英国利兹大学Simon W. Poulton团队追踪了中元古代海洋氧化还原变异的空间范围。2025年7月2日出版的《地质学》杂志发表了这项成果。

新出现的地球化学证据表明，中元古代海洋具有相当大的氧化还原非均质性。然而，对不同模式缺氧程度的定量估计仍然缺乏约束。由于铀和钼的氧化还原相关行为具有互补性，因此可以将铀和钼同位素数据结合起来重建古代海洋氧化还原景观，但这种方法尚未应用于中元古代。

研究组提供了华北克拉通约1.4 Ga塔里木盆地下马岭组海相岩石的δ²³⁸U和δ⁹⁸Mo数据，以及独立的氧化还原指示剂（铁形态和氧化还原敏感痕量金属）。研究发现，在缺氧或缺氧条件下沉积的样品中，U和Mo含量较低，δ²³⁸U和δ⁹⁸Mo值与大陆砾石难以区分，显示出明显的碎屑信号。相比之下，自生富集U和Mo的富氧样品的自生δ²³⁸U和δ⁹⁸Mo值最高，与U和Mo的有效还原一致。

在铁氧化条件下沉积的样品显示出较大的中间δ²³⁸U和δ⁹⁸Mo值，通常落在（天）氧和氧端元之间。利用一个耦合的U-Mo同位素质量平衡模型，研究组推断出约1.4 Ga海洋中有限的含氧环境（占全球海底面积的0.5%），但在中国大陆有广泛的低生产力（天）含氧环境和含铁环境。这种氧化还原景观可能为中元古代的真核生物进化提供了潜在的宜居条件。

附：英文原文

Title: Tracking the spatial extent of redox variability in the mid-Proterozoic ocean

Author: Yafang Song, Benjamin J.W. Mills, Fred T. Bowyer, Morten B. Andersen, Frantz Ossa Ossa, Alexander J. Dickson, Jason Harvey, Shuichang Zhang, Xiaomei Wang, Huajian Wang, Donald E. Canfield, Graham A. Shields, Simon W. Poulton

Issue&Volume: 2025-07-02

Abstract: Emerging geochemical evidence suggests considerable redox heterogeneity in the mid-Proterozoic ocean. However, quantitative estimates of the extent of different modes of anoxia remain poorly constrained. Due to their complementary redox-related behavior, uranium and molybdenum isotope data can be combined to reconstruct ancient marine redox landscapes, but this approach has not been applied to the mid-Proterozoic. We present new δ238U and δ98Mo data for marine rocks from the ca. 1.4 Ga Xiamaling Formation, North China craton, together with independent redox indicators (Fe speciation and redox-sensitive trace metals). We find that most samples deposited under oxic or dysoxic conditions retain low U and Mo contents, with δ238U and δ98Mo values indistinguishable from continental crust, demonstrating a dominant detrital signal. By contrast, euxinic samples with authigenic enrichments in U and Mo record the highest authigenic δ238U and δ98Mo values, consistent with efficient reduction of U and Mo. Samples deposited under ferruginous conditions exhibit a wider range of intermediate δ238U and δ98Mo values that generally fall between the (dys)oxic and euxinic end-members. Using a coupled U-Mo isotope mass balance model, we infer limited euxinia (<0.5% of the global seafloor area) but extensive low-productivity (dys)oxic and ferruginous settings in ca. 1.4 Ga oceans. This redox landscape would have provided potentially habitable conditions for eukaryotic evolution in the mid-Proterozoic.

DOI: 10.1130/G53447.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G53447.1/659343/Tracking-the-spatial-extent-of-redox-variabilityredirectedFrom=fulltext