the national geochemical survey of australia

Geochemical Atlas of Cyprus Symposium (Lefkosia, Cyprus, 5-7 Sep 2011)

The National Geochemical Survey of Australia

Patrice de CaritatGeoscience Australia

A collaborative project under National Geoscience Agreements with New South Wales Department of Primary Industries, Mineral Resources Tasmania,

GeoScience Victoria, Primary Industries and Resources South Australia, Geological Survey of Western Australia, Northern Territory Geological Survey,

Geological Survey of Queensland


Outline of Presentation

• Why geochemical surveys?• Review of pilot projects• Aims of NGSA• Strategy of NGSA• Results and preliminary interpretations

Total element concentrations Weak digestion concentrations Visible near-infrared spectroscopy

• Conclusions


Geochemical Surveys 101

What are geochemical surveys?• GS are the documentation of the chemical composition of the

Earth’s surface: concentration values & patterns• Fundamental dataset• Nature of end-product depends on a number of strategic

decisions: Purpose (minex, environmental, land-use, etc.) Size of area to cover (strategic v tactical) Sampling medium Sampling density Constraints: time, resources, history, etc

Gd+Sm

Ti

Neutron SpectrometryDataElphic et al. (1998, 2000)


Geochemical Surveys 101

• Initially developed for mineral exploration (“geochemical prospecting”)

• Reconnaissance geochemical surveys started in the 1960’s (Nichol et al., 1966)

• Gained widespread popularity in many parts of the world over ensuing decades

• Variety of applications: mineral exploration, environmental baseline, geohealth (e.g., drinking water!), land rehabilitation, risk assessment, etc.


Selected Results from Pilot Projects

• Curnamona: Broken Hill region; base metal, Cu-Au

• Riverina: Agriculture, Murray Basin; Au, base metal

• Gawler: Arid, flat, aeolian influence; Olympic Dam Fe-

oxide-Cu-Au-U, Au• Thomson:

Eromanga/GAB Basin cover; borders on Curnamona and Cobar (base metal, Cu, Au) districts

Pilot survey Approx area (km2)

Number of sampling sites

Average sampling density (1 site per X km2)

Curnamona 61,915 199 311

Riverina 122,976 142 866

Gawler 53,636 48 1117

Thomson 209,824 99 2119



Riverina: Th channel airborne radiometrics vs Th (ppm) in <180 um TOS

Caritat et al., GEEA, 2008



Riverina: Depth profiles

Fe

Fe

Pro

file

133

Pro

file

11

1 Zn

Zn


Shallow (<10 cm) and deep (>50 cm) levels aregeochemically distinct


Lakes

Australian coastline

Catchment Outline

Zn (<180 um) (ppm)

1 - 8

9 - 22

23 - 30

31 - 40

41 - 63

Hutchinson Group

Ifould Complex

Tunkillia Suite Granite

Glenloth Granite

Sleeford Complex

Harris Greenstone Belt Volcanics

0 60 12030

Kilometres

Hiltiba SuiteGranite

Upper Gawler Range Volcanics

Lower Gawler Range Volcanics

St Peters Suite Granite

¯

133°0'E

133°0'E

133°30'E

133°30'E

134°0'E

134°0'E

134°30'E

134°30'E

135°0'E

135°0'E

135°30'E

135°30'E

136°0'E

136°0'E 136°30'E

33°3

0'S

33°0

'S

33°0

'S

32°3

0'S

32°3

0'S

32°0

'S

32°0

'S

31°3

0'S

31°3

0'S

31°0

'S

31°0

'S

30°3

0'S

30°3

0'S

(TOS)

AI

Gawler: Zn (ppm) in <180 um TOS

0 60 12030

Kilometres




• Cu in Gawler: variation between sites >> variation between grain sizes

Grouped by size fraction:

Grouped by site:

Cu

(ppm

)

Fre

quen

cy (

%)

Cu

(ppm

)


A. <75 μm B. 75-180 μm C. <180 μm D. 180-500 μm E. 500-1000 μm F. 1000-2000 μm

• N = 72 (6 sites x 2 depths x 6 fractions )

• Finest size fraction has significantly elevated Cu concentrations compared to coarser• Thus, analysing a fine and a coarse fraction adds information• Regardless of depth or size fractions, some sites have significantly more elevated Cu values• This is why low-density geochemical mapping works!


National Geochemical Survey of Australia

• In August 2006, the Australian Government announced support for Onshore Energy Security Program (OESP)

• $59M over 5 years (2006-2011)• Uranium, thorium, geothermal, petroleum• Geoscience Australia established a multi-

disciplinary program to tackle this new focus (seismic, AEM, AWAGS2, geothermal, NGSA, etc.)

