IAP-26-100

Amakinite and green rust: mineral drivers for the origin of life?

The steep redox gradients generated by the mixing of alkaline hydrothermal vent fluid with seawater are regarded as one of the most likely sources of sustained chemical disequilibria required to drive the origin of life on the early Earth. At modern day alkaline vents such as the Lost City Hydrothermal Field, upwelling alkaline hydrothermal fluids are fed by the recirculating of seawater or freshwater through an up-thrust segment of lower crust unearthing the unstable olivine-rich rock peridotite. Heated water that permeates down into the peridotite reacts with olivine, forming alkaline fluids that are emitted at hydrothermal chimneys predominantly made of calcium and magnesium hydroxide minerals. When life originated in the Hadean or early Archean, however, oxygen-free seawater would have likely contained significant dissolved concentrations of Fe2+. This would have resulted in the formation of Fe-rich mineral precipitates at hydrothermal chimneys and mounds that are not commonly present in modern systems, including highly redox active Fe(II)-minerals such as amakinite ((Fe(OH)2) and mixed Fe(II)/Fe(III) minerals such as green rusts (layered double hydroxide minerals). Many of these initial Fe-rich mineral precipitates would have been unstable and overtime transformed to other minerals. For example Fe(OH)2 can, depending on environmental factors including pH, disproportionate to form a more oxidised mineral such as magnetite (Fe3O4), and a more reduced phase of metallic Fe. It has been suggested that this disproportionation reaction is analogous to the electron bifurcation reaction in bacteria, where a more energetically favourable reaction is used to drive less favourable reactions in the cell that would otherwise not take place; a key property of life.

In this studentship you will explore further the potential role of these redox active Fe-minerals in the context of the alkaline hydrothermal vent theory for the origin of life. You will test the hypothesis that redox active Fe-minerals such as amakinite and green rusts (with or without additional trace elements) are capable of driving the fixation of inorganic carbon and nitrogen into a range of prebiotic organic molecules.

You will help design and use a variety of experimental set ups (including ‘one pot’ batch experiments, h-cell diffusion experiments, and continuous flow pressurised h-cell diffusion experiments) to mimic the mixing of ancient seawater or freshwater with alkaline hydrothermal vent fluid. You will characterise how the mineral phases that precipitate change with time, assess evidence for disproportionation reactions, and test their abilities to fix inorganic carbon and nitrogen compounds into organic molecules. You will have access to a wide range of analytical facilities, including ion chromatography, gas and liquid chromatography-mass spectrometry, x-ray diffraction, x-ray photoelectron emission spectrometry, and electron microscopy. You will compare experimental results to predictions from thermodynamic geochemical models.

Year 1

Initial literature review into the alkaline hydrothermal vent theory for the origin of life, alongside relevant Fe mineralogy. Training in experimental design, core analytical techniques, and geochemical modelling. Initial ‘one pot’ and ambient pressure h-cell experiments. Presentation of initial results at a UK workshop/conference, and opportunity to participate in science outreach activities.

Year 2

Further h-cell experiments using continuous flow to maintain pH gradients. Presentation of results at UK or international conference (e.g. Goldschmidt), and opportunity to participate in science outreach activities.

Year 3

Final experiments focused on continuous flow pressurised h-cell experiments. Preparation of second manuscript, and presentation of results at a UK or international conference (e.g. AGU).

Year 3.5

Completion of final thesis/further manuscripts.

At the start of your studies an analysis of your training requirements will be undertaken and a tailored programme of training and support developed by yourself and their supervisory team. Project specific training will include experimental design, analytical inorganic and organic geochemistry, and thermodynamic modelling.