大气影响地球最早的硫循环
1Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA. E-mail: jfarquha@ucsd.edu (J.F. ); hbao@ucsd.edu (H.B.); and MHT@chem.ucsd.edu (M.T.).
Science (New York, N.Y.)
|August 5, 2000
概括
前坎布里亚时期的硫循环在2.090亿至2.450亿年前发生了重大变化. 在这个时期之前,由于氧气水平较低,大气反应而不是微生物活动主导了硫循环.
科学领域:
- 地质化学 地质化学
- 古气候学 古气候学
- 同位素地质学的同位素.
背景情况:
- 硫循环是早期地球条件的关键指标.
- 质量独立的硫同位素特征 (delta(33) S,delta(34) S,delta(36) S) 提供了对大气过程的洞察力.
- 了解前坎布里亚硫循环是重建早期大气组成和生物活动的关键.
研究的目的:
- 为了研究前坎布里亚时代硫循环的演变.
- 确定硫循环机制发生重大转变的时间.
- 评估大气化学与生物过程对硫同位素的影响.
主要方法:
- 在前坎布里亚岩石中的硫化物和硫酸盐中分析质量独立的同位素特征 (delta(33) S,delta(34) S,delta(36) S).
- 地质化学建模以解释在大气和生物硫转换的背景下同位素数据.
主要成果:
- 证据表明,在2.090亿至2.450亿年前之间,硫循环发生了重大变化 (Ma).
- 在2450万年前,气相大气反应显著影响了硫循环.
- 推断出低大气氧局部压力,限制氧化气候和微生物硫循环.
结论:
- 前坎布里亚硫循环经历了根本性的转变,从大气反应主导转向其他过程.
- 早期大气化学,而不是微生物活动,主要控制了2450万年前的硫同位素分离.
- 在解释硫同位素时必须考虑大气分离,以了解早期微生物生命和地球历史.
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