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Underground Delineation Drilling at Northgate Minerals Young-Davidson Mining Project Confirms Zone Geometry and Grade
Results Show Potential for Higher "As Mined" Grade from the Underground
VANCOUVER, May 26, 2011 /CNW/ - Northgate Minerals Corporation (TSX:
NGX, NYSE Amex: NXG) is pleased to announce results from a highly
successful underground delineation drill program at its 100% owned
Young-Davidson Mining Project located in northern Ontario.
Delineation drilling was initiated to define the stope limits for
underground mining within the Upper Boundary Zone ("UBZ").
Results from
the drill program have confirmed the grade, continuity and width of the
UBZ, which contains 3.64million tonnes of ore and is scheduled for
mining in the early years of underground production.
Young-Davidson is
currently forecasting an initial 15-year mine-life with production
commencing in 2012 from a small open pit before mining moves
underground in 2014.
The area of delineation drilling covers
approximately half of the ore tonnage in the UBZ.
UBZ Drill Highlights
-
The UBZ delineation drill program consisted of 66 holes with much
closer-spaced drilling than what was used to develop the initial
reserve.
When combined with the historic "as mined" ore grade on the
property of 3.39 grams per tonne (g/t), results continue to suggest a
strong probability that the ore grade will be closer to the historic
"as mined" grade when the underground orebody is actually mined.
-
Of the 66 holes that were drilled in the UBZ, 26 holes returned a
significant result of greater than 95 gram-metres and 70% of the holes
returned greater than 50 gram-metres.
-
Hole YR-36: returned 11.13 g/t uncut over 44.0 metres ("m") (estimated 37.0 m true
thickness).
-
Hole YR-17: returned 6.34 g/t uncut over 44.0m (estimated 43.6 m true thickness).
-
Hole YR-16: returned 5.32 g/t over 54.8 m (estimated 45.9 m true thickness).
-
Hole YM10-16: returned 4.64 g/t over 58.8 m (estimated 51.3 m true thickness).
-
Drill results reported herein will be used to update reserve and
resource estimates at the end of the year.
"The delineation drill program within the Upper Boundary Zone has been
extremely successful" commented Ken Stowe, President and CEO.
"Results
from this delineation program are essential as we move closer to our
first gold pour in 2012, as this information gives us confidence in the
orebody, confirming the grade, continuity and width of the zone.
In
addition, the comparison between cut and uncut drill results from the
recent drilling continues to indicate that there is strong potential
for the actual "as mined" grade of the current underground reserve to
be up to 10% higher than our current reserve grade, which we will look
for when the first underground ore is delivered to the mill in 2014."
UBZ Delineation Drill Program
The UBZ delineation drill program began in 2008.
Results from the 2008
drill program were used in the current reserve and resource estimate,
but have not been individually reported before.
The program was put on
hold in 2009 and part of 2010 as Northgate had sufficient drill
information to form its initial proven and probable reserve estimate of
2.8million ounces of gold1.
Drilling re-commenced in the fall of 2010 with approximately 6,350 m
drilled.
In total, 66holes have been completed (28 NQ and 38 BQ
diameter core holes) in the near-surface portion of the UBZ. These
holes are required to define final stoping boundaries with increased
resolution and to plan for an efficient and safe mining sequence over
the life of the mine.
The UBZ in relation to the current Young-Davidson reserve is shown on
the longitudinal section in Figure 1. The UBZ is located on the
structural footwall of a steeply south-dipping syenite contact with
meta-sediments over an area equivalent to three hectares.
The area of
infill drilling covers approximately half of the ore tonnage in the UBZ
(see Figure 2).
The mineralization style is disseminated with pyrite
associated with sheeted quartz-pyrite veinlets in well developed
potassic alteration. Delineation drilling has been conducted on
sections spaced 15 m to 30m apart from ramp access located 50 m - 70 m
in the footwall of the mineralization.
Previous drilling completed to
develop the current reserve was wider-spaced (30 m to 45 m centres).
