Rare-Earth Element (REE) Potential in the Ray Mountains Area, Central AlaskaA.L. Tuzzolino1*, R.J. Newberry1, and L.K. Freeman2

1 Department of Geology and Geophysics, University of Alaska Fairbanks, 2 Alaska Division of Geological & Geophysical Surveys, Fairbanks, AK, * altuzzolino@alaska.edu

Alaska Miners Association2013 Annual Convention

Anchorage, Alaska6-10 November 2013

Project Overview Panned Concetrates

Background

• The Ruby Batholith, located within the Ray Mountains and Hodzana Uplands, is a Cretaceous monzogranitic unit that contains numerous plutons. This study will focus on ten of these plutons.

• This area has been investigated for the past few decades. There are several reports of anomalous Sn, W, Nb, Ta and rare-earth elements (REEs) (Barkey and Foley, 1986; Barker 1992).

• The rare-earth-bearing minerals, allanite, monazite and xenotime, have been identi�ed in heavy mineral panned concentrates as well as the Ruby Batholith granites.

Purpose

• Assess the REE potential within the Ray Mountains area as part of Alaska’s Strategic and Critical Minerals (SCM) Assessment Program.

• Locate sources of elevated REEs.• Characterize the mineralogy of the plutons.

Methods• Extensive, helicopter-supported geologic mapping and sampling, including whole-rock, gravels, stream

sediments, and heavy mineral panned concentrates.

• Modal analyses via chemical stains, petrography, geochronology, major-oxide and trace element analyses, slab XRF analyses, electron probe microanalysis (EPMA) wavelength dispersive spectroscopy (WDS) routines and elemental mapping, initial Sr isotopic ratios.

Rare-Earth Elements

Study Area

Initial Sr Isotopic Ratios

Radiometric Dating

95

100

105

110

115

120

Pluton

Rad

iom

etric

Age

(Ma)

Zircon U/PbHbl K/Arbiotite K/Ar and Ar/ArRb/Sr

Melazitna

Ray Mntns W

Sithylemenkat

Hot Springs

Kanuti

Hodzana

Fractionation Trends

References

Future Work

Conclusions

No Name Creek Pluton

Acknowledgements

Y39

La57

Ce58

Pr59

Nd60

Pm61

Sm62

Eu63

Gd64

Tb65

Dy66

Ho67

Er68

Tm69

Yb70

Lu71

Light Rare-Earth Elements (LREEs)Heavy Rare-Earth Elements + Y (HREYs)

Silicate Phosphate

Allanite(Ce,Ca,Y,La)2(Al,Fe

2+,Fe3+)3(SiO4)3(OH)Monazite

(Ce,La,Nd,Th)(P,Si)O4

Xenotime(Y,HREE)PO4

Mineralogy• There are hundreds of REE minerals you’ve never heard of!• The common REE minerals in the Ruby Batholith:

• Allanite and monazite have crystal lattice structures that favor the larger LREEs, while xenotime is dominated by the smaller HREYs.

150°W

150°W

150°W

150°W

152°W

152°W 66°N

Ray MountainsEast

Sithlyemenkat Ray River Fort HamlinHills

No Name Creek

Hot Springs

Kanuti

Bonanza

150°W

150°W

150°W

150°W

152°W

152°W 66°N

25km

Dalton Highway

Trans-Alaska PipelineTANANA

BEAVERBETTLES

LIVENGOODMELOZITNA

Tanana

Alatna

Rampart

Fairbanks

Bettles

Stevens Village

20Kilometers

Yukon

River Tertiary

TbTd

KgrRuby Batholith

Ruby Terrane

PzZsrMzZmrPzcr

Pzpr

Quaternary

QTglQTgr

Qua

Tozitna/Angayuchum TerraneJDvMzPzum

• The �eld area is located 125 miles NW of Fairbanks.

Ray MountainsWest

Coal Creek

150°0'0"W150°30'0"W151°0'0"W

66°0

'0"N

0 5 10 15 202.5Kilometers

HREY/LREE1.02 - 1.89

0.56 - 1.01

0.33 - 0.55

0.13 - 0.32

0.00 - 0.12

Fort HamlinHills

150°W

150°W

150°W

152°W

152°W 66°N

25km

TREY (ppm)0 - 500

501 - 1000

1001 - 2000

2001 - 5000

5001 - 52921

0

5

10

15

20

25

30

35

40

45

0 10 20 30 40 50 60 70 80 90 100

Bonanza Coal Creek Fort Hamlin Hills Hot Springs

Kanuti Ray Mountains Ray River Sithylemenkat

QTZ

KSP PL

• The total rare-earth element (TREY) map to the right shows elevated concentrations (ppm) in the southern

portion of the �eld area.

