Precambrian granitic magmatism in Brazil

This article provides an overview on Precambrian granitic rocks of Brazil, highlighting their most outstanding aspects. In the Amazon craton, five gro ups of Archean granitoids (2.96 to 2.55 Ga) were identified in the Carajas region. Proterozoic A-type and within-plate rapakivi granites are grouped i nto several age intervals (1.88-0.98 Ga). They are meta- to peraluminous wi th subordinate peralkalic terms and are tin-mineralized with associated Y, REE, Th, F (cryolite), ZP. and Nb. Nine groups of Neoproterozoic granitoids and syenitoids are recognized in the Borborema province, northeastern Braz il, on the basis of mineralogical, geochemical and isotopic features. These characteristics indicate both lateral and vertical differences among the t hree major domains in this province, which are segarated from each other by continental-scale shear zones. Study of calc-alkalic to high-K calc-alkali c magmatic epidote-bearing granitoids, common in this area, yields a prelim inary estimate of the speed of magma upward transport and emplacement. The 0.58 Ga-old syenites in the syenitoid line in the Borborema province consti tute one of the few Neoproterozoic ultrapotassic plutonic provinces in the world. Granitoids in the Aracuail Coastal foldbelt in eastern Brazil, are d eeply exposed together with the roots of a Neoproterozoic mobile belt and r ecorded several of the evolutionary history of this belt. In central Brazil , the A-type granites of the Goias tin province, the Neoproterozoic are gra nitoids of Mara Rosa and Arenopolis, the Neoproterozoic peraluminous granit es of southern Goias and the late to post-orogenic bimodal magmatism are a proxy for the tectonic evolution of the Brasilia foldbelt. Most Neoproteroz oic granitic magmatism in southern Brazil is possibly related to mantle sou rce of the EM1 type.