- as highly concentrated carbonate brines, 100 ee = = 50 £2. California, is an intermittent Se no | 7 ° 31d ht ve » “\ mo Lake Magadi, Kenya & Ioke area ) oe ~~ 10 B4 86 ; BB 7 ’ / 4 90 92 94 @ Abert Lake basin, Ore. % Alkali Valley, Ore. ‘ ui Closed sug pond Deep Springs Valley, Calif. ; 6 Springs 98 pH — 100 | i 104 102 _& bake and inflow creas L 106 108 TO Fig. 1. Silica in solution versus pH. The three solid curves are (from low to high SiOz) for Si(OH) ,, SiO(OH)., and Si0,(OH). ~~ Areas a—d are discussed in text. saline water body in a small basin (9); about a third of its 13-km? area is cov- . ered by saline crusts. Inflow is chiefly groups of springs | ™ (8). Deep Springs Lake, in Deep Springs MMe ET Samples came from several potholes Valley, ea 500 . and the main playa pond. a f 1000 which apparently result fro -term PP: tly &s from long evaporation of artesian waters at a rate roughly equivalent to discharge J from a prominent zone of recent fault- + 4+ Aqua de Ney Springs, Colif. x ing. Also within the fault zone are two sag ponds, one of which has no outlet TTT | — TT a 5000 ; discharging 1 and 1 m or more in depth; the largest contain masses of crystalline sodium salts, chiefly carbonate. Many of them also contain extremely variable and ; ! More than half the playa area contains numerous circular depressions or pot- 1 i | \ \ ately north of the Abert basin (7). from 1 I Alkali Lake, in Alkali Valley, is a holes, some as much as 9m across at low stage. Carbonate species pre- 1000 Baker (/0) has sum- geochemistry of the area; the lake lies in the Gregory Rift Valley and contains a vast deposit of trona (Na.CO,- NaHCo,-2H.O0). It is intermittently dry, but has a number of perennial brine pools (lagoons) near the margins; it has no visible outlet and is fed marily by a number of perennial springs and by runoff during rainy sons. Samples were collected from prihot seahot springs, open brine pools, and brines interstitial to trona crusts. 500 | studied. Lake Nokuru, Kenya + Owens + Lake, Calif. 100 i] were marized the geology, mineralogy, and me 1 50 = Figure 1 shows that the silica content increases drastically for brines having a pH greater than 9.2; this finding agrees with the reported increase in a & Lake Magadi, Kenya (2). With the exception of those for plotted in Fig. 1 are based on field measurements at ambient temperature; 1 | | eo Abert Lake basin, Ore. o f ] * Alkali Valley, Ore. | solubility of amorphoussilica with pH the interstitial solutions, most pH values Ob from Oregon and California, several samples from Lake Magadi in Kenya . TTT) dominate in the ponds and springs but are subordinate to sulfate in the lake area. In addition to the alkaline waters SiO, IN PARTS PER MILLION “ 1 5000 — LL brine. playa of approximately 13 km? immedi. J pedite 71 1/100th the concentration, feeds a pool of highly concentrated chlorocarbonate SiO, IN PARTS PER MILLION ‘ 10,000 CF Ko BD lake; here a small seep similar to the lake in solute composition, but of =|os bin! pad we ast _ woe \ 7 > ' * + 4 bow testtallies ae AATCoke a ate eet ahd, \ Ee 1 DeepSprings Valley, Calif. 10 1000 1 1] 5000 LELd 10,000 ' 1 Nat IN PARTS PER MILLION 1 m cresed sag pond] {pee 50,000 100,000 for samples not in immediate contact Fig. 2. Sodium versus SiOz for alkaline brines from Kenya, Oregon, and California. as 1 unit during subsequent storage. Small dots represent samples for which pH and total CO2 data were not obtained. with muds, pH may change by as much 8 DECEMBER 1967 Regression lines have been derived independently for the Oregon and Magadi points. 1311 JOA