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

9527462派尔提高对地幔环流系统学的理解是固体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区域分布图，可以获得有关地幔储层的大小、组成和分布、地幔温度变化、地幔对流搅动的效率以及单个地幔储层的寿命的定量信息。 这类问题中的一个非常重要的问题涉及印度洋上地幔独特的同位素和地球化学特征的起源和演变，可以通过表层取样和地壳钻探加以解决。在印度洋扩张中心喷发的熔岩与太平洋的熔岩同位素不同。在澳大利亚-南极不一致区内，沿沿着扩张脊，太平洋区和同位素区之间有一条独特而尖锐的边界。 本项目的目标是绘制远离脊顶的边界图，因为有限的现有数据往往表明，随着时间的推移，边界会向西迁移。在1996年初为期40天的研究航行期间，将在离轴地区收集地震反射、重力和磁力数据以及挖掘样本。这些数据还将提供现场勘测资料，以支持向大洋钻探方案提出的一项建议，即对旧地壳进行取样，以绘制边界的历史图。该项目涉及来自华盛顿大学、俄勒冈州州立大学和伍兹霍尔海洋研究所的科学家。 ***

9527462 Pyle 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 individual 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 upper mantle. Lavas erupted at 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-Antarctic 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. ***