CHAPTER IV. 



ARCHAEAN. 

 Mogok Gneiss. 



The southern boundary of the gneissic area in the Kuby Mines 

 District is fairly well defined, by the valley 

 Sout em boundary. ^ ^ e Nam-pai (Nampi or Mobi Chaung), 



which separates the district from the Shan State of Mong Long 

 (Mainglon) (C 1)- F° r a short portion of its course, to the north- 

 east of the town of Mong Long, the river flows through the gneiss, 

 but as a rule the latter is confined to the hills on the northern 

 bank, which extend in a succession of parallel ranges from north- 

 east to south-west, the direction of the prevailing strike of the 

 gneiss with its associated bands of limestone. As we proceed 

 northwards, the ranges increase in elevation, their crests rising to a 

 height of 4,000 to 6,000 feet above the sea, until they reach 7,514 

 feet in Taung Me (Toungnee, C. B. B.), immediately above Mogok, 

 (Fig. 2, p. 44), overlooking the broad level plain of the Shweli river. 

 The northward and north-eastward extension of this crystalline rock 

 mass has not been surveyed beyond the limits of the area mapped 

 on the one inch scale, but there is no doubt that it is continuous 

 with the gneisses of the country north of Bhamo, 1 and of south-western 

 Yunnan, where they possess a similar N.E.-S.W. strike. 2 



To the south of the Ruby Mines District the gneisses occupy 

 the whole of the country between the Nam- 



W estem boundary. , . . ,■»«• i i 



rek or Chaung Magyi river (Mobaychoung, 

 C. B. B.), as the Nam-pai is called in the lower parts of its course, 

 and the Irrawaddy. The Chaung Magyi is at the same time the 

 boundary between the Mandalay District and the Shan States and 

 roughly speaking, between the gneiss and the Lower Pahoozoic rocks. 

 In this area the strike is still south-west, but on the western bank 

 of the Irrawaddy it turns due south, and these rocks form the 

 narrow range of hills running parallel to the river which has its 



1 C. L. Griesbach, Geological Sketch of the country north of Bhamo ; Records, Oeol. 

 Surv. Ind., Vol. XXV. Pt. 3, p. 127. 



2 L. v Loezy, in Gral Bela Szcchcnyi's Rcise in Os(;isicn, Vol. [, p. 776. 



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