STRATIGRAPHY OF CHI-LI AND SHAN-SI. IOI 
T’AI-SHAN COMPLEX IN WESTERN CHI-LI. 
Gneisses near T’ang-hién.—The basal complex seen near ‘T’ang-hién 
is composed of gneisses and schists with abundant igneous dikes, some 
of which are more or less metamorphosed. It closely resembles the T’ai- 
shan complex of Shan-tung, but it contains certain rocks of sedimentary 
origin not seen in this association elsewhere. 
The prevailing gneiss is a brown quartzose rock in which the dark 
mineral is either hornblende or biotite. Although the texture varies 
through thick beds, the rock is usually fine-grained in detail; the structures 
called ‘‘augen’’ are only locally developed. A distinguishing feature of 
these gneisses is the inclusion of numerous lenticular masses of dark 
amphibole-schist and biotite-schist, varying in size from a few inches to 
many feet in length, but usually of moderate dimensions. 
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Fic. 17 (Blackwelder).—T’ang-hién, Chi-li. T’ai-shan complex (Archean). Detail of metamorphic 
succession showing variety of gneisses and schists with both altered and unaltered intrusives. a= 
gray gneiss cut by greenstone dikes; b= gray granite porphyry-dikes; c= gray biotite-gneiss and 
schist; d = light gray augen-gneiss; e = lenses of amphibolite in gneiss; / = gray granite- 
porphyry dikes; g = white sericite-schist; 4 = brown hornblende-gneiss with amphibolite lenses; 
2 = gray augen-gneiss; 7 = biotite-schist. 
In megascopic character the gneiss is notably variable (Fig. 17). 
On the one hand, it approaches an unaltered granite so closely that the 
term ‘‘gneissoid granite’? is most appropriate; such is a biotite-granite 
exposed along the border of the hills northwest of Wan-hién. On the 
other hand, the gneiss grades off into mica-schists. In many places the 
parallel injection of acid igneous material in thin laminz has given the rock 
a conspicuously banded appearance; and the subsequent folding of the mass 
has resulted in contorted banding. 
On the northern slope of the mountain, about 3 miles northeast 
of T’ang-hién, the gneiss contains biotite- and muscovite-schists with which 
is associated a small mass of coarse white marble. The marble contains 
streaks of muscovite and is in contact with whitish muscovite-schists, 
which are probably sedimentary in origin. ‘There is also in the vicinity 
a highly quartzose gneiss, containing very little feldspar and only thin 
streaks of biotite; it is thought that this may have been an ancient 
quartzite in which the grains of sand and mud have recrystallized. In the 
same region occur sericite-schists, amphibolites, and other rocks, which 
