Collaborative Research: Scientific Drilling in Hawaii: Physics and Chemistry of Mantle Plumes

该项目包括在夏威夷Hilo附近钻一个600米的导孔，为钻一个4.5公里的孔做准备，并使用一系列现代地球化学、岩石学和地球物理技术对返回的岩心样本和井位进行表征。这些孔的主要目的是获得海洋火山在其主要盾构活动阶段的长时间间隔内几乎连续有序的产出记录。任何一座夏威夷火山的产出和历史只有一小部分可以通过表面暴露接触到，而且这些火山的内部也不太可能被暴露出来，除非通过深度钻探。要解决的主要科学问题涉及热点的性质，特别是它们可能代表的“羽流”的组成和起源，以及在105至106年的时间尺度上，上涌的物质如何与岩石圈和周围的地幔物质相互作用。这些问题与岩浆同位素组成的性质和钻芯中遇到的熔岩的年龄密切相关，并将这个地球化学时间序列与羽流行为和熔体产生的动力学模型结合起来，为夏威夷的热点现象建立一个全面的动力学模型。其他主要的科学问题可以通过研究独特的钻探样品套件来解决，包括：单个夏威夷火山活跃多久？海底-陆上过渡和大型海洋火山海底部分的性质是什么？夏威夷火山的生长和生长速度的机制是什么，以及由于火山生长对岩石圈的负荷而引起的沉降是什么？作为深度和岩石学的函数，海洋火山岩的磁性是什么？这些与海山附近的磁性测量有什么关系？远离裂谷带的夏威夷火山侧翼内部的火成岩特征的热结构和保存状态是什么？

This project involves drilling a 600 m pilot hole preparatory to core-drilling a 4.5 km hole in the vicinity of Hilo, Hawaii, and characterizing the returned core samples and well site using an array of modern geochemical, petrological, and geophysical techniques. The principal objectives of the holes is to obtain a nearly continuous, ordered record of the output of an oceanic volcano over a long interval of its main shield-building phase of activity. Only small fractions of the output and history of any individual Hawaiian volcano are accessible through surface exposures and it is unlikely that the interiors of these volcanoes will ever be exposed except by deep drilling. The primary scientific questions to be addressed concern the nature of hot spots, in particular, the composition and origin of the "plumes" they may represent, and how the upwelling material interacts with the lithosphere and surrounding mantle material on time scales of 105 to 106 years. These problems are intimately related to the nature of magma isotopic compositions and ages of the lavas encountered in the drill core, and to invert this geochemical time series in conjunction with dynamical models for plume behavior and melt generation to develop a comprehensive model for the dynamics of the hot spot phenomenon at Hawaii. Other major scientific questions that can be addressed through study of a unique sample suite of the sort expected from drilling include: How long is an individual Hawaiian volcano active? What is the nature of the submarine-subaerial transition and of the submarine section of a major oceanic volcano? What are the mechanisms of growth and the rate of growth of a Hawaii volcano and of subsidence due to the load on the lithosphere from the growing volcano? What are the magnetic properties of oceanic volcanic rocks as a function of depth and petrology and how do these relate to magnetic surveys near seamounts? What is the thermal structure and state of preservation of igneous features in the interiors of the flanks of Hawaiian volcanoes far from rift zones.