IODP Expedition 399
Building Blocks of Life, Atlantis Massif
Daily science report for 31 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-244R through 249R, recovering 17.4 m of the 29.1 m cored, with core recoveries ranging from 31% to 79% (average recovery 60%).
Per instruction from shore, cores from this last coring bit run, starting with Core U1601C-242R, will not be split or sampled on board. Based on a petrographic assessment through the core liners, Cores 242R through 249R are entirely gabbro, except for most of Core 244R and a small interval of Core 245R, which are serpentinized harzburgite and dunite.
Daily science report for 30 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: The two junk baskets and a 9⅝ inch junk mill were retrieved back on the rig floor at 0050 h. A BHA with a new C7 coring bit was assembled. At 0330 h, after rig maintenance, the drill string was deployed to the seafloor and Hole U1601C was reentered for the seventh time at 0554 h. The drill string was lowered in the hole and encountered a bridge at 1053.6 mbsf. After washing down to bottom at 1182.2 mbsf, including a 30 bbl mud sweep, the wash core barrel was retrieved and a new barrel was dropped. At 1445 h coring in Hole U1601C resumed. By midnight we had recovered Cores U1601C-242R and 243R, recovering 6.5 m of the 8.0 m cored with an average recovery of 82%.
Daily science report for 29 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: The Kuster FTS was back on deck at 0055 h, completing the fourth FTS run in Hole U1601C. We retrieved the drill string equipped with a logging bit, which cleared the rig floor at 0335 h. This ended the wireline logging and water sampling bit run 6.
Before the next attempt to deepen Hole U1601C, we needed to clear the hole from metal debris left behind by previous coring runs, particularly the last one leaving behind a cone bearing. A BHA was assembled with two junk baskets and a 9⅝ inch junk mill. The drill string was lowered to the seafloor at 0430 h, filling the pipe every 15 stands from the rig. The subsea camera was launched at 0527 h and Hole U1601C was reentered for the sixth time at 0704 h. The bit was lowered further into the hole and a hard tag was encountered at 1074 mbsf. While washing down to bottom at 1182.2 mbsf, hard spots were encountered at 1084, 1094, 1123, and 1145 mbsf. Milling, which included slowing circulation and rotating and lifting the pipe twice per hour, was carried out from 1430 h to 1945 h. The hole cleaning action ended with pumping a 30 bbl mud sweep with two times the hole volume of seawater. At 1945 h we began retrieving the drill string.
Daily Science Report for 28 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: At 0045 h, rigging down the fourth logging tool string with the Formation Micro-Scanner (FMS) and Dipole Shear Sonic Imager tool (DSI) was complete. We still had the postponed Versatile Seismic Imager tool (VSI) to run as the fifth and final logging tool string. However, this required daylight, so we proceeded with borehole water sampling objectives instead. The plan was to deploy both Kuster Flow Through Samplers (FTS) in series, with the Elevated Temperature Borehole Sensor (ETBS) at the bottom, using the coring line. We planned to do this three times, for a total of 6 sampling stations down the borehole. The first run started at 0205 h and ended at 0340 h. After laying out the tools, removing the water samples, and resetting the tools, the second deployment started at 0515 h and ended at 0725 h. The third deployment started at 0830 h and ended at 1225 h.
The prior issues with the VSI had been resolved and the rig was again readied for wireline logging. The protected species watch began at 1430 h and the fifth logging tool string in Hole U1601C was deployed at 1435 h. An issue with the telemetry head required retrieval of the VSI string at 1515 h and replacement of the telemetry head. The air guns were prepared and at 1640 h the tool string was redeployed to 1069 mbsf. Given the remaining daylight hours, the measurement stations on the log up were set at 100 m intervals. The run was completed at 2105 h.
