Colleagues,
Please share with any potential PhD candidates.

I am submitting this on behalf of Dr. Anastassia Borisova; please direct all inquiries to Dr. Borisova.

PI of the PLANETAFELSIC (nom, prénom, qualité):
Anastassia Borisova (CR CNRS, HDR 2015)
Tél : 05-61-33-26-31 ;
E-mail : anastassia.borisova@get.omp.eumailto:anastassia.borisova@get.omp.eu

Many thanks,
Wendy B0hrson

PhD thesis (M/F) on kinetic modelling of zircon crystallization and dissolution

Context
Global geochemical fluxes via the planetary geodynamics (i.e., rock-forming reactions, transformations and movements) over 4.5 Gyr link the planetary interior with the surface. The understanding of these links is largely conditioned by the use of mineral proxies among which zircon (ZrSiO4) has been holding the first place. The understanding is especially important for the Hadean eon (> 4 Gyr), because no Hadean rock but uniquely zircon grain record was preserved. Zircon is silicate mineral which is the host of a plethora of elemental and isotopic tracers (e.g., Hf, Zr, Si, O, Th, U, Pb, Ti, Sc, Nb, Y, rare earth elements, REE, Cl, F) that record the fluid and melt sources, physicochemical conditions (temperature-pressure-oxygen fugacity-water activity, T-P-fO2-aH2O) and chronology of the host rock-forming processes. The existing systematics of zircons is based on suggestions of the zircon-melt thermodynamic equilibrium.

However, recent discoveries on zircon nucleation and crystallization mechanisms (e.g., based on the δ94/90Zr), suggest that zircon crystallization may happen out of equilibrium. In other words, the crystallization rate is high compared to the diffusion time of the elements, and a boundary layer is formed between the crystal and the melt. The boundary layer and the residual melts are highly enriched in Hf and other elements (rare earth elements, REE) due to major rock-forming silicate mineral crystallization. Such systems have to affect the zircon-melt partitioning, and influence the content of the resulting crystal.

Proposed work
The PhD work will further progress in estimating of the kinetic conditions of zircon growth/dissolution applicable to different natural settings. This will require an accurate model of zircon formation incorporating trace elements and zirconium isotopes. The modeling will be based on the frame proposed by Bindeman-Melnik. The model parameters will be calibrated using measured data available from the parallel work on experimental and natural zircons in the framework of the PLANETAFELSIC ERC project.

The PhD involves codirection by Dr. HDR Anastassia Borisova, GET, and Dr. HDR Jerome Fehrenbach, IMT, Toulouse, France, and collaboration with Prof. Oleg Melnik, Oxford, UK.

Required skills
numerical simulation, rock formation modelling, mineralogy, petrology, stable isotope geochemistry

Thèse de doctorat (H/F) sur la modélisation cinétique de la cristallisation et de la dissolution du zircon

Contexte
Les flux géochimiques globaux via la géodynamique planétaire (c'est-à-dire les réactions de formation des roches, les transformations et les mouvements) sur 4,5 Gyr relient l'intérieur de la planète à la surface. La compréhension de ces liens est largement conditionnée par l'utilisation de proxys minéraux parmi lesquels le zircon (ZrSiO4) occupe la première place. Cette compréhension est particulièrement importante pour l'éon Hadéen (> 4 Gyr), car aucune roche de l'Hadéen n'a été conservée, mais uniquement des grains de zircon. Le zircon est un minéral silicaté qui contient une pléthore de traceurs élémentaires et isotopiques (par exemple Hf, Zr, Si, O, Th, U, Pb, Ti, Sc, Nb, Y, terres rares, Cl, F) qui enregistrent les sources de fluides et des liquides silicatés, les conditions physicochimiques (température-pression-fugacité d'oxygène-activité de l'eau, T-P-fO2-aH2O) et la chronologie des processus de formation des roches d'accueil. La systématique actuelle des zircons est basée sur des suggestions d'équilibre thermodynamique entre le zircon et le liquide silicaté.

Cependant, des découvertes récentes sur les mécanismes de nucléation et de cristallisation du zircon (par exemple, sur la base du δ94/90Zr), suggèrent que la cristallisation du zircon peut se produire en dehors de l'équilibre. En d'autres termes, la vitesse de cristallisation est élevée par rapport au temps de diffusion des éléments, et une couche limite se forme entre le cristal et le liquide silicaté. La couche limite et les liquides résiduels sont fortement enrichis en Hf et en d'autres éléments (terres rares, REE) en raison de la cristallisation de minéraux silicatés. Ces systèmes doivent affecter le partage zircon-liquide et influencer le contenu du cristal résultant.

