Pampa Medina Drilling Returns 0.70% Copper Over 66 m in Basement Rock

• Step-out drilling at Pampa Medina in Chile's Antofagasta Region reached copper mineralization in basement metamorphosed sediments for the first time.
• Since 2024, the company has drilled to a model that treats the lower sedimentary units as the priority target horizons, with the metamorphosed sediments beneath them outside the target.
• The deepest drilling returned 0.70% copper over 66 meters (m) from 802 m depth inside that basement unit.
• Post-mineralization dykes affected the deepest intervals in the basement unit.
• Cachorro, the nearby discovery in the same district, is primarily hosted in basement tuffs and metamorphosed sediments.

What Has Happened

Marimaca Copper (TSX: MARI | ASX: MC2) reported further assay results from step-out drilling at its Pampa Medina deposit in Chile's Antofagasta Region, approximately 28 kilometers (km) east of the Marimaca Oxide Deposit (MOD). The central high-grade zone extended again, returning 2.65% copper and 13.9 grams per metric ton (g/t) silver over 20 meters (m) from 564 m depth, including 6.11% copper and 24.0 g/t silver over 6 m. A second intersection in the same hole returned 1.01% copper over 104 m from 664 m depth, including 2.04% copper and 11.1 g/t silver over 40 m.

The result that changes the shape of the target lies deeper in the section. For the first time, drilling reached mineralization in the basement metamorphosed sediments that underlie the units the exploration model treats as hosts, in the deepest hole completed at the deposit to date.

Host Units in the Pampa Medina Exploration Model 

Pampa Medina belongs to the family of manto-style copper deposits in which mineralization forms flat-lying sheets that follow the rock layering instead of cutting across it. Those sheets lie within Jurassic-Triassic sedimentary units of sandstones, conglomerates, tuffs, and black shales, overlain by andesitic volcanic rock and underlain by an Upper Paleozoic complex of metamorphosed sediments, volcanic rock, and intrusions. Copper was first identified near the surface in oxide minerals, and later in high-grade zones of bornite, chalcopyrite, covellite, and chalcocite, all copper sulfide minerals, which continue at depth past the oxide boundary.

After consolidating the project area and the surrounding land packages in 2024, the company reinterpreted the available geological information and built an updated model. In it the company identified the lower sedimentary units of interbedded sandstones, shales, tuffs, and conglomerates as the priority target horizons for future drilling, and the metamorphosed sediments below them formed the base of the published column, not part of the target.

The distinction governs how a drill program can grow the deposit. Where the prospective section is two units thick, step-outs widen it sideways and nothing else. Mineralization inside the unit beneath expands the prospective stratigraphy beyond the previously defined host units. 

Mineralization Below the Modeled Host Units 

The deepest hole passed through the sedimentary package and continued into the metamorphosed sediments beneath it. Through the sediments it returned 0.41% copper and 1.8 g/t silver over 660 m from 386 m depth, a broad envelope holding several richer sheets, among them 1.21% copper and 7.6 g/t silver over 98 m from 386 m and, inside that, 2.90% copper and 21.2 g/t silver over 16 m from 388 m. In the basement unit, the same hole returned 0.70% copper over 66 m from 802 m depth, including 1.05% copper over 14 m from 834 m depth, and 1.40% copper over 6 m from 862 m depth. Deeper again, it returned 0.65% copper over 34 m from 930 m. 

A second hole, drilled 300 m south of the hole that extended the central high-grade zone, also continued through favorable rock into the metamorphosed sediments. Higher in that hole, the drilling returned 1.26% copper and 2.6 g/t silver over 30 m from 440 m depth, holding two high-grade stacked sheets of 2.34% copper and 10.7 g/t silver over 6 m and 2.50% copper and 2.3 g/t silver over 6 m, followed by 0.85% copper and 4.4 g/t silver over 32 m from 506 m. In the metamorphosed sediments, it returned 0.77% copper and 2.0 g/t silver over 6 m from a depth of 940 m, and 1.05% copper and 8.3 g/t silver over 6 m from a depth of 1,006 m.

Neither result is free from structural interference. Post-mineralization dykes, sheets of younger barren rock that intrude a mineralized sequence after it forms, affected the basement intervals in the deeper hole, and the southern hole intersected multiple barren dykes oriented west-northwest. Across the deposit, the main rock units are intruded by a dyke swarm and affected by post-mineral normal faulting. Silver assays for two of the deepest copper intervals were still pending, and several other deep intervals returned silver below detection, so the metal accompanying the copper at that depth is only partly reported. Copper is present in the basement unit.

Thickness & Stacking Across the Drilled Column 

The new results again match a model of multiple high-grade stacked mantos, dominated by bornite and chalcocite, hosted in interbedded sediments and volcanically derived rock composed of volcanic fragments. Pampa Medina is a sediment-hosted copper deposit built from a series of sheets distributed through the vertical section, not a single mineralized seam. The company compares a typical deposit of that style, at a mineralized zone of 5 m, with 26 m in one Pampa Medina hole.

Chief Executive Officer of Marimaca Copper, Hayden Locke, separates that geometry from a single mineralized horizon: 

"We're talking about stacked horizons like this in a vertical sense, all of which are economic widths and grades for an underground sediment-hosted copper deposit."   

Reported intervals are downhole lengths, and true widths are estimated at approximately 80% of them, based on downhole bedding and structural measurements. Elevated silver grades appear in both the oxide and the sulfide copper zones and generally track copper grade.

Locke puts a floor under the thickness the drilling has returned so far:

"This is just a selection of the drilling. I mean, if I were to put every drill hole on, you'd see very consistently this high-grade or ultra-high-grade zone that is in excess of 10 m true thickness."

No resource has been estimated for the Pampa Medina sulfides, so thickness and stacking remain drilling observations rather than modeled parameters, and an additional unit at the base of the column is additional prospective ground, not additional metal.

Broader Context

The unit that the drilling has just reached already hosts copper elsewhere in the same district. Cachorro, the nearby Antofagasta Minerals discovery, is primarily hosted in basement tuffs and metamorphosed sediments, low in the same stratigraphic column, beneath the sedimentary package that has taken most of the drilling at Pampa Medina so far.

Marimaca holds ground across that discovery belt, which includes Cachorro and Pampa Medina. Cachorro holds 300 million metric tons at 1.0% copper, and Mantos Blancos holds 230 million metric tons at 0.6% copper. 

The area drilled to date at Pampa Medina covers only a very limited portion of the broader Sierra de Medina land package, now held in its entirety by one operator for the first time. The company has identified sulfide potential at depth across the package.

What to Watch Next  

A 30,000-meter drilling program is underway at Pampa Medina, combining step-outs with delineation to define the footprint of the mineralized system. The 2026 work focuses on infilling the high-grade center and probing the limits of the system, with Pampa Medina and the neighboring Madrugador ground at the resource-definition stage.   

The rig count Locke gives sets how quickly the delineation campaign can close on the questions the deep holes opened: 

"And then more importantly, we have six drill rigs on site at Pampa Medina drilling at the moment. They're doing step-outs and infill at the same time."    

The deployment was current as of July 17, 2026. Management says broad geophysics across the land package has identified multiple targets that resemble Pampa Medina, and that a scout drilling program is underway to get through the gravel cover.

Management is targeting an initial resource estimate covering the Pampa Medina sulfides and the oxides in early 2027. At that estimate the basement intervals either enter a modeled resource or stay exploration results.

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