IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT · IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I...

IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT

Doug Winzar, Brett Keillor, Sharon Bell and Mike Whitford

DECEMBER 2016

IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 2

Contents

1 SUMMARY ..................................................................................................................................................................................... 3

2 INTRODUCTION ............................................................................................................................................................................ 4

3 REGIONAL CONTEXT .................................................................................................................................................................. 4

4 PREVIOUS EXPLORATION .......................................................................................................................................................... 8

5 EXPLORATION CONCEPT ........................................................................................................................................................... 9

6 DETAILS OF THE COLLABORATIVE SURVEY ........................................................................................................................... 9

7 RESULTS AND INTERPRETATION ............................................................................................................................................ 12

8 BIBLIOGRAPHY .......................................................................................................................................................................... 13

List of Figures

FIGURE 1: LOCATION OF IGO’S LAKE MACKAY PROJECT OVER REGIONAL GRAVITY IMAGE ................................................. 3 FIGURE 2: CROSS SECTION (588,300E) LOOKING WEST AT BUMBLEBEE PROSPECT .............................................................. 5 FIGURE 3: LOCATION OF PROSPECTS WITHIN EL24915 OVER TMI RTP MAGNETIC IMAGE ..................................................... 6 FIGURE 4: SOIL ANOMALISM, DRILL HOLE LOCATION, DHEM PLATE LOCATION AND SIGNIFICANT DRILL INTERCEPTS AT

THE GRAPPLE PROSPECT ............................................................................................................................................ 8 FIGURE 5: IGO’S LAKE MACKAY TENURE IN RELATION TO GEOSCIENCE AUSTRALIA’S “ZONE 3” (BLACK DASHED

POLYGON) IDENTIFIED AS A RESULT OF PROSPECTIVITY MAPPING COMPLETED DURING THEIR

ASSESSMENT OF THE “IOCG POTENTIAL OF THE SOUTHERN ARUNTA REGION” .................................................. 9 FIGURE 6: COVERAGE OF 200M SPACED LINES FLOWN BY THOMSON AVIATION OVER THE LAKE MACKAY PROJECT .... 12

List of Tables

TABLE 1: SIGNIFICANT DRILL INTERCEPTS FROM 2015 DRILLING WITHIN EL24915 ............................................................... 5 TABLE 2: SIGNIFICANT DRILL INTERCEPTS FROM 2016 DRILLING OF THE GRAPPLE PROSPECT ........................................ 7 TABLE 3: AIRBORNE MAGNETIC SURVEY SPECIFICATIONS .................................................................................................... 10 TABLE 4: SURVEY BOUNDARY CORNERS (GDA94 Z52) ............................................................................................................ 10


1 Summary

The objective of the 200m spaced airborne magnetic survey was to obtain a more detailed dataset in an area

recently identified as having the potential to be highly prospective for iron oxide-copper-gold (IOCG) style

mineralisation.

The survey commenced on 17 August 2016 and ended on 5 October 2016. It was flown by Thomson

Aviation out of the Nyirripi Aboriginal Community and covered EL24915 and ELA’s 29748, 30729, 30730,

30731, 30732, 30733, 30739 and 30740 – a total of 6,052km2 (Figure 1).

Figure 1: Location of IGO’s Lake Mackay Project over Regional Gravity Image

The data acquired from this survey is currently being used to assist with:

Detailed mapping of the interpreted Andrew Young Igneous Complex (AYIC);

Enhanced identification of tectonic lineaments and fracture zones on a regional scale; and,

Prospect scale targeting of high amplitude magnetic anomalies.

The decision to conduct the survey over (predominantly) exploration licence applications (ELA’s) whilst

negotiations with the Central Land Council (CLC) are ongoing means that any potential discovery will be able

to be progressed as rapidly as possible once the ELA’s are granted.

If IOCG mineralisation is confirmed it is planned to utilise the survey data in conjunction with data obtained

from a planned 1km spaced ground gravity survey to be conducted once all the ELA’s are granted and

heritage clearance obtained.

