Das Projekt "Sub project: Structural and temporal evolution of the Hawaiian plume: Constraints from noble gases in surface samples and the HSDP drill core" wird vom Umweltbundesamt gefördert und von Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum durchgeführt. Ocean Island Basalts (OIBs) produced by intraplate volcanoes such as e.g. the Hawaiian ones are often geochemically characterized by variable isotopic signatures due to sampling of different mantle reservoirs. These variations can occur over short distances on a very local scale. The aim of the Hawaii Scientific Drilling Project (HSDP) was to investigate the chemical and isotopic heterogeneity of a single volcano, Mauna Kea, to better constrain the temporal evolution of the Hawaiian mantle plume. In addition to this we are interested to study the Hawaiian mantle plume in time and space. Thus we propose to investigate the spatial structure of the Hawaiian plume using noble gas isotopes of samples from several volcanoes of the 'Kea chain'. Noble gas data, especially Ne data, from the Kea trend volcanoes are scarce. Those data have not only the great potential for resolving different geochemical reservoirs but also to deduce mantle dynamic and magmatic processes being involved in melt generation and evolution.
Das Projekt "Sub project: Shock effects in sulfates: nature - experiments - modeling" wird vom Umweltbundesamt gefördert und von Fraunhofer-Institut für Kurzzeitdynamik, Ernst-Mach-Institut (EMI), Institutsteil Efringen-Kirchen durchgeführt. The release of CO2 and SOx by the Chicxulub impact event likely changed the composition and radiative balance of the atmosphere and consequently affected the climate at the K/T boundary. Our observations show that meting and devolatilization of carbonates and anhydrite is indeed documented in the ICDP wells YAX-1, which was successfully drilled into the Chicxulub impact crater. Recent theoretical assessments of the Chicxulub event stress that the greenhouse effect due to the CO2 input was probably minor compared to the prolonged cooling by sulfur-bearing aerosols. The amplitude of this 'impacr winter' is mostly determined by the so far unconstrained SOx amount. In 2004, we will therefore (i) perform final shock experiments on anhydrite with a newily developed high-explosive setup, enabling to reach pressures in the 1 Mbar range, (ii) extend our mineralogical investigations to the recently sampled Chicxulub drill cores (YAX-1, Y-6, C-1) with a special emphasis on sulfate clasts in impact melt breccias and (iii) model the so far unknown phase diagram of anhydrite. These investigations are aimed (i) to provede a basic understanding of the shock behavior of andydrite, (ii) to determine and model the p,T field relevant for devolatilization and (iii) to constrain the amount of SOx released by the Chicxulub impact.
Das Projekt "Sub project: The mobilisation of Platinum-Group Elements in altered oceanic crust from ODP-borehole 1256D for tracing the noble metal flux in the crust" wird vom Umweltbundesamt gefördert und von Karlsruher Institut für Technologie (KIT), Institut für Angewandte Geowissenschaften, Abteilung Mineralogie und Petrologie durchgeführt. Mafic volcanic rocks of different tectonic settings display a wide range of Pt/Pd-ratios lower than that of the primitive mantle (PM) which cannot be accounted for by known partition coefficients of Pd and Pt between sulphide melt and silicate melt. Various processes have been invoked to explain this observation, including hydrothermal rock/water interactions or serpentinisation. However, so far no study has systematically investigated the effects of hydrothermal alteration on the PGE budget for example on a complete section of altered upper oceanic crust. Hence, little is known on Pt-Pd fractionation during alteration. We propose to fill this gap by studying a complete profile of altered upper oceanic crust and the uppermost gabbroic section, formed at the East Pacific Rise some 15 Ma ago and drilled at the multicruise ODP-borehole 1256D (Wilson et al., 2006). Combined measurements of platinum-group elements (PGE) and Cu-Sisotopes in key pool samples, shared with other shipboard party members, will help to evaluate PGE mobility during alteration and to study quantitatively the fractionation behaviour of Pt and Pd along the hydrothermal fluid path in the oceanic crust. These insights are highly relevant for understanding ore forming processes in the oceanic crust, since large PGE deposits are related to mafic volcanism (i.e. Norils'k).
