Fluid-controlled crustal metasomatism within a high-pressure subducted mélange (Mt. Hochwart, Eastern Italian Alps)

The Nonsberg–Ultental Region of northern Italy contains a Palaeozoic mélange that was partially subducted during the Variscan orogeny. This mélange is constituted mainly by metapelites characterized by shale-type REE-patterns, displaying partial melting which began under high-pressure conditions. The resulting migmatites enclose minor slivers of mantle-wedge peridotites that have been incorporated into the mélange during subduction. Peridotites display important large ion lithophile elements (LILE) enrichment consequent to amphibole recrystallization contemporaneously with metapelite migmatization at P ≈ 2.7 GPa and T ≈ 850 °C in the garnet–peridotite field. Crustal and mantle (ultramafic) rocks of the mélange display the same Sm–Nd ages of about 330 ± 6 Ma, which dates both the metamorphic peak and the migmatization event. The zircon U–Pb age of the metasomatic amphibolitic contact between garnet peridotite and migmatite is identical (333.3 ± 2.4 Ma) within analytical errors. Therefore, metasomatism, migmatization and peak metamorphism are constrained to the same event. The presence of Cl-rich apatite and ferrokinoshitalite in the contact amphibolite, together with the trace-element patterns of peridotites, suggest that metasomatism was driven by Cl- and LILE-rich fluids derived from ocean water transported into the subduction zone by sediments and crustal rocks. These fluids interacted with the crust, prompting partial melting under water oversaturated conditions and partitioning LILE from the crust itself. Peridotites, which were well below their wet solidus temperature, could not melt but they recrystallized in the crustal mélange under garnet-facies conditions. Crustal fluids caused extensive hydration and LILE-enrichment in peridotites and severe Sm–Nd isotope disequilibrium between minerals, especially in the recrystallized peridotites. The proposed scenario suggests massive entrapment of crustal aqueous fluids at high-pressure conditions within subduction zones.     

First results of DORIS data analysis at Geodetic Observatory Pecný

In a cooperation between the Astronomical Institute, University of Bern (AIUB), the Geodetic Observatory Pecný (GOPE), and the Institut Géographique National (IGN), DORIS data analysis capabilities were implemented into a development version of the Bernese GPS software. The DORIS Doppler observables are reformulated such that they are similar to global navigation satellite system (GNSS) carrier-phase observations, allowing the use of the same observation models and algorithms as for GNSS carrier-phase data analysis with only minor software modifications. As such, the same algorithms may be used to process DORIS carrier-phase observations. First results from the analysis of 3 weeks of DORIS data (September 2004, five DORIS-equipped satellites) at GOPE are promising and are presented here. They include the comparison of station coordinates with coordinate estimates derived by the Laboratoire d’Etudes en Géophysique et Océanographie Spatiale/Collecte Localisation Satellites analysis centre (LCA) and the Institut Géographique National/Jet Propulsion Laboratory (IGN/JPL), and the comparison of Earth orientation parameters (EOPs) with the International Earth Rotation and Reference Frames Service (IERS) C04 model. The modified Bernese results are of a slightly lower, but comparable, quality than corresponding solutions routinely computed within the IDS (International DORIS Service). The weekly coordinate repeatability RMS is of the order of 2–3 cm for each 3D station coordinate. Comparison with corresponding estimates of station coordinates from current IDS analysis centers demonstrates similar precision. Daily pole component estimates show a mean difference from IERS-C04 of 0.6  mas in X _p and  ? 0.5  mas in Y _p and a RMS of 0.8  mas in X _p and 0.9  mas in Y _p (mean removed). An automatic analysis procedure is under development at GOPE, and routine DORIS data processing will be implemented in the near future.     

Speleoseismology: A critical perspective

Speleoseismology is the investigation of earthquake records in caves. Traces can be seen in broken speleothems, growth anomalies in speleothems, cave sediment deformation structures, displacements along fractures and bedding plane slip, incasion (rock fall) and co-seismic fault displacements. Where earthquake origins can be proven, these traces constitute important archives of local and even regional earthquake activity. However, other processes that can generate the same or very similar deformation features have to be excluded before cave damage can be interpreted as earthquake induced. Most sensitive and therefore most valuable for the tracing of strong earthquake shocks in caves are long and slender speleothems, such as soda straws, and deposits of well-bedded, water-saturated silty sand infillings, particularly in caves close to the earth's surface. Less easily proven is a co-seismic origin of an incasion and other forms of cave damage. The loads and creep movements of sediment and ice fillings in caves can cause severe damage to speleothems which have been frequently misinterpreted as evidence of earthquakes. For the dating of events in geological archives, it is important to demonstrate that such events happened at approximately the same time, i.e. within the error bars of the dating methods. A robust earthquake explanation for cave damage can only be achieved by the adoption of appropriate methods of direct dating of deformation events in cave archives combined with correlation of events in other geological archives outside caves, such as the deformation of lake and flood-plain deposits, locations of rock falls and active fault displacements.     

