Tres Cruces ranks among the highest-grade gold oxide development deposits globally with 424,000 contained ounces of gold in oxide material grading 1.37 gpt
The Tres Cruces project is located in north central Peru and accessible via a paved road 127 km from the city of Trujillo, located on the Pacific coast. Salaverry is the deep water port near the city of Trujillo. Infrastructure near the project includes an airstrip a few kilometres to the north as well as Barrick’s existing Lagunas Norte operations ~10km away. Lagunas produced over 10 million ounces gold from oxide material and has another 4.3 million ounces in resources. Tres Cruces and Lagnuas Norte share a project boundary.
Tres Cruces ranks among the highest-grade gold oxide development deposits globally with 424,000 contained ounces of gold in oxide material grading 1.37 gpt. There are an additional 205,000 ounces of leachable sulphides in material grading 1.18 gpt.
NI 43-101 Resource
The Tres Cruces project contains a NI 43-101 Resource Estimate of 2.47 million ounces of gold at 1.65 g/t gold in the indicated category, consisting of 46.5M tonnes of oxide and sulfide material. The deposit is 100% pit-constrained and is amenable for open-pit mining. Included in this resource are 630,000 leachable ounces at 1.28 g/t gold in the indicated category, contained in 15,343,000 tonnes.
The defined leachable resource consists of oxide material and leachable sulphides. The current defined oxide leachable ounces and the immediate underlying leachable sulfide ounces demonstrate the potential for an economic standalone heap leach operation with depth expansion into the sulphide part of the deposit. If processed first, the oxide and leachable sulphide ounces would significantly off-set the capital costs of a much larger sulphide operation.
New Oroperu updated the mineral Resource Estimate to include leachable mineralization for the Tres Cruces Project in the NI 43-101 Technical Report dated February 1, 2021 which updates the prior Resource Estimate in an NI 43-101 Technical Report dated September 2012. The updated Tres Cruces resource dated as of February 1, 2021 is summarized below and can be found on the following link and is filed on SEDAR.
Indicated Mineral Resources are estimated to contain 46.5 million tonnes grading 1.65 g/t Au for a total of 2.5 million ounces of contained Au in the indicated category. Inferred mineral Resources Estimate is 19.6 million tonnes grading 0.97 g/t Au or 0.6 million contained oz Au. These estimates are reported at 0.3 g/t Au cut-off for leachable resources and 0.9% g/t Au for non-leachable sulfides which cut off grades are considered appropriate for the deposit at current long-term average metal prices.
Potential exists to increase the size of, and the confidence in, the resource through further drilling. Near-surface oxide mineralization expansion opportunities are present in areas covered by shallow post-mineral rocks. Drilling areas presently classified as Inferred Mineral Resource and in areas where holes ended in mineralization, could add or upgrade significant resource tonnage. There is deep exploration potential for additional resources including for “bonanza vein” opportunities found in feeder zones of low sulfidation systems.
No estimate has been made by the NI 43-101 authors for Ag although significant potential for value exists at current Ag prices. Indications are that silver grades are generally low and concentrated mainly in the deeper, sulfide portion of the gold deposit. Based on this updated gold resource scenario, overall silver grades would be expected to range between 1.5 and 2.5 g/t, potentially containing 2.5 to 3.5 million ounces of silver. Any silver recovered with the gold would enhance overall project economics.
(0.3 g/t Au Cut-off)
(0.3 g/t Au Cut-off)
(0.9 g/t Au Cut-off)
|Tonnes (1,000s)||Au (g/t)||Oz Au (1,000s)||Tonnes (1,000s)||Au (g/t)||Oz Au (1,000s)||Tonnes (1,000s)||Au (g/t)||Oz Au (1,000s)||Tonnes (1,000s)||Au (g/t)||Oz Au (1,000s)|
|Min. Type||Cost ($/t)|
Tres Cruces Resource Summary
- 425,000 ounces of gold in oxide material at 1.37 g/t in the Indicated category, contained in 9,636,000 tonnes, using a 0.3 g/t Au cut-off (Table 1).
