Summary

Expedition 390 South Atlantic Transect Part 1 drilled additional holes at three sites in the South Atlantic, Sites U1556, U1557 and U1559. Sediment cores were recovered at Sites U1556 and U1559. Hard rocks were the target of the expedition and were recovered at all three sites. Due to a failure of an electromagnet brake on the drawworks, Expedition 390 operations ended prematurely and Hole U1559B could not be re-entered as initially scheduled.

Paleomagnetists measured archive half sections with the SRM and discrete samples from the working half sections for shipboard measurements with the JR6 spinner magnetometer. Most of discrete samples were shared with the Physical Properties group for MAD measurement.

For the first time, scientists used the new Agico MFK2-FA Kappabridge installed in the Pmag lab for AMS measurement. Scientists used several JR6 sample holders  - a sufficient amount of sample holders (especially the "cubic" sample holder) should be available at all times. Elevated background noise of the SRM, especially on the X axis still persists: a service call is planned during the tie-up in Cape Town later this year (Expedition 397P).

APC cores at Sites U1556 and U1559 were oriented using the Icefield magnetic tools. Icefield Tool 2007 stopped recording in Hole U1556C and Hole U1559D. Tests in the lab were run during the expedition to determine the cause. See Magnetic Orientation Tools (MOTs) for more details.

During the "free" time of Expedition 390 (e.g., transit, logging time), the paleomagnetists also measured archive half sections cored during previous expeditions (Expeditions 390C and 395E). Details are provided below.

Expedition 390 Material measured

Material from Expedition 390C (during transit from Cape Town to Site U1556)

Paleomagnetists measured sediment archive sections from Site U1559, U1556 and U1557 previously measured and demagnetized at 20mT during X390C to check if any alteration happened during storage in College Station. They measured the NRM, followed by AF demagnetization at 20 mT. Data are reproducible. To catch up with the core flow, paleomagnetists decided to directly AF demagnetize at 20 mT and measure the NRM only (which actually corresponds to the AF step at 20 mT performed during Expedition 390C). Four discrete samples were analyzed from Core 30X, 32X and 33X of Expedition 390C.

Material from Expedition 395E (at Site U1557)

Scientists measured hard rock sections of Site U1561 (Cores 8X and 9X). Two discrete samples were analyzed from Cores 8X and 9X of Expedition 395E.

Items received

• Five quartz trays for thermal demagnetization with the ACS furnace

• Two Icefield tools came back from the vendor after repair: Tools 2007 and 2052

Items shipped

• Broken pressure case snubber (#104) of Tool 2043 (cracked during X392 - see X392 Tech Report)

• KLY-4S Kappabridge - the instrument will be installed in College Station.

• Icefield Magnetic Tool 2007 (stopped recording during survey)

Items ordered

• JR6 sample holders (cubic, for J-cubes) - two holders were received before start of X393.

Instruments

Icefield magnetic orientation tools

Tools 2003 and 2052 came back from the vendor and needed to be tested. We (Beth and Myriam) performed a rotation test on the dock in Cape Town on April 11 with a 90° rotation between each measurement (for a full 360 degree rotation) for the two Icefield tools back from repair.

Observations: Tool 2007 did not show a full 360 degree rotation. Instead, it showed rotations of around 25 degrees each. "This was the same behavior that the tool was exhibiting on 395C and was the reason for returning to icefield. Tool 2052 looks better but rather than equal 90 degree rotations, the data shows rotations of approximately 40, 40, and 200 degrees. Again, this is the exact behavior this tool showed on X396 and was the reason that it was returned" [M. Higley].

Additional rotation tests were performed by Mark Higley on April 12 on the dock for all Icefield tools (i.e., 2007, 2052 and 2043).

Rotation test for Tool 2043: GOOD (Figure 1 below)

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Figure 1: Rotation test results for Tool 2043

Observations: We found out that Tool 2007 did not have an instrument calibration. Icefield company was contacted to have the calibration file. Tool 2052 used an old (out-of-date) instrument calibration.

• Once the files were received from Icefield, the Labview program CreateInclinFile.exe had to be rewritten to upload/embed the new instrument calibration of Tools 2007 and 2052 (done by Beth Novak). New rotation tests were conducted for Tools 2007 and 2052 before APC/XCB coring at Site U1556 (during preparation for logging). Tool 2007 was tested on May 3 (Figure 2 below) and Tool 2052 on May 4 (Figure 3 below). Both tools passed successfully the rotation test.

