186Os Investigations into the Origins of Osmium in Seawater

186Os 海水中锇的起源调查

• 批准号: 0116955
• 负责人: Richard Walker
• 金额: $ 14.8万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-10-01 至 2003-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0116955&HistoricalAwards=false
• 关键词: 186Os; Investigations; into; Origins; Osmium

ABSTRACTOCE-0116955The ultimate source of Os into the modern ocean is only partially constrained. At issue is whether radiogenic Os is derived from average upper continental crust or whether Os is the result of weathering of organic-rich sedimentary rocks. For this reason, a PI from the University of Maryland will develop the 190Pt-186Os isotope system as a tracer of chemical input into the oceans by carrying out the following research: (1) constrain the 186Os/188Os of the modern ocean via analysis of young oceanic Mn-nodules and oxidized metalliferous sediments; (2) constrain the average 186Os/188Os of the continental crust via the analysis of loess and freshwater Mn-concretions from a variety of locations in the United States, Europe and Asia; and (3) constrain the average evolution of 186Os/188Os in organic-rich sediments via the analysis black shales from the Proterozoic Chelmsford/Onwatin and Virginia Formations, Cambrian shales from the Hunan Province in China and Devonian shales from the Yukon Territory of Canada. Once these analysis have been completed and if any analytically discernable differences are confirmed between the 186Os/188Os ratio of felsic crust and organic-rich sediments, then the PI also will determine the evolution of 186Os/188Os in Cenozoic seawater via analysis of metalliferous sediments of known age.

进入现代海洋的Os的最终来源只有部分受到限制。争论的焦点是，放射性成因的Os是来自平均上大陆地壳，还是富含有机质的沉积岩风化的结果。为此，马里兰大学的一位PI将通过以下研究发展190Pt186Os同位素系统，作为向海洋输入化学物质的示踪剂：(1)通过分析年轻的大洋锰结核和氧化的金属沉积物来约束现代海洋的186Os/188Os：(2)通过对美国、欧洲和亚洲不同地点的黄土和淡水锰结核的分析来约束大陆地壳的平均186Os/188Os；(3)通过对元古界切姆斯福德/翁瓦丁组和弗吉尼亚组黑色页岩、中国湖南寒武系页岩和加拿大育空地区泥盆纪页岩的分析，约束了富有机质沉积物中186Os/188Os的平均演化。一旦这些分析完成，如果确认长英质结壳和富含有机质沉积物的186Os/188Os比值在分析上有任何可辨别的差异，那么PI还将通过对已知年龄的含金属沉积物的分析来确定新生代海水中186Os/188Os的演化。