Geochemistry of blackwall sequences in the Habachtal emerald deposit,Hohe Tauern,Austria Part 1: Presentation of geochemical data

Summary The Habachtal emerald deposit, Hohe Tauern, is composed of blackwall sequences of the type: serpentinite — talc schist — ±chlorite schist or actinolite schist — biotite schist —albite gneiss and/or micaschist. 2 serpentinites, 33 blackwall rocks, 9 micaschists, 10 albite gneisses, and 5 aplitic gneisses were analyzed for major elements, and for Li, Be, Cr, Ni, Zn, Zr, Sn, in 36 samples also for Sc, Cu, Rb, Sr, Cs, Ba, W. The blackwall formation is due to a metasomatic exchange involving a transfer of Mg from the serpentinite to the silicic country rock, and of Si, Ca, K, and Al from the country rock to the serpentinite. Some of the trace elements were also mobile: Compared to serpentinite, Li and Be were enriched in all the blackwall rocks, and Sn and Cs in the actinolite, chlorite, and biotite schists; Sr was concentrated in the dolomite-bearing talc schists, and Zn, Rb, and Ba predominantly in the biotite schists.

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Geochemie der Blackwall-Folgen in der Smaragd-Lagerstätte Habachtal, Hohe Tauern, Österreich. Teil 1: Darstellung der geochemischen Daten

Zusammenfassung Die Smaragd-Lagerstätte Habachtal, Hohe Tauern, besteht aus Blackwall-Folgen vom Typ: Serpentinit — Talkschiefer — ±Chloritschiefer oder Aktinolithschiefer — Biotitschiefer — Albitgneis und/oder Glimmerschiefer. Von 2 Serpentiniten, 33 Blackwall-Gesteinen, 9 Glimmerschiefern, 10 Albitgneisen und 5 Aplitgneisen wurden chemische Analysen der Hauptelemente und von Li, Be, Cr, Ni, Zn, Zr, Sn vorgelegt; 36 Proben wurden auch auf Sc, Cu, Rb, Sr, Cs, Ba und W analysiert. Die Blackwall-Bildung geht auf einen metasomatischen Austausch zurück, bei dem Mg aus dem Serpentinit ins Nebengestein, Si, Ca, K und Al aus dem Nebengestein in den Serpentinit transportiert wurden. Daneben waren auch einige Spurenelemente mobil: Im Vergleich zum Serpentinit wurden Li und Be in allen Blackwall-Gesteinen, Sn und Cs in den Aktinolith-, Chlorit- und Biotitschiefern angereichert; Sr wurde(n) in den dolomitführenden Talkschiefern, Zn, Rb und Ba hauptsächlich in den Biotitschiefern konzentriert.

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With 5 Figures     

New developments in FM-CW radar sounding

Simultaneous lidar and FM-CW (frequency modulated-continuous wave) radar observations are presented and both common and different features observed with the two remote sensors are described. Among the common features are Kelvin-Helmholtz (K-H) waves and turbulent structures. The potential of the FM-CW radar as a meteorological tool for aiding fog dissipation forecasts is illustrated. The data also indicate that the radar often detects echoes from height regions which coincide with cloud tops. A new FM-CW radar sounder is described which incorporates scanning capability and which is fully mobile. Examples of recent observations are presented illustrating the capabilities of this second generation radar sounder.Future applications of the FM-CW radar sounder, such as investigations of the exact nature of the mechanism responsible for the radar returns, require accurate calibration of the radar sounder. It is shown that resolution and sensitivity of a linear frequency-modulated FM-CW radar depend on the time delay of the signal. Range dependency on resolution and sensitivity is calculated for various periodic and stochastic perturbations in a linear modulation and good agreement is found between calculated and measured values.     

A relation between the driving force and geoid anomaly associated with mid-ocean ridges

The driving force and geoid anomaly associated with the thermal structure of the oceanic plates are shown to be proportional to the first moment of the density structure with respect to depth and, hence, to each other. Both quantities exhibit the same functional dependence on age and this is given for two different thermal models. For the plate model the geoid anomaly and ridge driving force only increase slowly for ages greater than 40 m.y. in contrast to the half-space boundary layer model where a linear dependence on age holds for all ages. Isolation of the geoid anomaly related to the thermal structure of the plates would provide a direct measure of the magnitude of the ridge driving force.     

Diagenesis and Sr isotopic evolution of seawater using data from DSDP 590B and 575

New Sr isotopic and concentration analyses of bulk carbonate and porewaters from a carbonate-rich Miocene section sampled at DSDP Site 575 are reported and used, along with our earlier data from a section of similar age at DSDP Site 590B, in a numerical model to determine for each site the rate of Sr exchange during diagenesis and the degree to which this amount of exchange has shifted the⁸⁷Sr⁸⁶Sr of the bulk carbonate from the ratio each increment of sediment had when first deposited. Despite the fact that the two sites have very different water depth (4536 m at 575 vs. 1299 m at 590B), different sedimentation rate ( 10 m/My at 575 vs. 40 m/My at 590B), and significantly different porewater Sr²⁺ gradients, we find that the rate of Sr exchange as a function of sediment age is almost indistinguishable between the two sites. The rate of Sr exchange determined at the two sites is such that the resulting shift in bulk carbonate⁸⁷Sr⁸⁶Sr due to diagenesis is small compared to the total range of⁸⁷Sr⁸⁶Sr values measured, but large compared to the analytical uncertainty of the individual isotopic ratio measurements. By taking this shift into account we reconstruct the original⁸⁷Sr⁸⁶Sr of each increment of carbonate sampled, which when plotted as a function of age becomes our best estimate of the Sr isotopic evolution of seawater. Because Sr is very well mixed in the ocean, at any given time there is a single worldwide value of seawater⁸⁷Sr⁸⁶Sr. Therefore, if we are quantitatively accounting for the effect Sr exchange, we should find the same seawater evolution curve regardless of what DSDP Site is used. When we compare the observed bulk carbonate⁸⁷Sr⁸⁶Sr vs. age at the two sites they are seen to differ by amounts that are sometimes large compared to the analytical uncertainties of the measurements. However, when these data are corrected for the post-depositional Sr isotopic shifts predicted by our diagenetic model, we find almost perfect agreement. This agreement suggests that we have made a realistic determination of the rate of Sr exchange and its consequences in terms of shifting the⁸⁷Sr⁸⁶Sr of the bulk carbonate, and more importantly, that Sr isotopes can be used to correlate marine sediments with an accuracy comparable to the very small analytical uncertainties of modern isotopic measurements.     

Gravitational deflection of light at 1 2 1 PPN order

We compute in parametrized form the effect of source-velocity terms in the gravitational deflection of light. Internal rotation corresponds to sources of order ³ where . We find for rigidly rotating models of the Sunand of Jupiter that, in each case, this effect is of order 10^–6 arc sec. A very high accuracy that may be achievable by future space-bourne instruments is thus necessary for its detection.     

Long-term crustal deformation monitored by gravity and space techniques at Medicina, Italy and Wettzell, Germany

Series of gravity recordings at the stations Medicina (Italy) and Wettzell (Germany) are investigated to separate seasonal gravity variations from long-term trends in gravity. The findings are compared to height variations monitored by continuous GPS observations. To study the origin of these variations in height and gravity the environmental parameters at the stations are included in the fact finding. In Medicina, a clear seasonal signal is visible in the gravity and height data series, caused by seasonal fluctuations in the atmosphere including mass redistribution, the ocean, groundwater but also by geo-mechanical effects such as soil consolidation and thermal expansion of the structure supporting the GPS antenna. In Wettzell, no seasonal effect could be clearly identified, and the long-term trend in gravity is mainly caused by ground water variations. The successful combination of height and gravity series with the derived ratio of gravity to height changes indicates that the long-term trends in height and gravity are most likely due to mass changes rather than to tectonic movements.     

Suakin deep: Brines and hydrothermal sediments in the deepest part of the Red Sea

The sea floor of the Red Sea declines in two steps to the Suakin-graben in the area of the Suakin Deep. The western step is occupied by the Suakin Deep-Sea Plain with detrital-organogenic marls but without significant hydrothermal traces. A high rate of deposition is remarkable. The bottom of the Suakin-graben consists at least locally of basalt below a thin sedimentary cover. The deepest holes of the graben are filled with brines of uniform composition in two separate basins. The sediments in the basins, however, are different.The sediments in the W-Basin show only slight hydrothermal influences; the hydrothermal supply is rather constant. The ferromanganoan component predominates, the sulfidic one occurs occasionally.In the E-Basin ferromanganoan and sulfidic ore muds alternate with regular marly sediments. The ore muds have been formed by supply of hydrothermal solutions of different intensity. The deposition of the ore muds increased the rates of sedimentation in the E-Basin compared with the W-Basin.

