Geochemical characterization of endmember mantle components
Workman, Rhea K.
MetadataShow full item record
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 -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. 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.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2005
Suggested CitationThesis: Workman, Rhea K., "Geochemical characterization of endmember mantle components", 2005-06, DOI:10.1575/1912/1622, https://hdl.handle.net/1912/1622
Showing items related by title, author, creator and subject.
Trace element geochemistry of oceanic peridotites and silicate melt inclusions : implications for mantle melting and ocean ridge magmagenesis Johnson, Kevin T. M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1990-06-15)The mantle melting process is fundamental to basalt genesis and crustal accretion at mid-ocean ridges. It is believed that melts ascend more rapidly than the surrounding mantle, implying a process similar to fractional ...
Warren, Jessica M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2007-09)I provide constraints on mantle convection through observations of the rheology and composition of the oceanic upper mantle. Convection cannot be directly observed, yet is a fundamental part of the plate tectonic cycle. ...
Macdonald, Alison M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1995-08)Data from fifteen globally distributed, modern, high resolution, hydrographic oceanic transects are combined in an inverse calculation using large scale box models. The models provide estimates of the global meridional ...