Please refer to 'Advanced Chemical Analysis' by M.L.Jackson, 1979 for detailed procedure to prepare and analyse clay minerals by xrd technique.

Probably what hapened was a interlayer space collapse caused by the cation exchange substitutions between Ca2+ and K+. The different hydration spheres around these elements contributes to different interlayer distances. 

1, are those random powder mounts or orientated slides? Clay ID is only useful on orientated slides by combining air-dried, ethylene-glycole solvated and calcined samples. I guess random powder because samples contain non-clay minerals. You did not define what you mean by clay fraction (< 0.2; < 2.0 or < 6.3 micron or smthelse?)

May be you right. It might be contain non-clay mineral such silicate minerals. For the first time, Actually all samples was carried out that samples was separated by particle density by flow velocity. But I thought that still,  >2㎛ particle remained and it confirmed by EDX-figures1.

Mostly, they contain Si, Al, and minor elements Fe, Mg, Ca etc..

In case of non-treatment samples, after XRD analysis, mineral identification confirmed by “MacDiff ” software program (Petschick 2000).  And most of smectite peak pattern showed ranging from 14~15Å, (montmorillonite(001), nontrite(001), saponite(001) etc).

I know that ethylene-glycole reagent is useful for detection of smectite. But, already, we confirmed existence of smectite from previous data reports.

And also, I know that in case of expansibility smectite samples need to dry enough, because I have experience that humid oriented samples( non-dry samples) showed expended peak range from 17-19Å (montmorillonite(001), nontrite(001), saponite(001) etc), in addition, it showed   high CPS tendencies, relaltively.  

2, I see no evidence whatsoever for distuingishing montmorillonite or saponite. The 060 peak has not been scanned, making a reliable ID of di- vs trioctahedral smectites impossible in my opinion.

Of course saponite (060) peak exist near 55°(2  ; Kloprogge et al., 1997; Clays and clay minerals. Vol 45, No1, pp1-7, 1997).  But in my study, it is important that (001) position smectite group ranging from 14~15°(2 ) because most of nitrogen such ammonium cation form can replace several cations(i.e. K, Al, Ca etc.) in interlayer of 2:1 smectite group.  In 2:1 clay mineral, they occur hexametric rings containing Si and Al to ab direction preferentially. And then followed by lateral growth (i.e. (060) peak position). Finally, some cation can absorb into interlayer site, to maintain ion balance between 2:1 clay mineral structure. Because Si4+ can replace Al3+ or Fe3+ in tetrahedral site and Mg2+ can replace Al3+ or Fe2+ in octahedral site. For this reason, I’m focus on (001) site in 2:1 silicate mineral, maybe you know right.         

3, your treatment will result in a (maybe partial) cation-exchange of the smectite interlayer with the potassium of your solutions. The interlayer cations have a strong impact on the d-spacing of the 001. So a comparision would only make sense if both pre-and post-treatment variants are saturated with the same cation.  

Yes. You right!

I carried out EA/ir-Mass analysis for TN(%), TC(%), OC-res(%),  IN(%) and TN-isotope value, IN-isotope value through pre- and post-treatment

Relatively, separated homogeneous samples such host sediments, most of clay silts showed near 0 1‰ (TN-isotope and IN-isotope. totally.).

However, some several samples around vent system might be contain non-homogeneous materials. And they showed anormal very light nitrogen isotopic value ranges. I guess, seafloor vent system related sediment-hosted Bay area can effect two or more phase materials.  

4, I imagine to see evidence for other clay minerals that have peaks at roughly 14 A. Chlorite maybe?

Yes, you right. Maybe several samples around vent system contain chlorite, if it is true that secondary they supplied from around Bay sediment complexs. because the temperature of flux where vent system was confirmed about 200~250℃. Of course, if existence of Chlorite, it is possible to effect the distributed nitrogen contents between biotite and muscovite in mica contained minerals. And the it is also possible to effect such nitrogen isotopic ratios ( Sadofsky et al., 2000; Geochimica et Cosmochimica Acta, Vol. 64, No. 16, pp. 2835–2849, 2000). However, chlorite separation from mineral samples is very difficult, practically.     

5, the counts are very low. What was the counting time and step-scan speed?

Because, in my university XRD machine is so old version. 35Kv 25 mA is maximum and counting time and step-scan speed are 0.02, 1.0, respectively.

And also, To increase the thickness of slide samples, I tried different methods below figure2.

However, obviously, it existed just small amount of clay contents in each samples by elements analysis. I think that is the big reason.

6, the low angles (below 5°) pull up too much relative to the actual peaks. This should not happen. Are you using an automatic divergence slit?

I don’t know about that.  What is mean the automatic divergence silt?

7: Read the book recommended by Dilip Kumar Pal and may I add X-Ray Diffraction and the Identification and Analysis of Clay Minerals by Moore & Reynolds, 1997

Thank you for your reference information

for clay mineral identifications you have to prepare oriented slides of the clay ( which has some pre-treatment to remove Fe , organic compounds ...etc which are not clay minerals) ,then run the oriented slides in at least three conditions :1- Normal run for the slide 2- Ethylene glycol saturated slides run  to distinguish smectite from chlorite and illite  (the peaks are at the same position of 2 theta ) 3- heat treated slides (600 -800C)  to identify kaolinite

The change in peak position is almost certainly related to changes in the interlayer cation following your treatment, i.e. the clays are now potassium saturated as suggested by others above.

Although you have not scanned the often used 06, 33 band (060 peak) to help distinguish trioctahedral from dioctahedral clays e.g. saponite versus montmorillonite.  you have scanned its cousin the 02,11 band which appears as a large asymmetric peak iin all your patterns.  If you examine and measure the position of this band precisely it will enable you to make some judgement about saponite, montmorillonite etc.  However, looking at your overlaid traces you often have peak shifts of non clay minerals between running traces which are likely to be due to errors such as sample displacement, so be sure to find a quartz peak or perhaps some other peak you can rely upon and correct the displacement errors before making your measurements. 

Although you have used a treatment that you idniacte was to remove organic matter, I'm not sure it was necessary as it looks you don't really gain an extra information about you minerals by doing it with these samples.

This results are not surprising me . because clay mineral can adsorb many molecules into it < therefor this adsorption could be in between clay layer so can change the d spacing

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