• The HREY/LREE map above shows only the southern plutons. The red squares indicate the highest relative HREY concentrations. These anomalous values were collected from Ray River and No Name Creek, draining plutons of the same names, respetively. Additionally, note that Fort Hamlin Hills appear to be draining material with low

SithylemenkatRay River

No Name Creek

Modal Composition

Mineralogy

• Though there is a great deal of variation in trace elements, the major oxide compositions of the Ruby Batholith specimens plot uniformly as monzogranites.

Petrography & Elemental Mapping

Petrography & Elemental Mapping

12RN344A

Th

100um

100um

100um

Zr Fe BSE

100um

100um100um100um

Zr BSE

• REE Trends: REEs are more abundant in the southern half of the �eld area, and HREYs particularly are abundanct in the southeast.

• The No Name Creek pluton is unlike any of the other nine: Elevated HREYs and the associated minerals, along with minimal fractionation.

0.707

0.706

0.716

0.706

0.714

0.710

0.707

0.7090.711

0.717

0.716

0.716

0.718

0.724 0.719

150°0'0"W

66°0

'0"N

0 2010km

• Left: A photomicrograph of a single allanite crystal within sample 12RN344A from the Sithylemenkat pluton. Note the orange-brown zoning and elongate structure.

• Right: Elemental maps using EPMA WDS on the same allanite crystal. Note that the scales di�er for each element. Elevated Th corresponds with the middle, light-hued zone shown in transmitted light. An enrichment of Ce is evident in the lighter portions as well.

Th Ce Y100um 100um

• Inset: The top-left crystal is zircon, the bottom-right is xenotime. Both crystals are tetragonal, so (as long as xenotime is being crystallized) it’s common the �nd the HREY-beaing mineral in close association with zircon.

• Right: Elemental maps using EPMA WDS aid in identi�cation (even of crystals we can’t see!): The top and bottom grains are monazite, while the largest middle crystal is xenotime--with an inclsuion of monazite. Also in the middle of the cluster, as well as at the bottom, are zircons.

Ce Y100um 100um 100um

100um

12RN319A

LREE Mineralogy

• Top Left: From the No Name Creek pluton, a photomicrograph of a biotite crystal with inclusions of (in order of likely abundance) zircon, monazite, and xenotime. The three grains clustered on the right are the same as those in the elemental map.

100um

Zircon

Xenotime

150°0'0"W

66°0

'0"N

MonaziteAllanite

0 3015km

• The map to the left shows locations of samples with known allanite or monazite.

• Allanite is the typical REE mineral in the north, while monazite is more common in the south.

• Why the segregation?• Allanite is formed in high-Ca systems with a relatively

high fO2. It is also found with apatite and hornblende.

• Monazite requires phosphorous, and is associated with xenotime.

Copyright:© 2013 National Geographic Society,i-cubed

3km

• The Melozitna pluton is south of the study area. Meanwhile, the Hodzana pluton is north of the study area. It is included to dispute a potential N-S trend.

• The Hot Springs and Kanuti plutons are younger than the others. Though the sample locations were not adjacent to the known Tertiary volcanics, it is plausible that the ages were a�ected due to reheating.

Arth, J.G., Zmuda, C.C., Foley, N.K., and Criss, R.E., 1989, Isotopic and trace element variations in the Ruby Batholith, Alaska, and the nature of the deep crust beneath the Ruby and Angayucham Terranes: Journal of Geophysical Research, v. 94, no. B11, p. 15,941-15,955.

Bachmann, E.N., Blessington, M.J., Freeman, L.K., Newberry, R.J., Tuzzolino, A.L., Wright, T.C., and Wylie, William, 2013, Geochemical major-oxide, minor-oxide, trace-element, and rare-earth-element data from rocks and streams sediments collected in 2012 in the Ray Mountains area, Beaver, Bettles, Livengood, and Tanana quadrangles, Alaska: Alaska Division of Geological & Geophysical Surveys Raw Data File 2013-5, 4 p. http://www.dggs.alaska.gov/pubs/id/25386

Barker, J.C., 1992, Investigation of tin-rare earth element placers in the Ray River watershed: USBM OFR 34-91, 63 p., 1 sheet, scale 1:63,360. http://dggs.alaska.gov/pubs/id/21385

Barker, J.C., and Foley, J.Y., 1986, Tin reconnaissance of the Kanuti and Hodzana rivers uplands, central Alaska: U.S. Bureau of Mines IC9104, 27 p. http://dggs.alaska.gov/pubs/id/21287

Freeman, L.K., Newberry, R.J., Bachmann, E.N., Blessington, M.J., Tuzzolino, A.L., and Werdon, M.B., 2012, Geologic Resource Assessment of Strategic and Critical Minerals, Ray Mountains Area, Central Alaska [abs.]: Alaska Miners Association Annual Convention, Nov. 5-11, 2012, p. 16-18. http://akminers.accountsupport.com/abstracts2012.pdf

Miller, T.P., 1989, Contrasting Plutonic Rock Suites of the Yukon-Koyukuk Basin and the Ruby Geanticline, Alaska: Journal of Geophysical Research, v. 94, no. B11, p. 15,969-15,987.

