IODP Expedition 330 Louisville Seamount Trail

Location

After a new drill string was assembled with a shorter bottom hole assembly and dedicated logging bit, Hole U1374A was successfully re-entered in the early morning. The following time was spent with preparing Hole U1374A for downhole logging and attempts to start the actual logging operations. Unfortunately, the first logging tool suite (Triple Combo) was not able to advance more then a few meters beyond the drill pipe due to formation blockage. In response, the blockage was cleared by circulating and rotating the drill pipe further down, and the logging depth (end of the drill pipe) was deepened to bridge any potentially tight spot further above. At midnight, a new attempt to deploy the logging tool string was made. Meanwhile, splitting and description of the last cores recovered from this hole continued. After splitting the core sections it became clear that many of the basaltic units that were recovered from the deeper part of the hole (below 336 mbsf) represent dikes rather then lava flows. A beautiful example was found in Core U1374A-59 with multiple steep contacts between the aphyric dike and the surrounding plagioclase-phyric volcanoclastic breccia, with the dike displaying chilled margins and edge-parallel vesicle bands. The dikes show a strong magnetic signal and ship-board paleomagnetic investigations are currently underway.