Characteristics of hydrate-bound gas retrieved at the Kedr mud volcano (southern Lake Baikal)
Characteristics of hydrate-bound gas retrieved at the Kedr mud volcano (southern Lake Baikal)
复制标题
DOI：
10.1038/s41598-020-71410-2
复制
发表时间：
2020-09-08
影响因子：
4.6
通讯作者：
Khlystov, Oleg
中科院分区：
文献类型：
--
作者：
Hachikubo, Akihiro;Minami, Hirotsugu;Khlystov, Oleg
我们报告了贝加尔湖凯德尔泥火山湖底沉积物中水合物结合碳氢化合物的特征。取回了 20 个含有水合物的沉积物岩心，水合物结合气体的甲烷稳定同位素（δ C-13 和 δ H-2 分别为 -47.8% 至 -44.0% V-PDB 和 -280.5% 至 -272.8% V-SMOW）表明其热成因起源于次生微生物甲烷。晶体的粉末 X 射线衍射图和水合物结合气体的分子组成表明，结构 II 晶体显示出高浓度的乙烷（约占水合物结合烃的 14%），而结构 I 晶体显示出相对较低浓度的乙烷（水合物结合烃的 2-5%）。这些不同的晶体结构由湖底沉积物中的复杂层组成，表明天然气水合物部分解离、浓缩乙烷并形成结构II晶体。我们得出的结论是，高浓度的生热乙烷主要控制气体水合物的晶体结构，并且丙烷、异丁烷（2-甲基丙烷）和新戊烷（2,2-二甲基丙烷）在重结晶过程中被包裹在晶体中。
We reported the characteristics of hydrate-bound hydrocarbons in lake-bottom sediments at the Kedr mud volcano in Lake Baikal. Twenty hydrate-bearing sediment cores were retrieved, and methane-stable isotopes of hydrate-bound gases (delta C-13 and delta H-2 of -47.8% to -44.0% V-PDB and -280.5% to -272.8% V-SMOW, respectively) indicated their thermogenic origin accompanied with secondary microbial methane. Powder X-ray diffraction patterns of the crystals and molecular composition of the hydrate-bound gases suggested that structure II crystals showed a high concentration of ethane (around 14% of hydrate-bound hydrocarbons), whereas structure I crystals showed a relatively low concentration of ethane (2-5% of hydrate-bound hydrocarbons). These different crystallographic structures comprised complicated layers in the sub-lacustrine sediment, suggesting that the gas hydrates partly dissociate, concentrate ethane and form structure II crystals. We concluded that a high concentration of thermogenic ethane primarily controls the crystallographic structure of gas hydrates and that propane, iso-butane (2-methylpropane) and neopentane (2,2-dimethylpropane) are encaged into crystals in the re-crystallisation process.