ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    Experimental evidence for melt partitioning between olivine and orthopyroxene in partially molten harzburgite (2016)
    Wiley
    Details
    Publication Date: 2016-08-04
    Description: Observations of dunite channels in ophiolites and uranium-series disequilibria in mid-ocean ridge basalt suggest that melt transport in the upper mantle beneath mid-ocean ridges is strongly channelized. We present experimental evidence that spatial variations in mineralogy can also focus melt on the grain-scale. This lithologic melt partitioning, which results from differences in the interfacial energies associated with olivine-melt and orthopyroxene-melt boundaries, may complement other melt focusing mechanisms in the upper mantle such as mechanical shear and pyroxene dissolution. We document here lithologic melt partitioning in olivine/orthopyroxene-basaltic melt samples containing nominal olivine to orthopyroxene ratio of 3 to 2 and melt fractions of 0.02 to 0.20. Experimental samples were imaged using synchrotron-based X-ray micro-computed tomography at a resolution of 700 nm per voxel. By analyzing the local melt fraction distributions associated with olivine and orthopyroxene (opx) grains in each sample, we found that the melt partitioning coefficient, i.e. , the ratio of melt fraction around olivine to that around orthopyroxene grains, varies between 1.1 and 1.6. The permeability and electrical conductivity of our digital samples were estimated using numerical models and compared to those of samples containing only olivine and basaltic melt. Our results suggest that lithologic melt partitioning and preferential localization of melt around olivine grains might play a role in melt focusing, potentially enhancing average melt ascent velocities.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    Melt extraction pathways at segmented oceanic ridges: Application to the East Pacific Rise at the Siqueiros transform (2011)
    Wiley
    Details
    Publication Date: 2011-06-15
    Description: Throughout the global mid-ocean ridge system, transform faults offset spreading centers. Conductive cooling may be more efficient beneath transform faults, producing a thickened lithosphere that directs melt away from the transform. However, recent observations of thickened crust along transform faults at fast ridges suggest melt redistribution toward transforms, intra-crustal melt production, or efficient extraction of melt. We apply a 3-D model of melt migration and extraction along an oceanic transform domain bounded by ridge segments. Melt is assumed to travel vertically before collecting and migrating beneath a low-permeability boundary inclined towards the ridge axis. A melt extraction zone, which may be geologically interpreted as the presence of faults and/or dikes leading to rapid lateral and vertical melt migration toward plate boundaries, affects the pattern of crustal accretion at segmented ridges. First, we examine a generic ridge-transform-ridge geometry and then a model that represents the Siqueiros transform on the East Pacific Rise. On the basis of crustal thickness variations within the intra-transform spreading centers along the fast-slipping Siqueiros fault, we constrain the presence of a melt extraction zone within 10 km of the transform zone.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Slip-rate-dependent melt extraction at oceanic transform faults (2015)
    Wiley
    Details
    Publication Date: 2015-01-21
    Description: Crustal thickness differences between oceanic transform faults and associated mid-ocean ridges may be explained by melt migration and extraction processes. Slow-slipping transform faults exhibit more positive gravity anomalies than the adjacent spreading centers, indicating relative thin crust in the transform domain, whereas at intermediate- and fast-spreading ridges, transform faults are characterized by more negative gravity anomalies than the adjacent spreading centers, indicating thick crust in the transform domain. We present numerical models reproducing these observations and infer that melt can be extracted at fast-slipping transforms, but not at slow-slipping ones. Melt extraction is modeled as a three-step process [ Montési et al ., 2011]. 1) Melt moves vertically through buoyancy-driven porous flow enhanced by sub-vertical dissolution channels. 2) Melt accumulates in and travels along a decompaction channel lining a low-permeability barrier at the base of the thermal boundary layer. 3) Melt is extracted to the surface when it enters a melt extraction zone. A melt extraction width of 2 – 4km and a melt extraction depth of 15 – 20km are needed to fit the tectonic damages associated with oceanic plate boundaries that reach into the upper mantle. Our conclusions are supported by the different degrees of magmatic activities exhibited at fast- and slow-slipping transforms as reflected in geological features, geochemical signals and seismic behaviors. We also constrain that the maximum lateral distance of crust-level dike propagation is about 50 to 70km. This article is protected by copyright. All rights reserved.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    Distributed deformation ahead of the Cocos-Nazca Rift at the Galapagos triple junction (2011)
