Aeromagnetic Surveys: When Spending on Flights Actually Makes Sense

A friend called me last month. He'd just been quoted $340,000 for an aeromagnetic survey over a 180 sq km block in Chagai. He wanted to know if I thought it was worth it.

My answer wasn't a clean yes or no.

Because here's the thing about aeromagnetic surveys — they're incredible when you actually need them, and a complete waste of money when you don't. And most mine owners I talk to in Pakistan can't tell the difference. Honestly, I couldn't either when I started GeoMine AI. I used to think every serious exploration program needed a flight. Then I realized we were burning capital on data we already had answers for.

Let me explain how I think about it now.

What an Aeromagnetic Survey Actually Does

A plane (or sometimes a drone these days) flies a tight grid pattern over your block, usually 100 to 250 meters above ground, with a magnetometer hanging off it. The instrument reads tiny variations in the Earth's magnetic field. Different rocks have different magnetic signatures. Magnetite-rich intrusions light up. Faults and shear zones show as linear breaks. Hidden plutons that never reach the surface — the kind that often host copper-gold porphyries — they show up too.

That's the magic of a magnetic survey for mineral targeting. It sees through cover. Soil, alluvium, weathered rock, even a few hundred meters of overburden. Satellite data can't do that. Sentinel-2 stops at the surface. ASTER stops at the surface. SAR penetrates a little, but not enough to map a buried intrusion at 400m depth.

So when someone asks me "is aeromagnetic exploration still relevant in 2025" — yes. For certain problems, nothing replaces it.

But "certain problems" is doing a lot of work in that sentence.

When the Flight Is Worth It

I'll give you the four scenarios where I tell clients to spend the money.

One — you're chasing a porphyry system. Reko Diq sits on a magnetic anomaly. So does Saindak. If your geology team thinks there's a buried intrusive somewhere in your block and you've got reasonable surface indications (alteration halos picked up by ASTER, structural intersections from SRTM DEM analysis), aeromagnetic survey mining work will tell you where to drill. A 12,000 meter drill program costs $2-4 million in Balochistan. A $300K survey that cuts your drill targets from 40 down to 6 pays for itself before the rig even moves.

Two — you have thick alluvial cover. Large parts of Chagai, Kharan, and even some valleys in Gilgit-Baltistan have meters of post-mineralization cover. Satellites are blind there. I own a block near Skardu where surface mapping showed almost nothing interesting, but the regional magnetic data hinted at a structure underneath. We haven't flown it yet (cost, weather, permits — the usual), but that's exactly the kind of situation where a flight makes sense.

Three — you're at the pre-feasibility stage with serious capital behind you. If you're spending $50M+ on a project, $400K on aeromagnetic data is rounding error. Don't be cheap at the wrong moment.

Four — chromite and iron targets specifically. These minerals have strong magnetic contrast against host rocks. The signal-to-noise ratio is excellent. For chromite work in the Muslimbagh or Khanozai belts, magnetic data is almost mandatory if you want to go beyond surface scratching.

When You're Lighting Money on Fire

Now the other side. And this is where most of my clients land.

If you're at the early reconnaissance stage — meaning you have a license or you're evaluating a license, and you haven't even confirmed what's on surface — flying an aeromagnetic survey first is backwards. You don't need it yet. You need to know what's outcropping, what alteration is present, what structures are controlling mineralization. That's a satellite intelligence job. That's what we built geomines for.

For under $15,000 we can run Sentinel-2, ASTER, SAR, and SRTM DEM analysis across a 500 sq km block and tell you the top 5% of ground worth walking. Then you walk it. Then you sample. Then — only then — if the geology justifies it, you fly.

I've seen mine owners in Gilgit-Baltistan get talked into $200K aeromagnetic programs over blocks where nobody had even done a proper structural interpretation. The data came back, sat on a hard drive, and nobody knew how to integrate it with anything else. That's not exploration. That's expensive theater.

Also — and this is something the flight contractors won't tell you — aeromagnetic data over rugged terrain in northern Pakistan is genuinely hard to acquire and harder to interpret. Terrain clearance issues, magnetic noise from drape variations, military airspace restrictions near borders. I've had two pilots tell me they won't fly certain valleys in GB at the line spacing needed for proper resolution. So you pay full price for compromised data.

How I Actually Sequence It Now

Here's the order I run on my own 15 blocks, and what we recommend to GeoMine AI clients:

First, satellite analysis across the whole license. Surface alteration, lithology, structure, drainage anomalies. Cheap, fast, no permits needed.

Second, ground truthing on the top targets. Geologist boots, rock chip samples, maybe a small soil grid.

Third — and only if the first two justify it — geophysics. That might be aeromagnetic. It might be ground IP. It might be both.

Fourth, drilling.

Skipping straight to step three because someone sold you on "comprehensive coverage" is how exploration budgets die in Pakistan. I've watched it happen to people I respect.

So when my friend asked about that $340K Chagai quote — I asked him what his ASTER analysis showed. He paused. He didn't have one yet.

Guess what I told him to do first?