GEOLOGY AND OEE DEPOSITS OF SU-AN 5 



liill which forms a barrier between the valley just mentioned and 

 that of Pai-chhi-gol ^\ On the n o r t h side alone, the ground 

 is open for a certain distance along a fine gorge stream which, 

 rising in the southern hill range of the mine, discharges its contents 

 into the U-gang river near S'ok-tari. The latter, as already stated, 

 runs eastward parallel to the northern equatorial liills for about 

 12. hm {oOli), and joins the river Sin-gy'ôi-gang. On the south 

 of the Morai-chhl valley, the ground rises considerably, culminating 

 in the On-jin massive about 4 km from the mine. 



B. Geology of the District 



The geology of Hol-gol and its neighborhood is composed of 

 highly metamorphosed argillite, calcareo-siliceous slate and lime- 

 stone, porphyritic granite and basalt. The siliceous and argilla- 

 ceous metamorphics mainly occur on the west side of the Hol-gol 

 valley, which separates them from the thick limestone (^30 in) ; 

 the latter extends through the hill range on the east side of the 

 valley for a considerable distance, covering the whole of the Pai- 

 chhi-gol and Kul-lyang-kol'\ 



The line of demarcation between the scliists and tlie limestone 

 is the trace of meridional fault of Hol-gol^ as is proved by the slicken- 

 sided face often visible along the plane of contact exposed in cut- 

 tings near the mine, as well as by the sudden change of topographic 

 relief on both sides of this tectonic line. 



The schistose complex together with the limestone constitutes 

 the basement of the region, of which brief descriptions will be 

 given in the following : — 



1) %nm 2) liüiläi 