    Wiley
    Details
    Publication Date: 2011-11-08
    Description: The Galapagos triple junction is not a simple ridge-ridge-ridge (RRR) triple junction. The Cocos-Nazca Rift (C-N Rift) tip does not meet the East Pacific Rise (EPR). Instead, two secondary rifts form the link: Incipient Rift at 2°40′N and Dietz Deep volcanic ridge, the southern boundary of the Galapagos microplate (GMP), at 1°10′N. Recently collected bathymetry data are used to investigate the regional tectonics prior to the establishment of the GMP (∼1.5 Ma). South of C-N Rift a band of northeast-trending cracks cuts EPR-generated abyssal hills. It is a mirror image of a band of cracks previously identified north of C-N Rift on the same age crust. In both areas, the western ends of the cracks terminate against intact abyssal hills suggesting that each crack initiated at the EPR spreading center and cut eastward into pre-existing topography. Each crack formed a short-lived triple junction until it was abandoned and a new crack and triple junction initiated nearby. Between 2.5 and 1.5 Ma, the pattern of cracking is remarkably symmetric about C-N Rift providing support for a crack interaction model in which crack initiation at the EPR axis is controlled by stresses associated with the tip of the westward-propagating C-N Rift. The model also shows that offsets of the EPR axis may explain times when cracking is not symmetric. South of C-N Rift, cracks are observed on seafloor as old as 10.5 Ma suggesting that this triple junction has not been a simple RRR triple junction during that time.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    Controls on melt migration and extraction at the ultraslow Southwest Indian Ridge 10°–16°E (2011)
    Wiley
    Details
    Publication Date: 2011-10-04
    Description: Crustal thickness variations at the ultraslow spreading 10–16°E region of the Southwest Indian Ridge are used to constrain melt migration processes. In the study area, ridge morphology correlates with the obliquity of the ridge axis with respect to the spreading direction. A long oblique “supersegment”, nearly devoid of magmatism, is flanked at either end by robust magmatic centers (Joseph Mayes Seamount and Narrowgate segment) of much lesser obliquity. Plate-driven mantle flow and temperature structure are calculated in 3-D based on the observed ridge segmentation. Melt extraction is assumed to occur in three steps: (1) vertical migration out of the melting region, (2) focusing along an inclined permeability barrier, and (3) extraction when the melt enters a region shallower than ∼35 km within 5 km of the ridge axis. No crust is predicted in our model along the oblique supersegment. The formation of Joseph Mayes Seamount is consistent with an on-axis melt anomaly induced by the local orthogonal spreading. The crustal thickness anomaly at Narrowgate results from melt extracted at a tectonic damage zone as it travels along the axis toward regions of lesser obliquity. Orthogonal spreading enhances the Narrowgate crustal thickness anomaly but is not necessary for it. The lack of a residual mantle Bouguer gravity high along the oblique supersegment can be explained by deep serpentization of the upper mantle permissible by the thermal structure of this ridge segment. Buoyancy-driven upwelling and/or mantle heterogeneities are not required to explain the extreme focusing of melt in the study area.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 6
    facet.materialart.
    Unknown
    Deflection of mantle flow beneath subducting slabs and the origin of sub-slab anisotropy (2014)
    Wiley
    Details
    Publication Date: 2014-09-17
    Description: Global compilations of sub-slab shear wave splitting parameters show a mix of trench-parallel and trench-perpendicular fast directions that often directly contradict predictions from two-dimensional models of slab-entrained flow. Here we show that sub-slab anisotropy is consistent with three-dimensional geodynamic models that feature the interaction between subducting slabs and regional mantle flow. Each model represents a specific region for which high-quality source-side shear wave splitting data are available. We compare the distribution of finite strain in the models with shear wave splitting observations, showing that both trench-parallel and trench-perpendicular fast directions can be explained by deflection of regional mantle flow around or beneath subducted slabs. Sub-slab maximum elongation directions calculated from our models depend on a combination of geometry factors (such as slab dip angle and maximum depth), mechanical parameters (such as decoupling between the slab and the subjacent mantle), and the orientation and magnitude of the regional mantle flow.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 7
    facet.materialart.
