Crustal growth and recycling during continental collision

Prof Martin Palmer, Dr Thomas Gernon, Dr Rex Taylor, Prof Craig Storey (University of Portsmouth)
Rationale: 

There is general consensus that the major site of continental crustal generation is at convergent plate margins, with only ~10% of crustal generation occurring in continental collision zones. It is also apparent, however, that the rate of crustal recycling into the mantle at convergent margins is almost identical (possibly greater) than the rate of crustal generation in this setting. In addition, recent studies have highlighted that the crustal recycling rate may have been overestimated and the crustal generation rate may have been underestimated in collision zones (Couzinié et al., 2016). This hypothesis has important implications for our understanding of Phanerozoic crustal evolution and the impacts on areas as diverse as mineral deposit formation to the evolution of the oceans and atmosphere.

The eastern Mediterranean represents an ideal natural laboratory to test this hypothesis as there is an extensive geochemical data set for well-dated magmatic rocks from the Cretaceous to Recent that documents the tectonic evolution of the region from convergent margin to continental collision (e.g. Palmer et al., 2019). In addition, long-established partnerships with Turkish geologists from Dokuz-Eylul University will provide access to an extensive sample set that will allow the student to undertake novel whole-rock and zircon analyses.

 

Methodology: 

The project will start with refinement of ~5000 published analyses of magmatic rocks from the region to provide a data set that is well characterized in terms of the age, location and tectonic setting of magmatism in the region (e.g. Ersoy & Palmer, 2013). A combination of petrological and statistical modelling will be used to set limits on the most probable proportions of crustal generation versus recycling in this region, together with how these have varied with tectonic evolution. This will be further constrained by zircon Hf isotope analyses (Portsmouth) and possibly oxygen isotope analyses (Edinburgh ion micro-probe facility). Many of the samples are already available, but if travel conditions allow, new samples will be collected from a field trip to Turkey.

Hypotheses developed from the eastern Mediterranean will be compared with the Himalayas where MRP has long-standing links with colleagues at the China University of Geoscience (Wuhan) who are working in this more complex, and less well-studied, region.

The project will also consider how the nature of the composition of crust generated in collisional tectonic zones differs from that generated in convergent zones and how this may have impacted ocean chemistry in Wilson cycles of supercontinent assembly and break-up.

 

Location: 
University of Southampton
Training: 

All doctoral candidates will enrol in the Graduate School of NOCS (GSNOCS), where they will receive specialist training in oral and written presentation skills, have the opportunity to participate in teaching activities, and have access to a full range of research and generic training opportunities. GSNOCS attracts students from all over the world and from all science and engineering backgrounds. There are currently around 200 full- and part-time PhD students enrolled (~60% UK and 40% EU & overseas).  Specific training will include: statistical analysis of large data sets (e.g. Bayesian and Monte Carlo), petrological modelling (e.g. MELTS) and laser ablation ICP-MS analyses of zircons.

 

Eligibility & Funding Details: 
Background Reading: 

Ersoy EY, Palmer MR 2013. Eocene-Quaternary magmatic activity in the Aegean: Implications for mantle metasomatism and magma genesis in an evolving orogeny. Lithos, doi: 10.1016/j.lithos.2013.06.007.

Palmer MR,  Ersoy EY, Akal C, Uysal I, Genç SC, Banks LA, Cooper MJ, Milton JA, Zhao KD 2019. A short, sharp pulse of potassium-rich volcanism during continental collision and subduction. Geology, 47, 1079-1082.

 

Couzinié S, Laurent O, Moyen J-F, Zeh A, Bouilhol P, Villaros A 2016. Post-collisional magmatism: Crustal growth not identified by zircon Hf-O isotopes: Earth and Planetary Science Letters, v. 456, p. 182 - 195.