I'HE SOITTHEUN COMPLEX. 



Ill 



grained schists adjacent to tlie yranite area not nnfrequently contnin massive 

 granite. Tliis granite is sometimes t'onnd as a l)oss upon whicli tlic scliist 

 rests, bnt more often constitutes one partof an exposure, tlie-schists cut hy 

 it composing tlie otlier uart (Fig. 3). In some places the manner in whicli 



Fio. 3.— Sohist cut by inassivi- gr-iiiite, NW. }, Sec. 4, T. 40 Is'.. U. 2 K., WiscciiKsin. 



the granites cut the schists is such as to leave no doubt of the eruptive 

 character of the latter (Fig. 4). 



Schist 



' Gf-ajvt-te, 



Fir,. 4.— .Schist cut by granite, NE. cor. Sec. 28, T. 47 N., K. 4J W.. irichijr;"!. 



Macroscopically the gneisses of the area, are light gray to very (hirk 

 green. They vary in coarseness from aphanitic to the texture of a gneissoid 

 granite. In all of the rocks a schistose sti-nctm-e is very strongly developed. 

 In the coarser gneisses the foliation is marked in hand specimen and in 

 exposure, but in the finer grained varieties it is often only exhibited bv a 

 readier cleavage in one direction. The ditt'erent phases descril)ed unthn' 

 the microscope differ from each other but httle inacroscopically. Home of 

 the syenite-schists are an exception to this stiitement in that thev a})])roacli 

 in structure to a basic eruptive. 



One of the most characteristic and abumlant phases of scliist, as seen 

 in thin section (PI. xv, Fig\ 3), is that which has a white graindar background 

 composed of quartz and feldspar. The propoi-tions of tlu^se two minerals 

 vary widely in the different specimens, running from those in which (piartz 

 is preponderant to tho.se in which the feldspiir almost entirelv excludes that 

 mineral. The individuals of each of these minerals in this l)ackground are 



