From paddling in the bathtub to swimming the deep ocean: the reality of this exploration metaphor in the Curnamona Province and adjacent regions

Steve Hill

Director

Geological Survey of South Australia

OPEN THE DOOR TO SOUTH AUSTRALIA

Murphy’s “Haystacks” (Photo: S.Hill)

Pre-competitive Geoscience Data… finding mineral system “Haystacks”

Moon Plain, Stuart Shelf, SA (Photo S.Hill)

Deep Cover Exploration Impediment…

Love thy Enemy• Lots of cruel things said about the cover….• “Impediment”• “punch through” it!• The rocks “suffered” weathering• Ignore it• “Stuff”• “Overburden”• “Crud”• “Dirt”• “*^#>” !!!

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Why are people so unkind?Fear and loathing. Where does it come from?We don’t know it properly?We don’t trust it

Be a Cover Lover!

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This presentation1. Geological Processes in the Cover (What are some of the

special things that can happen?)

2. Implications of these processes (How the cover can be our BFF)

3. Characterising the cover (What do we really know about our new found love?)

4. How to get to know the cover better into the future (our enduring love)

5. Cover savvy geoscientists of the future (Who will be part of this love affair?) 6

Geological Processes in the Cover: What are some of the special things that can happen?

• Weathering / erosion / sediment and element accumulation• Element mobility – source, transport, accumulation,

preservation• Supergene enrichments• Biogeochemical processes• Placer concentration and recycling• Geochemical footprint enlargement• -------------------------------------------• Dilution• Barren cover (‘blind” deposits)• Erosion / poor preservation

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Weathering

ErosionSedimentation

PreservationLeaching

Poor PreservationPhysical Dispersion

BurialRe-accumulation(“False anomaly”)

DynamicEquilibrium

Cover Processes and MaterialsWeathering

ErosionSedimentation

PreservationLeaching

DenudationPhysical Dispersion

BurialRe-accumulation(“False anomaly”)

DynamicEquilibrium

Weathering

ErosionSedimentation

In situDeep

Weathering“Residuum”

Variable profile Materials exposed

Sediments /Transported

material

PROCESS

MATERIAL

Gossans

Ferricrete

Weathered Fe-skarn

Kaolinised Granite

Joints / Faults

Basal Gravels

Reduced/Oxidised clays & sands

Regolith CarbonatesBarren aeolian sands

Supergene Cu zone

HILLSIDE REGOLITH PROFILE

Tunkillia biogeochemical model

(Lowrey & Hill, in prep.)

Central Gawler CratonDeep cover Plant biogeochemistry

UoA Honours studentsBlack oak sampling April 2009

Minotaur ExplorationDrilling April 2010

Tunkillia, Gawler Craton

Implications of these processes: How the cover can be our BFF

• Haloes / footprints

• 3D dispersion

• Secondary accumulations

• Other resources • e.g groundwater, soils …..

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After R E Smith & B Singh, 2007

Implications of these processes: How the cover can be our BFF

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• Eastern Gawler Craton – Curnamona Province links

• ~1590 Ma mineralising event

But dominated by differentexploration strategies

Eastern Gawler: IOCG in basementCurnamona: sedimentary U

IOCG – Porphyry – Epithermal Continuum (Claire Wade, GSSA)Into the overlying cover???

Curnamona Province dispersion haloes shown on radiometrics image

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Mt Painter

Broken Hill

50 km

Scale of the distal footprint of the Broken Hill mineral system

• Lateral dispersion for >100 km– High grade garnets in beach sands

at Menindee Lakes (>100 km to SE)

– Staurolite and other high grade metamorphic minerals in sediments overlying low-grade metamorphic rocks in the Fowlers Gap and Bancannia Basin (>100 km to N)

–Lateral dispersion onto Mundi Mundi Plains (30-50 km to W and NW)

Catchment headwaters within Barrier Ranges

Mundi Mundi Plains

Umberumberka Reservoir

Umberumberka Creek - Broken Hill (Charlotte Mitchell, DET CRC)

Catchment headwaters within Barrier Ranges

Mundi Mundi Plains

Umberumberka Reservoir

Umberumberka Creek - Broken Hill (Charlotte Mitchell, DET CRC)

Mundi Mundi Plain• Lateral dispersion

and reaccumulation

• Important balance between processes of erosion, sedimentation and weathering / soil formation

Characterising the cover: What do we really know about our new found love?

• Characterising the cover – a big opportunity!

• Greater amount of surficial data but really decreases with depth

• Key attributes:• Detailed lithological logging• Whole-rock geochemistry (chemical context?)• Mineralogy (XRD and spectral)• Physical properties

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Deep Cover Reference Sections

• Geological type sections and their associated data have received diminished attention, particularly since the GSSA work in basin areas in 1970s and 1980s

• These are important reference sections, particularly as exploration moves into surrounding covered areas.

