Isotopic and chemical compositions of rocks and minerals from the TAG hydrothermal mound, ODP Site 957

Strontium- and oxygen-isotopic measurements of samples recovered from the Trans-Atlantic Geotraverse (TAG) hydrothermal mound during Leg 158 of the Ocean Drilling Program provide important constraints on the nature of fluid-rock interactions during basalt alteration and mineralization within an active hydrothermal deposit. Fresh Mid-Ocean Ridge Basalt (MORB), with a 87Sr/86Sr of 0.7026, from the basement beneath the TAG mound was altered at both low and high temperatures by seawater and altered at high temperature by near end-member black smoker fluids. Pillow breccias occurring beneath the margins of the mound are locally recrystallized to chlorite by interaction with large volumes of conductively heated seawater (>200°C). The development of a silicified, sulfide-mineralized stockwork within the basaltic basement follows a simple paragenetic sequence of chloritization followed by mineralization and the development of a quartz+pyrite+paragonite stockwork cut by quartz-pyrite veins. Initial alteration involved the development of chloritic alteration halos around basalt clasts by reaction with a Mg-bearing mixture of upwelling, high-temperature (>300°C), black smoker-type fluid with a minor (<10%) proportion of seawater. Continued high-temperature (>300°C) interaction between the wallrock and these Mg-bearing fluids results in the complete recrystallization of the wallrock to chlorite+quartz+pyrite. The quartz+pyrite+paragonite assemblage replaces the chloritized basalts, and developed by reaction at 250-360°C with end-member hydrothermal fluids having 87Sr/86Sr ~0.7038, similar to present-day vent fluids. The uniformity of the 87Sr/86Sr ratios of hydrothermal assemblages throughout the mound and stockwork requires that the 87Sr/86Sr ratio of end-member hydrothermal fluids has remained relatively constant for a time period longer than that required to change the interior thermal structure and plumbing network of the mound and underlying stockwork. Precipitation of anhydrite in breccias and as late-stage veins throughout most of the mound and stockwork, down to at least 125 mbsf, records extensive entrainment of seawater into the hydrothermal deposit. 87Sr/86Sr ratios indicate that most of the anhydrite formed from ~2:1 mixture of seawater and black smoker fluids (65%±15% seawater). Oxygen-isotopic compositions imply that anhydrite precipitated at temperatures between 147°C and 270°C and require that seawater was conductively heated to between 100°C and 180°C before mixing and precipitation occurred. Anhydrite from the TAG mound has a Sr-Ca partition coefficient Kd ~0.60±0.28 (2 sigma). This value is in agreement with the range of experimentally determined partition coefficients (Kd ~0.27-0.73) and is similar to those calculated for anhydrite from active black smoker chimneys from 21°N on the East Pacific Rise. The d18O (for SO4) of TAG anhydrite brackets the value of seawater sulfate oxygen (~9.5?). Dissolution of anhydrite back into the oceans during episodes of hydrothermal quiescence provides a mechanism of buffering seawater sulfate oxygen to an isotopically light composition, in addition to the precipitation and dissolution of anhydrite within the oceanic basement during hydrothermal recharge at the mid-ocean ridges.

Noble metals and associated trace elements in sulfides from the active TAG mound, ODP Site 158-957

Primary sulfides from cores of ODP Holes 158-957M, 158-957C, and 158-957H on the active TAG hydrothermal mound (Mid-Atlantic Ridge, 26°08'N) have been studied for concentrations of several chemical elements. Based on 262 microprobe analyses it has been found that the sulfides have extremely heterogeneous distribution of noble metals (Au, Ag, Pt, and Pd) and several associated elements (Hg, Co, and Se). Noble metals are arranged in the following order in terms of decreasing abundance, i.e. concentration level above detection limits (the number of analyses containing a specific element is given in parentheses): Au (65), Ag (46), Pt (21), and Pd (traces). The associated trace elements have the following series: Co (202), Hg (132), and Se (49). The main carriers of "invisible" portion of the noble metals are represented by pyrite (Au, Hg), marcasite and pyrite (Ag, Co), sphalerite and chalcopyrite (Pt, Pd), and chalcopyrite (Se). Noble metal distribution in sulfides reveals a lateral zonality: maximal concentrations and abundance of Au in chalcopyrite (or Pt and Ag in chalcopyrite and pyrite) increase from the periphery (Hole 957H) to the center (holes 957C and 957M) of the hydrothermal mound, while Au distribution in pyrite displays a reversed pattern. Co concentration increases with depth. Vertical zonality in distribution of the elements mentioned above and their response to evolution of ore genesis are under discussion in the paper.

Composition of hydrothermal massive sulfide deposits from ODP Site 158-957 and Leg 169 sites

Sulfide mineral major and trace element analyses were performed on more than 50 polished slabs representing mineralization from three seafloor hydrothermal massive sulfide deposits. Samples from the Bent Hill and ODP Mound massive sulfide deposits, both on the Juan de Fuca Ridge, can be contrasted with samples from the Trans-Atlantic Geotraverse (TAG) hydrothermal mound on the Mid-Atlantic Ridge. The massive sulfide at Bent Hill is predominantly pyrite and pyrrhotite, with increasing amounts of copper-bearing sulfide minerals at the base of the massive sulfide body and through the stockwork to an interval 200 m below seafloor that hosts high copper mineralization (Deep Copper Zone). ODP Mound contains much more abundant sphalerite and copper-bearing sulfides as compared to either Bent Hill or TAG, which are predominantly pyrite with much less abundant chalcopyrite. Copper-bearing sulfides from the Deep Copper Zone beneath Bent Hill and the lowest sampled interval of ODP Mound are petrographically and chemically similar, but distinct from copper-bearing minerals higher in either sequence.

