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Title: Cumulus processes and melt-migration in layered intrusions and the use of image analysis to quantify microscopic textures in cumulates.
Author: Elias, Ralph Thomas.
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 1991
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This thesis presents three studies carried out to investigate the relationship between small scale structures and large scale processes in layered intrusions. The first is a field-based study from the Eastern Layered Series of the Rhum intrusion. Lateral variations were found to be significant in the allivalite of unit 12 on Hallival, and the cumulate stratigraphy was shown to thin by approximately 50% over less than 800 metres down-dip. This thinning was associated with the development of layeringparallel zones of intense deformation and the entire cumulate package is interpreted to have evolved as a sequence of alternating troctolitic and peridotitic mass flows initiated by the intrusion of basaltic melts into marginal cumulates. In addition, a series of gabbroic cumulates were interpreted as preserving melt-migration pathways within still-porous cumulates. Cumulus textures were found to control porosity-permeability relationships in the crystal pile. The effect of anisotropy on the movement of melts was studied. Core material from the Muskox layered intrusion was analysed to constrain compaction and showed it to be a widespread process which reduced melt contents to -10% over cumulate depths of 1000 metres, in less than 600 years. Progressive contamination of Muskox primary melts resulted in a change from olivine-rich to pyroxene-rich cumulates and this lea to an increase in matrix viscosity from <5x10 15 Pa s to -4x1016. The final part of the thesis concentrates on the quantification of interfacial curvature, a parameter which dominates the evolution of textures by surface energy minimization. Software is presented to allow the determination of variations in two dimensional grain boundary curvatures by curve-fitting method using a cubic spline. The software is tested on experimental olivinebasalt aggregates.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Geology Geology Mineralogy Sedimentology Geochemistry