Alto Metals Ltd (ASX:AME) has identified a number of high-priority targets at the historical high-grade Hacks and Oroya gold mines and near-mine areas at its 100%-owned Sandstone Gold Project that could still hold significant mineralised material.
Work has begun to develop the initial drill targets through a combination of structural and geological targeting and review of the old data sets and recently acquired digitised historic mined void models.
The Oroya North, Hacks North and Hacks West target areas contain multiple walk-up drill targets and are all within 10 kilometres of Sandstone’s Alpha Domain.
Outstanding targets
Alto managing director Matthew Bowles said: “In parallel with the ongoing resource step-out and extensional drilling at Indomitable, Alto has been progressing a regional review focused on the multiple advanced prospects within our Sandstone Gold Project portfolio.
“Oroya and Hacks are outstanding targets and demonstrate the quality of the prospects within our regional exploration pipeline.
"Both were exceptionally high-grade historic gold mines and have significant remaining mineralisation that has potential to be extended, as well as the surrounding area which remains highly prospective for repeat orebodies.
“With drilling ongoing, focused on continuing to grow our current 635,000-ounce shallow gold resource, we are excited to be planning to test our first high-priority regional targets, outside the Alpha domain.”
Long forgotten mines
The historical mines were major gold producers in the early 1900s, together accounting for almost 40% of the total gold production from the Sandstone Greenstone Belt.
Regional prospect map showing gold in soils over 1VD magnetics, highlighting the +20-kilometre-long gold corridor of the Alpha Domain, the Oroya/Hacks area and multiple high-priority targets within Sandstone.
Oroya Mine
Oroya produced 220,000 ounces at 16.5 g/t gold from underground mining between 1904-1920 and a further 25,000 ounces at 2.3 g/t gold from open pit mining from 1994-1995.
The open pit was last mined by Herald from 1994-1995 when the gold price was about US$384 per ounce.
Alto intends to extend the known zones along strike further to the north and northwest as significant mineralisation remains both immediately below the shallow open pit and west of the pit, and the unmined Juno Lode.
The company believes there is considerable potential to define additional shallow resources at Oroya based on the remnant high-grade mineralisation, which remains open, and based on the current gold price.
Hacks Reef
The Hacks Mine produced about 200,000 ounces at 24 g/t gold from underground mining between 1907-1916.
Historical drilling targeting the northwest extension of the reef returned significant gold results including 0.3 metres at 430 g/t gold from 186.6 metres.
The high-grade unmined gold intersections at Hacks North may represent the offset to the main Hacks high-grade reef on the north-western side of the cross-course fault.
Since underground mining ceased at Hacks Reef, there has been limited modern exploration.
Hacks West
The Hacks West target area covers more than 16 square kilometres and is considered prospective for additional 'repeat' high-grade gold reefs, which may link to the regional Youanmi shear corridor.
The target area hosts numerous old workings and historic shafts, which predominantly are north-south striking but has had limited modern exploration.
Given the limited outcrop in the area, Alto recently completed a first-pass surface geochemistry program to define targets for follow-up infill soil sampling and RC drilling. Results are pending.
Other ongoing activities
Follow-up drilling at the Oroya and Hacks target areas will commence once the program of works (POWs) and regulatory approvals have been received.
In the meantime, further interpretation is ongoing to support improved targeting ahead of drilling, while a fine-fraction soils program has commenced over the Hacks West target area to define potential drill targets.
Other advanced regional targets within the Sandstone Gold Project, which includes other historical mines such as Bulchina, are being assessed.
Reverse circulation drilling is ongoing at the Indomitable Camp, with assays currently pending from holes sunk at the Musketeer prospect.