Understanding the abundance and spatial distribution of chemical elements in the Earth’s near-surface environment is critical for many human endeavours ranging from locating our future mineral resources to monitoring changes in the chemistry of the Earth caused by natural processes or human activities. There is worldwide concern about the potentially damaging effects of chemicals in the environment on the health of humans, animals, agriculture and ecosystems. Economic and population growth are increasing rapidly, exacerbating such problems as land degradation and pollution from uncontrolled urbanisation, industrialisation, intensive agricultural practices and over-exploitation of aquifers. These and other problems are having an impact on the geochemistry of the Earth’s surface and the sustainability of its life-support systems from the local to the global scale. On the other hand, there is also worldwide concern about securing mineral and energy resources to meet the demand of our growing population. Understanding the geochemistry of the Earth’s surface is vital in locating these resources and in exploiting them in an environmentally responsible manner.
Systematic geochemical mapping is the best method available to assess and provide a basis for monitoring changes in the levels of chemical elements at the Earth’s surface. Geochemical maps have traditionally been valuable in addressing a whole range of environmental problems, as well as for identifying potential mineral resources at the local to national scale. The present proposal is to develop for Africa a land base multi-element geochemical baseline database for mineral resource and environmental management according to the specifications of IGCP 259 "International Geochemical Mapping" (Darnley et al., 1995).
Africa is the world's second-largest and second-most-populous continent. Its area, including adjacent islands, is 30,221,532 km². According to Wikipedia, Africa consists of 54 sovereign states and 10 non-sovereign territories (https://en.wikipedia.org/wiki/List_of_sovereign_states_and_dependent_territories_in_Africa#Sovereign_states). In order for Africa to develop its vast mineral resources, and also to safeguard its environment, it urgently needs a harmonised geochemical baseline database for planning and decision-making. To develop such a database it is necessary to start a capacity-building programme for training professional applied geochemists from all African countries.
This project proposal for Africa is within the vision of GEO "To realise a future wherein decisions and actions, for the benefit of humankind, are informed by coordinated, comprehensive and sustained Earth observations and information". It also will be an important contribution to AfriGEOSS (2014), and the IUGS initiative "Resourcing Future Generations" (IUGS, 2014; Nickless, 2015).
Activities for the period
To develop a geochemical baseline database for the entire African continent through systematic sampling and chemical analysis according to the specifications of IGCP 259 "International Geochemical Mapping" (Darnley et al., 1995) We propose using only one sample medium, depending on terrain type, namely overbank or floodplain or catchment basin sediment, which is generally alluvial (or agricultural soil).
The framework for the sampling is the Global Geochemical Reference Network (GRN) established by IGCP 259 (Darnley et al., 1995). The GRN consists of about 5000 grid cells, each approximately 160 x 160 km in size (area 25,600 km2). The 54 countries in Africa are covered by approximately 1500 GRN grid cells (see Figure 1). Five sites are identified within each cell for a total of 7500 sample sites for the continent (approximately 1 site per 4000 km2).
At each site, two samples will be collected, a top and a bottom. The top (surface) sample will be collected from 0-25 cm, and the bottom (deeper) 25-cm thick sample below a depth of 75 cm. Thus, the total number of samples will be in the order of 15,000. Duplicate field samples will be collected from at least 3 per cent of the sampling sites, giving a total of 225 duplicated field sites, with a total of about 450 samples.
The samples, after preparation at a central facility in Africa, will be analysed for 76 elements at the laboratories of the China Geological Survey (UNESCO International Research Centre on Global-scale Geochemistry). Splits of each sample will be archived and stored for future investigations at either a central facility within Africa or at a facility designated by each participating African country.
To monitor the quality of geochemical data, five large standard samples with different element concentrations (low to high) will be prepared.
The cost of sampling and sample preparation for the whole African continent, and preparation of the five standard samples, is approximately in the order of 5 million Euros.
The cost of laboratory chemical analysis for 76 elements is approximately 3 million Euros, which may be funded by China.
€ 300,000 (indicative amount).
Participating Organizations: EuroGeoSurveys; IUGS; UNESCO.
Others: Geological Society of Africa; Organisation of African Geological Surveys.
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