Pretium Resources Inc.: Mineral Resource Estimate Adds Measured
Gold Resources, Increases Grade at Valley of the Kings
VANCOUVER, BRITISH COLUMBIA--(Marketwired - Dec 19, 2013) -
Pretium Resources Inc. (TSX:PVG)(NYSE:PVG) ("Pretivm") is pleased
to report the NI 43-101-compliant 2013 Valley of the Kings Mineral
Resource estimate for its Brucejack Project, completed by Snowden
Mining Industry Consultants ("Snowden"). Measured and Indicated
Mineral Resources total 8.7 million ounces of gold at a grade of
17.6 grams of gold per tonne.
Valley of the Kings High-Grade Gold Mineral
Resources
High-grade gold resources in the Valley of the Kings (5.0 g/t
gold-equivalent cut-off) total:
- 8.7 million ounces of gold in the Measured and Indicated
Resource categories (15.3 million tonnes grading 17.6 grams of gold
per tonne); and
- 4.9 million ounces of gold in the Inferred Mineral Resource
category (5.9 million tonnes grading 25.6 grams of gold per
tonne).
The Mineral Resource estimate incorporates data from all
exploration surface and underground drilling completed to date, as
well as the drilling and processing results from 2013's Valley of
the Kings Bulk Sample Program (the "Program"). Program drilling and
underground exploration drilling has increased the confidence of
the Mineral Resource in the Program area to the Measured Mineral
Resource category. The Valley of the Kings remains open to the east
and west along strike and at depth. (See Table 1 for a summary of
the 2013 Valley of the Kings Mineral Resource estimate.)
An isometric view of the Valley of the Kings block model is
available at http://media3.marketwire.com/docs/blockmodel.pdf.
Valley of the Kings Geological Confidence
The Mineral Resource estimate has been informed by extensive
work focused on the geological interpretation of the Valley of the
Kings. The high-grade mineralization in the Valley of the Kings is
hosted in a broad deformed stockwork, and a key outcome from the
Program was the underground confirmation of both lateral and
vertical continuity of the vein systems comprising this stockwork
and the location of high-grade corridors of mineralization.
A detailed view of the underground mapping of the veining in the
bulk sample area is available at
http://media3.marketwire.com/docs/undergroundmapping.pdf.
Drill data, in conjunction with underground mapping and surface
mapping, has resulted in a robust geological model for the Valley
of the Kings with well-defined mineralized domains.
Cleopatra Structure
The high-grade Cleopatra structure was first encountered during
Program excavation targeting an area of high-grade mineralization
predicted by the November 2012 Mineral Resource estimate (see
news release dated July 23, 2013). The Cleopatra structure was
subsequently defined for approximately 85 meters along strike and
50 meters above and below the 1345-meter level. Geological mapping,
mineralogical characteristics, assay ratios of the different
elements and underground observations have demonstrated that the
Cleopatra structure is a northerly trending component of the
deformed mineralized stockwork system. This interpretation has been
developed and supported by geological mapping elsewhere
underground.
A sensitivity for the mineralization interpreted to be from the
Cleopatra structure contained within the 2013 Valley of the Kings
Mineral Resource estimate is shown in Table 2 below. A separate
resource model is being prepared for the entire Cleopatra structure
based on all drilling and underground exploration of the Cleopatra
structure, which is expected to be completed in the first quarter
of next year.
