The Geochemical Characteristics of the Hawaiian Plume: Constraints From Studies of Lavas Forming the Koolau and Kahoolawe Shields

陆地火山与三种不同的构造背景有关。两个与板块边界有关，即板块的发散和会聚区域，第三个是板内火山活动，在不同的环境中喷发的岩浆具有明显不同的地球化学特征。在这项拟议的研究中，目的是了解决定夏威夷熔岩地球化学特征的来源和过程。这一端元非常有趣，因为它可能部分地代表了俯冲带洋壳向地幔深处俯冲的后果。方法将是确定这两个地幔不同年龄熔岩中主要和微量元素的丰度以及O、Sr、ND、Pb、Hf和Os的同位素比率。对于Koolau来说，要研究的样品来自最近钻探的岩心，与之前研究的表面暴露的样品相比，该岩心穿透屏蔽的深度更深，年龄更老。对于尚未被深入研究的Kahoolawe，样品将来自屏蔽的几个地层剖面。主要目的是了解造成岩浆的来源成分；因此，重点将放在评估高度不相容元素的丰度比之间的相关性，例如，Ba/Th、Ce/Pb和La/Nb以及同位素比值。这些地球化学特征将使用电感耦合等离子体质谱和热电离质谱仪等分析设施进行测定。由于其洋盘背景、相对简单的矿物学和丰富的互补性研究，夏威夷火山为了解再循环地壳成分在大洋岛火山活动中的作用提供了最好的机会。特别是，这项研究将有助于限制形成夏威夷盾状熔岩的地球化学元素的过程和来源成分。

FreyEAR-0105557Terrestrial volcanoes are associated with three different tectonicsettings. Two are associated with plate boundaries, that is, regions ofplate divergence and convergence, and the third is intraplate volcanism.Magmas erupted in these different environments differ significantly ingeochemical characteristics. In this proposed research the goal is tounderstand the source and processes which determine the geochemicalcharacteristics of Hawaiian lavas. This endmember is of great interestbecause it may in part represent the consequences of subducting oceaniccrust deep into the mantle at subduction zones.The approach will be to determine abundances of major and trace elementsand isotopic ratios of O, Sr, Nd, Pb, Hf and Os in lavas of varyingrelative age from these two shields. For Koolau the samples to be studiedare from a recently drilled core, that penetrates the shield to a greaterdepth and older age than previously studied surficially exposed samples.For Kahoolawe, which has not been intensively studied, the samples will befrom several stratigraphic sections across the shield. The principalobjective is to understand the source components contributing to thesemagmas; hence emphasis will be on evaluating correlations between abundanceratios of highly incompatible elements, e.g., Ba/Th, Ce/Pb and La/Nb, andisotopic ratios. These geochemical characteristics will be determinedusing analytical facilities such as inductively couples plasma massspectrometry and thermal ionization mass spectrometry.Because of their oceanic plate setting, relatively simple mineralogy and awealth complementary studies, Hawaiian volcanoes present the bestopportunity for understanding the role of recycled crustal components inoceanic island volcanism. In particular, this research will aid inconstraining the processes and source components which create a geochemicalendmember of Hawaiian shield lavas.