1 Mount Isa Mines, Queensland, 4825, Australia. 2 … exploration parameters for Mount Isa-style and IOCG ... 3 China University of ... Co, Cu, Ga, Li, Mg, Mo, Pb, Ti, Zn and the Rare

Geochemical trials in weathered overburden:

Defining exploration parameters for Mount Isa-style and IOCG mineralisation in NW Queensland, Australia

Richard Lilly1, Keith Hannan2, Mingqui Wang3

AUSIMM Tech Talk Tues 8th April 2014

1 Mount Isa Mines, Queensland, 4825, Australia. 2 Geochem Pacific, Coorparoo, Queensland, 4151, Australia. 3 China University of Geosciences, Beijing, 100083, China

Presentation Outline: •Locations •Geochemical Techniques •QAQC •Results •Summary •Case Studies

‘The continued demand for world-class ore deposit discoveries and the decreasing chance of finding outcropping ore deposits increases the need to explore for potentially buried mineralisation in areas of thick overburden and cover sequences’.

The Challenge: Ernest Henry before…….

3

and after.......

30-50m

Previous Studies Ernest Henry Cover Project (Hannan 1994, 1995, 1998, Sheppard, 2001)

• Identified low amplitude geochemical anomalies in overlying sediments

• MECHANICAL dispersion of gossan/soil profile (some concentrated in palaeo-river channels)

• HYDROMORPHIC dispersions in overlying Cretaceous (reduced) shales and sandstones

• FAULT RELATED dispersion of halogens and metals

• GASEOUS dispersion related to oxidation, fault and porosity controls

4

Gaseous Dispersion

GTC PROJECT AIMS • Establish most accurate, repeatable, practical and effective method • Define pathfinder element associations (Isa Cu, IOCG), background

levels and anomaly thresholds in different cover units. • Develop an improved geochemical sample strategy

Geochemical Techniques

Geochemical Techniques Commercially available methods and emerging research:

• 1281 samples

• 7 Methods

• 5 Labs • 3 Countries

6

Method (Abr.) Laboratory Location

Medium sampled Digest Detection

Limits Base metals

targeted

GORE Soil Gas (GORE)

Gore Survey, Maryland,

USA Soil gas - Not

Specified -

Metal Soil Gas (MSG)

University of Queensland,

Brisbane Soil gas Total

(acid) .ppb ü

Soil Gas Hydrocarbon

(SGH)

Activation Laboratories,

Ancaster, Canada

Soil gas

(hydrocarbons) -

.ppt -

Aqua Regia Soils (AQR)

ALS Minerals, Brisbane Soil Partial

(strong acid) .ppm ü

Mobile Metal Ions (MMI)

SGS Minerals, Perth Soil Partial .ppb ü

Hydroxylamine Hydrochloride

(HXH) ALS Minerals,

Brisbane Soil Partial .ppb ü

Bulk Cyanide Leach (BCL)

ALS Minerals, Brisbane Soil Partial .ppb ü

GORE® Soil Gas (GORE) (Gore Labs, USA)

• Soil-Gas technique, developed in 1990’s for oil-gas industry, but also used for mineral exploration.

• Measures compounds released during oxidation of sulphides at depth.

• GORE Module porous to vapors, water/particles remain outside.

• Emplaced to depth of ~60cm, remains in-situ for 10-60 days (this survey 28 days).

7

6034

57

String

Module Loop

Tag (with serial number)

Adsorbent

Pre-cut insertion pocket

Minimum 60cm

GeoGas: Metal Soil Gas (MSG) (analysed at UQ, Brisbane)

8

(1)

(3)

• Soil-Gas technique, developed in China by Prof. Wang Minqi over past 15 years (Beijing University of Geoscience).

• Measures mainly chalcophile metal elements contained in soil gas (Geogas).

• Involves passing Geogas through an ultra pure collector (Nitric acid: HNO3). Analysis at UQ.

• First trial in Australia.

Soil Gas Hydrocarbon (SGH) Activation Labs, Canada

• Technique has been used by oil-gas industry for over 25 years

• Heats soil sample to release organic compounds absorbed within the soil

• Up to 160 complex hydrocarbon compounds can be detected (ppt detection limits)

• Same collection as other soil samples

• Uses all metal implements to reduce risk of contamination by contact with hydrocarbons in plastics

9

Mobile Metal Ion (MMI) SGS Labs, Perth

• Partial leach technique in use for over 20 years.