Intercomparison of Boron Isotope and Concentration Measurements. Part II: Evaluation of Results

The Istituto di Geoscienze e Georisorse (IGG), on behalf and with the support of the International Atomic Energy Agency (IAEA), prepared eight geological materials (three natural waters and five rocks and minerals), intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials were distributed to twenty seven laboratories - virtually all those performing geochemical boron isotope analyses in the world -which agreed to participate in the intercomparison exercise. Only fifteen laboratories, however, ultimately submitted the isotopic and/or concentration results they obtained on the intercomparison materials. The results demonstrate that interlaboratory reproducibility is not well reflected by the precision values reported by the individual laboratories and this observation holds true for both boron concentration and isotopic composition. The reasons for the discrepancies include fractionations due to the chemical matrix of materials, relative shift of the zero position on the δ¹¹B scale and a lack of well characterized materials for calibrating absolute boron content measurements. The intercomparison materials are now available at the IAEA (solid materials) and IGG (waters) for future distribution.     

Erste Resultate über die Verteilung von Schwermineralen in verschiedenen Flyschkomplexen der Schweiz

Zusammenfassung Im Zusammenhang mit Herkunftsuntersuchungen von Flyschgeröllen aus den oligocänen Schuttfächern der subalpinen Molasse der Zentralschweiz wurden einige Flyschkomplexe des Rücklandes auf ihren Schwermineralgehalt getestet. Untersucht wurden, neben der subalpinen Molasse, Proben aus dem nordhelvetischen Altdorfer Sandstein, dem ultrahelvetischen Habkern-, Schlieren- und Gurnigelflysch, ferner aus dem nordpenninischen Niesenflysch, dem Wäggitaler, Vorarlberger und Vaduzer Flysch sowie aus den Flyschen der präalpinen Decken. Mitausgewertet wurden auch die vonBouma (1959) untersuchten Proben des Oligocänflyschs von Peïra-Cava (S-Frankreich). Den internsten und externsten Flyschtrögen, die gekennzeichnet sind durch einen rotbraunen Spinell, stehen die ultrahelvetischen und nordpenninischen Flyschbildungen gegenüber, denen der Spinell vollständig fehlt (vgl. Abb. 2). Der Granat, dessen Gehalt sich auf die Summe der übrigen durchsichtigen Schwerminerale bezieht, ist in den externsten Trögen angereichert, fehlt jedoch in den Flyschen der präalpinen Decken fast ganz. Die dazwischenliegenden ultrahelvetischen und nordpenninischen Flyschräume weisen einen stark variierenden, schwachen bis mittleren Granatgehalt auf. Die zuletztgenannten Flyschzonen sind charakterisiert durch eine Turmalin-Apatit-Zirkon-Kombination. Ob in dieser Kombination noch weitere Aufteilungen möglich sind, müssen künftige, detaillierte sedimentpetrographische Untersuchungen der einzelnen Flyschkomplexe zeigen. Erstaunlich konstant ist die laterale Verbreitung der Schwermineralprovinzen im alpinen Deckengebäude, worauf der spinellführende Oligocänflysch von Peïra-Cava (Bouma 1959) und die Spinellvormacht in der ostalpinen Oberkreide (Woletz 1963) deutlich hinweisen. Wir hoffen durch mehr und detailliertere Untersuchungen unser Schema derart zu verfeinern daß unter Umständen Aussagen zur Klärung alpintektonischer Probleme gemacht werden können.

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Summary In connection with studies about the origin of Oligocene conglomerates in the Subalpine Molasse the heavy mineral content of some alpine Flysch deposits has been examined. Apart from the Subalpine Molasse, the following units have been sampled: the Altdorfer Sandstone, which belongs to the North Helvetic facies belt; the Habkern, Schlieren and Gurnigel Flysch from the Ultra Helvetic realm; the Niesen, Wäggitaler, Vorarlberger and Vaduzer Flysch from the Valais facies belt as well as the more internal Flysch sediments of the prealpine nappes. Furthermore, the results ofBouma's (1959) studies about the Oligocene Flysch deposits in Southern France have been applied. The heavy mineral assemblage of alpine Flysch deposits shows a very distinct distribution: The internal Flysch troughs of the alpine geosyncline and the most external ones are characterized by redbrown spinel. This mineral is absent in the Ultra Helvetic and the North Helvetic facies belt (see fig. 2). The garnet, the content of which refers to the amount of the remaining non-opaque heavy minerals, dominates the heavy mineral suites of the most external troughs. In the internal ones this mineral is lacking, while in the intermediate Ultra Helvetic and North Penninique facies belts garnet varies significantly in abundance. In these belts tourmaline, apatite and zircon are the most important minerals. Further research might prove, if a more detailed subdivision of this mineral suite is possible. An astonishing lateral constancy of the heavy mineral facies in the corresponding tectonic units is observed. This is particularly the case in the spinel-bearing assemblage as the results ofBouma's (1959) investigations on the Oligocene Flysch of Southern France and ofWoletz's (1963) studies on the Upper Cretaceous in the Austroalpine nappes show.More detailed investigations are necessary to prove the reliability of our scheme. More data shall contribute to solve some of the tectonic problems of the Alps.

