

HOLLAND: CHARNOCKITE SERIES. 



might have been formed by any metamorphic agency, this zone 

 is characterised by the abundance of a peculiar purple garnet which 

 is also found in other less doubtful cases of contact action as, for 

 instance, when the Mercara series is altered by the great granite 

 stock which protrudes through it in the central portions of Coorg. 



Although, naturally, the testimony of these cases of apparent 

 contact action would be insufficient in themselves to prove the 

 igneous nature of the charnockite series, their value is accentuated 

 by their agreement with the other evidences. 



As the charnockite series never comes into contact with un- 

 altered sedimentary rocks, but is always bordered by rocks already 

 crystalline, contact phenomena are naturally rare ; the chances 

 of studying such instances as do actually exist are still more reduced 

 by the frequency, almost constancy, with which the junction lines 

 are hidden by detrital material or the thick jungle which invariably 

 clothes the foot regions of the charnockite hill-masses in South India. 

 The frequent association of the charnockite series with scapo- 

 litic rocks and with the crystalline limestones, cipolins and calci- 

 Scapolitic .granules P h y res containing an abundance of acces- 

 and caiciphyres. sor y m i nera i s ^ would naturally call for a place 



in this discussion of contact phenomena ; but the field evidence 

 bearing on the relation of these rocks to the charnockite series is 

 altogether too imperfect to settle the question as to whether the 

 crystalline limestones have developed their accessory minerals as 

 part of the metamorphism of ancient sedimentary limestones, or 

 whether they are the extreme results of alteration in the pyroxenic 



rocks themselves. 



That this association is accidental is in the highest degree 

 improbable, for the scapolitic rocks, cipolins and caiciphyres are 

 found associated with the pyroxene-granulites in many parts of 

 the world. 1 One's first impulse is to regard the accessory minerals 

 in the limestones as exogenous contact phenomena and the scapo- 

 lites, anorthites, lime-augites and sphenes in their pyroxenic neigh- 



« Cf. Lacroix, Rec. Geol. Surv. Ind., Vol. XXIV, pp. 157 and 199. 



( 114 ) 



