Accession Number:

ADA426948

Title:

Petrologic and Microstructural Constraints on Focused Melt Transport in Dunites and Rheology of the Shallow Mantle

Descriptive Note:

Doctoral thesis

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE

Personal Author(s):

Report Date:

2004-06-01

Pagination or Media Count:

215.0

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 unequilibrated 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 permeability of the shallow mantle,

Subject Categories:

  • Physical Chemistry
  • Geology, Geochemistry and Mineralogy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE