Project development Field methods for Regional Surveys

Field methods for Regional Surveys

Field Methods for Regional Surveys

The principal demand for systematic geochemical data collection is at the regional and/or national level. In general, a much greater data density is required than can be provided as part of a Global Geochemical Reference Network. Thus, national or regional agencies, using methods selected by them, will continue to be the producers of most of the world’s geochemical data. It is strongly recommended that the detailed data they collect should be tied into, and be compatible with, the Global Geochemical Reference Network data, so that data at any level of detail may be compiled and/or compared across organizational and political boundaries. Data collected for detailed national or regional surveys should be compatible, regarding methods and spatial overlap, with those collected as part of the Global Geochemical Reference Network.  Therefore, the IGCP 259 report (Darnley et al., 1995) provides recommendations relating to the conduct of these more detailed surveys, since these should provide the major part of the future global geochemical database.


Sample Collection

  • Regional and national mapping should be performed according to internationally compatible and agreed standards;

  • At least one sampling procedure should be applicable and used consistently in any given geographical area, from global to regional scales;

  • Stream sediment samples from tributary drainages are the preferred sample medium;

  • Stream water should be sampled in conjunction with stream sediments wherever possible;

  • If stream sediments cannot be collected, acceptable substitutes are till or lake sediment;

  • Where a change in landscape requires a change in sample media, sample media collected in neighbouring blocks must overlap to allow comparison of data;

  • Stream sediment catchment basins should be not more than 100 km2;

  • Analyses should be undertaken on all collected samples (NO laboratory composites);

  • Duplicate samples should be obtained from at least 3 per cent of sites;

  • Systematic labelling and documentation is essential.


Sample Preparation

  • Contamination must be avoided in sample collection, preparation and storage by appropriate choice of tools, equipment and containers.


Stream Sediment 


  • Depending on field sample site conditions wet or dry sieving of stream sediment may be employed; if sieving is not possible in the field, then the samples are sieved in the laboratory after drying at either room temperature or in thermostatically controlled ovens at a temperature of <40oC.

  • Upper limit of drainage sediment grain-size fraction analysed should be in the range of 0.10 to 0.18 mm; if this fraction is scarce, then a coarser fraction should be used.

  • A minimum of 100 g of the sieved fraction is required for analysis;

  • Sample material not required for immediate analysis should be archived for future use in contaminant-free permanent containers;

  • Systematic labelling and documentation is essential.