990 resultados para 104-642A
Resumo:
Molecular and isotope compositions of headspace and total (free + sorbed) hydrocarbon gases from drilled cores of the three ODP Leg 104 Sites 642, 643, and 644 of the Voring Plateau are used to characterize the origin and distribution of these gases in Holocene to Eocene sediments. Only minor amounts of methane were found in the headspace (0.1 to < 0.001 vol%). Although methane through propane are present in all of the total gas samples, different origins account for the concentration and composition variations found. Site 643 at the foot of the outer Voring Plateau represents a geological setting with poor hydrocarbon generating potential, (sediments with low TOC and maturity overlying oceanic basement). Correspondingly, the total gas concentrations are low, typical for background gases (yield C1 - 4 = 31 to 232 ppb, C1/C2+ = 0.6 to 4; delta13C(CH4) -22 per mil to -42 per mil) probably of a diagenetic origin. Holocene to Eocene sediments, which overlie volcanic units, were drilled on the outer Vdring Plateau, at Holes 642B and D. Similar to Site 643, these sediments possess a poor hydrocarbon generating potential. The total gas character (yield C1 - 4 = 20 to 410 ppb; C1/C2+ = 1.7 to 13.3; delta13C(CH4) ca. -23 per mil to -40 per mil) again indicates a diagenetic origin, perhaps with the addition of some biogenic gas. The higher geothermal gradient and the underlying volcanics do not appear to have any influence on the gas geochemistry. The free gas (Vacutainer TM) in the sediments at Site 644 are dominated by biogenic gas (C1/C2+ > 104; delta13C(CH4) -77 per mil). Indications, in the total gas, of hydrocarbons with a thermogenic signature (yield C1 - 4 = 121 to 769 ppb, C1/ C2+ = 3 to 8; delta13C(CH4) = -39 per mil to -71 per mil), could not be unequivocally confirmed as such. Alternatively, these gases may represent mixtures of diagenetic and biogenic gases.
Resumo:
La figura de Servio y su comentario a la obra virgiliana constituye la summa opera de la tradición escolar tardoantigua; su importancia reside porque es el resultado de numerosas estratificaciones que recogen diversos abordajes exegéticos. Al tratarse de un comentario ?continuo?, los Commentarii servianos comprenden un conjunto de saberes que examinan la obra literaria desde la perspectiva histórica y de todo aquello que se relacionaba con esta. A partir de esta mirada lectora, la comunicación se centrará en el análisis que Servio realiza sobre la naumaquia del libro V de la Eneida (vv. 104-285), donde el texto base expone una secuencia narrativa caracterizada por epicismos homéricos y pos-homéricos que el gramático desarticula, privilegiando aspectos como el lingüístico, retórico, fabuloso y histórico-arqueológico. Asimismo, se comprobará que el certamen virgiliano constituye un pretexto para instalar un nuevo contexto que garantice la continuidad del sistema burocrático imperial
Resumo:
Trace element and isotopic signatures of magmatic rock samples from ODP Hole 642E at the Vøring Plateau provide insight into the interaction processes of mantle melt with crust during the initial magma extrusion phases at the onset of the continental breakup. The intermediate (basaltic-andesitic) to felsic (dacitic and rhyolitic) Lower Series magmas at ODP Hole 642E appear to be produced by large amounts of melting of upper crustal material. This study not only makes use of the traditional geochemical tools to investigate crust-mantle interaction, but also explores the value of Cs geochemistry as an additional tool. The element Cs forms the largest lithophile cation, and shows the largest contrast in concentration between (depleted) mantle and continental crust. As such it is a very sensitive indicator of involvement of crustal material. The Cs data reinforce the conclusion drawn from isotopic signatures that the felsic magmas are largely anatectic crustal melts. The down-hole geochemical variation within ODP Hole 642E defines a decreasing continental crustal influence from the Lower Series into the Upper Series. This is essential information to distinguish intrinsic geochemical properties of the mantle melts from signatures imposed by crustal contamination. A comparison with data from the SE Greenland margin highlights the compositional asymmetry of the crust-mantle interactions at both sides of the paleo-Iapetus suture. While Lower Series and Middle Series rocks from the SE Greenland margin have isotopic signatures reflecting interactions with lower and middle crust, such signatures have not been observed at the mid-Norwegian margin. The geochemical data either point to a dissimilar Caledonian crustal composition and/or to different geodynamic pre-breakup rifting history at the two NE Atlantic margin segments.
Resumo:
La figura de Servio y su comentario a la obra virgiliana constituye la summa opera de la tradición escolar tardoantigua; su importancia reside porque es el resultado de numerosas estratificaciones que recogen diversos abordajes exegéticos. Al tratarse de un comentario ?continuo?, los Commentarii servianos comprenden un conjunto de saberes que examinan la obra literaria desde la perspectiva histórica y de todo aquello que se relacionaba con esta. A partir de esta mirada lectora, la comunicación se centrará en el análisis que Servio realiza sobre la naumaquia del libro V de la Eneida (vv. 104-285), donde el texto base expone una secuencia narrativa caracterizada por epicismos homéricos y pos-homéricos que el gramático desarticula, privilegiando aspectos como el lingüístico, retórico, fabuloso y histórico-arqueológico. Asimismo, se comprobará que el certamen virgiliano constituye un pretexto para instalar un nuevo contexto que garantice la continuidad del sistema burocrático imperial
