| Wed 17 Jun 2009, 16:09 | | GBG - Great Basin Gold - Great Basin Gold Revises Hollister Mineral Resources |
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GBG
GBG
GBG - Great Basin Gold - Great Basin Gold Revises Hollister Mineral Resources
Based On Trial Mining & Drilling Results: Gold Equivalent Ounces Increase By 27%
GREAT BASIN GOLD LIMITED
(Incorporated in Canada and registered as an External Company in South Africa)
(Registration No. 2006/021304/10)
Share Code: GBG ISIN Number: CA3901241057
("Great Basin Gold" or "the Company")
GREAT BASIN GOLD REVISES HOLLISTER MINERAL RESOURCES BASED ON TRIAL MINING &
DRILLING RESULTS: GOLD EQUIVALENT OUNCES INCREASE BY 27%
June 17, 2009, Vancouver, BC - Great Basin Gold Ltd. ("Great Basin Gold" or the
"Company"), (TSX: GBG; NYSE Amex: GBG; JSE: GBG) announced today that a revised
mineral resource estimate had been completed for the Company`s Hollister Project
on the Carlin Trend in Nevada, USA. The overall contained gold equivalent ounces
at Hollister have increased by 27% from 2.3 million in June 2008 to 2.9
million1. At a cut-off grade of 0.25 oz/ton (8.57 g/t Au), the combined measured
and indicated mineral resources contain 1.45 million gold equivalent ounces
grading 1.167 oz/ton (40.00 g/t) for gold and 8.59 oz/ton (295 g/t) for silver.
A further 1.43 million gold equivalent ounces are contained in inferred mineral
resources of 1.03 million tons at a grade of 1.340 oz/ton (45.95 g/t) for gold
and 2.72 oz/ton (93 g/t) for silver; gold equivalent ounces in the estimated
inferred resources increased 111% from June 2008.
The resource estimate has benefited significantly from over nine months of trial
mining, which generated data from channel sampling and delineation drilling for
stope development. As a result of the integration of empirical data from
geological observations and ore control sampling into the vein model, more
stringent parameters have been applied to measured and indicated
classifications. In addition, 161 additional boreholes (totaling 51,430 feet)
completed in the period from April 2008 to March 31, 2009 were integrated into
the model. The drilling program, mostly conducted from underground, has provided
infill data to delineate stopes for trial mining, and significantly improved our
understanding of the lateral and vertical geological continuity of the vein
system. The resource estimate reflects depletion of material mined in 2008 and
2009 (up to March 31 2009), totaling 103,746 gold equivalent ounces at an
average grade of 1.55 oz/ton.
Results of the resource estimate based on all drilling and ore control channel
sampling to March 31, 2009 are tabulated below.
Resource Cut-off Tons Tonnes Au Au
Category oz/ton oz/ton g/t
Measured 0.25 199,300 180,800 1.895 64.98
Indicated 0.25 911,900 827,200 1.008 34.54
Total 0.25 1,111,200 1,008,000 1.167 40.00
Measured
& Indicated
Inferred 0.25 1,035,300 939,200 1.340 45.95
Resource Contained Ag oz/ton Ag Contained ContainedAu
Category Au oz2 g/t Ag oz2 eq oz1
Measured 377,700 29.02 994.8 5,782,800 468,100
Indicated 918,700 4.13 141.5 3,763,300 977,500
Total 1,296,400 8.59 294.6 9,546,100 1,445,600
Measured
& Indicated
Inferred 1,387,500 2.72 93.2 2,815,400 1,431,500
1 Gold equivalent ounces (Au eq oz) were calculated by using the following
metal prices: US$800/oz for Au and US$12.5/oz for Ag.
2 Metallurgical recoveries are not applied to resource values. Contained
metal estimates assume 100% recoveries.
Some figures may not add due to rounding.
The total estimated measured and indicated mineral resources prior the depletion
from trial mining was 1.549 million gold equivalent ounces and is comparable
with the 1.569 million gold equivalent ounces in 1.615 million tons grading 0.87
oz/ton (29.71 g/t) Au and 4.57 oz/ton (156.68 g/t) Ag at a 0.25 oz/ton cut-off
announced in June 2008.
