长安大学杨秀清团队在研究古元古代晚期强氧化风化的脉冲中取得新进展。该研究于2024年9月25日发表于国际一流学术期刊《地质学》杂志上。

据悉，中元古代(ca.1.8-0.8Ga)的主要特征是大气含氧量低和海洋普遍缺氧，并伴有充氧脉冲。然而，这些短暂事件背后的原因仍然是未知的。

本研究报道了华北克拉通串岭沟组16.4亿年的黑色页岩和白云岩，它们代表了哥伦比亚超大陆分裂时期的沉积。岩石的特征是初始¹⁸⁷Os/¹⁸⁸Os值高，与现代海水值相当，同时铜的正同位素组成与25亿至22亿年前，大氧化事件期间沉积的页岩相似。

此外，研究人员注意到其Th/U比率和化学蚀变指数值较高。总的来说，数据显示，大陆分裂引发的正反馈，使得陆地上氧化风化增加，海洋的营养供应增加，海洋蓝藻的初级生产力增加，最终，提高了氧气生产速率，使反馈循环永续下去。

附：英文原文

Title: Pulse of intense oxidative weathering during the latest Paleoproterozoic

Author: Xiuqing Yang, Guowei Yang, Chao Li, Kurt O. Konhauser, Changzhi Wu, Fang Huang, Jingwen Mao

Issue&Volume: 2024-09-25

Abstract: The mid-Proterozoic (ca. 1.8-0.8 Ga) is broadly characterized by low atmospheric oxygen and pervasive oceanic anoxia punctuated by pulses of oxygenation. However, the causes underpinning these transient events remain elusive. Here, we report on 1.64 billion-year-old black shales and dolostone from the Chuanlinggou Formation in the North China Craton that represent sediment deposited during the break-up of the supercontinent Columbia. The rocks are characterized by high initial ¹⁸⁷Os/¹⁸⁸Os values, comparable to modern seawater values, alongside positive isotopic compositions of copper similar to those found in shales deposited during the Great Oxidation Event between 2.5 and 2.2 billion years ago. Additionally, we note high Th/U ratios and Chemical Index of Alteration values. Collectively, our data suggest a positive feedback initiated by continental fragmentation, with increased oxidative weathering on land, greater nutrient supply to the oceans, enhanced primary production of marine cyanobacteria, and ultimately, higher rates of oxygen production, perpetuating the feedback loop.

DOI: 10.1130/G52373.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G52373.1/648695/Pulse-of-intense-oxidative-weathering-during-theredirectedFrom=fulltext