Table 1: Valley of the Kings Mineral Resource estimate
- December 2013(1),(4) |
(Based on a cut-off grade of 5.0 grams of
gold-equivalent/tonne(5)) |
Category |
Tonnes (millions) |
Gold (g/t) |
Silver (g/t) |
Contained(3) |
Gold (million oz) |
Silver (million oz) |
Measured |
2.0 |
19.3 |
14.4 |
1.2 |
0.9 |
Indicated |
13.4 |
17.4 |
14.3 |
7.5 |
6.1 |
M & I |
15.3 |
17.6 |
14.3 |
8.7 |
7.0 |
Inferred(2) |
5.9 |
25.6 |
20.6 |
4.9 |
3.9 |
(1) Mineral Resources which are not Mineral Reserves do not
have demonstrated economic viability. The estimate of Mineral
Resources may be materially affected by environmental, permitting,
legal, marketing, or other relevant issues. The Mineral Resources
in this news release were estimated using the Canadian Institute of
Mining, Metallurgy and Petroleum (CIM), CIM Standards on Mineral
Resources and Reserves, Definitions and Guidelines prepared by the
CIM Standing Committee on Reserve Definitions and adopted by CIM
Council. |
(2) The quantity and grade of reported Inferred resources in
this estimation are uncertain in nature and there has been
insufficient exploration to define these Inferred Resources as an
Indicated or Measured Mineral Resource and it is uncertain if
further exploration will result in upgrading them to an Indicated
or Measured Mineral Resource category. |
(3) Contained metal figures and totals may differ due to
rounding of figures. |
(4) The Mineral Resource estimate stated in Table 1 is defined
using 10 m by 10 m by 10 m blocks in the in Valley of the
Kings. |
(5) The gold equivalent value is defined as AuEq = Au +
Ag/53. |
|
Table 2: Cleopatra Structure Sensitivity - December
2013(1),(2),(4) |
(Based on a cut-off grade of 5.0 grams of
gold-equivalent/tonne(5)) |
Category |
Tonnes (millions) |
Gold (g/t) |
Silver (g/t) |
Contained(3) |
Gold (million oz) |
Silver (million oz) |
Measured |
0.06 |
38.8 |
23.2 |
0.075 |
0.045 |
(1), (3), (4) and (5) see footnotes to Table 1. |
(2)The above sensitivity is a subset of the Valley of the Kings
Mineral Resource estimate and is not meant to supersede or replace
the results of the Valley of the Kings Mineral Resource
Estimate. |
Mineral Resource Modeling and Estimation
The December 2013 Mineral Resource estimate for Valley of the
Kings was completed by Snowden on behalf of Pretivm. The Mineral
Resources are classified as Measured, Indicated and Inferred
Resources in accordance with the CIM Standards on Mineral Resources
and Reserves, Definitions and Guidelines prepared by the CIM
Standing Committee on Reserve Definitions and adopted by CIM
Council.
Classification is applied based on geological confidence, data
quality and grade variability. Areas classified as Measured are
informed by 5 meter by 10 meter to 10 meter by 10 meter underground
fan drilling in the vicinity of the Program. Areas classified as
Indicated Resources are informed by 20 meter by 20 meter to 20
meter by 40 meter drilling. The remainder of the Mineral Resource
is classified as an Inferred Resource where there is some drilling
information and the blocks lie within the mineralized
interpretation. Areas where there is no informing data and/or the
lower grade material that is outside of the mineralized
interpretation are not classified as a part of the Mineral
Resource.
The Mineral Resources are reported above a cut-off grade of 5.0
grams of gold-equivalent/tonne (5.0 g/t AuEq). The gold-equivalent
calculation used is: Au + (Ag/53).
The Brucejack Project comprises several gold-silver mineralized
areas. These areas include West Zone, Valley of the Kings, Bridge
Zone, Gossan Hill and Shore Zone. The majority of the Mineral
Resource lies within Valley of the Kings and West Zone. West Zone,
Gossan Hill, Shore Zone and Bridge Zone were not updated for this
Mineral Resource as there has been no additional drilling in these
areas. The focus of the 2013 drilling has been on the high-grade
Valley of the Kings area.
The Valley of the Kings mineralization is approximately 500
meters south of West Zone. The Valley of the Kings mineralized zone
trends approximately west-northwest to east-southeast. Its
orientation mirrors that of Electrum Ridge, a pronounced
topographic feature near the southern margin of the zone, and
drilling to date has extended its strike to over 1000 meters. The
zone is up to 170 meters wide and remains open to the west, beyond
the Brucejack fault, at depth and to the east. Surface mapping and
Pretivm's extensive drilling defined a number of lithologic
contacts which outline a broad syncline in which fragmental
volcanic and clastic sedimentary rocks, along with minor flows of
Upper Triassic to Lower Jurassic age appear to plunge moderately to
the east.
Pretivm and Snowden used Pretivm's interpretation of the
lithological units at the Valley of the Kings, together with a
nominal 1 to 3 g/t Au grade cut-off to update the mineralized
domains for estimation at the Valley of the Kings.
The input data for the Valley of the Kings estimate comprises
922 drillholes for 218,127 meters including 9 historical surface
drillholes (579 meters), 24 surface drillholes completed since the
previous November 2012 Mineral Resource (5,100 meters) and 409
underground exploration drillholes completed since the previous
November 2012 Mineral Resource (38,829 meters). These figures
exclude intervals with no gold values and drillholes outside of the
Valley of the King area.
As part of the Bulk Sample Program, Snowden ran a series of test
estimates in the local area surrounding the bulk sample excavation.
