Isotopic characterization of the metabasites and amphibolites of the Acungui and Setuva Groups of the Ribeira Belt

Pb, Rb, Sr, Sm and Nd isotope analyses were carried out on amphibolitic rocks from Campo Largo (PR), Rio Branco do Sul (PR) and Adrianópolis (PR) and for the metabasite from Adrianópolis and Apiai (SP), all belonging to the Açungui and Setuva Groups, southern portion of the Ribeira Belt. These occurrences were chosen because each exhibits geochemical data indicative of a mantle source, having different signatures. Geochronologic determinations are available only for the Apiai metagabbro with Neoproterozoic ages of 617 ± 4 Ma (U/Pb in zircon) and 839 ± 85 Ma (Rb/Sr, whole rock). Age determinations by Sm/Nd mineral isochron using whole rock, plagioclase and pyroxene yield values of 885 ± 53 Ma for the Apiai metagabbro and 820 ± 84 Ma for the Adrianópolis metabasite. These results agree within error with the Rb/Sr isochron of 839 ± 85 Ma may possibly be interpreted as the time of extraction of the magma from the mantle, as suggested by positive εNd(850) values (+2,76) from an Adrianópolis sample. An εNd values versus 87Sr/86Sr diagram shows that each studied occurrence plots in a different position, following approximately the mantle array trend, the most primitive being the metabasite of Adrian-acopolis, near the MORB field, and the most enriched being the amphibolite from the same region, near the enriched mantle and or crustal contamination field. The distinct difference in isotopic signatures between the amphibolite and metabasite suggests derivation from different mantle sources, as supported by available geochemical data. Nevertheless, some of the samples show isotopic evidence of the action of metamorphism, crustal contamination and weathering.

U-Pb geochronology of the southern Brasília belt (SE-Brazil): Sedimentary provenance, Neoproterozoic orogeny and assembly of West Gondwana

The Brasília belt borders the western margin of the São Francisco Craton and records the history of ocean opening and closing related to the formation of West Gondwana. This study reports new U-Pb data from the southern sector of the belt in order to provide temporal limits for the deposition and ages of provenance of sediments accumulated in passive margin successions around the south and southwestern margins of the São Francisco Craton, and date the orogenic events leading to the amalgamation of West Gondwana. Ages of detrital zircons (by ID-TIMS and LA-MC-ICPMS) were obtained from metasedimentary units of the passive margin of the São Francisco Craton from the main tectonic domains of the belt: the internal allochthons (Araxá Group in the Áraxá and Passos Nappes), the external allochthons (Canastra Group, Serra da Boa Esperança Metasedimentary Sequence and Andrelândia Group) and the autochthonous or Cratonic Domain (Andrelândia Group). The patterns of provenance ages for these units are uniform and are characterised as follows: Archean- Paleoproterozoic ages (3.4-3.3, 3.1-2.7, and 2.5-2.4Ga); Paleoproterozoic ages attributed to the Transamazonian event (2.3-1.9Ga, with a peak at ca. 2.15Ga) and to the ca. 1.75Ga Espinhaço rifting of the São Francisco Craton; ages between 1.6 and 1.2Ga, with a peak at 1.3Ga, revealing an unexpected variety of Mesoproterozoic sources, still undetected in the São Francisco Craton; and ages between 0.9 and 1.0Ga related to the rifting event that led to the individualisation of the São Francisco paleo-continent and formation of its passive margins. An amphibolite intercalation in the Araxá Group yields a rutile age of ca. 0.9Ga and documents the occurrence of mafic magmatism coeval with sedimentation in the marginal basin. Detrital zircons from the autochthonous and parautochthonous Andrelândia Group, deposited on the southern margin of the São Francisco Craton, yielded a provenance pattern similar to that of the allochthonous units. This result implies that 1.6-1.2Ga source rocks must be present in the São Francisco Craton. They could be located either in the cratonic area, which is mostly covered by the Neoproterozoic epicontinental deposits of the Bambuí Group, or in the outer paleo-continental margin, buried under the allochthonous units of the Brasília belt. Crustal melting and generation of syntectonic crustal granites and migmatisation at ca. 630Ma mark the orogenic event that started with westward subduction of the São Francisco plate and ended with continental collision against the Paraná block (and Goiás terrane). Continuing collision led to the exhumation and cooling of the Araxá and Passos metamorphic nappes, as indicated by monazite ages of ca. 605Ma and mark the final stages of tectonometamorphic activity in the southern Brasília belt. Whilst continent-continent collision was proceeding on the western margin of the São Francisco Craton along the southern Brasília belt, eastward subduction in the East was generating the 634-599Ma Rio Negro magmatic arc which collided with the eastern São Francisco margin at 595-560Ma, much later than in the Brasília belt. Thus, the tectonic effects of the Ribeira belt reached the southernmost sector of the Brasília belt creating a zone of superposition. The thermal front of this event affected the proximal Andrelândia Group at ca. 588Ma, as indicated by monazite age. The participation of the Amazonian craton in the assembly of western Gondwana occurred at 545-500Ma in the Paraguay belt and ca. 500Ma in the Araguaia belt. This, together with the results presented in this work lead to the conclusion that the collision between the Paraná block and Goiás terrane with the São Francisco Craton along the Brasília belt preceded the accretion of the Amazonian craton by 50-100 million years. © 2003 Elsevier B.V. All rights reserved.

