dc.contributor.advisor	Brandon, Alan D.
dc.contributor.committeeMember	Snow, Jonathan E.
dc.contributor.committeeMember	Fu, Qi
dc.contributor.committeeMember	Sager, William W.
dc.contributor.committeeMember	Costin, Gelu
dc.creator	Sen, Atlanta
dc.date.accessioned	2022-06-15T22:32:38Z
dc.date.created	December 2021
dc.date.issued	2021-12
dc.date.submitted	December 2021
dc.date.updated	2022-06-15T22:32:39Z
dc.description.abstract	Mantle peridotites have been widely sampled in the ocean basins. These are considered residues of the melting process that ultimately results in the formation of the oceanic crust. However, the exact mechanism for their evolution has not been comprehensively understood. Plagioclase-bearing mantle rocks, for example, may be formed by fractional crystallization, melt-rock reaction and assimilation in the crust and shallow mantle. Nearly all mid-ocean ridge basalts (MORB) are believed to have at least some melt-rock reaction process in their evolutionary history. Yet, there is a lack of direct evidence that captures the reaction textures or intermediate compositions of the melt-rock reaction process. Spreading centers and oceanic core complexes (OCC) provide a window to understand melt evolution processes in the lower crust and upper mantle. In this study we address the ongoing debate about the mechanism of melt transport in the mantle by textural and chemical analysis (major and trace elements) of samples from two unique tectonic regimes; a. the Hess Deep (fast spreading center in the Equatorial Pacific Ocean) and the Mado Megamullion (an OCC in the Shikoku back-arc basin). Magnetic anomaly data suggested that spreading in the Shikoku basin ceased after 15 Ma although the age of termination of spreading has not been constrained from geochronologic evidences until now. We integrated the model results with the natural samples to quantify the evolution of the peridotites. We dated zircons from amphibole-chlorite bearing veins that crosscut the peridotites of the Mado Megamullion. The U-Pb age of 13.37 ± 0.24 Ma and the trace and rare earth element (REE) chemistry of the zircons and the amphiboles suggests the possibility that magmatic activity and back-arc spreading at the Shikoku basin continued till 13 Ma. We could model the elevated TiO2 content in melt-reacted plagioclase-bearing peridotites from Hess Deep through assimilation fractional crystallization (AFC) process which could not be modelled by fractional crystallization process alone and has remained a topic of debate. Our results also show that back-arc basin peridotites at Mado Megamullion appear to have a unique petrographic and geochemical character that is distinct from those mid-ocean ridges or fore-arcs.
dc.description.department	Earth and Atmospheric Sciences, Department of
dc.format.digitalOrigin	born digital
dc.format.mimetype	application/pdf
dc.identifier.uri	https://hdl.handle.net/10657/9192
dc.language.iso	eng
dc.rights	The author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).
dc.subject	Hess Deep
dc.subject	Mado Megamullion
dc.subject	partial melting
dc.subject	melt-rock reaction
dc.subject	amphibole bearing peridotites
dc.subject	zircon geochronology
dc.title	Geochemistry and Evolution of the Earth’s Mantle at the Hess Deep and the Mado Megamullion
dc.type.dcmi	Text
dc.type.genre	Thesis
dcterms.accessRights	The full text of this item is not available at this time because the student has placed this item under an embargo for a period of time. The Libraries are not authorized to provide a copy of this work during the embargo period.
local.embargo.lift	2023-12-01
local.embargo.terms	2023-12-01
thesis.degree.college	College of Natural Sciences and Mathematics
thesis.degree.department	Earth and Atmospheric Sciences, Department of
thesis.degree.discipline	Geology
thesis.degree.grantor	University of Houston
thesis.degree.level	Doctoral
thesis.degree.name	Doctor of Philosophy

Geochemistry and Evolution of the Earth’s Mantle at the Hess Deep and the Mado Megamullion

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