There are internal differences to the current and 2008 estimates, which are
mainly related to modifications to resource estimation procedures described
below:
- Empirical geological measurements have confirmed the previous model
over estimated the width of the veins, hence, tons were over
estimated tons but, at the same time, grade was under estimated. The
current estimate utilises an improved method for modelling the veins
(a mathematical algorithm with a minimum tolerance of a 6" vein width)
and, coupled with a partial percentage estimate, has led to a higher
accuracy in estimating the volume from the wire-frame model of the
veins;
- Grade interpolation within the vein wire-frames was done using Inverse
Distance Squared statistics in the current estimate (instead of
Ordinary Kriging geo-statistics);
- Search radii utilized to categorize the confidence of grades within
the vein wire-frames were decreased (100 feet/30 meters for measured
and 280 feet/85 meters for indicated) and the average distance of
informing samples was introduced, which increased the stringency for
the measured and indicated categories; and
- The minimum number of samples to inform a given block was increased to
3 (compared to 2 in the previous estimate).
The outcome of these changes is a more conservative approach to resource
classification that more closely reflects what is observed empirically
underground. Consequently, the tonnage in the measured category has decreased
but grade has increased. Tonnage in the indicated category has increased due to
reclassification and tonnage in the inferred category has increased due to re-
classification and additional drilling testing the extent of mineralization.
As the mine development progresses, the evaluation and upgrade of the mineral
resources from the inferred and indicated to a measured category will provide
data to assess the potential for reducing cut-off grade. Also the current
testing of various mining technologies may reduce stoping costs, and expand the
opportunity to exploit certain narrow veins that would otherwise not be
considered in the mine plan. Employing a lower cut-off grade would allow lower
grade material in the indicated category to be included in the resource.
The depth extent of the vein system is yet to be fully established, therefore,
to be conservative, inferred resources have been constrained to a depth of 4,350
feet (1,318 meters) above mean sea level (approximately 1,200 feet or 380 meters
below surface). Certain areas of previous indicated resource have also been re-
categorized into inferred because of lesser density of sampling data. Inferred
resource grades have increased from 0.510 oz/ton to 1.34 oz/ton for gold and
1.43 oz/ton to 2.72 oz/ton for silver due to the localized extrapolation of well
defined areas of higher grade pay shoots in the measured and indicated
categories. There is a noticeable decrease in silver grades from measured to
inferred categories which reflects the occurrence of the Ag-selenide naumanite
in the well drilled and sampled high grade shoots as opposed to lesser borehole
data in the inferred zones. The lack of sample density in the inferred material
underpins the lesser confidence in the resources in this category.
The ongoing program will continue to focus primarily on extensions of the
Gwenivere and Clementine vein system to the west/northwest and at depth. Also,
further investigation of Blanket zone mineralization hosted in Tertiary
volcanics above the Gwenivere/Clementine vein system is planned. Detailed
reassessment and modeling of all Blanket zone intersections is currently
underway, as there is potential for a significant resource in this area as
indicated by previous surface drilling. The Company currently has three drill
rigs in operation underground, undertaking stope delineation, resource infill
and exploration drilling. Surface exploration is currently focused on collating
and reviewing all geophysical, geological and drilling data for the property,
with the intent of better delineating basement structures that control
mineralisation. Additional drilling is also being considered for the Hatter
Graben area (press release January 29, 2009) during the third and fourth
quarters of 2009.
Ferdi Dippenaar, President and CEO, commented:
"Our ongoing exploration drilling programs and results from trial mining
continue to confirm the prospectivity of the Hollister property, evidenced in
the substantial increase in the reported resources. The tighter geological
controls constraining the estimate are also improving trial stope tonnage and
grade estimates and, as a consequence, our mine planning is benefiting from more
accurate information. As the underground development continues, there will be
further opportunities to drill test the depth extensions of a number of high
grade zones that are emerging from the evaluation. The continued exploration
drilling from underground is bearing success with tracking the lateral
extensions of the Hollister veins both eastward towards Hatter Graben, but also
stepping northwestward into the major Butte Fault bounding structure.
Furthermore, the review of Blanket style mineralization in the overlying
volcanics may provide an interesting upside to the current resource profile, as
it could be mined from the current infrastructure."
