Geochemistry of the oceanic crust from ocean drilling samples

This book presents new data on chemical and mineral compositions and on density of altered and fresh igneous rocks from key DSDP and ODP holes drilled on the following main tectonomagmatic structures of the ocean floor: 1. Mid-ocean ridges and abyssal plains and basins (DSDP Legs 37, 61, 63, 64, 65, 69, 70, 83, and 91 and ODP Legs 106, 111, 123, 129, 137, 139, 140, 148, and 169); 2. Seamounts and guyots (DSDP Legs 19, 55, and 62 and ODP Legs 143 and 144); 3. Intraplate rises (DSDP Legs 26, 33, 51, 52, 53, 72, and 74 and ODP Legs 104, 115, 120, 121, and 183); and 4. Marginal seas (DSDP Legs 19, 59, and 60 and ODP Legs 124, 125, 126, 127, 128, and 135). Study results of altered gabbro from the Southwest Indian Ridge (ODP Leg 118) and serpentinized ultramafic rocks from the Galicia margin (ODP Leg 103) are also presented. Samples were collected by the authors from the DSDP/ODP repositories, as well as during some Glomar Challenger and JOIDES Resolution legs. The book also includes descriptions of thin sections, geochemical diagrams, data on secondary mineral assemblages, and recalculated results of chemical analyses with corrections for rock density. Atomic content of each element can be quantified in grams per standard volume (g/1000 cm**3). The suite of results can be used to estimate mass balance, but parts of the data need additional work, which depends on locating fresh analogs of altered rocks studied here. Results of quantitative estimation of element mobility in recovered sections of the upper oceanic crust as a whole are shown for certain cases: Hole 504B (Costa Rica Rift) and Holes 856H, 857C, and 857D (Middle Valley, Juan de Fuca Ridge).

Lithium concentrations and isotope composition of basalt samples from ODP/DSDP Sites from Costa Rica Rift

Ocean Drilling Program (ODP) Hole 504B near the Costa Rica Rift is the deepest hole drilled in the ocean crust, penetrating a volcanic section, a transition zone and a sheeted dike complex. The distribution of Li and its isotopes through this 1.8-km section of oceanic crust reflects the varying conditions of seawater alteration with depth. The upper volcanic rocks, altered at low temperatures, are enriched in Li (5.6-27.3 ppm) and have heavier isotopic compositions (delta7Li=6.6-20.8?) relative to fresh mid-ocean ridge basalt (MORB) due to uptake of seawater Li into alteration clays. The Li content and isotopic compositions of the deeper volcanic rocks are similar to MORB, reflecting restricted seawater circulation in this section. The transition zone is a region of mixing of seawater with upwelling hydrothermal fluids and sulfide mineralization. Li enrichment in this zone is accompanied by relatively light isotopic compositions (-0.8-2.1?) which signify influence of basalt-derived Li during mineralization and alteration. Li decreases with depth to 0.6 ppm in the sheeted dike complex as a result of increasing hydrothermal extraction in the high-temperature reaction zone. Rocks in the dike complex have variable isotopic values that range from -1.7 to 7.9?, depending on the extent of hydrothermal recrystallization and off-axis low-temperature alteration. Hydrothermally altered rocks are isotopically light because 6Li is preferentially retained in greenschist and amphibolite facies minerals. The delta7Li values of the highly altered rocks of the dike complex are complementary to those of high-temperature mid-ocean ridge vent fluids and compatible to equilibrium control by the alteration mineral assemblage. The inventory of Li in basement rocks permits a reevaluation of the role of oceanic crust in the budget of Li in the ocean. On balance, the upper 1.8 km of oceanic crusts remains a sink for oceanic Li. The observations at 504B and an estimated flux from the underlying 0.5 km of gabbro suggest that the global hydrothermal flux is at most 8*10**9 mol/yr, compatible with geophysical thermal models. This work defines the distribution of Li and its isotopes in the upper ocean crust and provides a basis to interpret the contribution of subducted lithosphere to arc magmas and cycling of crustal material in the deep mantle.

(Table 2) Chlorine geochemistry and mineralogy of altered oceanic crust samples

Bulk chlorine concentrations and chlorine stable isotope compositions were determined for hydrothermally altered basalt (extrusive lavas and sheeted dikes) and gabbro samples (n = 50) from seven DSDP/ODP/IODP drill sites. These altered oceanic crust (AOC) samples span a range of crustal ages, tectonic settings, alteration type, and crustal depth. Bulk chlorine concentrations range from < 0.01 wt.% to 0.09 wt.%. In general, higher chlorine concentrations coincide with an increase in temperature of alteration and amphibole content. d37Cl values of whole rock AOC samples range from -1.4 to +1.8 per mil. High d37Cl values (>=~0.5 per mil) are associated with areas of higher amphibole content. This observation is consistent with theoretical calculations that estimate amphibole should be enriched in 37Cl compared to co-existing fluid. Negative to near zero d37Cl values are found in areas dominated by clay minerals. Chlorine geochemistry is a rough indicator of metamorphic grade and mineralogy. AOC is a major Cl host in the subducting oceanic lithospheric slab. Here we show that bulk chlorine concentrations are ~3 times higher than previous estimates resulting in a greater contribution of Cl to the mantle.