Patton, W.W., Jr., Stern, T.W., Arth, J.G., and Carlson, Christine, 1987, New U/Pb ages from granite and granite gneiss in the Ruby Geanticline and southern Brooks Range, Alaska: Journal of Geology, v. 95, no. 1, p. 118-126.

Ucore Rare Metals, Inc., 2012, Ucore con�rms widespread rare earth mineralization in central Alaska: Press Release January 16, 2012, Halifax, Nova Scotia. http://ucore.com/ucore-con�rms-widespread-rare-earth-mineralization-in-central-alaska

• In the summer of 2013, additional �eld mapping and sample collection (red dots on map) were performed in the No Name Creek area, about ten miles north of the Yukon Bridge.

• The samples will undergo major-oxide and trace element analyses and geochronolgic (Ar-Ar and U-Pn), petrographic and microprobe studies.

The Ray Mountains rare-earth element mineral assessment project is a component of the Strategic and Critical Minerals (SCM) assessment under the Alaska Airborne Geophysical/Geological Mineral Inventory (AGGMI) program funded by the Alaska State Legislature. This student research is being conducted under the Joint Support for Graduate Student Research Internship Program through a Memorandum of Agreement between the Alaska Division of Geological & Geophysical Surveys (ADGGS) and the University of Alaska Fairbanks (UAF) Department of Geology and Geophysics.This poster has been reviewed by Karri Sicard (karri.sicard@alaska.gov).

• Thorough petrographic investigations characterizing mineralogy and alteration.• Construction of an EPMA WDS routine to analyze for monazite and its zoning.• Ar-Ar and U-Pb dating on samples from No Name Creek, Ray River, Hot Springs and Kanuti plutons. • Initial Sr isotopic compositions for the Bonanza, Coal Creek, Fort Hamlin Hills, Ray Mountains and Ray River

plutons.

• Geochemical analyses and petrographic studies of the 2013 No Name Creek samples• Compilation of an REE resource assessment report by the summer of 2014.

• The initial Sr isotopic ratios (SIR) are calculated from an age of 110 Ma.• SIR data taken from Arth et al. (1989)

• The SIR is the ratio: of 87Sr / 86Sr.• Minerals in di�erent geologic settings have variable ratios.• The initial SIR vary greatly in the Ruby Batholith because the starting material

for each pluton appears to be di�erent. Even within plutons, there appears to be a lack of homogeneity.

• SIR in the Ruby Batholith increase to the south.

100

200

300

400

500

600

700

800

900

1000

00.10.20.30.40.50.60.7

wt % TiO2

ppm

Rb

RayMtnE

RayMtnW

Melozi

Ray R

Sith

FHH

NNC

CoalCk

HS

Bonan

Kanuti

Pow er (Sith)

Pow er(Bonan)Pow er(CoalCk)Log. (Ray R)

Pow er(RayMtnE)Pow er(Kanuti)Pow er(FtHH-S)Pow er(RayMtnW)Pow er (HS)

Pow er(Melozi)Pow er (FtHH-N)

0

1

2

3

4

5

6

00.10.20.30.40.50.60.7

wt % TiO2

Ce/

Y

NNC

HS

Kanuti

RayMtnE

Ray R

Sith

Bonan

CoalCk

FtHH

Power(FtHH-S)Power(Kanuti)Power(Ray R)Power(Sith)Power(RayMtnE)Power(Bonan)Power (FtHH-N)Power(HS)

LEFT: The plutons are divided into two

categories when plotted back to an original Rb

value. The northern plutons (Kanuti, Hot

Springs, Bonanza) yeild initial Rb values of 180 ±

20. The remaining plutons plot an original Rb

value of 300 ± 30. Yet within that range, Coal

Creek and FHH behave as the northern plutons

do, with Rb only incerasing slightly with

fractionation.

RIGHT: All plutons* express an increase in

HREY/LREE (with Y & Ce acting as proxies for

such) with fracctionation, just at di�ering rates.

* Notice that No Name Creek has no apparent

change in the ratio with fractionation and that

all rocks have low Ce/Y ratios to start.