• Modern data for these sections can include:• GPS coordinates• Lithological logging• Biostratigraphy• HyLogger mineralogy• Lithogeochemistry• Detrital zircon dating• et al……

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Trinity Well type section, Marree 1:250k mapsheet

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Trinity Well Reference Section

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Deep cover atlas of SA (DET CRC)…

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Exploration Sampling Media within the Cover (DET CRC)

• An ideal sampling medium needs to be:• Abundant• Generic (e.g. not just restricted to a particular stratigraphic

unit)• Readily identifiable (esp. down-hole)• Hosts target geochemical suite for mineral system • Can be linked to dispersion vectors (can be used as

geochemical vector to mineralisation)• Able to be effectively and efficiently sampled

Some examples of efficient and effective approaches to exploring

in covered terrains?

1. Understanding the geological history of gold dispersion at Tibooburra

2. Exploring through sediment for Broken Hill type mineralisation at the Pinnacles

3. Putting it all together for sedimentary uranium exploration through the cover at Four Mile

CASE STUDY 1: Tibooburra Au provenance...

Tors of Tibooburra Granodiorite (photo S.Hill)

Tibooburra-Milparinka Au-fields (Thomson Orogen NSW)From Hill et al 2009

Tibooburra-Milparinka Au-fieldsDepth of Basin Cover (Mesozoic and younger)

From Hill et al 2009

Radial ‘shedding’ modelTibooburra Inlier

No! This applies to contemporary drainage but not the Mesozoic system

Mesozoic hinterland-basin geochemical reconstruction needed!

Au hosted in basal Mesozoic sediments

(Hill, 2005)

Late Jurassic(basal Mesozoic) palaeolandscape

Au-bearing Basal Mesozoic palaeocurrent vectorsTibooburra Inlier (Hill et al 2009)

Tibooburra: Mesozoic palaeoflow model in relation to historic Au diggings (Hill et al 2009)

Emergent

.The Granites. Easter Monday

. Tunnel Hill

. Six Mile

Deeply buried Au Provenance? (Hill et al 2009)

Mt Browne Inlier

Au bearing Basal Mesozoic flow vectors

Buried Au source target areas

Tibooburra Inlier

Deeply Buried Au Provenance?

Tibooburra Inlier

NSW GS, 1VD magnetics

Mt Browne Inlier

CASE STUDY 2: The Pinnacles …

Looking South down Pine Creek from Middle Pinnacle

Pinnacles Mine

Pine CreekSouth

Pinnacle

S.Hill Pinnacles pilot study: river red gum leaves (~250 m sample spacing)

0

50

100

150

200

250

300

350

0 2 4 6 8 10 12

Channel Distance (km)

Pb

(p

pm

) Pinnacles mineralisation?

Wasn’t sure if this staggering result was current mine or new mineralisation? What does an academic do when they don’t know something? ……

Get a PhD student to work on it –Karen Hulme

Pine Creek… Sample spacing – every collectable RRG

• 215 River Red gums sampled– Media

• Leaves• Chest height• Sample size~300g

Middle Pinnacle

Pinnacles Mine

Staurolite Ridge

Pin

e

Creek

Lead…

•Pb up to 205 times background levels

•Geochemical footprint ~ 2.5 km

0 – 36 ppm

37 – 99 ppm

100 – 190 ppm

191 – 411 ppmHyperspectral Image, courtesy NSW DPI

N2 km

Silver…

• Ag up to 136 times background value

• Geochemical footprint 2.2 km

0.005 – 0.100 ppm

0.101 – 0.340 ppm

0.341 – 0.710 ppm

0.711 – 1.360 ppm Hyperspectral Image, courtesy NSW DPIN

2 km

Zinc…

• Zn up to 7 times background values

• Erratic pattern (repeated)– mobility– peaks related to

floodouts

17 - 47 ppm

48 - 80 ppm

81 - 141 ppm

141 – 338 ppm Hyperspectral Image, courtesy NSW DPIN

2 km

It was time to dig… Sarah ‘Gibbo’ Gibbons (earnest, hard-working CRC LEME Honours student)

Photos: Karen Hulme

Pinnacles - lodes extensions

Photographs: Steve Hill Mineralisation continues near surface but below main road!

