Abstract
This study analyzes the area along the Azimuth 125° Lineament (Az 125°) supposed to occur from Rondonia to Rio de Janeiro, in Brazil. The lineament is an important structural feature in association with great carbonatite and kimberlite complexes in Brazil (e.g., Goias and Alto Paranaiba Alkaline Provinces), consisting of extensive NW-SE oriented faults. The origin of the Az 125° Lineament and its dikes emplacement are widely discussed. The main intention of this work is to propose a model of emplacement of the Az 125° dikes. Also, some important magnetic characteristics of the lineament are presented. The magnetic data clearly define the features of the Az 125° in the southern portion of the study area, but we found no magnetic geophysical evidence that this lineament occurs from the Mato Grosso state to the Rondonia state. The dikes that compose the great Az 125° feature have distinct magnetic attributes, as their polarities (normal and reversed). It is suggested that the alternating polarity is due to local re-magnetization sometime after their intrusion. It is proposed that the dikes were positioned along a zone of lithospheric weakness and their propagation was facilitated due to the occurrence of mid-crustal axial feeder chambers.
Highlights
The Azimuth 125° (Az 125°) Lineament was first described by Bardet (1977) as a sequence of diamond deposits aligned from Abaeté (Minas Gerais) to Rio Machado (Rondônia) oriented on an NW-SE belt
It was important to explain the expression of such great continental-scale dike swarms and to show the efficiency of geophysical methods for mapping areas of dike swarms where they are set in the subsurface
We found no relevant geophysical evidence that this lineament occurs between the states of Mato Grosso and Rondônia
Summary
The Azimuth 125° (Az 125°) Lineament was first described by Bardet (1977) as a sequence of diamond deposits aligned from Abaeté (Minas Gerais) to Rio Machado (Rondônia) oriented on an NW-SE belt. Bardet (1977) defined it as a belt with 1800 km long and about 200 to 300 km wide. The Azimuth 125° (Az 125°) Lineament was first described by Bardet (1977) as a sequence of diamond deposits aligned from Abaeté (Minas Gerais) to Rio Machado (Rondônia) oriented on an NW-SE belt. Chaves and Neves (2005) called it as Pará de Minas Dike Swarm and Schobbenhaus et al (1975) named the Az 125°, in the Triângulo Mineiro region, as the Alto Paranaíba Lineament. As similar as Bardet (1977), Gonzaga and Tompkins (1991) indicated that Az 125° occurs in the state of Rondônia, they pointed that the lineament follows to the state of Rio de Janeiro (Fig. 1)
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