Washington — Charnockite Series of Igneous Rocks. 337 



In India the series extends from highly silicic granites 

 through quartz diorites and norites to hornblendic pyroxenites, 

 the intermediate members being rather complex and varied, 

 and some olivinic rocks occur. Anorthosites and peridotites 

 are found in southern India, but their comagmatic and geo- 

 logical relationships to the charnockite series are as yet uncer- 

 tain. In their hypersthenic rocks the west Norway districts 

 are strikingly like the Indian, and Kolderup, who examined 

 sections of the charnockite series types, speaks of many of 

 these as "almost identical" with the Norwegian. But in 

 Norway these are associated with much larger masses of labra- 

 dorite or andesine anorthosites, pyroxenites are comparatively 

 rare, peridotites are unknown, though there are a few olivine 

 gabbros. There are also present dikes of ilmenite-norite and 

 ilmenitite. 



The Ellesmere Land region corresponds remarkably — so far 

 as known — with the Indian, though the series here does not 

 reach so femic an end-member as the pyroxenites. According 

 to Bugge, anorthosites seem to be absent. In the Cortlandt 

 Series the relations in the small areas are complex and many 

 varying types are present. A mica granite without hyper- 

 sthene is present, but is comparatively unimportant and its rela- 

 tions to the main mass are somewhat uncertain. The chief 

 rocks are norites and pyroxenites, often hornblendic, with sub- 

 ordinate oli vine-rich types. There are no anorthosites or 

 ilmenite rocks. At the Ivory Coast the variation closely 

 resembles that of India as pointed out by Lacroix, the types 

 running from hypersthene granite to norite. True pyroxenite 

 has not yet been found, but Lacroix thinks it probable that 

 further search will reveal this type. Anorthosites and 

 peridotites are unknown. 



Conclusion. 



Thus there are at least five or six comagmatic regions of 

 ancient plutonic rocks which show in common certain peculiar 

 mineralogical and chemical features. Mineralogically the rocks 

 are characterized by the constant abundance of a peculiar 

 hypersthene, with subordinate hornblende of a constant kind, 

 paucity in augite and biotite, prevalence of a soda-microcline 

 along with soda-lime feldspar. In some cases these rocks are 

 associated with anorthosites, and to a much less extent with 

 olivine and ilmenite rocks. 



Chemically they are characterized by the dominance of iron 

 oxides over magnesia and lime, the two latter being present in 

 about equal amount; rather high alkalies with soda pre- 

 dominating, and alumina in the majority of the types about 



