TY - GEN A1 - Rottler, Erwin A1 - Bronstert, Axel A1 - Bürger, Gerd A1 - Rakovec, Oldrich T1 - Projected changes in Rhine River flood seasonality under global warming T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Climatic change alters the frequency and intensity of natural hazards. In order to assess potential future changes in flood seasonality in the Rhine River Basin, we analyse changes in streamflow, snowmelt, precipitation, and evapotranspiration at 1.5, 2.0 and 3.0 ◦C global warming levels. The mesoscale Hydrological Model (mHM) forced with an ensemble of climate projection scenarios (five general circulation models under three representative concentration pathways) is used to simulate the present and future climate conditions of both, pluvial and nival hydrological regimes. Our results indicate that the interplay between changes in snowmelt- and rainfall-driven runoff is crucial to understand changes in streamflow maxima in the Rhine River. Climate projections suggest that future changes in flood characteristics in the entire Rhine River are controlled by both, more intense precipitation events and diminishing snow packs. The nature of this interplay defines the type of change in runoff peaks. On the sub-basin level (the Moselle River), more intense rainfall during winter is mostly counterbalanced by reduced snowmelt contribution to the streamflow. In the High Rhine (gauge at Basel), the strongest increases in streamflow maxima show up during winter, when strong increases in liquid precipitation intensity encounter almost unchanged snowmelt-driven runoff. The analysis of snowmelt events suggests that at no point in time during the snowmelt season, a warming climate results in an increase in the risk of snowmelt-driven flooding. We do not find indications of a transient merging of pluvial and nival floods due to climate warming. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1164 Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-522962 SN - 1866-8372 ER - TY - GEN A1 - Fischer, Melanie A1 - Korup, Oliver A1 - Veh, Georg A1 - Walz, Ariane T1 - Controls of outbursts of moraine-dammed lakes in the greater Himalayan region T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Glacial lakes in the Hindu Kush–Karakoram–Himalayas–Nyainqentanglha (HKKHN) region have grown rapidly in number and area in past decades, and some dozens have drained in catastrophic glacial lake outburst floods (GLOFs). Estimating regional susceptibility of glacial lakes has largely relied on qualitative assessments by experts, thus motivating a more systematic and quantitative appraisal. Before the backdrop of current climate-change projections and the potential of elevation-dependent warming, an objective and regionally consistent assessment is urgently needed. We use an inventory of 3390 moraine-dammed lakes and their documented outburst history in the past four decades to test whether elevation, lake area and its rate of change, glacier-mass balance, and monsoonality are useful inputs to a probabilistic classification model. We implement these candidate predictors in four Bayesian multi-level logistic regression models to estimate the posterior susceptibility to GLOFs. We find that mostly larger lakes have been more prone to GLOFs in the past four decades regardless of the elevation band in which they occurred. We also find that including the regional average glacier-mass balance improves the model classification. In contrast, changes in lake area and monsoonality play ambiguous roles. Our study provides first quantitative evidence that GLOF susceptibility in the HKKHN scales with lake area, though less so with its dynamics. Our probabilistic prognoses offer improvement compared to a random classification based on average GLOF frequency. Yet they also reveal some major uncertainties that have remained largely unquantified previously and that challenge the applicability of single models. Ensembles of multiple models could be a viable alternative for more accurately classifying the susceptibility of moraine-dammed lakes to GLOFs. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1160 Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-522050 SN - 1866-8372 ER - TY - THES A1 - Stuff, Maria T1 - Iron isotope fractionation in carbonatite melt systems T1 - Fe-Isotopenfraktionierung in karbonatitischen Schmelzen N2 - Carbonatite magmatism is a highly efficient transport mechanism from Earth’s mantle to the crust, thus providing insights into the chemistry and dynamics of the Earth’s mantle. One evolving and promising tool for tracing magma interaction are stable iron isotopes, particularly because iron isotope fractionation is controlled by oxidation state and bonding environment. Meanwhile, a large data set on iron isotope fractionation in igneous rocks exists comprising bulk rock compositions and fractionation between mineral groups. Iron isotope data from natural carbonatite rocks are extremely light and of remarkably high variability. This resembles iron isotope data from mantle xenoliths, which are characterized by a variability in δ56Fe spanning three times the range found in basalts, and by the extremely light values of some whole rock samples, reaching δ56Fe as low as -0.69 ‰ in a spinel lherzolite. Cause to this large range of variations may be metasomatic processes, involving metasomatic agents like volatile bearing high-alkaline silicate melts or carbonate melts. The expected effects of metasomatism on iron isotope fractionation vary with parameters like melt/rock-ratio, reaction time, and the nature of metasomatic agents and mineral reactions involved. An alternative or additional way to enrich light isotopes in the mantle could be multiple phases of melt extraction. To interpret the existing data sets more knowledge on iron isotope fractionation factors is needed. To investigate the behavior of iron isotopes in the carbonatite systems, kinetic and equilibration experiments in natro-carbonatite systems between immiscible silicate and carbonate melts were performed in an internally heated gas pressure vessel at intrinsic redox conditions at temperatures between 900 and 1200 °C and pressures of 0.5 and 0.7 GPa. The iron isotope compositions of coexisting silicate melt and carbonate melt were analyzed by solution MC-ICP-MS. The kinetic experiments employing a Fe-58 spiked starting material show that isotopic equilibrium is obtained after 48 hours. The experimental studies of equilibrium iron isotope fractionation between immiscible silicate and carbonate melts have shown that light isotopes are enriched in the carbonatite melt. The highest Δ56Fesil.m.-carb.melt (mean) of 0.13 ‰ was determined in a system with a strongly peralkaline silicate melt composition (ASI ≥ 0.21, Na/Al ≤ 2.7). In three systems with extremely peralkaline silicate melt compositions (ASI between 0.11 and 0.14) iron isotope fractionation could analytically not be resolved. The lowest Δ56Fesil.m.