Geophysical reassessment of the Azimuth 125° Lineament: emplacement model and propagation of its dikes

Abstract

This study analyzes the area along the Azimuth 125° Lineament (Az 125°) supposed to occur from Rondônia 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., Goiás and Alto Paranaíba 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 Rondônia 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.

Cryptic trans-lithospheric fault systems at the western margin of South America: implications for the formation and localization of gold-rich deposit superclusters

“…Map of South America showing the outline of Archean-Proterozoic cratons, the main geochronologic provinces of the Amazonian craton, the limits of orogenic fronts (i.e., Transamazonian, Rio Negro, Sunsás-San Ignacio, Andes), the location of pre-Neoproterozoic basement inliers within the Andes (a-j), the location of Neoproterozoic ophiolites (u-z) and oceanic tracts, and recent oceanic ridges and fracture zones (compiled and modified after Jacques, 2003;Loewy et al, 2004;Santos et al, 2004;Cordani et al, 2010;2016;Teixeira et al, 2010;Bettencourt et al, 2010;Rapela et al, 2010;Ibanez-Mejia et al, 2011;Escayola et al, 2011;Tassinari et al, 2011;Casquet et al, 2012;Rizzotto and Hartmann, 2012;de Castro et al, 2014;Ramos et al, 2015;Kroonenberg et al, 2016;Ramos, 2018;da Silva et al, 2018;Gómez et al, 2019;Motta et al, 2019;Rocha et al, 2019;López et al, 2020;Nedel et al, 2021;Assis et al, 2021;Wiemer et al, 2022). Note: both the extended (including the Parana basin, PPB; Santos et al, 2019), and the limited extent (RdlP limit; Rapela et al, 2011) of the Rio de la Plata craton are indicated.…”

“…The Brasiliano orogeny included the collision of Archean-Paleoproterozoic cratonic blocks with, and to the east of, the Amazonian Craton, marking the closure of the Clymene and the Goias-Pharusian oceans, as well as the Adamastor Ocean further to the east (Figure 4D; e.g., Caxito et al, 2020). The polyphase orogeny included the formation of the Brasilia fold belt between the Goias Archean block and outboard magmatic arc and the São Francisco-Congo Craton, the collision of the São Francisco-Congo Craton with the Rio de la Plata-Parana cratonic block, which possibly led to the early establishment of the AZ125 lineament, and the formation of the Borborema belt between the northern São Francisco-Congo Craton and the Sahara Metacraton (e.g., Rocha et al, 2019;Caxito et al, 2020). The latter composite of tectonic entities collided with the Amazonian Craton and West African Craton during closure of the Clymene Ocean, which ultimately resulted in the formation of the Paraguai-Araguaia belts and the tectonic emplacement of Neoproterozoic ophiolites around the eastern margin of the Amazonian Craton.…”