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Mantle dynamics, magma and crust formation in an oceanic island arc - back-arc system: a case study from the Tonga arc and Valu Fa Ridge

大洋岛弧-弧后系统中的地幔动力学、岩浆和地壳形成：以汤加岛弧和瓦鲁法海岭为例

基本信息

批准号：
352466535
负责人：
Professor Dr. Karsten Matthias Haase
金额：
--
依托单位：
GEMOC, ARC National Key Centre
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/352466535?language=en
关键词：
Mantle dynamics magma crust formation

项目摘要

Subduction zones are important regions of the Earth where crustal material is recycled into the mantle and where crust is formed that may be a precursor for continents. Oceanic subduction systems often consist of volcanoes at the island arc front as well as in extensional back-arc rifts and thus provide insights into magma formation and mantle wedge dynamics. Here we suggest studying the petrology and geochemistry of abundant volcanism in an about 250 km long section of the southern Tonga island arc and the 40 km distant Valu Fa back-arc ridge as well as of numerous off-axis volcanoes between the two structures. The abundance of young volcanoes that have been sampled makes this region an ideal natural laboratory for the study of magmatic processes at subduction zones. We propose the analysis of a large sample set of some 200 back-arc and 300 arc and off-axis samples using modern geochemical methods to generate a data set of major and trace elements as well as Sr-Nd-Pb-Hf-O-Th-U-Ra isotopes on glasses, whole rocks and minerals. On the basis of these data we will be able to define 1) the mantle and melt flow in this region, 2) the melting, mantle depletion and mixing processes between arc front and back-arc magmas, and 3) the variation of magma evolution and crust formation in the different settings.

俯冲带是地球上重要的区域，在那里地壳物质被循环到地幔中，地壳的形成可能是大陆的前身。海洋俯冲系统通常由岛弧前缘和伸展弧后裂谷的火山组成，因此提供了对岩浆形成和地幔楔动力学的见解。在此，我们建议研究汤加岛弧南部约250公里长的火山活动和40公里远的Valu Fa弧后脊以及两个构造之间的许多离轴火山的岩石学和地球化学。丰富的年轻火山样本使该地区成为研究俯冲带岩浆过程的理想天然实验室。我们建议使用现代地球化学方法分析大约200个弧后和300个弧和离轴样品的大样本集，以生成玻璃，整个岩石和矿物上的主要和微量元素以及Sr-Nd-Pb-Hf-O-Th-U-Ra同位素的数据集。根据这些数据，我们将能够定义1)该地区的地幔和熔体流动，2)弧前和弧后岩浆的熔融、地幔衰竭和混合过程，以及3)不同背景下岩浆演化和地壳形成的变化。