PhD project in magmatic petrology and geochemistry on
alkaline rocks in Portugal

Project title: The behavior of high field-strength elements (HFSE) in F-rich peralkaline systems

Project summary: Peralkaline igneous rocks (rocks with a molar (Na+K)/Al ratio > 1) are strongly enriched in halogens, rare earth elements (REE), and high field strength elements (HFSE; Zr, Hf, Nb, Ta) and represent some of the most promising sources for future HFSE and REE supply. This project investigates the behaviour of halogens and HFSE/REE-bearing phases in the texturally and compositionally zoned peralkaline plutonic Monchique complex (Portugal) that evolved from gabbroic to foid syenitic compositions. The special role of sodalite, fluorite and various F-rich Na-Ca-HFSE disilicates (FDC) for the retention of halogens in peralkaline magmas will be investigated and the variable effects of fractional crystallization, fluid exsolution/degassing and fluid-wall rock interaction on halogen systematics and HFSE/REE mobility will be distinguished from each other. The following three working hypotheses will be guiding the workflow of the anticipated project:

  • Halogen abundances and halogen systematics (F/Cl, Cl/Br ratios) in the Monchique rocks reflect the effects of fractional crystallization during magmatic stages and redistribution of halogens caused by fluid exsolution and accompanied (autometasomatic) hydrothermal alteration.
  • The Monchique complex shows vertical and horizontal zonation with respect to the relative abundance of sodalite-FDS assemblages, which may or may not correlate with the HFSE distribution in this tabular body.
  • Locally developed fenites around the Monchique complex are Cl-rich but F-poor and therefore devoid of FDS but zircon- and titanite-bearing, which is mainly controlled by the low F/Cl ratio of the fenitizing fluids.

To test these hypotheses, we will combine detailed petrography, whole-rock analysis (XRF, ICP-MC, CIC), mineral chemistry (EPMA, CIC, LA-ICP-MS), thermodynamic modelling, and fluid inclusion investigations (microthermometry, LA-ICP-MS). The expected results of this project will not only decipher halogen and HFSE behaviour in such a peralkaline system, but will certainly have general implications on the formation and migration of halogen-bearing fluids that are capable of HFSE transport within a shallow-level plutonic complex. Geochemical monitors (e.g., whole rock halogen data, HFSE data) will be combined with mineralogical observations (e.g., FDS, sodalite, fluorite distribution) and will allow for a detailed view on fluid exsolution/degassing processes in tabular magma bodies.

Supervisors: PD Dr. Michael Marks, PD Dr. Benjamin Walter, and Prof. Dr. Gregor Markl, (Tübingen University, Germany)

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.

We offer an attractive international work place with modern state-of-the-art geochemical lab equipment. We have a strong team in petrology, geochemistry, hydrothermal ore deposits, and a partnership with other national and international research partners. This will give you an interesting and challenging environment, in which you have the chance to play a significant role.

Equal opportunity is an inherent part of our personnel policy. Therefore, we are particularly welcoming applications from qualified women; disabled persons will be given preferential treatment in the case of equal qualification.

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 ( latest by February, 15th, 2024. The CV should include your 1) contact details and nationality, 2) wider 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 participations, 8) professional memberships, 9) suggested referees, and 10) full evidence of your qualifications. This includes copies of your degree certificate(s) in original language and officially translated into English where relevant, transcript of academic degree results (in original language and officially translated into English where relevant). Non-native English-speaking applicants include evidence of English proficiency (IELTS Academic/TOEFL iBT/PTE Academic/Cambridge English Advanced & Proficiency scores).

All documents should be merged into one pdf file (< 10Mb), with a brief (less than one page) motivation letter being the starting page. Applications consisting of more than one pdf will not be considered*! * If you have published any of your research in international journals, please send separate pdfs of these publications (and ONLY of these, no national journals here!) as well.

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.

posted: 17 January 2024     Please mention EARTHWORKS when responding to this advertisement.