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

海洋玄武岩的挥发性特征为地球动力学演化提供了关键制约因素。这项研究将通过对马努斯盆地(俾斯麦海)弧后盆地内喷发的大洋玄武岩的He-Ne-Ar-H2O-CO2同位素和浓度系统学的综合研究来解决这些问题。所有分析都将在主要元素化学和微量元素化学以及产生放射性的同位素特征良好的样品上进行。这项工作的目标有三个方面：(1)将马努斯盆地的主要和稀有气体挥发性体系分解成它们的组成部分，表明它们来自或与盆地底部的热点、MORB、弧和弧后地幔和(或)玄武岩地壳有关；(2)通过对经历过不同程度脱气的样品的比较，考虑岩浆脱气对大洋玄武岩挥发性体系的影响。监测作为脱气历史函数的CO2/3He比率是这方面的一个特别相关的参数；以及(3)通过与通过传统粉碎和阶梯加热技术获得的相同样品的数据进行比较，评估激光提取方法对稀有气体和主要挥发物的实用性。特别是，将尝试校准通过不同方法获得的挥发性异质性(囊泡与基质)的长度-标度。

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.