Geochemistry, Geophysics, Geosystems

Cover image for Geochemistry, Geophysics, Geosystems

January 2012

Volume 13, Issue 1

    1. On recent seismic tomography for the western United States

      T. W. Becker

      Article first published online: 7 MAR 2012 | DOI: 10.1029/2011GC003977

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      Key Points

      • All new western U.S. tomography models show the same patterns
      • Shear and compressional wave anomaly amplitudes are hugely different
      • Small-scale structure is mapped robustly, but interpretation for density unclear
    2. Online preconcentration ICP-MS analysis of rare earth elements in seawater

      Ed C. Hathorne, Brian Haley, Torben Stichel, Patricia Grasse, Moritz Zieringer and Martin Frank

      Article first published online: 31 JAN 2012 | DOI: 10.1029/2011GC003907

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      Key Points

      • Commercially available fully automated preconcentration system coupled to ICP-MS
      • Technique has good precision and accuracy for open ocean seawater samples
      • Advantageous for minimal sample preparation and small volume consumed (7 mL)
    3. Deformation and seismicity associated with continental rift zones propagating toward continental margins

      V. Lyakhovsky, A. Segev, U. Schattner and R. Weinberger

      Article first published online: 31 JAN 2012 | DOI: 10.1029/2011GC003927

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      Key Points

      • Rock weakening in the rift zone provides solution for the tectonic force paradox
      • Rift development and seismicity depends on tectonic force and rock memory
      • Rift zone may terminate at the continental margins where new fault system forms
    4. High precision nitrogen isotope measurements in oceanic basalts using a static triple collection noble gas mass spectrometer

      P. H. Barry, D. R. Hilton, S. A. Halldórsson, D. Hahm and K. Marti

      Article first published online: 31 JAN 2012 | DOI: 10.1029/2011GC003878

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      Key Points

      • New system for the simultaneous static triple-collection of nitrogen isotopes
      • Measured nitrogen isotopes (delta15N), concentrations and N2/Ar ratios on 11 basalts
      • Reduced analytical times and CO and blank corrections improve reproducibility
    5. Global oceanic microseism sources as seen by seismic arrays and predicted by wave action models

      G. Hillers, N. Graham, M. Campillo, S. Kedar, M. Landès and N. Shapiro

      Article first published online: 31 JAN 2012 | DOI: 10.1029/2011GC003875

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      Key Points

      • Microseisms are excited in the deep oceans and along the coast
      • Global excitation patterns follow the seasons
      • Wave action models suggest global excitation hot spots
    6. Generation and evolution of hydrothermal fluids at Yellowstone: Insights from the Heart Lake Geyser Basin

      J. B. Lowenstern, D. Bergfeld, W. C. Evans and S. Hurwitz

      Article first published online: 28 JAN 2012 | DOI: 10.1029/2011GC003835

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      Key Points

      • Combines heat and mass flux data to reveal origins of thermal fluid
      • Uses chemical and isotopic data to model boiling and mixing processes
      • Helps understand broader impact for Yellowstone hydrothermal system
    7. Physical properties of surface outcrop cataclastic fault rocks, Alpine Fault, New Zealand

      C. Boulton, B. M. Carpenter, V. Toy and C. Marone

      Article first published online: 28 JAN 2012 | DOI: 10.1029/2011GC003872

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      Key Points

      • Cataclasites and fault gouges have distinct physical properties
      • Quantitative XRD results reveal in situ and along-strike changes in mineralogy
      • Fault gouges have repeatedly accommodated coseismic slip
    8. Reconstructing past upwelling intensity and the seasonal dynamics of primary productivity along the Peruvian coastline from mollusk shell stable isotopes

      James Sadler, Matthieu Carré, Moufok Azzoug, Andrew J. Schauer, Jesus Ledesma, Fredy Cardenas, Brian M. Chase, Ilhem Bentaleb, Serge D. Muller, Magloire Mandeng, Eelco J. Rohling and Julian P. Sachs

      Article first published online: 27 JAN 2012 | DOI: 10.1029/2011GC003595

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      Key Points

      • Methodological advance for the use of mollusk geochemistry in paleoceanography
      • New shell d13C and d18O interpretation model
      • New perspectives for the study of long-term variability in coastal upwellings
    9. Origin of localized fast mantle flow velocity in numerical models of subduction

