Geochemistry of the Estrela Granite Complex, Carajلs region, Brazil: an example of an Archaean A-type granitoid

The Estrela Granite Complex is an Archaean granite batholith which outcrops to the east of the Serra dos Carajلs, northern Brazil. This complex, surrounded by supracrustal sequences metamorphosed under medium- to high-grade conditions, was affected by heterogeneous ductile deformation. Petrographically, this body exhibits a relatively wide faciés variation where hornblende ± pyroxene monzogranites and hornblende ± biotite monzogranites dominate. The high alkali contents, the extremely high FeO1(FeO1 + MgO) ratios and the elevated values of some high field strength elements (HFSE) demonstrate the alkaline affinities of the studied rocks. Al2O3-poor metaluminous monzogranites and Al2O3-rich weakly peraluminous monzogranites have been distinguished. Partial melting of meta-igneous or undepleted granulitic rocks could generate such granitic magmas. On the basis of its geochemical signature, the Estrela Granite Complex is thought to be an unequivocal example of A-type granite magmatism, being thus very different from granitoids reported southward in the Rio Maria Archaean granite-greenstone terrain, where the calc-alkaline and trondhjemitic suites are predominant.