Euv Spectroscopy of the Sunspot Region Noaa 7981 Using Soho – I. Line Emission and Time Dependence

EUV spectra of a medium-size sunspot and its surroundings, NOAA 7981, were obtained on 2 August 1996 with the Coronal Diagnostic Spectrometer (CDS) and the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on the Solar and Heliospheric Observatory (SOHO). The spectral lines formed in the transition region and corona show considerable structure and large deviations from a uniform spatial distribution over the active region. Enhanced EUV emissions in transition region lines are concentrated in small regions outside the umbra of the sunspot throughout most of the observing sequence. Only during a short, active period do we find an enhanced line emission that reaches into the umbra. Preliminary values for the umbral intensity are given.Marked changes are detected between the spatial distribution of line emission in the transition region and the low corona. The difference is not limited to cool and hot non-flaring loops not being cospatial, but includes differences both regarding the time variability and the orientation and size of the emission features. Whereas both rapid ( 4 and 2 min) and slow ( 10 and 12 h) temporal variations are found in the chromosphere (Hei 584 Ú) and transition region (Ov 629 Ú), the response in the low corona (Mgix 368 Ú) is slow ( 5 h). Furthermore, marked differences between the spatial distributions in the Mgviii 315 Ú, Mgix 368 Ú lines formed in the low corona and the coronal Fexiv 334 Ú, Fexvi 360 Ú lines are detected.     

Liquidus temperatures and phase compositions in the system Qz-Ab-Or at 5 kbar and very low water activities

Liquidus phase relations have been experimentally determined in the systems Qz-Ab-Or-(H₂O), Qz-Ab-(H₂O) and Qz-Or-(H₂O) at H₂O-undersaturated conditions (a _H2O = 0.07) and P = 5 kbar. Starting materials were homogeneous synthetic glasses containing 1 wt% H₂O. The liquidus temperatures were bracketed by crystallization and dissolution experiments. The results of kinetic studies showed that crushed glasses are the best starting materials to overcome undercooling and to minimize the temperature difference between the lowest temperature of complete dissolution (melting) and the highest temperature at which crystallization can be observed. At P = 5 kbar and a _H2O = 0.07, the Qz-Ab eutectic composition is Qz₃₂Ab₆₈ at 1095 °C (±10 °C) and the Qz-Or eutectic is Qz₃₈Or₆₂ at 1030 °C (±10 °C). The minimum temperature of the ternary system Qz-Ab-Or is 990 °C (±10 °C) and the minimum composition is Qz₃₂Ab₃₅‐ Or₃₃. The Qz content of the minimum composition in the system Qz-Ab-Or-H₂O remains constant with changing a _H2O. The normative Or content, however, increases by approximately 10 wt% with decreasing a _H2O from 1 to 0.07. Such an increase has already been observed in the system Qz-Ab-Or-H₂O-CO₂ at high a _H2O and it is concluded that the use of CO₂ to reduce water activities does not influence the composition of the minima in quartz-feldspar systems. The determined liquidus temperature in melts with 1 wt% H₂O is very similar to that obtained in previous nominally “dry” experiments. This discrepancy is interpreted to be due to problems in obtaining absolutely dry conditions. Thus, the hitherto published solidus and liquidus temperatures for “dry” conditions are probably underestimated. Received: 27 March 1997 / Accepted: 1 October 1997     

Formation and ascent of granitic magmas

New results obtained by the investigation of liquidus and solidus phase relationships in the haplogranite system Qz-Ab-Or are used to discuss the evolution of magmas during their ascent in the crust. It is assumed that the magmas are formed at 720°C, 820°C, 920°C and at a depth corresponding to a pressure of 8 kbar. The starting composition of the magma is taken as 50% melt plus 50% quartz and feldspars. In case of a closed system (no heat exchange and no transfer of elements) the melt fraction of magmas, the water activity and the viscosity increase with decreasing pressure. The temperature slightly decreases. At 700°C the viscosity is approximatively 2 orders of magnitude lower than at 900°C. This is related to the higher amount of water in the (H₂O-undersaturated) melt at low T. It is also shown that dehydration melting is only realistic at high T (900°C). At lower temperatures water has to be added from outside to obtain an intrusive magma with approximatively 50% melt.