- 205,000 ounces of gold in leachable sulfide material at 1.12 g/t, in the Indicated category, contained in 5,707,000 tonnes, using a 0.3 g/t Au cut-off (Table 1).
- Total Leachable Mineralization: 630,000 ounces at 1.28 gpt gold
Total Mineral Resource
- 2.5 million ounces of gold at 1.65 g/t in the Indicated category, contained in 46,475,000 tonnes of oxide and sulfide material.
- Non-leachable sulfide resources were estimated using 0.9 g/t Au cut-off.
- Leachable resources were estimated using 0.3 g/t Au cut-off.
New Oroperu’s 100% owned Tres Cruces property is located within a NW-SE trending belt of Paleogene volcanic rocks of predominantly andesitic composition called the Calipuy Volcanics. This volcanic belt trends from central to northern Peru and hosts world-class deposits like Newmont & Buenaventura’s Yanacocha Mine and Barrick’s Pierina Mine. The Tres Cruces property lies near the heart of the Quiruvilca mining district, which includes the Quiruvilca copper-lead-zinc-silver vein systems. Precious metal deposits in the area include the Lagunas Norte mine, an epithermal gold deposit which has produced over 10 million ounces of gold and has current resources of 4.3 million ounces (Barrick Annual Report 2020).
The Calipuy volcanic package overlies a Cretaceous sedimentary sequence (Chimu Formation) of quartz arenite and mudstone that shows a strong degree of deformation resulting from early Cenozoic SW-NE compression. This was later followed by E-W extension allowing loci of volcanic activity to develop. The Quiruvilca District is host to several mineral deposits all classified as epithermal type including Barrick’s Laguna Norte located 10 km north-northeast of Tres Cruces is classified as a high sulfidation system. Tres Cruces is considered to be of the low to intermediate sulfidation epithermal type. Age dating at Tres Cruces indicated the age of mineralization to be between 22-25 million years. This is older than the nearby Quiruvilca intrusive rocks hosting vein mineralization and the age dated alteration at Lagunas Norte.
Gold mineralization at Tres Cruces is hosted by a bimodal suite of andesitic to rhyolitic flows, domes, breccias, and volcaniclastics. Gold occurs with a fine grained dark arsenical pyrite, generally disseminated within its volcanic host, along structural zones and lithologic contacts. Accompanying the pyrite, trace amounts of associated minerals include marcasite, arsenopyrite, galena, stibnite, realgar, orpiment and enargite. Silver shows a moderate correlation with gold at a ratio of about 3:1. The gold is extremely fine, with over 95% having a diameter of less than 5μ. Rare coarse visible gold occurs in quartz veinlets. Oxidation of the gold mineralization has occurred from a few meters up to 100 meters below surface, developed primarily in rhyolitic host rocks.
The Tres Cruces property hosts gold deposits that have characteristics of a low- to moderate-sulfidation type epithermal system. Hydrothermal alteration in the core of the Tres Cruces deposit is dominated by illite with chalcedonic quartz, kaolinite, and smectite in the upper part. At depth, illite alteration is dominant with minor quartz and sericite. Geochemically, the gold mineralization is associated with arsenic, and at high levels, mercury.
Figure 1-1 below is a plan map of the geological lithologies at Tres Cruces. The figure also identifies the proposed pit outline for oxide and sulfide mineralization in the solid blue and red lines respectively.
Metallurgical test work has indicated a baseline recovery of about 82% or better of the contained gold for heap leaching of oxide mineralization, and 65% for heap leaching low sulfide content mineralization. For the balance of the sulfides, 88% recovery is expected from test work using flotation followed by pressure oxidation and carbon in leach (“CIL”).
