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The Lithological Profile of the Deposit

The bauxites of Trombetas are associated with the plateaus, high areas with relatively plan ridges and elevations between 200 and 160 meters, which were formed from lateritization processes acting on sedimentary rocks (which contained aluminous minerals) from the Paleogene period (about 40 million years).

The mineralization of bauxite occurs at the top of the plateau and is normally covered by a layer of clay, 4 to 10 meters thick. However, near the edges of the plateaus, bauxite might even be outcropping in the soil.

Bauxite is a rock made up of different minerals (gibbsite, kaolinite and quartz), the first being the source of aluminum.

A typical bauxitic profile consists of the following horizons:

  • 4 - organic soil with a maximum thickness of 0.5m;
  • 3 - yellow clay covering most bauxitic profiles, consisting of kaolinite (80%) and quartz, with a maximum thickness at the center of the plateau, decreasing to its edges;
  • 2 - bauxitic layer with an average thickness of 4 m, subdivided into three subhorizons:
  • 2c – nodular bauxite;
  • 2b – ferruginous laterite;
  • 2a – massive to granular bauxite;
  • 1 - variegated clay.
The lithological profile of the deposit  
Ore Characteristics
Gibbsite 81%
Organic Carbon Negligible
Zinc Negligible
Mercury Negligible

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