The mineral resources reflect an in situ vein model, and tonnages and grades
were estimated by using a combination of a partial percentage block model and
constrained inverse distance statistics. There is no mining dilution included
within the vein model.
The estimates were completed by Dale Richards, Pr.Sci.Nat., Great Basin Gold`s
Group Mineral Resource Geologist, and signed off by Phil Bentley, Pr.Sci.Nat.,
Great Basin Gold`s Vice President: Geology & Exploration, a Qualified Person as
defined by Canadian Securities Regulations in National Instrument 43-101, who
has reviewed and approved the information and this news release. Details of the
estimate will be included in a technical report filed on www.sedar.com in 45
days.
Ferdi Dippenaar
President and CEO
For additional details on Great Basin Gold Ltd. and its gold properties, please
visit the Company`s website at www.grtbasin.com or contact Investor Services:
Tsholo Serunye in South Africa 27 (0)11 301 1800
Melanee Henderson in North America 1 800 667-2114
Barbara Cano at Breakstone Group in the USA (646) 452-2334
Samples collected from the Hollister Development Block Project are delivered to
Inspectorate America Corporation (Inspectorate) in Sparks, Nevada. Vein samples
are analyzed by standard fire assay procedures. For standard fire assay, vein
sample preparation consists of drying and jaw-crushing the entire sample to 90%
passing 10-mesh, taking a 300 g sub-sample using a Jones splitter, and then
pulverizing the 300 g sub-sample to 90% passing 150-mesh using a large capacity
ring and puck pulverizer. A 30 g charge is fire assayed. All metal
determinations are by gravimetric finish. Laboratory Quality Assurance/Quality
Control (QA/QC) is monitored using coarse reject blanks and assay standards,
duplicate fire assays, and Inspectorate`s internal standards and blanks. Coarse
blanks (barren rhyolite or landscape marble) and assay standards are inserted
into the sample sequence as blind samples prior to submitting the samples to the
laboratory. Inspectorate also inserts assay standards and blanks into the
sample stream. QA/QC results are within acceptable limits.
No regulatory authority has approved or disapproved the information contained in
this news release.
This release includes certain statements that may be deemed "forward-looking
statements". All statements in this release, other than statements of historical
facts, that address possible future commercial production, reserve potential,
exploration drilling results, development, feasibility or exploitation
activities and events or developments that Great Basin Gold expects to occur are
forward-looking statements. Although the Company believes the expectations
expressed in such forward-looking statements are based on reasonable
assumptions, such statements are not guarantees of future performance and actual
results or developments may differ materially from those in the forward-looking
statements. Factors that could cause actual results to differ materially from
those in forward-looking statements include market prices, exploitation and
exploration successes, continuity of mineralization, uncertainties related to
the ability to obtain necessary permits, licenses and title and delays due to
third party opposition, geopolitical uncertainty, changes in government policies
regarding mining and natural resource exploration and exploitation, and
continued availability of capital and financing, and general economic, market or
business conditions. Investors are cautioned that any such statements are not
guarantees of future performance and those actual results or developments may
differ materially from those projected in the forward-looking statements. For
more information on the Company, Investors should review the Company`s annual
Form 40-F filing with the United States Securities and Exchange Commission and
its home jurisdiction filings that are available at www.sedar.com.
Information Concerning Estimates of Measured, Indicated and Inferred Resources
This news release also uses the terms "measured resources", "indicated
resources" and "inferred resources". The Company advises investors that although
these terms are recognized and required by Canadian regulations (under National
Instrument 43-101 Standards of Disclosure for Mineral Projects), the U.S.
Securities and Exchange Commission does not recognize them. Investors are
cautioned not to assume that any part or all of the mineral deposits in these
categories will ever be converted into reserves. In addition, `inferred
resources` have a great amount of uncertainty as to their existence, and
economic and legal feasibility. It cannot be assumed that all or any part of an
Inferred Mineral Resource will ever be upgraded to a higher category. Under
Canadian rules, estimates of Inferred Mineral Resources may not form the basis
of feasibility or pre-feasibility studies, or economic studies except for
Preliminary Assessment as defined under 43-101. Investors are cautioned not to
assume that part or all of an inferred resource exists, or is economically or
legally mineable.
Date: 17/06/2009 16:09:01 Produced by the JSE SENS Department.
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