Of the 66 holes completed from the UBZ delineation program, 26 holes
returned intervals greater than 95 gram-metres and are presented in
Table 1 (in bold).
Complete drill results can be found in Appendix 1 at
the end of this press release. Results are presented as interval
totals for cut (to 20 g/t gold) and uncut analyses.
Delineation
drilling for the near-surface sector of the UBZ has been highly
successful confirming the grade, continuity and widths of the original
resource model and has added new resource potential in the footwall of
the UBZ (see Figures 3 - 7) as shown by the red lines appearing outside
of the resource outline (in magenta).
Uncut delineation drill results averaged 3.76 g/t gold or 3.39 g/t gold
when cut to 20g/t. The 11% difference between cut and uncut assays is
consistent with the difference noted in the wider-spaced exploration
drilling that was used to generate the 2.8 million ounce reserve at
Young-Davidson.
Capping is a technique that is employed in the
estimation of resources and reserves to apply a margin of conservation
to these estimates in the event that higher grade nuggets are
disproportionately represented in the sparse sampling.
The fact that
the difference between cut and uncut grades continues to be the same in
the closer-spaced delineation drilling that was recently completed
combined with the fact that the historic "as mined" grade on the
property was 12.7% higher than the current reserve grade, suggests the
strong possibility that "as mined" ore grades from the underground
orebody will exceed the current reserve grade.
Next Steps
Results from this drill program will be incorporated into the annual
reserve and resource update at the end of the year.
Delineation
drilling on the property is ongoing and future efforts will focus on
the upper part of the Lucky Zone ore lenses.
Figure 1 - Young-Davidson Longitudinal Section (looking north).
UBZ in
red with black outline.
www.northgateminerals.com/Theme/Northgate/files/Releases/2011/YDUBZFig1.JPG
Figure 2 - Young-Davidson Upper Boundary Zone
www.northgateminerals.com/Theme/Northgate/files/Releases/2011/YDUBZFig2.JPG
Figures 3 - 7 illustrate each drilling section through the UBZ
confirming the original geometry and widths determined from the initial
2008 resource work.
The red lines are the mineralized portions of the
drill holes reported in Table 1 and Appendix 1, while magenta shows the
resource outline for the UBZ.
Mineralized portions of the drill holes
appearing outside of the resource outline demonstrate new resource
potential in the footwall of the UBZ.
At the west end of the resource,
there is a post-mineral diabase dyke, which is actually located in a
