After nearly two years of work, the long-awaited inaugural mineral resource estimate for Mantaro Precious Metals’ (TSXV:MNTR, OTCQB:MSLVF, FSE:9TZ) Golden Hill property in Bolivia has arrived, offering a glimpse of the project’s upside.
The resource estimate, prepared by P&E Mining Consultants Inc., contains 857,000 tonnes of material in the inferred resource category at a grade of 4.4 grams per tonne (g/t) gold for 121,000 ounces of gold (at a 1.5 g/t gold cut-off grade).
This estimate, however, was based just on 14 diamond drill holes totalling 2,405 metres completed on the property, equivalent to an inferred mineral resource of 50.21 ounces of gold for every metre drilled.
The resource covers a strike length of only 400 metres from surface to a vertical depth generally less than 90 metres — representing only a small portion of the exploration footprint of Golden Hill.
“Since optioning Golden Hill in August 2021, our technical team completed a very successful diamond drill program, received excellent recovery results from metallurgical testwork and carried out a petrographic study confirming high-grade primary gold deposition that is not a result of supergene enrichment,” Mantaro’ CEO Darren Hazelwood commented in a news release.
So far, we know that the gold mineralization at Golden Hill is of orogenic or greenstone-hosted style.
This style of mineralization has been a major source of the world’s gold production for the past 100+ years, as illustrated by prolific production from deposits in the Abitibi of Canada, the West African Shield and Western Australia.
A common theme links orogenic deposits: multiple large deposits form along crustal-scale to regionally extensive gold mineralized structures. Individual deposits typically comprise multiple high-grade shoots within a lower-grade gold mineralized envelope, that extend over several kilometres of strike to depths that often exceed +1,000 metres.
Mineralization at Golden Hill is found to be contained within sub-vertically dipping quartz shear zones of 1 to 5 metres wide, typically found along faults at the contacts between mafic volcanic and metasedimentary units of pre-Cambrian age.
To date, Mantaro has identified four major gold-mineralized zones — La Escarcha, Gabby, Garrapittilia and Brownfields — across a 4 km strike length (see below). Historical drilling on the property was only limited to the La Escarcha pit area.
As such, the focus of the company’s drilling — and the maiden mineral resource estimate — has been the La Escarcha zone.
The Golden Hill resource is found to be hosted within several closely-spaced, sub-vertical to vertical, gold-mineralized shear zones with true widths of up to 13 metres.
However, this could be easily expanded since the mineralization at La Escarcha is open in all directions, and Mantaro noted it already has a number of high-reward, relatively shallow step-back and step-out drill holes around the resource area.
The deep potential at La Escarcha is also highly prospective, the company added. There are multiple quartz vein targets hosted along the main controlling structure yet to be drill tested, and an additional 6 km of the regional structure shedding alluvial gold that is yet to be mapped and sampled.
“That Mantaro was able to define a maiden mineral resource estimate after only 2,405 metres of angled diamond drilling, is a testament to the technical teams understanding of the mineralized system and deposit, their ability to generate high-reward near-surface drill targets and the exceptional caliber of the deposit,” Dr. Chris Wilson, principal consultant to Mantaro, commented.
“Significantly, with true widths of up to 13 metres and near-surface nature of sub-vertical to vertical mineralized lodes, demonstrated metallurgy, and the fact that Golden Hill is a permitted mining concession with immediate optionality — underscores that the mineral resource estimate is based on a robust cut-off grade of 1.5 g/t Au,” he continued.
“It is also worth noting that at a higher cut-off of 2.0 g/t Au, the inferred mineral resource estimate only decreases by approximately 4,000 ounces to 117,000 at 4.71 g/t Au, further underscoring the robust nature of the mineral resource estimate and style of mineralization at La Escarcha.”
To get a full grasp of the Golden Hill resource and its sheer growth potential, we need to acknowledge the geological setting on which the property is found.
Golden Hill is a fully permitted 5,976-hectare mining concession situated within Bolivia’s underexplored Precambrian Shield. It is located on a crustal-scale structure hosting at least six other significant gold occurrences and deposits along a 25 km strike length, all of which have been mined by open pit to shallow levels.
From a regional perspective and comparison with other greenstone belts worldwide, Golden Hill is an attractive project.
The Bolivian Pre-Cambrian shield is larger than the famous Abitibi greenstone belt in Canada, yet the Bolivian shield has produced less than 10 million oz compared to 170+ million oz in the Abitibi.
Similarly, the gold endowments of the West African Shield, the greenstone belts of northeast South America (Venezuela, Guyana, Suriname and Brazil) and the Yilgarn province of Western Australia, were much greater than equivalent areas of the Bolivian Shield, as the latter remains largely underexplored.
As with other greenstone belts and mineralized provinces, mineralization in the Bolivian shield is hosted along major crustal structures with juxtaposing lithologies.
Regional-scale structures focus the mineralizing fluids, while rocks of different competencies provide a regime for both ductile and brittle deformation, creating a space for deposition of quartz, pyrite and gold.
