Química mineral de apatita dos depósitos São Jorge e São Chico, Província Mineral do Tapajós, Cráton Amazônico

Abstract

The geochemical signatures of certain accessory minerals such as zircon, apatite, titanite, and rutile can serve as valuable petrological and metallogenetic indicators of mineralized bodies or economically significant deposits. Apatite, the focus of this study, is a common accessory phase in granitoid rocks and is considered a resistate indicator mineral capable of providing insights into the geological conditions to which its host rock was subjected. In this work, apatite crystals from moderately to intensely hydrothermally altered granitoid rocks hosting the São Jorge (DSJ) and São Chico (DSC) gold deposits – both located in the Tapajós Mineral Province (TMP) - were analyzed. The main objective of this research is to identify the morphological features and geochemical signatures of these crystals, assessing the parameters that may serve as potential indicators for this type of mineralization. To determine the mineral chemistry of apatite, semi-quantitative analyses were performed for elements commonly incorporated in its structure, such as O, F, Ca, P, Na, Si, Sr, Fe, Cu, Pd, Ag, Hg, Pb, Bi, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Ho, and Yb. The resulting data were treated using specific diagrams to distinguish mineralized rocks from barren ones chemically. Morphologically, subhedral to anhedral apatite crystals, locally more fractured and corroded, are dominant in the most altered and mineralized zones. Compositionally, these crystals exhibit higher concentrations, or a tendency toward enrichment, in F, Y, Hg+Pb+Bi, and F/Cl. The effectiveness of this methodology demonstrates its potential as a complementary tool for mineral exploration in regions beyond the Tapajós Domain.