ATERRA Metals Reports Maiden Totora Cu-Au Project

Inferred Mineral Resource of 159.8 Mt Grading 0.51% CuEq

Toronto, Ontario--(Newsfile Corp. - September 24, 2026) - ATERRA Metals Inc. (CSE: ATC) (OTCQB: CSSCF) ("ATERRA" or the "Company") is pleased to report a maiden Inferred Mineral Resource (the "Inferred Resource") for its Totora Copper-Gold Project (the "Totora Project" or the "Project"), located in Region III, Chile, approximately 60 kilometres south of Vallenar. The Inferred Resource was estimated by SRK Consulting (Chile) SpA ("SRK") in accordance with the CIM Definition Standards for Mineral Resources and Mineral Reserves adopted by the CIM Council, as amended (the "CIM Definition Standards"), which are incorporated by reference in National Instrument 43-101 - Standards of Disclosure for Mineral Projects ("NI 43-101").

Highlights

Maiden Inferred Mineral Resource: 159.8 million tonnes ("Mt") grading 0.30% copper ("Cu") and 0.15 grams per tonne ("g/t") gold ("Au"), or 0.51% copper equivalent ("CuEq"), at a base-case cut-off grade of 0.20% Cu.

Contained Metals: 1,067.3 million pounds ("Mlb") of copper and 792.9 thousand troy ounces ("koz") of gold, equivalent to 1,790.8 Mlb CuEq.

Established Mining District: The Project is located in Chile's Dos Amigos Mining District with nearby highway and high-voltage power infrastructure.

Multiple Porphyry Systems: The Inferred Resource comprises four near-surface copper-gold porphyry deposits: Frontera, Totora, Algarrobilla and Clinton.

Phase II Exploration Plans: Phase II drilling is expected to focus on testing extensions to the current Inferred Resource, increasing drill density and obtain samples for metallurgical testing. Untested Cu-Au targets within the Project boundaries will also be examined.

ATERRA's Totora Project lies within Chile's Dos Amigos Mining District, approximately 15 kilometres south of Tintina Mines' Domeyko Sulfuros project, 15 kilometres southwest of Hot Chili's La Verde discovery an