Marimaca Copper Completes A$80,000,000 Bookbuild

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

Marimaca Copper Corp. (TSX: MARI,OTC:MARIF) (ASX: MC2) ("Marimaca" or the "Company") is pleased to announce that it has secured binding commitments for a brokered placement in Australia and select other jurisdictions, excluding Canada, of 8,247,423 new Chess Depositary Interests ("CDI") of the Company at a price of A$9.70 per CDI for gross proceeds of approximately A$80,000,000 or approximately C$72,080,000 (the "Placement").

The Placement was strongly supported by both new institutional and sophisticated investors and existing shareholders, with demand for the Placement significantly exceeding the targeted quantum. The Company is pleased to welcome new institutional shareholders to its register and looks forward to the increased ASX liquidity expected to result from the Placement.

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.

The CDIs will be issued pursuant to the ASX Listing Rule 7.1 waiver granted to Marimaca. Completion of the Placement is expected on or about September 11 ^th , 2025 and is subject to certain closing conditions, including but not limited to the receipt of all necessary regulatory and other approvals, including the approval of the Toronto Stock Exchange (" TSX ").

Macquarie Capital (Australia) Limited, Euroz Hartleys Limited, and Beacon Securities Limited are acting as joint lead managers in respect to the Placement.

Canaccord Genuity (Australia) Limited is acting as a co-manager in respect to the Placement.

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.

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 participation in and size of the Placement, anticipated timing and closing date of the Placement, advisory fees payable, 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 timing of 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.