Mineralização de torita associada ao Depósito Madeira (Sn-Nb-Ta), Pitinga, Amazonas, Brasil

O depósito Madeira (Sn, Nb, Ta) está localizado na mina de Pitinga (norte do Brasil). O depósito é associado à fácies albita granito do Granito Madeira, de tipo A (~1,820 Ma). A mina extrai comercialmente Sn (cassiterita), Nb e Ta (U-Pb-pirocloro e zircão). Flúor (criolita), Y, REE (xenotima), Zr (zircão), U (U-Pb-pirocloro e zircão) e Th (torita) são subprodutos em potencial. Este trabalho apresenta um estudo detalhado da mineralização de torita nas subfacies do albita granito: albita granito de núcleo, albita granito de borda e pegmatitos associados. O depósito Madeira é apresentado neste trabalho como um dos maiores depósitos de Th do mundo, com 164 Mt de minério disseminado, teor médio de 759 ppm ThO2 na rocha, e concentrações maiores (de até 1,8 wt.% ThO2) em pegmatitos pequenos (média de ~0,51 wt.% ThO2). Composicionalmente, a torita deste estudo pode ocorrer próxima do polo da torita ou representar substituições relativamente limitadas no sistema de soluções sólidas torita-zircão-xenotima-coffinita. A concentração de Fe na torita varia entre 0,11 wt.% Fe2O3 e 29,56 wt.% Fe2O3 e, em muitos casos, é considerada de natureza estrutural, assim como o conteúdo de F (de até 6,02 wt.% F). A torita de todas as subfacies foram fortemente afetadas por alterações hidrotermais relacionadas a fluidos aquosos ricos em F de baixa temperatura. A hidratação da torita permitiu a introdução de M3+ cátions (Y, ETR, Fe e Al) e F, e causou perdas no conteúdo de Si e Th (média de ~0,51 wt.% ThO2). A alteração também foi responsável pela formação de uma auréola de Fe nos grãos de torita, com minerais secundários associados, provavelmente Th-Fe-hidroxifluoretos e Y-Th-Fe-fluorcarbonatos. A média da razão Th/U em rocha total é de 1,85 no albita granito de borda, 3,82 no albita granito de núcleo, e 19,85 nos pegmatitos associados. Esta variação reflete um padrão de evolução magmática, com maior disponibilidade de U em estágios precoces e empobrecimento de U em estágios tardios. Em Pitinga, as mineralizações de Th e U são divididas em diferentes minerais, formados em estágios distintos da evolução. Esta característica está relacionada à riqueza de flúor e à alta alcalinidade do magma, que inibiram a cristalização precoce de zircão, bem como de columbita, e favoreceu a formação precoce de U-Pb-pirocloro. Quando a cristalização de silicatos hidratados reduziu a alcalinidade do magma, a cristalização de zircão (de um magma previamente empobrecido em U, Nb, Ta e ETRL) se tornou intensa, acompanhado de torita e xenotima.The world-class Sn-Nb-Ta Madeira deposit is located at the Pitinga mine (northern Brazil). The deposit is associated with the albite-enriched granite facies of the A-type Madeira Granite (~1,820 Ma). The mine commercially extracts tin (cassiterite), Nb and Ta (U-Pb-pyrochlore and columbite). Fluorine (cryolite), Y, REE (xenotime), Zr (zircon), U (U-Pb-pyrochlore and zircon) and Th (thorite) are potential byproducts. This work presents a detailed study on the thorite mineralization from the albite-enriched granite subfacies: the core albite-enriched granite, the border albite-enriched granite and the associated pegmatites. The Madeira deposit is revealed in this work to be among the largest Th deposits in the world, with 164 Mt of homogeneously dispersed ore, with an average grade of 759 ppm ThO2 in the rock, and higher concentrations (up to 1.8 wt.% ThO2) in small pegmatites (average of ~ 0.51 wt.% ThO2). Thorite compositions are either close to the thorite pole or correspond to relatively limited substitutions in the thorite-zircon-xenotime-coffinite solid solution system. The Fe concentration in thorite ranges from 0.11 wt.% to 29.56 wt.% Fe2O3 and in many cases is considered of structural nature, as well as part of the F content (up to 6.02 wt.% F). Thorites from all subfacies were strongly affected by hydrothermal alterations related to F-rich low-temperature aqueous fluids. The hydration of thorite allowed the introduction of M3+ cations (Y, REE, Fe, and Al) and F, and caused losses in Si and Th (average of ~48 wt.% ThO2). The alteration also created a Fe-rich halo in thorite, with associated secondary minerals, likely Th-Fe-hydroxyfluorides and Y-Th-Fe-fluorcarbonates. The Th/U average ratio values in bulk-rock are 1.85 in the border albite-enriched granite, 3.82 in the core albite-enriched granite, and 19.85 in the associated pegmatites. This variation reflects a magmatic evolution pattern, with higher availability of U in the earlier stages and depletion of U in late stages. At Pitinga, Th and U mineralization are divided into different minerals formed in different stages of the magma evolution. This feature is related to the richness of fluorine and the high alkalinity of the magma that greatly inhibited the early crystallization of zircon, as well of columbite, and favored the early appearance of U-Pb-pyrochlore. When the crystallization of hydrous silicates reduced the alkalinity, the crystallization of zircon (from a magma depleted in U, Nb, Ta and LREE) become intense, accompanied by thorite and xenotime

