Untersuehungen an den Sedimenten der Tongrube von Willershausen

Zusammenfassung Nach der Profilaufnahme sind die Sedimente der Tongrube der Ziegelei von Willershausen in zwei Gruppen einzuteilen : A. Die unteren hellen Schichten, B. die oberen dunklen Schichten.Die unteren hellen Schichten bestehen aus Sandsteinen, Sanden, tonigen Sanden und Grobtonen, welche Quarz, Feldspäte und Glimmer als Hauptminerale und in geringeren Mengen Illit, Chlorit und manchmal Montmorillonit füren. Als Schwerminerale dieser Sande und Sandsteine treten der Häufigkeit nach Apatit, Zirkon, Granat, Anatas, Rutil, Turmalin und Opakminerale auf.Die oberen dunklen Schichten bestehen hauptsächlich aus mm-rhythmisch geschichteten Tonen mit Einschaltung einzelner Mergelbänke und toniger Sandschichten. Dioktaedrischer Illit ist das häufigste Tonmineral, dann folgen Chlorit und in geringeren Mengen in feinen Fraktionen Montmorillonit. Die Chlorit-Reflexe verschwinden bereits bei Erhitzung auf 450° C. Chemisch handelt es sich um die dem Pennin naheliegenden Diabantite.Die Unterschiede in Beschaffenheit und Menge der Quarze, Feldspäte und Glimmer, die unterschiedliche Verteilung der Schwerminerale sprechen dafür, daß die hellen Schichten wahrscheinlich zum Mesozoikum, vielleicht zum Buntsandstein gehören.Von der Mathematisch-Naturwissenschaftlichen Fakultät der Georg-August-Universität zu Göttingen genehmigte Dissertation.     

Petrogenesis of Glaucophane Schists

Some glaucophane schists are chemically indistinguishable fromgreenschists and epidote amphibolites. Provided all three rocktypes represent equilibrium assemblages, they must have formedunder differing physical conditions. The mineralogy of suchglaucophane schists taken in conjunction with experimental evidencesuggests that these rocks formed at low temperatures and atrelatively elevated pressures. The relatively high-pressure,low-temperature phases lawsonite, jadeitic pyroxene, and metamorphicaragonite are diagnostic of physical conditions attending thismetamorphism. Differential stress may aid in the attainmentof the appropriate mean pressure necessary for the productionof these phases. Graphic analysis and approximated thermodynamic calculationsindicate that relatively elevated pressures, or relatively lowtemperatures, or both, promote the formation of glaucophanein rocks of a wide range of bulk compositions while restrictingthe compositional range of albite-bearing rocks. It is concludedthat the coexistence of glaucophane with carbonate, calcium-aluminumsilicate or paragonite results from such physical conditions,and it is on the basis of these associations or, equally well,the presence of lawsonite, jadeitic pyroxene, or metamorphicaragonite that the blueschist facies should be defined. High pressures are not required for the production of glaucophaneitself. It is stable under physical conditions present in thegreenschist and epidote amphibolite facies in rocks deficientin CaO and rich in Na₂O and MgO relative to A1₂O₃. Such bulkcompositions might result from exchange of material betweenserpentinite and albite-bearing country rocks, and could accountfor glaucophane aureoles around, and inclusions of glaucophanerock within, some serpentinites.     

Röntgenmikroanalytische untersuchungen an titanomagnetiten tertiärer eflfusiva zur lösung gesteinsmagnetischer fragen

Zusammenfassung Gesteinsmagnetische Studien haben gezeigt, daß für das Verstandnis des jeweiligen magnetischen Verhaltens von Gesteinen u. a. detaillierte mineralogischoptische und nicht zuletzt chemische Untersuchungen nötig Bind. Zum Studiurim der Verteilung der Elemente im Erzkorn wurde die Röntgenmikroanalyse benutzt.Die Methode der Röntgenmikroanalyse wird beschrieben. Die Ergebnisse der Untersuchungen an Titanomagnetiten tertiärer Effusiva kennzeichnen die Inhomogenität der chemischen Verteilung im Erzkorn und lassen die Klärung von Phänomenen zu, die mit Hilfe der durchschnittlichen chemischen Analyse Bowie magnetothermischen u. a. Untersuchungen nicht möglich war.

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Studies on magnetic rocks have demonstrated that detailed informations on composition within ore-particles are needed in order to understand the respective magnetic behaviour. For studying such compositions microanalytic X-ray methods are used.The applied microanalyser is described.Results, gained on this way with tertiary effusiva, let recognize the inhomogenity of composition e.g. within titanomagnetites. They allow clarifying of phenomena, which cannot be understood on another way.

