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Animals and vegetables for minerals Biogeochemical exploration through sedimentary cover from tropical savannahs to arid shrublands of the Northern Territory

Steve Hill

AGES 2016, Alice Springs Animals and vegetables for minerals Biogeochemical exploration through sedimentary cover from tropical savannahs to arid shrublands of the Northern Territory Steve Hill Director

Geological Survey of South Australia www.statedevelopment.sa.gov.au

3 Department of State Development

3 main sections…

1.Biogeochemical exploration and the Context and Background to this presentation

2.Some results from and relating to major NT plant communities 3.Some themes and challenges for further investigation

Today’s presentation…

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Collaboration

Students • >500 undergraduates a year (of which 120 a year would collect and prepare a plant sample for analysis) • 48 Honours students since 1998 • 15 PhDs since 2003

Industry • >50 companies represented by industry collaborators

Researchers • Helen Waldron & Colin Dunn annual visits • Stephen Hore (Geological Survey of South Australia) • CRC LEME • Deep Exploration Technologies Cooperative Research Centre

Commercial Laboratory • ACME Laboratories, Vancouver (Bill Macfarlane) • Becquerel Laboratories (Dave Garnett & Helen Waldron) • Genalysis Laboratories (Helen Waldron)

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Geoscience MoU between NT and SA…

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1. Biogeochemical Exploration: Context and Background

Biogeochemistry: biota providing chemical expression of geochemistry • Plants; • Animals; • Micro-organisms….

Cost and Time efficient subsurface biogeochemical information (help prioritise 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 • Potential for depth penetration (via sinker roots) and amalgamation /

homogenisation (largely via lateral roots)


• To provide an expression of buried substrates …. especially if mineralised.

• This best occurs where variables that influence the biogeochemical result, other than buried substrates, are well constrained

Main Objective of Biogeochemical Methods for Mineral Exploration

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snappy gum

spinifex

soil / regolith / landform - carbonate -ferruginous materials -silicified materials

Dispersion -weathering - sedimentation - erosion - transport

termitaria

beefwood

Surface to subsurface interaction -chemical -physical

Time …. - rates & balance of process - evolution models

Map & characterise


Consistency is the key!

• Sampling Procedures • Analytical Procedures • Sampling Site Selection Procedures and

Recognition

• The better constrained the variables other then buried substrate in sampling design - then the best chance of constraining buried substrate

• Methodologies widely published but also talk to people that have done it before

Main Objective of Biogeochemical Methods for Mineral Exploration

12 Colin Dunn under the shade of a coolabah tree, Strzelecki Track

Biogeochemical Case Studies

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1.King River (Cameco) 2.Pine Creek (Australasian Gold) 3.Coyote (CRC LEME - Tanami Gold) 4.Titania (CRC LEME - Newmont) 5.Indee (Range River) 6.Lander River (Tanami Gold) 7.Napperby (Toro) 8.Tibooburra – Milparinka (NSW GS) 9.Broken Hill (NSW GS) 10.Mt Caroline – Woodroofe (PepinNinni) 11.Alcurra (GSSA) 12.Mt Painter (GSSA – Heathgate Res) 13.Olary – White Dam (UoA) 14.Tunkillia – Tarcoola (Minotaur Expl) 15.Wudinna (Adelaide Resources) 16.Middleback Ra (Arrium) 17.Yorke Peninsula – Hillside (Rex Min) 18.Kangaroo Island (UoA) 19.Bookpornong (UoA) 20.Fowlers Gap (UoA) 21.Aileron (NuPower) 22.W.Gawler-Coompana (GSSA – Dunn & Waldron)

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22 CSIRO / AMIRA

GSQ, JCU, MIM


What has been sampled and analysed…? Eucalyptus Corymbia Acacia Triodia Heteropogon Maireana Atriplex Callitris Casuarina / Allocasuarina Eremophila Macropod scats Termitaria Meat Ants Meat Ant nests Terrestrial Gastropod shells

BIOTA TYPES

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Media where n > 100


2. Results from NT plant communities

1. Eucalyptus / Corymbia forest / woodlands 2. Acacia Woodlands 3. Hummock Grasslands 4. Chenopod Shrublands 5. Riparian Eucalypts


