Abstract Sanukitoid rocks make up a complete magmatic series with distinct geochemical characteristics of TTG suites and granitoids from modern magmatic arcs and are regarded as markers of the transition from typically Archean geodynamics to modern plate tectonics. Although most known sanukitoid suites formed during the Neoarchean and Mesoarchean, numerous papers have characterized Paleoproterozoic magmatic arc granitoid rocks showing affinity with the sanukitoid series. This work presents new data from field, lithogeochemistry, zircon U-Pb geochronology, and Sm-Nd and Sr isotopic studies on granodioritic granulites with sanukitoid signatures from the Juiz de Fora Complex (JFC), one of the Paleoproterozoic tectonic components of the Minas-Bahia Orogenic System (MBOS), southern São Francisco Paleocontinent (southeastern Brazil). These rocks crystallized at ~2175 Ma and present values of εNdt between −4.0 and +0.5, TDM between 2.57 and 2.12 Ga, and 87Sr/86Sri between 0.6937 and 0.7137. We interpret these rocks as the result of crystallization of magmas from a hybrid mantle source extensively contaminated by crustal material during protracted subduction. In southeastern São Francisco Paleocontinent, the association of sanukitoid rocks with other magmatic arc rocks points to a complex and prolonged Rhyacian accretionary system similar to modern plate tectonics.

Abstract New petrography, geochemistry and Sm-Nd and Sr data from the orthogranulites of the Juiz de Fora complex in southern Rio de Janeiro State and compiled information provide insights on the petrogenetic and tectonic evolution. The complex comprises several geochemical groups including mafic orthogranulites (three tholeiitic and one alkaline) and felsic orthogranulites (three calc-alkaline and one tholeiitic/low K calc-alkaline). New geochemical and isotope data, combined with available U-Pb data suggest a long evolutionary history from the Paleoproterozoic to the Neoproterozoic. The oldest magmatic episode produced juvenile to slightly contaminated arc-type Rhyacian rocks, as well as granitic rocks related to collision or post-collision episodes. Altogether these rocks integrate part of a dismembered Rhyacian orogen within the Ribeira belt. Few TDM Nd model ages yielded 2.75 to 2.58 Ga, suggesting minor Archean contribution for magma genesis. Some of the basic granulites’ bodies yield Meso- to Neoproterozoic TDM Nd model ages, which may refer to an extensional magmatism. Orthogranulites present granulite facies paragenesis, related to the youngest tectonic episode in the Juiz de Fora Complex (Brasiliano Orogeny). The new data are potentially important for Paleoproterozoic reconstruction models, due to the predominantly juvenile character of the Juiz de Fora complex, as similarly worldwide.

Abstract Combined Sm-Nd isotope studies and U-Pb ages of detrital zircons have shown significant differences between the provenance patterns of Neoproterozoic metasedimentary successions in the Southern Brasília belt. The Vazante and Canastra groups are passive margin deposits with source areas in the Archean/Paleoproterozoic São Francisco Craton basement and Mesoproterozoic cover units. In literature, the younging trend of Nd model ages observed in the Vazante Group is interpreted as resulting from the contribution of the Neoproterozoic Goiás Magmatic Arc. Also, detrital zircons younger than 0.90 Ga were not recorded in the Vazante or Canastra groups, which zircon populations are older than 0.93 Ga. This work presents new Sm-Nd and Sr isotope data of metasedimentary rocks from the Vazante and Canastra groups, collected in a 400 km2 area in northwest Minas Gerais, Brazil. The improved database of previously published and new data corroborates with the younging pattern of TDM along the Vazante Group. Isochronic diagrams show that samples from Vazante and Canastra groups scatter along mixing lines between the fields defined by the older cratonic rocks and the more juvenile ones. Here we present the Tonian Intraplate Magmatism within the São Francisco Craton as the juvenile source.

Procedimentos químicos e espectrométricos do método geocronológico U-Pb em monazita, recentemente instalado no Laboratório LAGIR, são descritos em detalhe. Adicionalmente, resultados preliminares de amostras de monazita das faixas Brasília e Ribeira são relatados e discutidos no contexto geológico regional. Vários experimentos de calibração de colunas de troca iônica com resina AG-1x8 foram realizados com HCl, usando amostras de monazita naturais dissolvidas. Os brancos de Pb dos reagentes são ∼0,5 pg/g em ácidos e ∼1 pg/g em H2O. Os brancos de Pb nos procedimentos químicos foram inferiores a 22 pg. Os resultados preliminares são apresentados nos três estudos de casos relatados em faixas orogênicas Brasilianas da região SE do Brasil, que se correlacionam muito bem com determinações prévias de idade da literatura: dois grãos subconcordantes de um quartzito do Grupo Araxá (faixa Brasília meridional) definem uma idade concórdia de 602,6 ± 1,4 Ma; Um grão -0,8% discordante de um quartzito do Grupo São Fidelis (Domínio Costeiro, Faixa Ribeira central) forneceu uma idade concórdia de 535,3 ± 2,4 Ma; dois grãos de monazita 0,4% e 1,3% discordantes do Granito poscolisional Itaoca (Domínio Costeiro, faixa Ribeira central) definem uma idade concórdia de 476,4 ± 1,8 Ma.

