Geochemistry, Geophysics, Geosystems

Cover image for Geochemistry, Geophysics, Geosystems

April 2013

Volume 14, Issue 4

Pages 759–1320

  1. Research Letter

    1. Top of page
    2. Research Letter
    3. Regular Articles
    4. Technical Brief
    1. Temporal trends in vent fluid iron and sulfide chemistry following the 2005/2006 eruption at East Pacific Rise, 9°50′N (pages 759–765)

      Mustafa Yücel and George W. Luther III

      Article first published online: 17 APR 2013 | DOI: 10.1002/ggge.20088

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      Key Points

      • Vent chemistry undergoes dramatic variations after eruptions at EPR 9N
      • Decreasing sulfide and increasing iron concentrations after the 2006 eruption
      • Dramatic yearly variability in the vent fluxes of Fe-S species
  2. Regular Articles

    1. Top of page
    2. Research Letter
    3. Regular Articles
    4. Technical Brief
    1. Stochastic modeling of the Earth's magnetic field: Inversion for covariances over the observatory era (pages 766–786)

      N. Gillet, D. Jault, C. C. Finlay and N. Olsen

      Article first published online: 3 APR 2013 | DOI: 10.1002/ggge.20041

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      Key Points

      • Modeling the geomagnetic secular vartiation
      • Use of the stochastic processes framework
      • Obtain realistic model covariances
    2. Re-evaluating genetic models for porphyry Mo mineralization at Questa, New Mexico: Implications for ore deposition following silicic ignimbrite eruption (pages 787–805)

      Joshua M. Rosera, Drew S. Coleman and Holly J. Stein

      Article first published online: 5 APR 2013 | DOI: 10.1002/ggge.20048

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      Key Points

      • New model ties caldera cycle magmatism to economic Mo mineralization
      • New application of Re-Os as a thermochronometer
      • Incremental pluton assembly linked to economic mineralization
    3. Velocity-conductivity relations for cratonic lithosphere and their application: Example of Southern Africa (pages 806–827)

      Alan G. Jones, Stewart Fishwick, Rob L. Evans, Mark R. Muller and Javier Fullea

      Article first published online: 5 APR 2013 | DOI: 10.1002/ggge.20075

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      Key Points

      • Velocity and conductivity of rocks are related through dependence on temperature
      • Southern African seismic and EM data inter-related as predicted petro-physically
      • Water content map of Southern Africa exhibits tectonic correlation
    4. You have full text access to this OnlineOpen article
      How do “ghost transients” from past earthquakes affect GPS slip rate estimates on southern California faults? (pages 828–838)

      E. H. Hearn, F. F. Pollitz, W. R. Thatcher and C. T. Onishi

      Article first published online: 5 APR 2013 | DOI: 10.1002/ggge.20080

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      Key Points

      • Viscoelastic perturbations affect the southern CA GPS velocity field
      • Such perturbations may bias the inferred slip rate along the SAF by 5 mm/yr
      • Perturbations from the Garlock fault are too small to bias slip rates
    5. Geomagnetic jerks as chaotic fluctuations of the Earth's magnetic field (pages 839–850)

      E. Qamili, A. De Santis, A. Isac, M. Mandea, B. Duka and A. Simonyan

      Article first published online: 12 APR 2013 | DOI: 10.1029/2012GC004398

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      Key Points

      • Predictive and definitive geomagnetic models diverge exponentially in time
      • A predictability time window of 5–9 years is found
      • >The epochs when the predictability deteriorates coincide with jerk occurrences
    6. Tidal modulation of continuous nonvolcanic seismic tremor in the Chile triple junction region (pages 851–863)

      A. Gallego, R. M. Russo, D. Comte, V. Mocanu, R. E. Murdie and J.C. VanDecar

      Article first published online: 16 APR 2013 | DOI: 10.1002/ggge.20091

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      Key Points

      • Non Volcanic Tremors were found in southern Chile
      • They are located in the forearc region
      • They are modulated by soli-lunar tides
    7. Depths and temperatures of <10.5 Ma mantle melting and the lithosphere-asthenosphere boundary below southern Oregon and northern California (pages 864–879)

      Christy B. Till, Timothy L. Grove, Richard W. Carlson, Julie M. Donnelly-Nolan, Matthew J. Fouch, Lara S. Wagner and William K. Hart

      Article first published online: 17 APR 2013 | DOI: 10.1002/ggge.20070

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      Key Points

      • <10.5 Ma basalts are from 37–60 km depth and 1185–1383°C
      • The Moho and lithosphere-asthenosphere boundary are located very close to one another (5–10 km) in this region
      • Anhydrous mantle melting is driven by subduction-related mantle flow
    8. Structures of the oceanic lithosphere-asthenosphere boundary: Mineral-physics modeling and seismological signatures (pages 880–901)