2.1 Eucalyptus / Corymbia forest / woodlands

Distribution • Top-end

• Arnhem land • Pine Creek

Species sampled • Eucalyptus tetrodonta

(Darwin stringybark) • Eucalyptus miniata

(Darwin woollybutt) • Corymbia polycarpa

(long-fruited bloodwood)

Stringybark – Bloodwood woodland, King River region, NT



Beatrice U prospect • 3.37 ppm U in Corymbia

polycarpa leaves • Below detection U in sand

palm

Great Western Au prospect Ag (28 ppm) and Au (8.7 ppb) assays in Xanthostemon paradoxus and very high Zn contents (53.9-119.3 ppm)


2.1 Eucalyptus / Corymbia forest / woodlands Species Availability along Toposequence

Eucalyptus miniata

Eucalyptus tetradonta

Corymbia polycarpa

Melaleuca viridiflora



Canopy Sampling

Extendable shears Anchored line (use a stick)

Tree selection important WARNING! Do not use heavily weighted line



Watch Out For Green Ants!



Green vs burnt leaves

Eucalyptus miniata tested near Pine Creek • Significant differences for La, Zn, Co, S • Not significant for As, Mo, Cu, Pb, Cr, Hg


2.2 Acacia Woodlands

Distribution

Widespread across southern half of NT

Acacia aneura, Dunja Bore, NT



Species Sampled

Acacia kempeana

Acacia aneura

Acacia bivenosa



Examples

Tanami Gold Lander River Tenements • Sabre, Yataghan, Falchion…

Arafura Resources • Nolans Bore (also Eucalyptus / Corymbia

at site)

NuPower • Reynolds Range / Ti-tree Basin

Alcurra 1:100k sheet (SA) Sabre Prospect, Lander River, NT



Alcurra 1:100k SA

~200 mulga sample points • Along roads / tracks

(but sampled > 20 m off tracks)

• ~2 km sample spacing • ~2.5 days sampling • Area has 80% regolith

cover



Alcurra SA

• Not only detection of mafic dyke swarms

• Expressions of ‘geochemical fertility’!



Challenges

• Dust • Phyllode separation

from twigs • Sub-species • Mosaic distribution

Xmas-tree form (Alcurra SA)

Standard form (Alcurra SA)


2.3 Hummock Grasslands

Distribution

Much of southern 2 thirds of NT



Species Sampled (Nathan Reid’s PhD thesis and papers has best collection of these results)

• Porcupine grass / spinifex (Triodia pungens, T. irritans) Also trees / shrubs from hummock grasslands: • Snappy gum (Eucalyptus brevifolia) • Corkwood (Hakea lorea) • Beefwood (Grevillea striata) • Bloodwood (Corymbia opaca) • Smooth barked coolibah (Eucalyptus victrix) • Inland tea-tree (Melaleuca glomerata) • Acacias (e.g. A bivenosa, A. aneura, A. victoriae) • Mallee eucalypts (e.g. blue mallee – Eucalyptus gamophylla)



Examples • Tanami (Titania and Coyote)

Coyote Gold Mine, WA Tanami Spinifex detected a buried gold deposit (within white curve line) much better

than other surficial techniques

Arsenic Gold

(Reid et al., 2008)

Arsenic

Gold Titania Gold Prospect NT, Tanami (Reid et al,2009)

<0.2 0.2-0.3 0.3-0.5 0.5-0.7 0.7-2.9

Au (ppb)

0.1-0.3 0.3-0.4 0.4-0.6 0.6-1.1 1.1-1.9

As (ppm)

TANAMI AU MINERALISATION Conceptual multi-element dispersion and footprint

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Zn As Au

spinifex



Challenges / Advantages

• Who would have known that they are prickly? • Species and availability mosaic • Resinous (detritus sticking and can be difficult to mill)


2.4 Chenopod Shrublands

Distribution

In NT, locally abundant but not extensive (e.g. calcareous bedrock, calcretes, hydrocarbon seeps, saline flats…) Not as exstensive as in SA, NSW, WA

Bluebush (Maireana sedifolia) plains, Hiltaba Station, SA

Western Gawler / Eucla Basin Geochemistry / Biogeochemistry

~450 plant samples ~170 sample sites

Colin Dunn & Helen Waldron)

