Castle Resources Inc. (TSX VENTURE:CRI) has provided shareholders and investors with a new NI 43-101 resource estimate for the past producing Granduc Copper Mine near Stewart B.C.
Mike Sylvestre, President & COO, stated, "This initial resource estimate and the defined exploration potential conclusively demonstrates the exciting potential for the Granduc. Based on significant historical data and a limited 8,300 metre drill program completed in Castle's first drill program last year, we have begun the process of building a large high grade copper resource with excellent operating infrastructure already in place."
Mr. Sylvestre continued, "This exciting initial resource clearly justifies management's determination to aggressively drill the numerous exploration targets at the Granduc this year. Our primary focus now is to upgrade much of the initial resource from the inferred to the indicated category and grow the resource by drilling new zones down dip and along strike so as to expand the Granduc resource estimate later this year."
The mineral resource estimate was prepared by SRK Consulting (Canada) Inc. (SRK) of Vancouver B.C., an independent, international consulting practice that provides focused advice and solutions to clients, mainly from the earth and water resource industries.
SRK believes the Mineral Resource is most accurately represented at a 0.8% cut-off. Mineral resources that are not mineral reserves do not have demonstrated economic viability. All figures have been rounded to reflect the relative accuracy of the estimates. SRK is not aware of any environmental, permitting, legal, title, taxation, socio-political or marking issues that would materially affect the mineral resource. The resource estimate was completed under the supervision of independent Qualified Person Marek Nowak, P.Eng and Principle Geostatistician with SRK.
The resource estimate is based on a database containing approximately 2000 drillholes and 40,000 assays. Historical data was verified wherever possible against mine records including logs, sections and plans, however not all survey or assay data could be verified. Assays from the 2010 drillholes and re-sampling of historical core were used to further validate the data. All assays from the 2010 drilling were independently verified by SRK. SRK completed a site visit to the property in September 2010 during the Castle drill program but did not complete any independent sampling. SRK believes the data of sufficient quality for the definition of the mineral resource.
The Granduc copper deposit is a volcanogenic massive sulphide deposit ("VMS") with tabular, stratified mineralization zones which have been deformed by several phases of folding. SRK created grade shell models at a 0.7% cut-off for 13 domains, using historical sections and plans as a guide. Eleven of these domains lie within the Main Zone where historical mining took place and two zones were defined within the North Zone, approximately 1 km north of the Main Zone. All domains were modelled at a minimum width of 1.5 m. Mineralized domains at the extents of the deposits are open down-dip as well as along strike.
For the Main Zone, the blocks were estimate by ordinary kriging into blocks of 2 m by 10 m by 10 m. The North Zone was estimated using inverse distance squared methods into similar sized blocks. For volumetric accuracy, blocks were sub-blocked to 0.5m by 2.5m by 2.5m. Average bulk density values were applied to all blocks within the mineralized domains.
Estimated blocks were categorized into indicated and inferred classes based upon the density of drilling information available as well as overall confidence in the available data for domain interpretation. Blocks immediately below the lower limits of the underground mining where density of underground drilling was highest, were classed as indicated. Blocks further away from the mining levels where drillhole spacing was wider and there is less certainty in correlating between mineralized intercepts, was classed as inferred.
The mineral resources are limited to unmined areas based on a model of the historic mining limits. The historic mining limits were determined from mine closure records filed with the government in 1984. At this time SRK has not gained underground access and therefore cannot directly verify the boundary. SRK believes that this boundary has been conservatively defined on reliable records.
In addition to the mineral resources, SRK assessed the exploration potential defined by wider spaced drilling data. The exploration potential is based upon approximately 20 Main Zone and 13 North Zone drill holes that have been correlated with the resource domains, but are too widely spaced to define a resource. In the main zone, wide spaced drilling has intersect mineralized intervals down to the 325m (1065 ft) level and the exploration potential is largely defined by the down-dip extension of the mineralization from the inferred mineral resource. In the North Zone, the exploration potential has been defined by correlating widely space drillholes largely above the mineral resource. The resource is defined in an area where drilling density from an exploration drift was high enough to accurately quantify the resource. Fans of widely spaced surface and underground drillholes have been used to quantify the exploration potential.
The potential quantity and grade of the exploration potential is conceptual in nature and there has been insufficient exploration to define a mineral resource. It is uncertain if further exploration will result in the exploration targets being delineated as a mineral resource.
Gold and silver grades were not estimated as the historical assay data for both commodities was unavailable. However, given that Newmont and Esso reported yearly gold and silver production figures during the life of mine, and Castle's recent drill results demonstrated gold and silver mineralization (see press release dated Dec 6, 2010), it suggests that future resource updates should include analysis of precious metals where supported by available data.
Granduc Highlights:
- Newmont and Esso Minerals operated the Granduc Mine between 1971-1984; processed over 15 million tonnes of ore grading 1.71% Cu; produced 420 million pounds of copper (plus gold and silver credits); the mine was closed in 1984 due to low copper prices
- Operators of the Granduc Mine invested over $115 million from Oct 1965 until start-up operations began in 1971
- 17 km haulage tunnel remains in good condition today
- Mining operations at the Granduc Mine consisted of crushing underground then processing of up to 9000 tpd. The concentrate was trucked on a 54 km all weather road to the year-round deep sea port facility in Stewart which remains in operation today
- Bell Copper's exploration activities between 2004 and 2007 have confirmed mineralization within 4 kms to the north and south of the main Granduc orebody
Brad Leonard, P. Geo., Castle's Exploration Manager, is the Qualified Person responsible for the scientific and technical work (as defined under National Instrument 43-101) discussed in this press release, and has reviewed this press release.
Source: Castle Resources Inc.