华北中元古界不同类型硫化合物的硫同位素变化

项目名称： 华北中元古界不同类型硫化合物的硫同位素变化

项目编号： No.41272041

项目类型： 面上项目

立项/批准年度： 2013

项目学科： 天文学、地球科学

项目作者： 张同钢

作者单位： 中国石油大学（北京）

项目金额： 85万元

中文摘要： 元古代海洋环境的变化可能对真核生物的出现和早期演化产生了重要影响。据太古和早元古广泛分布的条带状铁质层（BIF），地质学界一致认为那时期的海洋缺氧并富含亚铁离子。但是，对18.4亿年前之后BIF消失所标志的海洋环境变化还存在争议。Holland 认为BIF的消失标志18.4亿年前之后海洋已经完全变氧化了，而Canfield认为中元古代的海洋表层是氧化的而广泛深海是缺氧硫化的。这种硫化海洋环境抑制了BIF的形成，并限制了微生物固氮作用和真核生物的发展。最新的报道认为18亿年前左右的海洋表层是氧化的，硫化水体仅存在于陆架和陆缘的中等水深区域，广泛的深海水体仍是缺氧并富含亚铁离子。但是目前还缺乏对18亿年前之后的整个中元古代海洋化学的系统研究，导致对中元古代海洋氧化还原的演化过程认知有限。本项目将通过对华北地区中元古界地层的不同组分硫同位素和微量元素的分析研究，恢复中元古代海洋氧化还原条件演化。

中文关键词： 中元古代；碳同位素；硫同位素；环境演化；氧化还原条件

英文摘要： The evolution of Proterozoic oceanic environment probaly played an important role in both the occurence and evolution rate of eukaryotes. According to widespread depositons of band iron formation (BIF), it is thought that oceans were predominantly anoxic and rich in ferrous iron during the Archen and Paleoproterozoic. However, the evlolution history of oceanic chemistry associated with BIF disappearance after 1.84 billion years ago remains debated. Holland suggested that BIF disappearance indicated that deep ocean became oxidized about 1.84 billion years ago. Canfield argued that the suface waters were oxygenated, whereas open deep oceans were dominated by rather anoxic and sulfidic (euxinic) conditions than oxic conditions after 1.84 billion years ago. The euxinic environment prevented the development of BIF and restricted the microbial nitrification and the eukaryote evolution. Recent report suggested that the euxinia only dominated in the shelf and continental margins, however, deep ocean waters still remained anoxic and rich in dissoved iron at ~1.8 billion years. As a result of the scarcity of geochemical data of Mesoproterozoic sediments, the evolution history of Mesoproterozoic ocean redox conditions remains unclear. Here, we propose to conduct analyses of sulfur isotopic compositons of different sulfur c

英文关键词： Mesoproterozoic；carbon isotope；sulfur isotope；environmental evolution；redox condition