-carb.melt (mean) of 0.02 ‰ was determined in a system with an extremely peralkaline silicate melt composition (ASI ≤ 0.11 , Na/Al ≥ 6.1). The observed iron isotope fractionation is most likely governed by the redox conditions of the system. Yet, in the systems, where no fractionation occurred, structural changes induced by compositional changes possibly overrule the influence of redox conditions. This interpretation implicates, that the iron isotope system holds the potential to be useful not only for exploring redox conditions in magmatic systems, but also for discovering structural changes in a melt. In situ iron isotope analyses by femtosecond laser ablation coupled to MC-ICP-MS on magnetite and olivine grains were performed to reveal variations in iron isotope composition on the micro scale. The investigated sample is a melilitite bomb from the Salt Lake Crater group at Honolulu (Oahu, Hawaii), showing strong evidence for interaction with a carbonatite melt. While magnetite grains are rather homogeneous in their iron isotope compositions, olivine grains span a far larger range in iron isotope ratios. The variability of δ56Fe in magnetite is limited from - 0.17 ‰ (± 0.11 ‰, 2SE) to +0.08 ‰ (± 0.09 ‰, 2SE). δ56Fe in olivine range from -0.66‰ (± 0.11 ‰, 2SE) to +0.10 ‰ (± 0.13 ‰, 2SE). Olivine and magnetite grains hold different informations regarding kinetic and equilibrium fractionation due to their different Fe diffusion coefficients. The observations made in the experiments and in the in situ iron isotope analyses suggest that the extremely light iron isotope signatures found in carbonatites are generated by several steps of isotope fractionation during carbonatite genesis. These may involve equilibrium and kinetic fractionation. Since iron isotopic signatures in natural systems are generated by a combination of multiple factors (pressure, temperature, redox conditions, phase composition and structure, time scale), multi tracer approaches are needed to explain signatures found in natural rocks. N2 - Karbonatitische Schmelzen, die im Erdmantel gebildet werden, transportieren Material aus dem Erdmantel zur Erdkruste und ermöglichen somit Einblicke in Chemismus und Dynamiken des Erdmantels. Die Analyse stabiler Eisenisotopenverhältnisse ist eine neue und vielversprechende Methode um Schmelzprozesse und Interaktionen von Schmelzen im Erdmantel nachzuverfolgen, insbesondere da Eisenisotopenfraktionierung vom Oxidationszustand und der Bindungsumgebung in der Schmelze abhängig ist. Mittlerweile existiert ein großer Datensatz zur Eisenisotopenfraktionierung in magmatischen Gesteinen, der sowohl Zusammensetzungen von Gesamtgesteinen als auch von separierten Mineralgruppen umfasst. Karbonatite weisen extrem leichte Eisenisotopensignaturen und gleichzeitig eine breite Spannweite der δ56Fe auf. Darin ähneln sie Mantelxenolithen, die ebenfalls sehr variable und teilweise extrem leichte δ56Fe aufweisen, wie zum Beispiel -0.69 ‰ in einem Spinelllherzolith. Ein möglicher Grund für diese große Spannweite sind metasomatische Prozesse, an denen Fluide wie hochalkalische Silikatschmelzen oder Karbonatschmelzen beteiligt sind. Welche Auswirkung Metasomatose auf die Eisenisotopenfraktionierung hat, hängt von Parametern wie dem Verhältnis von Schmelze zu Gestein, der Reaktionszeit und der Art der beteiligten metasomatischen Fluide sowie den Mineralreaktionen ab. Auch mehrere aufeinanderfolgende Phasen der Schmelzextraktion könnten zur Heterogenisierung von Teilen des Erdmantels beigetragen haben. Bisher existieren allerdings nur wenige Untersuchungen zur Eisenisotopenfraktionierung zwischen Silikat- und Karbonatphasen. Um Eisenisotopenfraktionierung im Karbonatitsystem besser zu verstehen, wurden im Rahmen dieser Arbeit Experimente im Natrokarbonatitsystem durchgeführt. Dazu wurden unmischbare Silikat- und Karbonatschmelzen bei Temperaturen zwischen 900 und 1200 °C und Drücken von 0,5 und 0,7 GPa in einem intern beheizten Autoklaven bei intrinsischen Redoxbedingungen equilibriert. Im Anschluss wurden die Silikat- und Karbonatschmelzen separiert, aufgeschlossen und die Eisenisotopenverhältnisse beider Phasen mittels MC-ICP-MS analysiert. Dabei konnte gezeigt werden, dass die Proben nach spätestens 48 Stunden Fe-isotopisch equilibriert sind und dass im Gleichgewicht leichte Eisenisotope in der Karbonatschmelze angereichert sind. Die größte Isotopenfraktionierung von Δ56Fesil.m.-carb.melt (mean) = 0,13 ‰ wurde in einem System mit stark peralkalischer Zusammensetzung der Silikatschmelze (ASI ≥ 0,21, Na/Al ≤ 2,7) gemessen. In den Systemen mit extrem peralkalischer Zusammensetzung der Silikatschmelze (ASI zwischen 0,11 and 0,14) hingegen war die Eisenisotopenfraktionierung analytisch nicht auflösbar. Zusätzlich wurde die Eisenisotopenfraktionierung zwischen Magnetit- und Olivinkörnern in situ mittels UV-Femtosekunden-Laserablation gekoppelt mit MC-ICP-MS untersucht. Bei der Probe handelt es sich um eine Melilititbombe aus der Salt-Lake-Crater-Gruppe in Honolulu (Oahu, Hawaii), die deutliche Anzeichen für Kontakt mit einer karbonatitischen Schmelze aufweist. Während die Magnetite eher homogen hinsichtlich ihrer Eisenisotopenzusammensetzung sind (-0,17 ‰, ± 0,11 ‰, 2SE, to +0,08 ‰, ± 0,09 ‰, 2SE), weisen die Olivine eine weitaus größere Spannweite an δ56Fe auf (-0,66 ‰, ± 0,11 ‰, 2SE, to +0,10 ‰, ± 0,13 ‰, 2SE). Da Eisen unterschiedliche Diffusionskoeffizienten in Olivin und Magnetit hat, sind in beiden unterschiedliche Informationen zur kinetischen und Gleichgewichtsisotopenfraktionierung enthalten. Die Beobachtungen aus den Experimenten und in den Eisenisotopenanalysen in situ deuten darauf hin, dass die extrem leichten Eisenisotopensignaturen in Karbonatiten durch Isotopenfraktionierung in mehreren Schritten während der Karbonatitgenese entstanden sind, die sowohl Gleichgewichts- als auch kinetische Fraktionierung umfassen können. Da die Eisenisotopensignaturen in natürlichen Systemen durch eine Kombination mehrerer Faktoren (Druck, Temperatur, Redoxbedingungen, Phasenzusammensetzung und -struktur, Zeitskala) entstehen, werden Multi-Tracer-Ansätze benötigt, um die in natürlichen Gesteinen beobachteten Signaturen zu erklären. KW - MC-ICP-MS KW - silicate melt KW - carbonate melt KW - melilitite KW - UV fs laser ablation KW - MC-ICP-MS KW - Silikatschmelze KW - Karbonatschmelze KW - IHPV KW - Melilitit Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-519928 ER - TY - THES A1 - Ruiz-Monroy, Ricardo T1 - Organic geochemical characterization of the Yacoraite Formation (NW-Argentina)-paleoenvironment and petroleum potential T1 - Organische geochemische Charakterisierung der Yacoraite-Formation (NW-Argentinien) – Paläoumgebung und Erdölpotenzial T1 - Caracterización geoquímica orgánica de la Formación Yacoraite (NO-Argentina) -paleoambiente y potencial petrolero N2 - This dissertation was carried out as part of the international and interdisciplinary graduate school StRATEGy. This group has set itself the goal of investigating geological processes that take place on different temporal and spatial scales and have shaped the southern central Andes. This study focuses on claystones and carbonates of the Yacoraite Fm. that were deposited between Maastricht and Dan in the Cretaceous Salta Rift Basin. The former rift basin is located in northwest Argentina and is divided into the sub-basins Tres Cruces, Metán-Alemanía and Lomas de Olmedo. The overall motivation for this study was to gain new knowledge about the evolution of marine and lacustrine conditions during the Yacoraite Fm. Deposit in the Tres Cruces and Metán-Alemanía sub-basins. Other important aspects that were examined within the scope of this dissertation are the conversion of organic matter from Yacoraite Fm. into oil and its genetic relationship to selected oils produced and natural oil spills. The results of my study show that the Yacoraite Fm. began to be deposited under marine conditions and that a lacustrine environment developed by the end of the deposition in the Tres Cruces and Metán-Alemanía Basins. In general, the kerogen of Yacoraite Fm. consists mainly of the kerogen types II, III and II / III mixtures. Kerogen type III is mainly found in samples from the Yacoraite Fm., whose TOC values are low. Due to the adsorption of hydrocarbons on the mineral surfaces (mineral matrix effect), the content of type III kerogen with Rock-Eval pyrolysis in these samples could be overestimated. Investigations using organic petrography show that the organic particles of Yacoraite Fm. mainly consist of alginites and some vitrinite-like particles. The pyrolysis GC of the rock samples showed that the Yacoraite Fm. generates low-sulfur oils with a predominantly low-wax, paraffinic-naphthenic-aromatic composition and paraffinic wax-rich oils. Small proportions of paraffinic, low-wax oils and a gas condensate-generating facies are also predicted. Here, too, mineral matrix effects were taken into account, which can lead to a quantitative overestimation of the gas-forming character. The results of an additional 1D tank modeling carried out show that the beginning (10% TR) of the oil genesis took place between ≈10 Ma and ≈4 Ma. Most of the oil (from ≈50% to 65%) was generated prior to the development of structural traps formed during the Plio-Pleistocene Diaguita deformation phase. Only ≈10% of the total oil generated was formed and potentially trapped after the formation of structural traps. Important factors in the risk assessment of this petroleum system, which can determine the small amounts of generated and migrated oil, are the generally low TOC contents and the variable thickness of the Yacoraite Fm. Additional risks are associated with a low density of information about potentially existing reservoir structures and the quality of the overburden. N2 - Diese Dissertation wurde im Rahmen des internationalen und interdisziplinären Graduiertenkollegs StRATEGy durchgeführt. Diese Gruppe hat sich zum Ziel gesetzt, geologische Prozesse zu untersuchen, die auf unterschiedlichen zeitlichen und räumlichen Skalen ablaufen und die südlichen Zentralanden geprägt haben. Diese Studie konzentriert sich auf die Tonsteine und Karbonate der Yacoraite Fm., die zwischen Maastricht und Dan im kreidezeitlichen Salta-Grabenbecken abgelagert wurden. Das ehemalige Riftbecken liegt im Nordwesten Argentiniens und gliedert sich in die Teilbecken Tres Cruces, Metán-Alemanía und Lomas de Olmedo. Die übergreifende Motivation für diese Studie war es, neue Erkenntnisse über die Entwicklung der marinen und lakustrinen Bedingungen während der Ablagerung der Yacoraite Fm. in den Tres Cruces und Metán-Alemanía Sub-Becken zu gewinnen. Weitere wichtige Aspekte, die im Rahmen dieser Dissertation untersucht wurden, sind die Umwandlung von organischer Materie der Yacoraite Fm. in Öl sowie deren genetische Beziehung zu ausgewählten produzierten Ölen und natürlichen Ölaustritten. Die Ergebnisse meiner Studie zeigen, dass die Ablagerung der Yacoraite Fm. unter marinen Bedingungen begann und sich bis zum Ende der Ablagerung in den Tres Cruces- und Metán-Alemanía-Becken ein lakustrines Milieu entwickelte. Im Allgemeinen besteht das Kerogen der Yacoraite Fm. überwiegend aus den Kerogentypen II, III und II/III-Mischungen. Der Kerogentyp III findet sich vor allem in Proben aus der Yacoraite Fm., deren TOC-Werte niedrig sind. Aufgrund der Adsorption von Kohlenwasserstoffen an den Mineraloberflächen (Mineralmatrixeffekt) könnte der Gehalt an Typ-III-Kerogen mit der Rock-Eval-Pyrolyse in diesen Proben überschätzt werden. Untersuchungen mittels organischer Petrographie zeigen, dass die organischen Partikel der Yacoraite Fm. hauptsächlich aus Alginiten und einigen Vitrinit-artigen Partikeln bestehen. Die Pyrolyse-GC der Gesteinsproben zeigte, dass die Yacoraite Fm. schwefelarme Öle mit einer überwiegend Wachs-armen paraffinisch-naphthenisch-aromatischen Zusammensetzung und paraffinische Wachs-reiche Öle generiert. Geringe Anteile paraffinischer, Wachs-armer Öle und einer Gaskondensat-generierenden Fazies werden ebenfalls vorausgesagt. Auch hier wurden Mineralmatrixeffekte berücksichtigt, die zu einer quantitativen Überschätzung des gasbildenden Charakters führen können. Die Ergebnisse einer zusätzlich durchgeführten 1D-Beckenmodellierung zeigen, dass der Beginn (10 %TR) der Ölgenese zwischen ≈10 Ma und ≈4 Ma stattfand. Der größte Teil des Öls (von ≈50 % bis 65 %) wurde vor der Entwicklung struktureller Fallen gebildet, die während der plio-pleistozänen Diaguita Deformatiosphase gebildet wurden. Nur ≈10 % des insgesamt generierten Öls wurde nach der Entstehung struktureller Fallen gebildet und potentiell darin gefangen. Wichtige Faktoren in der Risikobewertung dieses Erdölsystems, welche die geringen Mengen an generiertem und migriertem Öl bestimmen können, stellen die allgemein niedrigen TOC-Gehalte und die variable Mächtigkeit der Yacoraite Fm. dar. Weitere Risiken sind mit einer niedrigen Informationsdichte über potentiell vorhandene Reservoirstrukturen und die Qualität der Deckgesteine verbunden. N2 - This dissertation was carried out within the framework of the international and interdisciplinary research training group StRATEGy whose aim is to study geological processes occurring at different times and spatial scales that have shaped the southern Central Andes. The study focuses on the shales and carbonates of the Yacoraite Fm. deposited in the Salta rift basin (NW Argentina) during the Maastrichtian to Danian, and is divided into the Tres Cruces, Metán-Alemanía, and Lomas de Olmedo sub-basins. The Yacoraite Fm. is considered the potential source rock for most oil fields in NW Argentina. The overall motivation for this research was to provide new insights into the occurrence of marine and lacustrine settings during the deposition of the Yacoraite Fm. in the Tres Cruces and Metán-Alemanía sub-basins. Other important aspects assessed in this research are the likely transformation of organic matter of the Yacoraite Fm. into oil as well as its genetic relation to selected produced oils and natural oil seep samples. Fifty-two outcropping samples from the Yacoraite Fm. collected in the Tres Cruces and Metán-Alemanía sub-basins, seven oil seep samples from the Tres Cruces and Lomas de Olmedo sub-basins and eight produced oils from the latter sub-basin were evaluated. Characterization of the depositional environment and kerogen types of the Yacoraite Fm. was performed using various geochemical analyses encompassing pyrolysis, chromatography, spectrometry and petrography. Minerals were analyzed by X-ray diffraction. The elemental composition of rock samples was determined by X-ray fluorescence and more precise quantification was done by ICP-MS analysis. The study of the hydrocarbon potential of the Yacoraite Fm. was addressed by the following analyses of its organic matter and modeling procedures: • The assessment of the amount, quality, and thermal maturity of the organic matter; • Measurement of the rate of thermal cracking (bulk kinetics) of the organic matter into oil; • The extrapolation of high heating rate kinetics to low heating rates at geological conditions using the first-order kinetic approach provided by the Arrhenius equation; • The prediction of the composition (compositional kinetics) and the phase behavior of its first-formed petroleum; • The specific activation energy distribution of the bulk kinetics of representative samples collected in the Tres Cruces sub-basin were used in the 1D-basin modeling, enabling a comparison between the timing of oil generation and the timing of the formation of structural traps. Subsequently, the implications of these variables on the accumulation of oil in the Tres