Chesapeake Gold Corp.: Excellent Pilot Plant Scale Metallurgical Test Results on Metates
21 9월 2011 - 6:58AM
Marketwired
Chesapeake Gold Corp. ("Chesapeake") (TSX VENTURE: CKG) is pleased
to announce the results of feasibility level, pilot plant scale
metallurgical test work recently completed on its 100% owned
Metates gold-silver project located in Durango State, Mexico.
Metates hosts one of the world's largest undeveloped gold and
silver deposits containing measured and indicated mineral resources
of 17.2 million ounces gold, 466 million ounces silver and 3.4
billion pounds zinc and inferred resources of 2.6 million ounces
gold, 62 million ounces silver and 360 million pounds zinc.
The metallurgical processing flowsheet at Metates involves the
production of a bulk sulphide flotation concentrate followed by
pressure oxidation of the concentrate in an autoclave to oxidize
the sulphides prior to cyanidation to recover the gold and silver.
Hazen Research of Golden, Colorado ("Hazen") has undertaken
extensive lab scale work on individual and composite metallurgical
samples as well as a pilot scale sulphide flotation test. Sherritt
Technologies of Fort Saskatchewan, Alberta ("Sherritt") has
conducted a series of batch pressure oxidation tests followed by a
pilot scale continuous run on various concentrate samples. Current
metallurgical testing results indicate overall recoveries based on
the above flowsheet average about 90% for gold, ranging from 85% to
94%, 77% for silver, ranging from 71% to 84%, and 81% for zinc,
ranging from 77% to 86%.
Sulphide Flotation Work
-- A feed sample of 3,292 kilograms were processed over four days of semi-
continuous operation (34 hours total) to produce 555 kilograms of
sulphide concentrate
-- The composite sample tested represents about 1,650 meters of Chesapeake
drill core and is comprised of approximately 60% intrusive hosted and
40% sediment hosted mineralization
-- The average head grade of the sample was 0.70 g/t gold, 24.6 g/t silver
and 0.25% zinc (similar grades and host rock types as expected to be
mined during years 1-5 of the proposed 120,000 tpd operation)
-- The bulk sulphide concentrate assayed 3.2 g/t gold, 112 g/t silver and
1.17% zinc representing recoveries of about 94.5% gold, 82.9% silver and
87.8% zinc
-- More recent work indicates higher recoveries are consistently achieved
from a coarser grind (P80-100 microns versus - 200 microns in pilot
test) together with different flotation reagents
Pilot Scale Pressure Oxidation Work
-- Sherritt processed 442 kilograms of the concentrate from Hazen during 96
hours of continuous operation in an autoclave divided into different
periods with varying temperature, retention time and oxygen pressure
-- The flotation concentrate responded well to pressure oxidation with
excellent gold and silver recoveries achieved within typical parameters
employed in existing commercial pressure oxidation plants
-- Sulphide oxidation was rapid and was over 99.5% at the conclusion of all
tests
-- The oxidized sulphide slurry from the autoclave was subject to a
conditioning or hot cure step followed by a washing and solid/liquid
separation step with some solids being subject to a lime boil step
followed by batch cyanidation gold/silver recovery tests
-- At the optimal pressure oxidation conditions, gold recovery from the
oxidized solids was consistently in the range of 95% to 97% while silver
recovery following lime boil averaged 87%, ranging from 85% to 90%
-- Liquids were either partially neutralized with limestone to allow for
zinc recovery or fully neutralized with limestone and lime and subjected
to a solid/liquid separation step to simulate conditions suitable for
discharge to the environment
-- Based on initial results from ongoing test work it is expected that
about 85% to 90% of the zinc in the concentrate can be recovered into
zinc cathode following pressure oxidation using solvent
extraction/electrowinning ("SX/EW") methods
Discussion of Results
Management is very pleased with the pilot scale metallurgical
test results and believe the reported metal recoveries are a major
milestone in de-risking the Metates project. The results provide
broad validation of the assumed 85% overall, weighted metallurgical
recoveries for the gold, silver and zinc as provided in the PEA
(June 2010) and updated PEA (April 2011) technical reports on
Metates.
