Project highlights

  • This project will unravel the timing of the least understood and most intriguing processes of plate tectonics: subduction initiation
  • This project will apply a recently developed geochronological method (Lu-Af) to date rocks formed during past subduction initiation events
  • The project will require field work in the Balkan ophiolites (Serbia, Albania, Macedonia, and Greece) and lab work in several world-leading geochronological and palaeomagnetic laboratories.

 

 

Overview

Plate tectonics is the most unifying and revolutionary theory in Earth sciences. However, 50 years after its formulation fundamental questions about how plate tectonics works still remain unanswered. In particular, the formation of new subduction zones (whereby one tectonic plate starts to sink underneath another) is poorly understood. Current models suggest that subduction can either initiate spontaneously due to gravitational instability, or upon external tectonic forces. In the last decade ophiolites (emerged relics of ancient oceanic lithosphere) have been crucial to study subduction initiation processes. Most ophiolites, in fact, form during subduction initiation above an incipient subduction zone. A recent work in the Oman ophiolite (Guilmette et al., 2018) used the time lag between the formation of the ophiolitic crust and the formation of the metamorphic layer found at its base to unravel the timing of subduction initiation in the Neotethys. These metamorphic rocks, known as metamorphic sole, are key to constrain the age of subduction initiation as they form during the initial moment of subduction development. Age constraints will also help to discriminate between different subduction initiation styles (i.e,. forced versus spontaneous).

The primary aim of this project is to reconstruct the age of a past, major subduction initiation event to understand its style and geodynamic causes. The ideal natural laboratory to study subduction initiation processes is an oph

Plate tectonics is the most unifying and revolutionary theory in Earth sciences. However, 50 years after its formulation fundamental questions about how plate tectonics works still remain unanswered. In particular, the formation of new subduction zones (whereby one tectonic plate starts to sink underneath another) is poorly understood. Current models suggest that subduction can either initiate spontaneously due to gravitational instability, or upon external tectonic forces. In the last decade ophiolites (emerged relics of ancient oceanic lithosphere) have been crucial to study subduction initiation processes. Most ophiolites, in fact, form during subduction initiation above an incipient subduction zone. A recent work in the Oman ophiolite (Guilmette et al., 2018) used the time lag between the formation of the ophiolitic crust and the formation of the metamorphic layer found at its base to unravel the timing of subduction initiation in the Neotethys. These metamorphic rocks, known as metamorphic sole, are key to constrain the age of subduction initiation as they form during the initial moment of subduction development. Age constraints will also help to discriminate between different subduction initiation styles (i.e,. forced versus spontaneous).

The primary aim of this project is to reconstruct the age of a past, major subduction initiation event to understand its style and geodynamic causes. The ideal natural laboratory to study subduction initiation processes is an ophiolite belt running for hundreds of kilometers from the Alps in northern Italy to the Dinarides and Hellenides in the Balkan Peninsula. These ophiolites are relics of oceanic lithosphere formed during, and as a result of a major subduction initiation event occurred within the Neotethys Ocean during the Jurassic. Available geochronological ages from both the crust and metamorphic sole of the Balkan ophiolites are similar, suggesting a spontaneous subduction initiation. However, ages from the ophiolitic crust are sparse and those from the metamorphic sole used Ar39-Ar40 method, which does not date the actual metamorphism but rather the cooling occurring after it. Obtaining new ages from these ophiolites is key to better understand one of the major subduction initiation events of the Earth’s history.

iolite belt running for hundreds of kilometers from the Alps in northern Italy to the Dinarides and Hellenides in the Balkan Peninsula. These ophiolites are relics of oceanic lithosphere formed during, and as a result of a major subduction initiation event occurred within the Neotethys Ocean during the Jurassic. Available geochronological ages from both the crust and metamorphic sole of the Balkan ophiolites are similar, suggesting a spontaneous subduction initiation. However, ages from the ophiolitic crust are sparse and those from the metamorphic sole used Ar39-Ar40 method, which does not date the actual metamorphism but rather the cooling occurring after it. Obtaining new ages from these ophiolites is key to better understand one of the major subduction initiation events of the Earth’s history.

Host

University of Birmingham

Theme

  • Dynamic Earth

Supervisors

Project investigator

  • Marco Maffione (UoB)

Co-investigators

How to apply

Methodology

Two to three sampling campaigns will be carried out in the ophiolite belt running through Serbia, Albania, Macedonia, and Greece. The new Lu-Hf dating method on garnet will be coupled with the standard U-Pb geochronology on zircons to date the metamorphic sole underlying these ophiolites.