Das Projekt "Silicon kerf loss recycling (SIKELOR)" wird vom Umweltbundesamt gefördert und von Helmholtz-Zentrum Dresden-Roßendorf e.V., Institut für Sicherheitsforschung durchgeführt. Solar energy direct conversion to electricity is expanding rapidly to satisfy the demand for renewable energy. The most efficient commercial photovoltaic solar cells are based on silicon. While the reuse of feedstock is a severe concern of the photovoltaic industry, up to 50% of the valuable resource is lost into sawdust during wafering. Presently, the majority of silicon ingots are sliced in thin wafers by LAS (loose abrasive sawing) using slurry of abrasive silicon carbide particles. The silicon carbide is not separable from the silicon dust in an economical way. The newer FAS (fixed abrasive sawing) uses diamond particles fixed to the cutting wire. It is expected that FAS will replace LAS almost completely by 2020 for poly/mono-crystalline wafering. The intention of the proposed project is to recycle the FAS loss aiming at a sustainable solution. The main problem is the large surface to volume ratio of micron size silicon particles in the kerf loss, leading to formation of SiO2 having a detrimental effect on the crystallisation. The compaction process developed by GARBO meets the requirements of a reasonable crucible-loading factor. Overheating the silicon melt locally in combination with optimised electromagnetic stirring provides the means to remove SiO2. The technology developed by GARBO removes the organic binding agents, leaving about 200 ppm wt diamond particle contamination. If untreated, the carbon level is above the solubility limit. Formation of silicon carbide and precipitation during crystallisation is to be expected. The electromagnetic mixing, in combination with the effective means to separate electrically non-conducting silicon carbide and remaining SiO2 particles from the silicon melt by Leenov-Kolin forces and the control of the solidification front, is the proposed route to produce the solar grade multi-crystalline silicon blocks cast in commercial size in a unified process.
Das Projekt "Development of an automatic system for controlling the process of metal recovery from slags" wird vom Umweltbundesamt gefördert und von Cytec Datensysteme GmbH durchgeführt. Objective: The objective is better recovery of nickel from slags through better process control in order to raise productivity and save energy in ferronickel production. General Information: An automatic process control system will be developed for the recovery of mechanical nickel losses in slag arising from the production of ferronickel in the electric reduction furnace of LARCO at the Larymna plant. Methodological development will help applicability to other comparable processes. The project will be in the following stages. Construction and setup of a dedicated induction furnace with a graphite susceptor and a refractory crucible and with the possibilities of temperature control and gas injection from the top or from the side of the crucible. The development of a laser based system for assessing and monitoring the metal content of the slag is proposed. The proposed system, laser induced breakdown spectroscopy (LIBS), will speed up the analysis of the recovery of metal, provide more efficient process control and enable further optimization. The basic steps in LIBS are: atomization of the sample; excitation of the resulting atoms; and detection of the emitted radiation from the atoms. Both atomization and excitation can be achieved by focusing a neodymium, yttrium aluminium garnet(YAG) laser on the molten slag free surface, resulting in the creation of a microplasma. The emitted radiation will be spectrally resolved by means of a monochromator coupled with an optical multichannel analyzer (OMA III). The work parts to be done are: preliminary measurements on solid slag containing nickel and ferronickel in order to be used as reference standards; online monitoring with data acquisition and sensor system integration for the actual molten systems; testing and validation; and metallurgical support during the experiments. The control system stage will involve: metal concentration values given by the LIBS system modelled to obtain the actual metal content in the slag; thermal control linked with the process computer; control of the gas (or gas mixtures) flow rates to be injected into the slag melt linked with the process computer. The information processing stage will involve: observed values continuously stored in an appropriate database in order to be compared to the simulated values; special, easy to solve, mathematical model of ordinary differential equations developed to simulate the recovery process; and a simulation programme developed in advanced continuous simulation language (ACSL) to allow online simulation. The final stage is system integration. Achievements: Research was carried out in order to develop an automatic process control system for the recovery of metal from slags and therefore contribute with better process control to better recovery of the mechanical metal losses from the ERF slags in the ferronickel production. The combination of metallurgical experiments with the high technology of laser based analysis was the first ...
