amenable to clear understanding with our present 

 methods. As pointed out by Mills and Zwarich 

 (1972), the recognition and interpretation of in- 

 terstratifications in clay mineral assemblages is 

 often extremely difficult, and in the fine clay 

 fractions attention must also be given to line- 

 broadening effects on diffraction maxima result- 

 ing from very small particle sizes. 



Smectitic materials are those which possess 

 residual interlayer charges resulting from devia- 

 tions from electrostatic neutrality within the 

 "basic lattice" of the minerals such that equilib- 

 rium exchange of K"*" coordinated with water 

 molecules into the interlayer sites is manifested 

 by a basal spacing in the 12. 5 A region by X-ray 

 analysis, under our experimental conditions. In 

 "degraded" micas, etc., this residual interlayer 

 charge is somewhat higher (of a more negative 

 character) such that K"*" ions enter the exchange 

 sites without the water molecules, leading to the 

 smaller (~10A) interplanar distances observed. 

 The other treatments described in this section are 

 further examples of this approach. 



3. Saturation with NaCl (IN) — This is done 

 to ascertain the effects of the interaction between 

 Na"*" ions, the various clay mineral phases, and 

 the aqueous phase. The Na"*" ion as such is appar- 

 ently not as stable in the interlayer sites of de- 

 graded micas as the larger K"*" ion, and its rela- 

 tionship to degraded phases is not clearly defined 

 under our experimental conditions. However, 

 smectitic materials effect an equilibrium with 

 Na"*" and coordinated water molecules such that 

 basal spacings in the 12. 5A region are observed 

 by X-ray analysis. 



4. Saturation with MgCl2 (IN) — Although 

 both vermiculitic and smectitic phases appear to 

 adopt an equilibrium with Mg"*""*" and water such 

 that a basal spacing of about 14A results, the 

 smectitic materials will subsequently reequilib- 

 rate with ethylene glycol in such a manner that a 

 basal spacing in the neighborhood of 17 A results, 

 whereas vermiculites do not seem to show the 

 same effect. "Degraded" chlorites, representing 

 the chloritic analogs of vermiculites and "de- 

 graded" micas, also readily equilibrate with 

 Mg"*""^ ions and the aqueous phase, with a 14A 

 basal periodicity the result. 



5. Saturation with Ca(C2H302)2 

 (IN) — Smectites, Ca"^"*^, and water equilibrate in 



such a manner that a basal spacing of about 15A 

 results, whereas the behavior of vermiculties and 

 degraded micas is somewhat indeterminate. Al- 

 though this treatment was not overly useful in 

 itself in delineating clay mineral species, it 

 served as a necessary antecedent in effecting 

 exchange of the same ion onto smectite phases in 

 all samples prior to further heat treatments of 

 these samples. The latter treatments did prove to 

 be quite informative. 



6. Saturation with filtered sea water — This 

 treatment was performed to investigate the mutual 

 equilibrium relationships among the major ca- 

 tions present in sea water, the aqueous phase, 

 and the clay mineral phases, having analogous 

 data from the other treatments described above 

 for individual cations. 



7. Saturation with ethylene glycol of each 

 cation saturated sample, after X-ray diffraction 

 analysis — to compare the effects of the various 

 cation treatments, each specimen was saturated 

 with ethylene glycol, and reanalyzed by X-ray 

 diffraction. The resultant differences, for a given 

 sample, in peak positions and intensities, were 

 quite informative with respect to characterizing 

 the mineral phases. 



8. Heat treatment, one hour at 300°C — 

 After X-ray analysis each calcium acetate treated 

 specimen was heated in a muffle furnace for one 

 hour at 300°C, and reanalyzed by X-ray diffrac- 

 tion. This treatment drives off the loosely bound 

 interlayer water molecules from smectitic and 

 vermiculitic materials, but has no appreciable 

 effect on illitic, kaolinitic, or chloritic compo- 

 nents. The resultant basal spacing for smectites 

 and vermiculites coincides, in general, with that 

 of illites and micas, in the neighborhood of lOA. 

 A useful comparison is possible here between the 

 efficacy of KCl treatment and the 300°C treat- 

 ment, for a given sample, in "collapsing" the 

 hydrated "expandable" smectitic-vermiculitic 

 layers present to this lOA periodicity. 



9. Heat treatments, one hour at 430°C fol- 

 lowed by one hour at 550°C. Such step-wise heat 

 treatment helps to differentiate kaolinite from 

 chlorite (Brown, 1961; Grim, 1968). The same 

 Ca * saturated specimens previously heated at 

 300°C and 430°C were utilized for the 550°C 

 heat treatment. 



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