2024-06-03 ゲーテ大学
＜関連情報＞
- https://aktuelles.uni-frankfurt.de/english/did-warmer-seas-lead-to-methane-release/
- https://www.science.org/doi/10.1126/sciadv.adn0155
炭酸塩∆47/∆48分析によるメタン湧出域の古温度に関する運動論的バイアスの解明と補正 Resolving and correcting for kinetic biases on methane seep paleotemperature using carbonate ∆47/∆48 analysis
PHILIP STAUDIGEL, DONG FENG, JÖRN PECKMANN, MIGUEL BERNECKER, […], AND JENS FIEBIG
Science Advances Published:29 May 2024
DOI:https://doi.org/10.1126/sciadv.adn0155
Abstract
Methane-derived authigenic carbonate often constitutes the sole remaining record of relic methane seeps. The clumped (∆47) and oxygen isotopic composition of seep carbonates often yield inaccurate temperatures, attributed to kinetic isotope effects and modification of seawater isotope composition by hydrate water. Here, we analyzed the dual-clumped isotope (∆47/∆48) composition of authigenic carbonate from a modern methane seep. We demonstrate that aragonite forms closest to isotopic equilibrium such that its ∆47 can directly yield the correct formational temperature, whereas calcite is unambiguously biased by kinetic isotope effects. Numerical models show that the observed bias in the isotopic composition arises from rate-limiting dehydration/dehydroxylation of HCO3− alongside diffusive fractionation, which can be corrected for with analysis of carbonate ∆47/∆48 values. We demonstrate the utility of dual-clumped isotope analysis for studying seep carbonates, as it reveals the origin and magnitude of kinetic biases and can be used to reconstruct paleotemperature and seawater δ18O.
