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FRINATEK-Fri prosj.st. mat.,naturv.,tek

Unravelling redox variations and natural H2 formation in subduction zones through rock magnetism

Alternative title: Avdekke redoksvariasjoner og naturlig H2-dannelse i subduksjonssoner gjennom bergartsmagnetisme

Awarded: NOK 3.9 mill.

Subduction zones are regions of the Earth where two tectonic plates, converge and collide, causing the denser plate to dive beneath the other. Here, interactions between fluids and rocks play a key role in the mobilization of elements such as iron, carbon and hydrogen. The cycling of these elements within the lithosphere is critical for the Earth’s habitability and can promote the formation of reservoirs of energy resources. However, the chemical and physical mechanisms, regulating this cycling in deep systems, such as subduction zones, remain poorly understood. The overall scope of the project is to improve the understanding of these mechanisms in these systems with particular interest in their potential to generate natural hydrogen. This is an essential puzzle piece to assess the recovery potential of this primary energy resource. The study will achieve the scope by detailed investigation of chemical and physical properties of exhumed rocks from subduction zones. A major focus will be on magnetic properties of rocks which are intimately linked to chemical reactions and have therefore the potential to inform on deep chemical processes. Furthermore, because changes in rock magnetic properties are reflected in the magnetic anomalies, i.e. local variation of the Earth’s magnetic field, by linking the chemical reactions to the magnetic properties, the project will provide tools to correlate chemical reactions and magnetic anomalies in subduction zone on a global scale. This will be of value in the future to target areas of interest for potential volatile (H2 and CH4) reservoirs, on Earth and maybe even on other Planets. Furthermore, by investigating chemical reactions and their by-products, this project may provide important insights on geological processes producing gases with strong global warming potential such as abiotic CH4.

In subduction zones fluid-rock interactions play a key role in the mobilization of redox-sensitive elements such as iron, carbon and hydrogen. The cycling of these elements within the lithosphere is critical for the Earth’s habitability and can promote the formation of energy resources reservoirs. However, while gaining increasing scientific attention, the redox mechanisms, regulating this cycling in deep settings, such as subduction zones, remain poorly understood. This project will contribute to filling this knowledge gap, taking advantage of the intimate link between redox reactions and magnetic properties. The latter are affected by redox reactions, which can create or destroy the magnetic mineralogy. This potential for magnetic properties to inform on deep redox processes, such as those at subduction zones, is largely unexplored and requires a detailed study of the variables controlling the magnetic properties in these deep settings. Serpentinites are key players of volatile recycling in subduction zones. Their formation and transformation may exert a strong control over the redox state of deep fluids and their global effects. The scope of the project is to investigate the link between redox reactions and magnetic properties with attention on the in-situ control of micro-to-meso-scale structures on the magnetic properties of deep serpentinites. Deformation can affect the permeability of the rock, create preferential pathways for fluid-rock interactions and alter the magnetic properties of the rock. The study of mineralogical and microstructural properties of rock samples is therefore vital to predict mechanisms and products of these fluid-rock interactions. Furthermore, because changes in rock magnetic properties are reflected in the magnetic anomalies, by linking the redox reactions to the magnetic properties, the project will provide a new tool for the redox-oriented interpretation of magnetic anomalies in subduction zones.

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FRINATEK-Fri prosj.st. mat.,naturv.,tek