Manual Information

Contents 

Introduction

Method Overview

Core specimens for moisture and density (MAD) analysis are extruded from a section half for:

• Mass: measured using a motion-compensating dual analytical balance system and a drying oven.
• Volume: measured using a caliper or by a helium displacement pycnometer that employs Archimedes’ principle of fluid displacement to determine the volume of solid objects.

The MAD properties of interest are:

• Water content
• Bulk density

Dry density

• Porosity
• Void ratio

These properties are calculated based on three out of four measured values:

• Wet mass
• Dry mass
• Wet volume
• Dry volume

Method Theory

Phase relationships of mineral density, porosity, void ratio, and water content are basic sediment and rock properties that are found most accurately through mass and volume determinations. The mass or volume of the bulk (wet) material, the dried material, and the extracted water (assumed to be interstitial pore fluid) is corrected for the mass and volume of salt evaporated during the drying process. The mass and volume of the evaporated pore water salts are calculated for standard seawater salinity, seawater density at laboratory conditions, and an average seawater salt density.

Soils can be either 2-phase or 3-phase compositions (i.e., completely dry or partially saturated). For MAD measurements the analyst determines whether the sample contains a 2- or 3-phase system:

• Completely dry soil contains 2 phases: solid soil particles and pore air.
• Fully saturated soil also contains 2 phases: solid soil particles and pore water.
• Partially saturated soil contains 3 phases: solid soil particles, pore water, and pore air.

MAD data provide a direct estimate of porosity and void ratio and the average density of constituent minerals. Porosity variations are controlled by consolidation and lithification, composition, alteration, and deformation of the sediments or rocks. MAD data can be used to calibrate high-resolution gamma ray attenuation (GRA) bulk density data, which are sampled at a much higher resolution than is possible with the MAD method. If mineral density can be defined with sufficient precision, GRA bulk density can be expressed as porosity.

Selecting the Appropriate Analysis Sub-method

The user needs to decide which sub-method (A, B, C, or D) should be used for the MAD analysis. The choice depends primarily on the type of sample material to be measured. In addition, Sub-methods A and B are not recommended from an analytical quality point of view. Therefore, the choice is generally limited to Sub-methods C and D based on the following criteria:

• • Fine-grained, saturated sediments or fine-grained igneous material: Sub-method C
  • Porous rocks (e.g., vesicular basalt and limestone) that cannot be confidently saturated: Sub-method D

Definition of LIMS Analyses

Analyses in the context of the Laboratory Information Management System (LIMS) are defined based on the data acquisition systems that provide sets of data. The MADMax software application captures the data from all three types of analysis. For the MAD group of analyses, these are as follows.

Caliper analyses (CALIPER)

Volume is calculated after measuring the sample’s geometric dimensions using micrometer calipers.

Pycnometer analysis (PYC)

Sample volume is measured using a helium pycnometer.

MAD mass analysis (MAD_MASS)

Wet or dry mass is measured using the motion-compensating dual balance system.

• “Wet” refers to the saturated (undrained) state of a sediment or rock sample
• “Dry” refers to the state after drying 24 hr at 105°C and holding in the desiccator 2–3 hr.

MAD analysis (MAD)

This set of calculations is applied as appropriate for each sub-method.

Apparatus, Reagents, & Materials

• Dual balance system
• Hexapycnometer system
• Caliper
• Sample drying equipment
• Sampling tools and sampling containers

Hardware

Dual balance system

Two Mettler-Toledo XS204 analytical balances compensate for ship’s motion while weighing samples (see the Shipboard Analytical Balance User Guide for a detailed description of the mass determination system). In Figure 1 note that the left balance is the REFERENCE balance and the right balance is the UNKNOWN balance.

Figure 1. Dual Mettler Toledo XS-204 Analytical Balance System.

Hexapycnometer System

Six custom-configured Micromeretics AccuPyc 1330TC helium-displacement pycnometers can be run simultaneously (Figure 2). The six cells are mounted in a chassis to protect the electronics and to help provide temperature stability. Although the cells are centrally controlled, they can be started and stopped independently

Figure 2. Helium-Displacement Hexapycnometer.

