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Joubin James Lecture: Dr. Alberto Vitale Brovarone – Abiotic hydrocarbons on Earth: controversial theories, serpentinization, and new perspectives from subduction zones
November 21, 2019 @ 12:00 pm - 1:00 pm
Hydrocarbons in the Universe are widespread and abiotic in origin, i.e. produced without the contribution of biology. Zooming in on Earth, the origin of geological hydrocarbons becomes a more challenging issue owing to the presence of biologically produced equivalents. Paradoxically, the available global hydrocarbon budgets on Earth consider only biogenic sources. Beside the uniqueness of biology on our planet, the reason for that is that the geological processes generating abiotic hydrocarbons and their distribution on Earth are still largely unexplored. The “Deep gas theory”, conversely, considers that hydrocarbon reservoirs on Earth may abiotic in origin and reflect a cosmic origin inheritance. The theory was first supported by the Russian community, and successively reprised by Thomas Gold, who suggested that most deep hydrocarbons form through abiotic processes in the mantle and migrate towards shallower reservoirs in the crust (the “Deep hot biosphere”). The theory remains highly controversial, yet quite fascinating. Nevertheless, a series of geological processes producing abiotic light hydrocarbons such as methane are indeed documented, especially in shallow crustal settings, and some of them have gathered great international effort over the last decades. In this talk, I will focus on the most intriguing natural process associated with abiotic methane production, called serpentinization. I will introduce the process of serpentinization at shallow terrestrial conditions based on literature data and original images from the South-Western Indian Ridge. Then I will move to a completely new chapter of this topic, which is the genesis of metamorphic abiotic hydrocarbons in subduction zones and their potential role in the deep C and H cycles.
Everyone is welcome!