Geochemical characterization of granites of distinctly different ages in the Alto Pajeu Terrane, Borborema Province, Northeast Brazil

This work presents geochemical data for granitic plutons that intruded the Alto Pajeu terrane, Borborema Province, northeastern Brazil, during several distinct tectonic cycles. The Alto Pajeu terrane is represented in the stu dy area by metasedimentary (Sao Caetano Formation) and metavolcanosedimenta ry (Irajar Formation) sequences overlying a gneissic-migmatitic basement. S everal granitic plutons of different ages, mineralogical proportions, and c hemical compositions have invaded the supracrustal and basement rocks. Two deformational events, one tangential (older) and the other transcurrent (yo unger), were identified. The metamorphic grade determined for the metasedim entary rocks varies from amphibolite to high amphibolite facies, with tempe ratures ranging from 600 to 680 degrees C and pressures from 6.0 to 7.5 kba r. Three magmatic events with distinct ages were identified for the tectoni c evolution of the Alto Pajeu terrane in the study area. The older magmatic event is related to the Transamazonico orogenic cycle (similar to 2.0 Ga), the intermediary magmatic event to the Cariris Velhos cycle (similar to 0. 97 Ga), and the younger magmatic event to the Brasiliano orogenic cycle (si milar to 0.55 Ga). The Cariris Velhos- and Brasiliano-age granites are geoc hemically classified as peraluminous, subalkalic granites of the calc-alkal ic series, whereas the Transamazonico-age granite is metaluminous and alkal ine. Geochemical data presented and discussed here suggest that the magmati sm related to the three tectonic events had distinctly different sources an d petrogenetic evolutions.