62 



MARINE BOTTOM SAMPLES OF LAST CRUISE OF CARNECaE 



attempted elimination of carbonate calcium is magnesium. 



The north Pacific clays always contain about eight- 

 tenths per cent of titanium dioxide. Noncalcareous sili- 

 ceous oozes and south Pacific clays contain about one- 

 half of 1 per cent of this substance, and it is present in 

 widely varying amounts in Globigerina oozes, depending 

 on the amount of noncalcareous material. 



Analyses of Colloidal Fractions 



The above discussions of the molecular ratios for 

 deep-sea clays do not give a true picture of the compo- 

 sition of the clay minerals present in the samples owing 

 to the presence, shown by X-ray analysis, of quartz and 

 other unaltered minerals in the coarser fractions. Par- 

 tial chemical analyses were therefore made of the parts 

 of samples 31, 34, 72, 73, and 77 which were less than 1 

 micron in particle diameter, separated during the me- 

 chanical analyses, and combined with other separates 

 from the same samples separated by centrifuging or re- 

 peated decantations after settling for twenty-four-hour 

 periods. Although X-ray powder diagrams of these finer 

 fractions also give a very faint quartz pattern, it was 



hoped that the results, shown in tables 12 and 13, would 

 indicate at least approximately the composition of the 

 clay minerals themselves. The samples were not dried 

 thoroughly and therefore have wide varying water con- 

 tents. Comparison of table 12 with table 9 shows, how- 

 ever, that the percentages of silica and Ti02 in the col- 

 loidal fractions are less than in the whole samples, 

 whereas alumina, iron, and manganese have increased in 

 every case. There is no constant variation in the 

 amounts of bases. During the process of mechanical 

 analysis and separation of the fine fractions, a certain 

 amount of cations may have been dissolved, and these 

 would be concentrated in the colloidal separates or, as 

 in the case of sample 34, some cations may have been 

 removed by washing. 



The silica sesquioxide ratios vary between 2.3 in 

 sample 72 and 3.1 in sample 34, averaging about 2.7; the 

 silica alumina ratios range between 3.2 in sample 72 and 

 4.2 in sample 34, averaging about 3.5; whereas the mo- 

 lecular amount of alumina is, on the average, more than 

 three times that of ferric oxide. In samples 31, 73, and 

 77 the average silica-base ratio is slightly over 6. Mag- 

 nesium is always the principal divalent base, whereas 

 sodium and potassium are present either in about equal 



Table 11. Average and extreme molecular ratios for various types of deposits 



Molecular 

 ratios 



N. E. Pac. 

 clays (nos. 

 61, 62, 64- 

 66, 69, 70, 

 72, 73, 77) 



N.W. Pac. 



siliceous mud 



and oozes 



(nos. 56-60) 



S. Pac. clays 



(nos. 31,34, 



35) 



Globigerina 



oozes (nos. 



16-19, 21-23, 



25-27,29, 



41, 44, 45) 



Siliceous 



globigerina 



oozes (nos. 



13, 14, 81, 



82) 



Siliceous 



oozes (nos. 



79, 80) 



Si02 



AI2O3 + Fe203 

 Extremes 



Si02 



AI2O3 



Extremes 



_Si02_ 



FegOg 



Extremes 



Fe203 



AI2O3 



Extremes 



Si02 

 total bases 



CaO + MgO 

 Na20 + K2O 



Na20 

 K2O 



4.01 



4.10 

 3.85 



5.15 



5.39 (64) 

 4.89 (73) 



18.3 



21 

 16 



,7 (72) 

 ,4 (64) 



0.28 



0.33 (64) 

 0.23 (72) 



6.69 



1.47 



0.61 



0.58 (with- 

 out no. 62) 



0.14 



5.94 



(72) 6.18 (60) 



(70) 5.61 (58) 



7.55 



8.07 

 6.67 



\n] 



28.6 



35.2 

 26.4 



0.27 



0.31 (60) 

 0.19 (58) 



7.85 



2.01 



1.85 (with- 

 out no. 56) 



0.94 



0.49 



0.46 (with- 

 out no. 56) 



5.04 



5.27 

 4.81 



6.34 



6.67 

 6.00 



24.6 





(58) 25.0 (35) 



(60) 24.3 (34) 



0.26 



0.27 

 0.25 



8.87 



7.76 (with- 

 out no. 34) 



1.13 



1.42 (with- 

 out no. 34) 



0.89 



1.11 



0.36 (with- 

 out no. 34) 



1.97 



3.23 (26) 

 0.76 (19) 



6.57 



14.4 (41) 

 1.98 (45) 



3.46 



7.18 (27) 

 0.87 (21) 



3.05 



(35) 8.22 (21) 



(34) 0.48 (45) 



3.1 ? 



3.7 ? 



[0.9] 



0.5 ? 



11.6 



.3 (13) 5.82 (80) 



.55 (82) 5.53 (79) 



16.3 (13 

 6 



21.0 



39 

 8 



34.4 



47 

 25 



.5 (13| 

 .0 (14) 



0.68 



1.60 (14) 

 0.24 (82) 



9.0 ? 



2.1 ? 

 [1.1] 



0.4 ? 



5.68 



5. 

 5. 



.8 (14) 8.08 (80) 



.15 (82) 7.10 (79) 



7.59 



8. 



7. 



22.9 



25.0 (79) 

 20.8 (80) 



0.34 



0.39 (80) 

 0.29 (79) 



6.33 



1.94 



0.45 



0.23 



