ASX ANNOUNCEMENT / MEDIA RELEASE ASX: ABU
19 August 2016
Old Pirate Updated Mineral Resource Estimate
ABM Resources NL ("ABM" or the "Company") advises that CSA Global Pty Ltd (CSA Global) have prepared an updated Mineral Resource estimate for the Company's Old Pirate deposit.
Between March 2015 and March 2016, ABM operated five small open pits at Old Pirate with a total of 155,357 tonnes of ore grading 5.9g/t mined and processed to produce 29,376 ounces of gold.
Following the completion of mining, CSA Global were engaged to prepare an independent estimate of remaining Mineral Resources at Old Pirate in accordance with the 2012 Edition of the JORC Code. CSA Global's Mineral Resource estimate for Old Pirate is 760,000 tonnes at an average grade of 4.7g/t for 114,900 ounces of contained gold, classified as Indicated and Inferred, as detailed in Table 1 below.
Table 1: Old Pirate Mineral Resource Estimate by Classification and Domain (Au > 1g/t)
|
Domain
|
Classification
|
Tonnes
|
Grade (g/t)
|
Contained Ounces
|
|
Western Limb
|
Indicated
|
10,000
|
7.5
|
3,000
|
|
Inferred
|
280,000
|
5.5
|
49,700
|
|
Central
|
Indicated
|
20,000
|
3.1
|
2,400
|
|
Inferred
|
420,000
|
4.2
|
56,300
|
|
East
|
Indicated
|
5,000
|
7.6
|
500
|
|
Inferred
|
10,000
|
4.9
|
1,600
|
|
Golden Hind
|
Indicated
|
5,000
|
3.5
|
500
|
|
Inferred
|
5,000
|
4.1
|
900
|
|
Sub-Total
|
Indicated
|
40,000
|
4.6
|
6,500
|
|
Inferred
|
720,000
|
4.7
|
108,500
|
|
Total
|
Indicated + Inferred
|
760,000
|
4.7
|
114,900
|
Note: Totals may vary due to rounding
The updated Mineral Resource estimate represents a significant reduction in both tonnage and grade compared to previous estimates, the most recent of which was produced in September 2014 (ASX 30 September 2014). Other than depletion due to mining, key changes in the resource estimate are:
-
A reduction in the top-cut from 300g/t to 100g/t
-
Adoption of a minimum horizontal width of 1.0m instead of 0.5m
-
Interpolation of grade using ordinary kriging in place of inverse distance squared
-
Limiting of input data to post 2010 RC and diamond drilling
The CSA Global resource model was extended into the voids of the four main open pits enabling a comparison of modelled tonnage and grade with reconciled mine production. This material is not included in the Mineral Resource estimate reported above. As shown in Table 2 below, the CSA Global model has lower tonnage, higher grade and contains approximately 7% less ounces of gold than actually produced. Mining dilution, ore loss, the mining of mineralisation not identified by exploration drilling and typical margins of error for a Mineral Resource estimate could explain these differences.
Table 2: CSA Global modelled resource within the mined open pits (Au > 1g/t)
|
Source
|
Tonnes
|
Grade (g/t)
|
Contained Ounces
|
|
CSA Mineral Resource Estimate
|
125,000
|
6.6
|
26,400
|
|
Mill Reconciled Mine Production1.
|
149,264
|
5.94
|
28,483
|
1. Excludes Old Glory
As previously advised, ABM now intends to assess all reasonable opportunities available to it for the realisation of value from the Old Pirate deposit and immediately surrounding tenure, which may include the potential farm-out or divestment of the properties.
Brett Lambert
Chief Executive Officer
Geology and Geological Interpretation
Old Pirate is a coarse gold system that is hosted within bedded parallel quartz veins located in two regional-scale, southerly plunging anticlines. Quartz veins ranging from 20cm to 6m in width host the gold mineralisation. Gold can be very coarse with grains up to 5 mm observed in hand-specimen. The mineralised quartz veins preferentially follow key shale horizons within the host turbidite package. The key shale horizons are generally thicker shales, with some up to 25 metres thick.
For the purpose of Mineral Resource estimation, Old Pirate has been split into several individual geological domains, each a part of the anticlinal structure, and each with its own geologic characteristics. The geology of each individual domain has been used to guide the resource estimation for that domain.
Drilling Techniques
Drilling supporting the Mineral Resource was predominantly Reverse Circulation (RC) with a minor number of diamond drill holes. The Mineral Resource estimate is based on assay data from 799 reverse circulation and 16 diamond drill holes completed by ABM between 2010 and 2015. Assay data generated by previous operators and from other drilling methods were excluded. Grade control samples were used to constrain the geological interpretation but the sample assays were not used as part of the Mineral Resource estimate.
Sampling Techniques
RC samples of 1 m length were split by a cone splitter into three portions. All ABM RC samples were taken using a 12.5:1 static cone splitter mounted under a polyurethane cyclone. One portion of ~4kg was sent to the lab for assay, where it was pulverised to produce a 30g or 50g charge for fire assay. One portion was used by geologists for logging, and one portion retained in case of future verification. Sample weights were monitored at the drill site by the responsible geologist to ensure adequate recovery. Upon receipt by the laboratory, samples were logged, weighed, and dried if wet. Samples were then crushed to 2mm (70% pass), then split using a riffle splitter, with 250g crushed to 75 µm (85% pass).
Sample Analysis Method
50g charges from the pulp were fire assayed. Gold was assayed using Fire Assay (FA) with an Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) finish.
Estimation Methodology
A block model with parent cells 1 m (easting) by 5 m (northing) by 10 m (RL) was constructed, and Au grades interpolated using Ordinary Kriging. Samples were top cut to 100 g/t and composited to 1 m sample lengths. Variograms were modelled, with a slight to moderate plunge modelled for each pit. A moderate sample support was used to quell the influence of the perceived high relative nugget effect, with a maximum of 24 samples used to estimate any one parent block. Density values of 2.3 t/m3 (oxide), 2.5 t/m3 (transitional) and 2.65 t/m3 (primary) were assigned to the block model. The grade estimation models were depleted by mining voids, and validated prior to final reporting.
.
Cut-off grades
Wireframe and geological modelling used a 0.5g/t cut-off for geological and grade continuity and block reporting uses a 1g/t cut-off which approximates the cut-off grade used during mining.
Mineral Resource Classification
The Mineral Resource was classified as a combination of Indicated and Inferred. The geological evidence for mineralisation occurrence and continuity was observed in drill sample, and pit wall and floor exposure, with the pit exposure providing an assumed level of confidence (and therefore satisfying the Indicated classification) that the veins containing mineralisation would extend down dip, and along strike for up to 10 m below or beyond the open pit walls. Beyond this extent, grade location and continuity is implied, with a lower confidence, resulting in an Inferred classification. Drill sampling and analytical techniques associated with the RC and DD data are well documented by ABM, with QA/QC results sufficient to support an Indicated classification where the geological confidence also allows it.
Competent Persons Statement
The information in this report that relates to Mineral Resources is based on information reviewed by Mr. David Williams, a Competent Person, who is a Member of the Australasian Institute of Mining and Metallurgy. David Williams is a full-time employee of CSA Global Pty Ltd, an independent consulting company. Mr. Williams has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person as defined in the 2012 Edition of the "Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves". David Williams consents to the inclusion in the report of the matters based on his information in the form and context in which it appears.