226 



HOLLAND: CHARNOCKITE SERIES. 



its neighbour ; but when thin tongues of the two are so completely 

 dove-tailed, it is difficult to see how the charnockite could escape 

 the metamorphism which has been so evidently disastrous to the 

 tongues of the gneiss. The most straightforward inference to be 

 drawn is, it seems to me, that the charnockite attained its present 

 position after the crushing of the gneiss, that, in fact, it has trespassed 

 across the foliation planes of the iatter. This implies that the 

 charnockite has behaved after the fashion of an igneous rock, and 

 that it is younger than this particular biotite-gneiss near Salem. 



f5lxir&s. 



Fig. 8. — Plan showing tongues of unaltered charnockite (ir88g) corroding 

 crushed biotite-gneiss ii'8go, j| miles S. of Salem. 



So far the evidence is simple enough ; but there are other 

 points which must be taken into consideration : — Whilst the tongues 

 of charnockite are easily, at a glance, distinguished from the gneiss 

 they protrude into, close examination of the junctions show that, 

 instead of there being a sharp line between the two rocks, there is a 

 very rapid, though gradual, transition from one to the other. 

 Besides this, dark patches occur in the charnockite parallel to the 

 ( 108 ) 



