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IGO LIMITED — Audit Report / Information 2012
Oct 16, 2012
65111_rns_2012-10-16_4cb543a5-00b3-4490-bb74-82930dfa77f9.pdf
Audit Report / Information
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A S X R E L E A S E
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17 October 2012
Total Pages: 8
ASX Company Announcements Australian Securities Exchange Level 4, 20 Bridge Street SYDNEY NSW 2000
STOCKMAN PROJECT (100% IGO) MINERAL RESOURCES STATEMENT AS OF 30 JUNE 2012
HIGHLIGHTS
- Global Mineral Resource: 13,986,000 Cu t @ 2.1% Cu, 4.3% Zn, 38 g/t Ag & 1.0 g/t Au
Independence Group NL (“IGO”) is pleased to announce new Mineral Resource estimates at the Stockman Project in Victoria, in accordance with the 2004 Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (the “JORC” Code 2004).
The Project was acquired by IGO via the off market takeover of Jabiru Metals Ltd in the June quarter of 2011. The Project is located in eastern Victoria, 300km north-east of Melbourne and encompasses two copper-zinc-silver-gold VMS (volcanogenic massive sulphide) deposits, Currawong and Wilga. During the year successful exploration has increased the Mineral Resources at both deposits to:
Currawong Deposit:
- Mineral Resource: 10,329,000t @ 2.0% Cu, 4.0% Zn, 40 g/t Ag & 1.1 g/t Au
Wilga Deposit:
- Mineral Resource: 3,657,000t @ 2.3% Cu, 4.9% Zn, 32 g/t Ag & 0.5 g/t Au
High Grade Resource Subset:
A feasibility study is being undertaken on the Currawong and Wilga deposits in conjunction with the State and Federal permitting processes. At the same time exploration is continuing proximal to the Currawong and Wilga deposits and regionally, across 130 square kilometres of the Company’s tenure.
Encouraging results from the Bigfoot prospect close to the Currawong deposit (see Figure 1) received during the year include 7.45m @ 0.7% Cu, 4.4% Zn, 153g/t Ag and 10.6g/t Au – down hole width. Big Foot mineralisation has not been included in the June 2012 Stockman Mineral Resource estimate and further evaluation has been planned after successful metallurgical testwork.
Suite 4, Level 5, South Shore Centre I 85 South Perth Esplanade i South Perth I Western Australia 6151 PO Box 496 I South Perth I Western Australia 6951 Telephone +61 8 9238 8300 I Facsimile + 61 8 9238 8399 Email [email protected] I Website www.igo.com.au
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Figure 1: Stockman Project – Regional geology plan showing prospects of interest
Table 1: Stockman Copper-Zinc-Silver-Gold Project – June 2012 Global Mineral Resource Comparison
| 2012 | Tonnes Cu% Zn% Pb% Ag ppm Au ppm1 |
|---|---|
| Currawong Wilga |
Indicated 9,548,000 2.0 4.2 0.8 42 1.2 Inferred 781,000 1.4 2.2 0.3 23 0.5 Sub Total 10,329,000 2.0 4.0 0.8 40 1.1 Indicated 2,987,000 2.0 4.8 0.5 31 0.5 Inferred 670,000 3.7 5.5 0.4 34 0.4 Sub Total 3,657,000 2.3 4.9 0.5 32 0.5 |
| Total 13,986,000 2.1 4.3 0.7 38 1.0 |
|
| 2011 | Tonnes Cu% Zn% Pb% Ag ppm Au ppm1 |
Indicated 9,130,000 2.0 4.2 0.8 42 1.2 Inferred 305,000 1.4 4.1 0.6 34 0.5 Sub Total 9,435,000 2.0 4.2 0.8 42 1.2 Indicated 2,368,000 2.1 5.5 0.5 32 0.5 Inferred 887,000 3.0 2.9 0.2 23 0.2 Sub Total 3,255,000 2.4 4.8 0.4 30 0.4 |
|
| Currawong | |
| Wilga | |
| Total 12,690,000 2.1 4.4 0.7 39 1.0 |
|
Notes to accompany Table 1 :
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1 Au grades for Wilga are all inferred due to paucity of Au data in historic drilling.
