242 HOLLAND! CHARNOCKITE SERIES. 



CHAPTER IX. 



Summary. 

 It is proposed to employ locally the term charnochite series for a 

 group of hypersthene-bearing rocks which form the largest single 

 section of the Archaean gneisses in Peninsular India. The nearest 

 foreign equivalents of the types included in this group are found 

 amongst the rocks known to German petrographers as (t pyroxene- 

 granulites" and to the French as " pyroxene-gneisses ;" but in many 

 points members of the charnockite series present analogies also to the 

 "hyperites "■ and "norites" of Scandinavia, as well as to the "anortho- 

 sites " of America. In consequence of these facts, and with a view to 

 facilitate the description and mapping of our Archaean sub-divisions, 

 a distinct name with a purely local application is given, and this is not 

 intended at present for use outside India. 



The members of the charnockite series are considered to be igneous 

 in origin, and to present intrusive relations to the associated older 

 schists and gneisses. Although the evidences on this score, as might 

 be expected with any very ancient eruptive, have been partially oblit- 

 erated and masked, the remarkably long geological quiescence experi- 

 enced by South India has afforded rare and unusual chances for the 

 preservation of the original features in our Archaean gneisses. With 

 so many significant characters in perfect accord it is difficult to avoid 

 the conclusion that the phenomena presented by the charnockite series 

 are really original features due to an igneous origin and an intrusive 

 habit, not merely fortuitous or produced by subsequent metamorphism. 

 The following features — for which we have no reasons to regard 

 as other than original — indicate an igneous origin for these rocks : — 



(i) Large uniform masses of the charnockite series, either quite 

 irregular in shape, or showing a roughly lenticular form, 

 stand up in the midst of the more complex groups of 

 gneisses and schists, forming mountain masses like the 

 Nilgiris, the Palnis, the Shevaroys and smaller hills in the 

 ( 124 ) 



