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Technique for clay separation requires the use of acetic acid. To dispose acid solution properly and environment-friendly, use the black sink in the Chemistry Lab or in the Thin Section Lab (Figure XX). These sinks are directly connected to a specific container in the ship dedicated to acid treatment. DO NOT USE OTHER SINKS !!! Use flowing water to dilute.
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4. Black sink to dispose acid solution
Clay Separation Procedure
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- Removing carbonates (to better identify the clay minerals)
- Suspending material particles (to separate the < 2 μm clay size fraction from the rest of the particles)
- Heating samples (to identify the presence of kaolinite and chlorite)
Removing Carbonates before Clay Separation
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This is the recommended treatment for carbonate removal. The process is slightly more involved than the HCl procedure, but far less damage is done to the mineral structure. The following steps are from Kitty Milliken (UT-Austin) and are shown in Figures XX 5 to XX 8.
- Place ~2 cm3 (or 5 mL) of undried (preferred) sample into a centrifuge tube (Figure XX5, Step #1).
- Add ~25 mL of 10 % Acetic Acid (Figure XX5, Step #2).
- Mix and shake well (Figure XX5, Step #3). Let sit for at least 1 hour to decarbonate (until the reaction ceases). Close the centrifuge tube with its cap but not too tight to avoid unnecessary overpressure.
- It helps to place the centrifuge tubes on the shaker in the cold room of the Chemistry Lab (Figure XX6, Step #4). Do not tight the tube too strong in the arm as it can break while vibrating. Set a shaking time of about 30 seconds (it is a good start) and a power value of 1. After using the shaker, shake the tube to ensure the reaction has stopped (i.e., no more bubbles).
Note: Please note that sample with a large amount of carbonate (more than 50%) may require more than 1 treatment of Acetic Acid to reach complete decarbonation. - Next step is to spin the sample in the centrifuge (Figure XX7, Step #5). Make sure to choose the correct tube holders. It is very important to balance the centrifuge, and to evenly distribute weight. Put samples Put samples diametrically opposite to each other. If you run a odd number of samples, keep the balance by filing up an additional centrifuge tube with DI to have an even number of tubes in the centrifuge. Turn on the centrifuge in the Chemistry Lab (Figure XXA7, arrow A). Press the "Speed" button (Figure XXB7, arrow B) and select a speed of 1500 rpm (rotation per min) by using the arrows to increase or decrease the value (Figure XXD7, arrow D). Press the "Time" button and select a time of 15 min by using the arrows to increase or decrease the value (Figure XXC7, arrow C). Press the "Start" button to start the centrifuge (Figure XXE7, arrow E).
- Decant the acetic acid solution and dispose of the acid solution properly in an appropriate sink (Figure XX8, Step #6).
- Add 25 mL of DI (nanopure water) to the centrifuge tube (Figure XX8, Step #7). Shake to get rid of the acetic acid. Centrifuge again for 15 min at 1500 rpm.
- Decant the clear water. Repeat the "wash cycle" (i.e., centrifugation) with DI. Wash at least 3 times to remove all Acetic Acid (until it does not smell vinegar too strong).
Note: If the centrifuge in the Chemistry Lab is busy/used by Scientists, there is another centrifuge in the Paleo Prep room of the Core Deck.
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5. Decarbonation with acetic acid
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6. Using the shaker to help decarbonation reaction.
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7. Setting the centrifuge.
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8. Disposal of acid solution and DI washing cycle.
Hydrochloric Acid Treatment
HCl is the simplest method for removing carbonate from sediment but does have severe drawbacks. Strong acids damage the mineral structure, especially within trioactahedral trioctahedral minerals. Before proceeding, be aware that this treatment may affect clay crystallinity.
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The dismembrator setup is shown in Figure XX10. The The power source is connected to the probe. The probe fits into the case through a hole in the top.
- After removing the supernatant (after the last wash), add ~25 mL of a 1 % Borax solution into the centrifuge tube (Figure XX9, Step #8). Borax prevents the sample from flocculating. Too much Borax however will increase flocculation.
- Put the tube into the bottom clamp inside the dismembrator case (Figure XX9, Step#9). Put the probe into the top clamp and the sample tube into the bottom clamp. Adjust the positions so the probe goes into the tube. The probe should be about half-way into the sample material without touching the sides of the tube. The probe releases a lot of energy, and if it is touches the sides it will heat up the tube and the sample.
- When satisfied with the positioning, flip the "ON" Switch (Figure XXA10, arrow A). The settings are already set to our needs: Mode = Continuous, Amplitude = 65 (Figure XX10). To run as is, press the "Test" button (Figure XXD10, arrow D), the screen will display 'rdy' for 'ready'.then, press the "Start" button (Figure XXE10, arrow E). If you need to change a setting, press the "Mode" button (Figure XXB10, arrow B) and then the "Set" button (Figure XXC10, arrow C). From these two panels, you have access to the power, time, and displayed units. For more information, reference the Manufacturer Manual located in the side pocket of the dismembrator case (Figure XX10).
- Press the "Start" button on the probe power supply (Figure XX9, Step #10 and Figure XX10). If the material does not appear to be circulating throughout the whole tube or the tube is heating up, adjust the probe position and start the dismembration over.
- After the suspension, settle down the tube for about 12 hours (Figure XX9, Step #11).
