0.8 192 0.6 0.65 4.7 4


2 0 870 0 0 0 7 25 5 40 45 138 514 2392 0.4 0.5 77 0.2 0.27 0.5 b1


12 32 31746 12 0 11,905 349 23 305 227 2479 562 1666 1347 0.9 2.1 208 0.6 2.58 13.1 4


9 9 214 0 0 43 35 3 3 164 200 999 160 93 1.1 0.6 4 0.2 0.09 0.7 b1


0 0 0 0 0 0 6 2 14 151 219 887 607 125 1.0 0.4 12 0.3 0.09 1.4 b1

12-MPB-1016 Down ice 0.3 SW of FireTower Zone

0 0 0 0 0 0 29 5 11 374 203 1156 596 197 1.3 0.6 29 0.2 0.26 1.6 b1

12-MPB-1022 Down ice 0.7 SSE of FireTower Zone

0 0 661 0 0 0 19 4 24 479 359 851 571 374 1.2 0.3 12 0.6 0.05 1.1 b1

12-MPB-1023 Down ice 2.2 SE of FireTower Zone

0 0 561 0 0 0 13 4 3 76 64 166 496 99 0.3 0.4 6 0.2 0.07 0.6 b1

159M.B.M

cClenaghanetal./JournalofG

eochemicalExploration

172(2017)

151–166

Fig. 7. Colour photographs of indicator mineral grains from theMount Pleasant deposit area: a) loellingite in the 0.25–0.5 mm fraction of till sample 12-MPB-1001; b) zairite in the 0.25–0.5mm fraction of till sample 12-MPB-1002; c) eulytite in the 0.25–0.5mm fraction of till sample 12-MPB-1019; d) anglesite in the 0.25–0.5mm fraction of till sample 12-MPB-1004; ande) beudantite in the 0.25–0.5 mm fraction of till sample 12-MPB-1002. Grains were photographed by Michael Bainbridge Photography (modified from McClenaghan et al., 2015d).


tourmaline observed in till samples is unknown, and may simply be thelocal sedimentary rocks surrounding the deposit (Lentz and McAllister,1990; Lentz, 1994). Therefore, tourmaline is not an indicator mineral ofthese deposits.

Till samples 500m to the northwest of the North Zone contain someof the highest contents of indicator minerals, most notably cassiterite.The source of these grains in the till may be unrecognized Sn-rich bodiesnearby. It is also possible that the source of the indicator mineral grainsin till in this area is contamination from previous exploration activityand that man-made disturbance is not recognizable in the present day.

The presence of cassiterite grains in till has been reported in a fewstudies (e.g. Brundin and Bergström, 1977; Mattila and Peuraniemi,1980; Peuraniemi and Heinänen, 1985; Ryan et al., 1988; Turner andStea, 1990). Identification of cassiterite in some of these studies wasmade only for selected till samples after they were first determined tohave elevated Sn contents. Recovery of cassiterite in these older studieswas carried out using a variety of concentration procedures (sluicing,panning, heavy liquid separation) that contrast withmodern systematicmethods that are now used in commercial laboratories (McClenaghan,2011). In contrast, this study reported the presence of cassiterite in tillusing modern methods that were applied to all till samples, not justthe Sn-rich samples.

5.2. Till geochemistry

Till geochemistry has been used for many years for Sn exploration inglaciated terrain (e.g. Szabo et al., 1975; Matilla and Peuraniemi, 1980;Toverud, 1982; Stea and O'Reilly, 1982; Rogers and Garrett, 1987;Rogers et al., 1990; Lamothe, 1990; Aario and Peuraniemi, 1992). Mostpublished reports and case studies describe till sampling surveys or pro-grams thatwere carried out between the 1960s and the early 1990s. Thelist of indicator/pathfinder elements identified in the b0.063 mm frac-tion of till this study (Ag, As, Bi, Cd, Cu, In, Mo, Pb, Re, Sn, Te, Tl, andZn) is more extensive than the few elements (Sn, Mo, Cu, Pb, and Zn)that were identified in earlier soil and till studies around Mount Pleas-ant (Riddell, 1967; Szabo et al., 1975) or in the other till studies aroundSn mineralization in glaciated terrain. The extensive suite of elementslisted above reflects the ability of modern ICP-MS techniques to deter-mine a broader suite of elements at lower detection limits.

Till analytical methods for Sn have improved significantly in the past30 years, and consequently, the determination of the Sn content in till isnow routine and inexpensive. In this study, lithium tetra/metaborate fu-sionwas used to determine the total Sn andW content of till samples. Acomparison of values determined after borate fusion and aqua regia di-gestions indicates that aqua regia recovered only 5 to 35% of the total Sn

Image of Fig. 7

Fig. 8.Distribution of cassiterite grains in the 0.25–0.5mmfraction of till (normalized to 10 kg) plotted on the local bedrock geology of thedeposit area. Bedrock geology fromMcLeod et al.(2005).(Modified from McClenaghan et al. (2015a).)


content and 8 to 65% of the total W content in the till. Aqua regia diges-tion data for the other pathfinder and indicator elements are acceptablebecause they are hosted in sulphide and other minerals (Table 1) thatare easily dissolved by aqua regia (Chao, 1984; Chao and Sanzolone,1992).

