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    Distributed deformation ahead of the Cocos-Nazca Rift at the Galapagos triple junction

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    2011GC003689.pdf (5.357Mb)
    Date
    2011-11-08
    Author
    Smith, Deborah K.  Concept link
    Schouten, Hans A.  Concept link
    Zhu, Wenlu  Concept link
    Montesi, Laurent G. J.  Concept link
    Cann, Johnson R.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/4937
    As published
    https://doi.org/10.1029/2011GC003689
    DOI
    10.1029/2011GC003689
    Keyword
     East Pacific Rise; Galapagos triple junction; Crack propagation; Triple junction 
    Abstract
    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.
    Description
    Author Posting. © American Geophysical Union, 2011. 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 12 (2011): Q11003, doi:10.1029/2011GC003689.
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    • Geology and Geophysics (G&G)
    Suggested Citation
    Geochemistry Geophysics Geosystems 12 (2011): Q11003
     

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