OUTLINES OF GEOLOGY OF YUNNAN. ;,[ 



nephcline syenite. Accessory minerals include an amphi- 

 bole of the arfvedsonite family, lepidomelane, sphene, 

 socialite and cancrinite. 

 (e) Scattered localities in south-eastern Yunnan. — -Crystalline 

 rocks are not widely developed in Eastern Yunnan. 

 In the deep valley of the Red River, and on the borders 

 of the Meng-tzu basin, mica schists accompanied by 

 cipolins and amphibolites occur. Masses of leptynitc 

 and tourmaline-bearing pegmatites are associated with 

 them. In the Ko-chiu neighbourhood these rocks carry 

 cassiterite, and the weft-known tin deposits are partly 

 the product of their disintegration. 



(2) The Kao -Liang System. 



I have given this name to a series of ancient, unfossilifcrous, 

 metamorphosed rocks which are common in Western Yunnan, 

 and are generally found between the crystalline rocks and the 

 oldest, undoubted Palaeozoic sediments. They consist of phyllites, 

 slates, quartzitcs and subordinate calcareous horizons and there is 

 invariably a most distinct unconformity between them and the 

 underlying crystallines. A band of rocks belonging to this system 

 and at least 10 miles across crops out just beyond the Mekong on 

 the Teng-yiieh — Ta-li-Fu route. Slates, talc Schists and bluish- 

 white qiiartzites are the prevailing types. To the South the band 

 broadens out and covers a wide extent of broken, deeply dissected 

 country between Shun-ning Fu and Yung-Ch'ang Fu. 



These rocks are very similar to the Chaung Magyi rocks of the 

 Northern Shan States, except that they contain calcareous hori- 

 zons. It is probable that when they come to be examined they 

 will be found to contain beds corresponding both with the Hu-t'o 

 system of Western Shan-si, and perhaps even with the Cambrian 

 in part. This system is well developed in Eastern Yunnan and 

 it may be that the greater amount of metamorphism which rocks 

 of this age must have undergone in the tectonic upheavals of the 

 Mekong ranges has destroyed any traces of fossils they originally 

 contained. 



(3) The Cambrian System. 



Rocks of this age are only known in Eastern Yunnan, though 

 it is possible that some of the beds classified as Kao-liang in the 



