Iron-rich metalliferous sediments on the East Pacific Rise: prototype of undifferentiated metalliferous sediments on divergent plate boundaries

Sediments in a zone on the East Pacific Rise with an especially high spreading rate were studied chemically, mineralogically, and microscopically. They consist of a mixture of metalliferous sediments and plankton tests. The metalliferous sediments were formed by an acidic, hydrothermal leaching of tholeiitic basalt with seawater and subsequent precipitation in contact with cold near-bottom seawater. We assume the precipitation from hydrothermal solutions in this part of the East Pacific rise to be undifferentiated due to the high spreading rate and the resulting rapid flow on the water through the basalt. Thus, these metalliferous sediments are an initial stage type that have not undergone differentiation.Mn, Mo, La, Cu, V, Ni, Fe, Zn, Co, and Y, all of which are leachable in acidic, hydrothermal solutions, are enriched in the metalliferous sediments in comparison to the tholeiitic basalts.Zr, Al, and Ti, on the other hand, which under the same conditions are not easily leached, are reduced in their concentrations.All components of the metalliferous sediments precipitated as hydroxides or as adsorbed ions on the hydroxides of other elements. This is due to the oxidizing conditions in the near-bottom seawater. The sedimentation rate is high; the almost 3-m-long cores reach only to the Late Pleistocene. The only distinctly observable diagenetic process for this period of time is the formation of goethite from amorphous iron oxides.Only for Na, K, and Rb does it seem possible that a distinct enrichment in the sediments by adsorption from the seawater could have taken place.Ca, Sr, Pb, and perhaps Sc, are primarily bound to the planktonic carbonate part of the sediments.     

Material balance in manganese nodule formation (north central Pacific)

All data necessary to calculate the metal balance for Mn nodules in a well-investigated area of the North Central Pacific are now available. The nodules lie on porous siliceous ooze, and receive more than 96% of their metal content from the underlying ooze by diagenetic mobilisation. Only a very small portion of the metal contained in the sediment has to be mobilised to form the nodules, which explains why the expected depletion of metals from the sediments has never been demonstrated.     

TheUrquiola oil spill,La Coruña,Spain: Impact and reaction on beaches and rocky coasts

The supertankerUrquiola grounded, exploded, and burned at the entrance to La Coruña harbor (Spain) on May 12, 1976. A total of 100,000 tons of Persian Gulf crude oil was lost, of which about 30,000 tons washed onto shoreline environments. From May 17 to June 10, 1976, the impact and interaction of oil on fine-sand, coarse-sand, and gravel beaches and on sheltered and exposed rocky coasts was monitored in detail. At 32 localities, the beach was profiled, trenched, extensively sampled, and photographed. Another 67 stations were examined for surficial oil coverage and distribution. The surficial distribution of oil on the beaches was influenced primarily by wave activity, tidal stage, and oil quantity. Heaviest accumulations formed along the high-tide swash line. Within beach sediments, oil was present at distinct oiled sediment layers, which were often deeply buried. The depth of burial was related to wave energy and sediment type. Deepest burial (1 m) was on a high-energy, coarse-sand beach (M_z=0.82φ). Burial on fine-sand beaches was less than 30 cm. The thickness of oiled sediment depended on sedimentary characteristics, the quantity of oil present, wave action, and capillary forces. Oil-soaked sediment, as much as 65-cm thick, occurred on coarse-grained beaches. On fine-sand beaches, oiled sediment was limited to thicknesses of 10 cm or less. On rocky shores, oil distribution was determined primarily by wave energy. Along high-energy, cliffed, or steeply dipping rocky areas, wave reflection kept the oil approximately 5 m offshore and contamination was minimal. In low-energy, sheltered areas, oil readily accumulated, causing apparent environmental damage.     

Über die Natur des Sedimentgleichgewichtes im Litoral

Zusammenfassung Unter Beachtung der Fortschritte der modernen Brandungsforschung sowie neuerer Beobachtungsergebnisse im Litoral erscheint die vonCornaglia entwickelte Theorie der neutralen Linie, die das einzelne Sedimentkorn isoliert in Ansatz brachte, unhaltbar. An ihre Stelle tritt die den tatsächlichen Verhältnissen besser Rechnung tragende Theorie des «Massenmomentes» der brandenden Wellen, die nicht mehr das einzelne Korn, sondern die gesamte unter der Einwirkung der Oszillation entstehende Suspensionswolke betrachtet. Die Vorteile dieser neuen Betrachtungsweise werden kurz skizziert und an Hand einiger Beispiele näher erläutert.

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Summary With respect to the attainments of the modern surf phenomena research and based on new results of observations in the littoral zone the theory of the neutral line, developed byCornaglia, which looked upon the wave-moved grain as an isolated individual, is no longer useful. In its place the better theory of the surging wave's «momentum of mass» is set, which considers the whole cloud of material whirled up by the oscillatory undulation near the bottom. The advantages of this new consideration are shortly sketched and particularly illustrated by means of some examples.

     

Die Temperatur in Grönlandischen Inlandeis

Zusammenfassung Auf Grund der Temperaturmessungen in Schächten 1930/31 und Bohrungen 1948/1951, die berichtigt wurden, wird die wahrscheinlichste Temperaturverteilung in Inlandeis gewonnen.

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Summary The measurements of temperature in holes 1930/1931 and the (corrected) measurements of the temperature in drilled holes 1948/1951 are used, to construct the distribution of the temperature in the inlandice of Greenland.

     

Die östliche Fortsetzung des Kaukasus

Ohne ZusammenfassungDie älteren Arbeiten sind nur dann angeführt, wenn sie im Text genannt sind; weitere Literatur siehe in den Verzeichnissen bei den jüngeren Arbeiten.Die russischen Orts- und Verfassernamen sind in deutschen Lautwerten umschrieben mit sh==franz. j.     

The metamorphic evolution of garnet-cordierite-sillimanite-gneisses of the Gruf-Complex,Eastern Pennine Alps

Metapelitic gneisses occuring as lenses and bands within the migmatites of the Gruf-Complex in the eastern Pennine Alps contain various combinations of the minerals quartz, biotite, cordierite, garnet, sillimanite, plagioclase. K-feldspar, spinel, orthopyroxene, anthophyllite and muscovite. The most common rock type is represented by a darkschistosebiotiterichcordierite-garnet-sillimanite-gneiss. A consistent pressure-temperature range of 3–4 kb and 600–650° C has been calculated for the last metamorphic equilibration from six geological thermobarometers. However, from textural evidence it may be concluded that the rocks were at both higher temperatures and pressures prior to the PT-conditions calculated from thermobarometry. Although the maximum conditions reached are unknown and earlier stages are poorly preserved it is suggested that they coincide with the maximum conditions deduced from rare occurrences of sapphirine granulite in the Gruf-Complex. These are 10 kb and 800° C (Droop and Bucher 1983). Sillimanite+K-feldspar, orthopyroxene+quartz, spinel+quartz and garnet-K-feldspar persisting in rocks with low activity of H₂O are strong evidence for this. The H₂O required to make the observed high degree of equilibration at 3–4 kb and 600–650° C possible was presumably released by crystallizing migmatitic melts present in the quartzo-feldspathic gneisses of the Gruf-Complex. Further evidence comes from the PT-coordinates of the H₂O-saturated muscovite granite solidus which coincides with the high temperature limits of inferred equilibration above and which the rocks must have crossed along the decompression and cooling path during their metamorphic evolution.