Geochemical Study of Lavas from the North Hawaiian Arch Flood Basalt Province

最近GLORIA的调查和疏浚发现了一大片年轻的碱性洪水玄武岩，横跨夏威夷岛链北部的弯曲拱。这些岩石代表了夏威夷火山历史上一个重要的、以前不为人知的部分，有望极大地促进我们对热点火山作用的理解。Drs。马奥尼和辛顿将监督对该地区20-30个疏通样本的同位素和微量元素分析，以确定地幔来源，并深入了解这个大流场的大部分岩浆历史。以往对热点、中板块火山（如夏威夷群岛的火山）的认识确定了三个阶段：1)拉斑岩组成的主要盾构期；2)少量碱帽（体积比1%）；3)经过几百万年的沉寂，少量涌出的缺乏二氧化硅的“恢复活力”的熔岩。Clague（美国地质勘探局，该项目的免费合作伙伴）的初步研究表明，拱形火山在性质上最接近最后一组“恢复活力”的morb样岩石。Mahoney和Sinton希望更好地了解可能的地幔源的性质和可变性，以及部分熔融、岩浆混合和分离结晶各自的作用。

Recent GLORIA surveys and dredging have discovered a large field of young alkalic flood basalts across the flexural arch north of the Hawaiian island chain. These rocks represent a significant and previously unknown part of Hawaiian volcanic history, and promise to advance greatly our understanding of hot-spot volcanism. Drs. Mahoney and Sinton will oversee isotopic and trace element analyses on 20-30 dredge samples from this region in order to determine mantle sources and gain insight into the magmatic history of this largery of this large flow field. Previous understanding of hotspot, mid-plate volcanic (like those of the Hawaiian islands) have identified three phases: 1) the major shield building episode of tholeitic composition; 2) a minor (1% by volume) alkalic cap; and 3) a small outpouring of silica-poor, " rejuvenated" lavas after a few million years of quiesence. Initial studies by Clague (USGS, a not-cost collaborator on this request) show the arch volcanics are closest in character to this last, "rejuvenated" suite of MORB-like rocks. Mahoney and Sinton hope to gain better understanding of the nature and variability of probable mantle sources, and the respective roles of partial melting, magma mixing and fractional crystallization.