Not for release to United States news wire services or for dissemination in the United States

Vancouver, B.C., February 26, 2026 – Marimaca Copper Corp. (TSX: MARI) (ASX: MC2) (“Marimaca” or the
“Company”) is pleased to announce the closing of the Australian secondary offering of 15,200,913 existing CHESS Depositary Interests of the Company (the “CDIs”) at a price of A$10.35 per CDI owned and controlled by Greenstone Resources II L.P. and other shareholders (the “Selling Shareholders”) for aggregate gross proceeds of A$157 million (the “Australian Secondary Offering”).

The previously announced global treasury and secondary offering has now been fully completed for aggregate gross proceeds of C$409 million, or A$423 million¹ (the “Global Offering”). See the Company’s prior press release dated February 26, 2026 in respect of the completion of the Canadian offering (the “Canadian Offering”) for aggregate gross proceeds of C$257 million, comprised of a treasury offering for aggregate gross proceeds of C$136.5 million (the “Canadian Treasury Offering”) and a secondary offering for aggregate gross proceeds of C$120.5 million (the “Canadian Secondary Offering” and together with the Australian Secondary Offering, the “Secondary Offering”).

The Australian Secondary Offering was completed as a brokered placement of CDIs by Euroz Hartleys Limited, Canaccord Genuity (Australia) Limited, Beacon Securities Limited and BMO Capital Markets (the “Joint Lead Managers”), who acted as co-lead agents and joint bookrunners to the Global Offering.

The net proceeds of the Australian Secondary Offering were paid to the Selling Shareholders, and the Company did not receive any proceeds thereunder.

¹ Based on an AUD.CAD exchange rate of 0.9661