We decided to conduct a fourth water sampling run because one of the samplers on a previous run recovered only ~5% of the chamber volume, and because the results from the other water samples were encouraging. The dual Kuster FTS and ETBS configuration was deployed once more at 2215 h. The borehole water sampling effort yielded a total of 8 samples at 6 targeted depths intervals (mbsf): 146, 368, 465, 675 (sampled twice with ~5% and 100% recovery, respectively), 970, and 1074–1065 mbsf (repeated at 1065 mbsf to avoid mud sampled at 1074 mbsf).
Daily Science Report for 27 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: The second logging tool string deployed in Hole U1601C, including the neutron Accelerator Porosity Sonde (APS), the High-Resolution Laterolog Array (HRLA) resistivity tool, and the Ultrasonic Borehole Imager (UBI), was completed at 0225 h. Logging with the third tool string including the spectral natural gamma ray tool and the Magnetic Susceptibility Sonde (MSS) began at 0300 h and ended at 0830 h. For the fourth tool string, including the Versatile Seismic Imager (VSI), we targeted the daylight hours to comply with the wildlife protection protocols. At 1030 h the protected species watch and preparation of the air guns began. At 1400 h the logging attempt was aborted and postponed due to issues with cabling or software. Instead, we deployed the Formation MicroScanner (FMS) and Dipole Shear Sonic Imager tool (DSI) as the fourth logging tool string. This run began at 1445 h and ended at 2350 h with two upward log passes completed.
Daily Science Report for 26 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: A 3-stand BHA with a logging bit was assembled, without floating valve and including a large bore landing saver. The rig was serviced and at 0145 h we began deploying the drill string. The subsea camera was launched at 0248 h and Hole U1601C was reentered for the fifth time at 0406 h. The bit was positioned at 30.9 mbsf and the camera was back on deck at 0448 h.
The first wireline logging tool string was assembled including the Schlumberger tools for borehole and tool temperature, spectral natural gamma radiation, and bulk density and photoelectric factor. We also added the IODP ETBS to the bottom of the tool string. The ETBS does not transmit data in real time but is the best temperature tool available on board. Logging started at 0715 h and ended at 1530 h. The log down tagged hard at 1077 mbsf. During both the log down and the log up, the tool string was held every 100 m for 10 min for the ETBS to acquire temperature equilibration time series.
The second logging tool string includes the neutron acceleration porosity sonde, a resistivity tool, and the UBI. The log down started at 1700 h and the log up was in progress at the end of the day.
Cores U1601C-235R through 240R from the last coring run in Hole U1601C remain racked because a newly mandated full stop on core processing has not allowed splitting, description, and subsampling of these 16 sections. In addition, Core 227R is quarantined because of an abundance of chrysotile veins.
Daily Science Report for 25 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-237R through 240R to 1182.2 mbsf. After Core 236R, the sinker bar did not exit through the blocks, requiring troubleshooting and a slip and cut of 50 m of coring line. A 20 bbl mud sweep was pumped after Core 238R. After cutting Core 240R the bit had reached 50 h on bottom and needed to be replaced. At 1330 h, a final 30 bbl mud sweep was pumped, and the hole was replaced 6 times with seawater (2223 bbl, 19,000 strokes). The hole was then replaced with freshwater (5550 bbl, 4710 strokes) in preparation for wireline logging. The last core barrel was on the rig floor at 1800 h. The drill string was retrieved to 55.5 mbsf where another 20 bbl of freshwater was pumped to top off the hole. Retrieval of the drill string continued and the bit was on the rig floor at 2355 h. The tips off all four roller cones were lost and one of the cones had kicked inward as well, losing parts of the bearing. These kinds of damage can happen when the bit stands up on a pedestal of core that was left behind from previous coring. This concluded the fourth coring bit run in Hole U1601C, which advanced the hole by 208.6 m and recovered 129.6 m, with core recoveries ranging from 22% to 94% (average recovery 62%).
We decided to conduct a full suite of wireline logging operations as well as borehole water sampling in Hole U1601C before attempting a final coring run in this hole. The intent of this sequencing was to minimize the various risks of not gathering the logging data for this >1 km deep legacy hole.
