Haploclioritic and Belated Magmas. 



179 



discussed. The mixture, AfyAn, 85 per cent-diopside 15 per 

 cent (D, fig. 13), begins to crystallize at 1375° with the sepa- 

 ration of plagioclase of composition Ab,An 4 . As the tem- 

 perature falls the plagioclase increases in amount and changes 

 in composition until at 1300° the liquid has the composition P 

 and plagioclase the composition Ab x An 3 (G- of fig. 12). When the 

 temperature has fallen to 1216° diopside begins to crystallize, 



Fig. 13. 



Fig. 13. Crystallization of mixtures in the plagioclase field. 



the liquid then having the composition M (fig. 13) and plagi- 

 oclase the composition S (AbjAn 2 ), SM being the three-phase- 

 boundary through D. With further lowering of temperature 

 the liquid follows the boundary curve, both diopside and 

 plagioclase crystallizing, and at 1200° the liquid is all used up. 

 The composition of the plagioclase is now Ab 1 An l (F), EH 

 being a three-phase-boundary. 



In the case of the liquid E (Ab 18 An 82 90 per cent — diopside 

 10 per cent) crystallization begins at 1180° with the separation 

 of Ab 6 An 96 and the composition of the liquid follows the curve 

 ERN. At 1245° diopside begins to crystallize. The com- 



