Time relationships between magmatism,tectonics and metamorphism in three plutonic belts in Southern Tibet: new K-Ar data

From North to South, the three plutonic belts in Southern Tibet are the Transhimalaya (or Kangdese), the North Himalaya (or Lhagoi Kangri) and the High Himalaya. 25 new mineral and whole rock K-Ar dates, added to previous data, enable a precise analysis to be made of the time relationships between different magmatic, tectonic and metamorphic events that occurred on both sides of the Indus-Tsangpo suture zone. These include: 1 - The emplacement of a large part of the eastern Transhimalaya magmatism occurred during Eocene time, suggesting a close relationship between this emplacement and the late stages of conver-gence between India and Eurasia. 2 - South of the suture, the ages obtained fall mainly between 11 and 15 MA. The greatest age allows us to fix a lower limit on the timing of metamorphic recrystallization of the Paleozoic North Himalaya granites; an intermediate age may correspond to a minimum age of emplacement of the High Himalaya and part of the North Himalaya Cenozoic granitoids; finally, the youngest age may characterize the northernmost Cenozoic granitoids of the North Himalaya belt. The consistency of these tenuous age variations with field and structural data suggests that they may be significant. 3 - Our determinations give ages often significantly younger than those usually proposed for the same events. As suggested by some authors, such a discrepancy might reflect relatively late India-Eurasia collision in this eastern part of the suture.

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Zusammenfassung Die drei plutonischen Gürtel sind, im Süd-Tibet, von Norden nach Süden, der Transhimalaya (oder Kangdese), der Nordhimalaya (oder Lhagoi Kangri) und der Hochhimalaya. 25 neue K/Ar-Datierungen an Mineralien und Gesamtgestein wurden frühen Werten hinzugefügt und erlauben eine Präzisierung der chronologischen Beziehungen der verschiedenen magmatischen, tektonischen und metamorphen Ereignisse, die beiderseits der Indus-Tsangpo-Suturzone stattfanden. 1 - Die Platznahme des größten Teils des Transhimalayaplutons scheint im Eozän erfolgt zu sein, was eine enge Beziehung des magmatischen Ereignisses mit dem Finalstadium der Konvergenz Indiens und Eurasien vermuten läßt. 2 - Im Süden der Suturzone schwanken die Alterswerte im wesentlichen zwischen 11 und 15 Mia. Jahren. Das höchste Alter erlaubt die Festlegung der unteren chronologischen Grenze der metamorphen Rekristallisation der paläozoischen Granitoide des Nordhimalayas; ein mittleres Alter könnte der unteren Grenze für die Platznahme der känozoischen Granitoide des Hochhimalayas und z. T. des Nordhimalayas entsprechen; das jüngste Alter könnte schließlich die nördlichsten Granitoide des Nordhimalayasgürtel kennzeichnen. Die große Kohärenz zwischen diesen Altersbestimmungen und den im Gelände gemessenen Werten legt nahe, daß die schwachen chronologischen Unterschiede signifikant sein können. 3 - Unsere Bestimmungen ergeben oft bedeutend jüngere Alter, als meistens für die gleichen magmatischen Ereignisse angegeben worden ist. Wie nahegelegt wurde, könnte diese Diskrepanz ein relativ spätes Kollidieren der Indischen und Eurasischen Platte im Östlichen Teil der Sutur bedeuten.

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Résumé Du Nord au Sud, les trois ceintures plutoniques du Tibet méridional sont celles du Transhimalaya (ou Kangdese), Nord Himalaya (ou Lhagoi Kangri) et Haut Himalaya. 25 nouvelles datations par K-Ar, sur minéraux et roches totales, associées à des données antérieures permettent de préciser les relations chronologiques de différents événements magmatiques, tectoniques et métamorphiques intervenus de part et d'autre de la zone de suture Indus-Tsangpo. Ainsi: 1 - La mise en place d'une part importante du magmatisme Transhimalayen oriental se révèle d'âge Eocène, ceci suggérant l'existence d'une étroite relation causale entre cette mise en place et le stade final de convergence entre l'Inde et l'Eurasie. 2 - Au Sud de la suture, les âges obtenus oscillent essentiellement entre 11 et 15 MA. L'âge le plus ancien permet de fixer une limite chronologique inférieure à la recristallisation métamorphique des granitoïdes paléozoïques du Nord Himalaya; un âge intermédiaire pourrait correspondre à une limite minimale pour la mise en place des granitoïdes cénozoïques du Haut Himalaya et pro parte du Nord Himalaya; enfin, l'âge le plus récent caractériserait les granitoïdes les plus septentrionaux de la ceinture nord himalayenne. La grande cohérence existant entre ces datations et les données de terrain suggère que les faibles écarts chronologiques mis en évidence sont réellement significatifs. 3 - Les âges que nous obtenons sont souvent nettement plus jeunes que ceux habituellement proposés pour les mêmes évènements. Comme cela a été suggéré, une telle discordance pourrait être l'indice du caractère relativement tardif de la collision Inde-Eurasie au niveau de cette partie orientale de la suture.

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Publication of the C.R.P.G., contribution n 591.     

Beiträge zur Limnologie des Walen-, Zürich-Ober-und Zürichsees

Chemical and physical conditions of the Walensee are discussed on the basis of values analyzed during an investigation period in the years 1972–1975. Thereby values of selected parameters have been compared with data of other Swiss lakes to estimate the trophic condition of the lake.      