The chemical and spectrometric procedures of the U-Pb geochronology method on monazites, recently installed in the LAGIR laboratory, are described in detail. In addition, preliminary results on monazite samples from the Brasília and Ribeira belts are reported and discussed in the context of the regional geology. Several experiments for calibration of ion exchange chromatographic columns with the AG-1x8 resin, were performed with HCl, using dissolved natural monazite samples. The Pb blanks of reagents are ∼0.5 pg/g in acids and ∼1 pg/g in H2O. The total Pb blanks in chemical procedures were below 22 pg. Preliminary results are presented from three case studies related to Brasiliano orogenic belts of SE-Brazil, which correlate very well with previous age determinations from literature: two sub-concordant grains from an Araxá Group quartzite (southern Brasília belt) define a concordia age of 602.6 ±1.4 Ma; a -0.8% discordant grain from a quartzite of the São Fidelis Group (Costeiro Domain, central Ribeira belt) yielded a concordia age of 535.3 ± 2.4 Ma; two 0.4 % and 1.3 % discordant monazite grains from the post-collisional Itaoca Granite (Costeiro Domain, central Ribeira belt) define a concordia age of 476.4 ± 1.8 Ma.

OBJETIVO: Descrever a prevalência de consumo de drogas ilícitas em adolescentes e os motivos que os levam a experimentá-las. MÉTODOS: Estudo transversal com 2.499 adolescentes de 17 anos, com base numa coorte designada por EPITeen, iniciada em 2003/2004 com adolescentes nascidos em 1990 que estudavam nas escolas públicas e privadas da cidade do Porto, Portugal. Foi realizada nova avaliação em 2007/2008, sendo recuperados 1.716 adolescentes (79,4%) e avaliados 783 novos participantes. Informações sobre características sociais e demográficas, história familiar e pessoal de doença e comportamentos foram obtidas com questionários estruturados autoadministrados. O teste de qui-quadrado foi utilizado para testar as associações. A análise estatística foi realizada no programa informático SPSS® versão 17. RESULTADOS: Dos adolescentes, 14,6% referiram ter experimentado drogas alguma vez na vida. A droga ilícita mais experimentada foi a cannabis (12,5%), seguida pelo álcool em simultâneo com cannabis (5,5%) e pelos tranquilizantes (1,7%). A razão mais referida para experimentar drogas foi a curiosidade (77,5%). Os amigos foram a forma mais frequentemente referida para obter a droga e a escola era vista por 24,2% dos adolescentes como um local em que se podia comprar cannabis. CONCLUSÕES: Os resultados fundamentam a necessidade de intervir em idades precoces e sugerem que essa intervenção deve ser integrada com estratégias dirigidas a outros comportamentos de risco, nomeadamente em meio escolar.

OBJECTIVE: To describe the prevalence of illicit drug consumption among adolescents and the motives that led these adolescents to try them. METHODS: Cross-sectional study with 2,499 adolescents aged 17 years, based on a cohort called EPITeen, which was started in 2003/2004 with adolescents born in 1990 who studied in public and private schools of the city of Porto, Portugal. A new assessment was carried out in 2007/2008: 1,716 adolescents (79.5%) were recovered and 783 new participants were evaluated. Information about social and demographic characteristics, family and personal history of diseases and behaviours were obtained through self-administered structured questionnaires. The chi-square test was used to test the associations. The statistical analysis was performed in the program SPSS® version 17. RESULTS: Of the adolescents, 14.6% had tried drugs at least once in their lives. The most tried illicit drug was cannabis (12.5%), followed by alcohol together with cannabis (5.5%) and tranquilizers (1.7%). The most cited reason for trying drugs was curiosity (77.5%). Friends were the most frequently cited form of obtaining drugs and the school was seen by 24.2% of the adolescents as a place where it was possible to buy cannabis. CONCLUSIONS: The results support the need to intervene at an early age and suggest that this intervention should be integrated with strategies targeted at other risk behaviors, particularly in schools.

OBJETIVO: Describir la prevalencia de consumo de drogas ilícitas en adolescentes y los motivos que los llevan a experimentarlas. MÉTODOS: Estudio transversal con 2.499 adolescentes de 17 años, con base en una cohorte designada por EPITeen, iniciada en 2003/2004 con adolescentes nacidos en 1990 que estudiaban en las escuelas públicas y privadas de la ciudad de Porto, Portugal. Se realizó nueva evaluación en 2007/2008, siendo recuperados 1.716 adolescentes (79,4%) y evaluados 783 nuevos participantes. Informaciones sobre características sociales y demográficas, historia familiar y personal de enfermedad y comportamientos fueron obtenidas con cuestionarios estructurados auto-administrados. La prueba de chi-cuadrado fue utilizada para evaluar las asociaciones. El análisis estadístico fue realizado en el programa informático SPSS® versión 17. RESULTADOS: De los adolescentes, 14,6% relataron haber experimentado drogas alguna vez en la vida. La droga ilícita más experimentada fue la cannabis (12,5%), seguida por el alcohol simultáneamente con cannabis (5,5%) y por los tranquilizantes (1,7%). La tasa más referida para experimentar drogas fue la curiosidad (77,5%). Los amigos fueron la forma más frecuentemente referida para obtener la droga y la escuela era vista por 24,2% de los adolescentes como un lugar donde se podía comprar cannabis. CONCLUSIONES: Los resultados fundamentan la necesidad de intervenir en edades precoces y sugieren que dicha intervención debe ser integrada con estrategias dirigidas a otros comportamientos de riesgo, específicamente en medio escolar.

