CHARACTERIZATION OF THE BOCAINA PHOSPHATIC TARGET, EASTERN OF PARNAÍBA BASIN: AN INTEGRATED SYSTEMATIC OF SEDIMENTARY FACIES, MINERALOGY, GEOCHEMISTRY AND REFLECTANCE SPECTROSCOPY

Abstract

Sedimentary phosphate ores in northeastern Parnaíba Basin are known since the 1970s due to researches conducted by CPRM and DNPM. Phosphatic ores are found mainly in the Devonian sequence associated with Pimenteira Formation rocks. Because there is a need for the detailing and discovery of new targets in the Bocaina and also a necessity to evaluate prospecting methods, this research aims to characterize sedimentological and spectral of phosphatic rocks in Pimenteira Formation using X-ray diffraction (XRD), portable X-ray fluorescence (XRF) and reflectance spectroscopy (ER). The rocks were individualized into four sedimentary facies: Sm (massive sandstone), Sp (planar sandstone), Fm (massive mudstone and siltstone) and Fl (laminated mudstone and siltstone). The depositional environment appears to be evolving from a distal deltaic environment for a shallow-platform in a transgressive system. P anomalies (> 450 ppm) are associated with recognized phosphate levels between units. By XRD analysis, carbonate hydroxyapatite is the main phosphate phase found in the study area and kaolinite, illite, smectite, and the main phyllosilicates used. Reflectance spectroscopy analysis made it possible to individualize four sedimentary facies and suggests that kaolinite, illite, and goethite can be used as endmembers in spectral mapping in the region.