Mg---NH4 exchange on humic acid: A radiotracer technique for conditional exchange constants in a seawater medium

A radiotracer technique, employing ²⁷Mg, is used to determine the Mg released by ammonium exchange on undis-solved humic acid in a seawater medium. This new method allows for the measurement of exchangeable Mg on the solid phase surface, which eliminates the problem caused by the high-Mg background in the seawater matrix. The precision calculated from the counting statistics is better than ±2%; the reproducibility among repeated counts ranged from ±1% to ±3%. The higher sensitivity of the method allows for monitoring the Mg---NH₄ exchange at concentrations as low as 30 mM NH₄. This is a major improvement relative to the data obtained with the analytical methods used so far, which allow detection of exchangeable Mg only at NH₄ concentrations higher than 1 M. The lower experimental concentrations are more in accordance with the natural ammonium levels found in anoxic marine sediments. For the undissolved humic acid used in this experiment, the amount of exchangeable Mg in apparent equilibrium with an ammonium-free seawater matrix was found to be 96.6 ± 0.4 meq/100g. The Mg---NH₄ exchange on humic acid in seawater comes to a steady-state value in < 18 min. The conditional equilibrium constant obtained for this reaction, K_cond = 0.039 ± 0.001 M⁻¹. The technique can be expanded to other geochemical solid phases in seawater and it can be modified to study the behavior of the major cations by using ²⁴Na, ⁴²K and ⁴⁹Ca.     

Historical Climatology In Europe – The State Of The Art

This paper discusses the state of European research in historical climatology. This field of science and an overview of its development are described in detail. Special attention is given to the documentary evidence used for data sources, including its drawbacks and advantages. Further, methods and significant results of historical-climatological research, mainly achieved since 1990, are presented. The main focus concentrates on data, methods, definitions of the “Medieval Warm Period” and the “Little Ice Age”, synoptic interpretation of past climates, climatic anomalies and natural disasters, and the vulnerability of economies and societies to climate as well as images and social representations of past weather and climate. The potential of historical climatology for climate modelling research is discussed briefly. Research perspectives in historical climatology are formulated with reference to data, methods, interdisciplinarity and impacts.     

A system for line profile studies at the 150-foot tower on Mount Wilson

We describe enhancements to the hardware and software for the 150-foot tower system on Mt. Wilson which make possible the acquisition of high precision line profile measurements. This system utilizes the 75-foot pit spectrograph with a photomultiplier detector system to scan line profiles repeatedly in order to study variations induced by the passage of waves vertically through the solar atmosphere. Oscillations of line profile parameters with an amplitude as low as 1.7 m s^–1 have been detected with this system using integrated sunlight. Phase relations between oscillations of different parts of the line profile are appropriate to upward energy transport. Consistent with the previous conclusion by Mein and Schmieder (1981), we find that the magnitude of the energy transport is compatible with the 5-min oscillations making an important contribution to the heating of the low chromosphere.The Mount Wilson Observatory is operated by the Mount Wilson Institute under agreement with the Carnegie Institution of Washington.     

GETEMME—a mission to explore the Martian satellites and the fundamentals of solar system physics

GETEMME (Gravity, Einstein??s Theory, and Exploration of the Martian Moons?? Environment), a mission which is being proposed in ESA??s Cosmic Vision program, shall be launched for Mars on a Soyuz Fregat in 2020. The spacecraft will initially rendezvous with Phobos and Deimos in order to carry out a comprehensive mapping and characterization of the two satellites and to deploy passive Laser retro-reflectors on their surfaces. In the second stage of the mission, the spacecraft will be transferred into a lower 1500-km Mars orbit, to carry out routine Laser range measurements to the reflectors on Phobos and Deimos. Also, asynchronous two-way Laser ranging measurements between the spacecraft and stations of the ILRS (International Laser Ranging Service) on Earth are foreseen. An onboard accelerometer will ensure a high accuracy for the spacecraft orbit determination. The inversion of all range and accelerometer data will allow us to determine or improve dramatically on a host of dynamic parameters of the Martian satellite system. From the complex motion and rotation of Phobos and Deimos we will obtain clues on internal structures and the origins of the satellites. Also, crucial data on the time-varying gravity field of Mars related to climate variation and internal structure will be obtained. Ranging measurements will also be essential to improve on several parameters in fundamental physics, such as the Post-Newtonian parameter ?? as well as time-rate changes of the gravitational constant and the Lense-Thirring effect. Measurements by GETEMME will firmly embed Mars and its satellites into the Solar System reference frame.     