      T. M. Olugboji, S. Karato and J. Park

      Article first published online: 17 APR 2013 | DOI: 10.1002/ggge.20086

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      Key Points

      • A new subsolidus model to explain the lithosphere asthenosphere boundary
      • Examine the partial-melt and subsolidus models to explain seismological results
      • Our model explains most features of the LAB with implications for further tests
    9. Upper mantle seismic structure beneath central East Antarctica from body wave tomography: Implications for the origin of the Gamburtsev Subglacial Mountains (pages 902–920)

      Andrew J. Lloyd, Andrew A. Nyblade, Douglas A. Wiens, Samantha E. Hansen, Masaki Kanao, Patrick J. Shore and Dapeng Zhao

      Article first published online: 17 APR 2013 | DOI: 10.1002/ggge.20098

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      Key Points

      • Archean/Paleoproterozoic lithosphere underlies the Gamburtsev Mountains
      • Mesoproterozoic/Neoproterozoic lithosphere underlies the Polar Subglacial Basin
      • Our results suggest an ancient compressional origin for the Gamburtsev Mts
    10. Micromagnetics and magnetomineralogy of ultrafine magnetite inclusions in the Modipe Gabbro (pages 921–928)

      A. R. Muxworthy and M. E. Evans

      Article first published online: 18 APR 2013 | DOI: 10.1029/2012GC004445

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      Key Points

      • Magnetite inclusions in the Modipe Gabbro have excellent recording fidelity
      • Micromagnetic models agree well with measured hysteresis parameters
      • The paleointensity response of the samples was found to be near-perfect
    11. Refining benthic foraminiferal Mg/Ca-temperature calibrations using core-tops from the western tropical Atlantic: Implication for paleotemperature estimation (pages 929–946)

      Amandine A. Tisserand, Trond M. Dokken, Claire Waelbroeck, Jeanne-M. Gherardi, Vincent Scao, Christophe Fontanier and Frans Jorissen

      Article first published online: 23 APR 2013 | DOI: 10.1002/ggge.20043

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      Key Points

      • New benthic foraminiferal Mg/Ca-BWT calibrations
    12. Measuring the Curie temperature (pages 947–961)

      K. Fabian, V. P. Shcherbakov and S. A. McEnroe

      Article first published online: 24 APR 2013 | DOI: 10.1029/2012GC004440

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      Key Points

      • Theory of Curie measurements
      • New method for Curie point determination
      • Comparability of Curie point measurements
    13. Seasonal moisture sources and the isotopic composition of precipitation, rivers, and carbonates across the Andes at 32.5–35.5°S (pages 962–978)

      Gregory D. Hoke, Julieta N. Aranibar, Maximiliano Viale, Diego C. Araneo and Carina Llano

      Article first published online: 24 APR 2013 | DOI: 10.1002/ggge.20045

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      Key Points

      • Variable influence of westerly sourced precipitation on eastern Andean slopes
      • Soil water compositions show variability consistent with that of precipitation
      • Isotopically, rivers are not simple proxies for precipitation in narrow ranges
    14. Mantle composition controls the development of an Oceanic Core Complex (pages 979–995)

      S. C. Wilson, B. J. Murton and R. N. Taylor

      Article first published online: 24 APR 2013 | DOI: 10.1002/ggge.20046

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      Key points

      • Amagmatic parts of the ridge are currently producing normal amounts of melt
      • Mantle geochemistry triggers a change from magmatism to amagmatism
      • Unusually, the mid-segment lithosphere is cold and thick
    15. High-resolution bathymetry reveals contrasting landslide activity shaping the walls of the Mid-Atlantic Ridge axial valley (pages 996–1011)

      Mathilde Cannat, Anne Mangeney, Hélène Ondréas, Yves Fouquet and Alain Normand

      Article first published online: 24 APR 2013 | DOI: 10.1002/ggge.20056

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      Key points

      • Landslides shape slopes of axial valley at the Mid-Atlantic Ridge
      • Mass-wasting is different in serpentinized peridotite and in basalts
      • Landslides limit overall slopes of ultramafic outcrops to about 20 degrees
    16. Laboratory observation of acoustic fluidization in granular fault gouge and implications for dynamic weakening of earthquake faults (pages 1012–1022)

