A Pore Water/Solid Phase Diagenetic Model for Manganese in Marine Sediments

A steady state diagenetic model is developed which accounts for changes in both the pore water and solid phase manganese profiles in marine sediments as a result of advection, diffusion, and redox reactions. The model is applied to observations on two cores in the E equatorial Atlantic in which pore water and solid phase manganese data are available. In situ reaction rates for manganese oxidation and reduction are estimated. The oxidation rates calculated here are in good agreement with rates measured in laboratory studies. In addition, the calculated manganese oxidation and reduction rates are compared with other estimated rates for these processes in natural environments

Der Membran-Salzfühler als geignetes Gerät zur Registrierung der Schichtung im Meere

An Hand von erzielten Resultaten mit dem Membran-Salzfühler wird die Genauigkeit dieser Methode zur Registrierung der Salzschichtung diskutiert. Die Reproduzierbarkeit der Meßergebnisse wird besprochen. Einige Messungen in der Ostsee werden als Beispiele angeführt. With the aid of some results the accuracy of the membrane salinity sensor is discussed. The reproducibility of the measurements is determined. Some recordings in the Baltic Sea demonstrate the usefulness of the method

Some investigations intothe sensitivity of the membrane salinometer for various ions

The sensitivity of the membrane salinometer to the various ionic species that constitute the dissolved salts in sea water is investigated. Mixtures of various salts with sodium chloride are investigated with regards to changes in the electromotive force upon dilution with water, and also with regards to changes in the composition of the mixed electrolyte. The results are expressed in terms of changes in the activity of sodium chloride. Also sea water is investigated upon a similar basis. Die Empfindlichkeit des Membransalinometers für die verschiedenen Ionensorten, welche im Meersalz vorhanden sind, wird untersucht. Mischlösungen von verschiedenen Salzen mit Natriumchlorid werden im Zusammenhang mit Veränderungen in der elektromotorischcn Kraft sowohl bei Verdünnung mit Wasser, als auch bei Änderung der Zusammensetzung, untersucht. Mit der Aktivität von Natriumchlorid als Referenz werden die Resultate von modifizierten Nernst-Gleichungen beschrieben

58. INTERACTION BETWEEN SEDIMENT AND INTERSTITIAL WATER NEAR THE JAPAN TRENCH, LEG 57, DEEP SEA DRILLING PROJECT

ABSTRACT Analyses of water samples taken by means of an in-hole sampler generally show good agreement with analyses of samples collected by routine shipboard squeezing techniques. At Sites 438 and 439, a decrease in salinity with depth is related to former freshwater flow from an aquifer that crops out at an anticline on a deep sea terrace between Japan and the top of the trench slope of the Japan Trench. This former subaerial recharge suggests significant late Cenozoic subsidence of the terrace, because it now lies at a water depth of 1500 meters. Samples from the trench slope at Site 440 have extremely high values of alkalinity and ammonia, presumably because of a favorable combination of high sedimentation rate and organic carbon content. Diagenetic conditions on the trench slope favor formation of the Fe-Mg carbonate mineral, ankerite; at Site 440 it first occurs at a depth below the sea floor of only 29 meters in late Pleistocene strata. Undissolved diatoms persist to relatively great depth at the sites of Leg 57 because of a low geothermal gradient caused by subduction. Secondary silica lepispheres first appear at 851 meters at the most landward and warmest site, Site 438, in strata 16 million years old with an ambient temperature of 31 °C. SAMPLING AND ANALYTICAL PROCEDURES During Leg 57 Shipboard in-hole data on pH, alkalinity, chlorinity, calcium, and magnesium (except Mg from Site 438) generally show good agreement with the samples obtained by routine shipboard squeezing techniques The results for ammonia and silica were obtained from the overflow water of the in-hole sampler and had to be corrected for dilution by distilled water. Agreement for Site 438 with routinely collected samples is good In general, however, we conclude that the in-hole samples essentially confirm the validity of the interstitial water sample data collected by routine squeezing, even for the minor constituents, silica and ammonia. This is in agreement with the conclusions of Barnes and others (1979). SALINITY DECREASE WITH DEPTH An interesting phenomenon at Sites 438 and 439 (water depth about 1600 m) is a downhole decrease in salinity and chlorinity. The chlorinity at the deepest sample at Site 438 is only about 50 per cent of that of seawater. These data imply that fresh water has been advected to the sites from an outcrop area. A possible source of fresh water is through sandstone and conglomerate layers in the deeper strata of the sites. Because boulders in the conglomerate are very large, 126

