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é interpretado como um complexo estratiforme anorogênico e seu acamamento mergulha de 30 a 50° para NW. O maciço é composto por cinco unidades acamadadas que contêm várias associações de fases cumulus e proporções variadas de minerais inter-cumulus. As transições entre as unidades são caracterizadas por mudanças abruptas na composição destas fases. Da base para o topo, a seqüência compreende anfibolitos (PICB1) sobrepostos por serpentinitos (PICB2), metawebsteritos (PICB3) e metagabros (PICB4 and PICB5). A seqüência era originalmente formada por micrograbros, peridotitos, websteritos e gabros. Dados isotópicos indicam que o magma parental do Complexo de Cana Brava evoluiu da seguinte forma: (a) Derivação mantélica há cerca de 2,5 Ga e subseqüente residência subcrustal; (b) Intrusão na Seqüência vulcano-sedimentar de Palmeirópolis e cristalização ígnea há cerca de 2,0 Ga; (c) Metamorfismo e deformação dúctil-rúptil em ambiente compressivo a 1,3 Ga, e (d) Metamorfismo posterior e re-equilíbrio durante o Ciclo Brasiliano, a cerca de 0,77 Ga. Palavras-chave: Cana Brava, complexo estratiforme, intrusão acamadada, máfico-ultramáfica, geocronologia ABSTRACT The Cana Brava complex is an anorogenic stratiform complex, whose layers dip from 30° to 50°N W. The massif is made up of five units composed of layers containing several associations of cumulus phases and variable amounts of inter-cumulus minerals. Transition between units are characterized by abrupt changes in the composition of these phases. From base to top, the sequence consists of amphibolites (PICB1), overlain by serpentinites (PICB2), metawebsterites (PICB3), and metagabbros (PICB4 and PICB5). This sequence was originally formed by microgabbros, peridotites, websterites, and gabbros. Isotopic data indicate that the parental magma of the Cana Brava complex evolved as follows: (a) Mantle derivation at about 2.5 Ga and subsequent retention at subcrustal levels; (b) Intrusion within the Palmeirópolis volcano-sedimentary sequence and igneous crystallization at about 2.0 Ga; (c) Metamorphism and ductile-ruptile deformation under compression at about 1.3 Ga; and (d) Further metamorphic reequilibration during the Brasiliano Cycle at about 0.77 Ga.

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The Cana Brava body is a 2.0 Ga, anorogcnic, stratiform complex whose layers dip from 30" to ~"NW. The massif is made up of five units, composed of layers containing several associations of cumulus ph:oses :rnd variable amounts of inter-<::umulus minerals. Transitiorul betw~n units ;ore characteriud by changes in the composition and/or in the rebtive abundo.nce of tbese phases. Stratigraphically, the lowen sequence is ~omposed of amphibolites (PICBI), overlain by serpentinite. (PICB2), metawebsterites (PICB3) and metagabbroic rocks (PICB4 and PleB5) at tbe top. This sequence was originally formed by microgabbros, peridotites, websterites and gabbroic rocks.The rock sequence of the complex can be attributed to a ,ingle magmatic fractionation. Tbere is no evidence of multiple injections. Met amorphic events affe"ed tbe different units heterogeneously. The gabbroic rocks (pICB4 and PICBS) were the least tranuormed; hence their chemical compositions are close to tb e original ones. Units PICBI lU PICB) were tbe most affected by post-magmatic proces..,s.Geochemical evidences suggest tbat PICBt may be the chilled border of the massif.However, due to pon_magmatic phenomena, tbe compositioo of the parent magm a was calculated u.sing the chemiul compositions and inferred volumes of unils PICBl to PICBS. For PIeB2 and PICE3 the compositions of mineral phases were utiliud. Tbe possible Cana Brava parent magma is olivine-tholeiite, similar to tb e majority of tbe complexes utilized for compar;ron. In amount of normative olivine is within the range for liquids derived from 25 to 35% of mantle melting. Pbase equilibria can dictions point to pressures under 6-7 Kbar duringcrystallizo.tion.The possible parental magma of the Cana Brava complex is compared with tbe a1cali-olivine basaltic magma of the Palmeiropolis metavolcano.sedimentary sequence, and witb the possible parental magma of th e Serra da Bota satellite body. RESUMO