mid-cretaceous orogenic gold and molybdenite

Yukon Exploration and GEoloGY 2012 73

Mid-Cretaceous orogenic gold and molybdenite mineralization in the independence Creek area,

dawson range, parts of ntS 115J/13 and 14

Greg G. McKenzie, Murray M. Allan1, James K. Mortensen, Craig J.R. Hart, Matías SánchezMineral Deposit Research Unit, University of British Columbia, Vancouver, BC

Robert A. Creaser2

Department of Earth & Atmospheric Sciences, University of Alberta, Edmonton, AB

McKenzie, G.G., Allan, M.M., Mortensen, J.K., Hart, C.J.R., Sánchez, M., and Creaser, R.A., 2013. Mid-Cretaceous orogenic gold and molybdenite mineralization in the Independence Creek area, Dawson Range, parts of NTS 115J/13 and 14. In: Yukon Exploration and Geology 2012, K.E. MacFarlane, M.G. Nordling, and P.J. Sack (eds.), Yukon Geological Survey, p. 73-97.

aBStraCt

The Boulevard gold prospect, located in the Independence Creek area of the Dawson Range, comprises sheeted, auriferous quartz-sulphide-carbonate veins and fault breccia, hosted mainly by mafic schist. The nearby Toni Tiger molybdenum showing is characterized by quartz-molybdenite veins cutting Late Permian meta-aplite and garnet-pyroxene skarn of uncertain age. We present geochronological evidence that gold and molybdenum were deposited at 96-95 Ma, approximately 3 m.y. after intrusion of the Dawson Range batholith and Coffee Creek granite. Fluid inclusions from mineralized quartz veins suggests that gold at Boulevard and molybdenite at Toni Tiger were formed from similar H2O-CO2-NaCl type fluids between 279 and 310°C and >1 kbar. We conclude that both are part of the same mineralizing system, and that structurally-hosted gold at the nearby Coffee deposit and in the Moosehorn Range of western Yukon may be broadly related, post-arc orogenic systems developed during exhumation of the Dawson Range in mid-Cretaceous time.

1 [email protected]

Yukon GeoloGical ReseaRch

Yukon Exploration and GEoloGY 201274

introduCtionThe Independence Creek area is a broad upland plateau within the Dawson Range of west-central Yukon, and is incised by stream systems draining north into the Yukon River. The area is located approximately 140 km south of Dawson, 40 km south of the Golden Saddle gold deposit (Kinross Gold Corp.), which contains 1.4 Moz of gold (Underworld Resources Inc., January 19, 2010 press release), and approximately 10 km southwest of the Coffee gold deposit, which contains 3.2 Moz of gold (Kaminak Gold Corp., December 13, 2012 press release) (Fig. 1).

Gold mineralization of the Boulevard zone was first identified by Rimfire Minerals Corp. in 2007 in the headwaters of the Independence Creek drainage. It is a northwest-trending, 450 m by 1.2 km, gold-arsenic-

antimony soil geochemical anomaly with sporadic tellurium and bismuth. Exploration at Boulevard was pursued further by Rimfire in 2008, Silver Quest Resources Ltd. from 2009 to 2011, and Independence Gold Corp. in 2012. Exploration methods at Boulevard have included stream sediment geochemistry, soil geochemistry, trenching, mapping, prospecting, induced polarization and magnetometry surveys, airborne aeromagnetic and radiometric surveys, and diamond drilling.

The Toni Tiger molybdenum showing (Yukon MINFILE 115J 052) is located approximately 2 km east of the Boulevard trend (Fig. 2). Mineralization was discovered by regional silt survey in 1969 by Archer, Cathro and Associates, and the anomaly was attributed to disseminated molybdenite in skarn with associated

Figure 2

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¯0 20 4010

kilometres

VOLCANIC ROCKS

PLUTONIC ROCKS

Paleocene to Eocene plutonic rocks

Late Cretaceous plutonic rocks

mid-Cretaceous plutonic rocks

Early Jurassic plutonic rocks

Neogene volcanic rocks

Paleocene to Eocene subvolcanic to volcanic rocks

Late Cretaceous volcanic rocks

mid-Cretaceous volcanic rocks

Pennsylvanian volcanic rocks

Devonian to Mississippian metavolcanic rocks

Devonian to Mississippian metaplutonic rocks

Paleozoic metamorphic rocks (undifferentiated)

Triassic volcanic rocks

Paleozoic metamorphic rocks (undifferentiated)

Permian metaplutonic rocks

Permian metavolcanic rocks

Paleozoic ultramafic rocks

METAMORPHIC ROCKS

fault (undifferentiated)

D A W S O N R A N G E

M O O S E H O R N R A N G E

Figure 1. Geological map of the Dawson Range (in greater Yukon Plateau), showing significant mineral deposits and prospects (geology modified from Gordey and Ryan (2005) and Gordey and Makepeace (2003)). The Independence Creek study area is indicated by the black box. Datum: NAD83; Projection: UTM zone 7N.


McKenzie et al. – Mid-cRetaceous oRoGenic au and Mo, independence cReek aRea

75

chalcopyrite, arsenopyrite, scheelite, and pyrite (Craig, 1970). Trenching at the prospect exposed quartz-molybdenite veins, and Craig (1970) inferred that

molybdenite was associated with, and restricted to, the skarn alteration.

Figure 2. Geologic map of the Independence Creek area, showing geochronological data and mineralized trends in the Boulevard and Coffee prospects (Datum: NAD83; Projection: zone 7N). Additional sources of information include: Tempelman-Kluit, 1974; Jilson, 2000; Gordey and Ryan, 2005; Chartier et al., 2013; J. Ryan, pers. comm., 2012. The white line defines Silver Quest property limits as of June 2011.

inferred contactsgeologic contacts

mineralized trends

U-Pb Ages (Ma)

Re-Os Ages (Ma)

Ar-Ar Ages (Ma)

inferred faults/fracturesfaults

( thrust faults

quartz-feldspar porphyry

leucogranite (alaskite)

biotite granite

biotite-hornblende granodiorite

Volcanic Rocks

Plutonic Rocks

serpentinized harzburgite and dunite

impure quartzite with micaceous layers

quartz-K-feldspar augen schist and biotite-quartz schist

quartz-feldspar leucogranite with blue quartz augen

chlorite-biotite-actinolite schist and minor quartz-feldspar augen schist

quartz-muscovite schist and minor quartz-feldspar augen schist

Metamorphic Rocks

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95 ± 0.4

99.6 ± 0.8

57.2 ± 1.0

99.0 ± 0.3

99.4 ± 0.9102.0 ± 0.4

257.6 ± 4.9260.6 ± 5.1

267.2 ± 5.9

100.2 ± 0.3

255.2 ± 0.6251.3 ± 1.3

249.6 ± 3.2

102.5 ± 0.9

95.9 ± 0.9

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Boulevard Trend

Toni Tiger

Coffee Trends

Independence Creek

Carlisle Creek

Halfway C

reek

0 2 41km

¯ YUKON RIVER

Co�ee deposit outline



The Boulevard and Toni Tiger prospects present an opportunity to investigate the age and geological characteristics of two proximal mineralized systems that have contrasting metal associations (Au-As-Sb and Mo-Cu-W, respectively) and uncertain metallogenesis. The geologic relationships presented below are based on mapping, interpretations of airborne magnetic and radiometric data, and detailed observations of diamond drill core. We present U-Pb zircon ages both for metamorphic rocks (including those hosting molybdenite mineralization), and for samples of the Dawson Range batholith, Coffee Creek plutonic suite, and local subvolcanic units. Petrographic observations and reconnaissance-level fluid inclusion data from mineralized veins are also included. Finally, we present 40Ar/39Ar muscovite ages for gold-bearing veins at Boulevard and Re-Os molybdenite ages for Toni Tiger, both of which are interpreted to date mineralization directly.

