Modeling the signature of sulfur mass-independent fractionation produced in the Archean atmosphere
Modeling the signature of sulfur mass-independent fractionation produced in the Archean atmosphere
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DOI：
10.1016/j.gca.2014.06.032
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发表时间：
2014-09-15
影响因子：
5
通讯作者：
Meadows, Victoria S.
中科院分区：
文献类型：
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作者：
Claire, Mark W.;Kasting, James F.;Meadows, Victoria S.
少量的硫同位素异常表明太古宙大气中没有O-2。丰富的数据集显示了保存在硫酸盐和硫化物中的S-33三角洲和S-36三角洲的大小和符号变化，这表明对太古宙大气化学的进一步限制是可能的。我们回顾了前人对大气三角洲S-33产量的定量限制，并建议需要一种新的方法。我们将含有S-33和S-34的硫物种加入到一维光化学模式中，并描述了确保准确预测太古宙大气产生和沉积的S-33三角洲的级别和符号所需的数值方法。这种方法可以测试多种大气成分条件下的多个MIF-S形成机制，得出可以与岩石记录相比较的三角洲S-33预测。我们系统地测试了SO2光解中的SO2同位素吸收效应(Danielache等人，2008年)，这是三角洲S-33形成的主要机制之一。我们发现，通过Danielache等人的差异吸收。(2008)断面能够改变预测的德尔塔S-33作为多个大气变量的函数，包括痕量O-2浓度、总硫通量、二氧化碳含量和碳氢化合物的存在，但发现对OCS和H_2S的作用有限。在所有现实条件下，Danielache等人。(2008)的剖面给出了三角洲S-33的预测，与地质记录不符，这意味着硫MIF的形成存在额外的途径和/或剖面有很大的误差。一旦MIF-S生产过程的额外实验测量结果可用，这里提出的方法将允许在没有O-2的情况下对太古宙大气进行定量限制。(C)2014年提交人。爱思唯尔有限公司出版。
Minor sulfur isotope anomalies indicate the absence of O-2 from the Archean atmosphere. A rich dataset showing large variations in magnitude and sign of Delta S-33 and Delta S-36, preserved in both sulfates and sulfides, suggests that further constraints on Archean atmospheric chemistry are possible. We review previous quantitative constraints on atmospheric Delta S-33 production, and suggest that a new approach is needed. We added sulfur species containing S-33 and S-34 to a 1-D photochemical model and describe the numerical methodology needed to ensure accurate prediction of the magnitude and sign of Delta S-33 produced by and deposited from the Archean atmosphere. This methodology can test multiple MIF-S formation mechanisms subject to a variety of proposed atmospheric compositions, yielding Delta S-33 predictions that can be compared to the rock record. We systematically test SO2 isotopologue absorption effects in SO2 photolysis (Danielache et al., 2008), one of the primary proposed mechanisms for Delta S-33 formation. We find that differential absorption through the Danielache et al. (2008) cross sections is capable of altering predicted Delta S-33 as a function of multiple atmospheric variables, including trace O-2 concentration, total sulfur flux, CO2 content, and the presence of hydrocarbons, but find a limited role for OCS and H2S. Under all realistic conditions, the Danielache et al. (2008) cross sections yield Delta S-33 predictions at odds with the geologic record, implying that additional pathways for sulfur MIF formation exist and/or the cross sections have significant errors. The methodology presented here will allow for quantitative constraints on the Archean atmosphere beyond the absence of O-2, as soon as additional experimental measurements of MIF-S producing processes become available. (C) 2014 The Authors. Published by Elsevier Ltd.