Origin of methane and heavier hydrocarbons entrapped within Miocene methane-seep carbonates from central Japan
Origin of methane and heavier hydrocarbons entrapped within Miocene methane-seep carbonates from central Japan
复制标题
日本中部中新世甲烷渗透碳酸盐中甲烷和较重碳氢化合物的起源
DOI：
10.1016/j.chemgeo.2018.09.014
复制
发表时间：
2018
期刊：
影响因子：
3.9
通讯作者：
Hasegawa Takashi
中科院分区：
文献类型：
--
作者：
Miyajima Yusuke;Ijiri Akira;Miyake Akira;Hasegawa Takashi
我们研究了在日本收集的中新世甲烷衍生碳酸盐岩中残留气体的碳同位素和分子组成。甲烷、乙烷和丙烷通过粉末碳酸盐的酸消化提取。提取的烃类的同位素和分子组成与常规的热成因和微生物气体不一致。尽管δ 13 C值在−67‰到−38‰之间（相对于维也纳皮迪贝莱姆岩（VPDB）），但释放出的烃类产生的甲烷与乙烷+丙烷的比例始终很低（2-30）。萃取出的乙烷和丙烷的δ 13 C值异常低至−84‰，低于共存的甲烷。乙烷和丙烷最有可能是在埋藏过程中保存在渗漏碳酸盐中的有机化合物热裂解产生的。所观察到的不寻常的同位素趋势可能是由两种热成因气体组分的混合与不同的碳同位素和分子组成。然而，在一个研究地点（Nakanomata），甲烷和相对不成熟的碳酸盐的δ 13 C值之间的正相关性表明，虽然甲烷被氧化为碳酸氢盐，碳酸盐沉淀，但它被保存在宿主碳酸盐胶结物中。这种情况表明，残留的甲烷至少部分来源于中新世渗漏流体。在加热和粉碎碎片样品的过程中也释放出少量的甲烷。结果表明，甲烷主要被困在晶体内的包裹体，这是支持在一个单独的晶体中观察到的丰富的纳米级的空隙。
We examined the carbon isotopic and molecular compositions of residual gases within Miocene methane-derived carbonates collected in Japan. Methane, ethane, and propane were extracted by acid digestion of powdered carbonates. The isotopic and molecular compositions of the extracted hydrocarbons are inconsistent with conventional thermogenic and microbial gases. Despite a range of δ13C values from −67‰ to −38‰ (relative to Vienna Pee Dee Belemnite (VPDB)), the liberated hydrocarbons yielded consistently low methane to ethane + propane ratios (2–30). The extracted ethane and propane yielded anomalous δ13C values as low as −84‰, lower than those of the coexisting methane. The ethane and propane were most likely produced through thermal cracking of organic compounds preserved within the seep carbonates during burial. The observed unusual isotopic trends may be explained by the mixing of two thermogenic gas components with different carbon isotopic and molecular compositions. Nevertheless, a positive correlation between δ13C values of methane and relatively immature carbonates at one study site (Nakanomata) indicates that while methane was oxidized to bicarbonate from which carbonates precipitated, it was preserved within the host carbonate cements. Such a scenario indicates that the residual methane at least partly originates from the Miocene seep fluid. Smaller amounts of methane were also released during heating and crushing of chipped samples. The results suggest that methane was entrapped mainly within intracrystal inclusions, which is supported by the observation of abundant nanometer-scale voids in an individual crystal.
登录
查看更多内容
影响因子：
2.1
作者：
Ijiri, Akira;Tsunogai, Urumu;Saito, Saneatsu
通讯作者：
Saito, Saneatsu
DOI：
10.1016/j.palaeo.2012.11.020
发表时间：
2013-11-15
影响因子：
3
作者：
Agirrezabala, Luis M.;Kiel, Steffen;Reitner, Joachim
通讯作者：
Reitner, Joachim
24. 智利大陆边缘沉积物中气体的同位素组成1
DOI：
--
发表时间：
1995
期刊：
--
影响因子：
--
作者：
A. Waseda;B. M. Didyk
通讯作者：
B. M. Didyk
智利大陆边缘沉积物中气体的同位素组成 1
DOI：
10.2973/odp.proc.sr.141.024.1995
发表时间：
2006
期刊：
--
影响因子：
--
作者：
A. Waseda;B. M. Didyk
通讯作者：
B. M. Didyk
弧前沉积物中流体和气体运移的稳定同位素研究
DOI：
--
发表时间：
2003
期刊：
--
影响因子：
--
作者：
井尻 暁
通讯作者：
井尻 暁