Oxygen isotope variations in oceanic magmatic rock suites: assimilation-fractional crystallization processes versus mantle source variations

大洋岩浆岩组中的氧同位素变化：同化分异结晶过程与地幔源变化

• 批准号: 84784881
• 负责人: Professor Dr. Karsten Matthias Haase
• 金额: --
• 依托单位: Forschungsschwerpunkt Krustendynamik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2009-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/84784881?language=en
• 关键词: Oxygen; isotope; variations; oceanic; magmatic

Oxygen isotopes are an important tool to study reactions between ascending mantle-derived magmas and material in the oceanic lithosphere that has been altered by surface processes like for example, sediments or hydrothermally altered rocks. Furthermore, crystal fractionation processes can also affect the O isotope composition especially of evolved magmas because different mineral phases fractionate O isotopes. Both assimilation and crystal fractionation thus impede the study of O isotope compositions of the magma sources in the mantle which could give important insights into recycling processes at subduction zones and in deep mantle plume-derived intraplate magmas. Here we suggest a study of the O isotope variation of five well-characterized lava series from different oceanic magmatic settings (mid-ocean ridge, oceanic intraplate, back-arc, and island arc settings) in order to define the variations between basaltic and silicic lavas and the processes affecting the O isotope ratios. Based on the understanding of lithospheric processes we will be able to distinguish the O isotope composition of the mantle sources of the magmas and draw conclusions on crustal recycling into the deep mantle and into the mantle wedge beneath subduction zones.

氧同位素是研究上升地幔岩浆与大洋岩石圈物质之间反应的重要工具，这些物质已被表面过程改变，例如沉积物或热液蚀变岩石。此外，晶体分馏过程也会影响氧同位素组成，特别是演化岩浆的氧同位素组成，这是因为不同的矿物相分馏了氧同位素。同化作用和晶体分馏都阻碍了地幔岩浆源的氧同位素组成的研究，这可能为俯冲带和深部地幔热柱来源的板内岩浆的循环过程提供重要的认识。我们建议对不同大洋岩浆环境(大洋中脊、大洋板内、弧后和岛弧环境)的五个特征较好的熔岩系列的氧同位素变化进行研究，以确定玄武岩和硅质熔岩之间的变化以及影响氧同位素比值的过程。基于对岩石圈过程的了解，我们将能够区分岩浆地幔来源的氧同位素组成，并得出地壳再循环到深部地幔和俯冲带下的地幔楔体的结论。

项目成果

Oxygen isotope evidence for the formation of silicic Kermadec island arc and Havre-Lau backarc magmas by fractional crystallisation

• DOI: 10.1016/j.epsl.2011.07.014
• 发表时间: 2011-09
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: K. Haase;S. Krumm;M. Regelous;M. Joachimski