Tasmanian Tertiary basalts, the Balleny plume, and opening of the Tasman Sea (southwest Pacific Ocean)

Abstract

A seamount chain extending from the Balleny Islands to the East Tasman Plateau records the passage of the Australian and Antarctic plates over the Balleny plume. A poorly known seamount chain trending northeast from the East Tasman Plateau across the Tasman Sea to the western edge off the Lord Howe Rise represents a possible older trace of the plume. Late Cretaceous inception of this plume, and of another beneath Marie Byrd Land on the stationary Antarctic plate, may have been involved in the initiation of spreading at ∼80 Ma in the Tasman Sea and southwest Pacific Ocean. The Balleny plume isotopic and trace element signature, indicative of a high U/Pb mantle source, is recorded in Cenozoic Tasmanian basalts but is not present in the adjacent Victorian mafic lava-field province, located farther from the plume trace.