Source Contamination vs. Crustal Contamination in Subduction Processes

本工作将评价跨墨西哥火山带近代岩浆的来源和演化。具体来说，有一个基本的问题，即形成火山岩的岩浆是否与大陆地壳发生了很大的相互作用，或者地幔衍生的岩浆是否没有与地壳发生相互作用。这是一个古老的问题，已被证明难以回答许多同位素系统，包括那些Sr和Nd。然而，结合Os和O同位素研究，有可能强烈地约束这个问题。这个问题的答案对大陆火山弧岩石成因、地壳演化、区域构造和地幔化学演化模式具有重要意义。跨墨西哥火山带是研究地壳对弧岩浆活动的贡献的一个很好的野外实验室，因为地壳的年龄和化学成分从西向东发生了巨大的变化。墨西哥西部地壳为三叠纪，墨西哥东部地壳为早元古代。如果岩浆与地壳相互作用，这一显著差异应该记录在最近的火山岩中。

9814891RuizThis work will evaluate the source and evolution of recent magmas of the Trans Mexican Volcanic Belt. Specifically, there is a fundamental question as to whether the magmas that formed the volcanic rocks have interacted greatly with the continental crust, or whether the mantle derived magmas have not interacted with the crust. This is an old question that has proven difficult to answer with many isotopic systems including those of Sr and Nd. However, there is a potential to strongly constrain the question with a combined Os and O isotopic study. Answers to this question have important implications to models of continental volcanic arc petrogenesis, crustal evolution, regional tectonics and the chemical evolution of the mantle. The Trans Mexican Volcanic Belt is an excellent field laboratory to study the crustal contribution to arc magmatism, because the age and chemistry of the crust changes dramatically from west to east. The crust in western Mexico is Triassic in age and in eastern Mexico, the crust is early Proterozoic in age. This is a significant difference that should be documented in the recent volcanic rocks if the magmas interacted with the crust.