Source Contamination vs. Crustal Contamination in Subduction Processes

这项工作将评估横贯墨西哥火山带的近期岩浆的来源和演化。具体地说，存在一个根本的问题，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，或者地幔岩浆是否没有与地壳相互作用。这是一个古老的问题，事实证明，许多同位素系统都很难回答这个问题，包括锶和钕的同位素系统。然而，通过结合Os和O同位素研究，有可能强烈限制这一问题。这一问题的解答对大陆火山弧成因模式、地壳演化模式、区域构造模式和地幔化学演化模式具有重要意义。横贯墨西哥的火山带是研究地壳对弧岩浆作用贡献的优秀野外实验室，因为地壳的年龄和化学成分从西到东变化很大。墨西哥西部的地壳时代为三叠纪，墨西哥东部的地壳时代为早元古代。如果岩浆与地壳相互作用，这是一个重大的差异，应该在最近的火山岩中记录下来。

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.