Das Projekt "Sub project: Petrogenesis of TTG veins in oceanic gabbro: constraints from partial melting experiments in the presence of NaCl-rich H2O-CO2 fluids" wird vom Umweltbundesamt gefördert und von Leibniz Universität Hannover, Institut für Mineralogie durchgeführt. Intermediate to felsic igneous rocks (referred to as plagiogranites in the literature) are widely reported in ophiolite complexes and from recently formed oceanic crust. The mechanisms proposed for their genesis include late-stage differentiation of a parental MORB melt and partial melting of gabbroic rocks triggered by water-rich fluids. This last mechanism has received a realistic experimental confirmation (Koepke et al., 2004) although the nature of these fluids is still under debate (magmatic or hydrothermal sea-water derived). The current experimental project is aimed to contribute to the better understanding of the role of NaCI-rich fluid phase on the major element composition of silicate melts generated during partial melting of gabbro. In addition, it is planned to elucidate the role of NaCI on trace element partitioning between partial melts, solid phases and CI-H2O-CO2-bearing fluids at low pressures. These pilot partial melting experiments will be performed at 200 MPa, 900-1000 degree C using a typical gabbro from the IODP site U1309, Expedition 304/305 (MAR 30 degree 10.12'N, 42 degree 07.11'W, central dome of Atlantis Massif) as starting material. The investigation of deep anatexis within the ocean crust driven by water- and Cl-rich fluids has also the potential to shed light on the formation of the first continental crust in the early Earth history, since as was suggested recently (Rollinson, 2008) similar hydrous melting of a mafic protolith may have operated during Haedean, to create small volumes of felsic rocks.
Das Projekt "Large grained, low stress multi-crystalline silicon thin film solar cells on glass by a novel combined diode laser and solid phase crystallization process (HIGH-EF)" wird vom Umweltbundesamt gefördert und von Institut für Photonische Technologien e.V. durchgeführt. Objective: HIGH-EF will provide the silicon thin film photovoltaic (PV) industry with a unique process allowing for high solar cell efficiencies (potential for greater than 10 percent) by large, low defective grains and low stress levels in the material at competitive production costs. This process is based on a combination of melt-mediated crystallization of an amorphous silicon (a-Si) seed layer (less than 500 nm thickness) and epitaxial thickening (to greater than 2 mym) of the seed layer by a solid phase crystallization (SPC) process. Melting the a-Si layer and solidifying large grains (about 100 mym) will be obtained by scanning a beam of a diode laser array. Epitaxial thickening of the large grained seed layer (including a pn-junction) is realized by deposition of doped a-Si atop the seed layer and a subsequent SPC process by way of a furnace anneal. Such a combined laser-SPC process represents a major break-through in silicon thin film photovoltaics on glass as it will substantially enhance the grain size and reduce the defect density and stress levels of multi-crystalline thin layers on glass compared e.g. to standard SPC processes on glass, which provide grains less than 10 mym in diameter with a high density of internal extended defects, which all hamper good solar cell efficiencies. It is, however, essential for the industrial laser-SPC implementation that such a process will not be more expensive than the established pure SPC process. A low cost laser processing will be developed in HIGH-EF using highly efficient laser diodes, combined to form a line focus that allows the crystallization of an entire module (e.g. 1.4 m x 1 m in the production line or 30 cm x 39 cm in the research line) within a single scan. Specific attention has been given to identify each competence needed for the success of the project and to identify the relevant partners forming a balanced, multi-disciplinary consortium gathering 7 organizations from 4 different member states with 1 associated country.
