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  • 1
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    Focusing of magma in the upper mantle through dike interaction (2002)
    In:  J. Geophys. Res., Amsterdam, Schweizerbart'sche Verlagsbuchhandlung, vol. 107, no. B10, pp. ECV 6-1-ECV 6-17, pp. 2223, (ISSN 0016-8548, ISBN 3-510-50045-8)
    Details
    Publication Date: 2002
    Description: We use laboratory experiments and numerical models to quantify the effects of dike interaction on the focusing of magma as it ascends in the upper mantle. Laboratory experiments involve injecting buoyant fluid into the base of a tank filled with solidified gelatin. When we initiate two dikes parallel to each other, but separated by a horizontal distance x, they tend to merge as they ascend. This behavior is also predicted by numerical models of two-dimensional dikes. The key parameters that control the maximum horizontal separation x c over which dikes will intersect are dike driving pressures, dike head lengths L (i.e., the length over which driving pressure is large), and the difference between the principal stresses of the remote stress field. When the remote differential stress is small compared to the dike driving pressure, two dikes of equal driving pressure and length will intersect over distances of x c ? L. This distance decreases with increasing remote differential stress. We quantify the effects on magma transport from a broad lateral distribution of magma using numerical simulations of multiple-dike interaction. When the average dike spacing prior to interaction is within ?3 L and remote differential stresses are insignificant, dike interaction can focus magma over horizontal distances many times L but at least ?6 L. Dike interaction can focus magma in the asthenosphere beneath mid-ocean ridges for low mantle viscosities (?10 19 Pa s) and if dikes initiate with average separations of a few hundred meters, or less. Such focusing is predicted to grow dikes of increasing magma flux approaching lateral separations of a kilometer.
    Keywords: Fluids ; Plate tectonics ; ascent ; sheeted ; dykes ; Modelling ; JGR ; 8434 ; Volcanology: ; Magma ; migration ; 8145 ; Tectonophysics: ; Physics ; of ; magma ; and ; magma ; bodies ; 8120 ; Dynamics ; of ; lithosphere ; and ; mantle--general ; 3035 ; Marine ; Geology ; and ; Geophysics: ; Midocean ; ridge ; processes
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Conditions for plumes to penetrate the mantle phase boundaries (2000)
    In:  J. Geophys. Res., Zagreb, 3-4, vol. 105, no. B3, pp. 5679-5693, pp. 1431, (ISSN: 1340-4202)
    Details
    Publication Date: 2000
    Keywords: Mineralogy ; ConvolutionE ; JGR ; 1025 ; Geochemistry ; (new ; field, ; replaces ; rock ; chemistry) ; Composition ; of ; the ; mantle ; 3939 ; Mineral ; physics ; Physical ; thermodynamics ; 8121 ; Tectonophysics ; Dynamics, ; convection ; currents ; and ; mantle ; plumes
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    Observational and theoretical studies of the dynamics of mantle plume-mid-ocean ridge interaction (2003)
    In:  Rev. Geophys., Amsterdam, Schweizerbart'sche Verlagsbuchhandlung, vol. 41, no. 4, pp. ECV 6-1-ECV 6-17, pp. 1017, (ISSN 0016-8548, ISBN 3-510-50045-8)
    Details
    Publication Date: 2003
    Keywords: Plate tectonics ; hot ; spot ; earth mantle ; GeodesyY ; Iceland ; ROG
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    Effects of volcano loading on dike propagation in an elastic half-space (2001)
    In:  J. Geophys. Res., Dordrecht, Netherlands, Dr. W. Junk, vol. 106, no. B6, pp. 11101-11114, pp. L08304, (ISSN: 1340-4202)
    Details
    Publication Date: 2001
    Description: We use laboratory experiments and numerical models to examine the effects of volcano loading on the propagation of buoyant dikes in a two-dimensional elastic half-space. In laboratory experiments we simulate the propagation of buoyant dikes in an isotropic regional stress field by injecting air into tanks of solidified gelatin. A weight resting on the surface of the gelatin represents a volcanic load. A numerical model is used to simulate these experiments. Both experiments and numerical simulations show that as a dike ascends, it begins to curve toward the load in response to the local stress field imposed by the load. The lateral distance over which dikes curve to the load increases with the ratio of average pressure at the base of the load to the dike driving pressure. For realistic volcano and dike dimensions this pressure ratio is going to be large, suggesting that dikes can converge to a volcano over lateral distances several times the load width. Numerical calculations involving an anisotropic regional stress field, however, predict that the lateral extent of dike attraction shrinks as the regional horizontal compressive stress decreases relative to the vertical compressive stress. Dike focusing will be substantial if the regional differential stresses are less than the average pressure at the base of the load. If this is the case, then our models predict a positive feedback between the size of volcanoes and the area of dike attraction. This feedback may promote the development of large discrete volcanoes and also predicts a positive correlation between the spacing and sizes of adjacent volcanoes. To test this prediction, we examine nearest-neighbor pairs of the 21 largest volcanoes in the Cascade Range. The 14 pairs examined show a large range in volcano spacing (6 - 115 km) and a statistically significant correlation between spacing and average volcano height. This result is consistent with our model results and suggests that the local compressive stress induced by these volcanoes may be an important factor in controlling magma transport in the lithosphere.
