A Submersible Study of Axial Processes, East Pacific Rise 10-12'N

最近海洋地质研究的一个主要重点是将地壳岩石的详细地球化学和岩石学与洋中脊沿线的精细特征联系起来。海底扩张过程的最初模型假设地壳是由长而相当连续的轴向岩浆房形成的。尽管在这些模型中允许化学成分的微小变化，但喷发的熔岩的成分被认为是相当恒定的。随着Seabeam和Seamarc等详细测绘系统的出现，山脊测深中出现了一类全新的过程。从这些数据中产生的新模型表明，脊轴是由一系列小的、离散的岩浆段或单个火山组成的。在许多情况下，这些火山产生的熔岩在化学上似乎是不同的。本项目的目的是利用研究潜水器“阿尔文号”（Alvin），在东太平洋隆起的几个部分检查玄武岩的化学成分。以前的水面船采样已经定义了玄武岩化学的总体变化，这些变化与重叠扩散中心、偏移脊轴和转换断层等特征有关。Alvin现在将用于在这些特征之间的边界处进行详细采样。这些数据将用于约束地下岩浆房的性质和分布，以及它们与沿脊轴的单个形态段的关系。主要研究人员完全有资格完成拟议的项目。

A major emphasis of recent marine geological studies has been to relate the detailed geochemistry and petrology of crustal rocks to the fine-scale features present along mid-ocean ridges. Initial models of the sea-floor spreading process had assumed that crust was created from long, fairly continuous, axial magma chambers. Although minor variations in chemistry were allowed in these models, the composition of the erupted lavas was assumed to be fairly constant. With the advent of detailed mapping systems such as Seabeam and Seamarc, a whole new class of processes were revealed in ridge crest bathymetry. New models emerging from these data indicate that the ridge axis is composed of a series of small, discrete magmatic segments or individual volcanoes. The lavas produced from these volcanoes appears in many cases to be chemically distinct. The objective of the present project is to examine the chemistry of basalts in several of these segments along the East Pacific Rise using the research submersible Alvin. Previous surface ship sampling has defined the gross changes in basalt chemistry related to features such as overlapping spreading centers, off-set ridge axis, and transform faults. Alvin will now be used to sample in detail at boundaries between such features. These data will be used to constrain the nature and distribution of subsurface magma chambers and their relation to the individual morphological segments along the ridge axis. The principal investigators are well qualified to complete the proposed project.