项目名称: 铁、钼同位素对新元古代碳同位素负异常的约束
项目编号: No.41303003
项目类型: 青年科学基金项目
立项/批准年度: 2014
项目学科: 天文学、地球科学
项目作者: 闫斌
作者单位: 中国地质科学院地质研究所
项目金额: 25万元
中文摘要: 华南埃迪卡拉系陡山沱组碳同位素演化曲线具有数次显著的负异常,这一特征已被广泛应用于地层划分与对比研究中,可能反映了陡山沱时期海洋和大气的变化,但目前对这些负异常事件的性质和形成机制的认识还存在着争议。铁和钼同位素作为不同尺度的氧化还原状态的替代指标,能够示踪区域性或全球性的海洋环境信息。本项目以铁、钼同位素体系为主要手段,以华南陡山沱组典型地质剖面存在碳同位素负异常的地层序列为研究对象,查明碳酸盐岩和黑色页岩中铁、钼同位素分布特征,探讨铁、钼同位素可能存在的分馏机制,厘定新元古代晚期海水的铁、钼同位素组成。同时,基于铁、钼同位素所反映的不同尺度的氧化还原信息,制约埃迪卡拉纪碳同位素负异常的性质和形成机制,揭示影响新元古代晚期海洋环境变化的主导因素,为进一步探讨新元古代海洋环境的变化和生物演化提供新视角。
中文关键词: 铁同位素;钼同位素;稀土元素;碳同位素负异常;陡山沱组
英文摘要: The carbon isotope profiles of the Ediacaran Doushantuo Formation in South China exhibit significant negative carbon isotope excursions, reflecting the changes of ocean and atmosphere, and closely relating to biological evolution, but there are still controversy over the characters and formation mechanisms of these negative carbon isotope excursions. In this study, elements and isotopes geochemistry, especially Fe and Mo isotopes which can trace out the redox state of ocean on different scales, are used for the sequences of negative carbon isotope excursions events in the typical profiles of the Doushantuo Formation. The Fe and Mo isotopic compositions of the carbonates and black shales from the stratigraphic sequence of negative carbon isotope excursions will be analyzed. These will help us to find the Fe and Mo isotope distribution characteristics of the sedimentary rocks during negative carbon isotope excursions events, explore the fractionation mechanism of Fe and Mo isotopes, determine the Fe and Mo isotopic compositions of ocean during Late Neoproterozoic. Meanwhile, using the redox conditions on different scales of Fe and Mo isotopes can constraint the characters and formation mechanisms of these negative carbon isotope excursions, and dominant the main factor of the marine environment changes in Late Neo
英文关键词: iron isotope;Mo isotope;rare trace element;negative δ13Ccarb excursion;the Doushantuo Formation