MARGINS: Collaborative Research: Temporal and Spatial Variations in Magma Generation and Slab Influence Across the Central American Subduction Zone

在这笔资金下，PI将开展一项Ar/Ar测年试验计划，以确定是否可以在危地马拉东南部一个特征良好的跨弧断面上发现具有适当年龄和化学性质的火山岩样品。如果是这样的话，那么就有可能确定（1）通量和减压过程对部分熔化的相对贡献（2）这些过程如何在弧上变化，以及（3）这些过程如何随时间变化，与变化的地球动力学边界条件有关。危地马拉东南部提供了一个跨弧断面，最近的火山活动几乎连续发生约125公里横向俯冲带。本研究的主要目的是整理流体加入的时机及其对部分熔融的影响。铀系列同位素分析最终将被用来约束的时间和性质的板流体添加到弧岩浆的来源和它们的关系，部分熔融过程。最终将对从火山前缘到前缘后100多公里的年轻火山岩进行铀钍拉帕不平衡研究。对年轻的前缘和前缘后熔岩进行~（40）Ar/~（39）Ar定年，作为U系列的必要前奏。

Under this funding, the PIs will carry out a pilot program of Ar/Ar dating to determine whether volcanic rock samples can be found of appropriate age and chemistry along a well-characterized across-arc transect in SE Guatemala. If so, it may then be possible to determine (1) the relative contributions of flux and decompression processes to partial melting (2) how these processes vary across the arc and (3) how these processes have changed in time, associated with changing geodynamic boundary conditions. Southeastern Guatemala provides access to an across-arc transect with recent volcanism occurring nearly continuously for ~125 km transverse to the subduction zone. Sorting out the timing of fluid addition and its influence on partial melting is the main goal of the this study. U-series isotopic analyses will eventually be used to constrain the timing and character of slab fluid additions to the source of arc magmas and their relationship to partial melting processes. A U-Th-Ra-Pa disequilibrium study will eventually be done on young volcanic rocks from the volcanic front to over 100 km behind the front. 40Ar/39Ar dating of the young front and behind-the-front lavas will be carried out as an integral prelude to U-series.