• Measures metallic ions brought to surface from oxidising mineralisation at depth.

• Interface technique (sample from soil-air contact).

• Produce sharp anomalies: recently arrived (less potential dispersion).

• Field sample is not prepared: simply mixed with chemical ligand (which bonds with metallic ions) and left overnight prior to analysis by ICP-MS.

• Impressive Au resolution (0.1ppb)

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•Aquaregia Soils (AQR) ALS Minerals, Brisbane

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Soil Sampling Methodology • Scrape away uppermost 10cm (50cm x 50cm) to remove potentially

contaminated surface material

• Within hole loosen and mix 30cm x 30cm area to depth of 25cm with paint-free mattock

• Remove material from secondary excavation and sieve to -5mm discarding coarse fraction

• Collected at least 2kg of material in plastic sample bowl and mixed with clean plastic trowel prior to collecting soil samples for 4 soil techniques (AQR, MMI, HXH, BCL)

Other Partial Leach Techniques

•Hydroxylamine Hydrochloride (HXH) ALS minerals, Brisbane •Bulk Cyanide Leach (BCL) ALS minerals, Brisbane

Locations

Trial Survey Locations

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•8 locations (3 ore bodies, 4 targets) •3 in Western Succession •5 in Eastern Succession

Survey Site (Target style)

Topographic and Soil Class Depth of Cover

Isa 1100 (Isa-Cu)

Low-moderate relief stony silt; colluvial and

alluvial

Discontinuous, thin (<10m) regolith.

Shovel Flats (Isa-Cu Background)

Low relief, stony silt colluvial tracts.


Biotite (Isa-Cu)

Moderate relief, stony to sandy silt

colluvial & alluvial tracts


Cabbage Tree (IOCG)

BLIND TARGET

Low relief, Alluvial and channel

Thick (>25m) regolith. 60-160m lithified

Ernest Henry Mine (IOCG)

BLIND TARGET

Low relief ‘black soil’ Alluvial plain

Disturbed cover. 5-50m lithified

Ernest Henry North (IOCG-background)

BLIND TARGET


Thin (<5m) 30-50m lithified

FC9 (IOCG-Background)

BLIND TARGET


Thin (<5m) 30-50m lithified

Eloise Mine (Hi-Sulphur Cu-Au-Ag)

BLIND TARGET


Disturbed thin (<5m) 50-70m lithified

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• Globally significant Cu Ore body

• Located between 700-1000m below surface

• Hosted in westerly dipping Urquhart Shale (Mt. Isa Group)

• Controlled by Paroo Fault ‘ramp’

• Classic Isa-Style silica-dolomite alteration halo with high-grade Cu core

1100 Ore Body 1100 OB Up-dip projection

1100 OB to surface

Sample Site

500m

"

15

• Globally significant Cu Ore body

• Located between 700-1000m below surface

• Hosted in westerly dipping Urquhart Shale (Mt. Isa Group)

• Controlled by Paroo Fault ‘ramp’

• Classic Isa-Style silica-dolomite alteration halo with high-grade Cu core

1100 Ore Body 1100 OB Up-dip projection

1100 OB to surface

Sample Site

500m

" Urquhart Shale

Nat

ive

Bee

Silt

ston

e

Magazine Shale

East

ern

Cre

ek

Volc

anic

s

Judenan Beds

A B

A B

W E

• Geology interpreted from sterilization drilling and geophysics, sampled as background for IOCG targets

• Altered proterozoic metavolcanics and metasediments

• Covered by 1-5m black soil and

• 30-50m of Mesozoic and Cenozoic sediments (sands-shales)

• Classic ‘black soil’ plains, smectitic soils, grassland, undisturbed

EH-N Ernest Henry waste dumps

Eastern Succession Ernest Henry North and FC-9

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17








18 Watch out for seasonal variation!

QAQC

QAQC SUMMARY

• Rigorous use of DUPs and REPs enabled comparison between varied techniques (15% of samples were QA).

• Aquaregia and MMI most precise overall.

• BCL best results for Au (unsurprisingly)

• All partial leach methods gave similar QAQC results

(MMI, HXH, BCL)

• MSG proved to be most precise soil-gas technique (most repeatable sample).

• GORE technique displayed extremely poor reproducibility and precision which overshadows the application of technique to metals exploration.

• GORE also required require specific information about the sample site to aid with the interpretation and allocation of gas species.