---

Zusammenfassung Neue Ergebnisse, erzielt durch Untersuchungen von Liquidus und Solidus Phasenbeziehungen des Granitsystems Qz-Ab-Or, werden benutzt, um die Entwicklung eines granitoiden Magmas während seines Aufstiegs zu diskutieren. Es wird vorausgesetzt, daß die Magmen bei Temperaturen von 720°C, 820°C und 920°C gebildet werden, sowie in einer Tiefe die einem Druck von 8 kbar entspricht. Die anfängliche Zusammensetzung des Magmas wird mit einem Verhältnis von 50% Schmelze sowie 50% Quarz und Feldspäten angenommen. Im Falle eines geschlossenen Systems (kein Austausch von Wärme und Elementen) steigt die Teilschmelzbildung von Magmen, die Aktivität des Wassers und die Viskosität bei abnehmenden Druck; hierbei sinkt die Temperatur leicht. Bei 700°C ist die Viskosität um ca. 2 Größenordnungen geringer als bei 900°C. Dies wird bedingt durch den höheren Gehalt an Wasser in der (H₂O-untersättigten) Schmelze bei tieferen Temperaturen. Es wird außerdem gezeigt, daß Magmenbildung durch Dehydratation nur bei hohen Temperaturen realistisch ist (900°C). Bei tieferen Temperaturen muß Wasser von außen zugeführt werden um ein intrusives Magma zu erhalten, das ungefähr 50% Schmelze besitzt.

---

Résumé L'évolution des magmas granitiques au cours de leur ascension dans la croûte est discutée à la lumière de données nouvelles relatives aux relations entre phases liquides et solides dans le système Q-Ab-Or. On suppose que les magmas se forment à des températures de 720°C, 820°C, 920°C et à une profondeur correspondant à une pression de 8 Kb. On admet pour leur composition initiale un mélange de 50% de liquide et 50% de quartz + feldspaths. Dans le cas d'un système fermé (pas d'échange de chaleur ni de matière), la fraction liquide du magma, l'activité de l'eau et la viscosité augmentent quand la pression diminue; en même temps, la température décroît légèrement. A 700°C, la viscosité est d'environ 2 ordres de grandeur plus basse qu'à 900°C. Cette propriété est en relation avec la teneur en eau plus élevée dans le liquide (sous-saturé en eau) à basse température. On peut également montrer qu'une fusion déshydratante n'est vraisemblable qu'à haute température (900°C). Aux températures plus basses, de l'eau doit être apportée de l'extérieur pour l'obtention d'un magma à 50% de liquide.

---

. , 720°, 820°, 920°, 8 . , 50% 50% . , , , , . . 700° 2 , 900°. ( ) . , 900°. , 50% , - .

     

Verbreitung und Ausbildung der Siegener Schichten in der Osteifel

Ohne ZusammenfassungVortrag, gehalten auf der Hauptversammlung der Geologischen Vereinigung zu Frankfurt a. M., Januar 1933.     

V. Bücher- und Zeitschriftenschau

Ohne Zusammenfassung     

Die Graubündner Erdbeben und Wetterstürze im August 1927

Ohne Zusammenfassung     

Das Vorland der Alpen und die Vorgeschichte der Alpenfaltung

Ohne Zusammenfassung     

Acoustic investigations of mud volcanoes in the Sorokin Trough, Black Sea

The Sorokin Trough (Black Sea) is characterized by diapiric structures formed in a compressional tectonic regime that facilitate fluid migration to the seafloor. We present acoustic data in order to image details of mud volcanoes associated with the diapirs. Three types of mud volcanoes were distinguished: cone-shaped, flat-topped, and collapsed structures. All mud volcanoes, except for the Kazakov mud volcano, are located above shallow mud diapirs and diapiric ridges. Beyond the known near-surface occurrence of gas hydrates, bottom simulating reflectors are not seen on our seismic records, but pronounced lateral amplitude variations and bright spots may indicate the presence of gas hydrates and free gas.     

Mud volcanoes and gas hydrates in the Black Sea: new data from Dvurechenskii and Odessa mud volcanoes

Meteor cruise M52/1 documented the presence of gas hydrates in sediments from mud volcanoes in the Sorokin Trough of the Black Sea. In a mud flow on the Odessa mud volcano, a carbonate crust currently forms in association with anaerobic methane oxidation. Dvurechenskii mud volcano (DMV), a flat-topped mud pie-type structure, appeared to be very active. Pore water in sediments of DMV is enriched in several constituents, such as ammonium and chloride, which seem to originate at depth. High sediment temperatures of up to 16.5 °C in close contact to the ambient bottom water of 9 °C also suggest strong advective transport of material from greater depth. Steep temperature gradients indicate a high fluid and/or mud flux within DMV, which is confirmed by the shape of the pore water profiles. Active fluid expulsion sites are evidenced by direct seafloor observation, and a potential flux of methane from the sediment to the bottom water is indicated by water-column methane measurements.