234 HOLLAND : CHARNOCKITE SERIES. 



mica schist the quartzose lenses with garnet and other contact 

 minerals, staurolite, kyanite and sillimanite, are developed as the 

 intrusive rock is approached. At the immediate contact, the rocks 

 become felspathic and their structure changes to a harder, more 

 massive form. The eruptive rocks take on alumina and lime with 

 simultaneous loss of silica and alkalies to the schists, and develope 

 garnets, scapolite and other reaction minerals. The limestones 

 become bleached and develope hornblende and pyroxene, whilst the 

 invading rocks become simultaneously more calcareous, and the 

 rhombic ferromagnesian pyroxene, hypersthene, is replaced by the 

 monoclinic lime-bearing diallage. 1 



(d) Included fragments of foreign rocks. 

 The tendency for fragments of foreign rocks to lose their 

 individuality by contact metamorphism when immersed in a plutonic 

 mass becomes accentuated when the latter suffers subsequent meta_ 

 morphism itself. In all attempts to prove the igneous nature of any 

 formation amongst the crystalline schists it is consequently only 

 natural to expect that evidence on this score will be comparatively 

 difficult to obtain. But there are cases of bodies included in the 

 charnockite series which I should consider to belong to this category, 

 and the ellipsoidal masses of corundum-bearing rock found within, 

 but near, the border of the charnockite series in the Salem District 

 are probably examples. 8 



1 Williams' papers on the Cortlandt series, appeared in the Amer. Journ. Sci., Vol. 

 XXXI (1886), pp. 26-41 = Vol. XXXIII (1887), pp. 1 35— 144 and 191-199 ; XXXV (1888), 438 

 —448. The references made to them here are not intendedlto imply that the charnockite 

 series are strictly comparable to the Cortlandt series ; but the comparison of phenomena pre- 

 sented by known eruptives should guide us to an interpretation of those which characterise 

 mineralogically similar rocks whose origin is under investigation. In many points the minera- 

 logy of the charnockite series presents close analogies to that of the rocks which have been 

 worked out so exhaustively by Williams in the Cortlandt area. 



2 These corundum-bearing bodies have been described by Mr. Middlemiss as lenticles, 

 but the word ellipsoid is more accurate and indicates an essential difference in meaning. 

 Lenses are eye-shaped in section j that is, they have pointed ends, and inclusions of this 

 shape, which are so common in the gneisses, are regarded as drawn' out schlieren or 

 pinched-out bands; but the rounded ends of these corundum-bearing inclusions and the 

 peripheral concentration of biotite indicate corrosion and reaction with the surrounding 

 rocks. 



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