The Perkoa deposit lies in a felsic to intermediary series of volcanic and volcanoclastic rocks, within the Paleoproterozoic Birimian Supergroup of West Africa. The prospective Birimian-aged rocks in Burkina Faso are the same sequences that host major gold deposits in Burkina Faso and in the neighbouring countries of Ghana and Mali. The Birimian Supergroup of West Africa is renowned for their gold mineralization; however, known occurrences of base metals are scarce. The Perkoa deposit represents the only significant zinc-silver massive sulphide mineralization discovered in the Birimian to date and it is also the first zinc-silver massive sulphide mineralization discovered in this region.

The Perkoa project area is located in the central part of the Boromo greenstone belt, which comprises volcanic and sedimentary rocks of the Lower Palaeozoic Birimian Supergroup that have been metamorphosed to lower greenschist facies. At least three phases of deformation have affected the Boromo belt and mafic to felsic dykes and granitic bodies were emplaced in several intrusive phases. The zinc-silver mineralization has been dated at 2.12 to 2.14 billion years ago.

In the Perkoa area, the Birimian sediments, lavas, and pyroclastics strike from northeast to southwest and generally dip steeply to the northwest. Several units of andesitic lavas with subordinate andesitic tuffs, separated by sequences of tuffs interlayered with fine grained clastic sediments, make up the lithological package in the project area. A number of syn-tectonic and post-tectonic intrusive bodies have been emplaced within the meta-sediments, which range from large plutons of granitic and dioritic composition, to smaller ultramafic to rhyolitic intrusions. Crosscutting lineaments with a northwest-southeast orientation are common although major displacements along these lineaments are rare.

The Perkoa deposit has been classified as a volcanogenic massive sulphide (VMS) deposit. VMS deposits are lenses and sheets of massive sulphide that form from seafloor hydrothermal systems where metal rich fluids precipitate on (exhalative) or near the seafloor (sub-seafloor replacement.). The Perkoa mineralization occurs as a series of stacked, northeast-southwest striking tabular VMS lenses hosted, and separated by, tuffaceous material that has been overturned with an average dip of approximately 70°. The deposit is unusual for its high concentrations of zinc and barium mineralization, and relatively low levels of lead and copper.

Perkoa Mineral Reserves as at December 31, 2021^{(1, 2, 4)}

(1) All Mineral Reserves have been estimated in accordance with the Canadian Institute of Mining, Metallurgy and Petroleum (“CIM”) — Definition Standards adopted by CIM Council on May 10, 2014 (the “CIM Definition Standards”). Numbers may not add due to rounding. The Mineral Reserve is shown at 100% ownership, Trevali holds a 90% joint venture interest in the Perkoa Mine.
(2) The technical report entitled “Technical Report on the Perkoa Mine, Burkina Faso” dated April 12, 2018, is the current technical report for the Perkoa property.
(3) The Perkoa Underground Mine Mineral Reserve estimate is reported based on planned stopes with a net smelter return cut-off grade of US$90/tonne, with average metal prices of: US$1.39/lb zinc.
(4) The Perkoa Underground Mine Mineral Reserve estimate has been prepared by Trevali’s Technical group with an effective date of December 31, 2021, under the supervision of and approved by Yan Bourassa (P.Geo.), a Qualified Person as defined in NI 43-101. Mr. Bourassa is Vice President Technical Services & Exploration of the Company and accordingly, is not independent.