Migration of the Pacific-Indian Isotopic Boundary and Evolution of the Australian-Antarctic Discordance: A Drilling Site Survey

9403395增进对地幔环流系统学的了解是固体地球地球物理学的一个高度科学优先事项。通过绘制洋底关键区域地壳成分的面积分布图，可以获得关于地幔储集层的大小、组成和分布、地幔温度的变化、地幔对流搅拌效率和地幔储集层的寿命的定量信息。这种类型的一个非常重要的问题可以通过地表采样和地壳钻探来解决，它涉及印度洋扩张中心的独特同位素和地球化学特征的起源和演化，这些特征在同位素上与太平洋的扩张中心不同。在沿扩张海脊的澳大利亚-南极不整合带内，已经确定了太平洋省和同位素省之间独特而尖锐的边界。本项目的目标是绘制远离山脊的这条边界的地图，因为有限的现有数据往往表明，随着时间的推移，边界向西迁移。1996年初，在一次为期40天的研究巡航期间，将在离轴地区收集地震反射、重磁数据和疏浚样品。这些数据还将提供现场勘测信息，以支持海洋钻探方案的一项建议，即对古老的地壳进行采样，试图绘制边界的历史地图。该项目涉及来自华盛顿大学、俄勒冈州立大学和伍兹霍尔海洋研究所的科学家。

9403395 An improved understanding of the systematics of mantle circulation is a high scientific priority in solid earth geophysics. By mapping the areal distribution of crustal compositions over key areas of ocean floor, quantitative information about the size, composition, and distribution of mantle reservoirs, variations in mantle temperatures, the efficiency of convective stirring in the mantle, and the longevity of mantle reservoirs can be obtained. One very important problem of this type, which can be addressed by surficial sampling and crustal drilling, concerns the origin and evolution of the distinctive isotopic and geochemical signature of the Indian Ocean spreading centers are isotopically distinct from those of the Pacific. A unique and sharp boundary between Pacific and isotopic provinces has been identified within the Australian- Antartic Discordance along the spreading ridge. The objective of the present project is to map this boundary away from the ridge crest, since limited available data tends to indicate a westward migration of the boundary over time. Seismic reflection, gravity and magnetic data and dredge samples will be collected in the off-axis area during a 40 day research cruise in early 1996. These data will also provide site-survey information in support of a proposal to the Ocean Drilling Program to sample old crust in an attempt to map the history of the boundary. The project involves scientists from the University of Washington, Oregon State University, and Woods Hole Oceanographic Institution.