DATE2026.01.14 #Press Releases

Organic Matter Discovered in Rocks Derived from the Sub-oceanic Mantle

-Evidence for Abiotic Organic Synthesis in the Upper Mantle-

Summary

A joint research team led by Itaru Mitsukawa, a doctoral student, Ryo Miyake, Professor, and Yohei Igami, Associate Professor at the Graduate School of Science, Kyoto University—together with researchers from Kyoto University, Hiroshima University, Ritsumeikan University, Tohoku University, the Japan Synchrotron Radiation Research Institute (JASRI), Waseda University, the University of Tokyo, and the Institute of Materials Structure Science at the High Energy Accelerator Research Organization (KEK)—has discovered organic matter dominated by polycyclic aromatic hydrocarbons within inclusions in mantle xenoliths collected on Tahiti Island in the South Pacific.

The possibility that organic compounds can be synthesized abiotically within Earth’s mantle has long been suggested. However, reports of such organic matter detected in natural mantle-derived materials originating from the sub-oceanic mantle have been extremely limited.

In this study, the research team analyzed microscopic inclusions within mantle xenoliths using advanced analytical techniques, including synchrotron radiation X-ray computed tomography (CT) and micro-Raman spectroscopy. The results revealed that organic matter dominated by polycyclic aromatic hydrocarbons is distributed within the inclusions together with carbon dioxide and carbon monoxide.

These findings demonstrate that abiotic organic synthesis can occur in the sub-oceanic mantle, providing important insights into the processes responsible for organic matter formation within Earth’s mantle and contributing to a deeper understanding of the global carbon cycle.

This research was published online in the international scientific journal Scientific Reports at 10:00 a.m. (UK time) on 14 January 2026.

Notably, Prof. Yoshio Takahashi of the Department of Earth and Planetary Science also participated in this study.

Figure：(a) Mantle xenoliths are rocks that are incorporated into magma from the surrounding mantle wall rocks as magma ascends toward the Earth’s surface and are subsequently transported to the surface. (b) Synchrotron radiation X-ray nano-CT image of an inclusion analyzed in this study. The inclusion, hosted within clinopyroxene constituting the mantle xenolith, contains platinum-group minerals, Fe–Ni–Cu sulfide minerals, silicate glass, and a mixture of CO₂, CO, and organic matter.

Links

Kyoto University;  Hiroshima University;  Ritsumeikan University;  Tohoku University; Japan Synchrotron Radiation Research Institute (JASRI);  Waseda University; High Energy Accelerator Research Organization (KEK)

Journals

Journal name	Nature Communications
Title of paper	Abiotic polycyclic aromatic hydrocarbons originating from the sub-oceanic mantle