FiEld rElationSHipS

GEoloGY

The Independence Creek area is underlain by a 3 km-wide, west-northwest-trending belt of predominantly schistose and gneissic rocks (Figs. 1, 2 and 3). This rock package includes the following map units (Fig. 2): (a) serpentinized harzburgite and dunite; (b) variably pyritic chlorite-biotite-actinolite schist, containing minor quartz-feldspar augen schist; (c) quartz-muscovite schist, containing minor calcareous schist; (d) impure quartzite with micaceous layers; (e) foliated quartz-feldspar-muscovite leucogranite and quartz-feldspar augen schist with distinctive blue quartz augen; and (f) quartz-K-feldspar augen schist and minor biotite-quartz schist. Peak metamorphic grade is inferred to be middle greenschist facies on the basis of biotite-chlorite-actinolite assemblages in mafic schists. Lithological heterogeneities are common on the scale of metres to hundreds of metres, due to a combination of original stratigraphic and intrusive contact relationships, and repetition by tight to isoclinal folding and faulting. Ultramafic rocks are exposed as small lenticular bodies near the south margin of the metamorphic package (Figs. 2 and 3f), and are inferred to delineate a major crustal-scale fault (Templeman-Kluit, 1974; Gordey and Makepeace, 2003; Zagorevski et al., 2012).

The metamorphic package is intruded to the south by medium to coarse-grained biotite-hornblende granodiorite of the Dawson Range batholith, a phase of

the mid-Cretaceous Whitehorse plutonic suite (Figs. 1, 2, and 3a). The rock is massive to lineated with locally aligned hornblende and stretched quartz. To the north, metamorphic rocks are intruded by the Coffee Creek phase of the Whitehorse plutonic suite (Templeman-Kluit, 1974), which is composed of medium to coarse-grained biotite granite with volumetrically minor aplitic and pegmatitic phases (Figs. 1, 2, and 3b). A garnet-bearing, quartz-phyric porphyry phase is recognized at the western tip of the Coffee Creek granite. No crosscutting relationships are observed between plutonic rocks and gold mineralization at Boulevard or molybdenite-bearing veins at Toni Tiger.

Locally, subcrop of porphyritic rhyodacite and basalt are observed near the northern margin of the Dawson Range batholith (unit too small to represent on Fig. 2). This unit has been mapped and interpreted as a hypabyssal intrusion (J. Ryan, pers. comm., 2012).

StruCturES

The principal fabric within metamorphic rock units in the study area strikes 280-290°N and is steeply dipping between ~70 and 90°. West of the Coffee Creek granite, the strike of the regional metamorphic fabric rotates to 315°N (Fig. 2). This structural pattern in the metamorphic rocks mirrors a major change in the regional strike of the Dawson Range batholith approximately 20 km west of the study area (Fig. 1).

The main metamorphic fabric has strongly transposed any original depositional features within the metamorphic rock units. The development of this fabric is likely due to D1 and D2 collisional deformation accompanying peak metamorphism of Yukon-Tanana terrane rocks in Late Permian time (Berman et al., 2007; MacKenzie et al., 2008a; Beranek and Mortensen, 2011). Isoclinal, rootless fold hinges and boudinaged quartz veins are interpreted to represent D2 phase folds that overprint the earlier S1 fabric.

A third deformation event (D3) can be recognized as locally developed crenulations (S3) and tight disharmonic folding of the pre-existing metamorphic fabric, and is best developed within micaceous lithologies. These folds have axial traces that are subparallel to the regional west-northwest map trend of the metamorphic rock package and axial planes that are subvertical. Ultramafic bodies along the northern margin of the Dawson Range define a lineament that extends eastward toward the Casino Cu-Mo-Au porphyry deposit and the Sonora Gulch porphyry prospect (Fig. 1), and are interpreted to define a crustal-



77

scale fault that was partially intruded by the Dawson Range batholith (Zagorevski et al., 2012). The origin of this structure is uncertain, but it was likely active in the Early Jurassic, when regional scale thrust faulting imbricated slivers of Slide Mountain oceanic crust within the Yukon-Tanana terrane (MacKenzie et al., 2008a,b; MacKenzie and Craw, 2012).

Locally-developed stretching lineations within the Dawson Range batholith are subhorizontal and parallel to the regional west-northwest strike of metamorphic rocks to the north. The Coffee Creek granite is almost entirely massive, suggesting that either fabrics in the Dawson Range batholith were formed prior to emplacement of the Coffee Creek granite, or that syn to post-magmatic deformation was partitioned more strongly in the Dawson Range batholith.

Figure 3. Typical rock types in the Independence Creek area: (a) biotite hornblende granodiorite of the Dawson Range batholith; (b) biotite granite of the Coffee Creek granite; (c) strongly deformed chloritic schist (typical host rock to gold mineralization); (d) folded metagranite; (e) banded diopside-garnet skarn and biotite schist (typical host rock at the Toni Tiger molybdenum showing); and (f) serpentinitzed harzburgite.

a b

c d

e f



A fault trending 330°N is obvious in aeromagnetic data, and cuts the metamorphic package and the Dawson Range batholith with 1 km of dextral offset (southwest quadrant of Fig. 2). This fault is the most prominent in a series of northwest to north-northwest-trending structures that truncate the west-northwest-trending magnetic grain of the metamorphic package (Fig. 2). A similar northwest to north-northwest orientation is observed for gold-bearing structures at the Boulevard prospect. The offset of the northern intrusive contact of the Dawson Range batholith by this fault generation indicates that this fault set occurred after emplacement of the Dawson Range batholith in mid-Cretaceous time.

VEinS, altEration, and MinEralization

Observations on veining, alteration, and mineralization are presented for the Boulevard and Toni Tiger prospects separately, since field relationships do not provide sufficient information about the relative timing of these adjacent systems.

BoUlEVARD

Detailed observations of diamond drill core reveal five separate vein generations (Fig. 4), all of which are hosted primarily in biotite-chlorite ± actinolite schist. A paragenetic scheme is presented in Figure 5 and petrographic observations are shown in Figure 6.

V1: The first vein generation

(V1) comprises sugary quartz ± pyrite veins, and is found in all metamorphic rock types in the study area (Fig. 4a). V1 veins are typically ~1 cm wide and contain less than 1% pyrite and trace chalcopyrite as inclusions in pyrite. V1 veins are conformable with the metamorphic fabric, and commonly occur as boudins and rootless hinges in mesoscopic folds. V1 veins are early and are interpreted to be

metamorphic segregations formed during Late Permian tectonism.

V2: V2 veins are composed of quartz, pyrrhotite ±

chalcopyrite, are 5 to 30 mm wide, have irregular margins, and no alteration envelopes (Fig. 4b). V2 veins are generally discordant to the S1/S2 fabric, suggesting they post-date peak deformation.

