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Paleomagnetic Standards Measurements

Updated 2/19/20

Scripps Institute for Oceanography Standards

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Paleomagnetic standards (IODPSTD01 through IODPSTD12) were provided by Lisa Tauxe to confirm instrument measurements are correct. The standards were prepared specifically for the SRM although they can be used in the other instruments as well. Do not measure them in the JR-6 spinner. These standards were prepared and measured at Sripps Institute for Oceanography in California. Standards are kept in a cardboard box (figure 1) and stored in the Pmag lab in the smaller MU metal shielding chamber (figure 2).

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Table 1 Paleomagnetic Standards Values

Sample Name

Text ID

Declination

Inclination

Intensity (A/m) as provided (assumes 1cc)

Intensity (A/m) assuming 7cc volume

csd

IODPSTD01

CUBE11242251

217.4

33.9

3.17E-01

4.529E-02

0.9

IODPSTD02

CUBE11242261

134.2

35.5

8.48E-02

1.211E-02

0.8

IODPSTD03

CUBE11242271

143.5

-29.1

9.40E-02

1.343E-02

1.3

IODPSTD04

CUBE11242281

227.5

-22

6.36E-02

9.086E-03

0.1

IODPSTD05

CUBE11242291

18.9

-24.9

9.09E-02

1.299E-02

0.4

IODPSTD06

CUBE11242301

137.6

28.2

4.20E-01

6.00E-01

0.5

IODPSTD07

CUBE11242311

326

34

5.86E-01

8.371E-02

0.7

IODPSTD08

CUBE11242321

221.8

-12.2

7.82E-02

1.117E-02

0.6

IODPSTD09

CUBE11242331

34.7

-28.4

1.13E-01

1.614E-02

1

IODPSTD10

CUBE11242341

316.2

-19.8

6.39E-02

9.129E-03

0.4

IODPSTD11

CUBE11242351

333.3

24.3

9.78E-02

1.40E-02

1

IODPSTD12

CUBE11242361

28.4

40.2

1.96E-01

2.80E-02

0.4


Standard Orientation

The Samples are oriented as if they were taken from an archive half. This means that the arrow etched into the cube points in the negative Z (i.e. towards the top of the core) on the ARCHIVE HALF SPLIT FACE (not the working half split face as a cube normally collected onboard would be). This can be confusing as most of the time, discrete samples would be collected from the working half.  The arrow on the orange dot sticker points in the positive X direction of the IODP coordinate system. Be sure to keep this orientation in mind when loading into the instruments.  See Figure 3 for sample orientation arrows

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Figure 3 Cube Orientation for Standards


IODP created Standards

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Because the standards provided by Lisa Tauxe at Scripps were not designed to be used in the JR-6, 4 new standards were created which can be used in the JR-6. A strip of magnetic tape was glued to a stick which is secured inside a J-cube. The standards were then given an IRM and measured in the JR-6 followed by the SRM. These standards are oriented as if they were collected from a working half with an assumed volume of 7cc . Each standard was measured 20 times. The process included inserting and removing the standard between each measurement. The mean intensity was calculated as well as fischer stats for inclination and declination. See table below.

Sample Name

TextID

Int (x10-3 A/m)

Stdev (x10-3 A/m)

Geo Dec (°)

Geo Inc (°)

κ

α95 (°)

IODPSTD13

CUBE11242371

41.41

0.05

309.4

-11.1

1197

0.9

IODPSTD14

CUBE11242381

47.75

0.06

329.0

-33.0

565

1.4

IODPSTD15

CUBE11242391

27.43

0.04

263.2

31.5

354

1.8

IODPSTD16

CUBE11242401

14.91

0.03

274.0

34.6

4062

0.5

Table 2. IODP standards measurements in JR-6

Measuring in the SRM

When measuring the standards in the SRM, install the discrete sample tray and set up your measurement preset to reflect a discrete J-Cube collected from the archive half. For sample shape select Discrete J-Cube. Face orientation should be Top and the Arrow Orientation (-Z) should be set to Away. Be sure to select Archive Half under From Section. In Dimensions, set the sample area to 1.0 cm2. Although this says sample area and the unit is an area unit, we are telling IMS what the volume of the J-cube is (i.e. 1.0 cm3). Name your measurement preset something useful such as Discrete Archive. More information on setting up a sample preset can be found in the SRM user guide.

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When the measurements are complete, the data will go to the In folder . This data cannot and can then be uploaded with MUT. Move the .dsc files out of the IN folder and save them in: V:\IODP_Share\PMAG_Documents\SRM\Pmag StandardsOpen the .dsc file with a text editor. Under the Header <MULTI>, scroll to the far right. You are looking for the values inclination_w_bkgrd_w_drift, declination_w_bkgrd_w_drift, and intensity_w_bkgrd_w_drift. These are your background and drift corrected values that you can compare to the listed values of the standards. Record the values in the laboratory notebookto LORE.


Measuring In the JR6

Do not measure the standards created at Scripps (IODPSTD01 through IODPSTD12) in the JR6. Load the standard into the automatic sample holder with the up arrow that is etched into the cube body facing up and to the left, as shown in figure 7. Be sure that sample type is set to cube in instrument configurations. Use a volume of 7cc. Use 0 for the azimuth and 90 for the dip. With these settings, you will look at the geographic inclination and declination (not specimen coordinates).

Image Added

Figure 7. Standard loading position for JR-6 automatic sample holder

Viewing the Data

All of the standards have been given a LIMS text ID so they can be scanned and the data uploaded to the database. The data can be viewed in LORE by selecting QAQC in the Expedition drop down, CORELAB as site, MAGNETICS for hole.


Archive Versions:

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