Pretium Resources Inc.: Updated, Interim High-Grade Mineral Resource Estimate Completed for Brucejack Project
VANCOUVER, BRITISH COLUMBIA -- (Marketwire) -- 09/07/12 -- Pretium Resources Inc. (TSX: PVG)(NYSE: PVG) ("Pretivm") is pleased to report an updated, interim high-grade Mineral Resource estimate for its wholly-owned Brucejack Project, completed by Snowden Mining Industry Consultants ("Snowden") independent Qualified Persons. The Mineral Resource estimate, which reflects refined resource modelling as a result of infill drilling, will be used as the basis for feasibility study mine planning now underway.
The September 2012 estimate has been based on a consolidated interpretation prepared by geologists from Pretivm and Snowden to cover the drilled part of the Brucejack property. Of significance to the new interpretation is that the mineralized domains have been better defined and more tightly constrained than the previous estimate. On top of this, the new interpretations and model have been prepared including results of drilling information which comprises, since the April 2012 Mineral Resource estimate, an additional 175 drillholes (55,849 meters), into the Valley of the Kings. This has resulted in increased confidence in the definition of the mineralized zones, and subsequent increased confidence in the estimated Mineral Resource.
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:
-- 5.1 million ounces of gold in the Indicated Resource category (9.9
million tonnes grading 16.2 grams of gold per tonne); and
-- 5.1 million ounces of gold in the Inferred Resource category (4.6
million tonnes grading 35.0 grams of gold per tonne).
The Mineral Resource estimate incorporates drilling up to hole SU-466, with ongoing drilling at the Brucejack Project currently up to hole SU-547. The Valley of the Kings now extends over 800 meters in strike length, and the Mineral Resource is defined over approximately 450 meters of the 800 meters of strike length. A majority of the Mineral Resource in the upper portion of the Valley of the Kings, between the 1200 meter and 1500 meter levels, is in the Indicated Resource category. An isometric view of Snowden's updated Valley of the Kings block model along with current drilling not included in this block model is available at http://media3.marketwire.com/docs/8173881.pdf.
Table 1: Valley of the Kings Mineral Resource estimate
- September 2012 (1)(4)
(Based on a cut-off grade of 5.0 grams of gold-equivalent/tonne(5))
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Contained(3)
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Tonnes Gold Silver Gold Silver
Category (millions) (g/t) (g/t) (million oz) (million oz)
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Indicated 9.9 16.2 14.1 5.1 4.5
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Inferred(2) 4.6 35.0 13.3 5.1 2.0
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(1), (2), (3), (4) and (5) See footnotes to Table 3
High-grade Mineral Resources for the West Zone are summarized in Table 2:
Table 2: West Zone Mineral Resource estimate
- April 2012(1)(4)
(Based on a cut-off grade of 5.0 grams of gold-equivalent/tonne(5))
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Contained(3)
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Tonnes Gold Silver Gold Silver
Category (millions) (g/t) (g/t) (million oz) (million oz)
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Measured 2.4 5.85 347 0.5 26.8
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Indicated 2.5 5.86 190 0.5 15.1
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M+I 4.9 5.85 267 0.9 41.9
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Inferred(2) 4.0 6.44 82 0.8 10.6
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(1), (2), (3), (4) and (5) See footnotes to Table 3
Combined high-grade Mineral Resources for the Valley of the Kings (September 2012 estimate) and West Zone (April 2012 estimate) are summarized in Table 3:
Table 3: Mineral Resource estimate: Valley of the Kings
and West Zone(1)(4)
(Based on a cut-off grade of 5.0 grams of gold-equivalent/tonne(5))
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Contained(3)
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Tonnes Gold Silver Gold Silver
(millions) (g/t) (g/t) (million oz) (million oz)
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Measured Resources
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West Zone 2.4 5.85 347 0.5 26.8
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Indicated Resources
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Valley of the Kings 9.9 16.2 14.1 5.1 4.5
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West Zone 2.5 5.86 190 0.5 15.1
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Total - Measured and Indicated Resources
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Total 14.7 12.7 98 6.0 46.3
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Inferred(2) Resources
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Valley of the Kings 4.6 35.0 13.3 5.1 2.0
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West Zone 4.0 6.44 82 0.8 10.6
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Total -Inferred(2) Resources
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Total 8.6 21.6 45.5 5.9 12.5
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(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 and 2 is defined using 5
m by 5 by 5 m blocks in the well drilled portion of West Zone (5 m by 10 m
drilling or better) and 10 m by 10 m by 10 m blocks in the remainder of West
Zone and in Valley of the Kings
(5) The gold equivalent value is defined as AuEq = Au + Ag/53.
