198 



COOKE 



2380 



2360 



g 2340 



nj 

 O 



aj 

 O 

 E 

 o 

 o 

 E 



2320 



2300 



2280 



Background C0 2 

 CO§" and HCO3 



200 400 



PRESSURE, atm 



600 



Fig. 6 Dissolution behavior in orthodox artificial seawater. 



Figure 8 represents a class of experiments in which artificial seawater 

 compounded in accordance with Lyman and Fleming, 15 but with sodium ion 

 replacing magnesium ion, was used as the fluid medium. The results shown 

 indicate that a profound change in the system behavior has occurred. No 

 precipitation could be secured at any pressure. Dissolution began immediately 

 once the artificial seawater began to flow, and the solubility of the calcite 

 increased nonlinearly with increase in pressure. Thus the presence of magnesium 

 in solution is necessary for the maintenance of a lysocline. Further experiments 

 showed that the introduction of magnesium into the magnesium-free seawater 

 produced the effect of the lysocline. A further experiment which demonstrated 

 that the precipitated phases do in fact contain magnesium in proportion to the 

 pressure at which they are stable was then performed. Results are shown in 

 Fig. 9. Analytical calcite within a column was coated with a precipitate laid 

 down from seawater at a selected pressure and then removed from the column, 

 dissolved in dilute HCl, and analyzed for magnesium by atomic absorption. 

 Figure 9 shows the results of these incorporation experiments, which were done 

 at pressures of 142.9, 287.2, and 389.9 atm. In the first two, precipitation was 

 allowed to proceed to completion (240 min); no precipitation took place in the 



