In Southeastern Bolivia, the field relations, geochemical
and isotopic data collected in the Manomó
area, along with the occurrence of apatite-rich lenses,
carbonate blocks and the extensive enrichment in U, Th
and REE probably point to a complex history:
1. An old BIF-like formation with E-W orientation,
formed and metamorphosed during Mesoproterozoic
times, cuts an older compressive
structure at the border of the Amazonic craton;
2. Probable intrusion and fenitization by carbonatitic
magma in (Early, Late?) Cretaceous times;
3. Lateritization processes and formation of a thick
duricrust in Tertiary-Quaternary times.
A more detailed field sampling, as well as additional
systematic and extensive geological, mineralogical,
petrographic and geochemical studies are required to
obtain a more accurate regional picture.