V3: V3 veins are composed mainly of quartz and ferroan

carbonate with muscovite/illite-pyrite-arsenopyrite

gn-sph-stb

pyaltered schist

qtz

qtzpy

po-cpy

py

Figure 4. Major vein types from the Boulevard gold prospect: (a) foliaform quartz veins, likely formed by silica segregation during peak metamorphism, possibly in the late Permian (V

1); (b) irregular quartz-

pyrrhotite-chalcopyrite veins (V2);

(c) planar quartz vein with a bleached, gold-bearing pyritic alteration halo (V

3); (d) gold-bearing silica-sericite-

pyrite altered fracture zone with ferroan carbonate fracture fill (V

3);

(e) gold-bearing quartz-pyrite-galena-sphalerite-stibnite vein breccia (late phase of V

3); and (f) chalcedonic quartz

(V4). py = pyrite; po = pyrrhotite; cpy =

chalcopyrite; qtz = quartz; gn = galena; sph = sphalerite; stb = stibnite

a b

c d

e

f



79

gold

arsenopyrite

pyrite

ferroan carbonate

quartz

sphalerite

V1

V2

V3

V4

V5

pyrrhotite

chalcopyrite

galena

stibnite

tetrahedrite

Aupy

aspy

sph

Au

py qtz

gn

gn

Au

sphpy

gn

py

500µm

50µm

Figure 5. Mineral paragenesis for veins present in the Boulevard gold prospect.

Figure 6. Examples of gold mineralization from the Boulevard area: (a) typical V3-generation quartz-carbonate

vein with a gold-bearing pyrite halo (combined cross-polarized transmitted light and reflected light); (b) backscattered electron microscope image of gold associated with pyrite and arsenopyrite; (c) reflected light photomicrograph of a <5 µm gold grain as an inclusion in galena; (d) backscattered electron microscope image of a 10 µm gold grain associated with galena, sphalerite and pyrite. aspy = arsenopyrite (other mineral abbreviations as in Figure 4).

a b

c d



alteration envelopes (Figs. 4c,d, 6a, and 8a). A paragenetically late phase of sphalerite-galena-pyrite- tetrahedrite ± stibnite is observed in some veins, especially where brecciation has also taken place (Fig. 4e). Veins are typically 2 to 20 mm wide, planar, and occur in sheeted sets that cut the S1/S2 fabric at a high angle. Approximations of vein orientations (using the local metamorphic fabric as a reference plane in unoriented drill core) yield a predominantly northwest strike and a dip of approximately 30o to the southwest. V3 vein swarms are spatially related and subparallel to mineralized fault gouge. The faulting is interpreted to post-date V3 veining since vein fragments have been noted in the fault gouge. Gold has two petrographic associations: (1) inclusions and fracture fillings in pyrite or arsenopyrite in alteration haloes (Fig. 6b); and (2) inclusions in sphalerite-galena- pyrite-tetrahedrite ± stibnite (Fig. 6c,d). Gold grains are typically less than 10 mm.

V4: A fourth vein generation (V4) is characterized by thin,

colloform banded chalcedonic quartz-carbonate ± pyrite ± chalcopyrite veins (Fig. 4f). They vary in width from 5 to 60 mm. Carbonate is typically pink and manganiferous. V4 veins crosscut both the metamorphic fabric and V3 stage veins.

V5: Thin (1-5 mm) ferroan carbonate veinlets (V5) cut the

metamorphic foliation and all pre-existing vein types. This vein generation has no known association with sulphides or gold.

ToNI TIGER

The local host rocks include meta-aplite (Fig. 7a,b), biotite- quartz-feldspar schist (Fig. 7c-e), biotite hornfels, and garnet-diopside skarn (Fig. 7f). All rock types are cut by 1 cm to 1 m-wide, milky white quartz ± molybdenite veins (Figs. 7c-e and 8c) that occupy subvertical, conjugate fracture sets trending north and northeast. Molybdenite is also observed as wall rock disseminations in vein halos in biotite-quartz-feldspar schist and skarn. Veins have biotite-destructive chlorite-muscovite envelopes where they cut biotite-bearing host rocks (Fig. 7c,f). Idiomorphic garnet of hydrothermal origin is common along the margins of quartz ± molybdenite veins cutting the skarn unit.

Fluid inCluSion propErtiES

BoUlEVARD

Petrographic observations and a small number of microthermometric analyses were carried out on samples

of quartz-hosted fluid inclusions from gold-stage V3 veins at Boulevard. A homogenous population of aqueous-carbonic fluid was observed, which, based on clathrate melting and CO2 homogenization temperatures, contains 15 to 24 mol % CO2, ~2 to 3 wt % NaCl, and a bulk density of 0.8 to 0.85 g/cm3 (Fig. 8a,b). Homogenization temperatures and equation-of-state modeling, using the approach of Allan et al. (2011), suggest that fluids were trapped between 280 and 310°C or greater, at a pressure of 1100 bar or more. This pressure corresponds to a minimum depth of approximately 4.0 km at lithostatic pressures (assuming a rock density of 2800 kg/m3).

ToNI TIGER

A homogenous population of aqueous-carbonic fluid inclusions was observed in vein quartz from Toni Tiger (Fig. 8c). Microthermometric measures of clathrate melting and CO2 homogenization demonstrate that this fluid contains ~16 mol % CO2 and ~3 wt % NaCl, with a bulk density of ~0.88 g/cm3 (Fig. 8d). Fluids were trapped at 280°C or more, at a minimum pressure of 1050 bar (>3.8 km at lithostatic pressure, assuming a rock density of 2800 kg/m3). The composition and trapping conditions of fluid inclusions from Toni Tiger veins are therefore indistinguishable from those in V3 veins at Boulevard.

u-pb GEoCHronoloGY

SaMplES and MEtHodoloGY

U-Pb dating of zircon was used to determine the crystallization age of various units in the Independence Creek area, including the metamorphic rock package, Dawson Range batholith, Coffee Creek granite, and subvolcanic rocks. The sample suite includes six samples of metaplutonic rocks, including meta-aplite cut by quartz-molybdenite veins at Toni Tiger (I034207); orthogneiss containing minor disseminated molybdenite (I034224); and quartz-feldspar-biotite schist (GM11-9b, MA11-004BV, MA11-005BV, MA11-006BV). The suite also includes three samples of the Dawson Range batholith (I034239, YGR-BV-004, 99M-106-b); three samples of the Coffee Creek phase (YGR-BV-002, 99M-105, 99M-107); and a single sample of quartz-feldspar rhyodacite porphyry (MA11-001BV).

Zircon grains recovered from plutonic and metaplutonic rocks are all relatively coarse grained (up to 200 mm long) and show a similar range of external morphology and internal structure. Zircons are typically clear, euhedral,



81

moly

moly

Figure 7. Rock types and vein features of the Toni Tiger molybdenum occurrence: (a) weakly foliated meta-aplite from the Toni Tiger occurrence; (b) same meta-aplite as in (a), but interfoliated with biotite schist and affected by a later phase of folding; (c) biotite metagranitoid cut by a quartz-molybdenite vein with a chloritic alteration halo; (d) typical milky quartz vein with molybdenite from the Toni Tiger occurrence; (e) milky quartz vein with molybdenite along its margins (and as wall rock disseminations); and (f) pyroxene-garnet skarn with domains of biotite hornfels. moly = molybdenite.

a b

c d

e f



and colourless to pale yellow-brown. No obvious internal zoning was observed and morphologies range from stubby octahedral prisms to multi-faceted terminations.

