290 



PENTTI ESKOLA 



found obtaining in the well-known limestone-bearing area of 

 Parainen (Pargas)/ 



Another feature with which the non-occurrence of assimilation I 

 is evidently connected is that this granite which forms veined! 

 gneisses or migmatites with all kinds of siliceous rocks has never] 

 been intruded into limestones to form intimate mixtures. There- 

 fore the writer made the following general statement:^ "The! 

 resistance offered by limestones against granitization is very 

 remarkable. Even in the midst of a migmatite area, where all] 

 siliceous rocks have been thoroughly mixed or assimilated with the ■ 

 granite magma, the limestones are generally quite free from granitic j 

 injections, and are intersected only by rectilinear dikes." Morei 

 evidence of assimilation of limestone by granite magma wasj 

 brought forth during an investigation of certain areas in Trans- 

 baikalia.^ 



The peninsula of Sviatoy Noss, on the east coast of Lake] 

 Baikal, is made up of crystalline schists, among which are numerous! 

 masses of limestones, and of huge batholiths and smaller bodies] 

 of granites intrusive into the schists. The granites, when meeting 

 limestone either as dikes or as large masses, show no endomorphic 

 change whatever at the contacts, while in certain intrusive masses] 

 there is a very remarkable change in the whole rock bodies, the] 

 rocks (called sviatonossite) being composed of alkali feldspars 

 with aegirite-augite and andradite. The high percentage of lime 

 present has clearly been derived from the limestone, but the process] 

 of assimilation has taken place in such a way that andradite- 

 clinopyroxene skarn has first been formed from the limestone and! 

 the skarn has subsequently been absorbed. This is evident from] 

 the common occurrence of fragments of skarn in the rock showing] 

 every degree of assimilation. Finally, all the minerals have crystal- 

 lized out from the magma and the rock is now an ordinary unalteredj 

 igneous rock. 



' Laitakari, op. cii. 

 ^ Op. cit., p. 36. 



3 P. Eskola, "On the Igneous Rocks of Sviatoy Noss in Transbaikalia," Oversik^ 

 av Finska Vet.-Soc. ForhandUngar, Vol. LXII, A, No. i (1921). 



