Noble Gases and Isotope Systematics in Continental and Hot Spot Volcanism

目前，从地球上大约40个热点地区的少量样品中获得的氦数据显示，同位素比率大于和小于MORB值的双峰分布非常明显。该提案的一部分是测量来自卡罗琳和马克萨斯岛链的熔岩套件的3He/4He比率，已知其比率大于MORB（卡罗琳），等于或小于MORB（马克萨斯，仅基于少数样本）。第二个，也是提出的主要工作，是继续研究三个主要大陆裂谷地形的同位素系统：埃塞俄比亚裂谷（加上东非裂谷南端的Rungwe玄武岩），蛇河平原（也包括哥伦比亚河洪水玄武岩的研究），以及来自玛丽伯德地和维多利亚地的南极玄武岩。第三项工作是继续研究来自OIB熔岩的斑晶（橄榄石，cpx）和玻璃中的稀有气体系统（He-Ne-Ar），并将其应用于“未耗尽地幔”源的Ne和Ar同位素比率与大气比率的比较。

Helium data now available on small numbers of samples from about 40 of the earth's hotspots, show a well- marked bimodal distribution of isotope ratios greater and less than MORB values. One part of this proposal is for the measurement of 3He/4He ratios on suites of lavas from the Caroline and Marquesas island chains, which are known to have ratios greater that MORB (Carolines) and equal or less than MORB (Marquesas, based on a few samples only). The second, and major proposed effort, is the continuation of studies of the isotopic systematics of three major continental rift valley terrains: the Ethiopian Rift (plus the Rungwe basalts at the southern terminus of the East African Rift), the Snake River Plain with studies also of the Columbia River flood basalts, and the Antarctic basalts from Marie Byrd Land and Victoria Land. The third effort is the continuing study of rare-gas systematics (He-Ne-Ar) in phenocrysts (olivine, cpx) and glass from OIB lavas as applied to the question of the Ne and Ar isotope ratios of the "undepleted mantle" source as compared to atmospheric ratios.