内蒙古温都尔庙蛇纹石化橄榄岩气体组成及成因探讨

The Gas Composition and Genesis of the Serpentinized Peridotitein in the Wenduermiao Area,Inner Mongolia,China

橄榄岩的蛇纹石化过程可驱动热液系统并产生CH_4和氢气,并为生物体提供能量和电子来源的分子氢。对蛇纹石化气体的研究,可为非生物成因CH_4的形成提供证据,也具备有利的有机化合物合成条件,进而探索地球生命起源。本文采用分步加热质谱法测定了内蒙古温都尔庙地区蛇纹石化橄榄岩(大理岩)气体化学组成和碳同位素组成,结果表明,CO_2占有极高的比例,N_2和H_2的含量较高,CH_4和C_2H_6在400~600℃温度段释出含量较高。CO_2的δ^(13)C为-18.6‰~2.6‰,CH_4的δ^(13)C_1为-8.1‰^-51.8‰,CH_4、C_2H_6、C_3H_8和C_4H_(10)的碳同位组成随着碳数增加具有正序分布,完全反序和局部反序的分布特征,显示气体来源具有多样性,具有非生物成因气和生物成因气(热成因或细菌)的来源。

Serpentinization process may be the driving force of the hydrothermal system and can produce methane and hy- drogen, the molecular hydrogen which can provide energy and electrons for microbial communities. Study of the serpentini- zation gas not only provides evidences of abiotic methane formation, but also provides favorable conditions for synthesizing organic compound. In addition, the study of the serpentinized ultrabasic rocks is helpful for systematically explore the ori- gins of life on earth. Chemical compositions and carbon isotopes of the gas released from the serpentinized peridotite（ mar- ble） in the Wenduermiao area in Inner Mongolia have been determined in this paper by using stepwise heating mass spec- trometer. Results show that CO2 is the dominant component with relatively high contents of N2and H： in the gas released from the serpentinized peridotite in the Wenduermiao area. In addition, CH4 and C2H6 contents are relatively high in the gas released from the serpentinized peridotite at temperatures varying from 400℃ to 600℃. δ13C values of COs and CH4 va- ry from -18.6‰to 2.6‰ and from -8.1‰ to -51.8‰, respectivley. With the increase of the number of carbon in vari- ous gases, the distribution pattern of carbon isotopic compositions of CH4, C2H6, C3Hs, and C4H10 are varied from the positive sequence distribution, the completely inverted sequence distribution, to the partially inverted sequence distribu-tion. This shows that there are multiple origins, including abiotic and biotic（thermal or bacterial）origins, of the gases re- leased from the serpentinized peridotite.