      Kaiwen Xia, Sheng Huang and Chris Marone

      Article first published online: 24 APR 2013 | DOI: 10.1002/ggge.20076

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      Key Points

      • Observation of acoustic-fluidization for fault gouge under seismogenic stresses
      • We induce dynamic weakening of the fault gouge using excitation by stress waves
      • Our data could explain aspects of earthquake triggering by dynamic stressing
    17. Apparent overconsolidation of mudstones in the Kumano Basin of southwest Japan: Implications for fluid pressure and fluid flow within a forearc setting (pages 1023–1038)

      Junhua Guo, Michael B. Underwood, William J. Likos and Demian M. Saffer

      Article first published online: 25 APR 2013 | DOI: 10.1029/2012GC004204

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      Key Points

      • Values of preconsolidation pressure indicate overconsolidation.
      • Drainage through landward-dipping turbidites leads to hydrostatic pore pressure.
      • Cementation in the lower basin is responsible for apparent overconsolidation.
    18. Constraining clay hydration state and its role in active fault systems (pages 1039–1052)

      Anja M. Schleicher, Heiko Hofmann and Ben A. van der Pluijm

      Article first published online: 25 APR 2013 | DOI: 10.1002/ggge.20077

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      Key Points

      • Investigating smectite swelling behavior
      • Humidity chamber connected to an X-ray diffractometer
      • Implications for weak fault behavior
    19. A core-top study of dissolution effect on B/Ca in Globigerinoides sacculifer from the tropical Atlantic: Potential bias for paleo-reconstruction of seawater carbonate chemistry (pages 1053–1068)

      R. Coadic, F. Bassinot, D. Dissard, E. Douville, M. Greaves and E. Michel

      Article first published online: 29 APR 2013 | DOI: 10.1029/2012GC004296

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      Key Points

      • Planktonic foraminifera as geochemical tracer
      • Seawater paleo-pH reconstruction
      • B/Ca of planktonic foraminifera modified by dissolution
    20. You have full text access to this OnlineOpen article
      The mode of deformation in the orogenic mid-crust revealed by seismic attribute analysis (pages 1069–1086)

      Taija Torvela, Julien Moreau, Robert W. H. Butler, Annakaisa Korja and Pekka Heikkinen

      Article first published online: 29 APR 2013 | DOI: 10.1002/ggge.20050

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      Key Points

      • We re-open the discussion of applicability of seismic attributes for 2D data
      • Attributes can be used to get more detailed information from seismic data
      • Detailed strain distribution during orogenic crustal deformation is revealed
    21. Crustal structure across the Costa Rican Volcanic Arc (pages 1087–1103)

      Jorden L. Hayes, W. Steven Holbrook, Dan Lizarralde, Harm J. A. van Avendonk, Andrew D. Bullock, Mauricio Mora, Steven Harder, Guillermo E. Alvarado and Carlos Ramírez

      Article first published online: 29 APR 2013 | DOI: 10.1002/ggge.20079

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      Key Points

      • Thickened crustal substrate has an effect on bulk composition in Costa Rica
      • Seismic velocities beneath Costa Rica are close to continental velocities
      • A crust-mantle transition zone is interpreted from many seismic reflections
    22. Early Aptian paleoenvironmental evolution of the Bab Basin at the southern Neo-Tethys margin: Response to global carbon-cycle perturbations across Ocean Anoxic Event 1a (pages 1104–1130)

      Kazuyuki Yamamoto, Masatoshi Ishibashi, Hideko Takayanagi, Yoshihiro Asahara, Tokiyuki Sato, Hiroshi Nishi and Yasufumi Iryu

      Article first published online: 29 APR 2013 | DOI: 10.1002/ggge.20083

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      Key Points

      • Establishing high-resolution d13C profile of carbonates deposited during OAE1a
      • Delineating biotic response to environmental changes during OAE1a
      • Showing OAE1a is a long lasting event during the second-order transgression
    23. High-resolution 3D numerical modeling of thrust wedges: Influence of décollement strength on transfer zones (pages 1131–1155)

      Jonas B. Ruh, Taras Gerya and Jean-Pierre Burg

      Article first published online: 29 APR 2013 | DOI: 10.1002/ggge.20085

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      Key Points

      • High-resolution numerical modelling of thin-skinned wedges
      • Structural evolution of critical wedges along a transfer zone
      • Comparison to the Zagros-Makran transition zone
    24. Upper-mantle fabrics beneath the Northern Apennines revealed by seismic anisotropy (pages 1156–1181)