Cores U1601C-225R through 334R (1104.6–1153.1 mbsf) consist mainly of variably altered gabbro with subordinate gabbronorite and troctolite, and highly serpentinized harzburgite and dunite.
Daily Science Report for 24 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-228R through 236R to 1162.8 mbsf, recovering 22.1 m of the 43.7 m cored, with core recoveries ranging from 23% to 76% (average recovery 51%). 20 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-220R through 224R (1080.3–1153.1 mbsf) consist mainly of variably altered gabbro with subordinate gabbronorite and troctolite, and a lesser proportion of highly serpentinized harzburgite and dunite.
Daily Science Report for 23 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-217R through 227R to 1119.1 mbsf, recovering 33.6 m of the 53.3 m cored, with core recoveries ranging from 22% to 92% (average recovery 63%). 20 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-210R through 219R (1031.8–1080.3 mbsf) consist mainly of variably altered gabbro with subordinate olivine gabbro, gabbronorite, and troctolite, and a lesser proportion of highly serpentinized harzburgite and dunite.
Daily Science Report for 22 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-205R through 216R to 1065.8 mbsf, recovering 36.0 m of the 58.2 m cored, with core recoveries ranging from 24% to 94% (average recovery 62%). 20 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-198R through 209R (973.6–1031.8 mbsf) consist mainly of variably altered gabbro, and some harzburgite and dunite.
Daily Science Report for 21 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Tripping of the drill string to the seafloor continued until Hole U1601C was reentered for the fourth time at 0020 h. At 0105 h the camera was back on deck and we continued to lower the drill string to the bottom of the hole. Tight hole conditions were encountered from 944.5 to 959.1 mbsf. A 20 bbl mud sweep was pumped at 973.0 mbsf. The core barrel was retrieved to confirm it was fully functional and dropped once more down the pipe. At 0800 h coring resumed from 973.6 mbsf. We recovered Cores U1601C-198R through 204R to 1007.6 mbsf, recovering 25.9 m of the 34.0 m cored, with core recoveries ranging from 57% to 92% (average recovery 76%). 20 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-187R through 197R (920.3–973.6 mbsf) consist of strongly to completely serpentinized harzburgite and dunite, and variably altered gabbro, olivine gabbro, and gabbronorite.
Shipboard personnel took a moment to celebrate Hole U1601C joining the exclusive club of >1000 m deep holes drilled by the JOIDES Resolution (JR). After nearly half a century, this club still has only 5 members that were cored >1000 m into igneous rocks. When it comes to penetrating ultramafic rocks, Hole U1601C has already far exceeded the previous record of ~200 m.
Daily Science Report for 20 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-192R through 197R to 973.6 mbsf. We recovered 14.8 m of the 29.1 m cored, with core recoveries ranging from 15% to 77% (average recovery 51%). 20 bbl mud sweeps were pumped every ~10 m. The bit had reached 50 h on bottom, and we decided to retrieve and replace it. At 1230 h, after a final 30 bbl mud sweep, the pipe was pulled out of the hole and cleared the seafloor at 1535 h. We used this opportunity to test the ETBS, which malfunctioned on previous deployments and had been repaired in the meantime. The test deployment inside the drill string was concluded at 1815 h and the drill string was retrieved, with the bit clearing the rig floor at 2000 h. This ended coring bit run 3 (overall bit run 4) in Hole U1601C. The used coring bit was missing 16 tungsten carbide teeth, a degree of wear considered acceptable and not traceable to a particular event. The ETBS returned valid temperature data, following closely the temperature profile measured by the Conductivity-Temperature-Depth (CTD) sonde ~6 h later outside the drill string, and is ready again for downhole deployment.
A 4-stand BHA with a new C7 bit was reassembled and the rig was serviced until 2200 h. The drill string was deployed for the fourth coring run in Hole U1601C. The subsea camera frame was launched at 2305 h. By midnight the bit was at 830.6 mbrf.
