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

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，其量化需要了解弧长速率，即每一次增加到弧壳中的体积。弧长速率通常用容积法测定。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的喷发，要么被迅速侵蚀，要么被沉积在远离火山遗址的地方。通过对远端火山喷发尘埃的分析，可以更严格地评估喷发频率以及化学成分，这些化学成分应与地壳生长的一级相关。因此，我建议在弧形火山岩的成分和弧形生长速率之间建立定量的联系。该方法建立在Plank和Langmuir(1988)观测到的弧主要元素的系统全球变化的基础上，表明地壳厚度与弧下地幔熔融程度成反比关系，并与弧增长速度有关。为了验证Plank和Langmuir(1988)模型，我建议使用现代微观分析方法(如LA-ICPMS、离子探针)在调查充分的墨西哥火山带和伊豆·博宁岛弧进行选定的案例研究，并对已公布的弧形火山岩数据进行深入评估。最后，将开发模型，通过体积法和地球化学法相结合的方法得出弧长速率。

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.