Marimaca’s thick Pampa Medina copper-silver hit: growth and pit design notes for engineers
Reviewed by Tom Sullivan
First reported on MINING.com
30 Second Briefing
Marimaca Copper has intersected 216 metres grading 0.96% copper and 7.2 g/t silver from 466 metres in hole SPRD-15 at Pampa Medina in Chile’s Antofagasta Region, including 62 metres at 2.2% copper and 21.5 g/t silver from 602 metres, extending the copper-silver system 300 metres. Step-out holes such as SPD-13 (222 metres at 0.5% copper from 194 metres) and SPRD-12 (56 metres at 0.95% copper from 748 metres) support continuity of oxide and sulphide mineralisation across a 3 km by 1.5 km footprint. With 30,000 metres of drilling planned in 2026 and Pampa Medina only 28 km from the fully permitted Marimaca oxide project (179 Mt at 0.42% copper, 50,000 t/y cathode over 13 years), the results point to a potentially large sulphide growth option adjacent to near-term heap-leach development.
Technical Brief
- Marimaca estimates true mineralised widths at ~80% of reported downhole intercept lengths, affecting tonnage calculations.
- SPD-13, at the south-eastern drilling edge, intersected 222 m at 0.5% Cu from 194 m, including 48 m at 1.05% Cu from 368 m.
- SPRD-12, collared ~300 m west of prior drilling, cut 56 m at 0.95% Cu and 4.2 g/t Ag from 748 m, including 22 m at 1.8% Cu and 9.7 g/t Ag from 750 m.
- SPRD-17, drilled 150 m east of an earlier hole, returned 104 m at 0.65% Cu from 522 m, with internal zones of 30 m at 0.96% Cu and 40 m at 0.89% Cu.
- Four scout RC holes (to 540–700 m) failed to reach the targeted sedimentary units, so are being extended with diamond tails to test deeper contacts.
- Hole SWR-13 ended in mineralisation, cutting 8 m at 1.47% Cu and 7.5 g/t Ag from 580 m within volcanic rocks above the interpreted sedimentary contact.
- Drilling has traced copper mineralisation across a 3 km × 1.5 km footprint through multiple sedimentary horizons, with both near-surface oxides and deeper sulphides (bornite, chalcopyrite, covellite, chalcocite).
Our Take
With Marimaca Copper already committing $587 million of pre-production capital to the Marimaca oxide heap-leach project, the emerging sulphide-style copper-silver system at Pampa Medina 28 km away could materially extend the district-scale pipeline rather than just bolting on marginal tonnage.
The feasibility study economics at the Marimaca oxide deposit (post-tax NPV of $709 million at an assumed $4.30/lb copper and 31% IRR) mean that if Pampa Medina grades around 1% Cu over long intervals are later shown to be mineable, they are likely to be competitive against many Latin American copper projects in our database that rely on lower grades and higher capital intensity.
Earlier coverage of Marimaca Copper’s plan to relocate the second-hand Dos Amigos acid plant suggests that securing low-cost sulphuric acid supply for the oxide operation may also de-risk future optionality if any Pampa Medina mineralisation proves amenable to acid-consuming processing routes within the same Antofagasta-region hub.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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