The methodology for laser ablation ICP-MS analysis at the Pacific Centre for Isotopic and Geochemical Research (PCIGR), University of British Columbia, follows that described in Tafti et al. (2009) and Beranek and Mortensen (2011). The 206Pb/238U age is the most precisely determined age for the Phanerozoic zircons in question and is interpreted as the best estimate for the crystallization age of the samples. Assigned ages are based on a weighted average of overlapping, concordant 206Pb/238U ages of individual analyses for each sample. Errors are quoted at the 2s level.

rESultS

Results are presented in conventional U-Pb concordia plots and weighted average 206Pb/238U age summary plots in Figures 9-12 and are shown with sample locations in Table 1. Full analytical data are presented in Appendix 1.

All meta-igneous samples yielded Late Permian crystallization ages in the range of 250 to 267 Ma (Figs. 9 and 10). The molybdenite-bearing, weakly foliated meta-aplite sample (I034207) from Toni Tiger yields a well-constrained age of 251.3 ± 1.3 Ma (Fig. 9b), which suggests that this unit may be part of a post-D2 intrusive suite of crustally derived intrusions that includes the Jim Creek pluton of the southern Klondike District (Beranek and

Figure 8. (a) photomicrograph of a V3-generation quartz-carbonate vein (cross-polarized light) from the

Boulevard gold prospect; (b) quartz-hosted fluid inclusions from the vein in (a), containing aqueous liquid (aq), Co

2 liquid, and Co

2 vapour (photograph taken at 25°C); (c) photomicrograph of molybdenite in quartz from

the Toni Tiger occurrence (combined cross-polarized transmitted light and reflected light); (d) photomicrograph of fluid inclusions in quartz associated with molybdenite mineralization in (c). Fluid inclusions contain aqueous liquid and a supercritical Co

2 phase (photograph taken just above the homogenization temperature of the

carbonic liquid and vapour phase at 29°C). The inset shows both Co2 phases below the homogenization

temperature (~25°C), for the same large fluid inclusion in (d). cb = carbonate; g = gas phase; l = liquid phase; aq = aqueous phase (other abbreviations as in Figures 4 and 7).

cb

qtz

CO2(g)aq

CO2(l)

aqCO2

moly

qtz

100 µm

100 µm

10 µm

10 µm

aq

CO2(g)

CO2(l)

25°C

29°C25°C

a b

c d



83

weighted average = 255.2 ± 0.6 Ma(MSWD = 0.92; prob. of fit = 0.56)



270

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206 P

b/23

8 U

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b/23

8 U20

6 Pb/

238 U

Figure 9. Conventional concordia diagrams and plots of weighted average 206Pb/238U ages for meta-igneous samples from the study area: (a) and (b) sample I034207 – molybdenite-bearing meta-aplite from Toni Tiger; (c) and (d) sample I034224 - orthogneiss with disseminated molybdenite; (e) and (f) sample GM11-9b – quartz-feldspar-biotite schist. Error ellipses on concordia diagrams and error bars on weighted average age plots are shown at 2s level. Red bars on weighted average age plots were used in the age calculation; blue bars were rejected.

a b

c d

e f






290

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0.037

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0.24 0.26 0.28 0.30 0.32 0.34 240

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b/23

8 U

207Pb/235U

206 P

b/23

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238 U

207Pb/235U

207Pb/235U

Figure 10. Conventional concordia diagrams and plots of weighted average 206Pb/238U ages for meta-igneous samples from the study area: (a) and (b) sample MA11-004BV - quartz-feldspar-biotite schist; (c) and (d) sample MA11-00BV – quartz-feldspar-biotite schist; (e) and (f) sample MA11-006BV - quartz-feldspar-biotite schist. Symbols as in Figure 9.

a b

c d

e f



85

Mortensen, 2011) and the Teacher intrusion in the White Gold area (Mortensen, unpublished data). A sample of quartz-feldspar-biotite schist (GM11-9b) yields a similar age of 249.6 ± 4.4 Ma (Fig. 9f); however, only a small amount of zircon was recovered from this sample and the age is therefore relatively imprecise (based on only seven analyses). All of the other well-foliated meta-igneous rock units yield Late Permian ages ranging from 255 to 267 Ma, which are consistent with ages reported elsewhere for metavolcanic and metaplutonic phases of the Klondike arc assemblage (Mortensen, 1990; Ruks et al., 2006; Beranek and Mortensen, 2011).

Two samples of granodiorite from the Dawson Range batholith give ages of 102.0 ± 0.4 Ma and 100.2 ± 0.3 Ma (Fig. 11b,d). An aplite dyke that cuts Dawson Range granodiorite gives an age of 102.5 ± 0.9 Ma (Fig. 11f). Three biotite granite samples of the Coffee Creek granite give ages ranging from 99 to 100 Ma (Fig. 12b,d,f). The ages are therefore consistent with the Coffee Creek granite being a slightly younger magmatic phase of the Whitehorse plutonic suite than the Dawson Range batholith.

The sample of quartz-feldspar rhyodacite porphyry from subcrop in the study area (sample MA11-001BV) gives an age of 57.2 ± 1.0 Ma (latest Paleocene), which is similar to ages obtained for felsic dykes and plugs throughout the Dawson Range and areas to the north (Mortensen, unpublished data).

40ar/39ar GEoCHronoloGY

SaMplE and MEtHodoloGY

40Ar/39Ar geochronology was used to determine the age of a sample of hydrothermal sericite from a quartz-carbonate-stibnite-gold vein with a strong sericite selvage (sample BV23_70.37m from diamond drill core). The hydrothermal sericite is interpreted to have formed at the same time as gold and stibnite mineralization.

Sericite grains were hand-picked from the sample under a binocular microscope, wrapped in aluminum foil, and stacked in an irradiation capsule with similar-aged samples and neutron flux monitors (Fish Canyon Tuff sanidine (FCS); 28.03 Ma (Renne et al., 1998). The methodology used in this study for 40Ar/39Ar dating at PCIGR is similar to that described by Mortensen et al. (2010). The Boulevard sericite sample was irradiated from May

4 to 5, 2011 at the McMaster Nuclear Reactor in Hamilton, Ontario, for 45 MWH, with a neutron flux of approximately 6 x 1013 neutrons/cm2/s. Analyses (n = 45) of 15 neutron flux monitor positions produced errors of <0.5% in the J value. The sample was split into two separate aliquots after irradiation, and the samples were analysed from June through October 2011 at the Noble Gas Laboratory in the PCIGR.

rESultS

The first aliquot of hydrothermal sericite yielded a plateau age of 95.9 ± 0.9 Ma (MSWD = 0.97, probability = 0.41; plateau based on 74.3% of the 39Ar; Fig. 13; Table 2). The duplicate analysis did not settle to enough steps to yield a plateau age, but the results are consistent with the age obtained from the first aliquot.

187re/187os GEoCHronoloGY

SaMplES and MEtHodoloGY

187Re/187Os dating methods were utilized to constrain the age of molybdenite mineralization at the Toni Tiger showing. Two samples of molybdenite were dated: (a) a quartz-molybdenite vein crosscutting a meta-aplite (I034208); and (b) a quartz-molybdenite vein crosscutting garnet-actinolite-diopside skarn (I034229). Molybdenite in each sample occurs as coarse-grained rosettes mantled by vein quartz.

