Fractionation of highly siderophile elements in the lower oceanic crust

下洋壳中高亲铁元素的分馏

• 批准号: 180346143
• 负责人: Professor Dr. Harry Becker
• 金额: --
• 依托单位: Institut für Geologische Wissenschaften
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2013-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/180346143?language=en
• 关键词: Fractionation; highly; siderophile; elements; lower

The processes that lead to the strong fractionation of highly siderophile elements (HSE, the platinum group elements, rhenium and gold) in the crust are not well understood. Compared to the mantle, abundances of some HSE in ocean ridge basalts are lower by a factor of 1000 or more, with Re, Au and Pd being more abundant than other HSE. Because most erupting basalts are sulphide saturated it has been suggested that the highly variable abundances of the HSE in basalts may reflect crystal fractionation processes in the deeper oceanic crust. The relevance of magmatic HSE fractionation in the crust vs. the mantle is still an unresolved major question, particularly because of the limited availability of HSE data and systematic work on lower crustal rocks. We propose to study oceanic middle to lower crustal rocks from ODP site 735B on the SW Indian ridge. The main goals will be to constrain HSE, Se and Te abundances in typical lithologies, to identify HSE carrier phases and their composition, and to assess their impact on the HSE budget of oceanic crust. This will produce constraints on possible magmatic enrichment of HSE in the lower crust and will improve our knowledge of the fractionation of the HSE in the crust-mantle system.

导致地壳中高度亲铁元素(HSE、铂族元素、Re和Au)强烈分馏的过程尚不清楚。与地幔相比，洋脊玄武岩中某些HSE的丰度比地幔低1000倍以上，Re、Au和Pd的丰度高于其他HSE。由于大多数喷发的玄武岩都是硫化物饱和的，因此有人认为玄武岩中HSE的高度可变的丰度可能反映了洋壳深处的晶体分馏过程。地壳和地幔中岩浆HSE分馏的相关性仍然是一个悬而未决的主要问题，特别是因为HSE数据的可获得性和对下地壳岩石的系统研究有限。我们建议对西南印度海脊735B站位的大洋中下地壳岩石进行研究。主要目标将是限制典型岩性中的HSE、Se和Te丰度，确定HSE载体相及其组成，并评估它们对洋壳HSE收支的影响。这将对HSE在下地壳中可能的岩浆富集产生限制，并将提高我们对HSE在壳幔系统中的分馏作用的认识。