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2 Resources include massive sulphide and stringer sulphide mineralisation. Massive sulphide resources are geologically defined, stringer sulphide resources are reported above a cut-off grade of 0.5% Cu or 2% Zn.
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3 Block modelling used ordinary kriging grade interpolation methods within wireframes for all elements and density.
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4 Refer to Table 3 for Mineral Resource estimation parameters.
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Figure 2: Stockman Cu-Zn-Ag-Au Project: Currawong Deposit - 3D isometric projection showing mineralised envelopes, drilling, planned development and down plunge mineralised
intersections.
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Figure 3: Stockman Cu-Zn-Ag-Au Project: Wilga Deposit - 3D isometric projection showing mineralised envelopes, drilling, planned development and down plunge mineralised intersections.
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Table 2: Stockman Copper-Zinc-Silver-Gold Project – June 2012 High Grade Mineral Resource Subset Comparison.
| 2012 HIGH GRADE SUBSET Tonnes Cu% Zn% Pb% Ag ppm Au ppm1 |
|
| Currawong Indicated Wilga Indicated Inferred |
High Cu (>1.2%) 4,997,000 3.0 4.2 0.8 43 1.2 High Zn (>3%) 2,043,000 0.9 6.5 1.1 48 1.5 Sub Total 7,040,000 2.4 4.9 0.9 44 1.3 High Cu (>1.2%) 995,000 3.0 6.5 0.6 36 0.7 High Zn (>3%) 838,000 0.8 7.4 0.6 36 0.5 Sub Total 1,833,000 2.0 6.9 0.6 36 0.6 High Cu (>1.2%) 317,000 6.4 6.2 0.5 39 0.5 High Zn (>3%) 171,000 1.0 8.2 0.6 37 0.5 Sub Total 488,000 4.5 6.9 0.5 38 0.5 |
| Total 9,361,000 2.4 5.4 0.8 42 1.1 |
|
| 2011 HIGH GRADE SUBSET Tonnes Cu% Zn% Pb% Ag ppm Au ppm1 |
|
| Currawong Indicated High Cu (>1.2%) 4,818,000 2.9 4.3 0.8 42 1.2 High Zn (>3%) 1,964,000 0.9 6.7 1.2 48 1.5 Sub Total 6,782,000 2.3 5.0 0.9 44 1.3 Wilga Indicated High Cu (>2%) 644,000 3.8 6.6 0.5 34 0.6 High Zn (>4%) 1,032,000 1.1 7.0 0.6 36 0.6 Sub Total 1,676,000 2.1 6.8 0.5 35 0.6 Inferred High Cu (>2%) 191,000 8.3 5.4 0.3 38 0.4 High Zn (>4%) 117,000 1.3 7.6 0.5 33 0.5 Sub Total 308,000 5.6 6.2 0.4 36 0.4 |
|
| Total 8,766,000 2.4 5.4 0.8 42 1.1 |
Notes to accompany Table 2 :
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1 Au grades for Wilga are all inferred due to paucity of Au data in historic drilling.
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2 Resources include massive sulphide and stringer sulphide mineralisation. Internal high grade domains are modelled and reported above cut-off grades of 1.2% Cu and 3% Zn.
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3 Block modelling used ordinary kriging grade interpolation methods within wireframes for all elements and density.
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Yours sincerely
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Chris Bonwick Managing Director Independence Group NL
COMPETENT PERSONS STATEMENT
Stockman Project Mineral Resource:
The information in this report that relates to the Stockman Mineral Resources is based on information compiled by Mr Bruce Kendall who is a member of the Australian Institute of Geoscientists and is a full-time employee of the Company. Mr Kendall has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration, and the activity which he is undertaking, to qualify as a Competent Person as defined in the 2004 edition of the JORC Code. Mr Kendall consents to the inclusion in the report of the matters based on his information in the form and context in which it appears.
