14S HOLLAND: GEOLOGY OF THE NEIGHBOURHOOD OF SALEM. 



which they are distinguished merely by being more thoroughly 

 crystalline (pp. 8—14). 



The charnockite series includes members of the acid, inter- 

 mediate, basic and ultra-basic divisions which are described in a 

 separate paper [Mem % , GeoL Surv. y Ind., Vol. XXVIII, part 2). 

 The lenticular habit, especially of the basic forms and associated 

 pyroxenites, is very well illustrated near Salem. The garnets 

 found so abundantly in the uncrushed varieties are considered to 

 have originated as the result of metachemic alteration of the 

 pyroxenes at a high temperature short of actual fusion, the silica 

 eliminated by the process generally crystallizing as granular clear 

 quartz included in the spongy garnets (pp. 14—27). The so-called 

 " trap-shotten " bands frequently displayed by the charnockite 

 series near Salem are not due to injection of basic material, but are 

 brecciation lines along which the mylonite has been fritted into a 

 compact black mass by heat, probably the heat generated by friction 



(p. 37)- 



For the reason that they do not come into actual contact 

 with one another, the relative ages of the younger eruptives cannot 

 be determined in the neighbourhood of Salem. The three exposures 

 of wide trap-dykes, and their lateral subsidiary apophyses, are 

 augite-diorites (diabases) with micropegmatite, and are similar to 

 those described in a separate paper (Rec, GeoL Surv. t Ind., 

 Vol. XXX, p. 31) as the probable dyke- representatives of the 

 Cuddapah lava flows. The magnesian rocks of the so-called " Chalk 

 hills" are chiefly dunites (much decomposed to form magnesite), 

 mica-augite peridotites and picrites. The "White Elephant 

 rocks " in the Shevaroy hills are masses of quartz having the 

 characters of plutonic quartz and containing much liquid carbonic 

 acid (pp. 27 — 36). 



Messrs. King and Foote suggested (Mem., GeoL Surv., Ind., 

 Vol. IV, p. 325) that the magnesite of the « Chalk hills M was formed 

 ( 44 ) 



