Resumo O Terreno Granito-Greenstone do Tocantins é composto por domos granito-gnáissicos e estreitas faixas de greenstone, formados em ambiente de subducção no Paleoproterozoico. As ocorrências de ouro nesse terreno são hospedadas em quartzo de veios associados a produtos de alteração hidrotermal de anfi bolito, formação ferrífera bandada e rochas graníticas em zonas de cisalhamento. Sugere-se que as ocorrências e depósitos de ouro do Terreno Granito-Greenstone do Tocantins formaram-se durante a orogênese Brasiliana, com a participação de fl uidos hidrotermais de origem metamórfi ca, com contribuição granítica. Os dados obtidos até o presente revelam critérios de exploração mineral para ouro no Terreno Granito-Greenstone do Tocantins.Palavras-chave: Tocantins, greenstone, ouro, exploração mineral. Abstract Geology of and gold occurrences in the Granite-Greenstone Terrane of Tocantins, Central Brazil: state of the art and guide lines for mineral exploration programs.The Paleoproterozoic Tocantins GraniteGreenstone Terrane is composed of granite-gneissic domes and narrow intervening greenstone belts. Tholeiitic metabasalts and calc-alkaline metatonalites have chemical composition characteristic of subduction tectonic environment. The main gold concentrations occur in iron-rich amphibolite, banded iron formation and granitic rocks. It is suggested that the Tocantins Granite-Greenstone Terrane gold occurrences and deposits were formed by dominantly metamorphic hydrothermal fl uids during the Brasiliano Orogeny, with granitic contribution. Guide lines for mineral exploration programs for gold in the Tocantins Granite-Greenstone Terrane are presented.

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The Pirineus Syntaxis (PSX) is a concave to the foreland (toward the craton) curve in the otherwise NS-trending structural grain of the orogenic province bordering the west side of the São Francisco craton. Its geometry reflects the intersection between two non-parallel foldthrust belts of different ages and style, formed during two separate non-coaxial deformation episodes during the Brasiliano Orogenic period of Neoproterozoic (probably around 900-600 Ma). These ages are not well constrained, since very little radiometric dating is available. The two limbs of the syntaxis are here interpreted as the younger and narrower Northern Brasília belt (NBB), and the older and more complete Southern Brasília belt (SBB). Rocks involved in the deformation that formed the PSX include the Paranoá, Canastra and Araxá Groups, generally accepted as passive margin environment and more restricted to the SBB. The Rio do Peixe Group is a volcanic-sedimentary sequence that prevalently occurs in the SBB, while the Intrusive Rock Suite and Related Metasedimentary Rocks predominantly occur in the NBB. The Granite-gneiss complex of the Goiás Massif (GCM) to the west, comprises the metamorphic core of the syntaxis. The collision of the Rio de la Plata (Paranapanema?) craton with the São Francisco craton formed the SBB, that preceded the final collision and accretion of the GCM with the SFC that formed the NBB. A weak collision of GCM with the southern border of the Amazonian craton determined the last deformation phase in the syntaxis. This is the first attempt to subdivide the Brasiliano of central Brazil and thus contributed to a better understanding of the evolution of western Gondwana. The conclusions of this paper were primarily based on field structural analysis.

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The distribution of gold occurrences/deposits in the GoiÁs Massif and Brasília Belt reflects the tectonic controls that operated during their geologic evolution. Their distribuiton shows three main regional trends: northwest-southeast, northeast-southwest and north-south, which correspond to tectonic discontinuities generated during the Brasiliano event. Since the regional structural features are an important control for the location of the main gold occurrences/deposits in both massif and belt, further studies of the regional tectonic regime and the establishment of structural models for these geotectonic units are essential to mineral exploration programs for gold in central Brazil.

Há mais de meio século a utilização de dados geofísicos representa importante ferramenta auxiliar nas pesquisas em geociências. Dentre outras características, tais produtos facilitam a discriminação de feições estruturais, ajudam a caracterização de corpos geológicos em subsuperfície e permitem a delimitação de domínios geofísicos com correspondentes geológicos. O Graben de Água Bonita, localizado nos estados de Goiás e Tocantins, foi definido na metade da década de 60 do século XX como uma estrutura de 80 km por 7 km, com bordas paralelas e retilíneas de direção N35-40◦E. O conhecimento desta estrutura restringe-se ao mapeamento geológico, inexistindo dados em profundidade. O presente trabalho trata da interpretação de dados aerogeofísicos do Levantamento Geofísico Brasil-Canadá (PGBC); aquisição e interpretação de dados gravimétricos terrestres visando contribuir ao conhecimento geológico-estrutural do Graben de Água Bonita, situado no contexto do Lineamento Transbrasiliano. A interpretação qualitativa e quantitativa dos dados geofísicos e geológicos originada de modelagem 2D, sugere que o Graben de Água Bonita inclina-se para oeste, devido às baixas anomalias e ao mergulho das sequências sedimentares detríticas. Esta inclinação evidencia que o depocentro da Formação Água Bonita localiza-se a aproximadamente 4 km de profundidade a oeste do limite superficial desta Formação. ABSTRACT: For over half a century geophysical data is an important auxiliary tool used in geosciences research. Among other features, these products facilit at ethe discrimination of structural features, aid the characterization of subsurface geological bodies and allow the delimitation of areas with corresponding geophysica land geological data. The Água Bonita Graben (GAB), which straddles the border of Goiás and Tocantins states, was defined in the mid-60s as an 80-km long by 7-km wide structure, with parallel, straight borders towards N35-40◦E. This paper presents an interpretation of the geophysical data obtained by the the Geophysical Survey Brazil-Canada (Programa de Levantamentos Geofísicos Brasil-Canadá, PGBC), as well as acquisition and interpretation of ground gravity data aiming at improving the geological knowledge of the Água Bonita Graben, situated in the Transbrasilian Lineament. The PGBC geophysical data allowed the extraction of lineaments and geophysical delineation of the GAB limits. The 2D model suggests that the Água Bonita Graben leans to the west, due to the observed low gravity anomaly values and inclined detrital sedimentary sequences dipping 8◦-12◦, in the direction 300◦ to 330◦, suggesting that the depocenter of the Água Bonita Formation is near by the western edge of the graben.Keywords: ground gravity, Água Bonita Graben, Transbrasilian Lineament.