176 HOLLAND: CHARNOCKITE SERIES. 



of veins of pyroxenite, 3 to 5 feet wide, cutting through the norite. 

 Although the pyroxenite dykes run in some 



Pyroxenite. & VJ J . 



cases parallel to the general direction of folia- 

 tion, Dr. King and myself, whilst tracing one on the west side of 

 the hill in September 1893, found it to distinctly ramify, one 

 branch running westwards almost at right angles to the strike 

 of foliation. The pyroxenites never show any chilled edges, so the 

 fissures which they occupy must have been filled whilst the norites 

 were still hot, and from the evidence of their occurring in distinct 

 and ramifying dykes amongst this norite, they are probably part of 

 the same series and derived from the same magma after the manner 

 of some forms of Reyer's so-called Schliereng'dnge. 



On a hill to the north-east of the Pallavaram railway station a 

 9-inch vein of hornblende pyroxenite (No. 9*667) in a hornblende-augite 

 norite more completely displays the character of a Schliere* The vein 

 is aligned parallel to the direction of foliation, that is, N.-N. E.— 

 W.-S.-W. ; and a section across its junction with the norite shows the 

 ferro-magnesian silicates interlocking across the border (p. 164). 



The rocks of St. Thomas' Mount and Pallavaram show a dis- 

 tinctly linear arrangement of their minerals in a N.-N.-E. — S.-S.-W 

 or a N.-E-— S.-W. direction parallel, that is, to the adjoining 

 Coromandel coast-line. Although this linear 



Foliation. , . 



arrangement of the constituent minerals has been 

 referred to as u foliation ", this term is generally used to imply the 

 effects of dynamo-metamorphism developed to a much greater degree 

 than has probably been the case with the charnockite series at 

 Pallavaram. There is no evidence of the rocks having been folded 

 since consolidation, and only local signs of their having been crushed. 

 As pointed out in another section of this paper, it is probable that 

 the linear arrangement of the minerals was probably induced during 

 the process of consolidation, although of course it may have been 

 accentuated in many, perhaps in most, exposures by continued exer- 

 tion of the forces which determined the main physical conformation 

 of South India in very early geological times. 

 ( 58 ) 



