How Farmonaut used satellite gold detection to map 31 target zones along a greenstone-belt structural corridor — turning a promising but under-tested block into a ranked, drill-ready list.
Region: West African greenstone belt
Method: Multispectral + SAR + DEM
Scale: Structural corridor
This case study is anonymised. The block name, licence holder, coordinates and precise location have been removed at the client’s request; only country-level context (a West African greenstone belt) is retained. All quantities are satellite-derived Exploration-Target estimates — a conceptual screening output, not a Mineral Resource or Reserve under JORC, NI 43-101, S-K 1300 or SAMREC, and not a substitute for drilling.
Not every gold search starts with a blank map. Often an operator already holds a block that looks right — the correct belt, the right structures nearby, maybe old workings on the boundary — but has never systematically tested where the mineralisation actually concentrates. That is exactly where satellite gold detection in a greenstone belt earns its place: it reads the whole corridor at once and converts a vague “this ground is prospective” into a ranked list of discrete, mappable targets.
This anonymised case study covers one such structural corridor. Farmonaut processed the block through its satellite mineral-detection pipeline and returned 31 ranked gold target zones with a conceptual grade-and-tonnage envelope and a synthetic drill-and-pit planning pack. The result gave the operator a defensible, evidence-backed drilling sequence — without first spending a season on the ground.
“31 gold targets ranked along one corridor — a drilling sequence, not a guess.”
The challenge: a promising corridor, untested
The block sits along a well-endowed greenstone-belt structure — the type of setting where gold clusters around faults, fold hinges and lithological contacts. The geology was encouraging, but the operator faced the classic mid-stage bottleneck: how to decide, quickly and cheaply, which parts of the corridor deserved drill metres first.
- ⚠ Under-sampled ground — prior work was patchy, leaving most of the corridor untested.
- ⚠ Structural complexity — multiple intersecting trends make it hard to know which controls the gold.
- ⚠ Cover & detectability — laterite and vegetation mask surface expression in places.
- ⚠ Budget discipline — the operator needed a ranked plan before committing to a drill programme.
The brief: screen the corridor from orbit, flag every credible gold-associated anomaly, rank them, and return a conceptual economic frame to build a phased drill programme around.
On a known-prospective corridor, the winning move is sequencing, not discovery from scratch. Satellite detection ranks the corridor so the first holes go into the strongest, lowest-risk targets.
Have a corridor or block you want ranked? Get a satellite mineral-intelligence quote — supply a polygon and target mineral, and we do the rest.
How satellite gold detection reads a greenstone belt
Gold metal is invisible from orbit, but the company it keeps is not. Hydrothermal gold systems leave alteration halos, iron staining, clay minerals and structural corridors that each carry a distinctive spectral or terrain signature. Farmonaut fuses several public Earth-observation datasets to read those fingerprints and combine them into one prospectivity surface.
| Data layer | Role in a greenstone-belt gold screen |
|---|---|
| Multispectral optical | Iron-oxide and clay alteration mapping; bare-earth and extraction signatures. |
| Shortwave infrared | Sericite / argillic alteration typical of orogenic gold systems. |
| Radar (SAR) | Structural fabric and roughness; cloud-independent coverage. |
| Digital elevation model | Faults, lineaments and fold structures that channel mineralising fluids. |
| Surface & hydrology indices | Drainage, moisture and flow context to separate signal from noise. |
The layers are normalised and merged into a composite gold prospectivity index — a weighted blend of alteration, structure, host-rock favourability and detectability sub-scores. Conceptually:
alteration ,
structure ,
host-rock ,
detectability
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→ per-pixel score → ranked anomaly zones
The approach is deliberately conservative: an anomaly must appear across several independent evidence lines to survive filtering, which suppresses single-sensor artefacts. Each surviving zone receives a per-pixel grade estimate, a signal-strength class and an Exploration-Target confidence class (Class A / B / C).
On a structurally complex corridor, pay attention to where anomalies line up with mapped structures. Coincidence of alteration signal and a controlling structure is a much stronger drill argument than either alone.
A cascade that eliminates before it ranks
Good corridor screening is subtractive. The pipeline works as a cascade of filters rather than a single score: it first asks whether the host rock and structural setting are favourable at all, then tests for alteration and iron-oxide signatures, then for coincidence with mapped structure, and finally for detectability and false-positive risk. Ground that fails any stage drops out. The 31 zones that remained on this corridor each cleared several independent tests — which is what separates a defensible drill list from a wish list of bright pixels.
Signal strength as a ranking axis
Each zone is tagged with a signal-strength class — Strong, Moderate, Weak or Marginal — reflecting how decisively it stands out from its surroundings across the contributing layers. Along a structural corridor this is especially useful, because it lets the operator see at a glance which segments of the trend carry the most emphatic signal and should be tested first, and which are secondary.