slightly lower position than originally modeled.
Table 1: Selected Assay Results from UBZ Delineation Drill Program (>95
gram-metres in bold)
Hole ID
|
From
(m)
|
To
(m)
|
Interval
(m)
|
True
Thickness
(m)
|
Gold Uncut
(g/t)
|
Gold Cut
20 g/t
|
Comment
|
YM10-13
|
35.7
|
78.1
|
42.4
|
38.9
|
3.41
|
2.85
|
Upper UBZ
|
incl
|
35.7
|
51.5
|
15.8
|
14.5
|
5.84
|
4.34
|
|
incl
|
65.5
|
78.1
|
12.6
|
11.6
|
3.75
|
3.75
|
|
YM10-15
|
38.0
|
52.5
|
14.5
|
14.1
|
1.26
|
1.26
|
Upper UBZ
|
incl
|
38.0
|
46.5
|
8.5
|
8.2
|
8.50
|
8.50
|
Upper UBZ
|
|
65.0
|
81.8
|
16.8
|
16.5
|
1.46
|
1.46
|
Upper UBZ
|
|
97.5
|
123.5
|
26.0
|
25.5
|
3.86
|
3.86
|
Upper UBZ
|
YM10-16
|
10.3
|
12.4
|
2.1
|
1.8
|
3.65
|
3.65
|
UBZ Footwall
|
|
28.3
|
30.2
|
1.9
|
1.6
|
5.58
|
5.58
|
UBZ Footwall
|
|
57.8
|
116.6
|
58.8
|
51.3
|
4.64
|
4.64
|
|
incl
|
59.9
|
109.0
|
49.1
|
42.7
|
5.27
|
5.27
|
|
incl
|
82.3
|
104.5
|
22.2
|
19.3
|
6.43
|
6.43
|
|
YM10-20
|
59.5
|
113.6
|
54.1
|
52.0
|
4.32
|
2.48
|
|
incl
|
59.5
|
77.5
|
18.0
|
17.3
|
9.78
|
4.24
|
|
incl
|
82.9
|
98.3
|
15.4
|
14.8
|
2.51
|
2.51
|
|
incl
|
102.6
|
108.8
|
6.2
|
6.0
|
2.45
|
2.45
|
|
YM10-21
|
47.5
|
52.0
|
4.5
|
4.3
|
5.22
|
5.22
|
|
|
58.0
|
61.0
|
3.0
|
2.9
|
4.34
|
4.34
|
|
|
80.5
|
113.3
|
32.8
|
31.4
|
4.27
|
3.53
|
|
YM10-23
|
64.0
|
68.5
|
4.5
|
4.0
|
3.02
|
3.02
|
|
|
78.3
|
104.0
|
25.7
|
22.9
|
6.26
|
6.26
|
|
YM10-24
|
51.7
|
104.1
|
52.4
|
51.4
|
1.92
|
1.92
|
|
incl
|
51.7
|
65.5
|
13.8
|
13.5
|
2.21
|
2.21
|
|
incl
|
72.7
|
104.1
|
31.4
|
30.8
|
2.19
|
2.19
|
|
YM10-26
|
51.2
|
111.2
|
60.0
|
53.8
|
1.96
|
1.96
|
|
incl
|
51.2
|
77.8
|
26.6
|
23.9
|
2.73
|
2.73
|
|
YM10-28
|
60.5
|
65.0
|
4.5
|
3.7
|
3.30
|
3.30
|
Hole extended to test syenite
|
|
70.5
|
115.1
|
44.6
|
36.8
|
2.61
|
2.61
|
|
incl
|
77.4
|
108.5
|
31.1
|
25.5
|
3.15
|
3.15
|
|
YM11-29
|
72.01
|
109.2
|
37.19
|
33.3
|
5.37
|
5.37
|
|
YM11-31
|
52.65
|
55.65
|
3.0
|
3.0
|
3.08
|
3.08
|
|
|
70.83
|
105.8
|
34.97
|
34.9
|
3.72
|
3.67
|
|
|
113
|
117.0
|
4.0
|
4.0
|
1.54
|
1.54
|
|
YM11-39
|
81.9
|
95.0
|
13.1
|
11.9
|
14.68
|
7.31
|
|
incl
|
84.9
|
95.0
|
10.1
|
9.2
|
18.77
|
9.21
|
|
YR-12
|
34.1
|
71.0
|
36.9
|
35.9
|
3.59
|
3.59
|
|
YR-13
|
38.4
|
87.1
|
48.7
|
47.3
|
2.61
|
2.38
|
|
YR-14
|
61.0
|
117.1
|
56.1
|
44.9
|
4.85
|
4.85
|
|
YR-15
|
28.8
|
36.0
|
7.2
|
4.9
|
1.95
|
1.95
|
|
|
64.9
|
109.8
|
44.9
|
31.0
|
4.05
|
4.05
|
|
|
122.0
|
132.4
|
10.4
|
7.3
|
2.67
|
2.67
|
|
YR-16
|
47.0
|
101.8
|
54.8
|
45.9
|
5.32
|
5.32
|
|
YR-17
|
29.0
|
73.0
|
44.0
|
43.6
|
6.34
|
6.18
|
|
YR-25
|
34.5
|
45.7
|
11.2
|
9.2
|
4.73
|
4.73
|
|
|
64.2
|
101.5
|
37.3
|
30.7
|
3.18
|
3.18
|
|
YR-30
|
48.8
|
97.3
|
48.5
|
43.3
|
3.88
|
3.87
|
|
YR-31
|
39.1
|
77.6
