Highlights
- Intersected 18.4 metres of 1.65% Cu, 4.03% Zn, 0.82g/t Au, 55g/t Ag extending the deposit by 150 metres
- Borehole electromagnetic surveys suggest further down plunge extensions likely
- Additional new drilling results include:
- 57.4 metres of 0.37% Cu, 7.08% Zn, 0.17g/t Au, 9g/t Ag
- 44.5 metres of 0.49% Cu, 6.51% Zn, 0.43g/t Au, 29g/t Ag
- 40.5 metres of 0.76% Cu, 4.82% Zn, 0.18g/t Au, 18g/t Ag
- 84.0 metres of 0.80% Cu, 4.72% Zn, 0.27g/t Au, 15g/t Ag
- Preliminary VTEM survey results highlight numerous new untested shallow drill targets
Cliff Davis, Nevsun CEO, commented, “The new drilling demonstrates that the already sizeable Harena resource extends 150 metres beyond its currently modelled limits, further enhancing the potential for underground mining. We are particularly encouraged by the increasing copper content which indicates the mineralizing system is strengthening”. Mr. Davis went on to say, “The recently completed airborne survey over the Mogoraib River and Tabakin Exploration Licenses that were acquired in 2016 has highlighted a significant number of new shallow drill targets. Evaluation of the highest priority anomalies is currently underway but the full suite of targets will take years to pursue. As we have always stated, Bisha is evolving into a large VMS district with exploration still in its infancy.”
Harena
Harena is located 10 kilometres south of the Bisha processing plant and drilling continues to expand the deposit at depth. Some of the results reported in today’s update are part of an in-fill program designed to upgrade the mineral resource and tighten the drill spacing at Harena to 100 metre centres, while others are from an on-going program focused on expanding the deposit. A drill-hole plan map, longitudinal section and representative cross section through Harena can be found in Figures 1, 2 and 3.
Hole HX-083, which is the deepest hole yet drilled at Harena, is relatively higher in copper than recent holes drilled above it and has an 11.0 metre interval grading 2.23% Cu, 4.92% Zn, 1.10 g/t Au, 79 g/t Ag including 2.6 metres grading 4.88% Cu, 7.79% Zn, 2.49 g/t Au, 201 g/t Ag. This suggests that the mineralizing system is strengthening and Borehole transient electromagnetic (BHEM) modeling indicates that the mineralization should continue down dip. Further drilling will determine if this is the case.
The mineralization at Harena displays a well-defined base metal and host rock alteration zonation pattern consisting of a sphalerite and pyrite, zinc-rich upper portion and a lower chalcopyrite and pyrite, copper-rich basal section. The copper-rich basal area is focussed along the northeastern edge of the deposit and is commonly underlain by a thick zone of highly altered felsic volcanics indicative of the high temperature focus point of the mineralizing system. The zinc-rich upper portion tends to be displaced to the southwest and has much less alteration associated with the volcanic rocks below it, indicating that it is somewhat distal from the active mineralizing centre.
BHEM surveys are routinely completed in all holes drilled at Harena. The results of these surveys are typically interpreted and modeled as plates of various conductivities in three dimensional space. These models, along with the geology and alteration patterns, have been instrumental in guiding the drilling at Harena. Chalcopyrite is the main conductive mineral and the borehole survey results preferentially focus our efforts toward copper enriched mineralization. Sphalerite is not conductive, but is associated with pyrite, which is less conductive than chalcopyrite giving weaker anomalies. A longitudinal section with the interpreted borehole plate models derived from hole HX-083 is shown in Figure 4.
The highly predictable nature of the geology at Harena, coupled with the borehole geophysical modeling, has allowed us to aggressively step out with our drill pattern. This will ultimately enable us to quickly define the full geometry of Harena.
VTEM Survey
A 6,386 line kilometre VTEM survey has been recently completed by helicopter over the Mogoraib River and Tabakin Exploration Licenses covering an area of 825 square kilometres. These licenses were acquired in mid-2016 and much of the area had never been covered by any geophysical survey. Preliminary results have highlighted many new anomalies that, by the nature of the survey, should be relatively shallow (i.e., less than 100 metre depth). Field evaluation is underway to determine the nature of the anomalies and over 11,000 metres of drilling has been allocated for the testing of targets.
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