Das Projekt "Sub project: Rock magnetic properties and their anisotropy from host rock and impact lithologies of drillings at the Chesapeake Bay impact structure, USA" wird vom Umweltbundesamt gefördert und von Karlsruher Institut für Technologie (KIT), Institut für Angewandte Geowissenschaften, Abteilung Strukturgeologie & Tektonik durchgeführt. The ICDP-USGS Eyreville drilling at Chesapeake Bay produced one of the most complete geologic sections of an impact structure. Core samples from the 1766 m deep drilling into the central zone of the 35 Ma old impact structure allows the study of different target and impact lithologies and their rock magnetic properties. The dominant magnetic minerals creating crustal magnetic anomalies are pyrrhotite and magnetite. The main target of this study is to find new clues about the different hypotheses on remagnetization mechanisms during impact-related processes. Our initial investigations have shown that the target rocks contain magnetite and pyrrhotite, which are responsible for the regional magnetic anomaly pattern. This pattern is disrupted by the impact, which is in accordance with an interpretation of displaced basement-derived megablocks embedded in the lithic and suevitic breccia unit. The only modification of magnetic minerals has been observed in this latter unit, while the basement-derived blocks do not show any shock deformation. We found shock-induced remanent magnetization and chemical remanent magnetization to be the only remagnetization mechanisms, and no indication for a TRM can be confirmed, in contrast to most hypothesis in literature. Shocked pyrrhotite (4C modification with abundant mechanical twins and defect structures, a significant metal deficieny and a TC at 360 centigrade) and secondary magnetite in the suevite matrix (interpreted to be formed from Febearing fluids, which derived mainly from melt alteration) are the magnetic carriers of a stable remanent magnetization (Jr greater than Ji) in the suevite unit. Because only one NRM direction has been observed in the suevite, probably both minerals have acquired their magnetization close to the timing of the impact event. We plan to conduct low-temperature magnetization experiments with the suevite samples as well as with experimentally shocked pyrrhotite. These data might enhance our understanding of shock-induced acquisition processes in impact rocks and help to understand the relation between microstructures in pyrrhotite and shock pressure, which is not well constrained up to now. Furthermore, the magnetite only bearing samples will also be studied in order to learn if these samples do show any indications of superparamagnetic behaviour as we would suspect from the observed nanocrystals, and to find clues on the large range of Curie temperatures from 500 to 640 centigrade.
Das Projekt "Modeling the Greenland ice sheet response to climate change on different timescales" wird vom Umweltbundesamt gefördert und von Potsdam-Institut für Klimafolgenforschung e.V. durchgeführt. The Greenland ice sheet could potentially contribute up to 7 m to sea level rise in the coming millennia due to anthropogenic global warming. As temperatures increase, the ice sheet experiences more surface melt and will eventually no longer be able to sustain its current size. It is generally believed that if the global Earth's temperature will exceed a certain threshold value, the Greenland ice sheet will eventually melt completely. However, the magnitude of global warming which will lead to crossing this threshold is not well known. The sensitivity of the ice sheet to climate change on long timescales will largely depend on surface mass balance change. In this project, a novel approach will be developed for modeling the surface mass balance of the Greenland ice sheet by using a regional climate model of intermediate complexity coupled to an ice sheet model via a physically-based surface energy and mass balance interface. Such an approach will allow us to perform a large ensemble of long-term simulations of the Greenland ice sheet under different climate change scenarios to refine estimates of the Greenland ice sheet sensitivity to climate change and the critical climate thresholds leading to its complete melting. With this project, we will contribute to a better understanding of the Greenland Ice Sheet contribution to future sea level rise and to the assessment of the probability of irreversible changes in the Earth system.
