TAWNG-PENG SYSTEM : BAWD WIN VOLCANIC STAGE. 



55 



to those obtaining in China at the beginning of the Sinian period, 

 as conjectured by Bailey Willis 1 (see beloiv, p. 349). 



Bawdwin Volcanic Stage. 



At certain localities along the boundary between the rocks just 

 described and the overlying fossiliferous Pal- 

 ters ^nd^istabutira^ ^^oic formations a series of beds is exposed 

 which are undoubtedly of volcanic origin. 

 These consist mainly of tuff or ash beds, but among them layers 

 of true rhyoiites are interstratified, the remains of ancient lava 

 flows. The most important development of these beds that has 

 yet been met with occurs at Bawdwin, or Bawdwingyi (Burm. 

 ' The great Silver mine'), the northern part of the Tawng-Peng 



sub-State, a few miles to the west of the 

 Bawdwin silver mines. . . .. 



ISam-Iu, beyond the northern limits of the 



map. This place is well known as the site, for many hundreds 

 of years, of extensive mining operations on the part of the Chinese, 

 who extracted very large quantities of silver-bearing lead ores from 

 the rocks, and who have left abundant traces of their activity in 

 the enormous heaps of lead slag, now being exploited by a smelt- 

 ing company, covering the hill slopes surrounding the mines, and 

 in the numerous adits and galleries with which the hills are honey- 

 combed. An account of the geology and mineralogy of these 

 mines will be found in the Records of the Geological Survey of 

 India, Vol. XXXVII, Pt. 3, the result of observations made by 

 Mr. J. Coggin Brown and myself during a visit to the mines in Feb- 

 ruary 1907. At the time of our visit the Company had not yet 

 begun operations, beyond prospecting the slag heaps, and the place 

 was in much the same state as when the Chinese deserted it, 

 owing, it is supposed, to political troubles and the incursions of the 

 Kachins, over 50 years ago. For the present it is sufficient to say 

 that the ores occur among the tuffs and rhyoiites of the volcanic 

 series, and that the mineralisation of the rocks is due to the pre- 

 sence of a great dislocation or overthrust, in the neighbourhood of 

 which they are intensely crushed and shattered. 



This dislocation is one of the most striking features of the 

 o { lt structure of the rocks in this part of the 



Shan Hills, and it has been traced for many 



1 Op. cii., Vol. II, p. 32. 