Samples were prepared and analysed by R. Creaser at the Radiogenic Isotope Laboratory at the University of Alberta according to the methods described by Selby and Creaser (2004) and Markey et al. (2007).

rESultS

Analytical results for the two samples are given in Table 3. Sample I034208 yielded a Re-Os age of 95.0 ± 0.4 Ma. Sample I034229 contains high common Os, hence the derived age is sensitive to assumed initial 187Os/188Os ratio. Assuming an initial 187Os/188Os value of 0.3, a somewhat younger age of 92.4 ± 0.7 Ma is determined for this sample.



Figure 11. Conventional concordia diagrams and plots of weighted average 206Pb/238U ages for samples of the Dawson Range batholith in the study area: (a) and (b) sample I034239 - biotite-hornblende granodiorite; (c) and (d) sample YGP-BV-004 - biotite-hornblende granodiorite; (e) and (f) sample 99M-106-b – aplite dyke cutting granodiorite. Symbols as in Figure 9.

106

104

102

100

98

96

0.0148

0.0152

0.0156

0.0160

0.0164

0.0168

0.092 0.096 0.100 0.104 0.108 0.112 0.116 96

98

100

102

104

106

108

104

100

96

0.0146

0.0150

0.0154

0.0158

0.0162

0.0166

0.0170

0.0174

0.08 0.09 0.10 0.11 0.12 0.13 95

97

99

101

103

105

107

109

116

112

108

104

100

96

0.0145

0.0155

0.0165

0.0175

0.0185

0.08 0.09 0.10 0.11 0.12 0.13 0.14 94

98

102

106

110

114




206 P

b/23

8 U

207Pb/235U

206 P

b/23

8 U20

6 Pb/

238 U

207Pb/235U

207Pb/235U

a b

c d

e f



87

114

110

106

102

98

94

90

86

0.013

0.014

0.015

0.016

0.017

0.018

0.08 0.09 0.10 0.11 0.12 0.13 86

90

94

98

102

106

110

114

220

180

140

100

0.010

0.014

0.018

0.022

0.026

0.030

0.034

0.038

0.04 0.08 0.12 0.16 0.20 0.24 0.28

70

90

110

130

150

170

190

210

230

108

104

100

96

0.0144

0.0148

0.0152

0.0156

0.0160

0.0164

0.0168

0.08 0.09 0.10 0.11 0.12 0.13

93

95

97

99

101

103

105

107

90

80

70

60

50

40

0.005

0.007

0.009

0.011

0.013

0.015

0.00 0.04 0.08 0.12 0.16 40

50

60

70

80

90





206 P

b/23

8 U

207Pb/235U

206 P

b/23

8 U20

6 Pb/

238 U

206 P

b/23

8 U

207Pb/235U

207Pb/235U

207Pb/235U

Figure 12. Conventional concordia diagrams and plots of weighted average 206Pb/238U ages for samples of the Coffee Creek intrusions and a young subvolcanic rock in the study area: (a) and (b) sample YGR-BV-002 – biotite granite; (c) and (d) sample 99M-105 – biotite granite; (e) and (f) sample 99M-107 – biotite granite; (g) and (h) sample MA11-001BV - quartz-feldspar rhyodacite porphyry. Symbols as in Figure 9.

a b

c d

e f

g h



Sample rock description unitlocation (nad83

utM zone 7n) age (Ma) ± 2sEasting northing

MEtaMorpHiC roCkS

I034207 meta-aplite* Klondike assemblage 577980 6966729 251.3 1.3

I034224 felsic orthogneiss* Klondike assemblage 578139 6966731 255.2 0.6

GM11-9b quartz-feldspar-biotite schist Klondike assemblage 572444 6980691 249.6 4.4

MA11-004BV quartz-feldspar-biotite schist Klondike assemblage 563229 6972572 267.2 5.9



plutoniC roCkS

I034239 biotite-hornblende granodioriteDawson Range batholith

574610 6963807 100.2 0.3

YGR-BV-004 biotite-hornblende granodioriteDawson Range batholith

566127 6967606 102.0 0.4

99M-106-b aplite cutting granodioriteDawson Range batholith

566278 6961313 102.5 0.9

YGR-BV-002 biotite granite* Coffee Creek granite 573497 6968539 99.5 0.7

99M-105 biotite granite Coffee Creek granite 577775 6968097 99.2 0.9

99M-107 biotite granite Coffee Creek granite 560386 6973241 99.0 0.3

SuBVolCaniC roCkS

MA11-001BVquartz-feldspar rhyodacite porphyry

Skukum volcanic suite 574845 6964377 57.2 1.0

*molybdenite observed in heavy mineral separates

Table 1. 206Pb/238U zircon ages for Independence Creek samples.

0

40

80

120

160

0 20 40 60 80 100

plateau age = 95.9 ± 0.9 MaMSWD = 0.97, prob. of fit = 0.41

includes 74.3% of the 39Ar

age

(Ma)

cumulative 39Ar percent

Figure 13. Age spectra for step-heating of sericite sample BV23-70.37m from the Boulevard property. Error boxes and the calculated age are given at the 2s level. Steps shown in red define the calculated plateau age; steps in blue were rejected.



89

diSCuSSion

u-pb GEoCHronoloGY

The 250 to 267 Ma age range of meta-igneous rocks in the Independence Creek area overlaps with that of the Late Permian Klondike volcanic arc assemblage and intrusive equivalents (Sulphur Creek orthogneiss) elsewhere in western Yukon (Mortensen, 1990; Ruks et al., 2006; Beranek and Mortensen, 2011). We therefore concur with recent mapping by the Geological Survey of Canada which demonstrates that exposures of Klondike arc rocks in the Ladue River area (NTS 115N) continue eastward along the northern margin of the Dawson Range batholith into the Stevenson Ridge map sheet (NTS 115J) (Ryan et al., in prep.).

The mid-Cretaceous crystallization ages determined for the Dawson Range batholith (ca. 100 to 103 Ma) are consistent with current geochronological compilations (Breitspreicher and Mortensen, 2004). The slightly younger 99 to 100 Ma zircon ages for the Coffee Creek granite are consistent with the interpretation of Templeman-Kluit and Wanless (1975) that this unit is a slightly younger intrusive phase of the Whitehorse plutonic suite.

Subvolcanic rocks cutting the Dawson Range batholith were determined to be 57.2 ± 1.0 Ma, and are therefore age-equivalent to the previously mapped Paleocene Skukum volcanic rocks 4 km to the south (Templeman-Kluit, 1974), and volcanic and subvolcanic rocks elsewhere in western Yukon (Breitsprecher and Mortensen, 2004).

isotope ratios

laser power (%) 40ar/39ar 1s 37ar/39ar 1s 36ar/39ar 1s Ca/k %40ar atm f 39ar 40ar*/39ark age 2s

2.20 W 22.38 0.40 0.62 0.09 0.067 0.006 1.13 88.77 0.34 2.515 27.44 ± 39.95

2.60 W 24.21 0.22 0.07 0.03 0.061 0.002 0.12 74.58 1.54 6.154 66.43 ± 12.64

3.00 W 13.67 0.09 0.47 0.02 0.010 0.000 0.87 22.50 6.68 10.596 112.92 ± 2.08

3.50 W 10.72 0.07 0.28 0.01 0.002 0.000 0.52 4.35 14.70 10.259 109.44 ± 1.43

4.00 W 9.20 0.06 0.01 0.00 0.001 0.000 0.02 2.27 51.34 8.987 96.21 ± 1.17

4.40 W 9.26 0.06 0.01 0.00 0.001 0.000 0.02 2.69 12.50 9.014 96.50 ± 1.23

5.00 W 9.70 0.06 0.02 0.01 0.003 0.000 0.04 8.38 5.12 8.891 95.22 ± 1.59

6.00 W 10.11 0.06 0.06 0.01 0.004 0.000 0.10 12.15 5.39 8.883 95.13 ± 1.61

7.00 W 13.01 0.14 0.02 0.02 0.016 0.001 0.03 35.99 2.39 8.330 89.36 ± 5.12

J = 0.0060810 ± 0.0000304 Volume 39ArK = 0.378 Integrated Date = 99.34 ± 0.58 Ma

Plateau age = 95.93 ± 0.89 Ma (2s, including J-error of 0.6%)

MSWD = 0.97, probability = 0.41

Includes 74.3% of the 39Ar (steps 5 through 8)

Inverse isochron (correlation age) results, plateau steps: Model 1 Solution (± 95%-conf.) on 9 points

Age = 98.4 ± 7.6 Ma

Initial 40Ar/36Ar = 350 ± 170 MSWD = 75, probability = 0

Table 2. 40Ar/39Ar data for Boulevard sericite (Sample BV23_70.37m)

Sample re (ppm) ± 2s 187re (ppb) ± 2s 187os (ppb) ± 2s total common os (pg)

Model age (Ma)

± 2s

I034208 42.96 0.11 27002 71 42.76 0.04 1.6 95.0 0.4

I034208 (duplicate)

43.00 0.11 27029 70 42.76 0.04 1.6 94.9 0.4

I034228 27.62 0.08 17361 53 26.74 0.16 90.8 92.4 0.7

Table 3. Re-os data for Toni Tiger molybdenite samples.



tiMinG oF MinEralization

The 95.0 ± 0.4 Ma 187Re/187Os model age for molybdenite at Toni Tiger overlaps within 2s error with the 95.9 ± 0.9 Ma 40Ar/39Ar cooling age for hydrothermal sericite at Boulevard. While the latter age could be interpreted as a minimum, there is sufficient geological evidence (e.g., common structural style and fluid inclusion properties) that Boulevard and Toni Tiger are related hydrothermal systems. Therefore, we interpret the 187Re/187Os and 40Ar/39Ar methods as recording coeval mineralizing events at ca. 96-95 Ma. Importantly, the mineralization age post-dates crystallization of the Dawson Range batholith and Coffee Creek granite by 3-4 m.y. No younger phase of the Whitehorse plutonic suite has yet been recognized in the Independence Creek area (or anywhere else in western Yukon), nor do the field relationships suggest a magmatic role in mineralization. It is likely that heat and fluid flux related to the emplacement of the Dawson Range batholith and Coffee Creek plutonic suites were responsible for hornfelsing and skarnification in the vicinity of the Toni Tiger showing. However, the geochronologic results of this study suggest that Au-As-Sb-(Pb-Zn-Cu) and Mo mineralization record a distinct and younger event.

The low-salinity, aqueous-carbonic composition of fluids attending mineralization is consistent with orogenic fluids documented worldwide (Groves et al., 2003). The association between gold and pyritic alteration halos to quartz-carbonate veins suggests that wall rock sulphidation is an important gold-precipitating mechanism. Depressurization associated with faulting and brecciation may also play an important role in destabilizing gold-bisulphide complexes (e.g., Wilkinson and Johnston, 1996).

Molybdenite is not commonly reported in orogenic systems; however, the geochronological and fluid inclusion evidence suggests that Toni Tiger is part of the same post-magmatic orogenic system as Boulevard. The association of molybdenite with moderate temperature, moderate pressure, dilute aqueous-carbonic fluids implies that molybdenite transport occurs in nature at P-T-X conditions quite dissimilar to those encountered in high-temperature, low-pressure systems such as porphyry Mo deposits. We speculate that molybdenite may have been remobilized from the felsic metaplutonic host rocks, which locally contain significant background concentrations of molybdenite.

rEGional SiGniFiCanCE

This study contributes to the metallogenic framework of the Dawson Range, and may be relevant to other structurally-hosted gold prospects, such as the Coffee gold deposit northeast of the Independence Creek drainage (Kaminak Gold Corp.), and gold in the Moosehorn Range (parts of NTS 115N and 115K; Fig. 1). Mineralization in the Coffee area occurs within a series of structural corridors that cut all rock units, including the mid-Cretaceous Coffee Creek granite (Wainwright et al., 2011). A common, ca. 96-95 Ma metallogenesis for gold mineralization at Boulevard and Coffee is permissible given field relationships, although Coffee is dominated by brittle (shallow?) features, whereas vein swarms at Boulevard more likely represent deeper crustal levels. In the case of the Moosehorn Range, mineralization has been dated by 40Ar/39Ar methods to 93-92 Ma, which post-dates the main phase of the magmatism by ~8 m.y. (Joyce, 2002). Fluid inclusions associated with the Moosehorn veins also overlap strongly in composition and trapping conditions with those at Boulevard. On the basis of currently available geochronological data and geological relationships, we propose a general model in which exhumation of the Dawson Range shortly after cessation of arc magmatism in mid-Cretaceous time was accompanied by brittle deformation, fluid flow, and mineralization. However, the tectonic and structural setting of the Dawson Range at this time is still not completely understood.

aCknoWlEdGEMEntSThis study is part of GGM’s MSc project, which was a component of the Yukon Gold Project, a collaborative research venture between the Mineral Deposit Research Unit (UBC) and a consortium of industry participants, including Aldrin Resource Corp., Barrick Gold Corp., Full Metal Minerals Corp., Gold Fields Canada Exploration, Northern Freegold Resources Ltd., Kinross Gold Corp., Radius Gold Inc., Silver Quest Resources Ltd., Taku Gold Corp., Teck Resources Ltd., and Underworld Resources Inc. The Natural Science and Engineering Research Council of Canada (NSERC) also provided matching funds for the industry contribution. We are grateful for the logistical, financial, scientific, and editorial contributions of Silver Quest Resources (now Independence Gold Corp.) and Equity Exploration Ltd., and in particular Kendra Johnston, Darcy Baker, Dave Pawliuk, Randy Turner, and Ryan Congdon. Jim Ryan of the Geological Survey of Canada is thanked for his thoughtful review and his contributions to the geological understanding of the Dawson Range.



91

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Selby, D. and Creaser, R.A., 2004. Macroscale NTIMS and microscale LA-MC-ICP-MS Re-Os isotopic analysis of molybdenite: Testing spatial restrictions for reliable Re-Os age determinations, and implications for the decoupling of Re and Os within molybdenite. Geochimica et Cosmochimica Acta, vol. 68, p. 3897-3908.

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93

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Frac

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isot

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rat

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isot

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age

sB

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n co

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s pe

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ap

pEn

dix

1 (c

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: LA

-ICP-

MS

data

for

U-P

b an

alys

is o

f zirc

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50.

0019

810

0.4

4.0

101.