Reutilización del Treebank de dependencias del euskera para la construcción del gold standard de la sintaxis superficial de la gramática de restricciones (CG)

El objetivo del trabajo consiste en reutilizar el Treebank de dependencias EPECDEP (BDT) para construir el gold standard de la sintaxis superficial del euskera. El paso básico consiste en el estudio comparativo de los dos formalismos aplicados sobre el mismo corpus: el formalismo de la Gramática de Restricciones (Constraint Grammar, CG) y la Gramática de Dependencias (Dependency Grammar, DP). Como resultado de dicho estudio hemos establecido los criterios lingüísticos necesarios para derivar la funciones sintácticas en estilo CG. Dichos criterios han sido implementados y evaluados, así en el 75% de los casos se derivan automáticamente las funciones sintácticas para construir el gold standard.

„Nemek kultúrája”: előzetes eredmények egy multinacionális cég vizsgálatából

A tanulmány a szervezeti kultúra fogalmán belül értelmezi a nemek szerinti elvárás rendszer, a nemekhez kapcsolódó normák és értékek megragadhatóságát. A szervezetkutatások az elmúlt évtizedek során intenzíven foglalkoztak a kultúrakutatással, a feminista elméletek pedig egyre gyakrabban vizsgálták a szervezeteket a nemek szerinti rétegződés szempontjából. E két terület összekapcsolásaként is értelmezhető ez a kísérlet, amely során egy gazdálkodószervezetben végeztünk kutatást a nemekre vonatkozó vélemények és értékek, a nemek helyzetének feltárására. A kutatás során a fókuszcsoportos beszélgetés módszerét alkalmaztuk, és két beosztotti csoport elemzését végeztük el. A kutatásra 2011 tavaszán került sor egy szolgáltató informatikai cég közép-magyarországi telephelyén.

Determinação de marcadores orgânicos no perfil sedimentar do complexo estuarino de Paranaguá (PR) por CG-EM

A avaliação do aporte de matéria orgânica no ambiente aquático por atividades antrópicas pode ser realizada através da identificação e quantificação de marcadores moleculares. Diversos estudos apontam à aplicação dos marcadores moleculares com esta finalidade, no entanto, poucos avaliam a variação das concentrações desses compostos ao longo do tempo, registrada nas camadas sedimentares. O presente trabalho realiza um estudo a partir de três classes de marcadores moleculares presentes em perfis sedimentares da região do Complexo Estuarino de Paranaguá (CEP) no Paraná (PR), que nos últimos anos vêm sofrendo com o crescente desenvolvimento de atividades antrópicas. Como objetivo, tem-se identificar as principais fontes de matéria orgânica e estudar o histórico destes aportes em colunas sedimentares do CEP, relacionando as taxas de sedimentação com a deposição de origem natural e antrópica. A legislação vigente para o monitoramento ambiental, no que diz respeito à contaminação por esgoto fecal, sugere a avaliação por indicadores microbiológicos, porém, indicadores químicos como os esteróides fecais são uma alternativa bastante promissora, pois estes são persistentes, sendo menos sensíveis a variações ambientais. Outros dois marcadores moleculares de aportes antrópicos ao ambiente que foram determinados neste estudo são os alquilbenzenos lineares (LABs), presente em detergentes, que indicam aportes antrópicos oriundos de esgoto doméstico e a determinação de cafeína, tendo em vista que os esteróides fecais podem ser originários de fezes de animais de sangue quente, podendo indicar outras fontes. Para o presente trabalho foram coletados 12 testemunhos de até 1 m de profundidade em maio de 2006, totalizando 12 pontos de coleta e um montante de 121 amostras. As análises foram realizadas por cromatografia em fase gasosa com detecção por espectrometria de massas (CG-EM). Os esteróides encontrados em maior concentração foram o β- sitosterol (71,4 µg g-1), estigmasterol (8,7 µg g-1), colestanol (3,6 µg g-1) e o estigmastanol (2,8 µg g-1), todos oriundos de fonte natural, indicando que a maior contribuição para o CEP é por aporte biogênico. O coprostanol, que é um esterol fecal, foi encontrado entre as concentrações de 0,001 e 4,10 µg g-1, outros dois esteróides de origem fecal também foram detectados, coprostanona e epicoprostanol, onde as maiores concentrações foram 3,6 e 0,2 µg g-1, respectivamente, sendo encontrados em regiões próximas a centros urbanos, indicando origem antrópica. As maiores concentrações para o ∑LABs também foram encontradas em regiões próximas às cidades de Antonina e Paranaguá, sendo a maior encontrada no testemunho #3 Gererês (208 ng g-1). Para o último marcador molecular analisado, a cafeína, foi encontrada a maior concentração de 18,41 ng g-1, sendo este ponto localizado longe dos centros urbanos, porém este contaminante é bastante solúvel em água podendo ser transportado na coluna d’água e percorrer grandes distâncias. Através dos compostos analisados, pode-se perceber que a intervenção antropogênica foi mais marcante nos testemunhos coletados no eixo leste-oeste do CEP, ficando registrado nas camadas sedimentares.