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Regional to deposit scale geochemical and spectral footprints of the ~1.6 Ga thermal event in the eastern Gawler Craton – a case study from the Punt Hill region, South Australia A.Fabris, G.Gordon, T.Keeping, G.Reed, L.Katona, G.Gouthas

Geological Survey of South Australia

28th June 2016, AESC

www.statedevelopment.sa.gov.au

Olympic Dam (~1Bt resource)

Prominent Hill (~270Mt resource)

Carrapateena (~200Mt resource)

Hillside (~200Mt resource)

Olympic Cu-Au Province

Punt Hill

IOCG DEPOSITS Definition – very broad

– Magnetite-apatite deposits (Kiruna-type)

– Carbonatite-Fe-oxide-F-REE deposits

– Cu-Au-Fe porphyry (alkalic) deposits

– Cu-Au-Fe skarn deposits

– Ironstone replacement Au-Cu deposits

– Fe oxide-Cu-Au breccia deposits

– Sediment-hosted Fe oxide-Cu-Au deposits

No Cu

Direct intrusion association

IOC

G s

ensu la

to IOCG

sensu stricto

Olympic Dam (~1Bt resource)

Prominent Hill (~270Mt resource)

Carrapateena (~200Mt resource)

Hillside (~200Mt resource)

Olympic Cu-Au Province

Punt Hill - skarn

Emmie Bluff

Red Lake – skarn

Acropolis Wirrda Well

Cairn Hill - magnetite

Geochemical and spectral footprints

Department of State Development

Drillhole Sampling

• 104 drillholes sampled

• >2700 intervals assayed

• Hematite-dominated IOCG - 63 dh’s

• Skarn IOCG - 18 dh’s

• Magnetite-dominated IOCG - 31 dh’s

Punt Hill

Bouger gravity • Power of integrating spectral and

geochemical data



Punt Hill Study – Monax Mining

• Cu-Au-Ag-Zn-Pb (REE) skarn

• 40 holes intersecting basement (green & red)

• 39 spectrally logged drillholes (yellow); 24 from Monax with >17000 spectral measurements after rescaling

• ~3000 geochemical samples

• >5000 petrophysical measurements

Groundhog

PUNT HILL REGION


Regional Geology • Host – Wallaroo Gr (~1760Ma)

within NW-trending grabens (gravity high)

• Cover: 400-800m Mesoproterozoic to Recent

• Cu-Au-Fe skarn style mineralisation age equivalent to Olympic Dam (Sm-Nd - Reid et al., 2011)

Bouger gravity – Monax Mining Ltd

Red Lake – Mag skarn

Groundhog




Objectives • Characterise alteration leading to

improved understanding of system

• Spectral and geochemical vectors in addition to geophysics

• Map regional trends under cover



Sampling Strategy

• Collect consistent, high quality geochemical data from drill holes at 1m per 10m. Each samples analysed (65 elements); • Lead collection fire assay – Au, Pt, Pd • 4 acid (ICP-OES) – Cu, Li, Ni, Pb, S, Zn • Carbonate fusion/SIE – F • 4 acid (ICP-MS) – Ag, As, Bi, Cd, Co, Cs, Ge, In, Mo, Nb, Re, Sb, Se, Te, Tl • Lithium borate fusion (ICP-OES) – Al, Ca, Cr, Fe, K, Mg, Mn, Na, P, Si, Ti, V • Lithium borate fusion (ICP-MS) – Ba, Be, Ce, Dy, Er, Eu, Ga, Gd, Hf, Ho, La, Lu, Nd, Pr, Rb,

Sc, Sm, Sn, Sr, Ta, Tb, Th, Tm, U, W, Y, Yb, Zr



Spectral - HyloggerTM

• HyloggerTM – automated hyperspectral scanner • Enables objective and consistent mineral analysis

• 125 spectra/metre of core • Wavelengths :

• VSWIR (380nm-2500nm) white micas, carbonates, chlorite, iron oxides, amphiboles, smectites.

• TIR (6000nm – 14,500nm) feldspars, pyroxenes, garnets, serpentine, dark micas, olivine.

