Santo Tomás Project Overview

Santo Tomás hosts a large, outcropping porphyry copper deposit comprised of fracture-hosted and disseminated Cu and Mo sulphides with significant Au and Ag credits. The Project lies within the Laramide Belt, a NW-SE trending copper belt extending from southwestern USA into southern Mexico that includes numerous world-class copper deposits, including the Cananea district, which hosts one of the largest copper deposits in the world.

Map with star on Santo Tomas

Oroco’s Santo Tomás Project is located at low elevation in the municipality of Choix adjacent to the Fuerte River, in the western Sierra Madre mountain range. The project straddles the border between the Mexican States of Sinaloa and Chihuahua. Santo Tomás is situated within the infrastructure rich “La Entrada al Pacífico,” a multi-modal transport and trade corridor recognized by the US and Mexican federal governments. Proximal infrastructure includes the deep-water port of Topolobampo, located 160km to the south-west, connected by sealed roads, a rail line, high voltage power supply, and a high-pressure gas pipeline, all within 20km or less of Santo Tomás. The region is home to numerous mining operations and has a strong regional mining culture and highly supportive local community.

Preliminary Economic Assessment (PEA)

Following a 48,500 m (76 hole) diamond drill program, completed in Q1 2023, and a Mineral Resource Estimate (“MRE”) published in May 2023, in October 2023 Oroco released an updated Mineral Resource Estimate and a maiden Preliminary Economic Assessment (“PEA”) for Santo Tomás. The PEA results support a staged open pit mine and processing plant starting at 60,000 tonnes per day (“t/d”) in year 1 of production, expanding to 120,000 t/d in year 2 over a 20.1-year Life of Mine (“LOM”). Production is preceded by two years of construction and pre-stripping. The PEA was prepared by Ausenco Engineering USA South Inc. (“Ausenco”). The updated MRE and geologic model were prepared by SRK Consulting (US), Inc. of Denver, Colorado and SRK Consulting (Canada), Vancouver, BC (“SRK”).  SRK (Canada) was responsible for geotechnical modeling.  The mine planning and mine costs components of the PEA were prepared by Mining Plus Canada Consulting Ltd. (“Mining Plus”).

Highlights of the Santo Tomas PEA include:

PEA DCF Price Assumptions; Cu US $ / lb 3.85, Mo US $/lb 13.50, Au US $/oz         1,700, Ag         US$/oz. 22.50

The Full Technical Report may be downloaded HERE.

Commenting on the PEA, Richard Lock stated: “This is a significant start to the process of evaluating Santo Tomas. The PEA firmly demonstrates the economic viability of the Santo Tomas Project and justifies its continued development. The combination of excellent infrastructure, simple metallurgy, a cohesive and consistent grade distribution, and a low strip ratio, along with the identification of several existing opportunities for resource expansion, provide additional strength and certainty to the Project. We have also identified a high probability of additional upside in Project economics through the future application of mine and process design improvements, all of which confirm that we have a substantial resource at Santo Tomas. In summary, the Santo Tomas Project clearly has robust potential for the development of a large, low-cost open-pit, copper mining operation.”

The PEA is the result of a two-year Phase 1 drill program (2021-2023) that relied upon historical drilling and a 14 square kilometers 3D induced polarization (3D-IP) survey for the targeting of some 48,500 meters of drilling across 76 holes. The results confirmed and extended the historical resource and demonstrated the potential for significant resource expansion. Mineralization was identified extending to the north and south beyond the current economic pit shell.

Santo Tomás Project Mineral Resource Statement Highlights

The Resource Statement in the MRE has been replaced by the Resource Statement in the PEA. The earlier MRE report can be found HERE.

PEA Economic Sensitivities
Project economics and cash flows are most sensitive to changes in the price of copper (Figure 1). Mined However, the highest potential for change in economics is anticipated to result from future changes in copper pricing.
grade and recovery sensitivity is high and future studies will seek to optimize these parameters.

Ongoing and Upcoming work at Santo Tomás
Throughout H1 2024 Oroco will be focusing on PEA optimization as detailed in its news release of October 17, 2023. 

“Project Enhancement Opportunities"

Several further opportunities to improve the Project have been identified during the PEA Study. These include but are not limited to:

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These historical resource estimate models are based upon historical resource estimates prepared by John Thornton in 2011. While, in the opinion of Dane A. Bridge, author of the revised NI 43-101 standard technical report, Geology, Mineralization and Exploration of the Santo Tomas Cu-(Mo-Au-Ag) Porphyry Deposit, Sinaloa, Mexico dated April 21, 2020 (the “Report”), reliable estimation practices were used, in order to upgrade or verify the historical estimations, resampling and assay of historical drill samples, twinning of historical drill holes, and a new program of regularly spaced drilling is required. No qualified person has undertaken sufficient work to classify the current mineral resources or mineral reserves upon which these models are based and the Company is not treating the estimates as current estimates of the mineral resources. The Company gives no assurance that either these models or the historical resource estimates upon which they are based are accurate, and does not undertake any obligation to update the models or to release publicly any update or revisions of the resource estimates except as required by applicable securities law. The reader is cautioned not to rely upon these models or the historical resource estimates upon which they are based.

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