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.

Mapping New IOCG Mineral Systems in Brazil: The Vale do Curaçá and Riacho do Pontal Copper Districts

“…Geologic characteristics of the world-class Carajás IOCG deposits are distinct and show a complex interplay between geologic structures, fluid flows, and forms of hydrothermal alteration [12][13][14][15][16][17][18][19][20][21][22][23][24]. For example, the flow of mineralized fluids along regional shear zones is responsible for the "sigmoidal-shape" structural pattern and magnetic signature of the Carajás province and Vale do Curaçá district [6,14,20,25].…”

“…High concentrations of sulfides, however, can also occur in norite-and biotite-rich shear rocks and in calcsilicate rocks. Recently, new geologic [24,[26][27][28][29], tectonic [26,30], isotopic, and geochemical [27] studies have shown evidence that copper mineralization is related to the diverse family of IOCG deposits. In the last 10 years, high-resolution airborne geophysical surveys have been completed.…”

“…Both the Vale do Curaçá and the Riacho do Pontal copper districts can be considered among the most important areas for IOCG prospectivity in Brazil [24,26,27]. Globally, IOCG deposits are a significant source of base and precious metals, which is key to supporting and expanding economic growth.…”

“…Despite these important metal endowments, there is a lack of knowledge that would provide broad insight into how the deposits formed and concerning the larger mineral systems that were active during their emplacement. A previous study [24] used multiparameter geologic and geochemical remote sensing and airborne geophysical data to statistically identify new areas of IOCG prospectivity Minerals 2020, 10, 1074 3 of 29 related to shallow mineralization along the northern border of the São Francisco Craton (Figure 1). Areas of known mineralization and targets of new prospectivity were identified in a previous data integration study [24].…”

“…A previous study [24] used multiparameter geologic and geochemical remote sensing and airborne geophysical data to statistically identify new areas of IOCG prospectivity Minerals 2020, 10, 1074 3 of 29 related to shallow mineralization along the northern border of the São Francisco Craton (Figure 1). Areas of known mineralization and targets of new prospectivity were identified in a previous data integration study [24]. The study presented here expands on this previous work in three different ways.…”