Marimaca Secures MOD Grid Connection Authorization and Agrees Key Commercial Terms for Power Supply; Provides Project Update

VANCOUVER, BC / ACCESS Newswire / October 1, 2026 / Marimaca Copper Corp. ("Marimaca Copper" or the "Company") (TSX:MARI)(ASX:MC2) is pleased to announce various development activities at the Marimaca Oxide Deposit ("MOD"), including the receipt of the grid connection authorization for the MOD and the key commercial terms for a Power Purchase Agreement ("PPA") framework. Marimaca has also received an overall "A" rating in its 2025 independent Digbee sustainability assessment, its third consecutive "A" rating.

Hayden Locke, CEO and Director of Marimaca Copper, commented:

"The approval of our grid connection is an important de-risking milestone for the Marimaca Oxide Deposit. Together with the preliminary Power Purchase Agreement framework, it provides a clear pathway to securing 100% renewable power at a cost closely aligned with our Definitive Feasibility Study ("DFS") assumptions. Importantly, the proposed commercial structure provides the flexibility required during commissioning and ramp-up.

"More broadly, we continue to make steady progress towards construction readiness. Access-road upgrades are advancing, early-works packages are out for tender, key permits remain on track and detailed engineering is progressing well.

"Our third consecutive ‘A' rating from Digbee, achieved under the more rigorous Development Phase framework, further reinforces the MOD's strong sustainability credentials. These achievements reflect the team's disciplined approach to planning and commercial execution as we advance the MOD."

Key Project Updates

• Power/Electrical Connection
  • On September 22^nd, 2026, following a review and challenge period, the Panel of Experts upheld the National Electric Coordinator's ("CEN") approval of Marimaca's application to connect to the 110kV El Lince Line, located approximately 13km from the MOD Project Area.
  • Additionally, Marimaca has signed a preliminary PPA framework agreement with a well-known energy provider in Chile to supply the MOD with 100% renewable energy from the national grid.
    • Agreed to long-term energy pricing resulting in an estimated all-in cost closely aligned with the energy cost provided in the MOD DFS (US$93/MWh).
    • Contract structured with flexibility to achieve commercial production with a ramp-up period that does not include any take-or-pay provisions.
    • Initial five-year term after the ramp-up period, post completion of the MOD construction.
• Detailed Engineering and Site Early Works
  • Upgrades to the primary MOD access road, which spurs from Ruta B-12, a paved national highway, are progressing well and are expected to be completed by the end of 2026.
  • Site early works are on schedule to commence in Q4, with contractor packages currently out for tender.
    • Activities will focus on establishing key facilities, roads, and utilities to accommodate full-scale construction activities.
    • An additional workstream is planned to bring forward preparatory work for the seawater pipeline route to enable construction commencement in 2027.
  • Permitting workstreams progressing according to plan, with further key permits to enable full construction expected in early October.
  • Detailed engineering is ongoing, with a globally recognized EPCM firm selected as lead engineer, working alongside the Marimaca Owner's team.
    • Priority focus is site-layout optimization from the DFS and progressing detailed engineering for core project areas.
    • Key engineering procurement packages, including the Dry Area (crushing plant) and Wet Area (heap leaching and SX-EW plant), are expected to be awarded in H1 2027.
• Sulphuric Acid
  • Further to the announcement on May 20^th, 2026, Marimaca is pleased to announce that as part of the non-binding Memorandum of Understanding ("MOU") with a leading local acid producer, it has commenced the conceptual engineering study to define the optimal development pathway of the Dos Amigos Acid Plant ("PADA plant").
  • The engineering study will focus on evaluating the optimal approach to developing the PADA plant to support the MOD via a self-produced acid option, which has the potential to reduce exposure to acid price volatility.

