Theoretical modeling of rhenium isotope fractionation, natural variations across a black shale weathering profile, and potential as a paleoredox proxy
Theoretical modeling of rhenium isotope fractionation, natural variations across a black shale weathering profile, and potential as a paleoredox proxy
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铼同位素分馏的理论模型、黑色页岩风化剖面的自然变化以及作为古氧化还原代理的潜力
DOI：
10.1016/j.epsl.2015.08.008
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发表时间：
2015
影响因子：
5.3
通讯作者：
E. Schauble
中科院分区：
文献类型：
--
作者：
C. A. Miller;B. Peucker‐Ehrenbrink;E. Schauble
我们提出了第一个记录铼同位素组成环境变化的数据，以及第一个平衡铼同位素分馏因子的理论模型。现代表面温度下 δ 187 Re 的变化预计将达到氧化还原 (Re VII⇌ Re IV) 和高铼酸盐硫醇化反应 (Re VII O 4−⇌ Re VII O X S 4− X−⇌ Re VII S 4−) 的水平。核体积分馏经计算小于质量相关效应。这项工作和之前的研究中提出的新奥尔巴尼页岩样品的 δ 187 Re 值显示，在 20 m 的地层间隔内，其范围为 0.8‰。变化幅度与理论预测一致，可能为过去地质时期海水δ 187 Re 的变化提供证据。在 14 m 水平黑色页岩风化剖面上，δ 187 Re 变化 0.3‰，伴随着 Re 浓度下降 100 倍，有机碳下降 75%，与从还原环境向氧化风化环境的转变有关。我们将 δ 187 Re 的减少归因于有机结合 Re 成分的损失（δ 187 Re=− 0.28‰）。补充碎屑硅酸盐部分的铼同位素组成在− 0.59 至− 1.5‰ 之间变化，具体取决于硅酸盐铼浓度的选择。
We present the first data documenting environmental variations in the isotope composition of Re, and the first theoretical models of equilibrium Re isotope fractionation factors. Variations of δ 187 Re at modern surface temperatures are predicted to be‰ level for redox (Re VII⇌ Re IV) and perrhenate thiolation reactions (Re VII O 4−⇌ Re VII O X S 4− X−⇌ Re VII S 4−). Nuclear volume fractionations are calculated to be smaller than mass dependent effects. Values of δ 187 Re from New Albany Shale samples presented in this work and in a previous study show a range of 0.8‰ over a stratigraphic interval of∼ 20 m. The magnitude of variation is consistent with theoretical predictions and may provide evidence for changing δ 187 Re of seawater in the geologic past. A− 0.3‰ change in δ 187 Re across a 14 m horizontal black shale weathering profile is accompanied by a hundred-fold decrease in Re concentration and a 75% decrease in organic carbon associated with the transition from reducing to oxic weathering environment. We attribute decreasing δ 187 Re to the loss of organically bound Re component (δ 187 Re=− 0.28‰). The Re isotope composition of the complementary detrital silicate fraction varies from− 0.59 to− 1.5‰, depending on the choice of silicate Re concentration.
影响因子：
5.8
作者：
Montoya-Pino, Carolina;Weyer, Stefan;Arz, Helge W.
通讯作者：
Arz, Helge W.