Old regional geochemical data as targeting tool for exploration - A data compilation project of Mozambique

As part of Mineral Resource Management Capacity Building Project of Mozambique, Geochemical and Industrial Mineral Surveys project (GIM) was carried out in 2005-2007. The project, valued 1.5 million USD, was financed by AfDB and implemented by the GTK Consortium. The main objective of the project was to increase private mining sector investments in Mozambique by providing the basic background information for exploration companies. Besides the data compilation of the earlier surveys, new geochemical surveys were implemented for training purposes in collaboration with DNG.
The geochemistry part of the GIM project consisted of three phases:
• Compilation and synthesis of existing geochemical data
• Execution of new surveys - (i) regional stream sediment and (ii) follow-up soil surveys
• Final Products - GIS-based digital geochemical database
Wide areas of Mozambique (sized about 800 000 km²) have been targeted over the years for regional and more detailed, exploration type of geochemical surveys. Particularly early 1980s was an intensive stage of activity and now about 30 % of the country is covered by regional geochemical surveys. The earlier geochemical surveys with available analytical data carried out in Mozambique concentrate on crystalline bedrock areas.
The nature of the existing surveys is rather heterogeneous in terms of sampling methodologies and analytical procedures. As early geochemical programmes normally targeted for base metals, the element combination is usually limited – gold was not analysed.
The most extensive sampling was done by the Italian Aquater including 15454 stream sediment samples, which were variably analysed up to 34 elements. Another example of the major existing data sets is the Hunting Team survey implemented in 1981-1983 and covering an area of 55000 km². It included about 5500 samples collected from 20 geologically selected target areas. These samples were originally analysed only for Cu, Pb, Zn, Ni and Co but 1150 samples were selected for complementary Au, Te and Pd analysis by the GIM project.
In addition to the data compilation, a new stream sediment survey was done as part of the GIM project. It covered about 5000 km²and included 476 composite samples taken from pre-defined and pre-numbered locations. This was followed by detailed soil survey in five anomalous areas.
The outcome of the project, the digital and easy-to-use Geochemical Database (GDB), is commercially available for the exploration companies at DNG. In the Final Report of the GIM project the geochemically interesting target areas were delineated using also the results of the recent geological mapping projects.