2025 Digbee Assessment

• The Company is pleased to announce the completion of its fifth independent ESG performance assessment via the Digbee ESG reporting framework.
• First assessment completed under the "Development Phase" framework, reflecting the Company's progression on the MOD following the release of the DFS in 2025.
  • Development Phase framework includes a more rigorous disclosure standard than prior submissions, including a focus on closure planning, community development commitments, workforce planning, and water management.
• Third consecutive year of achieving an "A" rating highlights the MOD's industry-leading ESG credentials:
  • Very favourable access to regional infrastructure given the MOD's location within 25km of the Port of Mejillones.
  • No impact on local water supply - recycled seawater secured from the Port of Mejillones for Life of Mine water requirements.
  • A pathway to securing 100% renewable energy from Chile's national grid, supported by the approved grid connection and PPA framework.
  • Use of leaching processing method removes the requirement of a wet Tailings Storage Facility ("TSF").
  • Production of copper cathode through SX/EW removes the ‘Scope 3' emissions generated from smelting and refining of copper concentrates.
• The full report is available on the Marimaca Copper website.

Contact Information

For further information please visit www.marimaca.com or contact:
Tavistock
+44 (0) 207 920 3150
Emily Moss
marimaca@tavistock.co.uk

About Marimaca Copper

Marimaca is a TSX ("MARI") and ASX ("MC2")-listed copper company focused on the development of high-quality copper assets in northern Chile. The Company's flagship asset is the Marimaca Oxide Deposit Project ("MOD"), located in Chile's prolific Antofagasta region. It is one of the few globally significant greenfield copper discoveries made in the last decade and represents a low-risk development opportunity, given the proximity to the city of Antofagasta and port of Mejillones, with substantial exploration upside. The Company also controls additional exploration properties at Pampa Medina and Madrugador within the Sierra de Medina region, located 30 kilometers from the MOD, where recent drilling has identified both oxide extensions and high-grade sulphide mineralization at depth.

Forward Looking Statements

This news release includes certain "forward-looking statements" under (without limitation) applicable Canadian securities legislation, including, without limitation, the development of activities at the PADA Plant and the MOD. There can be no assurance that such statements will prove to be accurate, and actual results and future events could differ materially from those anticipated in such statements. Forward-looking statements reflect the beliefs, opinions and projections on the date the statements are made and are based upon a number of assumptions and estimates that, while considered reasonable by Marimaca Copper, are inherently subject to significant business, economic, competitive, political and social uncertainties and contingencies. Many factors, both known and unknown, could cause actual results, performance or achievements to be materially different from the results, performance or achievements that are or may be expressed or implied by such forward-looking statements and the parties have made assumptions and estimates based on or related to many of these factors. Such factors include, without limitation: risks that the development activities at the MOD will not progress as anticipated, or at all, risks related to the PADA Plant development and associated capital costs, risks related to the execution of a formal JV with Noracid (of which there can be no assurance), risks related to share price and market conditions, the inherent risks involved in the mining, exploration and development of mineral properties, the uncertainties involved in interpreting drilling results and other geological data, fluctuating metal prices, sulfuric acid prices, elemental sulfur prices, the possibility of project delays or cost overruns or unanticipated excessive operating costs and expenses, uncertainties related to the necessity of financing, uncertainties relating to regulatory procedure and timing for permitting submissions and reviews, the availability of and costs of financing needed in the future as well as those factors disclosed in the annual information form of the Company dated March 31, 2026 and other filings made by the Company with the Canadian securities regulatory authorities (which may be viewed at www.sedar.com). Readers should not place undue reliance on forward-looking statements. Marimaca Copper undertakes no obligation to update publicly or otherwise revise any forward-looking statements contained herein whether as a result of new information or future events or otherwise, except as may be required by law.

None of the TSX, ASX or the Canadian Investment Regulatory Organization accepts responsibility for the adequacy or accuracy of this release.

This announcement was authorised for release to the ASX by the Board of Directors of the Company.

SOURCE: Marimaca Copper Corp.