(Table 1) Strontium concentrations and isotope ratios of anhydrite from DSDP/ODP Hole 504B

In samples from 1575 to 1982 mbsf anhydrite leached from whole-rock powders. 87Sr/86Sr and Sr/Ca determined following methods described in (Teagle et al., 1996, doi:10.2973/odp.proc.sr.148.113.1996, Teagle et al., 1998, doi:10.2973/odp.proc.sr.158.223.1998). For the period of the analysis (Jan. 1994-Dec. 1995) NIST SRM 987 gave 87Sr/86Srs0.710244 +/- 0.000018 (2 sigma, n = 115). Full analytical procedural blanks were <50 pg for Sr. delta18O following (Pickthorn and O´Neil, 1985). Repeated extractions and measurements of samples and standards were reproducible within +/- 0.5.

Sapientia, 1983, Vol. XXXVIII, nº 148 (número completo)

Contenido: El ser : su constitución, su expresión conceptual / Octavio N. Derisi – En la génesis de la metafísica / Gabriel Ferrer – Qué es la filosofía, en el pensamiento de J. Dewey / William R. Darós – Fundamentos sapienciales de la ecología : oikos y téjne en la perspectiva clásica y cristiana / Héctor Aguer -- Notas y comentarios -- Bibliografía

Diário da Constituinte [gravação de vídeo] : [programa n. 148 A]

O deputado Ulysses Guimarães (PMDB-SP), presidente da Assembleia Nacional Constituinte (ANC), reuniu os lideres partidários para discutir a proposta do Deputado Plínio Arruda Sampaio (PT-SP), que almeja a divisão dos debates por temas no Plenário. O Deputado José Lourenço (PFL-BA) diz que o regimento é muito rígido e os debates devem seguir a ordem de inscrição. O Deputado Plínio Arruda Sampaio sugere mais sessões pela manhã com a discussão de temas pré-estabelecidos. O Deputado Ulysses Guimarães esclarece que, se houver acordo entre as lideranças, verificará a possibilidade de serem adotadas tais medidas. O Deputado Brandão Monteiro (PDT-RJ) explica que o Presidente da Assembleia Nacional Constituinte (ANC) está sensível no sentido de utilização de outros dias, em que o Plenário não funciona, para a definição prévia de temas. O Senador Humberto Lucena (PMDB-PB) acredita que as questões polêmicas da Assembleia Nacional Constituinte devem passar por uma decisão final do eleitorado brasileiro, através de um referendo. Na Convenção do PMDB, o partido definiu pontos importantes sobre a reforma agrária. O Deputado Mário Covas (PMDB-SP) esclarece que o substitutivo elaborado pelo Senador Severo Gomes (PMDB-SP) repete basicamente o Estatuto da Terra, com exceção de dois artigos, sendo que um deles trata da criação de varas da justiça agrária e outro trata da imissão de posse. Ele também define o que seria a função social da terra e afirma que a reforma agrária vai multiplicar o número de proprietários.

Diário da Constituinte [gravação de vídeo] : [programa n. 148]

Chegou a Assembleia Nacional Constituinte uma emenda popular, com mais de sessenta e sete mil assinaturas, que propõe a manutenção do ensino religioso nas escolas de 1º e 2º graus. O Deputado Bernardo Cabral, Relator da Comissão de Sistematização, pede que as emendas populares não cheguem no último dia. Tão logo termine o prazo de apresentação de emendas, ele pretende iniciar a elaboração de uma espécie de rascunho do substitutivo, de tal forma que o Presidente da Assembleia Nacional Constituinte (ANC), Ulysses Guimarães, as lideranças partidárias e ele próprio possam trocar ideias sobre esse esboço . O Relator quer também a ajuda dos Ministros de Estado para ouvir setores da sociedade envolvidos em temas polêmicos. O Deputado Aloysio Teixeira (PMDB-RJ) teme que a nova Carta não dure, devido a sua grande extensão, com muitos detalhes. O Deputado Chagas Rodrigues (PMDB-PI) acredita que os trabalhos da Assembleia Nacional Constituinte (ANC), estão iniciando agora. O Deputado José Carlos Coutinho (PL-RJ) considera absolutamente necessário que, dentro de um espírito de patriotismo, haja um acordo para que todas essas grandes questões nacionais sejam resolvidas nesta Constituinte. O Deputado Victor Faccioni (PDS-RS) espera que a fase do Plenário seja mais objetiva, para se alcançar resultados concretos e de tal forma que a Constituição represente a média dos anseios da população. O Deputado João Hermann (PMDB-SP) apresentou emenda para que grande parte da receita do governo federal seja repassada para o município.

Resolución N° 148 ¿Cual es el efecto que tienen los recursos propios de la vía gubernativa frente al acto de registro que expiden las Cámaras de Comercio?

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