igo core geophysics collaboration final report feb 2019€¦ · collaboration final report andrew...

IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT

Andrew Young Igneous Complex- Airborne

Electromagnetic Survey

Lake Mackay Project

EL30733, EL30739, and EL30740

Doug Winzar and Mike Whitford

27 FEBUARY 2019

[email protected]

1:250,000 Mapsheets: Lake Mackay (SF 5211), Mount Rennie (SF 5215)

1:100,000 Mapsheets: Ehrenberg (4951), Carey (4952)

GDA94 Zone 52

IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I 27 FEBUARY 2019 PAGE 2

ACKNOWLEDGEMENT AND WARRANTY

1. Subject to 2, the tenure holder acknowledges that this Report, including the material, information and

data incorporated in it, has been made under the direction or control of the Northern Territory (the

NT) within the meaning of section 176 of the Copyright Act 1968.

2. To the extent that copyright in any material included in this Report is not owned by the NT, the tenure

holder warrants that it has the full legal right and authority to grant, and hereby does grant, to the NT,

subject to any confidentiality obligation undertaken by the NT, the right to do (including to authorise

any other person to do) any act in the copyright, including to:

• use;

• reproduce;

• publish; and

• communicate in electronic form to the public, such material, including any data and

information included in the material.

3. Without limiting the scope of 1 and 2 above, the tenure holder warrants that all relevant

authorisations and consents have been obtained for all acts referred to in 1 and 2 above, to ensure

that the doing of any of the acts is not unauthorised within the meaning of section 29(6) of the

Copyright Act.


Abstract

This Collaboration program was a SPECTREM 25Hz Airborne Electromagnetic Survey covering distinct linear

magnetic features within the Lander Rock Formation to the east of the pyrrhotite associated Grapple prospect,

and circular magnetic features interpreted to be mafic intrusions prospective for massive sulphide

mineralisation. The survey is within the Aileron Province, just north of the Central Australian Suture that marks

the contact between the Warumpi and Aileron Provinces of the Arunta Region. The survey commenced on the

7th November 2018 and was completed on 28th November 2018.

The objective of this survey was to detect conductors that could be derived from “Grapple Style” mineralisation,

further define areas that could be amenable to soil sampling techniques, and test for conductors which could

be associated with mafic intrusions. This has been successfully achieved with the program identifying late

time conductors which are indicative of massive sulphides. Additionally, the depth of regolith derived from this

survey has defined areas in which soil sampling will be an effective test for mineralisation that may not have a

conductive signature.


Contents

1 INTRODUCTION ............................................................................................................................................................................ 5

2 REGIONAL CONTEXT .................................................................................................................................................................. 5

3 PREVIOUS EXPLORATION .......................................................................................................................................................... 8

4 EXPLORATION CONCEPT ........................................................................................................................................................... 8

5 DETAILS OF THE COLLABORATIVE SURVEY ........................................................................................................................... 8

6 RESULTS AND INTERPRETATION .............................................................................................................................................. 8

7 CONCLUSION ............................................................................................................................................................................. 10

8 BIBLIOGRAPHY .......................................................................................................................................................................... 10

List of Figures

FIGURE 1: LOCATION OF THE WESTERN CONTACT AIRBORNE ELECTROMAGNETIC SURVEY. GDA 94 ZN 52 .......................... 5 FIGURE 2: LOCATION OF PROSPECTS AND THE AIRBORNE EM SURVEY BOUNDARY ON TMI 1VD FROM 2016

COLLABORATION SURVEY. GDA94 ZN 52 .......................................................................................................................................... 7 FIGURE 3: DEPTH OF REGOLITH DERIVED FROM THE RECENT SPECTREM SURVEY .................................................................. 9 FIGURE 4: SPECTREM SURVEY SHOWING LATE TIME X COMPONENT TAU AND IGO TARGET ................................................109

List of Tables

TABLE 1: SPECTREM SURVEY PARAMETERS .................................................................................................................................... 8


1 Introduction

The Lake Mackay Project is located approximately 450km northwest of Alice Springs, directly north of the

Kintore Community, with the survey area located to the west and south of Lake Bennet (Figure 1).

Access to the area of the survey is via the Stuart Highway, Tanami Road and Newhaven Road.

Figure 1: Location of the Airborne Electromagnetic Survey. GDA 94 Zn 52

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.

2 Regional Context

The airborne electromagnetic 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 considered a possible source and fluid flow driver for the “Grapple Style” 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 and Grapple Prospects during drilling of soil geochemical anomalies by IGO

has potentially validated this interpretation, with mineralisation currently interpreted to have affinities with

Cloncurry style IOCG mineralisation. Ground and Downhole Time Domain Electromagnetic surveys have

confirmed that these prospects are associated with conductors that are amenable to exploration using airborne

electromagnetic surveys.

