Favorability potential for IOCG type deposits in the Riacho do Pontal Belt: new insights for identifying prospects of IOCG‑type deposits in NE Brazil

Abstract

Archean iron oxide-copper-gold (IOCG) deposits have been systematically described in the world class Carajás IOCG district, Amazonian region of Brazil. More recently, several Neoproterozoic (ca 1.13 to 0.96 Ga) IOCG deposits have been identified in the Riacho do Pontal mobile belt situated in the Borborema Province on the northern border of the São Francisco Craton. In these Neoproterozoic deposits, several copper occurrences have been mapped along shear zones. The primary hydrothermal mineral associations resulted in sodic, calcic-potassic and potassic-ferric alteration. The copper grades of the main prospects range between 0.5 and 0.8 wt% with an average of ~0.7 wt%. This study uses a fuzzy logic approach to create regional to district scale predictive exploration models. Specifically, multi-parameter geologic, geochemical, remote sensing, and airborne geophysical data incorporated into regional and local models predict known copper mineralization and, importantly, highlight prospective areas for new IOCG targets in the Borborema Province. At district scale, multiple higher resolution geological, soil geochemical, and airborne geophysical data that cover the Riacho do Pontal Belt, were analyzed. A drilling exploration program implemented on target RIA4 validated these model results. Drill hole RIA4-DH0001 crosscuts a mineralized zone with 32 m of 1.15 wt% copper.