Cruces sub-basin were assessed. The characterization of produced oils and oil seep samples was carried out by chromatographic and spectrometric techniques. Genetic relationships (source rock-oil correlation) of the oil seep samples in the Tres Cruces sub-basin was studied by comparing their compositional affinities to rock extracts from outcropping samples of the Yacoraite Fm. in the same sub-basin. Since no rock samples were available from the Lomas de Olmedo sub-basin, the source-rock correlation for the oil seep samples and the produced oils assume that the Yacoraite Fm. in this sub-basin has similar organofacies as in the Tres Cruces and Metán-Alemanía sub-basins. The results of this research indicate that the deposition of the Yacoraite Fm. began in marine environments. Lacustrine settings developed during the middle part and predominated towards the end of the deposition in the Tres Cruces and Metán-Alemanía sub-basins. In general, the kerogen of the Yacoraite Fm. is predominantly composed of Type II, II/III, and Type III kerogens. The latter is largely found in samples from the Yacoraite Fm. whose TOC values were low. In these samples, the content of Type III kerogen could be overestimated with Rock-Eval pyrolysis due to hydrocarbon adsorption on mineral surfaces (mineral-matrix effect). Organic petrography showed that the organic particles of the Yacoraite Fm. correspond mainly to alginites and some vitrinite-like particles. Pyrolysis-GC of whole-rock samples indicated that the Yacoraite Fm. generates low sulphur oils with a mainly Paraffinic-Naphthenic-Aromatic Low Wax composition and Paraffinic High Wax oils. Minor contributions of Paraffinic Low Wax Oil and Gas condensate-generating facies are also predicted. Mineral-matrix effects can lead to an overestimation of the gas-prone character and were considered. Extrapolation of bulk kinetics experiments to a geological heating rate of 3 K/Myr reveals that the oil generation from the Yacoraite Fm. in the Tres Cruces sub-basin occurs in a range of approximately 60 °C. The onset (10%TR) of oil generation occurs at geological temperatures from 108 °C to 132 °C. The complete transformation of the organic matter into oil (90%TR) is reached at temperatures between 142 °C and 169 °C. The gas exsolution from the oil occurs at pressures below 200 bar as predicted from PVT-compatible compositional kinetics with subsequent separation of two phases and the increase in liquid viscosity at depths <1.8 km. The analysis of outcrop samples of the Yacoraite Fm. collected in the Metán-Alemanía and Tres Cruces sub-basins document that their maturity is at least at the onset of oil generation. The formation is more mature in the deeper buried centers of the basins being in the main oil window, as indicated by the presence of genetically related oil seep samples and supported by predictions of thermal modeling. The results of 1D-basin modeling indicate that the onset (10%TR) of oil generation occurred between ≈10 Ma and ≈4 Ma. Most of the oil (from ≈50% to 65%) was generated before the structural traps associated with the Diaguita tectonic phase (c.a. 2.5 Ma) formed. The amount of oil generated after the formation of structural traps and potentially accumulated in them accounts for ≈10%. The petroleum system risk assessment identifies the generally low TOC content and variable thickness of Yacoraite Fm. as important factors that may determine the low volumes of generated and migrated oil. Additional risks are associated with the lack of information regarding the existence of reservoirs and the quality of the seals. Oil-source rock correlations based on depositional-, age- and maturity-related biomarkers show that the oil samples of the Caimancito oil field and from Well-10 of the Martinez del Tineo oil field were generated from the Yacoraite Fm., while partial correlations are determined between this formation and the oil samples from Well-18 and Chirete x100-1. The oil samples from well-11 and Río Pescado show no correlation and were sourced from a different rock. According to the project partners, it is most likely the Devonian Los Monos Fm. The oil-oil correlations reflect the source oil-source rock correlations mentioned above and were supported by the ratios of light hydrocarbons using the classical approach of Halpern (1995). The Río Pescado and well-11 oil samples lack most of the biomarkers, which distinguishes them from the rest of the oils. The sample from well-11 was found to be a mixture of oils of varying thermal maturity. The least mature oil in this mixture contains stigmastane and correlates with the oil sample from the Caimancito-21 well. The most mature sample is characterized by higher concentrations of diamantanes and adamantanes. An anomalously high uranium content was measured in one sample at the base of the Yacoraite Fm. in the west sector of the Metán-Alemanía sub-basin. High radiation doses appear to be the cause for the very low hydrocarbon generation during Rock-Eval pyrolysis. The sample is composed mainly of alginites with minor amounts of terrigenous material and plots in the field of Type IV kerogen in a pseudo-Van Krevelen diagram. Since radiation induces aromatization in the kerogen structure, it potentially mimics higher thermal maturity as determined by vitrinite reflectance. The higher Tmax is caused by the high adsorption of hydrocarbons on the highly-aromatized kerogen and the contribution of hydrocarbons adsorption on mineral surfaces. The lack of biomarkers in the solvent-extracted portion (bitumen) of the same highly-irradiated sample prevents the characterization of kerogen type and the depositional environment. However, unlike Py-GC results for kerogen, GC-FID analysis on extracted bitumen still shows n-alkanes, pristane, and phytane. This may not only indicate a different response of bitumen and kerogen to radiation, at least in the magnitude, but also offers an alternative for kerogen typing in samples where the kerogen is highly affected by radiation which makes its classification unreliable. In this example, the ratios of pristane/n-C17 and phytane/n-C18 in bitumen indicate that a Type II/III kerogen composes this sample, which is consistent with the presence of alginite as the main organic component and some vitrinite-like particles. In conclusion, molecular geochemical analyses have documented the presence of gammacerane in extracts of the Yacoraite Fm. which indicate the development of hypersaline conditions as well as the changing depositional environment of the Yacoraite Fm. from marine towards lacustrine settings. The variability of organofacies of this formation in the Tres Cruces and Metán-Alemanía sub-basins is a consequence of the changes in the depositional environment. Future work may provide insights into the evolution of paleosalinity during Yacoraite Fm. deposition by using specific proxies e.g., methyltrimethyltridecylchromans. Future research may include characterizing the NSO fraction of these oils as well as elucidating possible fractionation during expulsion, migration, and accumulation. A regional study is needed to clarify the uncertainties associated with the existence of the reservoir, the quality of the seals and to improve the data-input for thermal modeling for the Tres Cruces sub-basin. Studies that aim to increase the database of the concentration of methyldiamantanes (3- + 4-) and methyladamantanes (1- + 2-) in produced oils will provide a threshold for the assessment of oil cracking. Further research is aimed at helping to understand