Integrated Spectral Mapping of Gold Related...

GSWA OPEN DAY 2016, 26 FEBRUARY

MINERALS RESOURCES

‘Promoting the Prospectivity of Western Australia’

M. A. WELLS, C. LAUKAMP AND L. HANCOCK

Integrated Spectral Mapping of Gold Related Alteration Mineral Footprints, Nanjilgardy Fault, WA.

Acknowledgments

GSWA Perth Core Library Northern Star Resources Ltd. CSIRO – MR Colleagues

Nanjilgardy | GSWA Open Day 2016 2 |

Geological setting: Capricorn Orogen


Mt Olympus

Paulsens

10GA-CP1

50 km

Wyloo Group Shingle Creek Gp

Dolerite sills

Capricorn Orogen: General Stratigraphy

Au at Mt Olympus in meta-sediments of the McGrath Formation • Duck Creek Dolomite • Dated at 1740 Ma

(xenotime analysis)

Carlin-style deposit • Solid-solution, inclusions of

Au in pyrite


Johnson et al., 2013

Johnson et al., 2013*

WylooGroup

Ashburton Fm. Mudstone, siltstone, wacke, conglomerate

Duck Creek Dolomite

Dolomite, siltstone, chert

Mount McGrath Fm.

Ferruginous epiclasticsedimentary rocks

Cheela Springs Basalt

Basalt, subordinate tuff and sandstone

Beasley River Quartzite

Quartz sandstone

Angular Unconformity

- Mount Olympus, Stynes,Marcus, Zeus, Styx, Hermes

- Amphitheatre, AugustusAu

mineralisation

- West Olympus

WylooGroup

ShingleCreekGroup

Johnson et al., 2013 Australian Journal of Earth Sciences, 60, 681–705

Johnson et al. 2013

Alteration Mineralogy Au-related to strong sulfide alteration and variously: • Quartz or quartz-sericite • Silica, sericite and carbonate

Other minerals? Sulfates, kaolin minerals • Low-T, hydrothermal alteration

Strongly spectrally active: • SWIR, 1.0–2.5 µm • TIR, 6–14.5 µm


GSWA HyLogger-3. Photo from Lena Hancock

Project Objectives

Opportunity to develop 3D mineral characterisation of potential structurally related, alteration footprints that may be associated with Au-mineralisation along the NF corridor Integrate HyLogging-3™ and remotely sensed data (ASTER), within a validated mineralogical framework: • Approach follows a ‘bottom-up’ methodology • Adds value to GSWA’s precompetitive spectral data


HyLogging

Validation: XRD and Geochemistry

Core-scale alteration mineralogy

Deposit scale 3D-visualisation

Local scale alteration patterns (ASTER, regolith geochem)

Proximal Sensing

Remote Sensing

Regional scale alteration patterns (ASTER, AEM, regolith geochem)

Hydrothermal Alteration: Mineral Indicators

Two mineral groups used as indicators of hydrothermal alteration: • Al-clay minerals (white

mica, kandites) • Sulphates (alunite,

jarosite)


Parameter Mineral Group Geological environment Active wavelength range [nm]

Advanced argillic alteration Pyrophyllite Porphyry ~ 2160

Advanced argillic alteration Alunite Epithermal ~ 1480, ~ 1760

(Advanced) argillic alteration

Kaolinit/Dickite Epithermal ~ 2160/2180, ~ 2200

Tschermak exchange due to pH and/or T

White mica, Al-smectites Hydrothermal (metamorphic?)

~ 2200

Spectral parameters of ‘indicator’ mineral groups and examples of the associated geological environment.

HyLogging and Spectral Mineralogy Sulfates • Alunite, KAl3(SO4)2(OH)6

• Jarosite, KFe33+(SO4)2(OH)6

– Increasing T favours Na-alunite over K-alunite

Absorption features are relatively unique • Spectral separation of sulfate types • In the core sulfate phases hard to distinguish


Jarosite K-alunite Na-alunite

Alteration Mineralogy vs. Au mineralisation (MOD4) Siltstones interlayered with carbonates, dolomites and sandstones

Au in sandstone and siltstone • 33 ppm @54 and 82 m

Jarosite (proximal) to Au mineralisation altered to Na/K-alunite

Kaolinite with alunite

More distally kaolinite replaced by dickite+mus • No carbonate or chlorite

detected • No major changes in quartz

abundance (TIR data)