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Résumé En relation avec des études sur l'origine des conglomérats oligocènes de la molasse subalpine, les minéraux lourds de divers complexes de flysch ont été éxaminés. Il s'agit — mise à part la molasse subalpine — d'échantillons recueillis dans les grès d'Altdorf (zone nord-helvétique), dans le Habkern-, Gurnigel- et Schlieren-flysch (zone ultra-helvétique), puis dans le flysch du Niesen et celui du Wäggital, du Vorarlberg et de Vaduz (zone nord-pennine) et enfin dans les flyschs des nappes préalpines. Nous avons par ailleurs tenu compte d'un travail deBouma (1959) dans le Flysch oligocène de Peïra-Cava (Alpes-Maritimes, France). Dans l'association des minéraux lourds des flyschs alpins on peut distinguer une répartition clairement déterminée: les parties les plus internes autant que les parties les plus externes de la géosynclinale alpine sont riches en spinelle, tandis que ce minéral bran-rougeâtre manque totalement dans les zones ultra-helvétiques et nord-pennines (voir fig. 2). Le grenat dont la teneur se rapporte à la somme des autres minéraux non-opaques, est très fréquent dans les parties les plus externes et disparaît vers l'intérieur de la géosynclinale. Les zones des flyschs ultra-helvétiques et nord-pennines sont caractérisées par une association de tourmaline, d'apatite et de zircon avec une fréquence très variable de grenat. Des recherches détaillées démontreront, s'il est possible de faire des distinctions plus précises. La régularité de la répartition latérale des minéraux lourds — surtout du spinelle — dans les unités tectoniques correspondantes est remarquable: le travail deBouma (1959) dans le flysch oligocène de Peïra-Cava et celui deWoletz (1963) dans le crétacé supérieur des austrides ont abouti à des résultats semblables aux nôtres dans les unités analogues.Nous espérons qu'en perfectionnant notre schéma nous pourrons contribuer à la solution des problèmes de la tectonique alpine.

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. Altdorfer Sandstein, Habkern-Schlieren - Gurnigelflysch ( ), Niesenflysch, Wä ggitaler, Vorarlberger Vaduzer Flysch ( ) . , , ; , , .

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Die vorliegende Arbeit wurde ermöglicht durch die Unterstützung des Schweizerischen Nationalfonds zur Förderung der wissenschaftlichen Forschung. Sie umfaßt Teilresultate eines größeren Forschungsprojektes in Sedimentologie unter der Leitung von Prof. Dr. W.Nabholz. Dem Schweizerischen Nationalfonds und speziell Herrn Prof. Dr. W.Nabholz, der mich zu dieser Arbeit anregte, möchte ich herzlich danken. Ferner gilt mein Dank den Herren Dr. F.Allemann und Dr. R.Herb vom Geologischen Institut der Universität Bern für die zahlreichen sachkundigen Hinweise sowie Herrn W.Flück, Bern, für die Überlassung von Probenmaterial.     

Meteoritic trace elements in lunar rock 14321, 184

The 16 trace elements (Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Rb, Re, Sb, Se, Te, Tl and Zn) were measured by radiochemical neutron activation analysis in six samples of 14321, 184: microbreccia-2 (15), microbreccia-3 (14A, 16A and 19A), basaltic clast (1A), and light matrix material (9A). The 14321 microbreccias typically contain a siderophile-rich ancient meteoritic component, poor in volatiles, which is characterized by low $\text{Ir}\text{Au}$ and $\text{Re}\text{Au}$ ratios (0.25-0.38 and 0.34-0.50, respectively, normalized to Cl). This component also occurs in Apollo 12 KREEP glasses, norite fractions of Apollo 14 1–2 mm soils, Apennine Front breccias, and Cayley Formation material, and may represent ejecta from the Imbrian basin.The basaltic clast 14321, 184-1A closely resembles 14053 in trace element content, and both are 5–10 times higher than mare basalts in volatile trace elements (Br, Cd, Tl). The light matrix material contains 9.2 ± 0.5 per cent of microbreccias, judging from its siderophile content.     

DETERMINATION OF FLUORINE, CHLORINE, BROMINE AND IODINE IN SEVEN GEOCHEMICAL REFERENCE SAMPLES

The concentrations of fluorine, chlorine, bromine and iodine of seven geochemical reference samples have been determined. Analytical techniques were neutron activation analysis for chlorine, bromine and iodine and ion-selective potentiometry for fluorine. After irradiation of the samples, these halogens were separated from the matrix elements by pyrohydrolysis in presence of vanadium (V) oxide. This extraction allows to measure the four halogens in the same sample.     

A set of elements based on polar coordinates in the KS-space and its applications

A new set of canonical elements is introduced into the field of KS-theory. The close relationship of these elements with a set of elements proposed by Scheifele (1970) is analysed. Some applications are outlined.Presented at the Conference on Celestial Mechanics, Oberwolfach, Germany, August 27–September 2, 1972.