Archean kerogen as a new tracer of atmospheric evolution: Implications for dating the widespread nature of early life
Archean kerogen as a new tracer of atmospheric evolution: Implications for dating the widespread nature of early life
复制标题
太古代干酪根作为大气演化的新示踪剂：对早期生命广泛存在的年代测定的影响
作者：
D. Bekaert;M. Broadley;F. Delarue;G. Avice;F. Robert;B. Marty
太古宙干酪根中丰富的古空气揭示了大气Xe的时空演化，为早期有机质提供了测年工具。了解太古宙大气的组成对于解开挥发物的来源和导致生命发展的环境条件至关重要。太古宙大气中氙气的同位素组成随着时间的推移从一种包括彗星和太阳/球粒陨石贡献的前体(称为U-Xe)经过质量分馏而演变。评估太古宙大气的组成是具有挑战性的，因为在形成过程中，有限数量的大气气体被困在矿物中。我们表明，有机物质可以有效地保存大量的惰性气体，可以作为大气惰性气体的新档案。从西澳大利亚皮尔巴拉克拉通30亿年前的法雷尔石英岩中分离出的干酪根中的Xe同位素，每原子质量单位的质量分馏为9.8±2.1mil(‰)(2σ)，与向现代大气值的递进演化一致。太古代大气Xe在干酪根中的特征为追踪大气成分随时间的演化开辟了一条新的途径。Xe同位素相对于现代大气的质量分馏程度可以提供太古宙干酪根测年的时间戳，从而缩小了太古宙早期生命多样化的时间窗口。
Abundant ancient air in Archean kerogen reveals temporal atmospheric Xe evolution, providing a dating tool for early organics. Understanding the composition of the Archean atmosphere is vital for unraveling the origin of volatiles and the environmental conditions that led to the development of life. The isotopic composition of xenon in the Archean atmosphere has evolved through time by mass-dependent fractionation from a precursor comprising cometary and solar/chondritic contributions (referred to as U-Xe). Evaluating the composition of the Archean atmosphere is challenging because limited amounts of atmospheric gas are trapped within minerals during their formation. We show that organic matter, known to be efficient at preserving large quantities of noble gases, can be used as a new archive of atmospheric noble gases. Xe isotopes in a kerogen isolated from the 3.0–billion-year–old Farrel Quartzite (Pilbara Craton, Western Australia) are mass fractionated by 9.8 ± 2.1 per mil (‰) (2σ) per atomic mass unit, in line with a progressive evolution toward modern atmospheric values. Archean atmospheric Xe signatures in kerogens open a new avenue for following the evolution of atmospheric composition through time. The degree of mass fractionation of Xe isotopes relative to the modern atmosphere can provide a time stamp for dating Archean kerogens and therefore narrowing the time window for the diversification of early life during the Archean eon.
加拿大熊猫金伯利岩钻石中微包裹体的挥发性成分：对地幔中化学和同位素异质性的影响
影响因子：
5
作者：
Burgess R
通讯作者：
Burgess R
DOI：
10.1073/pnas.1419563112
发表时间：
2015-05-12
影响因子：
11.1
作者：
French, Katherine L.;Hallmann, Christian;Summons, Roger E.
通讯作者：
Summons, Roger E.