Ein Pyrrhotin-Gefüge aus der Grube Bayerland bei Waldsassen (Oberpfalz)

The question of preferred orientation of the a-axes of pyrrhotite in metamorphic ores was studied on a fold of cm-dimension in pyrrhotite-ore from the Bayerland mine. A fabric with very good orientation of (0001) in a single s-plane appeared to be superimposed on the fold fabric. Nevertheless, also a weak preferred orientation of\([11\bar 20]\) (?)//B was found which could have been formed by translation with T = (0001) and\(t = [10\bar 10]\). In this favorable case a partial preservation of an older orientation is probable; the two orientations, however, seem to belong to a single orogenetic phase (main deformation with axis B II afterSpross 1954). The orientation of the c-axes of pyrrhotite was determined conoscopically from polarization figures in reflected light, that of the prism faces with an X-ray texture goniometer. The temperature of recrystallization was apparently about 450–500° C.     

Die Beziehung zwischen Luft-Temperatur,Sonnen-Strahlung und Boden

Zusammenfassung An Rand besonders der Ergebnisse der « Deutschen Grönland-Expedition Alfred Wegener » werden die Zusammenhänge zwischen Luft-Temperatur, Sonnenstrahlung und Boden in einfacher Weise entwickelt.

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Summary The results of the « German Grönlandexpedition Alfred Wegener » are used, to give a picture of the relation between air-temperature, solar radiation and the soil.

     

Zur Genese der kretazischen Eisenerze von Auerbach (Oberpfalz)

Zusammenfassung Die kretazischen Auèrbacher Eisenerze sind in Erosionsrirmän in Malmkalk bzw. -dolomit überwiegend syngenetisch-sedimentär durch, Ausfällung von Fe⁺⁺-und HCO₃ -Ionen enthaltenden Lösungen als Siderit bzw. — nach Oxydation des Eisens - als Nadeleisenerz zur Ablagerung gelangt. Ein Teil der heute vorliegenden Nadeleisenerze ist auch auf spätere Oxydation von primärem Eisenkarbonat zurückzuführen. Wesentliche Hinweise auf die Genese geben — außerden Lagerungsverhältnissen — vor allem der geringe Aluminiumgehalt der hochprozentigen Erze und der hohe Kohlenstoffgehalt der Weißerze; daneben werden auch andere Elemente, wie Bor, Yttrium, Phosphor, Mangan, Titan usw. zur Dentung herangezogen.Den Herren der Maxhütte möchten wir für die Förderung der Arbeit und die Erlaubnis zur Veröffentlichung und Herrn Prof. Dr. C. W.,Correns für seine vielseitige Unterstützung aufrichtig danken, außerdem auch Herrn Prof. Dr. Tx. ERNST, in dessen Institut ein Teil der abschließenden Arbeiten durchgeführt wurde. Herrn Dr. H.Tilliviann (Bayer. Geol, Landesamts danken wir für zahlreiche, freundliche Hinweise und die Überlassung von Proben.     

Calorimetric study of high pressure polymorphism in FeTiO3: Stability of the perovskite phase

A calorimetric study of the ilmenite and lithium niobate polymorphs of FeTiO₃ was undertaken to assess the high-pressure stabilities of these phases. Ilmenite is known to be the stable phase at ambient pressure, but the lithium niobate form may be a quench phase from a perovskite form which has been previously observed in situ at high pressure.In this study, the lithium niobate phase of FeTiO₃ was synthesized from an ilmenite starting material at 15– 16 GPa and 1473 K, using a uniaxial split-sphere high-pressure apparatus (USSA 2000). The energetics of the ilmenite to lithium niobate transformation were investigated through transposed-temperature drop calorimetry. The heat of back-transformation of lithium niobate to ilmenite was measured by dropping the sample in argon from ambient conditions to a temperature where the transformation occurs spontaneously. In drops made at 977 K, an intermediate x-ray amorphous phase was encountered. At 1273 K, the transformation went to completion. A value of -13.5±1.2 kJ/mol was obtained for the heat of transformation.     

Lithospheric response to volcanic loading in the Southern Cook Islands

The response of the ocean lithosphere to volcanic island loading has been investigated for the Southern Cook Islands of Rarotonga, Mangaia and the Aitutaki-Mauke group using (1) estimates of the change—with distance from the load—of uplift of islands located on the flexure-created arch, (2) geoid height perturbations as observed with the GEOS 3 and SEASAT radar altimeters, and (3) bathymetric evidence for the moat and arch about the island loads. The effective flexural rigidity for Rarotonga is found to be higher than for the older and nearby islands of Mangaia and Aitutaki. This, together with an earlier result for Tahiti [1], suggests that stress relaxation of the lithosphere has occurred and that this layer behaves as a viscoelastic material with an effective viscosity of about 5–10×10²⁵ poise. The observations for the flexural rigidity do not indicate any dependence on the age of the lithosphere at the time the loading occurred. This suggests that there are no significant differences in lithospheric properties for plates in the age range of 6–7×10⁷ years. Altimeter passes to the east of Mauke indicate that there may be an uncharted submarine extension of the Aitutaki-Mauke chain.