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dc.contributor.authorLaubier, Muriel
dc.contributor.authorGale, Allison
dc.contributor.authorLangmuir, Charles H.
dc.date.accessioned2017-04-13T16:42:53Z
dc.date.issued2012
dc.identifierQuick submit: 2013-07-18T14:13:35-04:00
dc.identifier.citationLaubier, Muriel, Allison Gale, and Charles H. Langmuir. 2012. Melting and crustal processes at the FAMOUS segment (Mid-Atlantic Ridge): New insights from olivine-hosted melt inclusions from multiple samples. Journal of Petrology 53, no. 4: 665-698.en_US
dc.identifier.issn0022-3530en_US
dc.identifier.urihttp://nrs.harvard.edu/urn-3:HUL.InstRepos:32116888
dc.description.abstractMost published studies of olivine-hosted melt inclusions from mid-ocean ridges have been based on a single sample. Here we present a comprehensive melt inclusion study of major and trace elements from a single ocean ridge segment, the FAMOUS segment of the Mid-Atlantic Ridge. The melt inclusion dataset includes 312 olivine-hosted (Mg-number 85–92) melt inclusions from 14 samples distributed along the segment. This permits a more comprehensive assessment of the variability within melt inclusions from a single region, and of the relationship between melt inclusion and lava compositions. One recent question has been the extent to which melt inclusions truly preserve the original melt compositions, or instead are modified by late-stage processes occurring at shallow levels. In the FAMOUS inclusions, major elements have been affected by post-entrapment processes, but trace elements show no evidence of such processes, suggesting that diffusion coefficients for incompatible elements are small. Melt inclusions can be divided into three groups. (1) High-Mg inclusions are the most primitive and may potentially constrain the composition of the parental magmas that contribute to other melt inclusion and lava compositions. Although their trace element contents range from highly depleted to almost as enriched as the FAMOUS segment lavas, they are on average more depleted and the melts appear to be derived by greater extents of melting than the lavas. (2) Low-Al inclusions occur in the lower Mg-number olivines, and their major and trace element characteristics reflect mixing between high-Mg melt inclusion and lava compositions. (3) High-Al melt inclusions display Al\(_{2}\)O\(_{3}\) contents as high as 18·4 wt %, SiO\(_{2}\) as low as 46·6 wt %, a strong depletion in the most incompatible elements and distinctively low middle to heavy rare earth element (MREE/HREE) ratios. The high Al\(_{2}\)O\(_{3}\) and low SiO\(_{2}\) contents, as well as positive Sr anomalies in some of the high-Al melt inclusions, are best explained by assimilation of plagioclase-bearing cumulates. The trace element variability in the high-Mg melt inclusions is not consistent with a simple continuous melting column and requires pooling of near-fractional melts within the melting regime and a variable mantle source composition. Because the mean composition of these melt inclusions reflects greater extents of melting than the lavas, we propose that the melt inclusions come from the upper portions of the melting regime. Lavas, in contrast, sample the entire melting regime, including low-degree melts from the wings of the regime that are transported more directly to the surface along high-porosity channels. The high-Al, trace element ultra-depleted, low MREE/HREE melt inclusions derive from melting of a residual mantle source formed by previous melt extraction in the garnet stability field. There is a marked lack of correspondence between major and trace element variations in the melt inclusions. This may reflect a combination of processes, such as cumulate assimilation and re-equilibration of the magmas during ascent, which can reset major elements while having little effect on the trace element variations. The melt inclusions are not simply representative unpooled melts from the melting regime and they do not fully reflect the range of melt compositions contributing to the lavas. Their compositions reflect source heterogeneity as well as melting processes, and major and trace element indicators of depth of origin do not correspond. Combined comprehensive studies of lavas and melt inclusions have much more to reveal than studies based on either data source alone.en_US
dc.description.sponsorshipEarth and Planetary Sciencesen_US
dc.language.isoen_USen_US
dc.publisherOxford University Pressen_US
dc.relation.isversionofdoi:10.1093/petrology/egr075en_US
dash.licenseMETA_ONLY
dc.subjectmelt inclusionen_US
dc.subjectmid-ocean ridgeen_US
dc.subjectolivineen_US
dc.subjectpartial meltingen_US
dc.titleMelting and Crustal Processes at the FAMOUS Segment (Mid-Atlantic Ridge): New Insights from Olivine-hosted Melt Inclusions from Multiple Samplesen_US
dc.typeJournal Articleen_US
dc.date.updated2013-07-18T18:14:07Z
dc.description.versionVersion of Recorden_US
dc.rights.holderLaubier, Muriel Gale, Allison Langmuir, Charles H.
dc.relation.journalJournal of Petrologyen_US
dash.depositing.authorLangmuir, Charles H.
dash.embargo.until10000-01-01
dc.identifier.doi10.1093/petrology/egr075*
workflow.legacycommentsLangmuir emailed 2016-04-20 MM Langmuir emailed 2017-02-18 MM meta.darken_US
dash.contributor.affiliatedGale, Allison
dash.contributor.affiliatedLaubier, Muriel
dash.contributor.affiliatedLangmuir, Charles


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