30 
Records of the Geological Survey of India. 
[vOL. XIII. 
rock is a true syenitic gneiss, consisting of quartz felspar and hornblende. This 
is, however, not always the case, since I have ah’eady shovm ‘ that the gneiss of 
Dras has a true gi-anitic composition, consisting of quartz, felspar, and two kinds 
of mica. Near the village of Himis, to the west of Leh, I collected the following 
varieties of crystalline rocks,® via .— 
Gneiss. Mica in small flakes, (Granitoidite.) 
Sjeuitio gneiss : a. Pink ortlioclase. (Syeuitoidite.) 
i. White do. 
Peguiatitio gneiss. (Pcgmatoidite.) 
Hornblende roek a. Small crystals of Hornblende, 
h. Largo ditto. 
The hornblende rock usually occurs in small irregular patches. 
At Tankse, 40 miles to the east of Leh, the greater portion of the gneiss is 
porphyritio, containing numerous crystals of white orthoclaso; near Shushal, 
45 miles to the south-east, the orthoclaso is pink colored. In the Chimray 
valley, on the Leh and Tankse road, the gneiss is traversed in all directions by 
veins of an intrusive rock, agi-eeing with some specimens of the albite granite of 
Dr. Stoliezka. This granite is very light-colored, and consists of quartz, albite 
felspar, and black mica: the latter occurs in larg’e flakes, and not unfrequontly 
forms a thin coating to quartz crystals of very largo size. This albite-granite 
intrusion is very characteristic of the central gneiss.® 
With regard to the relations of the Ladak gneiss to other rocks, the most 
clear sections are displayed near Tankse and the Pangong lake, and I accord- 
ingly commence with those districts. At Tankse itself we find the crystalline 
rock to be a massive white, and generally porphyritic, symnitic-gneiss, the higher 
beds consisting frequently of alternations of dark and light bands. To the 
south-east of the village of Ohilam, near Tankse, this porphyritio gneiss is 
distinctly scon to he overlaid by w bite and greenish quartzitic sandstones, black 
and green slates, banded jaspideo us rocks, a few conglomerates, and the peculiar 
massive half-slaty half-sandy rock, so characteristic of the Silurians of the Dras 
river. The whole of the slaty series, both in structure and in position, exactly 
resembles the slate series of Dras, and there seems to me but little doubt that 
they are one and the same series. This slate series forms a long narrow ellipse 
extending from near Tayar, in a south-easterly direction, to a point south of the 
Pangiir lake. The centre of this ellipse shows hero and there a central core of 
white non-porphyritic gneiss underlying the slates, and forming the highest 
peaks of the range. 
In the Ohilam valley the northern boundary of this ellipse appears to be a 
faulted one, as on the north side of that valley we have hills of gneiss with a 
northerly’’ dip, while to the south there are dark slates underlaid by gneiss (at 
the base of valley) with a southerly dip; this fault is apparently continued far 
* Rco. Geol. Surv. India, Vol. XII, p. 19. 
’ In bis last notes (Geology of 2n(l Yarkand E.vpedition, p. 16), Dr. Stoliezka mentions the 
varied composition of tlie Ladak gneiss, wbicb he had previously described as syonitic. 
2 Stol.: Mem. Geol. Surv. India, Vol. V, p. 13. 
Mc’Mabon; Ecc. Geol. Surv. India, Vol, X, p. 221, 