Alltag des Kindergartens im deutsch-deutschen Vergleich. [Symposion 8. Schule und Unterricht in Ost und West]

Das DFG-Projekt "Alltag des Kindergartens im deutsch-deutschen Vergleich", das gemeinsam vom "Zentrum für empirische pädagogische Forschung" und vom "Institut für Kleinkindpädagogik und familienbegleitende Kinderbetreuung (BIK)e.V." durchgeführt wird, hat in einem ersten Untersuchungsteil das Ziel, den Kindergartenalltag Ende 1993 in den neuen und alten Bundesländern in zentralen Dimensionen zu beschreiben, um eine Basis für die Erfassung von Veränderungsprozessen zu sichern. In einem zweiten Untersuchungsteil wird versucht, den Kindergartenalltag in der DDR kurz vor der Wende anhand schriftlicher Dokumente und retrospektiver Interviews zu rekonstruieren. Die Autoren gehen auf die Konzeption der Studie ein und präsentieren die Ergebnisse der Early Childhood Environmental Rating Scale (ECERS). Sie stellen die Elternarbeit aus der Sicht der Gruppenleiterin anhand der Ergebnisse der Interviews dar. Und klären die Frage: zwei Kindergartenwelten in Ost und West? Dabei konstatieren sie, dass auch im Jahre 1993, vier Jahre nach der Wende, sich der Kindergartenalltag in den neuen und den alten Bundesländern in bestimmten Aspekten beträchtlich unterscheiden. (DIPF/Orig./ah

Estudo de inclusões fluidas do Granito Parapente, Gaspar - SC, Brasil: implicações para a evolução da Zona de Cisalhamento Itajaí-Perimbó

TCC(graduação) - Universidade Federal de Santa Catarina. Centro de Filosofia e Ciências Humanas. Geologia.A Zona de Cisalhamento Itajaí-Perimbó (ZCIP) é uma importante descontinuidade crustal no Escudo Catarinense relacionada à evolução do Cinturão Dom Feliciano. As ativações desta zona de falha abrangem um período que vai de aproximadamente 600 Ma até 250 Ma. O Granito Parapente (GP) encontra-se alojado em meio à ZCIP e possui uma idade de cristalização de 843 Ma (SHRIMP), podendo ser utilizado como marcador da evolução desta zona de cisalhamento. Neste trabalho são analisadas inclusões fluidas de diferentes gerações de quartzo do granito. O objetivo é estimar condições de pressão e temperatura (e profundidade) relacionadas a diferentes etapas de evolução da ZCIP e do próprio GP. As inclusões analisadas representam fluidos de baixa salinidade (2-6% peso eq. NaCl) com temperaturas mínimas de aprisionamento com intervalos entre 220ºC-190ºC no quartzo considerado mais antigo (observado no granito menos deformado); 160ºC-130ºC em quartzo de filonito; e 260ºC-220ºC e 190ºC-170ºC em quartzo de um veio mais recente. Os dados obtidos, e sua comparação com dados disponíveis na bibliografia, mostram que a ZCIP funcionou como conduto para fluidos diversos durante um longo período de tempo. O GP contém rochas cuja evolução se associa a diferentes níveis crustais (16 km, 10 km e <8,5 km). Os filonitos se formaram em condições de aproximadamente 350ºC de temperatura e pressão na ordem de 4 kbar. Estas condições condizem com o limite de transição de deformação plástico-frágil em falhas crustais pondo em evidência a importância dos fluidos para a formação desta rocha, pois sem a ação de um fluido, em vez de filonitos, ter-se-iam formado cataclasitos.The Itajaí Perimbó Shear Zone (IPSZ) is an important crustal dicontinuity in the Catarinense Shield, related to the evolution of the Dom Feliciano Belt. The age range for the activations of this fault zone lie between around 600 Ma and 250 Ma.The Parapente Granite (PG), hosted within the IPSZ context with a cristalization age of 843 Ma, can be a evolution marker of the IPSZ. Fluid inclusions from different quartz generations of the granite were used to estimate the pressure and temperature conditions during the shear zone activation. These inclusions represent low salinity fluids (2-6wt% NaCl), and the minimum trapping temperatures for these fluids ranges from about 220°C to 190°C in the less deformed granite (oldest); from 160°C to 130°C in a phyllonite; and from about 260ºC to 220ºC and from 190ºC to 170ºC in a quartz vein (latter). These data shows that the ZCIP worked as a conduit for different fluids over a long period of time. The isochores obtained by the study on the Parapente Granite inclusions pointed that the shear zone was active in different crustal levels (16 km, 10 km and <8.5 km). The data indicates the formation of phyllonites in temperature conditions of about 350°C and pressures in the order of 4 kbar. These conditions are consistente with the transition threshold between plastic-brittle in crustal faults. This points to the importance of fluids in the phyllonites formation considering that without the presence of a fluid, rather than phyllonites, it would have been formed cataclasites