Cores U1601C-175R through 186R (862.1–920.3 mbsf) consist of strongly to completely serpentinized harzburgite and dunite, and variably altered gabbro, olivine gabbro, troctolite, and diorite.
Daily Science Report for 19 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-179R through 191R to 944.5 mbsf. We recovered 46.6 m of the 63.0 m cored, with core recoveries ranging from 52% to 89% (average recovery 74%). 20 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-164R through 174R consist of strongly to completely serpentinized harzburgite and dunite, and variably altered gabbro, olivine gabbro, diabase and diorite. The mafic intrusions make up ~18% of the recovered material so far.
Subsampling of section halves for shipboard analysis resumed today after we made further adjustments to our special core handling procedures. The ~12 cores (average of ~40 sections) recovered in a day are split the next day in a single ~2 h session. Immediately after splitting, the archive section halves are shrink-wrapped and racked for paleomagnetic measurements, which can be done without removing the shrink wrapping, and some physical properties measurement that require a few days. The working section halves are kept damp while being described over the ~24 h after splitting. When the “rapid descriptions” are complete, the section halves are shrink-wrapped and made available for subsampling for another ~24 h before they are moved to storage. Some of the shipboard samples will be analyzed on board, while others will be shipped to shore for further processing.
Daily Science Report for 18 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-167R through 178R to 881.5 mbsf. We recovered 39.5 m of the 58.2 m cored, with core recoveries ranging from 24% to 98% (average recovery 68%). 20 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-152R through 163R consist of strongly to completely serpentinized harzburgite and dunite, and variably altered gabbro, olivine gabbro, and diabase.
Daily Science Report for 17 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-154R through 166R to 823.3 mbsf. We recovered 52.9 m of the 63.1 m cored, with core recoveries ranging from 59% to 112% (average recovery 84%). 30 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-140R through 151R consist of strongly to completely serpentinized harzburgite and dunite, and variably altered gabbro and diabase.
Daily Science Report for 16 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-141R through 153R to 760.2 mbsf. We recovered 47.8 m of the 63.0 m cored, with core recoveries ranging from 32% to 112% (average recovery 76%). 30 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-126R through 139R consist of strongly to completely serpentinized harzburgite and dunite, and abundant, variably altered gabbro, olivine gabbro, and gabbronorite intrusions.
Daily Science Report for 15 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Assembly of the BHA with a new C7 bit was completed and deployment of the drill string began at 0030 h. The subsea camera was launched at 0043 h, the pipe was tripped to the seafloor, and Hole U1601C was reentered for the third time (third coring bit run; overall bit run 4 in Hole U1601C) at 0212 h. The camera was back on deck at 0310 h and the bit was lowered down the hole until the top of a soft fill was tagged at 636 mbsf. A core barrel was dropped, and the hole was washed to total depth at 658.4 mbsf, which resulted in high pressure readings. A second core barrel was dropped and the pressure normalized. At 0830 h coring resumed. At the end of the day, we had recovered Cores U1601C-133R through 140R to 697.2 mbsf. We recovered 31.8 m of the 38.8 m cored, with core recoveries ranging from 45% to 96% (average recovery 82%). 30 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-121R through 125R consist predominantly of strongly to completely serpentinized harzburgite, with intervals of dunite and variably altered gabbro, olivine(-bearing) gabbro, and gabbronorite. Core splitting with special PPE has caught up with core recovery (down to ~1 day lag), and “rapid core description” has caught up with core splitting, reestablishing a steady-state core handling process. Strategies for reestablishing subsampling for ship and shorebased analyses are being discussed onboard and with shore management.
