ausblenden:
Schlagwörter:
Borborema Province, complex REL pegmatites, parental granites, possiblity of related REE-deposits
Zusammenfassung:
Electron probe microanalyses (EPMA) of rare earth elements (REE) in xenotime, monazite, zircon, thorite and uraninite from different facies of pegmatitic granites supposed to be parental to complex rare element (REL) pegmatites of the Borborema Province (BPP) in Northeastern Brazil indicated monazite and xenotime as most common heavy accessory phases with significant enrichment in these elements. Averages of Nd and Eu in monazite are respectively 13.06 and 0.54 wt. % oxide and mean contents of Dy, Yb, Gd, and Er (respectively 4.77, 3.39, 3.15 and 3.86 wt. % oxide) are found in xenotime. The other common accessory minerals like zircon, thorite, uraninite showed no significant enrichment in REE. Low xenotime and monazite contents in pegmatitic granites and their irregular distribution and reserves in pegmatites, turn the extraction directly from the hard rock impracticable. The REE-enriched minerals could however be enriched in and easily extracted from alluvial placers within the province. Ion adsorption REE enrichment could hypothetically form in parental granites of the pegmatites at the intersection with paleogeomorphologic plateaus culminated by the early Cenozoic siliciclastic Serra dos Martins Formation, because at this unconformity it is possible to observe an intensive kaolinization of the basement and lateritization of the covering sediments.