Kangaroo Prospectors– Western Grey Kangaroos

• Selective browser• Well defined home range• Scat chemistry reflects Broken Hill mineralisation (esp. Pb, Zn, Cd)• Implications for exploration and geo-health

Kangaroo Prospectors

Broken Hill Roo Poo Pb

0

100

200

300

400

500

600

700

-60 -40 -20 0 20 40 60

Dist (km)

Pb

(p

pm

)

Broken Hill

West East

Pinnacles

Zn and Cd in roo poo

Broken Hill Roo Poo Zn

0

200

400

600

800

1000

1200

-60 -40 -20 0 20 40 60

Dist (km)

Zn

(p

pm

)

Broken Hill Roo Poo Cd

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

-60 -40 -20 0 20 40 60

Dist (km)

Cd

(p

pm

)

Broken HillBroken

Hill

West East West East

Skippy knows where to find the ore?

• The kangaroos very effectively intake chemical signatures from buried rocks when they eat plants.

• They do this over a range of 10s of kilometres• They redeposit this chemical signature in their

poo• Mineral explorer samples the poo, prepares it

and gets it analysed to look for its chemical signatures

CASE STUDY 3: Four Mile U(Steve Hore & Steve Hill, GSSA)

Four Mile East

Dead Tree SectionFour Mile Creek

Four Mile West

Beverley

F

Four Mile East

Dead Tree Section – Eyre Formation sample locations

20m

Four Mile West: Deadtree Section

Namba Fm

Pedogenic Silcrete

Eyre Fm

Bulldog Shale &Cadna-owie Fm

Saprolite

(Hill, 2005)

Late Jurassic

Mesozoic Glaciations• Widespread dispersal of U-rich detritus in

Early Cretaceous glaciers

Recorder Hill

Mesozoic Glaciations• Important context for Four Mile West U

deposit

Palaeoredox interfaces in Mesozoic diamictite at Deadtree section (Hore & Hill, 2009)

(Hill, 2005)

Early Cretaceous

Mt Babbage Inlier(U-rich granites)

Oxidised Bulldog Shale

Mt Babbage Inlier

U-rich bedrock

Mesozoic sediments

(Hill, 2005)

Palaeogene

Eyre Formation (Palaeogene)

• Flinders Ranges existed at this time– Palaeoflow along range-front (rather than across it!)– Highly weathered provenance

• Warm-wet palaeoclimate– Abundant vegetation cover– Weathering rate > erosion rate– Organic detritus

Eyre Formation (palaeo-redox fronts) – Important U host (Four Mile, Honeymoon, Goulds Dam, Oban)

Namba Fm (Miocene) – hosts Beverley

Namba Formation

Top of Namba Fm

Top of Saprolite(Wooltana Volcanics)

Willawortinna Fm outwash gravels

(Hill, 2005)

Neogene

Proterozoic basementWillawortina Ftm

Eyre Formation

geologists

~ 5 km

Four Mile East

Four Mile West

?

?

~ 5 km

~ 5 km

Preserved Tertiary

Exposed Mesozoic

Four Mile Stream Sediments (GSSA Radiometrics)

NB. High U content of detritus from ranges overlying basin prospective for buried sedimentary U

Four Mile Prospect soil U

Neimanis et al 2007

Four Mile Stream Sediments (McMahon & Hill, 2007)

0

20

40

60

80

100

120

0 1000 2000 3000 4000 5000 6000 7000

Sample distance downstream (m)

U (

pp

m)

Fine sediment fraction(-80 mesh)

Mineralisation surface projection

Four Mile Regolith Carbonates (Gallasch & Hill, 2007)

Media Comparison of U vs Th (Four Mile Catchment)

0

50

100

150

200

250

300

350

0 50 100 150 200 250 300

U (ppm)

Th (ppm)

Carbonate

Bedrock

Th > U

U > Th

Radium Ridge

Image: Steve Hill

Eucalyptus gillii

0.12 – 6.59 ppm U

4.79 – 33.42 ppm Cu

0.01 – 0.02 ppm ThEucalyptus intertexta

0.06 – 6.49 ppm U

2.74 – 12.21 ppm Cu

0.01 – 0.04 ppm Th

FOUR MILE BIOGEOCHEMISTRY: TARGET SPECIESAllows subsurface access to culturally and environmentally sensitive sites

River Red Gum

Inland tea-tree

Neimanis, Hill & Hore, 2007

Inland Tea-tree shows similar results to stream sediments!(shallow alluvial aquifer)

Neimanis, Hill & Hore, 2007

River red gum shows deeper mineralisation expression along structures(deeper fractured aquifer)

U2 / Thriver red gum

leaves

Ant biogeochemistry (Iridomyrmex spp.)

