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
Filter
  • Composition  (2)
  • Oceanic transform fault  (2)
  • 2020-2024  (1)
  • 2010-2014  (3)
  • 1
    facet.materialart.
    Unknown
    Relationship between seismic P-wave velocity and the composition of anhydrous igneous and meta-igneous rocks (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union 2003. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 4 (2003): 1041, doi:10.1029/2002GC000393.
    Description: This study presents a new approach to quantitatively assess the relationship between the composition and seismic P-wave velocity of anhydrous igneous and meta-igneous rocks. We perform thermodynamic calculations of the equilibrating phase assemblages predicted for all igneous composition space at various pressure and temperature conditions. Seismic velocities for each assemblage are then estimated from mixing theory using laboratory measurements of the elastic parameters for pure mineral phases. The resultant velocities are used to derive a direct relationship between Vp and major element composition valid to ±0.13 km/s for pressure and temperature conditions along a normal crustal geotherm in the depth range of 5–50 km and equilibration pressures ≤12 kbar. Finally, we use the calculated velocities to invert for major element chemistry as a function of P-wave velocity assuming only the in situ temperature and pressure conditions are known. Compiling typical velocity-depth profiles for the middle and lower continental and oceanic crust, we calculate compositional bounds for each of these geologic environments. We find that the acceptable compositional range for the middle (15–30 km) and lower continental (≥35 km) crust is broad, ranging from basaltic to dacitic compositions, and conclude that P-wave velocity measurements alone are insufficient to provide fundamental constraints on the composition of the middle and lower continental crust. However, because major oxides are correlated in igneous rocks, joint constraints on Vp and individual oxides can narrow the range of acceptable crustal compositions. In the case of the lower oceanic crust (≥2 km), observed velocities are 0.2–0.3 km/s lower than velocities calculated based on the average bulk composition of gabbros in drill cores and exposed ophiolite sequences. We attribute this discrepancy to a combination of residual porosity at crustal depths less than ∼10 km and hydrous alteration phases in the lower crust, and suggest caution when inferring mantle melting parameters from observed velocities in the lower oceanic crust.
    Description: This research was supported by National Science Foundation Grants OCE- 9819666, EAR-9910899, and EAR-0087706 (P.B. Kelemen).
    Keywords: Continental crust ; Oceanic crust ; Seismic P-wave velocity ; Igneous rocks ; Composition
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 2
    facet.materialart.
    Unknown
    Melt generation, crystallization, and extraction beneath segmented oceanic transform faults (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 114 (2009): B11102, doi:10.1029/2008JB006100.
    Description: We examine mantle melting, fractional crystallization, and melt extraction beneath fast slipping, segmented oceanic transform fault systems. Three-dimensional mantle flow and thermal structures are calculated using a temperature-dependent rheology that incorporates a viscoplastic approximation for brittle deformation in the lithosphere. Thermal solutions are combined with the near-fractional, polybaric melting model of Kinzler and Grove (1992a, 1992b, 1993) to determine extents of melting, the shape of the melting regime, and major element melt composition. We investigate the mantle source region of intratransform spreading centers (ITSCs) using the melt migration approach of Sparks and Parmentier (1991) for two end-member pooling models: (1) a wide pooling region that incorporates all of the melt focused to the ITSC and (2) a narrow pooling region that assumes melt will not migrate across a transform fault or fracture zone. Assuming wide melt pooling, our model predictions can explain both the systematic crustal thickness excesses observed at intermediate and fast slipping transform faults as well as the deeper and lower extents of melting observed in the vicinity of several transform systems. Applying these techniques to the Siqueiros transform on the East Pacific Rise we find that both the viscoplastic rheology and wide melt pooling are required to explain the observed variations in gravity inferred crustal thickness. Finally, we show that mantle potential temperature Tp = 1350°C and fractional crystallization at depths of 9–15.5 km fit the majority of the major element geochemical data from the Siqueiros transform fault system.
    Description: This research was supported by WHOI Academic Programs Office (PMG), NSF grants OCE-0649103 and OCE-0623188 (MDB), and the Charles D. Hollister Endowed Fund for Support of Innovative Research at WHOI (J.L.).
    Keywords: Mid-ocean ridge ; Oceanic transform fault ; Siqueiros transform
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 3
    facet.materialart.