Die Matrix der Fische

Summary An apparatus has been developed and demonstrated, which may be used for measuring the motility and the vitality of fish and other animals under the action of different influences, for instance poisons. Under favorable experimental conditions, the energy can be estimated, which is shown by the animals in theirmilieu extérieur.      

Metallogenic provinces in South America

This paper discusses the broadscale distribution of some ore deposit types in South America, trying to discern possible relations with major geotectonic features. It does not cover all ore deposits but rather a selection based on available information, genetic types, geographic distribution, and a representation of deposit types which are either abundant or very rare in South America. Included are porphyry copper, zoned copper-zinc-lead-silver, contact-metasomatic, red-bed copper-uranium-vanadium, lead-zinc (including Mississippi Valley type), mercury, tin, pegmatite, carbonatite and alkalic complex, diamond, nickelcobalt-chromite-asbestos-talc, iron, bauxite, tungsten, titanium, uranium, gold, potash and phosphate deposits. Comparisons are made with the distribution of these deposit types in other continents, especially in North America and Africa. This leads to some speculations bearing on theories of ore genesis. The evidence suggests that upper crustal processes predominate in the formation of the majority of ore deposits considered (excepting carbonatites, alkalic complexes and diamond pipes). Also, the relative level of an orogenic belt exposed by erosion seems to be an important factor bearing on the presently known distribution of many ore deposit types. Furthermore, the fact that ore deposits of given types tend to be aligned along the Cordillera in more or less defined belts with changing chemical composition accross the Andes, which partake in all its inflections, and in patterns which are similar in North and South America, indicates that they are either dependent on the distribution of eugeosynclinal vs miogeosynclinal sediments in the original geosynclinal prism, or that their character is related to distance from the major batholitic masses or to shallow stocks and volcanic activity. The indicated correlation with sediment character and evaporites speaks in favor of modem concepts viewing hydrothermal fluids as mainly meteoric but heated and circulated largely by igneous activity. This study raises more questions than it can answer and calls attention to a number of problems requiring further research. From a practical point of view, this investigation reveals several possibilities for future exploration, as well as opportunities for further development of mineral resources in South America. Several countries could probably improve or diversify their mineral production significantly, thus raising the standard of living of their increasing population. Whereas in North America both Canada and the U.S.A. span from east to west the whole range of geological environments, from cratonic to geosynclinal and orogenic, in South America the distribución of countries is essentially either along the Cordillera or over shield areas, a fact of obvious geopolitical implications with regard to mineral resources.     

Quartz as indicator mineral in the Central Swiss Alps: the quartz recrystallization isograd in the rock series of the northern Aar massif

Earlier observations on the deformation of rock-forming quartz during Alpine metamorphism that were made by Voll (1976) along a traverse following the Reuss valley (Aar massif, Central Swiss Alps) are still relevant but can be explained in more modern term. Voll found that a few kilometres south of the contact between the Aar massif and its sedimentary cover quartz has partly undergone a combination of dynamic recrystallization and nucleation along grain boundaries and fractures at the expense of the deformed parent grains. Further to the south, increasing grain growth of quartz under nearly static conditions is observed, with polygonal grain shapes typical of annealed microfabrics. Comparable stages of recrystallization could be found in several N–S traverses through the Aar massif so that “points of first occurrence” of newly formed quartz could be connected to define a quartz recrystallization isograd. This isograd extents over 90 km through the northern Aar massif, following a course parallel to the sanidine/microcline isograd but at a distance of 10–15 km further to the north. The evolution of the quartz microfabric is discussed with respect to recent estimates of the T-t path of the Aar massif.