IODP Expedition 402
Tyrrhenian Continent–Ocean Transition
Daily science report for 7 April 2024
Location:
- Hole U1612B (40°11.0329′N, 12°37.9598′E; water depth 3573.8 m)
- Underway to Napoli, Italy
Science Update: The drill ahead (Interval U1612B-11) in Hole U1612B reached a depth of 318.1 mbsf before contacting a hard layer. The center bit was recovered and RCB coring proceeded with Cores U1612B-2R through 4R. These three cores advanced 16.8 m to a total hole depth of 334.9 mbsf and recovered 3.80 m of breccia, granitoids, and peridotite (23% recovery). Rate of penetration (ROP) was ~5.0 m/h. Following recovery of Core 4R, pipe was tripped back to the surface and the rig floor was secured for the transit to Napoli, Italy. At 2126 h, the vessel transitioned from DP to cruise mode, ending Hole U1612B and operations for Expedition 402. At midnight, we had completed 23.5 nmi of the 89.5 nmi transit to Napoli at an average speed of 10.2 kt.
Cores U1612B-2R through 4R were split and described. No shipboard discrete samples were taken. Core 2R contains a matrix-supported polymict consolidated breccia. The lithologies found in Cores 3R and 4R are predominantly mylonitized granitoids, gneissic granitoids, and harzburgites.
Scientists finalized site reports and held a wrap-up meeting where they shared their personal scientific highlights of the expedition.
Daily science report for 6 April 2024
Location:
- Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)
- Underway to Site U1612
- Hole U1612B (40°11.0329′N, 12°37.9598′E; water depth 3573.8 m)
Science Update: Pipe was tripped toward the surface after the failed logging attempt in Hole U1616E, stopping to circulate when the logging bit reached the casing shoe. The logging bit was recovered onto the rig floor at 0630 h, ending operations in the hole and at Site U1616. A new RCB BHA was made up and pipe was tripped toward the seafloor. While tripping, the vessel began moving the 3 nmi distance to Site U1612 in DP mode. We arrived on location at 1242 h and performed a standard cut and slip of the drill line prior to picking up the top drive, filling the pipe, and deploying the center bit to prepare to spud. The plan is to drill ahead to basement with a center bit and then recover as many cores as time allows before the end of the expedition. Hole U1612B was spudded at 1921 h; the drill ahead was in progress at the end of the day.
Scientists worked on reports for Site U1616.
Daily science report for 5 April 2024
Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)
Science Update: While tripping pipe toward the seafloor to begin logging in Hole U1616E, we launched the VIT camera system to facilitate reentry. The seventh reentry into Hole U1616E occurred at 0538 h and the VIT was recovered. We picked up the top drive and used it to lower the drill string with the logging bit to 317.1 mbsf before racking the top drive again. We deployed the standard triple combo tool string, with the radioactive source removed from the Hostile Environment Litho-Density Sonde (HLDS) due to concerns about hole stability. The bottom of the triple combo tool string passed ~25 m out of the logging bit, reaching a depth of 342.0 mbsf in the open hole before an obstruction was encountered and the entire tool string was recovered. The hole was reamed from 317.1 to 417.0 mbsf where we encountered significant fill, ~10 m above the total hole depth. We then pumped a mud sweep to condition the hole prior to pulling the pipe back up for a second logging attempt; however, we lost rotation and became stuck. We were able to work the stuck pipe and eventually back ream to the casing shoe. At midnight, we were preparing to trip pipe back to the surface and end operations at Site U1616.
Scientists worked on reports for Site U1616.
Daily science report for 4 April 2024
Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)
Science Update: Core U1616E-30R was recovered from Hole U1616E at 0045 h, with 1.23 m of basement rocks recovered out of a 4.8 m advance (26%), reaching a total hole depth of 427.2 mbsf. During core recovery, the drill pipe was pulled up above the hole bottom in order to circulate drill fluid. For the next ~9 h, we reamed and cleaned the hole in an effort to remove cuttings and/or fill, but we were unable to reach hole bottom again. The drill string experienced repeated high torque and overpull at ~421 mbsf. At 1000 h, the decision was made to terminate coring in Hole U1616E and begin logging operations. A ghost core, Core U1616E-31G, was recovered, containing 0.78 m of rubble from an unknown depth within the hole. Pipe was tripped back to the surface and the BHA was laid out. A new BHA with a logging bit was made up and deployed. At midnight, we were tripping pipe back toward the seafloor to reenter Hole U1616E and begin logging.
Cores U1616E-28R through 31G were split and described. The primary lithologies include plagioclase-bearing harzburgite and lherzolite, dunite, gabbro, and diabase. Static alteration is moderate to high, with alteration minerals including serpentine, amphibole, magnetite, and clay minerals. Density and natural gamma radiation (NGR) are relatively constant with depth, while magnetic susceptibility (MS) measurements on the Whole-Round Multisensor Logger (WRMSL) are more variable.
Daily science report for 3 April 2024
Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)
Science Update: At the beginning of the day, we had reentered Hole U1616E and were tripping pipe toward the hole bottom at 400.0 mbsf. Core U1616E-25R advanced to 404.0 mbsf; prior to recovery, we worked the pipe and circulated drill fluid to remove cuttings or fill. Coring proceeded through Cores 29R, advancing to a total hole depth of 422.4 mbsf and recovering 4.01 m out of the 22.4 m advance (18%). Core 29R reached 118.9 m into basement from the breccia/basement interface at 303.5 mbsf. Frequent wiper trips and drill fluid circulation were used to keep the hole stable.
Cores U1616E-25R through 27R were split and described. Observed lithologies include diorite, gabbro, dolerite, and plagioclase-bearing harzburgite. Most of the recovered material is highly altered, with amphibole as the primary alteration mineral.
Daily science report for 2 April 2024
Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)
Science Update: The drill ahead through the hard, rubbly interval in Hole U1616E succeeded, advancing to a depth of 400.0 mbsf from 371.0 mbsf. We tripped pipe out of the hole, recovered the tricone bit used during the drill ahead, and made up a rotary core barrel (RCB) BHA for coring. We began tripping the pipe back toward the seafloor, and we launched the VIT camera system to facilitate reentry into Hole U1616E. Reentry occurred at 2208 h and the VIT was recovered.
Scientists worked on reports for Site U1617.
Daily science report for 1 April 2024
Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)
Science Update: The vessel completed the 43 nmi transit to Site U1616 and transitioned to dynamic positioning (DP) mode at 0324 h, with an average speed of 11.3 kt. The transit included bathymetric surveying with the 3.5 and 12.0 kHz sonar systems, with the ship’s path crossing regions of geological interest. Once positioned over Hole U1616E, a bottom-hole assembly (BHA) with a tricone bit was made up and pipe was tripped toward the seafloor. We aim to drill ahead through an interval that caused substantial torque and overpull during previous coring efforts in this hole.
The vibration isolated television (VIT) camera system was launched to observe reentry, following a standard cut and slip of the drill line. Hole U1616E was reentered at 1400 h, the VIT was recovered, and drill pipe was tripped toward the current hole depth of 371.0 mbsf. Ledges or obstructions in the hole were encountered starting at 254.8 mbsf; the top drive was picked up and drill fluid was circulated to clear out the hole. The hole was reamed to a depth of 371.0 mbsf, and then was drilled from 371.0 to 377.0 mbsf. Drilling, reaming, and continual hole cleaning efforts will proceed until a depth of ~400 mbsf.
Scientists worked on reports for Site U1617.