Five things to do when using legacy geology data
1. Make full use of WAMEX and GeoVIEW.WA. Many reports in the WAMEX database have geological logs, maps, assay data and other useful quantitative and qualitative information hidden within them. When looking for old reports don’t restrict your search. Look in the surrounding area, at different commodities and projects which may have had a different focus in the past. GeoVIEW.WA is an online GIS-based mapping tool that allows users to view, query, and map various geoscientific and related datasets of selected areas.
2. Geo-reference old maps. Old maps can hide a wealth of information such as locations of old workings, mineral occurrences, structural measurements or legacy drilling. Although the maps may be in a local grid there are usually landmarks such as bends in rivers, tracks or topographic features that enable the maps to be positioned to a good level of accuracy. Old maps can be digitised and fact-checked on the ground, then used as a base map to make a new up to date map. Combining an old map with new observations and new technology such as Landsat, ASTER and Google Earth can provide an immediate area of focus for new exploration.
Digitising legacy maps can reveal the location of features such as old workings.
3. Use 3D software. Use legacy maps, geochemistry and drilling in 3D packages. The data may never have been plotted in 3D and can give a different perspective, or allow identification of previously unrecognised patterns.
Geological and structural data from legacy map used to create 3D extension of surface feature
4. Locate and validate legacy diamond core. Legacy drill core is a fountain of knowledge. If possible, put together and redo the metre marks on diamond core. If old geological logs and assays are available they can be compared with the core to validate historic work. This can save on drilling costs of new holes. Validated legacy core can be used in an up-to-date Resource. SJS recently completed a legacy drill core validation program consisting of re-marking, re-logging and assaying core from the 1970’s. Specific gravity measurements were taken from the core, adding valuable data to historic work. This validation exercise resulted in the announcement of a significant Inferred Resource of more than 11 million MTU of tungsten.
Examples of legacy drill core carefully stored.
Top Left: Washing-down legacy core. Top Right: Replacing old core blocks with more legible new ones. Bottom Left: Slotting the old, chiseled half core back together, and re-marking metres. Bottom Right: Write-up ‘start of tray’ and ‘end of tray’ depths on the trays.
5. Find drill collars on the ground. Collar locations combined with quality re-logging of core and comparison to historical geology enables legacy drilling to be used in a JORC 2012 Resource. Ground reconnaissance fieldwork should be done to ‘pick-up’ legacy drill collars, initially using a handheld GPS. Legacy WAMEX reports and maps will assist in narrowing-down a search area when locating collars. If legacy drilling is located in areas of subsequent disturbance, then a good estimation of collar location can be made using residual evidence such as: old-sumps, an obvious old pad/area of less-mature vegetation and old drill equipment left behind.
Left: Digging a bit under the surficial soil reveals a collar of a 1970 drill hole, Right: Plugged collar from 1978 exposed at surface.
Left: Old sump, partially filled-in, the collar would be located within a few metres of here. Right: An old core-catcher found on the ground in an area of less-mature vegetation.