Experiments on δ34S mixing between organic and inorganic sulfur species during thermal maturation
Experiments on δ34S mixing between organic and inorganic sulfur species during thermal maturation
复制标题
DOI：
10.1016/j.gca.2006.07.030
复制
发表时间：
2006-10
影响因子：
5
通讯作者：
A. Amrani;Ward Said-Ahamed;M. Lewan;Z. Aizenshtat
中科院分区：
文献类型：
--
作者：
A. Amrani;Ward Said-Ahamed;M. Lewan;Z. Aizenshtat
研究了死海地区合成聚硫交联大分子（PCLM）、模型含硫分子与天然富硫油根、沥青和石油的同位素交换混合约束。PCLM代表富硫、热不稳定的原干酪根。PCLM与HS-(aq)（添加为（NH4）2S(aq)）在中低温度（50-200℃）下的混合速率很快。在200°C的热解条件下，单质硫和H2S（气体）与PCLM充分混合同位素。在这些反应中，PCLM发生了显著的结构变化，形成多硫二聚体、硫烷和噻吩。随着热解温度或反应时间的增加，PCLM热产物转化为更多的芳香族硫化合物。同位素混合率随热解温度和时间的增加而增加。PCLM中的多硫化物键（S-S）由于其低稳定性而导致了大多数这些结构和同位素变化。相反，二苯并噻吩（芳香S）或十六烷醇（C - sh）与HS-(aq)在200℃下48h后不发生硫同位素混合。这表明，硫同位素混合速率在很大程度上取决于有机质中硫的功能。有机质的同位素混合速率顺序为干酪根b>沥青>油，与硫热稳定性成反比。含难熔硫较多的沥青和油的同位素混合率明显低于含不稳定硫较多的干酪根。在此基础上，我们认为硫同位素混合可能发生在成岩早期至裂裂作用阶段，导致无机和有机还原硫池同位素均质化。
Reduced sulfur species were studied to constrain isotopic exchange-mixing with synthetic polysulfide cross-linked macromolecules (PCLM), model sulfur containing molecules and natural sulfur-rich kerogen, asphalt and oil of the Dead Sea area. PCLM represents protokerogens that are rich in sulfur and thermally unstable. Mixing rates of PCLM with HS-(aq) (added as (NH4)2S(aq)) at low to moderate temperatures (50–200°C) are rapid. Elemental sulfur and H2S(gas)fully mix isotopes with PCLM during pyrolysis conditions at 200°C. During these reactions significant structural changes of the PCLM occur to form polysulfide dimers, thiolanes and thiophenes. As pyrolysis temperatures or reaction times increase, the PCLM thermal products are transformed to more aromatic sulfur compounds. Isotopic mixing rates increase with increasing pyrolysis temperature and time. Polysulfide bonds (S–S) in the PCLM are responsible for most of these structural and isotopic changes because of their low stability. Conversely, sulfur isotope mixing does not occur between dibenzothiophene (aromatic S) or hexadecanthiol (C–SH) and HS-(aq) at 200°C after 48h. This shows that rates of sulfur isotope mixing are strongly dependent on the functionality of the sulfur in the organic matter. The order of isotopic mixing rates for organic matter is kerogen>asphalt>oil, which is inverse to their sulfur thermal stability. Asphalt and oil with more refractory sulfur show significantly lower isotopes mixing rates than the kerogen with more labile sulfur. Based on the findings of the present study we suggest that sulfur isotopes mixing can occur from early diagenesis into catagenesis and result in isotopic homogenization of the inorganic and organic reduced sulfur pools.