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Figure 2: Rotation test results for Tool 2007

Figure 3: Rotation test results for Tool 2052

• Tools 2007 and 2052 were deployed for core orientation in Hole U1556C. Tool 2043 was not used because the corresponding pressure case (#104) has a crack (noticed during X392). Tool 2007 stopped recording before the end of the survey, after 8.5 hours during its first run and after 2 hours during the second run. The battery was okay, so the instrument issue had another origin to be further investigated. Tests were conducted in the downhole logging room for 20+ hours and were all good. It might be possible that the APCT-3 runs and/or barrel firing have destabilized the tool while in the hole. It might also be due to some issue with the Palm device used for Tool 2007 (i.e., Ice Cube). Tool 2052 had no issue. See Magnetic Orientation Tools (MOTs) for details.

• Tool 2052 was deployed for core orientation in Hole U1559C. There is no issue related to this tool. To test Tool 2007, I asked the permission to run the tool in Hole U1559D which was initially a non-oriented hole. Permission was granted. Tool 2052 was deployed to orient Cores 1H to 3H in Hole U1559D (non oriented in Hole U1559C) and Tool 2007 was deployed to orient Cores 4H to 6H. Again, Tool 2007 stopped recording for a few minutes while in the hole. Tool 2007 was again tested in the lab (4-day long survey) and recorded properly with no issue. It may be possible that the tool has a technical/mechanical issue triggered by shock during firing. See Magnetic Orientation Tools (MOTs) for details.

• Tool 2007 was sent to shore. Use Tools 2043 and 2052 for core orientation.

Superconducting Rock Magnetometer (SRM)

• Wifi has been known to create additional noise in the SRM (see Shanghai assessment). During a test broadcast, high disturbance noticed by J. Dinares-Turrell happened in a running tray background measurement when EO officer approached the SRM with connected Ipad. Science party and core lab users have been informed about that, and should be emphasized for next expeditions.

• The field inside the SRM was trapped shortly after leaving port. The SRM keeps experiencing high noise on X and Z axis. This was not an issue for measuring weaker sediment sections of X390 because their intensity was higher than the SRM background noise.

• The SRM experienced several high flux jumps on the Y-axis when scientists measured hard rock sections. This phenomenon has been documented in previous expeditions. It is likely due to antennae effects. Repeated consecutive intense cleaning with antistatic solution and slower measurement speed seem to solve the issue.

• Several empty tray measurements were conducted and data files were sent to shore to give a status of the SRM to schedule a service call/visit of a technician during the tie-up in Cape Town (Expedition 397P).

• As the operations ended earlier, the SRM was warmed up during transit back to Cape Town to perform a vacuum pump down on May 28, 2022. After 84 hours, the best vacuum pump down pressure achieved was 3.2e-3 hPa on May 31, 2022. The SRM was not immediately cooled down. See Super Conducting Rock Magnetometer (SRM) for details. The SRM reached optimal cold temperature (superconducting state) on June 3, 2022.

• After the vacuum pump down, a field profile was measured before field trapping on June 4, 2022. The field was trapped and another field profile was measured (Figure 4).

JR6 Spinner Magnetometer

• Sample holder correction gave sometimes suspicious values. A physical cleaning (with DI) and AF demagnetization at 80 mT seem to fix the issue.

• Four “cubic” sample holders were used during the expedition. Sample holder broke where it usually breaks at the actuator hole (Figure 5). This is very common and a sufficient number of "cubic" sample holders should be available in the pmag lab. The last cubic sample holder was dedicated to hard rock measurements, while a cylindrical sample holder was used to measure J-cubes.

• Java was updated to run PuffinPlot on the PC connected to the JR6. To open the JR6 data in PuffinPlot and do the PCA analysis, it is necessary to use the “custom format” of PuffinPlot. To have geographic coordinates in PuffinPlot similar to the geographic coordinates obtained from Remasoft JR6, use 0 for formation dip azimuth and 90 for formation dip. Leave other fields blank.

MFK2 Kappabridge

• The MFK2 was used during X390 to measure the AMS of sediment and hard rock samples. Measurements were done with the 1-axis rotator aka 2D holder (3 positions).

• The sample holder correction shows suspicious values due to a noisy environment. Values given by the MFK2 are however in the same range of values than the holder correction done by the KLY4 (see MFK2 FA Multi-function Kappabridge). The user just needs to accept the data and move on to the measurement stage.

