How did the Cameroon Volcanic Line form?

Overview

The Cameroon Volcanic Line (CVL) extends southeast from Cameroon towards the mid-Atlantic ridge (Figure 1). Sustained magmatism has occurred along the CVL for tens of millions of years, and volcanic volumes are significant (e.g. Mt. Cameroon is >4000 m tall).

Why does this volcanic chain exist? A linear chain of volcanoes can be related to a deep thermal mantle plume (e.g., Hawaii-Emperor chain hotspot and the Walvis Ridge, lying further south of the Cameroon Line; Gassmoeller et al., (2016)). However, the CVL lacks a clear age progression, meaning that more complex processes need to be invoked (e.g. lithospheric delamination, Ballmer et al., 2011). Non-plume mechanisms have been proposed, but are typically discipline-specific, with geophysical, geochemical, and geodynamical models each designed in isolation to match only their respective observations. For example, edge-driven convection, locally elevated mantle volatile contents, the breakup of Pangea, or small-scale convection have all been dynamically proposed (Kaislaniemi & van Hunen, 2014, Figure 2). A geodynamical model that reconciles independent constraints from seismology, petrology and geochemistry is lacking. The key objective of this project is to find such unifying model.

The relevance of this project goes beyond understanding the origin of the CVL: the outcome directly affects our knowledge of lithosphere development, evolution and stability, and sheds new light on processes shaping our continents such as craton destruction, continental breakup, and lithosphere-asthenosphere interaction.

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Image Captions

Figure 1: Map of NE part of the Cameroon Line, with intraplate volcanism exhibiting a NE-SW line across the continent-ocean boundary.
Figure 2. Numerical modelling of edge-driven convection with application to the Atlas mountains volcanism. Mantle shearing triggers linear convection rolls (green sheets showing downwellings, and arrows showing velocity patterns), with decompression melting (red regions) occurring in the upwelling convective limbs (Kaislaniemi and van Hunen, 2014)

Methodology

This project combines geodynamical, petrological and geochemical data and modelling to determine the most likely explanation for the CVL. The main tool of project is geodynamical modelling using the state-of-the-art community-supported code ASPECT (https://aspect.geodynamics.org) to study lithosphere and mantle dynamics around the CVL. This will be coupled to the widely used thermodynamic software tool Perple-X (http://www.perplex.ethz.ch/) to integrate the petrology of the melting regime. Finally, a literature compilation of CVL geochemistry will be used to ground-truth dynamic models.

ASPECT has been designed for a range of different geodynamical problems and uses cutting-edge numerical techniques for optimal performance. It is very well documented, and is extensible to tailor for individual project needs.

The project builds on from previous work by the supervisors on intraplate volcanism (e.g. Ballmer et al., 2011; Kaislaniemi and van Hunen, 2014; Figure 2) and experience in combining geodynamic and geochemical data (e.g., Perrin et al. 2016). The project benefits from international project partners at the Universities of Edinburgh (Linda Kirstein), Madrid (Ana Negredo), Florida (Juliane Dannberg), and Melbourne (Eleanor Green).

The student will join a vibrant research culture in the department of Earth Sciences, in which ~70 PhD students work on a wide range of Earth Science research projects. The student will closely collaborate with academic staff, postdoctoral researchers and fellows, and postgraduate students in the geodynamics and geochemistry research groups.

A geodynamical background, affinity with code development, and an interest in geochemical processes are desirable. Training will be provided in geodynamical modelling (programming, code development, model setup, and usage), data management of high-performance computing systems, and interpretation and integration of key geochemical data and techniques. The project allows the student to become proficient in computer programming and large dataset analysis, with support from an enthusiastic ASPECT community. The code is open source with an importance placed on member participation in development (which is done in the open at https://github.com/geodynamics/aspect), allowing for worldwide collaboration and education (e.g., through Hackathons and public meetings). In addition, the student will receive training in general and transferable skills.

The student will have the opportunity to attend national and international conferences to disseminate research results and to spend time away from Durham to collaborate with some of the project partners at the partner institutes.

Project Timeline

Year 1

Literature review, including compilation of geochemical data, training in numerical modelling and the software package ASPECT, IAPETUS DTP training, 9-month progress report.

Year 2

Model development and testing; international academic secondment; 21-month progress report; preparation for publication of first key results in a peer-reviewed journal.

Year 3

Key stage in hypothesis testing; continuation of writing towards scientific publications; major international conference attendance.

Year 3.5

Finalizing further publications of research outcomes; thesis completion and submission.

Training
& Skills

The student will join a vibrant research culture in the department of Earth Sciences, in which ~70 PhD students work on a wide range of Earth Science research projects. The student will closely collaborate with academic staff, postdoctoral researchers and fellows, and postgraduate students in the geodynamics and geochemistry research groups.

A geodynamical background, affinity with code development, and an interest in geochemical processes are desirable. Training will be provided in geodynamical modelling (programming, code development, model setup, and usage), data management of high-performance computing systems, and interpretation and integration of key geochemical data and techniques. The project allows the student to become proficient in computer programming and large dataset analysis, with support from an enthusiastic ASPECT community. The code is open source with an importance placed on member participation in development (which is done in the open at https://github.com/geodynamics/aspect), allowing for worldwide collaboration and education (e.g., through Hackathons and public meetings). In addition, the student will receive training in general and transferable skills.

The student will have the opportunity to attend national and international conferences to disseminate research results and to spend time away from Durham to collaborate with some of the project partners at the partner institutes.

References & further reading

Ballmer, M.D., Ito, G., van Hunen, J. & Tackley, P.J. (2011). Spatial and temporal variability in Hawaiian hotspot volcanism induced by small-scale convection. Nature Geoscience 4(7): 457-460.
Belay, I. G., Tanaka, R., Kitagawa, H., Kobayashi, K., & Nakamura, E. (2019). Origin of ocean island basalts in the West African passive margin without mantle plume involvement. Nature Communications, 10(1), 3022.
Heister, T., Dannberg, J., Gassm̦ller, R., Bangerth, W. (2017). High accuracy mantle convection simulation through modern numerical methods РII: realistic models and problems, Geophysical Journal International, vol. 210(2), pp. 833-851.
Kaislaniemi, L. & van Hunen, J. (2014). Dynamics of lithospheric thinning and mantle melting by edge-driven convection: Application to Moroccan Atlas mountains. Geochemistry, Geophysics, Geosystems 15(8): 3175-3189.
Gassmoeller, R., J. Dannberg, E. Bredow, B. Steinberger, and T. H. Torsvik (2016), Major influence of plume-ridge interaction, lithosphere thickness variations, and global mantle flow on hotspot volcanism—The example of Tristan, Geochem. Geophys. Geosyst., 17, 1454-1479, doi:10.1002/ 2015GC006177.
Perrin, A., Goes, S., Prytulak, J., Davies, R., Wilson, C., Kramers, S. 2016. Reconciling mantle wedge thermal structure with arc lava thermobarometric determinations in oceanic subduction zones. G-cubed, 17(10) 4105-4127.

Further Information

For any information on the project, the tectonics or geodynamics research groups, the department of Earth Sciences or, more generally, matters related to doing a PhD in Durham, please contact Jeroen van Hunen (jeroen.van-hunen@durham.ac.uk).

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