Helium Supply and Gauge

The system depends on a reservoir of helium. Gauges at the gas bottle reservoir ensure no more than 90 psi are delivered on the lines. A gauge at the hexapycnometer enables finer pressure control. Conventionally the local gauge is set so no more than 20psi (150Kpa?) are delivered to the pycnometer cell inlets.

The cells are plumbed in parallel, which while it has no effect on the observation computations, does lead to observable fluctuations in the real-time pressure monitoring provided in software.

Precision Caliper

The caliper (Figure 3) is used to measure the dimensions of cylinder and rectangular prism-shaped samples. The information is entered in the MADMax software, which calculates the volumes of the solid samples.

Figure 3. Precision Digital Caliper for measuring dimensions of certain samples.

Thermo Scientific HERATHERM AP Oven and Desiccator Boxes

The HERATHERM AP oven (Figure 4) used in the moisture determination step is back-vented to the ship’s fume hood system to carry away the moisture liberated from the samples as they dry. The mechanical convection oven has a 60 L capacity and is set to 105°C for the MAD process. The butterfly valve (Figure 5) should be kept in the horizontal position to minimize the draw by the hood system; opening this valve will cause disrupting air currents inside the oven and will decrease the quality of the measurement.

The desiccator boxes hold samples after they have been dried in order to prevent reintroduction of water weight. The Drierite used on the JR is indicating. The color should be blue, indicating that the desiccant is good. If the desiccant is purple, it is close to being saturated, and once it becomes pink, it should be replaced.

Figure 4. Thermo Scientific HERATHERM AP 60 L oven, mounted underneath the bench. Back-vented, the oven does not warm the benchtop and alter the results from the analytical balances.

Figure 5. Exhaust tubing and the butterfly valve control (circled in green). The butterfly is completely closed; this is the correct position! Enough air flow goes around the valve blades to exhaust the oven. Do not open the butterfly valve. The desiccator boxes are to the left of the exhaust tubing.

Electronics and Control System

The software control system is a mixed language tool. MADMax is a C#/.NET application providing sample management, mass measurement, and methods computation. The C#/.NET component integrates with a LabVIEW component to manage volumetric measurement.

Masses are obtained via serial communication (RS232) with dual Mettler Toledo balances. The pycnometer control system supplies the control signals to manage helium flow for the duration of experiments and acquires the resulting data.

Sampling Tools and Sample Containers

Sampling Tools

• For soft materials, syringes/plugs are used to extract sediment samples with a nominal volume of 10 cm³ from the section halves.
• For hard materials, it is necessary to use drills and saws to cut cylindrical and rectangular prism-shaped rock samples; this is done in the core splitting room.

Sample Containers

Sample containers for the MAD analysis are either glass Wheaton vials or anodized aluminum cups. Each of them has a numeric identifier that is used to track the container and its sample throughout the process. Each container’s mass and volume are recorded in the database and the MADMax program uses these values to subtract the container mass and volume from the sample values.

• Wheaton type 800 vials are used for soft to indurated sediment samples; basically if it fits in the glass vial, use a glass vial. The glass vials have a density of 2.48-2.50 g/cm³ and their volume has been calculated from the mass determined on shore prior to shipment; their mass is approximately 21 grams and volume is about 8.3 cm³.

Anodized aluminum sample cups are used for igneous or consolidated sedimentary samples. The mass of each of the cups was determined experimentally (approximately 14.8 g) and the volume of 5.842 cm³ was estimated from the dimensions and confirmed by experiment.

MADMax Software and Procedure

MADMax is a C^# application that controls all of the measurements used in the MAD process. It can be found on the applications web page. Due to browser compatibility issues, MADMax must be installed from Microsoft Internet Explorer; any other browser is unlikely to install properly.

Login

Users must authenticate to the database in order to use the MADMax application. Upon starting the application, the user will see the login screen (Figure 7). If a new version of MADMax is available, the user will be prompted to install it.

