Thermal conductivity at DSDP Leg 60 Holes

A total of 1547 thermal conductivity values were determined by both the NP (needle probe method) and the QTM (quick thermal conductivity meter) on 1319 samples recovered during DSDP Leg 60. The NP method is primarily for the measurement of soft sedimentary samples, and the result is free from the effect of porewater evaporation. Measurement by the QTM method is faster and is applicable to all types of samples-namely, sediments (soft, semilithified, and lithified) and basement rocks. Data from the deep holes at Sites 453, 458, and 459 show that the thermal conductivity increases with depth, the rate of increase ranging from (0.18 mcal/cm s °C)/100 m at Site 459 to (0.72 mcal/cm s °C)/100 m at Site 456. A positive correlation between the sedimentary accumulation rate and the rate of thermal conductivity increase with depth indicates that both compaction and lithification are important factors. Drilled pillow basalts show nearly uniform thermal conductivity. At She 454 the thermal conductivity of one basaltic flow unit was higher near the center of the unit and lower toward the margin, reflecting variable vesicularity. Hydrothermally altered basalts at Site 456 showed higher thermal conductivity than fresh basalt because secondary calcite, quartz, and pyrite are generally more thermally conductive than fresh basalt. The average thermal conductivity in the top 50 meters of sediments correlates inversely with water depth because of dissolution of calcite, a mineral with high thermal conductivity, from the sediments as the water depth exceeds the lysocline and the carbonate compensation depth. Differences between the Mariana Trench data and the Mariana Basin and Trough data may reflect different abundances of terrigenous material in the sediment. There are remarkable correlations between thermal conductivity and other physical properties. The relationship between thermal conductivity and compressional wave velocity can be used to infer the ocean crustal thermal conductivity from the seismic velocity structure.

Geochemistry at DSDP Leg 60

Eocene to Pleistocene volcanogenic sediments from the Mariana Trough and the Mariana arc-trench system have been studied by X-ray diffraction, X-ray fluorescence, and atomic absorption, and with a scanning electron microscope with an X-ray-energy-dispersive attachment. The mineralogical composition of the volcaniclastic sediments (tuffs) is the same as that of the other associated sediments (mudstones). Diagenetic alterations are significant and seem to result from two processes. The first (low-temperature alteration) develops with age and depth; it consists of the genesis of pure smectite, coupled with zeolites (phillipsite, clinoptilolite). The second is limited to sediments immediately overlying basalts and to the altered basalts themselves. It consists of the massive development of palygorskite, and seems to be linked with hydrothermal activity in the igneous basement.

Geochemistry of carbon at DSDP Leg 60 Holes

The 11 frozen cores from the Mariana Trough area from Holes 452 through 455, 459B, 460, and 460A are characteristically low in organic carbon (less than 0.2%) and contain a predominance of n-alkanes within the saturates fraction. There is no odd-predominance of n-alkanes as is typical of immature recent sediments. However, recent sediments containing immature organic matter with normal distributions of n-alkanes {OEP1 approximately equal to 1) are characteristic of sediments derived from purely marine sources (Brooks, 1970; Powell and McKirdy, 1973; Tissot et al., 1975). This type of sediment is very rare. However, at least one case where an immature sediment contains an OEP of near 1 has been reported in samples similar to those reported herein - that is, the Cariaco Trench (Hunt, 1979).

Interstitial water chemsitry at DSDP Leg 60 Holes

Interstitial water data obtained during Leg 60 show complex gradients at Site 453 in a sediment pond on the west side of the Mariana Trough. Concentrations of Ca, Mg, Sr, as well as of K and Li, suggest that slightly altered sea water penetrates below the sediments, most likely through brecciated igneous and metamorphic rocks, mainly gabbros, lying at the base of the pond. Interstitial water concentration gradients suggest that reactions involving igneous matter lead to increases in calcium and strontium in the pore fluids and to decreases in magnesium. Upward advection of water through the sediments does not appear to occur, so that the advected sea water most likely penetrates deeper into the breccias, perhaps leading to further hydrothermal activity elsewhere in this area. Interstitial water gradients at Sites 458 (conservative) and 459 suggest that reactions in the sediments and underlying basalts are responsible for increases in dissolved calcium and decreases in magnesium and potassium.

