First Precise U-pb Baddeleyite Ages Of 1500ma Mafic Dykes From The São Francisco Craton, Brazil, And Tectonic Implications

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The São Francisco Craton (SFC) is an Archaean-Proterozoic craton that hosts a significant number of mafic intrusions. Previous attempts to date the igneous emplacement of these rocks are limited to a few poor precision Rb-Sr and Sm-Nd isochrons. Here, dykes from the Curaçá belt, in the northeastern portion of the craton, as well as from the Chapada Diamantina region in the central part, were dated using U-Pb on baddeleyite (ID-TIMS). These dykes yielded similar baddeleyite U-Pb ages of 1506.7. ±. 6.9. Ma (Curaçá) and 1501.0. ±. 9.1. Ma (Chapada), with converging trends indicating a possible magmatic centre located near the western margin of the São Francisco Craton. The two dyke swarms are subalkaline, and have light rare earth enriched chondrite-normalized patterns but the Curaçá dykes have lower Mg-number and higher abundances of most incompatible trace elements than the Chapada dykes. Geochemical modelling and trace element ratios suggest that the two dyke swarms had different petrogenesis, with the Chapada dykes being derived from more depleted mantle sources and the Curaçá dykes from enriched sources, however the mantle sources of both dyke swarms appear to have had contributions from an enriched plume. Current geochronological and palaeomagnetic data suggest a coherent São Francisco-Congo block from at least the late Mesoproterozoic until the opening of the South Atlantic (ca. 130. Ma ago). The discovery of ca. 1500. Ma intrusions in the São Francisco Craton is a major step forward to a more complete barcode record for the SFC-Congo Craton, which can be used in future palaeo-continental reconstructions. © 2012 Elsevier B.V.174144156#302590/2008-0; CNPqConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Alkmim, F.F., Brito Neves, B.B., Alves, J.A.C., Arcabouço tectÔnico do Cráton do São Francisco - uma revisão (1993) O Cráton do São Francisco, pp. 45-62. , Sociedade Brasileira de Geologia, Salvador, J.M.L. Dominguez, A. 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The geological roots of South America: 4.1 Ga and 3.7 Ga zircon crystals discovered in N.E. Brazil and N.W. Argentina

International audienceWe present new LA-ICP-MS in situ geochronological results for seven Eoarchean zircons dated at 3.7 Ga coming from Cretaceous ash layers of NW Argentina and one Hadean single crystal sampled within the São Francisco Craton in NE Brazil. This zircon comprises a zoned magmatic core dated at 4.1 Ga surrounded by a 1.9 Ga overgrowth related to Paleoproterozoic reworking. This Hadean age is consistent with previously published Nd model ages on orthogneisses from the same domain. These two results represent among the oldest geological witnesses discovered to date in South America, which demonstrates the occurrence of a primitive crust. The contrasting age patterns recorded in both samples and localities indicate that at least two different nuclei of early crust survived in the continental domain. The São Francisco Craton in Brazil can be now considered as one of the very few areas where rare occurrences of Hadean zircon record the early evolution of the Earth

Surto de pitiose cutânea em bovinos Outbreak of cutaneous pythiosis in cattle

Setenta e seis bovinos, sem raça definida, jovens, de ambos os sexos, apresentaram lesões cutâneas multifocais nodulares, ulceradas e crostosas nas faces medial e lateral dos membros anteriores e posteriores, região ventral do pescoço, esterno e cauda. A doença ocorreu no verão e as lesões foram observadas nas regiões do corpo que ficavam grande tempo em contato com a água em canais de irrigação. Histologicamente observaram-se múltiplos granulomas e piogranulomas contendo escassas imagens negativas de hifas na área central, as quais foram melhor evidenciadas através da técnica de metenamina nitrato de prata de Grocott. O diagnóstico etiológico definitivo foi baseado na técnica de imuno-histoquímica com anticorpo policlonal anti-Pythium insidiosum. Adicionalmente, foi realizado o teste de ELISA indireto. Surtos de pitiose cutânea bovina são incomuns e, particularmente neste relato, todos os animais afetados tiveram cura espontânea das lesões dentro de duas a três semanas.<br>Seventy-six young mixed breed cattle of both sexes, presented multifocal ulcerated nodular cutaneous lesions localized in the medial and lateral aspects of fore and hindlimbs, ventral neck, sternum, and tail. The disease occurred during summer and lesions were observed on areas of the body which were in contact with water of irrigation channels for long periods. Histologically, there were multiple granulomas and pyogranulomas with few negative profiles of hyphae, which were better visualized throughout Grocott methenamine silver stain. Definitive etiologic diagnosis was based on immuno-histochemistry with anti-Pythium insidiosum polyclonal antibody. Additionally, an indirect ELISA test was performed. Bovine cutaneous pythiosis outbreaks are uncommon and, particularly as occurred in the cattle of this report, all affected animals had spontaneous healing within two to three weeks