Geology of Madagascar

Geologic map of Madagascar

The geology of Madagascar comprises a variety of rocks of Precambrian age which make up the larger part of the east and centre of the island. They are intruded by basalts and rhyolites of Mesozoic to Cenozoic age. In contrast, the western part of the island is formed from sedimentary rocks of Carboniferous to Quaternary age. Archean rocks occur from the northeast portion of the island down to the south in the Ranotsara shear zone. Rocks in the northern portion of Madagascar are greenstone belts, from the Archean or Paleoproterozoic age.[1]

Tectonics

A NW-SE trending sinistral shear belt separates northern and southern crustal terranes. The Ampanihy ductile shear zone was created by flattening events associated with granulite metamorphism, isoclinal folding, flattened sheaths, steep to vertical foliations and sheath-like geometry of massif-type anorthosite bodies.[2]:144

Paleontology

The Maevarano Formation, dated to late Maastrichtian age, has provided a diverse faunal assemblage, including the giant frog Beelzebufo, gondwanathere mammals, dinosaurs, crocodylians and other groups. The Middle Jurassic Isalo III Formation contains fossil dinosaurs. Typical Gondwanan flora of Glossopteris is found in the Permian formations in Madagascar.

Economic geology

Madagascar is the world's leading producer many colored gemstones, including sapphires, rubies, multi-coloured tourmalines, emeralds, amethysts, cordierites, aquamarines and garnets. Madagascar is also a major source of graphite, making it the second-largest producer in Africa. Additionally, Madagascar is Africa's third leading producer of chromite.[3] Titanium oxide is found in significant quantities in beach sands located near Toalagnaro, however, 75% of the coastal forest zone in that area would have to be destroyed in order to exploit it, which has not been done.[2]

Huge oil fields lie to the west of Madagascar, however they would require steam injection to extract, which is both technologically difficult and expensive. The oil fields of Tsimiroro and Bemolanga are estimated to hold combined reserves of 11.5 billion barrels.[3]

See also

References

  1. ↑ "Madagascar, geology Extractive Industries Source Book". Extractive Industries. Retrieved October 23, 2016.
  2. 1 2 Schlüter, Thomas (April 19, 2008). Geological Atlas of Africa: With Notes on Stratigraphy, Tectonics, Economic Geology, Geohazards, Geosites and Geoscientific Education of Each Country. Springer Science & Business Media. Retrieved October 23, 2016.
  3. 1 2 "Extractive Industries: Mining". Extractive Industries. Retrieved October 23, 2016.
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