The geochemistry of these prospects is complex. They are associated with pyrrhotite sulphide breccias and

contain significant Cu-Au-Ag-Co-Zn mineralisation.

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.

The Blaze soil anomaly has “Grapple Style” anomalism and the Grimlock and Swoop Prospects have

anomalous Co-Ni-Mn, but these two prospects are yet to be drilled.

Figure 2 shows the location of these prospects in relation to the survey boundary on a TMI 1VD image from

the 2016 collaborative aeromagnetic survey.


Figure 2: Location of prospects and the 2018 airborne EM survey boundary on TMI1VDRTP data from 2016 collaboration survey. GDA94 Zn 52

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

3 Previous Exploration

The only record of exploration within this tenement was a very limited GEOTEM AEM program conducted by

BHP over a small part of the area. This was not considered to be an appropriate screening method and IGO

considers the present program to be the first effective exploration program to be conducted over this region.

4 Exploration Concept

IGO’s exploration concept is to target “Grapple Style” pyrrhotite breccia sulphide mineralization that is

conductive, while additionally testing for conductors which could be associated with nickel mineralisation.

This style of mineralisation is of interest to IGO because it is a precious and base metal rich system that could

represent a high value ore and it is amenable to detection using airborne electromagnetic systems. This will

allow for the rapid screening of the project area for large conductive mineralized systems under areas of

shallow transported cover that would not be detectable using surface geochemical techniques.

5 Details of the Collaborative Survey

Spectrem Air was contracted by IGO to conduct a large AEM survey, which was partly co-funded by the

Northern Territory Geological Survey. Surveying of this area began on the 7th of November 2018 and was

completed on the 28th of November.

Spectrem Air deployed their SPECTREMPLUS system to simultaneously collect electromagnetic and total field

magnetic data, with both magnetic and electromagnetic sensors towed behind the aircraft in “birds”. The

contractors report provided describes these systems in detail. Data were collected on North-South oriented

lines spaced 300m apart, with no tie lines flown.

A summary of the Survey is provided in Table 1 below, with the survey outline illustrated in figure 2.

Table 1: Spectrem Survey Parameters

Line Type

Line Spacing (m)

No of Lines

Line Km

Orientation (Degrees)

Transmitter Terrain Clearance (m)

EM Bird Terrain Clearance (m)

Survey 300 110 1487 0-360 90 51.2

6 Results and Interpretation

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

with the targeting of “Grapple Style” anomalism. It is known that the mineralisation at Grapple is associated

with pyrrhotite sulphide breccias and contain significant Cu-Au-Ag-Co-Zn mineralisation. This makes them

good targets for both electromagnetic surveys and soil geochemistry.

The data are in the process of generating targets to test in the near future, however the “depth of regolith”

product generated from the AEM survey has provided a very useful layer when designing future soil sampling

programs. This depth of regolith product has been generated by the contractor through inversion of the AEM

data to provide conductivity depth sections (CDIs) using the inversion code EMFlow (Macnae et al, 1998) with

the inverted sections additionally provided as a survey deliverable. The depth of regolith product is illustrated

in Figure 3 below with the map showing areas with deeper than 75m regolith shown in red. Clearly this is


related to the deep Paleo drainage and as such in these areas soil sampling will be ineffective and will not be

conducted.

Figure 3: Depth of Regolith Derived from the recent Spectrem survey

First pass interpretation of the data is provided by the “Late Tau X” component Image. In areas of conductive

cover, due to the geometry of the system the X component is very descriptive defining targets beneath

conductive overburden, with the EM data collected at later delay times highlighting the most conductive targets.

As such the Tau, or time constant product generated from the survey provides some early indications of targets

for further investigation. Additionally, Spectrem have provided some interpreted conductive targets which are

supplied with the AEM data. The figure below illustrates predominantly the network of paleo drainage, however

a subtle conductive response, associated with shallow cover is highlighted by the pink circle. This will be a

target that receives further attention and could represent conductive mineralisation


Figure 4: Spectrem survey showing late time X component Tau and IGO Target

7 Conclusion

It is anticipated that IGO will continue to analyse this data and generate targets consistent with “Grapple Style”

mineralisation with an objective of testing these targets throughout the 2019 field season. The targets already

identified will be followed up with ground-based EM surveying to confirm and further define the anomalies prior

to being ranked for drill testing.

The identification of the areas suitable for soil sampling and preliminary exploration targets support the

exploration methodology and highlights the potential for further intersections in an 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.

Macnae, J., King, A., Stolz, N., Osmakoff, A., & Blaha, A., (1998). Fast AEM data processing and Inversion:

Exploration Geophysics, 29, 163-169.

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