GEOLOGYAND GEOCIl RONOLOG YOF ARCIlEAN GRANITOIDS OFTflE XINGUARA REGION: IMPLICATIONS FOR TilE EVOWI1ON OF THE RIO MARIA GRANITE-GREENSTONE TERRANE. AMAZONIAN CRA1VNThe Xinguaraarea. located in the Rio Maria Granite-Greenstone Terrain -Para, is composed of several Archaean granitoids. Structures and fabric elements visible at outcrop and microscopic scales, and zircon Pb-Pb ages suggest that these granitoids were emplaced in two distinct episodes of growth of the Archaean crust (i) 2.948 ± 5 to 2.924 ±2 Ma, genesis, emplacement and deformation of Caracol tonalitic complex, related to Arco Verde tonalite, wich outcrops in Marajoara area, and to TTG rocks of the Sao Felix do Xingu region. This period was marked by the formation of thick greenstone sequences and TTG plutons, form ing dome-and-keel structures, related to a vertica l tectonics, like those reported in the east Pilbara (Autralia) and Dharwar (India) cratons; (ii) 2.878 ± 4 to 2.865 ± I Ma, genesis, emplacement and deformation of the Rio Maria granodiorite, Agua Fria trodhjemite and Xinguara granite. In this period, some 50 Ma after formation of the last TTG, distinct magmatic series were formed in a short time span (10-I5 Ma). In this stage, plate convergence and subduction processes were operative.Keyworks: TTG Archean granitoids, leucogranites, Pb-Pb zircon geochronoloogy, Carajas Mineral Province, Rio Maria GraniteGreenstone Terrane, Amazon ian Craton.
RcsumoA regiao de Xinguara , no Terreno Granito-Greenstone de Rio Maria -PA, C composta por varies tipos de rochas granit6ides arqueanas. Relacccs de campo e dados isot6picos Pb-Pb por cvaporecao de zircao indica rn que a formacao destas rochas ocorreu em dois perfodos principais, com caracterfsticas tcctonicas distintas: (i) 2.948 ±5 a 2.924 ±2 Ma, geracao, colocacao e dcformacao do Tonalito Caracol, correlac ionado ao Tonalito Arco Verde, da reglao de Marajoara, e aos granit6ides TTO da reglao de Sao Felix do Xingu. Este perfodo foi marcado pela formacao de urn terreno abase de domos TTG c bacias de greellSfOll e belts associado a uma tectonica vertical, similar aos dos cratons Pilbara (Australia) e Dharwar (India); (ii ) 2.878 ± 4 a 2.865 ±J Ma, geracao, colocacao e dcformacao do Granodiorito Rio Maria, Trondhjemite Agua Fria c do Granito Xinguara. Neste pcrfodo, que ocorreu cerca de 50 Ma ap6s a formacao des ultimos granit6ides TTG, fonn aram-se varies granit6idcs geneticamente difererues em urn curtocspaco de tempo ( 10-15 Ma). Nesta cta pa, 0 processo de convergencla e subduccao de placas parecc ter sido mais efetivo.Pulavras-chave: granit6idcs arqucanos TTG, leucogranitos, geocronologia Pb-Pb em zircfio, Provincia Mineral de Carajas. Terreno Granito-Greem tone de Rio Maria, Craton Amazonico.INT RO DUl;:AO A Provincia M ineral de Carajas situa-se na porcao ar iental do Craton Amaz6nico, SE do eslado do Para (Fig. 1). E m virtud e das suas im i merasriqu eza s minerais , torno u-se um a das regioes me lhor estuda das da Am azonia . No e nta nto, nesta pr o vin ci a ex is te m a lg uma...
