Claudio de Morisson Valeriano, Caio Vinicius Gabrig Turbay, Henrique Bruno, Antonio Simonetti, Monica Heilbron, Samuel Moreira Bersan, Rob Strachan. Paleo- and Mesoarchean TTG-sanukitoid to high-K granite cycles in the southern São Francisco craton, SE Brazil[J]. Geoscience Frontiers, 2022, 13(5): 101372. DOI: 10.1016/j.gsf.2022.101372
Citation: Claudio de Morisson Valeriano, Caio Vinicius Gabrig Turbay, Henrique Bruno, Antonio Simonetti, Monica Heilbron, Samuel Moreira Bersan, Rob Strachan. Paleo- and Mesoarchean TTG-sanukitoid to high-K granite cycles in the southern São Francisco craton, SE Brazil[J]. Geoscience Frontiers, 2022, 13(5): 101372. DOI: 10.1016/j.gsf.2022.101372

Paleo- and Mesoarchean TTG-sanukitoid to high-K granite cycles in the southern São Francisco craton, SE Brazil

  • The generation of the continental crust is widely accepted to have taken place predominantly in the Archean, when TTG magmatism associated with greenstone-belt supracrustal succession development was typically followed by emplacement of high-K granites before crustal stabilization. This study focuses on the Campos Gerais complex (CGC), which is an Archean granite-greenstone belt lithological association in a tectonic window located in the southwesternmost portion of the São Francisco craton (SFC). The CGC is an important segment of Paleo- to Mesoarchean continental crust to be integrated into paleogeographic reconstructions prior to the transition into the Paleoproterozoic. This investigation reports field relationships, 28 major and trace element compositions, U-Pb (zircon) geochronological results, and Hf and Sm-Nd isotope data for orthogneiss and amphibolite samples. The results indicate that the CGC records a complex Archean crustal evolution, where voluminous 2.97 Ga TTG tonalites and trondhjemites (εNd(t)=-4.7; TDM=3.24 Ga) were followed by 2.89 Ga sanukitoid tonalite production (εNd(t)=-1.9; TDM=3.02 Ga), broadly coeval with the development of the Fortaleza de Minas and Pitangui greenstone-belts. These events are interpreted to represent the initial stage of an important subduction-accretion tectonic cycle, which ended with the emplacement of 2.82-2.81 Ga high-K leucogranites and migmatization of the TTG-sanukitoid crust, with hybrid and two-mica, peraluminous compositions (εNd(t)=-8.0 to-8.6; TDM=3.57-3.34 Ga). The presence of inherited zircons with 207Pb/206Pb ages of 3.08 Ga, 3.29 Ga, 3.55 Ga and 3.62 Ga indicates that the Mesoarchean tectonic processes involved reworking of Meso- to Eo-archean crust. Renewed TTG magmatism took place at ca. 2.77 Ga represented by juvenile tonalite stocks (εNd(t)=+1.0 to-1.5; TDM=2.80-2.88 Ga) which intrude the TTG-greenstone belt association. Crustal stabilization was attained by 2.67 Ga, allowing for the emplacement of within-plate tholeiitic amphibolites (εNd(t)=-3.1; TDM=2.87 Ga). The CGC shows important tectonic diachronism with respect to other Archean terrains in the southern São Francisco craton, including an independent Meso- to Neoarchean crustal evolution.
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