April 28, 2011
As part
of ongoing Definitive Feasibility Study, Orsu
announces positive results of the final metallurgical test work for its Karchiga Project in Eastern Kazakhstan. The test work
indicates that the composite ore material from the two lodes should
produce a 27.9% Cu concentrate, with 95.76% recovery, and the ores from
the North East and Central lodes should produce a 21.6% and 24.15% Cu
concentrate, with 91.59% and 96.2% recoveries, respectively.
Orsu Metals
Corporation (TSX:OSU),
the London-based precious and base metals exploration and development
company, is pleased to announce the results of the final metallurgical
test work, which was carried out by the Eastern Research Institute for
Base Metals ("VNIITsvetMet") based in
Ust-Kamenogorsk, Kazakhstan as part of ongoing Definitive Feasibility
Study ("DFS"). All test work was conducted under the direction
of Orsu personnel and our lead consultant SRK
Consulting (UK) Limited, Cardiff, UK ("SRK").
The
metallurgical test work was conducted on 1.5 tonnes
of metallurgical samples, selected from the drill core of metallurgical
holes drilled in late 2010 as part of the DFS in both the Central and
North East lodes of the deposit. Test results indicate an amenability to
produce marketable copper concentrates (see technical report entitled
"Preliminary Assessment of The Karchiga
Copper Project, East Kazakhstan Region, Kazakhstan", dated May 25,
2010). The recent testwork is the most
representative study to date, which was focussed
on:
- Improvement
of copper grade in concentrate without loss of copper recovery and
improved zinc rejection in the ores from the Central and North East
lodes and their composite samples ("Froth Flotation");
- Development
of a copper heap leaching process to potentially treat the oxide
ores and transitional secondary sulphide
components of the Central lode ("Heap Leaching").
Froth Flotation
A testwork programme, staged in three phases, was performed on a
composite sample of sulphide ores from both the
Central and North East lodes, mixed in the proportion of 40% to 60%,
respectively (the "Main Composite").
During Phase 1,
various grinds, reagents and flow sheets were tested. During Phase 2,
combinations of the Phase 1 tests with improved parameters were examined.
Phase 3 tests were finally comprised of variability testing of the optimised process on spatial diversity of the lodes
plus locked cycle testing on composite samples, individually representing
the massive and disseminated ores from the Central and North East lodes
(the "Central and North East Composites", respectively).
For the Main
Composite, reduced quantities of the flotation collectors (Butyl Xanthate and Aerofloat) and
the Na2S (Sodium Sulphide) modifier, coupled
with extended flotation times in rougher, scavenging and cleaning
sections of the flow sheet, gave the desired improvements in the copper
concentrate grade. The result for the locked cycle test performed on the
Main Composite is given in the Table 1 in comparison with the result from
locked cycle test, performed by VNIITsvetMet in
2009 on a similar composite sample.
Table 1 - Locked cycle tests for Main Composite
Table 1 shows a
significantly improved copper recovery into concentrate from 91.05% to
95.76%, achieved during the Phase 3 test work programme.
At the same time, the copper grade of the concentrate produced from the
Main Composite has increased from 19.9% Cu to 27.9% Cu, whereas the
overall mass recovery into the concentrate has been lowered from 10.11%
to 8.86%, which will ultimately translate to reduced transportation
costs.
The zinc recovery
has been lowered from 83.84% to 81.54% while the zinc grade in the
concentrate has increased, partly due to the higher zinc head grade,
still remaining at an acceptable level of 5% Zn. The greater flotation
selectivity, achieved in this round of testwork,
affords the opportunity to operate at a lower concentrate grade of, for
instance, 25% Cu, which would result in an increase in the copper
recovery and a decrease in the zinc grade in the concentrate.
In addition,
the gold grade in the Main Composite concentrate was 1.57 g/t Au, with
50.44% recovery.
Table 2 shows
results from locked cycle tests performed on the samples, representing
the Central and North East Composites of the two individual lodes and
respective potential pits of the Karchiga
deposit. The Central Composite is a blend of 15% massive and 85%
disseminated ores, whereas the North East Composite is a blend of 25%
massive and 75% disseminated ores.
Table 2 - Locked cycle test for the Central
and North East Composites
The results for
the Central Composite are on a par with those of the Main Composite in
terms of copper and zinc grades. The gold grade in the Central Composite
concentrate is 0.34 g/t Au.
In the North
East Composite, however, the copper grade in concentrate is 21.6%, with
the gold grade of 1.65 g/t Au. The level of zinc in the concentrate was
higher than expected. This is thought to be related to a build up of frother in the
locked cycle test, leading to poor selectivity between the copper and
zinc sulphides. This might be simple to
rectify. For instance, the ore from the Central pit may be processed
alone in the Year 1. A blend of ores from the Central and North East pits
may then be processed during Years 2 to 6, and this may be followed by
just over 4 years of further processing of ore from the North East pit
only. Optimization for mine planning and milling will be undertaken as
part of the DFS to determine the best way to blend and treat these ores.
Variability
testing using the optimised flotation process
has been performed on nine different samples from different locations in
the deposit or their composite make up. The variability test results did
not highlight any major behavioural deviation
in metallurgical response from that of the standard composite in terms of
recovery and grade.
Heap Leaching
The Central lode of the Karchiga
deposit has an indicated resource of the oxide ore in the amount of 0.923Mt
(at 0.5% Cu cutoff) grading 1.39% Cu and containing 12,868 t Cu (see
technical report entitled "Updated Report on the Karchiga
Property held by Orsu Metals Corporation,
Kazakhstan" and dated March 22, 2010). Three acid leach columns were
loaded with a blend of oxide and transitional secondary sulphide from the Central pit area and subsequently
irrigated with a weak acid solution. Of the three columns, one, which
contained added bacteria and which was aerated at the base, significantly
outperformed the other two columns. This result was not unexpected and
serves to demonstrate the efficiency of bacterial leaching for this type
of ore. After 100 days, this column had achieved 68% Cu recovery, which
corresponds very closely to 100% of the total material that was available
in the sample for leaching.
The reported
results of the metallurgical test work are part of the ongoing DFS.
Completion of DFS is expected in September 2011.
Dr Sergey V Kurzin, Executive Chairman of Orsu
commented: "The sulphide ore flotation
tests demonstrate a possibility to achieve a significantly higher copper
grade in concentrate and copper recoveries into concentrate from the Karchiga ores than indicated in the May 2010 Scoping
Study. They show a marked improvement over all previous test work. These
positive results will allow progressing further a detailed engineering
design of the ongoing Definitive Feasibility Study. In addition, the
positive results of the leaching test work of oxide and transitional ores
demonstrate an additional potential economic benefit for the Karchiga Project, which is likely to be realized from
the cash flow generated during mining and production of copper from the sulphide ores."
________________________________________________________
For further
information please contact:
Ray Oates, Technical Director, Orsu Metals Corporation
Tel: +44 (0) 20 7518 3999
Ryan Gaffney / Andrew Chubb, Canaccord
Genuity Limited
Tel: +44 (0) 20 7050 6500
Vanguard Shareholder Solutions
Tel: +1 604 608 0824
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