• NGSA is but one of the OESP projects


Aims of NGSA

• To provide pre-competitive data and knowledge to support exploration for energy resources in Australia

Specifically To improve the existing knowledge on the concentration

and distribution of energy-related elements such as uranium (U) and thorium (Th) at the national scale

• But it will also provide new data for a range of commodity related elements such as gold (Au), copper (Cu), nickel (Ni) and zinc (Zn), among others, as well as several elements of interest for other applications, e.g. environmental management, at the national scale


Strategy for NGSA

• To keep costs down, an ultra-low sampling density strategy was adopted, backed by results from pilot projects

• Transported sediment: ‘a well-mixed composite sample of dominant lithologies upstreams’ as sampling medium

• Collect a proper sediment sample (fine-grained material, overbank/floodplain environment, outlet sediment, away from disturbed or polluted sites)

• Sample at 2 depths and separate 2 grain-size fractions to enhance geochemical information

• Analyse for major, minor & trace elements after total + aqua regia + Mobile Metal IonTM digests

• Identify areas where sediment chemistry indicates lithologies or mineralisation of interest

• Industry can focus further exploration investment in those selected areas and save $$


National Geochemical Survey of Australia (NGSA)

• Landscape divided in large catchments

• Only mainland Australia + Tas

• Topographic analysis to split or amalgamate catchments

• Hydrologic analysis to determine catchment outlets

• Ignore catchments <1000 km2 (mostly coastal)

• 91% coverage• Emphasis on QA/QC

from field to reporting


National Geochemical Survey of Australia (NGSA)

• Sample transported regolith at outlets of 1186 catchments over mainland Australia

• 123 of these catchments have been sampled in duplicate for quality control

• 6 other, large catchments also sampled higher up

• Average density ~1 site/5200 km2 (similar to FOREGS European Atlas)

• 86% of the catchments have been sampled

• Over 6 million km2 (or 80% of Australia) has been sampled

www.ga.gov.au/ngsawww.ga.gov.au/ngsa

Contact: [email protected]


National Geochemical Survey of Australia

0-10 cm depth: Top Outlet Sediment (TOS)

ca 60-80 cm depth: Bottom Outlet Sediment (BOS)

Air-dried, homogenised, split into ‘Bulk’, or sieved to <2 mm (‘Coarse’) and to <75 um (‘Fine’) grain size fractions

Analysed for TOTAL, AQUA REGIA and

MMITM element contentwww.ga.gov.au/ngsa


Archean cratons & basins

Paleoproterozoic basins &complexes

Neoproterozoic basins

Paleozoic metamorphic & igneous rocks

Cenozoic & Quaternary sediments

Mesozoic sedimentary basins

Mesoproterozoic basins &complexes

Archean cratons & basins

Paleoproterozoic basins &complexes

Neoproterozoic basins

Paleozoic metamorphic & igneous rocks

Cenozoic & Quaternary sediments

Mesozoic sedimentary basins

Mesoproterozoic basins &complexes

Geology

Distribution of MMI™ extractable Ga (ppm) in Australia

Distribution of MMI™ extractable La (ppm) in Australia

Distribution of MMI™ extractable Cu (ppm) in Australia

ConclusionsThe distributions of MMI™ extractable elements in catchment outlet sediments from Australia demonstrate that geochemical signaturesfrom the underlying and/or surrounding bedrock, whether barren or mineralised, can be detected and interpreted in terms of lithology or mineralisation potential. Many known deposits are reflected by elevated MMI™ values, and many more anomalous results indicate potential for future mineral discovery.

ReferencesCaritat & Cooper, 2011. Geoscience Australia Record 2011/20 (Available at: http://www.ga.gov.au/ngsa)SGS, 2011. MMI™ Theory (Available at: http://www.geochem.sgs.com/mmi-theory.htm)

Geology


Validation of NGSA pH against existing datasets

Caritat et al. (2011)



A

C

B

D

E

F

G

H

Preliminary interpretation of NGSA results



Comparison airborne vs soil geochemistry

‘Corrected’ U channel image

TOS U ppm vs Airborne eU ppm (300m radius average)with > 25% 2mm fraction removed

R2 = 0.3319

0

1

2

3

4

5

6

7

8

0 2 4 6 8 10 12 14Soil U ppm

Air

bo

rne

eU

pp

m

(p<0.01)

Existing U channel image

Green: 0 ppm U --- Red: 12 ppm U Wilford et al. (2011)


Caritat & Cooper (2011)

