350 



LIEUT.-GEN. C. A. MCMAHOtf ON 



[May 1900, 



whole hillside is intersected in every direction by the granite. I 

 imagine, therefore, that the metamorphism is pretty complete, as 

 there does not appear to be any difference between the rock near 

 the dykes and that far away.' 



Between Noma! and Chalt a dark variety of the Hatu Pir Granite 

 — the darker colour being due to the abnormal size of the biotite- 

 flakes — is cut by a diorite composed of well-crystallized horn- 

 blende set in plagioclase-felspar with epidote, magnetite, pyrite, 

 a little haematite in microscopic grains, and chlorite as secondary 

 minerals. The hornblende is in long lath-shaped prisms, the cross- 

 sections of which are fairly idiomorphic. It is pleochroic in green, 

 greenish-yellow, and bluish-green tints. This diorite, which cuts 

 the granite, is also cut by it. 



At Gwech a quartz -rock occurs, which 

 coloured green by the deposition of chlorite, 

 chlorite-epidote-felspar schists which 

 microscopic evidence to be altered lavas, and by a tremolite- 

 schist. These are succeeded by quartz and by a ferruginous calc- 

 schist: the last-named rock contains 59 per cent, of silica, 8 per 

 cent, of iron, and about 33 per cent, of the carbonates of iron, 

 lime, and magnesia. 



Fig. 1. — Diagrammatic section from SherJcila on the Yasin River 

 to Pasu on the Gilgit River. 



Hunza Peak 

 (Boiohaghurdoanas) 



is here and there 

 It is followed by 

 I believe from the 



Igneous dykes in Chalt Nilt-Hini 



amphibolites Micaceous Limestone 



(altered diontes) Slates 



Mica-schist Stink- Schists with 



stone igneous dykes 



Limestone Slate-beds 



What I regard as altered volcanic rocks need a few words 

 in passing. One specimen contains chloritic pseudomorphs after 

 idiomorphic felspars. The groundmass, tinged green with chlorite, 

 was probably felspathic to begin with, and it still contains countless 

 colourless microliths suggestive of the felspar-microliths of certain 

 lavas : they cannot be chlorite, as they extinguish at an average 

 angle of 11|°. A second specimen bears a still closer resemblance 

 to a lava, for the felspar-phenocrysts are comparatively unaltered 

 and still exhibit plagioclase-twinning. The felspar is apparently 

 oligoclase, for the angle of extinction, when fairly symmetrical, 

 ranges from 3° to 12|°, and averages 8°. Both specimens contain 

 numerous grains of calcite and epidote, indicating the operation of 

 aqueous agents. 



At Chalt slaty rocks come in. They are bluish-grey, have a 

 micaceous glaze, and split readily under the hammer. One of the 

 specimens is calcareous, and is veined with quartz. 