Figure 7. MADMax login screen. Note that the application is aimed at the SHIP database.

If the user cannot login, please see a technician to ensure that the appropriate database authorization has been granted to the user account.

Main Screen

The main screen of the application (Figure 8) is the central command center for the entire process. Various actions on this screen initiate the balance measurements, the pycnometer measurements, the entry of caliper data, and the calculation of the derived MAD results.

Figure 8. MADMax main screen. Note the pycnometer display screens below the main application window.

It is recommended to click the “Display ON” button to turn the live pycnometer monitoring off unless troubleshooting a problem. The live display is memory-intensive and will slow down the functioning of the software.

Once a sample has been assigned to a MAD vial using the Sample Master program, it will be available to the MADMax application. Click the “Refresh Sample List” button to cause the sample to appear in the table.

IMPORTANT! Note that once the samples are in the MAD vials, they are tracked solely by their vial number. Care should be taken not to confuse the samples at any point in the process.

PRO TIP! Keep good logs!

MAD Method C is the most common one used on the JOIDES Resolution, so the MADMax application defaults to the “Method C” mode. The method indicator is a pull-down menu to switch between the four methods A, B, C, and D. Again, Method A and Method B are not recommended.

Regardless of method, the user can make up to five discrete types of measurements:

• Wet mass determination by analytical balance
• Dry mass determination by analytical balance
• Dry volume determination by pycnometer
• Wet volume determination by pycnometer (not recommended)
• Wet or dry volume determination by precision caliper

Depending on the method selected, different actions will be available by double-clicking on the color-coded section of the main screen appropriate to the method. For example, to make a wet mass measurement on a sample, double-click on the left-hand yellow cell as shown in Figure 9. This action will invoke the balance control software portion of MADMax.

Figure 9. Activating a wet mass measurement.

Order of Actions by Method

For each method, the measurements should be done in a specific order, as given below. Note that the MADMax interface does not sort these columns by this order, but the columns can be rearranged to do so if the user wishes.

• Method A: Wet volume (caliper), wet mass (balance), dry mass (balance)
• Method B: Wet mass (balance), wet volume (pycnometer), dry mass (balance)
• Method C: Wet mass (balance), dry mass (balance), dry volume (pycnometer)
• Method D: Wet volume (caliper), dry mass (balance), dry volume (pycnometer)

In Method D’s case, “wet volume” is better stated as “bulk volume,” because the method is used only for samples with such high porosity that the water cannot be kept inside the sample (e.g., vesicular basalt or corals). Figure 10 shows all of the methods and the required measurements for each one.

Figure 10. All of the MADMax methods shown in cascade style.

In Figure 10, note that the colored columns for the measurements (yellow for balance, green for pycnometer, and blue for caliper) are slightly different for each method. The pink Methods Completed column is the same for each method and will be discussed later in the MAD Calculations section.

Wet Mass Determination by Analytical Balance

As shown in Figure 9, above, double-click on the “Mass Wet (g)” column in the field adjacent to the sample to be analyzed. This will invoke the Balance Measurement dialog box as shown in Figure 11. The container number and the full Label ID of the sample will be displayed to ensure the correct sample was selected. Select the number of measurements to average (at least 300 is recommended, more if the sea state is high) and click “Measure.” The measurement speed of the XS-204 balances is 5 Hz, so 300 measurements will take 60 seconds. 

Figure 11. Balance Measurement dialog box. A typical expedition Label ID would be formatted as follows: 360-U1473A-21R-2-W 10/12-20127.

The next screen will appear in a minimal size with some detail hidden. If the window is expanded as shown in Figure 12, additional information can been seen.

Taring the Balances

The first step to be taken is to tare the balances; measure the tare with empty pans. This step measures the differential tare between the two balances and is used to create a motion-compensated tare value. Do not try to tare the balances by using the Tare button on the keypad; the balances must be tared using the software. The window header will show the Text ID of the sample, what measurement is being done (e.g, “Mass Wet (g)”), and the container number.