Mafic volcanics are especially favorable hosts due to the high iron content that reacts with sulfur in mineralizing fluids to form pyrite — causing gold to precipitate from the fluids.
The Golden Hill concession is centered on a broadly north-south trending regional structure that hosts the La Escarcha underground mine and the Gabby, Garrapatillia and Brownfields workings and gold-bearing vein occurrences in its western hanging wall.
The same structure hosts numerous saprolite gold and hard rock gold deposits to the north and south of the Golden Hill concession over a strike length of at least 25 km — underpinning the significant control the structure exerts on gold mineralization.
A northwest-trending splay of this structure hosts areas of alluvial and saprolitic/hard rock workings within the Golden Hill concession and immediately to the north.
At least 6 strike km of these structures are known within the concession — in addition to the four kilometers between La Escarcha and Brownfield which have been mapped in detail.
Known mineralization and surface anomalism is open along strike on all structures.
Since Mantaro took over the project in 2021, it has acquired remote sensing data as a foundation for geological and structural mapping, and completed a focused geochemical sampling program for input into drill targeting.
The company also took a 10-tonne bulk sample from the -45 metre level of the C3 vein at La Escarcha, providing a 170 kg sub-sample which was sent to SGS Lakefield (Canada) for metallurgical test work.
The test work confirmed a head grade of 5.53 g/t gold by 50 g fire assay and 5.96 g/t gold by cyanide leach bottle roll, and demonstrated that unoptimized recoveries of 73.6 % gold are achievable by gravity separation and 94 % gold by cyanidation.
These results provided insight into gold grade and distribution at La Escarcha ahead of the maiden diamond drill program in 2022.
Of the drilling (>3,000 m, 21 holes), 14 holes totalling 2,405 metres were drilled at La Escarcha, focusing on a strike length of only 400 metres to a vertical depth of generally <100 metres. The remainder were drilled as scout reconnaissance holes at other prospects.
Drill results from the La Escarcha and Gabby zones are shown in the figure above. Highlights include the following:
As a final step in the company’s initial exploration plan, a detailed petrographic study was recently carried out on the drill core to assist with deposit modelling, drill targeting and input to process metallurgy. The study noted the absence of near-surface supergene enrichment and confirmed the gold grades are primary or hypogene.
“The findings of the petrological study and bench-scale metallurgical testing by SGS, have further de-risked the project,” Dr. Wilson commented in a June 28 news update.
“Given that Golden Hill is a permitted mining concession, the petrographic data will assist in review of near-term mining scenarios, and design of a high-reward Phase 2 drill program to target along strike and deeper extensions of La Escarcha mineralized system.”
With the maiden resource estimate completed to establish a proof of concept, the next step for Mantaro is quite straightforward: to drill the aforementioned “high-reward targets” as last year’s drilling only tested a small “panel” beneath the La Escarcha open pit.
The company has already presently designing a 5,000m Phase 2 angled diamond drill program to test the along strike extension and deeper extension of mineralization to depths of approximately 300m vertical. The depth potential below this level is extremely robust and will be the focus of subsequent drill programs, Mantaro says.
It will also look to test the exploration potential of Gabby, Brownfields and Westfield with further drilling. Five scout diamond drill holes were completed at Gabby in the 2022 program. Gabby is located approximately 500 m to the south of La Escarcha and is characterized by a number of gold-bearing quartz veins in outcrop.
The veins extend a further 2 km to the Brownfield target where one drill hole was completed. There are over 2 km of auriferous quartz veins approximately 500 m to the west of La Escarcha and Gabby which have only been tested by a single shallow drill hole.
In addition to the known prospects, there are over 6 km of unmapped regional structures that have shed alluvial gold into drainages on either side. Significantly, the main controlling structure runs northwards from La Escarcha, before hosting the Puqui Norte deposit about 1 km to the north of the concession boundary. The exploration potential of this structure is robust and will be the near-term focus of mapping and sampling by Mantaro.
What the maiden resource estimate really is that it places Mantaro on its way toward the next project milestone: a preliminary economic assessment (PEA). The PEA essentially outlines the mine’s economic viability, which should look promising as long as the company continues its drilling.
Since Golden Hill is a permitted mining concession, Mantaro is fully able to commence these activities without the need for further permits, and so the PEA should also be streamlined. Once that is done, it would officially put the Golden Hill project on the industry’s notice.
The maiden resource has already been well received by investors, with Mantaro’s stock closing the session 50% higher on 10x the average trading volume.
In an era where exploration assets are continuously being sized up by the gold majors, its Golden Hill property should at least get plenty of interest, given the number of deposits hosted and its geologic resemblance to world-class districts like Canada’s Abitibi. Most important of all, much of Bolivia is still vastly underexplored to this day!
Also worth pointing out is that the company originally held an option on 80% of the Golden Hill project, but decided to exercise a 51% majority stake even before finishing last year’s drilling, showing its confidence. With the high-grade results yielded from the program and the resource calculated, we can see why.
Mantaro Precious Metals Corp.
TSXV: MNTR, OTCQB: MSLVF, FSE: 9TZ
Shares Outstanding 71.2m
Market cap Cdn$4.3m
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