Department of Geological Sciences, Stockholm University, Sweden.
Geochem Trans. 2011 Jun 27;12(1):6. doi: 10.1186/1467-4866-12-6.
Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH4 and H2 formation potential of forsteritic olivine.The results show low temperature CH4 production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH4 source trapped in the crystal structure of the olivine showed no signs of incorporated CH4. Also, the available sources of organic carbon were not enough to support the total amount of CH4 detected in our experiments. There was also a linear relationship between silica release into solution and the net CH4 accumulation into the incubation bottle headspaces suggesting that CH4 formation under these conditions could be a qualitative indicator of olivine dissolution.It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH4, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH4 formation both on Earth and on other terrestrial bodies.
甲烷等碳氢化合物已知是通过水热系统中的费托或萨巴蒂埃型反应形成的，通常在 100°C 以上的温度下。有时认为橄榄石的风化作用通过其氧化还原降低和水分解特性来解释 CH4 的非生物形成。了解低温下 CH4 和 H2 的形成过程对于研究早期地球和火星 CH4 的起源和成因以及 CO2 封存具有重要意义。我们进行了一系列低温、长期风化实验，在这些实验中，我们测试了镁橄榄石的 CH4 和 H2 形成潜力。结果表明，低温 CH4 的产生可能受到铬铁矿和磁铁矿作为催化剂的影响。对可能被困在橄榄石晶体结构中的 CH4 源的广泛分析表明没有结合 CH4 的迹象。此外，有机碳的可用来源不足以支持我们实验中检测到的总 CH4 量。进入孵育瓶顶空的净 CH4 积累与溶液中释放的二氧化硅之间也存在线性关系，这表明在这些条件下 CH4 的形成可能是橄榄石溶解的定性指标。由于系统温度低，橄榄石表面发现的磁铁矿、铬铁矿和其他富金属矿物等矿物可能会催化 CH4 的形成。这可能会扩大地球上和其他类地天体上合理的非生物 CH4 形成环境范围。
