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

在这笔资金的支持下，ppi将开展一项Ar/Ar定年的试点项目，以确定是否可以在危地马拉东南部的一个具有良好特征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)这些过程在弧上如何变化以及(3)这些过程如何随地球动力学边界条件的变化而随时间变化。危地马拉东南部提供了一个跨弧样带，最近的火山活动在俯冲带横向约125公里的范围内几乎连续发生。厘清加入流体的时机及其对部分熔融的影响是本研究的主要目的。u系列同位素分析最终将用于确定弧岩浆源的板状流体添加的时间和特征及其与部分熔融过程的关系。U-Th-Ra-Pa不平衡研究最终将在火山锋后100多公里的年轻火山岩上进行。年轻的前部和后方熔岩的40Ar/39Ar测年将作为u系列的一个完整的前奏进行。

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.