Evaluation of the notifiable disease surveillance system in Gauteng Province, South Africa

Objectives. To describe the qualitative aspects of the notifiable diseases surveillance system of the Gauteng Province, South Africa; to conduct a cross-sectional survey on knowledge and practices pertaining to disease notification among private sector primary health care providers in Gauteng Province; to measure the degree of underreporting of notifiable diseases versus positive laboratory diagnoses using malaria as a cases study; and to identify the correctible short-comings in the Gauteng Health Department’s diseases surveillance system and to recommend ways of addressing these to improve the system and its performance. Design. This is an evaluation study consisting of both the qualitative aspects and quantitative descriptive components of the notifiable disease system in Gauteng Province. The study designs used for the qualitative description were literature and policy review and a semi-structured interview with communicable disease coordinators. The quantitative research comprised of a telephonic questionnaire administered to a random sample of private general practioners and secondary data analysis comparing malaria cases notified to the Gauteng Provincial Department of Health with public and private sector laboratory data and clinical surveillance data. Setting. The study setting was the Gauteng Provincial Health Department and public and private health care service providers in Gauteng Province. The study period extended from 1 January to 30 June 2006. Subjects. The subjects of the study were the Gauteng Health Department’s disease surveillance system, public and private sector health care providers including private primary health care practitioners. Outcome measures. Outcome measures for the qualitative system description were the status of selected system attributes namely usefulness, simplicity, flexibility, data quality, acceptability, sensitivity, positive predictive value, representativeness and stability. Outcome measures for the knowledge and practice survey of private general practitioners were reporting compliance and knowledge of notifiable conditions. The primary outcome measure for the secondary data analysis was the proportion of laboratory diagnosed cases of malaria notified to the provincial health department. Results. The notifiable disease surveillance system in Gauteng is deemed useful by the public sector communicable disease coordinators but less so by the private sector general practitioners. Data quality as indicated by completeness of residential detail reporting on meningococcal notifications varied between 29% and 57% by district. Thirty seven percent of general practitioners report compliance with notifications and the mean score for knowledge on notification status of medical conditions was 56%. The sensitivity of notifications of malaria compared with laboratory notifications was 26% with relatively higher notification rates where cases occurred in children under 15 years of age. Conclusions. The notifiable disease surveillance system in Gauteng Province is relatively flexible and reasonably structured however this research suggests that there is suboptimal use of the information for local action in certain areas. Private General Practitioners self-report a low level of compliance citing time constraints and lack of motivation; knowledge of the notification status of selected medical conditions is lower than expected. The completeness and accuracy of notification data, as demonstrated in malaria notifications, is insufficient to gauge a true picture of burden of disease in the province.Dissertation (MMed)--University of Pretoria, 2007.School of Health Systems and Public Health (SHSPH)Unrestricte