Daily Science Report for 14 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-124R through 132R to 658.4 mbsf. We recovered 36.4 m of the 43.7 m cored, with core recoveries ranging from 62% to 109% (average recovery 83%). 30 bbl mud sweeps were pumped every ~10 m, and a final 50 bbl sweep was pumped with two times the open hole volume. At 1715 h the coring bit had accumulated 54 h on bottom and we decided to retrieve it. Rig servicing was conducted during the pipe retrieval and the bit cleared the rig floor at 2230 h, ending coring bit run 2 (overall bit run 3 in Hole U1601C). The science party is still enthusiastic about deepening this phenomenal hole; thus, the rig crew began reassembly of the BHA with a new C7 bit for the next coring run.
Cores U1601C-101R through 120R consist predominantly of strongly to completely serpentinized harzburgite, with intervals of dunite and variably altered gabbro, olivine gabbro, and gabbronorite. Subsampling of core sections and shipboard analyses are still largely on hold.
Daily Science Report for 13 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-111R through 123R to 614.7 mbsf. We recovered 57.3 m of the 63.0 m cored, with core recoveries ranging from 65% to 106% (average recovery 91%). 30 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-83R through 100R consist predominantly of strongly to completely serpentinized harzburgite, with intervals of dunite and variably altered gabbro, olivine gabbro, and gabbronorite. Subsampling of core sections and shipboard analyses are still largely on hold due to rapid core recovery and various core handling constraints.
Daily Science Report for 12 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-97R through 110R to 551.7 mbsf. We recovered 62.1 m of the 67.9 m cored, with core recoveries ranging from 60% to 105% (average recovery 91%). 30 bbl mud sweeps were pumped every ~10 m.
Cores U1601C-56R through 82R consist predominantly of strongly to completely serpentinized harzburgite, with intervals of dunite and variably altered gabbro, olivine gabbro, and gabbronorite. Subsampling of core sections and shipboard analyses are still largely on hold due to rapid core recovery and various core handling constraints.
Daily Science Report for 11 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-82R through 96R to 483.8 mbsf. We recovered 61.6 m of the 72.8 m cored, with core recoveries ranging from 30% to 112% (average recovery 85%). 30 bbl mud sweeps were pumped every ~10 m.
Given the special core handling circumstances, it will take us at least another week to catch up with core splitting and description. Subsampling of core sections and shipboard analyses are still largely on pause due to various constraints.
Cores U1601C-38R through 55R consist predominantly of strongly to completely serpentinized harzburgite, with intervals of dunite, websterite, variably altered gabbro, gabbronorite, troctolite, and leucocratic diorite.
Daily Science Report for 10 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-67R through 81R to 411.0 mbsf. We recovered 54.8 m of the 77.5 m cored, with core recoveries ranging from 24% to 103% (average recovery 71%). 30 bbl mud sweeps were pumped every ~10 m.
After a pause of 5 days, splitting of core sections resumed under a special safety protocol. Rapid core description methods were established to catch up with the backlog and the hourly core recovery. Subsampling of core sections is still on pause due to space, time, and personnel constraints, as well as the special core handling protocols.
Cores U1601C-19R through 37R consist predominantly of strongly to completely serpentinized dunite, orthopyroxene-bearing dunite, and harzburgite, with intervals of variably altered gabbro, olivine gabbro, and gabbronorite.
Daily Science Report for 9 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: At 0030 h, the subsea camera was deployed while the drill string with the second coring bit for Hole U1601C was being deployed. Hole U1601C was reentered for the second time at 0200 h. The camera was back on board at 0300 h, the rig floor was reassembled at 0330 h, the top drive was picked up, and the bit was lowered to 266.0 mbsf where a bridge or fill was tagged. At 0430 h the core barrel was deployed, the soft fill was washed to 284.9 mbsf, and coring resumed. By the end of the day, we had recovered Cores U1601C-56R through 66R to 338.3 mbsf. We recovered 44.7 m of the 53.5 m cored, with core recoveries ranging from 52% to 106% (average recovery 84%). 30 bbl mud sweeps were pumped every ~10 m.
Core processing and subsampling were still largely on hold while core handling procedures were being refined, and approvals to proceed were sought from shore.