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Zusammenfassung Im Gebiet des Suakin-Tiefs fällt der Boden des Roten Meeres treppenförmig zum Grabentiefsten ab. Die westliche Treppenstufe bildet die Suakin-Tiefsee-Ebene mit detritisch-organogenen, mergeligen Sedimenten ohne wesentliche hydrothermale Einschaltungen, aber mit hohen Sedimentationsraten. Der Boden des Suakin-Grabens besteht zumindest lokal aus Basalt unter einer dünnen Sedimentdecke. Die tiefsten Stellen des Grabens nehmen zwei mit Solen einheitlicher Zusammensetzung gefüllte Becken ein. Die Sedimente der beiden Becken sind jedoch verschieden.Die Sedimente des Westbeckens sind nur schwach hydrothermal beeinflußt, und die hydrothermale Zufuhr ist ziemlich gleichmäßig. Die manganitisch-limonitische Komponente herrscht vor, während die sulfidische nur gelegentlich eingeschaltet ist.Im Ostbecken liegen manganitisch-limonitische und sulfidische Erzschlämme vor, die sich durch verschieden starke hydrothermale Zufuhr gebildet haben. Die Entstehung von Erzschlämmen hat die Sedimentationsraten im Ostbecken gegenüber denen im Westbecken stark erhöht.

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Résumé Dans la région du «Suakin Deep»le fond de la Mer Rouge descend en deux marches vers le fond. du fossé. La «Suakin Deep-Sea Plaine » forme la marche ouest, avec ses sédiments détritiques-organogènes marneux sans traces hydrothermales de quelque importance, mais marqués par une forte vitesse de sédimentation. Le fond du Fossé de Suakin consiste — du moins localement — en basalte sous une mince couverture sédimentaire. Les dépressions les plus profondes du fossé, réparties en deux bassins séparés, sont remplies d'une saumure de composition uniforme. Les sédiments des deux bassins sont cependant différents.Les sédiments du bassin ouest montrent seulement une faible influence hydrothermale; l'apport hydrothermal est assez constant. Des précipitations de manganitelimonite prédominent, tandis que celles de sulfures sont seulement occassionnelles.Dans le bassin est, des boues chargées de manganite-limonite et de sulfures alternent avec des sédiments marneux. Le minerai a été formé par l'apport de solutions hydrothermales de différente intensité. La formation des boues minéralisées a considérablement augmenté la vitesse de sédimentation dans le bassin est, par rapport au bassin ouest.

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Revised form of a paper presented March 1, 1973 at the 63 rd Annual Meeting of the Geologische Vereinigung in Salzburg/Austria.     

Die tektonische Baugeschichte von Süd-Devonshire als Beispiel einer mehrphasigen variszischen Prägung

Five movement-phases during the Variscan tectogenesis shaped the structural cast of the Devonian rocks in South Devon. The first movement-phase, i. e. the main tectonic phase, resulted in the mappable fold system trending E-W or ENE-WSW in the west accompanied by related minor folds, and the first cleavage (s ₁) parallel to the axial planes. The cleavage planes dip to the south as far as the line Slapton-Bigbury, while farther to the south they dip to the north and finally to the south again, thus forming a huge fanning. In the second movement-phase a second cleavage (s ₂) with E-W strike associated with minor folds, was superimposed on the older structures south of the line Berry Head-Cornworthy. The trend of these folds is, more or less E-W. Furthermore the second cleavage shows a fanning which does not coincide with that of the first cleavage. South-vergent minor folds of bedding and cleavage planes, associated with small-scale southward thrusts represent structures of a third movement-phase. The fourth movement-phase was the kinking of mainly the first cleavage in the southern part of South Devon. There are two groups: one shows flat-lying kink-bands affecting mainlys ₁; seldoms ₂, and having a southward thrusting sense of movement while the other consists of nearly vertical kink-bands trending N-S which displace to the south on their eastern sides. Subsequently with the commencement of the New Red deposition, repeated tectonic stretching took place, resulting in N-S and WSW--ENE trending faults. The succession of the different tectonic events led to occasionally very complicated superimpositions. The rocks in the middle and southern part of South Devon suffered a regional metamorphosis that increases slowly towards the south. Finally, the tectonic structures of South Devon are compared with those in South Cornwall where the same movements-phases caused a completely different structural style.