15 March 2017
The Company Announcements Office Australian Securities Exchange Limited
Higher gold grades and improved metallurgical recoveries confirmed by additional testwork
Key Points
LeachWELL™ bottle roll results of 223 2.4kg composite samples of the transition, lower transition and primary zones, indicate that average grade at Aphrodite is statistically 17% higher when compared with the 50g fire assay results for these samples
An average grade of 2.9g/t resulted from the LeachWELL™ tests of the transition zone samples compared with the average calculated fire assay grade of these samples of 2.2g/t.
The LeachWELL™ results extended the lower transition zone to a depth of 130 metres below surface, approximately 40 metres deeper than previously modelled.
The LeachWELL™ results also indicated that 18% of the primary zone mineralisation has yielded cyanide leachable metallurgical recoveries of >70% to a depth of at least 180 metres below surface. Previous metallurgical recoveries of 35% have been reported for the primary zone mineralisation.
Aphrodite Gold Limited ("Aphrodite" or "the company") wishes to provide an update of the metallurgical and LeachWELL™ testwork on drill core generated by the recent Pre-Feasibility drilling program completed in Late-2016.
The principal purpose of the resource definition and metallurgical PFS drill program was to provide reliable samples for assay and metallurgical testwork with particular focus on the oxide and transition zone mineralisation. Previous metallurgical testwork indicated that acceptable metallurgical recoveries could be achieved by conventional CIL/CIP processing of the oxide/transition zone mineralisation.
A program of LeachWELL™ testwork was initiated to better define the metallurgical boundaries between the transition, lower transition and primary mineralisation relative to depth below surface.
LeachWELL™ Testwork
Intertek Genalysis Laboratory Services completed testwork utilising the LeachWELL™ bottle roll testing on 223 composite samples from the PFS Resource Drill program. LeachWELL™ testwork determines the cyanide extractable gold and provides an indication of metallurgical recoveries and provides checks on the original fire assay results.
The LeachWELL™ results have provided an understanding and guide to the metallurgical recoveries with depth and on defining the transition-primary zone mineralization boundary in conjunction with geological logging. The location of this boundary will improve the pit optimization studies.
The 223 composite samples comprised of 2 or 3 original fire assayed core samples represents approximately 446 metres of diamond core, or 14% of the total resource metres drilled for the PFS program. The composites consisted of 2.4kg of pulp residue from the original core samples. The samples represent both Alpha and Phi mineralization from the transition, lower transition and primary zones.
LeachWELL™ Results
The composite 223 samples representative of the transition, lower transition and primary zone mineralisation indicate that the average grade at Aphrodite is statistically 17% higher when compared with the original fire assay calculated grades of the composite samples.
The LeachWELL™ were also analysed by depth below surface. Table 1 shows the number of samples at 10 metres intervals below surface, and the comparison between composite grade of the original fire assays and the head grade determined from the LeachWELL™ results. The recovery is based on cyanide leachable gold only.
Depth below Surface | Number of Samples | Composite grade based on original fire assays | Head Grade from LeachWELL™ | Variance | Recovery | Oxidation |
50 | 3 | 2.42 | 2.93 | 17% | 90 | T |
60 | 16 | 3.25 | 4.52 | 28% | 93 | T |
70 | 20 | 2.48 | 2.88 | 14% | 93 | T |
80 | 29 | 1.96 | 2.71 | 28% | 79 | T |
90 | 18 | 1.42 | 1.62 | 12% | 33 | T |
100 | 22 | 3 | 2.83 | -6% | 28 | LT |
110 | 31 | 3.09 | 3.35 | 8% | 23 | LT |
120 | 16 | 3.54 | 3.87 | 9% | 40 | LT |
130 | 22 | 2.79 | 3.1 | 10% | 48 | LT |
140 | 9 | 4.11 | 4.57 | 10% | 34 | P |
150 | 8 | 4.91 | 5.43 | 10% | 26 | P |
160 | 12 | 3.72 | 4.06 | 8% | 37 | P |
170 | 5 | 2.24 | 2.52 | 11% | 18 | P |
180 | 5 | 4.03 | 3.85 | -5% | 76 | P |
190 | 3 | 3.66 | 3.99 | 8% | 41 | P |
200 | 4 | 7.3 | 24.49 | 335% | 7 | P |
Table 1- LeachWELL results by depth below surface Note: Oxidation Zone T= Transition, LT
= Lower Transition, P = Primary
A review of the results above by oxidation zone is in Table 2 and shows the average grade of the transition zone LeachWELL™ samples was 2.9g/t compared to the average calculated grade of 2.2g/t based on the original fire assays. The lower transition zone reported the average LeachWELL ™ grade of 3.3g/t. compared to the composite grade of 3.1g/t based on the original fire assays.
Oxidation Zone | Number of Samples | Average Comp Grade | Average LeachWELL Grade | Average Recovery |
Transition | 86 | 2.2 | 2.9 | 76 |
Lower Transition | 91 | 3.1 | 3.3 | 33 |
Primary | 46 | 4.1 | 5.9 | 34 |
Table 2- LeachWELL™ Sample Analysis by Oxidation Zone
A detailed review of the primary mineralization LeachWELL™ samples results also show that 45 metres of the 255.7 metres or 18% of the primary mineralization tested reported recoveries greater than 70% to a depth of at least 180 metres below surface.
The statistical increase in grade from the LeachWELL™ results was reviewed by Lode, Grade and Oxidation is summarised in Table 3. The analysis indicates that the grade increase is not dependant on oxidation or grade range. The results show variability in the grade increase when reviewed by Lode. The Phi Lode LeachWELL™ results reported a 9% increase in grade while the Alpha Lode reported a 19% increase in grade. The variability could be influenced by the portion of free gold and sulphide content in the two lodes.
Category | Value | Count | Mean |
All Samples | 223 | 17% | |
By Lode | Alpha Phi | 167 56 | 19% 9% |
By Grade | >0.5 | 212 | 17% |
>1 | 167 | 18% | |
>3 | 71 | 19% | |
By Oxidation | T P | 89 | 17% |
134 | 17% |
Table 3- LeachWELL™ Sample Analysis of Grade Increase
Aphrodite Gold Limited published this content on 15 March 2017 and is solely responsible for the information contained herein.
Distributed by Public, unedited and unaltered, on 14 March 2017 23:19:14 UTC.
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