The nanogeochemistry of abiotic carbonaceous matter in serpentinites from the Yap Trench, western Pacific Ocean

Abstract

Serpentinization may provide a unique environment for the abiotic formation of condensed carbonaceous matter. This could support the deep biosphere and contribute to the deep carbon cycle, and may have provided the first building blocks for life. However, thus far, condensed carbonaceous matter has been found only in association with the minor mineral constituents of serpentinites. In contrast, here we show the direct association between carbonaceous matter and the dominant Fe oxide in serpentinites, magnetite. Our samples were recovered from the Yap Trench, western Pacific Ocean, with a human-occupied vehicle at a depth of 6413 m below sea level. The carbonaceous matter coincides with some micron-sized magnetite grains, but particularly with nanosized Fe oxides within serpentinite nanopores. Vibrational spectroscopy reveals that the condensed carbonaceous matter contains both aliphatic and aromatic compounds, but there is no evidence for functional groups typical for biological organics. Based on these observations, we suggest that physicochemical phenomena in serpentinite nanopores and nanosized catalytically active minerals may play a key role in the abiotic synthesis of complex carbonaceous matter.

Deciphering the Origin of Abiotic Organic Compounds on Earth: Review and Future Prospects

“…4d). In a similar case, Nan et al (2021) show the direct association between CCM and a nanosized Fe-oxide phase within serpentinite nanopores (recovered from the Yap Trench, western Pacific Ocean by human-occupied vehicle Jiaolong at 6413 m below sea level; Figs. 4e-f).…”

“…In summary, evidence has surfaced over the past 10 years that abiotic geological processes can form small molecules, e.g., CH 4 in hydrothermal vents, to more complex polymeric organics, e.g., aliphatic chains and PAHs (Mé nez et al, 2012;Sforna et al, 2018;Nan et al, 2021), and biochemical precursors, e.g., aromatic amino acids (Mé nez et al, 2018b). These discoveries may lay the foundations of a deep geological alternative to other theories for the emergence of carbon-based life on other planetary bodies.…”

“…(2) Solid abiotic organic compounds In addition to the abiotic synthesis of low-molecularweight organic compounds, in situ highly temporal/spatial resolved spectroscopic characterization techniques have allowed for the identification and imaging of condensed carbonaceous matter (CCM), as well as the textural relationship of these compounds with their mineral parageneses (Andreani and Mé nez, 2019). Recently, abiotic macromolecular CCMs (solid organic compounds) have been found in abyssal serpentinites and high-P serpentinite (at < 0.6 GPa) (Mé nez et al, 2018a, b;Sforna et al, 2018;Nan et al, 2021;Debret et al, 2022), demonstrating that serpentinization reactions can produce both solid and gaseous/liquid abiotic organic compounds. Sforna et al (2018) used scanning electron microscopy (SEM), Raman spectroscopy (Raman), and infrared spectroscopy (FTIR) to elucidate the relationship between minerals and CCM in the Tethyan Ligurian ophiolite, Italy.…”

Chemolithotrophic biosynthesis of organic carbon associated with volcanic ash in the Mariana Trough, Pacific Ocean

“…Previous work has shown the proportion of Fe-bound organic carbon in ash layers is roughly twice as high as in background sediments in the Bering Sea 13 . All this points toward CM in deep sea rocks being the product of chemolithotrophic communities 26,55,56 , and/or produced via mineral-catalyzed Fischer-Tropsch reactions 57,58 . This biogenic and/or abiogenic organic matter may also provide support for the generation and maintenance of other microbial life in rocks 59,60 .…”

Evidence for abundant organic matter in a Neoarchean banded iron formation

“…4). In addition, magnetite is a common effective catalyst in Fischer-Tropsch-type reactions, during which CO 2 and H 2 are converted into a wide spectrum of abiogenic hydrocarbons (e.g., McCollom, 2013;Nan et al, 2021). However, this process requires a H 2 -rich condition that can be produced by hydrothermal alternation of ultramafic rocks (McDermott et al, 2015).…”