This combination of detailed magnetic and gravity data should allow Independence group NL (IGO) to

directly target IOCG mineralisation under cover by detecting hematite accumulations (gravity high) and

magnetite accumulations (magnetic and gravity highs). This approach already been used successfully in

Queensland and South Australia, with the discovery of the Ernest Henry, Olympic Dam, Prominent Hill and

Carrapeteena IOCG deposits.


This detailed geophysics will also aid in a greater understanding of the southwestern Aileron Province where

very limited outcrop exposures exist.

2 Introduction

The Lake Mackay Project is located approximately 450km northwest of Alice Springs.

Access to EL24915, (the only granted tenement in project at this stage) is via the Stuart Highway, Tanami

Road and Gary Junction Road to Sandy Blight Junction, then along the graded road to the north that goes

through to Emu Bore and Nyirripi. Temporary access tracks were cleared in order to gain access from the

Kintore Road / Central Petroleum turn-off in the southeast, and from the Sandy Blight Junction / Nyirripi track

to the west.

The CLC represents Traditional Owners in and around the Lake Mackay Project. As a result, IGO is in

constant communication with them.

IGO notified the CLC of its intention to fly the survey and, as requested, provided them with a month’s prior

notice in which to communicate with the relevant Traditional Owners.

3 Regional Context

The aeromagnetic survey focused on the southwestern Aileron Province, just north of the Centralian Shear

Zone (CSZ) that marks the boundary between the Warumpi Province (1690-1600Ma) in the south and the

Aileron Province (1860-1700Ma) in the north.

The development of the CSZ is interpreted to have occurred during the oblique accretion of the Warumpi

Province to the North Australian Craton during the Liebig Orogeny (1640-1625Ma). Extension to the north of

the CSZ allowed the development of the Andrew Young Igneous Complex (AYIC) during the Liebig Orogeny.

The AYIC is interpreted as being prospective for IOCG mineralisation by Geoscience Australia (Schofield,

Huston, & Kemp, 2013). It is considered a possible source and fluid flow driver for IOCG mineralizing fluids,

with the surrounding Lander Rock Beds and Dufaur Suite containing suitable fault architecture, depositional

sites and mechanisms to allow mineralisation to be concentrated.

The discovery of the Bumblebee Prospect (Bumblebee) during drilling of soil geochemical anomalies

generated by IGO has potentially validated this interpretation, with mineralisation currently interpreted to

have strong affinities with Cloncurry style IOCG mineralisation.

The geochemistry of Bumblebee is complex. It contains significant Cu-Au-Ag-Co-Zn-Pb-Mo mineralisation as

well as anomalous As, Bi, Cd, F, Hg, Mo, Ni, Sb, Se, Sn and Te.

Drilling at Bumblebee intersected low grade base metal mineralisation comprising chalcopyrite, sphalerite

and galena.

The intersection of these sulphides coincident with elevated Au, Ag, Cu, Pb and Zn provides further support

for the prospectivity of the Lake Mackay Project.

Two other prospects also returned significant drill intercepts – Springer and Prowl. Mineralisation at the

Springer Prospect is currently considered to be genetically related to that at Bumblebee, while mineralisation

at the Prowl Prospect is (considered to be) associated with an older “Tanami style” orogenic mineralisation.

Significant drill intercepts from the Bumblebee, Springer and Prowl Prospects are summarised in Table 1.


