Collaborative Research: Resolving Mantle, Crustal and Slab Fluxes to Arc Magmatism in Central America Using Geothermal Fluids and Volcanic Rocks

希尔顿/步行者/费歇尔-0003628/0003664/0003668这项建议的目的是通过量化俯冲板片、地幔楔和上覆地壳对整个弧预算的贡献，为中美洲俯冲带建立一个不稳定的物质平衡。选择中美洲弧是因为它具有一些独特的特征，可以在火山产出的系统变化与俯冲参数的变化之间建立明确的联系，特别是板块倾角、沉积物供应和地壳厚度。 我们的方法是耦合CO2和氦的测量（同位素和相对丰度），允许识别和定量评估的各种贡献者的岩浆输出。 虽然是一个强大的技术，任何通量估计的准确性是有限的不确定性的影响，岩浆脱气所得的CO2/3 He比和假设的同位素和丰度特征分配到潜在的端元成分参与弧岩浆作用。 通过分析和比较地热流体中的CO2-He关系与镁铁质矿物都沿着和整个中美洲弧，我们的目标是探索这些限制的程度，并评估方法与潜在的规避任何困难。此外，我们将通过COSPEC和气体化学研究得出当今的CO2通量。 这提供了获得N2和H2O的绝对通量的进一步的可能性，也限制了它们的源区在俯冲带工厂。

Hilton/Walker/FischerEAR-0003628/0003664/0003668 This proposal is aimed at producing a volatile mass balance for the Central American subduction zone by quantifying the contributions from the subducting slab, mantle wedge and overlying crust to the overall arc budget. The Central American arc was chosen because it possess a number of unique features which allow explicit linkages to be forged between systematic variations in volcanic output and variations in subduction parameters, specifically slab dip, sediment supply and crustal thickness. Our approach is to couple CO2 and helium measurements (isotopes and relative abundances) which allows for identification and quantitative assessment of the various contributors to the magmatic output. Although a powerful technique, the accuracy of any flux estimates is limited by uncertainties in the effects of magmatic degassing on resultant CO2/3He ratios and on assumptions on the isotopic and abundance characteristics assigned to potential endmember compositions involved in arc magmagenesis. By analyzing and comparing the CO2-He relationships in geothermal fluids with mafic minerals both along and across the Central America arc, we aim to explore the extent of these limitations and to assess approaches with the potential to circumvent any difficulties. Additionally, we will derive present-day CO2 fluxes through combined COSPEC and gas chemistry studies. This offers the further possibility of deriving absolute fluxes for N2 and H2O and for also constraining their provenance in the subduction zone factory.