Tonalite–Trondhjemite and Leucogranodiorite–Granite Suites From the Rio Maria Domain, Carajás Province, Brazil: Implications For Discrimination and Origin of the Archean Na-Granitoids

Abstract

Abstract The Mesoarchean Na-granitoids exposed in the Rio Maria domain, southeastern Amazonian craton, are represented by tonalite–trondhjemite and leucogranodiorite–granite suites. The 2.98–2.92 Ga tonalite–trondhjemites are the most voluminous rock type in the Rio Maria domain and host 2.86 Ga leucogranodiorite–granite plutons. These rocks share common geochemical characteristics, such as relatively high Al 2 O 3 and Na 2 O and low Yb and Y contents, as well as the behavior of the REE. However, based on an extensive geochemical data set, it is possible to show that the leucogranodiorite–granites have higher K 2 O, Ba, Sr, and Rb and lower CaO contents than the tonalite–trondhjemites. The latter are compositionally similar to typical tonalite–trondhjemite–granodiorite (TTG) series and probably originated from partial melting of garnet amphibolites, derived from tholeiitic rocks or from metabasalts of the Identidade greenstone belt, at pressure conditions suitable to produce high, medium, and low La/Yb tonalite–trondhjemite groups. The leucogranodiorite–granites show geochemical affinity with the Transitional TTG of the Yilgarn craton and are related to the Hybrid granitoid group. The ambiguous geochemical character of the Rio Maria leucogranodiorite–granite suite, which shares some characteristics that are typical of the tonalite–trondhjemite rocks and others more commonly observed in the sanukitoid suites, may be related to complex processes involving TTG and sanukitoid magmas. The discrimination of these two Na-granitoid groups helps us estimate the true volume of TTG magmatism in the Rio Maria domain and in understanding the dynamics of petrogenetic processes in the terrane at the end of the Archean.