222 ALBERT JOHANNSEN 



described by Daly,^ as well as a contact rock against granite 

 described by Miller.^ 



(3214) Melamonzodiorite. Based on Daly's^ average analysis 

 of 161 basalts, as named by the original authors, Leith and Mead'* 

 computed the mineral composition of the average "basalt" and 

 found that it contained oligoclase 35.4, orthoclase 10.75, augite 

 36.90, olivine 7.58, magnetite 5.80, ilmenite 0.73, and titanite 

 2.84. This rock, according to the computed mode, therefore, is 

 not of the gabbro family at all, but of the monzodiorite. Included 

 in Daly's average, of course, are all rocks named "basalts" by the 

 original authors, consequently including many which at the present 

 time would be called andesites. 



(3215) Meladiorite. Here belong, among dike rocks, many 

 camptonites, kersantites, and spessartites, and some diabases and 

 basalts, though most of the latter rocks belong to Class 2. Among 

 deep-seated rocks there are a few meladiorites. 



(3217) Oligoclase-shonkinite. Andesine-shonkinite. It would 

 be very desirable if there were terms to express the acid-plagioclases 

 exclusive of albite (CaiVaf, of the present system) and the basic 

 plagioclases exclusive of anorthite (NaCaf). Rosenbusch^ found 

 the same difficulty when in his description of granite he said: 

 "Oligoklas steht hier und im Folgenden fiir sauren'Plagioklas." 

 A single term would thus cover the rocks of this family. See note 

 under (3 11 6). 



CLASS 3, ORDER 3 



(337) Mela-calcigranite. This term is too awkward. The 



only modal analysis yet found in this family does not lie near the 

 center point." 

 (339) Melagranogabbro. See notes under (127) and (239). 



=^ Reginald A. Daly, "Geology of the North American Cordillera at the Forty- 

 ninth Parallel," Geol. Surv. Canada, Mem. 38, Part I (1912), p. 361. 



2 William J. Miller, " Geology of the North Creek Quadrangle, Warren County, 

 New York," N.Y. State Museum, Bidl. 170 (1914), P- 37- 



3 Reginald A. Daly, "Average Chemical Compositions of Igneous Rock-Types," 

 Proc. Amer. Acad. Arts and Sci., XLV (1910), 224. 



■» C. K. Leith and W. J. Mead, Metamorphic Geology (New York, 1915), p. 74- 

 s H. Rosenbusch, Elemente der Gesteinslehre (Stuttgart, 1898), p. 76. 



