Acfer 094, a uniquely primitive carbonaceous chondrite from the Sahara

Abstract— The Saharan meteorite Acfer 094 is a unique type of carbonaceous chondrite. Mineralogical and petrological considerations and O isotopes are unable to distinguish unambiguously between a CO3 vs. CM2 classification. The other important light elements, C and N, have systematics that do not match any previously recognised meteorite group. Particularly important in this respect is the very low C/N ratio and δ¹³C of the macromolecular C. Acfer 094 has more diamond and SiC, especially X type grains, than any other specimen studied, suggesting minimal thermal or aqueous processing to decrease its very primitive status.     

Volcanic particles in agriculture and gardening

Volcanic pyroclasts of small size, such as lapilli and small pumice stones, are widely used in agriculture, gardening, and for pot plants as natural inorganic mulch. The technique of using pyroclasts to enhance topsoil stems from the eighteenth century, and specifically from the ad 1730–1736 eruption on Lanzarote. Critical observations on plant development during and after the eruption showed that the vegetation died when buried under a thick layer of lapilli, but grew vigorously when covered thinly. While the agriculture of Lanzarote was restricted to cereals before the eruption, it diversified to many kinds of fruit and vegetables afterwards, including the production of the famous Malvasía wines in the Canaries. The population of Lanzarote doubled in the years after the eruption, from about 5000 in 1730 to near 10 000 in 1768, predominantly as a result of the higher agricultural productivity. This outcome led to widespread use of lapilli and pumice fragments throughout the islands and eventually the rest of the globe. Lapilli and pumice provide vesicle space for moisture to be retained longer within the planting soil, which can create an environment for micro‐bacteria to thrive in. Through this route, nutrients from volcanic matter are transported into the surrounding soil where they become available to plant life. The detailed processes that operate within the pyroclasts are less well understood, such as the breakdown of nutrients from the rock matrix and transport into the soil by biological action. Further studies promise significant potential to optimize future agricultural efforts, particularly in otherwise arid areas of the globe.     

Experimentelle Untersuchungen über das Verhalten der Bachforellenbrut in der Laichgrube

Ohne Zusammenfassung Herrn Professor Dr. Fritz Baltzer zum 80. Geburtstag gewidmet     

Thermodynamics of (Fe2+, Mn2+, Mg, Ca)3− Al2Si3O12 garnet: a review and analysis

Summary The thermodynamic properties of garnets in the system (Fe²⁺, Mn²⁺, Mg, Ca)₃A1₂Si₃O₁₂ are reviewed. The thermodynamic properties of the three end-member garnets pyrope, almandine and grossular, including their volume, enthalpy of formation, entropy, compressibility and thermal expansion have been well determined. For spessartine enthalpy of formation and heat capacity at low temperatures are needed. Pyrope's unusual behavior in some of its properties is probably related to the presence of the small, light Mg cation, which has a large anisotropic thermal vibration. The thermodynamic mixing properties of the six binaries are also discussed. Good volume of mixing data exist now for all of the binaries, but much work is still required to determine the enthalpies and third-law vibrational entropies of mixing. It is shown that the magnitude of the positive deviations in the volumes of mixing is related to the volume difference between the two end-member components. It is probable that excess entropies, if present, originate at low temperatures below 200 K. Recent²⁹Si NMR experiments have demonstrated the presence of short-range ordering (SRO) of Ca and Mg in pyrope-grossular solid solutions. Short-range order will have to be considered in new models describing the entropies of mixing. Its possible presence in all garnet solid solutions needs to be examined. The mixing properties of pyrope-grossular garnets, which are the best known for any garnet binary, can, in part, be described by the Quasi-Chemical approximation, which gives insight into the microscopic interactions which determine the macroscopic thermodynamic mixing properties. Microscopic properties are best investigated by spectroscopic and computational approaches. Hard mode IR measurements on binary solid solutions show that the range of local microscopic structural distortion is reflected in the macroscopic volumes of mixing. The nature of The contents of this contribution was presented at the IMA Meeting in Toronto in August, 1998. It precedes issues of Mineralogy and Petrology containing thematic sets of IMApapers strain tiields and site relaxation needs to be studied in order to obtain a better understanding of the solid-solution process and energetics in garnet. Critical areas for future experimentation are also addressed.[/p]

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Eine kritische Zusammenstellung und Analyse der thermodynamischen Daten der (Fe²⁺, Mn²⁺, Mg, Ca)₃Al₂Si₃O₁₂ granate