11.

351

.397

.622

035

5516

846

355

385

1892

2836

47

160.

1013

90.

0030

50.

0158

80.

0001

60.

330.

0464

80.

0014

298

.12.

810

1.6

1.0

22.4

70.6

9821

5410

253

779

8093

529

1842

9910

170.

1043

20.

0032

80.

0159

40.

0001

70.

340.

0482

30.

0015

410

0.8

3.0

101.

91.

111

0.5

73.6

111

057

9828

297

811

6648

3159

4594

89

180.

1054

80.

0036

80.

0157

90.

0001

80.

330.

0480

40.

0017

010

1.8

3.4

101.

01.

110

1.0

81.6

810

3905

189

459

4695

320

9731

2493

190.

1000

10.

0037

50.

0156

70.

0002

00.

340.

0479

90.

0018

396

.83.

510

0.2

1.3

97.4

89.1

418

4915

237

479

5538

327

8239

6486

200.

1121

10.

0085

00.

0168

40.

0004

30.

340.

0481

10.

0037

110

7.9

7.8

107.

62.

710

4.6

172.

912

312

3241

157

379

4086

316

4124

3420

Cof

fee

Cre

ek g

rani

te (s

ampl

e Y

GR

-BV

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)

10.

1026

60.

0028

30.

0156

00.

0001

50.

350.

0472

30.

0013

099

.22.

699

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060

.664

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056

0927

110

9210

0851

2652

4019

05

20.

1035

10.

0031

40.

0155

50.

0001

70.

360.

0486

30.

0014

810

0.0

2.9

99.5

1.1

130.

169

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353

1826

476

377

001

2568

3822

95

30.

1025

40.

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50.

0156

20.

0001

90.

340.

0466

70.

0016

799

.13.

499

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232

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034

1516

245

340

592

1598

2444

94

40.

1105

30.

0028

20.

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30.

0001

50.

370.

0500

20.

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610

6.4

2.6

101.

91.

019

5.8

57.7

16

1777

390

737

6440

9591

8271

1247

606

50.

1018

10.

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80.

0154

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0002

10.

360.

0475

60.

0018

298

.43.

698

.51.

376

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5525

092

082

488

2477

3746

15

60.

1017

60.

0065

10.

0146

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0003

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360.

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00.

0032

598

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093

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119

0.5

144.

733

1939

3820

088

868

418

1987

3018

34

70.

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10.

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00.

0151

90.

0001

70.

360.

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80.

0015

298

.63.

097

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111

3.0

72.4

08

1031

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612

4716

3869

5025

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97

80.

1023

80.

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30.

0154

00.

0003

00.

350.

0478

70.

0027

199

.05.

398

.51.

991

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0.0

014

3232

157

468

3818

015

5623

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90.

1040

20.

0036

90.

0154

90.

0002

00.

360.

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70.

0017

210

0.5

3.4

99.1

1.2

112.

481

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1050

2524

689

779

070

2401

3633

08

100.

1059

10.

0083

40.

0155

70.

0004

40.

360.

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90.

0037

910

2.2

7.7

99.6

2.8

73.3

180.

413

1431

3115

045

841

514

1447

2253

12

110.

1060

10.

0051

20.

0155

00.

0002

80.

370.

0505

50.

0024

710

2.3

4.7

99.2

1.8

220.

210

9.3

024

7264

372

1020

1106

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7152

5287

120.

1057

70.

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50.

0160

50.

0003

90.

340.

0495

30.

0035

910

2.1

6.9

102.

62.

517

3.0

160.

70

3218

4292

252

2876

688

912

8710

Frac

tion

isot

opic

rat

ios

isot

opic

age

sB

ackg

rou

nd c

orre

cted

mea

n co

unt

s pe

r se

cond

at

spec

ifie

d m

ass

207 p

b/23

5 u%

1s

206 p

b/23

8 u%

1s

rho

207 p

b/20

6 pb

% 1

s 20

7 pb/

235 u

± 1s

20

6 pb/

238 u

± 1s

20

7 pb/

206 p

b±

1s

202

204

206

207

208

232

235

238

ap

pEn

dix

1 (c

ontin

ued)

: LA

-ICP-

MS

data

for

U-P

b an

alys

is o

f zirc

ons



130.

1026

60.

0053

50.

0155

60.

0002

70.

330.

0477

70.

0025

199

.24.

999

.51.

786

.912

1.1

00

1877

9022

224

641

901

1353

31

140.

1044

80.

0052

90.

0156

60.

0002

70.

340.

0483

70.

0024

710

0.9

4.9

100.

21.

811

7.5

116.

20

026

0012

743

742

164

1242

1862

88

150.

1096

50.

0033

20.

0154

10.

0001

70.

360.

0515

80.

0015

510

5.6

3.0

98.6

1.1

266.

967

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087

5345

612

6811

9562

4250

6372

30

160.

1032

20.

0045

80.

0158

30.

0002

50.

360.

0466

40.

0020

899

.74.

210

1.2

1.6

30.7

103.

60

1577

8236

616

0314

2208

3631

5520

01

170.

1093

20.

0080

50.

0166

90.

0004

20.

340.

0470

70.

0035

010

5.3

7.4

106.

72.

752

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8.7

013

2355

111

322

3047

610

4815

8469

180.

1011

00.

0038

00.

0152

10.

0002

00.

350.

0474

90.

0017

897

.83.

597

.31.

373

.187

.50

548

8023

373

760

813

2368

3602

74

190.

1026

10.

0032

60.

0157

60.

0001

80.

360.

0472

80.

0014

999

.23.

010

0.8

1.1

62.9

73.7

300

7450

354

1101

9932

535

4853

0908

200.

1047

60.

0042

10.

0154

40.

0002

20.

350.

0479

90.

0019

310

1.2

3.9

98.8

1.4

97.5

93.7

01

1056

650

931

8929

5478

5004

7690

69

Cof

fee

Cre

ek g

rani

te (s

ampl

e 99

M-1

05)

10.

1033

90.

0032

00.

0153

40.

0001

70.

360.

0482

50.

0014

399

.93.

098

.11.

111

1.5

68.4

016

1173

158

019

9018

9507

6334

8777

76

20.

1047

40.

0031

20.

0156

10.

0001

70.

370.

0486

90.

0013

810

1.1

2.9

99.8

1.1

132.

965

.20

1820

315

1013

3402

3337

8810

921

1493

286

30.

1082

40.

0036

10.

0159

90.

0002

00.

380.

0496

30.

0016

010

4.4

3.3

102.

31.

217

7.9

73.3

06

9917

504

2341

2211

7052

5671

1046

40.

2439

80.

0074

60.

0345

80.

0003

90.

370.

0514

90.

0014

822

1.7

6.1

219.

22.

426

3.0

64.5

1020

2918

915

3830

7915

0998

7117

9674

39

50.

1015

00.

0048

60.

0148

10.

0002

50.

350.

0484

60.

0023

198

.24.

594

.81.

612

1.7

108.

40

039

0619

356

455

271

2151

3019

57

60.

1000

90.

0049

40.

0151

20.

0002

70.

360.

0483

70.

0023

896

.94.

696

.81.

711

7.6

112.

00

039

1919

346

645

604

2183

2965

40

70.

1028

10.

0035

10.

0151

40.

0001

90.

370.

0482

40.

0015

899

.43.

296

.81.

