Tectono-Magmatic Evolution of the Amazonian and São Francisco Cratons: Insights From Thermochronological and Geochronological Data

Dear Colleagues,

The São Francisco and Amazonian Cratons are among the most extensively studied geological formations on Earth. Their importance is highlighted by their expansive areas, intricate geological histories, tectonic features, and rich mineral and energy resources. The São Francisco Craton (SFC) is especially significant for exploring aspects of Archean geology, enhancing our understanding of Earth's early geodynamics, a period during which large portions of the continental crust were formed and stabilized. The oldest components detected in the São Francisco Craton (SFC) include tonalite–trondhjemite–granodiorite (TTG) rocks, granite–greenstone associations, and high-grade metamorphic rocks. These features provide an isotopic record dating from approximately 4.1 to 2.5 billion years ago (Ga). Archean rock units can be found in both the southern and northern parts of the craton. Additionally, smaller exposures are visible within a fault-bounded block in the central region of the Paramirim Aulacogen, located in the north area of the craton, as well as in tectonic windows within the interior and along the edges of the São Francisco basin. Thermochronological data in the São Francisco Craton (SFC) are primarily concentrated in its northeastern region, corresponding to a segment of the Brazilian passive margin. The first cooling event, which occurred approximately between 130 and 95 million years ago (Ma), is linked to the formation of local relief and changes in base level due to the rifting process, as evidenced by samples collected along the coast. The second cooling event, occurring around 70 to 55 Ma, is interpreted as a denudation response to post-rift tectonic reactivation. Additionally, AFT (apatite fission track) dating results from the continental interior segment of the SFC, particularly in its southern areas that are far from the Atlantic Ocean, reveal two distinct cooling phases. The first phase occurred during the Paleozoic era, and the second phase took place from the Late Cretaceous to the Paleocene. The Paleozoic cooling phase appears to have affected several areas of the West Gondwana basement, in addition to the SFC itself. On the other hand, the Amazonian Craton is one of the most complete examples of continental crust growth from the Archean to the Mesoproterozoic eras. The geological evolution during this period involved the accretion of juvenile materials related to subduction and fragments of possible exotic terranes. Despite significant advances in research, the ages, structures, and compositions of rock units and orogenic events within this craton are still not completely understood. The Amazonian Craton is essential for understanding the history of supercontinents, as its accretionary and collisional processes are linked to the formation of supercontinents throughout Earth's history. Based on geological, structural, and paleomagnetic evidence, researchers have proposed reconstructions of paleocontinents for both the Archean and more recent periods. Consequently, the Amazonian Craton has played a crucial role in major paleogeographic reconstructions, including the formation of the Columbia and Rodinia supercontinents. Thermochronological data indicate that the Amazonian craton underwent significant denudation, characterized by key exhumation and cooling events. Analysis of apatite thermochronology in Paleoproterozoic crystalline rocks reveals three distinct cooling phases: i) a mid-to-late Paleozoic cooling episode occurring between 392 and 270 million years ago (Ma); ii) a Triassic heating event that took place between 260 and 180 Ma; and iii) another cooling phase during the Cretaceous period around 100 Ma. Additionally, ages identified along the eastern edge of the Amazonian craton range from the Upper Carboniferous (309 Ma) to the Lower Cretaceous (137 Ma). The Paleozoic ages suggest a significant degree of denudation within the craton's interior, which appears to be largely uncorrelated with tectonic activities. The Cretaceous ages align with the convergent movement of the Andean subduction zone and the opening of the eastern equatorial Atlantic. Current models indicate that the Late Cretaceous experienced renewed denudational cooling, interpreted as a consequence of varying relative plate motions between the South American and African plates. This reactivation of Proterozoic shear zones resulted in intracontinental deformation across the cratonic area during that period.

This Special Issue will bring together significant contributions from thermochronological and geochronological studies that enhance our understanding of the tectonic and magmatic evolution of the Amazonian and São Francisco cratons.

Prof. Dr. Airton Natanael Coelho Dias
Prof. Dr. Cândido Augusto Veloso Moura
Guest Editors

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• São Francisco Craton
• Amazonian Craton
• thermochronology
• geochronology
• Archean geology
• Earth's geodynamics
• TTG rocks
• geological evolution
• supercontinents