Hydrogen in natural fluid inclusions, Troodos - Cyprus
Hydrogen in natural fluid inclusions in serpentinized and rodingitized ultramafic rock, Troodos (Cyprus) - a combined field and experimental study.
The interest in hydrogen is recently inflated due to its economic value for sustainable energy supply and mobility. Natural hydrogen is part of this interest due to the occurrence of abundant H2-rich seeps. Processes that produce natural hydrogen are serpentinization, radiolysis, and fluid-rock interactions at highly reduced conditions in general, and part of this hydrogen is preserved in fluid inclusions. Mafic/ultramafic rocks in ophiolites are often affected by serpentinization, which is locally accompanied with rodingitization processes. The mineralogy of fine-grained serpentinites does not favour trapping and conservation possibilities of fluids in inclusions, and H2-rich fluids will mainly occur freely in pore spaces (seeps). However, coeval rodingites may trap these fluids in coarse-grained diopside and garnet crystals. These fluid inclusions provide understanding of timing and temperature-pressure-composition-density conditions of the fluids that traversed the rock during serpentinization and rodingitization processes. A preliminary study of rodingites and chromitites from the ophiolitic complex of Troodos (Cyprus) reveals the presence of abundant hydrogen in fluid inclusions.
The central hypothesis is that H2-rich fluids can be preserved in inclusions in serpentinized and rodingitized ultramafic rock, and that this fluid provides direct information about H2-producing processes in the geological past. The conditions where H2-rich fluid inclusions will behave as isolated systems without any diffusional modifications are to be determined.
Samples from Troodos are the main objects of research in this proposal, in which we will locate the occurrence of hydrogen and which will be used to understand processes of hydrogen formation by studying natual fluid inclusions. Post-entrapment modifications are suspected due to the enhanced mobility of H2 (diffusion), which will be studied by experimental work with synthetic and natural fluid inclusions, in order to describe the efficiency of diffusion, and to learn about the conditions that allow preservation of hydrogen in fluid inclusions. Mineral assemblages and fluid inclusions will be analysed with Raman spectroscopy, microthermometry, cryo-Raman spectroscopy, and LA-ICP-MS.
If we are successful with our combined strategy we should be able to extrapolate our results from Troodos to other ophiolitic complexes, and to improve the accuracy and significance of petrogenetic interpretations regarding the occurrence of natural hydrogen in the crust and mantle. This project may improve our knowledge of potential natural "hydrogen fields", that may play an important role in the exploration of economically valuable natural hydrogen.