Ciência e pedagogia científica: um estudo das práticas acadêmicas no Instituto de Física da Universidade Federal do Rio de Janeiro

O Instituto de Física da Universidade Federal do Rio de Janeiro foi criado pela resolução nº 21 de 1964 do Conselho Universitário da Universidade do Brasil, e mantido pelo Decreto nº 60.455-A de 13.03.67 que aprovou o plano de reestruturação da Universidade Federal do Rio de Janeiro - ex-Universidade do Brasil. O Instituto é uma unidade desta Universidade , subordinado ao Centro de Ciências Matemáticas e da Natureza. Este está dividido em departamentos que são a menor fração da estrutura acadêmica da Universidade. A responsabiliade deste é de planejar, executar e controlar a pesquisa e o ensino na sua área de conhecimento. Assim, as atividades desenvolvidas no Instituto sãa de pesquisa e ensino e devem envolver todo o corpo docente. Mas, verifica-se que há no Instituto um profundo desinteresse pelo ensino. A educação científica é uma atividade de rotina, burocratizada, baseada na repetição de textos de manuais, severamente criticados pelo seu caráter simplificador dos conceitos e da própria visão de ciência. Essa prática, assim conduzida, vem se repetindo, ao longo dos anos, formando professores reprodutores e pesquisadores de ciência normal. Para repensar a prãtica pedagógica científica é necessário analisar, em profundidade, a ciência e a pedagogia, científica, suportes teóricos das práticas realizadas no Instituto. Isso significa explicitar a concepção de ciência que fundamenta as formas de ensinar e pesquisar. Para tanto, o trabalho, aqui desenvolvido. pautou-se em estudo da realidade acadêmica do Instituto, bem como, em concepções de filosofia da ciência, relevantes na atualidade, como as de Bachelard e Kuhn. Estes subsídios assim construidos, indicam caminhos para a elaboração de uma nova pedagogia que se contrapõe à vigente.

Petrological parameters of sands and sandstones from DSDP and ODP holes in arc-related areas

Detrital modes for 524 deep-marine sand and sandstone samples recovered on circum-Pacific, Caribbean, and Mediterranean legs of the Deep Sea Drilling Project and the Ocean Drilling Program form the basis for an actualistic model for arc-related provenance. This model refines the Dickinson and Suczek (1979) and Dickinson and others (1983) models and can be used to interpret the provenance/tectonic history of ancient arc-related sedimentary sequences. Four provenance groups are defined using QFL, QmKP, LmLvLs, and LvfLvmiLvl ternary plots of site means: (1) intraoceanic arc and remnant arc, (2) continental arc, (3) triple junction, and (4) strike-slip-continental arc. Intraoceanic- and remnant-arc sands are poor in quartz (mean QFL%Q < 5) and rich in lithics (QFL%L > 75); they are predominantly composed of plagioclase feldspar and volcanic lithic fragments. Continental-arc sand can be more quartzofeldspathic than the intraoceanic- and remnant-arc sand (mean QFL%Q values as much as 10, mean QFL%F values as much as 65, and mean QmKP%Qm as much as 20) and has more variable lithic populations, with minor metamorphic and sedimentary components. The triple-junction and strike-slip-continental groups compositionally overlap; both are more quartzofeldspathic than the other groups and show highly variable lithic proportions, but the strike-slip-continental group is more quartzose. Modal compositions of the triple junction group roughly correlate with the QFL transitional-arc field of Dickinson and others (1983), whereas the strike-slip-continental group approximately correlates with their dissected-arc field.