美国耶鲁大学Alexie E.G. Millikin小组利用新的Re-Os年龄限制，揭示了大氧化事件的动态。该项研究成果发表在2024年9月9日出版的《地质学》上。

据介绍，古元古代早期(ca.2.5-2.2Ga)代表了地球历史上的一个关键时刻，标志着含氧大气的开始，同时见证了潜在的多次广泛而严重的冰川作用。然而，由于缺乏直接的放射性年龄限制，对有争议的地层对比的依赖阻碍了破译这个冰川期的性质及其与大气氧化的关系。

这一点在南非Transvaal超群中表现得最为明显：在这里，虽然Duitschland和Rooihoogte地层都报道了氧敏感的质量无关硫同位素分异(S-MIF)的损失，但围绕这些单位的时间等效性的分歧意见促使作者争论截然不同的氧化轨迹。

为了解决这一争论，研究人员从上Duitschland组岩芯中保存的辉长岩样品中测定了沉积Re-Os年龄(2443±33Ma)。Duitschland组地层与之前假定的等效地层之间的1亿年间隔，揭示了至少两次S-MIF的孤立消失，这要求大氧化事件是动态的，并且是通过离散的氧化事件进行的，其结构仍然不完全清楚。

重要的是，研究修订的框架将下Duitschland混杂岩与低纬度冰川期Makganyene组地层对齐，支持了广泛的区域性，甚至可能是全球的古元古代早期冰川作用的假设。

附：英文原文

Title: A new Re-Os age constraint informs the dynamics of the Great Oxidation Event

Author: Alexie E.G. Millikin, Benjamin T. Uveges, Gareth Izon, Ann M. Bauer, Roger E. Summons, David A.D. Evans, Alan D. Rooney

Issue&Volume: 2024-09-09

Abstract: The early Paleoproterozoic (ca. 2.5-2.2 Ga) represents a critical juncture in Earth history, marking the inception of an oxygenated atmosphere while bearing witness to potentially multiple widespread and severe glaciations. Deciphering the nature of this glacial epoch and its connection with atmospheric oxygenation has, however, proven difficult, hindered by a reliance on disputed stratigraphic correlations given the paucity of direct radiometric age constraints. Nowhere is this more acute than within the South African Transvaal Supergroup: Here, while the loss of oxygen-sensitive mass-independent sulfur isotope fractionation (S-MIF) has been reported from both the Duitschland and Rooihoogte formations, divided opinion surrounding the time-equivalence of these units has prompted authors to argue for vastly different oxygenation trajectories. Addressing this debate, we present a depositional Re-Os age (2443 ± 33 Ma) from diamictite samples preserved in drillcore of the upper Duitschland Formation. The 100-million-year separation between the Duitschland Formation and its previously presumed equivalent reveals at least two isolated disappearances of S-MIF, requiring that the Great Oxidation Event was dynamic and proceeded via discrete oxygenation episodes whose structure remains incompletely understood. Importantly, our revised framework aligns the lower Duitschland diamictite with the low-latitude glacigenic Makganyene Formation, supporting hypotheses of widespread regional, and potentially global, early Paleoproterozoic glaciation.

DOI: 10.1130/G52481.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G52481.1/648332/A-new-Re-Os-age-constraint-informs-the-dynamics-of