Die pelagischen Rotatorien des Sempachersees,mit spezieller Berücksichtigung der Brachioniden und der Ernährungsfrage

The pelagic Rotifers of the mesotrophic lake of Sempach (Switzerland) were investigated qualitatively and quantitatively from 1969 to 1971. The Rotifer reproduction rate was highest from spring until early summer, with peaks of 0.86 million individuals below 1 dm² in 1969, and 0.92 in 1970. During summer stratification, production was comparatively low. During both yearsKeratella cochlearis made up on an average of 50% of the total number of Rotifers.Keratella cochlearis, K. quadrata andKellicottia longispina reproductive rates were calculated, using the egg ratio method of Edmondson. The highest yearly rates of the three species were noted in spring at a depth of 0 to 5 m. From spring until early summer in 1970, 88% of the biomass of the first large phytoplankton peak were nannoplankton, 70% of which consisted of Cryptophycease and Chrysophyceae from the end of April until the middle of June. During the investigation of the three Brachionidae, inquiries into the food relation of nannoplankton algae showed close relations to these algae groups and more over to μ-algae. In spring the ChrysophyceaeErkenia subaequiciliata seems to be the most important food for the three Rotifer species.     

Spatio-temporal patterns of throughfall and solute deposition in an open tropical rain forest

The brief interaction of precipitation with a forest canopy can create a high spatial variability of both throughfall and solute deposition. We hypothesized that (i) the variability in natural forest systems is high but depends on system-inherent stability, (ii) the spatial variability of solute deposition shows seasonal dynamics depending on the increase in rainfall frequency, and (iii) spatial patterns persist only in the short-term. The study area in the north-western Brazilian state of Rondônia is subject to a climate with a distinct wet and dry season. We collected rain and throughfall on an event basis during the early wet season (n = 14) and peak of the wet season (n = 14) and analyzed the samples for pH and concentrations of , Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, , and DOC. The coefficient of variation for throughfall based on both sampling intervals was 29%, which is at the lower end of values reported from other tropical forest sites, but which is higher than in most temperate forests. Coefficients of variation of solute deposition ranged from 29% to 52%. This heterogeneity of solute deposition is neither particularly high nor particularly low compared with a range of tropical and temperate forest ecosystems. We observed an increase in solute deposition variability with the progressing wet season, which was explained by a negative correlation between heterogeneity of solute deposition and antecedent dry period. The temporal stability of throughfall patterns was low during the early wet season, but gained in stability as the wet season progressed. We suggest that rapid plant growth at the beginning of the rainy season is responsible for the lower stability, whereas less vegetative activity during the later rainy season might favor the higher persistence of “hot” and “cold” spots of throughfall quantities. The relatively high stability of throughfall patterns during later stages of the wet season may influence processes at the forest floor and in the soil. Solute deposition patterns showed less clear trends but all patterns displayed a short-term stability only. The weak stability of those patterns is apt to impede the formation of solute deposition-induced biochemical microhabitats in the soil.     

Microseismicity induced during fluid-injection: A case study from the geothermal site at Groß Schönebeck,North German Basin

The technical feasibility of geothermal power production in a low enthalpy environment will be investigated in the geothermal site at Groß Schönebeck, North German Basin, where a borehole doublet was completed in 2007. In order to complete the Enhanced Geothermal System, three massive hydraulic stimulations were performed. A seismic network was deployed including a single 3-component downhole seismic sensor at only 500 m distance to the injection point. Injection rates reached up to 9 m³/min and the maximum injection well-head pressure was as high as ～60 MPa. A total of 80 very small (?1.8 < M _W < ?1.0) induced seismic events were detected. The hypocenters were determined for 29 events. The events show a strong spatial and temporal clustering and a maximum seismicity rate of 22 events per day. Spectral parameters were estimated from the downhole seismometer and related to those from other types of induced seismicity. The majority of events occurred towards the end of stimulation phases indicating a similar behavior as observed at similar treatments in crystalline environments but in our case at a smaller level of seismic activity and at lower magnitudes.     

Der Einfluss der Strömung auf die Zusammensetzung der Lebensgemeinschaften im Experiment

Ohne Zusammenfassung     

A method to reconstruct flood scenarios using field interviews and hydrodynamic modelling: application to the 2017 Suleja and Tafa,Nigeria flood

Natural Hazards - The scarcity of model input and calibration data has limited efforts in reconstructing scenarios of past floods in many regions globally. Recently, the number of studies that use...     

Nitric oxide emissions from soils: a case study with temperate soils from Saxony, Germany

Nitrogen oxides (NO _x ) are involved in acid rain and ozone formation, as well as destruction. NO _x are climate-relevant trace gases in the atmosphere. Atmospheric NO _x originate from anthropogenic emissions (mainly combustion processes). NO from natural processes derives from thunderstorms and soil microbial processes. They may play a crucial role in soil?Catmosphere feedback processes. This study aims to investigate NO _x -emissions from soils under different land use, geographical and meteorological conditions. NO _x -emissions were quantified in both field and laboratory experiments with a closed static chamber. Disturbed soil samples have been used for laboratory experiments. A climate chamber was used to regulate soil temperature of the samples. Field experiments showed that NO-soil emissions strongly depend on soil temperature. NO-emissions from a soil under meadow showed significant daily variations, unlike soil below spruce forest. Peak emission values were 18???g NO?CN?m^?2?h^?1 above meadow and 1.3???g NO?CN?m^?2?h^?1 under forest canopy. In addition, NO-emissions of meadow and forest soil were studied in a climate chamber, enhanced by an additional experiment with agricultural soil. These experiments revealed strong exponential correlations of NO-emissions and soil temperature. Maximum values reached above 400???g NO?CN?m^?2?h^?1 from agricultural soils at soil temperatures above 50°C. This study shows that soil NO-emissions strongly depend on temperature, vegetation type and geographical position. Consequently, NO-emissions may have a positive feedback effect on climate change.