In addition to the geochronological analysis, palaeomagnetic analysis will also be carried out to reconstruct the initial orientation of the subduction zone (Maffione et al., 2017; Maffione and van Hinsbergen, 2018). Palaeomagnetic samples will be collected from the sheeted dyke section of these ophiolites, and the paleomagnetic directions will be computed using standard palaeomagnetic techniques. A net tectonic rotation analysis (Allerton and Vine, 1987) using the computed paleomagnetic directions will then be applied to reconstruct the geometry of the subduction zone and infer the potential geodynamic causes of subduction initiation.

Training and skills

Training in both geochronology and palaeomagnetism will be provided by the main supervisor Maffione. Also, field training in ophiolite geology will be provided by Dr Maffione. The student will acquire new knowledge in the use of Lu-Hf and U-Pb dating techniques, as well as in palaeomagnetism, rock magnetism, and the application of net tectonic rotation analysis, which has a wide application in tectonic and structural geological studies.

Further details

For further info please contact Dr Marco Maffione at: m.maffione@bham.ac.uk

For more info on the scientific activity of the main supervisor go to: www.marcomaffione.com


Applications need to be submitted via the University of Birmingham postgraduate portal, https://sits.bham.ac.uk/lpages/LES068.htm, by midnight 11.01.2021. Please first check whether the primary supervisor is within Geography, Earth and Environmental Sciences, or in Biosciences, and click on the corresponding PhD program on the application page.

This application should include

  • a brief cover letter, CV, and the contact details for at least two referees
  • a CENTA application form
  • the supervisor and title of the project you are applying for under the Research Information section of the application form.

Referee’s will be invited to submit their references once you submit your application, but we strongly encourage applicants to ensure referees are aware of your submission and expecting a reference request from us. Students are also encouraged to visit and explore the additional information available on the CENTA website.

Possible timeline

Year 1

Literature review; one or two field sampling campaign in Serbia and Albania; paleomagnetic analysis of rocks from the Serbian and Albanian ophiolites; geochronological dating of these two ophiolites.

Year 2

One or two field sampling campaign in Macedonia and Greece; paleomagnetic analysis of rocks from the Macedonian and Greek ophiolites; geochronological dating of these two ophiolites.

Year 3

Continuation of the palaeomagnetic and geochronological analysis; paper and thesis writing.

Further reading

Allerton, S. and Vine, F.J., 1987. Spreading structure of the Troodos ophiolite, Cyprus: Some paleomagnetic constraints. Geology15(7), pp.593-597.

Guilmette, C., Smit, M.A., van Hinsbergen, D.J., Gürer, D., Corfu, F., Charette, B., Maffione, M., Rabeau, O. and Savard, D., 2018. Forced subduction initiation recorded in the sole and crust of the Semail Ophiolite of Oman. Nature Geoscience11(9), 688-691.

Maffione, M. and van Hinsbergen, D.J., 2018. Reconstructing plate boundaries in the Jurassic neo‐Tethys from the east and west Vardar ophiolites (Greece and Serbia). Tectonics37(3), 858-887.

Maffione, M., Thieulot, C., Van Hinsbergen, D.J., Morris, A., Plümper, O. and Spakman, W., 2015. Dynamics of intraoceanic subduction initiation: 1. Oceanic detachment fault inversion and the formation of supra‐subduction zone ophiolites. Geochemistry, Geophysics, Geosystems16(6), 1753-1770.

Stern, R.J. and Gerya, T., 2018. Subduction initiation in nature and models: A review. Tectonophysics746, 173-198.

Stern, R.J., Reagan, M., Ishizuka, O., Ohara, Y. and Whattam, S., 2012. To understand subduction initiation, study forearc crust: To understand forearc crust, study ophiolites. Lithosphere4(6), 469-483.

Stern, R.J., 2004. Subduction initiation: spontaneous and induced. Earth and Planetary Science Letters226(3-4), 275-292.

van Hinsbergen, D.J., Peters, K., Maffione, M., Spakman, W., Guilmette, C., Thieulot, C., Plümper, O., Gürer, D., Brouwer, F.M., Aldanmaz, E. and Kaymakcı, N., 2015. Dynamics of intraoceanic subduction initiation: 2. Suprasubduction zone ophiolite formation and metamorphic sole exhumation in context of absolute plate motions. Geochemistry, Geophysics, Geosystems16(6), 1771-1785.

Wakabayashi, J. and Dilek, Y., 2003. What constitutes ‘emplacement’of an ophiolite?: Mechanisms and relationship to subduction initiation and formation of metamorphic soles. Geological Society, London, Special Publications218(1), 427-447.

 

COVID-19

This project has a clear field component that is instrumental to acquire rock samples for dating and palaeomagnetic analysis and to make field structural geological observations. Therefore, the occurrence of COVID-related national lockdowns in the UK or in the destination countries may represent an obstacle to this project. In case one or more of the four Balkan countries targeted by this project will close to international travel, the project may focus entirely on the remaining available countries. If all these four countries will be subjected to lockdown, a different area outside the Balkans may be selected for sampling and fieldwork.