OBJETIVO: Descrever a prevalência de consumo de drogas ilícitas em adolescentes e os motivos que os levam a experimentá-las. MÉTODOS: Estudo transversal com 2.499 adolescentes de 17 anos, com base numa coorte designada por EPITeen, iniciada em 2003/2004 com adolescentes nascidos em 1990 que estudavam nas escolas públicas e privadas da cidade do Porto, Portugal. Foi realizada nova avaliação em 2007/2008, sendo recuperados 1.716 adolescentes (79,4%) e avaliados 783 novos participantes. Informações sobre características sociais e demográficas, história familiar e pessoal de doença e comportamentos foram obtidas com questionários estruturados autoadministrados. O teste de qui-quadrado foi utilizado para testar as associações. A análise estatística foi realizada no programa informático SPSS® versão 17. RESULTADOS: Dos adolescentes, 14,6% referiram ter experimentado drogas alguma vez na vida. A droga ilícita mais experimentada foi a cannabis (12,5%), seguida pelo álcool em simultâneo com cannabis (5,5%) e pelos tranquilizantes (1,7%). A razão mais referida para experimentar drogas foi a curiosidade (77,5%). Os amigos foram a forma mais frequentemente referida para obter a droga e a escola era vista por 24,2% dos adolescentes como um local em que se podia comprar cannabis. CONCLUSÕES: Os resultados fundamentam a necessidade de intervir em idades precoces e sugerem que essa intervenção deve ser integrada com estratégias dirigidas a outros comportamentos de risco, nomeadamente em meio escolar.

OBJECTIVE: To describe the prevalence of illicit drug consumption among adolescents and the motives that led these adolescents to try them. METHODS: Cross-sectional study with 2,499 adolescents aged 17 years, based on a cohort called EPITeen, which was started in 2003/2004 with adolescents born in 1990 who studied in public and private schools of the city of Porto, Portugal. A new assessment was carried out in 2007/2008: 1,716 adolescents (79.5%) were recovered and 783 new participants were evaluated. Information about social and demographic characteristics, family and personal history of diseases and behaviours were obtained through self-administered structured questionnaires. The chi-square test was used to test the associations. The statistical analysis was performed in the program SPSS® version 17. RESULTS: Of the adolescents, 14.6% had tried drugs at least once in their lives. The most tried illicit drug was cannabis (12.5%), followed by alcohol together with cannabis (5.5%) and tranquilizers (1.7%). The most cited reason for trying drugs was curiosity (77.5%). Friends were the most frequently cited form of obtaining drugs and the school was seen by 24.2% of the adolescents as a place where it was possible to buy cannabis. CONCLUSIONS: The results support the need to intervene at an early age and suggest that this intervention should be integrated with strategies targeted at other risk behaviors, particularly in schools.

OBJETIVO: Describir la prevalencia de consumo de drogas ilícitas en adolescentes y los motivos que los llevan a experimentarlas. MÉTODOS: Estudio transversal con 2.499 adolescentes de 17 años, con base en una cohorte designada por EPITeen, iniciada en 2003/2004 con adolescentes nacidos en 1990 que estudiaban en las escuelas públicas y privadas de la ciudad de Porto, Portugal. Se realizó nueva evaluación en 2007/2008, siendo recuperados 1.716 adolescentes (79,4%) y evaluados 783 nuevos participantes. Informaciones sobre características sociales y demográficas, historia familiar y personal de enfermedad y comportamientos fueron obtenidas con cuestionarios estructurados auto-administrados. La prueba de chi-cuadrado fue utilizada para evaluar las asociaciones. El análisis estadístico fue realizado en el programa informático SPSS® versión 17. RESULTADOS: De los adolescentes, 14,6% relataron haber experimentado drogas alguna vez en la vida. La droga ilícita más experimentada fue la cannabis (12,5%), seguida por el alcohol simultáneamente con cannabis (5,5%) y por los tranquilizantes (1,7%). La tasa más referida para experimentar drogas fue la curiosidad (77,5%). Los amigos fueron la forma más frecuentemente referida para obtener la droga y la escuela era vista por 24,2% de los adolescentes como un lugar donde se podía comprar cannabis. CONCLUSIONES: Los resultados fundamentan la necesidad de intervenir en edades precoces y sugieren que dicha intervención debe ser integrada con estrategias dirigidas a otros comportamientos de riesgo, específicamente en medio escolar.