Site U1496: Expedition 366

Abstract

Site U1496 is located at the summit of Asut Tesoru Seamount (informally known as Big Blue Seamount), a serpentinite mud vol­cano about 72 km from the trench axis and 18 km above the down­going plate. The major fault trend that controlled the growth of the edifice has a north-northeast trend and a crosscutting fault with a north-northwest trend. The sea­mount is topped by a roughly circular summit mound, approxi­mately 3 km wide and 200 m high, which itself has three smaller circular mounds. The largest of these, about 350 m in diameter and 40 m high, was the focus of Site U1496 operations. This location was chosen because gravity, piston, and ROV Jason II push coring operations revealed fluid discharge in the center of the largest of the three mounds. The primary goals were to recover material from an active conduit for deep-sourced fluids and to deploy a casing-screened borehole that intersects the hydrologic conduit, providing the foundation for future experiments, sampling opportunities, and monitoring of physical conditions of volcanism with the aid of a CORK-Lite struc­ture.