how the distribution of uranium can affect the different responses of bitumen and kerogen to radiation. KW - Yacoraite Formation KW - Argentina KW - Caimancito oil field KW - Salta basin KW - Cretaceous basin KW - Martinez del Tineo KW - Chirete KW - Ramos X-11 KW - Río Pescado KW - radiolysis KW - kerogen kinetics KW - PhaseKinetics KW - radiation and chemical properties KW - oil seeps KW - organofacies KW - organofacies KW - mineral matrix KW - age-related biomarkers KW - maturity-related biomarkers KW - biodegradation KW - Diaguita KW - Argentinien KW - Caimancito-Ölfeld KW - Chirete KW - Kreidebecken KW - Diaguita KW - Martinez del Tineo KW - Phasenkinetik KW - Ramos X-11 KW - Río Pescado KW - Salta-Becken KW - Yacoraite Formation KW - biologischer Abbau KW - Kerogenkinetik KW - Reifegradbezogene Biomarker KW - mineralische Matrix KW - natürlichen Ölaustritten KW - Organofazies KW - radiolyse KW - Strahlung und chemische Eigenschaften KW - Argentina KW - Campo petrolero Caimancito KW - Chirete KW - Cuenca Cretácica KW - Diaguita KW - Martinez del Tineo KW - Cinética de fases KW - Formación Yacoraite KW - biomarcadores diagnósticos de edad KW - biodegradación KW - Cinética del querógeno KW - biomarcadores diagnósticos de madurez KW - matríz mineral KW - manaderos de petróleo KW - radiólisis KW - radiación y propiedades químicas Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-518697 ER - TY - JOUR A1 - Izgi, Gizem A1 - Eibl, Eva P. S. A1 - Donner, Stefanie A1 - Bernauer, Felix T1 - Performance test of the rotational sensor blueSeis-3A in a huddle test in Fürstenfeldbruck JF - Sensors N2 - Rotational motions play a key role in measuring seismic wavefield properties. Using newly developed portable rotational instruments, it is now possible to directly measure rotational motions in a broad frequency range. Here, we investigated the instrumental self-noise and data quality in a huddle test in Fürstenfeldbruck, Germany, in August 2019. We compare the data from six rotational and three translational sensors. We studied the recorded signals using correlation, coherence analysis, and probabilistic power spectral densities. We sorted the coherent noise into five groups with respect to the similarities in frequency content and shape of the signals. These coherent noises were most likely caused by electrical devices, the dehumidifier system in the building, humans, and natural sources such as wind. We calculated self-noise levels through probabilistic power spectral densities and by applying the Sleeman method, a three-sensor method. Our results from both methods indicate that self-noise levels are stable between 0.5 and 40 Hz. Furthermore, we recorded the 29 August 2019 ML 3.4 Dettingen earthquake. The calculated source directions are found to be realistic for all sensors in comparison to the real back azimuth. We conclude that the five tested blueSeis-3A rotational sensors, when compared with respect to coherent noise, self-noise, and source direction, provide reliable and consistent results. Hence, field experiments with single rotational sensors can be undertaken. KW - rotational seismology KW - huddle test KW - coherency KW - source direction KW - coherent noise KW - blueSeis-3A sensors Y1 - 2021 U6 - https://doi.org/10.3390/s21093170 SN - 1424-8220 VL - 21 IS - 9 PB - MDPI CY - Basel ER - TY - GEN A1 - Izgi, Gizem A1 - Eibl, Eva P. S. A1 - Donner, Stefanie A1 - Bernauer, Felix T1 - Performance Test of the Rotational Sensor blueSeis-3A in a Huddle Test in Fürstenfeldbruck T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Rotational motions play a key role in measuring seismic wavefield properties. Using newly developed portable rotational instruments, it is now possible to directly measure rotational motions in a broad frequency range. Here, we investigated the instrumental self-noise and data quality in a huddle test in Fürstenfeldbruck, Germany, in August 2019. We compare the data from six rotational and three translational sensors. We studied the recorded signals using correlation, coherence analysis, and probabilistic power spectral densities. We sorted the coherent noise into five groups with respect to the similarities in frequency content and shape of the signals. These coherent noises were most likely caused by electrical devices, the dehumidifier system in the building, humans, and natural sources such as wind. We calculated self-noise levels through probabilistic power spectral densities and by applying the Sleeman method, a three-sensor method. Our results from both methods indicate that self-noise levels are stable between 0.5 and 40 Hz. Furthermore, we recorded the 29 August 2019 ML 3.4 Dettingen earthquake. The calculated source directions are found to be realistic for all sensors in comparison to the real back azimuth. We conclude that the five tested blueSeis-3A rotational sensors, when compared with respect to coherent noise, self-noise, and source direction, provide reliable and consistent results. Hence, field experiments with single rotational sensors can be undertaken. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1150 KW - rotational seismology KW - huddle test KW - coherency KW - source direction KW - coherent noise KW - blueSeis-3A sensors Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-518556 SN - 1866-8372 IS - 1150 ER - TY - THES A1 - Spooner, Cameron T1 - How does lithospheric configuration relate to deformation in the Alpine region? T1 - Was ist der Zusammenhang zwischen der lithosphärischen Zusammensetzung der Alpen, ihrer Vorländer und deren Deformation? N2 - Forming as a result of the collision between the Adriatic and European plates, the Alpine orogen exhibits significant lithospheric heterogeneity due to the long history of interplay between these plates, other continental and oceanic blocks in the region, and inherited features from preceeding orogenies. This implies that the thermal and rheological configuration of the lithosphere also varies significantly throughout the region. Lithology and temperature/pressure conditions exert a first order control on rock strength, principally via thermally activated creep deformation and on the distribution at depth of the brittle-ductile transition zone, which can be regarded as the lower bound to the seismogenic zone. Therefore, they influence the spatial distribution of seismicity within a lithospheric plate. In light of this, accurately constrained geophysical models of the heterogeneous Alpine lithospheric configuration, are crucial in describing regional deformation patterns. However, despite the amount of research focussing on the area, different hypotheses still exist regarding the present-day lithospheric state and how it might relate to the present-day seismicity distribution. This dissertaion seeks to constrain the Alpine lithospheric configuration through a fully 3D integrated modelling workflow, that utilises multiple geophysical techniques and integrates from all available data sources. The aim is therefore to shed light on how lithospheric heterogeneity may play a role in influencing the heterogeneous patterns of seismicity distribution observed within the region. This was accomplished through the generation of: (i) 3D seismically constrained, structural and density models of the lithosphere, that were adjusted to match the observed gravity field; (ii) 3D models of the lithospheric steady state thermal field, that were adjusted to match observed wellbore temperatures; and (iii) 3D rheological models of long term lithospheric strength, with the