    Unknown
    The Impact of a Pressurized Regional Sea or Global Ocean on Stresses on Enceladus (2017)
    Wiley
    Details
    Publication Date: 2017-05-23
    Description: Liquid water is likely present in the interior of Enceladus, but it is still debated whether this water forms a global ocean or a regional sea, and whether the present-day situation is stable. As the heat flux of Enceladus exceeds most heat source estimates, the liquid water is likely cooling and crystallizing, which results in expansion and pressurization of the sea or ocean. We determine, using an axisymmetric Finite Element Model, the tectonic patterns that pressurization of a regional sea or global ocean might produce at the surface of Enceladus. Tension is always predicted above where the ice is thinnest and generates cracks that might be at the origin of the Tiger Stripes. Tectonic activity is also expected in an annulus around the sea if the ice shell is in contact with, but slips freely along the rocky core of the satellite. Cracks at the North Pole are expected if the shell slips along the core or if there is a global ocean with thin ice at the pole. Water is likely injected along the base of the ice when the shell is grounded, which may lead to cycles of tectonic activity with the shell alternating between floating and grounded states and mid-latitude faulting occurring at the transition from grounded to floating states.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 8
    facet.materialart.
    Unknown
    The Generation of Barriers to Melt Ascent in the Martian Lithosphere (2017)
    Wiley
    Details
    Publication Date: 2017-12-16
    Description: Planetary mantles can be regarded as an aggregate of two phases: a solid, porous matrix and a liquid melt. Melt travels rapidly upwards through the matrix due to its buoyancy. When this melt enters the colder lithosphere it begins to crystallize. If crystallization happens at a high rate, the newly formed crystals can clog the pore space, reducing its permeability to essentially zero. This zone of zero permeability is the permeability barrier. We use the MELTS family of thermodynamic calculators to determine melt compositions and the crystallization sequence of ascending melt throughout Martian history and simulate the formation of permeability barriers. At lower strain rates (10 -17 – 10 -15 s -1 ) permeability barriers form deep in the lithosphere, possibly contributing to the formation of localized volcanic edifices on the Martian surface once fracturing or thermal erosion enables melt to traverse the lithosphere. Higher strain rates (10 -13 s -1 ) yield shallower permeability barriers, perhaps producing extensive lava flows. Permeability barrier formation is investigated using an anhydrous mantle source or mantle sources that include up to 1000 ppm H 2 O. Introducing even small amounts of water (25 ppm H 2 O) reduces mantle viscosity in a manner similar to increasing the strain rate, and results in a shallower barrier than in the anhydrous case. Large amounts of water (1000 ppm H 2 O) yield very shallow weak barriers or no barriers at all. The depth of the permeability barrier has evolved through time, likely resulting in a progression in the style of surface volcanism from widespread flows to massive, singular volcanoes.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 9
    facet.materialart.
    Unknown
    MeltMigrator: A MATLAB-based software for modeling three-dimensional melt migration and crustal thickness variations at mid-ocean ridges following a rules-based approach (2017)
    Wiley
    Details
    Publication Date: 2017-01-04
    Description: MeltMigrator is a MATLAB®-based melt migration software developed to process three-dimensional mantle temperature and velocity data from user-supplied numerical models of mid-ocean ridges, calculate melt production and melt migration trajectories in the mantle, estimate melt flux along plate boundaries and predict crustal thickness distribution on the seafloor. MeltMigrator is also capable of calculating compositional evolution depending on the choice of petrologic melting model. Programmed in modules, MeltMigrator is highly customizable and can be expanded to a wide range of applications. We have applied it to complex mid-ocean ridge model settings, including transform faults, oblique segments, ridge migration, asymmetrical spreading, background mantle flow and ridge-plume interaction. In this technical report, we include an example application to a segmented mid-ocean ridge. MeltMigrator is available as a supplement to this paper, and it's also available from GitHub and the University of Maryland Geodynamics Group website. This article is protected by copyright. All rights reserved.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 10
    facet.materialart.
    Unknown
    Fault-bound valley associated with the Rembrandt basin on Mercury (2016)
    Wiley
    Details
    Publication Date: 2016-11-17
    Description: The Rembrandt basin is crosscut by the largest fault scarp on Mercury, Enterprise Rupes, and a second scarp complex, Belgica Rupes, extends to the basin's rim. Topographic data derived from MESSENGER orbital stereo images show that these tectonic landforms bound a broad, relatively flat-floored valley with a mean width of ~400 km. Crosscutting relations suggest that the accumulation of structural relief likely postdates the formation and volcanic infilling of the Rembrandt basin. The valley floor, bound by fault scarps of opposite vergence, is significantly offset below the elevation of the back-scarp terrains. Along with an offset section of Rembrandt's rim, the elevation differences are evidence that the valley floor was lowered as a result of the formation of bounding fault scarps. The localization of the widely spaced thrust faults of Enterprise and Belgica Rupis and the offset of the valley floor may be the result of long-wavelength buckling of Mercury's lithosphere.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...