The initial reverse circulation (RC) drilling assays of up to 4.3% copper and 0.1% cobalt has confirmed a significant mineralised system over an extensive strike length at the Mt Venn prospect.
Great Boulder’s shares were trading circa 70% higher intra-day, at $0.39.
Stefan Murphy, managing director, commented: “To achieve such intersections of cobalt, copper and nickel from the first nine holes is simply outstanding.
“Given that we are conducting scout drilling over a strike length of 7.5 kilometres, it is remarkable to have intersected such widths and grades from these initial holes.
“The potential at Mt Venn is becoming very apparent, with knowledge gained from recent drilling and an improved understanding of the ore-forming systems further confirming the prospectivity of the project.”
Mt Venn background
In late 2015 Gold Road (ASX:GOR) drilled and assayed an RC drill hole on the edge of an electromagnetic anomaly, identifying copper-nickel-cobalt mineralisation at the Mt Venn prospect.
Great Boulder subsequently re-assayed the hole and confirmed primary bedrock sulphide mineralisation, with peak assay results of 1.7% copper, 0.2% nickel and 528 ppm cobalt.
Wide zone of near-surface mineralisation
The maiden reverse circulation drilling program is now complete with a total of 20 holes drilled.
Results from the first nine holes reveal the presence of a wide zone of primary, near-surface copper-nickel-cobalt sulphide mineralisation which remains open in all directions.
Mineralisation is copper-dominant with discrete nickel-cobalt-rich zones.
The highlight results include 18 metres at 0.82% copper, 0.07% nickel and 0.02% cobalt from 187 metres including 1 metre at 4.34% copper from 191 metres.
Importantly, the grades up to 0.3% nickel and 0.1% cobalt within the massive sulphide zones are much higher than anticipated based on previous Gold Road drilling and Great Boulder aircore geochem.
Further drilling planned
A downhole electromagnetic (EM) survey has now commenced with the objective of identifying offhole conductors along the main mineralised trend.
This information will be used with the drill hole data to better constrain the EM plate modelling.
Great Boulder is also building a magnetic inversion model to generate a 3D model of the interpreted sulphide zone.
The results from the inversion model and updated EM plate modelling will be used for planning the next phase of drilling in December.