Hydrogen gas of organic origin in shales and metapelites
Hydrogen gas of organic origin in shales and metapelites
复制标题
页岩和变泥岩中有机来源的氢气
DOI：
10.1016/j.coal.2017.02.014
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发表时间：
2017
影响因子：
5.6
通讯作者：
T. Hoshino
中科院分区：
文献类型：
--
作者：
N. Suzuki;H. Saito;T. Hoshino
随着加热温度的升高，页岩和变泥岩中保留的无机和有机气体的变化尚不完全清楚。本研究研究了海相页岩和变泥岩中埋藏成岩和变质作用过程中残留气体（例如 H2、CH4 和 CO2）的成分和同位素变化。从新泻沉积盆地的钻孔岩心和日本高知地区暴露的露头中收集了经历过 100-600 °C 古温度的页岩和变泥岩。实验室粉碎过程中页岩或变泥岩碎片中释放的气体被分析为残余气体。随着温度的升高，页岩和变泥岩中的主要残余气体依次从CO2、CH4到H2变化。沉积有机质脱羧产生的CO2急剧减少是由于溶解有CO2的孔隙流体被排出。残余气体中的 CH4 浓度随后随着有机物的成熟而增加，并在古温度约 250 °C 时达到最大值。在变质后期到变质作用期间，CH4 浓度降低，可能是由于氢气和石墨的形成。 H2 在古温度约 200 °C 时开始增加。 H2气体是变泥岩残余气体中最丰富的气体。页岩和变泥岩中 H2 的 δ2H 值相当低，在大约 –850 至 −650‰ 范围内。随着古温度的升高，主要残余气体从CH4转变为H2，并且H2的δ2H值显着降低，这表明页岩和变泥岩中的H2气主要来源于有机质中氢的释放。
The changes in inorganic and organic gases retained in shales and metapelites with increasing heating temperature are not fully understood. The compositional and isotopic changes of residual gases such as H2, CH4, and CO2in marine shales and metapelites during burial diagenesis and metamorphism were investigated in the present study. Shale rocks and metapelites which experienced paleo-temperatures in the range of 100–600 °C were collected from the borehole cores in Niigata sedimentary basin and outcrops exposed in Kochi district, Japan. Gases released from shale or metapelite fragments during pulverization in the laboratory were analyzed as the residual gas.The major residual gas in shales and metapelites changes from CO2, CH4, to H2in this order with increasing temperature. Drastic decrease of CO2derived from decarboxylation of sedimentary organic matter is due to the expulsion of pore fluids with dissolved CO2. The CH4concentration in residual gas subsequently increases with organic maturation and reaches the maximum at paleo-temperature ofca.250 °C. The CH4concentration decreases during late metagenesis to metamorphism probably due to the formation of H2gas and graphite. The H2starts to increase at paleo-temperature ofca.200 °C. The H2gas is the most abundant gas in residual gas of metapelite. Theδ2Η value of H2in shales and metapelites is quite low to be in the range ofca.–850 to − 650‰. The change of major residual gas from CH4to H2with increasing paleo-temperature and the significantly lowδ2H values of H2suggest that H2gas in shales and metapelites is largely derived from liberation of hydrogen in organic matter.