On Pressing McNollgast to the Limits: The Problem of Regulatory Costs

The rationale for and the utility of the procedures that an administrative agency must follow in order to adopt rules are discussed. The Administrative Procedure Act\u27s rulemaking procedure is examined for cost effectiveness

Origins of chemical diversity of back-arc basin basalts: a segment-scale study of the Eastern Lau Spreading Center

We report major, trace, and volatile element data on basaltic glasses from the northernmost segment of the Eastern Lau Spreading Center (ELSC1) in the Lau back-arc basin to further test and constrain models of back-arc volcanism. The zero-age samples come from 47 precisely collected stations from an 85 km length spreading center. The chemical data covary similarly to other back-arc systems but with tighter correlations and well-developed spatial systematics. We confirm a correlation between volatile content and apparent extent of melting of the mantle source but also show that the data cannot be reproduced by the model of isobaric addition of water that has been broadly applied to back-arc basins. The new data also confirm that there is no relationship between mantle temperature and the wet melting productivity. Two distinct magmatic provinces can be identified along the ELSC1 axis, a southern province influenced by a “wet component” with strong affinities to arc volcanism and a northern province influenced by a “damp component” intermediate between enriched mid-ocean ridge basalts (E-MORB) and arc basalts. High–field strength elements and rare earth elements are all mobilized to some extent by the wet component, and the detailed composition of this component is determined. It differs in significant ways from the Mariana component reported by E. Stolper and S. Newman (1994), particularly by having lower abundances of most elements relative to H_(2)O. The differences can be explained if the slab temperature is higher for the Mariana and the source from which the fluid is derived is more enriched. The ELSC1 damp component is best explained by mixing between the wet component and an E-MORB-like component. We propose that mixing between water-rich fluids and low-degree silicate melts occurs at depth in the subduction zone to generate the chemical diversity of the ELSC1 subduction components. These modified sources then rise independently to the surface and melt, and these melts mix with melts of the background mantle from the ridge melting regime to generate the linear data arrays characteristic of back-arc basalts. The major and trace element framework for ELSC1, combined with different slab temperatures and compositions for difference convergent margins, may be able to be applied to other back-arc basins around the globe

Cinco modelos de adjudicação administrativa (justiça administrativa)

Regimes regulatórios e de distribuição de benefícios ocasionam um grande número de disputas individuais entre agências governamentais e particulares. Cada país precisa de um sistema de adjudicação administrativa para solucionar essas disputas corretamente, com justiça e eficiência. Esses sistemas geralmente compreendem três fases – decisão inicial, reconsideração administrativa e revisão judicial. Entretanto, os detalhes dos vários sistemas empregados ao redor do mundo são impressionantemente diferentes, e muitos países tendem a investir a maior parte dos recursos adjudicatórios em apenas uma dessas três fases (e os particulares que têm uma disputa com o governo tendem a confiar mais em uma das fases do que nas outras duas). Este artigo propõe uma metodologia para a classificação desses sistemas. Ele identifica quatro variáveis importantes: agências com funções combinadas ou tribunals separados; procedimento inquisitório ou adversarial; revisão judicial que pode ser aberta à introdução de novas provas ou fechada a elas; e revisão judicial feita por cortes de competência comum ou especializada. O artigo identifica cinco modelos mais usados ao redor do mundo, que envolvem diferentes combinações dessas variáveis. Os Estados Unidos, por exemplo, utilizam agências com funções combinadas, procedimento adversarial e revisão judicial fechada procedida por cortes de competência comum. Por outro lado, o Reino Unido utiliza um tribunal independente para reconsiderar decisões iniciais das agências. A França utiliza o sistema de revisão judicial aberta efetuada por uma corte especializada. Cada um desses modelos pode oferecer decisões corretas e eficientes, preservando a justiça. Finalmente, o artigo discute transplantes de um sistema de adjudicação administrativa para outro. Existem vários exemplos de transplantes bem sucedidos. O artigo sugere que os Estados Unidos deveriam considerar a adoção de um tribunal para a seguridade social (à semelhança dos tribunals do Reino Unido e da Austrália) para substituir o atual sistema de adjudicação nos litígios envolvendo a seguridade social

Origins of Chemical Diversity of Back-Arc Basin Basalts: A Segment-Scale Study of the Eastern Lau Spreading Center

We report major, trace, and volatile element data on basaltic glasses from the northernmost segment of the Eastern Lau Spreading Center (ELSC1) in the Lau back-arc basin to further test and constrain models of back-arc volcanism. The zero-age samples come from 47 precisely collected stations from an 85 km length spreading center. The chemical data covary similarly to other back-arc systems but with tighter correlations and well-developed spatial systematics. We confirm a correlation between volatile content and apparent extent of melting of the mantle source but also show that the data cannot be reproduced by the model of isobaric addition of water that has been broadly applied to back-arc basins. The new data also confirm that there is no relationship between mantle temperature and the wet melting productivity. Two distinct magmatic provinces can be identified along the ELSC1 axis, a southern province influenced by a wet component with strong affinities to arc volcanism and a northern province influenced by a damp component intermediate between enriched mid-ocean ridge basalts (E-MORB) and arc basalts. High field strength elements and rare earth elements are all mobilized to some extent by the wet component, and the detailed composition of this component is determined. It differs in significant ways from the Mariana component reported by E. Stolper and S. Newman (1994), particularly by having lower abundances of most elements relative to $H_2O$. The differences can be explained if the slab temperature is higher for the Mariana and the source from which the fluid is derived is more enriched. The ELSC1 damp component is best explained by mixing between the wet component and an E-MORB-like component. We propose that mixing between water-rich fluids and low-degree silicate melts occurs at depth in the subduction zone to generate the chemical diversity of the ELSC1 subduction components. These modified sources then rise independently to the surface and melt, and these melts mix with melts of the background mantle from the ridge melting regime to generate the linear data arrays characteristic of back-arc basalts. The major and trace element framework for ELSC1, combined with different slab temperatures and compositions for difference convergent margins, may be able to be applied to other back-arc basins around the globe.Earth and Planetary Science

Advances in Shock Compression of Mantle Materials and Implications

Hugoniots of lower mantle mineral compositions are sensitive to the conditions where they cross phase boundaries including both polymorphic phase transitions and partial to complete melting. For SiO_2, the Hugoniot of fused silica passes from stishovite to partial melt (73 GPa, 4600 K) whereas the Hugoniot of crystal quartz passes from CaCi_2 structure to partial melt (116 GPa, 4900 K). For Mg_2SiO_4, the forsterite Hugoniot passes from the periclase +MgSiO_3 (perovskite) assemblage to melt before 152 GPa and 4300 K, whereas the wadsleyite Hugoniot transforms first to periclase +MgSiO_3 (post-perovskite) and then melts at 151 GPa and 4160 K. Shock states achieved from crystal enstatite are molten above 160 GPa. High-pressure Grüneisen parameters for molten states of MgSiO_3 and Mg_2SiO_4 increase markedly with compression, going from 0.5 to 1.6 over the 0 to 135 GPa range. This gives rise to a very large (>2000 K) isentropic rise in temperature with depth in thermal models of a primordial deep magma ocean within the Earth. These magma ocean isentropes lead to models that have crystallization initiating at mid-lower mantle depths. Such models are consistent with the suggestion that the present ultra-low velocity zones, at the base of the lowermost mantle, represent a dynamically stable, partially molten remnant of the primordial magma ocean. The new shock melting data for silicates support a model of the primordial magma ocean that is concordant with the Berkeley-Caltech iron core model [1] for the temperature at the center of the Earth