Activate the tare function by clicking the “Tare” button on the upper left-hand corner of the screen (circled in green) and the tare will begin. The reference balance trace is green, the unknown balance trace is red, and the corrected mass (in this case the tare value) is a blue trace.

The balances should be tared relatively often as many things can affect the balance reading. The most common causes of these changes are:

• spilling something on the balance pan (and please don’t leave it there!)
• cleaning something that was spilled on the balance pan
• temperature changes in the laboratory may affect the zero point of each balance

It is recommended that the user tare no less frequently than six hours, but certainly if the user suspects anything may have changed on either balance. 

Figure 12. Taring the paired balances at 300 measurements.

Making the Measurement

Once the tare is complete, place the sample container on the unknown balance and close the sliding door. Place counterweights from the standard box as close to the mass of the unknown as possible and close the reference balance door. It may be useful to look at the balance LCD screens; the circle shows the rough load on the balance and masses can be roughly equalized by using them. It is important to get the masses within 5 grams. If the red and green traces are more than 5 grams apart after the measurement is started, then press the “Stop” button, add or subtract reference masses, and start the measurement over.

The “Reference Mass” field should be filled with the total mass of the reference masses before the measurement is started. Figure 13 shows the Reference Mass (circled in blue) and the traces of the two balances and their corrected result mass. Note that the reference mass balance began at a value of just under 19 grams and the unknown balance started close to 21 grams; the difference between them is ≤5 grams, so this measurement could be allowed to continue.

Figure 13. Mass measurement on a sample.

Once the analysis is completed (Figure 14), the mass determined by the measurement process will be displayed (in this case 22.120 grams). The Tare button is active again, but it not appropriate to use it at this time without removing the sample and reference masses. The user has three choices:  accept the result and send it to the main screen display and the LIMS database by clicking the “Accept” button, reweigh the mass by clicking the “Weigh” button again, or completely cancel the measurement and discard all results by clicking the “Cancel” button.

The user should note that the instantaneous values of the balances varied by more than 20 grams in this example because of ship’s heave, but the measured mass (22.110 grams of known masses) was accurate to within 0.010 grams.

Note: At the time of writing this manual, the Std Deviation field is recording the standard deviation of the unknown mass measurement (which obviously varies highly). An upcoming upgrade will switch this to the corrected mass value.

Figure 14. Completed measurement.

Reassigning Results

The result should be in the appropriate field, but in case the user double-clicked the wrong mass measurement, MADMax provides the capability to switch the mass measurement from “wet” to “dry” and vice-versa. As shown in Figure 15, right-click the mass cell and select the “Swap the result with Mass Dry (g)” option. If two masses are already present, this option will instead state “Swap Mass Dry (g) and Mass Wet (g)” to swap the mass measurements. 

Figure 15. Right-click options for the mass measurement.

Once the user clicks the “Swap” options, a window will pop up to confirm the action as shown in Figure 16; the window for moving a result from wet-to-dry or dry-to-wet is very similar.

Figure 16. Reassign Result window. It is important to be able to do this as the drying step is irreversible and the wet mass cannot be repeated without taking a new sample.

Cancel Mass Result

The user can also cancel a result using the same right-click option, with a confirmation window as shown in Figure 17. A developer or technician can uncancel the result if this was done in error.

Figure 17. Cancel mass result pop-up window.

Review Results

If the user wishes, they can also look at the details of the mass results as shown in Figure 18. This is a summary of all of the parameters used to determine both the wet and dry masses with the parameters labeled by their database names.

Figure 18. Review wet mass results window.

The mass_dry and mass_wet components are the mass of the sample. The mass_dry_container and mass_wet_container components are the mass of the sample and the container together.

Dry Mass Determination by Analytical Balance

This step is performed the same way as the wet mass determination. Double-click on the “Mass Dry (g)” column in the field adjacent to the sample to be analyzed. Follow the rest of the instructions in Wet Mass Determination by Analytical Balance, except that it applies to the dry mass measurement.