COMPANY INFORMATION
BOARD OF DIRECTORS STOCK EXCHANGE LISTING Peter Bilbe Non-Executive Chairman Australian Stock Exchange Chris Bonwick Managing Director ASX 200 Code: IGO Kelly Ross Non-Executive Director Rod Marston Non-Executive Director John Christie Non-Executive Director CONTACT CAPITAL STRUCTURE Postal Address PO Box 496 Shares on Issue 232.9M South Perth WA 6951 Telephone: (08) 9238 8300 Email: [email protected] Website: www.igo.com.au
| SHARE REGISTRY Security Transfer Registrars Pty Ltd 770 Canning Highway Applecross, WA 6153 Telephone: (08) 9315-0933 Facsimile: (08) 9315-2233 |
TOP 5 SHAREHOLDERS* |
|---|---|
| JP Morgan 22.58% National Nominees 19.61% HSBC Custody Nominees 18.36% Citicorp Nominees 5.59% BNP Paribas Nominees 3.69% *as at 14 September 2012 |
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Table 3: Stockman Project – Currawong and Wilga Minera Resources Parameters
| Geological setting | Currawong and Wilga are V(H)MS style deposits, occurring as polymetallic (pyrite-sphalerite- chalcopyrite) massive sulphide lenses within a volcano-sedimentary succession. Wilga is a single stratabound lens whereas Currawong comprises multiple stratabound lenses with a series of faults offsetting and stacking the lenses. |
|---|---|
| Drilling techniques | All year 2010-2012 holes were diamond drilled from surface using a combination of HQ and NQ core sizes. Historical holes were principally diamond drilling with the exception of several RC precollars drilled by Denehurst and Austminex. None of the RC samples have been used in the resource estimates. The surface diamond drilling is a mixture of HQ, NQ and BQ core sizes, with BQ occurring only in the older WMC holes. The underground holes at Wilga were drilled LTK46 (Ø = 35.6mm). |
| Drillhole Spacing | Diamond drill coverage in the massive sulphide at Wilga and Currawong is on a nominal 25x25m pattern. In the stringer sulphide lenses of both deposits, drillhole spacing ranges from 25x25m to 50x50m. Minimum hole spacing ~10m and maximum hole spacing ~70m. Some holes were twinned in the 2008 drilling campaign and in 2012, one twin hole was completed (12WGDD030 was a twin of 12WGDD028). |
| Drillhole Collar Positions |
Most historic drillhole collar positions were surveyed by licensed or company surveyors. The JML/IGO (2008-2012) drillhole collar positions were located using RTK GPS equipment with a horizontal accuracy of +/-10mm and a vertical accuracy of +/-20mm. All resource work has been conducted on local grids. |
| Drillhole directional control |
Dip and Azimuth readings – generally good quality surveys using downhole camera shots at about 30m intervals. Multi-shot surveys were introduced during the 2010/2011 drilling campaign with downhole readings taken every 6m and these were continued through 2011/2012. |
| Geometry of intercepts |
Surface drilling intersects the massive sulphide lenses almost perpendicular to the lens orientation at both Currawong and Wilga. The underground fan drilling at Wilga has some intercepts that are almost dip parallel. Some sample bias will occur in the Wilga deposit due to this fan drilling orientation but most of the affected area has already been mined and is excluded from the resource estimate. Two down-plunge or down-dip holes were drilled at Currawong however these were excluded from the estimate. They were drilled to detect offsetting faults, cross-cutting intrusions and test the grade continuity along strike. In the resource estimate they were used solely for geometry purposes. No down-plunge or down-dip holes were drilled at Wilga. Three of the 2012 stringer drillholes at Wilga were drilled at low angles to the mineralisation due to the lack of more appropriate drilling locations. These holes also do not represent a large volume of the resource estimate. |
| Sampling techniques | Mostly sawn half-core samples of NQ, BQ and LTK46, or quarter-core samples of HQ varying in length up to 1.3m in the massive sulphide and adjusted to geological boundaries. Some quarter- core NQ samples by Austminex where core was needed for metallurgical testwork. The 2010- 2012 drilling campaigns included a combination of sawn half-core NQ or quarter-core HQ, with a typical sample length of 1m. A minimum sample length of 0.3m and maximum sample length 1.5m in mineralised domains were adjusted to geological boundaries. All massive sulphide intercepts have been sampled and sampling generally extends 10m into waste rock. |
| Data spacing and distribution |
The data spacing and distribution is more than sufficient to establish geological and grade continuity appropriate for the Mineral Resource estimation procedure and classification applied. |
| Sample preparation and assaying |
