Marimaca Copper Announces Closing of A$80,000,000 Placement

Not for release to U.S. wire services or for distribution in the United States

VANCOUVER, British Columbia, Sept. 11, 2025 (GLOBE NEWSWIRE) — Marimaca Copper Corp. (TSX: MARI) (ASX: MC2) (“Marimaca” or the “Company”) is pleased to announce the closing of the previously announced brokered placement in Australia and select other jurisdictions, excluding Canada (the “Placement”).

Pursuant to the closing of the Placement, the Company issued 8,247,423 Chess Depositary Interests (“CDI”) each at a price of A$9.70 for gross proceeds of approximately A$80,000,000 or approximately C$72,080,000.

Net proceeds from the Placement will be used for exploration at the Pampa Medina Project and Marimaca sulphide target, detailed design and engineering and project related workstreams at the Marimaca Oxide Deposit (the “MOD”), and for general corporate purposes.

Euroz Hartleys Limited, Beacon Securities Limited and Macquarie Capital (Australia) Limited, acted as joint lead managers in respect of the Placement. Canaccord Genuity (Australia) limited acted as a co-manager in respect of the Placement. Allotment of the CDIs will occur on September 12, 2025 (AEST). The Placement is subject to the receipt of final approval from the Toronto Stock Exchange (the “TSX”).

This announcement has been prepared for publication in Australia and may not be released to U.S. wire services or distributed in the United States. This news release does not constitute an offer to sell, or the solicitation of an offer to buy, securities in the United States, nor shall there be any sale of these securities in any jurisdiction in which such offer, solicitation or sale would be unlawful. The securities offered in the Placement have not been, and will not be, registered under the U.S. Securities Act of 1933, as amended (the “U.S. Securities Act”) or any U.S. state securities laws, and may not be offered or sold in the United States or to, or for the account or benefit of, United States persons absent registration or an applicable exemption from the registration requirements of the U.S. Securities Act and applicable U.S. state securities laws.

Related Party Transaction Disclosure

Existing insiders of the Company Assore International Holdings Limited (“AIH”) and Ithaki Ltd. participated in the Placement for 1,376,289 CDIs and 1,226,805 CDIs, respectively. Additional information regarding their participation will be disclosed in the material change report to be filed by the Company in accordance with Canadian securities laws.

Other Information

In connection with the Placement, Greenstone Resources L.P. and certain of its affiliates have waived their participation rights. AIH participated directly in the Placement. Mitsubishi Corporation has a participation right to purchase shares pro rata on the same terms as the Placement, exercisable for a period of 30 business days from the closing of the Placement. Mitsubishi’s current ownership, prior to the closing of the Placement, is approximately 4.4% based on public filings.

About Marimaca

Marimaca is a copper exploration and development company focused on its 100%-owned flagship Marimaca Copper Project and surrounding exploration properties located in Antofagasta Region, Chile.

The Marimaca Copper Project hosts the Marimaca Oxide Deposit (the “MOD”), an IOCG-type copper deposit. The Company is currently progressing the Marimaca Copper Project through the Definitive Feasibility Study led by Ausenco Chile Ltda. In parallel, the Company is exploring its extensive land package in the Antofagasta region, including the >15,000ha wholly-owned Sierra de Medina property block, located 25km from the MOD.

This news release is authorized for release by the Board of Directors of Marimaca.

Contact Information

For further information please visit www.marimaca.com or contact:

Tavistock
+44 (0) 207 920 3150
Emily Moss / Ruairi Millar

marimaca@tavistock.co.uk

Forward-Looking Statements
This news release includes certain “forward-looking statements” under applicable Canadian securities legislation, including statements related to the anticipated CDI allotment timing, the use of proceeds and receipt of regulatory approvals and other approvals, including approval of the TSX. 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, 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 related to the receipt of required regulatory approvals, including final approval by the TSX, 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, 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 reviews, the availability of and costs of financing needed in the future. The intended use of the proceeds of the Placement by the Company might change if the board of directors of the Company determines that it would be in the best interests of the Company and amounts actually allocated and spent will depend on a number of factors, including the Company’s ability to execute on its business plan. Many of these risks and uncertainties and additional risk factors generally applicable to the Company are described in the Company’s annual information form of the Company dated March 27, 2025 and other filings made by the Company with the Canadian securities regulatory authorities (which may be viewed at www.sedarplus.ca). Accordingly, readers should not place undue reliance on forward-looking statements. The Company 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.