      Magali I. Billen and Margarete Jadamec

      Article first published online: 27 JAN 2012 | DOI: 10.1029/2011GC003856

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      Key Points

      • Fast mantle flow surrounding subducting slabs arise from rheology and geometry
      • Simple models demonstrate fast flow is not an artifact of numerical methods
      • Locally, mantle flow rates may be many times faster than plate speeds
    10. You have free access to this content
      Correction to “Lithospheric control on geochemical composition along the Louisville Seamount Chain”

      Christoph Beier, Loÿc Vanderkluysen, Marcel Regelous, John J. Mahoney and Dieter Garbe-Schönberg

      Article first published online: 27 JAN 2012 | DOI: 10.1029/2011GC004012

      This article corrects:

      Lithospheric control on geochemical composition along the Louisville Seamount Chain

      Vol. 12, Issue 9, Article first published online: 30 SEP 2011

    11. Distribution of major elements in Atlantic surface sediments (36°N–49°S): Imprint of terrigenous input and continental weathering

      Aline Govin, Ulrike Holzwarth, David Heslop, Lara Ford Keeling, Matthias Zabel, Stefan Mulitza, James A. Collins and Cristiano M. Chiessi

      Article first published online: 20 JAN 2012 | DOI: 10.1029/2011GC003785

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      Key Points

      • Mapping major element distribution in Atlantic surface sediments
      • Imprint of terrigenous input on continental margin sediments
      • Terrigenous element ratios allow reliable reconstructions of terrestrial climate
    12. Magma chamber properties from integrated seismic tomography and thermal modeling at Montserrat

      M. Paulatto, C. Annen, T. J. Henstock, E. Kiddle, T. A. Minshull, R. S. J. Sparks and B. Voight

      Article first published online: 20 JAN 2012 | DOI: 10.1029/2011GC003892

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      Key Points

      • We image an active magma chamber with seismic tomography in unique detail
      • Integration of tomography with thermal models gives new insight into magmatism
      • Shallow magma chambers beneath arc volcanoes are transient and short lived
    13. Pliocene shortening direction in Nankai Trough off Kumano, southwest Japan, Sites IODP C0001 and C0002, Expedition 315: Anisotropy of magnetic susceptibility analysis for paleostress

      Toshiya Kanamatsu, Josep M. Parés and Yujin Kitamura

      Article first published online: 19 JAN 2012 | DOI: 10.1029/2011GC003782

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      Key Points

      • Magnetic fabrics of accretionary prism units were measured
      • They show NW–SE shortening directions
      • The directions agree with the direction of past plate subduction
    14. Geophysical and geochemical survey of a large marine pockmark on the Malin Shelf, Ireland

      M. T. Szpak, X. Monteys, S. O'Reilly, A. J. Simpson, X. Garcia, R. L. Evans, C. C. R. Allen, D. J. McNally, D. Courtier-Murias and B. P. Kelleher

      Article first published online: 19 JAN 2012 | DOI: 10.1029/2011GC003787

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      Key Points

      • A large composite pockmark on the Malin Shelf off the Irish coast was surveyed
      • Geophysical data confirmed the subsurface presence of fluids within the sediment
      • NMR microbial signatures coincide with spikes in conductivity
    15. Time domain parallelization for computational geodynamics

      Henri Samuel

      Article first published online: 18 JAN 2012 | DOI: 10.1029/2011GC003905

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      Key Points

      • Presents the first time domain parallel algorithm for computational geodynamics
      • Parallel linear speedups measured up to ∼10 using 40 CPUs
      • The algorithm can be combined with other parallel algorithms
    16. Fluid flow during slab unbending and dehydration: Implications for intermediate-depth seismicity, slab weakening and deep water recycling

      Manuele Faccenda, Taras V. Gerya, Neil S. Mancktelow and Louis Moresi

      Article first published online: 18 JAN 2012 | DOI: 10.1029/2011GC003860

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      Key Points

      • Double hydrated zone forms during slab unbending
      • Double Seismic Zones can be reconciled with the models
      • Implications for slab weakening and global water cycle
    17. A geodynamic model of plumes from the margins of Large Low Shear Velocity Provinces

      Bernhard Steinberger and Trond H. Torsvik

      Article first published online: 18 JAN 2012 | DOI: 10.1029/2011GC003808

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      Key Points

      • Sinking subducted slabs form a heavy chemical layer to dome-shaped structures
      • Slabs also push the thermal boundary layer toward the chemical domes
      • The TBL begins to rise at the steep edges of domes and forms mantle plumes
    18. Geochemical record of Holocene to Recent sedimentation on the Western Indus continental shelf, Arabian Sea