Table 1: Significant Drill Intercepts from 2015 Drilling within EL24915

Prospect Hole_ID From (m)

To (m)

Interval (m)

Au (g/t)

Ag (g/t)

Cu (%)

Pb (%)

Zn (%)

Bi (%)

Co (%)

Bumblebee

15LMAC030 29 31 2 1.3 34.6 7.43 1.32 1.6 0.08 0.09

15LMAC031 35 42 7 3.29 37.7 3.25 0.87 1.34 0.09 0.08

15LMAC032 56 61 5 2.37 12.4 1.43 0.19 0.97 0.04 0.1

65 66 1 2.05 2.53 0.03 0.12 0.01 0 N/A

Springer

15LMAC033 19 20 1 2.75 0.18 0.04 0 0 0 0

15LMAC034 51 52 1 1.35 0.16 0.01 0 0 0 0

Prowl

15LMAC071 7 8 1 2.42 <0.05 0 0 0.01 0 0

15LMAC073 27 28 1 3.43 0.46 0.02 0 0.01 0.01 0

An interpreted cross section of mineralisation at Bumblebee is shown in Figure 2.

Figure 2: Cross Section (588,300E) looking West at Bumblebee Prospect


Extension and infill soil geochemical sampling in and around Bumblebee identified significant Au-Ag-Co-Cu-

Pb-An anomalism at the Grapple Prospect.

Figure 3 shows the location of all of the aforementioned prospects.

Figure 3: Location of Prospects within EL24915 over TMI RTP Magnetic Image

Upon completion of the airborne survey the subject of this report, additional RC drilling was carried out at the

Grapple, Springer and Prowl Prospects.

Drilling at Grapple intersected pyrrhotite, pyrite, chalcopyrite, sphalerite and galena matrix sulphides within a

package of sediments.

While this mineralisation appears similar to that previously identified at Bumblebee, the Grapple

mineralisation is more extensive and is associated with a downhole electromagnetic (EM) conductor (Table 2

and Figure 4).


Table 2: Significant Drill Intercepts from 2016 Drilling of the Grapple Prospect

Prospect Hole_ID From (m)

To (m)

Interval (m)

Au (ppm)

Ag (ppm)

Cu (%)

Zn (%)

Pb (%)

Bi (%)

Co (%)

Grapple

16GRRC001 22 24 2 2.32 0.7 0.16 0.13 0.00 0.01 0.09

26 27 1 1.92 2.3 0.29 0.17 0.01 0.02 0.02

16GRRC003

64 74 10 1.57 50.1 1.05 2.55 1.71 0.06 0.09

85 94 9 1.81 49.1 3.26 3.63 1.09 0.08 0.26

95 100 5 1.07 40.9 4.61 4.61 0.67 0.06 0.25

102 103 1 0.88 21.4 2.87 1.45 0.34 0.05 0.04

131 132 1 0.94 5.1 1.81 0.06 0.00 0.01 0.02

151 153 2 2.16 64.5 0.62 2.39 1.56 0.10 0.03

16GRRC005 151 155 4 0.76 32.9 1.14 2.44 0.69 0.04 0.07

16GRRC005 157 158 1 0.86 23.1 1.08 0.98 0.44 0.04 0.04

165 166 1 1.80 15.9 0.72 1.58 0.30 0.04 0.15

16GRRC007 38 44 6 8.98 23.5 1.45 1.40 0.26 0.07 0.15

Including 40 43 3 13.93 30.1 1.29 1.72 0.35 0.11 0.20

71 75 4 3.77 11.0 1.94 0.50 0.07 0.03 0.04

16GRRC008 22 23 1 1.19 5.1 0.88 0.41 0.43 0.03 0.14

57 58 1 4.14 9.8 1.14 0.44 0.16 0.05 0.11

16GRRC009

69 70 1 3.02 35.3 3.09 1.48 0.49 0.03 1.71

71 72 1 2.06 7.2 1.30 0.18 0.05 0.01 0.06

112 113 1 1.15 27.0 1.35 0.78 0.34 0.03 0.01

117 119 2 4.51 40.9 1.16 1.51 0.77 0.08 0.16

16GRRC010 116 125 9 5.23 12.8 1.40 0.57 0.23 0.11 0.07

Including 116 118 2 14.01 18.5 1.95 0.72 0.32 0.27 0.03

127 130 3 2.60 72.6 0.24 0.45 2.70 0.09 0.01

Including 129 130 1 4.92 147.4 0.10 0.03 5.50 0.18 0.01

16GRRC011 141 142 1 0.85 17.1 3.85 0.22 0.14 0.01 0.06

144 149 5 0.43 34.1 2.69 3.12 0.85 0.03 0.19

This mineralisation is currently interpreted to be volcanogenic massive sulphide (VMS) in style (as opposed

