Saplodioritic and Related Magmas. 



163 







Table II. 





Composition 



Tempera- 







Diopside 



Albite 



ture 



Time 



Sesult 



75 



25 



1337 



1 hr. 



Glass and diopside 



75 



25 



1342 



1 hr. 



Glass only- 



50 



50 



1283 



1 hr. 



Glass and diopside 



50 



50 



1287 



1 hr. 



Glass only 



25 



75 



1208 



1 hr. 



Glass and diopside 



25 



75 



1212 



1 hr. 



Glass only 



10 



90 



1142 



1 hr. 



Glass and diopside 



10 



90 



1147 



1 hr. 



Glass only 



The Binary Systems. 



It was necessary to study first the three binary systems : 

 anorthite-albite, anorthite-diopside, and albite-diopside, and 

 these results will be presented first. 



Anorthite-A Ibite. 



The system anorthite-albite had been studied formerly and, 

 for details, reference can be made to the original paper.* The 

 equilibrium diagram is reproduced in fig. 1. 



Diopside- Anorthite. 



The system diopside-anorthite is an ordinary eutectic sys- 

 tem with the eutectic at 1270° and 42 per cent anorthite. The 

 system is sufficiently described by presenting the equilibrium 

 diagram fig. 2. The quenching determinations are given in 

 Table I. 



Diopside- Albite. 



The diopside-albite system is also a eutectic system. It 

 exhibits in emphasized form the location of the eutectic close 

 to the low-melting component, being in this respect analogous 

 to the silver-lead system among the metals. The equilibrium 

 diagram is given in fig. 3 and the quenching determinations in 

 Table II. 



The liquidus of diopside was determined as far as 90 per 

 cent albite but in mixtures richer in albite the high viscosity 

 prevented the attainment of equilibrium. The position of the 

 eutectic can, therefore, only be estimated by extrapolation of 

 the liquidus, but it is clear that it must lie close to albite, proba- 

 bly at about 97 percent albite. The temperature of the eutec- 

 tic is not far below the melting-point of albite, probably at 



* N. L. Bowen, this Journal (4), xxxv, p. 577, 1913. 