Daily Science Report for 8 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-48R through 55R to a depth of 284.9 mbsf. The coring bit had accumulated 50 hours on bottom. We decided to end this bit run and, given the scientific excitement about this record serpentinite hole, begin a second coring run. We recovered 35.2 m of the 38.8 m cored interval, with core recoveries ranging from 61% to 115% (91% average recovery). 30 bbl mud sweeps were conducted every ~10 m, with a final 50 bbl sweep at total depth. The subsea camera was launched at 1310 h, while the drill string was being retrieved. At 1456 h a clean exit of the bit from the reentry cone was observed, confirming that the reentry system installation was fully successful. From 1500–1530 h we navigated over Holes U1601A and U1601B, identified the cutting cones, and confirmed that the seafloor was clear of any artifacts. The drill string was retrieved, clearing the rig floor at 1830 h. At 2215 h, after conducting rig servicing activities, the crew began to reassemble the 4-stand BHA with a new C7 coring bit for the second coring run.
Core processing was on hold while we were discussing safety amendments to the core handling procedures, ways to implement them, and implications for shipboard sampling and analysis of the rapidly accumulating cores. The petrologists started to describe whole-round core sections through the core liner to the degree this was possible.
Daily Science Report for 7 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-36R through 47R to a depth of 246.1 mbsf. We recovered 53.5 m of the 63.0 m cored interval, with core recoveries ranging from 42% to 106% (85% average recovery). 30 bbl mud sweeps were conducted every ~10 m. We waited on weather due to intermittently high waves from 0100 h to 0445 h, during which time the rig crew slipped and cut 100 m of coring line.
Due to concerns about the potential health hazard of asbestiform chrysotile observed in the veins of serpentinized peridotite material, the whole-round sections were sealed in core liners and capped without splitting. Whole-round measurements are being taken, but detailed description, subsampling, or analyses are on hold starting with Core U1601C-19R. Exceptions were Cores U1601C-22R, 25R, 35R, and 36R, which consist of gabbro, gabbronorite, and troctolite, and are being fully processed. Proposed core handling procedures for the serpentinized peridotite were sent to management.
Daily Science Report for 6 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-23R through 35R to a depth of 187.9 mbsf. We recovered 27.8 m of the 63.0 m cored interval, with core recovery ranging from 20% to 71% (44% average recovery). 30 bbl mud sweeps were conducted every ~5 or ~10 m.
Cores U1601C-13R through 18R consist of strongly to completely serpentinized orthopyroxene-bearing dunite, gabbronorite, oxide-bearing gabbronorite, disseminated oxide gabbronorite, harzburgite, and orthopyroxenite.
Daily Science Report for 5 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Today we recovered Cores U1601C-10R through 22R to a depth of 124.9 mbsf. We recovered 30.9 m of the 63.1 m cored interval, with core recovery ranging from 27% to 91% (49% average recovery). 30 bbl mud sweeps were conducted every ~10 m.
Cores U1601C-10R through 12R consist of strongly to completely serpentinized harzburgite.
Daily Science Report for 4 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: At the beginning of the day the reentry assembly, consisting of a FFF and 23 m of 14¾ inch casing, had just been dropped through the moonpool and down the drill string, with the bit at ~15 mbsf in Hole U1601C. At 0005 h, the subsea camera was launched to confirm that the reentry assembly had properly landed in the pre-drilled 23 m deep hole, which was visually confirmed. The Niskin bottles on the camera frame were triggered and returned to the moonpool by 0105 h. The first core barrel was dropped and indicated unusually high pressure, which could have resulted from plugged jet nozzles. A second barrel was dropped without incident, and coring began. By the end of the day, we had recovered Cores U1601C-2R through 9R to a depth of 61.8 mbsf. We recovered 13.8 m of the cored interval of 38.8 m, with core recovery ranging from 12% to 71% (36% average recovery). Mud sweeps were conducted at 37, 46, 56, and 60 mbsf.
