Ilaplodioi'itic and Related Magmas. 



165 



about 1085°, at which temperature apparent traces of melting 

 were found in a finely-ground mixture of crystalline diopside 

 and Amelia County albite. This location of the eutectic does 

 not depend entirely on extrapolation of the diopside liquidus, 

 for it is confirmed by the shape of the fusion surface in the 

 ternary system. 



Fig. 3. 



1350 



12O0 



1150 



1 



\— , 



V 



DIOPSIDE 



20 30 40 50 60 70 80 90 



WT. PERCENT ALBITE 



A rapid increase in the cbnvexity of the diopside liquidus as 

 it approaches albite is necessary in order to carry it below the 

 melting point of albite. This increase has already begun at 

 the last determined point (90 per cent albite) and is, theoreti- 

 cally, a general property of any liquidus as it approaches the 

 other component."* We are accustomed to having the eutectic 

 in a median position, so that the liquidus ends by meeting the 

 other liquidus before passing into this region of increased 

 curvature. 



The Ternary System. 



In the ternary system the expectation is that the composition 

 triangle should be divided into two fields, one containing all 



* See Eoozeboom, Heterogene Gleichgewichte II, p. 275, fig. 103. 



