Streamlining geochemical exploration to cut cost

Joseph Tang

Geological Survey of Queensland, DNRME

• Background and maximise the cost benefit

• Cost rationalization 1. Understanding geologic setting, taking appropriate samples

and using suitable techniques

2. Reduce the number of new samples

3. Reduce number of analysis

4. Use archival data and free information

5. Seek alternative methods/technologies – pXRF, pan con

6. Leverage from research and integrate geoscientific data -hyperspectral, continuous geochemistry scan, geophysics, etc.

• Summary

Talk Outline

Background

• The exploration geochemistry philosophy has changed from measuring few total digested elements to highly specialised multi-element analyses

• Emergence of new sample types, sampling techniques, preparation method, digestion, extraction, analytical approaches and sophisticated instrumentation

• Geochemistry has a mounting cost factor; the challenge is to balance data wealth and budget without compromising the ability to find a geochemical anomaly

Hydrofluoric acid

An Evolving Science

Modified from Hannan et al. 2018 The Geochemical Tool Kit

• New thinking

• New technology

• New equipment

• Understand

geologic setting

for target specific

exploration

methods

• Knowing regional controls

• High precision, high sensitivity, sufficient sample density

OUTCROP/HARDROCK EXPLORATION THROUGH COVER EXPLORATION

HydrogeochemistryBiogeochemistry

GossanPartial extraction, soil

Bedrock or soil geochemistry

Structural controlled geochemistry

No signal unless porous for gas

Structural controlled

Fault

Fault

Fault

Fault

Ore body

Geochemical halo

Cover sequences

Proterozoic host rocks

Intrusive

1. Geochemical settings

Bedrock drilling

• Outcrop/hardrock Domain

• Outcropping and blind deposits

• Gossans and ironstone

• Stable and Pb isotopes

• Conventional geochemistry

• Undercover Domain

• Effective if geochemical footprint

reaches sampling zone

• Chemical transport through cover

• Faults and fractures

• Secondary dispersion

• Unconventional geochemistry - partial

leaching, biogeochemistry, soil gas,

groundwater, etc.QDEX Report CR108260

• Over reliant on data and not geology

• Effective first pass screening

• Cost saving without compromising accuracies

• Follow up only if necessary

2. Reduce new samples

Core sectioned

1m split

10% component

Composite sample

I. Composite sampling e.g. Drill core

Example

A 10 cm 1 ppm Au vein in this 10m core will give:

1 ppm X 0.1/1 X 10% = 10ppb Au in the composite

sample. This value warrants follow up analysis.

First Order

First Order

Infill as needed

Infill as needed

II. Staged assay and rationalise further work based on results

• Sampling is a significant operational cost

• Batch assay

• Infill only as needed

• Reduce redundant samples

1

2

2

2

2

2

3

3

3

3

2

4

4 4

4

4

2

III. Ordered assaying - Drainage samples

• Pre-planning

• Ordered based on the drainage system hierarchy

• Analyse first and second order as reconnaissance stage

• High sensitivity analytical method

Sample order

First order

Second order

Third order

Forth order

Number refers to stream hierarchy ordering

3. Reduce number of analysis

$-

$50.00

$100.00

$150.00

$200.00

$250.00

$300.00

0 1 2 3 4 5 6 7 8 9 10

Analytical cost for 68 element analysis

Catchment geochemistry Rock geochemistry

No. of analysis types

$268.80

$225.93

• Over prescribed testing

• Good orientation study or use archival data

• Understand roles of various elements

• Only ordered what is relevant

• Always question data usage

Understanding the Periodic table

Elemental association in geochemical models

4. Use archival data and free information

• Geochemistry, geophysics and geology,

pre-competitive studies, collaboration

researches

• Geochemistry Tool Kit (CR108260)

• Geochemistry Through Cover (CR100262)

• Cape York Regional Mineralisation

Potential (CR99246)

• NGSA Queensland mineral Prospectivity

Atlas (CR90119), Spinifex biogeochemistry

(CR88754), Phoscorite rocks (CR99169)