All samples were crushed and a sub-sample pulverised followed by three or four acid digest with AAS or ICP determination. All samples apart from the WMC samples were prepared and analysed at independent laboratories. The assay techniques are for total digestion of the sulphides and are considered appropriate for this type of mineralisation. For the 2010-2012 drill programs, all samples were assayed at Genalysis Adelaide Laboratory using a 4 acid ore grade digest with an ICP-OES finish. Au was assayed using a fire assay 50g charge and AAS determination. Lower detection limits were to 50ppm for Cu, Pb, Zn, 1ppm/5ppm for Ag and 0.005ppm for Au. |
| Audits or reviews | The Stockman database was rigorously checked during a data compilation and validation stage in 2008. Since then, routine validation of the database has been conducted in-house. |
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| Sample compositing | 1m downhole composites with length and density weighting, face sampling at Wilga and recent probe drillholes at Wilga were not used for grade interpolation nor were the down plunge holes at Currawong. |
|---|---|
| Density | Many samples had measured densities using either water immersion or air pycnometer techniques. All IGO/JML samples were measured for density using water immersion techniques. For those samples with no density measurement, a calculated density was applied to the sample. The assays for Cu, Pb, Zn and Fe were compared with the measured densities and a second power regression curve developed for each deposit. Densities were used in the sample compositing. |
| Quality Control procedures |
In comparison with modern requirements, minimal quality control procedures were adopted by companies completing the drilling programs before JML (eg. inclusion of only 17 field standards, 62 duplicates, 84 external laboratory checks in total). This shortfall was recognised by JML and more rigorous check sampling programs were implemented. Quality control procedures in the IGO/JML drilling programs included the insertion of standards, blanks, duplicates and cross-lab checks. The check samples allowed detection of low order sample contamination at the laboratory during the sample preparation stage and subsequent change in procedures for preparation of JML samples (insertion of barren flushes between samples), along with a positive bias in Zn assays using the four acid digest ICP/OES technique (up to 10% higher than anticipated Zn grades). This technique was reviewed and changed to an alternate technique at Genalysis in 2010. The four acid digest was altered to include the addition of bromide (method code 4AHBr) for Cu, Zn and Pb with ICP/OES determination. Detection limits using the 4AHBr method with ICP/OES finish were 50ppm Cu, Zn and Pb. Samples returning values higher than 100ppm Ag using the original four acid digest method (4AB/OES, detection limit 1ppm for Ag) were re-analysed using the 4AHBr technique (detection limit 5ppm for Ag). Elements analysed are within acceptable limits. Results from duplicate sampling indicate that stringer zone Cu has poor repeatability. Repeatability is moderate to good for most other elements of interest. In 2011, IGO implemented sizing checks to be completed at the laboratory on 10% of the samples submitted for assay. |
| Drill sample recovery | Core sample recovery was good to excellent. Some lost core intervals have been recorded, particularly where structures such as faults or underground workings (Wilga) were intersected by the drilling. These intervals do not affect the resource estimate. One small area of poor sample recovery at Wilga has been identified and isolated. This area corresponds with the presence of chalcocite and has been classified as inferred. Core recoveries in new drilling are reviewed regularly to ensure there are no new areas of poor sample recovery. |
| Geological logging and photography |
Holes were logged and photographed by the various companies completing the drilling programs. JML/IGO core has been photographed both wet and dry. Geological logging is very thorough and more than adequate for resource estimation. Logging has previously been on paper logs, which were data entered and then loaded into the AcQuire database. Paper logs were scanned and stored on the server. Over the last 3 years graphical paper logs have been generated but geological logging has been digital via AcQuire data entry objects which were then uploaded directly into the database. AcQuire data entry objects have in-built rules that allow for validation of data as it is logged. |
| Geological interpretation |
Confidence in the geological interpretation for Wilga is high, with the mineralisation and geological setting being simple and the availability of underground drilling, mapping and plans confirming the interpretation. Currawong is more structurally complex and whilst confidence in the geological interpretation is good, there is room for improvement with more drilling and further data review required to firm up some of the structural detail. Both deposits have been modelled using the massive sulphide as the main geological constraint. The main factors controlling continuity at Currawong are a series of post-mineralisation faults which are interpreted as disrupting the lenses. |
