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dc.contributor.advisorTimothy L. Grove.en_US
dc.contributor.authorParman, Stephen Wayneen_US
dc.contributor.otherMassachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences.en_US
dc.date.accessioned2010-05-25T20:37:19Z
dc.date.available2010-05-25T20:37:19Z
dc.date.copyright2001en_US
dc.date.issued2001en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/55064
dc.descriptionThesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, February 2001.en_US
dc.descriptionIncludes bibliographical references.en_US
dc.description.abstractExperimental phase equilibria, whole rock major and trace element concentrations, and mineral major and trace element concentrations are used to constrain the petrogenesis of high degree, hydrous melts of the mantle, with particular focus on komatiites from the Barberton Mountainland, South Africa. Chapter 1 presents experiments on a Barberton komatiite composition under anhydrous and H20 saturated conditions. A comparison of the compositions of augite in the experiments with augite in the samples indicates that at least 4.5 wt.% H20 was present in the komatiite melts prior to emplacement. The presence of H20 in the magmas would allow them to be produced at lower temperatures than required by anhydrous models of komatiite genesis, and would obviate the need for extremely high temperatures in the Archean mantle. In Chapter 2, ion probe analyses of augite in Barberton komatiites are used to quantify the effects that metamorphism has had on the bulk rock compositions. The results indicate that high field strength elements and most rare earth elements were not significantly mobilized by metamorphism, while Eu and Sr were mobilized. Some Barberton magmas were enriched in light rare earth elements and Sr, and depleted in high field strength elements, which are the chemical characteristics of modem subduction related magmas. Chapter 3 presents melting experiments that explore the effect of H20 on melts in equilibrium with olivine and orthopyroxene at 1.2 to 2.4 GPa. The results of the experiments are used to infer the thermodynamic properties of H20 in silicate melts, and to construct a numerical model that predicts the composition of high degree mantle melts. The model is used to estimate the melting conditions that produced high-MgO andesites, boninites, and komatiites. It is shown that Barberton komatiites can be produced by melting at low pressures (2.4-3.0 GPa) and temperatures (1440-1500 °C). Chapter 4 demonstrates that basaltic komatiites overlap the compositions of modem boninites and display nearly identical trace element systematics. Komatiites are also shown to have numerous chemical similarities to boninites as well. It is proposed that komatiites and basaltic komatiites were produced by the same processes that produce modem boninites. The lack of komatiites in modem subduction zones is attributed to -100*C secular mantle cooling that has occurred since 3.5 Ga.en_US
dc.description.statementofresponsibilityby Stephen Wayne Parman.en_US
dc.format.extent239 p.en_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsM.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582en_US
dc.subjectEarth, Atmospheric, and Planetary Sciences.en_US
dc.titlePetrology and geochemistry of high degree mantle meltsen_US
dc.typeThesisen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
dc.identifier.oclc48069856en_US


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