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.     

NOAA卫星探测数据对B-模式分析预报系统性误差的影响

本文报告极轨气象卫星探测数据对B-模式的海平面气压场预报和500hPa高度预报的系统性误差的影响.主要结果是:(1)B-模式预报海平面气压的强度偏弱,即高压系统太低,低压太高;(2)500hPa高度预报的系统性误差情况不如海平面气压场误差情况明显.但也能发现槽区的高度预报不够低,而脊区的高度预报不够高;(3)应用卫星数据对B-模式分析预报系统的预报有正作用,对海洋上的地面低压和500hPa槽区附近的系统性误差有明显减小,但对其它地区天气系统预报的正负影响参差不齐,其作用难下结论。     

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.     

An evaluation of the apparent dissociation constants of carbonic acid in seawater

The internal consistency of five sets of apparent dissociation constants of carbonic acid in seawater obtained by Buch (1951), Lyman (1956), Edmond and Gieskes (1970), Hansson (1973) and Mehrbach et al. (1973) have been tested using the GEOSECS Atlantic data for the total alkalinity, the total CO₂ concentration and the partial pressure of CO₂. As a measure of the consistency for each of the five sets of the dissociation constants with the data, the 77 measured values of the partial pressure of CO₂ have been compared with those calculated from the alkalinity and total CO₂ values determined for these samples. It has been found that: (1) the apparent dissociation constants of Lyman (1956), Hansson (1973) and Mehrbach et al. (1973) appear to be internally consistent with the data, whereas those of Buch (1951) and of Edmond and Gieskes (1970) appear to be markedly inconsistent with the GEOSECS data; and (2) on the basis of a statistical analysis of the data grouped in three temperature ranges, the dissociation constants of Lyman (1956) and of Mehrbach et al. (1973) appear to be most satisfactory.     

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.     

Aspèct Isotopique δ34S‰ d'un Processus de Mobilisation et de Réconcentration de Sulfures en Amas à Structure Filoniénne

Résumé Beaucoup de minéralisations sulfurées filoniennes sont encaissées dans des formations qui contiennent les mêmes éléments mais à l'état disséminé. En ce cas, on admet généralement que ces éléments ont été mobilisés et reconcentrés dans des structures tectoniques distensives. Le même mécanisme peut encore être envisagé quand de telles minéralisations sont spatialement éloignées des formations réservoirs de soufre et de métaux. Connaissant la composition isotopique des sulfures filoniens ainsi que les conditions physico-chimiques de leur dépôt il est possible de calculer la valeur théorique de la composition isotopique des sulfures du réservoir. Celle-ci peut alors être comparée aux compositions isotopiques effectives des sulfures provenant des différents réservoirs potentiels dans le but de déterminer quel est le réservoir de soufre et de métaux le plus probable. Une série d' analyses isotopiques a été entreprise sur les sulfures des minéralisations de Henderson et de Campbell Chibougamau Main Mine. Ces minéralisations du type Cu-Au sont en relation spatiale avec des zones de cisaillement développées dans le complexe du Lac Doré. La composition isotopique moyenne de la pyrite de Henderson vaut –2.9. Cette valeur est très proche de la moyenne des compositions isotopiques de la pyrite de Chibougamau Main Mine (–2.8). La composition isotopique moyenne de la chalcopyrite de Henderson est de –3.2. En se fondant sur le modèle thermodynamique proposé d'une part, sur les compositions isotopiques de la pyrite et de la chalcopyrite d'une minéralisation stratiforme encaissée dans le réservoir présumé d'autre part, il est possible de conclure que les sulfures des minéralisations filoniennes ont été remobilisés des formations volcano-sédimentaires.

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Many sulphide concentrations occur in formations containing the same elements in a disseminated state. It is generally admitted that these elements may be mobilised and reconcentrated into open spaces. The same mechanism has been envisaged in cases where vein deposits are spatially separated from the rocks which acted as a reservoir for sulphur and metals. Knowing the isotopic composition of the sulphide from the veins as well as the physico-chemical conditions of deposition, the theoretical value of the sulphur isotopic composition of the reservoir can be calculated and this can be compared with the values of the sulphides from the different reservoirs in order to indicate the most likely source. A series of isotopic analyses were untertaken on the sulphides from Henderson and Campbell Chibougamau Main Mines. These two deposits belong to the Cu-Au type of mineralisation associated with shear zones within the Lac Doré Complex. The mean isotopic composition of pyrite at Henderson is –2.9 which is close to the mean values measured at Campbell Chibougamau Main Mine (–2.8). The mean value of the chalcopyrite from the Henderson Mine is –3.2. Different possibilities concerning the provencance of sulphur are discussed. Based on existing thermodynamic model and on a set of new isotopic datas (pyrite and chalcopyrite) from volcanogenic mineralisation, it is possible to conclude that measured values correspond to mobilised volcanogenic sulfur.

     

Noble gas components in clasts and separates of the Abee meteorite

The noble gas components and their distributions were studied in a variety of clasts and in separated phases of clast 2,2 using a detailed stepwise release program. The results show the presence of two distinct trapped components: one appears to be similar to Kenna-type gas [28], the other is characterized by element ratios³⁶Ar/⁸⁴Kr < 370 and³⁶Ar/¹³²Xe ≥ 900 and is termed Ar-rich component. Silicate phases are identified as carriers of both components; but since they are differentially released, the results imply that multiple carrier phases are required. Unlike results from other meteorites, HF attack removes all but 15% of the xenon. Substantial amounts of trapped and, in many cases, unfractionated air were observed, apparently in reaction products of reduced and easily oxidized minerals. The¹²⁹Xe_r release systematics imply the presence of two distinct carriers of extinct¹²⁹I and suggest lithophilic behavior of I in Abee. The U/Th-⁴He and K-⁴⁰Ar data are consistent with a 4.5 Gy age. Amounts of spallogenic He, Ne and Ar yield a cosmic ray exposure age of 8 My. We compare the Ar-rich component to noble gas abundances in planetary atmospheres and we discuss a suggested model of origin.