Travail proposé
Le travail de thèse permettra de progresser dans l'estimation des conditions cinétiques de croissance/dissolution du zircon applicables à différents environnements naturels. Cela nécessitera un modèle précis de formation du zircon intégrant des éléments traces et des isotopes de zirconium. La modélisation sera basée sur les modèles proposés par Bindeman-Melnik. Les paramètres du modèle seront calibrés à l'aide de données mesurées disponibles à partir des travaux parallèles sur les zircons expérimentaux et naturels dans le cadre du projet ERC PLANETAFELSIC.

Le doctorat est codirigé par le Dr HDR Anastassia Borisova, GET, et le Dr HDR Jerome Fehrenbach, IMT, Toulouse, France, et en collaboration avec le professeur Oleg Melnik, Oxford, Royaume-Uni.

Compétences requises
Simulation numérique, modélisation de la formation des roches, minéralogie, pétrologie, géochimie des isotopes stables

PI of the PLANETAFELSIC (nom, prénom, qualité):
Anastassia Borisova (CR CNRS, HDR 2015)
Tél : 05-61-33-26-31 ;
E-mail : anastassia.borisova@get.omp.eumailto:anastassia.borisova@get.omp.eu

Laboratory : (code unité, adresse) : Géosciences Environnement Toulouse, UMR 5563 CNRS, 14 avenue Edouard Belin, 31400 Toulouse, France

Références bibliographiques:
Bindeman, I. N., & Melnik, O. E. (2016). Zircon survival, rebirth and recycling during crustal melting, magma crystallization, and mixing based on numerical modelling. Journal of Petrology, 57(3), 437-460.
Bindeman I.N., Melnik O.E. (2022). The rises and falls of zirconium isotopes during zircon crystallization. Geochemical Perspectives Letters, 24, 21, doi: 10.7185/geochemlet.2241.
Fehrenbach J., O.E. Melnik, A.Y. Borisova (2024). Inverse Stefan problem from indirect measurements, application to zircon crystallization. Maths In Action (revised version in review), https://hal.science/hal-04416738/document.
Grimes, C. B., Wooden, J. L., Cheadle, M. J., & John, B. E. (2015). “Fingerprinting” tectono-magmatic provenance using trace elements in igneous zircon. Contributions to Mineralogy and Petrology, 170, 1-26.
Guo, J. L., Wang, Z., Zhang, W., Moynier, F., Cui, D., Hu, Z., & Ducea, M. N. (2020). Significant Zr isotope variations in single zircon grains recording magma evolution history. Proceedings of the National Academy of Sciences, 117(35), 21125-21131.
Holycross, M. E., & Bruce Watson, E. (2016). Diffusive fractionation of trace elements in basaltic melt. Contributions to Mineralogy and Petrology, 171, 1-15.

My working hours may not be the same as your working hours.  Please do not feel obligated to reply to me outside of your chosen working hours.

Wendy A. Bohrson
Professor
Geology and Geological Engineering
Colorado School of Mines
1516 Illinois Street
Golden, CO 80401
Berthoud 221D
303.273.3819

Dear Colleagues,

We are seeking a Full-Time Postdoctoral Research Associate to join our newly established Global Center: A Microbe-Mineral Atlas for a Sustainable Energy Future (Cornell, Weill Cornell Medicine, and Michigan State) supported by the US National Science Foundation. This center is dedicated to addressing some of the most pressing challenges in climate mitigation, securing critical elements, and developing novel energy sources through an interdisciplinary collaboration between mineralogy, geochemistry, microbiology, computational genomics, epigenetics, and synthetic biology.

For the mineralogy-geochemistry component, we are looking for a candidate with a background in mineralogy, petrology, or geochemistry open to new opportunities that transcend traditional disciplinary boundaries. The ideal candidate should possess advanced expertise in Earth materials formation processes, alteration, and characterization (i.e., XRD, XRF, EMPA/SEM, LA-ICP-MS, TEM, etc.). Proficiency in numerical modeling and independent field sampling experience is preferred. A strong background in inorganic chemistry and knowledge of organic chemistry and biogeochemistry are highly advantageous.

Requirements:

• A Ph.D. in geoscience

• Peer-reviewed publications that demonstrate the candidate’s field expertise, laboratory skills, and computational abilities.

Please contact Esteban Gazel at egazel@cornell.edu for further information.

--
Esteban Gazel, Ph.D.
Charles N. Mellowes Professor in Engineering
Professor, Earth and Atmospheric Sciences
Faculty Fellow, Atkinson Center for Sustainability
Cornell University
2161 Snee Hall, Ithaca, NY, 14853
Office: 4164 Snee Hall
Lab Website: https://gazelresearchgroup.eas.cornell.edu
Cornell Mass Spectrometry: https://cmas.eas.cornell.edu