Gravity Anomaly Interpretation for Gold Exploration: A Pakistani Case Study Approach

A gravity anomaly can point you toward gold, but not the way most people think. Gold itself is too scarce and too finely spread to show up on a gravity survey. What you're really reading is the dense host rock, the sulphide bodies, and the structural traps that gold likes to sit near. So the survey doesn't find gold — it finds the geology that carries it.

Let me explain how this actually works, and how we use it at GeoMine AI alongside satellite data for exploration across Pakistan.

What a gravity anomaly actually tells you about gold

Gravity surveys measure tiny differences in the Earth's gravitational pull. Denser rock underground pulls a little harder. Less dense rock pulls a little less. You map those differences and you get a picture of what's sitting below the surface — before anyone drills a single hole.

Here's the thing about gold. It's dense (around 19 g/cm³), sure. But an economic gold deposit might run a few grams per tonne. That's nowhere near enough mass to bend a gravity reading on its own.

So what are we chasing?

• Associated sulphides — pyrite, arsenopyrite and other heavy minerals that often travel with gold. These create a positive density contrast.
• Dense host rocks — mafic and ultramafic bodies, banded iron formations, skarn zones.
• Structural controls — faults, shear zones and contacts where fluids moved and dropped their mineral load. Gravity gradients often trace these boundaries clearly.
• Low-density alteration halos — sometimes the rock around a deposit gets chewed up by hydrothermal fluids and turns less dense, showing a negative anomaly next to a positive one.

That last pairing — a sharp gravity high sitting beside a gravity low — is one of the more interesting signatures in gravity survey gold exploration. It can mark a mineralized structure with an alteration envelope around it.

Reading gravity data in a Pakistani context

Pakistan's gold potential mostly ties into two settings. The Chagai belt in Balochistan (porphyry copper-gold, the same system as Reko Diq). And the metamorphic and vein-hosted systems threading through Gilgit-Baltistan and Kohistan.

These two settings behave very differently on a gravity map.

In Chagai-style porphyry systems, you're looking at intrusive bodies that create broad, regional-scale density contrasts. The gravity anomaly here is big and smooth. You use it to outline the intrusion and the surrounding country rock, then zoom in with other tools.

In the vein and shear-hosted systems up north — the kind of ground I know well, since I own mines in Gilgit-Baltistan — the useful signals are narrow. A thin sulphide-rich shear zone. A fault contact. These show up as tight, linear gravity gradients rather than big blobs. You need close survey spacing to catch them, and honestly, a lot of regional surveys just miss them because the stations are too far apart.

So the same technique, two completely different reading strategies.

The mistakes people make interpreting gravity for gold

I've seen good ground get written off because of sloppy interpretation. And bad ground get hyped for the same reason.

Watch for these:

• Treating any gravity high as a gold target. A dense rock is just a dense rock. Basalt, limestone, an iron-rich intrusion — none of them are gold. The anomaly is a clue, not a conclusion.
• Skipping the terrain correction. In Gilgit-Baltistan the topography is brutal. Steep valleys and high ridges throw off gravity readings badly. If your terrain correction is weak, your "anomaly" might just be a mountain. This matters more here than almost anywhere.
• Ignoring the regional trend. You have to subtract the broad regional field to see the local target. Get that wrong and small deposits vanish into the background.
• Using gravity alone. This is the big one. Gravity narrows the search. It doesn't confirm gold. You still need magnetics, geochemistry and eventually drilling.

Look, gravity data is one input. Powerful, but partial. Anyone selling you a gravity survey as a standalone gold-finder is overselling it.

How we combine gravity with satellite data at GeoMine AI

Here's where our approach differs. Full ground gravity surveys are slow and expensive, especially across the terrain we work in. So we start from space and work down.

At GeoMine AI we pull Sentinel-2, ASTER, SAR and SRTM DEM data and run it through our AI to map the surface indicators first — alteration zones, iron staining, structural lineaments, favourable rock types. That tells you where on the map deserves a gravity survey at all.

Think of it this way:

• Satellite AI narrows a 1,000 km² block down to a handful of priority zones.
• Gravity survey then interrogates those zones for buried density structure.
• Geochemistry and drilling confirm what's actually there.

That sequence saves money. You're not paying for a gravity crew to walk ground that satellite data already ruled out. And the DEM data we use feeds directly into better terrain corrections for whatever gravity work follows — so the two datasets actually strengthen each other.

Our geomine reports flag structural intersections and alteration halos that make sense to follow up with a gravity survey. We don't run the gravity survey ourselves — that's ground work — but we tell you where it's worth doing.

What to ask before you commission a gravity survey

If you're about to spend money on geophysical survey gold exploration in Pakistan, ask these first:

• What station spacing are you proposing, and does it match my target size? (Tight veins need tight spacing.)
• How are you handling terrain correction in mountainous ground?
• Have we already narrowed the target zones with satellite or geochemical data, or are we surveying blind?
• What other datasets will we integrate — magnetics, spectral, structural?
• Who interprets the anomalies, and do they know Pakistani geology specifically?

That last question matters more than it sounds. Interpretation is where the value lives.

Want to know which parts of your ground actually justify a gravity survey before you spend on one? Send us your block coordinates or licence area through geomines.org and we'll show you what the satellite data flags first.