• GSQ data portal QDEXDATA (http://qdexdata.dnrm.qld.gov.au/flamingo/)

QLD Exploration Geochemistry and Drill hole database

• 5.2 million points (2016)

• Heterogeneous data

• Data gaps = opportunity

• False negatives below detection limits = new grounds

• Used for pre-planning and “Orientation studies”

Exploration Geochemistry - usage

• Single element plot

• Multi-element filters

Cape York regional prospectivityassessment -Pre-competitive study

Tang J., Brown D. & Purdy D. 2016. Cape

York Catchment Geochemistry Assessment

– Regional Mineralisation Potential. GSQ

Record 2016/07. CR99246

• Identify anomalous catchments

• Provide geochemical association

Tang J., Brown D. & Purdy D. 2016. Cape

York Catchment Geochemistry Assessment

– Regional Mineralisation Potential. GSQ

Record 2016/07. CR99246

• Provide geochemical association and possible mineralisation models

Cape York regional prospectivityassessment -Pre-competitive study

Biogeochemistry, MIM Battle AxeDifferent analytical methods, partial

leaching and extractions methods

5. Use alternative technologies = Cost benefit

• pXRF

• Geophysics

• Geology

• Innovative data processing (Partnered with CSIRO on AI and machine learning)

HyLogger, GSQ Continous pXRF scanner e.g. Minalyzer & TruScan

Minalyzer

Continuous pXRF e.g. Minalyzer

1.E+00

2.E+05

4.E+05

700 720 740 760 780 800 820 840 860 880 900

Lead Assay (ppm)

0

1000

2000

700 720 740 760 780 800 820 840 860 880 900

Arsenic Assay (ppm)

Maronan,

NW QueenslandGrey is ore zone based on Lab

results

0

500

1000

5 10 15 20 25 30

Uranium (ppm)

0

200

400

600

800

5 10 15 20 25 30

Thorium (ppm)

Mary Kathleen,

NW QueenslandGrey is ore zone defined by

Minalyzer

Geochemical indices/filters calculated from Minalyzer data

0.0

0.5

1.0

1.5

2.0

700 720 740 760 780 800 820 840 860 880 900

Maronan Pb-As-Zn-P (normalised and levelled)

Maronan: Pb-As

+ Zn-Ca-Sr-P-Ni

0

1

2

80 90 100 110 120 130

Tick Hill (As+Cu+Pb)/Mn (normalised and levelled)

Tick Hill: (Au)-As-

Pb-Cu and

negative Mn

0

2

4

5 10 15 20 25 30

Mary Kathleen U-Th-V-Cr-Pb-Ba (normalised and levelled)

Mary Kathleen: U-

Th-V-Cr-Pb-Ba

5

3

1

1

Never afraid to apply archaic technique

• Panning and gold count technique

• Useful for mineralisation associated with visible gold

• Discover many major deposits

6. Leverage from researches and integrate with

other geoscientific programs

Soil gas, MIM Battle Axe, Beijing

University of Geoscience and University

of Adelaide (GTC, 2016)

Hydrogeochemistry, NW Queensland,

CSIRO & QUT

• Mineral System Atlas (UTAS)

• Geochemical Footprint (UTAS)

• Deposit Atlas (UQ)

• Geophysics (new)

• Geology (New)

• Mineral occurrences (GSQ)

• Ultrafines (CSIRO)

E.g. Hydrogeochemistry Program

• Partnered with CSIRO and

QUT

• Based on a <2 km well

radius, ~365 boreholes will

be sampled in the Cloncurry,

Clonagh, Quamby and

Coolullah map sheets

• Program to commence this

year

Summary• Geochemical exploration is challenging and expensive

• Good orientation studies and sampling strategies will cut exploration cost

• Understanding geochemistry using mineral specific techniques to recognise distal expression of ores will streamline exploration program

• Geochemistry must integrate other data types, take advantage of archival data, use new technologies and leverage from researches

ContactDr Joseph Tang

Principal geochemist

Geological Survey of Queensland

P: 07 3096 6149

E: joseph.tang@dnrme.qld.gov.au