MOD4: 190.6 m (11.7–202.3 m), above interval 70–95 m

Mineralised zone81–85 m

Au (p

pm)

kaolinite

dickite

alunite and/or kaolin group

kaolin group

white mica

Na-alunite

K-alunite

jarosite

Kaol

inite

+K-

Alun

ite

Kaol

inite

K-Al

unite

Na-A

luni

te

Na-A

luni

te+

Jaro

site

Jaro

site

Dick

ite

Dick

ite

Kand

ite

Musc

ovite

Kaol

inite

+Na

-Alu

nite

Kand

ite

K-Al

unite

Na-A

luni

te

K-Al

unite

Kaol

inite

+Na

-Alu

nite

Kaol

inite

+Na

-Alu

nite

Kand

ite

Musc

ovite

Musc

ovite

Quar

tz

Alun

ite an

d/or

kaol

in

grou

p ab

unda

nce

inde

x

Al-c

lay

abun

danc

e in

dex

Sulp

hate

ab

unda

nce

inde

x

Sulp

hate

ab

unda

nce

inde

x

B

C

D

Sandstone Siltstone Qtz-veinA

E

Mineralisation Styles Au-related mineral alteration patterns identified in common rock types at Mount Olympus • Sandstone (Type-A, B) • Siltstone (Bright/Black) • Conglomerate

Potential hydrothermal minerals interpreted as: • Na/K-alunite (proximally) • Well-ordered kaolinite, dickite and pyrophyllite

– (indicative of advanced argillic alteration) • Muscovite

– (indicative of phyllic alteration) • Fe/Mg-chlorite and carbonate (distally)


Mt Olympus

Paulsens

10GA-CP1

50 km

Wyloo Group

Shingle Creek Gp

Dolerite sills

Visualisation of Alteration Mineralogy

Deposit-scale alteration patterns Only drill holes closest to Mt Olympus included • 17 drill holes


Shingle Creek Gp

Wyloo Gp

3D modelling: Au and sulphate Zoe Fault steeply inclined, striking NW-SE • Most significant structural feature

Isovolumes define: • Highest sulphate abundance (yellow) (A) • Au (>0.5 ppm) and sulphate abundance (B) • Largest Au zone exhausted(?) • Mt Olympus pit

Smaller, poddy zones of Au mineralisation plunging to the SE (intersected by Zoe Fault) • Similar trend for sulphates


Plunge +20° Azimuth 073°

500 m


300 m

MOD4

White-mica and chlorite visualisation Al-poor white-mica proximal and shows a similar trend as Au and sulphate alteration

Al-rich white mica in Mt Olympus pit associated with main Au zone

Fe-rich chlorite ‘envelopes’ Al-poor white mica

Change to Mg-rich chlorite proximal to the largest zone of Au mineralisation

In the pit ore zone • Fe-rich chlorite in the upper part • Underlying Mg-rich chlorite



300 m

Nanjilgardy | GSWA Open Day 2016

ASTER vs. HyLogger: Spectral Mineralogy Hyperspectral indicator minerals as ASTER products • Diagnostic mineral features ‘lost’ in

ASTER data

• 1480 nm alunite feature not detected

• Kaolin Group Index Product maps only ‘Kaolinite/Alunite’

• Still ‘track’ white-mica and chlorite related features

14 |

HyLogger ASTER

ASTER Alteration Mapping Patterns in MgOH Group Content and Opaques Index • Correlated with major structures around Mt

Olympus • Widespread, elevated MgOH content related to

pervasive white mica+chlorite assemblages • Close to joint/fault intersections (black arrow)

Elevated Opaques Index values coincident to elevated MgOH values • Potential occurrence of black shales, e.g., in

MOD13


MgOH

Mt Olympus

Opaques

Mt Olympus

ASTER vs. AEM Correlating remotely sensed mineral patterns to deeper, sub-surface features • Inversion modelling of AEM data • FID59 Tempest line

No significant change in the MgOH Group Content along NF • High conductivity domain (South)

separated from low conductivity domain (North)

3 conductivity highs between OF1 and NF (pink arrows) continue East and West, mapped by MgOH Group Content Product


Lower Wyloo Grp

Upper Wyloo Grp

NN

A B

C

D

NMOD005NMOD004

NMOD002MOD04

SPD001

2200 m Mt Olympus

Shingle Creek Group

Wyloo Group

ASTER MgOH Group Content product (blue - low content, red -high content) over greyscale DEM

ASTER vs. Regional Geochemistry ASTER Silica Index, Ferric Oxide Content and AlOH Group showed coherent patterns related to distinct lithologies South of NF, high Silica Index values may follow WNW-trending lithologies • Correlate with modelled high SiO2 contents

Shingle Creek Grp, low/void of Silica Index • Matches high MgOH/Carbonate abundances

North of NF (Hamersley Basin), low/void Silica Index values • Correlates with modelled low SiO2 contents