5.3. Source of high metal contents in till

As described above, the Fire Tower Zone is a significant resource ofW, Mo, As, and Bi. The North Zone is a significant resource of Sn, Zn,and In (McCutcheon et al., 2010, 2013). Thus it is not unexpected that

till eroded from the deposits contains significant contents of Sn, Mo, Bi(hundreds ppm), As, Zn (thousands of ppm), and In (ones to tenppm) (Tables 3, 4). The high Sn values in till likely reflect the presenceof cassiterite, and possibly stannite and other Sn-sulphide mineralsthat are present in the deposit (Table 1).

Till overlying and just down ice of the deposits contains between 1and 13 ppm In; these values are some of the highest ever reported fortill. By comparison, recently published till geochemical studies have re-ported In contents in till up to a maximum of only 4.2 ppm overlyingvolcanogenic massive sulphide or intrusion-hosted W deposits (e.g.Parkhill and Doiron, 2003; Hicken et al., 2012; Budulan et al., 2013;

Image of Fig. 8

Fig. 9. Distribution of wolframite grains in the 0.25–0.5 mm fraction of till (normalized to 10 kg) plotted on the local bedrock geology of the deposit area. Dashed line indicates location ofthe Saddle Zone at depth. Bedrock geology from McLeod et al. (2005).(Modified from McClenaghan et al. (2015a).)


McClenaghan et al., 2013; Plouffe and Ferbey, 2016). Elevated In con-centrations in till at Mount Pleasant are likely derived from the mainIn-bearing minerals in the deposits reported to be present (e.g.Hosking,1963; Boorman and Abbott, 1967; Sinclair et al., 2006;Goeddeke et al., 2015) such as sphalerite and roquesite, and, to a lesserextent, chalcopyrite and stannite (Table 1).

Elevated Bi content in till (tens to hundreds of ppm) is likely derivedfrom Bi-bearingminerals such as native bismuth (Bi), bismuthinite, andother Pb-Bi sulphides that occur in the deposits (Table 1). Arsenopyrite,loellingite, other As-bearing sulphides, and scorodite also occur in the

deposits (Table 1), and are the most likely source of the high As values(100 s to 1000s ppm) in till. Sphalerite is a major mineral in theMount Pleasant Sn-Zn-In deposits, and is likely the source of elevatedZn (hundreds of ppm) and Cd (N1 ppm) in the till. Silver bearing min-erals in the deposit include native silver, freibergite, and pyrargyrite(Kooiman et al., 1986; Sinclair et al., 2006) and galena (Hosking,1963). These minerals may be the source of elevated Ag (hundreds tothousands of ppb) in till overlying the deposits.

Galena and other Pb-sulphide, sulphate, or oxide minerals listed inTable 1 are the likely source of the high Pb contents (hundreds to

Image of Fig. 9

Fig. 10. Distribution of Sn (ppm) in the b0.63 mm fraction of till plotted on the local bedrock geology of the deposit area. Bedrock geology from McLeod et al. (2005).(Modified fromMcClenaghan et al. (2015c).)


thousands of ppm) in the till. There are no reported tellurideminerals inthe Mount Pleasant deposits. The highest Te values in the till (0.65 to2.58 ppm correspond to the highest Pb values the till (1798 to2479 ppm) and Mo (305 to 386 ppm) suggesting that galena or molyb-denite might be the source of some of the Te. Copper is present in sev-eral Sn sulphide minerals as well as several Cu sulphide mineralsdescribed for Mount Pleasant (Table 1) and these are the likely sourcesof elevated Cu contents (hundreds of ppm) in the local till. In general, Reis known to be present in the mineral molybdenite (eg. Giles andSchilling, 1972; Golden et al., 2013;Millensifer et al., 2014), thus the de-tectable Re contents in till in this studymay reflect the presence of Re inmolybdenite in the till.

Copper, Pb, Zn, Ag, As, and In values are high formany of the till sam-ples proximal to themineralized zones; however, the abundance of pri-mary sulphideminerals that are the host of these elements (e.g. galena,sphalerite, chalcopyrite, arsenopyrite, loellingite) is low to zero in thesesame samples. Instead, Pb-bearing secondary minerals beudantite, an-glesite, and plumbogummite are present in these same till samples.These observations suggest that the primary sulphide mineralswere destroyed, either during pre- or post-glacial oxidation, orboth, and that the metals are now hosted in till in these secondaryminerals or adsorbed onto the surfaces of clay minerals (cf., Shilts,1975). Further study is required to determine their actual residencesites in the till.

