Fate of Hydrocarbons in Iron-Bearing Mineral Environments during Subduction
Fate of Hydrocarbons in Iron-Bearing Mineral Environments during Subduction
复制标题
俯冲过程中含铁矿物环境中碳氢化合物的归宿
作者：
A. Serovaiskii;E. Mukhina;L. Dubrovinsky;Aleksey Chernoutsan;D. Kudryavtsev;C. McCammon;G. Aprilis;I. Kupenko;A. Chumakov;M. Hanfland;V. Kutcherov
俯冲沉积在大陆地壳和上地幔演化中起着关键作用。作为深层碳循环的一部分，碳氢化合物积聚在俯冲带的沉积物中，最终可能随着地壳下的板块运输，从而影响地球深处内部的过程。然而，人们对油气在俯冲过程中的行为知之甚少。实验研究了下地壳和上地幔压力-温度条件下（高达2000（±100）K和10（±0.2）GPa）含铁硅酸盐和氧化物（代表可能的岩石形成物质）与模型烃类混合物或天然油的化学相互作用，并利用拉曼光谱、Mössbauer光谱和x射线衍射对运行产物进行了表征。我们的研究结果表明，复杂碳氢化合物在对应深度超过50公里的热压条件下本身是稳定的。在板块俯冲过程中，烃类与含铁岩石发生化学反应，形成了氢化铁和碳化铁。熔化温度相对较低的氢化铁可能形成具有负浮力的液体，可以将还原铁和氢输送到更深的深度。
Subducted sediments play a key role in the evolution of the continental crust and upper mantle. As part of the deep carbon cycle, hydrocarbons are accumulated in sediments of subduction zones and could eventually be transported with the slab below the crust, thus affecting processes in the deep Earth’s interior. However, the behavior of hydrocarbons during subduction is poorly understood. We experimentally investigated the chemical interaction of model hydrocarbon mixtures or natural oil with ferrous iron-bearing silicates and oxides (representing possible rock-forming materials) at pressure-temperature conditions of the Earth’s lower crust and upper mantle (up to 2000(±100) K and 10(±0.2) GPa), and characterized the run products using Raman and Mössbauer spectroscopies and X-ray diffraction. Our results demonstrate that complex hydrocarbons are stable on their own at thermobaric conditions corresponding to depths exceeding 50 km. We also found that chemical reactions between hydrocarbons and ferrous iron-bearing rocks during slab subduction lead to the formation of iron hydride and iron carbide. Iron hydride with relatively low melting temperature may form a liquid with negative buoyancy that could transport reduced iron and hydrogen to greater depths.