Fosfatos da região de Santa Luzia (nordeste do estado do Pará)

Abstract

Four occurrences of aluminum phosphates in Santa Luzia, Pará State. Brazil were studied in terms of their field relations, mineralogy and trace element contents. Crandallite is the dominant phosphate and less frequently wavellite can be found. The phosphates occur in metamorphic pre-Cambrian rocks of the Gurupi Group and are essentially structurally controled. A disseminated level of crandallite at the basis of the metamorphic sequence, problably originated from the alteration of sedimentary apatite, is considered to be the source of phosphate which was dissolved by solutions flowing through it. These phosphorous-rich solution moved upward and precipitated phosphate-bearing minerals in the upper units of that metamorphic sequence. The occurrences have no economical value in the mapped area but the presence of a crandallite level with about 16 wt. % P2O5 leads to consider prospecting for phosphate in the neighboring areas to be attractive.