In Southeastern Bolivia,the field relations,geochemical and isotopic data collected in the Manomóarea,along with the occurrence of apatite-rich lenses,carbonate blocks and the extensive enrichment in U,Th and REE...In Southeastern Bolivia,the field relations,geochemical and isotopic data collected in the Manomóarea,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.展开更多
基金financial support from the Italian MURST-PRIN 2008 and the Brazilian agencies,FAPESP and CNPq.
文摘In Southeastern Bolivia,the field relations,geochemical and isotopic data collected in the Manomóarea,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.