TOS Th ppm vs Airborne eTh ppm (300m radius average)with > 25% 2mm fraction removed

R2 = 0.5768

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40 45Soil Th ppm

Air

bo

rne

eT

h p

pm

Wilford et al. (2011)

Comparison airborne vs soil geochemistry


B

A

D

C

E

F




• Horizontal/lateral dispersion from ore deposit, mineralisation, secondary enrichment or alteration zone

• Vertical migration of chemical elements due to processes to be determined that could include groundwater (advection & diffusion), soil gas, plants or micro-organisms, electro-chemical currents over sulfide bodies or even lightning strikes

• Contamination due to mining activities (e.g., dust), but (1) sites selected away from mines, (2) anomalies also in deeper BOS sample, (3) found equally around open-pit and underground mines, and (4) do not outline ore transport routes

Possible causes of geochemical anomalies


B

AC




B

A

D

C




Preliminary interpretation of NGSA resultsConcentration-Area (C-A) fractal analysis of Zn distribution


9 mg/kg40

72

105

“Background” “Anomalous”

Class 1 2 3 4 5

Class 1 (4-9 ppm)Class 2 (9-40 ppm)Class 3 (40-70 ppm)Class 4 (70-105 ppm)Class 5 (>105 ppm)

Zn depositZn occurrence


Extraction Methods and Bio-Availability

Mann et al. (2011)

SGS


Ba (MMI)<0.01-0.180.18-0.340.34-0.480.48-0.650.65-0.890.89-1.171.17-1.501.50-2.192.19-3.363.36-15.3

MMITM extractable Ba (ppm)



La (MMI)<0.001-0.0020.002-0.0050.005-0.0100.010-0.0210.021-0.0400.040-0.0680.068-0.1200.120-0.2010.201-0.3360.336-3.310

La (MMI)<0.001-0.0020.002-0.0050.005-0.0100.010-0.0210.021-0.0400.040-0.0680.068-0.1200.120-0.2010.201-0.3360.336-3.310

MMITM extractable La (ppm)



Au (MMI)<0.1 ppb<0.1-0.10.1-0.20.2-0.30.3-0.40.4-0.50.5-0.70.7-0.90.9-1.31.3-1.98

Au (MMI)<0.1 ppb<0.1-0.10.1-0.20.2-0.30.3-0.40.4-0.50.5-0.70.7-0.90.9-1.31.3-1.98

Au (MMI)<0.1 ppb<0.1-0.10.1-0.20.2-0.30.3-0.40.4-0.50.5-0.70.7-0.90.9-1.31.3-1.98

Ernest Henry

Vera Nancy

Osborne

Mt Rawdon

Sarsfield

The Peak, Tritton,Endeavor, North Parkes

Cowal, Peak Hill,Ridgeway, Cadia

Stawell, FostervilleBroken Hill

Roseberry

Olympic Dam

Prominent Hill

Coyote The GranitesTelfer

Plutonic

Meekatharra

Jundee-Nimary

Golden Grove

Agnew, Thunderbox,Hill 50, Lalwers, GrannySmith, Darlot-Centenary

Sons of Gwalia

Marvel Loch, Bullfinch

Bounty, Frog’s Leg,Norseman, Kundana

Primarily Au MinePrimarily Cu or Zn MinePrimarily Au MinePrimarily Cu or Zn MinePrimarily Au MinePrimarily Cu or Zn Mine

MMITM extractable Au (ppb)



Average % Bioavailability

NGSA Overbank Sampling

Based on 1190 Comparisons MMI vs Total Analysis for Ca, Fe, P1176 for Cu, 1188 for K, 1161 for Mg, 1138 for Mn, 1169 for Zn

Ca Cu Fe K Mg Mn P Zn0

2

4

6

8

10

12

14

16

% Bioavailability

Mann et al. (2011)

MMI/Total: A measure of bio-availability?


110 115 120 125 130 135 140 145 150 155-45

-40

-35

-30

-25

-20

-15

-10

0

200

400

600

800

NGSA Overbank SamplingIsotropic Kriging MMI ImageGeoscience Australia - SGS

. O verbank Sam pling Location

MMI Ca(ppm)Ca

Nullarbor Plain(limestone)

Arid Zone

LimestoneLithology

Mann et al. (2011)


110 115 120 125 130 135 140 145 150 155-45

-40

-35

-30

-25

-20

-15

-10

0

50

100

150

200



MMI K(ppm)K

Arid Zoneand/orSalt lakes

Mann et al. (2011)


110 115 120 125 130 135 140 145 150 155-45

-40

-35

-30

-25

-20

-15

-10

0

2

4

6

8



MMI Mn(ppm)Mn

HighRainfallZonesc.f. Fe

Mann et al. (2011)


