Project Development

One of the IUGS Commission on Global Geochemical Baselines' aims is to encourage the adoption of standardised methods for conducting broad-scale geochemical surveys.  Taking into account the experience obtained from the FOREGS/EuroGeoSurveys Geochemical Baseline Mapping project the cost will be considerable if all sample types are taken according to the specifications of IGCP 259 (Darnley et al., 1995; Salminen, Tarvainen et al., 1998), i.e., stream sediment, stream water, overbank sediment (top and bottom), residual soil (top and bottom), humus, and floodplain sediment (top and bottom).  However, it is worth making such an investment, because the resulting geochemical databases can be used in mineral exploration, farming, forestry, water quality, land use policy, health issues, and environmental policy, to mention but a few.

 

As cost is an important parameter, countries that are collecting floodplain sediment only must remember that by using only floodplain sediment, the data obtained are of limited value, because they cannot be closely correlated with, nor provide reference materials for, the sampling media commonly collected in detailed national regional surveys, and that the objective for the establishment of the global Geochemical Reference Network is to provide sufficient data for all recommended sample media in order to link geochemical mapping at all scales (Darnley et al., 1995).  Further and, most importantly, the result of the decision to collect only floodplain sediment would be to increase the cost of the overall project, and not to reduce it, due to the necessity to revisit every GTN grid cell at a later date to collect the other recommended sample types.  It is again stressed that the other sample media are important in order to provide reference materials for geochemical surveys at the national level, and more clearly indicate the range of abundance variations in the geochemical background (Darnley et al., 1995).

 

To assist this work, the UNESCO International Centre on Global-Scale Geochemistry (ICGG) in collaboration with the Institute of Geophysical and Geochemical Exploration (IGGE) of China Geological Survey (CGS) is offerring free analysis to developing countries that wish to carry out geochemical surveys within their GTN cells. 

 

For more information with respect to:

• Sampling - contact Alecos Demetriades, Chairperson of IUGS CGGB Sampling Committee [Email: alecos.demetriades@gmail.com], and
• Sample analysis - contact Xueqiu Wang, Executive Director of UNESCO ICGG [Email: wangxueqiu@igge.cn].

 

Project development according to IGCP 259 Recommendations

IGCP 259 (International Geochemical Mapping) had as one of its objectives to develop recommendations for producing a global-scale geochemical database (Darnley et al., 1995).  These recommendations are summarised below.

 

Phase I – IGCP 259:  International Geochemical Mapping

• Summary of principal recommendations

• A Global Reference Network

• Site Location and Sampling Media

• Sample Quantities

• Analytical Arrangements

• Field Methods for Regional Surveys

• Sample Collection

• Sample Preparation

• Geoanalytical Requirements

• Radioelement Mapping

• Data Management

• Map Presentation Recommendations

• Implementation

• Conclusions

 

Summary of principal recommendations

 The following were identified by IGCP 259 as basic prerequisites for a global geochemical database of permanent value:

• commonly available representative sample media, collected in a standardised and harmonised manner;

• continuity of data across different types of landscape;

• adequate quantities of the designed sample media for future reference and research requirements;

• analytical data for all elements of environmental or economic significance;

• the lowest possible detection limits for all elements, and

• tight quality control at every stage of the process.

 

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 artificial laboratory composites - see Pitfalls to Avoid);

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

• Systematic labelling and documentation is essential.

 

Implementation

In order to obtain a global multi-element geochemical database, the following practical considerations need to be addressed

• If a more rapid and relatively low cost global overview is required, a preliminary reconnaissance confined to floodplain sampling could be undertaken. However, floodplain data alone are of somewhat restricted value. The cost of the overall project would be increased by the necessity to re-visit every grid cell at a later date to collect the other recommended sample media, which would better indicate the ranges of element abundance, and provide the preferred means of correlating global and national datasets.

• Irrespective of the rate or mode of progress, the quality and consistency of data must be controlled throughout the acquisition period;

• Standard reference materials must be provided and renewed as necessary;

• A mechanism is required for assessing and introducing new techniques as they become available;

• No useful purpose will be served unless global and regional data are readily accessible; and

• Globally interlinked geochemical data centres are required, which connect to population, environmental, natural resource and global change data centres.

 

Because the scientific and technical requirements of systematic geochemical mapping have practical significance for all countries:

• Countries should be encouraged to support and participate in the work, and extract maximum value from the information which is obtained;

• Appropriate training and technical assistance should be made available where needed, and

• Regional centres should be established to encourage cooperative research and the dissemination and application of geochemical data.

 

Conclusions

• Central coordination is necessary for the duration of the project.

• Progress must be expedited and facilitated by a small technical secretariat, funded and administered through a recognised international organisation.