Mineral exploration Madagascar


	Stream sediment survey in south-eastern Madagascar (2005 - 2006)

Position held: Head of section Mining, Infrastructure and Mineral Exploration, Fugro Consult GmbH, Germany

Scope of project

Since 2003 the World Bank funds a major project in Madagascar to restructure the country’s minerals sector and to reinterpret the crystalline basement. The aim of the project is to provide digital geological maps and data for interested national and international mining companies and other interested parties. The structural and metallogenetic interpretation of the existing maps, based on work carried out by the geological surveys of Madagascar and France in the middle of the past century, are outdated.


	In this sub-project, an area of 150,000 km² is re-mapped on two scales and a 2,000 samples stream sediment survey is carried out on a 14,000 km² subset in the SE. The geochemical survey was designed by me and field work started in 2005. It will last until end 2006. More pictures are found in the photo galleries.

Services provided

Conceptual design of work program
Sampling of 2,000 stream sediment samples
Recovery of 2,000 panning concentrates and coarse fractions for the determination of the mineralogical composition
Description of outcrop geology and possible mineralization
Sample preparation in the field for chemical analysis
Statistical treatment of more than 60 different elements
Geological and geochemical interpretation of results
On-the-job-training of Malagasy counterpart geologists

Approach

Besides metasomatic and high-grade metamorphic sedimentary rocks, granitic rocks dominate the rugged south-east of the island. The region is known for primary sapphire and uranothorianite deposits. The ilmenite beach placers around Fort Dauphin (Tôlanaro) are amongst the most important in the world.
The geochemical prospection does not aim at a single mineral or chemical element, it is rather a tool to evaluate the overall mineral potential of the area. The georeferenced stream sediment samples are sieved to –80 mesh in the field. The fine fraction is submitted for chemical analysis, the panning concentrates and the coarse fraction are inspected visually for valuable minerals such as gold, colored gemstones or tantalite.




		Presentation of stream sediment survey results (detail)

The chemical analysis for gold, palladium and platinum is done by fire assay/ICP-ES. The easy soluble elements as copper, lead, zinc are analyzed by ICP-MS after aqua regia digestion. The refractory elements like REE, tantalum, tin, uranium are analyzed by Li-borate fusion/ICP-MS. The quality control of the laboratory is assured by the introduction of blank and duplicate samples.

After a statistical treatment of the chemical analysis, the results are plotted on digital and analog maps which can be acquired after the project by mining and exploration companies.

Another important aspect of the project is the training of Malagasy counterparts in modern techniques of geochemical mineral exploration. In total, some 10 Malagasy geologists participate in the on-the-job-training.


	Stream sediment sampling at the Manambolo River, Madagascar