Dry Volume Determination by Helium Pycnometer

Calibration of the Pycnometer Cells

Before any pycnometer measurements can be made, the pycnometer cells must be calibrated. On the main screen, click the “Calibrate Pycnometer” button on the right side of the main screen in order to invoke the calibration window as shown in Figure 19.

Figure 19. Calibrating the pycnometer cells.

First select the standard to be used in the calibration. For the 35 cm³ inserts (Wheaton vials and aluminum cups), the best results are obtained by using “SPHERE_10,” which is actually a 3 cm³ and 7 cm³ standard used together.

Once the standard is selected (again, the normal standard used is “SPHERE_10”), assign it to a pycnometer cell using the pull-down selector as shown in Figure 20. Use at least 3 repetitions for good precision between measurements.

Figure 20. Selecting the standard and then assigning it to the cell.

Click “Calibrate” once the standard and the cell have been assigned and the number of replicates is chosen. A window will appear for the cell that was chosen as shown in Figure 21. The first calibration step is to measure the empty cell. Ensure that the cell is empty before clicking “Done.” The measurement will start immediately.

Figure 21. Cell 1 calibration window.

The pycnometer will step through its full measurement cycle once for each of the replicates selected (so three times if “3” was selected) as shown in Figure 22.

Figure 22. Pycnometer analysis steps.

The steps are detailed here:

1. The purge pulse and release step will repeat as many times as the number of replicates prior to moving on to the analytical steps below.
   1. Purge (no.) Gas Pulse—fills the main chamber with helium
   2. Purge (no.) Release Gas—empties the helium through both chambers
2. The following steps will repeat as many times as the number of replicates (without going back to the purge step).
   1. Stabilize—allows the chambers to come to equilibrium with each other after the purge step.
   2. Measure Atmospheric Pressure—measures the zero-point pressure in the analytical chamber (only).
   3. Initial Pressure—opens the helium inlet to fill the analytical chamber.
   4. Measure Initial Pressure—measures the initial pressure in the charged analytical chamber.
   5. Measure Expansion Pressure—opens the expansion valve and then measures the equilibrated pressure in the analytical plus expansion chambers.
   6. Exhaust Cell—releases the helium from both chambers.

Once the empty cell has been measured the specified number of times, the unit will prompt the user to add the standard(s) to the cell; the “SPHERE_10” standards are found in the wooden box shown in Figure 23. Open the pycnometer cell and place the standard ball(s) into the cell, then close securely. Clicking “Done” will trigger the above analytical steps, including purges, for the standard ball(s). After the replicate measurements on the steel ball(s) are done, the system will prompt the user to remove the standards from the cell. Pressing done at this point shows the expansion (red circle) and analytical cell (black circle) volumes determined by the calibration experiment as shown in Figure 24.

Figure 23. Six sets of steel balls are kept in this box along with the wire tool to extract them from the cells. Do not touch the spheres with bare fingers! Fingerprints don’t significantly affect the volume measurement, but will cause the spheres to begin corroding. Wipe them thoroughly off with a Kim-Wipe if it is necessary to do so.

Figure 23. Final calibration screen for the pycnometer cell.

Click the “Accept” button (blue circle) to complete the calibration process for this cell. Once a cell’s calibration is completed the pycnometer measurement on unknowns can be started independently of the other cells undergoing calibration.

Frequency of Calibration/Calibration Check Standards

The pycnometer has proven to be quite stable, so the standard practice is to calibrate the instrument at the beginning of an expedition. To ensure quality, each set of five samples should be accompanied by a standard rotated through the cells. So long as the standards continue to give an acceptable value (less than 0.5% deviation), recalibration is not necessary (NOTE: As of X375 the recommendation is to Calibrate the beginning of each shift, and then +/- 0.5% deviation).