    Unknown
    Frictional behavior of oceanic transform faults and its influence on earthquake characteristics (2012)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): B04315, doi:10.1029/2011JB009025.
    Description: We use a three-dimensional strike-slip fault model in the framework of rate and state-dependent friction to investigate earthquake behavior and scaling relations on oceanic transform faults (OTFs). Gabbro friction data under hydrothermal conditions are mapped onto OTFs using temperatures from (1) a half-space cooling model, and (2) a thermal model that incorporates a visco-plastic rheology, non-Newtonian viscous flow and the effects of shear heating and hydrothermal circulation. Without introducing small-scale frictional heterogeneities on the fault, our model predicts that an OTF segment can transition between seismic and aseismic slip over many earthquake cycles, consistent with the multimode hypothesis for OTF ruptures. The average seismic coupling coefficient χ is strongly dependent on the ratio of seismogenic zone width W to earthquake nucleation size h*; χ increases by four orders of magnitude as W/h* increases from ∼1 to 2. Specifically, the average χ = 0.15 ± 0.05 derived from global OTF earthquake catalogs can be reached at W/h* ≈ 1.2–1.7. Further, in all simulations the area of the largest earthquake rupture is less than the total seismogenic area and we predict a deficiency of large earthquakes on long transforms, which is also consistent with observations. To match these observations over this narrow range of W/h* requires an increase in the characteristic slip distance dc as the seismogenic zone becomes wider and normal stress is higher on long transforms. Earthquake magnitude and distribution on the Gofar and Romanche transforms are better predicted by simulations using the visco-plastic model than the half-space cooling model.
    Description: This work was supported by NSF-EAR award 1015221, NSF-OCE award 1061203, and a J. Lamar Worzel Assistant Scientist Fund to Y. Liu at WHOI.
    Description: 2012-10-26
    Keywords: Earthquake scaling relation ; Oceanic transform fault
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 4
    facet.materialart.
    Unknown
    WISTFUL: whole‐rock interpretative seismic toolbox for ultramafic lithologies (2023)
    American Geophysical Union
    Details
    Publication Date: 2023-02-28
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Shinevar, W., Jagoutz, O., & Behn, M. WISTFUL: whole‐rock interpretative seismic toolbox for ultramafic lithologies. Geochemistry, Geophysics, Geosystems, 23(8), (2022): e2022GC010329, https://doi.org/10.1029/2022gc010329.
    Description: To quantitatively convert upper mantle seismic wave speeds measured into temperature, density, composition, and corresponding and uncertainty, we introduce the Whole-rock Interpretative Seismic Toolbox For Ultramafic Lithologies (WISTFUL). WISTFUL is underpinned by a database of 4,485 ultramafic whole-rock compositions, their calculated mineral modes, elastic moduli, and seismic wave speeds over a range of pressure (P) and temperature (T) (P = 0.5–6 GPa, T = 200–1,600°C) using the Gibbs free energy minimization routine Perple_X. These data are interpreted with a toolbox of MATLAB® functions, scripts, and three general user interfaces: WISTFUL_relations, which plots relationships between calculated parameters and/or composition; WISTFUL_geotherms, which calculates seismic wave speeds along geotherms; and WISTFUL_inversion, which inverts seismic wave speeds for best-fit temperature, composition, and density. To evaluate our methodology and quantify the forward calculation error, we estimate two dominant sources of uncertainty: (a) the predicted mineral modes and compositions, and (b) the elastic properties and mixing equations. To constrain the first source of uncertainty, we compiled 122 well-studied ultramafic xenoliths with known whole-rock compositions, mineral modes, and estimated P-T conditions. We compared the observed mineral modes with modes predicted using five different thermodynamic solid solution models. The Holland et al. (2018, https://doi.org/10.1093/petrology/egy048) solution models best reproduce phase assemblages (∼12 vol. % phase root-mean-square error [RMSE]) and estimated wave speeds. To assess the second source of uncertainty, we compared wave speed measurements of 40 ultramafic rocks with calculated wave speeds, finding excellent agreement (Vp RMSE = 0.11 km/s). WISTFUL easily analyzes seismic datasets, integrates into modeling, and acts as an educational tool.
    Description: Funding for this study was provided by NSF Grants EAR-17-22935 (OJ) and EAR-18-44340 (MB).
    Keywords: Seismic velocity ; Seismic wave speed ; Thermodynamic modeling ; Density ; Composition ; Elastic moduli
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...