      Helena Munzarová, Jaroslava Plomerová, Vladislav Babuška and Luděk Vecsey

      Article first published online: 29 APR 2013 | DOI: 10.1002/ggge.20092

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      Key Points

      • Joint analysis of body-wave anisotropy identifies regions of different fabrics
      • The asthenospheric-flow pattern suggests the end of the subduction roll-back.
      • The mantle lithosphere is formed by domains retaining their fossil fabric
    25. Phase transitions of harzburgite and buckled slab under eastern China (pages 1182–1199)

      Yanfei Zhang, Yanbin Wang, Yao Wu, Craig R. Bina, Zhenmin Jin and Shuwen Dong

      Article first published online: 30 APR 2013 | DOI: 10.1002/ggge.20069

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      Key Points

      • Mineral constituents of oceanic lithosphere have been determined at high P and T
      • The results are used to examine signatures of stagnant slabs
      • A bucked slab model can interpret seismic tomography images under eastern China
    26. An adaptive staggered grid finite difference method for modeling geodynamic Stokes flows with strongly variable viscosity (pages 1200–1225)

      T. V. Gerya, D. A. May and T. Duretz

      Article first published online: 30 APR 2013 | DOI: 10.1002/ggge.20078

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      Key Points

      • Adaptive staggered grid method for variable viscosity Stokes
      • Stress conservative hanging node approximation
      • Demonstrated robustness of new adaptive staggered grid stencil
    27. Influence of rotation on the metal rain in a Hadean magma ocean (pages 1226–1244)

      A. Moeller and U. Hansen

      Article first published online: 30 APR 2013 | DOI: 10.1002/ggge.20087

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      Key Points

      • Rotation can have a strong influence on iron droplets an a Hadean magma ocean
      • Iron droplets stay suspended at the equator at high enough rotation rates
      • At the poles rotation has no influence on the settling of the iron
    28. High-resolution estimate for the depositional duration of the Triassic Latemar Platform: A new magnetostratigraphy and magnetic susceptibility cyclostratigraphy from basinal sediments at Rio Sacuz, Italy (pages 1245–1257)

      Z. P. Spahn, K. P. Kodama and N. Preto

      Article first published online: 30 APR 2013 | DOI: 10.1002/ggge.20094

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      Key Points

      • Magnetostratigraphy at Rio Sacuz limits deposition to 1-2 myr
      • Cyclostratigraphy at Rio Sacuz furthers refines deposition to 1 myr
      • Correlation to Latemar shows 1 m cycles are sub-Milankovitch in duration
    29. Changes in planktic and benthic foraminifer assemblages in the Gulf of Lions, off south France: Response to climate and sea level change from MIS 6 to MIS 11 (pages 1258–1276)

      Aleix Cortina, Francisco Javier Sierro, Gabriel Filippelli, José Abel Flores and Serge Berné

      Article first published online: 30 APR 2013 | DOI: 10.1002/ggge.20096

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      Key Points

      • We used benthic and planktic foraminifers to monitor past climate variability
      • Eustatic changes are mainly driven by obliquity and the 100 ka cycle
      • Precessional forcing drove changes in the intensity of the northwesterly winds
    30. Confounding effects of coral growth and high SST variability on skeletal Sr/Ca: Implications for coral paleothermometry (pages 1277–1293)

      Craig A. Grove, Sebastian Kasper, Jens Zinke, Miriam Pfeiffer, Dieter Garbe-Schönberg and Geert-Jan A. Brummer

      Article first published online: 30 APR 2013 | DOI: 10.1002/ggge.20095

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      Key Points

      • Two corals of same species and location display opposite Sr/Ca long-term trends
      • The same two corals display opposite Sr/Ca anomalies during ENSO years
      • Sr/Ca differences related to opposing coral growth parameters and SST
    31. Seismic stratigraphic evidence for glacial expanse during glacial maxima in the Yakutat Bay Region, Gulf of Alaska (pages 1294–1311)

      Christopher R. Elmore, Sean P. S. Gulick, Bryce Willems and Ross Powell

      Article first published online: 30 APR 2013 | DOI: 10.1002/ggge.20097

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      Key Points

      • Erosion and depositional surfaces map glacial advance -retreat
      • Malaspina Glacier controls glacial sequences in Yakutat region
      • grounding zone wedges mark retreat sequences
  3. Technical Brief

    1. Top of page
    2. Research Letter
    3. Regular Articles
    4. Technical Brief
    1. Unmixing of stable isotope signals using single specimen δ18O analyses (pages 1312–1320)

      J.C. Wit, G.J. Reichart and G.M. Ganssen

      Article first published online: 30 APR 2013 | DOI: 10.1002/ggge.20101

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      Key Points

      • Foraminiferal single specimen stable isotope analyses can identify bioturbation
      • Bioturbation can be quantified and corrected using a simple model

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