What is usually available
- Geological maps at regional scales, commonly 1:250,000 and 1:100,000, with explanatory reports
- Regional geochemistry, most often stream-sediment surveys, sometimes with archived samples that have been re-analysed
- Airborne geophysics, mainly magnetic and radiometric surveys
- Mineral occurrence databases listing known deposits and prospects
- Mining cadastres showing titles, holders and status
- Global datasets that fill gaps: satellite imagery and digital elevation models with worldwide coverage
Who publishes it
Each country has a geological survey and, usually separately, an authority that administers mining titles. The main geological surveys are:
- Argentina: SEGEMAR, the Servicio Geológico Minero Argentino. Mining titles are administered by the provinces, so cadastres are provincial.
- Chile: SERNAGEOMIN, the Servicio Nacional de Geología y Minería, which also holds the national register of mining concessions.
- Peru: INGEMMET, the Instituto Geológico, Minero y Metalúrgico, which publishes geology and the mining cadastre through its GEOCATMIN map portal.
- Mexico: the Servicio Geológico Mexicano (SGM).
- Brazil: the Serviço Geológico do Brasil (SGB, formerly known as CPRM), with titles administered by the Agência Nacional de Mineração.
- Colombia: the Servicio Geológico Colombiano (SGC), with titles administered by the Agencia Nacional de Minería.
Portals, formats and licence terms change. Check the terms of use on the publishing site before redistributing anything.
Why it is underused
The data is free but not ready to use. Map sheets were compiled decades apart and do not match at their edges. Older products use local datums. Geochemistry comes as tables per sheet, with different element lists and methods. Some of it exists only as scanned reports. Portals are built for viewing a map on screen, not for downloading a district.
For a small team, the days needed to assemble all this compete with everything else, and the usual result is a geological map as a backdrop and nothing more.
Using it with care
- Check the datum. Older Argentine sheets, for example, were compiled in Campo Inchauspe, not in a modern geocentric datum. The shift is large enough to put a sample in the wrong drainage.
- Respect the scale. A contact on a 1:250,000 map is located to within a few hundred metres at best. It is context, not a drilling guide.
- Read the method. Old geochemical values may come from partial digestions and coarse measurement steps. See Can you use legacy assay data?
- Date the cadastre. A title map is a snapshot. Record when it was extracted and confirm anything you act on with the authority.
- Mind the gaps. No anomaly where nobody sampled is not evidence of barren ground.
What it can do for a project
Brought into one map with a project's own data, public layers answer questions that are otherwise guessed at. Does the structure that hosts the target continue beyond the title? Do the streams draining the property carry more metal than their neighbours? Which ground on trend is open? Where should the first field season go?
In one piece of our work, public geophysics, geology, stream-sediment geochemistry and neighbouring titles within 20 km of a project were combined in a single browser map and used to place the next sampling points. It is described in the story A district on one map, before the field season.
Where this fits
Assembling public data around a project is the core of district and tenure intelligence, and making it consistent with your own data is data integration.