      David R. Limmer, Philipp Böning, Liviu Giosan, Camilo Ponton, Cornelia M. Köhler, Matthew J. Cooper, Ali R. Tabrez and Peter D. Clift

      Article first published online: 14 JAN 2012 | DOI: 10.1029/2011GC003845

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      Key Points

      • Some widely used geochemical proxies not suitable for weathering
      • Reworking is an important process in the Indus region
      • Continental shelves not necessarily good places for continental weathering
    19. Disentangling the Hettangian carbon isotope record: Implications for the aftermath of the end-Triassic mass extinction

      A. Bartolini, J. Guex, J. E. Spangenberg, B. Schoene, D. G. Taylor, U. Schaltegger and V. Atudorei

      Article first published online: 14 JAN 2012 | DOI: 10.1029/2011GC003807

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      Key Points

      • It concerns the interactions between biological events and carbon cycle
      • It highlights a new major positive organic carbon isotope event
      • It shows a perturbed carbon cycle during the end-Triassic post -crisis interval
    20. Hydrothermal plumes over the Carlsberg Ridge, Indian Ocean

      Durbar Ray, K. A. Kamesh Raju, Edward T. Baker, A. Srinivas Rao, Abhay V. Mudholkar, John E. Lupton, L. Surya Prakash, Rekha B. Gawas and T. Vijaya Kumar

      Article first published online: 14 JAN 2012 | DOI: 10.1029/2011GC003888

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      Key Points

      • Exploration for hydrothermal plumes over slow spreading Carlsberg Ridge
      • We report evidence for two vent fields on a segment that is sparsely magmatic
      • Fluid-rock interaction similar to Rainbow/Logatchev fields is inferred
    21. Conditions of Mytilus edulis extracellular body fluids and shell composition in a pH-treatment experiment: Acid-base status, trace elements and δ11B

      Agnes Heinemann, Jan Fietzke, Frank Melzner, Florian Böhm, Jörn Thomsen, Dieter Garbe-Schönberg and Anton Eisenhauer

      Article first published online: 12 JAN 2012 | DOI: 10.1029/2011GC003790

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      Key Points

      • Delta 11B Mytilus edulis shell material does not represent ambient water pH
      • Body fluid pCO2 in Mytilus edulis is in general high and pH therefore low
      • Elemental and isotope ratios are highly variable between and within individuals
    22. Volcanic-plutonic connections in a tilted nested caldera complex in Hong Kong

      Roderick J. Sewell, Denise L. K. Tang and S. Diarmad G. Campbell

      Article first published online: 12 JAN 2012 | DOI: 10.1029/2011GC003865

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      Key Points

      • Tilted nested caldera complex discovered in Hong Kong
      • Magmatic plumbing revealed in exceptional detail
      • Superscale activities comparable with other large caldera systems
    23. The case of the 1981 eruption of Mount Etna: An example of very fast moving lava flows

      Mauro Coltelli, Maria Marsella, Cristina Proietti and Silvia Scifoni

      Article first published online: 11 JAN 2012 | DOI: 10.1029/2011GC003876

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      Key Points

      • The time averaged discharge rate of the 1981 eruption and peak value
      • Comparison between the 1981 eruption and other basaltic eruption rates
      • Discharge mechanism model to explain the unusually high rate
    24. Temporal variations in 87Sr/86Sr and ɛNd in sediments of the southeastern Arabian Sea: Impact of monsoon and surface water circulation

      Vineet Goswami, Sunil K. Singh, Ravi Bhushan and Vinai K. Rai

      Article first published online: 6 JAN 2012 | DOI: 10.1029/2011GC003802

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      Key Points

      • Significant temporal variation in 87Sr/86Sr, eNd of sediments of SE Arabian Sea
      • Two major excursions at ∼9 ka and ∼20 ka coincide with known climate events
      • Results show significant control of climate on erosion and dispersal of sediments
    25. The role of the overriding plate thermal state on slab dip variability and on the occurrence of flat subduction

      Juan Rodríguez-González, Ana M. Negredo and Magali I. Billen

      Article first published online: 6 JAN 2012 | DOI: 10.1029/2011GC003859

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      Key Points

      • The effect of the thermal state of the upper plate is shown to be significant
      • We reproduce different subduction styles: flat, low angle, and steep subduction
      • Results are compared to the large dip variability of the Cocos slab

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