Caracterização geológica e análise do potencial cuprífero em ocorrências na Província Pegmatítica da Borborema.

Abstract

The Borborema Pegmatite Province (PPB) is recognized for comprising a complex geological framework, encompassing several lithologies containing a set of mineralized pegmatites of industrial and gemological interest. However, even with the increase in exploratory and research activities, there is little information regarding the occurrences of cupriferous mineralization in the PPB, since the presence of this metal in pegmatites and their surrounding rocks is not common. Therefore, this work aimed to carry out geological studies through the characterization of samples collected in the region, as well as analysis, both from a petrographic and mineral characterization point of view, in order to map, understand the mode of occurrence and pattern associated with minerals that carry this metal present in PPB. The macroscopic and petrographic study identified the majority presence of copper minerals of secondary origin, such as malachite (Cu2CO3(OH)2), azurite (Cu3(CO3)2(OH)2), chrysocolla Cu2-xAlx(H2-xSi2O5)( OH)4·nH2O and, occasionally, primary sulfides such as bornite (Cu5FeS4) and digenite (Cu9S5), hosted mainly in pegmatites in the form of patinas or as infiltrations, resulting from possible supergene alterations, or along the foliations in the surrounding rocks of the Formation Seridó or Ecuador. Some of these occurrences were confirmed through XRD analysis of mineral phases, including rock-forming minerals. The XRF analysis showed the copper content reaching 24.94% CuO. Using SEM-EDS, the presence of primary copper sulfides cut by malachite venules was identified, in addition to the predominance of minerals of secondary origin filling fractures, in the form of anhedral crystals included in the pegmatite matrix, or even accompanying the foliation or fractures in schists and pegmatites. Magnetometric and gamma spectrometric maps of the investigated area were generated, with the help of the lithological map, highlighting local variations that made it possible to delineate the contact between large structures and oriented segments by taking into account the high and low values of anomalies present. When integrating the results obtained in this study, similarities were noted in the pattern of cupriferous mineralizations, where the mineral phases of this metal in pegmatites and emplacements are the result of complex chemical processes and compositional controls that deposited the occurrences in the form, mainly, of secondary minerals. The results obtained in this research are relevant, as they can be taken as a basis for future mineral prospecting work related to copper in PPB.