Evolution of the oceanic sulfur cycle at the end of the Paleoproterozoic
Evolution of the oceanic sulfur cycle at the end of the Paleoproterozoic
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DOI：
10.1016/j.gca.2006.08.001
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发表时间：
2006-12-01
影响因子：
5
通讯作者：
Farquhar, James
中科院分区：
文献类型：
--
作者：
Johnston, David T.;Poulton, Simon W.;Farquhar, James
在这里，我们提出了新的测量S-32，S-33，S-34，和S-36在沉积硫化物和耦合这些测量与建模处理研究晚古元古代海洋盆地的硫循环。我们的目标是从古元古代铁地层（Gunflint形成，Biwabik形成，Trommald形成，和Mahnomen铁地层）的沉积海洋化学的过渡，推断硫化物海洋条件记录上覆页岩（Rove形成）。这些数据表明，全球硫循环的某些特征，如硫酸盐还原原核生物的控制，以及海洋硫酸盐的低浓度（mM），在这一转变过程中得以维持。这表明，过渡与这些沉积物沉积过程中的盆地规模的硫循环的结构变化。从铁地层的硫化物数据进行解释，以反映沉积硫化物形成的微生物还原孔隙水硫酸盐，通过稳态交换与上覆的海洋硫酸盐储层。富氧Rove地层页岩的硫化物数据反映了硫循环的操作，包括由类瑞利过程造成的硫化物损失。我们认为，在Rove Formation硫化物矿物中观察到的大的和可变的重同位素富集的流行反映了从富氧水柱硫化物的持续和显著的净损失，无论是作为一个浅的化学跃层和脱气到大气中的结果，还是作为一个水柱黄铁矿汇的结果。包括S-36测量值（除S-32、S-33和S-34外）说明了这些沉积环境的质量依赖性，排除了太古代硫化物风化的贡献，并指出至少有适度的持续大气氧水平（> 10（-5）目前大气中的O-2水平）。(c)2006年爱思唯尔公司All rights reserved.
Here, we present new measurements of S-32, S-33, S-34, and S-36 in sedimentary sulfides and couple these measurements with modeling treatments to study the sulfur cycle of a late Paleoproterozoic marine basin. We target the transition in ocean chemistry from the deposition of Paleoproterozoic iron formations (Gunflint Formation, Biwabik Formation, Trommald Formation, and Mahnomen iron formations) to the inferred sulfidic ocean conditions recorded by overlying shale (Rove Formation). The data suggest that certain features of the global sulfur cycle, such as a control by sulfate reducing prokaryotes, and low (mM) concentrations of oceanic sulfate, were maintained across this transition. This suggests that the transition was associated with changes in the structure of the basin-scale sulfur cycle during deposition of these sediments. Sulfide data from the iron formations are interpreted to reflect sedimentary sulfides formed from microbial reduction of pore-water sulfate that was supplied through steady-state exchange with an overlying oceanic sulfate reservoir. The sulfide data for the euxinic Rove Formation shales reflect the operation of a sulfur cycle that included the loss of sulfide by a Rayleigh-like process. We suggest that the prevalence of large and variable heavy isotope enrichments observed in Rove Formation sulfide minerals reflect a sustained and significant net loss of sulfide from the euxinic water column, either as a result of a shallow chemocline and degassing to the atmosphere or as a result of a water column pyrite sink. The inclusion of S-36 measurements (in addition to S-32, S-33, and S-34) illustrates the mass-dependent character of these sedimentary environments, ruling out contributions from the weathering of Archean sulfides and pointing to at least modest levels of sustained atmospheric oxygen (> 10(-5) present atmospheric levels of O-2). (c) 2006 Elsevier Inc. All rights reserved.