104 RESEARCH IN CHINA. 
T’aI-SHAN COMPLEX IN NORTHERN SHAN-SI. 
Granites in the Hin-chou district.—The prevailing rock of the complex 
in the Hin-chéu basin is a coarse-grained reddish granite, which contains 
orthoclase, biotite, and blue-gray quartz. This is the only rock which 
appeared in the basal system where it is exposed in the slopes southeast 
of Han-yang. Five to 1o miles, 8 to 16 kilometers, northeastward, in the 
base of the same mountain, the red granites are associated in an unknown 
relation with schistose greenstones, ancient dioritic rocks, and more recent 
brown feldspar-porphyries. 
Southwest of the city the red granite appears in company with dark 
biotite-schists and a highly acid gray granite of fine texture. Being harder 
than the other components of the mass, the gray granite is the last to 
be reduced during erosion, and forms the low monadnocks visible in the 
vicinity of the city. 
Both the red and the gray granites are massive rocks not conspicuously 
gneissoid or schistose. Like the granites of the T’ai-shan complex of Shan- 
tung, they have probably been intruded into the mica-schists with which 
they are in some sections associated, and are probably of Algonkian age. 
Gneisses in the Wu-t’at district.—The Wu-t’ai-shan consists chiefly of 
metamorphic rocks of sedimentary origin, which we assign to the Wu-t’ai 
system of the Eo-Algonkian, but the T’ai-shan complex is represented by 
gneisses, which flank the range on both sides. 
The basal T’ai-shan complex, which is so wide-spread about Féu-p’ing- 
hién, Chi-li, was followed up the Sha-ho and found to form the larger part 
of the mountains along which stretches the South Branch of the Great 
Wall. The rock is for the most part a firm biotite-gneiss, frequently red- 
dish in color, though often gray, and it grades insensibly into gray mica- 
schists. From the intimate association of the schists and gneisses, it is 
inferred that the two are portions of a single mass of variable composition, 
in which the effects of metamorphism have been correspondingly unlike. 
The upper limit of the T’ai-shan in this section is the unconformity with 
the Shi-tsui group of the Wu-t’ai system. The contact, which we take to be 
the unconformity or a plane of bedding near it, was seen at two points 
in the hills southeast of Shi-tsui, but was not traced further. In a general 
line, however, it extends northeast and southwest along the southeastern 
side of the Wu-t’ai mass. 
The T’ai-shan complex is likewise represented in a wide area trav- 
ersed by the Hu-t’o-ho, northwest of the Wu-t’ai-shan. Von Richthofen, 
crossing the range in 1871, found the northern foothills composed of red- 
dish mica-gneiss.* This he considered to be the same as the basal gneiss, 
*Von Richthofen, China, vol. 11, page 364. 