Mineral Resource Modeling and Estimation
The September 2012 Mineral Resource estimates for Brucejack were 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 Resources are within the well informed portion of West Zone where the resource is informed by 5 meter by 5 meter or 5 meter by 10 meter spaced drilling. Areas classified as Indicated Resources are informed by 20 meter by 20 meter to 20 meter by 40 meter drilling. With respect to some of the areas in the high grade zones at the Valley of the Kings that have drill spacing nearing that of the Measured Resource of West Zone, Snowden has elected to retain the Indicated Resource classification until underground sampling has demonstrated a high level of confidence in these estimates. This is because of the high grade nature of the mineralization. The remainder of the Mineral Resource is classified as an Inferred Resource where there is some drilling information and the blocks lie within the mineralised interpretation. Areas where there is no informing data and/or the lower grade material that is outside of the mineralised 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 Property comprises several gold-silver mineralised areas. These areas include West Zone, Valley of the Kings, Galena Hill, Bridge Zone, Gossan Hill and Shore Zone. The majority of the Mineral Resource lies within Valley of the Kings and West Zone. West Zone was not updated for this Mineral Resource as there has been very little additional drilling in this area. The West Zone estimate created as part of the previous, April 2012 Mineral Resource, and for which there has been no new information collected has been combined with the updated estimate for Valley of the Kings to produce a combined estimate.
The Valley of the Kings mineralisation 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 800 meters. The zone is up to 150 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.
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 define a series of mineralised domains for estimation at the Valley of the Kings. At West Zone a nominal 0.3 g/t Au grade cut-off was used to define the mineralised domains.
The input data for the Valley of the Kings estimate comprises 331 drillholes for 114,949 meters including 9 historical surface drillholes (579 meters) and 175 surface drillholes completed in the 2012 Brucejack Exploration Program (55,849 meters). The input data for the West Zone estimate comprises 756 drillholes for 62,208 meters including 439 underground drillholes (24,688 meters), 269 historical surface drillholes (21,321 meters) and 48 surface drillholes completed since 2009 (17,199 meters). These figures exclude intervals with no gold values and drillholes outside of the main deposit areas.
Both West Zone and the Valley of the Kings exhibit 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 mineralisation can be split into a pervasive background mineralisation and a separate high-grade but discreet mineralisation 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 and West Zone. The silver data was treated using the same method with a threshold of 50 g/t Ag for Valley of the Kings and 300 g/t Ag for West Zone.
The lower grade population was estimated using ordinary kriging into 10 meter by 10 meter by 10 meter parent blocks, except for the well informed portion of West Zone which used a 5 m by 5 m by 5 m parent block. These estimates validate 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 380 g/t Au for the Valley of the Kings and 93 g/t Au for West Zone. 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 twice the size of those used for the lower grades to further limit the influence of the highest grades in the highest grade areas. With the additional data in the Valley of the Kings, the quality of the high grade variography has improved and now indicates an anisotropy in the grade continuity with a shorter range of continuity in the cross strike direction. This anisotropy matches the expectation based on the geological model and has been applied to the search parameters for the high grade estimation resulting in a tighter constraint on the higher-grade material in the estimate.
