A Multichannel Seismic Investigation of the EPR at 9'N and 13'N

由于缺乏对洋中脊结构的详细地球物理制约因素，对全面了解洋壳形成过程的努力受到严重限制。增生板块边界新洋壳和岩石圈的生成是板块构造理论的基础。目前地壳生成过程的地质模型包括地壳浅部岩浆腔的存在。尽管越来越多的支持模型，数据定义轴向岩浆房的存在和几何形状仍然存在争议。该项目是在东太平洋海隆北纬9度和北纬13度两个经过充分研究的部分之间进行多道地震调查。通过一系列的疏浚和ALVIN潜水计划对火山岩石学进行了检查。用侧扫声纳和多波束测深仪检查了构造和结构组构。现有的地震折射数据表明存在一个轴向低速带，推测与上升峰下的岩浆房有关。本奖项的目的是完成对这一独特数据集的分析和解释。需要解决的具体问题包括：1）岩浆房反射层以下物质的物理性质; 2）岩浆房壁和底板的形状; 3）海洋地壳结构在最初几百万年期间的发展; 4）记录的地震反射的基底形态的影响; 5）岩浆房特性沿着上升轴的变化。

The lack of detailed geophysical constraints on the structure of mid-ocean ridges has severely limited efforts to develop a comprehensive understanding of the processes forming the oceanic crust. The generation of new oceanic crust and lithosphere at accretionary plate boundaries is fundamental to plate tectonic theory. Current geological models for the crustal generation process include the existence of shallow crustal magma chamgers. Despite the growing support for the models, data defining both the existence and geometry of axial magma chambers remain controversial. This project is a multichannel seismic investigation between two well-studied segments of the East Pacific Rise at 9 degrees north and 13 degrees north. The volcanic petrology has been examined through a series of dredging and ALVIN dive programs. The tectonic and structural fabric has been examined with side scan sonar and multibeam bathymetry. Existing seismic refraction data indicate the presence of an axial low velocity zone, presumably associated with a magma chamber beneath the rise crest. The objective of the present award is to complete the analysis and interpretation of this unique data set. Specific problems to be addressed include: 1) The physical properties of the material below the magma chamber reflector; 2) the shape of the magma chamber walls and floor; 3) the development of ocean crustal structure during its first few million years; 4) the effect of basement morphology of recorded seismic reflections; and 5) variations in magma chamber characteristics along the rise axis.