Cores U1601C-2R through 7R consist of strongly to completely serpentinized harzburgite, dunite, and olivine websterite, with two small pieces of basalt at the very top.
Daily Science Report for 3 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Drilling the initial 14¾ inch wide and 23 m deep hole for the reentry system in Hole U1601C was completed at 0615 h. The drill string was retrieved, with the bit clearing the rig floor at 1025 h. Two joints of 10¾ inch casing, with a 10¾ inch to 13⅜ inch crossover at the top, were welded together and staged in the moonpool area. An RCB BHA with a new 9⅞ inch C7 bit was made up and deployed through the casing, starting at 1345 h. The subsea camera was launched at 1610 h. As the ship was maneuvered to the Hole U1601C coordinates, we passed Hole U1601B, which had a hole in the center of a cuttings cone. At the Hole U1601C coordinates, 20 m to the northeast, a “pond” of white sepiolite slurry came into sight, but the hole was not visible. After a short period of poking into the “pond,” the bit reentered Hole U1601C at 1925 h and reached the bottom of the hole without detecting any fill. The bit was raised 8.7 m and the camera frame was retrieved, arriving on the rig floor at 2125 h. The rig crew installed the FFF around the drill string and attached it to the top of the 13⅜ inch casing crossover. At 2334 h, the casing-cone assembly was dropped into the moonpool and down the drill string.
Daily Science Report for 2 May 2023
Location: Hole U1601C (30°7.9417′N, 42°7.2072′W; water depth 850 m)
Science Update: Assembly of the BHA with a 14-3/4 inch drilling bit was complete at 0130 h. After reinstalling the upper guide horn once more, deployment of the drill string began at 0315 h, was paused at 0400 h for general rig servicing, and was complete at 0630 h. The rest of day we made slow but steady progress towards drilling the 23 m deep casing hole at Hole U1601C.
Daily Science Report for 1 May 2023
Location: Hole U1601C (30°7.934′N, 42°7.217′W; water depth 850 m [preliminary])
Science Update: Today we recovered Cores U1309D-310R through 313R from 1478.6 to 1498.0 mbsf. We recovered a total of 12.42 m from the 19.4 m cored interval, with core recoveries ranging from 38% to 83% (average of 64% recovery). 30 bbl mud sweeps were pumped every ~5 m. At this point, the bit had accumulated 50 h on bottom, and we decided to terminate this coring run. At 1145 h, we began retrieving the drill string and the bit cleared the seafloor at 1620 h.
This was a good opportunity to test the Elevated Temperature Borehole Sensor (ETBS), which had malfunctioned on previous runs and had been worked on since. With the bit several meters above the seafloor, we installed the top drive again, installed the sinker bars, and deployed the ETBS. The test results were negative and repair efforts will continue. At 1900 h we continued to retrieve the drill string and the bit cleared the rig floor at 2245 h, ending the third bit run (first coring bit run) in Hole U1309D on this expedition.
The plan is to return to Site U1601 and set a reentry system in a new Hole U1601C. This will be a different system from the one we were not able to release in Hole U1601B. It will have neither an underreamer nor a casing release tool. We will drill a 14-3/4 inch, ~22 m deep hole, deploy and reenter a 9-7/8 inch coring bit into the hole, free-fall a casing-cone assembly into the hole using the drill string as a guide, and begin coring. By 2254 h the ship had moved the 2 nmi distance to Hole U1601C in DP mode. Hole U1601C is located 20 m northeast of Hole U1601B. At midnight, assembly of the BHA with a 14-3/4 inch drilling bit was in progress.
The scientists continued to describe cores and thin sections from Hole U1309D and conducted other laboratory analyses. Cores 306R through 313R consist predominantly of slightly to moderately altered, coarse to medium-grained gabbro, olivine-bearing gabbro, orthopyroxene-bearing gabbro, gabbronorite, and one interval of diabase.