CENTRAI, TS'lN-WNG-SHAN. 17 



it was supposed to. It apparently runs to a point west of Si-an-fu, about 

 longitude 109, and is a triangular area bounded on the southwest by 

 metamorphosed Paleozoics and granites intruded into them. 



The next section toward the west, across the Ts'in-ling-shan, is that 

 observed by the expedition of 1904-05, between Chou-chi-hien and Shi- 

 ts'uan-hien, in longitude 108 30' E. It lies not more than 65 miles, 100 

 kilometers, west of Loczy's eastern route and 80 miles, 125 kilometers, east 

 of von Richthofen's. 



In approaching the Ts'in-ling-shan from the Wei' valley, in longitude 

 1 08 15', from Chou-chi-hien, we expected to find the front of the range 

 composed of granite, as shown by von Richthofen. Instead, the foothills 

 and northern slopes consist of green schists, prevailingly chloritic, in which 

 occur thin beds of quartzite and highly siliceous marble. These rocks dip 

 toward the north at their northern margin, but a short distance south dip 

 steeply southward. They maintain a uniform southern dip of bedding 

 and schistosity for 5.5 miles to their southern limit at Liu-yue-ho, where 

 they are succeeded by white quartzite and massive gray limestone, folded 

 in a syncline. The contact was not observed, but a coarse conglomerate 

 of quartz, quartzite, and granite pebbles in a reddish or dark purple matrix 

 is supposed to be the lowest stratum overlying the schists. It occurred in 

 large masses in a brook, which flowed along and near the contact. These 

 occurrences very closely resemble the relations observed by von Richt- 

 hofen, who describes similar rocks in the statement quoted below. We 

 agree with him entirely as to the petrographic likeness between the green 

 schists of these sections and those of the Wu-t'ai system of Shan-si. Their 

 position beneath a distinct series, which can not be younger than Paleozoic 

 and from which they appear to be separated by a marked unconformity, 

 is that of pre-Sinian terranes. 



Von Richthofen's description of the rocks which he assigns provision- 

 ally to pre-Sinian series, can not be better stated than in his own words.* 

 After describing the general aspect of the northern slope of the Ts'in-ling- 

 shan as it rises from the plain of the Wei, he says, with reference to the 

 Archean zone : 



The first rock seen in place near Yi-monn is granite, in part of medium grain, in part 

 very coarse, a mixture of red orthoclasc, some white plagioclase, quartz, and black mica. 

 Here and there occurs a thinly laminated mica gneiss, which occasionally goes over into 

 hornblende and chlorite gneiss. It is everywhere penetrated by granite. I saw no other 

 rocks during this day. Typical gneiss and typical eruptive granite (with the exception of 

 gneiss-granite) predominate probably in the entire width of the northern zone of the moun- 

 tain range, for in the alluvial cones along the northern base, west of Kwei-tschonn, I saw 

 only these rocks, which were there developed in great variety. 



* China, vol. n, pp. 563 and 565 



