Department of Earth and Planetary Sciences, Yale University, 210 Whitney Avenue, New Haven, CT, 06511, USA.
California Institute of Technology, Division of Geological and Planetary Sciences, 1200 E California Boulevard, Pasadena, CA, 91125, USA.
Nat Commun. 2020 Dec 4;11(1):6220. doi: 10.1038/s41467-020-19993-2.
The fate of subducted CO remains the subject of widespread disagreement, with different models predicting either wholesale (up to 99%) decarbonation of the subducting slab or extremely limited carbon loss and, consequently, massive deep subduction of CO. The fluid history of subducted rocks lies at the heart of this debate: rocks that experience significant infiltration by a water-bearing fluid may release orders of magnitude more CO than rocks that are metamorphosed in a closed chemical system. Numerical models make a wide range of predictions regarding water mobility, and further progress has been limited by a lack of direct observations. Here we present a comprehensive field-based study of decarbonation efficiency in a subducting slab (Cyclades, Greece), and show that ~40% to ~65% of the CO in subducting crust is released via metamorphic decarbonation reactions at forearc depths. This result precludes extensive deep subduction of most CO and suggests that the mantle has become more depleted in carbon over geologic time.
俯冲 CO 的命运仍然存在广泛的争议，不同的模型预测俯冲板块要么完全（高达 99%）脱碳，要么碳损失极其有限，因此大量 CO 被深埋。俯冲岩石的流体历史是这场争论的核心：经历含水流体大量渗透的岩石可能释放的 CO 比在封闭化学系统中变质的岩石多几个数量级。数值模型对水的流动性做出了广泛的预测，而进一步的进展受到缺乏直接观测的限制。在这里，我们对俯冲板块（希腊基克拉迪群岛）中的脱碳效率进行了全面的实地研究，并表明俯冲地壳中约有 40%至 65%的 CO 通过前弧深度的变质脱碳反应释放。这一结果排除了大部分 CO 的广泛深埋，并表明随着时间的推移，地幔中的碳含量已经变得更加匮乏。