The metal recoveries to the flotation concentrate appear to be
dependent on both the host rock type, either intrusive or sediment
hosted, and the head grades in the samples. Generally, the
intrusive hosted mineralization gives slightly better metal
recoveries than does sediment hosted mineralization. In addition,
higher silver and zinc feed grades seem to result in higher
recoveries to the concentrate, while gold recoveries seem to be
largely independent of feed grade.
Follow-up lab scale flotation optimization work on blended work
type composites similar to Hazen's bulk sulphide concentrate has
and continues to improve the metal recoveries which now range
between 90% to 97% for gold, 83% to 93% for silver and 90% to 95%
for zinc. The metal recoveries from the concentrate following
pressure oxidation have consistently exceeded 95% for gold and 85%
for silver. Based on these concentrate recoveries and the Sherritt
pressure oxidation results, overall metal recoveries accounting for
these two recovery components (flotation and pressure oxidation)
currently average about 90% for gold, ranging from 85% to 94%, 77%
for silver, ranging from 71% to 84%, and 81% for zinc, ranging from
77% to 86%.
Metallurgical studies continue to focus on defining and
optimizing the grinding characteristics and reagents to achieve
higher flotation recoveries in the upcoming pre-feasibility study
("PFS").
Other Pre-Feasibility Study Developments
To date, the 2011 core drill program has completed 50 holes
totalling 21,834 meters for metallurgical samples, exploration and
engineering investigations. Chesapeake has drilled 27 infill holes
totalling 13,597 meters to convert Inferred class material to
Measured class and 12 geo-technical holes totalling 3,219 meters to
support pit slope recommendations. The results of these holes will
be incorporated into a new resource estimate to be completed by
Independent Mining Consultants of Tucson, Arizona before year end.
The new resource will be the basis for the mine schedule and
reserve estimate for the PFS. A step-out drill program has
commenced to expand the resource by testing the mineralized
extensions along strike to the northwest and southeast.
M3 Engineering & Technology of Tucson, Arizona (lead
consultant) is moving forward with a wide range of project related
activities and are currently focused on developing the general
arrangement drawings and equipment lists in support of obtaining
vendor quotations for major capital cost items. M3 is also working
on the design and costing of an alternate shorter access road and
concentrate pipeline route leading downhill from the Metates mine
site to the Ranchito processing site in Sinaloa state.
Sherritt is conducting ongoing test work to evaluate the
recovery of zinc via SX/EW methods as well as follow-up
investigations to optimize gold and silver recovery options.
Sherritt will also be developing the design and capital and
operating cost estimates for the pressure oxidation circuit for the
PFS as well as the zinc recovery plant.
Ausenco Vector of Denver, Colorado has completed their
preliminary geotechnical investigations of the proposed plant sites
and waste rock and tailings storage facilities at both the Metates
and Ranchito sites and has concluded that the ground conditions at
both sites will support the proposed facility locations. Vector
have also determined that it is feasible to deposit both the
concentrate flotation tailings and mine waste rock in a common
storage facility at Metates. This development will result in a
significant cost saving and lessen the long term environmental
impact associated with a dedicated tailings facility.
The PFS will contain a mineral reserve and revised resource
estimate, provide updated capital and operating cost estimates and
revised project economics based on numerous reviewed technical
inputs including trade -off studies for power and alternative
crushing circuits. The PFS will be based on current long term
forecasted metal prices that have risen compared with the US$900
per ounce gold and US$18 per ounce silver price assumptions that
were used in the latest PEA. M3 and numerous other consultants
working on the PFS anticipate that the results of the study will
now be available in the first quarter of 2012.
Chesapeake currently has 39.8 million shares outstanding (47.5
million fully diluted) and $18 million in cash and liquid
investments.
Mr. Gary Parkison, CPG, Vice President Development and a
Qualified Person as defined by NI 43-101 supervised the preparation
of the technical information in this release. Sherritt has also
reviewed the information contained in this release.
For more information on Chesapeake and its Metates Project,
please visit our website at www.chesapeakegold.com.
CHESAPEAKE GOLD CORP.
P. Randy Reifel, President
The TSX Venture Exchange does not accept responsibility for the
adequacy or accuracy of this news release.
Contacts: Chesapeake Gold Corp. Investor Relations 604-731-1094
www.chesapeakegold.com
Chesapeake Gold (TSXV:CKG)
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