Lithium isotopic composition of pore fluids and sediments in the Costa Rica subduction zone

Pore fluid and sediment Li concentrations and isotopic ratios provide important insights on the hydrology, sediment contribution to the arc volcanoes and fluid-sediment reactions at the dominantly non-accretionary Costa Rica subduction zone. Ocean Drilling Program Site 1039 in the trench axis provides a reference section of 400 m of the incoming sediments, and Site 1040, situated arcward from the trench, consists of a deformed sedimentary wedge and apron sediments, the décollement, and the partially dewatered underthrust sediment section. At the reference site, pore fluids show important isotopic variations (delta6Li=-21.7 to -37.8 per mil), reflecting the interplay of in situ alteration of volcanic material and ion exchange with clay minerals. In the basal section, a reversal of Li concentration and delta6Li toward seawater values is observed, providing supporting evidence for a lateral seawater flow system in the upper oceanic basement underlying this sediment section. At Site 1040, pore fluid of the lower deformed wedge sediments and within the décollement is enriched in Li and the isotopic compositions are relatively light, suggesting infiltration of a deep-seated fluid. The delta6Li value of -22 per mil of this Li-enriched fluid (261 µM), when compared with the delta6Li value of the subducted sediment section (-11 per mil), suggests that the deep source fluid originates from mineral fluid dehydration and transformation reactions at temperatures of 100 to 150°C, consistent with the temperature range of the up-dip seismogenic zone and of transformation of smectite to illite. The distribution of Li and its isotopes in the underthrust section are similar to those at the reference site, indicating near complete subduction of the incoming sediments and that early dewatering of the underthrust sediments occurs predominantly by lateral flow into the ocean. The hemipelagic clay-rich sediment section of the subducting plate carries most of the Li into this subduction zone, and the pelagic diatomaceous and nannofossil calcareous oozes contain little Li. The Li isotopes of both the clay-rich hemipelagic sediments and of the pelagic oozes are, however, similar, with delta6Li values of -9 to -12 per mil. The observations that (1) the delta6Li values of the underthrust sediments are distinctly lower than that of the mantle, and (2) the lavas of the Costa Rican volcanoes are enriched in Li and 7Li, provide an approximation of the contribution of the subducted sediments to the arc volcanoes. A first order mass balance calculation suggests that approximately half of the Li flux delivered by subducted sediments and altered oceanic crust into the Middle American Trench is recycled to the Costa Rican arc and at most a quarter of sedimentary Li is returned into the ocean through thrust faults, primarily the décollement thrust.

(Table 1) Sr-isotope values of representative sediment samples from ODP sites at the Costa Rica margin

Two sealed borehole hydrologic observatories (CORKs) were installed in two active hydrogeochemical systems at the Costa Rica subduction zone to investigate the relationship between tectonics, fluid flow, and fluid composition. The observatories were deployed during Ocean Drilling Program (ODP) Leg 205 at Site 1253, ~ 0.2 km seaward of the trench, in the upper igneous basement, and at Site 1255, ~ 0.5 km landward of the trench, in the décollement. Downhole instrumentation was designed to monitor formation fluid flow rates, composition, pressure, and temperature. The two-year records collected by this interdisciplinary effort constitute the first co-registered hydrological, chemical, and physical dataset from a subduction zone, providing critical information on the average and transient state of the subduction thrust and upper igneous basement. The continuous records at ODP Site 1253 show that the uppermost igneous basement is highly permeable hosting an average fluid flow rate of 0.3 m/yr, and indicate that the fluid sampled in the basement is a mixture between seawater (~ 50%) and a subduction zone fluid originating within the forearc (~ 50%). These results suggest that the uppermost basement serves as an efficient pathway for fluid expelled from the forearc that should be considered in models of subduction zone hydrogeology and deformation. Three transients in fluid flow rates were observed along the décollement at ODP Site 1255, two of which coincided with stepwise increases in formation pressure. These two transients are the result of aseismic slip dislocations that propagated up-dip from the seismogenic zone over the course of ~ 2 weeks terminating before reaching ODP Site 1255 and the trench. The nature and temporal behavior of strain and the associated hydrological response during these slow slip events may be an analog for the response of the seaward part of the subduction prism during or soon after large subduction zone earthquakes.

