Self-funded PhD opportunities
Granites from the Mantle – the xenolith perspective.
- Application end date: Applications open all year round
- Funding Availability: Self-funded PhD students only
- Department: School of Earth and Environmental Sciences
- PhD Supervisor: Dr Mike Fowler, Prof James Darling, Prof Craig Storey
Project code: SEES4461018
The origins of granitic magmas through time is key to our understanding of crustal evolution on Earth. High Ba-Sr granites have geochemical characteristics traceable through related mafic magmas to enriched sources in the sub-continental lithospheric mantle (SCLM, e.g. Fowler et al., 2008). Fowler and Rollinson(2012) argue that they are Phanerozoic equivalents of sanukitoids, which first appeared in the Neoarchaean as a result of evolving plate tectonic regime (e.g. steepening of the down-going slab). Therefore, high Ba-Sr granites could represent the continued expression of juvenile granite genesis that originated nearly 3 Ga ago. This project would test their proposed mantle origin by defining and interpreting the distribution of the characteristic lithophile trace elements within xenoliths of the SCLM. The discovery of zircon in SCLM xenoliths from China (Liu et al., 2010), and silicate inclusions armoured in ophiolitic chromites (e.g. Robinson et al., 2015) lend considerable optimism that there is much to be discovered.
The SCLM beneath the Caledonian orogen has been sampled by numerous alkali basalt magmas; the xenoliths have been studied in great detail for many years. Recent publications have demonstrated significant isotopic (Bonadiman et al., 2008) and chemical (Hughes et al., 2015) overlap with the proposed source of the Caledonian high Ba-Sr granites (Fowler et al., 2008). Specifically, Bonadiman et al. (2008) defined Nd and Sr isotope compositions for xenoliths from Rinibar and Streap (in the Northern Highland Terrane within which the high Ba-Sr granites are located) that extend into the enriched region of εNd vs. 87Sr/86Sri space where Fowler et al. (2008) defined a Caledonian Parental Magma Array (CPMA). Hughes et al. (2015) presented REE patterns for the same xenolith suites ranging from flat to steeply light-REE enriched, in accord with varying enrichment implied by the isotopic extent of the CPMA. On the basis of the xenoliths, Bonadiman et al. (2008) postulated “the addition in the mantle wedge of a slab component, made up of altered oceanic crust plus…. subducted sediments”, while for the granites Fowler et al. (2008) independently suggested “mantle sources that include small fractions of subducted pelagic sediment”. It therefore seems possible that members of the xenolith suite represent source materials of the mafic parents to the granites – a hypothesis that can be tested with further detailed study of the Streap and Rinibar xenoliths using modern micro-beam instrumentation (electron microscopy and laser ablation ICP-MS). If confirmed, genuinely juvenile granites will need to be accounted for in global crustal growth models.
You’ll need a good first degree from an internationally recognised university (depending upon chosen course, minimum second class or equivalent) or a Master’s degree in an appropriate subject. Exceptionally, equivalent professional experience and/or qualifications will be considered. English language proficiency at a minimum of IELTS band 6.5 with no component score below 6.0.
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How to Apply
You can apply online at www.port.ac.uk/applyonline. You are required to create an account which gives you the flexibility to save the form, log out and return to it at any time convenient to you.
A link to the online application form and comprehensive guidance notes can be found at www.port.ac.uk/pgapply.
When applying, please quote project code: SEES4461018
Interview date: TBC
Start date: October 2018.
This is self-funded project, for infomration on fees and funding, please see our webpages.
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