Petrology and Tectonics of the Australian-Antarctic Discordance and Adjacent Ridges

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The Australian-Antarctic Discordance is a unique and enigmatic bathymetric and geologic feature of the mid-oceanic ridge system whose origin is poorly understood. The present award will support an integrated geophysical and geochemical project to study the Discordance zone. The combination of a comprehensive geochemical investigation with a SeaMARC II side-scan sonar survey and detailed magnetic and gravity analyses will provide a unique data set which will focus on two problems which are of fundamental significance, both on a global scale and with respect to the nature of the Discordance itself: (1) the geophysical and geochemical nature of the eastern boundary of the Discordance which is one of the most pronounced geochemical and bathymetric discontinuities in the global mid-ocean ridge system and (2) the interrelationships among axial depth, axial morphology, ridge segmentation, and along axis petrologic variations, all of which are unusually variable within and outside the Discordance. The study is a cooperative project between scientists at Lamont-Doherty Geological Observatory, Massachusetts Institute of Technology, and the University of Hawaii. Field work will be done from the R.V. Moana Wave.