     

The volcano-magnetic effect

Summary A geometrically simple volcano is considered, havig a spherical magma chamber of 2.5 km radius centred at 10 km depth. The Curie point isotherm is assumed to be a plane at 20 km depth, except for the spherical volume which is also non-magnetic. The stress pattern in the vicinity of the spherical chamber, due to regional stress of sufficient intensity to cause an eruptions, is used to calculate the change in magnetization which results from the piezomagnetic effect through the volume of solid rock. The consequent magnetic field anomaly at the surface is then obtaied by numerical integration of the dipole law of force over the stressed volume. For rocks of the type found on the volcanic island of St. Vincent (West Indies), this model gives a maximum local volcano-magnet c effect of about 7 gammas.     

IDENTIFYING AND ASSESSING PROBLEM AREAS IN SOIL EROSION SURVEYS USING AERIAL PHOTOGRAPHS

Gully erosion has for many years been a problem in Rhodesia1s Tribal Trust Lands. This paper describes how Soil Conservation Service staff, with no previous ground knowledge of these areas, used good quality 1/25,000 scale aerial photographs to measure the extent of the gully erosion and to pinpoint erosion “black spots.” This enabled quick and reliable estimates of the cost of reclamation work to be made without the need for time-consuming field survey. The survey method discussed is capable of wide application wherever gully erosion occurs and needs to be brought under control.     

Ion-exchange reactions on clay minerals and cation selective membrane properties as possible mechanisms of economic metal concentration

A series of exploratory experiments on the concentration of base metals through ion exchange reactions on clay minerals show promising results. The extraction of Pb, Zn and Cd from bentonite, illite, kaolinite and montmorillonite was successful and megascopic quantities of PbS, CdS and ZnS could be obtained at specific loci, depending essentially on the flow velocity, and the other cations present. These or similar exchange reactions are tentatively proposed as possible mechanisms of economic metal concentration during diagenesis.

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Zusammenfassung Es werden experimentelle Resultate zur Anreicherung von Schwermetallen durch Tonminerale (Montmorillonite, Illite und Kaolinite) mitgeteilt. Eine erste Anreicherung kann über den Kationenaustausch bewirkt werden. In dem darauffolgenden zweiten, sehr viel wirksameren Schritt werden die Schwermetallionen aus den Tonlagern extrahiert und in deren Nähe als schwerlösliche Sulfide oder Carbonate gefällt. Die Extraktion beruht darauf, daß Tonschichten als Kationen-permeable Membranen wirken können. Sie wird von der Art der Tonminerale und der Kationen, den Lösungsgenossen, den Konzentrationsverhältnissen, dem pH-Wert, der Reaktionstemperatur, dem Porenvolumen und der Porenverteilung im Sediment beeinflußt.

     

Electrochemical strengthening of clayey sandy soils

Most previous studies and applications of electrochemical stabilization of soils through electroosmosis have been made on clayey soils. The object of this investigation was to find out if relatively small amounts of clay (1.5%–3.5%, by weight) present in a sandy soil would be enough for stabilization and strengthening to be possible. The results indicate increases of cohesion of the order of 100–200 lb./sq.ft. X-ray analyses of treated soils indicate that sheet structures of clays are reduced and silicates destroyed upon treatment by electroosmosis. Newly-formed minerals also cement the soil. These neoformations include gibbsite, limonite, calcite, hydrohematite, hydrogoethite (hydrolepidocrocite), hisingerite, allophane, allophanoid, gypsum, hematite, magnetite, nontronite, trona and natron (Na₂ CO₃, 10H₂O). The process seems to be irreversible.     

Isotopic variation of fishes in freshwater and estuarine zones of a large subtropical coastal lagoon

We used stable C and N isotope ratios of tissues from 29 fish species from a large subtropical lagoon in southern Brazil to examine spatial variability in isotopic composition and vertical trophic structure across freshwater and estuarine habitats. Nitrogen isotope ratios indicated a smooth gradation in trophic positions among species, with most fishes occupying the secondary and tertiary consumer level. Fish assemblages showed a significant shift in their carbon isotopic signatures between freshwater and estuarine sites. Depleted carbon signatures (from −24.7‰ to −17.8‰) were found in freshwater, whereas more enriched signatures (from −19.1‰ to −12.3‰) were obtained within the estuarine zone downstream. Based on our survey of the C₃ and C₄ plants and isotopic values for phytoplankton and benthic microalgae reported for ecosystems elsewhere, we hypothesized that the observed δ¹³C differences in the fish assemblage between freshwater and estuarine sites is due to a shift from assimilating organic matter ultimately derived from C₃ freshwater marsh vegetation and phytoplankton at the freshwater site (δ¹³C ranging from −25‰ to −19‰), to C₄ salt-marsh (e.g. Spartina) and widgeon grass (Ruppia maritima), benthic microalgae and marine phytoplankton at the estuarine sites (from −18‰ to −12‰). Our results suggested that fish assemblages are generally supported by autochthonous primary production. Freshwater fishes that likely were displaced downstream into the estuary during periods of high freshwater discharge had depleted δ¹³C values that were characteristic of the upper lagoon. These results suggest that spatial foodweb subsidies can occur within the lagoon.