Alto Metals Ltd (ASX:AME) has hit the high-grade historical Oroya gold mine, at its 100%-owned Sandstone Gold Project, with a 2,000-metre maiden reverse circulation (RC) drill program.
The program follows a targeted review of both the old Hacks and Oroya gold mines, which identified a number of priority targets.
It targets the Sandstone reef mineralisation to the north-west beyond the north end of the pit, along with extensions to the south and down dip to the west, which Alto believes has not been adequately tested.
Long-forgotten mine
This is the first time Oroya has been RC drilled in more than 15 years.
The company thinks there is a good chance that significant mineralised material remains in the mine, given that historical mining activities at Oroya focused only on bonanza-style mineralisation within the reefs, leaving surrounding mineralisation – including the Juno Lode – unmined.
Added to that, the Oroya open pit was last mined by Herald in the nineties, when the gold price was sitting around US$384/oz.
The lack of recent exploration and numerous historical high-grade drill results at Oroya, provides an opportunity for Alto to re-explore this ‘long-forgotten mine’ and fits with the company’s strategy of continuing to grow its existing resource base within the Alpha Domain, while progressing regional prospects.
Past results promising
The Oroya Mine produced 220,000 ounces at 16.5 g/t gold from underground mining between 1904 and 1920 and a further 25,000 ounces at 2.3 g/t gold from open pit mining from 1994 to 1995.
Historical results highlight significant high-grade mineralisation remains below the shallow-mined Oroya pit (60 metres depth) and along strike and down dip of the underground workings of the main reef, including:
- 23 metres @ 6.2 g/t gold from 87 metres, including 2 metres @ 55.9 g/t gold from 89 metres – NW Extension;
- 8 metres @ 17.9 g/t gold from 69 metres, including 1 metre @ 137.0 g/t gold from 73 metres –Main Reef;
- 9 metres @ 14.6 g/t gold from 42 metres, including 1 metre @ 120.0 g/t gold from 42 metres –Juno/Main Reef;
- 6 metres @ 8.3 g/t gold from 49 metres, including 2 metres @ 23.2 g/t gold from 51 metres – Main Reef;
- 13 metres @ 3.1 g/t gold from 22 metres, including 2 metres @ 11.9 g/t gold from 28 metres – Juno; and
- 8 metres @ 10.1 g/t gold from 44 metres, including 1 metre @ 50 g/t gold from 47 metres – Oroya West.
Alto managing director Matthew Bowles said: “We are excited to be testing numerous targets at the Oroya Mine, which historically produced 220,000 ounces at 16.5 g/t gold from underground to a depth of only 140 metres below surface and is the first time this ‘long forgotten mine’ has had any drilling in over 15 years.
“Drilling is designed to test both plunge and strike extensions high-grade gold mineralisation of the Sandstone Reef, along with the unmined Juno reef to the west.
“While our focus remains on growing our current 635,000 ounce shallow gold resource, Oroya is an outstanding high-grade gold target, that demonstrates the quality of prospects in our project pipeline and is an exciting opportunity for Alto shareholders.”