Final stages of the Brasiliano Orogenesis in SE Brazil: U-Pb and 40Ar/39Ar evidence for overprinting of the Brasília Belt by the Ribeira Belt Tectonics

Around the southern margins of the São Francisco Craton, there is a zone of tectonic interference between the Brasília belt to the west and the younger Ribeira belt to the east. U-Pb monazite and 40Ar/39Ar cooling age determinations carried out in the area reveal the cooling histories of these belts and the timing of tectonic overprint, unraveling the final stages of Brasiliano Orogeny in SE Brazil. The U-Pb monazite data from migmatized paragneisses and late-stage pegmatites in the Socorro-Guaxupé Nappe System of the southern Brasília belt show that migmatization peaked between ca. 613±1 and 607±3 Ma. 40Ar/39Ar biotite and muscovite ages of paragneisses and schists in this area indicate that the northern high-grade core of the Nappe System (Guaxupé Domain) was uplifted and cooled through the 350°C isotherm between 599±1 and 587±1 Ma. In contrast, samples from the southern high-grade core of the Nappe System, the Socorro Domain, south of the Jacutinga shear zone, yields a broader and younger spectrum of 40Ar/39Ar biotite ages between 571±1 and 562±1 Ma, attributed to a later uplift and cooling of the crust. The cooling ages can be assigned to local resetting of the 40Ar/39Ar system during transpressive tectonic overprint due to reactivation as a result of collision of the Ribeira belt. A younger group of 40Ar/39Ar mica ages (537±1 to 521±1Ma) in schists of the Socorro Domain, are associated with transpressional structures of the Ribeira belt. Rock samples from the Jacutinga and Três Corações shear zones, yield 40Ar/39Ar biotite-muscovite ages around 520 Ma. These are typical cooling ages of the Ribeira belt, and are interpreted to mark the western limit of the Ribeira belt transpressional regime within the Brasília belt. The youngest biotite-muscovite cooling ages in schists of the Socorro Domain, between 510±2 and 491±1 Ma, mark the final cooling and exhumation of that part of the Brasília belt.

Resolución del VII Subcomité Técnico (Brasilia, diciembre de 1984) = Resolution of the Seventh Technical Sub-Committee (Brasilia, December 1984)

Contiene la propuesta de resolución a ser discutida en la reunión sobre el cambio de nombre del Instituto por el de: Instituto Latinoamericano y del Caribe de Planificación Económica y Social, y conservar la sigla ILPES.