Gold recoveries do not necessarily depend on sulfur content. Those samples with both high gold recovery and sulphur content are primarily derived from shallower depths while those with high sulphur and lower recoveries are from deeper intervals. It is probable that in those samples exhibiting higher recoveries, some of the sulfur occurs in sulfate minerals (oxide state) versus sulfides. Those higher recovery sulfides from the upper reaches of the deposit that have lower sulfur content may have been partially leached of sulfur following oxidation, or the gold may deport as free grains. Some of this mineralization may be treatable by heap leaching or other low-cost recovery techniques.
Why Tres Cruces?
Tres Cruces ranks among the highest oxide development deposits globally with 424,000 ounces gold of oxide material.
There are an additional 205,000 ounces of leachable sulphides.
Drilling at tres cruces
Drilling at Tres Cruces has only been completed to a depth of approximately 320 metres with many holes ending in mineralization. Drilling within and below the optimized pit shell could identify further sulphide mineralization and test the potential at depth. The presence of deep mineralization with strong alteration, positive geochemical signature, and deep seated hydrothermal breccias suggest there is an opportunity for deeper mineralization, possibly feeder zones attached to the current known mineralization. Moreover, there are opportunities for the Company to further identify more leachable (oxide and sulphide) gold resources on the Tres Cruces Project, in areas covered with nearby post mineral volcanics which would enhance project economics.
There has been over 72,000 metres of drilling completed on the Tres Cruces project from all drill programs carried out on the property. Following the gold discovery at Tres Cruces*, drilling was completed by New Oroperu and subsequent joint venture parties. The last drilling completed on the Tres Cruces project was done by Barrick in 2008.
Mining activity has been ongoing in the region since the 1920’s, when Compañía Minera Quiruvilca started mining high-grade Pb-Zn-Ag veins at Quiruvilca, a small mining town 4 km west of Tres Cruces. In 1996 New Oroperu acquired the key concessions of the Tres Cruces property and entered into a 50-50 joint venture with Pan American on a combined land package, including adjoining ground held by Pan American that covered portions of the Tres Cruces mineralization. Drill campaigns utilizing reverse circulation (RC) and diamond drilling equipment were conducted by New Oroperu in 1996 and 1997, completing 61 drill holes, and later by Battle Mountain Gold in 1998 and 1999. Battle Mountain Gold relinquished their option of the Project in 1999 after drilling 80 diamond core holes and 26 RC holes.
In May 2002, New Oroperu entered into an agreement to acquire Pan American’s 50% interest to increase its interest to 100%, subject to a 1.5% royalty. Concurrently, New Oroperu entered into an agreement with Minera Barrick Misquichilca S.A. (Barrick), the Peruvian subsidiary of Barrick Gold, that would further the exploration of the Project. In September 2003, the agreement with Barrick was finalized and a definitive option agreement was signed. In October 2003, New Oroperu finalized their agreement with Pan American regarding their interest in the Project, effectively acquiring 100% of Tres Cruces through issuance of New Oroperu shares and the granting a 1.5% NSR royalty to Pan American.
The Barrick exploration program began with geological mapping, re-logging of existing drill core, and Induced Polarization (IP) and gravity geophysical studies. Barrick managed exploration and technical work competed on Tres Cruces project from 2002. Barrick drilled 202 holes on the project which includes a combination of RC drilling and diamond core holes with the last drilling completed in 2008. The only additional work carried out on the project was metallurgical test work completed in 2011.
*In summary, Tres Cruces was a grass-roots discovery made by New Oroperu in 1995 and drilled the discovery holes in 1996. New Oroperu completed 61 drill holes by the end of 1997. Battle Mountain Canada Ltd. (BMC) optioned the Property and completed an additional 106 drill holes in 1998 and 1999. Barrick Gold Corporation, through its Peruvian operating subsidiary, Minera Barrick Misquichilca S.A. (Barrick), advanced the Project under an option agreement with New Oroperu by drilling an additional 202 drill holes from 2002 to 2008 and completing geotechnical and metallurgical studies. The results of these drill campaigns are contained in the NI 43-101 Technical Report dated February 1, 2021 by Jeffrey D. Rowe, James N. Gray, and Ruperto Castro.