Lithosphere versus asthenosphere mantle sources at the Big Pine Volcanic Field, California

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dc.citation.issueNumber1en_US
dc.citation.journalTitleGeochemistry Geophysics Geosystemsen_US
dc.citation.volumeNumber13en_US
dc.contributor.authorGazel, Estebanen_US
dc.contributor.authorPlank, Terryen_US
dc.contributor.authorForsyth, Donald W.en_US
dc.contributor.authorBendersky, Claireen_US
dc.contributor.authorLee, Cin-Ty A.en_US
dc.contributor.authorHauri, Erik H.en_US
dc.date.accessioned2013-01-30T17:03:39Zen_US
dc.date.available2013-07-31T05:10:05Zen_US
dc.date.issued2012en_US
dc.description.abstract[1] Here we report the first measurements of the H2O content of magmas and mantle xenoliths from the Big Pine Volcanic Field (BPVF), California, in order to constrain the melting process in the mantle, and the role of asthenospheric and lithospheric sources in this westernmost region of the Basin and Range Province, western USA. Melt inclusions trapped in primitive olivines (Fo82–90) record surprisingly high H2O contents (1.5 to 3.0 wt.%), while lithospheric mantle xenoliths record low H2O concentrations (whole rock <75 ppm). Estimates of the oxidation state of BPVF magmas, based on V partitioning in olivine, are also high (FMQ +1.0 to +1.5). Pressures and temperatures of equilibration of the BPVF melts indicate a shift over time, from higher melting temperatures (∼1320°C) and pressures (∼2 GPa) for magmas that are >500 ka, to cooler (∼1220°C) and shallower melting (∼1 GPa) conditions in younger magmas. The estimated depth of melting correlates strongly with some trace element ratios in the magmas (e.g., Ce/Pb, Ba/La), with deeper melts having values closer to upper mantle asthenosphere values, and shallower melts having values more typical of subduction zone magmas. This geochemical stratification is consistent with seismic observations of a shallow lithosphere-asthenosphere boundary (∼55 km depth). Combined trace element and cryoscopic melting models yield self-consistent estimates for the degree of melting (∼5%) and source H2O concentration (∼1000 ppm). We suggest two possible geodynamic models to explain small-scale convection necessary for magma generation. The first is related to the Isabella seismic anomaly, either a remnant of the Farallon Plate or foundered lithosphere. The second scenario is related to slow extension of the lithosphere.en_US
dc.embargo.terms6 monthsen_US
dc.identifier.citationGazel, Esteban, Plank, Terry, Forsyth, Donald W., et al.. "Lithosphere versus asthenosphere mantle sources at the Big Pine Volcanic Field, California." <i>Geochemistry Geophysics Geosystems,</i> 13, no. 1 (2012) American Geophysical Union: http://dx.doi.org/10.1029/2012GC004060.en_US
dc.identifier.doihttp://dx.doi.org/10.1029/2012GC004060en_US
dc.identifier.urihttps://hdl.handle.net/1911/69887en_US
dc.language.isoengen_US
dc.publisherAmerican Geophysical Unionen_US
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.en_US
dc.subject.keywordBasin and Rangeen_US
dc.subject.keywordlithosphere-asthenosphere boundaryen_US
dc.subject.keywordmelt inclusionsen_US
dc.subject.keywordshear wave tomographyen_US
dc.titleLithosphere versus asthenosphere mantle sources at the Big Pine Volcanic Field, Californiaen_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
dc.type.publicationpublisher versionen_US
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