Risk flags keep the plan honest
Old workings, bare bedrock and man-made disturbance can all counterfeit a mineral signature. Every zone therefore carries false-positive-risk flags that state why it might be misleading. A Strong zone with no flags is a clean drill target; a Strong zone with several flags is one to validate on the ground first. Surfacing those caveats next to the ranking is what makes the corridor screen trustworthy rather than merely encouraging.
The most valuable output on a corridor is not the single hottest zone — it is a ranked, flagged sequence that tells you the order to drill and where to pause for validation.
See it in action: Farmonaut satellite-based mineral detection converts a raw polygon into heatmaps, ranked zones, depth ranges and indicative quantities.
Results: 31 ranked gold target zones
Along the corridor, the pipeline flagged and ranked 31 discrete gold target zones. Aggregated, the satellite-derived Exploration-Target envelope came to roughly 757 kg of contained gold (about 24,323 troy ounces) within an indicative host tonnage of ~1.78 million tonnes at a corridor-wide weighted grade of 0.66 g/t. At USD 4,037/oz, that maps to an indicative in-situ gross value near USD 98 million, or about USD 79.5 million recoverable at an industry-standard 81% blended recovery.
These are conceptual, satellite-derived Exploration-Target figures, not a resource estimate. Grade and tonnage are modelled from remote sensing and must be confirmed by drilling. The 0.66 g/t weighted grade is a corridor-wide average; the best zones can run higher, while parts of the corridor are low-tenor. Use the totals as a screening-stage envelope for sequencing fieldwork.
Corridor at a glance
| Metric | Satellite-derived estimate | Basis |
|---|---|---|
| Target zones ranked | 31 | Multi-evidence anomaly polygons |
| Contained gold (in-situ) | ~757 kg / 24,323 oz | Sum across all zones |
| Indicative host tonnage | ~1.78 million tonnes | Conceptual envelope |
| Weighted average grade | 0.66 g/t Au | Corridor-wide, tonnage-weighted |
| Indicative gross value | ~USD 98 M | @ USD 4,037/oz spot |
| Indicative recoverable value | ~USD 79.5 M | @ 81% blended recovery |
| Confidence classes | Class A / B / C | Exploration-Target tiers |
As with any screen, the ranking matters more than the total. The 31 zones are ordered by prospectivity, signal strength and detectability, so the operator can drill the highest-confidence targets first and stage the remainder. In a corridor this size, a small number of Class A zones typically define the first drill campaign.
Class A — drill-ready targets
Zones with strong signal, multi-sensor agreement and few false-positive-risk flags — often where alteration coincides with a controlling structure. First-phase drill candidates.
Class B — validation targets
Credible zones with moderate signal or a risk flag or two. Best ground-truthed with mapping and geochemistry before drilling.
Class C — pipeline / watchlist
Weaker or higher-risk zones retained for completeness. Low near-term priority; useful for regional structural context and future phases.
From anomalies to a drill plan
To make the ranking actionable, Farmonaut delivered a conceptual planning pack built from the satellite grade surface: a synthetic drillhole layout, a regularised block model, closed ore-body solids for the strongest zones, and a floating-cone pit outline with a conceptual schedule. For this corridor the pack ran to a couple of hundred synthetic drill collars and a block model well into six figures of blocks.
The drillholes, block model and pit are generated from the satellite grade surface, not physical drilling. They let a mine-planning team rehearse the full Leapfrog / Vulcan / Surpac / Datamine workflow on realistic geometry and decide where real holes should go. Every layer is labelled synthetic with Exploration-Target confidence codes — explicitly not Measured / Indicated / Inferred material.
The operator ends up with a scoping geometry ready to drill against: ranked targets, a grade surface, indicative depths and a conceptual pit — so field time is spent confirming the best zones rather than deciding where to begin.
“On a known corridor, satellite detection turns ‘somewhere here’ into ‘drill these first’.”
Impact: time, cost and ESG
The economic case rests on the same three levers that make satellite screening compelling everywhere.
Time: a ranked corridor in days
Rather than a multi-month ground campaign to decide sequencing, the satellite screen delivered a ranked 31-zone target list in days — keeping the project on a single-season decision cycle.
Cost: front-end savings of up to 80–85%
By ranking the corridor before mobilising crews, the operator avoids spending drill metres to discover where not to drill. Front-end exploration cost falls by up to 80–85% versus blanket ground coverage.
A ranked, sequenced 31-zone drill plan is a concrete de-risking step that can be reached on a modest budget. It reframes the asset from “prospective corridor” to “staged drill programme with priorities” — a clearer story for financing.
