%0 Journal Article
%T Riacian Augen gneisses in Piranhas River-Serid車 Domain 每 Borborema Province, Brazil Northeast
%A Vladimir Cruz de Medeiros
%A Marcos Antonio Leite do Nascimento
%A Antˋnio Carlos Galindo
%A Elton Luiz Dantas
%J Geologia USP : S谷rie Cient赤fica
%D 2012
%I Instituto de Geoci那ncias da USP
%X Augen gneisses occurring at the Fazenda Genezar谷 in the Serra da Formiga east of Caic車, at the border of the S o Vicente-Florania (RN) nucleus, and in exposures SW and NW of S o Jos谷 do Serid車 (RN) were studied by geologic mapping,petrography, lithogeochemistry and U-Pb dating. These rocks consist of biotite augen gneisses, and granitic/granodioriticorthogneisses, with porphyro-granoblastic textures and light gray to pink colors. Their mineralogy consists of perthitic microcline,oligoclase, quartz, besides biotite and amphibole, with epidote, titanite, chlorite, opaque minerals, apatite, zirconand allanite as accessory minerals. Petrography indicates that these rocks were affected by amphibolite facies metamorphism,and a later greenschist facies retrometamorphism. They have a prominent low-angle NW-SE foliation containing ahigh rake stretching lineation. Lithogeochemistry indicates high-K, metaluminous to peraluminous and calc-alkaline geochemicalsignatures related to a collisional environment. U-Pb dating of zircon (LA-ICP-MS) provided an upper interceptage of 2252 ㊣ 17 Ma and 2171 ㊣ 20 Ma, for the rocks found north of Florania (RN), and east of Genezar谷, respectively. Inthe latter values of 2.84 Ga TDM and  Nd(0) of -20.76 were also obtained. The data allow attribution of the augen gneissesto the Rhyacian period, and are consequently associated with to the magmatism which formed the Caic車 Complex.
%K Borborema Province
%K S o Vicente-Florancia nucleus
%K Serra da Formiga
%K Augen gnaiss
%K Caic車 Complex
%U http://ppegeo.igc.usp.br/pdf/guspsc/v12n2/a01v12n2.pdf