POTASH SALTS AND OTHEE SALINES IN THE GEEAT BASIN EEGION. 49 



Through the kindness of Dennis Searles, E. E. Free obtained the samples from a 

 bore put down over 600 feet in the area northwest of the central salt area and near 

 the road leading from the plant of the California Trona Co. southeast of the salt area. 

 The exact location of this deep bore is not known. The series of samples is not com- 

 plete, and the notes accompanying them are also somewhat incomplete. The results 

 of analyses upon these samples are given in the accompanying tables. Table XXV 

 (Appendix) gives the total sodium and potassium, soluble sodium and potassium, 

 and insoluble sodium and potassium. Table XXVI (Appendix) gives the ratios of 

 Boluble sodium to potassium, of insoluble sodium to potassium, and of total sodium to 

 potassium. Tables XXVII (Appendix) and XXVIII (Appendix) show respectively 

 the percentage composition of the samples, and of the water-soluble material con- 

 tained in the samples. Accompanying is a brief description of a petrographic study 

 (Table XXX, Appendix) upon the samples of the deep bore by J. C. Jones. It is 

 unfortunate that the record is incomplete, but incomplete as it is, the results of our 

 examinations are of sufficient interest to warrant presentation. 



Before discussing the foregoing data, it is necessary to establish certain criteria 

 by which we may determine the nature of the events which took place during the 

 history of this lake. 



The progressive or fractional crystallization of brines and salt solutions has been 

 thoroughly discussed by Turrentine.^ On account of the similarity of conditions, I 

 have deemed it best to take the results which T. M. Chatard obtained in his experi- 

 ments upon the waters of Owens and Mono Lakes. These results are shown graphically 

 in figure 6.^ The waters from both lakes are similar in composition. Mono Lake 

 water has a slightly higher percentage of sodium sulphate than Owens. The water 

 in both cases contains carbonates, bicarbonates, sulphates, chlorides, and borates; 

 also sodium, potassium, and minor amounts of silica, calcium, magnesium, alumina, 

 and ferric oxide. The temperature conditions in the evaporations range from 18.3° C. 

 to 37.8° C. The two sets of experiments indicate similar results. The following are 

 the criteria from these experiments: 



1. At initial stages of evaporation calcium carbonate, mixed with more or less 

 ferric oxide, would be precipitated. 



2. Saturation would be indicated by a crystalline deposit in which carbonates 

 would predominate. Sulphates would be least and chlorides would be present in 

 moderate amount only. Potassium chloride would be less than 1 per cent of the 

 saline deposit. The ratio between sodium carbonate and bicarbonate in the deposited 

 ealines would approach unitv. 



3. Succeeding stages would be marked by decreasing amounts of carbonates and 

 increasing amounts of sulphates and chlorides. The ratio between sodium carbonate 

 and bicarbonate would rapidly increase. At an intermediate stage sulphates would 

 reach a maximum. Sodimn chloride would remain in about the same proportion, or 

 would be slightly increased. 



4. Approach to final desiccation would be indicated by the separation of a large 

 proportion of sodium chloride and a small increase in the proportion of potassium 

 chloride. 



5. Final desiccation would yield relatively small amounts of sulphates and a larger 

 proportion of chlorides and carbonates. Some borates would be present. The sodium- 

 carbonate and bicarbonate ratio would reach a maximum value, and relatively large 

 proportions of potassium salts would characterize this state. 



Four terms may be designated to indicate the progressive stages, and in their natural 

 order are: 



(1) The trona period — sodiiim carbonate and bicarbonate in about equal amounts 



preponderate; 



(2) The sulphate period — separation of sodium sulphate; 



(3) The sodium chloride period — ^maximum proportions of sodiiun chloride; 



(4) The complete desiccation period — maximum percentage of potassium chloride 



and presence of borates. 

 In the case of the uninterrupted desiccation of a saline lake the successive stages 

 mentioned above would grade insensibly one into the other. The actual case would 

 be further complicated by temperature variations, seasonal and periodical, by inter- 

 ruptions caused by the dilution of lake waters, by rainfall and stream discharge, and 

 by silt, mud, and seolian deposition. Wind and wave action would tend to thicken 

 the shore deposits. The thinning out of the lake waters at the margin wovild set up 

 there more favorable conditions for crystallization than in the deeper portions. In 



» The Occurrence of Potassium Salts in the Salines of the United States. Bui. No. 94, Bureau of Soils, 

 U. S. Dept. of Agr. 

 * Data for this figure were taken from Bui. No. 60, U. S. Geol. Survey, pp. 59-65. 



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