%0 Journal Article
%T Lithogeochemistry of Granitoids in the S o Sebasti o Flower Structure, S o Paulo
%A Coriolano de Marins e Dias Neto
%A Ciro Teixeira Correia
%A Jos¨¦ Manuel Urbano Munh¨¢
%A Colombo Celso Gaeta Tassinari
%J Geologia USP : S¨¦rie Cient¨ªfica
%D 2008
%I Instituto de Geoci¨ºncias da USP
%X The aim of this paper is to present lithochemical data from the granitoids found between Guaruj¨¢ and S o Sebasti o in a segment of the Costeiro Complex in S o Paulo, State, Brazil. This part of the Ribeira Folded Belt is composed of para-derived rocks on the eastern side, and ortho-derived rocks on the western side of the belt, organized in a ductile shear zone forming a positive flower structure, whose axis runs ENE-WSW. Large boudins of amphibolite occur within predominant kinzigitic gneisses along this axis. The intrusive basic protoliths of the amphibolites have a 580 Ma (U-Pb SHRIMP) crystallization age. SiO2 contents of the granitoids vary between 68 and 74%, corresponding to monzogranites and granodiorites. Some outcrops display mafic enclaves of quartz-monzodiorites. The granitoids show calc-alkaline affinity while their mafic enclaves tend towards an alkaline affinity. The lower content in SiO2 coupled with coherent differences on some trace element concentrations (e.g. Zr-Hf) contribute to clearly distinguish the enclaves from their country rocks and to suggest intense chemical interaction among the materials during crystallization. The REE pattern, the depletion in Sr, P-Ti, Ta-Nb, and the distribution of the samples on the R1-R2 diagram suggest a syn-collision island arc environment for generation of these rocks.
%K Costeiro complex
%K Ribeira fold belt
%K Brasiliano cycle.
%U http://ppegeo-local.igc.usp.br/pdf/guspsc/v8n2/07.pdf