Subsequently, the proportion of the higher-grade mineralisation 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 lower-grade halo domains and the background (non-mineralised) material were estimated using ordinary kriging with a top cut.
Tonnages were estimated on a dry basis with density values estimated into the models using simple kriging where sufficient data was available. Outside of these areas, the average density of 2.78 t/m3 was applied. There is little variation in density between the different rock types.
West Zone was depleted for previous underground mining prior to reporting. No mining has occurred at the other areas to date.
The updated Mineral Resource estimate for the Valley of the Kings is significantly higher in confidence than the previous April 2012 estimate as a result of the additional drilling and the higher confidence in the geological interpretation used in the estimation. The additional drilling confirms the location of the high-grade corridors and has allowed a better estimate of the boundaries of these corridors. The updated estimate has tightened the high-grade corridors resulting in a decrease in tonnes; however the additional confidence has allowed the majority of the mineralisation above 1200 mRL to be classified as Indicated.
Other Mineral Resource Estimates
High-grade Mineral Resource estimates for Galena Hill, Bridge Zone, Gossan Hill and Shore Zone will be posted on our web site along with an updated bulk tonnage Mineral Resource estimate for the entire Brucejack Project.
Drilling Program; Resource Update
Phase two of the 2012 Brucejack Exploration Program, which has been focused on definition drilling of the shallow high-grade resources at the Valley of the Kings and testing extensions of the Valley of the Kings and other high-grade targets, is expected to be completed early in the fourth quarter. A Mineral Resource estimate incorporating all assays for the 2012 drilling season, including approximately 50,000 meters of drilling expected to be completed after hole SU-466, will be prepared by Snowden and announced on completion.
A map showing the outline of drill intercepts in the Mineral Resource estimate and the subsequent drilling not yet included in a Mineral Resource is available at http://media3.marketwire.com/docs/8173882.pdf.
The above tables summarize the high-grade Mineral Resource estimate totals for the Brucejack Project. The Mineral Resource estimate contained in this news release was prepared by Ivor Jones (FAusIMM(CP)) and Lynn Olssen (MAusIMM(CP)) of Snowden, both of whom are independent Qualified Persons, as defined by National Instrument 43-101. Mr. Jones and Ms. Olssen have reviewed and approved the contents of this news release.
Snowden delivers a comprehensive range of technical consulting services, independent advice and technology solutions to the mining sector. Snowden's areas of expertise cover both open pit and underground mining operations, for the majority of mineral commodities, with projects ranging from exploration and resource evaluation to mine planning, metallurgy, and mine optimisation. Snowden was established 25 years ago in Perth, Australia, and has eight offices located in the world's major mining regions.
Technical Session/ Conference Call
The September 2012 Brucejack Interim High-Grade Mineral Resource estimate will be presented at a technical session/conference call on Wednesday, September 19, 2012 in Toronto featuring Pretivm's Senior Management and an independent Qualified Person representing Snowden. Dial-in details will be provided.
About Pretivm
Pretivm is creating value through gold at its high-grade gold Brucejack Project, located in northern British Columbia. Brucejack hosts a major undeveloped high-grade gold resource and mineralization remains open in all directions. A feasibility study for a high-grade underground mine in Brucejack's Valley of the Kings is underway and expected in the second quarter of 2013.
(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, risks related to our planned exploration and development activities, the adequacy of Pretivm's financial resources, the estimation of mineral resources, realization of mineral resource estimates, 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" 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 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 prospectus supplement to the short form base shelf prospectus dated March 19, 2012 filed on SEDAR at www.sedar.com and in the United States 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.
The TSX has neither approved nor disapproved of the information contained herein.
Contacts:
Pretium Resources Inc.
Robert Quartermain
President and Chief Executive Officer
(604)558-1784
Pretium Resources Inc.
Joe Ovsenek
Chief Development Officer
(604)558-1784
invest@pretivm.com
www.pretivm.com