Insights into the location, nature and influence of mantle heterogeneity in the Galápagos mantle plume

Ocean Island Basalts (OIBs) and Mid-Ocean Ridge Basalts (MORBs) provide a window into the composition, lithological properties, and volatile content of the Earth's, highly heterogeneous, convecting mantle. Our view of the Earth's mantle is, however, partially obscured by processes that influence mantle-derived melts as they transition through the lithosphere (e.g. mixing, assimilation). Nevertheless, via careful consideration of the magmatic processes that may influence these mantle-derived melts, we can use OIBs and MORBs to place important constraints on the composition and dynamics of the Earth's convecting mantle. This study focuses on the Galápagos Archipelago, one of the most volcanically active regions in the world, where volcanic activity is derived from melting in a deep-seated mantle plume (possibly originating at the core-mantle boundary). The Galápagos mantle plume is hypothesised to contain primordial and depleted mantle material, as well as at least one component that may represent recycled oceanic crust. Therefore, the Galápagos Archipelago, and nearby Galápagos Spreading Centre, represent an ideal location to study the location, nature and influence of mantle heterogeneity in an upwelling mantle plume. This thesis addresses four key aspects of magmatic activity in the Galápagos Archipelago: (i) the presence of pyroxenite (recycled) components in the Galápagos mantle plume [Chapters 2 and 3]; (ii) the nature and implications of plume-ridge interaction in the Galápagos [Chapters 3 and 4]; (iii) the volatile content of the Galápagos mantle plume [Chapters 4 and 6]; and (iv) the magmatic processes that operate beneath low-melt flux regions of the Galápagos Archipelago [Chapter 5]. As a result, this thesis provides fresh new insights into the nature of mantle heterogeneity beneath the Galápagos and the influence of mantle heterogeneity on the crustal processing of magmas in the Galápagos Archipelago.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2019

Author dc:creator

• Gleeson, Matthew

Advisor dc:contributor.advisor

• Gibson, Sally

• Geology
• Pyroxenite
• Mantle Geochemistry
• Volcanology
• Igneous Petrology

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/1235caf0-3862-481b-a71c-664714d6e5d2/download
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

eng

Author Identifier

0000-0003-0839-5492

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/308052