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，项目负责人将开展 Ar/Ar 测年试点计划，以确定是否可以在危地马拉东南部的一条特征明确的跨弧样带上找到具有适当年龄和化学成分的火山岩样本。如果是这样，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，与不断变化的地球动力学边界条件相关。危地马拉东南部提供了通往跨弧横断面的通道，最近的火山活动几乎连续发生在俯冲带横向约 125 公里的范围内。理清流体添加时机及其对部分熔化的影响是本研究的主要目标。 U系列同位素分析最终将用于限制板片流体添加到电弧岩浆源的时间和特征及其与部分熔融过程的关系。 U-Th-Ra-Pa 不平衡研究最终将针对从火山前缘到火山前缘后方 100 多公里的年轻火山岩进行。对年轻的前部和后部熔岩进行 40Ar/39Ar 测年将作为 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.