Mineral-mineral partition coefficients (D) measured on mantle peridotites by ICP-MS can compliment what is known from experimental studies and put additional constraints on the temperature, pressure and compositional dependence of trace element partitioning in the mantle. Analyses of the data collected here shows that temperature and Na content of the clinopyroxene have the largest effect on trace element partitioning between ortho-and clinopyroxene in spinel peridotites. The Ca-Tschermak molecule in clinopyroxene, in turn, has a lesser control on partitioning in the natural sample than observed experimentally. Importantly chemical disequilibrium or transient metasomatic effects appear to control the orthopyroxene/clinopyroxene partitioning for the most incompatible elements, and that partitioning is a function of orthopyroxene concentration. The first 57Mössbauer determinations of Fe3+/ΣFe ratios in lherzolitic spinels and pyroxenitic garnet-clinopyroxene pairs from xenoliths of the sub-oceanic mantle beneath Hawai'i give a range in calculated oxygen fugacity (fO2) of 4 log units (-3 to +1 ΔlogfO2 (FMQ)). The Hawaiian peridotites are more oxidized than the oceanic upper mantle as recorded in MORB and abyssal peridotites, but less oxidized than arc peridotites. There are no correlations between fO2 and temperature or major element compositions. Instead, correlations between light REE DOpx/Cpx and fO2 in the peridotites suggests that metasomatism affects oxygen fugacity decoupled from the degree of melt depletion. The garnet pyroxenites are more reduced than the peridotites and estimates of the oceanic upper mantle. The fO2 of Hawaiian pyroxenites is the product of complex interaction between melts buffered with changing volatile species from predominantly H2O at reducing conditions to CO2-rich at the pressure, temperature and fO2 of the peridotites. A relationship between Mg# and Fe3+/ΣFe ratios in both clinopyroxene and garnet that is not evident in garnet peridotites points to evolution of the parent melt as controlling the bulk Fe2O3 of the pyroxenite cumulates. Koidu eclogites, with Nb/Ta ratios varying from sub- to superchondritic, have Nd and Hf isotopic compositions that are decoupled. The Nd-Hf isotopic compositions indicate an origin other than subducted oceanic crust. Unradiogenic Pb-isotope ratios indicate these eclogites have an ancient component (>2 Ga). Coincidental high Nb/Ta ratios, unradiogenic Sr and Pb isotopes require the involvement of a fluid to fractionate Rb/Sr, U/Pb and Nb/Ta. This process is consistent with dehydration during Archean subduction, however, Nd and Hf isotopic compositions are complicated by multiple fractionation events and open system behaviour that does not identify a common precursor. If the high Nb/Ta reservoir is composed of Koidu type eclogite, the extreme isotopic compositions measured here preclude them from participating in any meaningful way to present day basaltic volcanism (MORB-OIB array). / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Sciences in partial fulfillment of the requirements for the degree of Doctor of
Philosophy. / Fall Semester, 2010. / October 25, 2010. / eclogite, Koidu, Sr isotopes, Nd isotopes, Pb isotopes, Hf isotopes, HI, garnet pyroxenite, xenolith, trace elements, LA-ICP-MS, Mossbauer, oxygen fugacity, spinel peridotite / Includes bibliographical references. / Vincent J. M. Salters, Professor Directing Dissertation; Michael Bizimis, Professor Co-Directing Dissertation; Albert E. Stiegman, University Representative; Munir Humayun, Committee Member; Leroy A. Odom, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_182717 |
| Contributors | Tibbetts, Nicole Jessica (authoraut), Salters, Vincent J. M. (professor directing dissertation), Bizimis, Michael (professor co-directing dissertation), Stiegman, Albert E. (university representative), Humayun, Munir (committee member), Odom, Leroy A. (committee member), Department of Earth, Ocean and Atmospheric Sciences (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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