Constraints on Volatile Provenance in a Back-Arc Basin and the Degassing History of the Mantle: The He-Ne-Ar-H2O-CO2 Isotope and Abundance Systematics of the Manus Basin

[804916]希尔顿海洋玄武岩的挥发性特征为地球动力学演化提供了关键的约束条件。本研究将通过对马努斯盆地（俾斯麦海）弧后盆地内海洋玄武岩He-Ne-Ar-H2O-CO2同位素和浓度系统的综合研究来解决这些问题。所有的分析都将在样品上进行，以确定其主要和微量元素的化学特征和放射性成因同位素特征。研究的主要目标有三个方面：(1)将马努斯盆地的主要和稀有气体挥发系统分解为它们的组成部分，这些组成部分表明它们来源于或与盆地底部的热点、MORB、弧后地幔和/或玄武质地壳有关；(2)通过对比不同脱气程度的样品，考虑岩浆脱气对海洋玄武岩挥发系统的影响。在这方面，监测CO2/3He比率作为脱气历史的函数是一个特别相关的参数；(3)通过与常规破碎和阶梯加热技术获得的相同样品的数据进行比较，评价激光提取稀有气体和主要挥发物的有效性。特别是，将尝试校准由不同方法获得的挥发性异质性（囊泡与基质）的长度尺度。

9804916HiltonThe volatile characteristics of ocean basalts provide key constraints on the geodynamic evolution of the Earth. This research will address these issues through an integrated study of the He-Ne-Ar-H2O-CO2 isotope and concentration systematics of oceanic basalts erupted within the Manus Basin (Bismark Sea) back-arc basin. All analyses will be undertaken on samples well-characterized for their major and trace element chemistry and radiogenic isotope characteristics. The objectives of the work are three-fold: (1) resolution of the major and rare gas volatile systematics of the Manus Basin into their component parts indicating derivation from or association with hotspot, MORB, arc and back-arc mantle and/or basaltic crust of the basin floor; (2) consideration of the effects of magmatic degassing on the volatile systematics of oceanic basalts through a comparison of samples having experienced varying degrees of degassing. Monitoring of the CO2/3He ratio as a function of degassing history is a particularly relevant parameter in this respect; and (3) evaluation of the utility of laser extraction methods for both rare gases and major volatiles by a comparison with data on the same samples obtained by conventional crushing and stepped-heating techniques. In particular, an attempt will be made to calibrate the length-scale of volatile heterogeneity (vesicles versus matrix) obtained by the different methods.