IGNEOUS ROCKS. 
6i 
been intruded. In the Kyi Chu valley, as at Gyantse and elsewhere 
the slates ate not infrequently calcareous and contain bands of lime- 
stone and calc-schist, and the absorption of these by the granite, at 
a stage prior to its complete solidification, would result in the pro- 
duction of such minerals as sphene and epidote, the excess of lime 
combining with carbonic acid to form calcite. 
A very handsome porphyritic granite, with large phenocrysts of 
flesh-coloured orthoclase, occurs on the right bank of the Kyi Chu at 
Nam, about 23 miles below Lhasa. 
Basic schlieren, probably representing fragments of the sedi- 
mentary rocks into which the granite has been intruded, and com- 
posed of idiomorphic crystals of felspar and ragged patches and rods 
of hornblende, frequently twinned., are very common in the granite 
both at Nam and also at Chushii on the left bank of the Tsangpo. 
It is evident therefore that the Kyi Chu granite differs essentially 
from the ordinary varieties of the Himalayan rock : from the typical 
foliated biotite-granite, it may be distinguished by the absence of 
foliation and the presence of hornblende as an essential constituent 
and from the muscovite-schorl-granite by the presence of hornblende 
and the absence of tourmaline and muscovite. It is interesting to 
note that Professor Garwood records the presence of fragments of an 
unfoiiated hornblende-granite among the blocks scattered over the 
surface of the Zemu glacier in Sikkim^ and also of a fine-grained 
hornblendic gneiss in the moraines of the Kinchinjunga glacier^ ; 
he does not, however, give a detailed description of either of these 
rocks, but notes the absence of hornblende from the prevailing 
gneiss of the Kinchinjunga area and suggests that the hornblendic 
variety may belong to a different rock into which the former has 
been intruded. He states also that intrusive veins of hornblende 
granite occur in the gneiss at Jongri^ ; the same rock apparently, was 
noticed by Mr. Bose.* 
> D. W. Freshfield : Round Kangckenjunga, Appendix by Prof. E. J. Gar- 
wood, 285. 
' 1. c. p. 289. 
' 1. c. p. 290. 
*Rec. Geol. Surv. Ind„ XXIV, 51- 
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