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9. Adding Borax and Suspending Material with the dismembrator. Make sure to adjust the probe half-way into the sample material
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10. Dismembrator set up and Probe with power source. Dismembrator power source control Panel. (A) On/Off switch (B) Start button (C) Set button (D) Mode button (E) Start button
Standard IODP Clay Separation Method: Not for Semi-quantitative Analysis
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Clay mounts are put onto a zero-background silicon disk that fits into a 2 mm steel sample holder (Figure XX11). Only put the disks into sample holders that have a hole drilled in the bottom (Figure XX11). The hole allows the disks to be taken out, otherwise they are stuck inside the holder.
The disk should sit flush with the sample holder. Some of the zero-background silicon disks are at different depths, so a quartz insert disk (Figure XX 11, Step #1) can also be put in the bottom of a sample holder with the silicon disk on top (Figure XX 11, Step #2). Do not force the zero background disks into the holder, it may break.
Figure XX11. Steel sample holder with quartz insert disk and zero-background silicon disk. Clay Mount for the D4 Bruker.
Clay Mount to use with the PANalytical Aeris
Insert a zero-background silicon disk in a sample holder in a 'back loading' way (Figure XX 12, Step #1). Add on top of it an Aluminum spacer disk (Figure XX 12, Step #2) and clip the whole thing (Figure XX 12, Step #3). Flip the sample holder (Figure XX 12, Step #4).
The zero-background silicon disk can be heated up to 550ºC, which makes it suitable for further clay treatments as described below. However, the rest of the sample holder assembly must not be heated (magnetic part of holders). Please remind to dismantle the mount and put only the Silicon disk in a muffle furnace for additional clay treatment (Figure XX14). Only the treatment with Ethylene Glycol is not 'destructive' because the temperature does not exceed 70ºC.
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12. Clay Mount with Aeris Sample Holders.
Putting Material on Mounts
1. Remove the <2 µm size fraction by collecting the uppermost 1 cm of solution with an eye dropper (Figure XX13). It helps to add a little isopropanol. If necessary, resuspend flocculated clay particles using the dismembrator and add more Borax solution.
2. If material is still very suspended, try centrifuging the samples for 4 minutes at 750 rpm. In this instance, the >2 µm size fraction will be the only fraction suspended in the liquid and all the larger grains will be packed in the bottom. Take the suspended material with an eyedropper and put it on the quartz disk.
3. Make an oriented clay mount by placing 2–3 drops (enough to cover the disk) of clay suspension directly onto the silicon disk (Figure 11, Step #3 and Figure 12, Step #5). If the material is not spreading evenly, add a drop or two of 70% isopropanol and spread the material around with a small glass rod (Figure 11, Step #4 and Figure 12, Step #6). Once spread, let the sample dry in the desiccator (Figure XX14A).
The clay particles orient themselves as the solution dries on the disc. Note that it can be difficult to determine if there is enough material on the disc for a scan. Sometimes it may appear as if there is no sediment in the upper 1-2cm and thus nothing on the disk. Try scanning in the XRD before assuming there is nothing in the water drops added to the silicon disk. It is surprising what the XRD will return with very little sample. If the scan is not satisfactory add a few more drops from a bit deeper in the test tube and rescanre-scan.
4. Once the sample is dry (Figure XX14B), you are ready to run it through the D4 or the Aeris. If there are additional treatments requested, continue to the sections below after running the samples through the X-Ray diffractometers.
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13. Collecting the suspended material with an eye dropper. Make sure to have enough clay material.
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14. A. Dessicator and oven for glycolation. B. Dried sample preparation after dessication.
Additional Clay Treatments before Scanning
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The following techniques are modified from the U.S. Geological Survey Open-File Report 01-041, A Laboratory Manual for X-Ray Powder Diffraction (hard copy available in the X-Ray Lab Library). Ethylene glycol can be used to expand swelling clays (e.g., smectites, montmorillonite, nontronite, and beidellite), some mixed-layer clays, and vermiculite as an aid to mineral identification. There are two ethylene glycol treatment methods:
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- Find the "glycolator" container stored in the ICP preparation oven below the Aeris (Figure XX14A).
- If empty, pour ethylene glycol to a depth of ~1 cm in the bottom of the container (Figure XXA15A).
- Take off the lid and place the samples on the rack inside the glycolator (Figure XXB15B).
- Place glycolator in an oven (60°–70°C) overnight (~12 hours) (Figure XXC15C).
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15. Glycolation: Vapor Treatment
Keep samples in the glycolator until ready to run through the XRDs. Glycolation only lasts for 4 hours after the samples are removed from the glycol atmosphere.
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- Prepare an oriented clay mount by adding several drops onto a zero-background Si disk in a sample holder and spreading it out evenly with a glass rod or eye dropper. See 'Preparing the Mount'.
- Put the clay mount in the desiccator until it dries.
- Put the sample in the muffle furnace in the Chemistry Laboratory (Figure XXA16A). Do not forget to dismantle the Aeris sample holder assembly - they must not be heated !! Only the Si disk should be put in the muffle furnace (Figure XXB16B). Different temperatures (at 400ºC and at 550ºC, following USGS Methods) and heating times (~1-2 hours) are used when trying to identify different minerals. Confer with your scientist to determine the parameters.
When the muffle furnace has finished its program and is cooling down, wait until the temperature reaches between 100° and 200°C before removing the sample (Figure XXC16C). The sample can be placed in the desiccator until it reaches room temperature. Once it has completely cooled down it can be run in the XRDs.
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16. A. Muffle furnace in the Chemistry Lab. B. Clay Mount in the muffle furnace. Note that only the Si disk of Aeris sample holder is put in the furnace. C. After heating.
Clay Separation Method for removal of Chlorite (not recommended onboard the JR)
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