Abiotic methane generation through reduction of serpentinite-hosted dolomite: Implications for carbon mobility in subduction zones
Abiotic methane generation through reduction of serpentinite-hosted dolomite: Implications for carbon mobility in subduction zones
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通过减少蛇纹岩白云石产生非生物甲烷：对俯冲带碳流动性的影响
DOI：
10.1016/j.gca.2021.07.033
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发表时间：
2021-10
影响因子：
5
通讯作者：
Tingting Shen
中科院分区：
文献类型：
--
作者：
Peng Weigang;Lifei Zhang;Simone Tumiati;Alberto Vitale Brovarone;Han Hu;Yachun Cai;Tingting Shen
在地球和其他类地行星的表面，越来越多地检测到非生物甲烷，这对化学自养生命的研究，从而对天体生物学产生了重要的影响。相比之下，俯冲带中非生物甲烷的产生与深层碳迁移机制等问题密切相关，但很少受到关注。实验阐明了在俯冲带条件下碳酸盐矿物还原产生大量非生物甲烷，而对天然岩石还原的详细地质条件和过程迄今知之甚少。本文报道了来自化石俯冲带(西南天山，中国)的白云岩化蛇纹岩(又称蛇绿岩)中的碳酸盐还原和非生物甲烷的成因。详细的岩石学、拉曼光谱、锶和碳同位素以及热力学结果提供了白云石还原为方解石+水镁石+甲烷的相组合的证据，可能与开始于7-9Kbar和410-430°C的俯冲带逆行蛇纹岩作用有关。白云石赋存流体包裹体的测温数据与岩相学观察结果一致，表明在折返过程中白云石还原开始后流体被捕获。模型计算表明，富水流体具有相对较高的氢逸度，可以为还原过程创造有利条件，但这并不排除先前研究报告的富氢流体使碳酸盐甲烷化的可能性。甲烷在这些岩石中的广泛存在证明了俯冲碳的复杂的氧化还原转化，这意味着升高的氢逸度可能有助于通过汇聚板块边界的白云石还原来促进甲烷的非生物合成。我们的工作表明，含白云石岩性的改变是俯冲带中非生物甲烷的潜在来源，这可能对俯冲碳的转移具有意义。
Abiotic methane has been increasingly detected at the surface of Earth and other terrestrial planets, exerting a strong effect on the study of chemolithoautotrophic life and thus astrobiology. In contrast, abiotic methane generation in subduction zones, which is intimately linked to questions such as the mechanisms of deep carbon mobility, has received scarce attention. Experiments elucidated the significant production of abiotic methane through reduction of carbonate minerals under subduction zone conditions, whereas detailed geological conditions and processes for the reduction in natural rocks are hitherto poorly understood. Here, we report carbonate reduction and genesis of abiotic methane in dolomitized serpentinites (referred to as ophidolomites) from a fossil subduction zone (SW Tianshan, China). Detailed petrological, Raman spectroscopic, strontium and carbon isotopic, and thermodynamic results provide evidence for dolomite reduction into the phase assemblage of calcite + brucite + methane, likely associated with retrograde serpentinization starting at 7–9 kbar and 410–430 °C in the subduction zone. Microthermometric data for dolomite-hosted fluid inclusions are consistent with petrographic observations, indicative of fluid entrapment postdating the onset of dolomite reduction during exhumation. Model calculations suggest that water-rich fluids characterized by relatively high hydrogen fugacities can create favorable conditions for the reduction process, which, however, do not exclude the possibility of carbonate methanation by hydrogen-rich fluids as reported in previous studies. The widespread occurrence of methane in these rocks gives credence to the intricate redox transformations of subducted carbon, implying that the elevated hydrogen fugacities may facilitate abiotic synthesis of methane through dolomite reduction at convergent plate boundaries. Our work shows that alteration of dolomite-bearing lithologies represents a potential source for abiotic methane in subduction zones, which may have implications for the transfer of subducted carbon.
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DOI：
10.1007/978-3-319-78527-1
发表时间：
1973
期刊：
Stable Isotope Geochemistry
影响因子：
--
作者：
J. Hoefs
通讯作者：
J. Hoefs
DOI：
10.1016/j.cageo.2012.01.022
发表时间：
2012-12
期刊：
Comput. Geosci.
影响因子：
--
作者：
M. Steele‐MacInnis;P. Lecumberri-Sanchez;R. Bodnar
通讯作者：
M. Steele‐MacInnis;P. Lecumberri-Sanchez;R. Bodnar
影响因子：
64.8
作者：
BERG, GW
通讯作者：
BERG, GW
影响因子：
4.6
作者：
Yang C;Ni Z;Wang T;Chen Z;Hong H;Wen L;Luo B;Wang W
通讯作者：
Wang W
中国西南天山含钛球粒陨石和钛斜腐铁矿的蛇纹石化超镁铁质岩石中记录的超高压变质作用
影响因子：
3.9
作者：
Shen Tingting;Hermann Jőrg;Zhang Lifei
通讯作者：
Zhang Lifei