Geochemische und petrologische Untersuchung zur Evaluierung der Hauptelement-Flüsse in Vulkanbogen und die sich daraus ergebenden Konsequenzen für den globalen Stoffkreislauf

地球化学和岩石学调查，以评估火山弧中的主要元素流动及其对全球物质循环的影响

• 批准号: 5397939
• 负责人: Professorin Dr. Susanne M. Straub
• 金额: --
• 依托单位: Lamont-Doherty Earth Observatory
• 依托单位国家: 德国
• 项目类别: Research Fellowships
• 财政年份: 2003
• 资助国家: 德国
• 起止时间: 2002-12-31 至 2005-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5397939?language=en
• 关键词: Geochemische; und; petrologische; Untersuchung; zur

The elemental outflux from volcanic arcs is a key variable in the global geochemical cycle, the quantification of which requires the knowledge of the arc growth rate, i.e. the volume added to the arc crust per time increment. The arc growth rate is commonly determined by volumetric methods. However, these methods often yield uncertain numbers, because so much of the material is actually erupted explosively and is either quickly eroded or deposited far from the volcanic site. Analysis of distal tephra fallout permits a more rigorous evaluation of eruption frequency, as well as the chemical composition, which should correlate to first order with crustal growth. Therefore, I propose to establish quantitative links between the composition of arc volcanic rocks and the arc growth rates. The approach builds on the systematic global variations of the arc major elements observed by Plank and Langmuir (1988), that indicate an inverse relationship between the crustal thickness and the degree of subarc mantle melting, and implicate the arc growth rate. To test the Plank and Langmuir (1988) model, I propose carrying out selected case studies in the well-investigated Mexican Volcanic Belt and the Izu Bonin Island arc, using modern microanalytical methods (e.g. LA-ICPMS, ion probe), and in-depth evaluation of published data on arc volcanic rocks. Finally, models will be developed to derive arc growth rates by a combination of volumetric and geochemical methods.

火山弧的元素外流是全球地球化学循环中的一个关键变量，要对其进行量化，就需要了解弧的增长率，即每一时间增量增加到弧壳中的体积。电弧生长速率通常由体积法确定。然而，这些方法往往产生不确定的数字，因为如此多的物质实际上是爆炸性喷发的，要么被迅速侵蚀，要么沉积在远离火山现场的地方。对火山灰远端沉降物的分析可以更严格地评估火山喷发的频率以及化学成分，这应该与地壳生长的一阶相关。因此，我建议建立定量的弧火山岩的组成和弧增长率之间的联系。该方法建立在Plank和Langmuir（1988）观测到的弧主量元素的系统性全球变化的基础上，表明地壳厚度与弧下地幔熔融程度之间存在反比关系，并暗示了弧的生长速率。为了检验普朗克和朗缪尔（1988）的模型，我建议在调查充分的墨西哥火山带和伊豆小笠原岛弧中进行选定的案例研究，使用现代微分析方法（如LA-ICPMS，离子探针），并对已发表的弧火山岩数据进行深入评价。最后，将开发模型，通过体积和地球化学方法相结合来推导电弧生长速率。