to the IOCG style of mineralisation originally proposed for Bumblebee). As a result, several samples have

been submitted for detailed petrographic and lithogeochemical analysis.


Figure 4: Soil Anomalism, Drill Hole Location, DHEM Plate Location and Significant Drill Intercepts at the Grapple Prospect

Assay results are still pending for Springer and Prowl.

4 Previous Exploration

Rock chip sampling of Andrew Young Hills in 1997 by Geoscience Australia indicated Ni-Cu prospectivity of

the AYIC near Lake Bennett.

A 400m spaced aeromagnetic survey flown by Northern Territory Geological Survey (NTGS) in 1998

identified magnetic features consistent with the AYIC were widespread to the southwest all the way from

Lake Bennett to Sandy Blight Junction, further upgrading the Ni-Cu prospectivity of area.

BHP Billiton (BHPB) signed a joint venture with Southern Tanami Exploration, who held the prospective

ground to the west, under which they targeted magmatic Ni-Cu within the AYIC. In 1999, they flew a 500m

spaced, 25Hz GEOTEM survey covering the majority of the prospective ground.

It wasn’t until 2003, when CLC Agreements were in place, that follow-up ground moving loop EM surveys

was carried out over 8 previously identified anomalies.

This was followed, in 2004, by orientation maglag sampling, ground fixed loop EM and RC drilling (9 holes

for 1,062m). Metadolorite and gabbro intersected in the north were interpreted to be Dufaur Mafic Suite and

pyroxenitic rocks intersected in the south were interpreted to be part of the AYIC.

Reconciliation of the results of this work with downhole EM confirmed that all of the anomalies had been

intersected by drilling and it was concluded that the conductive zones identified were related to clays

associated with shear zones and / or faults.

IGO does not, however, believe that this is the case i.e. that all 8 anomalies have been sufficiently explained

by the drilling conducted by BHPB.


5 Exploration Concept

IGO’s exploration concept is to target large IOCG systems associated with the AYIC.

This style of mineralisation is of interest to IGO because of the sheer size of the deposits that have been

successfully targeted to date using geophysical techniques to look undercover e.g. Ernest Henry in

Queensland and Olympic Dam, Prominent Hill and Carrapateena in South Australia.

In order to pursue this concept IGO, with the aid of its joint venture partner, ABM Resources Ltd, secured a

significant tenement package over Geoscience Australia’s “Zone 3” identified as a result of their assessment

of the “IOCG Potential of the Southern Arunta Region” (Schofield, Huston & Kemp, 2013) (Figure 5).

Figure 5: IGO’s Lake Mackay Tenure in relation to Geoscience Australia’s “Zone 3” (black dashed polygon) identified as a result of Prospectivity Mapping completed during their assessment of the “IOCG

Potential of the Southern Arunta Region”

The majority of the Zone 3 area is covered by aeolian sediments and an extensive palaeochannel system.

IGO is of the opinion that a “geophysical” approach is required to see more effectively undercover – hence

the recent airborne magnetic survey and planned ground gravity survey over Zone 3.

However, if the mineralisation identified at Grapple (and Bumblebee?) is confirmed to be VMS in style, then

IGO’s original geophysical approach would be broadened to include EM surveys over any / all prospective

horizons identified from the recently acquired magnetic data.

6 Details of the Collaborative Survey

Thomson Aviation was contracted by IGO to conduct the survey which commenced on 17 August 2016 and

was completed on 5 October 2016.