However GORE method does noted success in hydrocarbon exploration

• SGH (Soli Gas Hydrocarbons), lab states data is ‘semi quantitative’ and ‘fit for purpose’ analysis of selected organic compounds with poor reproducibility and precision. Lab procedures not transparent for independent testing.

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RESULTS: METAL SOIL GAS

Metal Soil Gas: 1100 OB

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• MSG results display elevated levels of Cu, Ag, As, Ba, Bi, Cd, Co, Ga, Li, Mo, Ni, Pb, Sb, Ti, Tl, U, W, Zn, and REE

Metal Soil Gas: 1100 OB

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Metal Soil Gas: FC-9 and Ernest Henry

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RESULTS: AQUAREGIA

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Aquaregia: 1100 OB

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Aquaregia: FC 9 and Ernest Henry North

RESULTS: MMI

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MMI: FC 9 and Ernest Henry North

Response Ratios Ernest Henry North

• Numerous elements display subtle variations which are interpreted to correspond with basement geology lithology changes.

• Combined Response Ratios were completed for AQR, MMI, HXH and BCL techniques (Ag, Ce, Co, Cu, Pb, Zn)

• Results are consistent with the interpretation that the methods are detecting changes in basement geology through cover sequence lithologies.

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SUMMARY

32

Geochemistry Through Cover (GTC) Project Summary • GTC project highlighted the importance of a thorough, systematic and repeatable

sampling procedure with regular collection of QA samples.

• Despite the availability of advanced soil-gas techniques and some encouraging results, this project clearly demonstrates the continued relevance of ‘traditional’ geochemical techniques (AQR), especially for chalcophile elements in areas of thin to moderate cover (1-10m).

• All partial leach technologies provide increased resolution in areas of thick cover (10m+) and may also provide lithochemical information through thick cover sequences.

• MMI was the preferred partial leach method based on QAQC results and Au resolution.

• MSG successfully identified metallic element anomalies above the 1100 OB, Biotite and Ernest Henry survey sites. However, there remain uncertainties regarding the commercial availability of the method.

• GORE displayed poor repeatability, complex field procedure and generally inconclusive results (and was the most expensive method).

• SGH had interesting but inconclusive results but was overshadowed by QAQC difficulties.

• Ag, As, Co, Cu, Ga, Li, Mg, Mo, Pb, Ti, Zn and the Rare Earth Elements (REE) La, Ce and U have proven to be the most significant mineralisation and lithological pathfinder elements identified by this study.

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Geochemistry Through Cover (GTC) Project Isa and IOCG Pathfinders

IOCG •Ag, As Au, Cu, Co, Li, Mg, Mn, Ti, REE (La, Ce), U

ISA STYLE •Ag, As, Cu, Ga, Mo, Pb, Zn, -ve Ce (REE)

CASE STUDIES

Exploration Success 2011 - AQR • Aquaregia (AQR) soil grid completed

to provide more size constraints on weak (1980’s) RAB anomaly (Zn) on covered target.

• Geochemical success: established concurrent Zn-Pb-Co anomaly

• Two RC holes drilled (total 482m)

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• Cover found to be:

• 2m alluvial cover

• ~18m cover sequence (consolidated sandstones)

• 2nd hole successfully intersected broad, low-grade Zn-Pb mineralisation hosted in black shales with potential for large tonnage low-grade deposit.

• Initial results from detailed MMI soil survey above E1 ore bodies has produced encouraging anomalies through 20-30m+ cover

• Data appear to map the E1 ore body at depth with numerous elements

• Inc: Ag, Au, Cu, Co, Mo, Mn, U

• Comparison AQR (split sample) data set displays several point anomalies (Cu, Ag, Au) above ore body but rest of data set does not correlate with MMI data.

• Evidence is consistent with interpretation that there has been minimal contamination of MMI data set……

MMI Geochemistry E1 Deposits (Pre-strip)

Cu

E1-N E1-E

E8-N

E1-S

Ag Au

MMI Geochemistry E1 Deposits (Pre-strip)

E1-N E1-E

E8-N

E1-S

Mount Margaret: E1-N

• 2012

20-30m

• 13th May 2013 22nd October 2013

Can geochemistry locate more of these through cover...I think so...

Documents

1 Mount Isa Mines, Queensland, 4825, Australia. 2 … exploration parameters for Mount Isa-style and IOCG ... 3 China University of ... Co, Cu, Ga, Li, Mg, Mo, Pb, Ti, Zn and the Rare