As part of the Program, this test area was drilled on an
approximately 5 meter by 10 meter grid using underground
exploration fan drilling with a dominantly north-south orientation
(parallel to, but not in, the Cleopatra structure). Initial
estimates were run in the local test area using the same parameters
as those used for the November 2012 Mineral Resource. The addition
of the close spaced fan drilling was used to prepare local
estimates which indicated the estimates needed to be more selective
(less tonnes and more grade for similar ounces) than the original
Mineral Resource. In addition, Snowden ran a series of test
estimates using varying parameters and domain boundary conditions
and compared these estimates to the results returned from the mill
within the bulk samples cuts. This test work was used to determine
the criteria which best locally reproduced the grade
distribution.
The result of these tests indicated that using a hard boundary
constraint on the north-south Cleopatra structure caused
overestimation of the local metal content around the bulk sample
excavation, while removing this constraint underestimated the local
metal in the north-south structure. The underestimation is partly
due to the underground drilling being orientated north-south, which
does not fully sample the north-south structures.
As a result of the test work and comparisons with fan drilling
and analysis of the Program results noted above, Snowden adjusted
the estimation parameters being used for the December 2013 Mineral
Resource to create a more selective resource estimate, in line with
the results seen in the local test area.
Based on the outcomes of the test work and bulk sample analyses,
Snowden and Pretivm agreed that the more conservative approach of
not using the north-south constraints should be applied. The
estimation methodology was kept the same as that used for the
November 2012 Mineral Resource, with parameters revised to provide
a more locally accurate estimate, as summarized below.
The Valley of the Kings exhibits extremely skewed grade
populations where the high grades and the majority of the metal are
located in less than 5% of the data, with individual raw gold
grades of up to around 41,500 g/t Au. Discussions with Pretivm and
analysis of the data indicated the mineralization can be split into
a pervasive background mineralization and a separate high-grade but
discreet mineralization style. As a result of this population
distribution, standard estimation techniques have been found to
significantly over smooth the grades.
In order to address the highly skewed nature of the data,
Snowden separated the lower grade 'background' population from the
higher grade population within these domains and estimated them
independently. All data was composited to the nominal sample length
of 1.5 meters prior to analysis and estimation. A threshold of 5
g/t Au was selected to separate the two populations at the Valley
of the Kings. The silver data was treated using the same method
with a threshold of 50 g/t Ag for Valley of the Kings.
The lower grade population was estimated using ordinary kriging
into 10 meter by 10 meter by 10 meter parent blocks. This estimate
validates well against the input data.
The higher grade populations were estimated using multiple
indicator kriging to control the skewness of the data. Indicator
variograms were modelled up to the 95th percentile of the data with
a mathematical model used to define the top end of the grade
distribution. The threshold for the 95th percentile of the higher
grade population is 503 g/t Au for the Valley of the Kings. The
result of this estimation method is that, while no top cut is used
to limit the higher grades, the higher grades are limited in their
influence using a mathematical model based on the higher grade data
rather than the individual extreme grades in the dataset. The
higher grade populations were estimated into small scale
discretized blocks and then reblocked into parent blocks the size
of those used for the lower grades. Previously the higher grade
population grades were reblocked into larger blocks than the size
of those used for the lower grades to try and limit the very high
grades having an undue influence on the grade estimate.
Subsequently, the proportion of the higher-grade mineralization
was estimated into each block and used to combine the two estimates
(the low grade portion and the high grade portion) in the
determination of the overall block grade. For example, if a block
had a probability of 5% high grade then the final block grade would
combine 95% of the low grade estimate with 5% of the high grade
estimate. The influence of the high-grade population above the 95th
percentile is therefore greatly restricted.
The numbers of samples used for estimation of the high grade
populations and the proportion of the higher-grade mineralization
were reduced compared to the previous estimate, and the reblocking
of the high grade was adjusted to provide a more selective
estimate.
The background (non-mineralized) material was estimated using
ordinary kriging with a top cut.
The database used to estimate density is based on pulp specific
gravity measurements. As part of the 2012 and 2013 drilling
programs, Pretivm's QP selected a portion of the samples (207
samples) to undergo core density measurements as well as pulp
specific gravity measurements in order to determine whether there
is any impact on the density as a result of porosity. The results
of the comparison indicate that the core density is similar to the
pulp specific gravity within the siliceous zone and 3% lower on
average in all other rock types. Tonnages were estimated on a dry
basis with specific gravity values estimated into the models using
simple kriging where sufficient data was available. Outside of
these areas, the average specific gravity of 2.80 t/m3 was applied.
Subsequently, density was calculated in the block model by
factoring down the specific gravity estimates by 0% (siliceous
zone) or 3% (other rock types). There is little variation in
density between the different rock types.
