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在现代海洋沉积物中,海水硫酸盐的细菌还原作用是形成成岩硫化物的原因,这种硫化物相对于原始硫酸盐而言一般强烈亏损~(34)S,而且其δ~(34)S值变化极大。相反,太古代沉积硫化物的δ~(34)S值一般变化不大,而在相同的沉积单元中硫酸盐的δ~(34)S值几乎不变。这一发现使得以前的研究者认为,或者硫酸盐还原细菌必须在太古代(特别是在2.75Ga前)发育,或者太古代海洋中的硫酸盐含量太少(<<1 mM,而在现代海洋中为28 mM),这意味着太古代大气层内所含的游离氧大大低于现代大气层中的。然而,如果硫酸盐还原细菌在温度为30—50℃,含有大量(>1mM)的硫酸盐、δ~(34)S值约为+3‰的海洋中就已经活跃,那么2.6—3.5Ga前的太古代沉积物的硫同位素资料就可以得到更满意的解释。
In modern marine sediments, the bacterial reduction of seawater sulphate is responsible for the formation of diagenetic sulphides, which are generally strongly depleted of ~ (34) S relative to the original sulphate and have a δ ~ (34) S Value varies greatly. In contrast, the δ ~ (34) S values of the Archean sedimentary sulphides generally do not change much, whereas the δ ~ (34) S values of the sulphate in the same sedimentary units show almost no change. This finding led former researchers to conclude that either sulfate-reducing bacteria must develop in the Archean (especially before 2.75 Ga) or too little in the Archean ocean (<< 1 mM, whereas in the modern ocean 28 mM), meaning that the free oxygen contained in the Archean atmosphere is much lower than in the modern atmosphere. However, if sulfate-reducing bacteria are already active in oceans with a large (> 1 mM) sulfate and a δ ~ (34) S value of about +3 ‰ at temperatures of 30-50 ° C, then 2.6-3.5Ga Archean sediments sulfur isotope data can be more satisfactory explanation.