186Os Investigations into the Origins of Osmium in Seawater

进入现代海洋的Os的最终来源仅受到部分限制。争论的焦点是放射成因的Os是否来自平均的上陆壳，或者Os是否是富含有机质的沉积岩风化的结果。 为此，马里兰州大学的一位研究员将开发190 Pt-186 Os同位素系统，作为海洋化学输入的示踪剂，开展以下研究：（1）通过分析年轻的大洋锰结核和氧化的含金属沉积物来限制现代海洋的186 Os/188 Os;（2）通过对美国、欧洲和亚洲不同地区的黄土和淡水锰结核的分析，确定了大陆地壳的平均~（186）Os/~（188）Os;和（3）通过分析元古代切姆斯福德/昂瓦廷和弗吉尼亚组的黑色页岩，限制了富含有机物沉积物中186 Os/188 Os的平均演化，中国湖南省的寒武纪页岩和加拿大育空地区的泥盆纪页岩。 一旦完成这些分析，如果确认长英质地壳和富含有机物的沉积物的186 Os/188 Os比率之间存在任何分析上可辨别的差异，则PI还将通过分析已知年龄的含金属沉积物来确定新生代海水中186 Os/188 Os的演变。

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.