Geochemical characerization of endmember mantle components
Name
65167495-MIT.pdf
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22.12 MB
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3559b257dc232c63df735737b552c47a
Author(s)
Workman, Rhea K
Advisor(s)
Stanley R. Hart.
Date Issued
2005
Publisher
Massachusetts Institute of Technology
Abstract
This thesis uses trace elements and radiogenic isotope tracers to define elemental abundances in reservoirs of the Earth's mantle, including EM2 (the Enriched Mantle 2), as seen in the Samoan hotspot track, and DMM (the depleted upper mantle), which is sampled at mid-ocean ridges. Together these components comprise up to [approx.] 50% of the total mantle mass. Much of the mantle's chemical heterogeneities are suspected to originate by either the removal of mass from the mantle (in the case of DMM) or the addition of mass to the mantle through subduction zones (in the case of EM2). We show that DMM represents mantle that 1) has been previously depleted by 2-3% melt removal, 2) mass-balances well with the continental crust, 3) has only 15% of the radiogenic heat production in primitive upper mantle and 4) can generate present-day ocean crust by 6% aggregated fractional melting. EM2 is classically interpreted as mantle material enriched in trace elements through the ancient, subduction-zone recycling of terrigenous sediments; here we show this model is unlikely and provide two other working hypotheses.
(cont.) The first is recycling of melt- impregnated oceanic lithosphere; the second is recycling of a mantle wedge impregnated with melt from a subducting oceanic plate.
Description
Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2005.
Includes bibliographical references.
Subjects
Joint Program in Oceanography.
Earth, Atmospheric, and Planetary Sciences.
Woods Hole Oceanographic Institution.
MIT Department
Joint Program in Oceanography
Woods Hole Oceanographic Institution
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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