igo core geophysics collaboration final report · igo core geophysics collaboration final report i...
TRANSCRIPT
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
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 3
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.
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 4
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.
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 5
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
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 6
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).
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 7
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.
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 8
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.
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 9
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.
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 10
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
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 11
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.
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 12
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.
IGO CORE GEOPHYSICS COLLABORATION FINAL REPORT I DECEMBER 2016 PAGE 13
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