Image of Fig. 10

Fig. 11. Distribution of In (ppm) in the b0.63 mm fraction of till plotted on the local bedrock geology of the deposit area. Bedrock geology from McLeod et al. (2005).(Modified from McClenaghan et al. (2015c).)

Table 4Summary of indicator minerals in bedrock and till and indicator + pathfinder trace ele-ments in till at the Mount Pleasant Sn-W-M-Bi-In deposits.

Media Indicator/ Pathfinderelements

Indicator Minerals

till Sn, W, Mo, Bi, In, Ag, As,Cd, Cu, Pb, Re, Te, Tl, Zn

cassiterite, wolframite, molybdenite, topaz,galena, arsenopyrite, pyrite, loellingite,fluorite, beudantite, anglesite,plumbogummite, plumboferrite

bedrock not determined cassiterite, molybdenite, sphalerite,chalcopyrite, pyrite, galena, arsenopyrite,fluorite, topaz


6. Conclusions

The Mount Pleasant study is the first detailed indicator mineralstudy around major Sn deposits in glaciated terrain. The deposits con-tain a variety of oxide, sulphide, and silicate indicatorminerals easily re-covered from till: oreminerals cassiterite, wolframite, andmolybdenite,as well as gangue minerals topaz, chalcopyrite, galena, sphalerite, arse-nopyrite, pyrite, and loellingite in the 0.25–0.5mm N3.2 SG fraction, andfluorite in the 0.25–2.0 mm 3.0–3.2 SG fraction. Secondary Pb mineralsbeudantite, anglesite, plumbogummite, and plumboferrite, whichformed from the oxidation of sulphides minerals, are also useful indica-tor minerals (Table 4). Topaz is the most physically robust (H= 8) and

Image of Fig. 11


abundant (thousands of grains) of the indicator minerals identified inthis study. It is expected to survive long distances (tens of km) of glacialtransport, and thuswill be a key indicatormineral, when combinedwiththe presence of the other minerals (Table 4), in sampling programs.

Collectively, the indicator minerals identified in till in this study re-flect the presence of Sn-Wmineralization aswell as the polymetallic na-ture of the deposit. The indicator mineral abundances for till reportedhere offer a guide to contents in till that might be expected proximalto intrusion-hosted Sn-W mineralization. These minerals can be usedto explore for Sn-W mineralization in the region, and elsewhere byusing HMC prepared from till or stream sediments. The restriction ofcoarse (0.5–2.0 mm) indicator minerals in till to an area b 1 km fromthe deposit indicates that the large size of theminerals can be indicatorsof close proximity.

The composition of the b0.063mm fraction of till clearly reflects gla-cial erosion and dispersal down-ice. It is cost effective to sample andgeochemically analyze and thus theuse of this till size fraction in region-al and local Sn exploration programs is recommended. Indicator ele-ments include the main ore elements Sn, W, Mo, Bi, Zn, and In andpathfinder elements include Ag, As, Cd, Cu, Pb, Re, Te, and Tl (Table 4).These elements reflect the presence of Sn mineralization as well as thepolymetallic nature of the Sn-Zn-In deposits. Also, these deposits con-tain a significant resource of In, which is reflected in the high In (up to13 ppm) contents of till overlying the deposit. This study is one of thefirst to report significant In contents in till.

Acknowledgments

TheMount Pleasant case studywas conducted as part of the Geolog-ical Survey of Canada's (GSC) Targeted Geoscience Initiative 4 (TGI-4)(2010–2015) program with a mandate to provide industry with thenext generation of geoscience knowledge and innovative techniquesfor more effective targeting of buried mineral deposits. It was a collabo-rative effort between the GSC and the New Brunswick Department ofEnergy and ResourceDevelopment (NBDERD). AdexMining Inc., in par-ticular G. Kooiman, is thanked for providing access to the Mount Pleas-ant property. K. Thorne, New Brunswick Department of Energy andMineral Resource Development, is thanked for her discussions of thelocal bedrock geology. J. Chapman (GSC) is thanked for sharing bedrocksamples from the deposit. Overburden Drilling Management Ltd. isthanked for providing all heavy mineral processing and picking lab ser-vices. R. Paulen (GSC), G. Simndal (British Columbia Geological Survey),and D. Lentz (University of New Brunswick) are thanked for their thor-ough and thoughtful reviews of the manuscript. Geological Survey ofCanada Contribution No. 20160126.

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http://www.minerals.org.au/file_upload/files/resources/victoria/minerals_fact_sheets/Minerals_-_Fact_Sheets_-_Tin.pdf

http://www.minerals.org.au/file_upload/files/resources/victoria/minerals_fact_sheets/Minerals_-_Fact_Sheets_-_Tin.pdf







































































http://minerals.usgs.gov/minerals/pubs/commodity/tin/

http://minerals.usgs.gov/minerals/pubs/commodity/tin/

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