A Cessna C210 using a Geometrics G822A magnetometer was used to collect the magnetic data. A

radiation solutions RS400 spectrometer containing a 33 litre NaI crystal detector pack was used to collect the

spectral data. These units were coupled with a GeOZ-DAS digital data acquisition system.


A Novatel OEMV-1VBS GPS receiver was used to locate the data.

Two Geometrics G856 proton precession magnetometers were at the Base Station used to continuously

record diurnal information for the duration of the survey.

All of this information can be found in Thomson Aviation’s “Airborne Geophysical Survey Operations Report

– Lake Mackay” which is included as Appendix 1.

Digital data pertaining to this survey airborne magnetic data is also included in Appendix 1.

Survey specifications are summarized in Table 3 below.

Table 3: Airborne Magnetic Survey Specifications

Line Type Line Spacing (m)

No of Lines Line Km Orientation (Degrees)

Mean Terrain Clearance (m)

Survey 200 1079 35,760 000-180 35

Tie 2000 24 3,943 090-270 35

Total 39,703

Co-ordinates for the survey boundary are listed in Table 4 below.

Table 4: Survey Boundary Corners (GDA94 Z52)

Point Easting

(GDA94_Z52) Northing

(GDA94_Z52)

1 499,740 7,471,300

2 499,780 7,446,860

3 506,540 7,446,900

4 506,780 7,445,060

5 513,380 7,444,940

6 513,340 7,443,220

7 516,580 7,443,260

8 516,820 7,441,340

9 520,240 7,441,350

10 520,180 7,439,660

11 523,580 7,439,540

12 523,620 7,437,660

13 526,980 7,437,740

14 526,940 7,430,340

15 558,220 7,430,260

16 558,220 7433860

17 617,860 7,433,500

18 618,300 7,437,220

19 677,140 7,436,620

20 677,780 7,440,380


Point Easting

(GDA94_Z52) Northing

(GDA94_Z52)

21 718,620 7,439,780

22 718,620 7,443,380

23 725,620 7,443,420

24 725,620 7,447,020

25 737,620 7,446,860

26 737,460 7,452,620

27 706,300 7,453,060

28 705,860 7,475,180

29 668,540 7,475,700

30 668,140 7,479,940

31 648,780 7,480,100

32 648,580 7,476,620

33 597,380 7,476,860

34 597,380 7,466,620

35 601,820 7,466,580

36 601,940 7,462,460

37 561,340 7,462,260

38 561,175 7,456,711

39 533,180 7,456,740

40 511,060 7,466,140

41 511,020 7,471,300

Figure 6 shows the location of the 200m spaced lines flown by Thomson Aviation.


Figure 6: Coverage of 200m Spaced Lines Flown by Thomson Aviation over the Lake Mackay Project

7 Results and Interpretation

As mentioned in Section 1, the data acquired from the airborne magnetic survey is currently being used to

assist with:

Detailed mapping of the interpreted Andrew Young Igneous Complex (AYIC);

Enhanced identification of tectonic lineaments and fracture zones on a regional scale; and,

Specific targeting of high amplitude magnetic anomalies on a prospect scale.

It is anticipated that this work will be completed by January 2017.

Work completed by IGO to date has tested less than 10% of the total Lake Mackay Project area.

The successful targeting and intersection of mineralisation from this (very) limited work clearly supports

IGO’s exploration concept and indicates that the Lake Mackay Project could represent a new and emerging

metallogenic province.


8 Bibliography

Schofield, A., Huston, D., & Kemp, C. (2013). Iron Oxide Copper-Gold Potential of the Southern Arunta

Region. Canberra: Geoscience Australia.

Suite 4, Level 5 PO Box 496 T. +61 8 9238 8300 igo.com.au 85 South Perth Esplanade South Perth WA 6951 F. +61 8 9238 8399 Independence Group NL South Perth WA 6151 Western Australia E. [email protected] ABN 46 092 786 304

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