Anomalia de ouro em sedimentos de corrente na região das rochas metassedimentares da Unidade Independência, Complexo Ceará, norte da Província Borborema

Abstract

Anomalous stream sediment gold contents have been found during regional geochemical survey in the 1:100.000 Independência and Várzea do Boi sheets, Ceará State, northeast Brazil. The highest geochemical gold values occur within the domain of metasedimentary rocks of the Neoproterozoic Independência Unit, Ceará Complex, north of Borborema Province. The effect of outlier values is observed in the boxplot analysis of gold content, with a lognormal distribution and a population of values in excess of 3 ppb. The values between 3 and 6 ppb of gold in stream sediment samples are very similar to concentrations found in famous mineralized areas worldwide, such as the gold-bearing domains of the Quadrilátero Ferrífero region, central Brazil. According to our preliminary interpretations on structural geology and aeromagnetic data, we might speculate the possibility of gold mineralization associated with the main NW-SE trending shear/fault zone, later displaced by a dextral NE-SW shear/fault zone.