The Cobb hot spot: HIMU-DMM mixing and melting controlled by a progressively thinning lithospheric lid Public Deposited

http://ir.library.oregonstate.edu/concern/articles/h415pc55w

To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at:  http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/%28ISSN%291525-2027/.

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  • The Cobb Seamount Chain in the northeast Pacific basin records the composition of the Cobb hot spot for the past 33 Myr, as the migrating Juan de Fuca Ridge approached and ultimately overran it ca. 0.5 Myr ago. In this first comprehensive geochemical study of the Cobb chain, major and trace element compositions and Sr, Nd, Pb, and Hf isotopic ratios were measured for whole-rock samples from throughout the chain, and He isotopes were acquired for olivine phenocrysts from one seamount. Trace element modeling indicates increased melting along the chain over time, with progressively more depleted lavas as the ridge approached the hot spot. The isotopic data reveal the first evidence of the high μ (μ = ²³⁸U/²⁰⁴Pb) (HIMU) mantle component in the north Pacific basin and are consistent with a progressively decreasing mixing proportion of HIMU melts relative to those from depleted mid-ocean ridge basalt mantle (DMM) in the chain over time. Decreasing lithospheric thickness over the Cobb hot spot due to the approach of the migrating Juan de Fuca ridge allowed adiabatic melting to continue to shallower depths, leading to increased melt fractions of the refractory DMM component in the hot spot and more depleted and MORB-like lavas in the younger Cobb seamounts.
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  • Chadwick, J., R. Keller, G. Kamenov, G. Yogodzinski, and J. Lupton (2014). The Cobb hot spot: HIMU-DMM mixing and melting controlled by a progressively thinning lithospheric lid. Geochemistry Geophysics Geosystems, 15(8), 3107–3122. doi:10.1002/2014GC005334
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  • description.provenance : Approved for entry into archive by Erin Clark(erin.clark@oregonstate.edu) on 2014-11-03T21:54:22Z (GMT) No. of bitstreams: 1 KellerRandallCEOASCobbHotSpot.pdf: 1352841 bytes, checksum: d7c3d0e988681ee436190a1e9d808448 (MD5)
  • description.provenance : Submitted by Erin Clark (erin.clark@oregonstate.edu) on 2014-11-03T21:54:00Z No. of bitstreams: 1 KellerRandallCEOASCobbHotSpot.pdf: 1352841 bytes, checksum: d7c3d0e988681ee436190a1e9d808448 (MD5)
  • description.provenance : Made available in DSpace on 2014-11-03T21:54:22Z (GMT). No. of bitstreams: 1 KellerRandallCEOASCobbHotSpot.pdf: 1352841 bytes, checksum: d7c3d0e988681ee436190a1e9d808448 (MD5) Previous issue date: 2014-08

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