| Dimensions | Currawong (Main Lens) is about 300m long, 240m wide (down-dip), up to 35m thick and located 100-300m below surface. Wilga is about 400m long, 220m wide (down-dip), up to 35m thick and located 50-150m below surface. |
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| Estimation and modelling techniques |
Ordinary kriging was used for grade estimation utilising Surpac v6.2 software. Search parameters were based on variogram models for each element. Grade estimation was constrained to the massive sulphide lens and stringer sulphide lens wireframes. At Wilga and Currawong, additional, internal subdomains of high grade Cu and Zn (Cu>1.2%, Zn>3%) were included in the massive sulphide lenses. Bulk density values were interpolated as for the other elements. No dilution was included in the resource models for Wilga or Currawong this year. Grade estimation for Au at Wilga may not be reliable due to a paucity of Au assays in the historic sample data. For this reason the Wilga Au has been classified as Inferred. |
|---|---|
| Block modelling | Currawong 10mX, 10mY, 10mZ parent cell size with subcelling to 1.25m in all directions. Wilga 10mX, 10mY, 5mZ parent cell size with subcelling to 1.25m in all directions. |
| Moisture | Tonnages have been estimated using densities some of which were dry (those analysed at external laboratories) and others that contained natural moisture. The natural moisture of the Stockman massive sulphides is typically low (<0.5%). |
| Cut-off grades, top-cut grades |
No cut-off grades have been applied to the massive sulphide outer boundary but cut-off grades were applied to help delineate the high grade Cu mineralisation (1.2%Cu) and the high grade Zn mineralisation (3%) within the massive sulphide zones for both deposits. Cut-off grades were also used to delineate the stringer mineralisation at both Wilga and Currawong. These cut-off grades were 0.5% Cu or 2% Zn. Mild top-cut grades have been used for elements where the Co-efficient of Variation was > 1.0. The top-cut grades were determined from disintegration points on log probability plots. (Currawong massive sulphide 8% Pb, 10g/t Au, no top-cut for Zn, Ag or Cu; Currawong stringer sulphide 3% Pb, 13.9% Zn, 106g/t Ag, 10g/t Au, no top-cut for Cu; Wilga massive sulphide 26% Cu, 4% Pb, 31% Zn, 110g/t Ag, 2.6g/t Au; Wilga stringer sulphide 15% Cu, 1% Pb, 11% Zn, 120g/t Ag, 0.95g/t Au). A geological constraint (the massive sulphide zone) has been used as it is stable and will not vary over time, unlike cut-off grades. Mineralisation within both the massive sulphide and stringer lenses has been reported. |
| Mining and metallurgical assumptions |
No assumptions about mining method, minimum mining width or internal mining dilution have been made. Similarly, no assumptions about metallurgical treatment processes and parameters have been made at this stage. |
| Previous mine production |
Wilga has been mined previously and the mining volume has been removed from the resource estimate using the available void wireframes. The accuracy of these wireframes was checked during 2012 after completion of an underground probe diamond drilling program. |
| Classification | Classification was based on sample density and confidence in the geometry of the lenses. All of the major massive sulphide lenses in both deposits were classified as Indicated. Stringer sulphide was classified as Indicated or Inferred or sometimes left as Unclassified if there was limited continuity across sections. Generally, where the sample density was 50x50m or less the resource was classified as Indicated, where the spacing was greater than 50x50m the resource was classified as Inferred. The Au grades at Wilga are considered Inferred due to a paucity of gold assays in the historic drilling data. |
| Tenement and land tenure status |
Currawong and Wilga are located within MIN5523, a granted tenement held 100% by Stockman Project Pty Ltd, which is a wholly owned subsidiary of IGO. There are no current Native Title claims over the area but an agreement is in place with a previous claimant group that makes provision for both the previous claimants and/or other indigenous groups who may assert an interest in the future. The tenement is located on crown land administered by the Department of Sustainability & Environment. The area is rugged and heavily forested with no significant heritage sites identified. No significant impediments are believed to exist. |
| Audits or reviews | An external review of the June 2012 resource estimate will be conducted during the second half of 2012. |
| Further work | No additional resource drilling is planned at this stage of the project. Underground grade control drilling will commence at both Wilga and Currawong once mine development begins. |
| Resource Model numbers |
CU_RSC_2012_07 and WG_RSC_2012_07 |
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