Alto Metals Ltd (ASX:AME)’s targeted review of the historical Bull Oak Gold Mine and surrounding historic workings at the Sandstone Gold Project has highlighted the potential for near-term resource growth.
Underexplored potential
The lack of recent exploration and untested mineralisation in significant intersections represents an opportunity for the company, which hopes to extend the mineralisation below the shallow-mined pit up and down dip, as well as along strike and at depth.
The style of gold mineralisation at the Bull Oak deposit features multiple stacked lodes hosted within a granodiorite, similar to that observed at Lord Nelson and Lord Henry.
The intrusion has a strike length of 500 metres and a width of up to 150 metres, with relatively steep dipping boundaries.
Encouragingly, it has not been defined at depth and the gold mineralisation is not constrained by the boundary of the granodiorite, extending into the mafic rocks.
Highlights
Unmined results below the shallow mined pit highlight considerable mineralisation remains, including:
- 13 metres at 2.4 g/t gold from 37 metres, including 1 metre at 17.1 g/t from 39 metres; and 10 metres at 8.3 g/t from 57 metres, including 3 metres at 25.8 g/t from 57 metres;
- 10 metres at 1.8 g/t from 55 metres, including 1 metre at 6.5 g/t from 58 metres; and
- 7 metres at 38.9 g/t from 64 metres, including 1 metre at 154 g/t from 65 metres.
Two deeper historical holes, drilled by WMC and Troy in 1985 and 2009, intersected multiple mineralised reefs, with numerous instances of visible gold.
The WMC diamond hole was only selectively assayed in mineralised zones, while the Troy hole returned 157 metres at 0.5 g/t gold from 143 metres, including 1 metre at 18.7 g/t from 297 metres.
Alto has drilled one RC hole at Bull Oak to date, to test and validate the deeper historical results and intersected multiple stacked lodes.
The intersection recorded 260 metres at 0.41 g/t gold from 36 metres, which included a high-grade intercept of up to 14.3 g/t, with the hole ending in mineralisation.
Mineralisation is completely open up and down dip, along strike and at depth.
Bull Oak historically produced some 10,600 ounces at 27 g/t gold between 1904 and 1943 from small underground shafts. It yielded a further 10,000 ounces at 1.9 g/t gold from open-pit mining in 1997.
The current mineral resource for Bull Oak is 65,000 ounces at 1.1 g/t gold constrained within a A$2,500 pit shell – capturing the majority of the historical shallow drilling, but Alto is confident in the potential for this resource to grow.
Instances of visible gold
Alto managing director Matthew Bowles said: “Most of the historical drilling at Bull Oak has been relatively shallow, however, two historical holes drilled to 300-metre depth intersected multiple lodes and reported numerous instances of visible gold.
“A follow-up deep hole drilled by Alto returned a wide zone 260 metres at 0.4 g/t gold from 36 metres, including 14.1 g/t gold and ended in mineralisation.
“The mineralisation is completely untested up and down dip of these intercepts, as well as at depth, and we are excited to have a reverse circulation (RC) rig arriving shortly to test these outstanding targets, that have the potential to drive near-term growth.”