Petrologic Studies of the Australian-Antarctic Discordance

澳大利亚-南极不一致（AAD）是一种 在一个分离的板块边界上， 重力和澳大利亚之间令人不安的深海海底， 南极洲 此外，该协定还包括太平洋之间的边界- 型和印度型全球同位素省。 的 在不协调的扩展轴上显示出一种不寻常的， 锯齿形偏移图案，并且在恒定（中等）扩展速率下， 几乎是轴向脊形态的全部谱。 加上 这种形态和构造的多样性是一种异常广泛的 地球化学多样性似乎需要广泛的 原始岩浆成分，反过来， 熔化条件的变化。 首席研究员带领 1988年成功巡航到该地区，并获得了15天的 SeaMARC II侧扫描覆盖范围和26个新的挖泥船拖运。 的 这项工作的目标是：确定，尽可能详细， 可能的，同位素边界的性质和位置;完全 确定AAD熔岩的地球化学和岩石学多样性， 了解这种多样性的潜在岩石成因， 一般与构造和MORB成因的关系;并定义和 评估沿海脊一段沿着熔岩的多样性， 它们进化过程中的不同特征。

The Australian-Antarctic Discordance (AAD) is the parsent-day manifestation, at a divergent plate boundary, of a region of low gravity and anomalously deep ocean floor between Australia and Antarctica. The AAD also contains the boundary between Pacific- type and Indian-type global-scale isotopic provinces. The spreading axis within the discordance displays an unusual, crenulate offset pattern and, at constant (medium) spreading rate, almost the full spectrum of axial ridge morphologies. Coupled with this morphologic and tectonic diversity is an unusually broad geochemical diversity that appears to require a broad range of primary magma compositions which require, in turn, a broad variation in conditions of melting. The principal investigator led a successful cruise to the area in 1988 and obtained 15 days of SeaMARC II side-scan coverage and 26 new dredge hauls. The objectives of this work are to: determine, in as fine detail as possible, the nature and location of the isotopic boundary; fully define the geochemical and petrologic diversity of AAD lavas and to understand the underlying petrogenetic causes for this diversity in relation to tectonics and MORB genesis in general; and define and evaluate the diversity of lavas along one section of the ridge in terms of distinctively different processes by which they evolved.