Resolución 650(XXXIII): Resolución de Brasilia.

Incluye Bibliografía

Resolution 650(XXXIII) Brasilia resolution

Includes bibliography

What kind of State? what kind of equality?: XI Regional Conference on Women in Latin America and the Caribbean: Brasilia, 13-16 July 2010

Available also in spanish and portuguese

Quel genre d'État pour quel genre d'égalité?: XI Conferénce régionale sur les femmes de l'Amérique latine et les Caraibes: Brasilia, 13 al 16 juillet 2010

Le document Quel genre d'état pour quel genre d'égalité? analyse les progrès de l'égalité entre les sexes dans la région, 15 ans après l'Adoption du Programme d'action de Beijing, 10 ans après la formulation des objectifs du Millénaire pour le développement et 3 ans après l'Adoption du Consensus de Quito à la dixième Conférence régionale sur les femmes de l'Amérique latine et des Caraïbes qui s'est tenue en 2007. Il examine en outre les succès et les défis auxquels sont confrontés les gouvernements à la lumière de l'interaction entre l'état, le marché et les familles, en tant qu'institutions sociales construites sur la base de politiques, de lois, d'us et coutumes qui, ensemble, créent les conditions pour rénover ou perpétuer les hiérarchies sociales et de genre.

Quel genre d'État pour quel genre d'égalité?: XI Conferénce régionale sur les femmes de l'Amérique latine et les Caraibes: Brasilia, 13 al 16 juillet 2010. Synthese

Le document Quel genre d'État pour quel genre d'égalité? analyse les progrès de l'égalité entre les sexes dans la région, 15 ans après l'adoption du Programme d'action de Beijing, 10 ans après la formulation des objectifs du Millénaire pour le développement et 3 ans après l'adoption du Consensus de Quito à la dixième Conférence régionale sur les femmes de l'Amérique latine et des Caraïbes qui s'est tenue en 2007. Il examine en outre les succès et les défis auxquels sont confrontés les gouvernements à la lumière de l'interaction entre l'État, le marché et les familles, en tant qu'institutions sociales construites sur la base de politiques, de lois, d'us et coutumes qui, ensemble, créent les conditions pour rénover ou perpétuer les hiérarchies sociales et de genre.

What kind of State? What kind of equality? XI Regional Conference on Women in Latin America and the Caribbean: Brasilia, 13-16 July 2010. Summary

The document What kind of State? What kind of equality? analyses the progress of gender equality in the region 15 years after the approval of the Beijing Platform for Action, 10 years after the drafting of the Millennium Development Goals and 3 years after the adoption of the Quito Consensus at the tenth session of the Regional Conference on Women in Latin America and the Caribbean, held in 2007. It also examines the achievements made and challenges faced by governments in light of the interaction between the State, the market and families as social institutions built on the foundation of policies, laws, and customs and habits which, together, establish the conditions for renewing or perpetuating gender and social hierarchies.

¿Qué Estado para qué igualdad?: XI Conferencia Regional sobre la Mujer de América Latina y el Caribe: Brasilia, 13 al 16 de julio de 2010. Síntesis

En el documento ¿Qué Estado para qué igualdad? se analiza el progreso de la igualdad de género en la región tras 15 años de la aprobación de la Plataforma de Acción de Beijing, 10 años de la formulación de los Objetivos de Desarrollo del Mileno y 3 años de la adopción del Consenso de Quito en la décima Conferencia Regional sobre la Mujer de América Latina y el Caribe realizada en 2007. Se examinan además los logros y desafíos que enfrentan los gobiernos a la luz de la interacción entre el Estado, el mercado y las familias como instituciones sociales construidas a partir de políticas, leyes, usos y costumbres que, en conjunto, establecen las condiciones para renovar o perpetuar las jerarquías sociales y de género.