Meat Ant Distributionwww.ento.csiro.au/science/ants

Courtesy Deanne Gallasch

Ant Nest Soils

Projected MineralisationLegend

Uranium (nest material)

Value (ppm)

3.5 - 30.0

30.1 - 57.0

57.1 - 118.0

´0 1,000 2,000500

Metres

GRID NORTHGDA 1994 (Zone 54)

351500.000000 352500.000000

353500.000000

353500.000000

354500.000000

354500.000000

355500.000000

355500.000000

356500.000000

356500.000000

357500.000000

357500.000000

358500.000000 359500.000000

666

00

00.0

00

00

066

61

00

0.00

00

00

666

20

00.0

00

00

066

63

00

0.00

00

00

666

45

00.0

00

00

066

65

50

0.00

00

00

666

65

00.0

00

00

0

(Jennings, Hill, Wright & Kirby, 2007)

Ant Biogeochemistry (Jennings, Hill, Wright & Kirby, 2007)

Projected MineralisationLegend

Uranium (ants)

Value (ppm)

0.027 - 1.417

1.418 - 4.302

4.303 - 13.035

´0 1,000 2,000500

Metres

GRID NORTHGDA 1994 (Zone 54)

351500.000000 352500.000000

353500.000000

353500.000000

354500.000000

354500.000000

355500.000000

355500.000000

356500.000000

356500.000000

357500.000000

357500.000000

358500.000000 359500.000000

666

00

00.0

00

00

066

61

00

0.00

00

00

666

20

00.0

00

00

066

63

00

0.00

00

00

666

45

00.0

00

00

066

65

50

0.00

00

00

666

65

00.0

00

00

0

Roo Poo Biogeochemistry (McMahon & Hill, 2007)

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Four Mile Uranium: summary

• Long history of U dispersion (at least Mesozoic) across landscape

• Abundant surface anomalism but links to buried mineralisation challenging

• Vegetation and to some extent carbonates have best links with buried mineralisation (via groundwater)

So what have we learnt

• The cover can be our friend and host some advantages to exploration (e.g. enlarged “footprints”)

• The cover needs to be dealt with the same geological rigor as hard rocks (e.g. palaeodrainage reconstruction)

• A range of sampling media are available within the cover and be efficiently and effectively used in different ways (e.g. the provide an exploration tool kit)

Plant biogeochemistry providing surficial expression of sub-surface chemistry

Biogeochemistry

→

Cost and Time efficient subsurface chemical information(help focus and rank drilling targets)

Advantages of plant biogeochemical exploration

• Provided sampling procedure is orientated and systematic:• Time efficient• Minimal environmental impact• Minimal cultural impact• Flexible site access needs• Cost equivalent to soil geochemistry

Cover savvy geoscientists of the future: Who will be part of this love affair?

• Part of integrated geoscience workflow• Given the expanse of cover …. Where are our

cover savvy geoscientists coming from?• Are training institutions engaged and providing

the relevant foundations?

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Photo: Steve Hill92

Western Gawler Craton – Eucla Basin….

South Australian Mineral Exploration Licences

January 2004 September 2013

Pre-competitive Geoscience workflow for western Gawler Craton – Eucla Basin

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Regional GeophysicsRegional Geochemistry

Regional Geological MappingLithospheric Architecture

Stratigraphic Drilling250k Geological Mapping

Targeted Geophysics and Geochemistry4D Geodynamic & Metallogenic evolution

Regional Mineral System DrillingGeophysical & Geochemical Case studies

‘Distal Footprint’ Characterisation

Mineral Occurrence StudiesCollaborative / Targeted drilling

Tenement Exploration

PACE FRONTIERS in 2014• Eucla Seismic Line• Regional MT survey• New airborne geophysics• Regional Biogeochemistry

Western Gawler / Eucla Basin Continental Seismic Transect (TMI backdrop)

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CoompanaAnomaly Fowler

DomainGawlerRanges

Eucla Basin – Gawler Craton MT

Western Gawler / Eucla Basin Regional Geophysics

• Magnetics

• RadiometricsOlder airborne surveys1600-3000 line spacing(did not always collect radiometrics)

Western Gawler / Eucla Basin Geochemistry / Biogeochemistry

• Regional Geochemistry– 2013-14

• Hydrogeochemistry• Soil • Calcrete • Biogeochemistry

~450 plant samples~170 sample sites

Western Gawler / Eucla Basin Future Program

• Gravity survey• Soil Geochemistry• Integration, Interpretation and value-add• REGIONAL DRILLING

• Coompana Competition?• Phase I: service provider data acquisition• Phase II: Geological Interpretations• Phase III: Regional Drilling and ‘real time’ reinterpretations

Thank-you….

Yours LovinglySteve

(Your Cover Lover Brother)

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DisclaimerThe information contained in this presentation has been compiled by the Department for Manufacturing, Innovation, Trade, Resources and Energy (DMITRE) 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.

DMITRE 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. DMITRE reserves the right to update, amend or supplement the information from time to time at its discretion.