Geochemistry of lavas from the Australian-Antarctic Ridge, easternmost Southeast Indian Ridge

Abstract

The intermediate spreading Australian-Antarctic Ridge (AAR), an easternmost extension of the South East Indian Ridge located in the south of Tasmania, is one of the largest unexplored regions of the global mid-ocean ridge system, owing to its remote location and a very limited workable weather window. In early and late 2011, the Korea Polar Research Institute (KOPRI) conducted two surveys of two segments at 160°E (KR1) and 152.5°E (KR2) using the icebreaker Araon, producing a multi-beam map, 48 rock core samples and a MAPR (Miniature Autonomous Plume Recorder) hydrothermal survey. The full spreading rate of the spreading center in this area is 68 mm/yr. The axial depth of KR1 is relatively shallow (~2,000m) and is a first-order segment bounded by two large offset transform faults. The axial morphology of KR1 varies substantially from an axial high plateau (Segment 1) in the west, to a small rift valley (Segment 2), to an axial high with graben (Segment 3), and to a substantial rift valley (Segment 4) in the east. These changes occur in the absence of marked offsets in the ridge, such as overlapping spreading centers. Even so, these segments can be divided still further into shorter scale segments based on small discontinuities in the linearity of the axis and variations in rock chemistry. Small offsets in bathymetry can be associated with large chemical changes, such as between Segments to its remote location and a very limited workable weather window. In early and late 2011, the Korea Polar Research Institute (KOPRI) conducted two surveys of two segments at 160°E (KR1) and 152.5°E (KR2) using the icebreaker Araon, producing a multi-beam map, 48 rock core samples and a MAPR (Miniature Autonomous Plume Recorder) hydrothermal survey. The full spreading rate of the spreading center in this area is 68 mm/yr. The axial depth of KR1 is relatively shallow (~2,000m) and is a first-order segment bounded by two large offset transfor