211

1.0

75.7

310

7273

358

1100

1093

9239

3254

9627

80.

1045

30.

0040

70.

0156

60.

0002

20.

360.

0495

40.

0018

810

1.0

3.8

100.

11.

417

3.3

86.5

00

5663

286

1160

1063

7130

9141

3592

90.

1037

40.

0032

50.

0157

70.

0001

80.

360.

0477

70.

0014

110

0.2

3.0

100.

91.

186

.869

.70

1320

375

992

4707

4410

6010

790

1474

918

100.

1028

10.

0040

60.

0153

20.

0002

20.

360.

0485

40.

0018

799

.43.

798

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412

5.9

88.1

00

8598

425

1609

1549

0746

6764

0612

110.

1047

30.

0036

60.

0155

80.

0002

00.

370.

0481

40.

0016

110

1.1

3.4

99.6

1.3

106.

377

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2094

2446

220

9019

3303

4977

6903

28

120.

1030

00.

0037

50.

0158

50.

0002

10.

360.

0467

50.

0016

499

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510

1.4

1.3

36.4

82.0

7414

6636

315

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1070

4434

5947

7455

130.

1051

40.

0052

90.

0155

60.

0002

80.

360.

0492

70.

0024

610

1.5

4.9

99.6

1.8

160.

611

2.7

6220

3412

170

494

5044

318

3324

9767

140.

1027

80.

0043

30.

0152

90.

0002

30.

360.

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50.

0020

299

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097

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514

5.7

93.8

740

8571

426

1615

1497

4046

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8081

150.

1058

40.

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60.

0153

70.

0002

10.

360.

0490

90.

0018

210

2.1

3.7

98.3

1.4

151.

984

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1686

9443

313

1012

2623

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6438

45

160.

1049

20.

0052

50.

0159

00.

0002

80.

350.

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90.

0023

810

1.3

4.8

101.

71.

810

3.5

113.

00

047

7523

371

074

355

2505

3415

46

170.

1086

10.

0039

20.

0152

10.

0002

00.

360.

0517

40.

0017

810

4.7

3.6

97.3

1.3

273.

977

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2720

121

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1502

498

180.

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70.

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10.

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360.

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00.

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110

5.1

4.2

97.8

1.5

249.

792

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1243

1922

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610

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3209

53

190.

1031

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30.

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360.

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20.

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599

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910

0.3

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29.9

92.8

027

5749

271

821

7638

029

6941

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200.

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20.

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80.

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50.

0001

90.

360.

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10.

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310

2.5

3.3

101.

41.

210

9.4

73.2

890

6101

929

7822

748

2E+0

631

613

4368

048

Cof

fee

Cre

ek g

rani

te (s

ampl

e 99

M-1

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10.

1034

90.

0014

30.

0156

10.

0000

90.

420.

0480

20.

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710

0.0

1.3

99.9

0.6

98.9

34.0

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1992

696

936

6740

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518

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7

20.

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80.

0160

90.

0000

90.

390.

0491

20.

0007

210

6.2

1.5

102.

90.

615

3.7

33.8

00

1750

187

118

4120

8355

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1537

814

30.

1046

90.

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90.

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20.

0000

90.

440.

0483

40.

0006

510

1.1

1.3

99.3

0.6

115.

931

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2027

749

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7450

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197

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153

40.

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80.

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60.

370.

0479

80.

0013

799

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799

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097

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096

1846

725

7628

2684

5296

8718

89

50.

1028

30.

0014

60.

0154

80.

0000

90.

410.

0481

10.

0006

999

.41.

399

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610

4.9

33.7

021

2596

212

6540

3445

1622

1442

623

6808

8

60.

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70.

0009

70.

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90.

0000

70.

480.

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80.

0004

599

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999

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487

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139

500

1911

6471

7063

6421

778

3577

980

70.

1058

90.

0015

60.

0154

10.

0000

90.

400.

0489

70.

0007

310

2.2

1.4

98.6

0.6

146.

334

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2318

733

929

2609

3128

5810

297

1716

416

80.

1019

70.

0014

00.

0153

90.

0000

90.

430.

0478

80.

0006

798

.61.

398

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692

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1227

552

1335

6336

7021

2415

385

2527

561

90.

1012

60.

0040

90.

0152

90.

0002

20.

360.

0470

80.

0019

497

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897

.81.

453

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80

4816

229

834

9173

826

6544

4486

100.

1026

60.

0016

70.

0153

40.

0001

00.

400.

0480

80.

0008

099

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598

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610

3.2

38.8

4244

2065

410

0538

8047

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1151

818

9984

2

110.

1032

80.

0014

60.

0154

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0000

90.

410.

0480

70.

0006

999

.81.

398

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610

2.8

33.6

430

2222

810

8127

4830

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7

120.

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80.

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70.

0000

70.

420.

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60.

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197

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098

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551

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229

494

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4534

5327

2716

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094

130.

1043

80.

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20.

390.

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0.8

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0.8

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11

140.

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90.

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60.

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10.

390.

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10.

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810

7.5

1.9

97.8

0.7

272.

442

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1224

701

1291

3507

4028

2913

647

2278

058

150.

1037

80.

0014

40.

0154

90.

0000

90.

420.

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30.

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710

0.3

1.3

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94.6

34.1

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2988

014

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2

160.

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610

0.8

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126

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90.

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10.

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350.

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610

2.6

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101.

12.

611

2.3

170.

00

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351

036

1344

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23

180.

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90.

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360.

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80.

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699

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298

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287

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2754

4549

78

190.

1065

00.

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50.

0155

80.

0001

00.

410.

0479

60.

0007

510

2.8

1.5

99.7

0.6

96.3

38.0

00

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9958

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1428

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7

200.

1078

90.

0017

50.

0159

10.

0001

00.

390.

0479

40.

0007

910

4.0

1.6

101.

80.

795

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1517

309

838

1980

2065

4392

0715

3050

8

SuB

Vo

lCa

niC

ro

Ck

S

Qua

rtz-

feld

spar

rhy

odac

ite p

orph

yry

(sam

ple

MA

11-0

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V)

10.

0730

90.

0107

80.

0087

50.

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80.

290.

0583

20.

0088

071

.610

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454

1.0

300.

50

049

428

106

1870

036

482

084

20.

0568

60.

0039

90.

0088

70.

0002

20.

350.

0456

70.

0032

856

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856

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40.

114

5.3

330

1799

8236

781

481

1336

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12

30.

0456

80.

0111

20.

0088

50.

0004

40.

200.

0353

10.

0086

945

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80.

10.

00

2651

218

115

2441

336

684

420

40.

0508

80.

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40.

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50.

0003

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tion

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for

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is o

f zirc

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Frac

tion

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age

sB

ackg

rou

nd c

orre

cted

mea

n co

unt

s pe

r se

cond

at

spec

ifie

d m

ass

207 p

b/23

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1s

206 p

b/23

8 u%

1s

rho

207 p

b/20

6 pb

% 1

s 20

7 pb/

235 u

± 1s

20

6 pb/

238 u

± 1s

20

7 pb/

206 p

b±

1s

202

204

206

207

208

232

235

238

ap

pEn

dix

1 (c

ontin

ued)

: LA

-ICP-

MS

data

for

U-P

b an

alys

is o

f zirc

ons

mid-cretaceous orogenic gold and molybdenite

Documents