ODP Leg 137, borehole fluid chemistry in Hole 504B

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95686/1/grl5867.pd

A study of the variability in the hydrochemical factors in the Baltic Sea on the basis of two anchor stations September 1967 and May 1968

The present study was undertaken to investigate the physical and chemical variability in the eastern Gotland Basin. This can serve as an example for the variability in the inner part of an adjacent sea with small tidal influence. Two anchor stations of about four days duration were made, with R.V. "Alkor" in September 1967 and with F.R.V. "Anton Dohrn" in May 1968. On the basis of variations in the physical parameters, and also from continuous recordings of salinity and temperature, c.f., of oxygen and temperature, the presence of internal waves is demonstrated. The variability in the chemical data not only indicate internal waves but also proves the patchlike structure of the water masses with regard to biochemical parameters. The two anchor stations were made during periods of partial and of total stagnation in the deeper parts of the Gotland Basin. Ziel dieser Arbeit ist eine Beschreibung der physikalisch chemischen Veränderlichkeit im östlichen Gotland-Becken, und zwar als Beispiel für die Veränderlichkeit im inneren Teil eines gezeitenarmen Nebenmeeres. Zwei viertägige Ankerstationen wurden durchgeführt, im September 1967 und Mai 1968, mit "Alkor" und "Anton Dohr". Auf Grund der Variationen in den physikalischen Parametern und auch von den kontinuierlichen Registrierungen von Salzgehalt und Temperatur, bzw. von Sauerstoff und Temperatur, werden interne Wellen nachgewiesen. Von der Veränderlichkeit der chemischen Parameter werden neben internen Wellen auch wolkenartige Strukturen der Wassermassen im Bezug auf biochemische Eigenschaften demonstriert. Beide Dauerstationen fielen in einer Periode von teilweiser und von voller Stagnation im Gotland-Becken

Evolution of structures and fabrics in the Barbados Accretionary Prism ; Insights from Leg 110 of the Ocean Drilling Program

The microstructures and crystal fabrics associated with the development of an amphibolite facies quartzo-feldspathic mylonitic shear zone (Torridon, NW Scotland) have been investigated using SEM electron channelling. Our results illustrate a variety of microstructures and fabrics which attest to a complex shear zone deformation history. Microstructural variation is particularly pronounced at low shear strains: significant intragranular deformation occurs via a domino-faulting style process, whilst mechanical incompatibilities between individual grains result in characteristic grain boundary deformation accommodation microstructures. A sudden reduction in grain size defines the transition to medium shear strains, but many of the boundaries inherited from the original and low shear strain regions can still be recognized and define distinctive bands oriented at low angles to the shear zone margin. Grains within these bands have somewhat steeper preferred dimensional orientations. These domains persist into the high shear strain mylonitic region, where they are oriented subparallel to the shear zone margin and consist of sub-20 μm grains. The microstructures suggest that the principal deformation mechanism was intracrystalline plasticity (with contributions from grain size reduction via dynamic recrystallization, grain boundary migration and grain boundary sliding). Crystal fabrics measured from the shear zone vary with position depending on the shear strain involved, and are consistent with the operation of several crystal slip systems (e.g. prism, basal, rhomb and acute rhomb planes) in a consistent direction (probably parallel to a and/or m). They also reveal the presence of Dauphine twinning and suggest that this may be a significant process in quartz deformation. A single crystal fabric evolution path linking the shear zone margin fabric with the mylonitic fabric was not observed. Rather, the mylonitic fabric reflects the instantaneous fabric which developed at a particular location for a particular shear strain and original parental grain orientation. The mature shear zone therefore consists of a series of deformed original grains stacked on top of each other in a manner which preserves original grain boundaries and intragranular features which develop during shear zone evolution. The stability of some microstructures to higher shear strains, the exploitation of others at lower shear strains, and a continuously evolving crystal fabric, mean that the strain gradient observed across many shear zones is unlikely to be equivalent to a time gradient

Einige Beobachtungen über Lösungsvorgänge am Boden des Ozeans

Changes in the dissolved oxygen content, the alkalinity, and the pH in sea water near the ocean floor are interpreted in terms of chemical and biochemical processes at the sediment water interface. A simple model provides a plausible explanation of the observed phenomena. Special emphasis is given to the importance of borate corrections in the calculation of the solution effects of calcium carbonate