• We encountered systematically an “Overflow Zero” error (error #555) when measuring with a field of 425 A/m. There is no error at the default field value of 200 A/m. There is no possibility to do the zeroing manually at 425 A/m with the auxiliary command. After contacting Agico, we moved the MFK2 to a different spot in the pmag lab (Figure 6) and we could finally measure at 425 A/m and run a Sigma Test. Email from Agico [Michal Almasi]: “Zeroing of the coils has some limitation - in higher magnetic field, the disturbing signal (induced in the coils) was so strong that the instrument was not able to zero it. It seems that new place is better, so the instrument is able to eliminate the disturbing signal”.

The MFK2 should be placed as shown on Figure 6. A different position (parallel to the rack for instance) may create an "Overflow error".

• MUT Uploader: uploading MFK2 data to LIMS with MUT2

MUT uploader version 2 and LORE report have been set up to upload MFK2 data. Three files are needed to upload MFK2 to LORE with MUT (.ams, .csv and .acs). The 4^th file generated by Safyr7, file with .ran extension, is no longer required for upload. The .ran file is to use in old Agico Anisoft version (version 4 and prior). However, it is recommended to upload the .ran file along with the three other files.

• Anisoft 5 beta version: version released on May 20, 2022

A beta version of Anisoft5 software (version 5.2.02), created by Martin Chadima (Agico), was installed on the KAPPA computer. This beta version allows the export of edited data (for instance if dip and azimuth were initially entered wrong by the scientists) into a .csv file formatted with IODP format. The edited data file can be uploaded with MUT2 to the LORE database.

• LIMS/LORE Report

A Word document with the definition of the different parameters in the LORE report, column by column, was sent to the developers to update LIMS/LORE contents (for both standard and expanded reports). As of June 4, 2022, the report was not yet updated online.

D-2000 AF demagnetizer

Scientists used extensively the AF demagnetizer on sediment and hard rock samples for AF demagnetization of the NRM. No issue was reported.

Thermal demagnetizer TD-48SC

Scientists carried out thermal demagnetization on selected hard rock samples. They used the broken quartz tray which is currently inside the oven. No issue was reported.

IM10-30 Impulse magnetizer

Scientists conducted IRM acquisition and backfield curve to determine the magnetic mineralogy. No issue with the IM10-30 was reported.

QA/QC

QCViewer

• Templates created for IODP Standard IODPSTD13, 15 and 16 (discrete samples) when they are measured with the SRM. They were measured once with the SRM but their data do not appear in QCViewer. This needs to be further investigated and checked with the developers in coming expeditions/tie-up/transit.

• Problem in display when looking at the JR6 data in a short time window (over a month for instance). The data do not show up clearly whereas they appear when we select a longer time period (over a year for instance) (Figure 7). Moreover the horizontal axis does not seem to update with the short-time query. On Figure 7 below, the bottom plot for ~ a month-time window does not have the horizontal axis - time/date - in agreement with the query. This needs to be further investigated and checked with the developers in coming expeditions/tie-up/transit.

• A QCViewer template was created for an SRM empty tray which is currently used in X390. The LIMS text_ID is SHLF577811. X-moment, Y-moment and Z-moment are the parameters to check for QA/QC. However, QCViewer cannot manage in its current version measurements with offset. To consider an empty tray as QA/QC, it might be necessary to average all points measured during an empty tray measurement with the SRM and plot this average point in the template. This needs further thoughts, especially on how we calculate moment average (independant calculation? embedded in QCViewer?)

Miscellaneous

• 3D-printed spare screws (Figure 8) for the 1-axis rotator (2D sample holder) of the MFK2 were made by Garrick. Original Agico screws easily break and only a couple were left. This new 3D-printed screw is stronger than the Agico screws. I would recommend to ask the ETs to make MFK2 screws as needed.

• Stand (Figure 9) for MOTs to unscrew the tool pressure case if one cannot open the pressure case easily. Stand was thought and made by Alejandro and Garrick.

• The library of the paleomagnetism laboratory got four books from Maggie’s old times. The list was updated and put on Confluence at Paleomagnetism Library.

• In preparation for the tie-up in Cape Town (X397P) where the lab workstations will be changed, a page listing all software available on the pmag lab computers was created on Confluence. See List of Software available in the Pmag lab. This page might also be useful for the scientists.

• Updates in Confluence pages of the Paleomag Notebook.