Copper Porphyry Potential in the Kohistan Island Arc: What We're Seeing Across Our Concessions

I was standing on a ridge above the Indus last October, roughly 40km northwest of Chilas, looking at malachite staining across an outcrop that ran maybe 300 metres along strike. My field geologist handed me a hand sample. Chalcopyrite in a quartz-sericite altered granodiorite. Textbook porphyry signature.

That's the moment I stopped talking about Kohistan porphyry potential in the abstract and started treating it as a drilling program.

Why the Kohistan Arc Matters (and Why Nobody Talks About It Enough)

The Kohistan Island Arc is a Cretaceous-Eocene intra-oceanic arc squeezed between the Indian and Eurasian plates. Same tectonic family that produced the Tethyan metallogenic belt — the belt that hosts Reko Diq in Balochistan, Sar Cheshmeh in Iran, and the giant porphyries of the Turkish-Iranian plateau. Kohistan is the eastern continuation of that story, and it's been chronically under-explored because of terrain, security perceptions, and — honestly — because the geological community outside Pakistan just doesn't know it well.

The arc runs roughly 300km east-west across northern Pakistan. It's got calc-alkaline plutons, volcanic sequences, and the kind of subduction-related magmatism that generates porphyry systems. The Chilas Complex, the Kohistan Batholith, the Jijal-Patan ultramafics — all of it points to a mature arc that should host copper-gold porphyries. And it does. The question has never been "is it there," it's been "who's going to drill it out properly."

I used to think the main prize here was gold. Placer gold in the Indus is real, and we produce from it. But the more we mapped the Kohistan arc copper indications across our licence blocks, the clearer it became that the porphyry story is the bigger one by an order of magnitude.

What We're Seeing on the Ground

Across our 16 concessions, four blocks sit squarely within Kohistan arc lithologies with strong porphyry indicators. I'll be specific about what we've documented, because vague geology is worthless to a serious buyer.

Block near Thak Valley (Chilas district): Quartz-sericite-pyrite alteration halo mapped over roughly 1.2 sq km. Surface grab samples returning 0.31% to 0.68% Cu with anomalous molybdenum (up to 180 ppm Mo) and gold values between 0.2 and 0.9 g/t. The alteration zoning — phyllic core grading outward into propylitic — is what you want to see. We haven't drilled it yet. Trenching is scheduled for Q2.

Block northwest of Chilas: The ridge I mentioned earlier. Malachite and azurite staining over a strike length we've now traced for about 800m. Host rock is a hornblende-biotite granodiorite with stockwork quartz veining. Chip sampling averaged 0.42% Cu across 14 samples. Molybdenite present in vein selvages.

Block in the Kohistan-Kaghan boundary zone: Different beast. More skarn-affinity, with garnet-pyroxene assemblages developed at a granodiorite-marble contact. Copper grades in the skarn zones are higher — we've hit 1.8% Cu in individual grab samples — but the tonnage question is open until we drill.

Block near Bunji: Early stage. Geochemical anomaly in stream sediments (copper, molybdenum, bismuth — a classic porphyry pathfinder trio), no significant outcrop work yet. On the exploration schedule for late this year.

Grades at surface don't tell you what's at depth in a porphyry system. Anyone who's worked Chilean or Peruvian porphyries knows the leached cap can look boring while the hypogene zone underneath is running 0.6-0.8% Cu over hundreds of metres. That's the bet we're making, and it's not a wild bet — it's the standard porphyry playbook applied to a underexplored arc.

The Reko Diq Comparison, Handled Carefully

I'm cautious about invoking Reko Diq because every junior in Pakistan does it and most of them shouldn't. Reko Diq is a Chagai arc deposit — different arc, different age, different setting. But the tectonic logic is the same: Tethyan subduction generated porphyry systems the length of the belt, and Kohistan is a legitimate segment of that belt.

What Reko Diq tells you is that Pakistani porphyries can be world-class. Barrick's published resource is around 5.9 billion tonnes. Nobody at GBX is claiming a Reko Diq analogue in Kohistan on the basis of surface work. What we are saying is that the geological permissiveness is there, the surface indications are strong, and the arc has never been systematically drilled by anyone with real capital.

That's the JV opportunity. Not "come look at our tenure and trust us," but "come look at real alteration, real grades, real geochemistry, and drill it with us."

What We Need from Partners

Honestly, the bottleneck isn't geology. It's drilling capacity and metallurgical testwork. We can run the surface programs — mapping, trenching, soil and rock chip geochem, ground magnetics — with local teams and Pakistani consultants. What we don't have in-house is a diamond drill fleet capable of 500m+ holes at altitude, and we don't have the lab relationships in Perth or Vancouver to turn drill core into a bankable resource estimate on a Western timeline.

That's where a JV partner earns their equity. Bring the drills, bring the QP-signed resource work, and we bring the ground, the licences, the local relationships and the operational footprint. GB's mineral licensing regime has genuinely improved under the SIFC framework — I'll write about that separately — and export logistics via Karachi and, increasingly, Gwadar are workable for concentrate.

Copper exploration in Pakistan is going to be a story of the next decade. The Kohistan arc is one of the last major underexplored porphyry provinces in Asia. I'd rather partners come look at it now, while entry costs are what they are, than read about someone else's discovery in the Mining Journal in 2028.

If you want the detailed alteration maps and assay tables for the four blocks, get in touch directly. I don't put full datasets on the public site — for reasons any exploration geologist will understand.