Ora Banda Mining Ltd (ASX:OBM)’s extensional drilling under the Riverina open pit in Western Australia has extended the Main Lode an additional 100 metres vertically with high-grade intercepts of 1.2 metres at 29.9 g/t gold and 2.8 metres at 6.0 g/t.
Intercepts have increased the depth of the known high-grade mineralisation from around 250 metres below surface to more than 350 metres below surface and the deposit remains open in all directions.
Further to this, a high-grade extension of the Murchison Lode has been discovered which runs parallel to Riverina’s existing Main lode.
The Murchison Lode is just 80 metres east of Main Lode, however, this was historically considered low grade near the surface, with no specific targeting of this lode at depth.
Initial intercepts from the Murchison Lode extension include:
- 0.3 metres at 171 g/t from 325 metres, with abundant visible gold;
- 1-metre at 30.8 g/t from 181 metres;
- 1.4 metres at 17.8 g/t from 12 metres, including 0.5 metres at 52.2 g/t; and
- 4.9 metres at 4.4 g/t from 34 metres.
OBM prioritised drilling of the underground extensions at Riverina in August 2022 and the program now underway is the first diamond drill exploration program in more than 12 months on the tenement package.
Phase 1 drilling consists of 30 holes of which 12 have been completed. It will continue until the end of December with a further 18 holes remaining in the program.
Figure 1 – Overview of OBM Tenement Package Figure 2 – Plan view of Riverina Project.
Exploration strategy moving along
OMB has implemented a three-year strategy targeting high-grade underground ore for the potential to increase annual production above 100,000 ounces.
The project had an existing high-grade underground resource of 151,000 ounces at 6.6 g/t with historical mining done down to around 120 vertical metres extracting 100,000 tonnes at ~12 g/t.
Developing the Riverina Underground is considered a relatively quick, low-capex option given the existing infrastructure in the area and the ability to develop a mine portal from the open pit.
The gold exploration and development company’s Riverina-Milline Project is about 44 driving kilometres north of the Davyhurst Processing Plant, with the Mulline Trend Area around 5 kilometres to its southwest.
Riverina ore has been processed at the Davyhurst mill and has recoveries of ~92%.
OBM owns 100% of the Davyhurst Gold Project in the highly productive Eastern Goldfields region of Western Australia.
The company will collate all exploration data and anticipates announcing a resource update in the March quarter.
“Whilst it is still early days, we are very excited with the continuing width and tenor of the Main lodes at depth and the discovery of the high-grade extension of the Murchison lode,” Ora Banda Mining’s managing director Luke Creagh said.
“What we now know is that this mineralised system is bigger than we first thought and that in parts it will host very high-grade gold.
“For Ora Banda, this is significant because it now means we can realistically consider starting an underground operation at Riverina which would look to simultaneously exploit a multi-lode system.
"The increased production profile stemming from multiple mining fronts will increase our grade profile to the Davyhurst plant, thus allowing an increase to our current production profile.”
Main Lode drilling
The Main Lodes are made up of two parallel structures (East and West) that are sub-vertical and ~10 metres apart.
Main Lode East is the prominent mineralised structure and OBM has further proven the continuity of the Main Lode structure for more than 1 kilometre and demonstrated that the system is open in all directions including high-grade intercepts at depth.
New intercepts include:
- 3.0 metres at 19.1 g/t from 147 metres;
- 2.0 metres at 12.1 g/t from 178 metres and 3.9 metres at 4.5 g/t from 165 metres;
- 1.2 metres at 29.3 g/t from 359 metres (~100 metres below previous extent of drilling); and
- 2.8 metres at 6.0 g/t from 357 metres (~100 metres below previous extent of drilling).
This complements the numerous high-grade intercepts previously reported in the main lodes, including:
- 7.0 metres at 22.7 g/t from 240 metres;
- 5.7 metres at 10.1 g/t from 144 metres;
- 5.0 metres at 16.7 g/t from 200 metres;
- 2.8 metres at 21.2 g/t from 254 metres; and
- 1.3 metres at 25.3 g/t from 218 metres.
Long Section of Main Lode East.
Emerging high-grade potential
Looking at the Murchison Lode, a new, narrow vein and high-grade extension of the Murchison lode has been identified in deeper drilling that runs parallel to the existing Main Lode.
The Murchison Lode is about 80 metres east of Main Lode and is presenting as an attractive, high-grade, narrow vein underground mining target.
New holes in the system include:
- 0.3 metres at 171 g/t from 325 metres and 1-metre at 30.8 g/t from 181 metres;
- 1.4 metres at 17.8 g/t, including 0.5 metres at 52.2 g/t from 12 metres;
- 4.9 metres at 4.4 g/t from 34 metres.
This lode system was not targeted in historical drilling as previous drilling in this area was shallow and largely from the west; therefore there were no deeper intersections.
Of the few historical intersections below 150 metres, key intercepts include:
- 1-metre at 41.2 g/t from 222 metres;
- 1-metre at 35.4 g/t from 170 metres; and
- 5.0 metres at 4.2 g/t from 87 metres and 1.3 metres at 11.1 g/t from 192 metres.
There is more than 400 metres between these holes which opens a large exploration window, both for infill and extensional drilling as the best hole is the deepest at ~300 metres below surface.
The Murchison Lode has five of the top ten grades ever sampled in the Riverina system and has a proven strike of more than 700 metres and is considered untested below 200 metres.
“We currently have two drill rigs operating at Riverina till the end of December and if the results remain consistent with those recently returned, the company should be in a good position to make a mining investment decision by the June quarter of next year,” Creagh said.
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