Abstract
Pb-Pb AGE AND PETROGRAPHIC AND LITHOGEOCHEMICAL ASPECTS OF THE FLORESTA AZUL ALKALINE COMPLEX, SOUTHERN STATE BAHIA The Floresta Azul Alkaline Complex (CAFA), is represented by a NE-SW elongated igneous body, with an exposed area of 200 km 2 , located in the central-northern region of the Southern Bahia State Alkaline Province. Two types of magmatic intrusion were recognized: (i) at the eastern part of complex, occur granitic rocks, presenting many dior itic inclusions, and (ii) the syenitic rocks are located in the western region. Pb-Pb ages obtained in single zircon crystals from g ranite (696 ± 11 Ma); diorite (688 ± 2 Ma) and syenite (688 ± 10 Ma) indicate that CAFA rocks were emplaced synchronously during a Neoproterozoic event. The main mafic mineral of the CAFA is biotite, whereas sodic amphibole and aegirine are sporadically foun d in the granitic and syenitic lithotypes. The textural features of these rocks, typified by the angular distribution of well-for med feldspar crystals, reflect the lack of significant deformation after crystallization. All the lithologic types from the complex have alk aline signature, characterized by the high contents of Nb (86-243 ppm), Y (22-43ppm), F (760-2600) and Cl (220-10.000). The distribut ion patterns of minor and trace elements suggest that the different rocks from CAFA are cogenetic.
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