ESG: a lighter early footprint
Screening happens from orbit, with no ground disturbance until targeted validation. On a corridor near communities or sensitive land, that means far less speculative fieldwork during the highest-uncertainty phase.
Fewer speculative trenches and tracks means less land disturbance and lower fuel and community impact — the field team only walks toward pre-ranked targets.
| Dimension | Traditional ground-first | Satellite-first screening |
|---|---|---|
| Time to ranked targets | Many months | Days |
| Early-stage cost | Full field budget | Up to 80–85% lower |
| Ground disturbance | Grids, trenches, tracks | None during screening |
| Coverage | Sampled subset | Entire corridor |
| Output | Sample points | Ranked zones + grade surface + conceptual plan |
Why greenstone corridors host gold — and where screening fits
The gold in a greenstone belt is rarely random. These belts are ancient volcanic and sedimentary sequences that were folded, faulted and metamorphosed over geological time, and gold-bearing fluids moved through the resulting fault and shear networks. Where those structures bend, branch or cross a favourable host rock, gold dropped out of solution. The product is structurally controlled orogenic gold — typically strung along a corridor as a series of zones rather than a single body. That is why a corridor screen so often returns a cluster of targets along a trend, as this one did with 31 zones: the structure organises the mineralisation, and the satellite reads the structure.
Reading the corridor through that deposit model is what elevates the screen above a heat map. A zone that sits on a structural intersection with coincident alteration is geologically coherent and eminently drillable; a bright spot with no structural context is a candidate for the watchlist, not the drill. Ranking the 31 zones against the model — not against a single index — is what makes the sequence defensible.
On a corridor, weight zones where alteration signal and a controlling structure coincide. That coincidence is the single best predictor of a drill-worthy orogenic gold target.
Where satellite screening sits in the exploration lifecycle
Screening does not replace the exploration pipeline — it makes every later stage cheaper and better aimed. A staged programme built on a corridor screen typically runs:
- Screening (this stage) — satellite detection ranks the corridor and returns a grade surface and conceptual plan in days.
- Ground validation — mapping and geochemistry over the Class A and B zones to confirm the surface signal.
- First-phase drilling — scout holes into the strongest zones, guided by the conceptual drill geometry.
- Resource definition — infill drilling on responsive zones toward a JORC / NI 43-101 Mineral Resource.
- Study & development — scoping and feasibility work on confirmed resources.
The 31-zone screen is stage one, but it sets the trajectory for the whole corridor: it decides which segments of the trend ever see a drill rig. On a known-prospective corridor, that sequencing decision is where most of the value — and most of the avoidable cost — sits.
Ranking a corridor before drilling turns an open-ended budget into a staged one with clear milestones. That is a far more financeable story than “we hold prospective ground and plan to explore it”.
What you actually receive
A corridor screen is only as valuable as the form it arrives in. For this study the deliverable set included, at minimum:
- 📊 A ranked anomaly inventory — all 31 zones with prospectivity score, signal-strength class, confidence class and false-positive-risk flags.
- 🗺 Prospectivity heatmaps and alteration overlays — full-resolution, georeferenced imagery behind the ranking, ready for any GIS.
- ⛰ A per-pixel grade surface and estimated depth ranges along the corridor.
- 🔧 A conceptual 3D and mine-planning pack — here on the order of 200 synthetic drill collars, a block model of roughly 148,000 blocks, closed ore-body solids for the strongest zones, and a floating-cone pit outline — exportable to Leapfrog Geo, Maptek Vulcan, GEOVIA Surpac and Datamine.
- 📄 A written geological interpretation linking the anomalies to the controlling structures.
All of it is georeferenced, so it drops straight onto the operator’s existing project grid and drill database.
The economic assumptions behind the numbers
The indicative values in this study rest on a short, stated set of industry-standard inputs: a gold price of USD 4,037 per troy ounce (the spot level at the time of analysis), an 81% blended metallurgical recovery, and grade and tonnage modelled per pixel from the satellite prospectivity surface. Contained gold is in-situ; recoverable value applies the recovery factor. No dilution, processing cost, royalty or discount rate is included in the headline — those are later-stage inputs. The right way to read the figures is as a relative, screening-stage frame for sequencing targets and sizing a drill programme, not as a valuation.
Reading a satellite scoping value as a project NPV. These are un-discounted, pre-cost, in-situ-to-recoverable estimates for sequencing and prioritisation — the NPV comes after drilling defines a resource.
How to get this for your own site
The same workflow is available for any block, corridor or licence you hold or are evaluating.
- Send us your area of interest as coordinates, KML/KMZ or a polygon, plus country/region and target mineral(s).
- We select and acquire the data (multispectral or hyperspectral) and run the detection pipeline.