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 "Sub project: Evolution of magma storage conditions along the track of Yellowstone Hotspot: investigation of the volcanic rocks from Snake River Plain" wird vom Umweltbundesamt gefördert und von Leibniz Universität Hannover, Institut für Mineralogie durchgeführt. The planed ICDP drilling in the Snake River Plain volcanic province (western United States) is aimed to trace the Snake River Plain - Yellowstone (SRPY) hotspot and its interaction with the lithosphere. This province represents one of the best examples of a thermal anomaly related to hotspot volcanism within the continental lithosphere. Over the last 15 Ma, the SRPY-hotspot migrated ca. 600 km eastwards resulting in a bimodal (rhyolitic-basaltic) magmatism. Understanding the interaction of the SRPY-hotspot with the lithosphere requires information on the evolution of chemistry, sources, differentiation and storage conditions of both the rhyolitic and basaltic magmas with time and space. The proposed project aims at understanding the evolution of the magma storage conditions in the SRPY-province in the last 12 Ma. This information will be gained (1) from the chemical analysis of natural minerals and glasses combined with (2) high pressure experimental studies to determine phase equilibria and (3) thermodynamic modeling. Particular attention will be given to trace the evolution of the depth and temperature of the rhyolitic magma chambers using the Bruneau-Jarbidge and Heise volcanic centers (12.5-8.0 Ma and 6.5-4.3 Ma, respectively) as reference materials. Concomitantly, the storage conditions of basaltic lavas of different ages will be explored. The results will also be useful to understand the interactions between basaltic and rhyolitic magma chambers at depth, to constrain the conditions prevailing during partial melting processes in the crust, and to discuss the vertical migration distance of rhyolitic melts (magmas) from the source to the magma chamber. This work will benefit from the cooperation with petrologists and geochemists from USA (e.g., E. Christiansen, B. Nash, J. Shervais).
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 "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 "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 "Sub project: The late-stage evolution of oceanic gabbros - Combined experimental and in-situ isotope study on gabbros of the ODP Legs 118/176 drilled at the Southwest Indian Ridge" wird vom Umweltbundesamt gefördert und von Leibniz Universität Hannover, Institut für Mineralogie durchgeführt. Gabbroic rocks from Hole 735B at the Southwest Indian Ridge (SWIR; Legs 118 and 176), represent the longest continuous section of in-situ oceanic lower crust ever drilled by ODP (Ocean Drilling Program). About 25 percent of the core is strongly influenced by late-stage magmatic processes leading to Ferich (ferrogabbros) and Si-rich (plagiogranites) compositions as endmembers. For a comprehensive understanding of the late magmatic processes ongoing in the deep oceanic crust, we present here a new approach, by combining experimental and analytical investigations in natural gabbros from the ca. 1500 m long section drilled at SWIR. In three experimental subprojects we attempt to clarify (1) the phase relations and phase compositions in a typical late-magmatic system, (2) whether liquid immiscibility is an important late-magmatic process, and (3) how percolating late-stage melts influence the just solidified normal gabbro. Particular attention will be given to the oxygen fugacity and the water activity in our experiments, since these volatiles are regarded to play a dominant role during the late-magmatic activity. Since it has been recently discussed whether magmatic late-stage processes can also be the result of hydrothermal circulation in the deep oceanic crust at very high temperatures, we attempt to perform in-situ Sr isotope analyses of late-stage phases in the 735B gabbros for clarifying the nature of these fluids, i.e., whether they are magmatic or seawater-influenced.
Das Projekt "Sub project: Viscous flow of magmas from Unzen volcano, Japan - implications for magma mixing and ascent" wird vom Umweltbundesamt gefördert und von Leibniz Universität Hannover, Institut für Mineralogie durchgeführt. In the proposed project the viscosity of magmas of the Unzen volcano in Japan (compositions: rhyodacite to andesite) will be determined at conditions relevant to the local geological situation. Effects of pressure, water content, redox state of iron and degree of crystallization on rheological properties of the magma are of special importance in our studies. At present the influence of these parameters on viscosity of rhyodacitic to andesitic melts can not be modeled due to a lack of reliable experimental data. In the high-viscosity range nearby the glass transition, viscosities will be measured under pressure using a parallel-plate viscometer developed in our institute. Previous measurements were performed only at ambient pressure in this viscosity range. In the low-viscosity range (stable melt), the fallingsphere method will be applied. Combining both methods, the temperature dependence of viscosity can be defined in a large T range. Based on our viscosity measurements and on data from literature we want to develop a viscosity model applicable to melts with rhyolitic to andesitic composition. Using the viscosity data and results on phase equilibria and volatile solubility (project Ho1337/3+7), an attempt will be made to reconstruct the evolution of Unzen magmas from pre-eruptive conditions to the beginning of the eruption.
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.
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