Dec 1 2010
Northgate Minerals Corporation (TSX: NGX, NYSE Amex: NXG) has reported assay results for the final 16 drill holes from its infill diamond drilling program at the Kemess Underground Project located five kilometres north of its Kemess South mine in north-central British Columbia.
Drilling Highlights
- Hole KN-10-13 intersected 80.0 metres ("m") of 2.4 grams per tonne ("g/t") gold and 0.78% copper within a broader interval of 185.6 m, which returned 1.556 g/t gold and 0.571% copper. - Hole KN-10-17 intersected 59.5 m of 1.15 g/t gold and 0.516% copper within a broader interval of 328.5 m, which returned 0.609 g/t gold and 0.268% copper. - Hole KN-10-25A intersected 46.0 m of 1.43 g/t gold and 0.489% copper within a broader interval of 266 m, which returned 0.559 g/t gold and 0.261% copper. - A higher grade zone in the northeast quadrant has been identified and is continuous and supported by several holes, including a previously- released hole KN-10-03, which returned one of the best intercepts in the Kemess resource database. - The weighted average grade of all holes drilled in the 2010 program were higher than previous resource block estimates in the block cave zone by 12% for gold and 3.5% for copper.
"We are excited to have completed the 2010 drill program at Kemess Underground, which has exceeded our expectations" commented Ken Stowe, President and Chief Executive Officer. "Now that all assay results are in hand, we see further confirmation with hole KN-10-13 that a compact, continuous higher grade zone exists beneath the eastern third of the resource area currently being considered for a bulk underground mining operation. The 2010 results from the higher grade sector consistently exceed grades for both copper and gold when compared to the 2005 resource model. We now look forward to completing a new underground resource estimate, which is expected early in the first quarter of 2011 and will support studies to determine the economics of the potential underground mine at Kemess."
Overview of the Kemess Underground Project and 2010 Exploration Program
The Kemess Underground diamond drill program, the final results of which are reported herein, was conducted in order to better define the 70+ million tonne proposed block cave portion of the Kemess North deposit estimated from previous drilling to contain in excess of 1.4 million ounces of gold and 500 million pounds of copper.
The Kemess Underground drill program was also designed to document the geotechnical characteristics of the higher grade core to determine the potential for large scale, underground, bulk mine production that could be milled at the existing Kemess infrastructure and utilize the existing permitted tailings capacity in the Kemess South pit.
The 2010 program in its entirety consisted of 30 drill holes totalling 16,439 m. Drilling contractors were successful in completing 26 holes to targeted depths. Only one drill hole from the program failed to intersect mineralization (hole 22), confirming the eastern fault-bound margin of the deposit. Geotechnical analysis is underway and the assay and geologic results from the 2010 program are being combined with previous drilling results in order to update the resource estimate for the 70+ million tonne, proposed block cave portion of the deposit. This updated resource estimate is expected to be released with Northgate's annual resource and reserve statement in the first quarter of 2011.
2010 Results Compared to 2005 Open Pit Resource
Comparison of all 2010 drill hole results against the previous 2005 Kemess North resource model shows that the current program's results are, on average, 12% higher for gold and 3.5% higher for copper, using a weighted average of resource blocks captured by a 20 x 20 m prism centered on each drill hole trace.
While the 2010 results show both positive and negative variance from the 2005 resource model, the comparison demonstrates that existing 2005 estimates are conservative globally and that a higher grade zone in the northeast quadrant, defined by holes KN-10-03, 05, 07A, 09A, 10, and 13, was significantly underestimated. These variations are believed to be attributable to the 2005 resource model being based on interpolation from wider-spaced drilling that was unconstrained with respect to important grade domains, such as different alteration and or geological controls, whereas the 2010 results now recognize these factors within the resource. With the benefit of the information provided by the 2010 results, it appears that the 2005 resource model tended to overestimate low grade regions and underestimate high grade regions. Work is now underway to update the resource for an underground mining scenario and to account for the distinct grade domains that exist in this subsection of the Kemess North deposit.
Quality Control - Analyses and Sample Location
Details of quality assurance/quality control procedures for sample analysis and drill hole survey methodology are reported in detail in the Canadian National Instrument 43-101 Standards of Disclosure for Mineral Projects ("NI 43-101") compliant Technical Report filed on SEDAR on May 6 2005. All 2010 drill holes have had their down hole surveys completed by non-magnetic based instruments such as gyroscope or DeviFlex.
Qualified Persons
The program design, implementation, quality assurance/quality control and interpretation of the results are under the control of Northgate's geological staff, which includes a number of individuals who are qualified persons as defined under NI 43-101. Carl Edmunds, PGeo, Northgate's Exploration Manager, has reviewed the technical contents of this release.
Source: Northgate Minerals Corporation