PhD project in magmatic petrology and geochemistry on the relationship between carbonatite and alkaline silicate rocks in the East African Rift Valley of Tanzania

Project title: Carbonatite-silicate rock associations in the Gregory Rift, Tanzania
Supervisors: Prof. Dr. Gregor Markl and PD Dr. Michael Marks (Tübingen University, Germany)
Application deadline: August 15^th, 2022

Project summary: This project concerns the magmatic evolution of carbonatite-nephelinite-phonolite-associations in the Gregory branch of the East African Rift, where carbonatites show highly variable enrichment of alkalis and halogens. The project will characterize the carbonatite-silicate rock associations of Kerimasi, Mosonik, and Shombole volcanoes and compare them to each other, to the extreme example of Oldoinyo Lengai (OL) with its peralkaline nephelinites, phonolites and natrocarbonatites and to further regional nephelinitic volcanoes (Sadiman, Burko, Essimongor). Such an integrated approach that compares carbonatites and associated silicate rocks from several spatially associated volcanoes in detail has not been done before - although it may explain the reasons for the observed variations of alkali- and halogen-enrichment in carbonatites and the role of the associated silicate rocks on a regional scale.

The preliminary working hypotheses are:

• Nephelinites and carbonatites from the three volcanoes derive from a common mantle source and evolved from a common parental magma via fractional crystallization followed by liquid-liquid immiscibility.
• Nephelinite-phonolite associations of the investigated volcanoes reflect variable amounts of assimilation during fractional crystallization (AFC processes).
• The variable Na/Ca-ratios of the carbonatites are caused by different "timing" of carbonatite unmixing during the evolution of the parental CO2-bearing melts.

Testing them involves a systematic textural and petrological approach using isotopic age-dating, whole-rock data (XRF, ICP-MS), mineral chemistry (SEM, EPMA) and phase equilibrium calculations (QUILF, PerpleX and others), spatially resolved radiogenic isotope data (LA ICP-MS), halogen data (CIC) and especially melt inclusion studies.

The start of the PhD scholarship will be in late 2022, the first fieldwork in Tanzania is scheduled for February 2023.

Candidate Selection Criteria

• We are looking for a highly motivated candidate holding a BSc and MSc degree in geosciences with a clear developed interest in magmatic petrology and geochemistry.
• The candidate must have a strong ability to communicate scientific knowledge, both orally and in written form. Good writing and speaking skills in English are essential.
• The candidate requires abilities to work independently, and collaboratively in a team.
• Knowledge of and experience in geoscience analytical techniques, particularly polarisation microscopy, electron microprobe and other in situ analysis techniques is desirable.
• Evidence of research experience, academic awards/publications/presentations at conferences is desirable.

How to Apply:

To apply, send a letter explaining why you are interested in this project and in doing a PhD and a complete CV to Dr. Michael Marks (michael.marks@uni-tuebingen.de) latest by August, 15^th, 2022. The CV should include 1) your contact details and nationality 2) research interests 3) education background and academic qualifications 4) research and work experience that address the selection criteria (detailed above) 5) awards and prizes 6) relevant skills and experience, 7) publications and conferences, 8) professional memberships, 9) referees and well as evidence of your qualifications. Please provide a copy of your degree certificate(s) (in original language and officially translated into English where relevant), and a transcript of your undergraduate degree results (in original language and officially translated into English where relevant). For non-native English-speaking applicants, please provide evidence of English proficiency (IELTS Academic/TOEFL iBT/PTE Academic/Cambridge English Advanced & Proficiency scores).

All documents should be merged into one pdf file. Applications consisting of more than one pdf will not be considered!

If you have published any of your research in international journals, please send pdfs of these publications (and ONLY of these, no national journals or theses!) as well (these may be sent as separate pdfs and not included into the merged file named above).

Scholarship description: The scholarship consists of a 3-year 75% E13 position (which is normal for most German PhD scholarships), which will approximately amount to 1700 € per month after deduction of taxes. Furthermore, all analytical and logistical costs (travel for field work and to conferences, to collaboration partners etc.) will be fully covered.