Zusammenfassung In dieser Studie werden die thermodynamischen Eigenschaften der Granate im System (Fe²⁺,Mn²⁺, Mg, Ca)₃Al₂Si₃O₁₂ kritisch zusammengestellt. Die thermodynamischen Eigenschaften der drei Endglied-Granate Pyrop, Almandin und Grossular, einschließlich ihrer Volumina, Bildungswärmen, Entropien, Kompressibilitäten und thermischen Ausdehnungen wurden bereits hinreichend gut bestimmt. Dagegen müssen die Bildungswärme und Tieftemperatur-Wärmekapazität von Spessartin noch gemessen werden. Die Eigenschaften des Pyrops sind wahrscheinlich mit den großen anisotropen Schwingungen des kleinen, leichten Mg-Kations verbunden. Die thermodynamischen Mischungseigenschaften der sechs binären Mischkristallreihen werden ebenfalls diskutiert. Während die Mischungs-Volumendaten der binären Mischreihen gut bekannt sind, müssen ihre Mischungs-Enthalpien und Standard-Mischungsentropien noch ermittelt werden. Es wurde gezeigt, daß die Größe der positiven Exzeß-Volumina mit dem Volumen-Unterschied der zwei Endglied-Komponenten der jeweiligen Mischreihe verknüpft ist. Es ist wahrscheinlich, daß Exzeß-Entropien, wenn vorhanden, erst bei Tieftemperaturen unter 200 K auftreten. Neue²⁹Si NMR-Experimente belegen, daß in Pyrop-Grossular-Mischkristallen Nahordnung von Mg und Ca vorliegt. Der Effekt der Nahordnung muß in künftigen thermodynamischen Modellen berücksichtigt werden. Hieraus ergibt sich die Notwendigkeit, alle Granat-Mischreihen auf mögliche Nahordnung hin zu untersuchen. Die Mischungseigenschaften der Pyrop-Grossular-Mischreihe, die von sämtlichen Granat-Mischreihen am besten bestimmt wurden, können teilweise mit dem Quasi-Chemical-Model beschrieben werden. Dieses Modell ermöglicht die Beschreibung der mikroskopischen Wechselwirkungen, die die makroskopischen thermodynamischen Eigenschaften bestimmen. Mikroskopische Eigenschaften werden am besten mit spektroskopischen Messungen und theoretischen Berechnungen untersucht. Hard-mode IR-Spektroskopie-Messungen an binären Mischreihen zeigen, daß die lokalen mikroskopischen strukturellen Verzerrungen in den makroskopischen Mischungs-Volumina widergespiegelt werden. Die Art der Spannungsfelder und Platz-Relaxationen muß detaillierter untersucht werden, um ein besseres Verständnis des Mischkristall-Bildungsprozsses und der Energetik der Granate zu erreichen. Darüber hinaus werden wichtige künftige Forschungsgebiete diskutiert.

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With 11 Figures     

Pumpspeicherwerke und Hechtbrut—ein Modellversuch

The effects of periodic, simulated water level fluctuations on northern pike fry produced by pumped-storage operations were examined. Daily fluctuations of 10 cm caused a significant increase in the daily mortality rate. Waves reduced the detrimental effect of water level lfuctuations, at least during the adhesive phase of fry.     

Overall-effective Measures for Sustainable Water Resources Management in the Coastal Areas of Shandong Province, China ——Case Study： the Huangshuihe River Catchment of Longkou City

In the coastal catchments of Shandong Province the water scarcity is aggravated due to saltwater intrusion, reducing the usability of water resources available. Such a situation calls for sustainable integrated water resources management （IWRM）. The idea for the objectives and implementation of the IWRM are explained in this paper. The general objective of the planned project disscussed in the present study is to bring together German traditional expertise in water resources management and newer developments in the context of the European Water Framework Directive; the research efforts aim to relieve the desperate water scarcity situation in the costal area of Shandong Province.     

XAFS characterization of the structural site of Yb in synthetic pyrope and grossular garnets

The incorporation and site preference of minor amounts (about 1 wt%) of Yb³⁺ in synthetic pyrope (Mg₃Al₂Si₃O₁₂) and grossular (Ca₃Al₂Si₃O₁₂) garnet were studied by X-ray Absorption Fine-Structure (XAFS) Spectroscopy. The measurements, performed in the temperature range 77–343 K at both Yb L_I- and L_III-edges, demonstrate that Yb³⁺ enters the garnet structure and is located in the dodecahedral site in both samples. The coordination environment of Yb³⁺ in the two samples was compared to that of the X-site cation in end-member synthetic pyrope and grossular and in Yb₃Al₅O₁₂ as determined by single-crystal X-ray diffraction. The local geometry around Yb³⁺ is different from that of Mg and Ca in the bulk of the garnet, and also from that of Yb³⁺ in Yb₃Al₅O₁₂. Τhe XAFS results indicate that, (1) structural relaxation occurs around Yb³⁺ in the garnet structure; (2) the host garnet matrix exerts a major structural control on the incorporation of Yb³⁺, and (3) minor amounts of Yb³⁺ in garnet are located in structural sites and not in ill-defined defects. Received: 15 January 1998/ Revised, accepted: 21 July 1998     

Evaluating the Potential of an Airborne Laser-scanning System for Measuring Volume Changes of Glaciers

Airborne laser scanning (ALS) is well suited for the production of digital elevation models (DEM), and can, in contrast to photographic methods, be used to acquire a DEM independently of surface texture and external light sources. ALS thus serves as a tool to generate DEMs of firn areas where photogram- metric methods often fail.
The potential of an integrated ALS system – comprising a laser scanner, precise differential global positioning system, and a gyro platform – for DEM generation of firn areas is currently being assessed. The Unteraargletscher, Bernese Alps, Switzerland, has been chosen as a test site. As part of a pilot project aimed at determining the mass balance distribution of that glacier without the use of in situ information, ALS measurements were conducted in autumn 1997. The DEM derived from laser measurements is extremely sensitive to the position and attitude of the aircraft. Currently the main work focuses on assessing and improving the system's accuracy by error modelling and by the development of error-correction algorithms.
Preliminary results from Unteraargletscher are presented, and the potential of this method for the generation of DEMs of firn areas is discussed.