Coupled Cr and Mo isotope investigations of post-GOE Paleoproterozoic sediments: Testing the hypothesis of an oxygen overshoot in atmospheric O2 levels

GOE 后古元古代沉积物的 Cr 和 Mo 同位素耦合研究：检验大气 O2 水平中氧超调的假设

基本信息

批准号：
398425896
负责人：
Professor Dr. Ronny Schönberg, Ph.D.
金额：
--
依托单位：
Arbeitsgruppe Isotopengeochemie
依托单位国家：
德国
项目类别：
Infrastructure Priority Programmes
财政年份：
2018
资助国家：
德国
起止时间：
2017-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/398425896?language=en
关键词：
Coupled Cr Mo isotope investigations

项目摘要

Coupled isotope investigations of the redox-sensitive elements Cr and Mo in 2.5 – 2.0-Gyr-old sediments of the Pechenga Greenstone Belt (PGB) and the Onega Basin (OB) in Russia will be used to reconstruct the redox evolution of the atmosphere and oceans postdating the Great Oxidation Event (GOE). The GOE marks the first significant increase in atmospheric oxygen levels and defines the transitions from anoxic to oxic environmental conditions. The aftermath of the GOE is characterized by major perturbations of the oxygen, carbon, and sulfur cycle - probably global - during the 2.22 – 2.05-Gyr-old Lomagundi and the following Shunga events. While the post-GOE sediments archive evidence for the burial of vast amounts of organic carbon, the expansion and contraction of the seawater sulfate reservoir, a proposed oxygen overshoot and the onset of effective continental weathering, the timing and response between the oxygenation of the atmosphere and oceans is poorly constrained. Moreover and more puzzling, even though the GOE marks the onset of oxygen-rich atmospheric conditions that was probably followed by an oxygen overshoot, Cr isotopes that are suggested as a tracer for free oxygen fail to identify oxygen-rich conditions in the Paleoproterozoic. This project seeks to perform detailed coupled Cr and Mo isotope investigations on various near-shore sedimentary environments from the Kuetsjärvi, Kolosjoki (PGB) and Zaonezhskaya (OB) formations. The first part of the project will characterize the paleoenvironmental conditions by major and trace elements and carbon isotopes, whereas the second part focuses on the combined Cr and Mo isotope investigations. Complementary geochemical investigations will be carried out on near-shore sediments from the 2.2 – 2.1-Gyr-old Pretoria Group (Botswana), because these sediments also capture the Lomagundi Event and will help to provide a more detailed, and probably global, understanding of the Paleoproterozoic atmosphere-ocean system.

对Pechenga Greenstone Belt（PGB）的2.5 - 2.0-GER型沉积物中对氧化还原敏感元件CR和MO的偶联同位素研究将使用俄罗斯的Onega Basin（OB）重建大气的氧化还原演化，并将大气的氧化还原进化（Goe）延伸到了大气层（GOE）。 GOE标志着大气中的氧气水平的首次显着增加，并定义了从缺氧到氧气环境条件的过渡。 GOE的后果的特征是在2.22 - 2.05 -gyr -gred Lomagundi和随后的Shunga事件中，氧，碳和硫周期的主要扰动（可能是全球）。虽然后期沉积物归档了大量有机碳的归档证据，但硫酸海水的膨胀和收缩，提议的氧气过冲以及有效的持续风化，大气和海洋氧气之间的时机和反应的开始，却很差。此外，即使GOE标志着富含氧气的大气条件的发作，可能随后是氧气过冲，CR同位素被认为是游离氧气的示踪剂，无法识别古古元中的富氧条件。该项目旨在对Kuetsjärvi，Kolosjoki（PGB）和Zaonezhskaya（OB）地层的各种近岸沉积环境进行详细的耦合CR和MO同位素调查。该项目的第一部分将通过主要和微量元素和碳同位素来表征古环境条件，而第二部分则集中在CR和MO同位素研究上。互补的地球化学研究将在2.2 - 2.1-gyr gorp的比勒陀利亚组（Botswana）的近岸沉积物上进行，因为这些沉积物还捕获了Lomagundi事件，并将有助于提供更详细的，可能是全球化的，可能是对古植物学气氛 - 环境系统的理解。