Western Gawler / Eucla Basin Geochemistry / Biogeochemistry

Trans Australia Railway

MESA Journal v75, p.32-44 (2014) GSSA Report Book 2014/00025


2.5 Riparian Eucalypts

Distribution

Ephemeral stream channels and floodplains, particularly in semi-arid areas. Coolibah becomes more dominant in lower catchments areas

Riparian river red gum woodland, Gidjya Bore, NT



Species sampled

• River red gum (Eucalyptus camaldulensis) • Coolibah (Eucalyptus coolabah)

Coolibah, Lake Eyre Basin



Examples

• Ephemeral catchment sampling • Barrier Ranges NSW • Flinders Ranges SA • Murray Basin SA

• Isolated NT samples, but potential for

catchment study • Reynolds Range • Lander River

Pine Creek, NSW… (~10 km west of Broken Hill)

Sample spacing – every collectable RRG

• 215 River Red gums sampled – Media

• Leaves • Chest height • Sample size~300g

Middle Pinnacle

Pinnacles Mine

Lead…

•Pb up to 205 times background levels

•Geochemical footprint ~ 2.5 km

0 – 36 ppm 37 – 99 ppm 100 – 190 ppm 191 – 411 ppm

Hyperspectral Image, courtesy NSW DPI N

2 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 DPI

N 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 DPI

N 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!


3. Some themes and challenges

For further investigation: Scale

• Key criteria for exploration “search space” volume reduction • Ideal sample spacing • Viability of samples at regional or local scale? • E.g. River red gums regionally used to regional detect buried U

mineralization flanking Flinders Ranges and Ag-Pb-Zn in Barrier Ranges. • Sampling at 200 - 250 m spacing • Could drive vehicle along lower reaches of creek and walked

headwater sections



For further investigation: Seasonality

Availability of plant organs • E.g. flowers, fruit, new leaves etc

Biogeochemical characteristics • E.g. Cruikshank & Pyke (1986) from Ranger U mine area. Better U

background to anomaly contrast in E. miniata prior to ‘wet season’ • Seasonal groundwater hydrogeochemistry changes are critical if plants

are tapping into these aquifers



For further investigation: Climatic patterns

El Niño and La Nina, where buried mineralisation may still be expressed but with significant variations in trace element concentrations (eg Mitchell et al 2015)

Modified from Climate Data Online, Bureau of Meteorology, 2013.



Pb concentrations vary enormously within climate cycle:

• Higher in dry year • (2005) • Lower in wet year

(2012) Mg concentrations stay much the same

From: Mitchell et al., 2015



For further investigation: Compatibility and Levelling

• Essential for developing useful regional data sets • Normalisation? • Potential exists for use of different element ratios and factors rather

than single elemental concentrations • U2/Th • Pb:Zn • Zn / In • Zr, Al, Fe associated elements and detritus



For further investigation: Sampling Confidence

• When is enough sample, enough? • Different for different elements, organs, species….. • Repeatability • “fit for purpose”

• Influence of fire?

• Other parts of the system? • Ground litter • Plant water • Gases / evapo-transpiration atmosphere



For further investigation: Other controls on biogeochemical results • Depth of cover • Target mineralogy • Hydrogeology • Hydrogeochemistry

(e.g. salinity elevating Mo results)

• Landscape setting (e.g. black soil plains?)

Napperby Prospect, NT Acacia bivenosa roots in carnotite but phyllodes only 0.11 ppm U (carnotite has low U bio-availability)

e.g. Arnhem land Eucalyptus / Corymbia Below detection Th (limits use of U2/Th) due to Th held in Fe-oxides


Australian Biogeochemical Ambition

Integrated into workflows for exploration undercover Not used in isolation

At regional scale (Geological surveys):

• Introduces ‘chemical fertility’ to geophysical systems • Provides ‘geochemical’ baseline information • Provides biogeochemical baseline results for detailed industry surveys

• Minimum number of species sampled for regional coverage? • SA currently biogeochemistry mapping: Mt Painter, Yorke Peninsula, NE Eyre Peninsula,

Kangaroo Island, Alcurra At tenement to camp scale (Industry):

• add depth to soil and stream sediment surveys; • add chemical fertility to geophysics; and, • refine drilling targets

Disclaimer The information contained in this presentation has been compiled by the Department of State Development 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. The Department of State Development 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. The Department of State Development reserves the right to update, amend or supplement the information from time to time at its discretion.

www.statedevelopment.sa.gov.au

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