536 DEPARTMENT OF THE INTERIOR 



2t3EORGE V., A. 1912 



lake and upper river. The walls of the tandem-cirques seem to be composed 

 throughout of the quartz-diorite phase. 



The typical specimen is a light-gray, medium to moderately coarse-grained, 

 granitic rock poor in quartz and speckled with abundant, brilliant prisms of 

 hornblende and black foils of biotite. The microscope shows that the dominant 

 constituent is an unzoned plagioclase, averaging labradorite, Ab x An x . Ortho- 

 clase appears to be entirely lacking. The amphibole is a common hornblende 

 with an extinction of about 17° on (010) and colour scheme as follows : — 

 a = pale yellowish green Avith olive tinge. 

 b == strong olive-green. 

 C = olive-green. 

 b > c > a. 

 The mica is a common brown biotite with the usual strong absorption. Quartz 

 is interstitial and in relatively small amount. Magnetite, apatite, and rare 

 zircon crystals are the accessories. 



The order of crystallization is : the accessories ; then plagioclase, followed in 

 order by biotite, hornblende, and quartz. The structure is the eugranitic. 



Professor Dittrich has analyzed this phase (specimen No. 7), with the 

 following result: — 



Analysis of quartz diorite, Chillhvack batholith (phase 1). 



Mol. 



SiO, 60-36 1-006 



TiO -70 -009 



ALO, 17-23 -169 



Fe 2 0', 1-93 -012 



FeO 3-74 -052 



MnO -14 -002 



MgO 3-66 -093 



CaO 6-07 -109 



Na^O 3-58 -058 



K a O 1-74 -018 



H 2 at 110°C -06 



H 2 above 110°C -55 



P 2 O c -11 -001 



CO, -08 



99-95 

 Sp.gr 2-757 



The calculated norm is :■ — 



Quartz 13-56 



Orthoclase 10-01 



Albite 30-39 



Anorthite 25-85 



Hypersthene 12-16 



Diopside 2-90 



Magnetite 2-78 



Ilmenite 1-37 



Apatite -31 



Water and C0 2 -69 



100-02 