A discussion of Fashion Victims: Various responses to the report by War on Want, Critical Perspectives on International Business, Vol. 3 Iss: 2, pp.170 - 185

Purpose – The purpose of this paper is to present a selection of responses to the report Fashion Victims, published by War on Want in December 2006. It offers a range of viewpoints presented by members of the Editorial Advisory Board of CPOIB. These are presented in chronological order of submission. There is some cross-reference by contributors to the work of others, but no attempt is made to present a unified argument. Design/methodology/approach – Presents the full contributions of involved participants, without mediation or editorial change. Findings – A number of different perspectives are presented on the central issue that is summarised by the opening heading in War on Want’s report – “How cheap is too cheap?” It is seen that the answer to this question is very much dependent upon the standpoint of the respondent. Originality/value – In presenting this form of commentary, members of the CPOIB Editorial Board seek to stimulate debate about an issue of concern to contemporary society, without resort to the time delay and mediating processes of peer-review normally attached to academic writing. It is hoped that this discussion will provoke further contributions and a widening of the debate. Keywords Corporate social responsibility, Multinational companies, Conditions of employment, Trade unions

Sapientia, 1988, Vol. XLIII, nº 170 (número completo)

Contenido: La realidad del concepto de la trascendentalidad y pridcamentalidad (Cont.) / Octavio Nicolás Derisi – El entender como posesión : la función gnoseológica del verbo mental (Cont.) / J. L. González Alió -- ¿El alma humana “entre intelectual en potencia”, según Tomás de Aquino? / Ricardo Marimón Batlló – Notas y comentarios -- Bibliografía

Diário da Constituinte [gravação de vídeo] : [programa n. 170 A]

Sessão extraordinária da Assembleia Nacional Constituinte (ANC) discutirá a Reforma Agrária, um debate que promete colocar, lado a lado nas galerias, representantes da UDR (União Democrática Ruralista) e dos trabalhadores rurais. O Deputado Gonzaga Patriota (PMDB-PE) explica o posicionamento do PMDB sobre a Reforma Agrária. O Deputado Victor Fontana (PFL-SC) informa ser necessário ter, ao lado das desapropriações de terras improdutivas, uma política agrícola. O Deputado Mário Assad (PFL-MG) considera que há necessidade de se fazer uma reforma agrária sem paixão, que atenda as contingências dos produtores rurais. Imagens de pessoas assinando a emenda popular da Reforma Agrária. José Francisco, Presidente da Confederação Nacional dos Trabalhadores Agrícolas (CONTAG), estima que são mais de quatrocentas mil assinaturas colhidas. Francisco Whitaker, Presidente do Grupo Pró-Participação Popular, declara que se o povo não conseguir tudo o que quer agora, que tenha oportunidade de propor melhorias mais tarde. O Deputado Brandão Monteiro (PDT-RJ) defende plebiscitos para que o povo se manifeste sobre o sistema de governo e sobre o mandato do Presidente Sarney. O Deputado Virgílio Guimarães (PT-MG) propõe plebiscitos para aprovar ou rejeitar o texto final da Constituição e para determinados temas mais importantes. O Deputado José Lourenço (PFL-BA) declara que o mandato que recebeu do povo baiano lhe transfere autoridade para redigir a Constituição e, portanto, é contra plebiscitos. O Deputado Haroldo Lima (PC do B-BA) afirma que é justa a consulta pública. O Deputado Bernardo Cabral (PMDB-AM) questiona que, se a Constituição não for aprovada no plebiscito, então haveria a necessidade de criar outra Constituinte.

Diário da Constituinte [gravação de vídeo] : [programa n. 170]

Donas de casa fazem ato público no Congresso, ao entregar proposta de emenda popular estabelecendo concessão de aposentadoria às mulheres que trabalham no lar. Lúcia Pacífico, representante do Movimento das Donas de Casa de Minas Gerais, declara que a proposta de aposentadoria corrige injustiça social. O Plenário Pró-Participação Popular na Constituinte apresentou 350.000 assinaturas pedindo instrumentos que garantam a participação do povo na elaboração das leis. A Deputada Moema São Thiago (PDT-CE) considera que o que está em jogo é o avanço ou o retrocesso da democracia. O Deputado Geraldo Alckmin (PMDB-SP) informa que a emenda popular é muito forte, ela traz a legitimidade daquilo que o povo deseja e torna mais fidedigna a Constituinte em relação aos anseios da sociedade. Em discurso, O Deputado Ulysses Guimarães (PMDB-SP) prometeu empenho para que as emendas populares se transformem em leis. Em mesa redonda, coordenada pelo Primeiro Secretário da Assembleia Nacional Constituinte (ANC), Deputado Marcelo Cordeiro (PMDB-BA), constituintes analisam a questão econômica. Sessão extraordinária da ANC discutiu ontem: redivisão territorial, fortalecimento dos estados e municípios e a reforma tributária. O Deputado Gastone Righi (PTB-SP) almeja que o país seja dividido administrativamente em União e municípios, com o fim dos governos estaduais na Constituição. O Deputado Siqueira Campos (PDC-GO) defende a divisão do Estado de Goiás para que seja criado o Estado de Tocantins e defende a realização de um plebiscito para definir a questão.