Das Projekt "Sub project: Origin of spinel-bearing peridotite from oceanic core complexes" wird vom Umweltbundesamt gefördert und von Universität Würzburg, Institut für Geographie, Arbeitsbereich Geodynamik und Geomaterialforschung durchgeführt. In many oceanic core complexes plagioclase-free, spinel-bearing mantle peridotite occurs directly on the seafloor. Peridotite samples collected on ODP leg 153 are variably serpentinised (50- 100 percent ) and are strongly depleted in light rare earth and other trace elements, indicating that they experienced some 10-20 percent melt loss. The genesis of this rock type on the ocean floor has remained highly speculative in spite of its enormous significance for our understanding of oceanic tectonic processes. The presence of spinel requires equilibration pressures of at least 8 kbar at 950 degree C. Significantly higher pressures in the excess of 20 kbar are however possible. This implies an exhumation of the spinel peridotite from depths between 25 and possibly more than 70 km, which is in strong contrast to the 4 to 7 km of exhumation that have been suggested previously. Geothermobaromeiric techniques (conventional thermobarornetry and phase diagram modelling) will be applied to these rocks to infer their equilibration depth and their pressure-temperature evolution. Ar-Ar age dating will be used in an attempt to put constraints on the exhumation rate and cooling history of these rocks. The timing of the partial melting event that is responsible for the residual geochemical character of the peridotite is debated. It could have occurred during recent uplift or in Proterozoic times. In order to resolve this controversy and to determine the timing of partial melting it is planned to carry out a Sm-Nd, Rb-Sr and Pb isotope study. The overall goal is to distinguish between different lithospheric components and to constrain the age of the source for the protoliths. With such new data and, together with the inferred PT evolution, we aim to assign the source and tectonic evolution of these rocks to Proterozoic and/or recent magmatic and tectonometamorphic events. Ultimately, the expected results will improve our understanding of abyssal peridotite whose origin is inconsistent with current partial melting in the global ridge system, of modern Earth.
Das Projekt "Entwicklung eines Verfahrens zur Erkennung, Analyse und Bekämpfung von Schaum bei Glasschmelzprozessen" wird vom Umweltbundesamt gefördert und von Technische Universität Freiberg, Institut für Keramik, Glas- und Baustofftechnik, Professur für Glas- und Emailtechnik durchgeführt. Ziel des Vorhabens war es, eine Möglichkeit der Schaumerkennung und Zerstörung in Glasschmelzanlagen zu untersuchen, um Emissionen zu reduzieren, Energieeinsparung zu ermöglichen, Minimierung der Korrosion in der Ofenkuppe und eine gute Produktion zu gewährleisten. Sowohl die Laborversuche als auch die Versuche am halbindustriellen Schmelzaggregat haben gezeigt, dass die gezielte Zuführung bestimmter Gase oder die Eindüsung bestimmter Chemikalien bzw. der Auftrag bestimmter reduzierender Substanzen auf die Schaumoberfläche einen Einfluss auf die Destabilisierung des Schaums haben. Die Schaumdestabilisierung über das Bubbling H2 plus O2 ist auch möglich.
Das Projekt "Sub project: Mineralogical and geochemical studies of impact melt products from the Chesapeake Bay impact structure" wird vom Umweltbundesamt gefördert und von Universität Münster, Institut für Planetologie durchgeführt. USGS and ICDP perform a drilling project into the 35 Ma old, ca. 85-km-sized submarine Chesapeake Bay impact structure, Virginia. This crater is source to the North American tektite strewn field and related microtektites in upper Eocene sediments. This proposal focuses on impact melt products (melt rocks, glass bombs/particles within impact breccias, tektites, microtektites, microkrystites) that originate during different stages of cratering. All named lithologies are supposed to occur at different geological settings in, around, or far off the Chesapeake crater. This gives a unique opportunity to - study the so far rather unconstrained different mechanisms for the origin of the various melts, - get insight into processes taking place in the vapor plume (mixing, high-temperature chemistry, redox conditions), - derive the different cooling paths of impact glasses, and - develop tools to distinguish microtektites from volcanic glass spherules. To reach this goals we intend to - characterize melt and target lithologies by mineralogical and geochemical techniques, - identify precursor rocks of impact glasses by geochemical and isotopic fingerprinting (Rb-Sr, Sm-Nd, REE with TIMS and LA-ICP-MS techniques), - determine volatile content and redox state by a novel complementary approach combining a Directly coupled Evolved Gas Analysing System (DEGAS) with Electron Energy Loss Spectroscopy (EELS) on a transmission electron microscope (TEM).
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