- You receive a premium mineral-intelligence report — heatmaps, ranked zones, depth ranges, indicative quantities and geological interpretation — typically in 5–20 business days.
- Add Premium+ TargetMax™ for optimal drill angles, 3D subsurface models and the conceptual planning pack.
Rank your corridor before you drill it
Farmonaut screens your whole block from space and hands back ranked targets, grade surfaces and a conceptual plan — georeferenced and drill-ready.
Go 3D: our satellite-driven 3D mineral prospectivity mapping shows how ranked zones extend into conceptual subsurface models — the geometry behind this study’s synthetic pit.
Limitations you should know
Honest screening means being clear about what satellite data can and cannot do. Remote sensing reads the surface and near-surface expression of a mineral system; it infers what lies beneath from those signals plus terrain and structure, but it does not see gold at depth directly. Thick transported cover, dense vegetation or extensive laterite can mute or distort the surface signal, and that is exactly why detectability is scored and why some zones carry risk flags. The grade surface is a model, not an assay — it is calibrated to be internally consistent and useful for ranking, but individual pixel grades will differ from what a drill core eventually returns.
None of this undermines the method; it defines where it fits. Satellite screening is a targeting and prioritisation tool that dramatically narrows the search and orders the drilling — and it is deliberately paired with ground validation and drilling, which remain the only ways to confirm grade, continuity and tonnage. The 31-zone corridor inventory should be read in that spirit: a rigorous, auditable head start, not a substitute for the geologist’s hammer or the drill rig.
Use the risk flags as a fieldwork checklist. A zone flagged for possible cover or disturbance tells your team exactly what to check on the ground before it earns a drill hole.
Frequently asked questions
Can satellites detect gold in a greenstone belt?
Satellites detect the alteration, iron staining, host rocks and structures that accompany greenstone-belt gold systems, not the gold metal itself. Those signals are combined into a prospectivity ranking that drilling then confirms.
Is the 31-zone inventory a Mineral Resource?
No. It is a set of satellite-derived Exploration Targets for prioritising fieldwork — not a Mineral Resource or Reserve under JORC, NI 43-101, S-K 1300 or SAMREC. Grade and tonnage require drilling to confirm.
What makes a Class A target on a corridor?
Strong signal across several independent evidence lines with few false-positive-risk flags — ideally where alteration coincides with a controlling structure. These are the first-phase drill candidates.
How long does a corridor screen take?
Typically 5–20 business days depending on area and complexity — far faster than the months a ground-first ranking campaign would need.
Why is the location withheld?
At the client’s request, the block name, licence holder and coordinates are removed to protect commercially sensitive ground. The geology, method and economics are shown in full; only the site identity is withheld.
How do I get started?
Provide your area of interest (coordinates, KML/KMZ or polygon), country/region and target mineral(s). Request a quote and we handle data selection and analysis.
How does satellite screening compare with airborne geophysics?
They are complementary, not competing. Airborne magnetic, radiometric and electromagnetic surveys are powerful but require aircraft mobilisation, permitting and significant cost, and they usually come after a target area is chosen. Satellite screening runs first, over any polygon on Earth, in days and at a fraction of the cost — it is the wide-area filter that decides where more expensive geophysics and drilling are worth deploying. On this corridor, the satellite screen produced the ranked target list that a follow-up ground or airborne programme could then refine over the strongest zones.
Can you screen for minerals other than gold?
Yes. The same approach is applied to copper, lithium, manganese, silver and many other commodities — each has its own diagnostic alteration and host-rock signatures. The detection model is tuned to the target mineral you specify when you submit your area of interest.
Glossary
- Greenstone belt
- A belt of ancient volcanic and sedimentary rocks that hosts many major gold deposits, especially in West Africa.
- Structural corridor
- A zone of faults, shears or fold structures that focuses mineralising fluids and localises gold along a belt.
- Prospectivity index
- A composite per-pixel score blending alteration, structure, host-rock and detectability signals into a measure of gold potential.
- Exploration Target
- A conceptual early-stage estimate of potential quantity and grade — explicitly not a Mineral Resource or Reserve.
- Blended recovery
- The share of contained gold expected to be recovered in processing; 81% is used here as an industry-standard scoping assumption.
Disclaimer: This anonymised case study presents satellite-derived Exploration-Target estimates for screening and target-prioritisation purposes only. All quantities are conceptual, modelled from remote-sensing data, and are not a Mineral Resource or Ore Reserve under JORC, NI 43-101, S-K 1300 or SAMREC. Economic figures use a spot gold price of USD 4,037/oz and an 81% blended recovery assumption for scoping illustration only. Drilling and further study are required to confirm any mineralisation. Farmonaut provides mineral-intelligence analytics and is not a mineral producer, marketplace or regulatory body.
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