The updated Mineral Resource estimate for the Valley of the
Kings is significantly higher in confidence than the previous
November 2012 estimate as a result of the increase in drilling
density and the test work carried out in the Program. The
additional drilling has resulted in higher confidence in the
geological interpretation used in the estimation, while the Program
has confirmed the local grade tenor and geological model. The
additional confidence has allowed the conversion of some Indicated
Resources to Measured Resources in the vicinity of the Program.
Next Steps
The NI 43-101-compliant Technical Report in support of the 2013
Valley of the Kings Mineral Resource estimate is expected to be
filed by the end of January 2014. The Technical Report will
include, among other things, the total number of ounces processed
from the Program on an individual cross-cut basis reconciled to the
local resource model prepared using the 2013 underground drilling.
An amended feasibility study for the Valley of the Kings based on
the updated Mineral Resource is expected in the first half of 2014.
Additionally, Pretivm expects to file its Environmental Assessment
Certificate application in the first quarter of 2014.
Ivor W.O. Jones, MSc, FAusIMM, CPgeo, Executive Consultant,
Snowden Mining Industry Consultants Pty Ltd., is the independent
Qualified Person (QP) responsible for the Mineral Resource for the
Brucejack Project. Ian I Chang, M.A.Sc., P.Eng., Vice President,
Project Development, Pretium Resources Inc. is the Qualified Person
(QP) responsible for Brucejack Project development. Kenneth C.
McNaughton, M.A.Sc., P.Eng., Chief Exploration Officer, Pretium
Resources Inc. is the Qualified Person (QP) responsible for the
Brucejack Project exploration program..
About Pretivm
Pretivm is creating value through gold at its high-grade gold
Brucejack Project, located in northern British Columbia. Permitting
of a high-grade underground gold mine at Brucejack is underway,
with commercial production targeted to commence in 2016.
(SEDAR filings: Pretium Resources Inc.)
Forward Looking Statements
This News Release contains "forward-looking information" and
"forward looking statements" within the meaning of applicable
Canadian and United States securities legislation. Forward-looking
information may include, but is not limited to, the preliminary
mill results from processing the 426585E cross-cut, the preliminary
mill results from the bulk sample program, the estimated gold to be
produced from the bulk sample program, the estimated contained gold
in the 426585E cross-cut from the sample tower, information with
respect to our planned exploration and development activities, the
adequacy of Pretivm's financial resources, the estimation of
mineral reserves and resources including the 2013 Valley of the
Kings Mineral Resource estimate, realization of mineral reserve and
resource estimates and timing of development of Pretivm's Brucejack
Project, costs and timing of future exploration, results of future
exploration and drilling, production and processing estimates,
capital and operating cost estimates, timelines and similar
statements relating to the economic viability of the Brucejack
Project, timing and receipt of approvals, consents and permits
under applicable legislation, Pretivm's executive compensation
approach and practice, and adequacy of financial resources.
Wherever possible, words such as "plans", "expects", "projects",
"assumes", "budget", "strategy", "scheduled", "estimates",
"forecasts", "anticipates", "believes", "intends", "targets" and
similar expressions or statements that certain actions, events or
results "may", "could", "would", "might" or "will" be taken, occur
or be achieved, or the negative forms of any of these terms and
similar expressions, have been used to identify forward-looking
statements and information. Statements concerning mineral reserve
and resource estimates may also be deemed to constitute
forward-looking information to the extent that they involve
estimates of the mineralization that will be encountered if the
property is developed. Any statements that express or involve
discussions with respect to predictions, expectations, beliefs,
plans, projections, objectives, assumptions or future events or
performance are not statements of historical fact and may be
forward-looking information. Forward-looking information is subject
to a variety of known and unknown risks, uncertainties and other
factors that could cause actual events or results to differ from
those expressed or implied by the forward-looking information,
including, without limitation, those risks identified in Pretivm's
Annual Information Form dated March 18, 2013 filed on SEDAR at
www.sedar.com and in the United States on Form 40-F through EDGAR
at the SEC's website at www.sec.gov. Forward-looking information is
based on the expectations and opinions of Pretivm's management on
the date the statements are made. The assumptions used in the
preparation of such statements, although considered reasonable at
the time of preparation, may prove to be imprecise. We do not
assume any obligation to update forward-looking information,
whether as a result of new information, future events or otherwise,
other than as required by applicable law. For the reasons set forth
above, prospective investors should not place undue reliance on
forward-looking information. Neither the TSX nor the NYSE has
approved or disapproved of the information contained herein.
Pretium Resources Inc.Robert QuartermainPresident and Chief
Executive Officer(604) 558-1784Pretium Resources Inc.Michelle
RomeroVice President, Corporate Relations(604)
558-1784invest@pretivm.comwww.pretivm.com
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