    Keywords: Elasticity ; Gravimetry, Gravitation ; Modelling ; magma ; ascent ; JGR ; 1829 ; Hydrology: ; Groundwater ; hydrology ; 8414 ; Volcanology: ; Eruption ; mechanisms ; 8429 ; Lava ; rheology ; and ; morphology ; 8499 ; General ; or ; miscellaneous
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    BIBLIOGRAPHY SEISMOLOGY
  • 5
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    Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply (2015)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2015-10-17
    Description: Recent studies have proposed that the bathymetric fabric of the seafloor formed at mid-ocean ridges records rapid (23,000 to 100,000 years) fluctuations in ridge magma supply caused by sealevel changes that modulate melt production in the underlying mantle. Using quantitative models of faulting and magma emplacement, we demonstrate that, in fact, seafloor-shaping processes act as a low-pass filter on variations in magma supply, strongly damping fluctuations shorter than about 100,000 years. We show that the systematic decrease in dominant seafloor wavelengths with increasing spreading rate is best explained by a model of fault growth and abandonment under a steady magma input. This provides a robust framework for deciphering the footprint of mantle melting in the fabric of abyssal hills, the most common topographic feature on Earth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Olive, J-A -- Behn, M D -- Ito, G -- Buck, W R -- Escartin, J -- Howell, S -- New York, N.Y. -- Science. 2015 Oct 16;350(6258):310-3. doi: 10.1126/science.aad0715.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Lamont-Doherty Earth Observatory, Columbia University, Palisades NY, USA. jaolive@ldeo.columbia.edu. ; Woods Hole Oceanographic Institution, Woods Hole MA, USA. ; University of Hawaii, Honolulu HI, USA. ; Lamont-Doherty Earth Observatory, Columbia University, Palisades NY, USA. ; CNRS, Institut de Physique du Globe de Paris, Paris, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26472905" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    T-Matrix and Radiative Transfer Hybrid Models for Densely Packed Particulates at Mid-Infrared Wavelengths (2017)
    Wiley
    Details
    Publication Date: 2017-04-19
    Description: Mid-infrared spectroscopy is a useful tool for remotely sensing the composition of Earth and other planets. Quantitative mineralogical investigations are possible using remotely sensed data, however the difficulty in modeling complex interactions of light with particles that are on the order of the wavelength limits the usefulness of the remote sensing data. As part of an effort to develop a more effective treatment of light scattering in planetary regolith, we explore the ability of T-matrix and radiative transfer (RT) hybrid models to produce emissivity spectra that are consistent with laboratory measurements. Parameters obtained from T-matrix calculations are used in three different RT models to construct emissivity spectra of enstatite particles of different sizes. Compared to the widely used Mie/RT hybrid models, the T-matrix/RT hybrid models produce more consistent emissivity spectra for the finest particle size fraction (3.3 µm). Overall, T-matrix hybrid models produce improved emissivity spectra, but larger particle sizes are still difficult to model. The improvement observed in T-matrix/RT hybrid models is a result of the inclusion of multiple scattering in closely packed media, and it demonstrates the importance of the implementation of physically realistic factors in developing a more effective light scattering model for planetary regolith. Further development and implementation of this and similar hybrid models will result in an improvement in quantitative assessments of planetary particulate surfaces from mid-infrared spectra.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Cooling Dynamics of Photoexcited C6- and C6H- (2014)
    American Physical Society (APS)
    Details
    Publication Date: 2014-05-09
    Description: Author(s): G. Ito, T. Furukawa, H. Tanuma, J. Matsumoto, H. Shiromaru, T. Majima, M. Goto, T. Azuma, and K. Hansen We report conclusive evidence of an efficient cooling mechanism via the electronic radiative transitions of hot small molecular anions isolated in vacuum. We stored C6- and C6H- in an ion storage ring and observed laser-induced electron detachment with delays up to several milliseconds. The terminal... [Phys. Rev. Lett. 112, 183001] Published Thu May 08, 2014