Rotation of the check standards through the cells is important, however, to ensure on a continuing basis that the system is still stable and functioning properly. An example measurement plan is given here:

• Measure a sample in Cell 2, 3, 4, 5, and 6. Measure the 10.2 standard (3 cm³ + 7 cm³ balls) in Cell 1.
• Measure a sample in Cell 1, 3, 4, 5, and 6. Measure the 10.2 standard in Cell 2.
• Measure a sample in Cell 1, 2, 4, 5, and 6. Measure the 10.2 standard in Cell 3.
• Measure a sample in Cell 1, 2, 3, 5, and 6. Measure the 10.2 standard in Cell 4.
• Measure a sample in Cell 1, 2, 3, 4, and 6. Measure the 10.2 standard in Cell 5.
• Measure a sample in Cell 1, 2, 3, 4, and 5. Measure the 10.2 standard in Cell 6.
• Repeat pattern.

The SPHERE_10 standard fills the 35 cm³ chamber to the fullest degree and will give the best precision in measurements. Using a smaller standard will give a larger headspace and a lower pressure drop, and therefore lower precision.

Making a Pycnometer Measurement on a Sample

After calibration is complete, the user can begin analyzing samples and one standard per six runs as noted above. Double-click on the Volume Dry (cm³) portion of the main screen next to the sample to be studied; normally the SPHERE_10 standards are also listed for the one cell in six to be dedicated for a standard measurement. A window will appear as shown in Figure 24 prompting the user to select a cell and to set the number of replicates. It is recommended to use the same number of replicates as the calibration.

Figure 24. Pycnometer measurement window. Ensure that the sample is correct and select the cell to be used and the number of replicate measurements to be performed.

Once the user has selected the cell and number of cycles, click the “Measure” button, which will open the pycnometer cell control window (Figure 25). Place the sample in the cell, seal it, and then click “Done” followed by clicking the “Start” button (circled in blue). Unlike the calibration measurement, the experiment will not start until the “Start” button is clicked.

Figure 25. Starting a pycnometer measurement on a sample.

The pycnometer will step through the same purge and measurement steps described in the calibration section and when it is finished, will show the screen shown in Figure 26.

Figure 26. Sample completed indicator for pycnometer.

Once the “Done” button is clicked, the volume of the sample (including the volume of the container) will appear in the “Calculated Volume” window. At this point, the user may select “Rerun,” which will redo the measurement, “Cancel” to reject the measurement, or “Accept” to keep the data and transfer it to the main screen.

Reassigning Results

The result should be in the appropriate field, but in case the user double-clicked the wrong volume measurement, MADMax provides the capability to switch the volume measurement from “wet” to “dry” and vice-versa. As shown in Figure 27, right-click the mass cell and select the “Send this result to the Volume Wet (cm³)” option. If two volumes are already present, this option will instead state “Swap Volume Wet (cm³) to Volume Dry (cm³).”

Figure 27. Right-click options for the volume measurement.

Once the user clicks the “Swap” options, a window will pop up to confirm the action, similar to that for the swap mass measurements window. 

Cancel Volume Result

The user can also cancel a result using the same right-click option, with a confirmation window similar to the one for canceling mass measurements mentioned earlier. A developer or technician can uncancel the result if this was done in error.

Review Results

If the user wishes, they can also look at a detail of the mass results as shown in Figure 28. This is a summary of all of the parameters used to determine the volume with the parameters labeled by their database names.

Figure 28. Review dry volume results window.

The volume_dry component is the volume of the sample. The volume_dry_container component is the volume of the sample and the container together. The pyc_stdev value is calculated from the individual measurements (in this case, three) done by the pycnometer.

Volume Determination by Caliper

Volume determination by caliper is best used on consolidated, high-porosity samples (e.g., coral or vesicular basalt) as part of Method D. It is not likely to give accurate results when used on soft sediments (Method A).

Double-click on the “Caliper Volume (cm³)” column in the field adjacent to the sample to be analyzed. This will invoke the caliper measurement window as shown in Figure 29. The user should select cube or cylinder depending on the sample to be measured with the precision caliper.

Figure 29. Caliper measurement entry screens.

Ensure that the sample being measured is the correct one and click either the “Cube” or “Cylinder” radio button. Make the measurements using the precision caliper (Figure 30). Enter the measurements for each dimension in centimeters. Once the measurements have been entered, click “Ok” and the result will be transferred to the main screen.