Alto Metals (ASX:AME) reports it has uncovered ‘high-grade’ gold targets at the Oroya and Hacks reefs where it has a focus on ‘bonanza style’ mineralisation.
The results are part of its ongoing regional evaluation of the multiple advanced prospects within the company’s 100% owned Sandstone Gold Project, where it reviewing both the historic ‘high-grade’ Hacks and Oroya gold mines.
Work towards developing initial drill targets is ongoing through a combination of structural and geological targeting and review of the historic data sets and recently acquired digitised historic mined void models.
The company considers there is potential for significant mineralised material to remain due to historical mining activities at Oroya and Hacks focusing only on ‘bonanza style’ mineralisation within the reefs (and later open-pit mining at a gold price of US$380/oz) leaving surrounding mineralisation unmined, as highlighted by the historical results drilled post mining.
The Oroya and Hacks mines were major gold producers, together accounting for almost 40% of the total gold production from the Sandstone Greenstone Belt. Despite the historical production and numerous old workings over the areas, there has been limited modern exploration undertaken over these prospects.
The lack of recent exploration and numerous historic ‘high-grade’ drill results provides an exciting opportunity for Alto to re-explore these ‘long forgotten mines’ and fits with the company’s strategy of continuing to focus on growing its existing resource base within the Alpha Domain, while progressing regional prospects.
While the company’s current focus remains firmly on resource step-out and extensional drilling at Indomitable Camp, which is continuing to deliver numerous high-grade results outside of the current resource, follow up drilling at Oroya and Hacks target areas is proposed to commence once program of works (POWs) and regulatory approvals have been received.
Alto’s immediate exploration strategy also remains focused on discoveries and resource growth within the Alpha Domain which hosts the Lords corridor, Vanguard, Indomitable and Havilah.
Based on its success of the systematic approach to exploration to date, Alto is continuing to review the multiple other early greenfield and advanced brownfield targets within the Sandstone Gold Project, as part of the company’s longer-term strategy to advance the overall project pipeline to support a stand-alone operation.
In the meantime, further interpretation is ongoing to support improved targeting ahead of drilling and a fine-fraction soils program has commenced over the Hacks West target area on 400m x 40m centres to define potential drill targets. The company is continually assessing its significant pipeline of advanced regional targets within the Sandstone Gold Project, which includes other historic mines such as Bulchina (250koz prod @ 3.4g/t gold).
RC drilling is ongoing at the Indomitable Camp, with assays currently pending from drilling at the Musketeer prospect.
Alto notes that priority targets identified so far from the review of the Oroya, Hacks and near mine area include potential extension of the Oroya Sandstone reef along NW strike, beyond the north end of the pit, which has not been adequately tested, along with the down-dip extensions of the shallow west dipping Main reef. It also includes testing the high-grade tenor of remnant mineralisation at Oroya and the unmined Juno Reef which have the potential to add additional shallow resources in the near term.
Historical results north of Hacks may represent the offset to the main Hacks high-grade reef on the north-western side of the cross-course. Hacks West, a +16km-square target area is considered ‘highly prospective’ for additional ‘repeat’ high-grade gold reefs, which may link to the regional Youanmi shear corridor.
The Oroya North, Hacks North, and Hacks West target areas contain multiple walk up drill targets and are all located within 10km of the Alpha Domain, which hosts the current 635,000oz shallow gold resource.
The historic Oroya Black Range Mine produced 410,000t at 16.5g/t gold for 220,000oz of gold from underground mining between 1904-1920. A further 25,100oz at a grade of 2.3 g/t was recovered by Herald Resources from open pit mining to a depth of 60m, during 1994-1995.
The Oroya Black Range underground mine has a strike length of approximately 1km. The workings stretched down-dip for about 350m extended up to 140m below surface.
Meanwhile, Alto reports that the NW strike extension of the Sandstone Reef also appears to have been poorly tested, and there is limited down-dip drilling in the entire northern half of the target area.
Several historical holes drilled close to the north-west edge of the Oroya pit returned notable ‘high-grade’ intersections, including:
- 23m @ 6.2 g/t gold from 87m, incl. 2m @ 55.9 g/t gold from 89m (NT5020R) 143 gt*m – NW Extension
- 6m @ 3.5 g/t gold from 53m, incl. 1m @ 17.1 g/t gold from 53m (MSGC0954) 21 gt*m – NW Extension
- 16m @ 1.4 g/t gold from 83m, incl. 1m @ 6.6 g/t gold from 87m (NT5022R)
The company considers there is significant potential for the Sandstone reef to continue along a NW strike beyond the north end of the pit which has not been adequately tested, along with the down-dip extensions to the west. Given that the historical drilling has already delivered significant intercepts and combined with the lack of modern exploration, this represents an exciting opportunity for Alto.
Several high priority targets have been identified at Oroya, with the first of these targets to be tested being the down-dip extensions of the Sandstone reef to the west, followed by testing of the NW strike potential at the northern end of the pit.
Several high priority targets have been identified at Oroya, with the first of these targets to be tested being the down-dip extensions of the Sandstone reef to the west
The Oroya Sandstone reefs are variably composed of quartz, quartz-carbonate and brecciated quartz and carbonate altered mafic rock. They occur within sheared country rock with carbonate alteration halos up to 15m in width.
Alto’s tenure currently covers a total of 740km-square and includes what it considers the most prospective areas of the Sandstone Greenstone Belt.. This tenure includes 5 granted Mining Licences within the Alpha Domain, hosting the current 635,000oz open-pitable gold resource and multiple priority targets including Oroya, Hacks, Hacks West, Bulchina, Bull Oak, Sandstone North and numerous advanced regional targets.
Write to Adam Orlando at Mining.com.au
Images: Alto Metals Ltd