Collaborative Research: Mass Independent Fractionation of Sulfur Isotopes, Re-Os Dating of Sedimentary Pyrite, and the Composition of the Late Archean Atmosphere

合作研究：硫同位素的质量独立分馏、沉积黄铁矿的铼锇测年以及晚太古代大气的组成

• 批准号: 0309197
• 负责人: Holly Stein
• 金额: $ 15万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0309197&HistoricalAwards=false
• 关键词: Collaborative; Research; Mass; Independent; Fractionation

ABSTRACTThe discovery of mass independent fraction (MIF) of the sulfur isotopes in pre-2.45 Ga sulfides and sulfates opened a new window on the chemical evolution of the atmosphere-ocean system. At present, the MIF data for sulfur in Archean sediments are few and contradictory. We propose to undertake a thorough study of the MIF of sulfur in pyrite for three pairs of highly carbonaceous sedimentary rock units deposited between 2.7 and 2.5 Ga in Western Australia, South Africa, and Canada. Pyrite will be selected for this study on the basis of textural, chemical, and isotopic evidence indicative of a syngenetic or diagenetic origin. Pyrite in each of the six rock units will be dated by the Re-Os method. Preliminary data show that it is possible to determine the age of 2.3 Ga sedimentary pyrites with a precision of 1 m.y. Initial 187Os/ 188Os ratios inferred from the pyrite isochrons will provide information on secular variations in the Os isotopic composition of seawater, which probably reflects changes in oxidative weathering and transport of Os from the continents. The dating of Archean sedimentary pyrite can therefore yield important information regarding Os cycling.The MIF measurements will be made on the MAT 253 mass spectrometer at the Geophysical Laboratory in Washington, D.C, using laser fluorination and continuous flow inlet technology. The Re-Os dating will be done at the AIRIE laboratory at Colorado State University (CSU) using Carius tube dissolution and negative thermal ionization mass spectrometry. Sample preparation, microscopy and trace element analyses will be done at Harvard University.We expect that our data will demonstrate to what extent local conditions determined the MIF of the sulfur isotopes in these rock units, to what extent global differences were important, and to what extent global differences reflected changes in the composition of the atmosphere during the last 200 Ma of the Archean.Broader Impacts CriterionThe project will promote training and learning through involvement of students at all levels (postdoctoral, graduate, undergraduate, and high school) with at least the younger students drawn from underrepresented groups. All will be engaged in application of state-of-the-art techniques, and will be encouraged to present their findings at professional meetings. New collaborations are established through this project between Harvard University and CSU, among researchers on three continents, and across geologic sub-disciplines. Dissemination of results will reach beyond immediate research communities, as the Harvard group reports to NASA through participation on the Astrobiology Team, and the AIRIE Program at CSU is based on international collaboration, and transfers new techniques and concepts quickly to applications of direct use in mineral exploration.

摘要在2.45 GA硫化物和硫酸盐中发现的质量独立分数（MIF）为大气 - 海洋系统的化学演化打开了一个新窗口。目前，大将沉积物中硫的MIF数据很少且矛盾。我们建议在西澳大利亚州，南非和加拿大的2.7至2.5 GA之间对黄铁矿中的硫MIF进行全面研究。将根据质地，化学和同位素证据来选择黄铁矿作为本研究，以表明合成性或成岩作用。六个岩石单元中每个单元中的黄铁矿将通过Re-OS方法进行日期。初步数据表明，可以以1 m.y的精度确定2.3 Ga沉积黄铁矿的年龄。从黄铁矿等质素推断出的最初的187OS/ 188OS比率将提供有关海水OS同位素组成中世俗变化的信息，这可能反映了OS从大陆的氧化风化和运输的变化。因此，使用激光氟化和连续流入进口技术，将在华盛顿州华盛顿州地球物理实验室的MAT 253质谱仪上进行MIF测量，可以在MIF 253质谱仪上进行MIF测量。 Re-OS年代将使用Carius管溶解和负热电离质谱法在科罗拉多州立大学（CSU）的空中实验室进行。样本准备，显微镜和痕量元素分析将在哈佛大学进行。我们希望我们的数据将证明当地条件在何种程度上确定了这些岩石单位中硫同位素的MIF，全球差异在多大程度上很重要，全球差异在多大程度上反映出在多大程度上反映了何种差异反映出在何种程度上，在整个级别的阶段都会促进筹备的学生在远古人的贡献中促进贡献的贡献。 （博士后，毕业生，本科和高中）至少是年轻的学生从代表性不足的群体中汲取灵感。所有人都将参与最新技术的应用，并鼓励在专业会议上介绍他们的发现。在哈佛大学和CSU之间，三大洲的研究人员以及跨地质的子学科之间，通过该项目建立了新的合作。由于哈佛大学小组通过参与天文学团队向美国国家航空航天局报告，因此结果将超出直接研究社区，而CSU的Airie计划基于国际合作，并将新技术和概念迅速转移到直接使用矿物探索中。