Geologic map and observed total-field magnetic anomaly data from the west of the state of Rio de Janeiro, Brazil. (a) Simplified geologic map showing the main groups and dykes that outcrop in the region. In pink is the Cabo Frio domain, dark red is the Italva group, purple is the São Fidelis group, orange is the Rio Negro complex, grey is the syn-collisional magmatism, red is the post-collisional magmatism, green are alkaline intrusions, yellow are the Quaternary deposits and the dashed lines are mafic and alkaline dykes. (b) The aeromagnetic flight-line data, overlaid by the outlines of the post-collisional magmatism and alkaline intrusions (solid black lines) and dykes (dashed lines). The geologic map was modified from Heilbron et al. (2016) and Dantas et al. (2017).