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

火山弧的元素流出量是全球地球化学循环中的一个关键变量，其量化需要了解弧的生长速率，即每增加一段时间弧壳的体积。电弧生长速率通常由体积法确定。然而，这些方法得出的数字往往不确定，因为很多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地点的地方。对远端火山灰沉降物的分析可以更严格地评估喷发频率，以及化学成分，这应该与地壳生长有关。因此，笔者建议在弧火山岩组成与弧生长速率之间建立定量联系。该方法建立在Plank和Langmuir（1988）观测到的弧主元素的系统全球变化的基础上，这些变化表明地壳厚度与弧下地幔融化程度之间存在反比关系，并暗示了弧的增长速度。为了验证Plank和Langmuir（1988）的模型，我建议使用现代微分析方法（例如LA-ICPMS、离子探针），在已经得到充分研究的墨西哥火山带和伊豆波宁岛弧中进行选定的案例研究，并对已发表的弧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方法的结合来推导弧的增长率。

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.