|
38.5
|
38.5
|
3.99
|
3.99
|
|
YR-35
|
45.5
|
79.1
|
33.6
|
30.9
|
4.65
|
4.65
|
|
YR-36
|
61.0
|
105.0
|
44.0
|
37.0
|
11.13
|
5.06
|
|
YR-37
|
58.0
|
128.0
|
70.0
|
52.8
|
2.66
|
2.66
|
|
YR-38
|
37.0
|
46.9
|
9.9
|
9.4
|
11.39
|
5.84
|
|
|
62.0
|
72.0
|
10.0
|
9.5
|
9.65
|
7.83
|
|
YR-50
|
67.5
|
89.4
|
21.9
|
19.8
|
6.41
|
5.86
|
|
|
94.5
|
100.4
|
5.9
|
5.3
|
3.55
|
3.55
|
|
|
117.0
|
127.5
|
10.5
|
9.5
|
2.15
|
2.15
|
|
Figure 3 - UBZ Drill Section 23510
(Red lines are mineralized portions of the drill holes reported in Table
1.
Magenta shows the resource outline for the UBZ.
Red lines appearing
outside of the resource outline represent new resource potential).
www.northgateminerals.com/Theme/Northgate/files/Releases/2011/YDUBZFig3.JPG
Figure 4 - UBZ Drill Section 23540
(Red lines are mineralized portions of the drill holes reported in Table
1.
Magenta shows the resource outline for the UBZ.
Red lines appearing
outside of the resource outline represent new resource potential).
www.northgateminerals.com/Theme/Northgate/files/Releases/2011/YDUBZFig4.JPG
Figure 5 - UBZ Drill Sections 23570
(Red lines are mineralized portions of the drill holes reported in Table
1.
Magenta shows the resource outline for the UBZ.
Red lines appearing
outside of the resource outline represent new resource potential).
www.northgateminerals.com/Theme/Northgate/files/Releases/2011/YDUBZFig5.JPG
Figure 6 - UBZ Drill Section 23600
(Red lines are mineralized portions of the drill holes reported in Table
1.
Magenta shows the resource outline for the UBZ.
Red lines appearing
outside of the resource outline represent new resource potential).
www.northgateminerals.com/Theme/Northgate/files/Releases/2011/YDUBZFig6.JPG
Figure 7 - UBZ Drill Section 23630
(Red lines are mineralized portions of the drill holes reported in Table
1.
Magenta shows the resource outline for the UBZ.
Red lines appearing
outside of the resource outline represent new resource potential).
www.northgateminerals.com/Theme/Northgate/files/Releases/2011/YDUBZFig7.JPG
Appendix 1: Complete Assay Results from UBZ Delineation Drill Program
Hole ID
|
From
(m)
|
To
(m)
|
Interval
(m)
|
True Thickness
(m)
|
Gold Uncut
(g/t)
|
Gold Cut
20 g/t
|
Comment
|
YM10-04
|
39.5
|
44.0
|
4.5
|
4.4
|
3.19
|
3.19
|
Upper UBZ
|
YM10-05
|
No significant values
|
YM10-06
|
37.7
|
42.9
|
2.64
|
3.9
|
2.64
|
2.64
|
Upper UBZ
|
|
60.8
|
63.9
|
3.1
|
2.3
|
2.48
|
2.48
|
Upper UBZ
|
|
83.0
|
91.9
|
8.9
|
6.9
|
2.94
|
2.94
|
Upper UBZ
|
YM10-07
|
80.8
|
88
|
7.2
|
6.6
|
1.19
|
1.19
|
Upper UBZ
|
YM10-08
|
No significant values
|
YM10-09
|
No significant values
|
YM10-10
|
31.6
|
|
|
|
|
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