Title: Extreme energy from the deep, at convergent margins
Interactions between fluids and rocks can produce energy sources life can take advantage of, from microorganisms to modern society. The hydroxylation of olivine-rich rocks, or serpentinization, is known to produce molecular hydrogen that may combine with carbon to form light hydrocarbons such as methane. These natural energy sources are abiotic, i.e. produced without the contribution of biology. Serpentinization is best known at shallow crustal levels such as at mid ocean ridges and on land, at depths largely overlapping with the deep subsurface biosphere. Because microbial life can take advantage of these gases and reprocess them, the identification of abiotic energy sources in these settings is challenging. However, serpentinization can extend to conditions much deeper and hotter compared to the biotic fringe, such as at convergent margins where serpentinization can take place down to at least 70-80 km depth. The genesis of molecular hydrogen and methane through serpentinization at these depths is, however, little studied, even though it may represent an unexplored source region of natural energy along thousands of kilometers of convergent plate margins. In this contribution, I will present the results of a multidisciplinary study aimed at determining the distribution, formation pathways, signatures, and fluxes of deep energy sources generated at the deepest roots of serpentinization. The fate and potential implications of the generation of these energy sources at extreme conditions will be discussed.
Short bio: Alberto Vitale Brovarone is Professor of petrology and petrography at the University of Bologna, Italy. His research centers on the fluid-rock interactions and the cycling of hydrogen and carbon in the lithosphere. Over the last five years, his work has focused on extending our knowledge about the process of serpentinization to its deepest and warmest conditions, on the related genesis of high-pressure energy sources, and on their implications on the sustainment of deep subsurface life at convergent margins.
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