    Keywords: Atomic, Molecular, and Optical Physics
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society (APS)
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  • 8
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    Investigating seismic anisotropy beneath the reykjanes ridge using models of mantle flow, crystallographic evolution, and surface wave propagation (2013)
    Wiley
    Details
    Publication Date: 2013-06-30
    Description: ABSTRACT Surface wave studies of the Reykjanes Ridge (RR) and the Iceland hotspot, have imaged an unusual and enigmatic pattern of two zones of negative radial anisotropy on each side of the RR. We test previously posed and new hypotheses for the origin of this anisotropy, by considering lattice preferred orientation (LPO) of olivine A-type fabric in simple models with 1-D, layered structures, as well as in 2-D and 3-D geodynamic models with mantle flow and LPO evolution. Synthetic phase velocities of Love and Rayleigh waves travelling parallel to the ridge-axis are produced and then inverted to mimic the previous seismic studies. Results of 1-D models show that strong negative radial anisotropy can be produced when olivine a axes are preferentially aligned not only vertically, but also sub-horizontally in the plane of wave propagation. Geodynamic models, show that negative anisotropy on the sides of the RR can occur when plate spreading impels a corner flow, and in-turn a sub-vertical alignment of olivine a axes, on the sides of the ridge-axis. Mantle dehydration must be invoked to form a viscous upper layer that minimizes the disturbance of the corner flow by the Iceland mantle plume. While the results are promising, important discrepancies still exist between the observed seismic structure and the predictions of this model, as well as models of a variety of types of mantle flow associated with plume-ridge interaction. Thus, other factors that influence seismic anisotropy, but not considered in this study, including power-law rheology, water, melt, and time-dependent mantle flow, are probably important beneath the Reykjanes Ridge.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Blocked radiative heat transport in the hot pyrolitic lower mantle (2020)
    In:  Earth and Planetary Science Letters
    Details
    Publication Date: 2020-12-08
    Description: The heat flux across the core-mantle boundary (QCMB) is the key parameter to understand the Earth’s thermal history and evolution. Mineralogical constraints of the QCMB require deciphering contributions of the lattice and radiative components to the thermal conductivity at high pressure and temperature in lower mantle phases with depth-dependent composition. Here we determine the radiative conductivity (krad) of a realistic lower mantle (pyrolite) in situ using an ultra-bright light probe and fast time-resolved spectroscopic techniques in laser-heated diamond anvil cells. We find that the mantle opacity increases critically upon heating to ∼3000 K at 40-135 GPa, resulting in an unexpectedly low radiative conductivity decreasing with depth from ∼0.8 W/m/K at 1000 km to ∼0.35 W/m/K at the CMB, the latter being ∼30 times smaller than the estimated lattice thermal conductivity at such conditions. Thus, radiative heat transport is blocked due to an increased optical absorption in the hot lower mantle resulting in a moderate CMB heat flow of ∼8.5 TW, on the lower end of previous QCMB estimates based on the mantle and core dynamics. This moderate rate of core cooling implies an inner core age of about 1 Gy and is compatible with both thermally-and compositionally-driven ancient geodynamo.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 10
    Electronic Resource
    Electronic Resource
    Laboratory investigation of the interaction of off-axis mantle plumes and spreading centres (1995)
    [s.l.] : Nature Publishing Group
    Nature 376 (1995), S. 758-761 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Recent laboratory8 and numerical experiments9 have considered the dynamics of plume-ridge interaction for the ridge-centred case; however, the difficult question remains as to how a plume and a ridge interact thermally, chemically and dynamically when the plume is located off axis. A model ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/376758a0
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    Paper (German National Licenses)
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