Precambrian Research 249 (2014) 273–287 Contents lists available at ScienceDirect Precambrian Research jo ur nal homep ag e: www.elsevier.com/locate/precamres Geophysical characterization of the Azimuth 125 ◦ lineament with aeromagnetic data: Contributions to the geology of central Brazil Loiane Gomes de Moraes Rocha ∗ , Augusto César Bittencourt Pires, Adriana Chatack Carmelo, José Oswaldo de Araújo Filho Universidade de Brasília, Instituto de Geociências, Campus Darcy Ribeiro, CEP: 70.910-900 Brasília, Distrito Federal, Brazil a r t i c l e i n f o Article history: Received 12 December 2013 Received in revised form 28 April 2014 Accepted 13 May 2014 Available online 24 May 2014 Keywords: Azimuth 125 ◦ lineament Magnetometry Alto Paranaíba Alkaline Province Goiás Alkaline Province Basic dikes a b s t r a c t This study analyzes a portion of the Azimuth 125 ◦ lineament (Az 125 ◦ ), located in the Brazilian states of Goiás and Minas Gerais, based on its magnetic signature and previous studies. In particular, the deter- mination of a chronology of events that shaped the Az 125 ◦ lineament is the focus of this contribution. Geological provinces with highly economically valuable mineralizations occur along Az 125, including the most important carbonatite and kimberlite complexes in Brazil. Az 125 ◦ is the main structural feature associated with these complexes, consisting of an extensive set of NW-SE oriented faults (approximately 850 km long and 70 km wide), however it is not mapped on geological maps at a regional scale as a continuous structural feature, because it is not consistently visible on the surface or in satellite images. Magnetic signature characterizes the lineament as a set of linear features with regional continuity in the subsurface. It is characterized by a higher magnetic susceptibility response that contrasts with the response exhibited by surrounding host rocks. Field data support geophysical data: occasional outcrops resulting from active erosion reveal dikes formed by gabbroic rocks and diabase and define the Az 125 ◦ lineament as a set of dikes of different ages. Other magnetic anomalies that occur along Az 125 ◦ are associated with intrusive rocks from the Goiás and Alto Paranaíba alkaline provinces. Based on magnetic signatures and mapped igneous rocks chronology, the Az 125 ◦ is partitioned, within the study area, into three main systems (called L1, L2, and L3). This subdivision, in conjunction with the dates assigned to various basic dikes within the azimuth, reveals that the evolution of the azimuth can be associated with three events. The first event occurred during the Brasiliano (950–520 Ma). The second event occurred during the Gondwana fragmentation (starting circa 180 Ma). The third event is related to the tectono- magmatic activity of The Trindade plume (90–80 Ma). We posit that the L1 system includes the older dikes, and the L3 system includes the youngest dikes; the L2 system which is intersected by L3, is there- fore, of intermediate age. The determination of a chronology of events that characterizes the segmented structure of the Az 125 ◦ lineament, here defined as L-systems (L1, L2, and L3), based on both geological and geophysical data, and not yet reported in earlier scientific articles, is the main contribution of this study. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Bardet (1977) first described the Azimuth 125 ◦ (Az 125 ◦ ) linea- ment as a succession of diamond deposits that were aligned from Abaeté (state of Minas Gerais) to Rio Machado (state of Rondô- nia) on a belt with an NW-SE orientation. This belt is 1800 km ∗ Corresponding author at: SQSW 303 Bloco G Apartamento 201, Setor Sudoeste, CEP: 70.673-307 Brasília, Distrito Federal, Brazil. Tel.: +55 61 8216 8711/3344 4469. E-mail addresses: loianemoraes@hotmail.com (L.G.d. Moraes Rocha), acbpires@unb.br (A.C.B. Pires), chatack@unb.br (A.C. Carmelo), oswaldo@unb.br (J.O.d. Araújo Filho). long and approximately 200–300 km wide. Az 125 ◦ lineament is known as the Pará de Minas Dike Swarm (Chaves and Neves, 2005) and as Alto Paranaíba lineament in the Triângulo Mineiro region (Schobbenhaus et al., 1975). According to Gonzaga and Tompkins (1991), Az 125 ◦ occurs from the state of Rondônia to the state of Rio de Janeiro (Fig. 1). Pereira et al. (2008) indicated that this azimuth is one of the most significant metallotects for kimberlite diatreme intrusions in Brazil and is a set of faults that operated as a conduit for kimberlite magma. In Brazil, alkaline–carbonatite complexes and kimberlite provinces are located in fault zones and arched areas on the edges of the Paraná, Paranaíba (Almeida, 1986), and Amazonas basins (Biondi, 2003; Fig. 1) along the three main structural lineaments, http://dx.doi.org/10.1016/j.precamres.2014.05.005 0301-9268/© 2014 Elsevier B.V. All rights reserved.