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的地幔岩浆与海洋岩石圈中因沉积物或热液蚀变岩石等表面过程而改变的物质之间反应的重要工具。此外，晶体分馏过程也会影响 O 同位素组成，尤其是演化岩浆的 O 同位素组成，因为不同的矿物相会分馏 O 同位素。因此，同化和晶体分馏都阻碍了对地幔中岩浆源的 O 同位素组成的研究，这可能为俯冲带和深部地幔柱衍生的板内岩浆的再循环过程提供重要的见解。在这里，我们建议对来自不同海洋岩浆环境（洋中脊、海洋板内、弧后和岛弧环境）的五个特征明确的熔岩系列的O同位素变化进行研究，以定义玄武质熔岩和硅质熔岩之间的变化以及影响O同位素比率的过程。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 O 同位素组成，并得出地壳再循环到地幔深处和俯冲带下方地幔楔的结论。

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