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

在这笔资金的资助下，PIS将开展Ar/Ar测年试点计划，以确定是否可以在危地马拉东南部一条特征良好的跨弧形断面上找到适当年龄和化学成分的火山岩样本。如果是这样的话，就有可能确定(1)助熔剂和减压过程对部分熔化的相对贡献，(2)这些过程如何在整个弧线上变化，(3)这些过程在时间上如何变化，与不断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条横跨弧形断面的通道，最近的火山活动几乎连续发生，横跨俯冲带约125公里。找出添加流体的时机及其对部分熔化的影响是本研究的主要目的。U系列同位素分析最终将被用来限制板条流体添加到弧岩浆来源的时间和特征，以及它们与部分熔融过程的关系。一项U-Th-Ra-Pa不平衡研究最终将在从火山前缘到前锋后100多公里的年轻火山岩上进行。将对年轻的前部熔岩和后部熔岩进行40Ar/39Ar测年，作为U系列的完整前奏。

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.