Vis-NIR Spectroscopy

PC1 PC2 PC3

PC1: hematite (-);2:1 clay minerals (+)

PC2: SOM, smectite (-); kaolinite (+)

Variance Variance Variance

PC3: illite, smectite, goethite? (-); SOM (+)

Viscarra-Rossel et al. (2010,2011)



PC clusters 1 (orange), 2 (red), 3 (blue) and 4 (green)

with central composition (stars) and average reflectance and continuum-removed spectra

(right)

1

2

4

3

1

2

3

4

1

2

3

4

SOM

SOM

kao

hem

goe

2:1

c2:1

c

2:1

c

kao

2:1

c

2:1

cViscarra-Rossel et al. (2010,2011)



Australian Soil Classification: Map of Soil Orders (Isbell 1996)

Distribution of PC clusters 1 (orange), 2 (red), 3 (blue) and 4 (green) and comparison

to Map of Soil Orders (right)

1

2

4

3



Vis-NIR SpectroscopyMap of “true colour” RGB composite

of Australian topsoil

NIODI uncertaintymap (right)

Normalised Iron Oxide Difference Index (NIODI):Red = hematite; Yellow = goethite probability



• Geochemical surveys provide a fundamental dataset for decision making

• Low to ultra-low density geochemical surveys yield data that makes geological sense

• Pilot projects in the Riverina, Gawler and Thomson areas provided proof-of-concept for the NGSA

• The Onshore Energy Security Program from the Australian Government provided the financial support for the NGSA

• From 2007 to 2011, field work was carried out, sample preparation and analysis took place, and map production was completed

Conclusions


• A new national geochemical dataset is available• Comparison with independent datasets indicates

reliability• Data quality assessed in dedicated report• NGSA data identifies a number of areas that may

have potential for discovery, e.g. in terms of U, Th, Au, Pb, Zn, REEs as shown here

• >500 geochemical maps available on website www.ga.gov.au/ngsa

• The dataset and atlas are useful pre-competitive assets in the exploration for energy and mineral resources

Conclusions


Acknowledgments• Australian Government for OESP funding• All States and Northern Territory for entering a National Geoscience Agreement• Land owners for access to sampling sites• Field sampling teams from State/NT geoscience agencies:

Gary Burton, Paul Flitcroft, Trevor Hegvold (NSW) Andrew Wygralak, Darren Bowbridge, Simon Fanning, Rod Maier, Clarke Petrick (NT) Joseph Tang, Phil Boyle, Stanley Briggs, Dominic Brown, Philip Burrows, Leonard Cranfield,

Terry Denaro, Glenys Diprose, Courteney Dhnaram, Melanie Fitzell, Dudley Fulton, Janice Harley, Jimmy Lam, Mark Livingstone, David McIntyre, Jack Skinner, Jack Ryle (Qld)

Roger Fidler, Katherine Brownlie, Stacey Curtis, Tania Dhu, Adrian Fabris, Claire Fricke, Georgina Gordon, Tiphaine Lavigne, Josine Parsons, Steve Sutton, Antony Whiting, Tania Wilson, Ben Uppill (SA)

Geoff Green, Shane Heawood (Tas) Emily House, Ken Sherry, Rachel Roberts (Vic) Colin Strickland, Richard Langford, Paul Morris, Amanda Thomson (WA)

• Sample preparation and analysis team: Christian Thun, Liz Webber, Bill Pappas, Matthew Brown, Jessica Byass, Nounou

Chanthapanya, John Furlonger, Amber Green, Keith Henderson, Zia Husain, Bozana Krsteska, Benjamin Linehan, Andris Lukss, Ador Makuei, Lucy McCabe, Gregory O’Connell, Billie Poignand, Mike Smith, Helen Tait, Kylia Wall, Tony Watson (GA)

• For assistance and collaboration on various aspects: Michelle Cooper, Evgeniy Bastrakov, Lindsay Highet, Subhash Jaireth, Megan Lech, Dan

McIlroy, Andrew McPherson, Donna Phillips, Lara Sedgmen, John Wilford (GA); John Greenfield, John Watkins (GSNSW); Martin Fairclough (PIRSA); Paul McDonald, Adele Seymon (GSV); Janet Stein, Mike Hutchinson, Peter Veth (ANU); Clemens Reimann (NGU); Rudi Dutter (VUT); Alan Mann (Consultant); Pierrette Prince (SGS); Raphael Viscarra-Rossel (CSIRO); Eric Grunsky (GSC)

the national geochemical survey of australia

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