The drilling continues to extend the base of the Tertiary horizontal gold mineralised layer to the east of the starter pit.
There were many economic gold grade intercepts returned, including 9 metres of 2.13 g/t from 58 metres and 9 metres of 1.58 g/t from 66 metres.
Holes in the central bedrock faulted zone all ended in gold mineralisation at bit refusal, as expected, and included 19 metres of 1.12 g/t from 96 metres.
Additional gold source
Havilah’s technical director Dr Chris Giles said: “The base of Tertiary mineralisation has now been shown to extend as a shallow horizontal gold layer over most of the area drilled during 2020 at West Kalkaroo.
“It provides an additional source of gold in the early stages of the planned gold-only start-up open pit at West Kalkaroo, that is not included in the current Kalkaroo JORC gold resource.”
The aircore drilling method is not able to penetrate hard rock and holes were drilled until bit refusal, which varied depending on the depth of weathering and softness of the rock.
Central zone hits
Drill holes in the central faulted zone usually ended in gold and/or native copper mineralisation.
Apart from the 19-metre intersection, other results from this zone included 6 metres of 1.11 g/t from 96 metres and 5 metres of 1.17 g/t from 105 metres.
A recurring feature in many drill holes is base of Tertiary gold mineralisation that often occurs over at least a 2-metre interval in the transition zone between the weathered bedrock and overlying younger Tertiary age clays.
Aside from the two 9-metre intersections, other results include:
- 5 metres of 1.27 g/t gold from 61 metres;
- 5 metres of 1.40 g/t gold from 61 metres;
- 5 metres of 1.80 g/t gold from 55 metres;
- 3 metres of 3.25 g/t gold from 64 metres;
- 2 metres of 3.51 g/t gold from 58 metres;
- 4 metres of 2.02 g/t gold from 63 metres; and
- 5 metres of 1.63 g/t gold from 65 metres.
This mineralisation is not included in the current Kalkaroo JORC gold resource and is potentially a source of early-stage shallower gold that would be mined during removal of the overburden in the Kalkaroo open pit.
Recent aircore drilling is immediately east of the planned stage 3 starter open pit. The target for future drilling (dashed red outline area) is at the intersection zone of two major faults.
The next series of drill holes will be near the intersection of two major faults, partially outside of the existing Kalkaroo resource, and will target vein and breccia style copper-gold mineralisation.
These will be deeper reverse circulation (RC) drill holes that are able to penetrate hard rock.
This area is considered to have high prospectivity as indicated by previous widely spaced drill holes that returned up to 82 metres of 1.14 g/t from 72 metres, including 34 metres of 2.02 g/t from 92 metres and 26 metres of 1.08% copper from 115 metres.
Targeting fault intersection
Giles said: “In coming weeks our drilling will target the fault intersection zone for higher-grade vein and breccia style gold mineralisation, where there are some long gold intersections within widely spaced drill holes.
“For the next round of drill holes, we will switch over to RC drilling, managed and operated by Havilah, so that we can drill to greater depths in the harder rock.