METALLOGENY
Metallogenic characteristics of the Archean and Katarachean areas
These areas are located at the North of Bogonlava-Ranotsara lineament. They can contain Cr, Ni, Au, Fe, Be, U ores, graphite and ilmenite.
|
|
Metallogenic characteristics of the Proterozoic areas
These areas are located South of the Bongolava - Ranotsara lineament.
Only Ambohipato, Daraina, Milanoa, Vohémar regions showing relatively restricted extension, belong to the Proterozoic in the Northern part of the island.
They contain : Be, Uu, Cu, Fe, Mica, Al, Ce, Ti and rare earths.
Metallogenic characteristics of the sedimentary formation
The main ores, which can be found in the sedimentary series in the west basins are : U, Pb-Zn, native Cu.
Mineralizations associated with recent subvolcanic intrusive rocks within the sedimentary basins
The sedimentary series is affected by Cretaceous to Tertiary subvolcanic intrusion in numerous places.
The most interesting intrusions are constituted by:
The alcalin complex of the Ampasindava peninsula mi-neralized dominantly in pyrochlore with Nb and Ta, and secondarily in other rare earths such as, Y, La, and Ce.
The igneous vein of Andavakoera containing quartzo-baritic veins mineralized in gold, but sometimes showing galena and blende.
Mineralizations associated with erosion surfaces
Iron and the aluminum can give residual deposits constituted by ferrugineous or bauxitic cuirasses. They result from the lateritic alteration of the eroded surfaces (Uppermost Late Cretaceous, Middle Tertiary and Late Tertiary peneplains).
These surfaces only residual portions, lightly extended due to the dismantling of the peneplains resulting from the relief rejuvenation (uplifting of the basement of Madagascar in discontinuous phases).
|
