Petrologic and microstructural constraints on focused melt transport in dunites and the rheology of the shallow mantle

Thumbnail Image
Date
2004-06
Authors
Braun, Michael Geoffrey
Linked Authors
Alternative Title
As Published
Date Created
Location
Oman ophiolite
DOI
10.1575/1912/1856
Replaced By
Keywords
Mid-ocean ridges
Mantle
Microstructure
Abstract
Observations at mid-ocean ridges indicate that magmas are focused to the ridge axis by a network of porous dunites in near chemical isolation. This thesis investigates several of the outstanding questions regarding the mechanisms of melt transport and its effects on the shallow mantle. Chapter 1 details the current understanding of melt migration from observations at mid-ocean ridges and ophiolites. Chapter 2 uses the size distribution and abundance of dunites measured in the Oman ophiolite to place limits on the potential mechanisms by which dunites form and subsequently estimate the flux of chemically unequilbrated melt which a network of dunites can supply. Chapter 3 characterizes the chemical composition of dunites and harzburgites from Oman to further constrain the process by which dunites form and relates the observed trends within dunites to variations in the time-integrated meltrock ratio. Chapter 4 examines the microstructures of peridotites in Oman to constrain the deformation mechanisms which determine the viscosity of shallow mantle. Chapter 5 is a numerical investigation of advection beneath ridges incorporating the rheology inferred from the observed microstructures. Chapter 6 integrates the conclusions of the previous chapters, reevaluating the potential melt flux through dunites and constraining the permeabilty of the shallow mantle.
Description
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 2004
Embargo Date
Citation
Braun, M. G. (2004). Petrologic and microstructural constraints on focused melt transport in dunites and the rheology of the shallow mantle [Doctoral thesis, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution]. Woods Hole Open Access Server. https://doi.org/10.1575/1912/1856
Cruises
Cruise ID
Cruise DOI
Vessel Name