Browsing by Author "Cordeiro de Sousa, Isabela Moreno"

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    Further evidence of Rhyacian arc magmatism in the basement of the Brasilia Belt, western Sao Francisco pericraton
    (2020) Filgueiras, Bernardo de Carvalho; de Oliveira, Claudinei Gouveia; Cordeiro de Sousa, Isabela Moreno; Cordeiro, Pedro
    A recently mapped area in central Brazil revealed a slice of Paleoproterozoic basement within Neoproterozoic metasedimentary rocks of the Brasilia Belt. The area, named here the Artulandia area for its proximity to the homonymous village, contains metatonalites and metagranodiorites in tectonic contact with a meta-volcanosedimentary sequence that encompasses felsic, intermediate and mafic metavolcanic rocks interlayered with clastic and chemical metasedimentary rocks. A sample of felsic orthogneiss from the metavolcano-sedimentary sequence, yielded a U-Pb zircon age of 2142 +/- 4.4 Ma, which is interpreted as the crystallization age of the volcanic protolith. Samples from the metagranite unit returned U-Pb zircon ages of 2130 +/- 7.4 Ma for a biotite metatonalite, 2157 +/- 9 for a biotite metagranite, and 2147 +/- 5 Ma for a sulfide-bearing meta-granodiorite, indicating roughly contemporaneous plutonic activity. Whole-rock geochemistry shows calcalkaline signatures for both units, and trace element results are compatible with an extensional setting, such as back-arc or intra-arc, for the metavolcano-sedimentary sequence, and a magmatic arc system for the metagranite unit. These rocks were generated in an episode of juvenile crust formation, as suggested by epsilon(Nd)(2.14Ga) values between 0 and +3.18. Based on lithological association, age and chemical signature, we suggest that the studied rocks represent a lateral continuation of the Campinorte Arc beyond the Rio Maranhao Thrust. Thus, the occurrence of Campinorte Arc rocks on both sides of the thrust argues against the thrust being a Neoproterozoic collisional suture. The geology of the Artulandia area in the context of the Campinorte Arc attests to the complexity of the Rhyacian amalgamation that generated the Sao Francisco Paleocontinent during a Rhyacian Orogeny.
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    The 2.26 to 2.18 Ga Arc-Related Magmatism of the Almas-Conceicao do Tocantins Domain: An Early Stage of the Sao Francisco Paleocontinent Assembly in Central Brazil
    (2020) Saboia, Andre Menezes; de Oliveira, Claudinei Gouveia; Dantas, Elton Luis; Scandolara, Jaime Estevao; Cordeiro, Pedro; Rodrigues, Joseneusa Brilhante; Cordeiro de Sousa, Isabela Moreno
    Paleoproterozoic (Rhyacian) rocks dominate within the basement of the Neoproterozoic Brasilia Belt and their genesis has been attributed to the orogenic amalgamation event that assembled the Sao Francisco-Congo paleocontinent from 2.18 to 2.07 Ga. However, the tectonic framework and genesis of the building blocks involved in this continent-wide amalgamation event are unclear, particularly in relation to terranes from the Almas-Conceicao do Tocantins Domain, in the Goi ' as Massif, central Brazil. This work provides new whole-rock chemical and geochronological data, which indicate the generation of felsic to intermediate magmatism around 2.29 and 2.28 Ga corresponding to the Monzogranitic Unit and the Quartz-dioritic Suite, respectively. Later magmatic events occurred in a continental arc setting, around 2.26 to 2.2 Ga represented by metaluminous to peraluminous I-type magmatism of the Granodioritic to Tonalitic Suite (GTS) and the Serra do Boqueirao Suite. Around 2.2 to 2.18 Ga a peraluminous I-type magmatism took place and generated the Peraluminous Suite (PS). Our data show that after an earlier Siderian magmatic event around 2.45-2.34 Ga, reported in previous works, the Almas do Conceicao do Tocantins Domain oversaw additional Rhyacian events of magmatic activity around 2.29 Ga to 2.18 Ga. Regional geotectonic correlations with the Sao Francisco Craton and other pericratonic belts indicate coeval magmatic events taking place during the early stages of the Columbia Supercontinent amalgamation.
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    The Siderian crust (2.47-2.3 Ga) of the Goias Massif and its role as a building block of the Sao Francisco paleocontinent
    (2020) Saboia, Andre Menezes; de Oliveira, Claudinei Gouveia; Dantas, Elton Luiz; Cordeiro, Pedro; Scandolara, Jaime Estevao; Rodrigues, Joseneusa Brilhante; Cordeiro de Sousa, Isabela Moreno
    The basement of the northern Brasilia Belt, in Central Brazil, is dominated by large volumes of TTG magmatism generated during the Early Paleoproterozoic, and represents a continental block formed prior to the welding of the Sao Francisco paleocontinent during the Rhyacian, holding important information concerning the mechanisms and products of Paleoproterozoic crustal growth and amalgamation. New U-Pb zircon geochronological data was obtained from metagranitoids and mafic-ultramafic intrusions from the Almas-Conceicao do Tocantins Domain (ACTD). This was coupled with geochemical data from the metagranitoids to better constrain the processes of continental crust evolution in this region during the Siderian period. Two main plutonic episodes were recognized in the mapped area: (i) an early suite (2.47 Ga) dominated by tonalites and trondhjemites with subordinate biotite granites (Ribeirao das Areias Complex - RAC); and (ii) a later suite (2.30 Ga) including tonalites and trondhjemites (Ribeirao Itaboca Suite - RIS). Most of the RAC trondhjemite-tonalite-granodiorite (TTG) rocks are marked by fractionated REE patterns with high (La/Yb)(N) = 15-107 and samples have medium to high Sr/Y ratio (28-257). These TTG include both high- and low-Al types and high- and medium-pressure groups. The RIS TTG suite displays higher HREE contents with high (La/Yb)(N) = 65-89 and high Sr/Y ratio (59-95) and contains the high-Al type and the medium pressure group. In spite of the wide age gap between them, both RAC and RIS are characterized by TTG rocks formed in a subduction-like tectonic setting. The biotite granites are related to a magmatic stage after the TTG formation. Mafic rocks of the Gameleira Suite have an abundance of zircon, interpreted as crustal contamination, with dominant (207)pb/(206)pb age populations of 2.48 and 2.30 Ga, and are interpreted to be associated with an extensional magmatic event following the Siderian period. Regional geotectonic correlations within the Sao Francisco Craton based on data compiled from the literature indicate a significant volume of Siderian crust generation that has been overlooked in continental amalgamation models and that TTG magmatism is a more common geochemical signature in Paleoproterozoic rocks than has been previously suggested.