164 AET 2.— B. KOTO: 



and is often penetrated l)y dykes of granodiorite, tourmaline- 

 microcline-microperthite, and porpliyrite (pp. 125-126). Though the 

 palaeogranite is highly diversified in structural development, yet 

 it has all the common traits by which other kinds, especially the 

 younger ones, can be easily discriminated. 1 shall, therefore, now 

 give a general description of it ; but before doing so, let me say 

 a few words as to where the palaeogranite occurs in the region 

 under question. 



The high So-päik-san^^ range of which the Chirl-san massif 

 forms a part, lies obliquely across the boundary of the two pro- 

 vinces of Kijönj-sancj-Do and ChffôI-îa-Do, and is entirely constituted 

 of the pala30granite ; moreover, the greater part of the area of Chu'ù!- 

 Ja-Do is an extension of the same, wliile that of Ky'ônfj-saiif/-Do 

 is occupied by the Mesozoic formation. 



The palaeogranite is a grayish, coarse magnophyric plutonic, 

 becoming slightly red on the weathered surface due to the par- 

 tial decomposition of feldspars into pinitoid particles mixed with 

 iron oxides. Essential components are quartz, orthoclase, micro- 

 cline, oligoclase, biotite and sometimes muscovite. Accessories 

 are allanite, garnet, titanite, zircon, apatite, cordierite, sillimanite 

 and tourmaline. The characteristic macro texture is its schisto- 

 sity which varies within wide latitudes according to the condi- 

 tion on which it is brought to bear and the quantity of micas 

 which take part in its mineralogical composition. We have 

 therefore all stages from almost normal granite to gneiss through 

 various phases of gneissoid granite, granite-gneiss, orthogneiss 

 and granulite. The second characteristic is its porphyry-like 

 texture, and accordingly w^e have eye-gneiss equivalents of the 



1) 'J' Û lU M 



