Redistriution of Major Elements in the Alteration of Some Basic Lavas during Burial Metamorphism

An Ordovician geanticlinal marine sequence is exposed in theCentral West of New South Wales, Australia. The sequence containingbasic lavas, labile sedimentary, and proclastic rocks, has undergoneextensive adjustment during regional burial metamorphism. Thebasic lavas have a patchy coloration due to the formation ofalternation minerals of the prehnite-pumpellyite facies whichapperar to have formed during the metamorphism. The hererogeneousappearance of the basic lavas reflects a pronouced chemicaland mineralogical departure from the original composition. Twodiverging trends result. One leads to the production of a Ca-enrichedlithology, the other, which by far dominates in area at eachouterop, leads to a ‘spilitic’ lithology. The alterationdomains in many cases cross–cut all primary textural featureand their chemical variation does not correspond to likely variationsin the original lava composition.     

Microstructures of High-grade Metamorpbic Rocks at Broken Hill, Australia

Frequency distributions of true interfacial angles in high-grade,regional metamorphic rocks from Broken Hill indicate that interfacialtension varies with relative crystallographic orientation incommon minerals. In some single-phase aggregates (e.g. quartz,feldspar, garnet, and calcite) the grains are equant and polygonal,anisotropy of interfacial tension having only a small effecton the appearance of such aggregates. This is also true of two-phaseaggregates of these phases, but their appearance is complicatedby the presence of inclusions, the relative proportions of ihephases, and the characteristic dihedral angle formed by a grainof one phase in contact with two grains of the other. In phases for which interfacial tension is more orientation-dependent,crystal forms exert some control on the appearance of the microstructure.For example, in hornblende and pyroxene aggregates, some interfacesare parallel to planes of the form {110}, although most areirrational. In still more anisotropic phases, low-energy forms(e.g. {001} of biotite and {110} of sillimanite) are very stable,giving rise to a predominance of planar, rational boundariesover curved, adjustment boundaries. Anisotropy of interfacial tension is expressed in the shapesof inclusions. However, even where strongly anisotropic mineralsare involved, inclusions with partly planar boundaries occuralongside inclusions with completely curved boundaries.     

Die Porositäten toniger Keuper- und Jura-Sedimente Südwestdeutschlands

After a short review of the basic principles governing compaction of clayey sediments, investigations of the porosities of Mesozoic shales from southwestern Germany are reported. The results reveal the influence of grain size, mineral content, temperature, and organic matter on the porosity of shales. All these and other factors have to be considered when evaluating primary porosities of shales at the time of deposition.     

Baryt und ankerit aus Ammoniten des Berner Juras (Schweiz)

Barite has been found for the first time in the Swiss Jura (Hirni, Passwang). Small, white crystals of barite with yellow ankerite grow on calcite in different chambers of a Bajocian ammonite. Chemical data (by microprobe analysis) and lattice parameters (refined by leastsquares from powder patterns) are given for the two minerals. There is a distinct correlation between the cell dimensions and the chemical composition for both of them. The genesis is discussed.     

The inhibition of microorganisms by heavy metals

This paper examines the effects of heavy metals on microorganisms in the aqueous environment; the mechanisms by which metals may exert toxic effects on microbes and the factors affecting microbial response to metals; the ways in which microbial activity may alter the metal balance of an environment and the modifications produced in microbes by heavy metal ions; the effects of the toxic copper ion on the growth, respiration, magnesium content, cytochrome synthesis and osmotic sensitivity of some organisms studied in the laboratory; and the feasibility of the participation of microbes in geochemical processes considering the demonstrable resistance to toxic metals by some bacteria and the fact that natural environments may contain high levels of metals rendered less toxic by binding to natural chelating compounds.

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Zusammenfassung In dieser Arbeit werden verschiedene Wirkungen von Schwermetallen auf Mikroorganismen in wäßrigem Milieu untersucht. Es wird gezeigt, daß Schwermetalle toxische Wirkungen auf Mikroorganismen ausüben können und welche Faktoren die Reaktionen von Mikroben gegenüber Metallen bestimmen. Weiter wird beschrieben, wie die Mikrobenaktivität das Metallgleichgewicht in einem gegebenen Milieu verändern und beeinflussen kann und wie andererseits Änderungen in den Mikroben selbst durch Schwermetall-Ionen hervorgerufen werden. Dabei wird besonders die Wirkung des toxischen Kupfer-Ions auf das Wachstum, die Atmung, den Magnesiumgehalt, die Cytochromsynthese und die osmotische Empfindlichkeit einiger Mikroorganismen dargestellt. Die Anwesenheit von Mikroben bei geochemischen Prozessen wird unter Berücksichtigung der Resistenz einiger Bakterien gegenüber toxischen Metall-Ionen diskutiert. Dabei spielt die Tatsache eine große Rolle, daß durch Chelatbildung die Schwermetall-Ionen in der natürlichen Umwelt der Mikroorganismen ihre toxische Wirkung verlieren.

     

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