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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities

Lead Supervisor: Marie Edmonds, Earth Sciences

Co-Supervisors: Bruce Houghton, University of Hawaii

Importance of the area of research concerned: 
Magma mingling and mixing are common processes at basaltic volcanoes and play a fundamental role in magma petrogenesis and eruption dynamics; yet there are rarely opportunities to constrain their mechanisms and consequences directly. Mixed magmas may be generated in magma storage areas throughout the crust and be recognised from whole rock and glass compositional arrays. Magmas which have contrasting rheological properties, or interact on short timescales, exhibit mingling textures, in which gross features of interaction (such as enclaves, bands and streaks of one magma inside the other) are preserved on a range of lengthscales. These textures are in general generated during eruptions and are common, but not well understood, in basaltic volcanic systems. Magmas may be erupted, degassed and then incorporated back into the conduit, or held and decompressed at shallow depths, and then mixed with more primitive, undegassed magmas when the latter ascend from depth. In this case the rheological differences between the two magmas control the mingling or mixing regime. Low pressure mingling events may have important implications for eruptive dynamics, but have been poorly characterised.
Project summary : 
This project will focus on understanding mixing and mingling in basaltic volcanic systems that occurs during eruptions. In particular, the project will focus on understanding the textures that arise, syn-eruption, when magmas drain back into a conduit; when tephra deposits fall back into vents and are mingled with erupting magmas; and when shallowly stored magmas are incorporated into ascending, juvenile magmas. Case studies will include Grímsvötn Volcano, Iceland; Kilauea Volcano, Hawaii; and Stromboli, Italy.
What will the student do?: 
The student will undertake textural analysis of erupted products, using Scanning Electron microscope and optical microscope, combined with image analysis tools to characterise the textural characteristics of erupted products. The samples will be analysed for their bulk and constituent compositions, using XRF as well as microanalysis (EPMA, SIMS). High temperature experiments will be carried out to understand the rheological, textural and geochemical implications of mixing of basaltic magmas at atmospheric pressure and high temperature, and the results compared to the natural samples. Models will be generated in order to understand the origin and implications of tachylite and sideromelane components in basaltic volcanic rocks.
References - references should provide further reading about the project: 
Lautze NC, Houghton BF. Linking variable explosion style and magma textures during 2002 at Stromboli volcano, Italy. Bulletin of Volcanology. 2007 Feb 1;69(4):445-60.
Deardorff N, Cashman K. Rapid crystallization during recycling of basaltic andesite tephra: timescales determined by reheating experiments. Scientific reports. 2017 Apr 12;7:46364.
You can find out about applying for this project on the Department of Earth Sciences page.
Prof Marie Edmonds
Department of Earth Sciences Graduate Administrator