results of each step used as input for the following steps. Results indicate that the highest strength within the crust (~ 1 GPa) and upper mantle (> 2 GPa), are shown to occur at temperatures characteristic for specific phase transitions (more felsic crust: 200 – 400 °C; more mafic crust and upper lithospheric mantle: ~600 °C) with almost all seismicity occurring in these regions. However, inherited lithospheric heterogeneity was found to significantly influence this, with seismicity in the thinner and more mafic Adriatic crust (~22.5 km, 2800 kg m−3, 1.30E-06 W m-3) occuring to higher temperatures (~600 °C) than in the thicker and more felsic European crust (~27.5 km, 2750 kg m−3, 1.3–2.6E-06 W m-3, ~450 °C). Correlation between seismicity in the orogen forelands and lithospheric strength, also show different trends, reflecting their different tectonic settings. As such, events in the plate boundary setting of the southern foreland correlate with the integrated lithospheric strength, occurring mainly in the weaker lithosphere surrounding the strong Adriatic indenter. Events in the intraplate setting of the northern foreland, instead correlate with crustal strength, mainly occurring in the weaker and warmer crust beneath the Upper Rhine Graben. Therefore, not only do the findings presented in this work represent a state of the art understanding of the lithospheric configuration beneath the Alps and their forelands, but also a significant improvement on the features known to significantly influence the occurrence of seismicity within the region. This highlights the importance of considering lithospheric state in regards to explaining observed patterns of deformation. N2 - Als Resultat der Kollision zwischen der Adriatischen und Europäischen Platte ist das Alpenorogen durch eine ausgeprägte Heterogenität der Lithosphäreneigenschaften gekennzeichnet, die auf die Geschichte der beiden Platten, ihre Interaktion, Wechselwirkungen mit anderen kontinentalen und ozeanischen Blöcken der Region und strukturell vererbte Merkmale aus früheren Orogenesen zurückzuführen sind. Entsprechend ist zu erwarten, dass die thermische und rheologische Konfiguration der Lithosphäre ebenfalls grundlegend innerhalb der Region variiert. Lithologie und Temperatur-/Druckbedingungen steuern maßgeblich die Festigkeit der Lithosphäre indem thermisch aktiviertes Kriechen die Tiefenlage der spröd-duktilen Übergangszone – die sogenannte brittle-ductile transition (BDT) bestimmt. Diese Tiefenlage kann als untere Grenze der seismogenen Zone betrachtet werden kann, weshalb sie die räumliche Verteilung der Seismizität in der Lithosphärenplatte entscheidend beeinflusst. Trotz der langjährigen und umfangreichen Forschung zur Dynamik und Struktur der Alpen gibt es immer noch verschiedene Hypothesen zum heutigen physikalischen Zustand des Systems und dazu, wie dieser mit der Verteilung und dem Auftreten von Seismizität zusammenhängt. Diese Dissertation hat das Ziel, die Lithosphärenkonfiguration der Alpen zu beschreiben und Zusammenhänge zwischen der Verteilung lithosphärischer Eigenschaften und Deformation, insbesondere der Verteilung der Seismizität abzuleiten. Dies wird durch einen integrierten Modellierungsansatz erreicht, mit dem verfügbare geophysikalische Beobachtungen in 3D Modellen zusammengeführt werden, die die heterogene lithosphärische Konfiguration abbilden. Dazu wird (1) ein mit geologischen, seismischen und gravimetrischen Daten konsistentes 3D-Dichtemodell erzeugt und genutzt, um Lithologien abzuleiten, (2) deren Konsequenzen für das dreidimensionale stationäre thermische Feld zu berechnen und, basierend darauf, schließlich (3) die räumliche Variation der Lithosphärenrheologie zu bestimmen. Diese räumliche Variation der rheologischen Eigenschaften wurde schließlich in Beziehung zur Verteilung der auftretenden Seismizität gesetzt. Die Ergebnisse zeigen, dass die größte Festigkeit innerhalb der Kruste (~1 GPa) und im oberen Mantel (> 2 GPa) oberhalb der Bereiche auftritt, wo Temperaturbedingte Phasenübergänge zu erwarten sind. Für die felsische Kruste umfasst dies den Temperaturbereich bis etwa 400° C, für die mafische Kruste und den lithospärischen Mantel bis etwa 600°, wobei Seismizität jeweils oberhalb dieser Temperaturen auftritt. Zusätzlich wurden Hinweise gefunden, dass diese Festigkeitsverteilung auf vererbte Lithosphäreneigenschaften zurückzuführen ist: so tritt seismische Aktivität in der dünneren und mafischen Adria Kruste (~22,5 km, 2.800 kg m-3, 1.30E -06 W m-3) bei höheren Temperatur (~600° C) auf als in der dickeren und eher felsischen europäischen Kruste (~27.5 km, 2750 kg m−3, 1.3–2.6E-06 W m-3, ~450 °C). Die Beziehung zwischen seismischer Aktivität und Lithosphärenfestigkeit im Bereich der Vorländer zeigt ebenfalls unterschiedliche Trends, die verschiedenene tektonische Randbedingungen wiederspiegeln. Während im Plattenrandsetting des südlichen Vorlands Seismizität in der rheologisch weicheren Lithosphäre in der Umrandung des adriatischen Indentors auftritt, korreliert die auftretende Seismizität im Intraplattensetting des nördlichen Vorlands räumlich mit wärmeren und rheologisch schwächeren Domänen im Bereich des Oberrheingrabens. Somit liefern die Ergebnisse in dieser Arbeit nicht nur ein verbessertes Verständnis der Lithosphärenkonfiguration der Alpen und ihrer Vorländer , sondern auch einen bedeutenden Fortschritt dazu, welche Faktoren Seismizität innerhalb der Region beeinflussen können. Sie zeigen, dass es wichtig ist, die Lithosphärenkonfiguration zu kennen und sie zur auftretenden Deformation in Beziehung zu setzen. KW - Gravity KW - Thermal KW - Rheology KW - Model KW - Alps KW - Alpen KW - Schwerkraft KW - Modell KW - Rheologie KW - Thermisch Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516442 ER - TY - GEN A1 - Samprogna Mohor, Guilherme A1 - Thieken, Annegret A1 - Korup, Oliver T1 - Residential flood loss estimated from Bayesian multilevel models T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Models for the predictions of monetary losses from floods mainly blend data deemed to represent a single flood type and region. Moreover, these approaches largely ignore indicators of preparedness and how predictors may vary between regions and events, challenging the transferability of flood loss models. We use a flood loss database of 1812 German flood-affected households to explore how Bayesian multilevel models can estimate normalised flood damage stratified by event, region, or flood process type. Multilevel models acknowledge natural groups in the data and allow each group to learn from others. We obtain posterior estimates that differ between flood types, with credibly varying influences of water depth, contamination, duration, implementation of property-level precautionary measures, insurance, and previous flood experience; these influences overlap across most events or regions, however. We infer that the underlying damaging processes of distinct flood types deserve further attention. Each reported flood loss and affected region involved mixed flood types, likely explaining the uncertainty in the coefficients. Our results emphasise the need to consider flood types as an important step towards applying flood loss models elsewhere. We argue that failing to do so may unduly generalise the model and systematically bias loss estimations from empirical data. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1148 KW - damage KW - insurance KW - Germany KW - transferability KW - preparedness KW - recovery Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-517743 SN - 1866-8372 SP - 1599 EP - 1614 ER - TY - JOUR A1 - Samprogna Mohor, Guilherme A1 - Thieken, Annegret A1 - Korup, Oliver T1 - Residential flood loss estimated from Bayesian multilevel models JF - Natural Hazards and Earth System Sciences N2 - Models for the predictions of monetary losses from floods mainly blend data deemed to represent a single flood type and region. Moreover, these approaches largely ignore indicators of preparedness and how predictors may vary between regions and events, challenging the transferability of flood loss models. We use a flood loss database of 1812 German flood-affected households to explore how Bayesian multilevel models can estimate normalised flood damage stratified by event, region, or flood process type. Multilevel models acknowledge natural groups in the data and allow each group to learn from others. We obtain posterior estimates that differ between flood types, with credibly varying influences of water depth, contamination, duration, implementation of property-level precautionary measures, insurance, and previous flood experience; these influences overlap across most events or regions, however. We infer that the underlying damaging processes of distinct flood types deserve further attention. Each reported flood loss and affected region involved mixed flood types, likely explaining the uncertainty in the coefficients. Our results emphasise the need to consider flood types as an important step towards applying flood loss models elsewhere. We argue that failing to do so may unduly generalise the model and systematically bias loss estimations from empirical data. KW - damage KW - insurance KW - Germany KW - transferability KW - preparedness KW - recovery Y1 - 2020 U6 - https://doi.org/10.5194/nhess-21-1599-2021 SN - 2195-9269 VL - 21 SP - 1599 EP - 1614 PB - European Geophysical Society CY - Katlenburg-Lindau ER - TY - THES A1 - Krstulovic, Marija T1 - Local structure of network formers and network modifiers in silicate melts at high pressure and temperature conditions T1 - Lokale Struktur der Netzwerkbildner und der Netzwerkwandler in silikatischen Schmelzen bei hohen Druck- und Temperaturbedingungen N2 - Silikatische Schmelzen sind wichtiger Bestandteil des Erdinneren und als solche leisten sie in magmatischen Prozessen einen wesentlichen Beitrag in der Dynamik der festen Erde und der chemischen Entwicklung des gesamten Erdköpers. Makroskopische physikalische und chemische Eigenschaften wie Dichte, Kompressibilität, Viskosität, Polymerisationsgrad etc. sind durch die atomare Struktur der Schmelzen bestimmt. In Abhängigkeit vom Druck, aber auch von der Temperatur und der chemischen Zusammensetzung zeigen silikatische Schmelzen unterschiedliche strukturelle Eigenschaften. Diese Eigenschaften sind am besten durch die lokale Koordinationsumgebung, d.h. Symmetrie und Anzahl der Nachbarn (Koordinationszahl) eines Atoms, sowie dem Abstand zwischen Zentralatom und Nachbarn (atomarer Abstand) beschrieben. Mit steigendem Druck und Temperatur, das heißt mit der zunehmenden Tiefe in der Erde, nimmt die Dichte der Schmelzen zu, welches zur Veränderung von Koordinationszahl und Abständen führen kann. Bei gleichbleibender Koordinationszahl nimmt der Abstand in der Regel zu. Kommt es zu Erhöhung der Koordinationszahl kann der Abstand zunehmen. Diese allgemeinen Trends können allerdings stark variieren, welches insbesondere auf die chemische Zusammensetzung zurückzuführen ist. Dadurch, dass natürliche Schmelzen der tiefen Erde für direkte Untersuchungen nicht zugänglich sind, um ihre Eigenschaften unter den relevanten Bedingungen zu verstehen, wurden umfangreiche experimentelle und theoretische Untersuchungen bisher durchgeführt. Dies wurde häufig am Beispiel von amorphen Proben der Endglieder SiO2, und GeO2 studiert, wobei letzteres als strukturelles und chemisches Analogmodell zu SiO2 dient. Meistens wurden die Experimente bei hohem Druck und bei Raumtemperatur durchgeführt. Natürliche Schmelzen sind chemisch deutlich komplexer als die einfachen Endglieder SiO2 und GeO2, so dass die Beobachtungen an diesen möglicherweise zu falschen Verdichtungsmodellen führen können. Weiterhin können die Untersuchungen an Gläsern bei Raumtemperatur potentiell starke Abweichungen zu Eigenschaften von Schmelzen bei natürlichen thermodynamischen Bedingungen aufweisen. Das Ziel dieser Dissertation war es zu erläutern, welchen Einfluss die Zusammensetzung und die Temperatur auf die strukturelle Eigenschaften der Schmelzen unter hohen Drücken haben. Um das zu verstehen, haben wir komplexe alumino-germanatische und alumino-silikatische Gläser studiert. Genauer gesagt, wir haben synthetische Gläser studiert, die eine Zusammensetzung wie das Mineral Albit und wie eine Mischung von Albit-Diopsid im eutektischen Punkt haben. Das Albitglas ähnelt strukturell einer vereinfachten granitischen Schmelze, während das Albit-Diopsid-Glas eine vereinfachte basaltische Schmelze simuliert. Um die lokale Koordinationsumgebung der Elemente zu studieren, haben wir die Röntgenabsorptionsspektroskopie in Kombination mit einer Diamantstempelzelle benutzt. Dadurch, dass die Diamanten eine hohe Absorption für Röntgenstrahlung mit Energien unterhalb von 10 keV aufweisen, ist die unmittelbare Untersuchung der geologisch sehr relevanten Elemente wie Si, Al, Ca, Mg etc. mit dieser Spektroskopie in Kombination mit einer Diamantstempelzelle nicht möglich. Deswegen wurden die Gläser mit Ge und Sr dotiert. Diese Elemente dienen teilweise oder vollständig als Ersatzelemente für wichtige Hauptelemente. In diesem Sinne, dient Ge als Ersatzelement für Si und andere Netzwerkbildner, während Sr Netzwerkwandler wie Z.B. Ca, Na, Mg etc., sowie andere Kationen mit großem Ionenradius ersetzt. Im ersten Schritt haben wir die Ge K-Kante im Ge-Albit-Glass, NaAlGe3O8, bei Raumtemperatur bis 131 GPa untersucht. Dieses Glas hat eine höhere chemische Komplexität als SiO2 und GeO2, aber es ist immer noch vollständig polymerisiert. Die Unterschiede im Verdichtungsmechanismus zwischen diesem Glas und den einfachen Oxiden können so eindeutig auf höhere chemische Komplexität zurückgeführt werden. Die partiell mit Ge und Sr dotierten Albit und Albit-Diopsid-Zusammensetzungen wurden bei Raumtemperatur für Ge bis 164 GPa und für Sr bis 42 GPa untersucht. Während das Albitglass wie NaAlGe3O8 nominelll vollständig polymerisiert ist, ist das Albit-Diopsid Glas teilweise depolymerisiert. Die Ergebnisse zeigen, dass in allen drei Gläsern strukturelle An̈derungen in den ersten 25 bis maximal 30 GPa stattfinden, wobei beide Ge und Sr die maximale Koordinationszahl 6 bzw. ∼9 erreichen. Bei höheren Drücken findet in den Gläsern nur eine isostrukturelle Schrumpfung der Koordinationspolyeder statt. Der wichtigste Befund der Hochdruckstudien an den alumino-silikatischen und alumino-germanatischen Gläsern ist, dass in diesen komplexen Gläsern die Polyeder eine viel höhere Kompressibilität aufweisen als bei den Endgliedern zu beobachten. Das zeigt sich insbesondere durch die starke Verkürzung der Ge-O Abstände in dem amorphen NaAlGe3O8 und Albit-Diopsid-Glas bei Drücken über 30 GPa. Zusätzlich zu den Effekten der Zusammensetzung auf den Verdichtungsprozess, haben wir den Einfluss der Temperatur auf die strukturelle Änderungen untersucht. Dazu haben wir das Albit-Diopsid-Glas untersucht, da es den Schmelzen im unteren Mantel chemisch am ähnlichsten ist. Wir haben die Ge K-Kante der Probe mit einer resistiv-geheizten und einer Laser-geheizter Diamantstempelzelle untersucht, für einen Druckbereich bis zu 48 GPa, sowie einen Temperaturbereich bis 5000 K. Hohe Temperaturen, bei denen die Probe flüssig ist und die für den Erdmantel relevant sind, haben einen bedeutenden Einfluss auf die strukturelle Transformation. Diese wird um ca. 30% zu deutlich niedrigeren Drücken verschoben, im Vergleich zu den Gläsern bei Raumtemperatur und unterhalb von 1000 K. Die Ergebnisse dieser Dissertation stellen einen wichtigen Beitrag fur das Verständnis der Eigenschaften von Schmelzen unter Bedingungen des unteren Mantels dar. Im Kontext der Diskussion über die Existenz und den Ursprung von silikatischen Schmelzen mit ultrahoher Dichte, welche an der Grenze zwischen Mantel und Erdkern aufgrund seismologischer Daten vermutet werden, zeigen diese Untersuchugen, dass die im Vergleich zur Umgebung höhere Dichte nicht durch strukturelle Besonderheiten, sondern durch eine besondere chemische Zusammensetzung erklärt werden müssen. Außerdem legen die Ergebnisse nahe, dass für Schmelzen im unteren Erdmantel nur sehr geringe Löslichkeiten von Edelgasen zu erwarten sind, so dass die strukturellen Eigenschaften deutlich den Gesamthaushalt und Transport der Edelgase im Erdmantel beeinflussen. N2 - Silicate melts are major components of the Earth’s interior and as such they make an essential contribution in igneous processes, in the dynamics of the solid Earth and the chemical development of the entire Earth. Macroscopic physical and chemical properties such as density, compressibility, viscosity, degree of polymerization etc. are determined by the atomic structure of the melt. Depending on the pressure, but also on the temperature and the chemical composition, silicate melts show different structural properties. These properties are best described by the local coordination environment, i.e. symmetry and number of neighbors (coordination number) of an atom, as well as the distance between the central atom and its neighbors (inter-atomic distance). With increasing pressure and temperature, i.e. with increasing depth in the Earth, the density of the melt increases, which can lead to changes in coordination number and distances. If the coordination number remains the same, the distance usually decreases. If the coordination number increases, the distance can increase. These general trends can, however, vary greatly, which can be attributed in particular to the chemical composition. Due to the fact that natural melts of the deep earth are not accessible to direct investigations, in order to understand their properties under the relevant conditions, extensive experimental and theoretical investigations have been carried out so far. This has often been studied using the example of amorphous samples of the end-members SiO2 and GeO2 , with the latter serving as a structural and chemical analog model to SiO2. Commonly, the experiments were carried out at high pressure and at room temperature. Natural melts are chemically much more complex than the simple end-member SiO2 and GeO2, so that observations made on them may lead to incorrect compression models. Furthermore, the investigations on glasses at room temperature can show potentially strong deviations from the properties of melts under natural thermodynamic conditions. The aim of this thesis was to explain the influence of the composition and the temperature on the structural properties of the melts at high pressures. To understand this, we studied complex alumino-germanate and alumino-silicate glasses. More precisely, we studied synthetic glasses that have a composition like the mineral albite and like a mixture of albite-diopside at the eutectic point. The albite glass is structurally similar to a simplified granitic melt, while the albite-diopside glass simulates a simplified basaltic melt. To study the local coordination environment of the elements, we used X-ray absorption spectroscopy in combination with a diamond anvil cell. Because the diamonds have a high absorbance for X-rays with energies below 10 keV, the direct investigation of the geologically relevant elements such as Si, Al, Ca, Mg etc. with this spectroscopic probe technique in combination with a diamond anvil cell is not possible. Therefore the glasses were doped with Ge and Sr. These elements serve partially or fully as substitutes for important major elements. In this sense, Ge serves as an a substitute for Si and other network formers, while Sr replaces network modifiers such as Ca, Na, Mg etc., as well as other cations with a large ionic radius. In the first step we studied the Ge K-edge in Ge-Albit-glass, NaAlGe3O8, at room temperature up to 131 GPa. This glass has a higher chemical complexity than SiO2 and GeO2, but it is still fully polymerized. The differences in the compression mechanism between this glass and the simple oxides can clearly be attributed to higher chemical complexity. The albite and albite-diopside compositions partially doped with Ge and Sr were probed at room temperature for Ge up to 164 GPa and for Sr up to 42 GPa. While the albite glass is nominally fully polymerized like NaAlGe3O8, the albite-diopside glass is partially depolymerized. The results show that structural changes take place in all three glasses in the first 25 to a maximum of 30 GPa, with both Ge and Sr reaching the maximum coordination number 6 and ∼9, respectively. At higher pressures, only isostructural shrinkage of the coordination polyhedra takes place in the glasses. The most important finding of the high pressure studies on the alumino-silicate and alumino-germanate glasses is that in these complex glasses the polyhedra show a much higher compressibility than what can be observed in the end-members. This is shown in particular by the strong shortening of the Ge-O distances in the amorphous NaAlGe3O8 and albite-diopside glass at pressures above 30 GPa. In addition to the effects of the composition on the compaction process, we investigated the influence of temperature on the structural changes. To do this, we probed the albite-diopside glass, as it is chemically most similar to the melts in the lower mantle. We studied the Ge K edge of the sample with a resistively heated and a laser-heated diamond anvil cell, for a pressure range of up to 48 GPa and a temperature range of up to 5000 K. High temperatures at which the sample is liquid and that are relevant for the Earth mantle, have a significant impact on the structural transformation, with a shift of approx. 30% to significantly lower pressures, compared to the glasses at room temperature and below 1000 K. The results of this thesis represent an important contribution to the understanding of the properties of melts at conditions of the lower mantle. In the context of the discussion about the existence and origin of ultra-dense silicate melts at the core-mantle boundary, these investigations show that the higher density compared to the surrounding material cannot be explained by only structural features, but by a distinct chemical composition. The results also suggest that only very low solubilities of noble gases are to be expected for melts in the lower mantle, so that the structural properties clearly influence the overall budget and transport of noble gases in the Earth’s mantle. KW - glasses KW - silicate melts KW - XAS KW - local structure KW - spectroscopy KW - high-pressure KW - EXAFS KW - XANES KW - compression KW - EXAFS KW - XANES KW - XAS KW - Verdichtung KW - Gläser KW - Hochdruck KW - lokale Struktur KW - silikatische Schmelzen KW - Spektroskopie Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516415 ER -