Mt Olympus

Conclusions HyLogger characterisation identified four Au-mineralisation alteration patterns • Logged lithology and gold assay data • Validation through XRD and compositional analyses

Potential hydrothermal alteration phases in common rock types along the Nanjilgardy Fault are: • Na/K-alunite, kaolin (kaolinite, dickite), pyrophyllite, white mica and chlorite

(proximal) (distal)

New alteration mineralogy identified • Sulfate-white mica-kaolin


Conclusions White mica and chlorite were widespread • White mica has a characteristic hydrothermal spectral signature and occurs throughout

alteration footprints for all mineralisation types

Chlorite abundance increased away from mineralisation • Difficult to differentiate between regional metamorphic and later hydrothermal types

Kaolinite and dickite occurred proximally to all four mineralisation types • Distribution restricted to certain intervals in drill cores

Jarosite probably formed during sulfide oxidation


Conclusions Identified small-scale hydrothermal mineral footprints (metre-decametre) in proximal (HyLogging) data

Some ASTER mineral products (MgOH Group Content), AEM data, mapped distinct, conductive, sub-surface geological domains • Define structures (faults, lithological contacts, bedding-parallel shear zones) not previously mapped

Evidence for significant alteration zonation associated with NF not found in multispectral, remotely sensed (ASTER) data • ASTER may not be sensitivity enough (spectrally/spatially) to detect small-scale alteration systems • Future exploration programmes use available airborne, hyperspectral (AMS or Hymap) data or soon to be

launched hyperspectral satellites (e.g. EnMAP) for detecting potential, small-scale alteration associated with large-scale structures, such as the Nanjilgardy Fault


Nanjilgardy | GSWA Open Day 2016

Thank you

Mineral Resources

Martin Wells Research Geologist: Iron Ore/Ni laterite t +61 8 6436 8812 e [email protected] w www.csiro.au

“Coffee time….”

References

Johnson, S.P., Thorne, A.M., Tyler, I.M., Korsch, R.J., Kennett, B.L.N., Cutten, H.N., Goodwin, J., Blay, O., Blewett, R.S., Joly, A., Dentith, M.C., Aitken, A.R.A., Holzschuh, J., Salmon, M., Reading, A., Heinson, G., Boren, G., Ross, J., Costelloe, R.D. and Fomin, T. 2013. Crustal architecture of the Capricorn Orogen, Western Australia and associated metallogeny. Australian Journal of Earth Sciences, 60, 681–705.

Sener, A.K., Young, C., Groves, D.I., Krapez, B. and Fletcher, I.R. 2005. Major orogenic gold episode associated with Cordilleran-style tectonics related to the assembly of Palaeoproterozoic Australia? Geology, 33 (3), 225–228.

Tyler, I.M., Johnson, S.M., Thorne, A.M. and Cutten, H.N. 2011. Implications of the Capricorn deep seismic survey for mineral systems. Capricorn Orogen seismic and magnetotelluric (MT) workshop 2011, 115–120.


Extra Slides


Chlorite Spectral Chemistry Changes in Fe:Mg ratio occur as a shift in the wavelength of the ≈2250 nm absorption feature Chlorite absorption feature shifts to longer wavelengths as %Fe content increases


Fe-rich

Mg-rich

Wavelength in nm1400 18001600 2000 2200 2400

Ref

lect

ance 1415

1406

1907 1992

1907 2008

22612360

2251

2345

Fe absorption near 1100 nm causes variable gradients in this region

Increasing Fe content

Chlorite Chemistry: Spectral vs. XRD validation

Influence of Fe substitution in chlorite • Odd-numbered (001 and 003),

basal peaks weaker (less intense) • Even-numbered (002 and 004),

basal peaks stronger

With increasing Mg content • odd-numbered peaks increase • even-numbered peaks decrease in

intensity


Mica Chemistry: Spectral composition Tschermak exchange in micas (AlIVAlVISiIV-1(Fe,Mg)VI

-1) reflects hydrothermal fluid composition (e.g., T and pH conditions): • muscovite = more acidic vs. phengite

= less acidic • muscovite = low-T recharge zones vs.

phengite = high T hydrothermal fluids


Wavelength in nm2200 2300 2400 250021002000

Reflectance(offset

forclarity)

2207

2189

Paragonite

Muscovite

Position of 2200 nm feature not related to Na-K exchange between paragonite-muscovite. Related more to decrease in AlVI content with replacement by Mg/Fe: • high-Al/low-Si micas (e.g. muscovite) to low-Al/high-Si micas (e.g. phengite)

Integrated Spectral Mapping of Gold Related...

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