HyLoggerTM Adelaide facility

• Also petrophysical measurements




• HyLoggerTM Punt Hill stats: 23,000 m scanned; 2.9 million spectra

• Validated against 100 petrological samples

TIR

SWIR

Skarn

Depth 1020m 0m




• Dominant minerals determined by HyloggerTM were extracted for each sample interval (TIR & SWIR).

• Key is co-located data. • Enables characterization of the alteration (summary). 32 assemblages • Prograde minerals: garnet, pyroxene • Retrograde minerals: amphibole, chlorite, talc, epidote,

(white mica)



Alteration

• Observe down hole trends



Retrograde assemblages Prograde assemblages



Prograde Retrograde

Groundhog prospect

PUNT HILL REGION

• Meaningful relationships at 100’s metre-scale


Cu mineralisation

• Mineralised zone: talc, amph, chl, gnt, pyx

• Background/distal: K-feld, white mica, carb, plag


• Trace elements associated with mineralisation include Au, Ag, As, Bi, Cd, Ce, Cu, La, Mo, Ni, Pb, Sb, Se, U, W, Zn

Probability plots

• Trace element associations with each alteration type and identify elements associated with key alteration assemblages.

PUNT HILL

Cu Ce

Bi

400 ppm 0

1.8 ppm 0

250 ppm

0

5km

5km

5km

Groundhog/Whistle pig

Marmot

Otcheck

• Bi highlights a mineralised

corridor •Sourced from the

Wallaroo Gr?


Trace element associations

• Key elements: Au, Ag, As, Bi, Cd, Ce, Cu, La, Mo, Ni, Pb, Sb, Se, U, W, Zn

10x crustal abundance

• Local – Cd, Ce, La, Mo ± Pb, Zn • Broad – Bi, Sb, As, ± Ag, Se, W



Prospectivity Index

• Prospectivity Index using Au, Ag, As, Bi, Ce, Cu, La, Mo, Ni, Pb, Sb, U, Zn (10x average crustal abundance as the threshold for each element)


Residual TMI grid Slice through 3D Magnetic inversion

RED LAKE

PUNT HILL (Groundhog)


HyloggerTM – spectral mineral mapping

Reflectance spectrum of a mineral mixture containing white mica and chlorite (From Schofield and Van der Wielen, 2007)



2212nm

2220nm

Cu ppm

w22

00

Spectral vector • High Cu values associated

with w2200 values that straddle the boundary between intermediate compositions and long wavelength phengitic white mica (>2218nm).

• Likely to relate to a pH or T control involved in the mineralisation process

Phengitic (>2218nm)

Muscovitic (<2207nm)



Conclusions • Alteration in the Punt Hill region was dominated by prograde and retrograde skarn

assemblages. • Cu mineralisation is most strongly associated with alteration assemblages dominated

by talc, amphibole, chlorite, garnet and pyroxene. • Trace elements associated with mineralisation include Au, Ag, As, Bi, Cd, Ce, Cu, La,

Mo, Ni, Pb, Sb, Se, U, W, Zn. The distribution of trace elements associated with the mineralising event support km-scale fluid flow along a corridor that hosts the Punt Hill prospects.

• Spectral methods very useful for mapping mineralogy in district and characterizing the alteration. Spectral mapping of white mica chemistry indicated that Cu mineralisation associated with an AlOH absorption feature with wavelengths of 2207-2218 nm and provide the potential as a vector to mineralisation in the district.

Disclaimer


The information contained in this presentation has been compiled by the Department of State Development (DSD) and originates from a variety of sources. Although all reasonable care has been taken in the preparation and compilation of the information, it has been provided in good faith for general information only and does not purport to be professional advice. No warranty, express or implied, is given as to the completeness, correctness, accuracy, reliability or currency of the materials. DSD and the Crown in the right of the State of South Australia does not accept responsibility for and will not be held liable to any recipient of the information for any loss or damage however caused (including negligence) which may be directly or indirectly suffered as a consequence of use of these materials. DSD reserves the right to update, amend or supplement the information from time to time at its discretion.

Contact


Department of State Development Level 4, 101 Grenfell Street Adelaide, South Australia 5000 GPO Box 320 Adelaide, South Australia 5001

T: +61 8 8463 3000

E: [email protected]

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